Hepatic triglyceride storage and ketonemia in rats fed high fat diets.

Hepatic triglycerides and ketonemia were studied on young rats fed a carbohydrate diet C or fat diets f (22.5% fat) and F (41.5% fat) for 8-15 days. Rats were sacrificed between 9 and 11 a.m. (1) Triglycerides and ketonemia varied proportionally to the diets but triglycerides were strikingly increased with protein deficient fat diets (10% proteic calories). Weight gains were then most reduced but ketonemia remained unchanged. (2) A 24-hour fasting was sufficient to suppress the excess of triglycerides while ketonemia remained still more elevated after 48 h of fasting in rats previously fed the fat diet F as compared to diet C. (3) During the adaptation to the fat diet F, liver triglycerides and plasma non-esterified fatty acids showed an acute rise on day 2 followed by a stabilization to lower levels after 8 days and an increase again with ageing (7 months) while ketonemia was relatively stable. The liver participates in adaptation to a fat diet that induces obesity, by the rapid esterification of the exogenous fatty acids and their output back into the circulation as lipoprotein-triglycerides.