Obesity and overnutrition during pregnancy affect fetal programming of adult disease. Children born after maternal bariatric gastrointestinal bypass surgery (AMS) are less obese and exhibit improved ...cardiometabolic risk profiles carried into adulthood compared with siblings born before maternal surgery (BMS). This study was designed to analyze the impact of maternal weight loss surgery on methylation levels of genes involved in cardiometabolic pathways in BMS and AMS offspring. Differential methylation analysis between a sibling cohort of 25 BMS and 25 AMS (2-25 y-old) offspring from 20 mothers was conducted to identify biological functions and pathways potentially involved in the improved cardiometabolic profile found in AMS compared with BMS offspring. Links between gene methylation and expression levels were assessed by correlating genomic findings with plasma markers of insulin resistance (fasting insulin and homeostatic model of insulin resistance). A total of 5,698 genes were differentially methylated between BMS and AMS siblings, exhibiting a preponderance of glucoregulatory, inflammatory, and vascular disease genes. Statistically significant correlations between gene methylation levels and gene expression and plasma markers of insulin resistance were consistent with metabolic improvements in AMS offspring, reflected in genes involved in diabetes-related cardiometabolic pathways. This unique clinical study demonstrates that effective treatment of a maternal phenotype is durably detectable in the methylome and transcriptome of subsequent offspring.
The mammalian target of rapamycin (mTOR)/p70 S6 kinase 1 (S6K1) pathway is a critical signaling component in the development of obesity-linked insulin resistance and operates a nutrient-sensing ...negative feedback loop toward the phosphatidylinositol 3-kinase (PI 3-kinase)/Akt pathway. Whereas acute treatment of insulin target cells with the mTOR complex 1 (mTORC1) inhibitor rapamycin prevents nutrient-induced insulin resistance, the chronic effect of rapamycin on insulin sensitivity and glucose metabolism in vivo remains elusive.
To assess the metabolic effects of chronic inhibition of the mTORC1/S6K1 pathway, rats were treated with rapamycin (2 mg/kg/day) or vehicle for 15 days before metabolic phenotyping.
Chronic rapamycin treatment reduced adiposity and fat cell number, which was associated with a coordinated downregulation of genes involved in both lipid uptake and output. Rapamycin treatment also promoted insulin resistance, severe glucose intolerance, and increased gluconeogenesis. The latter was associated with elevated expression of hepatic gluconeogenic master genes, PEPCK and G6Pase, and increased expression of the transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) as well as enhanced nuclear recruitment of FoxO1, CRTC2, and CREB. These changes were observed despite normal activation of the insulin receptor substrate/PI 3-kinase/Akt axis in liver of rapamycin-treated rats, as expected from the blockade of the mTORC1/S6K1 negative feedback loop.
These findings unravel a novel mechanism by which mTORC1/S6K1 controls gluconeogenesis through modulation of several key transcriptional factors. The robust induction of the gluconeogenic program in liver of rapamycin-treated rats underlies the development of severe glucose intolerance even in the face of preserved hepatic insulin signaling to Akt and despite a modest reduction in adiposity.
We provide here a detailed and comprehensive analysis of skeletal muscle metabolomic profiles in response to adiponectin in adiponectin knockout (AdKO) mice after high-fat-diet (HFD) feeding. ...Hyperinsulinemic-euglycemic clamp studies showed that adiponectin administration corrected HFD-induced defects in post/basal insulin stimulated R(d) and insulin signaling in skeletal muscle. Lipidomic profiling of skeletal muscle from HFD-fed mice indicated elevated triacylglycerol and diacylglycerol species (16:0-18:1, 18:1, and 18:0-18:2) as well as acetyl coA, all of which were mitigated by adiponectin. HFD induced elevated levels of various ceramides, but these were not significantly altered by adiponectin. Adiponectin corrected the altered branched-chain amino acid metabolism caused by HFD and corrected increases across a range of glycerolipids, fatty acids, and various lysolipids. Adiponectin also reversed induction of the pentose phosphate pathway by HFD. Analysis of muscle mitochondrial structure indicated that adiponectin treatment corrected HFD-induced pathological changes. In summary, we show an unbiased comprehensive metabolomic profile of skeletal muscle from AdKO mice subjected to HFD with or without adiponectin and relate these to changes in whole-body glucose handling, insulin signaling, and mitochondrial structure and function. Our data revealed a key signature of relatively normalized muscle metabolism across multiple metabolic pathways with adiponectin supplementation under the HFD condition.
