Cholesterol-lowering nature of unsaturated fat in rats may be due to its inability to increase hepatic iron

The present investigation was conducted to determine whether the cholestero l-raising properties of saturated fat and cholesterol-lowering properties o f unsaturated fat are associated with levels of hepatic iron. The magnitude of hepatic iron retention was manipulated by feeding rats diets that were either copper-deficient or -adequate, iron-adequate or -supplemented, and c ontained either beef tallow or corn oil. Weanling male Sprague-Dawley rats were randomly divided into eight dietary groups according to the type of di etary fat (beef tallow or corn oil) and level of dietary copper (0.74 or 6. 9 mu g Cu/g diet) or iron (44.4 or 86.7 mu g Fe/g diet). Beef tallow and co pper deficiency alone increased hepatic iron levels, which in turn were ass ociated with increased plasma cholesterol. When the three dietary factors w ere combined, ie, iron, beef tallow, and copper deficiency, they induced th e highest magnitude of hepatic iron retention, which in turn was associated with the highest concentration of plasma cholesterol, In contrast, when he patic iron retention was not increased, such as by feeding a diet containin g corn oil or by consumption of a copper-adequate diet, plasma cholesterol was not elevated. Based on these data, it is suggested that nutrients that have the ability to increase hepatic iron have the potential to increase pl asma cholesterol. Copyright (C) 1999 by W.B. Saunders Company.