[Show abstract][Hide abstract] ABSTRACT: Non-alcoholic fatty liver (NAFLD), particularly its more aggressive form, nonalcoholic steatohepatitis (NASH), is associated with hepatic insulin resistance. Osteocalcin, a protein secreted by osteoblast cells in bone, has recently emerged as an important metabolic regulator with insulin-sensitizing properties. In humans, osteocalcin levels are inversely associated with liver disease. We thus hypothesized that osteocalcin may attenuate NASH and examined the effects of osteocalcin treatment in middle-aged (12-month-old) male Ldlr(-/-) mice, which were fed a "Western-style" high-fat, high-cholesterol diet (WHFD) for 12 weeks to induce metabolic syndrome and NASH. Mice were treated with osteocalcin (4.5ng/hr) or vehicle for the diet duration. Osteocalcin treatment not only protected against WHFD-induced insulin resistance, but substantially reduced multiple NASH components, including steatosis, ballooning degeneration, and fibrosis, with an overall reduction in NAFLD activity scores. Further, osteocalcin robustly reduced expression of pro-inflammatory and pro-fibrotic genes (Cd68, Mcp1, Spp1 and Col1a2) in liver and suppressed inflammatory gene expression in white adipose tissue. Conclusion: These results suggest osteocalcin inhibits NASH development by targeting inflammatory and fibrotic processes.
[Show abstract][Hide abstract] ABSTRACT: Adipose tissue inflammation increases with obesity, but adipocyte vs. immune cell contributions are unclear. In the present study, transcriptome analyses were performed on highly-purified subcutaneous adipocytes from lean and obese women, and differentially expressed genes/pathways were determined in both adipocyte and stromal vascular fraction (SVF) samples. Adipocyte but not SVF expression of NOD-like receptor pathway genes, including NLRP3 and PYCARD, which regulate caspase-1-mediated IL-1β secretion, correlated with adiposity phenotypes and adipocyte class II major histocompatibility complex (MHCII) gene expression, but only MHCII remained after adjusting for age and body mass index. IFNγ stimulated adipocyte MHCII, NLRP3 and caspase-1 expression, while adipocyte MHCII-mediated CD4(+) T cell activation, an important factor in adipose inflammation, induced IFNγ-dependent adipocyte IL-1β secretion. These results uncover a dialogue regulated by interactions among T cell IFNγ and adipocyte MHCII and NLRP3 inflammasome activity that appears to initiate and escalate adipose tissue inflammation during obesity.
Molecular and Cellular Endocrinology 07/2014; · 4.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: Impaired bioenergetics is a prominent feature of the failing heart, but the underlying metabolic perturbations are poorly understood.
Methods and Results: We compared metabolomic, gene transcript, and protein data from six paired failing human left ventricular (LV) tissue samples obtained during left ventricular assist device (LVAD) insertion (heart failure (HF) samples) and at heart transplant (post-LVAD samples). Non-failing left ventricular (NFLV) wall samples procured from explanted hearts of patients with right heart failure served as novel comparison samples. Metabolomic analyses uncovered a distinct pattern in HF tissue: increased pyruvate concentrations coupled with reduced Krebs cycle intermediates and short-chain acylcarnitines, suggesting a global reduction in substrate oxidation. These findings were associated with decreased transcript levels for enzymes that catalyze fatty acid oxidation and pyruvate metabolism and for key transcriptional regulators of mitochondrial metabolism and biogenesis, peroxisome proliferator-activated receptor gamma co-activator1α (PGC1α) and estrogen-related receptor α (ERRα) and γ (ERRγ). Thus, parallel decreases in key transcription factors and their target metabolic enzyme genes can explain the decreases in associated metabolic intermediates. Mechanical support with LVAD improved all of these metabolic and transcriptional defects.
Conclusions: These observations underscore an important pathophysiologic role for severely defective metabolism in HF, while the reversibility of these defects by LVAD suggests metabolic resilience of the human heart.
[Show abstract][Hide abstract] ABSTRACT: -Impaired bioenergetics is a prominent feature of the failing heart, but the underlying metabolic perturbations are poorly understood.
