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Liu C, Shao M, Lu L, Zhao C, Qiu L, Liu Z. Obesity, insulin resistance and their interaction on liver enzymes. PLoS One 2021; 16:e0249299. [PMID: 33882064 PMCID: PMC8059853 DOI: 10.1371/journal.pone.0249299] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 03/15/2021] [Indexed: 01/17/2023] Open
Abstract
Introduction To investigate weight status, insulin resistance assessed by HOMA-IR, and their interaction on liver function in non-diabetic Chinese adults. Methods and results A total of 7066 subjects were included, and divided into normal weight (n = 3447), overweight (n = 2801), and obese (n = 818) groups. Data including weight, height, waist circumference, fasting blood glucose, fasting insulin, total cholesterol, triglycerides, y-glutamyl transferase (GGT), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were acquired. In multi-linear regression analysis for liver enzymes as dependent variables, insulin resistance emerged as a determinant of ALT (β = 0.165, P<0.001), AST (β = 0.040, P<0.001) and GGT (β = 0.170, P<0.001) after adjusting for age, sex, body mass index, triglyceride, and cholesterol. Interactions between insulin resistance and weight status by body mass index were observed in ALT (P<0.001), AST (P<0.001) and GGT (P = 0.0418). Conclusion Insulin resistance had significant associations with greater risk of elevated ALT, AST and GGT level in non-diabetic Chinese adults, especially among those who were overweight/ obese.
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Affiliation(s)
- Chenbing Liu
- Department of Health Management, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Min Shao
- Department of Health Management, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ling Lu
- Zhejiang Nutriease Health Technology Company Limited, Hangzhou, China
| | - Chenzhao Zhao
- Department of Health Management, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Lihong Qiu
- Department of Health Management, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Zhong Liu
- Department of Health Management, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
- * E-mail:
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Gundersen AE, Kugler BA, McDonald PM, Veraksa A, Houmard JA, Zou K. Altered mitochondrial network morphology and regulatory proteins in mitochondrial quality control in myotubes from severely obese humans with or without type 2 diabetes. Appl Physiol Nutr Metab 2019; 45:283-293. [PMID: 31356754 DOI: 10.1139/apnm-2019-0208] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Healthy mitochondrial networks are maintained via balanced integration of mitochondrial quality control processes (biogenesis, fusion, fission, and mitophagy). The purpose of this study was to investigate the effects of severe obesity and type 2 diabetes (T2D) on mitochondrial network morphology and expression of proteins regulating mitochondrial quality control processes in cultured human myotubes. Primary human skeletal muscle cells were isolated from biopsies from lean, severely obese nondiabetic individuals and severely obese type 2 diabetic individuals (n = 8-9/group) and were differentiated to myotubes. Mitochondrial network morphology was determined in live cells via confocal microscopy and protein markers of mitochondrial quality control were measured by immunoblotting. Myotubes from severely obese nondiabetic and type 2 diabetic humans exhibited fragmented mitochondrial networks (P < 0.05). Mitochondrial fission protein Drp1 (Ser616) phosphorylation was higher in myotubes from severely obese nondiabetic humans when compared with the lean controls (P < 0.05), while mitophagy protein Parkin expression was lower in myotubes from severely obese individuals with T2D in comparison to the other groups (P < 0.05). These data suggest that regulatory proteins in mitochondrial quality control processes, specifically mitochondrial fission protein Drp1 (Ser616) phosphorylation and mitophagy protein Parkin, are intrinsically dysregulated at cellular level in skeletal muscle from severely obese nondiabetic and type 2 diabetic humans, respectively. These differentially expressed mitochondrial quality control proteins may play a role in mitochondrial fragmentation evident in skeletal muscle from severely obese and type 2 diabetic humans. Novelty Mitochondrial network morphology and mitochondrial quality control proteins are intrinsically dysregulated in skeletal muscle cells from severely obese humans with or without T2D.
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Affiliation(s)
- Anders E Gundersen
- Department of Exercise and Health Sciences, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Benjamin A Kugler
- Department of Exercise and Health Sciences, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Paul M McDonald
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Alexey Veraksa
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Joseph A Houmard
- Human Performance Laboratory, East Carolina University, Greenville, NC 27858, USA.,Department of Kinesiology, East Carolina University, Greenville, NC 27858, USA.,East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27858, USA
| | - Kai Zou
- Department of Exercise and Health Sciences, University of Massachusetts Boston, Boston, MA 02125, USA
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Sevillano J, Sánchez-Alonso MG, Zapatería B, Calderón M, Alcalá M, Limones M, Pita J, Gramage E, Vicente-Rodríguez M, Horrillo D, Medina-Gómez G, Obregón MJ, Viana M, Valladolid-Acebes I, Herradón G, Ramos-Álvarez MP. Pleiotrophin deletion alters glucose homeostasis, energy metabolism and brown fat thermogenic function in mice. Diabetologia 2019; 62:123-135. [PMID: 30327824 DOI: 10.1007/s00125-018-4746-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 08/22/2018] [Indexed: 10/28/2022]
Abstract
AIMS/HYPOTHESIS Pleiotrophin, a developmentally regulated and highly conserved cytokine, exerts different functions including regulation of cell growth and survival. Here, we hypothesise that this cytokine can play a regulatory role in glucose and lipid homeostasis. METHODS To test this hypothesis, we performed a longitudinal study characterising the metabolic profile (circulating variables and tissue mRNA expression) of gene-targeted Ptn-deficient female mice and their corresponding wild-type counterparts at different ages from young adulthood (3 months) to older age (15 months). Metabolic cages were used to investigate the respiratory exchange ratio and energy expenditure, at both 24°C and 30°C. Undifferentiated immortalised mouse brown adipocytes (mBAs) were treated with 0.1 μg/ml pleiotrophin until day 6 of differentiation, and markers of mBA differentiation were analysed by quantitative real-time PCR (qPCR). RESULTS Ptn deletion was associated with a reduction in total body fat (20.2% in Ptn+/+ vs 13.9% in Ptn-/- mice) and an enhanced lipolytic response to isoprenaline in isolated adipocytes from 15-month-old mice (189% in Ptn+/+ vs 273% in Ptn-/- mice). We found that Ptn-/- mice exhibited a significantly lower QUICKI value and an altered lipid profile; plasma triacylglycerols and NEFA did not increase with age, as happens in Ptn+/+ mice. Furthermore, the contribution of cold-induced thermogenesis to energy expenditure was greater in Ptn-/- than Ptn+/+ mice (42.6% and 33.6%, respectively). Body temperature and the activity and expression of deiodinase, T3 and mitochondrial uncoupling protein-1 in the brown adipose tissue of Ptn-/- mice were higher than in wild-type controls. Finally, supplementing brown pre-adipocytes with pleiotrophin decreased the expression of the brown adipocyte markers Cidea (20% reduction), Prdm16 (21% reduction), and Pgc1-α (also known as Ppargc1a, 11% reduction). CONCLUSIONS/INTERPRETATION Our results reveal for the first time that pleiotrophin is a key player in preserving insulin sensitivity, driving the dynamics of adipose tissue lipid turnover and plasticity, and regulating energy metabolism and thermogenesis. These findings open therapeutic avenues for the treatment of metabolic disorders by targeting pleiotrophin in the crosstalk between white and brown adipose tissue.
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Affiliation(s)
- Julio Sevillano
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - María Gracia Sánchez-Alonso
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - Begoña Zapatería
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - María Calderón
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - Martín Alcalá
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - María Limones
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - Jimena Pita
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - Esther Gramage
- Department of Pharmaceutical and Health Sciences, Facultad de Farmacia, Universidad CEU San Pablo, Madrid, Spain
| | - Marta Vicente-Rodríguez
- Department of Pharmaceutical and Health Sciences, Facultad de Farmacia, Universidad CEU San Pablo, Madrid, Spain
| | - Daniel Horrillo
- Department of Basic Sciences of Health, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain
| | - Gema Medina-Gómez
- Department of Basic Sciences of Health, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain
| | - María Jesús Obregón
- Department of Endocrine and Nervous System Pathophysiology, Instituto de Investigaciones Biomédicas 'Alberto Sols', Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Autónoma de Madrid (UAM), Madrid, Spain
| | - Marta Viana
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain
| | - Ismael Valladolid-Acebes
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Gonzalo Herradón
- Department of Pharmaceutical and Health Sciences, Facultad de Farmacia, Universidad CEU San Pablo, Madrid, Spain
| | - María Pilar Ramos-Álvarez
- Department of Chemistry and Biochemistry, Facultad de Farmacia, Universidad CEU San Pablo, Ctra. Boadilla del Monte km 5,3, 28668, Madrid, Spain.
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Abstract
Hepatic steatosis is an underlying feature of nonalcoholic fatty liver disease (NAFLD), which is the most common form of liver disease and is present in up to ∼70% of individuals who are overweight. NAFLD is also associated with hypertriglyceridaemia and low levels of HDL, glucose intolerance, insulin resistance and type 2 diabetes mellitus. Hepatic steatosis is a strong predictor of the development of insulin resistance and often precedes the onset of other known mediators of insulin resistance. This sequence of events suggests that hepatic steatosis has a causal role in the development of insulin resistance in other tissues, such as skeletal muscle. Hepatokines are proteins that are secreted by hepatocytes, and many hepatokines have been linked to the induction of metabolic dysfunction, including fetuin A, fetuin B, retinol-binding protein 4 (RBP4) and selenoprotein P. In this Review, we describe the factors that influence the development of hepatic steatosis, provide evidence of strong links between hepatic steatosis and insulin resistance in non-hepatic tissues, and discuss recent advances in our understanding of how steatosis alters hepatokine secretion to influence metabolic phenotypes through inter-organ communication.
