Basic nutritional investigationEnergy restriction does not prevent insulin resistance but does prevent liver steatosis in aging rats on a Western-style diet

- A Western-style diet contributes to aging by increasing insulin resistance and lipid accumulation.
- Energy restriction did not prevent insulin resistance in aged rats on a Western-style diet.
- Energy restriction on a Western-style diet did not prevent lipid accumulation in plasma and skeletal muscle.
- Energy restriction prevented hepatic steatosis despite the Western-style diet.
- The nature of the diet is important when studying energy restriction.

ObjectiveThe aim of this study was to evaluate the effects of long-term energy restriction (ER) on plasma, liver, and skeletal muscle metabolite profiles in aging rats fed a Western-style diet.MethodsThree groups of male Sprague-Dawley rats were studied. Group 1 consisted of 2 mo old rats fed ad libitum; group 2 were 19 mo old rats also fed ad libitum; and group 3 were 19 mo old rats subjected to 40% ER for the last 11.5 mo. To imitate a Western-style diet, all rats were given a high-sucrose, very low ω-3 polyunsaturated fatty acid (PUFA) diet. High-resolution magic angle spinning-1H nuclear magnetic resonance spectroscopy was used for hepatic and skeletal muscle metabolite determination, and fatty acid profiles were measured by capillary gas chromatography on plasma, liver, and skeletal muscle.ResultsER coupled with a Western-style diet did not prevent age-induced insulin resistance or the increase in triacylglycerol content in plasma and skeletal muscle associated with aging. However, in the liver, ER did prevent steatosis and increased the percent of saturated and monounsaturated fatty acids relative to ω-6 and ω-3 PUFA.ConclusionsAlthough steatosis was reduced, the beneficial effects of ER on systemic insulin resistance and plasma and skeletal muscle metabolites observed elsewhere with a balanced diet seem to be compromised by high-sucrose and low ω-3 PUFA intake.