Pancreas-enriched miRNAs are altered in the circulation of subjects with diabetes: a pilot cross-sectional study

The clinical presentation of diabetes sometimes overlaps, contributing to ambiguity in the diagnosis. Thus, circulating pancreatic islet-enriched microRNAs (miRNAs) might be useful biomarkers of β-cell injury/dysfunction that would allow more accurate subtyping of diabetes. We measured plasma levels of selected miRNAs in subjects with prediabetes (n = 12), type 2 diabetes (T2D, n = 31), latent autoimmune diabetes of adults (LADA, n = 6) and type 1 diabetes (T1D, n = 16) and compared them to levels in healthy control subjects (n = 27). The study was conducted at the Translational Research Institute for Metabolism and Diabetes (TRI-MD), Florida Hospital. MiRNAs including miR-375 (linked to β-cell injury), miR-21 (associated with islet inflammation), miR-24.1, miR-30d, miR-34a, miR-126, miR-146, and miR-148a were significantly elevated in subjects with various forms of diabetes compared to healthy controls. Levels of several miRNAs were significantly correlated with glucose responses during oral glucose tolerance testing, HbA[subscript 1c], β-cell function, and insulin resistance in healthy controls, prediabetes, and T2D. These data suggest that miRNAs linked to β-cell injury and islet inflammation might be useful biomarkers to distinguish between subtypes of diabetes. This information could be used to predict progression of the disease, guide selection of optimal therapy and monitor responses to interventions, thus improving outcomes in patients with diabetes.Translational Research Institute for Metabolism and Diabetes (TRI

Reduced adipose tissue oxygenation in human obesity evidence for rarefaction, macrophage chemotaxis, and inflammation without an angiogenic response

OBJECTIVE-Based on rodent studies, we examined the hypothesis that increased adipose tissue (AT) mass in obesity without an adequate support of vascularization might lead to hypoxia, macrophage infiltration, and inflammation. RESEARCH DESIGN AND METHODS-Oxygen partial pressure (AT pO 2) and AT temperature in abdominal AT (9 lean and 12 overweight/obese men and women) was measured by direct insertion of a polarographic Clark electrode. Body composition was measured by dual-energy X-ray absorptiometry, and insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. Abdominal subcutaneous tissue was used for staining, quantitative RT-PCR, and chemokine secretion assay. RESULTS-AT pO 2 was lower in overweight/obese subjects than lean subjects (47 ± 10.6 vs. 55 ± 9.1 mmHg); however, this level of pO 2 did not activate the classic hypoxia targets (pyruvate dehydrogenase kinase and vascular endothelial growth factor [VEGF]). AT pO 2 was negatively correlated with percent body fat (R =-0.50, P \u3c 0.05). Compared with lean subjects, overweight/ obese subjects had 44% lower capillary density and 58% lower VEGF, suggesting AT rarefaction (capillary drop out). This might be due to lower peroxisome proliferator-activated receptor γ1 and higher collagen VI mRNA expression, which correlated with AT pO 2 (P \u3c 0.05). Of clinical importance, AT pO 2 negatively correlated with CD68 mRNA and macrophage inflammatory protein 1α secretion (R =-0.58, R =-0.79, P \u3c 0.05), suggesting that lower AT pO 2 could drive AT inflammation in obesity. CONCLUSIONS-Adipose tissue rarefaction might lie upstream of both low AT pO 2 and inflammation in obesity. These results suggest novel approaches to treat the dysfunctional AT found in obesity. © 2009 by the American Diabetes Association

Molecular Characterization of the Tumor Suppressor Candidate 5 Gene: Regulation by PPARγ and Identification of TUSC5 Coding Variants in Lean and Obese Humans

Tumor suppressor candidate 5 (TUSC5) is a gene expressed abundantly in white adipose tissue (WAT), brown adipose tissue (BAT), and peripheral afferent neurons. Strong adipocyte expression and increased expression following peroxisome proliferator activated receptor γ (PPARγ) agonist treatment of 3T3-L1 adipocytes suggested a role for Tusc5 in fat cell proliferation and/or metabolism. However, the regulation of Tusc5 in WAT and its potential association with obesity phenotypes remain unclear. We tested the hypothesis that the TUSC5 gene is a bona fide PPARγ target and evaluated whether its WAT expression or single-nucleotide polymorphisms (SNPs) in the TUSC5 coding region are associated with human obesity. Induction of Tusc5 mRNA levels in 3T3-L1 adipocytes by troglitazone and GW1929 followed a dose-response consistent with these agents' binding affinities for PPARγ. Chromatin immunoprecipitation (ChIP) experiments confirmed that PPARγ protein binds a ∼ −1.1 kb promotor sequence of murine TUSC5 transiently during 3T3-L1 adipogenesis, concurrent with histone H3 acetylation. No change in Tusc5 mRNA or protein levels was evident in type 2 diabetic patients treated with pioglitazone. Tusc5 expression was not induced appreciably in liver preparations overexpressing PPARs, suggesting that tissue-specific factors regulate PPARγ responsiveness of the TUSC5 gene. Finally, we observed no differences in Tusc5 WAT expression or prevalence of coding region SNPs in lean versus obese human subjects. These studies firmly establish the murine TUSC5 gene locus as a PPARγ target, but the significance of Tusc5 in obesity phenotypes or in the pharmacologic actions of PPARγ agonists in humans remains equivocal