Relative quantification is a commonly used method for assessing gene expression, however its accuracy and reliability is dependent upon the choice of an optimal endogenous control gene, and such ...choice cannot be made a priori. There is limited information available on suitable reference genes to be used for studies involving human epicardial adipose tissue. The objective of the current study was to evaluate and identify optimal reference genes for use in the relative quantification of gene expression in human epicardial fat depots of lean, overweight and obese subjects.
Some of the commonly used reference genes including 18S, ACTB, RPL27, HPRT, CYCA, GAPDH, RPLPO, POLR2A and B2M were quantified using real-time PCR analysis. The expression stability of these genes was evaluated using Genorm, Normfinder and Bestkeeper algorithms. In addition, the effect of sample size on the validation process was studied by randomly categorizing subjects in two cohorts of n = 2 and n = 33.
CYCA, GAPDH and RPL27 were identified as the most stable genes common to all three algorithms and both sample sizes. Their use as reference gene pairs might contribute to the enhanced robustness of relative quantification in the studies involving the human epicardial adipose tissue.
Evidence points to a role of the mammalian target of rapamycin (mTOR) signaling pathway as a regulator of adiposity, yet its involvement as a mediator of the positive actions of peroxisome ...proliferator-activated receptor (PPAR)γ agonism on lipemia, fat accretion, lipid uptake, and its major determinant lipoprotein lipase (LPL) remains to be elucidated. Herein we evaluated the plasma lipid profile, triacylglycerol (TAG) secretion rates, and adipose tissue LPL-dependent lipid uptake, LPL expression/activity, and expression profile of other lipid metabolism genes in rats treated with the PPARγ agonist rosiglitazone (15 mg/kg/day) in combination or not with the mTOR inhibitor rapamycin (2 mg/kg/day) for 15 days. Rosiglitazone stimulated adipose tissue mTOR complex 1 and AMPK and induced TAG-derived lipid uptake (136%), LPL mRNA/activity (2- to 6-fold), and fat accretion in subcutaneous (but not visceral) white adipose tissue (WAT; 50%) and in brown adipose tissue (BAT; 266%). Chronic mTOR inhibition attenuated the upregulation of lipid uptake, LPL expression/activity, and fat accretion induced by PPARγ activation in both subcutaneous WAT and BAT, which resulted in hyperlipidemia. In contrast, rapamycin did not affect most of the other WAT lipogenic genes upregulated by rosiglitazone. Together these findings demonstrate that mTOR is a major regulator of adipose tissue LPL-mediated lipid uptake and a critical mediator of the hypolipidemic and lipogenic actions of PPARγ activation.
The brown adipocyte: update on its metabolic role Sell, Henrike; Deshaies, Yves; Richard, Denis
The international journal of biochemistry & cell biology,
11/2004, Letnik:
36, Številka:
11
Journal Article
Recenzirano
Brown adipocytes are multilocular lipid storage cells that play a crucial role in non-shivering thermogenesis. These cells are located in brown adipose tissue (BAT) depots which are found in ...abundance in small mammals as well as in newborns of larger mammals, including humans. Brown adipocytes comprise a very large number of mitochondria packed with cristae and are densely innervated by the sympathetic nervous system (SNS). Sympathetic nerve endings release noradrenaline (NA) in the proximity of brown fat cells, where noradrenaline activates G-protein-coupled β-adrenergic receptors (AR) and by doing so initiates a cascade of metabolic events culminating in the activation of uncoupling protein 1 (UCP1). Uncoupling protein 1 is a unique feature of brown adipocytes that allows for the generation of heat upon sympathetic nervous system stimulation. It is found in the inner membrane of the mitochondrion, where uncoupling protein 1 uncouples the oxidation of fuel from adenosine triphosphate (ATP) production. The expression of uncoupling protein 1 is strongly induced by cold exposure, revealing the importance of this uncoupling protein in thermoregulation. The thermoregulatory role of uncoupling protein 1 has been emphasized in uncoupling protein 1-deficient mice, whose resistance to cold is impaired. Uncoupling protein 1 expression is modulated by diet and metabolic hormones such as leptin and glucocorticoids, which suggests that the protein is a player in energy balance regulation.
