Adipogen (South Korea)

Serum concentrations of retinol-binding protein 4 (RBP4) are elevated in type 2 diabetes and associated with the severity of insulin resistance; however, there are few data about the relationship between urinary RBP4 levels and metabolic parameters. We assessed urinary RBP4 as a new biomarker by establishing its relationship with clinical parameters associated with insulin resistance and urinary albumin excretion. We measured RBP4 in the serum and urine of 689 subjects with diverse glucose tolerance status. We also evaluated the relationship between urinary RBP4 and cardiometabolic risk factors, including insulin resistance, high-sensitivity C-reactive protein (hsCRP), arterial stiffness, and microalbuminuria. Urinary RBP4 levels were higher in insulin-resistant subjects with prediabetes or type 2 diabetes than in subjects with normal glucose tolerance (NGT) (type 2 diabetes>prediabetes>NGT; all P<0.001). Urinary RBP4 correlated strongly with homeostasis model assessments of insulin resistance (HOMA-IR), fasting glucose, triglycerides, blood pressure, hsCRP, arterial stiffness, estimated glomerular filtration rate, and urinary albumin-to-creatinine ratio (all P<0.01). HOMA-IR and arterial stiffness were found to be independent determinants of urinary RBP4 concentration. Furthermore, urinary RBP4 was highly predictive of microalbuminuria (odds ratio 2.6, 95% CI 1.6-4.2), even after adjustment for other metabolic parameters. The area under the ROC curve for urinary RBP4 to detect the presence of microalbuminuria was 0.80±0.02 (95% CI 0.76-0.84) and the cut-off value was 157.01 μg/gCr. Urinary RBP4 concentrations were elevated in patients with dysregulation of glucose metabolism and were related to various cardiometabolic risk factors including insulin resistance, inflammation, and microalbuminuria.

Recent studies have suggested that a novel adipokine, C1q/tumor necrosis factor-related protein-3 (CTRP-3), a paralog of adiponectin, may play an important role in the regulation of glucose metabolism and innate immunity. Pigment epithelium-derived factor (PEDF), a multifunctional protein with antioxidant and anti-inflammatory properties, is associated with insulin resistance and metabolic syndrome. We examined circulating CTRP-3 and PEDF concentrations in 345 subjects with diverse glucose tolerance statuses. Furthermore, we evaluated the involvement of CTRP-3 and PEDF with cardiometabolic risk factors including insulin resistance, high-sensitivity C-reactive protein (hsCRP), estimated glomerular filtration rate (eGFR), and brachial-ankle pulse wave velocity (baPWV). CTRP-3 concentrations were significantly higher in patients with type 2 diabetes or prediabetes than the normal glucose tolerance group, whereas PEDF levels were not different. Subjects with metabolic syndrome showed significantly higher levels of both CTRP-3 and PEDF compared with subjects without metabolic syndrome. Both CTRP-3 and PEDF were significantly associated with cardiometabolic parameters, including waist-to-hip ratio, triglycerides, HDL-cholesterol, alanine aminotransferase, eGFR, hsCRP, and baPWV. In conclusion, circulating CTRP-3 concentrations were elevated in patients with glucose metabolism dysregulation. Both CTRP-3 and PEDF concentrations were increased in subjects with metabolic syndrome and associated with various cardiometabolic risk factors.

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 enzyme-linked 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 Gα. 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.