Coletta, Dawn K.

Obesity is a persistent public health issue, often resulting in metabolic complications such as insulin resistance (IR). The secretion of pro-inflammatory cytokines from adipose tissue (AT) is increased during obesity, contributing to the impairment of systemic insulin sensitivity. While interventions in animal models have shown that reducing inflammation restores insulin sensitivity, human studies reducing systemic inflammation have produced inconsistent results. We recently demonstrated that three months of high-dose (4 g/daily) ω-3PUFA (fish oil, FO) supplementation improved insulin sensitivity, and decreased systemic and AT inflammation in individuals with obesity (BMI ≥ 30 kg/m2). Given recent studies highlighting the involvement of microRNA (miRNA) in inflammatory cytokine production, we investigated the effect of ω-3PUFA supplementation on AT miRNA expression in this cohort. AT biopsies were collected before and after ω-3PUFA supplementation. miRNA was processed on the Affymetrix miRNA 4.0 GeneChip and analyzed using existing inflammatory gene sets sourced from MSigDB. Unbiased, differentially expressed miRNA analysis identified miR-4498 and miR-5689 as significantly increased after three months of ω-3PUFA supplementation. Real-time PCR confirmed bioinformatic analysis findings. Our study reports the modulation of miRNA in AT, reductions in systemic and AT markers of inflammation, and the improvement of IR post ω-3PUFA supplementation. Further research is needed to elucidate the link between miR-4498, miR-5689, and whole-body insulin sensitivity.

The vitamin D receptor (VDR) is vital for maintaining calcium and phosphate balance and regulating bone metabolism. Recent research has suggested that VDR also plays an essential role in metabolic diseases. Previous studies on non-Hispanic whites have shown that VDR single nucleotide polymorphisms (SNP) are associated with cardiometabolic phenotypes. However, the association between VDR SNPs and cardiometabolic traits in Hispanics remains unclear. This study investigated the association between VDR SNPs and cardiometabolic phenotypic data in self-reported Hispanics (n = 1610) from the Arizona Insulin Resistance registry and Sangre Por Salud Biobank. The study population was predominantly female (66.4%) with a mean age of 40 ± 14 years (n = 121 <18 years) and an average body mass index (BMI) of 29.8 ± 6.3 kg/m2. We performed a genotyping association analysis of VDR SNPs (Taq1-rs731236, Fok1-rs2228570 and Apa1-rs7975232) with cardiometabolic traits using linear regression models. The results showed that Taq1 and Apa1 were strongly associated with systolic blood pressure (SBP) in children (<18 years), while Fok1 was associated with measures of adiposity, including fat mass, waist circumference, and BMI. In age-stratified adult (≥18 years) models, Taq1 was strongly associated with hemoglobin A1c, while Apa1 was associated with BMI and fasting glucose. Fok1 had no significant associations in the adult models. In conclusion, the VDR SNPs were associated with several cardiometabolic phenotypes in this Hispanic sample, but the type and strength of the associations varied by age group.

Skeletal muscle is highly plastic and dynamically regulated by the body’s physical demands. This study aimed to determine the plasticity of skeletal muscle DNA methylation in response to 8 weeks of supervised exercise training in volunteers with a range of insulin sensitivities. We studied 13 sedentary participants and performed euglycemic hyperinsulinemic clamps with basal vastus lateralis muscle biopsies and peak aerobic activity (VO2 peak) tests before and after training. We extracted DNA from the muscle biopsies and performed global methylation using Illumina’s Methylation EPIC 850K BeadChip. Training significantly increased peak aerobic capacity and insulin-stimulated glucose disposal. Fasting serum insulin and insulin levels during the steady state of the clamp were significantly lower post-training. Insulin clearance rates during the clamp increased following the training. We identified 13 increased and 90 decreased differentially methylated cytosines (DMCs) in response to 8 weeks of training. Of the 13 increased DMCs, 2 were within the following genes, FSTL3, and RP11-624M8.1. Of the 90 decreased DMCs, 9 were within the genes CNGA1, FCGR2A, KIF21A, MEIS1, NT5DC1, OR4D1, PRPF4B, SLC26A7, and ZNF280C. Moreover, pathway analysis showed an enrichment in metabolic and actin-cytoskeleton pathways for the decreased DMCs, and for the increased DMCs, an enrichment in signal-dependent regulation of myogenesis, NOTCH2 activation and transmission, and SMAD2/3: SMAD4 transcriptional activity pathways. Our findings showed that 8 weeks of exercise training alters skeletal muscle DNA methylation of specific genes and pathways in people with varying degrees of insulin sensitivity.