Cell facts
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brown adipocytes are multilocular lipid storage cells comprising a large number of mitochondria packed with cristae;
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brown adipocytes, which are unique to mammals, are densely innervated by sympathetic nervous system (SNS) nerve endings, which release noradrenaline (NA) to stimulate brown adipocytes and uncoupling protein 1 (UCP1);
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UCP1 is a unique feature of brown adipocytes and allows for the generation of heat;
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UCP1 is found in the inner membrane of the mitochondrion, where it uncouples fuel oxidation from adenosine triphosphate (ATP) production;
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brown adipocytes are involved in non-shivering thermogenesis and UCP1 is accordingly induced or repressed by factors such as cold, diet, leptin, corticosterone and obesity, which modulate thermogenesis.
In this study, we aimed to establish the mechanisms whereby peroxisome proliferator-activated receptor gamma (PPARgamma) agonism brings about redistribution of fat toward subcutaneous depots and away ...from visceral fat. In rats treated with the full PPARgamma agonist COOH (30 mg x kg(-1) x day(-1)) for 3 weeks, subcutaneous fat mass was doubled and that of visceral fat was reduced by 30% relative to untreated rats. Uptake of triglyceride-derived nonesterified fatty acids was greatly increased in subcutaneous fat (14-fold) and less so in visceral fat (4-fold), with a concomitant increase, restricted to subcutaneous fat only, in mRNA levels of the uptake-, retention-, and esterification-promoting enzymes lipoprotein lipase, aP2, and diacylglycerol acyltransferase 1. Basal lipolysis and fatty acid recycling were stimulated by COOH in both subcutaneous fat and visceral fat, with no frank quantitative depot specificity. The agonist increased mRNA levels of enzymes of fatty acid oxidation and thermogenesis much more strongly in visceral fat than in subcutaneous fat, concomitantly with a stronger elevation in O2 consumption in the former than in the latter. Mitochondrial biogenesis was stimulated equally in both depots. These findings demonstrate that PPARgamma agonism redistributes fat by stimulating the lipid uptake and esterification potential in subcutaneous fat, which more than compensates for increased O2 consumption; conversely, lipid uptake is minimally altered and energy expenditure is greatly increased in visceral fat, with consequent reduction in fat accumulation.
A High Fat/High Carbohydrate Diet Induces Aortic Valve Disease in C57BL/6J Mice
Marie-Claude Drolet, Elise Roussel, Yves Deshaies, Jacques Couet, Marie Arsenault
Until now, experimental aortic ...stenosis models implied severe hypercholesterolemia by feeding animals high amounts of cholesterol. We evaluated if a high-fat (no added cholesterol)/high carbohydrate diet could alter the aortic valve in normocholesterolemic (wild-type WT) or hypercholesterolemic (low-density lipoprotein receptor-deficient LDLr−/−) mice. The HF/HC diet induced mild hypercholesterolemia, obesity, and hyperglycemia in WT and severe hypercholesterolemia and diabetes in LDLr−/−. Both groups had smaller valve areas and higher transvalvular velocities than corresponding animals on normal diet. Leaflets showed significant tissue abnormalities in all animals on high-fat/high-cholesterol diet. In this mouse model, four months of mild hypercholesterolemia, obesity, and hyperglycemia significantly affected the aortic valve.
The purpose of this study was to compare aortic valve function and morphology in adult wild-type (WT) mice and in low-density lipoprotein receptor-deficient (LDLr−/−) mice fed or not fed a high-fat/high-carbohydrate (HF/HC) diet.
Observations suggest a link between degenerative aortic valve stenosis (AS) and atherosclerosis. Aortic valve stenosis has been successfully induced in animal models of extreme hypercholesterolemia, but these models are less relevant to humans. It is not known if a proatherogenic HF/HC diet without added cholesterol could have the same negative impacts.
Forty C57BL/6J mice were divided into four groups: WT + normal diet, WT + HF/HC diet, LDLr−/− with a normal diet, and LDLr−/− with a HF/HC diet. Aortic valve function and histology were evaluated by echocardiography after four months.
