Glucagon-like peptide-1 (GLP-1), an incretin hormone, plays an important role in regulating glucose homeostasis. In this study, the applicability of circulating GLP-1 levels as an early indicator of metabolic syndrome (MetS) risk was examined. Women without diagnosed diseases were grouped according to their number of MetS risk factors (MetS RFs) (no RFs as Super-healthy, n = 61; one or two RFs as MetS risk carriers, n = 60; 3 ≤ RFs as MetS, n = 19). The circulating GLP-1 levels and homeostasis model assessment insulin resistance (HOMA-IR) scores were significantly higher in the MetS group than in the other two groups. The GLP-1 levels correlated positively with adiposity, HOMA-IR, blood pressure, and high sensitivity C-reactive protein (hs-CRP), but not with fasting glucose and lipid profiles, whose significances were maintained after adjustments for age, smoking and drinking habits, menopausal status, and total calorie intake. The GLP-1 levels also increased proportionally with the number of MetS RFs. In the MetS group, the GLP-1 levels were much higher in individuals with obesity (body mass index ≥ 25 kg/m2). In conclusion, the circulating GLP-1 level may be applicable as a potential early indicator of MetS risk in women without diagnosed diseases. Further study with a large population is needed to confirm the conclusion.

Obesity, characterized by excessive fat mass, has been emerging as a major global epidemic and contributes to the increased risk of morbidity around the world. Thus, the necessity to find effective therapy and specific regulatory mechanisms is increasing for controlling obesity. Lately, many researchers have been interested in the linkage between obesity and adipokines/myokines, particularly adiponectin and brain-derived neurotrophic factor (BDNF). However, the role of adiponectin and BDNF in adiposity has not been clearly defined yet. We examined the association of adiposity with adiponectin and BDNF through human study (observational study) with Korean women and in vitro experiments. In the human study, we found a negative relationship between adiposity and circulating adiponectins but irregular patterns in the relationship between adiposity and circulating BDNFs. In the in vitro study using 3T3-L1 adipocytes, adiponectin treatment strongly promoted adipocyte differentiation and the fat browning process, whereas BDNF treatment attenuated adipocyte differentiation and the fat browning process in differentiated adipocytes. Our results demonstrate that adiponectin and BDNF play an important role in regulating fat mass and the expression of fat-browning markers in different ways, and also suggest that circulating adiponectin may be used as an important monitoring index for obesity status.