Elevated Secreted Frizzled-Related Protein 4 In Obesity: A Potential Role In Adipose Tissue Dysfunction

Objectives Rarefaction and inflammation of adipose tissue contributes to insulin resistance in obesity. It was hypothesized that angiostatic secreted frizzled-related protein 4 (SFRP4) causes adipose tissue rarefaction and leads to inflammation and ultimately insulin resistance in obese patients. Methods Abdominal subcutaneous adipose tissue (AbdAT), gluteal subcutaneous adipose tissue (GlutAT), and blood from 15 lean and obese subjects were collected. Circulating-SFRP4 was measured by ELISA. Body composition was measured by DEXA and insulin sensitivity by the euglycemic hyperinsulinemic clamp. Adipose tissue was analyzed using qRT-PCR for mRNA gene expression, Luminex system for tissue cytokine release, immunohistochemistry for labeling adipose capillaries, and osmium fixation and Coulter counting for adipocyte sizing. Results Circulating-SFRP4 was higher in obese vs. lean subjects (137.8-±-33.6 ng ml-1 vs. 64.1-±-23.8 ng ml-1, P-\u3c-0.05). Circulating-SFRP4 significantly (P-\u3c-0.05) correlated with body fat percentage (R-=-0.07), body mass index (R-=-0.07), insulin sensitivity (R-=-0.66). Circulating-SFRP4 correlated with AbdAT-VEGF (R-=-0.67, P-\u3c-0.05), AbdAT-capillary density (R-=-0.65, P-\u3c-0.05), secreted-MIP1α (R-=-0.74), and AbdAT-SFRP4 mRNA (R-=-0.60). AbdAT-SFRP4 mRNA significantly correlated with AbdAT-capillary density (R-=-0.71, P-\u3c-0.05), but not with AbdAT mean adipocyte size. There was no difference between AbdAT-SFRP4 and GlutAT-SFRP4 mRNA. Interestingly, GlutAT-SFRP4 correlated with AbdAT mean adipocyte size (P-\u3c-0.05). Conclusions The results suggested that AbdAT is a major contributor for circulating-SFRP4 and that SFRP4 has an important role in obese adipose tissue pathophysiology

Elevated and Correlated Expressions of miR-24, miR-30d, miR-146a, and SFRP-4 in Human Abdominal Adipose Tissue Play a Role in Adiposity and Insulin Resistance

Objective. We explored the relationships among microRNAs (miRNAs) and SFRP4, as they relate to adipose tissue functions including lipolysis, glucose and glycerol turnover, and insulin sensitivity. Methods. Abdominal adipose tissue (AbdAT) levels of thirteen microRNAs (miRNAs), SFRP4, and VEGF in lean nondiabetic subjects (n = 7), subjects with obesity (n = 5), and subjects with obesity and type 2 diabetes (T2DM) (n = 5) were measured by qPCR. Insulin sensitivity was measured by the euglycemic-hyperinsulinemic clamp. Osmium fixation and Coulter counting were used for adipocyte sizing. Data were analyzed using generalized linear models that adjusted for age, gender, and ethnicity. Results. AbdAT miR-24, miR-30d, and miR-146a were elevated in subjects with obesity (P < 0.05) and T2DM (P < 0.1) and positively correlated with measures of percent body fat by DXA (r[subscript miR.24] = 0.894, r[subscript miR.146a] = 0.883, P < 0.05), and AbdAT SFRP4 (r[subscript miR.30] = 0.93,r[subscript miR.146a]=0.88, P < 0.05). These three miRNAs additionally correlated among themselves (r[subscript miR.24 ~ miR.146a] = 0.90, r[subscript miR.30 ~ miR.146a] = 0.85, P = 0.05). Conclusions. This study suggests a novel association between the elevated levels of miRNAs miR-24, miR-30d, and miR-146a (apparently coregulated) and the level of SFRP4 transcript in AbdAT of subjects with obesity and T2DM. These molecules might be part of a regulatory loop involved in AbdAT remodeling/adiposity and systemic insulin resistance. This trial is registered with NCT00704197