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Ripplinger CM, Glukhov AV, Kay MW, Boukens BJ, Chiamvimonvat N, Delisle BP, Fabritz L, Hund TJ, Knollmann BC, Li N, Murray KT, Poelzing S, Quinn TA, Remme CA, Rentschler SL, Rose RA, Posnack NG. Guidelines for assessment of cardiac electrophysiology and arrhythmias in small animals. Am J Physiol Heart Circ Physiol 2022; 323:H1137-H1166. [PMID: 36269644 PMCID: PMC9678409 DOI: 10.1152/ajpheart.00439.2022] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/11/2022] [Accepted: 10/17/2022] [Indexed: 01/09/2023]
Abstract
Cardiac arrhythmias are a major cause of morbidity and mortality worldwide. Although recent advances in cell-based models, including human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), are contributing to our understanding of electrophysiology and arrhythmia mechanisms, preclinical animal studies of cardiovascular disease remain a mainstay. Over the past several decades, animal models of cardiovascular disease have advanced our understanding of pathological remodeling, arrhythmia mechanisms, and drug effects and have led to major improvements in pacing and defibrillation therapies. There exist a variety of methodological approaches for the assessment of cardiac electrophysiology and a plethora of parameters may be assessed with each approach. This guidelines article will provide an overview of the strengths and limitations of several common techniques used to assess electrophysiology and arrhythmia mechanisms at the whole animal, whole heart, and tissue level with a focus on small animal models. We also define key electrophysiological parameters that should be assessed, along with their physiological underpinnings, and the best methods with which to assess these parameters.
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Affiliation(s)
- Crystal M Ripplinger
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California
| | - Alexey V Glukhov
- Department of Medicine, Cardiovascular Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
| | - Bastiaan J Boukens
- Department Physiology, University Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Medical Biology, University of Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Nipavan Chiamvimonvat
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California
- Department of Internal Medicine, University of California Davis School of Medicine, Davis, California
- Veterans Affairs Northern California Healthcare System, Mather, California
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, Kentucky
| | - Larissa Fabritz
- University Center of Cardiovascular Science, University Heart and Vascular Center, University Hospital Hamburg-Eppendorf with DZHK Hamburg/Kiel/Luebeck, Germany
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Thomas J Hund
- Department of Internal Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
- Department of Biomedical Engineering, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Na Li
- Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Katherine T Murray
- Departments of Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Steven Poelzing
- Virginia Tech Carilon School of Medicine, Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech, Roanoke, Virginia
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Carol Ann Remme
- Department of Experimental Cardiology, Heart Centre, Amsterdam Cardiovascular Sciences, Heart Failure and Arrhythmias Amsterdam UMC Location University of Amsterdam, Amsterdam, The Netherlands
| | - Stacey L Rentschler
- Cardiovascular Division, Department of Medicine, Washington University in Saint Louis, School of Medicine, Saint Louis, Missouri
| | - Robert A Rose
- Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Nikki G Posnack
- Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, District of Columbia
- Department of Pediatrics, George Washington University School of Medicine, Washington, District of Columbia
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Olson B, Marks DL, Grossberg AJ. Diverging metabolic programmes and behaviours during states of starvation, protein malnutrition, and cachexia. J Cachexia Sarcopenia Muscle 2020; 11:1429-1446. [PMID: 32985801 PMCID: PMC7749623 DOI: 10.1002/jcsm.12630] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 09/04/2020] [Accepted: 09/07/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Our evolutionary history is defined, in part, by our ability to survive times of nutrient scarcity. The outcomes of the metabolic and behavioural adaptations during starvation are highly efficient macronutrient allocation, minimization of energy expenditure, and maximized odds of finding food. However, in different contexts, caloric deprivation is met with vastly different physiologic and behavioural responses, which challenge the primacy of energy homeostasis. METHODS We conducted a literature review of scientific studies in humans, laboratory animals, and non-laboratory animals that evaluated the physiologic, metabolic, and behavioural responses to fasting, starvation, protein-deficient or essential amino acid-deficient diets, and cachexia. Studies that investigated the changes in ingestive behaviour, locomotor activity, resting metabolic rate, and tissue catabolism were selected as the focus of discussion. RESULTS Whereas starvation responses prioritize energy balance, both protein malnutrition and cachexia present existential threats that induce unique adaptive programmes, which can exacerbate the caloric insufficiency of undernutrition. We compare and contrast the behavioural and metabolic responses and elucidate the mechanistic pathways that drive state-dependent alterations in energy seeking and partitioning. CONCLUSIONS The evolution of energetically inefficient metabolic and behavioural responses to protein malnutrition and cachexia reveal a hierarchy of metabolic priorities governed by discrete regulatory networks.
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Affiliation(s)
- Brennan Olson
- Medical Scientist Training ProgramOregon Health & Science UniversityPortlandORUSA
- Papé Family Pediatric Research InstituteOregon Health & Science UniversityPortlandORUSA
| | - Daniel L. Marks
- Papé Family Pediatric Research InstituteOregon Health & Science UniversityPortlandORUSA
- Brenden‐Colson Center for Pancreatic CareOregon Health & Science UniversityPortlandORUSA
| | - Aaron J. Grossberg
- Brenden‐Colson Center for Pancreatic CareOregon Health & Science UniversityPortlandORUSA
- Department of Radiation MedicineOregon Health & Science UniversityPortlandORUSA
- Cancer Early Detection Advanced Research CenterOregon Health & Science UniversityPortlandORUSA
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3
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Vialard F, Olivier M. Thermoneutrality and Immunity: How Does Cold Stress Affect Disease? Front Immunol 2020; 11:588387. [PMID: 33329571 PMCID: PMC7714907 DOI: 10.3389/fimmu.2020.588387] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 10/26/2020] [Indexed: 12/13/2022] Open
Abstract
One of the major challenges the scientific community faces today is the lack of translational data generated from mouse trials for human health application. Housing temperature-dependent chronic cold stress in laboratory rodents is one of the key factors contributing to lack of translatability because it reveals major metabolic differences between humans and rodents. While humans tend to operate at temperatures within their thermoneutral zone, most laboratory rodents are housed at temperatures below this zone and have an increased energy demand to generate heat. This has an impact on the immune system of mice and thus affects results obtained using murine models of human diseases. A limited number of studies and reviews have shown that results obtained on mice housed at thermoneutrality were different from those obtained from mice housed in traditional housing conditions. Most of those studies, focused on obesity and cancer, found that housing mice at thermoneutrality changed the outcomes of the diseases negatively and positively, respectively. In this review, we describe how thermoneutrality impacts the immune system of rodents generally and in the context of different disease models. We show that thermoneutrality exacerbates cardiovascular and auto-immune diseases; alleviates asthma and Alzheimer’s disease; and, changes gut microbiome populations. We also show that thermoneutrality can have exacerbating or alleviating effects on the outcome of infectious diseases. Thus, we join the call of others in this field to urge researchers to refine murine models of disease and increase their translational capacity by considering housing at thermoneutrality for trials involving rodents.
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Affiliation(s)
- Fiorella Vialard
- Department of Microbiology and Immunology, Program in Infectious Diseases and Immunity in Global Health, The Research Institute of the McGill University Health Centre, McGill University, Montreal, QC, Canada
| | - Martin Olivier
- Department of Microbiology and Immunology, Program in Infectious Diseases and Immunity in Global Health, The Research Institute of the McGill University Health Centre, McGill University, Montreal, QC, Canada
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Ono-Moore KD, Rutkowsky JM, Pearson NA, Williams DK, Grobe JL, Tolentino T, Lloyd KCK, Adams SH. Coupling of energy intake and energy expenditure across a temperature spectrum: impact of diet-induced obesity in mice. Am J Physiol Endocrinol Metab 2020; 319:E472-E484. [PMID: 32691631 PMCID: PMC7509245 DOI: 10.1152/ajpendo.00041.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Obesity and its metabolic sequelae are implicated in dysfunction of the somatosensory, sympathetic, and hypothalamic systems. Because these systems contribute to integrative regulation of energy expenditure (EE) and energy intake (EI) in response to ambient temperature (Ta) changes, we hypothesized that diet-induced obesity (DIO) disrupts Ta-associated EE-EI coupling. C57BL/6N male mice were fed a high-fat diet (HFD; 45% kcal) or low-fat diet (LFD; 10% kcal) for ∼9.5 wk; HFD mice were then split into body weight (BWT) quartiles (n = 8 each) to study DIO-low gainers (Q1) versus -high gainers (Q4). EI and indirect calorimetry (IC) were measured over 3 days each at 10°C, 20°C, and 30°C. Responses did not differ between LFD, Q1, and Q4; EI and BWT-adjusted EE increased rapidly when transitioning toward 20°C and 10°C. In all groups, EI at 30°C was not reduced despite lower EE, resulting in positive energy balance and respiratory exchange ratios consistent with increased de novo lipogenesis, energy storage, and relative hyperphagia. We conclude that 1) systems controlling Ta-dependent acute EI/EE coupling remained intact in obese mice and 2) rapid coupling of EI/EE at cooler temperatures is an important adaptation to maintain energy stores and defend body temperature, but less critical at thermoneutrality. A post hoc analysis using digestible EI plus IC-calculated EE suggests that standard IC assumptions for EE calculation require further validation in the setting of DIO. The experimental paradigm provides a platform to query the hypothalamic, somatosensory, and sympathetic mechanisms that drive Ta-associated EI/EE coupling.
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Affiliation(s)
| | - Jennifer M Rutkowsky
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, University of California, Davis, California
- Mouse Metabolic Phenotyping Center, University of California, Davis, California
| | - Nicole A Pearson
- Department of Pharmacology, University of Iowa, Carver College of Medicine, Iowa City, Iowa
| | - D Keith Williams
- Arkansas Children's Nutrition Center, Little Rock, Arkansas
- Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Justin L Grobe
- Department of Physiology and Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Todd Tolentino
- Mouse Metabolic Phenotyping Center, University of California, Davis, California
| | - K C Kent Lloyd
- Mouse Metabolic Phenotyping Center, University of California, Davis, California
- Department of Surgery, School of Medicine, University of California, Davis, California
| | - Sean H Adams
- Arkansas Children's Nutrition Center, Little Rock, Arkansas
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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5
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Huang Q, Lin SW, Hu WP, Li HY, Yao PS, Sun Y, Zeng YL, Huang QY, Kang DZ, Wu SY. Meteorological Variation Is a Predisposing Factor for Aneurismal Subarachnoid Hemorrhage: A 5-Year Multicenter Study in Fuzhou, China. World Neurosurg 2019; 132:e687-e695. [PMID: 31442657 DOI: 10.1016/j.wneu.2019.08.048] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/07/2019] [Accepted: 08/09/2019] [Indexed: 10/26/2022]
Abstract
OBJECTIVE The climatic characteristics of aneurysmal subarachnoid hemorrhage (aSAH) have been reported, but consensus has not yet been reached. It is of great significance to elucidate the relationships between meteorological variation and aSAH in regions with specific climate patterns. We analyzed the occurrence of aSAH in the capital city of Fujian Province, China, through a multicenter, 5-year study, and aimed to reveal the meteorological influences on aSAH in the coastal city of eastern Fujian under the subtropical marine monsoon condition. METHODS A total of 2555 consecutive patients with aSAH in Fuzhou were collected using specialized stroke admission database from January 2013 to December 2017. Meteorological parameters including temperature, atmospheric pressure, and humidity were obtained from China Surface Meteorological Station during the same period. Poisson regression was used to explore the association between meteorological parameters and aSAH to calculate the incidence rate ratios (IRRs) with corresponding 95% confidence intervals (CIs). Generalized additive model analysis further revealed the nonlinear relationships between weather and aSAH. RESULTS Daily minimum temperature (IRR 0.976, 95% CI 0.958-0.996) and maximum pressure (IRR 1.022, 95% CI 1.001-1.042) were independently correlated with the onset of aSAH. Low temperature (below 16°C) and excessive atmospheric pressure (above 1008 hPa) increased the risk of aSAH. In addition, March in spring and December in winter were the 2 ictus peaks in Fuzhou throughout the year. CONCLUSIONS Cold and excessive atmospheric pressure are triggers for the occurrence of aSAH; March in spring and December in winter are the predominant onset periods in Fuzhou.
