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Lopes KG, Farinatti P, Bottino D, Souza MDGD, Maranhão P, Bouskela E, Lourenço R, Oliveira RD. Exercise with blood flow restriction improves muscle strength and mass while preserving the vascular and microvascular function and structure of older adults. Clin Hemorheol Microcirc 2022; 82:13-26. [DOI: 10.3233/ch-221395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND: Changes in muscle mass, strength, vascular function, oxidative stress, and inflammatory biomarkers were compared in older adults after resistance training (RT) performed with low-intensity without blood flow restriction (RT-CON); low-intensity with BFR (RT-BFR); and high-intensity without BFR (RT-HI). METHODS: Thirty-two untrained individuals (72±7 y) performed a 12-week RT after being randomized into three groups: RT-CON –30% of 1 repetition maximum (RM); RT-BFR –30% of 1RM and mild BFR (50% of arterial occlusion pressure); RT-HI –70% of 1 RM. RESULTS: Improvements in handgrip strength were similar in RT-BFR (17%) and RT-HI (16%) vs. RT-CON (–0.1% ), but increases in muscle mass (6% vs. 2% and –1%) and IGF-1 (2% vs. –0.1% and –1.5%) were greater (p < 0.05) in RT-BFR vs. RT-HI and RT-CON. Changes in vascular function, morphology, inflammation, and oxidative stress were similar between groups, except for time to reach maximum red blood cell velocity which showed a greater reduction (p < 0.05) in RT-BFR (–55%) vs. RT-HI (–11%) and RT-CON (–4% ). CONCLUSION: RT with low intensity and mild BFR improved muscle strength and mass in older individuals while preserving vascular function. This modality should be considered an adjuvant strategy to improve muscle function in older individuals with poor tolerance to high loads.
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Affiliation(s)
- Karynne Grutter Lopes
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Paulo Farinatti
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Daniel Bottino
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Maria das Graças de Souza
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Priscila Maranhão
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Eliete Bouskela
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Roberto Lourenço
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
| | - Ricardo de Oliveira
- Laboratory for Clinical and Experimental Research on Vascular Biology, Rio de Janeiro State University, RJ, Brazil
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Kim S, Choi JY, Moon S, Park DH, Kwak HB, Kang JH. Roles of myokines in exercise-induced improvement of neuropsychiatric function. Pflugers Arch 2019; 471:491-505. [PMID: 30627775 DOI: 10.1007/s00424-019-02253-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/18/2018] [Accepted: 01/03/2019] [Indexed: 01/28/2023]
Abstract
Exercise is a well-known non-pharmacological intervention to improve brain functions, including cognition, memory, and motor coordination. Contraction of skeletal muscles during exercise releases humoral factors that regulate the whole-body metabolism via interaction with other non-muscle organs. Myokines are muscle-derived effectors that regulate body metabolism by autocrine, paracrine, or endocrine action and were reportedly suggested as "exercise factors" that can improve the brain function. However, several aspects remain to be elucidated, namely the specific activities of myokines related to the whole-body metabolism or brain function, the mechanisms of regulation of other organs or cells, the sources of "exercise factors" that regulate brain function, and their mechanisms of interaction with non-muscle organs. In this paper, we present the physiological functions of myokines secreted by exercise, including regulation of the whole-body metabolism by interaction with other organs and adaptation of skeletal muscles to exercise. In addition, we discuss the functions of myokines that possibly contribute to exercise-induced improvement of brain function. Among several myokines, brain-derived neurotrophic factor (BDNF) is the most studied myokine that regulates adult neurogenesis and synaptic plasticity. However, the source of circulating BDNF and its upstream effector, insulin-like growth factor (IGF-1), and irisin and the effect size of peripheral BDNF, irisin, and IGF-1 released after exercise should be further investigated. Recently, cathepsin B has been reported to be secreted from skeletal muscles and upregulate BDNF following exercise, which was associated with improved cognitive function. We reviewed the level of evidence for the effect of myokine on the brain function. Level of evidence for the association of the change in circulating myokine following exercise and improvement of neuropsychiatric function is lower than the level of evidence for the benefit of exercise on the brain. Therefore, more clinical evidences for the association of myokine release after exercise and their effect on the brain function are required. Finally, we discuss the effect size of the action of myokines on cognitive benefits of exercise, in addition to other contributors, such as improvement of the cardiovascular system or the effect of "exercise factors" released from non-muscle organs, particularly in patients with sarcopenia.
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Affiliation(s)
- Sujin Kim
- Department of Pharmacology and Hypoxia-related Disease Research Center, Inha University School of Medicine, Room 1015, 60th Anniversary Hall, 100, Inha-ro, Nam-gu, Incheon, 22212, Republic of Korea.,Department of Kinesiology, Inha University, Incheon, Republic of Korea
| | - Ji-Young Choi
- Department of Pharmacology and Hypoxia-related Disease Research Center, Inha University School of Medicine, Room 1015, 60th Anniversary Hall, 100, Inha-ro, Nam-gu, Incheon, 22212, Republic of Korea
| | - Sohee Moon
- Department of Pharmacology and Hypoxia-related Disease Research Center, Inha University School of Medicine, Room 1015, 60th Anniversary Hall, 100, Inha-ro, Nam-gu, Incheon, 22212, Republic of Korea
| | - Dong-Ho Park
- Department of Kinesiology, Inha University, Incheon, Republic of Korea
| | - Hyo-Bum Kwak
- Department of Kinesiology, Inha University, Incheon, Republic of Korea
| | - Ju-Hee Kang
- Department of Pharmacology and Hypoxia-related Disease Research Center, Inha University School of Medicine, Room 1015, 60th Anniversary Hall, 100, Inha-ro, Nam-gu, Incheon, 22212, Republic of Korea.