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Affiliation(s)
- Ruth C R Meex
- Monash Biomedicine Discovery Institute, Metabolic Disease and Obesity Program and the Department of Physiology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
- Department of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Matthew J Watt
- Monash Biomedicine Discovery Institute, Metabolic Disease and Obesity Program and the Department of Physiology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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Schumann U, Jenkinson CP, Alt A, Zügel M, Steinacker JM, Flechtner-Mors M. Sympathetic nervous system activity and anti-lipolytic response to iv-glucose load in subcutaneous adipose tissue of obese and obese type 2 diabetic subjects. PLoS One 2017; 12:e0173803. [PMID: 28346464 PMCID: PMC5367786 DOI: 10.1371/journal.pone.0173803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 02/16/2017] [Indexed: 01/25/2023] Open
Abstract
The study aim was to investigate the effect of endogenous insulin release on lipolysis in subcutaneous adipose tissue after adrenergic stimulation in obese subjects diagnosed with type 2 diabetes (T2D). In 14 obese female T2D subjects, or 14 obese non-T2D controls, glycerol concentration was measured in response to the α1,2,ß-agonist norepinephrine, the α1-agonist norfenefrine and the ß2-agonist terbutaline (each 10-4 M), using the microdialysis technique. After 60 minutes of stimulation, an intravenous glucose load (0.5 g/kg lean body mass) was given. Local blood flow was monitored by means of the ethanol technique. Norepinephrine and norfenefrine induced a four and three fold rise in glycerol dialysate concentration (p<0.001, each), with a similar pattern in adipose tissue. Following agonist stimulation and glucose infusion, endogenous insulin release inhibited lipolysis in the presence of norepinephrine, which was more rapid and pronounced in healthy obese controls than in T2D subjects (p = 0.024 obese vs T2D subjects). Insulin-induced inhibition of lipolysis in the presence of norfenefrine was similar in all study participants. In the presence of terbutaline the lipolysis rate increased two fold until the effect of endogenous insulin (p<0.001). A similar insulin-induced decrease in lipolysis was observed for each of the norfenefrine groups and the terbutaline groups, respectively. Adipose tissue blood flow remained unchanged after the iv-glucose load. Both norepinephrine and norfenefrine diminished blood flow slightly, but insulin reversed this response (p<0.001 over the entire time). Terbutaline alone and terbutaline plus increased endogenous insulin augmented local blood flow (p<0.001 over the entire time). In conclusion, a difference in insulin-induced inhibition of lipolysis was observed in obese T2D subjects compared to obese healthy controls following modulation of sympathetic nervous system activity and is assumed to be due to ß1-adrenoceptor mediated stimulation by norepinephrine.
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Affiliation(s)
- Uwe Schumann
- Division of Sports and Rehabilitation Medicine, Medical Center, University of Ulm, Ulm, Germany
| | - Christopher P. Jenkinson
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley, Harlingen, Texas, United States of America
| | - Andreas Alt
- Institute of Legal Medicine, University of Ulm, Ulm, Germany
| | - Martina Zügel
- Division of Sports and Rehabilitation Medicine, Medical Center, University of Ulm, Ulm, Germany
| | - Jürgen M. Steinacker
- Division of Sports and Rehabilitation Medicine, Medical Center, University of Ulm, Ulm, Germany
| | - Marion Flechtner-Mors
- Division of Sports and Rehabilitation Medicine, Medical Center, University of Ulm, Ulm, Germany
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Dongway AC, Faggad AS, Zaki HY, Abdalla BE. C-reactive protein is associated with low-density lipoprotein cholesterol and obesity in type 2 diabetic Sudanese. Diabetes Metab Syndr Obes 2015; 8:427-35. [PMID: 26379442 PMCID: PMC4567170 DOI: 10.2147/dmso.s85451] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Type 2 diabetes is emerging in Sudan and is associated with obesity. Deregulated lipid metabolism and inflammatory states are suggested risk factors for cardiovascular disease, which is a leading cause of diabetic death. This study aimed to investigate C-reactive protein (CRP) levels and the lipid profile in type 2 diabetic adult Sudanese compared with nondiabetics, and to test their associations with other characteristics. METHODS A cross-sectional study including 70 diabetics and 40 nondiabetics was conducted. Anthropometric measurements were assessed, and demographic and medical data were obtained using a structured questionnaire. Blood specimens were collected and biochemical parameters were analyzed applying standard methods. RESULTS CRP and triglycerides were significantly higher in the diabetic group (P<0.001 and P=0.01, respectively). Differences in total cholesterol, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were not statistically significant between the diabetic and nondiabetic groups. In the diabetic group, correlation analysis revealed that the CRP level had a significant positive correlation with LDL-C (r=0.255, P=0.034) and body mass index (r=0.29, P=0.016). Body mass index showed a significant positive correlation with triglycerides (r=0.386, P=0.001). Within the lipid parameters, a number of significant correlations were observed. Elevated levels of CRP, LDL-C, and triglycerides were markedly more prevalent in the diabetic group of patients. Diabetics showed significantly higher CRP levels compared with nondiabetics (odds ratio 5.56, P=0.001). CONCLUSION The high prevalence of obesity among diabetics, together with elevated levels of triglycerides and CRP, suggest coexistence of dyslipidemia and inflammation in diabetes. Our findings emphasize that diabetics were 5.6 times more likely to have high CRP levels than nondiabetics; as CRP is a predictor of cardiovascular disease risk, it can be recognized that diabetics are at more risk of cardiovascular disease than nondiabetics. Considering evaluation of CRP together with the lipid profile in prediction of cardiovascular disease risk in Sudanese diabetics should be further tested in large-scale studies.
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Affiliation(s)
- Angelo C Dongway
- Department of Biochemistry, Faculty of Medicine, Upper Nile University, Malakal, South Sudan
| | - Areeg S Faggad
- Department of Biochemistry and Nutrition, Faculty of Medicine, University of Gezira
- Department of Molecular Biology, National Cancer Institute-University of Gezira, Wad Medani, Sudan
- Correspondence: Areeg S Faggad, PO Box 20, Department of Molecular Biology, National cancer institute-University of Gezira, Wad Medani, Sudan, Email
| | - Hani Y Zaki
- Department of Biochemistry and Nutrition, Faculty of Medicine, University of Gezira
| | - Badreldin E Abdalla
- Department of Biochemistry and Nutrition, Faculty of Medicine, University of Gezira
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
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Abstract
OBJECTIVE Although elevated free fatty acid (FFA) levels in obesity have been considered to be of importance for insulin resistance, a recent meta-analysis suggested normal FFA levels in obese subjects. We investigated fasting circulating FFA and glycerol levels in a large cohort of non-obese and obese subjects. METHODS Subjects recruited for a study on obesity genetics were investigated in the morning after an overnight fast (n = 3,888). Serum FFA (n = 3,306), plasma glycerol (n = 3,776), and insulin sensitivity index (HOMA-IR,n = 3,469) were determined. Obesity was defined as BMI ≥ 30 kg/m 2 and insulin resistance as HOMA-IR ≥ 2.21. RESULTS In obese subjects, circulating FFA and glycerol levels were higher than in non-obese individuals (by 26% and 47%, respectively; both p < 0.0001). Similar results were obtained if only men, women or medication-free subjects were investigated. Insulin resistance and type 2 diabetes were associated with a further minor increase in FFA/glycerol among obese subjects. When comparing insulin-sensitive non-obese with insulin-sensitive or -resistant obese individuals, FFA and glycerol were 21–29% and 43–49% higher in obese individuals, respectively. CONCLUSION Circulating FFA and glycerol levels are markedly elevated in obesity but only marginally influenced by insulin resistance and type 2 diabetes. Whether these differences persist during diurnal variations in circulating FFA/glycerol, remains to be established
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Affiliation(s)
| | - Mikael Rydén
- *Prof. Dr. Dr. Mikael Rydén, C2-94, Karolinska Institutet, Department of Medicine (H7) and, Division of Endocrinology and Metabolism, Karolinska University Hospital, Huddinge, 141 86 Stockholm, Sweden,
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8
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Ramírez CM, Lin CS, Abdelmohsen K, Goedeke L, Yoon JH, Madrigal-Matute J, Martin-Ventura JL, Vo DT, Uren PJ, Penalva LO, Gorospe M, Fernández-Hernando C. RNA binding protein HuR regulates the expression of ABCA1. J Lipid Res 2014; 55:1066-76. [PMID: 24729624 DOI: 10.1194/jlr.m044925] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Indexed: 12/31/2022] Open
Abstract
ABCA1 is a major regulator of cellular cholesterol efflux and plasma HDL biogenesis. Even though the transcriptional activation of ABCA1 is well established, the posttranscriptional regulation of ABCA1 expression is poorly understood. Here, we investigate the potential contribution of the RNA binding protein (RBP) human antigen R (HuR) on the posttranscriptional regulation of ABCA1 expression. RNA immunoprecipitation assays demonstrate a direct interaction between HuR and ABCA1 mRNA. We found that HuR binds to the 3' untranslated region of ABCA1 and increases ABCA1 translation, while HuR silencing reduces ABCA1 expression and cholesterol efflux to ApoA1 in human hepatic (Huh-7) and monocytic (THP-1) cells. Interestingly, cellular cholesterol levels regulate the expression, intracellular localization, and interaction between HuR and ABCA1 mRNA. Finally, we found that HuR expression was significantly increased in macrophages from human atherosclerotic plaques, suggesting an important role for this RBP in controlling macrophage cholesterol metabolism in vivo. In summary, we have identified HuR as a novel posttranscriptional regulator of ABCA1 expression and cellular cholesterol homeostasis, thereby opening new avenues for increasing cholesterol efflux from atherosclerotic foam macrophages and raising circulat-ing HDL cholesterol levels.
