A CpG-SNP Located within the ARPC3 Gene Promoter Is Associated with Hypertriglyceridemia in Severely Obese Patients.

AIMS: To test the potential association of cytosine-phosphate-guanine dinucleotides (CpG)-single-nucleotide polymorphisms (SNPs) located within actin-related protein 2/3 complex subunit 3 (ARPC3), a gene recently linked to adipogenesis and lipid accumulation, with metabolic syndrome (MetS) features in severely obese patients. METHODS: Prioritized SNPs within the ARPC3 locus were genotyped and tested for associations with MetS features in a cohort of 1,749 obese patients with and without MetS. Association testing with CpG methylation levels was performed in a methylation sub-cohort of 16 obese men. RESULTS: A significant association was found between the CpG-SNP rs3759384 (C>T) and plasma triglyceride (TG) levels (false discovery rate-corrected p = 3.5 × 10-2), with 0.6% of the phenotypic variance explained by the CpG-SNP, and with TT homozygotes showing the highest plasma TG levels (1.89 mmol/l). The carriers of the rs3759384 T allele also showed a significant decrease in methylation levels of the ARPC3 promoter-associated CpG site cg10738648 in both visceral adipose tissue and blood. ARPC3 expression levels showed a strong correlation with plasma TG levels (r = 0.70; p = 0.02). CONCLUSIONS: The increased plasma TG levels found in homozygous rs3759384 T allele carriers argue for a relevant role of this CpG-SNP in lipid management among obese individuals, which may be driven by an epigenetic-mediated mechanism.

Metabolomic profiling in liver of adiponectin-knockout mice uncovers lysophospholipid metabolism as an important target of adiponectin action.

Adiponectin mediates anti-diabetic effects via increasing hepatic insulin sensitivity and direct metabolic effects. In the present study, we conducted a comprehensive and unbiased metabolomic profiling of liver tissue from AdKO (adiponectin-knockout) mice, with and without adiponectin supplementation, fed on an HFD (high-fat diet) to derive insight into the mechanisms and consequences of insulin resistance. Hepatic lipid accumulation and insulin resistance induced by the HFD were reduced by adiponectin. The HFD significantly altered levels of 147 metabolites, and bioinformatic analysis indicated that one of the most striking changes was the profile of increased lysophospholipids. These changes were largely corrected by adiponectin, at least in part via direct regulation of PLA2 (phospholipase A2) as palmitate-induced PLA2 activation was attenuated by adiponectin in primary hepatocytes. Notable decreases in several glycerolipids after the HFD were reversed by adiponectin, which also corrected elevations in several diacyglycerol and ceramide species. Our data also indicate that stimulation of ω-oxidation of fatty acids by the HFD is enhanced by adiponectin. In conclusion, this metabolomic profiling approach in AdKO mice identified important targets of adiponectin action, including PLA2, to regulate lysophospholipid metabolism and ω-oxidation of fatty acids.

Differential methylation in glucoregulatory genes of offspring born before vs. after maternal gastrointestinal bypass surgery.

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.

Early development of calcific aortic valve disease and left ventricular hypertrophy in a mouse model of combined dyslipidemia and type 2 diabetes mellitus.

OBJECTIVE: This study aimed to determine the potential impact of type 2 diabetes mellitus on left ventricular dysfunction and the development of calcified aortic valve disease using a dyslipidemic mouse model prone to developing type 2 diabetes mellitus. APPROACH AND RESULTS: When compared with nondiabetic LDLr(-/-)/ApoB(100/100), diabetic LDLr(-/-)/ApoB(100/100)/IGF-II mice exhibited similar dyslipidemia and obesity but developed type 2 diabetes mellitus when fed a high-fat/sucrose/cholesterol diet for 6 months. LDLr(-/-)/ApoB(100/100)/IGF-II mice showed left ventricular hypertrophy versus C57BL6 but not LDLr(-/-)/ApoB(100/100) mice. Transthoracic echocardiography revealed significant reductions in both left ventricular systolic fractional shortening and diastolic function in high-fat/sucrose/cholesterol fed LDLr(-/-)/ApoB(100/100)/IGF-II mice when compared with LDLr(-/-)/ApoB(100/100). Importantly, we found that peak aortic jet velocity was significantly increased in LDLr(-/-)/ApoB(100/100)/IGF-II mice versus LDLr(-/-)/ApoB(100/100) animals on the high-fat/sucrose/cholesterol diet. Microtomography scans and Alizarin red staining indicated calcification in the aortic valves, whereas electron microscopy and energy dispersive x-ray spectroscopy further revealed mineralization of the aortic leaflets and the presence of inflammatory infiltrates in diabetic mice. Studies showed upregulation of hypertrophic genes (anp, bnp, b-mhc) in myocardial tissues and of osteogenic genes (spp1, bglap, runx2) in aortic tissues of diabetic mice. CONCLUSIONS: We have established the diabetes mellitus -prone LDLr(-/-)/ApoB(100/100)/IGF-II mouse as a new model of calcified aortic valve disease. Our results are consistent with the growing body of clinical evidence that the dysmetabolic state of type 2 diabetes mellitus contributes to early mineralization of the aortic valve and calcified aortic valve disease pathogenesis.

