OBJECTIVE-Vaspin was identified as an adipokine with insulin-sensitizing effects, which is predominantly secreted from visceral adipose tissue in a rat model of type 2 diabetes. We have recently shown that vaspin mRNA expression in adipose tissue is related to parameters of obesity and glucose metabolism. However, the regulation of vaspin serum concentrations in human obesity and type 2 diabetes is unknown.RESEARCH DESIGN AND METHODS-For the measurement of vaspin serum concentrations, we developed an enzyme-linked immunosorbent assay (ELISA). Using this ELISA, we assessed circulating vaspin in a cross-sectional study of 187 subjects with a wide range of obesity, body fat distribution, insulin sensitivity, and glucose tolerance and in 60 individuals with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), or type 2 diabetes before and after a 4-week physical training program.RESULTS-Vaspin serum concentrations were significantly higher in female compared with male subjects. There was no difference in circulating vaspin between individuals with NGT and type 2 diabetes. In the normal glucose-tolerant group, circulating vaspin significantly correlated with BMI and insulin sensitivity. Moreover, physical training for 4 weeks resulted in significantly increased circulating vaspin levels.CONCLUSIONS-We found a sexual dimorphism in circulating vaspin. Elevated vaspin serum concentrations are associated with obesity and impaired insulin sensitivity, whereas type 2 diabetes seems to abrogate the correlation between increased circulating vaspin, higher body weight, and decreased insulin sensitivity. Low circulating vaspin correlates with a high fitness level, whereas physical training in untrained individuals causes increased vaspin serum concentrations.

Aberrant activation of innate immune receptors can cause a spectrum of immune disorders, such as Aicardi-Goutières syndrome (AGS). One such receptor is MDA5, a viral dsRNA sensor that induces antiviral immune response. Using a newly developed RNase-protection/RNA-seq approach, we demonstrate here that constitutive activation of MDA5 in AGS results from the loss of tolerance to cellular dsRNAs formed by Alu retroelements. While wild-type MDA5 cannot efficiently recognize Alu-dsRNAs because of its limited filament formation on imperfect duplexes, AGS variants of MDA5 display reduced sensitivity to duplex structural irregularities, assembling signaling-competent filaments on Alu-dsRNAs. Moreover, we identified an unexpected role of an RNA-rich cellular environment in suppressing aberrant MDA5 oligomerization, highlighting context dependence of self versus non-self discrimination. Overall, our work demonstrates that the increased efficiency of MDA5 in recognizing dsRNA comes at a cost of self-recognition and implicates a unique role of Alu-dsRNAs as virus-like elements that shape the primate immune system.

OBJECTIVE-Progranulin is an important molecule in inflammatory response. Chronic inflammation is frequently associated with central obesity and associated disturbances; however, the role of circulating progranulin in human obesity, type 2 diabetes, and dyslipidemia is unknown.RESEARCH DESIGN AND METHODS-For the measurement of progranulin serum concentrations, we developed an enzymelinked immunosorbent assay (ELISA). Using this ELISA, we assessed circulating progranulin in a cross-sectional study of 209 subjects with a wide range of obesity, body fat distribution, insulin sensitivity, and glucose tolerance and in 60 individuals with normal (NGT) or impaired (IGT) glucose tolerance or type 2 diabetes before and after a 4-week physical training program. Progranulin mRNA and protein expression was measured in paired samples of omental and subcutaneous adipose tissue (adipocytes and cells of the stromal vascular fraction) from 55 lean or obese individuals. Measurement of Erk activation and chemotactic activity induced by progranulin in vitro was performed using THP-1-based cell migration assays.RESULTS-Progranulin serum concentrations were significantly higher in individuals with type 2 diabetes compared with NGT and in obese subjects with predominant visceral fat accumulation. Circulating progranulin significantly correlates with BMI, macrophage infiltration in omental adipose tissue, C-reactive protein (CRP) serum concentrations, A1C values, and total cholesterol. Multivariable linear regression analyses revealed CRP levels as the strongest independent predictor of circulating progranulin. The extent of in vitro progranulin-mediated chemotaxis is similar to that of monocyte chemoattractant protein-1 but independent of G␣. Moreover, in type 2 diabetes, but not in IGT and NGT individuals, physical training for 4 weeks resulted in significantly decreased circulating progranulin levels.CONCLUSIONS-Elevated progranulin serum concentrations are associated with visceral obesity, elevated plasma glucose, and dyslipidemia. We identified progranulin as a novel marker of chronic inflammation in obesity and type 2 diabetes that closely reflects omental adipose tissue macrophage infiltration. Physical training significantly reduces elevated circulating progranulin in patients with type 2 diabetes. Diabetes 58:627-636, 2009