-We compared metabolomic, gene transcript, and protein data from six paired failing human left ventricular (LV) tissue samples obtained during left ventricular assist device (LVAD) insertion (heart failure (HF) samples) and at heart transplant (post-LVAD samples). Non-failing left ventricular (NFLV) wall samples procured from explanted hearts of patients with right HF served as novel comparison samples. Metabolomic analyses uncovered a distinct pattern in HF tissue: 2.6 fold increased pyruvate concentrations coupled with reduced Krebs cycle intermediates and short-chain acylcarnitines, suggesting a global reduction in substrate oxidation. These findings were associated with decreased transcript levels for enzymes that catalyze fatty acid oxidation and pyruvate metabolism and for key transcriptional regulators of mitochondrial metabolism and biogenesis, peroxisome proliferator-activated receptor gamma co-activator1α (PGC1A, 1.3 fold) and estrogen-related receptor α (ERRA, 1.2 fold) and γ (ERRG, 2.2 fold). Thus, parallel decreases in key transcription factors and their target metabolic enzyme genes can explain the decreases in associated metabolic intermediates. Mechanical support with LVAD improved all of these metabolic and transcriptional defects.
-These observations underscore an important pathophysiologic role for severely defective metabolism in HF, while the reversibility of these defects by LVAD suggests metabolic resilience of the human heart.
[Show abstract][Hide abstract] ABSTRACT: In heart failure mitochondrial dysfunction is thought to be responsible for energy depletion and contractile dysfunction. The difficulties in procuring fresh left ventricular (LV) myocardium from humans for assessment of mitochondrial function have resulted in the reliance on surrogate markers of mitochondrial function and limited our understanding of cardiac energetics. We isolated mitochondria from fresh LV wall tissue of patients with heart failure and reduced systolic function undergoing heart transplant or left ventricular assist device placement, and compared their function to mitochondria isolated from the non-failing LV (NFLV) wall tissue with normal systolic function from patients with pulmonary hypertension undergoing heart-lung transplant. We performed detailed mitochondrial functional analyses using 4 substrates: glutamate-malate (GM), pyruvate-malate (PM) palmitoyl carnitine-malate (PC) and succinate. NFLV mitochondria showed preserved respiratory control ratios and electron chain integrity with only few differences for the 4 substrates. In contrast, HF mitochondria had greater respiration with GM, PM and PC substrates and higher electron chain capacity for PM than for PC. Surprisingly, HF mitochondria had greater respiratory control ratios and lower ADP-independent state 4 rates than NFLV mitochondria for GM, PM and PC substrates demonstrating that HF mitochondria are capable of coupled respiration ex vivo. Gene expression studies revealed decreased expression of key genes in pathways for oxidation of both fatty acids and glucose. Our results suggest that mitochondria from the failing LV myocardium are capable of tightly coupled respiration when isolated and supplied with ample substrates. Thus energy starvation in the failing heart may be the result of dysregulation of metabolic pathways, impaired substrate supply or reduced mitochondrial number but not the result of reduced mitochondrial electron transport capacity.
Journal of Molecular and Cellular Cardiology 01/2014; · 5.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Clinical trials have demonstrated that it is possible to prevent diabetes through lifestyle modification, pharmacological intervention, and surgery. This review aims to summarize the effectiveness of these various therapeutic interventions in reducing the risk of progression of prediabetes to diabetes, and address the challenges to implement a diabetes prevention program at a community level. Strategies focusing on intensive lifestyle changes are not only efficient but cost-effective and/or cost-saving. Indeed, lifestyle intervention in people at high risk for type 2 diabetes mellitus (T2DM) has been successful in achieving sustained behavioral changes and a reduction in diabetes incidence even after the counseling is stopped. Although prediabetes is associated with health and economic burdens, it has not been adequately addressed by interventions or regulatory agencies in terms of prevention or disease management. Lifestyle intervention strategies to prevent T2DM should be distinct for different populations around the globe and should emphasize sex, age, ethnicity, and cultural and geographical considerations to be feasible and to promote better compliance. The translation of diabetes prevention research at a population level, especially finding the most effective methods of preventing T2DM in various societies and cultural settings remains challenging, but must be accomplished to stop this worldwide epidemic.
