The effect of spontaneous diabetes mellitus on fatty acid oxidation, beta-hydroxybutyrate dehydrogenase activity and respiratory coupling of hepatic mitochondria in the guinea-pig (Cavia porcellus).

1. The purpose of this study was to determine whether hepatic mitochondria of guinea-pigs with spontaneous diabetes mellitus differ from those of non-diabetic guinea-pigs in the oxidation of fatty acids, the activity of beta-hydroxybutyrate dehydrogenase, or respiration-linked oxidative phosphorylation. During the course of the study, a third group of animals (referred to as the unclassified group) was discovered which, on the basis of the clinical chemistry and histological changes in the pancreas, appeared to be in a pre-diabetic or post-diabetic state. 2. No differences in the respiratory control ratios were found between any of the three groups. Fatty-acid oxidation in hepatic mitochondria was greater in both the unclassified and diabetic groups than in the non-diabetic group. Beta-Hydroxybutyrate dehydrogenase activity, however, was increased only in the diabetic group. These findings suggest that increased fatty acid oxidation is probably an intermediate change in the development of or the recovery from diabetes mellitus, whereas the activity of beta-hydroxybutyrate dehydrogenase is affected only in more advanced stages.