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Obesity was associated with a significant increase in postabsorptive plasma concentrations of the branched-chain keto acids in men but not in women matched for body-mass index and age. Plasma glucose and serum insulin were significantly higher in obese subjects than in nonobese control subjects. Obese women had more adipose tissue than did obese men from the sum of triceps and subscapular skinfold thickness. It is suggested that augmentation in plasma branched-chain keto acids in obesity may reflect insulin resistance and that the apparent differences observed between obese women and men may be due to differences in body composition.

Valine (62.5 mg per kg), leucine (70 mg per kg) and equal amounts of the calcium salts of the corresponding keto acids, i.e., alpha-ketoisovaleric acid (KIVA) and alpha-ketoisocaproic acid (KICA) were orally administered to patients with cirrhosis and to control subjects. Valine or leucine ingestion increased serum valine and leucine levels and the corresponding keto acids, KIVA and KICA, in cirrhotics and controls. KIVA or KICA ingestion increased serum KIVA and KICA concentrations within a few minutes associated with a rise in valine and leucine. In cirrhotics, administration of valine or KIVA resulted in significantly higher serum valine or KIVA concentrations than in control subjects. The clearance of valine and KIVA from blood was also delayed in cirrhotic patients. No such differences were observed after leucine or KICA ingestion. It is suggested that cirrhotics have a diminished tolerance for valine. Since the tolerance for KIVA, but not KICA, is also impaired, it appears that cirrhotics have a derangement in one or more metabolic steps distal to the branched-chain keto acid dehydrogenase.

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