Chronic caloric restriction alters muscle membrane fatty acid content

Chronic caloric restriction (CR) has been demonstrated to increase longevit y in lower species and studies are ongoing to evaluate its effect in higher species, A consistent metabolic feature of CR is improved insulin sensitiv ity and lowered lifetime glycemia, yet the mechanism responsible is current ly unknown. However, the membrane's physiochemical properties, as determine d by phospholipid composition, have been related to insulin action in anima l and human studies and CR has been reported to alter membrane lipid conten t. We evaluated muscle membrane fatty acid content in rodents randomized to CR versus control diets for up to 29 months. CR was observed to increase t he membrane content of C22:6 (docosahexaenoate) and to decrease C18:2 conte nt. The membrane lipid content was related to insulin levels but not to par ameters assessing glycemic control. This study suggests that membrane lipid s, in particular 22:6, may contribute to the variation in insulin sensitivi ty seen with age. (C) 2000 Elsevier Science Inc. All rights reserved.