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Affiliation(s)
- Qing Huang
- The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China; School of Public Health, Fujian Medical University, Fuzhou, China
| | - Shao-Wei Lin
- School of Public Health, Fujian Medical University, Fuzhou, China
| | - Wei-Peng Hu
- The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China
| | - Huang-Yuan Li
- School of Public Health, Fujian Medical University, Fuzhou, China
| | - Pei-Sen Yao
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Yi Sun
- School of Public Health, Fujian Medical University, Fuzhou, China
| | - Yi-Le Zeng
- The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China
| | - Qiu-Yu Huang
- The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China
| | - De-Zhi Kang
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Si-Ying Wu
- School of Public Health, Fujian Medical University, Fuzhou, China.
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Hankenson FC, Marx JO, Gordon CJ, David JM. Effects of Rodent Thermoregulation on Animal Models in the Research Environment. Comp Med 2018; 68:425-438. [PMID: 30458902 DOI: 10.30802/aalas-cm-18-000049] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
To best promote animal wellbeing and the efficacy of biomedical models, scientific, husbandry, and veterinary professionals must consider the mechanisms, influences, and outcomes of rodent thermoregulation in contemporary research environments. Over the last 2 decades, numerous studies have shown that laboratory mice and rats prefer temperatures that are several degrees warmer than the environments in which they typically are housed within biomedical facilities. Physiologic changes to rodents that are cage-housed under standard temperatures (20 to 26 °C) are attributed to 'cold stress' and include alterations in metabolism, cardiovascular parameters, respiration, and immunologic function. This review article describes common behavioral and physiologic adaptations of laboratory mice and rats to cold stress within modern vivaria, with emphasis on environmental enrichment and effects of anesthesia and procedural support efforts. In addition, potential interventions and outcomes for rodents are presented, relative to the importance of repeating and reproducing experiments involving laboratory rodent research models of human disease.
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Affiliation(s)
- F Claire Hankenson
- Campus Animal Resources, Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA
| | - James O Marx
- University Laboratory Animal Resources, Department of Pathobiology, School of Veterinary Medicine; University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Christopher J Gordon
- Toxicity Assessment Division, Neurotoxicology Branch, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - John M David
- Comparative Medicine, Pfizer, La Jolla, California, USA
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7
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Chaudhary P, Schreihofer AM. Improved glucose homeostasis in male obese Zucker rats coincides with enhanced baroreflexes and activation of the nucleus tractus solitarius. Am J Physiol Regul Integr Comp Physiol 2018; 315:R1195-R1209. [PMID: 30256679 DOI: 10.1152/ajpregu.00195.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Young adult male obese Zucker rats (OZR) develop insulin resistance and hypertension with impaired baroreflex-mediated bradycardia and activation of nucleus tractus solitarius (NTS). Because type 1 diabetic rats also develop impaired baroreflex-mediated NTS activation, we hypothesized that improving glycemic control in OZR would enhance compromised baroreflexes and NTS activation. Fasting blood glucose measured by telemetry was comparable in OZR and lean Zucker rats (LZR) at 12-17 wk. However, with access to food, OZR were chronically hyperglycemic throughout this age range. By 15-17 wk of age, tail samples yielded higher glucose values than those measured by telemetry in OZR but not LZR, consistent with reports of exaggerated stress responses in OZR. Injection of glucose (1g/kg ip) produced larger rises in glucose and areas under the curve in OZR than LZR. Treatment with metformin (300 mg·kg-1·day-1) or pioglitazone (5 mg·kg-1·day-1) in drinking water for 2-3 wk normalized fed glucose levels in OZR with no effect in LZR. After metformin treatment, area under the curve for blood glucose after glucose injection was reduced in OZR and comparable to LZR. Hyperinsulinemia was slightly reduced by each treatment in OZR, but insulin was still greatly elevated compared with LZR. Neither treatment reduced hypertension in OZR, but both treatments significantly improved the blunted phenylephrine-induced bradycardia and NTS c-Fos expression in OZR with no effect in LZR. These data suggest that restoring glycemic control in OZR enhances baroreflex control of heart rate by improving the response of the NTS to raising arterial pressure, even in the presence of hyperinsulinemia and hypertension.
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Affiliation(s)
- Parul Chaudhary
- Department of Physiology and Anatomy, University of North Texas Health Science Center , Fort Worth, Texas
| | - Ann M Schreihofer
- Department of Physiology and Anatomy, University of North Texas Health Science Center , Fort Worth, Texas
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8
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Huang S, Li J, Zhang P, Zhang W. Detection of mental fatigue state with wearable ECG devices. Int J Med Inform 2018; 119:39-46. [PMID: 30342684 DOI: 10.1016/j.ijmedinf.2018.08.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/01/2018] [Accepted: 08/19/2018] [Indexed: 10/28/2022]
Abstract
Overwork-related disorders, such as cerebrovascular/cardiovascular diseases (CCVD) and mental disorders due to overwork, are a major occupational and public health issue worldwide, particularly in East Asian countries. Since wearable smart devices are inexpensive, convenient, popular and widely available today, we were interested in investigating the possibility of using wearable smart electrocardiogram (ECG) devices to detect the mental fatigue state. In total, 35 healthy participants were recruited from a public university in East China. Throughout the entire experiment, each participant wore a wearable device that was further linked to a smartphone to upload the data based on Bluetooth transmission. To manipulate the fatigue state, each participant was asked to finish a quiz, which lasted for approximately 80 min, with 30 logical referential and computing problems and 25 memory tests. Eight heart rate variability (HRV) indicators namely NN.mean (mean of normal to normal interval), rMSSD (root mean square of successive differences), PNN50 (the proportion of NN50 divided by total number of NNs), TP (total spectral power), HF (high frequency from 0.15 Hz to 0.4 Hz), LF (low frequency from 0.04 Hz to 0.15 Hz), VLF (very low frequency from 0.0033 Hz to 0.04 Hz) and the LF/HF ratio were collected at intervals of 5 min throughout the entire experiment. After the feature selection was performed, six indicators remained for further analysis, which were the NN.mean, rMSSD, PNN50, TP, LF, and VLF. Four algorithms, support vector machine (SVM), K-nearest neighbor (KNN), naïve Bayes (NB), and logistic regression (LR), were used to build classifiers that automatically detected the fatigue state. The best performance was achieved by KNN, which had a CV accuracy of 75.5%. The NN.mean, PNN50, TP and LF were the most important HRV indicators for mental fatigue detection. KNN performed the best among the four algorithms and had an average CV accuracy of 65.37% for all of the possible feature combinations.
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Affiliation(s)
- Shitong Huang
- Shanghai Jiaotong University, Antai College of Economics & Management, 1954 Huashan Rd., Shanghai 200030, China.
| | - Jia Li
- East China University of Science and Technology, School of Business, 130 Meilong Rd., Shanghai 200237, China.
| | - Pengzhu Zhang
- Shanghai Jiaotong University, Antai College of Economics & Management, 1954 Huashan Rd., Shanghai 200030, China.
| | - Weiqiang Zhang
- Shanghai Jiaotong University, Antai College of Economics & Management, 1954 Huashan Rd., Shanghai 200030, China.
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Osaka T. Hypothermia induced by inhibition of fatty acid metabolism in anesthetized rats: contributions of the forebrain and vagal afferents. Can J Physiol Pharmacol 2017; 95:652-660. [PMID: 28177663 DOI: 10.1139/cjpp-2016-0195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
2-Mercaptoacetate (MA) is an antimetabolic drug that inhibits the utilization of fatty acids as an energy source. The intravenous injection of MA (1.2 mmol·kg-1) elicited an increase in tail skin temperature and a decrease in body core temperature in urethane-chloralose-anesthetized, neuromuscularly blocked, artificially ventilated rats, although administration of the same amount of NaCl did not. The respiratory exchange ratio was significantly higher after administration of MA than that after the saline treatment. On the other hand, heat production was increased by either the MA- or NaCl-injection, suggesting a nonspecific effect caused by the hyperosmolality of the solutions. These results indicate that the MA-induced hypothermia was caused by an increase in heat loss but not by a decrease in heat production. The amplitudes of heat loss responses to MA in rats fasted overnight were significantly smaller than those in fed ones, suggesting a mechanism for suppression of heat loss in the fasted state. Rats pretreated with vagotomy, capsaicin-induced desensitization of sensory nerve fibers or decerebration did not exhibit the MA-induced hypothermic responses. It is possible that the MA-induced heat loss and hypothermia were mediated by the vagal afferents and required the forebrain for the full expression of the responses.
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Affiliation(s)
- Toshimasa Osaka
- Department of Nutritional Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku 162-8636, Japan.,Department of Nutritional Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku 162-8636, Japan
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10
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Western diet in the perinatal period promotes dysautonomia in the offspring of adult rats. J Dev Orig Health Dis 2016; 8:216-225. [PMID: 27931267 DOI: 10.1017/s2040174416000623] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The present study investigated the impact of a western diet during gestation and lactation on the anthropometry, serum biochemical, blood pressure and cardiovascular autonomic control on the offspring. Male Wistar rats were divided into two groups according to their mother's diet received: control group (C: 18% calories of lipids) and westernized group (W: 32% calories of lipids). After weaning both groups received standard diet. On the 60th day of life, blood samples were collected for the analysis of fasting glucose and lipidogram. Cardiovascular parameters were measured on the same period. Autonomic nervous system modulation was evaluated by spectrum analysis of heart rate (HR) and systolic arterial pressure (SAP). The W increased glycemia (123±2 v. 155±2 mg/dl), low-density lipoprotein (15±1 v. 31±2 mg/dl), triglycerides (49±1 v. 85±2 mg/dl), total cholesterol (75±2 v. 86±2 mg/dl), and decreased high-density lipoprotein (50±4 v. 38±3 mg/dl), as well as increased body mass (209±4 v. 229±6 g) than C. Furthermore, the W showed higher SAP (130±4 v. 157±2 mmHg), HR (357±10 v. 428±14 bpm), sympathetic modulation to vessels (2.3±0.56 v. 6±0.84 mmHg2) and LF/HF ratio (0.15±0.01 v. 0.7±0.2) than C. These findings suggest that a western diet during pregnancy and lactation leads to overweight associated with autonomic misbalance and hypertension in adulthood.
