Pubertal muscle mass and diabetes risks

Abstract

Type-2 diabetes is one of the most prevalent non-communicable diseases globally. The prevalence has increased rapidly in both developed and developing countries. Type-2 diabetes has become epidemic in China in the past three decades. With a relatively low obesity prevalence compared to western countries, such as the United States, the question has arisen as to why people in China are so susceptible to diabetes, but few studies have answered this question definitively. Asians have lower muscle mass than Caucasians which could be one possible explanation. This study aims to test the hypothesis that pubertal muscle mass acquisition, under the influence of testosterone, may be a risk factor for diabetes.

This study recruited from the population-representative Chinese “Children of 1997” birth cohort with 8327 participants (88% of all infants born in April and May 1997) in Hong Kong. Participants were aged 15 years at the time of this study. The main objective was to examine the association of pubertal muscle mass with diabetes risk factors, and to examine determinants of pubertal muscle mass in this non-western setting.

In June to August 2012, 502 participants from “Children of 1997” were recruited to complete a health assessment follow up at the Active Health Clinic in University of Hong Kong, including a questionnaire, blood tests and a physical examination. Multivariable linear regression was used to assess the associations of: (1) testosterone and pubertal muscle mass with diabetes risk factors, including fasting glucose, fasting insulin and homeostasis model assessment -insulin resistance (HOMA-IR), and any mediation of the association of testosterone with diabetes risk factors by pubertal muscle mass, and (2) environmental influences, including intergenerational influences, proxied by mother’s place of birth, and current life style influences (meat consumption and physical activity), with pubertal muscle mass.

Higher pubertal testosterone was associated with lower fasting glucose (-0.008, 95% confidence interval (CI) -0.015 to -0.002), fasting insulin (-0.44, 95% CI -0.57 to -0.31) and HOMA-IR (-0.090, 95% CI -0.12 to -0.063) after adjusting for potential confounders, i.e, sex, birth weight, highest parental education, mother’s place of birth and physical activity. The association was partially mediated by skeletal muscle mass and body fat percentage. Skeletal muscle mass was negatively associated with fasting glucose (-0.017, 95% CI -0.025 to -0.009), insulin (-0.876, 95% CI -1.033 to -0.719), and HOMA-IR (-0.180, 95% CI -0.214 to -0.147) after adjusted for potential confounders. High meat consumption (0.176, 95% CI 0.000 to 0.351) and physical activity (0.157, 95% CI 0.059 to 0.254) were both associated with higher skeletal muscle mass in adolescents; however birth weight and mother’s place of birth had no influence on pubertal skeletal muscle composition. Higher pubertal muscle mass and testosterone are association with better glucose metabolism in adolescence. Food intake and physical activity may also influence the development of skeletal muscle, thus adolescence may be a sensitive period for the development of diabetes where interventions to increase muscle mass could have long-term protective effects.