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Affiliation(s)
- Cristina M Ramírez
- Vascular Biology and Therapeutics Program, Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520 Departments of Medicine and Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Chin Sheng Lin
- Departments of Medicine and Cell Biology, New York University School of Medicine, New York, NY 10016 Division of Cardiology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Kotb Abdelmohsen
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Leigh Goedeke
- Vascular Biology and Therapeutics Program, Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520 Departments of Medicine and Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Je-Hyun Yoon
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Julio Madrigal-Matute
- Departments of Medicine and Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Jose L Martin-Ventura
- Vascular Research Lab, IIS-Fundación Jimenez Díaz, Autónoma University, Madrid 28040, Spain
| | - Dat T Vo
- Children's Cancer Research Institute, Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Philip J Uren
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Luiz O Penalva
- Children's Cancer Research Institute, Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Myriam Gorospe
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Carlos Fernández-Hernando
- Vascular Biology and Therapeutics Program, Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520 Departments of Medicine and Cell Biology, New York University School of Medicine, New York, NY 10016
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Kuang J, Hou X, Zhang J, Chen Y, Su Z. Identification of insulin as a novel retinoic acid receptor-related orphan receptor α target gene. FEBS Lett 2014; 588:1071-9. [PMID: 24583012 DOI: 10.1016/j.febslet.2014.02.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Revised: 01/27/2014] [Accepted: 02/14/2014] [Indexed: 02/05/2023]
Abstract
Insulin plays an important role in regulation of lipid and glucose metabolism. Retinoic acid receptor-related orphan receptor α (RORα) modulates physiopathological processes such as dyslipidemia and diabetes. In this study, we found overexpression of RORα in INS1 cells resulted in increased expression and secretion of insulin. Suppression of endogenous RORα caused a decrease of insulin expression. Luciferase and electrophoretic mobility shift assay (EMSA) assays demonstrated that RORα activated insulin transcription via direct binding to its promoter. RORα was also observed to regulate BETA2 expression, which is one of the insulin active transfactors. In vivo analyses showed that the insulin transcription is increased by the synthetic RORα agonist SR1078. These findings identify RORα as a transcriptional activator of insulin and suggest novel therapeutic opportunities for management of the disease.
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Affiliation(s)
- Jiangying Kuang
- Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Xiaoming Hou
- Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Jinlong Zhang
- Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yulong Chen
- Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Zhiguang Su
- Molecular Medicine Research Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
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Schuster DP. Obesity and the development of type 2 diabetes: the effects of fatty tissue inflammation. Diabetes Metab Syndr Obes 2010; 3:253-62. [PMID: 21437093 PMCID: PMC3047970 DOI: 10.2147/dmsott.s7354] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Obesity is a worldwide epidemic with multiple obesity-associated health problems including type 2 diabetes, hypertension, and cardiovascular disease. Adipose tissue serves as a fuel storage depot, but also plays a pivotal role in homeostasis of energy expenditure, appetite regulation, glucose regulation, and immunity. Both genetics and environment play important roles in adipose tissue function and dysfunction. Obesity represents an abnormal accumulation of adipose tissue resulting from chronic overnutrition and reduced physical activity. The nature of this increased accumulation of fat tissue, whether hyperplasia or hypertrophy, local or ectopic, is associated with deleterious perturbations including excess fatty acid secretion, increased production of inflammatory cytokines, and abnormal adipocyte hormone signaling resulting in insulin resistance. In the setting of obesity, insulin resistance and chronic inflammation is postulated to play a role in development of type 2 diabetes and other obesity-related comorbidities including obstructive sleep apnea, hepatic steatosis, polycystic ovarian syndrome, hypertension and cardiovascular disease. Although the exact mechanism of these relationships are complex and not completely understood, the ability to store and limit fatty acid deposition to adipose tissue is a common component to remaining insulin sensitive, controlling the inflammatory cascade and reducing the risk of developing obesity-related comorbidities.
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Affiliation(s)
- Dara P Schuster
- Correspondence: Dara P Schuster, 491 McCampbell Hall, 1581 Dodd Drive, Columbus, Ohio 43210, USA, Tel +1 614 292 0678, Fax +1 614 292 1550, Email
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11
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Abstract
Obesity has reached epidemic proportions in the USA with a nearly fourfold rise in the prevalence of childhood obesity. There are many possible etiologies of obesity as the adipose tissue plays a significant, complex role in the physiology of fuel metabolism and hormone regulation. The development of obesity represents a pathophysiologic increase in fat mass in which multiple metabolic pathways are deranged. The consequences of these metabolic derangements, including insulin resistance and inflammation, are reflected in obesity-related comorbidities and can be seen in the setting of pediatric obesity. Obese adolescents demonstrate increased rates of early maturation, orthopedic growth abnormalities, diabetes mellitus, obstructive sleep apnea, hypertension, steatosis, and polycystic ovarian syndrome, placing this group of children at risk for long-term health problems and reduced quality of life. Given the negative short- and long-term impact of obesity on children, careful attention should be paid to the unique health issues of this "at-risk" population with both prevention and early intervention strategies.
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Affiliation(s)
- Dara P Schuster
- Division of Endocrinology, Department of Pediatrics, The Ohio State University Hospitals and Nationwide Children's Hospital, Columbus, Ohio 43210, USA.
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12
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Miccoli R, Bianchi C, Penno G, Del Prato S. Insulin resistance and lipid disorders. ACTA ACUST UNITED AC 2008. [DOI: 10.2217/17460875.3.6.651] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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13
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Khan NA. Role of lipids and fatty acids in macrosomic offspring of diabetic pregnancy. Cell Biochem Biophys 2007; 48:79-88. [PMID: 17709877 DOI: 10.1007/s12013-007-0019-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/21/2022]
Abstract
Diabetic pregnancy frequently results in macrosomia or fetal obesity. It seems that the anomalies in carbohydrate and lipid metabolism in macrosomic infants of diabetic mothers are due to maternal hyperglycemia, which leads to fetal hyperinsulinemia. We have developed a rat model of macrosomic offspring and assessed the onset of obesity in these animals. The macrosomic offspring born to diabetic mothers are prone to the development of glucose intolerance and obesity as a function of age. It seems that in utero programming during diabetic pregnancy creates a "metabolic memory" which is responsible for the development of obesity in macrosomic offspring. We have demonstrated that the metabolism of lipids, and altered anti-oxidant status and immune system are implicated in the etiopathology of obesity in these animals. We have reported beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) in obese animals, born to diabetic dams.
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Affiliation(s)
- Naim Akhtar Khan
- Department of Physiology, UPRES Lipides & Signalisation Cellulaire, Université de Bourgogne, Dijon, France.
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14
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Penno G, Miccoli R, Pucci L, Del Prato S. The metabolic syndrome. Pharmacol Res 2006; 53:457-68. [PMID: 16714121 DOI: 10.1016/j.phrs.2006.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Accepted: 03/17/2006] [Indexed: 11/23/2022]
Affiliation(s)
- Giuseppe Penno
- Department of Endocrinology & Metabolism, Section of Diabetes and Metabolic Diseases, University of Pisa, Italy
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15
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Wang H, Reaves LA, Edens NK. Ginseng extract inhibits lipolysis in rat adipocytes in vitro by activating phosphodiesterase 4. J Nutr 2006; 136:337-42. [PMID: 16424109 DOI: 10.1093/jn/136.2.337] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Elevated concentrations of plasma free fatty acids (FFA) may cause insulin resistance. Inhibition of lipolysis reduces FFA availability and improves insulin sensitivity. Ginseng extract (Panax spp., GE) was shown to improve glycemia in Type 2 diabetes. In the present study, the antilipolytic effect of GE in rat adipocytes and the signaling pathway for GE antilipolysis were investigated. Adipocytes were isolated from rat fat tissue by collagenase digestion. The ability of GE to inhibit lipolysis was assessed by measuring glycerol and FFA release into the incubation medium. Phosphatidylinositol 3-kinase (PI3-K) inhibitor and various phosphodiesterase (PDE) inhibitors were applied to investigate the signaling pathway for GE antilipolysis. The present study showed that insulin and GE inhibited lipolysis by 42.4 and 49% compared with basal, respectively (P < 0.05). Unlike insulin, the PI3-K inhibitor wortmannin did not reverse GE antilipolysis, and GE did not affect phosphorylation of protein kinase B (PKB). The nonselective PDE inhibitor enprofylline reversed both insulin and GE antilipolysis. The specific phosphodiesterase 3 (PDE3) inhibitor cilostamide reversed insulin antilipolysis completely, but did not significantly affect GE antilipolysis. The specific phosphodiesterase 4 (PDE4) inhibitor rolipram did not significantly affect insulin antilipolysis, but almost completely reversed GE antilipolysis. Moreover, the combination of PDE3 and PDE4 inhibitors completely reversed GE antilipolysis. None of the ginsenosides (Rb1, Re, Rg1, Rc, Rb2, and Rd) were responsible for GE antilipolysis. The results suggest that ginseng exerts its antilipolytic effect through a signaling pathway different from that of insulin. GE antilipolysis is mediated in part by activating PDE4 in rat adipocytes.