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Mannerkorpi K, Landin-Wilhelmsen K, Larsson A, Cider Å, Arodell O, Bjersing JL. Acute effects of physical exercise on the serum insulin-like growth factor system in women with fibromyalgia. BMC Musculoskelet Disord 2017; 18:37. [PMID: 28122522 PMCID: PMC5264319 DOI: 10.1186/s12891-017-1402-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 01/14/2017] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Increased Serum insulin-like growth factor-1 (S-IGF-1) has been noted after physical activity in healthy subjects, while the acute release of S-IGF-1 in relation to exercise has not previously been studied in women with fibromyalgia (FM). S-IGF-1 and its binding protein (S-IGFBP-3) are mediated by growth hormone and have anabolic effects on the skeletal muscle. Aim of the study was to investigate acute release of IGF-1 after aerobic exercise in women with FM. METHODS The acute effect of physical exercise on S-IGF-1 and S-IGFBP-3 were studied in 22 women with FM and in 27 healthy controls during moderate and high-intensity cycling (i.e. ratings 12-13 and 15-17, on Borg's perceived exertion scale (RPE), respectively). Self-reported pain and fatigue were recorded. Differences within and between the two groups were analyzed. RESULTS After 15 min of bicycling, S-IGF-1 and S-IGFBP-3 increased both within the group with FM and in the healthy controls (p < 0.01). The increases in S-IGF-1 did not significantly differ between the women with FM and the healthy control group (mean increase 11 ± 10 vs. 11 ± 15 ng/ml and 13 ± 10 vs. 19 ± 22 ng/ml) when bicycling at moderate or high intensity, respectively. Self-reported pain and fatigue during exercise, irrespective of intensity, were higher in women with FM compared with healthy controls (p < 0.001). CONCLUSIONS Fifteen minutes bicycling at moderate intensity was sufficient to acutely mobilise S-IGF-1 in women with FM similarly to healthy controls in spite of higher score of fatigue and pain in women with FM. Hence, patients with FM were able to activate their skeletal muscle metabolism during a short, moderate bout of exercise and were not resistant to training effects. The result is important for encouraging clinical rehabilitation of patients with FM who commonly exercise at a moderate, rather than at a high-intensity level. TRIAL REGISTRATION ClinicalTrials.govNCT01592916 , May 4, 2012.
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Affiliation(s)
- Kaisa Mannerkorpi
- Institute of Neuroscience and Physiology, Section of Health and Rehabilitation, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. .,Sahlgrenska University Hospital, Physiotherapy and Occupational therapy, Göteborg, Sweden. .,Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Guldhedsgatan 10, Box 480, 40530, Göteborg, Sweden.
| | - Kerstin Landin-Wilhelmsen
- Section of Endocrinology, Sahlgrenska Academy, Sahlgrenska University Hospital, Institution of Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Anette Larsson
- Institute of Neuroscience and Physiology, Section of Health and Rehabilitation, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Åsa Cider
- Institute of Neuroscience and Physiology, Section of Health and Rehabilitation, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Olivia Arodell
- Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Guldhedsgatan 10, Box 480, 40530, Göteborg, Sweden
| | - Jan L Bjersing
- Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Guldhedsgatan 10, Box 480, 40530, Göteborg, Sweden.,Sahlgrenska University Hospital, Rheumatology, Göteborg, Sweden
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4
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Husak JF, Ferguson HA, Lovern MB. Trade‐offs among locomotor performance, reproduction and immunity in lizards. Funct Ecol 2016. [DOI: 10.1111/1365-2435.12653] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Jerry F. Husak
- Department of Biology University of St. Thomas St. Paul Minnesota 55105 USA
| | - Haley A. Ferguson
- Department of Biology University of St. Thomas St. Paul Minnesota 55105 USA
| | - Matthew B. Lovern
- Department of Integrative Biology Oklahoma State University Stillwater Oklahoma 74078 USA
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Phillips C, Baktir MA, Srivatsan M, Salehi A. Neuroprotective effects of physical activity on the brain: a closer look at trophic factor signaling. Front Cell Neurosci 2014; 8:170. [PMID: 24999318 PMCID: PMC4064707 DOI: 10.3389/fncel.2014.00170] [Citation(s) in RCA: 197] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 06/02/2014] [Indexed: 12/18/2022] Open
Abstract
While the relationship between increased physical activity and cognitive ability has been conjectured for centuries, only recently have the mechanisms underlying this relationship began to emerge. Convergent evidence suggests that physical activity offers an affordable and effective method to improve cognitive function in all ages, particularly the elderly who are most vulnerable to neurodegenerative disorders. In addition to improving cardiac and immune function, physical activity alters trophic factor signaling and, in turn, neuronal function and structure in areas critical for cognition. Sustained exercise plays a role in modulating anti-inflammatory effects and may play a role in preserving cognitive function in aging and neuropathological conditions. Moreover, recent evidence suggests that myokines released by exercising muscles affect the expression of brain-derived neurotrophic factor synthesis in the dentate gyrus of the hippocampus, a finding that could lead to the identification of new and therapeutically important mediating factors. Given the growing number of individuals with cognitive impairments worldwide, a better understanding of how these factors contribute to cognition is imperative, and constitutes an important first step toward developing non-pharmacological therapeutic strategies to improve cognition in vulnerable populations.
