Long‐Chain n‐3 Fatty Acids and Insulin‐Regulated Metabolism in Healthy Old Lean Rats

Abstract

This study assessed for the first time whether feeding EPA and DHA at a physiological dose to healthy, old, lean, Hooded Lister male rats aged of 14 months improves metabolic defects accompanying the ageing‐associated deterioration in insulin sensitivity. Rats were fed a basal semi‐purified diet meeting requirements (16.2 MJ/kg; 5.0% CP, 6.5% fat). Control oil or EPA & DHA supplements were fed over 60 d. Rats had similar intake (15 g/d), weight gain (625 to 649 g; P > 0.10) and body fat (21% MRI fat; P > 0.10). A mild loss in lean body mass (LBM) was monitored over the 2‐month period (530 to 515 g; P = 0.07 tendency). LCn‐3FA was numerically associated to lower age‐associated loss in LBM (‐18.8 vs. ‐9.7 g; P = 0.11). LCn‐3FA reduced fasting TG (2.37 vs. 1.85 mmol/l; P < 0.03) and LDL cholesterol (0.27 vs. 0.15 mmol/l; P < 0.001). Six‐h kinetics of D‐[U‐13C]glucose were conducted during an insulin‐stimulated state induced through an i.v. nutrition of dextrose and amino acids. Whole‐body glucose turnover was increased (99 to 106 µmol/kg·min; P = 0.02) in LCn‐3FA‐fed rats. This increased turnover combined to similar exogenous dextrose entry (81 µmol/kg·min) was sustained through increase in endogenous glucose production (19 to 25 µmol/kg·min; P = 0.04). LCn‐3FA supplement may be a novel approach to intervene on certain ageing‐associated deteriorations of metabolism.