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Affiliation(s)
- Hong Wang
- The Ohio State University, Columbus, OH 43210, USA
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16
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Virtanen KA, Hällsten K, Parkkola R, Janatuinen T, Lönnqvist F, Viljanen T, Rönnemaa T, Knuuti J, Huupponen R, Lönnroth P, Nuutila P. Differential effects of rosiglitazone and metformin on adipose tissue distribution and glucose uptake in type 2 diabetic subjects. Diabetes 2003; 52:283-90. [PMID: 12540598 DOI: 10.2337/diabetes.52.2.283] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We evaluated the effects of rosiglitazone (4 mg b.i.d.) and metformin (1 g b.i.d.) monotherapy for 26 weeks on adipose tissue insulin-stimulated glucose uptake in patients (n = 41) with type 2 diabetes. Before and after the treatment, glucose uptake was measured using 2-[(18)F]fluoro-2-deoxyglucose and positron emission tomography and adipose tissue masses were quantified using magnetic resonance imaging. Rosiglitazone improved insulin-stimulated whole-body glucose uptake by 44% (P < 0.01 vs. placebo). Mean body weight was unchanged in the rosiglitazone group, while it decreased by 2.0 kg in the metformin group (P < 0.05 vs. placebo). In visceral adipose tissue, glucose uptake increased by 29% (from 17.8 +/- 2.0 to 23.0 +/- 2.6 micro mol x kg(-1) x min(-1), P < 0.05 vs. placebo) in the rosiglitazone group but to a lesser extent (17%) in the metformin group (from 16.2 +/- 1.5 to 18.9 +/- 1.7 micro mol x kg(-1) x min(-1), P < 0.05 vs. baseline). Because the visceral adipose tissue mass simultaneously decreased with both treatments (P < 0.05), no change was observed in total visceral glucose uptake per depot. Rosiglitazone significantly enhanced glucose uptake in the femoral subcutaneous area, either when expressed per tissue mass (from 10.8 +/- 1.2 to 17.1 +/- 1.7 micro mol x kg(-1) x min(-1), P < 0.01 vs. placebo) or per whole-fat depot (P < 0.05 vs. placebo). In conclusion, metformin treatment resulted in improvement of glycemic control without enhancement of peripheral insulin sensitivity. The improved insulin sensitivity of the nonabdominal subcutaneous adipose tissue during treatment with rosiglitazone partly explains the enhanced whole-body insulin sensitivity and underlies the central role of adipose tissue for action of peroxisome proliferator-activated receptor gamma agonist in vivo.
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Affiliation(s)
- Kirsi A Virtanen
- Turku PET Centre, University of Turku and Turku University Hospital, Finland
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17
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Hällsten K, Virtanen KA, Lönnqvist F, Sipilä H, Oksanen A, Viljanen T, Rönnemaa T, Viikari J, Knuuti J, Nuutila P. Rosiglitazone but not metformin enhances insulin- and exercise-stimulated skeletal muscle glucose uptake in patients with newly diagnosed type 2 diabetes. Diabetes 2002; 51:3479-85. [PMID: 12453903 DOI: 10.2337/diabetes.51.12.3479] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Rosiglitazone, a thiazolidinedione, enhances peripheral insulin sensitivity in patients with type 2 diabetes. Because the synergic action of insulin and exercise has been shown to be decreased in insulin resistance, the aim of this study was to compare the effects of rosiglitazone and metformin on muscle insulin responsiveness at rest and during exercise in patients with type 2 diabetes. Therefore, 45 patients with newly diagnosed or diet-treated type 2 diabetes were randomized for treatment with rosiglitazone (4 mg b.i.d.), metformin (1 g b.i.d.), or placebo in a 26-week double-blind trial. Skeletal muscle glucose uptake was measured using fluorine-18-labeled fluoro-deoxy-glucose and positron emission tomography (PET) during euglycemic-hyperinsulinemic clamp and one-legged exercise before and after the treatment period. Rosiglitazone (P < 0.05) and metformin (P < 0.0001) treatment lowered the mean glycosylated hemoglobin. The skeletal muscle glucose uptake was increased by 38% (P < 0.01) and whole-body glucose uptake by 44% in the rosiglitazone group. Furthermore, the exercise-induced increment during insulin stimulation was enhanced by 99% (P < 0.0001). No changes were observed in skeletal muscle or whole-body insulin sensitivity in the metformin group. In conclusion, rosiglitazone but not metformin 1) improves insulin responsiveness in resting skeletal muscle and 2) doubles the insulin-stimulated glucose uptake rate during physical exercise in patients with type 2 diabetes. Our results suggest that rosiglitazone improves synergic action of insulin and exercise.
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Affiliation(s)
- Kirsti Hällsten
- Turku PET Centre, University of Turku, FIN-20521 Turku, Finland
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18
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Merzouk H, Madani S, Hichami A, Prost J, Belleville J, Khan NA. Age-related changes in fatty acids in obese offspring of streptozotocin-induced diabetic rats. OBESITY RESEARCH 2002; 10:703-14. [PMID: 12105294 DOI: 10.1038/oby.2002.95] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE The long-term effects of fetal hyperinsulinemia, time course of changes in liver and very-low-density lipoprotein (VLDL) lipid levels and fatty acid compositions were investigated in obese offspring of streptozotocin-induced mildly diabetic rats. RESEARCH METHODS AND PROCEDURES Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on day 5 of gestation. Control pregnant rats were injected with citrate buffer. Liver and VLDL lipids and fatty acids were analyzed in offspring at different ages. RESULTS At birth, obese pups had higher VLDL triglyceride levels, saturated fatty acids, and C20:4n-6. They also had lower C18:2n-6 proportions in VLDL triglycerides, phospholipids, and cholesteryl esters than controls pups. In 1-month-old male and female obese rats, VLDL and liver lipid amounts were similar to those in their respective controls; however, high levels of C18:2n-6 and C20:4n-6 were noted in liver and VLDL lipids. At the age of 2 months, liver and VLDL triglyceride levels were higher in obese females than in control females. Fatty acid abnormalities seen in obese rats included low C18:3n-3 and high C22:6n-3 proportions in liver triglycerides and phospholipids. At the age of 3 months, obese rats, both males and females, compared with control animals, had higher VLDL and hepatic lipids with reduced C20:4n-6 levels and polyunsaturated/saturated fatty acids ratios in hepatic and VLDL triglycerides and phospholipids. DISCUSSION Fetal obesity, associated with alterations in VLDL lipid fatty acid composition, represents an important risk factor for adult obesity and diabetes.
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Affiliation(s)
- Hafida Merzouk
- Laboratory of Animal Physiology, Tlemcen University, Tlemcen, Algeria
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19
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McTernan PG, Harte AL, Anderson LA, Green A, Smith SA, Holder JC, Barnett AH, Eggo MC, Kumar S. Insulin and rosiglitazone regulation of lipolysis and lipogenesis in human adipose tissue in vitro. Diabetes 2002; 51:1493-8. [PMID: 11978647 DOI: 10.2337/diabetes.51.5.1493] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lipolysis is an important process determining fuel metabolism, and insulin regulates this process in adipose tissue. The aim of this study was to investigate the long-term effects of insulin, an insulin enhancer (rosiglitazone [RSG]), and insulin in combination with RSG on the regulation of lipolysis and lipogenesis in human abdominal subcutaneous fat. Lipolysis and lipogenesis were assessed by protein expression studies of hormone-sensitive lipase (HSL) (84 kDa) and lipoprotein lipase (LPL) (56 kDa), respectively. In addition, lipolytic rate was assessed by glycerol release assay and tumor necrosis factor (TNF)-alpha release measured by enzyme-linked immunosorbent assay (n = 12). In subcutaneous adipocytes, increasing insulin doses stimulated LPL expression, with maximal stimulation at 100 nmol/l insulin (control, 1.0 +/- 0.0 [mean +/- SE, protein expression relative to control]; 1 nmol/l insulin, 0.87 +/- 0.13; 100 nmol/l insulin, 1.68 +/- 0.19; P < 0.001). In contrast, insulin at the 100 nmol/l dose reduced the expression of HSL (100 nmol/l insulin, 0.49 +/- 0.05; P < 0.05), while no significant reduction was observed at other doses. Higher doses of insulin stimulated both HSL (1,000 nmol/l insulin, 1.4 +/- 0.07; P < 0.01) and LPL (control 1.00 +/- 0.0; 1,000 nmol/l insulin, 2.66 +/- 0.27; P < 0.01) protein expression. Cotreatment with RSG induced an increased dose response to insulin for LPL and HSL (P < 0.05); RSG alone also increased LPL and HSL expression (P < 0.05). Insulin stimulated TNF-alpha secretion in a dose-dependent manner (P < 0.01); the addition of RSG (10(-8) mol/l) reduced TNF-alpha secretion (P < 0.05). In summary, chronic treatment of human adipocytes with insulin stimulates lipolysis and LPL protein expression. The addition of RSG reduced the lipolytic rate and TNF-alpha secretion. The increase in lipolysis is not explained by changes in HSL expression. These data, therefore, may explain in part why hyperinsulinemia coexists with increased circulating nonesterified free fatty acids and increased adiposity in obese and/or type 2 diabetic patients.
