Age-related changes in fatty acid composition in muscles.

Changes in lipid metabolism in muscles are closely related to insulin resistance. Insulin resistance is impaired during aging in hereditary hypertriglyceridemic rats. However, changes in the membrane fatty acid composition during aging are poorly understood. The aim of the study was to describe the fatty acid (FA) composition of muscle phospholipids in the diaphragm and in the m. soleus in relation to aging and insulin resistance. Female hereditary hypertriglyceridemic rats (HHTg) have been shown to have elevated levels of serum triglycerides. Fasting and post-load blood glucose and insulin concentrations were higher in HHTg lines as compared with controls of the same age. The most important changes observed in the m. soleus in the HHTg line included decreased saturated FA between 3 and 14 months of age (42.79 +/- 2.30 vs. 28.85 +/- 2.57mol.%, p<0.01) and increased polyunsaturated FA n-6 (27.99 +/- 1.66 vs. 39.37+2.29 mol.%, p<0.01). In the diaphragm we noted, in normotriglyceridemic controls, increased proportions of monounsaturated FA (5.73 +/- 0.80 vs. 11.02 +/- 0.75mol.%, p<0.001), while these proportions were decreased in HHTg rats (13.50 +/- 0.83 vs. 10.46 + 0.61 mol.%, p < 0.05). Age-related changes in muscle phospholipids seem not to be the key to explaining insulin resistance.