Project description:Insulin resistance progressing to type 2 diabetes mellitus (T2DM) is marked by a broad perturbation of macronutrient intermediary metabolism. Understanding the biochemical networks that underlie metabolic homeostasis and how they associate with insulin action will help unravel diabetes etiology and should foster discovery of new biomarkers of disease risk and severity. We examined differences in plasma concentrations of >350 metabolites in fasted obese T2DM vs. obese non-diabetic African-American women, and utilized principal components analysis to identify 158 metabolite components that strongly correlated with fasting HbA1c over a broad range of the latter (r?=?-0.631; p<0.0001). In addition to many unidentified small molecules, specific metabolites that were increased significantly in T2DM subjects included certain amino acids and their derivatives (i.e., leucine, 2-ketoisocaproate, valine, cystine, histidine), 2-hydroxybutanoate, long-chain fatty acids, and carbohydrate derivatives. Leucine and valine concentrations rose with increasing HbA1c, and significantly correlated with plasma acetylcarnitine concentrations. It is hypothesized that this reflects a close link between abnormalities in glucose homeostasis, amino acid catabolism, and efficiency of fuel combustion in the tricarboxylic acid (TCA) cycle. It is speculated that a mechanism for potential TCA cycle inefficiency concurrent with insulin resistance is "anaplerotic stress" emanating from reduced amino acid-derived carbon flux to TCA cycle intermediates, which if coupled to perturbation in cataplerosis would lead to net reduction in TCA cycle capacity relative to fuel delivery.
Project description:IntroductionChanges in sex hormones with weight loss might have implications for breast cancer prevention but have not been examined extensively, particularly in African-American (AA) women.MethodsWe conducted a prospective study of 278 overweight/obese postmenopausal women (38% AA) not taking hormone therapy within the Weight Loss Maintenance Trial. All participants lost at least 4 kg after a 6-month weight-loss phase and attempted to maintain weight loss during the subsequent 12 months. We evaluated the percentage changes in estrone, estradiol, free estradiol, testosterone, free testosterone, androstenedione, dehydroepiandrosterone sulfate and sex hormone-binding globulin (SHBG) using generalized estimating equations.ResultsIn all study phases, AA women had higher levels of estrogen and testosterone concentrations, independent of adiposity. On average, participants lost 7.7 kg during the weight-loss phase, and concentrations of estrone (-5.7%, P = 0.006), estradiol (-9.9%, P <0.001), free estradiol (-13.4%, P <0.0001), and free testosterone (-9.9%, P <0.0001) decreased, while the SHBG concentration (16.2%, P <0.001) increased. Weight change did not significantly affect total testosterone or other androgen concentrations. Compared with non-AA women, AA women experienced less change in estrogens per kilogram of weight change (that is, per 1 kg weight loss: estrone, -0.6% vs. -1.2%, P-interaction = 0.10; estradiol, -1.1% vs. -1.9%, P-interaction = 0.04; SHBG, 0.9% vs. 1.6%, P-interaction = 0.006; free estradiol, -1.4% vs. -2.1%, P-interaction = 0.01).ConclusionTo the best of our knowledge this is the first study to examine and compare the effects of intentional weight loss and maintenance on a panel of sex hormones in AA women and non-AA women. Although speculative, these data suggest hormonal differences may contribute to different racial patterns of breast cancer incidence and mortality and encourage further investigations to understand the long-term effects of weight loss on sex hormones in obese postmenopausal women.Trial registrationClinicalTrials.gov: NCT00054925.
