Docosahexaenoic Acid at 0.4% of Dietary Weight Enhances Lean Mass in Young Female Sprague-Dawley Rats

Abstract

Docosahexaenoic acid (DHA; 22:6n-3) is an n-3 (ω-3) fatty acid known for beneficial effects on body composition. The objective of the study was to test the dose response of lean and fat mass to DHA in healthy growing female rats. Female Sprague-Dawley rats (7 wk at baseline; n=12/diet) were randomly assigned to receive a control (AIN-93M; 60 g soybean oil/kg diet) or experimental diet for 10 wk. Experimental diets contained 0.1%, 0.4%, 0.8%, or 1.2% DHA (wt:wt of total diet). Imaging for whole-body and abdominal composition was conducted using dual-energy X-ray absorptiometry and microcomputed tomography, respectively, at weeks 0, 5, and 10. Fatty acid profiles of several tissues were analyzed using gas chromatography. Serum leptin, C-reactive protein, and plasma insulin-like growth factor I concentrations were measured at each time point using immunoassays. Data were tested using Pearson's correlations and mixed-model ANOVA. No differences were observed in weight at baseline or food intake throughout the study. Overall, a 6% increase (P<0.05) in whole-body and abdominal lean mass was observed in the 0.4%-DHA diet group compared with the control diet group. Moreover, the abdominal visceral fat mass was 31.4% lower in rats in the 0.4%-DHA than in the 1.2%-DHA diet group (P<0.001). Rats in the 1.2%-DHA diet group showed greater percent differences in whole-body (32.5% and 40.6% higher) and in abdominal (33.9% and 49.4% higher) fat mass relative to the 0.1%- and 0.4%-DHA diet groups, respectively (P<0.01). Accordingly, serum leptin concentration was lower in the 0.1%-DHA (38.2%) and 0.4%-DHA (43.8%) diet groups (P<0.01) than in the 1.2%-DHA diet group and positively related to whole-body fat mass (r=0.91, P<0.0001). Dietary DHA at 0.4% of dietary weight effectively enhances lean mass and proportionally reduces fat mass in growing female rats.