Highlights d RIPLET, not TRIM25, is the obligatory ubiquitin E3 ligase for RIG-I d RIPLET recognizes pre-assembled RIG-I oligomers on dsRNA and ubiquitinates RIG-I d RIPLET can cross-bridge RIG-I filaments formed on longer dsRNA d The two binding modes synergize for length dependent dsRNA discrimination by RIG-I

Oxidative stress plays an important role in the pathogenesis of insulin resistance and type 2 diabetes mellitus and in diabetic vascular complications. Thiazolidinediones (TZDs), a class of peroxisome proliferatoractivated receptor ␥ (PPAR␥) agonists, improve insulin sensitivity and are currently used for the treatment of type 2 diabetes mellitus. Here, we show that TZD prevents oxidative stress-induced insulin resistance in human skeletal muscle cells, as indicated by the increase in insulin-stimulated glucose uptake and insulin signaling. Importantly, TZD-mediated activation of PPAR␥ induces gene expression of glutathione peroxidase 3 (GPx3), which reduces extracellular H 2 O 2 levels causing insulin resistance in skeletal muscle cells. Inhibition of GPx3 expression prevents the antioxidant effects of TZDs on insulin action in oxidative stress-induced insulinresistant cells, suggesting that GPx3 is required for the regulation of PPAR␥-mediated antioxidant effects. Furthermore, reduced plasma GPx3 levels were found in patients with type 2 diabetes mellitus and in db/db/DIO mice. Collectively, these results suggest that the antioxidant effect of PPAR␥ is exclusively mediated by GPx3 and further imply that GPx3 may be a therapeutic target for insulin resistance and diabetes mellitus.

Circulating visfatin is independently associated with diabetes and resistin concentration, but is not related to adiponectin multimers or other metabolic covariates. These data are suggestive of a potential role of visfatin in subclinical inflammatory states.

Serum vaspin levels have a meal-related diurnal variation, suggesting a role for vaspin in metabolic regulation. However, the reciprocal relationship between serum vaspin and insulin may negate the importance of vaspin as an physiological insulin sensitizer.

Retinol binding protein 4 (RBP4) is a useful biomarker in the diagnosis of type 2 diabetes since its level in the serum is higher in insulin-resistant states. Accurate measurement of the serum RBP4 levels is hampered by conventional immunologic methods, such as enzyme-linked immunosorbent assay (ELISA). In this study, therefore, we have developed an aptamer-based surface plasmon resonance (SPR) biosensor that can be used to sense for RBP4 in serum samples. A single-stranded DNA (ssDNA) aptamer that showed high affinity (Kd = 0.2 +/- 0.03 microM) and specificity to RBP4 was selected. This RBP4-specific aptamer was immobilized on a gold chip and used in a label-free RBP4 detection using SPR. Analysis of RBP4 in artificial serum using SPR was compared with ELISA and Western blot analysis. Our results indicated that the RBP4-specific aptamer-based SPR biosensor gave better dose-dependent responses and was more sensitive than ELISA assays. As such, this RBP4 aptamer-based SPR biosensor can be potentially used to monitor the RBP4 levels within the serum as an indicator of type 2 diabetes.