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Affiliation(s)
- Cristy Phillips
- Department of Physical Therapy, Arkansas State University Jonesboro, AR, USA
| | - Mehmet Akif Baktir
- Department of Physiology, Erciyes University Kayseri, Turkey; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Malathi Srivatsan
- Department of Biological Sciences, Arkansas State University Jonesboro, AR, USA
| | - Ahmad Salehi
- VA Palo Alto Health Care System Palo Alto, CA, USA
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6
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Voss MW, Vivar C, Kramer AF, van Praag H. Bridging animal and human models of exercise-induced brain plasticity. Trends Cogn Sci 2013; 17:525-44. [PMID: 24029446 DOI: 10.1016/j.tics.2013.08.001] [Citation(s) in RCA: 630] [Impact Index Per Article: 57.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 12/20/2022]
Abstract
Significant progress has been made in understanding the neurobiological mechanisms through which exercise protects and restores the brain. In this feature review, we integrate animal and human research, examining physical activity effects across multiple levels of description (neurons up to inter-regional pathways). We evaluate the influence of exercise on hippocampal structure and function, addressing common themes such as spatial memory and pattern separation, brain structure and plasticity, neurotrophic factors, and vasculature. Areas of research focused more within species, such as hippocampal neurogenesis in rodents, also provide crucial insight into the protective role of physical activity. Overall, converging evidence suggests exercise benefits brain function and cognition across the mammalian lifespan, which may translate into reduced risk for Alzheimer's disease (AD) in humans.
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Affiliation(s)
- Michelle W Voss
- Department of Psychology, The University of Iowa, Iowa City, IA, USA; Aging Mind and Brain Initiative (AMBI), The University of Iowa, Iowa City, IA, USA.
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7
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Stigger F, do Nascimento PS, Dutra MF, Couto GK, Ilha J, Achaval M, Marcuzzo S. Treadmill training induces plasticity in spinal motoneurons and sciatic nerve after sensorimotor restriction during early postnatal period: new insights into the clinical approach for children with cerebral palsy. Int J Dev Neurosci 2011; 29:833-8. [PMID: 21925584 DOI: 10.1016/j.ijdevneu.2011.09.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 08/19/2011] [Accepted: 09/03/2011] [Indexed: 01/23/2023] Open
Abstract
The aim of the present study was to investigate whether locomotor stimulation training could have beneficial effects on the morphometric alterations of spinal cord and sciatic nerve consequent to sensorimotor restriction (SR). Male Wistar rats were exposed to SR from postnatal day 2 (P2) to P28. Control and experimental rats underwent locomotor stimulation training in a treadmill for three weeks (from P31 to P52). The cross-sectional area (CSA) of spinal motoneurons innervating hind limb muscles was determined. Both fiber and axonal CSA of myelinated fibers were also assessed. The growth-related increase in CSA of motoneurons in the SR group was less than controls. After SR, the mean motoneuron soma size was reduced with an increase in the proportion of motoneurons with a soma size of between 0 and 800 μm(2). The changes in soma size of motoneurons were accompanied by a reduction in the mean fiber and axon CSA of sciatic nerve. The soma size of motoneurons was reestablished at the end of the training period reaching controls level. Our results suggest that SR during early postnatal life retards the growth-related increase in the cell body size of motoneurons in spinal cord and the development of sciatic nerve. Additionally, three weeks of locomotor stimulation using a treadmill seems to have a beneficial effect on motoneurons' soma size.
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Affiliation(s)
- Felipe Stigger
- Programa de Pós-Graduação em Neurociências, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, RS, Brazil.
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8
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Abstract
Stem cells are uniquely able to self-renew, to undergo multilineage differentiation, and to persist throughout life in a number of tissues. Stem cells are regulated by a combination of shared and tissue-specific mechanisms and are distinguished from restricted progenitors by differences in transcriptional and epigenetic regulation. Emerging evidence suggests that other aspects of cellular physiology, including mitosis, signal transduction, and metabolic regulation, also differ between stem cells and their progeny. These differences may allow stem cells to be regulated independently of differentiated cells in response to circadian rhythms, changes in metabolism, diet, exercise, mating, aging, infection, and disease. This allows stem cells to sustain homeostasis or to remodel relevant tissues in response to physiological change. Stem cells are therefore not only regulated by short-range signals that maintain homeostasis within their tissue of origin, but also by long-range signals that integrate stem cell function with systemic physiology.
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9
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Nutritional intervention during gestation alters growth, body composition and gene expression patterns in skeletal muscle of pig offspring. Animal 2011; 5:1195-206. [DOI: 10.1017/s1751731111000176] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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10
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Bolós M, Fernandez S, Torres-Aleman I. Oral administration of a GSK3 inhibitor increases brain insulin-like growth factor I levels. J Biol Chem 2010; 285:17693-700. [PMID: 20351102 DOI: 10.1074/jbc.m109.096594] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Reduced brain input of serum insulin-like growth factor I (IGF-I), a potent neurotrophic peptide, may be associated with neurodegenerative processes. Thus, analysis of the mechanisms involved in passage of blood-borne IGF-I into the brain may shed light onto pathological mechanisms in neurodegeneration and provide new drug targets. A site of entrance of serum IGF-I into the brain is the choroid plexus. The transport mechanism for IGF-I in this specialized epithelium involves the IGF-I receptor and the membrane multicargo transporter megalin/LRP2. We have now analyzed this process in greater detail and found that the IGF-I receptor interacts with the transmembrane region of megalin, whereas the perimembrane domain of megalin is required for IGF-I internalization. Furthermore, a GSK3 site within the Src homology 3 domain of the C-terminal region of megalin is a key regulator of IGF-I transport. Thus, inhibition of GSK3 markedly increased internalization of IGF-I, whereas mutation of this GSK3 site abrogated this increase. Notably, oral administration of a GSK3 inhibitor to adult wild-type mice or to amyloid precursor protein/presenilin 1 mice modeling Alzheimer amyloidosis significantly increased brain IGF-I content. These results indicate that pharmacological modulation of IGF-I transport by megalin may be used to increase brain availability of serum IGF-I. Interestingly, GSK3 inhibitors such as those under development to treat Alzheimer disease may show therapeutic efficacy in part by increasing brain IGF-I levels, an effect already reported for other neuroprotective compounds.
