Is obesity an absolute evil? Increase in adipose tissue does not always decrease insulin sensitivity

Abstract Obesity and body fat distribution are important risk factors for the development of type 2 diabetes and metabolic syndrome. Evidence has accumulated that this risk is related to intrinsic differences in behavior of adipocytes in different fat depots. We recently identified LIM domain only 3 (LMO3) in human mature visceral adipocytes; however, its function in these cells is currently unknown. The aim of this study was to determine the potential involvement of LMO3-dependent pathways in the modulation of key functions of mature adipocytes during obesity. Based on a recently engineered hybrid rAAV serotype Rec2 shown to efficiently transduce both brown adipose tissue (BAT) and white adipose tissue (WAT), we delivered YFP or Lmo3 to epididymal WAT (eWAT) of C57Bl6/J mice on a high-fat diet (HFD). The effects of eWAT transduction on metabolic parameters were evaluated 10 weeks later. To further define the role of LMO3 in insulin-stimulated glucose uptake, insulin signaling, adipocyte bioenergetics, as well as endocrine function, experiments were conducted in 3T3-L1 adipocytes and newly differentiated human primary mature adipocytes, engineered for transient gain or loss of LMO3 expression, respectively. AAV transduction of eWAT results in strong and stable Lmo3 expression specifically in the adipocyte fraction over a course of 10 weeks with HFD feeding. LMO3 expression in eWAT significantly improved insulin sensitivity and healthy visceral adipose tissue expansion in diet-induced obesity, paralleled by increased serum adiponectin. In vitro, LMO3 expression in 3T3-L1 adipocytes increased PPARγ transcriptional activity, insulin-stimulated GLUT4 translocation and glucose uptake, as well as mitochondrial oxidative capacity in addition to fatty acid oxidation. Mechanistically, LMO3 induced the PPARγ coregulator Ncoa1, which was required for LMO3 to enhance glucose uptake and mitochondrial oxidative gene expression. In human mature adipocytes, LMO3 overexpression promoted, while silencing of LMO3 suppressed mitochondrial oxidative capacity. LMO3 expression in visceral adipose tissue regulates multiple genes that preserve adipose tissue functionality during obesity, such as glucose metabolism, insulin sensitivity, mitochondrial function, and adiponectin secretion. Together with increased PPARγ activity and Ncoa1 expression, these gene expression changes promote insulin-induced GLUT4 translocation, glucose uptake in addition to increased mitochondrial oxidative capacity, limiting HFD-induced adipose dysfunction. These data add LMO3 as a novel regulator improving visceral adipose tissue function during obesity. Key messages LMO3 increases beneficial visceral adipose tissue expansion and insulin sensitivity in vivo. LMO3 increases glucose uptake and oxidative mitochondrial activity in adipocytes. LMO3 increases nuclear coactivator 1 (Ncoa1). LMO3-enhanced glucose uptake and mitochondrial gene expression requires Ncoa1.

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Partial Deficiency of Zfp217 Resists High-Fat Diet-Induced Obesity by Increasing Energy Metabolism in Mice

International Journal of Molecular Sciences ◽

10.3390/ijms22105390 ◽

2021 ◽

Vol 22 (10) ◽

pp. 5390

Author(s):

Qianhui Zeng ◽

Nannan Wang ◽

Yaru Zhang ◽

Yuxuan Yang ◽

Shuangshuang Li ◽

...

Keyword(s):