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Affiliation(s)
- Philip G McTernan
- Division of Medical Sciences, Department of Medicine, University of Birmingham and Heartlands Hospital, Edgbaston, Birmingham, UK.
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20
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Lewis GF, Carpentier A, Adeli K, Giacca A. Disordered fat storage and mobilization in the pathogenesis of insulin resistance and type 2 diabetes. Endocr Rev 2002; 23:201-29. [PMID: 11943743 DOI: 10.1210/edrv.23.2.0461] [Citation(s) in RCA: 744] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The primary genetic, environmental, and metabolic factors responsible for causing insulin resistance and pancreatic beta-cell failure and the precise sequence of events leading to the development of type 2 diabetes are not yet fully understood. Abnormalities of triglyceride storage and lipolysis in insulin-sensitive tissues are an early manifestation of conditions characterized by insulin resistance and are detectable before the development of postprandial or fasting hyperglycemia. Increased free fatty acid (FFA) flux from adipose tissue to nonadipose tissue, resulting from abnormalities of fat metabolism, participates in and amplifies many of the fundamental metabolic derangements that are characteristic of the insulin resistance syndrome and type 2 diabetes. It is also likely to play an important role in the progression from normal glucose tolerance to fasting hyperglycemia and conversion to frank type 2 diabetes in insulin resistant individuals. Adverse metabolic consequences of increased FFA flux, to be discussed in this review, are extremely wide ranging and include, but are not limited to: 1) dyslipidemia and hepatic steatosis, 2) impaired glucose metabolism and insulin sensitivity in muscle and liver, 3) diminished insulin clearance, aggravating peripheral tissue hyperinsulinemia, and 4) impaired pancreatic beta-cell function. The precise biochemical mechanisms whereby fatty acids and cytosolic triglycerides exert their effects remain poorly understood. Recent studies, however, suggest that the sequence of events may be the following: in states of positive net energy balance, triglyceride accumulation in "fat-buffering" adipose tissue is limited by the development of adipose tissue insulin resistance. This results in diversion of energy substrates to nonadipose tissue, which in turn leads to a complex array of metabolic abnormalities characteristic of insulin-resistant states and type 2 diabetes. Recent evidence suggests that some of the biochemical mechanisms whereby glucose and fat exert adverse effects in insulin-sensitive and insulin-producing tissues are shared, thus implicating a diabetogenic role for energy excess as a whole. Although there is now evidence that weight loss through reduction of caloric intake and increase in physical activity can prevent the development of diabetes, it remains an open question as to whether specific modulation of fat metabolism will result in improvement in some or all of the above metabolic derangements or will prevent progression from insulin resistance syndrome to type 2 diabetes.
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Affiliation(s)
- Gary F Lewis
- Department of Medicine, Division of Endocrinology, University of Toronto, Canada M5G 2C4.
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21
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Abstract
Type 2 diabetes is a heterogeneous disorder due to prevalent insulin resistance associated with deficient insulin secretion or to a prevalent defect of insulin secretion associated with impaired insulin action. The definition is supported by the high frequency at which insulin resistance can be demonstrated in type 2 diabetic patients. Nonetheless, insulin resistance is not a sufficient mechanism to cause diabetes. Impaired beta-cell function is a necessary defect in all conditions of impaired glucose regulation; however, it manifests itself in a different manner in fasting and glucose-stimulated conditions. In the fasting state, the basal insulin secretory rate increases as a function of the progressive decline in insulin action. As such, the fasting plasma insulin concentration is often taken as a marker for insulin sensitivity. After glucose challenge, a specific alteration of acute insulin release is an early and progressive defect. The latter might represent an intrinsic defect, but its continuous decline is affected by glucotoxicity and lipotoxicity. To understand the impact of beta-cell dysfunction in type 2 diabetes on metabolic homeostasis, it is useful to consider the different phases of insulin secretion separately. Insulin secretion can be divided into basal (postabsorptive) and stimulated (postprandial) states. The former prevails during the interprandial phases and plays a major role during the overnight fast; the latter regulates glucose metabolism when carbohydrate is abundant and must be disposed of. Data in animals and humans support a crucial physiological role of first-phase insulin secretion in postprandial glucose homeostasis. This effect is primarily achieved in the liver, allowing prompt inhibition of endogenous glucose production and limiting the postprandial rise in plasma glucose level. In type 2 diabetes, loss of the early surge of insulin release is an early and quite common defect that may have a pathogenetic role in the development of postprandial hyperglycemia, possibly requiring specific therapeutic intervention.
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Affiliation(s)
- Stefano Del Prato
- Department of Endocrinology and Metabolism, Section of Diabetes, University of Pisa, Pisa, Italy.
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22
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Abstract
The role of postprandial hyperglycemia (PPHG) in diabetes mellitus is being increasingly recognized. It is known that PPHG contributes to the increased risk of both micro- and macrovascular complications in patients with diabetes mellitus. This review looks at the clinical significance of PPHG and the currently available therapeutic modalities. The causes of PPHG are influenced by many factors which include a rapid flux of glucose from the gut, impaired insulin release, endogenous glucose production by the liver and peripheral insulin resistance. Knowledge of the pathophysiology of PPHG is essential when adopting treatment options to tackle the problem. Although most oral antihyperglycemic agents and insulins lower both fasting and postprandial blood glucose levels, drugs are now available which specifically act to control PPHG. These drugs may be classified based on the site of their action. alpha-Glucosidase inhibitors like acarbose and miglitol attenuate the rate of absorption of sucrose by acting on the luminal enzymes. Adverse effects of these agents are predominantly gastrointestinal. Newer insulin secretagogues have been developed which attempt to mimic the physiological release of insulin and thus ameliorate PPHG. These include third generation sulfonylureas like glimepiride and nonsulfonylurea secretagogues like repaglinide and nateglinide. Rapid-acting insulin analogs, the amino acid sequences of which have been altered such that they have a faster onset of action, help to specifically target PPHG. Pre-mixed formulations of the analogs have also been developed. Finally, drugs under development which hold promise in the management of patients with PPHG include pramlintide, an amylin analog, and glucagon-like peptide-1 and its analogs.
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Affiliation(s)
- Rajasekaran Sudhir
- MV Diabetes Specialities Centre and Madras Diabetes Research Foundation, Chennai, India
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23
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Basu A, Basu R, Shah P, Vella A, Rizza RA, Jensen MD. Systemic and regional free fatty acid metabolism in type 2 diabetes. Am J Physiol Endocrinol Metab 2001; 280:E1000-6. [PMID: 11350782 DOI: 10.1152/ajpendo.2001.280.6.e1000] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine whether type 2 diabetes mellitus alters systemic and regional free fatty acid ([3H]palmitate) metabolism, 14 nondiabetic (ND) and 14 type 2 diabetic (D) subjects underwent hyperinsulinemic-hyperglycemic (approximately 9.3 mM) clamps. The subjects were matched for age, body mass index, percent body fat, and fat-free mass. D subjects had more (P < 0.05) visceral fat than ND. During somatostatin, replacement growth hormone, and glucagon infusions, insulin was infused to achieve moderate (approximately 75 pmol/l) and high (approximately 150 pmol/l) physiological insulin levels. D subjects had greater (P < 0.02) systemic and regional (splanchnic and leg) palmitate release than ND subjects during both insulin infusion intervals. The relative contributions of splanchnic, leg, and nonsplanchnic upper body regions to systemic palmitate release did not differ between groups, although the last contributed the most (approximately 75%) to systemic palmitate release. Visceral fat area correlated with systemic palmitate flux (r = 0.45, P < 0.03) during both insulin infusions. We conclude that type 2 diabetes is associated with a generalized impairment in insulin suppression of lipolysis compared with equally obese ND individuals.
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Affiliation(s)
- A Basu
- Endocrine Research Unit, Division of Endocrinology and Metabolism, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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24
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Del Prato S, Tiengo A. The importance of first-phase insulin secretion: implications for the therapy of type 2 diabetes mellitus. Diabetes Metab Res Rev 2001; 17:164-74. [PMID: 11424229 DOI: 10.1002/dmrr.198] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Type 2 diabetes is a heterogeneous disorder characterized by defects in insulin secretion and action. Insulin resistance is a key feature of type 2 diabetes. However, insulin resistance alone does not appear to be sufficient to cause diabetes. Longitudinal studies have shown that the development of overt hyperglycemia is associated with a decline in beta-cell secretion. In patients with impaired glucose tolerance or in the early stages of type 2 diabetes, first-phase insulin release is almost invariably lost despite the enhancement of second-phase secretion. Both animal and human studies support the critical physiologic role of the first-phase of insulin secretion in the maintenance of postmeal glucose homeostasis. This effect is primarily mediated at the level of the liver, allowing prompt inhibition of endogenous glucose production (EGP) and thereby restraining the mealtime rise in plasma glucose. In type 2 diabetes, the loss of the early surge of insulin release is a precocious and quite common defect that plays a pathogenic role in postmeal hyperglycemia and one that may require specific therapeutic intervention. This becomes even more apparent if the negative impact of prandial glucose spikes is taken into consideration. Epidemiological evidence exists to indicate that 2-h postload plasma glucose levels are strongly associated with all-cause and cardiovascular mortality relative risk. Indeed the acute elevation of plasma glucose concentration triggers an array of tissue responses that may contribute to the development of diabetic complications. Considering that type 2 diabetes begins with meal-related hyperglycemia in many patients, it becomes apparent that normalization of postmeal plasma glucose levels should be the target for rational therapy and the goal in the early stages of the disease. If a primary goal of diabetes therapy is control of postmeal glucose excursion, then the regulation of glucose absorption from the gut and entry into the circulation is an important mechanism to consider. The restoration of the rapid increase in plasma insulin concentration may be quite an efficient therapeutic approach.