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Affiliation(s)
- Marta Bolós
- Cajal Institute, Consejo Superior de Investigaciones Científicas, and Ciberned, Madrid 28002, Spain
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Rosa JS, Galassetti PR. Altered molecular adaptation to exercise in children with type 1 diabetes: beyond hypoglycemia. Pediatr Diabetes 2009; 10:213-26. [PMID: 18828794 DOI: 10.1111/j.1399-5448.2008.00452.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Jaime S Rosa
- Department of Pediatrics, Institute for Clinical Translational Science, University of California, Irvine, Orange, CA 92868, USA
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Groban L, Jobe H, Lin M, Houle T, Kitzman DA, Sonntag W. Effects of short-term treadmill exercise training or growth hormone supplementation on diastolic function and exercise tolerance in old rats. J Gerontol A Biol Sci Med Sci 2008; 63:911-20. [PMID: 18840795 DOI: 10.1093/gerona/63.9.911] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Whether the lusitropic potential of short-term exercise in aged rats is linked to an augmentation in the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and an alteration in the cardiac renin angiotensin system (RAS) is unknown. Old (28-month-old) male, Fischer 344xBrown Norway rats were randomized to 4 weeks of GH supplementation (300 microg subcutaneous, twice daily) or 4 weeks of treadmill running, or were used as sedentary controls. Six-month-old rats, sedentary or exercised, were used as young controls. Training improved exercise capacity in old animals. Exercise and GH attenuated age-related declines in myocardial relaxation despite an exercise-induced suppression of IGF-1. The regulatory protein, sarcoplasmic Ca2+ adenosine triphosphatase (SERCA2), increased with exercise but not GH. Among aged rats, the cardiac RAS was not altered by training or GH. Thus, the signaling pathway underlying the lusitropic benefit of short-term habitual exercise in the aged rat may be distinct from GH-mediated benefits and independent of the cardiac RAS.
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Affiliation(s)
- Leanne Groban
- Department of Anesthesiology, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1009, USA.
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Abstract
Insulin-like growth factor I (IGF-I) is present at high concentrations in the circulation. Tissue-specific genetic ablation has shown that the majority of serum IGF-I is secreted by liver cells, although all major organs synthesize it. IGF-I is an important signal during development, including brain growth. Although the biological role of IGF-I in organs such as muscle or ovary is reasonably well established, its biological significance in the adult brain is far from clear. In this regard, while local IGF-I synthesis decreases during brain development, protein levels remain relatively constant throughout life until old age, where a decline is found, not only in the brain but also in the bloodstream. This mismatch between declining local synthesis early after birth and steady protein levels may be explained by the ability of serum IGF-I to access the brain across the blood-brain-barrier. This peripheral IGF-I input to the brain is a physiologically meaningful process of potential impact in brain diseases. Numerous brain mechanisms are regulated by serum IGF-I. Many of these, such as cell energy modulation or growth and survival are common to other IGF-I target tissues but there are also a number of brain-specific mechanisms regulated by IGF-I which likely underlie the ability of serum IGF-I to modulate the major function of the brain: cognition. We propose that serum IGF-I forms part of the mechanisms involved in the "cognitive reserve" concept of brain responses to homeostasis breakdown. Based on IGF-I pleiotropy not only in brain but elsewhere, we consider that loss of IGF-I function is an important step towards disease.
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Affiliation(s)
- Eva Carro
- Cajal Institute, CSIC, Madrid, Spain
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14
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Implications of chronic heart failure on peripheral vasculature and skeletal muscle before and after exercise training. Heart Fail Rev 2008; 13:21-37. [PMID: 17955365 DOI: 10.1007/s10741-007-9056-8] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The pathophysiology of chronic heart failure (CHF) is typically conceptualized in terms of cardiac dysfunction. However, alterations in peripheral blood flow and intrinsic skeletal muscle properties are also now recognized as mechanisms for exercise intolerance that can be modified by therapeutic exercise. This overview focuses on blood delivery, oxygen extraction and utilization that result from heart failure. Related features of inflammation, changes in skeletal muscle signaling pathways, and vulnerability to skeletal muscle atrophy are discussed. Specific focus is given to the ways in which perfusion and skeletal muscle properties affect exercise intolerance and how peripheral improvements following exercise training increase aerobic capacity. We also identify gaps in the literature that may constitute priorities for further investigation.
