Quantification of lipids in human lower limbs using yellow bone marrow as the internal reference: gender-related effects

The main purpose of this study was to determine and compare extra- and intramyocellular (IMCL) lipids content in the calf and thigh muscles of normal male and female volunteers using high-spatial-resolution magnetic resonance spectroscopic imaging (MRSI). The study groups consisted of 10 females and 10 males. The subjects were healthy and normal-weight. Fat (yellow bone marrow) was used as the internal concentration reference. Total fat and IMCL content were computed for all muscles in the slice and for three muscle compartments in the thigh, whereas three muscles and three muscle compartments were evaluated in the calf. To avoid the confounding effects of physical activity and diet, measurements were performed in the same session. A common feature for both genders was that thigh muscles had approximately 2.5 times greater total fat content as compared to muscles of the calf. The mean IMCL level was, however, more than 3 times higher in the calf muscles compared with the thigh. No significant differences in lipid concentrations of correspondent regions of interest were found between genders. The high-spatial-resolution MRSI technique enables a more detailed study of muscle lipid distribution and can therefore improve understanding of muscle lipid metabolism in healthy volunteers and in studies of patients with metabolic disorders.