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11
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Geng Y, Zhu L, Liu F, Zhu X, Niu J, Li G. Effect of dehydration heat exposure on thoracic aorta reactivity in rats. Biomed Rep 2016; 5:613-617. [PMID: 27882226 DOI: 10.3892/br.2016.760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 09/13/2016] [Indexed: 11/06/2022] Open
Abstract
The aim of the present study was to investigate the effect of one week dehydration heat exposure on thoracic aorta reactivity in rats. Eighteen Male Sprague-Dawley rats were randomly divided into 3 groups (n=6 each group): Control group (CN), heat exposure group (HE), dehydration heat exposure group (DHE). The CN group was exposed to a room temperature of 24°C, while the HE and DHE groups were exposed to a heat temperature of 32°C. After 7 days of heat exposure, the heart rate and blood pressure of the rats were measured, and the noradrenaline (NA)-induced contraction on the aorta rings was measured by tension recording. The average contents of malondialdehyde (MDA) and superoxide dismutase (SOD) in serum were detected using ELISA. The expression of apoptotic genes in the thoracic aorta was measured using RT-PCR. Compared with CN, the heart rate in the HE and DHE groups had a tendency to become retarded, but there was no significant difference (P>0.05). In the HE group, the systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) of the rats were significantly higher than that of the CN (P<0.05). In the DHE group, the SBP of rats was significantly higher than that of the CN (P<0.05), while the SBP, DBP, and MAP of the rats were decreased compared to the rats in the HE group, although there was no statistical significance (P>0.05). In the HE and DHE groups, the NA-induced contraction on the rats thoracic aorta ring was larger than that of the CN (P<0.05), albeit there was no significant difference between the HE and DHE groups (P>0.05). The serum SOD content decreased in the HE and DHE groups, however, the reduction was significant only in the DHE group (P<0.05). The content of MDA in serum was significantly increased in the DHE group (P<0.05). The expression of BAX was significantly upregulated whereas Bcl2 expression was decreased in the DHE group (P<0.05). The results showed that a high temperature was harmful to the body, especially in the case of lack of food and water. Additionally, the heat exposure elevated blood pressure, and increased arterial reactivity, which were related to the elevated production of MDA, led to the impaired production of SOD, and an increase of cell apoptosis. These findings are useful to understand the influence of dehydrated heat exposure on the vascular function, and they provide certain theoretical and experimental guidance for protection under high temperature.
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Affiliation(s)
- Yao Geng
- Department of Physiology, School of Basic Medical Science, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
| | - Lingqin Zhu
- Department of Physiology, School of Basic Medical Science, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
| | - Fadong Liu
- Department of Physiology, School of Basic Medical Science, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
| | - Xiaodan Zhu
- Department of Physiology, School of Basic Medical Science, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
| | - Jianguo Niu
- Ningxia Key Laboratory of Cranial Cerebral Diseases, Yinchuan, Ningxia 750004, P.R. China
| | - Guanghua Li
- Department of Physiology, School of Basic Medical Science, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China; Ningxia Key Laboratory of Cranial Cerebral Diseases, Yinchuan, Ningxia 750004, P.R. China
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12
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Huber DA, Schreihofer AM. Exaggerated sympathoexcitatory reflexes develop with changes in the rostral ventrolateral medulla in obese Zucker rats. Am J Physiol Regul Integr Comp Physiol 2016; 311:R243-53. [PMID: 27280427 DOI: 10.1152/ajpregu.00085.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 06/01/2016] [Indexed: 11/22/2022]
Abstract
Obesity leads to altered autonomic reflexes that reduce stability of mean arterial pressure (MAP). Sympathoinhibitory reflexes such as baroreflexes are impaired, but reflexes that raise MAP appear to be augmented. In obese Zucker rats (OZR) sciatic nerve stimulation evokes larger increases in MAP by unknown mechanisms. We sought to determine the autonomic underpinnings of this enhanced somatic pressor reflex and whether other sympathoexcitatory reflexes are augmented. We also determined whether their final common pathway, glutamatergic activation of the rostral ventrolateral medulla (RVLM), was enhanced in male OZR compared with lean Zucker rats (LZR). Sciatic nerve stimulation or activation of the nasopharyngeal reflex evoked larger rises in splanchnic sympathetic nerve activity (SNA) (79% and 45% larger in OZR, respectively; P < 0.05) and MAP in urethane-anesthetized, ventilated, paralyzed adult OZR compared with LZR. After elimination of baroreflex feedback by pharmacological prevention of changes in MAP and heart rate, these two sympathoexcitatory reflexes were still exaggerated in OZR (167% and 69% larger, respectively, P < 0.05). In adult OZR microinjections of glutamate, AMPA, or NMDA into the RVLM produced larger rises in SNA (∼61% larger in OZR, P < 0.05 for each drug) and MAP, but stimulation of axonal fibers in the upper thoracic spinal cord yielded equivalent responses in OZR and LZR. In juvenile OZR and LZR, sympathoexcitatory reflexes and physiological responses to RVLM activation were comparable. These data suggest that the ability of glutamate to activate the RVLM becomes enhanced in adult OZR and may contribute to the development of exaggerated sympathoexcitatory responses independent of impaired baroreflexes.
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Affiliation(s)
- Domitila A Huber
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas; and Department of Physiology, Medical College of Georgia,* Augusta, Georgia
| | - Ann M Schreihofer
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas; and Department of Physiology, Medical College of Georgia,* Augusta, Georgia
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13
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Solymár M, Pétervári E, Balaskó M, Szelényi Z. The onset of daily torpor is regulated by the same low body mass in lean mice and in mice with diet-induced obesity. Temperature (Austin) 2015; 2:129-34. [PMID: 27227011 PMCID: PMC4843878 DOI: 10.1080/23328940.2015.1014250] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 01/28/2015] [Accepted: 01/29/2015] [Indexed: 11/17/2022] Open
Abstract
Effects of reducing body mass on body core temperature and locomotor activity of mice originally kept on conventional rodent diet (Group-1) were compared to those made obese by feeding them a high-fat diet (Group-2), both groups being kept at a cool ambient temperature. Based on earlier experience, threshold torpor core temperature of 31° was chosen as the endpoint to decreasing body mass. It was hypothesized that the onset of this hypothermia develops in obese mice only when their body mass approaches a similar low body mass as in lean mice. Mice in Group-1 maintained nocturnal core temperature but developed marked daytime hypothermia of 30–31°C with their body mass approaching 20 g by this time. Mice in Group-2 could maintain normal circadian temperature rhythm for 3 weeks before similar daytime hypothermia started to develop while their body mass dropped also to about 20 g. Mice belonging to Group-1 or Group-2 could regain original body mass after re-feeding with the original diet within 2 days or 5 weeks, respectively. In the course of the development of daily torpor, nighttime normothermia was accompanied by progressive increases in locomotor activity in both groups of mice. It is concluded that in mice a marked fall of daytime body core temperature is only induced when a similar low critical body mass is reached, irrespective of the initial body mass. In other words, in both groups of mice the nutritional state determines the threshold for the thermoregulatory change during torpor.
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Affiliation(s)
- Margit Solymár
- Department of Pathophysiology and Gerontology; Faculty of Medicine; University of Pécs , Hungary
| | - Erika Pétervári
- Department of Pathophysiology and Gerontology; Faculty of Medicine; University of Pécs , Hungary
| | - Márta Balaskó
- Department of Pathophysiology and Gerontology; Faculty of Medicine; University of Pécs , Hungary
| | - Zoltán Szelényi
- Department of Pathophysiology and Gerontology; Faculty of Medicine; University of Pécs , Hungary
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14
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Guimaraes PS, Huber DA, Campagnole-Santos MJ, Schreihofer AM. Development of attenuated baroreflexes in obese Zucker rats coincides with impaired activation of nucleus tractus solitarius. Am J Physiol Regul Integr Comp Physiol 2014; 306:R681-92. [PMID: 24573182 DOI: 10.1152/ajpregu.00537.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adult obese Zucker rats (OZR; >12 wk) develop elevated sympathetic nerve activity (SNA) and mean arterial pressure (MAP) with impaired baroreflexes compared with adult lean Zucker rats (LZR) and juvenile OZR (6-7 wk). In adult OZR, baroreceptor afferent nerves respond normally to changes in MAP, whereas electrical stimulation of baroreceptor afferent fibers produces smaller reductions in SNA and MAP compared with LZR. We hypothesized that impaired baroreflexes in OZR are linked to reduced activation of brain stem sites that mediate baroreflexes. In conscious adult rats, a hydralazine (HDZ)-induced reduction in MAP evoked tachycardia that was initially blunted in OZR, but equivalent to LZR within 5 min. In agreement, HDZ-induced expression of c-Fos in the rostral ventrolateral medulla (RVLM) was comparable between groups. In contrast, phenylephrine (PE)-induced rise in MAP evoked markedly attenuated bradycardia with dramatically reduced c-Fos expression in the nucleus tractus solitarius (NTS) of adult OZR compared with LZR. However, in juvenile rats, PE-induced hypertension evoked comparable bradycardia in OZR and LZR with similar or augmented c-Fos expression in NTS of the OZR. In urethane-anesthetized rats, microinjections of glutamate into NTS evoked equivalent decreases in SNA, heart rate (HR), and MAP in juvenile OZR and LZR, but attenuated decreases in SNA and MAP in adult OZR. In contrast, microinjections of glutamate into the caudal ventrolateral medulla, a target of barosensitive NTS neurons, evoked comparable decreases in SNA, HR, and MAP in adult OZR and LZR. These data suggest that OZR develop impaired glutamatergic activation of the NTS, which likely contributes to attenuated baroreflexes in adult OZR.
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15
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Kontos A, de Menezes RC, Ootsuka Y, Blessing W. Brown adipose tissue thermogenesis precedes food intake in genetically obese Zucker (fa/fa) rats. Physiol Behav 2013; 118:129-37. [PMID: 23685234 DOI: 10.1016/j.physbeh.2013.05.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Revised: 03/22/2013] [Accepted: 05/07/2013] [Indexed: 10/26/2022]
Abstract
In Sprague-Dawley rats, brown adipose tissue (BAT) thermogenesis occurs in an episodic ultradian manner (BAT on-periods) as part of the basic rest-activity cycle (BRAC). Eating occurs approximately 15min after the onset of BAT on-periods. Zucker obese (fa/fa) rats eat larger less frequent meals than control rats. In chronically instrumented conscious unrestrained Zucker obese rats we examined ultradian fluctuations in BAT, body and brain temperatures, and the relation between BAT temperature and eating. The interval between BAT temperature peaks for the 12hour dark phase was 121±3 (mean±SE) min for Zucker obese rats and 91±3min for control lean rats (p<0.01). Corresponding values for the light phase were 148±6 and 118±4min (p<0.01). Mean BAT and body temperatures were lower in Zucker obese rats, in comparison with lean controls, during both BAT on-periods and BAT off-periods. Mean brain temperatures were lower during BAT off-periods. Amplitudes of the BRAC-related increases in all 3 temperatures were greater in the Zucker obese rats. Meal onset in Zucker obese rats commenced 15±1min after the onset of a BAT on-period, not significantly different for the delay observed in lean control rats (18±1min, p>0.05). Thus periods between eating are increased in the Zucker obese rats, but the action of leptin, absent in these animals, is not crucial for the timing of eating in relation to increases in BAT and body temperature. Lack of the normal excitatory action of leptin on brain-regulated BAT sympathetic discharge could also contribute to lower BAT thermogenesis in Zucker obese rats.
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Affiliation(s)
- Anna Kontos
- Centre for Neuroscience, Department of Human Physiology, Flinders University, Adelaide, SA 5042, Australia
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Bello NT, Walters AL, Verpeut JL, Cunha PP. High-fat diet-induced alterations in the feeding suppression of low-dose nisoxetine, a selective norepinephrine reuptake inhibitor. J Obes 2013; 2013:457047. [PMID: 23431425 PMCID: PMC3570928 DOI: 10.1155/2013/457047] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 12/17/2012] [Indexed: 11/17/2022] Open
Abstract
Central noradrenergic pathways are involved in feeding and cardiovascular control, physiological processes altered by obesity. The present studies determined how high-fat feeding and body weight gain alter the sensitivity to the feeding suppression and neural activation to a selective norepinephrine reuptake inhibitor, nisoxetine. Acute administration of nisoxetine (saline: 0, 3, 10, and 30 mg/kg; i.p.) resulted in a dose-dependent reduction in the 24 h refeeding response in male Sprague Dawley rats maintained on standard chow. In a similar fashion, nisoxetine resulted in reductions in blood pressure and a compensatory increase in heart rate. From these studies, the 3 mg/kg dose was subthreshold. In a separate experiment, however, 10 wk exposure to a high-fat diet (60% fat) resulted in weight gain and significant feeding suppression following administration of nisoxetine (3 mg/kg) compared with animals fed a control diet (10% fat). Nisoxetine (3 mg/kg) also resulted in greater neural activation, as measured by c-Fos immunohistochemistry, in the arcuate nucleus of the hypothalamus in animals exposed to the high-fat diet. Such data indicate acute nisoxetine doses that suppress food intake can impact cardiovascular measures. It also suggests that the feeding suppression to a low-dose nisoxetine is enhanced as a result of high-fat diet and weight gain.
