Age effect on the shared etiology of glycemic traits and serum lipids: evidence from a Chinese twin study

Purpose Diabetes and dyslipidemia are among the most common chronic diseases with increasing global disease burdens, and they frequently occur together. The study aimed to investigate differences in the heritability of glycemic traits and serum lipid indicators and differences in overlapping genetic and environmental influences between them across age groups. Methods This study included 1189 twin pairs from the Chinese National Twin Registry and divided them into three groups: aged ≤ 40, 41–50, and > 50 years old. Univariate and bivariate structural equation models (SEMs) were conducted on glycemic indicators and serum lipid indicators, including blood glucose (GLU), glycated hemoglobin A1c (HbA 1c ), total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), in the total sample and three age groups. Results All phenotypes showed moderate to high heritability (0.37–0.64). The heritability of HbA 1c demonstrated a downward trend with age (HbA 1c : 0.50–0.79), while others remained relatively stable (GLU: 0.55–0.62, TC: 0.58–0.66, TG: 0.50–0.63, LDL-C: 0.24–0.58, HDL-C: 0.31–0.57). The bivariate SEMs demonstrated that GLU and HbA 1c were correlated with each serum lipid indicator (0.10–0.17), except HDL-C. Except for HbA 1c and LDL-C, as well as HbA 1c and HDL-C, differences in genetic correlations underlying glycemic traits and serum lipids between age groups were observed, with the youngest group showing a significantly higher genetic correlation than the oldest group. Conclusion Across the whole adulthood, genetic influences were consistently important for GLU, TC, TG, LDL-C and HDL-C, and age may affect the shared genetic influences between glycemic traits and serum lipids. Further studies are needed to elucidate the role of age in the interactions of genes related to glycemic traits and serum lipids.