Project description:Triglyceride content in the liver is regulated by the uptake, production and elimination of lipoproteins, and derangements in these processes contribute to nonalcoholic fatty liver disease (NAFLD). Previous studies show a direct relationship between intrahepatic fat and production of apolipoprotein B100 (apoB100) containing particles, VLDL and LDL, but little consensus exists regarding changes in lipoprotein production in the development of simple steatosis (SS) versus nonalcoholic steatohepatitis (NASH). Further, ethnic variations in lipoproteins among SS and NASH are unknown as is how such variations might contribute to the differential prevalence of disease among Caucasians versus African Americans. In this study, we assessed plasma lipoprotein profiles by nuclear magnetic resonance (NMR) spectroscopy in 70 non-diabetic class III obese females recruited from the surgical weight loss clinic. Of these, 51 females were stratified by biopsy-staged NAFLD severity (histologically normal, SS, or NASH). NASH females displayed increased circulating triglycerides and increased VLDL particle number and size relative to those with histologically normal livers, while total and large LDL concentration decreased in SS versus NASH and correlated with increased insulin resistance (via HOMA2-IR). When Caucasian women were examined alone (n = 41), VLDL and triglycerides increased between normal and SS, while total LDL and apoB100 decreased between SS and NASH along with increased insulin resistance. Compared to Caucasians with SS, African American women with SS displayed reduced triglycerides, VLDL, and small LDL and a more favorable small to large HDL ratio despite having increased BMI and HOMA2-IR. These findings suggest that ApoB100 and lipoprotein subclass particle number and size can delineate steatosis from NASH in obese Caucasian females, but should be interpreted with caution in other ethnicities as African Americans with SS display relatively improved lipoprotein profiles. This may reflect variation in the relationship between dyslipidemia and NAFLD progression across gender and ethnicity.
Project description:ObjectiveUnderstanding body size perceptions and discrepancies among African American women may have implications for effective weight-loss interventions. The purpose of this study is to examine body size perceptions of economically disadvantaged, overweight and obese African American women.DesignCross-sectional using baseline data from a randomized controlled trial.Setting18 census tracts in a central South Carolina city where ≥ 25% of residents were below poverty income.Participants147 economically disadvantaged, overweight and obese African American women.Main outcome measuresUsing Pulvers' figure rating scale, participants chose the figure: 1) closest to their current figure; 2) they would be satisfied with; and 3) with a body weight that would be a health problem for the average person. Mean body mass indices corresponding to each figure were compared with those in a large sample of White women.ResultsMost participants wanted to be smaller (mean=2.6 figures smaller) than their current size. A majority (67%) chose the largest figure as representing a body size that could lead to a health problem, and most (60%) chose a current figure smaller than the figure they believed would be associated with health problems. The mean body mass index for women selecting any given figure as their current size was significantly larger (5.2-10.8 kg/m(2) larger, P<.0001) than those established in the sample of White women.ConclusionsAlthough women desired a smaller body size, there nonetheless were misperceptions of body size and the associated health consequences. Body size misperceptions and/or satisfaction may pose barriers for effective weight-loss.
Project description:Inefficient muscle long-chain fatty acid (LCFA) combustion is associated with insulin resistance, but molecular links between mitochondrial fat catabolism and insulin action remain controversial. We hypothesized that plasma acylcarnitine profiling would identify distinct metabolite patterns reflective of muscle fat catabolism when comparing individuals bearing a missense G304A uncoupling protein 3 (UCP3 g/a) polymorphism to controls, because UCP3 is predominantly expressed in skeletal muscle and g/a individuals have reduced whole-body fat oxidation. MS analyses of 42 carnitine moieties in plasma samples from fasting type 2 diabetics (n = 44) and nondiabetics (n = 12) with or without the UCP3 g/a polymorphism (n = 28/genotype: 22 diabetic, 6 nondiabetic/genotype) were conducted. Contrary to our hypothesis, genotype had a negligible impact on plasma metabolite patterns. However, a comparison of nondiabetics vs. type 2 diabetics revealed a striking increase in the concentrations of fatty acylcarnitines reflective of incomplete LCFA beta-oxidation in the latter (i.e. summed C10- to C14-carnitine concentrations were approximately 300% of controls; P = 0.004). Across all volunteers (n = 56), acetylcarnitine rose and propionylcarnitine decreased with increasing hemoglobin A1c (r = 0.544, P < 0.0001; and r = -0.308, P < 0.05, respectively) and with increasing total plasma acylcarnitine concentration. In proof-of-concept studies, we made the novel observation that C12-C14 acylcarnitines significantly stimulated nuclear factor kappa-B activity (up to 200% of controls) in RAW264.7 cells. These results are consistent with the working hypothesis that inefficient tissue LCFA beta-oxidation, due in part to a relatively low tricarboxylic acid cycle capacity, increases tissue accumulation of acetyl-CoA and generates chain-shortened acylcarnitine molecules that activate proinflammatory pathways implicated in insulin resistance.