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Affiliation(s)
- S Del Prato
- Cattedra di Malattie del Metabolismo, School of Medicine, University of Pisa, Italy.
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25
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Manco M, Mingrone G, Greco AV, Capristo E, Gniuli D, De Gaetano A, Gasbarrini G. Insulin resistance directly correlates with increased saturated fatty acids in skeletal muscle triglycerides. Metabolism 2000; 49:220-4. [PMID: 10690948 DOI: 10.1016/s0026-0495(00)91377-5] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A close relationship between elevated plasma free fatty acid (FFA) levels and insulin resistance is commonly reported in obese subjects. The aim of the present study was to evaluate the role of intramuscular triglyceride (mTG) and FFA levels in insulin sensitivity in 30 nondiabetic normal-weight or obese subjects (18 with body mass index [BMI] = 21.8 +/- 3.3 kg/m2 and 12 with BMI = 34.6 +/- 2.7 kg/m2) who underwent minor abdominal surgery. Body composition was estimated by isotopic dilution, substrate oxidation by indirect calorimetry, and whole-body glucose uptake by euglycemic-hyperinsulinemic clamp (EHC). Glucose uptake (M) value negatively correlated with the MTG level (R2 = -.56, P < .0001), which was increased in obese patients (11.6 +/- 2.2 v 6.2 +/- 1.4 micromol/g wet weight muscle tissue, P < .0001). The TG fatty acid profile was significantly different in the 2 groups: an increased concentration of saturated fat was present in obese patients (unsaturated to saturated ratio, 1.89 +/- 0.40 v2.19 +/- 0.07, P < .0001). Stepwise linear regression analysis of total mTGs and palmitic and oleic fractions on the M value showed that only TGs and palmitic acid were significantly related to glucose uptake (R2 = .66, P < .0001). Furthermore, among the other anthropometric variables, only the BMI was significantly correlated with MTGs (R2 = .71, P < .0001). In conclusion, not only the MTG concentration but also the FFA pattern seems to affect insulin-mediated glucose uptake. A pivotal role might be played by a high saturated fatty acid content in the TGs.
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Affiliation(s)
- M Manco
- Department of Internal Medicine and the Consiglio Nazionale delle Ricerche, Centro Fisiopatologia Shock, Catholic University, Rome, Italy
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26
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Baldeweg SE, Golay A, Natali A, Balkau B, Del Prato S, Coppack SW. Insulin resistance, lipid and fatty acid concentrations in 867 healthy Europeans. European Group for the Study of Insulin Resistance (EGIR). Eur J Clin Invest 2000; 30:45-52. [PMID: 10620001 DOI: 10.1046/j.1365-2362.2000.00597.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Insulin resistance, dyslipidaemia and abnormal nonesterified fatty acid (NEFA) metabolism are features of the 'metabolic syndrome', but the mechanisms of these relationships are uncertain. MATERIALS AND METHODS We studied associations between insulin resistance and lipoprotein concentrations by retrospective analysis of euglycaemic hyperinsulinaemic clamp data from 867 normoglycaemic subjects in 21 European centres. Data on NEFA concentrations were available in a subgroup of 541 subjects from 9 clinical centres. These subjects' characteristics do not vary significantly from those of the whole cohort. RESULTS After adjustment for the effects of age, sex, obesity and intercentre variability, regression analysis showed relationships between triglycerides and markers of insulin sensitivity. There were significant correlations between triglycerides and fasting plasma glucose (P < 0.0001), fasting plasma insulin (P < 0.0001) and mean glucose infusion rate at steady state (M-value, P < 0.0001). Indices of insulin resistance were related to NEFA concentrations. Fasting NEFA were negatively correlated with the M-value (P < 0.0001). Non-esterified fatty acids at steady state were positively correlated with fasting markers of insulin resistance: fasting plasma glucose (P < 0.05), fasting plasma insulin (P < 0.005) and negatively correlated with the M-value (P < 0.0005). There were relationships between fasting concentrations of plasma lipids and of NEFAs. Non-esterified fatty acids at steady state correlated with fasting triglycerides (P < 0.0001), but not with any of the other plasma lipoprotein concentrations. The associations of fasting triglycerides with the M-value and with NEFAs at steady state were independent of each other. All these associations were independent of obesity and geographical location CONCLUSION The results in this large cohort of healthy European subjects suggest that triglyceride concentrations depend upon both insulin's gluco-regulation (estimated by glucose uptake) and antilipolytic insulin action (measured by NEFA levels) during an euglycaemic clamp.
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Affiliation(s)
- S E Baldeweg
- University College London Medical School, London, UK.
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27
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Mingrone G, Greco AV, Capristo E, Benedetti G, Giancaterini A, De Gaetano A, Gasbarrini G. L-carnitine improves glucose disposal in type 2 diabetic patients. J Am Coll Nutr 1999; 18:77-82. [PMID: 10067662 DOI: 10.1080/07315724.1999.10718830] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Aim of the present study is to evaluate the effects of L-carnitine on insulin-mediated glucose uptake and oxidation in type II diabetic patients and compare the results with those in healthy controls. DESIGN Fifteen type II diabetic patients and 20 healthy volunteers underwent a short-term (2 hours) euglycemic hyperinsulinemic clamp with simultaneous constant infusion of L-carnitine (0.28 micromole/kg bw/minute) or saline solution. Respiratory gas exchange was measured by an open-circuit ventilated hood system. Plasma glucose, insulin, non-esterified fatty acids (NEFA) and lactate levels were analyzed. Nitrogen urinary excretion was calculated to evaluate protein oxidation. RESULTS Whole body glucose uptake was significantly (p<0.001) higher with L-carnitine than with saline solution in the two groups investigated (48.66+/-4.73 without carnitine and 52.75+/-5.19 micromoles/kg(ffm)/minute with carnitine in healthy controls, and 35.90+/-5.00 vs. 38.90+/-5.16 micromoles/kg(ffm)/minute in diabetic patients). Glucose oxidation significantly increased only in the diabetic group (17.61+/-3.33 vs. 16.45+/-2.95 micromoles/kg(ffm)/minute, p<0.001). On the contrary, glucose storage increased in both groups (controls: 26.36+/-3.25 vs. 22.79+/-3.46 micromoles/kg(ffm)/minute, p<0.001; diabetics: 21.28+/-3.18 vs. 19.66+/-3.04 micromoles/kg(ffm)/minute, p<0.001). In type II diabetic patients, plasma lactate significantly decreased during L-carnitine infusion compared to saline, going from the basal period to the end-clamp period (0.028+/-0.0191 without carnitine and 0.0759+/-0.0329 with carnitine, p<0.0003). CONCLUSIONS L-carnitine constant infusion improves insulin sensitivity in insulin resistant diabetic patients; a significant effect on whole body insulin-mediated glucose uptake is also observed in normal subjects. In diabetics, glucose, taken up by the tissues, appears to be promptly utilized as fuel since glucose oxidation is increased during L-carnitine administration. The significantly reduced plasma levels of lactate suggest that this effect might be exerted through the activation of pyruvate dehydrogenase, whose activity is depressed in the insulin resistant status.
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Affiliation(s)
- G Mingrone
- Istituto di Medicina Interna, Catholic University, Rome, Italy
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Abstract
Non-esterified fatty acids (NEFA, or free fatty acids) are an important metabolic fuel. Both the concentration of NEFA and their flux through the circulation vary widely from hour to hour, reflecting nutritional state and physical activity. Inappropriately elevated plasma NEFA concentrations may have a number of adverse effects on both carbohydrate and lipid metabolism. These adverse effects are likely to be most marked in the postprandial period, when NEFA release from adipose tissue is usually suppressed. Although the regulation of NEFA release in the postabsorptive state is well understood in molecular terms, the predominant pathway for release of NEFA in the postprandial state is the action of lipoprotein lipase (LPL) in adipose tissue capillaries on chylomicron-triacylglycerol (TG). Fatty acids released by LPL may either be sequestered in the adipocytes by esterification, or released as NEFA into the plasma. The regulation of this branch-point, which may be of crucial significance for postprandial metabolism, is not well understood. Factors stimulating tissue retention of fatty acids include insulin and acylation stimulating protein. There is considerable indirect evidence that impaired regulation of this step occurs in insulin resistance and other conditions collectively recognised by an elevated concentration of apolipoprotein B (hyper-apo B). Inappropriate release of NEFA in the postprandial period is likely both to reduce the sensitivity of glucose metabolism to insulin and to accentuate postprandial lipaemia. Further study of the regulation of this pathway is much needed.
