The role of fat-free soft tissue in type 2 diabetes resilience in Asian Chinese and European Caucasian individuals: the TOFI_Asia study

Abstract

Background: Fat is a component of body composition, with ethnic differences in its accumulation being associated with increased type 2 diabetes (T2D) risk, even at lower BMI. Another component of body composition is fat-free soft tissue, which is inclusive of skeletal and non-skeletal muscle, internal organs and connective tissue. There is currently scant evidence regarding the relationship between fat-free soft tissue and T2D resilience by ethnicity. Aims: To determine whether fat-free soft tissue is associated with T2D resilience in all participants (n=357) and individual ethnic subgroups, i.e. Asian Chinese participants (n=199) and European Caucasian participants (n=158), enrolled in the thin-on-the-outside-fat-on-the-inside (TOFI)_Asia study. Method: Body composition in all participants was measured using dual energy X-ray absorptiometry (DXA), in which absolute and percentage fat-free soft tissue within the total body, appendicular and abdominal regions were derived using algorithms and calculations. Simple linear regressions and stepwise regression models were used to investigate associations between fat-free soft tissue measures and the following three glycaemic outcome variables: haemoglobin A1c (HbA1c), fasting plasma glucose (FPG) and homeostatic model of insulin resistance 2 (HOMA2-IR). Results: In stepwise regression models, no fat-free soft tissue measure was negatively associated with any of HbA1c, FPG and HOMA2-IR in all participants and individual ethnic subgroups. However, simple linear regressions highlighted several negative associations involving abdominal fat-free soft tissue percentage. In all participants, abdominal fat-free soft tissue percentage was inversely associated with HbA1c (P<0.0001) and FPG (P<0.0001). Abdominal fat-free soft tissue percentage was also inversely associated with HbA1c (P<0.0001) and FPG (P<0.0001) in the European Caucasian subgroup. In Asian Chinese participants, abdominal fat-free soft tissue percentage was inversely associated with HbA1c (P=0.03) and HOMA2-IR (P=0.04), but not FPG. Conclusions: Fat-free soft tissue, particularly in the abdominal region, may play an important role in T2D resilience in all participants and individual ethnic subgroups. Cross-sectional data was used in this thesis, meaning longitudinal associations between fat-free soft tissue and T2D resilience could not be established. Furthermore, collecting data on muscle insulin sensitivity, physical activity and muscle strength, would further clarify the association of fat-free soft tissue with T2D resilience.