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Affiliation(s)
- Nicholas T Bello
- Department of Animal Sciences, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, 84 Lipman Drive, New Brunswick, NJ 08901, USA.
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17
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Lehnen AM, Rodrigues B, Irigoyen MC, De Angelis K, Schaan BD. Cardiovascular changes in animal models of metabolic syndrome. J Diabetes Res 2013; 2013:761314. [PMID: 23691518 PMCID: PMC3647579 DOI: 10.1155/2013/761314] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 02/06/2013] [Accepted: 02/12/2013] [Indexed: 01/01/2023] Open
Abstract
Metabolic syndrome has been defined as a group of risk factors that directly contribute to the development of cardiovascular disease and/or type 2 diabetes. Insulin resistance seems to have a fundamental role in the genesis of this syndrome. Over the past years to the present day, basic and translational research has used small animal models to explore the pathophysiology of metabolic syndrome and to develop novel therapies that might slow the progression of this prevalent condition. In this paper we discuss the animal models used for the study of metabolic syndrome, with particular focus on cardiovascular changes, since they are the main cause of death associated with the condition in humans.
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Affiliation(s)
- Alexandre M. Lehnen
- Laboratório de Experimentação Animal e Laboratório de Cardiologia Celular e Molecular, Instituto de Cardiologia do Rio Grande do Sul/Fundação Universitária de Cardiologia do Rio Grande do Sul, Porto Alegre, Brazil
- Divisão de Endocrinologia, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Bruno Rodrigues
- Laboratório do Movimento Humano, Universidade São Judas Tadeu, São Paulo, Brazil
| | - Maria Cláudia Irigoyen
- Unidade de Hipertensão, Instituto do Coração (InCor), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Kátia De Angelis
- Laboratório de Fisiologia Translacional, Universidade Nove de Julho, São Paulo, Brazil
| | - Beatriz D'Agord Schaan
- Divisão de Endocrinologia, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- *Beatriz D'Agord Schaan:
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18
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Fellmann L, Nascimento AR, Tibiriça E, Bousquet P. Murine models for pharmacological studies of the metabolic syndrome. Pharmacol Ther 2012. [PMID: 23178510 DOI: 10.1016/j.pharmthera.2012.11.004] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Metabolic syndrome has been described as the association of insulin resistance, hypertension, hyperlipidemia and obesity. Its prevalence increased dramatically, mainly in developed countries. Animal models are essential to understand the pathophysiology of this syndrome. This review presents the murine models of metabolic syndrome the most often used in pharmacological studies. The most common metabolic syndrome models exhibit a non-functional leptin pathway, or metabolic disorders induced by high fat diets. In a first part, and after a short introduction on leptin, its receptor and mechanism of action, we provide a detailed description of each model: SHROB, SHHF, JCR:LA-cp, Zucker, ZDF, Wistar Ottawa Karlsburg W, and Otsuka Long-Evans Tokushima Fatty rats, ob/ob, db/db, agouti yellow and Mc4R KO mice. The second part of this review is dedicated to metabolic syndrome models obtained by high fat feeding.
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Affiliation(s)
- Lyne Fellmann
- Laboratory of Neurobiology and Cardiovascular Pharmacology, EA4438, Faculty of Medicine, University of Strasbourg, France
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19
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Knight WD, Witte MM, Parsons AD, Gierach M, Overton JM. Long-term caloric restriction reduces metabolic rate and heart rate under cool and thermoneutral conditions in FBNF1 rats. Mech Ageing Dev 2011; 132:220-9. [PMID: 21513729 DOI: 10.1016/j.mad.2011.04.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 02/14/2011] [Accepted: 04/02/2011] [Indexed: 12/21/2022]
Abstract
The long-term metabolic and cardiovascular responses to caloric restriction (CR) are poorly understood. We examined the responses to one year of CR in FBNF1 rats housed in cool (COOL; T(a)=15 °C) or thermoneutral (TMN; T(a)=30 °C) conditions. Rats were acclimated to COOL or TMN for 2 months, instrumented for cardiovascular telemetry and studied in calorimeters. Baseline caloric intake, oxygen consumption (VO(2)), mean arterial blood pressure (MAP), and heart rate (HR) were determined prior to assignment to ad lib (AL) or CR groups (30-40% CR) within each T(a) (n = 8). Groups of rats were studied after 10 weeks CR, one year CR, and after 4 days of re-feeding. Both 10 weeks and one year of CR reduced HR and VO(2) irrespective of T(a). Evaluation of the relationship between metabolic organ mass (liver, heart, brain, and kidney mass) and energy expenditure revealed a clear shift induced by CR to reduce expenditure per unit metabolic mass in both COOL and TMN groups. Re-feeding resulted in prompt elevations of HR and VO(2) to levels observed in control rats. These findings are consistent with the hypothesis that long term CR produces sustained reductions in metabolic rate and heart rate in rats.
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Affiliation(s)
- W David Knight
- Department of Biomedical Sciences and Program in Neuroscience, Florida State University, College of Medicine, Tallahassee, FL 32306-4340, USA
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20
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Tanner JM, Kearns DT, Kim BJ, Sloan C, Jia Z, Yang T, Abel ED, Symons JD. Fasting-induced reductions in cardiovascular and metabolic variables occur sooner in obese versus lean mice. Exp Biol Med (Maywood) 2011; 235:1489-97. [PMID: 21127345 DOI: 10.1258/ebm.2010.010171] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is not uncommon for laboratory animals to be fasted prior to experimentation. Fasting evokes marked reductions in heart rate (HR), blood pressure (BP), heat production and oxygen consumption (VO(2)) in rodents. Mice with diet-induced obesity exhibit elevated HR and BP, and lower VO(2) and heat production in the fed condition versus their lean counterparts. It is unknown whether body composition alters the tempo of response to fasting. We tested the hypothesis that cardiovascular and metabolic responses to fasting are delayed in obese versus lean male C57BL/6J mice. In the fed condition, mice that consumed high-fat (HF, 45% fat) chow for 98 ± 5 days had elevated (P < 0.05) body fat percentage (DEXA), serum leptin (ELISA), HR and BP (72-h biotelemetry), and lower (P < 0.05) heat production and VO(2) (72-h metabolic chamber) versus animals that consumed standard chow (CON, 10% fat; n = 16 per group). HR, BP, VO(2), heat production and serum leptin decreased (all P < 0.05) in response to a 16-h fast (16:00-08:00 h) in both groups. Although the overall fold changes in cardiovascular and metabolic parameters were similar in magnitude among animals, fasting-induced reductions in cardiovascular and metabolic variables occurred ∼4 and ∼7 h earlier (P < 0.05), respectively, in HF versus CON mice. These findings indicate that while metabolic and cardiovascular stress evoked by a 16-h fast at 22°C is not different between HF and CON mice, fasting-induced responses occur sooner in obese animals.
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Affiliation(s)
- Jason M Tanner
- College of Health, University of Utah, Salt Lake City, UT 84132, USA
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21
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Ye ZY, Li DP. Activation of the melanocortin-4 receptor causes enhanced excitation in presympathetic paraventricular neurons in obese Zucker rats. ACTA ACUST UNITED AC 2010; 166:112-20. [PMID: 20937332 DOI: 10.1016/j.regpep.2010.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 08/26/2010] [Accepted: 10/04/2010] [Indexed: 10/19/2022]
Abstract
Sympathetic nerve activity is increased in obesity-related hypertension. However, the central mechanisms involved in the increased sympathetic outflow remain unclear. The hypothalamic melanocortin system is important for regulating energy balance and sympathetic outflow. To understand the mechanisms by which the melanocortin systems regulates sympathetic outflow, we investigated the role of melanocortin 4 receptors (MC4R) in regulating presympathetic paraventricular nucleus (PVN) neurons. We performed whole-cell patch-clamp recordings on retrogradely labeled PVN neurons projecting to the rostral ventrolateral medulla in brain slices from obese zucker rats (OZRs) and lean zucker rats (LZRs). The MC4R agonists melanotan II (MTII) and α-melanocyte-stimulating hormone (α-MSH) increased the firing activity and depolarized the labeled PVN neurons from both LZRs and OZRs in a concentration-dependent manner. MTII produced significant greater increase in the firing activity in OZRs than in LZRs. Blocking MC4R with the specific antagonist SHU9119 had no effect on the basal firing rate but abolished the MTII-induced increase in the firing rate in both OZRs and LZRs. Furthermore, intracellular dialysis of guanosine 5'-O-(2-thodiphosphate), but not bath application of kynurenic acid and bicuculline, eliminated the MTII-induced increase in firing activity. In addition, MTII had no effect on the frequency and amplitude of glutamatergic excitatory postsynaptic currents and GABAergic inhibitory postsynaptic currents in labeled PVN neurons. Collectively, our findings suggest that MC4R contributes to the elevated excitability of PVN presympathetic neurons, which may be involved in obesity-related hypertension.
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Affiliation(s)
- Zeng-You Ye
- Department of Anesthesiology and Perioperative Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA
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22
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Osmond JM, Mintz JD, Stepp DW. Preventing increased blood pressure in the obese Zucker rat improves severity of stroke. Am J Physiol Heart Circ Physiol 2010; 299:H55-61. [PMID: 20418477 DOI: 10.1152/ajpheart.01111.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Obesity is a risk factor for stroke, but the determinants of increased stroke risk in obesity are unknown. We have previously reported that obese Zucker rats (OZRs) have a worse stroke outcome and display evidence of remodeling of the middle cerebral artery (MCA), in parallel with hypertension, compared with lean controls. This study tested the hypothesis that hypertension is an essential determinant of cerebral vascular remodeling and increased stroke damage in OZRs. Blood pressure was measured by telemetry in lean and obese rats with and without hydrochlorthiazide (HCT; 2 mg.kg(-1).day(-1)) from 8 to 15 wk of age. A separate group of rats was also chronically fed a low-sodium (LS) diet. Vessel structure was assessed in isolated, pressurized MCAs. Cerebral ischemia was induced for 60 min using an intralumenal suture technique, followed by 24 h of reperfusion. HCT treatment effectively prevented the increase in blood pressure in obese rats; however, the LS diet did not lower pressure. Importantly, infarct size was normalized by HCT after ischemia-reperfusion injury. Additionally, HCT improved the changes in MCA structure observed in untreated OZRs. There were no benefits of the LS diet on stroke injury or vessel structure. These results indicate that increased pressure is essential for driving the changes in infarct size in OZRs.
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Affiliation(s)
- Jessica M Osmond
- Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
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23
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Sainsbury A, Zhang L. Role of the arcuate nucleus of the hypothalamus in regulation of body weight during energy deficit. Mol Cell Endocrinol 2010; 316:109-19. [PMID: 19822185 DOI: 10.1016/j.mce.2009.09.025] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 09/21/2009] [Accepted: 09/28/2009] [Indexed: 12/14/2022]
Abstract
Acute or long-term energy deficit in lean or obese rodents or humans stimulates food intake or appetite and reduces metabolic rate or energy expenditure. These changes contribute to weight regain in post-obese animals and humans. Some studies show that the reduction in metabolic rate with energy deficit in overweight people is transient. Energy restriction has been shown in some but not all studies to reduce physical activity, and this may represent an additional energy-conserving adaptation. Energy restriction up-regulates expression of the orexigenic neuropeptide Y, agouti related peptide and opioids and down-regulates that of the anorexigenic alpha-melanocyte stimulating hormone or its precursor pro-opioomelanocortin and the co-expressed cocaine and amphetamine-regulated transcript in the arcuate nucleus of the hypothalamus. Recapitulating these hypothalamic changes in sated animals mimics the effects of energy deficit, namely increased food intake, reduced physical activity and reduced metabolic rate, suggesting that these energy-conserving adaptations are at least partially mediated by the hypothalamus.