Differential methylation in visceral adipose tissue of obese men discordant for metabolic disturbances.

Obesity is associated with an increased risk of Type 2 diabetes and cardiovascular diseases (CVD). The severely obese population is heterogeneous regarding CVD risk profile. Our objective was to identify metabolic pathways potentially associated with development of metabolic syndrome (MetS) through an analysis of overrepresented pathways from differentially methylated genes between severely obese men with (MetS+) and without (MetS-) the MetS. Genome-wide quantitative DNA methylation analysis in VAT of severely obese men was carried out using the Infinium HumanMethylation450 BeadChip. Differences in methylation levels between MetS+ (n = 7) and MetS- (n = 7) groups were tested. Overrepresented pathways from the list of differentially methylated genes were identified and visualized with the Ingenuity Pathway Analysis system. Differential methylation analysis between MetS+ and MetS- groups identified 8,578 methylation probes (3,258 annotated genes) with significant differences in methylation levels (false discovery rate-corrected DiffScore ≥ |13| ∼ P ≤ 0.05). Pathway analysis from differentially methylated genes identified 41 overrepresented (P ≤ 0.05) pathways. The most overrepresented pathways were related to structural components of the cell membrane, inflammation and immunity and cell cycle regulation. This study provides potential targets associated with adipose tissue dysfunction and development of the MetS.

PPARγ activation attenuates glucose intolerance induced by mTOR inhibition with rapamycin in rats.

mTOR inhibition with rapamycin induces a diabetes-like syndrome characterized by severe glucose intolerance, hyperinsulinemia, and hypertriglyceridemia, which is due to increased hepatic glucose production as well as reduced skeletal muscle glucose uptake and adipose tissue PPARγ activity. Herein, we tested the hypothesis that pharmacological PPARγ activation attenuates the diabetes-like syndrome associated with chronic mTOR inhibition. Rats treated with the mTOR inhibitor rapamycin (2 mg·kg(-1)·day(-1)) in combination or not with the PPARγ ligand rosiglitazone (15 mg·kg(-1)·day(-1)) for 15 days were evaluated for insulin secretion, glucose, insulin, and pyruvate tolerance, skeletal muscle and adipose tissue glucose uptake, and insulin signaling. Rosiglitazone corrected fasting hyperglycemia, attenuated the glucose and insulin intolerances, and abolished the increase in fasting plasma insulin and C-peptide levels induced by rapamycin. Surprisingly, rosiglitazone markedly increased the plasma insulin and C-peptide responses to refeeding in rapamycin-treated rats. Furthermore, rosiglitazone partially attenuated rapamycin-induced gluconeogenesis, as evidenced by the improved pyruvate tolerance and reduced mRNA levels of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. Rosiglitazone also restored insulin's ability to stimulate glucose uptake and its incorporation into glycogen in skeletal muscle of rapamycin-treated rats, which was associated with normalization of Akt Ser(473) phosphorylation. However, the rapamycin-mediated impairments of adipose tissue glucose uptake and incorporation into triacylglycerol were unaffected by rosiglitazone. Our findings indicate that PPARγ activation ameliorates some of the disturbances in glucose homeostasis and insulin action associated with chronic rapamycin treatment by reducing gluconeogenesis and insulin secretion and restoring muscle insulin signaling and glucose uptake.

Distinct metabolic and vascular effects of dietary triglycerides and cholesterol in atherosclerotic and diabetic mouse models.

