Inactivity-mediated insulin resistance is associated with upregulated pro-inflammatory fatty acids in human cell membranes

Abstract

Background & aims: Low-grade systemic inflammation and pro-inflammatory pattern of cell membrane fatty acid composition characterize patients affected by type 2 diabetes and metabolic syndrome. We hypothesize that inactivity-induced insulin resistance could affect levels of pro-inflammatory fatty acids in cell membranes.

Methods: Thirty healthy, male, young volunteers were investigated before and after 35-day experimental bed rest. Diet composition was adapted to previous dietary habits. Fatty acid composition of erythrocyte membranes was analyzed by gas-chromatography using flame ionization detector.

Results: Following bed rest, the HOMA index of insulin resistance significantly increased by +51+/-11% (P<0.01). Bed rest was associated with increased n-6 polyunsaturated (+4.7+/-2.2%; P<0.01) and decreased monounsaturated (-4.8+/-1.5%; P<0.01) fatty acid content in erythrocyte membranes. Fractional content of arachidonic acid increased by +14+/-12% (P=0.01) following inactivity. Delta5 and Delta9 desaturase indexes, as estimated from product-to-precursor ratios, significantly diminished following bed rest from 9.6+/-0.4 to 8.4+/-0.3 (P<0.001) and from 0.72+/-0.02 to 0.69+/-0.01 (P<0.05), respectively. The n-3 fatty acids, alpha-linolenic and eicosapentaenoic, were decreased (P=0.05) following inactivity by 4.7+/-13.2% and 3.8+/-5.2%, respectively.

Conclusions: Inactivity-mediated insulin resistance was associated with altered Delta5 and Delta9 desaturase indexes and with pro-inflammatory fatty acid pattern in erythrocyte membranes. These abnormalities could contribute to the low-grade inflammation associated to inactivity.