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Affiliation(s)
- A Sainsbury
- Neuroscience Research Program, Garvan Institute of Medical Research, Darlinghurst, Sydney, NSW 2010, Australia.
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24
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Huber DA, Schreihofer AM. Attenuated baroreflex control of sympathetic nerve activity in obese Zucker rats by central mechanisms. J Physiol 2010; 588:1515-25. [PMID: 20211978 DOI: 10.1113/jphysiol.2009.186387] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Adult obese Zucker rats (OZRs) have reduced sympathetic responses to evoked changes in arterial pressure (AP) compared to lean Zucker rats (LZRs). This study examined whether attenuated sympathetic baroreflexes in OZRs may be due to altered sensory or central mechanisms. The OZRs had elevated baseline splanchnic sympathetic nerve activity (SNA) and mean AP (MAP) compared to age-matched LZRs under urethane anaesthesia (P < 0.05). Aortic depressor nerve activity (ADNA) was measured while AP was altered by infusions of phenylephrine or nitroprusside (+/-60 mmHg over 60-90 s) in rats treated with atropine and propranolol to eliminate changes in heart rate. Although baseline ADNA was higher in the hypertensive OZRs, the relationship between MAP and ADNA was comparable in OZRs and LZRs. In contrast, electrical stimulation of the ADN afferent fibres (5 s train, 2 ms pulses, 4 V, 0.5-48 Hz) produced dramatically smaller reductions in SNA and MAP in OZRs compared to LZRs (P < 0.05). After blockade of alpha-adrenergic receptors to prevent sympathetically mediated depressor responses, OZRs still had reduced sympathetic responses to stimulation of the ADN. In addition, stimulation of vagal afferent nerves electrically or with phenylbiguanide (1, 2, 4 and 8 microg, i.v.) produced smaller inhibitions of SNA in OZRs compared with LZRs (P < 0.05). These data suggest that attenuated sympathetic baroreflexes are the result of altered central mechanisms in OZRs, and not deficits in the responsiveness of aortic baroreceptors to AP. Furthermore, central deficits in the regulation of SNA in OZRs extend to other sympathoinhibitory reflexes initiated by vagal afferent nerves.
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Affiliation(s)
- Domitila A Huber
- Department of Physiology, Medical College of Georgia, 1120 15th Street, CA-3147, Augusta, GA 30912-3000, USA
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25
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Li JY, Chai BX, Zhang W, Wang H, Mulholland MW. Expression of ankyrin repeat and suppressor of cytokine signaling box protein 4 (Asb-4) in proopiomelanocortin neurons of the arcuate nucleus of mice produces a hyperphagic, lean phenotype. Endocrinology 2010; 151:134-42. [PMID: 19934378 PMCID: PMC2803157 DOI: 10.1210/en.2009-0560] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ankyrin repeat and suppressor of cytokine signaling box-containing protein 4 (Asb-4) is specifically expressed in the energy homeostasis-related brain areas and colocalizes with proopiomelanocortin (POMC) neurons of the arcuate nucleus (ARC). Injection of insulin into the third ventricle of the rat brain increased Asb-4 mRNA expression in the paraventricular nucleus but not in the ARC of the hypothalamus, whereas injection of leptin (ip) increased Asb-4 expression in both mouse paraventricular nucleus and ARC. A transgenic mouse in which Myc-tagged Asb-4 is specifically expressed in POMC neurons of the ARC was made and used to study the effects of Asb-4 on ingestive behavior and metabolic rate. Animals with overexpression of Asb-4 in POMC neurons demonstrated an increase in food intake. However, POMC-Asb-4 transgenic animals gained significantly less weight from 6-30 wk of age. The POMC-Asb-4 mice had reduced fat mass and increased lean mass and lower levels of blood leptin. The transgenic animals were resistant to high-fat diet-induced obesity. Transgenic mice had significantly higher rates of oxygen consumption and carbon dioxide production than wild-type mice during both light and dark periods. The locomotive activity of transgenic mice was increased. The overexpression of Asb-4 in POMC neurons increased POMC mRNA expression in the ARC. The transgenic animals had no observed effect on peripheral glucose metabolism and the activity of the autonomic nervous system. These results indicate that Asb-4 is a key regulatory protein in the central nervous system, involved in the control of feeding behavior and metabolic rate.
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Affiliation(s)
- Ji-Yao Li
- Department of Surgery, University of Michigan, Ann Arbor, Michigan 48109, USA
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Osborn O, Sanchez-Alavez M, Brownell SE, Ross B, Klaus J, Dubins J, Beutler B, Conti B, Bartfai T. Metabolic characterization of a mouse deficient in all known leptin receptor isoforms. Cell Mol Neurobiol 2009; 30:23-33. [PMID: 19582570 DOI: 10.1007/s10571-009-9427-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Accepted: 06/05/2009] [Indexed: 01/19/2023]
Abstract
We have characterized a newly generated mouse model of obesity, a mouse strain deficient in all five previously described leptin receptor isoforms. These transgenic mice, named the db (333)/db (333) mice, were identified from an ENU mutagenesis screen and carry a point mutation in the seventh exon of the db gene encoding the leptin receptor, resulting in a premature stop codon (Y(333)Stop) and gene product that lacks STAT signaling domains. db (333)/db (333) mice have a morbidly obese phenotype, with body weights diverging from wild type as early as 4 weeks of age (P < 0.05). To determine the contribution of the short isoforms of the leptin receptor in this metabolic phenotype, we performed an extensive metabolic characterization of the db (333)/db (333) mouse in relation to the well-characterized db/db mouse lacking only the long form of the leptin receptor. db (333)/db (333) mice have similar endocrine and metabolic parameters as previously described in other leptin receptor transgenic mice including db/db mice that lack only the long isoform of the leptin receptor. However, db (333)/db (333) mice show a subtle trend toward higher body weight and insulin levels, lower oxygen, carbon dioxide production, respiratory exchange ratio (RER), and temperature than db/db mice suggesting the short isoforms may play an additional role in energy homeostasis.
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Affiliation(s)
- Olivia Osborn
- Molecular and Integrative Neurosciences Department, The Harold L. Dorris Neurological Research Institute, The Scripps Research Institute, La Jolla, CA 92037, USA.
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27
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Spyridopoulos I, Fichtlscherer S, Popp R, Toennes SW, Fisslthaler B, Trepels T, Zernecke A, Liehn EA, Weber C, Zeiher AM, Dimmeler S, Haendeler J. Caffeine enhances endothelial repair by an AMPK-dependent mechanism. Arterioscler Thromb Vasc Biol 2008; 28:1967-74. [PMID: 18757291 DOI: 10.1161/atvbaha.108.174060] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
OBJECTIVE Migratory capacity of endothelial progenitor cells (EPCs) and mature endothelial cells (ECs) is a key prerequisite for endothelial repair after denuding injury or endothelial damage. METHODS AND RESULTS We demonstrate that caffeine in physiologically relevant concentrations (50 to 100 micromol/L) induces migration of human EPCs as well as mature ECs. In patients with coronary artery disease (CAD), caffeinated coffee increased caffeine serum concentration from 2 micromol/L to 23 micromol/L, coinciding with a significant increase in migratory activity of patient-derived EPCs. Decaffeinated coffee neither affected caffeine serum levels nor migratory capacity of EPCs. Treatment with caffeine for 7 to 10 days in a mouse-model improved endothelial repair after denudation of the carotid artery. The enhancement of reendothelialization by caffeine was significantly reduced in AMPK knockout mice compared to wild-type animals. Transplantation of wild-type and AMPK(-/-) bone marrow into wild-type mice revealed no difference in caffeine challenged reendothelialization. ECs which were depleted of mitochondrial DNA did not migrate when challenged with caffeine, suggesting a potential role for mitochondria in caffeine-dependent migration. CONCLUSIONS These results provide evidence that caffeine enhances endothelial cell migration and reendothelialization in part through an AMPK-dependent mechanism, suggesting a beneficial role for caffeine in endothelial repair.
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Hayes MR, Skibicka KP, Grill HJ. Caudal brainstem processing is sufficient for behavioral, sympathetic, and parasympathetic responses driven by peripheral and hindbrain glucagon-like-peptide-1 receptor stimulation. Endocrinology 2008; 149:4059-68. [PMID: 18420740 PMCID: PMC2488211 DOI: 10.1210/en.2007-1743] [Citation(s) in RCA: 150] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 04/03/2008] [Indexed: 12/11/2022]
Abstract
The effects of peripheral glucagon like peptide-1 receptor (GLP-1R) stimulation on feeding, gastric emptying, and energetic responses involve vagal transmission and central nervous system processing. Despite a lack of studies aimed at determining which central nervous system regions are critical for the GLP-1R response production, hypothalamic/forebrain processing is regarded as essential for these effects. Here the contribution of the caudal brainstem to the control of food intake, core temperature, heart rate, and gastric emptying responses generated by peripheral delivery of the GLP-1R agonist, exendin-4 (Ex-4), was assessed by comparing responses of chronic supracollicular decerebrate (CD) rats to those of pair-fed intact control rats. Responses driven by hindbrain intracerebroventricular (fourth i.c.v) delivery of Ex-4 were also evaluated. Intraperitoneal Ex-4 (1.2 and 3.0 microg/kg) suppressed glucose intake in both CD rats (5.0+/-1.2 and 4.4+/-1.1 ml ingested) and controls (9.4+/-1.5 and 7.7+/-0.8 ml ingested), compared with intakes after vehicle injections (13.1+/-2.5 and 13.2+/-1.7 ml ingested, respectively). Hindbrain ventricular Ex-4 (0.3 microg) also suppressed food intake in CD rats (4.7+/-0.6 ml ingested) and controls (11.0+/-2.9 ml ingested), compared with vehicle intakes (9.3+/-2.1 and 19.3+/-4.3 ml ingested, respectively). Intraperitoneal Ex-4 (0.12, 1.2, 2.4 microg/kg) reduced gastric emptying rates in a dose-related manner similarly for both CD and control rats. Hypothermia followed ip and fourth i.c.v Ex-4 in awake, behaving controls (0.6 and 1.0 C average suppression) and CD rats (1.5 and 2.5 C average suppression). Intraperitoneal Ex-4 triggered tachycardia in both control and CD rats. Results demonstrate that caudal brainstem processing is sufficient for mediating the suppression of intake, core temperature, and gastric emptying rates as well as tachycardia triggered by peripheral GLP-1R activation and also hindbrain-delivered ligand. Contrary to the literature, hypothalamic/forebrain processing and forebrain-caudal brainstem communication is not required for the observed responses.
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Affiliation(s)
- Matthew R Hayes
- Graduate Groups of Psychology and Neuroscience, University of Pennsylvania, 3720 Walnut Street, Philadelphia, Pennsylvania 19104, USA.
