The mechanisms link obesity and hypertension are not well understood. One possibility is the alterations in adipose-derived adipokines that modulate insulin resistance (IR) and cardiovascular homeostasis. We aimed to assess the associations between hypertension and four adipokine levels in Chinese youth, and to examine to what extent the associations are mediated by IR. We utilized cross-sectional data from the Beijing Children and Adolescents Metabolic Syndrome (BCAMS) Study Cohort (n = 559, mean age = 20.2 years). Plasma leptin, adiponectin, retinol binding protein 4 (RBP4) and fibroblast growth factor 21 (FGF21) levels were assayed. The relationships between adipokines and hypertension and the possible mediation effect of IR were evaluated. Youth with hypertension have lower adiponectin and higher leptin, FGF21 (all P < 0.001) and RBP4 levels (p = 0.06) compared to their counterparts. Moreover, the co-existence of these two or more adipokine abnormalities in youth leads to a 9-fold increased risk for hypertension (OR: 9.19; 95% CI, 4.01–21.08) compared with these without abnormalities. However, in the fully adjusted and BMI-adjusted analyses, only FGF21 was a significant predictor of hypertension (OR: 2.12; 95% CI, 1.34–3.36). Mediation analysis revealed that the associations between leptin, adiponectin, RBP4 and hypertension are totally mediated by IR (proportion: 63.9%, 65.4%, and 31.6%, respectively), while BMI and IR partly mediated the association between FGF21 and hypertension (proportion: 30.6%, 21.2%). Our findings suggest that dysregulation of adipokines might result in hypertension in youth. Leptin, adiponectin and RBP4 may exert their functions in hypertension through adiposity-related IR, whereas FGF21 might be used as an independent marker of hypertension in youth.

Objective To investigate vitamin D levels among youth in Beijing and to explore its relationship with glucose metabolism.Methods A total of 517 subjects (aged 14-28 years) were recruited from the cohort of Beijing Children and Adolescents Metabolic Syndrome study.All subjects underwent a 2h-75 g oral glucose tolerance test.Insulin resistance (IR) was estimated using homeostasis model assessment of IR (HOMA-IR) and insulin sensitive index.Pancreatic β-cell function was assessed by HOMA-β,insulinogenic index (IGI),oral disposition index,and area under the curve of insulin.Percent body fat (Fat％) was measured by bioimpedance analysis.Serum 25-hydroxy vitamin D (25OHD) levels were measured by electro-chemiluminescence immunoassay.Results The prevalence of vitamin D deficiency (25OHD ＜50 nmol/L) is 78.7％ (male 69.0％ and female 89.4％).After adjusting for age,gender,and sun exposure,serun 25OHD levels were significant negatively correlated to fasting glucose (r =-0.088,P =0.046),2-hour glucose (r =-0.128,P =0.004),and HbA1 c (r =-0.088,P =0.047) level.After further adjusting for Fat％,the above differences between serum levels of 25OHD 2-hour glucose (r =-0.120,P =0.007),we also found positive correlation between serum 25OHD and 0.5-hour insulin levels (r =0.091,P =0.042).However,there was no association between 25OHD and IR (P ＞0.1).Covariance analysis showed that serum level of 25OHD was significantly lower in subjects with type 2 diabetes mellitus (T2DM) than those in healthy controls (P =0.003),impaired fasting glucose (P =0.009),and impaired glucose tolerance (P =0.010) subjects.Conclusion The prevalence of vitamin D deficiency in this cohort is relatively high.The significantly lower 25OHD level in youth with T2DM indicates that lower level of vitamin D may play a negative role in pancreatic β-cell function.

Betatrophin has been recently reported to play a role in glucose homeostasis by inducing beta-cell proliferation in mice. However, studies in human are inconsistent. As a nutritionally-regulated liver-enriched factor, we hypothesize that betatrophin might be regulated by vitamin D, and ignorance of vitamin D status may explain the discrepancy in previous human studies. The aims of this study were to assess the association between circulating betatrophin and glucose homeostasis as well as other cardiometabolic variables in a cohort of youths at risk for metabolic syndrome and test the possible influence of vitamin D status on the association.