ALANINE AS A LIPOGENIC PRECURSOR IN ISOLATED HEPATOCYTES FROM OBESE ZUCKER RATS

Isolated hepatocytes from obese Zucker rats showed an increased capaci ty for lipid synthesis measured as the incorporation of (H2O)-H-3 into lipid fractions. In addition lipid synthesis from 1 mM U-C-14-alanine was elevated as compared to those isolated from their lean counterpar ts. On these lines, the amino acid was a better lipogenic substrate th an U-C-14-lactate at 5 mM concentration. Insulin increased lipid synth esis from the amino acid in the lean animals while showed no effects o n this parameter in the obese. While the hepatocytes from the lean ani mals used to a similar extent U-C-14-alanine carbon from (CO2)-C-14 pr oduction, lipid syntesis and C-14-glycogen incorporation, those from t he obese animals showed a decreased oxidation and glycogen incorporati on while an augmented lipid synthesis. The total amount of the amino a cid taken up by the obese animals was also significantly elevated. Con versely, the metabolic fate of U-C-14-leucine was very similar between the two groups. It can be concluded that in the obese Zucker rat alan ine is a very inportant amino acid which contributes to sustain the hi gh liver hyperlipogenesis previously described.