Yao Nanfang, Liu Lan, Jiang Yuqi, Wang Dongmei, Lu Qianyi, Zeng Yi, Yu Genfeng, Ma Qintao, Li Peiyi, Liu Lingling, Shen Jie, Wan Heng
Department of Endocrinology and Metabolism, The Eighth Affiliated Hospital of Southern Medical University (The First People's Hospital of Shunde), Foshan, Guangdong, China.
School of Nursing, Southern Medical University, Guangzhou, Guangdong, China.
J Cachexia Sarcopenia Muscle. 2025 Oct;16(5):e70061. doi: 10.1002/jcsm.70061.
Body composition parameters, including fat-to-muscle ratio (FMR) and appendicular skeletal muscle mass (ASM), are closely associated with metabolic diseases. However, the mediating role of peripheral thyroid hormone sensitivity, reflected by the free triiodothyronine-to-free thyroxine ratio (FT3/FT4 ratio), in these associations remains unclear in euthyroid individuals. The current study aimed to investigate the associations of FMR and ASM/BMI with diabetes and to explore the potential mediating role of FT3/FT4 ratio in these relationships among euthyroid Chinese adults.
This cross-sectional study enrolled the participants from 10 communities in Guangdong Province, China, from November 2021 to September 2022. Body composition was measured using bioelectrical impedance analysis (BIA). Diabetes was defined based on fasting plasma glucose, 2-h postload glucose or glycated haemoglobin (HbA1c). Associations of FMR and ASM adjusted for body mass index (ASM/BMI) with diabetes were assessed using multivariable logistic regression. Structural equation modelling was applied to evaluate the mediating effect of FT3/FT4 ratio.
A total of 5089 participants (mean age = 46 years, SD = 12) were included in the final analysis, consisting of 1957 men (38.5%) and 3132 women (61.5%). Participants in the third tertile (T3) of FMR exhibited a 79% higher prevalence of diabetes compared to those in the first tertile (T1) (OR 1.79, 95% CI 1.27-2.54) (p < 0.05). Conversely, those in the T3 of ASM/BMI had a 56% lower prevalence of diabetes compared to participants in T1 (OR 0.44, 95% CI 0.31-0.64) (p < 0.05). Restricted cubic spline analysis confirmed linear associations for both FMR and ASM/BMI with diabetes (both p for overall < 0.001; p for non-linear > 0.05). FT3/FT4 ratio significantly mediated the association between ASM/BMI and diabetes, accounting for 4.6% of the total effect (p < 0.05), whereas no significant mediation was observed in the FMR-diabetes pathway (p > 0.05).
In euthyroid individuals, higher FMR and lower ASM/BMI were independently associated with increased diabetes prevalence. The inverse relationship between ASM/BMI and diabetes may be partially mediated by FT3/FT4 ratio, highlighting peripheral thyroid hormone sensitivity as a potential mechanistic biomarker linking ASM loss to glycaemic dysregulation in euthyroid individuals.
身体成分参数，包括脂肪与肌肉比率（FMR）和四肢骨骼肌质量（ASM），与代谢性疾病密切相关。然而，在甲状腺功能正常的个体中，由游离三碘甲状腺原氨酸与游离甲状腺素比率（FT3/FT4比率）反映的外周甲状腺激素敏感性在这些关联中的中介作用仍不清楚。本研究旨在调查FMR和ASM/BMI与糖尿病的关联，并探讨FT3/FT4比率在甲状腺功能正常的中国成年人这些关系中的潜在中介作用。
这项横断面研究于2021年11月至2022年9月在中国广东省的10个社区招募参与者。使用生物电阻抗分析（BIA）测量身体成分。糖尿病根据空腹血糖、餐后2小时血糖或糖化血红蛋白（HbA1c）定义。使用多变量逻辑回归评估调整体重指数后的FMR和ASM（ASM/BMI）与糖尿病的关联。应用结构方程模型评估FT3/FT4比率的中介作用。
最终分析纳入了5089名参与者（平均年龄 = 46岁，标准差 = 12），其中包括1957名男性（38.5%）和3132名女性（61.5%）。FMR处于第三个三分位数（T3）的参与者糖尿病患病率比处于第一个三分位数（T1）的参与者高79%（比值比1.79，95%置信区间1.27 - 2.54）（p < 0.05）。相反，ASM/BMI处于T3的参与者糖尿病患病率比T1的参与者低56%（比值比0.44，95%置信区间0.31 - 0.64）（p < 0.05）。受限立方样条分析证实FMR和ASM/BMI与糖尿病均呈线性关联（总体p均 < 0.001；非线性p > 0.05）。FT3/FT4比率显著介导了ASM/BMI与糖尿病之间的关联，占总效应的4.6%（p < 0.05），而在FMR - 糖尿病途径中未观察到显著的中介作用（p > 0.05）。
在甲状腺功能正常的个体中，较高的FMR和较低的ASM/BMI与糖尿病患病率增加独立相关。ASM/BMI与糖尿病之间的负相关关系可能部分由FT3/FT4比率介导，突出了外周甲状腺激素敏感性作为将ASM丢失与甲状腺功能正常个体血糖失调联系起来的潜在机制生物标志物。