We recently discovered persistent downregulation of the H + ‐ATP synthase catalytic subunit (β‐F1‐ATPase) in skeletal muscle of obese individuals, which was linked to comorbid hyperlipidemia. β‐F1‐ATPase expression is primarily regulated post‐transcription, i.e. miRNAs, but the precise mechanism impeding expression are unclear. We tested the hypothesis that hyperlipidemia reduces β‐F1‐ATPase translational efficiency and is mediated by miR‐127‐5p, a miRNA known to control β‐F1‐ATPase translation. Biopsies isolated from the vastus lateralis of lean (BMI蠄25; n=7) and obese (BMI蠅30; n=6) subjects were evaluated for mRNA/miRNA expression via qRT‐PCR, protein by Western blot, and translation efficiency was calculated as the mRNA/protein ratio. Our results confirmed β‐F1‐ATPase translation was lower in obese individuals (P<0.01; 0.25±0.05%) compared to healthy weight controls (0.59±0.09%), and correlated with miR‐127‐5p expression (P<0.01; r=‐0.67). Bisulfite sequencing analysis of the miR‐127‐5p promoter revealed two hypomethylated sites in obese individuals, which may sustain an upregulation. Moreover, we found miR‐127‐5p present in muscle‐derived blood exosomes suggesting putative involvement in intracellular cross‐talk. In primary myotubes from a lean volunteer, prolonged fatty acid exposure increased miR‐127‐5p expression. Free Fatty Acid (mEq/L) Unsaturated/ Saturated mRNA (2 ‐ DD Ct ) Protein (AU) Translation (%) CTRL 0.347 ‐ 1.70±0.113 0.216±0.062 0.130±0.040 Lo Fat 0.185 0.55 1.60±0.094 0.202±0.038 0.123±0.008 Hi Fat 0.251 2.29 1.35±0.133* 0.095±0.006* 0.073±0.010 Hi Fat 0.269 0.54 1.66±0.145 0.093±0.003* 0.050±0.004* * P <0.05; One‐way ANOVA, Tukey9s posttest Inhibiting miR‐127‐5p with locked nucleic acids dose‐dependently improved β‐F1‐ATPase translation. Inhibitor (nM) mRNA (2 ‐ DD Ct ) Protein (AU) Translation (%) 0 1.84±0.314 0.22±0.062 0.647±0.120 10 1.93±0.387 1.24±0.135* 0.500±0.148 50 2.00±0.498 1.24±0.242** 1.483±0.233* 100 1.76±0.207 1.54±0.086* 0.892±0.096 * P <0.05; ** P <0.01; *** P <0.001; 1‐way ANOVA, Tukey9s posttest Our results provide evidence implicating hyperlipidemia‐induced miR‐127‐5p expression in suppressing β‐F1‐ATPase translation in human obesity. Funding from NIH/NIDDK grant DK094062 to CSK

Background: Brain-derived neurotrophic factor (BDNF) is associated with body weight and other health conditions but remains understudied in the Latino population. The aim of this study was to examine the associations of BDNF serum levels with body mass index (BMI), physical activity, and the rs6265 nonconservative polymorphism among 349 Latinos aged ≥18 years enrolled in the Arizona Insulin Resistance Registry. Materials and Methods: Data on physical activity were acquired using a self-reported questionnaire. BDNF serum levels were measured utilizing a modified ELISA method, and the rs6265 polymorphism was genotyped by the Assay-by-Design service. Two sample t -tests or chi-squared tests were employed to compare demographics and outcomes between physically active and nonactive groups as well as between rs6265 CC and CT+TT groups. Results: BDNF levels and rs6265 polymorphism did not differ significantly between the physically active ( N = 195) and nonactive group ( N = 154). Participants with the rs6265 polymorphism did not show any significant difference in BDNF levels or BMI when compared with those with the normal functional variant. Higher BDNF levels were significantly associated with higher age ( r = 0.11, P = 0.04) and higher 2-hr glucose level ( r = 0.11, P = 0.04). Conclusions: In this cross-sectional study, the rs6265 polymorphism was not associated with a higher risk of obesity, or lower circulating levels of BDNF. Thus, the rs6265 polymorphism may have a different impact in Latinos as compared with other previously studied populations.

