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Objective: Despite studies on offspring obesity and delayed parenthood, little attention has been paid to the central obesity of offspring. The purpose of this study was to test the hypothesis that maternal age at childbirth (MAC) was associated with central obesity in offspring among the adult population, and fasting insulin may play a role in this association as a mediating factor. Methods: A total of 423 adults (mean age 37.9 years, 37.1% female) were included. Information about maternal variables and other confounders was collected by face‐to‐face interview. Waist circumference and insulin were determined through physical measurements and biochemical examinations. Logistic regression model and restricted cubic spline model were used to analyze the relationship between MAC and central obesity of offspring. The mediating effect of fasting insulin levels on association between MAC and offspring waist circumference was also analyzed. Results: There was a nonlinear relationship between MAC and central obesity in offspring. Compared with subjects with MAC 27–32 years, those with MAC 21–26 years (OR = 1.814, 95% CI: 1.129–2.915) and MAC ≥33 years (OR = 3.337, 95% CI: 1.638–6.798) had higher odds to develop central obesity. Offspring fasting insulin was also higher in MAC 21–26 years and MAC ≥33 years compared with those with MAC 27–32 years. Taking the group MAC 27–32 years as reference, the mediating effect of fasting insulin levels on the waist circumference was 20.6% and 12.4% for MAC 21–26 years and ≥ 33 years, respectively. Conclusion: MAC 27–32 years has the lowest odds of central obesity in offspring. Fasting insulin levels may have a partial mediating effect on the association between MAC and central obesity. [ABSTRACT FROM AUTHOR]

Background: Physical activity and vitamin D receptor (VDR) have been associated with type 2 diabetes mellitus (T2DM). However, the associations of VDR methylation with T2DM and physical activity remained unknown. We aimed to investigate whether VDR methylation was a link between physical activity and T2DM. Methods: A 1:1 matching case‐control study was designed based on the Henan Rural Cohort Study, including 272 pairs of T2DM patients and nonpatients. Physical activity level was assessed using the International Physical Activity Questionnaire. The high‐resolution melt method was applied to determine the methylation level of the promoter region of VDR. The association between physical activity and T2DM was analyzed with a conditional logistic regression model. The effect modification of VDR methylation levels on the association between physical activity and T2DM was conducted. A multivariate correlation analysis model was applied to investigate correlations of VDR methylation with insulin sensitivity. Results: Physical activity level was associated with T2DM risk (crude model: odds ratio [OR] 0.611; 95% CI, 0.416‐0.897; adjusted model: OR 0.619; 95% CI, 0.418‐0.917). In effect modification analysis, the effects of physical activity on T2DM were stronger for low VDR methylation levels than for high (P =.025). Moreover, VDR methylation levels were associated with insulin (r = −0.089, P =.039) as well as homeostatic model assessment of insulin resistance (r = −0.098, P =.022). Conclusions: The methylation status of the VDR promoter is associated with the secretion and sensitivity of insulin. VDR methylation attenuates the association between physical activity and T2DM, indicating that proactively physical activity may reduce the risk of T2DM, especially in people with low VDR methylation level. [ABSTRACT FROM AUTHOR]