Cholesterol and triglyceride-rich Western diets are typically associated with an increased occurrence of type 2 diabetes and vascular diseases. This study aimed to assess the relative impact of dietary cholesterol and triglycerides on glucose tolerance, insulin sensitivity, atherosclerotic plaque formation, and endothelial function. C57BL6 wild-type (C57) mice were compared with atherosclerotic LDLr(-/-) ApoB(100/100) (LRKOB100) and atherosclerotic/diabetic IGF-II × LDLr(-/-) ApoB(100/100) (LRKOB100/IGF) mice. Each group was fed either a standard chow diet, a 0.2% cholesterol diet, a high-fat diet (HFD), or a high-fat 0.2% cholesterol diet for 6 mo. The triglyceride-rich HFD increased body weight, glucose intolerance, and insulin resistance but did not alter endothelial function or atherosclerotic plaque formation. Dietary cholesterol, however, increased plaque formation in LRKOB100 and LRKOB100/IGF animals and decreased endothelial function regardless of genotype. However, cholesterol was not associated with an increase of insulin resistance in LRKOB100 and LRKOB100/IGF mice and, unexpectedly, was even found to reduce the insulin-resistant effect of dietary triglycerides in these animals. Our data indicate that dietary triglycerides and cholesterol have distinct metabolic and vascular effects in obese atherogenic mouse models resulting in dissociation between the impairment of glucose homeostasis and the development of atherosclerosis.

Major involvement of mTOR in the PPARγ-induced stimulation of adipose tissue lipid uptake and fat accretion.

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.

Lack of "immunological fitness" during fasting in metabolically challenged animals.

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."

Genetic contribution to C-reactive protein levels in severe obesity.

Obese individuals are characterized by a chronic, low-grade inflammatory state. Increased levels of C-reactive protein (CRP), a marker of inflammation, have been observed in subjects with the metabolic syndrome. We have previously reported that genes encoding proteins involved in the anti-inflammatory and immune response are differentially expressed in visceral adipose tissue of obese men with or without the metabolic syndrome. Among these genes, the interferon-gamma-inducible protein 30 (IFI30), CD163 molecule (CD163), chemokine (C-X-C motif) ligand 9 (CXCL9) and thymic stromal lymphopoietin (TSLP), were selected for further genetic analyses. The aim of the study was to verify whether IFI30, CD163, CXCL9 and TSLP gene polymorphisms contribute to explain the inter-individual variability of the inflammatory profile of obesity assessed by plasma high-sensitivity CRP concentrations. A total of 1185 severely obese individuals were genotyped for single nucleotide polymorphisms (SNPs) covering most of the sequence-derived genetic variability at the IFI30, CD163, CXCL9 and TSLP gene loci (total of 27 SNPs). Following measurement of plasma CRP levels, subjects were divided into two groups, low vs. high using the median value of plasma CRP levels (8.31 mg/L) as a cutoff point. Genotype frequencies were compared between groups. Associations between genotypes and plasma CRP levels (continuous variable) were also tested after adjustments for age, sex, smoking and BMI. The rs11554159 and rs7125 IFI30 SNPs showed a significant difference in genotype frequencies (p<0.05) between subgroups of low vs. high plasma CRP levels (wild type homozygotes: rs11554159=47% vs. 55%, rs7125=31% vs. 24%, for low vs. high CRP groups, respectively). The association between rs11554159 and CRP levels as a continuous variable remained significant (p=0.004). Both carriers of the GA and AA genotypes demonstrated, on average, a 13% lower CRP levels in comparison with GG homozygotes. No association was observed between SNPs in the CD163, CXCL9 and TSLP genes and CRP levels. The IFI30 rs11554159 polymorphism could partially explain the inter-individual variability observed in the inflammatory profile associated with obesity.

PPARγ activation attenuates cold-induced upregulation of thyroid status and brown adipose tissue PGC-1α and D2.

