Sex and muscle structural lipids in obese subjects - an impact on insulin action?

Long-chain polyunsaturated fatty acid (LCPUFA) especially the n-3-FA of skeletal muscle phospholipids may facilitate insulin action, whereas saturated and trans-FA act oppositely. Community studies show that non-diabetic weight matched obese men and women display similar insulin resistance, despite the fact that an android fat distribution is detrimental to insulin action.

The increased extramyocellular fat mass of obese women may act in a paracrine manner such that its release of free FA and cytokines may hamper in situ desaturation and elongation of FA in skeletal muscle phospholipids. To test the hypothesis that obese women may display an inferior FA composition compared to obese men, the FA composition of skeletal muscle phospholipids was determined in vastus lateralis biopsies obtained from 12 non-diabetic obese women with a typical gynoid fat distribution, nine non-diabetic obese men with a typical android fat distribution and 12 (seven females) lean age matched healthy controls (body mass index 34.6 +/- 1.0 kg m(-2), 36.5 +/- 1.2 and 22.5 +/- 0.5; age 47 +/- 2 years, 51 +/- 3 and 49 +/- 2).

Obese women displayed decreased LCPUFA n-3 and ratio of n-3/n-6 PUFA, whereas trans-FA and palmitic-FA (C16 : 0) were increased compared to obese men and controls (all Ps < 0.05). Plasma high-density lipoprotein cholesterol (HDL-C), triglycerides and a marker of insulin sensitivity were similar between obese women and men but impaired compared to controls (Ps < 0.05).

The data support the hypothesis that insulin resistant non-diabetic obese men display a more optimal skeletal muscle phospholipid FA composition than their female counterparts, which may be a mechanism to compensate the detrimental effect on insulin action of an android fat distribution.