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Borda JT, Alvarez X, Mohan M, Hasegawa A, Bernardino A, Jean S, Aye P, Lackner AA. CD163, a marker of perivascular macrophages, is up-regulated by microglia in simian immunodeficiency virus encephalitis after haptoglobin-hemoglobin complex stimulation and is suggestive of breakdown of the blood-brain barrier. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 172:725-37. [PMID: 18276779 DOI: 10.2353/ajpath.2008.070848] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Macrophages and microglia are the major cell types infected by human immunodeficiency virus and simian immunodeficiency virus (SIV) in the central nervous system. Microglia are likely infected in vivo, but evidence of widespread productive infection (ie, presence of viral RNA and protein) is lacking. This conclusion is controversial because, unlike lymphocytes, macrophages and microglia cannot be discreetly immunophenotyped. Of particular interest in the search for additional monocyte/macrophage-lineage cell markers is CD163; this receptor for haptoglobin-hemoglobin (Hp-Hb) complex, which forms in plasma following erythrolysis, is expressed exclusively on cells of monocyte/macrophage lineage. We examined CD163 expression in vitro and in vivo by multiple techniques and at varying times after SIV infection in macaques with or without encephalitis. In normal and acutely SIV-infected animals, and in SIV-infected animals without encephalitis, CD163 expression was detected in cells of monocyte/macrophage lineage, including perivascular macrophages, but not in parenchymal microglia. However, in chronically infected animals with encephalitis, CD163 expression was detected in activated microglia surrounding SIV encephalitis lesions in the presence of Hp-Hb complex, suggesting leakage of the blood-brain barrier. CD163 expression was also induced on microglia in vitro after stimulation with Hp-Hb complex. We conclude that CD163 is a selective marker of perivascular macrophages in normal macaques and during the early phases of SIV infection; however, later in infection in animals with encephalitis, CD163 is also expressed by microglia, which are probably activated as a result of vascular compromise.
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Affiliation(s)
- Juan T Borda
- Division of Comparative Pathology, Tulane National Primate Research Center, Tulane University Health Sciences Center, Covington, Louisiana 70433, USA
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Mejri S, Bchir F, Ben Rayana MC, Ben Hamida J, Ben Slama C. Effect of training on GH and IGF-1 responses to a submaximal exercise in football players. Eur J Appl Physiol 2005; 95:496-503. [PMID: 16151829 DOI: 10.1007/s00421-005-0007-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2005] [Indexed: 10/25/2022]
Abstract
To study the effects of regular football training on basal and exercise induced levels of growth hormone (GH) and insulin-like growth factor (IGF-1), 13 young football players were investigated by a submaximal exercise at the beginning of the sporting season in October (S1), at the middle of the season in January (S2) and at the end in May (S3). At each session, an exercise test on an ergogycle was performed for 25 min, beginning with an incremental exercise to reach 90% of theoretical maximal heart, which was maintained for the last 10 min of the test. Venous blood samples were collected at rest, at the end of the exercise and at 30 and 60 min during the recovery period. Plasma lactate and glucose concentrations increased during exercise with no difference found between sessions. GH level increased with exercise at each session but the response was significantly higher in S1 than in S2 and S3 (P<0.01). The GH area under the curve decreased significantly all along the football season (P<0.01); the IGF-1 level did not significantly change during exercise nor with training. Basal insulin-like growth factor binding protein-3 (IGFBP3) remained stable during the three sessions. Football training decreased significantly the exercise-stimulated GH levels all along the football season but did not have any significant effect on IGF-1 levels or on basal IGFBP3 levels.
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Affiliation(s)
- S Mejri
- Service d'Endocrinologie et Métabolisme, Institut National de Nutrition, 11, Rue Djebel-Lakhdar-Bab Saâdoun, 1007, Tunis, Tunisie
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17
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Sanchez OA, Snow LM, Lowe DA, Serfass RC, Thompson LV. Effects of endurance exercise-training on single-fiber contractile properties of insulin-treated streptozotocin-induced diabetic rats. J Appl Physiol (1985) 2005; 99:472-8. [PMID: 15831797 DOI: 10.1152/japplphysiol.01233.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to characterize the contractile properties of individual skinned muscle fibers from insulin-treated streptozotocin-induced diabetic rats after an endurance exercise training program. We hypothesized that single-fiber contractile function would decrease in the diabetic sedentary rats and that endurance exercise would preserve the function. In the study, 28 rats were assigned to either a nondiabetic sedentary, a nondiabetic exercise, a diabetic sedentary, or a diabetic exercise group. Rats in the diabetic groups received subcutaneous intermediate-lasting insulin daily. The exercise-trained rats ran on a treadmill at a moderate intensity for 60 min, five times per week. After 12 wk, the extensor digitorum longus and soleus muscles were dissected. Single-fiber diameter, Ca2+-activated peak force, specific tension, activation threshold, and pCa50as well as the myosin heavy chain isoform expression (MHC) were determined. We found that in MHC type II fibers from extensor digitorum longus muscle, diameters were significantly smaller from diabetic sedentary rats compared with nondiabetic sedentary rats ( P < 0.001). Among the nondiabetic rats, fiber diameters were smaller with exercise ( P = 0.038). The absolute force-generating capacity of single fibers was lower in muscles from diabetic rats. There was greater specific tension (force normalized to cross-sectional area) by fibers from the rats that followed an endurance exercise program compared with sedentary. From the results, we conclude that alterations in the properties of contractile proteins are not implicated in the decrease in strength associated with diabetes and that endurance-exercise training does not prevent or increase muscle weakness in diabetic rats.