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Xiang L, Dearman J, Abram SR, Carter C, Hester RL. Insulin resistance and impaired functional vasodilation in obese Zucker rats. Am J Physiol Heart Circ Physiol 2008; 294:H1658-66. [PMID: 18296567 DOI: 10.1152/ajpheart.01206.2007] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Individuals with metabolic syndrome exhibit insulin resistance and an attenuated functional vasodilatory response to exercise. We have shown that impaired functional vasodilation in obese Zucker rats (OZRs) is associated with enhanced thromboxane receptor (TP)-mediated vasoconstriction. We hypothesized that insulin resistance, hyperglycemia/hyperlipidemia, and the resultant ROS are responsible for the increased TP-mediated vasoconstriction in OZRs, resulting in impaired functional vasodilation. Eleven-week-old male lean Zucker rats (LZRs) and OZRs were fed normal rat chow or chow containing rosiglitazone (5 mg.kg(-1).day(-1)) for 2 wk. In another set of experiment, LZRs and OZRs were treated with 2 mM tempol (drinking water) for 7-10 days. After the treatments, spinotrapezius muscles were prepared, and arcade arteriolar diameters were measured following muscle stimulation and arachidonic acid (AA) application (10 muM) in the absence and presence of the TP antagonist SQ-29548 (1 muM). OZRs exhibited higher insulin, glucose, triglyceride, and superoxide levels and increased NADPH oxidase activity compared with LZRs. Functional and AA-induced vasodilations were impaired in OZRs. Rosiglitazone treatment improved insulin, glucose, triglyceride, and superoxide levels as well as NADHP oxidase activity in OZRs. Both rosiglitazone and tempol treatment improved vasodilatory responses in OZRs with no effect in LZRs. SQ-29548 treatment improved vasodilatory responses in nontreated OZRs with no effect in LZRs or treated OZRs. These results suggest that insulin resistance and the resultant increased ROS impair functional dilation in OZRs by increasing TP-mediated vasoconstriction.
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Affiliation(s)
- Lusha Xiang
- Dept. of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MI 39216-4505, USA
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Yamaoka I, Nakayama M, Miki T, Yokoyama T, Takeuchi Y. Dietary protein modulates circadian changes in core body temperature and metabolic rate in rats. J Physiol Sci 2008; 58:75-81. [PMID: 18237456 DOI: 10.2170/physiolsci.rp006707] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 01/31/2008] [Indexed: 11/05/2022]
Abstract
We assessed the contribution of dietary protein to circadian changes in core body temperature (Tb) and metabolic rate in freely moving rats. Daily changes in rat intraperitoneal temperature, locomotor activity (LMA), whole-body oxygen consumption (VO2), and carbon dioxide production (VCO2) were measured before and during 4 days of consuming a 20% protein diet (20% P), a protein-free diet (0% P), or a pair-fed 20% P diet (20% P-R). Changes in Tb did not significantly differ between the 20% P and 20% P-R groups throughout the study. The Tb in the 0% P group remained elevated during the dark (D) phase throughout the study, but VO2, VCO2, and LMA increased late in the study when compared with the 20% P-R group almost in accordance with elevated Tb. By contrast, during the light (L) phase in the 0% P group, Tb became elevated early in the study and thereafter declined with a tendency to accompany significantly lower VO2 and VCO2 when compared with the 20% P group, but not the 20% P-R group. The respiratory quotient (RQ) in the 0% P group declined throughout the D phase and during the early L phase. By contrast, RQ in the 20% P-R group consistently decreased from the late D phase to the end of the L phase. Our findings suggest that dietary protein contributes to the maintenance of daily oscillations in Tb with modulating metabolic rates during the D phase. However, the underlying mechanisms of Tb control during the L phase remain obscure.
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Affiliation(s)
- Ippei Yamaoka
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Miki-cho, Kagawa, Japan.
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31
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Novak CM, Levine JA. Central neural and endocrine mechanisms of non-exercise activity thermogenesis and their potential impact on obesity. J Neuroendocrinol 2007; 19:923-40. [PMID: 18001322 DOI: 10.1111/j.1365-2826.2007.01606.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The rise in obesity is associated with a decline in the amount of physical activity in which people engage. The energy expended through everyday non-exercise activity, called non-exercise activity thermogenesis (NEAT), has a considerable potential impact on energy balance and weight gain. Comparatively little attention has been paid to the central mechanisms of energy expenditure and how decreases in NEAT might contribute to obesity. In this review, we first examine the sensory and endocrine mechanisms through which energy availability and energy balance are detected that may influence NEAT. Second, we describe the neural pathways that integrate these signals. Lastly, we consider the effector mechanisms that modulate NEAT through the alteration of activity levels as well as through changes in the energy efficiency of movement. Systems that regulate NEAT according to energy balance may be linked to neural circuits that modulate sleep, addiction and the stress response. The neural and endocrine systems that control NEAT are potential targets for the treatment of obesity.
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Affiliation(s)
- C M Novak
- Mayo Clinic, Endocrine Research Unit, Rochester, MN, USA.
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Boustany-Kari CM, Gong M, Akers WS, Guo Z, Cassis LA. Enhanced vascular contractility and diminished coronary artery flow in rats made hypertensive from diet-induced obesity. Int J Obes (Lond) 2006; 31:1652-9. [PMID: 16819529 DOI: 10.1038/sj.ijo.0803426] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE To determine whether obesity-induced hypertension was associated with alterations in vascular contractility and/or cardiac function. DESIGN Male Sprague-Dawley rats were fed either a low fat (LF; 11% kcal as fat) or a moderately high fat (MHF; 32% kcal as fat) diet for 11 weeks. MEASUREMENTS Body weight; mean arterial pressure; angiotensin peptides; mesenteric contractile response to phenylephrine (PE), potassium chloride (KCl), serotonin, angiotensin II (AngII), calcium chloride; baseline and isoproterenol-induced cardiac contractility; baseline and isoproterenol-induced coronary artery blood flow. RESULTS Rats fed the MHF diet segregated into obesity-prone (OP) and obesity-resistant (OR) groups. OP rats exhibited elevations in mean arterial pressure (MAP) and elevations in systemic concentrations of angiotensin peptides. Mesenteric arteries from OP rats exhibited a greater contractile response to PE, KCl and serotonin (5-HT). Heightened responses to PE persisted in arteries from OP rats even after normalization of the response to KCl. In contrast, the response of permeabilized mesenteric arteries to a maximal concentration of calcium was similar in rats from each group. Isolated perfused hearts exhibited similar baseline and isoproterenol-induced contractility in rats from each group. However, isoproterenol was unable to increase coronary artery blood flow in hearts from OP rats. CONCLUSION Enhanced vascular reactivity may contribute to obesity-induced hypertension, while reductions in coronary artery relaxation would impair the ability of the heart to respond to increased myocardial demand.
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Affiliation(s)
- C M Boustany-Kari
- Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, KY 40536-0200, USA
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Knight WD, Swoap SJ, Parsons AD, Overton JM. Central thyrotropin-releasing hormone infusion opposes cardiovascular and metabolic suppression during caloric restriction. Neuroendocrinology 2006; 83:69-76. [PMID: 16785745 DOI: 10.1159/000094004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2006] [Accepted: 05/10/2006] [Indexed: 01/08/2023]
Abstract
Inhibition of hypothalamic thyrotropin-releasing hormone (TRH) neuronal activity is a well-established adaptation to caloric restriction (CR) that suppresses pituitary secretion of thyroid-stimulating hormone, but may also participate in modulation of autonomic function. Thus, we hypothesized that decreased hypothalamic TRH activity contributes to CR-induced bradycardia and decreased metabolic rate. To test this hypothesis, male Sprague-Dawley rats were instrumented with telemetry devices for measurement of heart rate (HR) and blood pressure (BP) and a lateral intracerebroventricular (i.c.v.) guide cannula for central infusions. After recovery, rats were housed in metabolic chambers and given either ad libitum(ad-lib) or CR treatments for 7 days; half of each diet group was then given continuous i.c.v. infusions of TRH (25 nmol/h) or saline (0.25 microl/h) for 7 days via osmotic pump. This dose of TRH did not significantly alter peripheral free T(4) levels. In ad-lib rats, TRH infusion produced small reductions in food intake and small increases in HR and BP over saline-infused controls. In CR rats, TRH infusion resulted in an increase in HR and also energy expenditure over saline-infused controls. These results support the hypothesis that suppression of central TRH activity contributes to the homeostatic suppression of energy expenditure and HR observed during CR.
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Affiliation(s)
- W David Knight
- Program in Neuroscience, Florida State University, Tallahassee, 32306-4340, USA
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34
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Evans SA, Parsons AD, Overton JM. Homeostatic responses to caloric restriction: influence of background metabolic rate. J Appl Physiol (1985) 2005; 99:1336-42. [PMID: 15932959 DOI: 10.1152/japplphysiol.01380.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The biological responses to caloric restriction (CR) are generally examined in rats with elevated metabolic rates due to being housed at ambient temperatures (Ta) below the zone of thermoneutrality. We determined the physiological and behavioral responses to 2 wk of 30–40% CR in male FBNF1 rats housed in cool (Ta = 12°C) or thermoneutral (TMN; Ta = 30°C) conditions. Rats were instrumented with telemetry devices and housed continuously in home-cage calorimeters for the entire experiment. At baseline, rats housed in cool Ta had reduced rate of weight gain; thus a mild CR (5%) group at thermoneutrality for weight maintenance was also studied. Rats housed in cool Ta exhibited elevated caloric intake (cool = 77 ± 1; TMN = 54 ± 2 kcal), oxygen consumption (V̇o2; cool = 9.9 ± 0.1; TMN = 5.5 ± 0.1 ml/min), mean arterial pressure (cool = 103 ± 1; TMN = 80 ± 2 mmHg), and heart rate (cool = 374 ± 3; TMN = 275 ± 4 beats/min). Cool-CR rats exhibited greater CR-induced weight loss (cool = −62 ± 3; TMN = −42 ± 3 g) and reductions in V̇o2 (cool = −2.6 ± 0.1; TMN = −1.5 ± 0.1 ml/min) but similar CR-induced reductions in heart rate (cool = −59 ± 1; TMN= −51 ± 7 beats/min). CR had no effect on arterial blood pressure or locomotor activity in either group. Unexpectedly, weight maintenance produced significant reductions in V̇o2 and heart rate. At thermoneutrality, a single day of refeeding effectively abolished CR-induced reductions in V̇o2 and heart rate. The results reveal that rats with low or high baseline metabolic rate exhibit comparable compensatory reductions in V̇o2 and heart rate and suggest that Ta can be used to modulate the metabolic background on which the more prolonged effects of CR can be studied.
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Affiliation(s)
- S A Evans
- Department of Biomedical Sciences, Florida State University, Tallahassee, 32306-4340, USA
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Kurtz TW, Griffin KA, Bidani AK, Davisson RL, Hall JE. Recommendations for Blood Pressure Measurement in Humans and Experimental Animals. Arterioscler Thromb Vasc Biol 2005; 25:e22-33. [PMID: 15731483 DOI: 10.1161/01.atv.0000158419.98675.d7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In experimental animals, as in humans, techniques for measuring blood pressure (BP) have improved considerably over the past decade. In this document, we present recommendations for measuring BP in experimental animals with the goal of helping investigators select optimal methods for BP monitoring in the research laboratory. The advantages and disadvantages of various BP measurement methods are discussed and specific recommendations are provided for selecting the optimal technique depending on the study objective. Although indirect techniques that permit only sporadic measurements of BP may be suitable for some purposes, methods for directly measuring BP are generally preferred because of their ability to monitor the highly dynamic nature of BP in a comprehensive fashion. Selection of the methods to be used should ultimately be guided by the study objectives to insure that the techniques chosen are appropriate for the experimental questions being explored.
