The Thigh is Relevant to Assess Myosteatosis, Through Proton Magnetic Resonance Spectroscopy, and Lean Mass in Adults with Metabolic Risk Factors

Fatty infiltration in the muscle, i.e., myosteatosis, is an undervalued parameter of muscle quality associated to cardiometabolic health. Appendicular muscle mass is also associated to cardiometabolic outcomes. Then, both muscle mass and quality should be evaluated in the same region. We explored the association of intramuscular lipids (IML) in the thigh, measured through proton magnetic resonance spectroscopy (1H-MRS), with body fat (BF), thigh lean mass, thigh fat mass and saturated free fatty acids (S-FFA) in a cohort of Colombian adults with metabolic risk factors.

Methods:

A cross-sectional study was performed in sedentary, overweighed adults of both sexes. Serum fasting triglycerides (TG), high-density lipoprotein (HDL) and glycemia were analyzed by conventional clinical laboratory methods. Intramyocellular and extramyocellular lipids were assessed through 1H-MRS in the right vastus lateralis muscle. BF and thigh composition were quantified by dual-energy X-ray absorptiometry. Serum stearic (SA) and palmitic acids (PA) were measured by gas chromatography. Associations were explored with Spearman´s rho.

Results:

We included a total of 53 subjects of 50.7±6.2 years old, 71% women. They showed mean TG of 169.4±85.8 mg/dL, HDL of 47.0±11.5 mg/dL, glycemia of 97.6±9.5 mg/dL. The waist circumference was 94.2±10.1 cm and the body mass index was 29.2±4.0 kg/m2. They had a BF percentage of 37.4±7.7% and visceral adipose tissue (VAT) of 721.2±215.6 g. Metabolic syndrome was diagnosed in 69% of the participants. Both intramyocellular and extramyocellular lipids correlated with BF percentage (r=0.31, P< 0.05 and r=0.38, P< 0.05, respectively) but not with VAT or S-FFA. The BF percentage also correlated with VAT (r=0.27, P< 0.05) and thigh fat (r=0.75, P< 0.01). The thigh lean mass negatively correlated with BF percentage (r=-0.44, P< 0.01), SA/PA ratio, (r=-0.31, P< 0.05) and IML (r=-0.44, P< 0.01).

Discussion/Conclusion:

The results highlight that the accumulation of IML is related to the total amount of BF, but not to markers of central obesity such as VAT or S-FFA. This finding does not fully agree with previous results, which, however, used very small cohorts and measured IML in the leg. Since both the IML and the muscle mass in the thigh correlated with variables of cardiometabolic risk, we propose that it is more practical and appropriate to measure muscle mass and quality in the same appendicular muscle region, such as the thigh.

Funding: CODI-University of Antioquia 58-1-948 (minutes 2020-34909, February 22, 2021, SIU) and 102 (minutes 2021-40430, October 20, 2021, IIM), Medellín, Colombia.