Adipose Tissue ◽

Weight Gain ◽

Insulin Sensitivity ◽

Energy Metabolism ◽

Glucose Tolerance ◽

High Fat Diet ◽

Chow Diet ◽

High Fat ◽

Glycolipid Metabolism ◽

Partial Deficiency

Obesity-induced adipose tissue dysfunction and disorders of glycolipid metabolism have become a worldwide research priority. Zfp217 plays a crucial role in adipogenesis of 3T3-L1 preadipocytes, but about its functions in animal models are not yet clear. To explore the role of Zfp217 in high-fat diet (HFD)-induced obese mice, global Zfp217 heterozygous knockout (Zfp217+/−) mice were constructed. Zfp217+/− mice and Zfp217+/+ mice fed a normal chow diet (NC) did not differ significantly in weight gain, percent body fat mass, glucose tolerance, or insulin sensitivity. When challenged with HFD, Zfp217+/− mice had less weight gain than Zfp217+/+ mice. Histological observations revealed that Zfp217+/− mice fed a high-fat diet had much smaller white adipocytes in inguinal white adipose tissue (iWAT). Zfp217+/− mice had improved metabolic profiles, including improved glucose tolerance, enhanced insulin sensitivity, and increased energy expenditure compared to the Zfp217+/+ mice under HFD. We found that adipogenesis-related genes were increased and metabolic thermogenesis-related genes were decreased in the iWAT of HFD-fed Zfp217+/+ mice compared to Zfp217+/− mice. In addition, adipogenesis was markedly reduced in mouse embryonic fibroblasts (MEFs) from Zfp217-deleted mice. Together, these data indicate that Zfp217 is a regulator of energy metabolism and it is likely to provide novel insight into treatment for obesity.

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Reducing glycosphingolipid content in adipose tissue of obese mice restores insulin sensitivity, adipogenesis and reduces inflammation

Chemistry and Physics of Lipids ◽

10.1016/j.chemphyslip.2009.06.130 ◽

2009 ◽

Vol 160 ◽

pp. S14

Author(s):

Marco van Eijk ◽

Jan Aten ◽

Nora Bijl ◽

Roelof Ottenhoff ◽

Cindy P.A.A. van Roomen ◽

...

Keyword(s):

Adipose Tissue ◽

Insulin Sensitivity ◽

Obese Mice

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Effects of cortisol and progesterone on insulin binding and lipogenesis in adipocytes from normal and diabetic rats

Journal of Endocrinology ◽

10.1677/joe.0.1060225 ◽

1985 ◽

Vol 106 (2) ◽

pp. 225-231 ◽

Cited By ~ 17

Author(s):

A.-M. Mendes ◽

R. J. Madon ◽

D. J. Flint

Keyword(s):

Body Weight ◽

Adipose Tissue ◽

Insulin Sensitivity ◽

Insulin Receptor ◽

Body Weight Gain ◽

Serum Insulin ◽

Insulin Binding ◽

Serum Glucose ◽

Diabetic Rats ◽

Receptor Concentration

ABSTRACT Cortisol implants in normal and diabetic rats reduced body weight, adiposity, insulin receptor concentration and both basal and insulin-stimulated rates of lipogenesis in isolated adipocytes, whilst insulin sensitivity was unchanged. In normal but not diabetic rats these changes were accompanied by increased serum glucose and insulin concentrations. In contrast, progesterone implants in normal and diabetic rats increased body weight gain, adiposity, insulin receptor concentration and both basal and insulin-stimulated rates of lipogenesis in adipose tissue, again without affecting insulin sensitivity. Progesterone did not affect serum insulin concentrations in normal or diabetic rats but accelerated the decline in serum glucose concentrations which occurred during an overnight fast in diabetic rats. The results suggest that (1) cortisol inhibits lipogenesis in adipose tissue without affecting insulin sensitivity, (2) cortisol reduces insulin binding in adipose tissue without a requirement for hyperinsulinaemia, which might itself indirectly lead to down-regulation of the insulin receptor, and (3) in diabetic rats progesterone stimulates lipogenesis in adipose tissue without any increase in food intake or serum insulin concentrations suggesting that progesterone may have a direct anabolic role in adipose tissue. J. Endocr. (1985) 106, 225–231

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Central Leptin Regulates Total Ceramide Content and Sterol Regulatory Element Binding Protein-1C Proteolytic Maturation in Rat White Adipose Tissue

Endocrinology ◽

10.1210/en.2008-0505 ◽

2008 ◽

Vol 150 (1) ◽

pp. 169-178 ◽

Cited By ~ 36

Author(s):

Elena Bonzón-Kulichenko ◽

Dominik Schwudke ◽

Nilda Gallardo ◽

Eduardo Moltó ◽

Teresa Fernández-Agulló ◽

...