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Evans SA, Messina MM, Knight WD, Parsons AD, Overton JM. Long-Evans and Sprague-Dawley rats exhibit divergent responses to refeeding after caloric restriction. Am J Physiol Regul Integr Comp Physiol 2005; 288:R1468-76. [PMID: 15695322 DOI: 10.1152/ajpregu.00602.2004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mature male Sprague-Dawley (SD) and Long-Evans (LE) rats were instrumented with telemetry transmitters for measurement of heart rate (HR) and housed in room calorimeters for assessment of food intake and oxygen consumption (Vo(2)) at standard laboratory temperatures (23 degrees C) to examine physiological responses to caloric restriction (CR; 60% of baseline ad libitum calories for 2 wk) and refeeding. Ad libitum controls had stable food intake (84-88 kcal/day) and gained weight at rates of 3-4 g/day. Groups from both strains assigned to CR exhibited similar patterns of weight loss and reductions in Vo(2) and HR. Upon refeeding, SD rats exhibited a mild, transient hyperphagic response (1 day) accompanied by sustained suppression of Vo(2) and HR that remained evident 8 days after refeeding. In contrast, LE rats exhibited sustained daily hyperphagia that persisted 8 days after refeeding and was accompanied by a complete restoration of HR and Vo(2). The lower HR and Vo(2) observed during refeeding in SD rats were not due to reduced locomotor activity. The results reveal a strain-dependent divergent response to recovery from CR. We conclude that during recovery from CR, homeostatic stimulation of appetite or suppression of energy expenditure may occur selectively to restore body weight.
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Affiliation(s)
- S A Evans
- Department of Nutrition, Food and Exercise Sciences and Program in Neuroscience, 236 Biomedical Research Facility, Florida State University, Tallahassee, FL 32306-4340, USA
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Kurtz TW, Griffin KA, Bidani AK, Davisson RL, Hall JE. Recommendations for Blood Pressure Measurement in Humans and Experimental Animals. Hypertension 2005; 45:299-310. [PMID: 15611363 DOI: 10.1161/01.hyp.0000150857.39919.cb] [Citation(s) in RCA: 225] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In experimental animals, as in humans, techniques for measuring blood pressure (BP) have improved considerably over the past decade. In this document, we present recommendations for measuring BP in experimental animals with the goal of helping investigators select optimal methods for BP monitoring in the research laboratory. The advantages and disadvantages of various BP measurement methods are discussed and specific recommendations are provided for selecting the optimal technique depending on the study objective. Although indirect techniques that permit only sporadic measurements of BP may be suitable for some purposes, methods for directly measuring BP are generally preferred because of their ability to monitor the highly dynamic nature of BP in a comprehensive fashion. Selection of the methods to be used should ultimately be guided by the study objectives to insure that the techniques chosen are appropriate for the experimental questions being explored.
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Duclos M, Timofeeva E, Michel C, Richard D. Corticosterone-dependent metabolic and neuroendocrine abnormalities in obese Zucker rats in relation to feeding. Am J Physiol Endocrinol Metab 2005; 288:E254-66. [PMID: 15383369 DOI: 10.1152/ajpendo.00087.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The obese Zucker (fa/fa) rat is characterized by hyperphagia, hyperinsulinemia, an increase in fat deposition, and a hyperactivity in the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis in fa/fa rats is hypersensitive to stressful experimental conditions. Food deprivation even leads to a stress reaction in obese fa/fa rats. The present study was conducted to investigate the role of corticosterone in obese rats on the basal, fasting, and postprandial metabolic rate as well as on the central expression of the thyrotropin-releasing hormone (TRH) in these conditions. In addition, the study was aimed at clarifying whether the high levels of corticosterone in obese rats are responsible for the induction of the stress reaction to food deprivation in these animals. The present results demonstrate that whole body fat oxidation and postprandial metabolic responses in obese Zucker rats were improved by adrenalectomy (ADX). At the level of the central nervous system, ADX reversed a decrease in TRH mRNA expression in the paraventricular hypothalamus (PVH) detected in fasting animals. Considering all feeding conditions, the obese rats demonstrated lower TRH mRNA levels compared with lean animals. ADX resulted in an enhanced postprandial activation of the parvocellular PVH. In contrast, the magnocellular part of the PVH was less responsive to refeeding in ADX animals. Finally, ADX failed to prevent the stress response of obese rats to food deprivation. The present results provide evidence that the removal of adrenals resolve some of the metabolic defects encountered in obese Zucker rats. They also demonstrate that not all the abnormalities of the obese Zucker rats are attributable to the hyperactivity of the HPA axis.
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Affiliation(s)
- Martine Duclos
- Laboratoire Neurogénétique, Université Laval, Quebec, Canada
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DeRuisseau LR, Parsons AD, Overton JM. Adaptive thermogenesis is intact in B6 and A/J mice studied at thermoneutrality. Metabolism 2004; 53:1417-23. [PMID: 15536595 DOI: 10.1016/j.metabol.2004.06.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To investigate mechanisms of resistance to obesity, the physiologic responses to short-term moderate fat feeding were studied at ambient temperature (T(a)) = 23 degrees C and thermonuetrality (T(a) = 30 degrees C) in mice susceptible (B6) or resistant (A/J) to obesity. We hypothesized that A/J mice would exhibit greater adaptive thermogenic responses to consumption of moderate-fat diets, and that this response would be attenuated in thermoneutral conditions due to reduced activity of brown adipose tissue (BAT). B6 and A/J mice were adapted to either T(a) = 23 degrees C or T(a) = 30 degrees C, implanted with telemetry devices, housed in metabolic chambers for measurement of food intake, oxygen consumption (Vo(2)), and heart rate (HR), and studied before and during 1 week of consuming a diet containing 32% of calories from fat. Access to 32% fat diet resulted in increased caloric intake in both strains, but caloric intake for A/J mice returned to baseline levels within 72 hours, while B6 mice remained hyperphagic. Both strains exhibited increased light-phase Vo(2) indicative of adaptive thermogenesis; however, there was no strain difference in light-phase Vo(2) during the 1-week feeding trial. Surprisingly, T(a) had no effect on diet-induced thermogenesis in either mouse strain. Moderate high-fat feeding produced mild tachycardia that was similar in B6 and A/J mice and more clearly evident at thermonuetrality. We conclude that adaptive thermogenic responses are intact in both mouse strains studied at thermoneutrality, suggesting a minimal role for BAT in the initial metabolic response to hyperphagia. Furthermore, the results suggest that differences in control of caloric intake, rather than capacity for adaptive thermogenesis, may contribute to the relative susceptibility to obesity in A/J and B6 mice.
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Affiliation(s)
- L R DeRuisseau
- Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL 32306-4340, USA
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40
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Nagashima K, Matsue K, Konishi M, Iidaka C, Miyazaki K, Ishida N, Kanosue K. The involvement of Cry1 and Cry2 genes in the regulation of the circadian body temperature rhythm in mice. Am J Physiol Regul Integr Comp Physiol 2004; 288:R329-35. [PMID: 15331384 DOI: 10.1152/ajpregu.00395.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The criptochrome genes (Cry1 and Cry2) are involved in the molecular mechanism that controls the circadian clock, and mice lacking these genes (Cry1(-/-)/Cry2(-/-)) are behaviorally arrhythmic. It has been speculated that the circadian clock modulates the characteristics of thermoregulation, resulting in body temperature (T(b)) rhythm. However, there is no direct evidence proving this speculation. We show here that T(b) and heat production in Cry1(-/-)/Cry2(-/-) mice are arrhythmic under constant darkness. In contrast, both rhythms occur under a light-dark cycle and/or periodical food restriction linked with spontaneous activity and/or eating, although they are not robust as those in wild-type mice. The relationship between heat production and T(b) in Cry1(-/-)/Cry2(-/-) mice is linear and identical under any conditions, indicating that their T(b) rhythm is determined by heat production rhythm associated with activity and eating. However, T(b) in wild-type mice is maintained at a relatively higher level in the active phase than the inactive phase regardless of the heat production level. These results indicate that the thermoregulatory responses are modulated according to the circadian phase, and the Cry genes are involved in this mechanism.
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Affiliation(s)
- Kei Nagashima
- Department of Integrative Physiology, School of Human Sciences, Waseda University, Mikajima 2-579-15, Tokorozawa, Saitama 359-1192, Japan.
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41
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Towa S, Kuwahara M, Tsubone H. Characteristics of autonomic nervous function in Zucker-fatty rats: investigation by power spectral analysis of heart rate variability. Exp Anim 2004; 53:137-44. [PMID: 15153676 DOI: 10.1538/expanim.53.137] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
We investigated the characteristics of autonomic nervous function in Zucker-fatty and Zucker-lean rats. For this purpose, a long-term electrocardiogram (ECG) was recorded from conscious and unrestrained rats using a telemetry system, and the autonomic nervous function was investigated by power spectral analysis of heart rate variability (HRV). Although heart rate (HR) in Zucker-fatty rats was lower than that in Zucker-lean rats throughout 24 h, apparent diurnal variation in HR was observed in both strains and HR during the dark period was significantly higher than that in light period. Diurnal variation in locomotor activity (LA) in Zucker-fatty rats was also observed, but LA was lower than that in Zucker lean rats, especially during the dark period. There were no significant differences, however, in high-frequency (HF) power, low-frequency (LF) power, and the LF/HF ratio between Zucker-fatty and Zucker-lean rats. The circadian rhythm of these parameters was mostly preserved in both strains of rats. Moreover, the effect of autonomic blockades on HRV was nearly the same in Zucker-fatty and Zucker-lean rats. These results suggest that the autonomic nervous function of insulin-resistant Zucker-fatty rats remain normal, from the aspect of power spectral analysis of HRV.
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Affiliation(s)
- Shuichi Towa
- Department of Comparative Pathophysiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
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Williams TD, Chambers JB, Roberts LM, Henderson RP, Overton JM. Diet-induced obesity and cardiovascular regulation in C57BL/6J mice. Clin Exp Pharmacol Physiol 2004; 30:769-78. [PMID: 14516417 DOI: 10.1046/j.1440-1681.2003.t01-1-03808.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. In the present study, we determined the effect of diet-induced obesity on cardiovascular and metabolic regulation in mice at standard laboratory temperatures (ambient temperature (Ta) = 22 degrees C) and during exposure to thermoneutrality (Ta = 30 degrees C). 2. Male C57BL/6J (B6) mice fed a high-fat diet (HFF; n = 17) or chow (CHW; n = 14) for 15 weeks were surgically instrumented with telemetry devices, housed in metabolic chambers and assigned to either control or atenolol treatment (25 mg/kg per day in drinking water) to determine the effects of obesity on baseline cardiovascular function and on the responses to thermoneutrality and 24 h fasting. Mean arterial pressure (MAP), heart rate (HR), arterial pressure and HR variability (time and frequency domain), oxygen consumption (VO2) and locomotor activity were determined. 3. The HFF mice exhibited increased bodyweight (+10.6 +/- 4.1 g), moderate light period hypertension (+8.6 +/- 2.6 mmHg), no difference in HR and increased HR variability at standard laboratory temperature compared with CHW controls. Atenolol produced less of a decrease in HR in HFF mice (-42 +/- 10 b.p.m.) compared with CHW controls (-73 +/- 15 b.p.m.). Acute exposure to thermoneutrality (Ta = 30 degrees C) reduced HR similarly in both HFF and CHW mice (approximately 175 b.p.m.), but reduced MAP less in HFF than in CHW mice (-7.3 +/- 2.5 and -15.2 +/- 1.0 mmHg), respectively. Atenolol treatment had only minor effects on the HR response to thermonuetrality (-114 +/- 13 and -129 +/- 8 b.p.m. in HFF and CHW mice, respectively). The HFF mice displayed greater fasting-induced reductions in light period MAP than did CHW mice (-10.0 +/- 1.1 vs-3.1 +/- 3.5 mmHg, respectively), whereas HR was decreased equally in both groups. Fasting-induced increases in HR variability were attenuated in HFF mice. 4. We conclude that diet-induced obesity produced generally minor changes in cardiovascular regulation in B6 mice at baseline, some of which are distinct from the effects of diet-induced obesity in larger animal models. In contrast, acute variations in Ta or caloric availability produce pronounced alterations in cardiovascular function in either lean or obese mice, which are generally evident after atenolol and, thus, presumably not due exclusively to variation in cardiac sympathetic activity. Interestingly, the degree of obesity induced hypertension was augmented when mice were studied at thermonuetrality. The results suggest an important unrecognized role for vagal tone in the regulation of cardiovascular function in mice and support the need for considerable caution when using mouse models of obesity to examine regulation of cardiovascular function. We argue that mouse physiology studies should be performed in thermoneutral conditions.