Here, we investigated whether pharmacological PPARγ activation modulates key early events in brown adipose tissue (BAT) recruitment induced by acute cold exposure with the aim of unraveling the interrelationships between sympathetic and PPARγ signaling. Sprague-Dawley rats treated or not with the PPARγ ligand rosiglitazone (15 mg·kg(-1)·day(-1), 7 days) were kept at 23°C or exposed to cold (5°C) for 24 h and evaluated for BAT gene expression, sympathetic activity, thyroid status, and adrenergic signaling. Rosiglitazone did not affect the reduction in body weight gain and the increase in feed efficiency, Vo(2), and BAT sympathetic activity induced by 24-h cold exposure. Rosiglitazone strongly attenuated the increase in serum total and free T4 and T3 levels and BAT iodothyronine deiodinase type 2 (D2) and PGC-1α mRNA levels and potentiated the reduction in BAT thyroid hormone receptor (THR) ß mRNA levels induced by cold. Administration of T3 to rosiglitazone-treated rats exacerbated the cold-induced increase in energy expenditure but did not restore a proper activation of D2 and PGC-1α, nor further increased uncoupling protein 1 expression. Regarding adrenergic signaling, rosiglitazone did not affect the changes in BAT cAMP content and PKA activity induced by cold. Rosiglitazone alone or in combination with cold increased CREB binding to DNA, but it markedly reduced the expression of one of its major coactivators, CREB binding protein. In conclusion, pharmacological PPARγ activation impairs short-term cold elicitation of BAT adrenergic and thyroid signaling, which may result in abnormal tissue recruitment and thermogenic activity.

Thymic stromal lymphopoietin: an immune cytokine gene associated with the metabolic syndrome and blood pressure in severe obesity.

A previous expression profiling of VAT (visceral adipose tissue) revealed that the TSLP (thymic stromal lymphopoietin) gene was less expressed in severely obese men with (n=7) compared with without (n=7) the MetS (metabolic syndrome). We hypothesized that TSLP SNPs (single nucleotide polymorphisms) are associated with TSLP gene expression in VAT and with MetS phenotypes. Following validation of lower TSLP expression (P=0.003) in VAT of severely obese men and women with (n=70) compared with without (n=60) the MetS, a detailed genetic investigation was performed at the TSLP locus by sequencing its promoter, exons and intron-exon splicing boundaries using DNA of 25 severely obese subjects. Five tagging SNPs were genotyped in the 130 subjects from the expression analysis to test whether these SNPs contributed to TSLP expression variability (ANOVAs) and then genotyped in two independent samples of severely obese men (total, n=389) and women (total, n=894). In a sex-stratified multistage experimental design, ANOVAs were performed to test whether tagging SNPs were associated with MetS components treated as continuous variables. We observed that the non-coding SNP rs2289277 was associated with TSLP mRNA abundance (P=0.04), as well as with SBP [systolic BP (blood pressure)] (P=0.004) and DBP (diastolic BP) (P=0.0003) in men when adjusting for age, waist circumference, smoking and medication treating hypertension. These novel observations suggest that TSLP expression in VAT may partly explain the inter-individual variability for metabolic impairments in the presence of obesity and that specific SNPs (rs2289277 and/or correlating SNPs) may influence TSLP gene expression as well as BP in obese men.

Obesity-associated improvements in metabolic profile through expansion of adipose tissue.

Excess caloric intake can lead to insulin resistance. The underlying reasons are complex but likely related to ectopic lipid deposition in nonadipose tissue. We hypothesized that the inability to appropriately expand subcutaneous adipose tissue may be an underlying reason for insulin resistance and beta cell failure. Mice lacking leptin while overexpressing adiponectin showed normalized glucose and insulin levels and dramatically improved glucose as well as positively affected serum triglyceride levels. Therefore, modestly increasing the levels of circulating full-length adiponectin completely rescued the diabetic phenotype in ob/ob mice. They displayed increased expression of PPARgamma target genes and a reduction in macrophage infiltration in adipose tissue and systemic inflammation. As a result, the transgenic mice were morbidly obese, with significantly higher levels of adipose tissue than their ob/ob littermates, leading to an interesting dichotomy of increased fat mass associated with improvement in insulin sensitivity. Based on these data, we propose that adiponectin acts as a peripheral "starvation" signal promoting the storage of triglycerides preferentially in adipose tissue. As a consequence, reduced triglyceride levels in the liver and muscle convey improved systemic insulin sensitivity. These mice therefore represent what we believe is a novel model of morbid obesity associated with an improved metabolic profile.

Basal adrenergic tone is required for maximal stimulation of rat brown adipose tissue UCP1 expression by chronic PPAR-gamma activation.

