Associations of intramyocellular lipid in vastus lateralis and biceps femoris with blood free fatty acid and muscle strength differ between young and elderly adults

Abstract

The present study aimed to determine relationships between intramyocellular lipid and biochemical profiles or muscle strength in elderly (n = 15; mean age, 71 years) and young (n = 15; mean age, 21 years) male and female adults. Levels of intramyocellular lipid in the vastus lateralis and biceps femoris muscles were determined using 1H-magnetic resonance spectroscopy. Fasting blood samples were collected to measure levels of glucose, insulin, haemoglobin A1c, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, free fatty acid, triglyceride, adiponectin, and high-sensitivity C-reactive protein. Muscle strength was assessed as maximal voluntary contraction during isometric knee extension. Muscle cross-sectional area in the vastus lateralis was measured using magnetic resonance imaging. Specific force (N cm−2) indicating force generation capacity was calculated as muscle strength (N) divided by the muscle cross-sectional area of the vastus lateralis (cm2). The intramyocellular lipid content was similar in both muscles in both groups. The intramyocellular lipid content in the biceps femoris significantly correlated with serum free fatty acid levels (r = 0·62, P<0·05), and that in the vastus lateralis significantly and inversely correlated with specific force (r = −0·58, P<0·05) in the young, but not in the elderly adults. The relationship between the intramyocellular lipid content in the thigh muscles and biochemical profiles, or specific force differed between elderly and young adults. Age-associated changes in morphology, function and metabolic factors apparently influence intramyocellular lipid metabolism in the thigh muscles.