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MESH Headings
- Adaptation, Physiological/physiology
- Animals
- Cells, Cultured
- Diabetes Mellitus, Experimental/chemically induced
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/physiopathology
- Insulin/therapeutic use
- Isometric Contraction
- Muscle Fibers, Skeletal
- Muscle, Skeletal/physiopathology
- Physical Conditioning, Animal/methods
- Physical Endurance
- Rats
- Rats, Sprague-Dawley
- Streptozocin
- Stress, Mechanical
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Affiliation(s)
- Otto A Sanchez
- School of Kinesiology, University of Minnesota Medical School, 420 Delaware Street, Minneapolis, MN 55455, USA
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18
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Fournier M, Huang ZS, Li H, Da X, Cercek B, Lewis MI. Insulin-like growth factor I prevents corticosteroid-induced diaphragm muscle atrophy in emphysematous hamsters. Am J Physiol Regul Integr Comp Physiol 2003; 285:R34-43. [PMID: 12689851 DOI: 10.1152/ajpregu.00177.2002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to evaluate whether recombinant human insulin-like growth factor I (rhIGF-I) could attenuate or prevent diaphragm (DIA) fiber atrophy with corticosteroid (CS) administration to emphysematous (EMP) hamsters. DIA muscle IGF-I responses to CS administration with and without exogenous rhIGF-I administration were evaluated. Three groups were studied: 1) EMP; 2) EMP + triamcinolone (T; 0.4 mg.kg-1.day-1 im); and 3) EMP + T + IGF-I (600 microg/day by constant infusion). After 4 wk, the DIA was analyzed histochemically and biochemically (IGF-I mRNA levels by RT-PCR and endogenous and exogenous IGF-I peptide levels immunochemically). Body weights of EMP-T progressively decreased, while those of EMP and EMP-T-IGF-I remained stable despite similarly reduced food intake in both T groups. DIA weight was reduced with T but preserved with rhIGF-I infusion. DIA fiber proportions were similar among the groups. The cross-sectional areas of types I, IIa, and IIx fibers were reduced (17 to 31%) with T administration but unchanged with rhIGF-I infusion. DIA IGF-I mRNA levels were similar across all groups. By contrast, the endogenous DIA IGF-I levels were reduced (41%) in the EMP-T-IGF-I animals. Total DIA IGF-I levels (endogenous + exogenous) were still significantly reduced. IGF-I immunoreactivity confirmed this reduction in all DIA fibers. We conclude that DIA fiber atrophy with T was completely prevented by exogenous rhIGF-I administration. This effect was likely mediated by the pharmacological influences of exogenously administered rhIGF-I. We speculate that this results from increased bioavailability of free IGF-I to react with muscle receptors. Reduced endogenous IGF-I levels in the DIA likely reflect a negative-feedback influence. These results may have important clinical implications for treatment options to offset the adverse effects of CS on the respiratory muscles in patients with chronic lung disorders.
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Affiliation(s)
- Mario Fournier
- Cedars-Sinai Medical Center, 8700 Beverly Blvd., Rm. 6732, Los Angeles, CA 90048, USA.
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19
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Carro E, Trejo JL, Núñez A, Torres-Aleman I. Brain repair and neuroprotection by serum insulin-like growth factor I. Mol Neurobiol 2003; 27:153-62. [PMID: 12777685 DOI: 10.1385/mn:27:2:153] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The existence of protective mechanisms in the adult brain is gradually being recognized as an important aspect of brain function. For many years, self-repair processes in the post-embryonic brain were considered of minor consequence or nonexistent. This notion dominated the study of neurotrophism. Thus, although the possibility that neurotrophic factors participate in brain function in adult life was prudently maintained, the majority of the studies on the role of trophic factors in the brain were focused on developmental aspects. With the recent recognition that the adult brain keeps a capacity for cell renewal, although limited, a new interest in the regenerative properties of brain tissue has emerged. New findings on the role of insulin-like growth factor I (IGF-I), a potent neurotrophic peptide present at high levels in serum, may illustrate this current trend. Circulating IGF-I is an important determinant of proper brain function in the adult. Its pleiotropic effects range from classical trophic actions on neurons such as housekeeping or anti-apoptotic/ pro-survival effects to modulation of brain-barrier permeability, neuronal excitability, or new neuron formation. More recent findings indicate that IGF-I participates in physiologically relevant neuroprotective mechanisms such as those triggered by physical exercise. The increasing number of neurotrophic features displayed by serum IGF-I reinforces the view of a physiological neuroprotective network formed by IGF-I, and possibly other still uncharacterized signals. Future studies with IGF-I, and hopefully other neurotrophic factors, will surely reveal and teach us how to potentiate the self-reparative properties of the adult brain.
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Affiliation(s)
- Eva Carro
- Laboratory of Neuroendocrinology, Instituto Cajal, CSIC, Madrid, Universidad Autonoma de Madrid, Spain
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20
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Kee AJ, Taylor AJ, Carlsson AR, Sevette A, Smith RC, Thompson MW. IGF-I has no effect on postexercise suppression of the ubiquitin-proteasome system in rat skeletal muscle. J Appl Physiol (1985) 2002; 92:2277-84. [PMID: 12015337 DOI: 10.1152/japplphysiol.01030.2001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Both exercise and insulin-like growth factor I (IGF-I) are known to have major hypertrophic effects in skeletal muscle; however, the interactive effect of exogenous IGF-I and exercise on muscle protein turnover or the ubiquitin-proteasome pathway has not been reported. In the present study, we have examined the interaction between endurance exercise training and IGF-I treatment on muscle protein turnover and the ubiquitin-proteasome pathway in the postexercise period. Adult male rats (270-280 g) were randomized to receive 5 consecutive days of progressive treadmill exercise and/or IGF-I treatment (1 mg. kg body wt(-1). day(-1)). Twenty-four hours after the last bout of exercise, the rate of protein breakdown in incubated muscles was significantly reduced compared with that in unexercised rats. This was associated with a significant reduction in the chymotrypsin-like activity of the proteasome and the rate of ubiquitin-proteasome-dependent casein hydrolysis in muscle extracts from exercised compared with unexercised rats. In contrast, the muscle expression of the 20S proteasome subunit beta-1, ubiquitin, and the 14-kDa E2 ubiquitin-conjugating enzyme was not altered by exercise or IGF-I treatment 24 h postexercise. Exercise had no effect on the rates of total mixed muscle protein synthesis in incubated muscles 24 h postexercise. IGF-I treatment had no effect on muscle weights or the rates of protein turnover 24 h after endurance exercise. These results suggest that a suppression of the ubiquitin-proteasome proteolytic pathway after endurance exercise may contribute to the acute postexercise net protein gain.