Keyword(s):

Nervous System ◽

Adipose Tissue ◽

Insulin Sensitivity ◽

White Adipose Tissue ◽

Binding Protein ◽

Regulatory Element ◽

Mrna Levels ◽

Element Binding Protein ◽

Ceramide Content ◽

Sterol Regulatory Element

Obesity and type 2 diabetes are associated with insulin and leptin resistance, and increased ceramide contents in target tissues. Because the adipose tissue has become a central focus in these diseases, and leptin-induced increases in insulin sensitivity may be related to effects of leptin on lipid metabolism, we investigated herein whether central leptin was able to regulate total ceramide levels and the expression of enzymes involved in ceramide metabolism in rat white adipose tissue (WAT). After 7 d central leptin treatment, the total content of ceramides was analyzed by quantitative shotgun lipidomics mass spectrometry. The effects of leptin on the expression of several enzymes of the sphingolipid metabolism, sterol regulatory element binding protein (SREBP)-1c, and insulin-induced gene 1 (INSIG-1) in this tissue were studied. Total ceramide levels were also determined after surgical WAT denervation. Central leptin infusion significantly decreased both total ceramide content and the long-chain fatty acid ceramide species in WAT. Concomitant with these results, leptin decreased the mRNA levels of enzymes involved in de novo ceramide synthesis (SPT-1, LASS2, LASS4) and ceramide production from sphingomyelin (SMPD-1/2). The mRNA levels of enzymes of ceramide degradation (Asah1/2) and utilization (sphingomyelin synthase, ceramide kinase, glycosyl-ceramide synthase, GM3 synthase) were also down-regulated. Ceramide-lowering effects of central leptin were prevented by local autonomic nervous system denervation of WAT. Finally, central leptin treatment markedly increased INSIG-1 mRNA expression and impaired SREBP-1c activation in epididymal WAT. These observations indicate that in vivo central leptin, acting through the autonomic nervous system, regulates total ceramide levels and SREBP-1c proteolytic maturation in WAT, probably contributing to improve the overall insulin sensitivity. Central leptin decreases total ceramide levels and prevents sterol regulatory element binding protein (SREBP-1C) proteolytic maturation in white adipose tissue, and probably, in this way, contributes to improve the overall insulin sensitivity.

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Reduced Oxygenation in Human Obese Adipose Tissue Is Associated with Impaired Insulin Suppression of Lipolysis

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2009-2377 ◽

2010 ◽

Vol 95 (8) ◽

pp. 4052-4055 ◽

Cited By ~ 50

Author(s):

Magdalena Pasarica ◽

Jennifer Rood ◽

Eric Ravussin ◽

Jean-Marc Schwarz ◽

Steven R. Smith ◽

...

Keyword(s):

Adipose Tissue ◽

Insulin Sensitivity ◽

Capillary Density ◽

Cross Sectional Study ◽

Fat Cell ◽

Euglycemic Hyperinsulinemic Clamp ◽

Cross Sectional ◽

Clinical Research Center ◽

Endothelial Growth Factor

Context: Adipose tissue in obese individuals is characterized by reduced capillary density and reduced oxygenation. Objective: Our objective was to test whether hypoxia is associated with reduced antilipolytic effect of insulin. Participants, Design, and Setting: Twenty-one lean and obese individuals participated in this cross-sectional study at a university-based clinical research center. Intervention: In all subjects, in situ adipose tissue (AT) oxygenation [AT oxygen partial pressure (ATpO2)] was measured with a Clark electrode, insulin sensitivity as well as basal and insulin-suppressed lipolysis (continuous infusion of (2H5)glycerol) were measured during a euglycemic-hyperinsulinemic clamp, and abdominal sc AT biopsies were collected to assess fat cell size (Coulter counting of osmium-fixed cells), capillary density (by staining of histological sections), and gene expression (by quantitative RT-PCR). Main Outcome Measure: In situ ATpO2 was evaluated. Results: The ability of insulin to suppress lipolysis (percent) was positively correlated with insulin sensitivity (r = 0.43; P < 0.05), ATpO2 (r = 0.44; P < 0.05), vascular endothelial growth factor mRNA (r = 0.73; P < 0.01), and capillary density (r = 0.75; P < 0.01). Conclusion: These results indicate that low capillary density and ATpO2 in AT are potentially upstream causes of AT dysfunction.

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