[Show abstract][Hide abstract] ABSTRACT: Treatment response to lipid-lowering therapy can vary in patients with the metabolic syndrome (MetS) due to various patient demographic and baseline characteristics.
This study assessed the relationships between baseline characteristics and changes in lipid variables, high-sensitivity C-reactive protein (hs-CRP) and attainment of prespecified low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol (non-HDL-C) levels in MetS patients treated with ezetimibe/simvastatin and atorvastatin.
This is a post-hoc analysis of a multicenter, double-blind, randomized, 6-week parallel study in >1000 hypercholesterolemic subjects (median age of 59 years) with MetS and moderately high/high coronary heart disease risk who were treated with ezetimibe/simvastatin (10/20 and 10/40 mg) or atorvastatin (10, 20, 40 mg). Factors that could affect these treatments were assessed by multivariate analysis.
Increasing age, abdominal obesity (waist circumference ≥40/35 inches for men/women), and lower baseline hs-CRP were significant predictors of greater reductions in LDL-C, non-HDL-C, apolipoprotein B, total cholesterol, triglycerides, and very-low-density lipoprotein cholesterol but not for changes in HDL-C or apolipoprotein AI; effects of race and baseline triglycerides, non-HDL-C, LDL-C, or HDL-C levels were more limited. Age ≥65 years (versus <65 years) was also associated with significantly greater attainment of all LDL-C and non-HDL-C targets, whereas abdominal obesity, gender (female > male) and lower baseline LDL-C, non-HDL-C, triglycerides, and hs-CRP were associated with improved attainment for some of these targets. Blood pressure, fasting glucose, Homeostasis Model Assessment of Insulin Resistance tertiles, and diabetes did not predict response for any efficacy variable. Ezetimibe/simvastatin treatment (versus atorvastatin) was a significant predictor for change in most efficacy variables.
Treatment responses to ezetimibe/simvastatin and atorvastatin in at-risk patients with the MetS were related to age (≥65 years), abdominal obesity, and lower baseline hs-CRP. Ezetimibe/simvastatin treatment was found to be consistently more effective than atorvastatin at the specified dose comparisons across these subgroups. The clinical value of predictive factors requires further study in outcome trials.
Journal of Clinical Lipidology 07/2013; 7(4):292-303. · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: PPARγ nuclear receptor agonists have been shown to attenuate macrophage inflammatory responses implicated in the metabolic complications of obesity and in atherosclerosis. However, PPARγ agonists currently in clinical use, including rosiglitazone (RSG), are often associated with severe side effects that limit their therapeutic use. Here, 200 nm PLGA/PVA nanospheres were formulated for the systemic delivery of RSG specifically to macrophages. RSG was encapsulated with over 50% efficiency in the hydrophobic PLGA core and released specifically within the acidifying macrophage phagosomes. In bone marrow derived macrophages, RSG-loaded nanoparticles (RSG-NPs) induce a dose dependent upregulation (1.5 to 2.5-fold) of known PPARγ target genes, with maximal induction at 5 μM; and downregulate the expression of genes related to the inflammatory process, with maximum effect at 10 μM. In Ldlr(-/-) mice fed high fat diet, treatment with RSG-NPs alleviated inflammation in white adipose tissue and liver but, unlike treatment with free RSG, did not alter genes associated with lipid metabolism or cardiac function, indicating a reduction in the RSG side effect profile. These biocompatible, biodegradable RSG-NPs represent a preliminary step towards the specific delivery of nuclear receptor agonists for the treatment of macrophage-mediated inflammatory conditions associated with obesity, atherosclerosis and other chronic disease states.
Journal of Controlled Release 06/2013; · 7.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The worldwide prevalence of obesity mandates a widely accessible tool to categorize adiposity that can best predict associated health risks. The body adiposity index (BAI) was designed as a single equation to predict body adiposity in pooled analysis of both genders. We compared body adiposity index (BAI), body mass index (BMI), and other anthropometric measures, including percent body fat (PBF), in their correlations with cardiometabolic risk factors. We also compared BAI with BMI to determine which index is a better predictor of PBF.