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Affiliation(s)
- Anthony J Kee
- Department of Surgery, Royal North Shore Hospital, University of Sydney, St. Leonards, New South Wales 2065, Australia.
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21
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Awede BL, Thissen JP, Lebacq J. Role of IGF-I and IGFBPs in the changes of mass and phenotype induced in rat soleus muscle by clenbuterol. Am J Physiol Endocrinol Metab 2002; 282:E31-7. [PMID: 11739080 DOI: 10.1152/ajpendo.2002.282.1.e31] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Clenbuterol induces hypertrophy and a slow-to-fast phenotype change in skeletal muscle, but the signaling mechanisms remain unclear. We hypothesized that clenbuterol could act via local expression of insulin-like growth factor I (IGF-I). Administration of clenbuterol to 3-mo-old female Wistar rats resulted in a 10 and 13% increase of soleus muscle mass after 3 and 9 days, respectively, reaching 16% after 4 wk. When associated with triiodothyronine, clenbuterol induced a dramatic slow-to-fast phenotype change. In parallel, clenbuterol administration induced in soleus muscle a fivefold increase in IGF-I mRNA levels associated with an eightfold increase in IGF-binding protein (IGFBP)-4 and a fivefold increase of IGFBP-5 mRNA levels on day 3. This increased IGF-I gene expression was associated with an increase in muscle IGF-I content, already detected on day 1 and persisting until day 5 without increase in serum IGF-I concentrations. These data show that muscle hypertrophy induced by clenbuterol is associated with a local increase in muscle IGF-I content. They suggest that clenbuterol-induced muscle hypertrophy could be mediated by local production of IGF-I.
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Affiliation(s)
- Bonaventure L Awede
- Unité de Physiologie Générale des Muscles, Université Catholique de Louvain, 1200 Brussels, Belgium
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22
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Chicharro JL, López-Calderon A, Hoyos J, Martín-Velasco AI, Villa G, Villanúa MA, Lucía A. Effects of an endurance cycling competition on resting serum insulin-like growth factor I (IGF-I) and its binding proteins IGFBP-1 and IGFBP-3. Br J Sports Med 2001; 35:303-7. [PMID: 11579061 PMCID: PMC1724386 DOI: 10.1136/bjsm.35.5.303] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES To determine whether consecutive bouts of intense endurance exercise over a three week period alters serum concentrations of insulin-like growth factor I (IGF-I) and/or its binding proteins. METHODS Seventeen professional cyclists (mean (SEM) VO(2)MAX, 74.7 (2.1) ml/kg/min; age, 27 (1) years) competing in a three week tour race were selected as subjects. Blood samples were collected at each of the following time points: t(0) (control, before the start of competition), t(1) (end of first week), and t(3) (end of third week). Serum levels of both total and free IGF-I and IGF binding proteins 1 and 3 (IGFBP-1 and IGFBP-3) were measured in each of the samples. Cortisol levels were measured in nine subjects. RESULTS A significant (p<0.01) increase was found in total IGF-I and IGFBP-1 at both t(1) and t(3) compared with t(o) (IGF-I: 110.9 (17.7), 186.8 (12.0), 196.9 (14.7) ng/ml at t(0), t(1), and t(3) respectively; IGFBP-1: 54.6 (6.6), 80.6 (8.0), and 89.2 (7.9) ng/ml at t(0), t(1), and t(3) respectively). A significant (p<0.01) decrease was noted in free IGF-I at t(3) compared with both t(o) and t(1) (t(0): 0.9 (0.1) ng/ml; t(1): 0.9 (0.1) ng/ml; t(3): 0.7 (0.1) ng/ml); in contrast, IGFBP-3 levels remained stable throughout the race. CONCLUSIONS It would appear that the increase in circulating levels of both IGF-I and its binding protein IGFBP-1 is a short term (one week) endocrine adaptation to endurance exercise. After three weeks of training, total IGF-I and IGFBP-1 remained stable, whereas free IGF-I fell below starting levels.
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Affiliation(s)
- J L Chicharro
- Departamento de Enfermería, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
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23
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Circulating insulin-like growth factor I mediates exercise-induced increases in the number of new neurons in the adult hippocampus. J Neurosci 2001. [PMID: 11222653 DOI: 10.1523/jneurosci.21-05-01628.2001] [Citation(s) in RCA: 667] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although the physiological significance of continued formation of new neurons in the adult mammalian brain is still uncertain, therapeutic strategies aimed to potentiate this process show great promise. Several external factors, including physical exercise, increase the number of new neurons in the adult hippocampus, but underlying mechanisms are not yet known. We recently found that exercise stimulates uptake of the neurotrophic factor insulin-like growth factor I (IGF-I) from the bloodstream into specific brain areas, including the hippocampus. In addition, IGF-I participates in the effects of exercise on hippocampal c-fos expression and mimics several other effects of exercise on brain function. Because subcutaneous administration of IGF-I to sedentary adult rats markedly increases the number of new neurons in the hippocampus, we hypothesized that exercise-induced brain uptake of blood-borne IGF-I could mediate the stimulatory effects of exercise on the adult hippocampus. Thus, we blocked the entrance of circulating IGF-I into the brain by subcutaneous infusion of a blocking IGF-I antiserum to rats undergoing exercise training. The resulting inhibition of brain uptake of IGF-I was paralleled by complete inhibition of exercise-induced increases in the number of new neurons in the hippocampus. Exercising rats receiving an infusion of nonblocking serum showed normal increases in the number of new hippocampal neurons after exercise. Thus, increased uptake of blood-borne IGF-I is necessary for the stimulatory effects of exercise on the number of new granule cells in the adult hippocampus. Taken together with previous results, we conclude that circulating IGF-I is an important determinant of exercise-induced changes in the adult brain.