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Affiliation(s)
- T D Williams
- Department of Nutrition, Food and Exercise Sciences, The Program in Neuroscience, Florida State University, Tallahassee, Florida 32306-4340, USA
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Swoap SJ, Overton JM, Garber G. Effect of ambient temperature on cardiovascular parameters in rats and mice: a comparative approach. Am J Physiol Regul Integr Comp Physiol 2004; 287:R391-6. [PMID: 15087284 DOI: 10.1152/ajpregu.00731.2003] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ambient air temperatures (T(a)) of <6 degrees C or >29 degrees C have been shown to induce large changes in arterial blood pressure and heart rate in homeotherms. The present study was designed to investigate whether small incremental changes in T(a), such as those found in typical laboratory settings, would have an impact on blood pressure and other cardiovascular parameters in mice and rats. We predicted that small decreases in T(a) would impact the cardiovascular parameters of mice more than rats due to the increased thermogenic demands resulting from a greater surface area-to-volume ratio in mice relative to rats. Cardiovascular parameters were measured with radiotelemetry in mice and rats that were housed in temperature-controlled environments. The animals were exposed to different T(a) every 72 h, beginning at 30 degrees C and incrementally decreasing by 4 degrees C at each time interval to 18 degrees C and then incrementally increasing back up to 30 degrees C. As T(a) decreased, mean blood pressure, heart rate, and pulse pressure increased significantly for both mice (1.6 mmHg/ degrees C, 14.4 beats.min(-1). degrees C(-1), and 0.8 mmHg/ degrees C, respectively) and rats (1.2 mmHg/ degrees C, 8.1 beats.min(-1). degrees C(-1), and 0.8 mmHg/ degrees C, respectively). Thus small changes in T(a) significantly impact the cardiovascular parameters of both rats and mice, with mice demonstrating a greater sensitivity to these T(a) changes.
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Affiliation(s)
- Steven J Swoap
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
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Abstract
Peripheral microvascular dysfunction is a common affliction in patients with the metabolic syndrome X. Previous studies have described a number of vascular impairments in vasomotor control in both human patients and animal models of syndrome X, but the net effect of these impairments on microvascular structure has not been examined. The goal of the current study was to test the hypothesis that syndrome X reduces muscle perfusion and induces vascular remodeling. The obese Zucker rat was used as a model of syndrome X, and the microcirculation of the hindlimb and brain were examined. Obese Zucker rats were obese, hyperlipidemic, hyperinsulinemic, and hyperglycemic. Blood flow to the hindlimb was reduced by 59% in obese rats relative to lean rats. Skeletal muscle resistance arteries of the hindlimb microcirculation of obese rats had thinner walls, smaller lumens, and reduced distensibility. Hindlimb microvessels from obese rats also demonstrated reduced expression of vascular smooth muscle cell markers. Each of these traits is consistent with low-flow remodeling. In contrast, the cerebral microcirculation, where flow is vigorously autoregulated, showed no vascular remodeling nor were there changes in microvascular smooth muscle marker expression. Neither physical activity nor muscle mass were significantly different between lean and obese rats. Taken together, these findings suggest that syndrome X, by reducing hindlimb blood flow, induces a marked remodeling of microcirculation to favor smaller, less distensible vessels. This remodeling may result in an architectural limitation of maximum perfusion capacity and may be an important maladaption in the progression of peripheral microvascular disease.
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Affiliation(s)
- David W Stepp
- Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912, USA.
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Leon LR, Walker LD, DuBose DA, Stephenson LA. Biotelemetry transmitter implantation in rodents: impact on growth and circadian rhythms. Am J Physiol Regul Integr Comp Physiol 2004; 286:R967-74. [PMID: 14726427 DOI: 10.1152/ajpregu.00380.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The implantation of a biotelemetry transmitter for core body temperature (T(c)) and motor activity (MA) measurements is hypothesized to have effects on growth and circadian rhythmicity depending on animal body-to-transmitter (B:T) size ratio. This study examined the impact of transmitter implantation (TM) on body weight, food intake (FI), water intake (WI), and circadian T(c) and MA rhythms in mice (23.8 +/- 0.04 g) and rats (311.5 +/- 5.1 g) receiving no treatment (NT), anesthesia, laparotomy (LAP), and TM. The B:T size ratio was 6:1 and 84:1 for mice and rats, respectively. In mice, body weight required 14 days to recover to presurgical levels and never attained the level of the other groups. FI recovered in 3 days, whereas WI never reached presurgical levels. Rat body weight did not decrease below presurgical levels. FI and WI recovered to presurgical levels in rats by day 2 postsurgery. Anesthesia decreased mouse body weight for 1 wk, but was without effect in rats. LAP significantly decreased body weight for 5 days in mice and 1 day in rats, showing a significant effect of the surgical procedure in the absence of TM in both species. Circadian T(c) and MA rhythms were evident within the first week in both species, indicating dissociation between circadian rhythmicity and recovery of growth variables. Cosinor analysis showed a TM effect on T(c) min, T(c) max, mesor, amplitude, and period of mice, whereas only the amplitude of the rhythm was affected in rats. These data indicate that a large B:T size ratio is associated with minimization of the adverse effects of surgical implantation. We recommend that B:T size ratio, recovery of presurgical body weight, and display of a robust circadian T(c) and MA rhythm be established before collection of biotelemetry data collection under an experimental paradigm.
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Affiliation(s)
- Lisa R Leon
- U.S. Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, 42 Kansas Street, Natick, MA 01760-5007, USA.
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Swoap SJ, Weinshenker D, Palmiter RD, Garber G. Dbh(-/-) mice are hypotensive, have altered circadian rhythms, and have abnormal responses to dieting and stress. Am J Physiol Regul Integr Comp Physiol 2004; 286:R108-13. [PMID: 12969876 DOI: 10.1152/ajpregu.00405.2003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used mice deficient in dopamine beta-hydroxylase [Dbh(-/-)] and their littermate controls [Dbh(+/-)] to examine the role of epinephrine (Epi) and norepinephrine (NE) in the maintenance of cardiovascular parameters during 7 days of caloric restriction and acute exposure to environmental stress. Cardiovascular parameters of the mice were monitored using blood pressure radiotelemeters at an ambient temperature of 29 degrees C. Under normal conditions, Dbh(-/-) mice had a low heart rate, were severely hypotensive, and displayed an attenuated circadian blood pressure rhythm. Upon 50% caloric restriction, Dbh(+/-) mice exhibited decreases in heart rate and mean blood pressure. However, the blood pressures of Dbh(-/-) mice did not fall significantly in response to caloric restriction, and the bradycardia associated with caloric restriction was attenuated in these mice. In response to an open-field test, the blood pressure and heart rate of Dbh(+/-) mice increased substantially and rapidly, whereas Dbh(-/-) mice had blunted changes in blood pressures and no change in heart rate. These data suggest a primary role of Epi and NE in mediating the hypotension induced by dieting. Furthermore, Epi and NE play a smaller, but still significant, role in the bradycardia induced by caloric restriction. In contrast, Epi and NE are required for the tachycardia in an open field but are not required for the increase in blood pressure.
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Affiliation(s)
- Steven J Swoap
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
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Affiliation(s)
- Harald M Stauss
- Dept. of Exercise Science, The Univ. of Iowa, Iowa City, IA 52242, USA.
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Nagashima K, Nakai S, Matsue K, Konishi M, Tanaka M, Kanosue K. Effects of fasting on thermoregulatory processes and the daily oscillations in rats. Am J Physiol Regul Integr Comp Physiol 2003; 284:R1486-93. [PMID: 12736180 DOI: 10.1152/ajpregu.00515.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate the mechanism involved in the reduction of body core temperature (T(core)) during fasting in rats, which is selective in the light phase, we measured T(core), surface temperature, and oxygen consumption rate in fed control animals and in fasted animals on day 3 of fasting and day 4 of recovery at an ambient temperature (T(a)) of 23 degrees C by biotelemetry, infrared thermography, and indirect calorimetry, respectively. On the fasting day, 1) T(core) in the light phase decreased (P < 0.05) from the control; however, T(core) in the dark phase was unchanged, 2) tail temperature fell from the control (P < 0.05, from 30.7 +/- 0.1 to 23.9 +/- 0.1 degrees C in the dark phase and from 29.4 +/- 0.1 to 25.2 +/- 0.2 degrees C in the light phase), 3) oxygen consumption rate decreased from the control (P < 0.05, from 24.37 +/- 1.06 to 16.24 +/- 0.69 ml. min(-1). kg body wt(-0.75) in the dark phase and from 18.91 +/- 0.64 to 14.00 +/- 0.41 ml. min(-1). kg body wt(-0.75) in the light phase). All these values returned to the control levels on the recovery day. The results suggest that, in the fasting condition, T(core) in the dark phase was maintained by suppression of the heat loss mechanism, despite the reduction of metabolic heat production. In contrast, the response was weakened in the light phase, decreasing T(core) greatly. Moreover, the change in the regulation of tail blood flow was a likely mechanism to suppress heat loss.
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Affiliation(s)
- Kei Nagashima
- Department of Physiology, School of Allied Health Sciences, Osaka University Faculty of Medicine, Suita, Osaka 567-0871, Japan.
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Williams TD, Chambers JB, Gagnon SP, Roberts LM, Henderson RP, Overton JM. Cardiovascular and metabolic responses to fasting and thermoneutrality in Ay mice. Physiol Behav 2003; 78:615-23. [PMID: 12782216 DOI: 10.1016/s0031-9384(03)00049-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Several lines of evidence support a role for reduced melanocortin signaling in the regulation of metabolic rate and cardiovascular function during negative energy balance. We tested the hypothesis that agouti yellow (B6.Cg-A(y)) mice would exhibit blunted physiologic responses to fasting and thermoneutrality. Male B6.Cg-A(y) mice (A(y); n=11, 34+/-2 g) and lean B6 littermates (B6; n=7, 26+/-2 g) were implanted with telemetry devices and housed in metabolic chambers (T(a)=23 degrees C) to determine the effects of a 24-h fasting and exposure to thermoneutrality (T(a)=30 degrees C) on mean arterial pressure (MAP), heart rate (HR), AP and HR variability (time and frequency domain), oxygen consumption (VO(2)), and locomotor activity. A(y) mice exhibited elevated baseline light-period MAP (A(y): 113+/-4; B6: 99+/-3 mm Hg) and VO(2) (A(y): 1.82+/-0.08 vs. B6: 1.45+/-0.13 ml/min) with no difference in HR (A(y): 530+/-12 vs. B6: 548+/-19 bpm). At 12-24 h after food removal, A(y) mice displayed normal fasting-induced bradycardia (A(y): -106+/-12; B6: -117+/-19 bpm) and reduction in VO(2) (A(y): -0.19+/-0.04 vs. B6: -0.28+/-0.05 ml/min), but with augmented hypotension (A(y): -9+/-2 vs. B6: -0.5+/-2 mm Hg) and blunted hyperactivity (A(y): 27+/-23 vs. B6: 122+/-42 m/11 h). Fasting was associated with increased HR variability in both time and frequency domain in B6 but not A(y) mice. Exposure to thermoneutrality produced comparable reductions in MAP, HR, and VO(2) in both strains. We conclude that inhibition of melanocortin signaling is not requisite for, but participates in, the metabolic and cardiovascular responses to negative energy balance.
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Affiliation(s)
- T D Williams
- Department of Nutrition, Food, and Exercise Sciences, Florida State University, 236 Biomedical Research Facility, Tallahassee, FL 32306-4340, USA
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Affiliation(s)
- Gerald F DiBona
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
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