Serum phospholipid fatty acid composition and insulin action in type 2 diabetic patients

Relationships have been demonstrated between insulin sensitivity and the fatty acid (FA) composition of serum and tissue lipids in adult humans. The present study aimed to investigate the above relationships in different groups of type 2 diabetic patients (DM2). The FA composition of serum phospholipids (S-PL) measured by gas liquid chromatography and insulin action during a 2-step hyperinsulinemic isoglycemic clamp (1 and 10 mU/kg. min) were determined in 21 newly diagnosed DM2 subjects (DMN), in groups of long-term DM2 patients treated with hypoglycemic agents (DMH; n = 21) or diet alone (DMD; n = 11), and in 24 healthy subjects (HS). In diabetics, the metabolic clearance rates of glucose at both insulin levels (MCR(glu)submax and MCR(glu)max) were significantly reduced compared with HS (MCR(glu)submax DMN, 5.35 +/- 2.7 mL x kg(-1) x min(-1), DMH, 5.38 +/- 2.17 mL x kg(-1) x min(-1); DMD, 5.48 +/- 2.35 mL x kg(-1) x min(-1) v HS, 10.9 +/- 3.3 mL x kg(-1) x min(-1); P <.01; MCR(glu)max DMN, 13.3 +/- 3.3 mL x kg(-1) x min(-1); DMH, 12.5 +/- 3.0 mL x kg(-1) x min(-1); DMD, 13.3 +/- 3.0 mL x kg(-1) x min(-1) v HS, 17.4 +/- 3.8 mL x kg(-1) x min(-1); P <.05). Increased contents of highly unsaturated n-6 family FA (P <.01), arachidonic acid in particular (DMN, 10.98% +/- 1.79%; DMD, 10.78% +/- 1.64%; DMH, 10.97% +/- 1.7% v HS, 8.51% +/- 1.53%; P <.001), were found in all groups of diabetics compared with HS, while lower levels of linoleic acid were seen in DMN (P <.001) and DMH (P <.05). The contents of saturated FA and monounsaturated FA were comparable in HS, DMN, and DMD. While in HS there were significant negative correlations between MCR(glu) and the contents of saturated FA and a positive association between insulin action and proportions of linoleic and arachidonic acids, no significant relationships were found in diabetic subjects. Different groups of DM2 patients show an altered FA pattern of S-PL, which is not related to insulin action. The above data support the hypothesis that changes in FA composition may play a role in modulating insulin action in peripheral tissues, but cannot explain the insulin resistance (IR) in DM2 patients.