We investigated the involvement of basal sympathetic tone in brown adipose tissue (BAT) recruitment and gene expression profile induced by peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activation. Innervated and surgically denervated BAT pads of rats treated or not with rosiglitazone (15 mg.kg(-1).day(-1), 7 days) were evaluated for weight, triacylglycerol (TAG) and DNA content, mitochondrial mass, and gene expression. Rosiglitazone induced BAT recruitment (increased mass, TAG and DNA content) and mRNA levels of lipolytic (adipose tissue triglyceride lipase and CGI58) and lipogenic (lipoprotein lipase, phosphoenolpyruvate carboxykinase, fatty acid binding protein 4, and diacylglycerol acyltransferase 1) proteins independently of tissue innervation status. Mitochondrial mass and mRNA levels of its regulators peroxisome proliferator-activated receptor coactivator-alpha and CCAAT/enhancer binding protein-beta were not affected by rosiglitazone, while being significantly reduced by denervation. By contrast, maximal stimulation of uncoupling protein 1 (UCP1) (thermogenesis), cell death-inducing DNA fragmentation factor-45-like effector A (inhibitor of UCP1 activity), monoacylglycerol lipase (lipolysis), small heterodimer partner (transcription), and glycerokinase (TAG synthesis) by rosiglitazone depended on the presence of intact BAT innervation. Cold exposure (5 degrees C, 24 h) significantly increased UCP1 mRNA levels in innervated BAT pads of untreated rats, without affecting the already high BAT UCP1 levels of rosiglitazone-treated animals. A similar pattern of response was found in denervated pads, but with markedly lower UCP1 expression than that in innervated BAT. In conclusion, whereas the mass (hyperplasia and hypertrophy), lipogenic, and lipolytic components of BAT recruitment induced by rosiglitazone occur independently of tissue sympathetic innervation, maximal UCP1 expression induced by PPAR-gamma in vivo depends on the presence of basal BAT adrenergic tone. The residual sympathetic tone found under rosiglitazone treatment is, therefore, involved in the modulation of a subset of major components of PPAR-gamma-mediated BAT recruitment.

Rosiglitazone-induced heart remodelling is associated with enhanced turnover of myofibrillar protein and mTOR activation.

We investigated cardiac hypertrophy elicited by rosiglitazone treatment at the level of protein synthesis/degradation, mTOR, MAPK and AMPK signalling pathways, cardiac function and aspects of carbohydrate/lipid metabolism. Hearts of rats treated or not with rosiglitazone (15 mg/kg day) for 21 days were evaluated for gene expression, protein synthesis, proteasome and calpain activities, signalling pathways, and function by echocardiography. Rosiglitazone induced eccentric heart hypertrophy associated with increased expression of ANP, BNP, collagen I and III and fibronectin, reduced heart rate and increased stroke volume. Rosiglitazone robustly increased heart glycogen content ( approximately 400%), an effect associated with increases in glycogenin and UDPG-PPL mRNA levels and glucose uptake, and a reduction in glycogen phosphorylase expression and activity. Cardiac triglyceride content, lipoprotein lipase activity and mRNA levels of enzymes involved in fatty acid oxidation were also reduced by the agonist. Rosiglitazone-induced cardiac hypertrophy was associated with an increase in myofibrillar protein content and turnover (increased synthesis and an enhancement of calpain-mediated myofibrillar degradation). In contrast, 26S beta5 chymotryptic proteasome activity and mRNA levels of 20S beta2 and beta5 and 19S RPN 2 proteasome subunits along with the ubiquitin ligases atrogin and CHIP were all reduced by rosiglitazone. These morphological and biochemical changes were associated with marked activation of the key growth-promoting mTOR signalling pathway, whose pharmacological inhibition with rapamycin completely blocked cardiac hypertrophy induced by rosiglitazone. The study demonstrates that both arms of protein balance are involved in rosiglitazone-induced cardiac hypertrophy, and establishes the mTOR pathway as a novel important mediator therein.

