The Regulatory Influences of Insulin Administration on Hepatic Lipogenesis of Fasted-Refed Growing Chicks

Abstract

The effects of fasting for 4 days and subsequent refeeding or refeeding combined with insulin administration for a similar length of time on the hepatic lipogenesis of 6-week-old meat-type growing chicks, were investigated. No difference in body weight was observed between the refed and the refed-insulin groups and both groups were significantly heavier than their fasted counterparts. Abdominal fat score was practically the same for all the three groups studied. As for liver weight, the value for the refed birds significantly increased with the reintroduction of feed and further rose to almost double the fasted birds' score when insulin was injeced subcutaneously.
Among the lipid fractions, liver triglyceride demonstrated the most drastic increase as a result of refeeding. Such an increase was further boosted with the administration of insulin that brought the hepatic triglyceride score to a level that was 29 times more than that of the fasted lot. Likewise, serum triglyceride markedly increased with refeeding, however, this level dropped by 25% in reaction to insulin thereby suggesting that that hormone has the effect of suppressing the release of hepatically synthesized triglycerides into the blood stream. Both cholesterol and phospholipid contents in the liver remained unaltered even after refeeding or insulin treatment. Serum cholesterol, however, displayed a negative reaction to refeeding when its score sank by 23% when feed was reintroduced. This reduced level further plummeted when insulin was administered. In contrast, serum phospholipid responded positively to refeeding and insulin treatment as evidenced by its increased values. Like serum triglyceride, both NEFA and β-lipoprotein responded quite positively to refeeding but dropped significantly as a result of insulin administration.