The cohort consisted of 698 Mexican Americans. We calculated correlations of BAI, BMI, and other anthropometric measurements (PBF measured by dual energy X-ray absorptiometry, waist and hip circumference, height, weight) with glucose homeostasis indices (including insulin sensitivity and insulin clearance from euglycemic clamp), lipid parameters, cardiovascular traits (including carotid intima-media thickness), and biomarkers (C-reactive protein, plasminogen activator inhibitor-1 and adiponectin). Correlations between each anthropometric measure and cardiometabolic trait were compared in both sex-pooled and sex-stratified groups.
BMI was associated with all but two measured traits (carotid intima-media thickness and fasting glucose in men), while BAI lacked association with several variables. BAI did not outperform BMI in its associations with any cardiometabolic trait. BAI was correlated more strongly than BMI with PBF in sex-pooled analyses (r = 0.78 versus r = 0.51), but not in sex-stratified analyses (men, r = 0.63 versus r = 0.79; women, r = 0.69 versus r = 0.77). Additionally, PBF showed fewer correlations with cardiometabolic risk factors than BMI. Weight was more strongly correlated than hip with many of the cardiometabolic risk factors examined.
BAI is inferior to the widely used BMI as a correlate of the cardiometabolic risk factors studied. Additionally, BMI's relationship with total adiposity may not be the sole determinate of its association with cardiometabolic risk.
PLoS ONE 06/2013; 8(6):e65954. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In obesity, reduced cardiac glucose uptake and mitochondrial abnormalities are putative causes of cardiac dysfunction. However, high fat diet (HFD) does not consistently induce cardiac insulin resistance and mitochondrial damage, and recent studies suggest HFD may be cardioprotective. To determine cardiac responses to HFD, we investigated cardiac function, glucose uptake and mitochondrial respiration in young (3-month-old) and middle-aged (MA; 12-month-old) male Ldlr(-/-) mice fed chow or 3 months HFD to induce obesity, systemic insulin resistance and hyperinsulinemia. In MA Ldlr(-/-) mice, HFD induced accelerated atherosclerosis and nonalcoholic steatohepatitis, common complications of human obesity. Surprisingly, HFD-fed mice demonstrated increased cardiac glucose uptake, which was most prominent in MA mice, in the absence of cardiac contractile dysfunction or hypertrophy. Moreover, hearts of HFD-fed mice had enhanced mitochondrial oxidation of palmitoyl carnitine, glutamate, and succinate, and greater basal insulin signaling compared to those of chow-fed mice, suggesting cardiac insulin sensitivity was maintained, despite systemic insulin resistance. Streptozotocin (STZ)-induced ablation of insulin production markedly reduced cardiac glucose uptake and mitochondrial dysfunction in HFD-fed, but not in chow-fed mice. Insulin injection reversed these effects, suggesting that insulin may protect cardiac mitochondria during HFD. These results have implications for cardiac metabolism and preservation of mitochondrial function in obesity.
[Show abstract][Hide abstract] ABSTRACT: AIMS/HYPOTHESIS: Insulin clearance is a highly heritable trait, for which few quantitative trait loci have been discovered. We sought to determine whether validated type 2 diabetes and/or glycaemic trait loci are associated with insulin clearance. METHODS: Hyperinsulinaemic-euglycaemic clamps were performed in two Hispanic-American family cohorts totalling 1329 participants in 329 families. The Metabochip was used to fine-map about 50 previously identified loci for type 2 diabetes, fasting glucose, fasting insulin, 2 h glucose or HbA1c. This resulted in 17,930 variants, which were tested for association with clamp-derived insulin clearance via meta-analysis of the two cohorts. RESULTS: In the meta-analysis, 38 variants located within seven loci demonstrated association with insulin clearance (p < 0.001). The top signals for each locus were rs10241087 (DGKB/TMEM195 [TMEM195 also known as AGMO]) (p = 4.4 × 10(-5)); chr1:217605433 (LYPLAL1) (p = 3.25 × 10(-4)); rs2380949 (GLIS3) (p = 3.4 × 10(-4)); rs55903902 (FADS1) (p = 5.6 × 10(-4)); rs849334 (JAZF1) (p = 6.4 × 10(-4)); rs35749 (IGF1) (p = 6.7 × 10(-4)); and rs9460557 (CDKAL1) (p = 6.8 × 10(-4)). CONCLUSIONS/INTERPRETATION: While the majority of validated loci for type 2 diabetes and related traits do not appear to influence insulin clearance in Hispanics, several of these loci do show evidence of association with this trait. It is therefore possible that these loci could have pleiotropic effects on insulin secretion, insulin sensitivity and insulin clearance.