The mechanisms of metabolic improvements after Roux-en-Y gastric bypass (RYGB) surgery are not entirely clear. Therefore, the aim of our study was to investigate the role of obesity and RYGB on the human skeletal muscle proteome. Basal muscle biopsies were obtained from seven obese (BMI &gt;40 kg/m2) female subjects (45.1 ± 3.6 years) pre- and 3 months post-RYGB, and euglycemic-hyperinsulinemic clamps were used to assess insulin sensitivity. Four age-matched (48.5 ± 4.7 years) lean (BMI &lt;25 kg/m2) females served as control subjects. We performed quantitative mass spectrometry and microarray analyses on protein and RNA isolated from the muscle biopsies. Significant improvements in fasting plasma glucose (104.2 ± 7.8 vs. 86.7 ± 3.1 mg/dL) and BMI (42.1 ± 2.2 vs. 35.3 ± 1.8 kg/m2) were demonstrated in the pre- versus post-RYGB, both P &lt; 0.05. Proteomic analysis identified 2,877 quantifiable proteins. Of these, 395 proteins were significantly altered in obesity before surgery, and 280 proteins differed significantly post-RYGB. Post-RYGB, 49 proteins were returned to normal levels after surgery. KEGG pathway analysis revealed a decreased abundance in ribosomal and oxidative phosphorylation proteins in obesity, and a normalization of ribosomal proteins post-RYGB. The transcriptomic data confirmed the normalization of the ribosomal proteins. Our results provide evidence that obesity and RYGB have a dynamic effect on the skeletal muscle proteome.

ObjectiveTo examine associations between circulating levels of the bone‐derived protein osteocalcin (OC) and type 2 diabetes (T2D) risk in Latino children and adults.MethodsSerum OC was measured in 136 children and 531 adults who had the following T2D risk factors assessed, body mass index (BMI), Hemoglobin A1c (HbA1c), fasting and 2‐hour glucose during an oral glucose tolerance test.ResultsOC was significantly higher in children than adults (209.0 ± 12.1 vs. 41.0 ± 0.9 ng/ml, p<0.0001). In adults, OC was inversely associated (all p<0.001) with BMI (r=‐0.2), HbA1c (r=‐0.2), fasting glucose (r=‐0.16), and 2‐hour glucose (r=‐0.21), while there were no significant associations in children. There was a stepwise decrease in OC with increasing dysglycemia in adults, normoglycemic (44.1 ± 1.3 ng/ml), prediabetic (39.3 ± 1.3 ng/ml), and T2D (31.8 ± 1.2 ng/ml), (p<0.0001), whereas there were no differences between normal and prediabetic youth (195.7 ± 16.1 vs. 194.7 ± 25.8 ng/ml, p=0.3).ConclusionsOC was inversely associated with T2D risk in Latino adults; however, this pattern was not observed in children. Am. J. Hum. Biol. 27:859–861, 2015. © 2015 Wiley Periodicals, Inc.

AbstractAimsThe molecular mechanisms by which muraglitazar (peroxisome proliferator‐activated receptor γ/α agonist) improves insulin sensitivity in Type 2 diabetes mellitus are not fully understood. We hypothesized that muraglitazar would increase expression of 5′‐monophosphate‐activated protein kinase and genes involved in adiponectin signalling, free fatty acid oxidation and mitochondrial function in skeletal muscle.MethodsSixteen participants with Type 2 diabetes received muraglitazar, 5 mg/day (n = 12) or placebo (n = 4). Before and after 16 weeks, participants had vastus lateralis muscle biopsy followed by 180 min euglycaemic hyperinsulinaemic clamp.ResultsMuraglitazar increased plasma adiponectin (9.0 ± 1.1 to 17.8 ± 1.5 μg/ml, P < 0.05), while no significant change was observed with placebo. After 16 weeks with muraglitazar, fasting plasma glucose declined by 31%, fasting plasma insulin decreased by 44%, insulin‐stimulated glucose disposal increased by 81%, HbA1c decreased by 21% and plasma triglyceride decreased by 39% (all P < 0.05). Muraglitazar increased mRNA levels of 5′‐monophosphate‐activated protein kinase, adiponectin receptor 1, adiponectin receptor 2, peroxisome proliferator‐activated receptor gamma coactivator–1 alpha and multiple genes involved in mitochondrial function and fat oxidation. In the placebo group, there were no significant changes in expression of these genes.ConclusionsMuraglitazar increases plasma adiponectin, stimulates muscle 5′‐monophosphate‐activated protein kinase expression and increases expression of genes involved in adiponectin signalling, mitochondrial function and fat oxidation. These changes represent important cellular mechanisms by which dual peroxisome proliferator‐activated receptor agonists improve skeletal muscle insulin sensitivity.