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Affiliation(s)
- K N Frayn
- Oxford Lipid Metabolism Group, Nuffield Department of Clinical Medicine, Radcliffe Infirmary, UK.
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Banerjee S, Saenger P, Hu M, Chen W, Barzilai N. Fat accretion and the regulation of insulin-mediated glycogen synthesis after puberty in rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:R1534-9. [PMID: 9362321 DOI: 10.1152/ajpregu.1997.273.4.r1534] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Peripheral insulin sensitivity decreases after puberty in both humans and rodents and can be explained mostly by a reduction in insulin-mediated glycogen synthesis. We tested the hypothesis that the increase in postpubertal fat mass (FM), reflecting an alternative energy store, regulates a decrease in the capacity to store muscle glycogen. We studied Sprague-Dawley rats (n = 21) before puberty (Pre) or after puberty (at 4 mo of age) in groups that were either ad libitum fed (Post) or moderately caloric restricted (CR). FM (by 3H2O isotope dilution technique) was decreased by >40% in CR compared with Post. Glucose uptake (Rd, by 18 mU x kg(-1) x min(-1) hyperinsulinemic clamp) was 63 +/- 8 mg x kg(-1) x min(-1) in Pre and decreased to 39 +/- 2 mg x kg(-1) x min(-1) in Post (P < 0.001). However, it increased in CR to 53 +/- 2 mg x kg(-1) x min(-1) (P < 0.001 vs. Post). This increase in Rd was mainly accounted for by an increase in glycogen synthesis (Rd glycolysis determined by the rate of conversion of 3H-labeled glucose to 3H2O) from 23 +/- 2 in Post to 33 +/- 2 mg x kg(-1) x min(-1) in CR (P < 0.001; 38 +/- 7 mg x kg(-1) x min(-1) in Pre). Correction of glycogen synthesis in CR to near-prepubertal levels was further supported by directly assayed muscle glycogen content after insulin stimulation that was 45% higher and by a 35% enhanced accumulation of [3H]glucose into glycogen. No changes in the enzyme kinetics of glycogen synthase or phosphorylase were observed. An additional group of 2-mo-old postpubertal ad libitum-fed rats was matched with CR for lean body mass but had more FM. This group demonstrated 25% lower rates of insulin-mediated glycogen synthesis compared with CR, further supporting the notion that a moderate reduction of FM prevents the decline in insulin responsiveness and glycogen synthesis occurring after puberty. These data suggest a cause-effect relationship between the increased deposition of fat and the reduced ability to store glucose in skeletal muscle after puberty.
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Affiliation(s)
- S Banerjee
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Avogaro A, Crepaldi C, Miola M, Maran A, Pengo V, Tiengo A, Del Prato S. High blood ketone body concentration in type 2 non-insulin dependent diabetic patients. J Endocrinol Invest 1996; 19:99-105. [PMID: 8778173 DOI: 10.1007/bf03349844] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
To assess the metabolic disturbances, and, in particular, the occurrence of high blood ketone body concentration in post-absorptive Type 2 (non-insulin-dependent) diabetic patients as compared to a matched normal population, a study was carried out in a group of 78 Type 2 diabetic outpatients matched for age and sex and in 78 normal individuals. In all subjects we measured HbA1c, and fasting levels of glucose, FFA, lactate, pyruvate, glycerol, alanine, 3-hydroxybutyrate, acetoacetate, uric acid, total cholesterol, triglycerides, creatinine, growth hormone, cortisol, glucagon, free insulin, and C-peptide. Multistix strips were used for urine ketone determination. As expected HbA1c, and plasma glucose were higher in Type 2 diabetics. This was associated with multiple metabolic disturbances as shown by higher circulating concentrations of FFA, glycerol and gluconeogenic precursors. Similarly, blood levels of ketones (351 +/- 29 vs 159 +/- 15 umol/l; P < 0.0001) were increased, in spite of higher plasma free-insulin (77 +/- 7 vs. 49 +/- 14 pmol/l; p < 0.0001) and C-peptide concentration (0.63 +/- 0.03 vs. 0.46 +/- 0.07 nmol/l; P < 0.05) and no differences in plasma levels of cortisol, and growth hormone. Plasma glucagon levels were higher in Type 2 diabetics. Blood ketone body levels were directly correlated with both plasma glucose and FFA concentrations. These observations clearly show that Type 2 diabetes is a pathologic condition characterised by multiple metabolic disturbances which are fully apparent in the basal state. Furthermore, we emphasise that Type 2 diabetic patients, though not insulin deficient, may present a significant increase in their fasting levels of ketone bodies.
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Affiliation(s)
- A Avogaro
- Dipartimento di Medicina Clinica e Sperimentale, Università degli Studi di Padova, Azienda Ospedaliera di Padova, Italy
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Del Prato S, Marchetto S, Pipitone A, Zanon M, Vigili de Kreutzenberg S, Tiengo A. Metformin and free fatty acid metabolism. DIABETES/METABOLISM REVIEWS 1995; 11 Suppl 1:S33-41. [PMID: 8529483 DOI: 10.1002/dmr.5610110506] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- S Del Prato
- Cattedra di Malattie del Metabolismo, University of Padova, Italy
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Monti LD, Brambilla P, Stefani I, Caumo A, Magni F, Poma R, Tomasini L, Agostini G, Galli-Kienle M, Cobelli C. Insulin regulation of glucose turnover and lipid levels in obese children with fasting normoinsulinaemia. Diabetologia 1995; 38:739-47. [PMID: 7672499 DOI: 10.1007/bf00401849] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To evaluate the early metabolic alterations induced by obesity, we studied glucose turnover and lipid levels in obese children with fasting normoinsulinaemia. Two experimental protocols were carried out. Protocol I consisted of a euglycaemic glucose clamp at two rates of insulin infusion. Protocol II was similar to protocol I except for a variable lipid infusion used to maintain basal non-esterified fatty acid (NEFA) levels. During protocol I, the glucose disappearance rates were lower in obese children, while no differences were found in hepatic glucose release. NEFA response to insulin was not substantially altered in obese children either at low or high insulin infusion. During protocol II, the NEFA clamp induced a 25% reduction in peripheral insulin sensitivity in control children whereas no changes were observed in obese children. Interestingly, lipid infusion in control children was not sufficient to reproduce the same degree of insulin resistance observed in obese children, suggesting that NEFA are only one of the determinants of insulin resistance at this stage of obesity. In conclusion, the present study provides a portrait of glucose metabolism and lipid levels in normoinsulinaemic obese children. Our results document that peripheral insulin resistance is the first alteration at this stage of obesity, whereas an increase in insulin secretion and a defect in the inhibition of hepatic glucose release by insulin may develop at a later stage. In addition, primarily receptor and post-receptor defects and some alterations of NEFA metabolism are likely to coexist in the induction of insulin resistance at this stage of obesity.