Wild-type mice on a HF/HC diet became mildly hypercholesterolemic, obese, and hyperglycemic. As expected, LDLr−/− mice became severely hypercholesterolemic. Both WT and LDLr−/− mice on a HF/HC diet displayed smaller valve areas and higher transvalvular velocities (p < 0.01) after four months. Aortic valve leaflets were thicker and infiltrated with lipids and macrophages in both HF/HC groups.
A HF/HC diet in mice results in significant aortic valve abnormalities. Putting WT mice on a HF/HC diet reproduced a combination of atherogenic factors (obesity, mild dyslipidemia, and hyperglycemia) more commonly encountered in humans than isolated severe hypercholesterolemia. Severe hypercholesterolemia was not a prerequisite in our model. This experimental model suggests that AS development is multifactorial and that hypercholesterolemia should not be the only target in this disease.
Background
Pulmonary arterial hypertension (PAH) is a vasculopathy characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation and suppressed apoptosis. This results in both ...increase in pulmonary arterial pressure and pulmonary vascular resistance. Recent studies have shown the implication of the signal transducer and activator of transcription 3 (STAT3)/bone morphogenetic protein receptor 2 (BMPR2)/peroxisome proliferator‐activated receptor gamma (PPARγ) in PAH. STAT3 activation induces BMPR2 downregulation, decreasing PPARγ, which both contribute to the proproliferative and antiapoptotic phenotype seen in PAH. In chondrocytes, activation of this axis has been attributed to the advanced glycation end‐products receptor (RAGE). As RAGE is one of the most upregulated proteins in PAH patients' lungs and a strong STAT3 activator, we hypothesized that by activating STAT3, RAGE induces BMPR2 and PPARγ downregulation, promoting PAH‐PASMC proliferation and resistance to apoptosis.
Methods and Results
In vitro, using PASMCs isolated from PAH and healthy patients, we demonstrated that RAGE is overexpressed in PAH‐PASMC (6‐fold increase), thus inducing STAT3 activation (from 10% to 40% positive cells) and decrease in BMPR2 and PPARγ levels (>50% decrease). Pharmacological activation of RAGE in control cells by S100A4 recapitulates the PAH phenotype (increasing RAGE by 6‐fold, thus activating STAT3 and decreasing BMPR2 and PPARγ). In both conditions, this phenotype is totally reversed on RAGE inhibition. In vivo, RAGE inhibition in monocrotaline‐ and Sugen‐induced PAH demonstrates therapeutic effects characterized by PA pressure and right ventricular hypertrophy decrease (control rats have an mPAP around 15 mm Hg, PAH rats have an mPAP >40 mm Hg, and with RAGE inhibition, mPAP decreases to 20 and 28 mm Hg, respectively, in MCT and Sugen models). This was associated with significant improvement in lung perfusion and vascular remodeling due to decrease in proliferation (>50% decrease) and BMPR2/PPARγ axis restoration (increased by ≥60%).
Conclusion
We have demonstrated the implications of RAGE in PAH etiology. Thus, RAGE constitutes a new attractive therapeutic target for PAH.
Subclinical inflammation is frequently associated with obesity. Here, we aim to better define the acute inflammatory response during fasting. To do so, we analyzed representatives of immune-related ...proteins in circulation and in tissues as potential markers for adipose tissue inflammation and modulation of the immune system. Lipopolysaccharide treatment or high-fat diet led to an increase in circulating serum amyloid (SAA) and α1-acid glycoprotein (AGP), whereas adipsin levels were reduced. Mouse models that are protected against diet-induced challenges, such as adiponectin-overexpressing animals or mice treated with PPARγ agonists, displayed lower SAA levels and higher adip-sin levels. An oral lipid gavage, as well as prolonged fasting, increased circulating SAA concurrent with the elevation of free FA levels. Moreover, prolonged fasting was associated with an increased number of Mac2-positive crown-like structures, an increased capillary permeability, and an increase in several M2-type macrophage markers in adipose tissue. This fasting-induced increase in SAA and M2-type macrophage markers was impaired in metabolically challenged animals. These data suggest that metabolic inflexibility is associated with a lack of “immunological fitness.”
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