Peroxisome proliferator-activated receptor-gamma-mediated positive energy balance in the rat is associated with reduced sympathetic drive to adipose tissues and thyroid status.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) activation up-regulates thermogenesis-related genes in rodent white and brown adipose tissues (WAT and BAT) without increasing whole-body energy expenditure. We tested here whether such dissociation is the result of a negative modulation of sympathetic activity to WAT and BAT and thyroid axis components by PPARgamma activation. Administration of the PPARgamma agonist rosiglitazone (15 mg/kg.d) for 7 d to male Sprague Dawley rats increased food intake (10%), feed efficiency (31%), weight gain (45%), spontaneous motor activity (60%), and BAT and WAT mass and reduced whole-body oxygen consumption. Consistent with an anabolic setting, rosiglitazone markedly reduced sympathetic activity to BAT and WAT (>50%) and thyroid status as evidenced by reduced levels of plasma thyroid hormones (T(4) and T(3)) and mRNA levels of BAT and liver T(3)-generating enzymes iodothyronine type 2 (-40%) and type 1 (-32%) deiodinases, respectively. Rosiglitazone also decreased mRNA levels of the thyroid hormone receptor (THR) isoforms alpha1 (-34%) and beta (-66%) in BAT and isoforms alpha1 (-20%) and alpha2 (-47%) in retroperitoneal WAT. These metabolic effects were associated with a reduction in mRNA levels of the pro-energy expenditure peptides CRH and CART in specific hypothalamic nuclei. A direct central action of rosiglitazone is, however, unlikely based on its low brain uptake and lack of metabolic effects of intracerebroventricular administration. In conclusion, a reduction in BAT sympathetic activity and thyroid status appears to, at least partly, explain the PPARgamma-induced reduction in energy expenditure and the fact that up-regulation of thermogenic gene expression does not translate into functional stimulation of whole-body thermogenesis in vivo.

Differential effect of fenofibrate and atorvastatin on in vivo kinetics of apolipoproteins B-100 and B-48 in subjects with type 2 diabetes mellitus with marked hypertriglyceridemia.

The specific impact of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors and fibrates on the in vivo metabolism of apolipoprotein (apo) B has not been systematically investigated in patients with type 2 diabetes mellitus with high plasma triglyceride (TG) levels. Therefore, the objective of this 2-group parallel study was to examine the differential effects of a 6-week treatment with atorvastatin or fenofibrate on in vivo kinetics of apo B-48 and B-100 in men with type 2 diabetes mellitus with marked hypertriglyceridemia. Apolipoprotein B kinetics were assessed at baseline and at the end of the intervention using a primed constant infusion of [5,5,5-D(3)]-l-leucine for 12 hours in the fed state. Fenofibrate significantly decreased plasma TG levels with no significant change in plasma low-density lipoprotein cholesterol (LDL-C) and apo B levels. On the other hand, atorvastatin significantly reduced plasma levels of TG, LDL-C, and apo B. After treatment with fenofibrate, very low-density lipoprotein (VLDL) apo B-100 pool size (PS) was decreased because of an increase in the fractional catabolic rate (FCR) of VLDL apo B-100. No significant change was observed in the kinetics of LDL apo B-100. Moreover, fenofibrate significantly decreased TG-rich lipoprotein (TRL) apo B-48 PS because of a significant increase in TRL apo B-48 FCR. After treatment with atorvastatin, VLDL and IDL apo B-100 PSs were significantly decreased because of significant elevations in the FCR of these subfractions. Low-density lipoprotein apo B-100 PS was significantly lowered because of a tendency toward decreased LDL apo B-100 production rate (PR). Finally, atorvastatin reduced TRL apo B-48 PS because of a significant decrease in the PR of this subfraction. These results indicate that fenofibrate increases TRL apo B-48 as well as VLDL apo B-100 clearance in men with type 2 diabetes mellitus with marked hypertriglyceridemia, whereas atorvastatin increases both VLDL and IDL apo B-100 clearance and decreases TRL apo B-48 and LDL apo B-100 PR.

PPARγ is a major regulator of branched-chain amino acid blood levels and catabolism in white and brown adipose tissues.