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24
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Nindl BC, Kraemer WJ, Marx JO, Arciero PJ, Dohi K, Kellogg MD, Loomis GA. Overnight responses of the circulating IGF-I system after acute, heavy-resistance exercise. J Appl Physiol (1985) 2001; 90:1319-26. [PMID: 11247930 DOI: 10.1152/jappl.2001.90.4.1319] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study evaluated the individual components of the insulin-like growth factor I (IGF-I) system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2 and -3, and the acid-labile subunit (ALS)] in 10 young, healthy men (age: 22 +/- 1 yr, height: 177 +/- 2 cm, weight: 79 +/- 3 kg, body fat: 11 +/- 1%) overnight for 13 h after two conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex). The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-repetition maximum sets with 90-s rest periods between sets. The Ex was performed from 1500 to 1700; blood was obtained immediately postexercise and sampled throughout the night (every 10 min for the first hour and every hour thereafter) until 0600 the next morning. For the first hour, significant differences (P < or = 0.05) were only observed for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2 increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 microg/ml) after exercise. The results from this study suggest that the impact that resistance exercise exerts on the circulating IGF-I system is not in the alteration of the amount of IGF-I but rather of the manner in which IGF-I is partitioned among its family of binding proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system that can be detected in the systemic circulation.
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Affiliation(s)
- B C Nindl
- Intercollege Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania 16801, USA.
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25
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Bamman MM, Shipp JR, Jiang J, Gower BA, Hunter GR, Goodman A, McLafferty CL, Urban RJ. Mechanical load increases muscle IGF-I and androgen receptor mRNA concentrations in humans. Am J Physiol Endocrinol Metab 2001; 280:E383-90. [PMID: 11171591 DOI: 10.1152/ajpendo.2001.280.3.e383] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The mechanism(s) of load-induced muscle hypertrophy is as yet unclear, but increasing evidence suggests a role for locally expressed insulin-like growth factor I (IGF-I). We investigated the effects of concentric (CON) vs. eccentric (ECC) loading on muscle IGF-I mRNA concentration. We hypothesized a greater IGF-I response after ECC compared with CON. Ten healthy subjects (24.4 +/- 0.7 yr, 174.5 +/- 2.6 cm, 70.9 +/- 4.3 kg) completed eight sets of eight CON or ECC squats separated by 6-10 days. IGF-I, IGF binding protein-4 (IGFBP-4), and androgen receptor (AR) mRNA concentrations were determined in vastus lateralis muscle by RT-PCR before and 48 h after ECC and CON. Serum total testosterone (TT) and IGF-I were measured serially across 48 h, and serum creatine kinase activity (CK), isometric maximum voluntary contraction (MVC), and soreness were determined at 48 h. IGF-I mRNA concentration increased 62% and IGFBP-4 mRNA concentration decreased 57% after ECC (P < 0.05). Changes after CON were similar but not significant (P = 0.06-0.12). AR mRNA concentration increased (P < 0.05) after ECC (63%) and CON (102%). Serum TT and IGF-I showed little change. MVC fell 10% and CK rose 183% after ECC (P < 0.05). Perceived soreness was higher (P < 0.01) after ECC compared with CON. Results indicate that a single bout of mechanical loading in humans alters activity of the muscle IGF-I system, and the enhanced response to ECC suggests that IGF-I may somehow modulate tissue regeneration after mechanical damage.
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Affiliation(s)
- M M Bamman
- Department of Human Studies, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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Abstract
The metabolic syndrome is associated with a marked increase in risk of type 2 diabetes and atherosclerotic vascular disease (AVD). The mechanism responsible for the metabolic syndrome is uncertain, but recent evidence suggests that a combination of low birth weight and adult obesity is associated with a markedly increased prevalence. Insulin resistance is the cardinal feature of the metabolic syndrome. Several hormones, have modes of action that either potentiate or reduce the biological actions of insulin and, therefore, attenuate or induce insulin resistance. Since insulin action may be modified, these hormones potentially contribute to the pathogenesis of the metabolic syndrome. The purpose of this review is to discuss programming of hormones that modulate insulin action. The review focuses on two major endocrine pathways: (i) glucocorticoid hormone action; and (ii) the growth hormone (GH)-insulin-like growth factor (IGF-1) axis, and discusses mechanisms linking abnormal activity of these pathways with reduced early growth, adult obesity and the metabolic syndrome.
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Affiliation(s)
- C D Byrne
- Endocrinology and Metabolism Unit, School of Medicine, University of Southampton, Southampton, UK
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Abstract
Physical exercise increases brain activity through mechanisms not yet known. We now report that in rats, running induces uptake of blood insulin-like growth factor I (IGF-I) by specific groups of neurons throughout the brain. Neurons accumulating IGF-I show increased spontaneous firing and a protracted increase in sensitivity to afferent stimulation. Furthermore, systemic injection of IGF-I mimicked the effects of exercise in the brain. Thus, brain uptake of IGF-I after either intracarotid injection or after exercise elicited the same pattern of neuronal accumulation of IGF-I, an identical widespread increase in neuronal c-Fos, and a similar stimulation of hippocampal brain-derived neurotrophic factor. When uptake of IGF-I by brain cells was blocked, the exercise-induced increase on c-Fos expression was also blocked. We conclude that serum IGF-I mediates activational effects of exercise in the brain. Thus, stimulation of the uptake of blood-borne IGF-I by nerve cells may lead to novel neuroprotective strategies.
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