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Affiliation(s)
- L D Monti
- Istituto Scientifico H. San Raffaele, Cattedra di Clinica Medica, Università di Milano, Italy
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Campbell PJ, Carlson MG, Nurjhan N. Fat metabolism in human obesity. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:E600-5. [PMID: 8178981 DOI: 10.1152/ajpendo.1994.266.4.e600] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Excessive fat turnover and oxidation might cause the insulin resistance of carbohydrate metabolism in obese humans. We studied the response of free fatty acid (FFA) metabolism in lean and obese volunteers to sequential insulin infusions of 4, 8, 25, and 400 mU.m-2.min-1. The insulin dose-response curves for suppression of FFA concentration, FFA turnover ([1-14C]palmitate), and lipolysis ([2H5]glycerol) were shifted to the right in the obese subjects (insulin concentrations that produced a half-maximal response, lean vs. obese: 103 +/- 21 vs. 273 +/- 41, 96 +/- 11 vs. 264 +/- 44, and 101 +/- 23 vs. 266 +/- 44 pM, all P < 0.05), consistent with insulin resistance of FFA metabolism in obesity. After the overnight fast, FFA turnover per fat mass was decreased in obese subjects (37 +/- 4 vs. 20 +/- 3 mumol.kg fat mass-1.min-1, P < 0.01) as the result of suppression of lipolysis by the hyperinsulinemia of obesity and an increased fractional reesterification of FFA before leaving the adipocyte (primary FFA reesterification; 0.14 +/- 0.03 vs. 0.35 +/- 0.06, P < 0.05). Nevertheless, FFA turnover per fat-free mass (FFM) was also greater in the obese volunteers (8.5 +/- 0.7 vs. 11.0 +/- 1.0 mumol.kg FFM-1.min-1, P < 0.05) but only as the result of increased reesterification of intravascular FFA (secondary reesterification; 1.8 +/- 0.5 vs. 4.8 +/- 1.1 mumol.kg FFM-1.min-1, P < 0.01), since FFA oxidation was the same in the two groups throughout the insulin dose-response curve.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P J Campbell
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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Bonadonna RC, Groop LC, Simonson DC, DeFronzo RA. Free fatty acid and glucose metabolism in human aging: evidence for operation of the Randle cycle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:E501-9. [PMID: 8166272 DOI: 10.1152/ajpendo.1994.266.3.e501] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We assessed insulin effects on plasma free fatty acid (FFA) and glucose metabolism in seven elderly (71 +/- 2 yr) and in seven younger (21 +/- 1 yr) subjects matched for body weight and body mass index but not for percent body fat (32.4 +/- 3.8% in elderly vs. 20.4 +/- 3.5% in young, P < 0.05), by performing sequential euglycemic clamps at five insulin doses (0.6, 1.5, 3, 6, and 15 pmol.min-1.kg-1) in combination with indirect calorimetry and [1-14C]palmitate plus [3-3H]glucose infusion. At baseline, plasma FFA concentration, turnover infusion. At baseline, plasma FFA concentration, turnover and oxidation, and total lipid oxidation were all increased in the elderly (897 +/- 107 vs. 412 +/- 50 mumol/l and 11.2 +/- 1.4 vs. 5.14 +/- 0.86, 3.45 +/- 0.65 vs. 1.37 +/- 0.25, and 4.63 +/- 0.72 vs. 3.01 +/- 0.33 mumol.min-1.kg-1 lean body mass, P < 0.05 for all comparisons), whereas glucose turnover was similar as a result of decreased glucose oxidation (8.2 +/- 1.4 vs. 13 +/- 1.9 mumol.min-1.kg-1 lean body mass, P < 0.05) and increased glucose storage (6.6 +/- 1.4 vs. 1.7 +/- 1.3 mmol.min-1.kg-1 lean body mass, P < 0.05). At all insulin infusions, plasma FFA concentration, turnover and oxidation, and total lipid oxidation were higher in the elderly than in the younger group (P < 0.05). However, if normalized per fat mass, all FFA and lipid metabolic fluxes, both in the postabsorptive state and during hyperinsulinemia, were comparable in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Raguso CA, Mingrone G, Greco AV, Tataranni PA, De Gaetano A, Castagneto M. Dicarboxylic acids and glucose utilization in humans: effect of sebacate. JPEN J Parenter Enteral Nutr 1994; 18:9-13. [PMID: 8164314 DOI: 10.1177/014860719401800109] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dicarboxylic acids have been proposed as an alternate lipid energetic substrate for total parenteral nutrition. No data are yet available on the possible effect of dicarboxylic acids on glucose metabolism in humans. Thus, we examined the effect of a continuous intravenous infusion of the sodium salt of the 10-carbon atom alyphatic dicarboxylic acid, sebacate (Sb), on insulin-dependent glucose metabolism in four control subjects, four patients with insulin-dependent diabetes mellitus, and four obese subjects. All subjects received a constant 5-hour infusion of saline or sebacate (6.6 g/h), in a randomized order on two different days. After 3 hours of infusion, a 120-minute euglycemic, hyperinsulinemic clamp procedure was performed (insulin infusion rate = 40 mU/m2 per minute). Glucose uptake, plasma sebacate, insulin, glucagon, C-peptide, and ketone bodies were measured. No significant differences in insulinemia were found among groups either during the saline infusion or the sebacate infusion. On the contrary, glucose uptake (molar) was significantly reduced during the sebacate vs the saline day in all three groups: 6.7 +/- 0.04 vs 3.7 +/- 1.3 in control subjects (p < .001), 4.6 +/- 0.4 vs 2.5 +/- 1.2 in patients with insulin-dependent diabetes mellitus (p < .001), and 4.8 +/- 0.5 vs 2.7 +/- 0.2 mg/kg per minute in obese subjects (p < .001). In conclusion, Sb administration was associated with a glucose-sparing effect as shown by the reduced glucose uptake in all patients studied. Sebacate did not stimulate insulin secretion, inasmuch as no modification of C-peptide plasma levels was observed after 3 hours of Sb infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C A Raguso
- Istituto di Clinica Medica, Catholic University, Rome, Italy
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Riccio A, Vigili de Kreutzenberg S, Dorella M, Da Tos V, De Biasi L, Marescotti MC, Tiengo A, Del Prato S. Mechanism(s) of the blood glucose lowering action of benfluorex. DIABETES/METABOLISM REVIEWS 1993; 9 Suppl 1:19S-27S. [PMID: 8299485 DOI: 10.1002/dmr.5610090505] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Benfluorex is a hypolipidaemic agent with biguanide-like properties. To evaluate its blood glucose lowering action, a single-blind study protocol was designed. Two groups of seven type II (non-insulin-dependent) diabetic patients matched for age (50 +/- 4 vs. 53 +/- 1 years), sex, body mass index (27.8 +/- 0.6 vs. 26.5 +/- 0.7 kg/m2), and duration of diabetes were studied before and after 1 month of treatment with benfluorex 150 mg tid (= tres in die = three times a day), PO (= per os = by mouth) or a placebo, respectively. All patients had previously been treated by diet alone. In all patients, parameters of glucose and lipid metabolism were obtained. Insulin sensitivity was assessed by means of a euglycaemic (5.1 +/- 0.1 mM) hyperinsulinaemic (516 +/- 28 pM) clamp performed in combination with [3(-3)H]glucose infusion and indirect calorimetry. In no case was there a significant change in body mass index (27.6 +/- 0.5 vs. 26.4 +/- 0.7 kg/m2). After 1 month of treatment, fasting plasma glucose (6.8 +/- 0.2 vs. 8.1 +/- 0.6 mM) and HbA1C (glycated haemoglobin; 6.5 +/- 0.2 vs. 8.0 +/- 0.7%) were lower in the benfluorex group than in the placebo-treated patients (both p < 0.05). No change was observed in hepatic glucose production (HGP) (13.5 +/- 1.4 vs. 13.9 +/- 1.1 mumol/min per kg), the basal rate of glucose, and lipid oxidation and non-oxidative glucose metabolism, or in plasma triglyceride and total cholesterol concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
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Cavallo-Perin P, Bruno A, Cassader M, Cesco L, Gruden G, Pagano G. The glucoregulatory and antilipolytic actions of insulin in abdominal obesity with normal or impaired glucose tolerance: an in vivo and in vitro study. Eur J Clin Invest 1992; 22:725-31. [PMID: 1478241 DOI: 10.1111/j.1365-2362.1992.tb01436.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To evaluate the effects of obesity and impaired glucose tolerance on insulin sensitivity, we performed a euglycaemic-hyperinsulinemic clamp at about 350 pmol l-1, combined with 3H-glucose infusion, in 14 obese patients, BMI 36.5 +/- 1.2 and in 12 matched controls, BMI 23.9 +/- 0.4. Six obese patients had normal glucose tolerance (oNGT), and eight had impaired glucose tolerance (oIGT). The ability of insulin to inhibit lipolysis in isolated adipocytes was also studied. Insulin-mediated glucose utilization was more severely impaired in oIGT than in oNGT with respect to the controls (621 +/- 51 vs. 897 +/- 83 vs. 1298 +/- 55 mumol m-2 min-1, P < 0.001). Plasma glycerol was higher in oIGT than in oNGT and in the controls, both fasting (238 +/- 12 vs. 179 +/- 14 vs. 112 +/- 8 mumol l-1, P < 0.001) and during the clamp (175 +/- 21 vs. 120 +/- 12 vs. 36 +/- 6 mumol l-1, P < 0.001). The correlation between glucose utilization and the percent reduction of plasma glycerol during the clamp was significant in the study group as a whole (r = 0.809, P = 0.0001), and in each of the groups separately (oIGT: r = 0.929, P = 0.002; oNGT: r = 0.943, P = 0.036; controls: r = 0.902, P = 0.0001). Inhibition by insulin of noradrenaline-stimulated lipolysis in isolated adipocytes was more severely impaired in oIGT than in oNGT compared with the controls (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Coppack SW, Evans RD, Fisher RM, Frayn KN, Gibbons GF, Humphreys SM, Kirk ML, Potts JL, Hockaday TD. Adipose tissue metabolism in obesity: lipase action in vivo before and after a mixed meal. Metabolism 1992; 41:264-72. [PMID: 1542265 DOI: 10.1016/0026-0495(92)90269-g] [Citation(s) in RCA: 176] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Physiological actions of insulin include suppression of fat mobilization from adipose tissue and activation of adipose tissue lipoprotein lipase. Here, we report measurements of adipose tissue hormone-sensitive lipase (HSL) and lipoprotein lipase (LPL) action in vivo in 10 normal and eight obese subjects, with the latter group having varying degrees of glucose intolerance. HSL and LPL actions (per gram of adipose tissue) were similar in the two groups, after an overnight fast. In the normal subjects, HSL action was suppressed after a meal (by 75% +/- 6% between 60 to 300 minutes, P less than .01), and the action of LPL was increased (clearance of circulating triacylglycerol [TAG] increased by 140% +/- 57% at 300 minutes, P less than .05). Despite hyperinsulinemia, these responses were blunted in the obese subjects (P less than .05 for each change being less than in normal group). The adipose tissue of the obese subjects showed continued nonesterified fatty acid (NEFA) release at a time when NEFA mobilization was completely suppressed in the normal group. Both impaired suppression of HSL and low fractional retention of fatty acids for reesterification within the adipose tissue contributed to this abnormal NEFA release. Impaired activation of LPL was associated with a greater absolute increase in plasma TAG concentration postprandially in the obese. In obese subjects, adipose tissue HSL and LPL fail to respond to immunoreactive insulin postprandially, which may be an important maladaptation in terms of lipoprotein metabolism and risk of coronary heart disease.
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Affiliation(s)
- S W Coppack
- Sheikh Rashid Diabetes Unit, Radcliffe Infirmary, Oxford, UK
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