Project description:Innate immune mediators of pathogen clearance, including the secreted C-type lectins REG3 of the antimicrobial peptide (AMP) family, are known to be involved in the regulation of tissue repair and homeostasis. Their role in metabolic homeostasis remains unknown. Here we show that an increase in human REG3A improves glucose and lipid homeostasis in nutritional and genetic mouse models of obesity and type 2 diabetes. Mice overexpressing REG3A in the liver show improved glucose homeostasis, which is reflected in better insulin sensitivity in normal weight and obese states. Delivery of recombinant REG3A protein to leptin-deficient ob/ob mice or wild-type mice on a high-fat diet also improves glucose homeostasis. This is accompanied by reduced oxidative protein damage, increased AMPK phosphorylation and insulin-stimulated glucose uptake in skeletal muscle tissue. Oxidative damage in differentiated C2C12 myotubes is greatly attenuated by REG3A, as is the increase in gp130-mediated AMPK activation. In contrast, Akt-mediated insulin action, which is impaired by oxidative stress, is not restored by REG3A. These data highlight the importance of REG3A in controlling oxidative protein damage involved in energy and metabolic pathways during obesity and diabetes, and provide additional insight into the dual function of host-immune defense and metabolic regulation for AMP.
Project description:Aims/hypothesisDrug and surgical-based therapies in type 2 diabetes are associated with altered gut microbiota architecture. Here we investigated the role of the gut microbiome in improved glucose homeostasis following bariatric surgery.MethodsWe carried out gut microbiome analyses in gastrectomised (by vertical sleeve gastrectomy [VSG]) rats of the Goto-Kakizaki (GK) non-obese model of spontaneously occurring type 2 diabetes, followed by physiological studies in the GK rat.ResultsVSG in the GK rat led to permanent improvement of glucose tolerance associated with minor changes in the gut microbiome, mostly characterised by significant enrichment of caecal Prevotella copri. Gut microbiota enrichment with P. copri in GK rats through permissive antibiotic treatment, inoculation of gut microbiota isolated from gastrectomised GK rats, and direct inoculation of P. copri, resulted in significant improvement of glucose tolerance, independent of changes in body weight. Plasma bile acids were increased in GK rats following inoculation with P. copri and P. copri-enriched microbiota from VSG-treated rats; the inoculated GK rats then showed increased liver glycogen and upregulated expression of Fxr (also known as Nr1h4), Srebf1c, Chrebp (also known as Mlxipl) and Il10 and downregulated expression of Cyp7a1.ConclusionsOur data underline the impact of intestinal P. copri on improved glucose homeostasis through enhanced bile acid metabolism and farnesoid X receptor (FXR) signalling, which may represent a promising opportunity for novel type 2 diabetes therapeutics.
