Distribution patterns of intramyocellular and extramyocellular fat by magnetic resonance imaging in subjects with diabetes, prediabetes and normoglycaemic controls

Abstract

Aim: To evaluate the distribution of intramyocellular lipids (IMCLs) and extramyocellular lipids (EMCLs) as well as total fat content in abdominal skeletal muscle by magnetic resonance imaging (MRI) using a dedicated segmentation algorithm in subjects with type 2 diabetes (T2D), prediabetes and normoglycaemic controls.

Materials and methods: Subjects from a population-based cohort were classified with T2D, prediabetes or as normoglycaemic controls. Total myosteatosis, IMCLs and EMCLs were quantified by multiecho Dixon MRI as proton-density fat-fraction (in %) in abdominal skeletal muscle.

Results: Among 337 included subjects (median age 56.0 [IQR: 49.0-64.0] years, 56.4% males, median body mass index [BMI]: 27.2 kg/m² ), 129 (38.3%) were classified with an impaired glucose metabolism (T2D: 49 [14.5%]; prediabetes: 80 [23.7%]). IMCLs were significantly higher than EMCLs in subjects without obesity (5.7% [IQR: 4.8%-7.0%] vs. 4.1% [IQR: 2.7%-5.8%], P < .001), whereas the amounts of IMCLs and EMCLs were shown to be equal and significantly higher in subjects with obesity (both 6.7%, P < .001). Subjects with prediabetes and T2D had significantly higher amounts of IMCLs and EMCLs compared with normoglycaemic controls (P < .001). In univariable analysis, prediabetes and T2D were significantly associated with both IMCLs (prediabetes: β: 0.76, 95% CI: 0.28-1.24, P = .002; T2D: β: 1.56, 95% CI: 0.66-2.47, P < .001) and EMCLs (prediabetes: β: 1.54, 95% CI: 0.56-2.51, P = .002; T2D: β: 2.15, 95% CI: 1.33-2.96, P < .001). After adjustment for age and gender, the association of IMCLs with prediabetes attenuated (P = 0.06), whereas for T2D, both IMCLs and EMCLs remained significantly and positively associated (P < .02).

Conclusion: There are significant differences in the amount and distribution ratio of IMCLs and EMCLs between subjects with T2D, prediabetes and normoglycaemic controls. Therefore, these patterns of intramuscular fat distribution by MRI might serve as imaging biomarkers in both normal and impaired glucose metabolism.

Keywords: body composition; cohort study; type 2 diabetes.