[Show abstract][Hide abstract] ABSTRACT: Tissue oxidative stress is a common hallmark of atherosclerosis and non-alcoholic steatohepatitis (NASH), 2 conditions linked epidemiologically and pathophysiologically. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the master regulator of inducible antioxidant responses, that can attenuate cellular injury from oxidative stress induced by obesity and other redox insults. Nrf2 expression and activation is reduced in mouse and human vessels that harbor accelerated atherosclerosis and in livers with histologic criteria of NASH. Systemic antioxidants have thus been attractive therapeutic targets, but clinical trials have been largely unsuccessful in improving cardiovascular health. Macrophage-selective Nrf2 activation may, however, provide an approach to reduce vascular and hepatocyte injury without the complications of systemic antioxidants, since macrophages play key roles in the development and progression of both atherosclerosis and NASH. In this article, we review the common mechanisms of oxidative stress and inflammation in atherosclerosis and NASH, and discuss the role of Nrf2 in vascular and hepatocyte protection.
Current Diabetes Reports 03/2013; · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adipose-resident T cells (ARTs) regulate metabolic and inflammatory responses in obesity, but ART activation signals are poorly understood. Here, we describe class II major histocompatibility complex (MHCII) as an important component of high-fat-diet (HFD)-induced obesity. Microarray analysis of primary adipocytes revealed that multiple genes involved in MHCII antigen processing and presentation increased in obese women. In mice, adipocyte MHCII increased within 2 weeks on HFD, paralleling increases in proinflammatory ART markers and decreases in anti-inflammatory ART markers, and preceding adipose tissue macrophage (ATM) accumulation and proinflammatory M1 polarization. Mouse 3T3-L1 and primary adipocytes activated T cells in an antigen-specific, contact-dependent manner, indicating that adipocyte MHCII is functional. HFD-fed MHCII mice developed less adipose inflammation and insulin resistance than did wild-type mice, despite developing similar adiposity. These investigations uncover a mechanism whereby a HFD-induced adipocyte/ART dialog involving MHCII instigates adipose inflammation and, together with ATM MHCII, escalates its progression.
[Show abstract][Hide abstract] ABSTRACT: The majority of cholesterol reduction therapies, such as the statin drugs, work primarily by inducing the expression of hepatic low-density lipoprotein receptors (LDLRs), rendering these therapeutics only partially effective in animals lacking LDLRs. Although thyroid hormones and their synthetic derivatives, often referred to as thyromimetics, have been clearly shown to reduce serum cholesterol levels, this action has generally been attributed to their ability to increase expression of hepatic LDLRs. Here we show for the first time that the thyroid hormone T(3) and the thyroid hormone receptor-β selective agonists GC-1 and KB2115 are capable of markedly reducing serum cholesterol in mice devoid of functional LDLRs by inducing Cyp7a1 expression and stimulating the conversion and excretion of cholesterol as bile acids. Based on this LDLR-independent mechanism, thyromimetics such as GC-1 and KB2115 may represent promising cholesterol-lowering therapeutics for the treatment of diseases such as homozygous familial hypercholesterolemia, a rare genetic disorder caused by a complete lack of functional LDLRs, for which there are limited treatment options because most therapeutics are only minimally effective.
