The effect of prolonged fasting and of glucose refeeding on rat serum and liver lipid levels

Abstract

AbstractThe effects upon serum lipids of prolonged fasting of rats followed by refeeding with glucose or chow was studied. Fasting caused a decrease in the levels of serum triglyceride, phospholipid and cholesterol ester, while the level of total cholesterol remained unchanged. Refeeding 20% glucose in water for one day after three days of fasting caused a significantly greater decrease in serum lipid levels than did an additional day of fasting, while refeeding chow for one day restored the serum lipid levels to normal. Seven days of fasting or one day of glucose refeeding following three days of starvation resulted in almost complete disappearance of all serum lipoprotein bands on paper electrophoresis. After four days of refeeding glucose to rats previously fasted for three days the serum lipid levels and lipoprotein patterns approached those seen in fed animals. Serum free fatty acids increased upon fasting, but after seven days of starvation their concentration dropped to that observed in the fed rats. Refeeding for one day with glucose or chow reduced the serum free fatty acid concentration to less than half of the starvation levels. Four days of starvation caused a great decrease in liver weight without causing very pronounced changes in the content of phospholipid and triglyceride in the whole liver; the cholesterol content, notably esterified cholesterol, decreased. Glucose feeding for one day after three days of starvation, while increasing liver weight, did not cause any appreciable change in the hepatic lipid content. Following the three days of starvation lipogenesis from glucose by liver slices is restored to the same extent by refeeding glucose or chow for one day. The role of liver, adipose tissue and diet in supplying fatty acids for serum lipids following fasting is discussed.