Project description:Obesity and type 2 diabetes mellitus are global emergencies and long noncoding RNAs (lncRNAs) are regulatory transcrips with elusive functions in metabolism. Here we report that an unexpectedly high fraction of lncRNAs, but not protein-coding mRNAs, is repressed during diet-induced obesity (DIO) and refeeding, whilst nutrient deprivation specifically induced lncRNAs in mouse liver. Similarly, lncRNAs were lost in diabetic humans. LncRNA promoter analyses, global cistrome and gain-of-function analyses confirmed that increased MAFG signaling during DIO curbs lncRNA expression. Silencing Mafg in primary hepatocytes and in vivo elicited a fasting-like expression profile, improved glucose metabolism, derepressed lncRNAs and prevented mammalian target of rapamycin (mTOR)-driven protein translation. We found that obesity-repressed lincIRS2 is controlled by MAFG and observed that genetic and RNAi-mediated lincIRS2 loss causes hyperglycemia, insulin resistance and aberrant glucose output in lean mice. Taken together, we identify a novel MAFG-lncRNA axis controlling hepatic glucose metabolism in health and metabolic disease.
Project description:Obstructive sleep apnoea (OSA) is associated with increased insulin resistance. Triglyceride-glucose index (TyG) is a simple marker of insulin resistance; however, it has been investigated only by two studies in OSA. The aim of this study was to evaluate TyG in non-diabetic, non-obese patients with OSA. A total of 132 patients with OSA and 49 non-OSA control subjects were included. Following a diagnostic sleep test, fasting blood was taken for the analysis of the lipid profile and glucose concentrations. TyG was calculated as ln(triglyceride [mg/dL] × glucose [mg/dL]/2). Comparison analyses between OSA and control groups were adjusted for age, gender, body mass index (BMI) and smoking. TyG was higher in men (p < 0.01) and in ever-smokers (p = 0.02) and it was related to BMI (ρ = 0.33), cigarette pack-years (ρ = 0.17), apnoea-hypopnoea index (ρ = 0.38), oxygen desaturation index (ρ = 0.40), percentage of total sleep time spent with oxygen saturation below 90% (ρ = 0.34), and minimal oxygen saturation (ρ = -0.29; all p < 0.05). TyG values were significantly higher in OSA (p = 0.02) following adjustment for covariates. OSA is independently associated with higher TyG values which are related to disease severity in non-obese, non-diabetic subjects. However, the value of TyG in clinical practice should be evaluated in follow-up studies in patients with OSA.
Project description:ImportancePeripartum cardiomyopathy (PPCM) disproportionately affects women of African ancestry, but well-powered studies to explore differences in severity of disease and clinical outcomes are lacking.ObjectiveTo compare the clinical characteristics, presentation, and outcomes of PPCM between African American and non-African American women.Design, setting, and participantsThis retrospective cohort study using data from January 1, 1986, through December 31, 2016, performed at the University of Pennsylvania Health System, a tertiary referral center serving a population with a high proportion of African American individuals, included 220 women with PPCM.Main outcomes and measuresDemographic and clinical characteristics and echocardiographic findings at presentation, as well as clinical outcomes including cardiac recovery, time to recovery, cardiac transplant, persistent dysfunction, and death, were compared between African American and non-African American women with PPCM.ResultsA total of 220 women were studied (mean [SD] age at diagnosis, 29.5 [6.6] years). African American women were diagnosed with PPCM at a younger age (27.6 vs 31.7 years, P < .001), were diagnosed with PPCM later in the postpartum period, and were more likely to present with a left ventricular ejection fraction less than 30% compared with non-African American women (48 [56.5%] vs 30 [39.5%], P = .03). African American women were also more likely to worsen after initial diagnosis (30 [35.3%] vs 14 [18.4%], P = .02), were twice as likely to fail to recover (52 [43.0%] vs 24 [24.2%], P = .004), and, when they did recover, recovery took at least twice as long (median, 265 vs 125.5 days; P = .02) despite apparent adequate treatment.Conclusions and relevanceIn a large cohort of women with well-phenotyped PPCM, this study demonstrates a different profile of disease in African American vs non-African American women. Further work is needed to understand to what extent these differences stem from genetic or socioeconomic differences and how treatment of African American patients might be tailored to improve health outcomes.