[Show abstract][Hide abstract] ABSTRACT: Abstract Objective: BP-CRUSH (Blood Pressure Control in All Subgroups With Hypertension) was a phase IV, prospective, open-label, multicenter, single-arm, dose-titration study (N=999). The present subgroup analysis reports the efficacy/safety of up to 20 weeks' treatment with amlodipine (AML)/olmesartan medoxomil (OM) ± hydrochlorothiazide (HCTZ) in obese and non-obese patients with hypertension uncontrolled on antihypertensive monotherapy. Research Design and Methods: Eligible obese (body mass index ≥30 kg/m(2); n=505) and non-obese (<30 kg/m(2); n=494) patients were switched to AML/OM 5/20 mg and uptitrated at 4-week intervals to AML/OM 5/40 mg, AML/OM 10/40 mg, AML/OM 10/40 mg + HCTZ 12.5 mg, and AML/OM 10/40 mg + HCTZ 25 mg. Uptitration to higher doses of AML/OM was permitted if mean seated systolic BP (SeSBP) was ≥120 mmHg, or mean seated diastolic BP (SeDBP) was ≥70 mmHg. HCTZ was added if mean SeSBP was ≥125 mmHg, or mean SeDBP was ≥75 mmHg. Clinical Trial Registration: ClinicalTrials.gov identifier: NCT00791258 Main Outcome Measures: The primary efficacy endpoint was the cumulative proportion of patients achieving SeSBP <140 mmHg (<130 mmHg for patients with diabetes) at 12 weeks. Secondary endpoints included SeBP goal rates, ambulatory BP target rates, and mean change from baseline in SeBP and ambulatory BP at Weeks 12 and 20. Results: At 12 weeks, 71.6% of obese patients (80.2% non-obese) achieved the primary endpoint of cumulative SeSBP <140 mmHg (<130 mmHg for patients with diabetes). The cumulative SeBP goal of <140/90 mmHg (<130/80 mmHg if diabetes) was achieved by 64.8% and 81.2% of obese patients by Weeks 12 and 20, respectively (vs. 77.9% and 88.5% of non-obese patients, respectively). Treatment was well tolerated, with 26.1% of obese patients (24.9% non-obese) experiencing treatment-emergent drug-related adverse events (none serious). Conclusion: An AML/OM ± HCTZ treatment regimen provided effective and safe BP control in obese patients with hypertension uncontrolled on monotherapy.
Current Medical Research and Opinion 10/2012; · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVE: To determine the impact of hematopoietic deletion of nuclear factor- (erythroid-derived 2) like 2 factor (Nrf2) on the development of atherosclerosis and liver injury in an obese, hypercholesterolemic mouse model. METHODS AND RESULTS: Two-month-old male low-density lipoprotein receptor-deficient mice were lethally irradiated and transplanted with either wild type or Nrf2-deficient (Nrf2(-/-)) bone marrow cells. At 3 months of age, mice were placed on an obesogenic high-fat diet (HFD), high-cholesterol diet for 7 months. Despite no differences in body weight, body fat percentage, liver fat, plasma glucose, lipids, or insulin, the HFD-fed Nrf2(-/-) bone marrow recipients had increased proinflammatory vascular gene expression, a significant increase in atherosclerosis area (18% versus 28%; P=0.018) and lesion complexity, and a marked increase in liver fibrosis. The acceleration of vascular and liver injury may arise from enhanced macrophage migration, inflammation, and oxidative stress resulting from myeloid Nrf2 deficiency. CONCLUSIONS: Myeloid-derived Nrf2 activity attenuates atherosclerosis development and liver inflammation and fibrosis associated with obesity. Prevention of oxidative stress in macrophage and other myeloid lineage cells may be an important therapeutic target to reduce inflammation-driven complications of obesity.
