Effect of starvation and refeeding a high-protein or high-carbohydrate diet on lipid composition and glycogen content of rat livers in relation to age.

Rats of two different ages (72 and 490 days) were subjected to a 3-day fast and then refed for the same period a high-protein (89%) or high-carbohydrate (99%) diet. This experimental model served to study whether alterations occur in the content of the main lipid components, triacylglycerol, phospholipids and cholesterol in liver. It also examined whether the aging process itself has any effect on the lipid pattern. With the high-protein diet the content of all lipids returned to or nearly to the control level regardless of age. Refeeding the 72-day-old rats the high-carbohydrate diet led to a 2.4-fold overshoot in the triacylglycerol content, while the phospholipids and the cholesterol remained far below their control levels. In the 490-day-old rats the total lipids, phospholipids and cholesterol remained at the starvation level. With aging, the total cholesterol content showed a marked increase of about four-fold when corrected for growth.