Association between gamma-glutamyl transferase and diabetes factors among elderly nonobese individuals

Type 2 diabetes mellitus is a significant health concern among elderly individuals in Taiwan, and liver dysfunction, particularly nonalcoholic fatty liver disease, is prevalent in this population. Gamma-glutamyl transferase (γ-GT), a key enzyme involved in glutathione metabolism, has been linked to metabolic disorders, including insulin resistance (IR) and diabetes. However, its association with insulin secretion phases (first-phase insulin secretion, FPIS; second-phase insulin secretion, SPIS) and glucose effectiveness (GE) remains unclear. This study aimed to investigate these relationships in elderly nonobese Chinese individuals. A total of 10,933 participants (5082 men and 5851 women) aged ≥ 65 years were enrolled. Participants were classified based on metabolic syndrome (MetS) status and γ-GT quartiles. Blood samples were analyzed for γ-GT, fasting plasma glucose, insulin resistance, and lipid profiles. The study used established equations to calculate IR, FPIS, SPIS, and GE. Pearson correlation analysis and statistical models were applied to assess the associations. 768 men and 794 women had MetS. Those with MetS had higher IR, FPIS, SPIS, γ-GT levels, and lower GE. Higher γ-GT levels were significantly associated with MetS components and increased IR, FPIS, SPIS, and decreased GE. GE had the strongest negative correlation (r = -0.198 for men, -0.158 for women), followed by positive correlations with IR (r = 0.183 for men, 0.132 for women), SPIS (r = 0.099 for men, 0.060 for women), and FPIS (r = 0.028 for men, 0.048 for women). γ-GT was positively associated with IR, FPIS, and SPIS but negatively correlated with GE in elderly individuals. Among the 4 diabetes factors, GE exhibited the strongest correlation with γ-GT, followed by IR, SPIS, and FPIS. These findings highlight the need for further research into the role of γ-GT in glucose metabolism and potential clinical implications for elderly nonobese Chinese populations.