Associations of percentage body cell mass with insulin resistance and type 2 diabetes: mediation effect of body mass index.

BACKGROUND AND OBJECTIVES: Type 2 diabetes (T2D) stems from metabolic dysregulation, and body cell mass (BCM) comprises the principal physiological substrate of basal metabolic rate (BMR); however, the as-sociation between BCM and diabetes is still unclear. This study examined the relationship of percentage body cell mass (PBCM) with insulin resistance (IR) and T2D, and evaluated the mediators of this association. METHODS AND STUDY DESIGN: This study utilized data from U.S. adults in the National Health and Nutrition Survey (1999-2004). Weighted multivariate regression, restricted cubic spline analysis, subgroup analyses, and sensitivity analysis were employed to investigate the relationship of PBCM with T2D risk biomarkers, IR and T2D. The potential mediating role of body mass index (BMI) was explored. RESULTS: A total of 2,923 participants aged 18 years or older were included. Preliminary analysis demonstrated an inverse association between PBCM and biomarkers of T2D risk. Further analyses revealed that higher PBCM was associated with lower odds of IR (OR = 0.91, 95% CI: 0.88-0.94, p <0.001) and T2D (OR = 0.89, 95% CI: 0.84-0.94, p <0.001) in the fully adjusted model. Mediation analysis indicated that BMI mediated 70.6% (95% CI: 55.1%-88.9%, p <0.001) of the total effect of PBCM on IR, and 29.9% (95% CI: 14.2%-65.9%, p <0.001) of that on T2D, respectively. CONCLUSIONS: PBCM was negatively associated with the prevalence of IR and T2D. Mediation analyses demonstrated a mediating effect of BMI, suggesting that PBCM might be related to IR and T2D, potentially mediated by BMI.