Intramyocellular lipid concentrations are correlated with insulin sensitivity in humans:: a 1H NMR spectroscopy study

Recent muscle biopsy studies have shown a relation between intramuscular lipid content and insulin resistance. The aim of this study was to test this relation in humans by using a novel proton nuclear magnetic resonance (H-1 NMR) spectroscopy technique, which enables non-invasive and rapid (similar to 45 min) determination of intramyocellular lipid (IMCL) content. Normal weight non-diabetic adults (n = 23, age 29 +/- 2 years, BMI = 24.1 +/- 0.5 kg/m(2)) were studied using cross-sectional analysis. Insulin sensitivity was assessed by a 2-h hyperinsulinaemic (similar to 450 pmol/l)-euglycaemic (similar to 5 mmol/l) clamp test. Intramyocellular lipid concentrations were determined by using localized H-1 NMR spectroscopy of soleus muscle. Simple linear regression analysis showed an inverse correlation (r = -0.692, p = 0.0017) between intramyocellular lipid content and M-value (100-120 min of clamp) as well as between fasting plasma non-esterified fatty acid concentration and M-value (r = -0.54, p = 0.0267). Intramyocellular lipid content was not related to BMI, age and fasting plasma concentrations of triglycerides, non-esterified fatty acids, glucose or insulin. These results show that intramyocellular Lipid concentration, as assessed non invasively by localized H-1 NMR spectroscopy, is a good indicator of whole body insulin sensitivity in non-diabetic, non-obese humans.