OBJECTIVE: We investigated whether PPARγ modulates adipose tissue BCAA metabolism, and whether this mediates the attenuation of obesity-associated insulin resistance induced by pharmacological PPARγ activation. METHODS: Mice with adipocyte deletion of one or two PPARγ copies fed a chow diet and rats fed either chow, or high fat (HF) or HF supplemented with BCAA (HF/BCAA) diets treated with rosiglitazone (30 or 15 mg/kg/day, 14 days) were evaluated for glucose and BCAA homeostasis. RESULTS: Adipocyte deletion of one PPARγ copy increased mice serum BCAA and reduced inguinal white (iWAT) and brown (BAT) adipose tissue BCAA incorporation into triacylglycerol, as well as mRNA levels of branched-chain aminotransferase (BCAT)2 and branched-chain α-ketoacid dehydrogenase (BCKDH) complex subunits. Adipocyte deletion of two PPARγ copies induced lipodystrophy, severe glucose intolerance and markedly increased serum BCAA. Rosiglitazone abolished the increase in serum BCAA induced by adipocyte PPARγ deletion. In rats, HF increased serum BCAA, such levels being further increased by BCAA supplementation. Rosiglitazone, independently of diet, lowered serum BCAA and upregulated iWAT and BAT BCAT and BCKDH activities. This was associated with a reduction in mTORC1-dependent inhibitory serine phosphorylation of IRS1 in skeletal muscle and whole-body insulin resistance evaluated by HOMA-IR. CONCLUSIONS: PPARγ, through the regulation of both BAT and iWAT BCAA catabolism in lipoeutrophic mice and muscle insulin responsiveness and proteolysis in lipodystrophic mice, is a major determinant of circulating BCAA levels. PPARγ agonism, therefore, may improve whole-body and muscle insulin sensitivity by reducing blood BCAA, alleviating mTORC1-mediated inhibitory IRS1 phosphorylation.

Loss of OcaB Prevents Age-Induced Fat Accretion and Insulin Resistance by Altering B-Lymphocyte Transition and Promoting Energy Expenditure.

The current demographic shift toward an aging population has led to a robust increase in the prevalence of age-associated metabolic disorders. Recent studies have demonstrated that the etiology of obesity-related insulin resistance that develops with aging differs from that induced by high-calorie diets. Whereas the role of adaptive immunity in changes in energy metabolism driven by nutritional challenges has recently gained attention, its impact on aging remains mostly unknown. Here we found that the number of follicular B2 lymphocytes and expression of the B-cell-specific transcriptional coactivator OcaB increase with age in spleen and in intra-abdominal epididymal white adipose tissue (eWAT), concomitantly with higher circulating levels of IgG and impaired glucose homeostasis. Reduction of B-cell maturation and Ig production-especially that of IgG2c-by ablation of OcaB prevented age-induced glucose intolerance and insulin resistance and promoted energy expenditure by stimulating fatty acid utilization in eWAT and brown adipose tissue. Transfer of wild-type bone marrow in OcaB-/- mice replenished the eWAT B2-cell population and IgG levels, which diminished glucose tolerance, insulin sensitivity, and energy expenditure while increasing body weight gain in aged mice. Thus these findings demonstrate that upon aging, modifications in B-cell-driven adaptive immunity contribute to glucose intolerance and fat accretion.

Depot-specific modulation of rat intraabdominal adipose tissue lipid metabolism by pharmacological inhibition of 11beta-hydroxysteroid dehydrogenase type 1.

The metabolic consequences of visceral obesity have been associated with amplification of glucocorticoid action by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in adipose tissue. This study aimed to assess in a rat model of diet-induced obesity the effects of pharmacological 11beta-HSD1 inhibition on the morphology and expression of key genes of lipid metabolism in intraabdominal adipose depots. Rats fed a high-sucrose, high-fat diet were treated or not with a specific 11beta-HSD1 inhibitor (compound A, 3 mg/kg.d) for 3 wk. Compound A did not alter food intake or body weight gain but specifically reduced mesenteric adipose weight (-18%) and adipocyte size, without significantly affecting those of epididymal or retroperitoneal depots. In mesenteric fat, the inhibitor decreased (to 25-50% of control) mRNA levels of genes involved in lipid synthesis (FAS, SCD1, DGAT1) and fatty acid cycling (lipolysis/reesterification, ATGL and PEPCK) and increased (30%) the activity of the fatty acid oxidation-promoting enzyme carnitine palmitoyltransferase 1. In striking contrast, in the epididymal depot, 11beta-HSD1 inhibition increased (1.5-5-fold) mRNA levels of those genes related to lipid synthesis/cycling and slightly decreased carnitine palmitoyltransferase 1 activity, whereas gene expression remained unaffected in the retroperitoneal depot. Compound A robustly reduced liver triacylglycerol content and plasma lipids. The study demonstrates that pharmacological inhibition of 11beta-HSD1, at a dose that does not alter food intake, reduces fat accretion specifically in the mesenterical adipose depot, exerts divergent intraabdominal depot-specific effects on genes of lipid metabolism, and reduces steatosis and lipemia.