Arteriosclerosis Thrombosis and Vascular Biology 09/2012; · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Thiazolidinediones (TZDs) act through peroxisome proliferator activated receptor (PPAR) γ to increase insulin sensitivity in type 2 diabetes (T2DM), but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of PPARγ ligand binding domain (LBD) and found that the ligand binding pocket (LBP) is occupied by bacterial medium chain fatty acids (MCFAs). We verified that MCFAs (C8-C10) bind the PPARγ LBD in vitro and showed that they are low-potency partial agonists that display assay-specific actions relative to TZDs; they act as very weak partial agonists in transfections with PPARγ LBD, stronger partial agonists with full length PPARγ and exhibit full blockade of PPARγ phosphorylation by cyclin-dependent kinase 5 (cdk5), linked to reversal of adipose tissue insulin resistance. MCFAs that bind PPARγ also antagonize TZD-dependent adipogenesis in vitro. X-ray structure B-factor analysis and molecular dynamics (MD) simulations suggest that MCFAs weakly stabilize C-terminal activation helix (H) 12 relative to TZDs and this effect is highly dependent on chain length. By contrast, MCFAs preferentially stabilize the H2-H3/β-sheet region and the helix (H) 11-H12 loop relative to TZDs and we propose that MCFA assay-specific actions are linked to their unique binding mode and suggest that it may be possible to identify selective PPARγ modulators with useful clinical profiles among natural products.
PLoS ONE 05/2012; 7(5):e36297. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Circadian clocks in adipose tissue are known to regulate adipocyte biology. Although circadian dysregulation is associated with development of obesity, the underlying mechanism has not been established. Here we report that disruption of the clock gene, brain and muscle Arnt-like 1 (Bmal1), in mice led to increased adipogenesis, adipocyte hypertrophy, and obesity, compared to wild-type (WT) mice. This is due to its cell-autonomous effect, as Bmal1 deficiency in embryonic fibroblasts, as well as stable shRNA knockdown (KD) in 3T3-L1 preadipocyte and C3H10T1/2 mesenchymal stem cells, promoted adipogenic differentiation. We demonstrate that attenuation of Bmal1 function resulted in down-regulation of genes in the canonical Wnt pathway, known to suppress adipogenesis. Promoters of these genes (Wnt10a, β-catenin, Dishevelled2, TCF3) displayed Bmal1 occupancy, indicating direct circadian regulation by Bmal1. As a result, Wnt signaling activity was attenuated by Bmal1 KD and augmented by its overexpression. Furthermore, stabilizing β-catenin through Wnt ligand or GSK-3β inhibition achieved partial restoration of blunted Wnt activity and suppression of increased adipogenesis induced by Bmal1 KD. Taken together, our study demonstrates that Bmal1 is a critical negative regulator of adipocyte development through transcriptional control of components of the canonical Wnt signaling cascade, and provides a mechanistic link between circadian disruption and obesity.
The FASEB Journal 05/2012; 26(8):3453-63. · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have previously documented a high heritability of insulin clearance in a Hispanic cohort. Here, our goal was to confirm the high heritability in a second cohort and search for genetic loci contributing to insulin clearance.
Hyperinsulinaemic-euglycaemic clamps were performed in 513 participants from 140 Hispanic families. Heritability was estimated for clamp-derived insulin clearance and a two-phase genome-wide linkage scan was conducted using a variance components approach. Linkage peaks were further investigated by candidate gene association analysis in two cohorts.
The covariate-adjusted heritability of insulin clearance was 73%, indicating that the majority of the phenotypic variance is due to genetic factors. In the Phase 1 linkage scan, no signals with a logarithm of odds (LOD) score >2 were detected. In the Phase 2 scan, two linkage peaks with an LOD >2 for insulin clearance were identified on chromosomes 15 (LOD 3.62) and 20 (LOD 2.43). These loci harbour several promising candidate genes for insulin clearance, with 12 single nucleotide polymorphisms (SNPs) on chromosome 15 and six SNPs on chromosome 20 being associated with insulin clearance in both Hispanic cohorts.
In a second Hispanic cohort, we confirmed that insulin clearance is a highly heritable trait and identified chromosomal loci that harbour genes regulating insulin clearance. The identification of such genes may improve our understanding of how the body clears insulin, thus leading to improved risk assessment, diagnosis, prevention and therapy of diabetes, as well as of other hyperinsulinaemic disorders, such as the metabolic syndrome and polycystic ovary syndrome.