Associations Of Subcutaneous Fat And Thyroid Hormones With Diabetes And Its High-risk Populations

Objective: We aimed to investigate the associations of thigh and abdominal subcutaneous fat with newly diagnosed diabetes(NDM),insulin sensitivity,and β cell function in a cross-sectional study of Chinese adults.We also aimed to investigate the associations of fat distribution related hormones with hyperglycemia and non-alcoholic fatty liver disease(NAFLD)in both cross-sectional and longitudinal analyses.Methods: Statistical analyses were performed using data from the Shanghai Nicheng cohort study and its substudy,the Shanghai Nicheng Atherosclerosis Study.Thigh subcutaneous fat area(TSFA),abdominal subcutaneous fat area(ASFA)and visceral fat area(VFA)were assessed by magnetic resonance imaging using a single slice of image at the level of mid-femur and the navel to estimate the absolute fat distribution,respectively.TSFA%,ASFA%,and VFA% were calculated respectively as the ratio of the relative fat area to the total area to estimate the propensity to store energy in this fat compartment.All adiposity indicators were standardized before entering the regression equation.Different glucose status was defined based on an oral glucose tolerance test.The Homeostatic model assessment of insulin resistance and the insulin sensitivity index proposed by Gutt were used to estimate insulin sensitivity,disposition indices were used to estimate β-cell function.Fatty liver was diagnosed by ultrasound.Results:(1)In 12137 subjects and the subgroup,TSFA was independently associated with lower risk of NDM in women(Odds ratio [OR] in all models: 0.65–0.87).After adjustment of body mass index(BMI),there is a U-shape association between TSFA and NDM risk in men(OR < 1 compared to the minimum value of TSFA).After adjustment for BMI,ASFA was negatively associated with NDM risk in women but not in men.Per SD increase in TSFA% and in ASFA% was associated with 32–45% and 13–18% lower risk of NDM in both genders.(2)In 3596 subjects,in terms of absolute quantity of fat compartment,after adjustment for BMI,TSFA was associated with higher insulin sensitivity(in women)and β cell function(in both genders);ASFA was associated with lower insulin sensitivity and β cell function in men,but higher insulin sensitivity and β cell function in women.In terms of the propensity to store energy in a specific fat compartment,TSFA% was independently associated with higher insulin sensitivity and β cell function.Adjustment for BMI,ASFA% was positively associatedwith insulin sensitivity and β cell function and the associations were very weak(standardized β ≤ 0.07).(3)In 3144 euthyroid subjects,there were positive associations of Free triiodothyronine(FT3)level with hyperglycemia,NAFLD,and the risk of NAFLD progression in euthyroid women.FT3 level increased with the occurrence of NAFLD(percentage change: 1.4%)and decreased with the remission of NAFLD(percentage change:-2.7%)in euthyroid women.Conclusion: Thigh subcutaneous fat(in both genders)and abdominal subcutaneous fat(in women)are protective for lower risk of NDM.The propensity to store energy in subcutaneous fat,especially in thigh subcutaneous fat compartment,is protective for lower risk of NDM.There is a positive association of FT3 level with hyperglycemia and NAFLD in euthyroid women and it may be an adaptive response to maintain energy and metabolic homeostasis.