CHANGES IN CARNITINE METABOLISM WITH KETONE-BODY PRODUCTION IN OBESE GLUCOSE-INTOLERANT PATIENTS

To elucidate the relationship between carnitine metabolism and plasma ketone body concentrations in moderately obese patients with mild gluc ose intolerance, the ketone body and carnitine levels in the basal sta te were determined in 72 obese patients: 20 with normal glucose tolera nce (NGT), 29 with impaired glucose tolerance (IGT), and 23 with non-i nsulin-dependent diabetes mellitus (NIDDM) having a fasting plasma glu cose (FPG) level of less than 200 mg/dl. Total ketone body (TKB) level s significantly (P < 0.05) increased in the order of NGT, IGT, NIDDM, while the FPG and free fatty acid (FFA) concentrations were significan tly (P < 0.05) higher in the NIDDM group than in the other two groups. In contrast, the insulin, glucagon and glycerol levels were comparabl e in the three groups. The plasma short-chain acylcarnitine (SCAC) con centration and the acylcarnitine/free carnitine (AC/FC) ratio were sim ilar in the IGT and NIDDM groups, and significantly (P < 0.05) greater than those in the NGT group. The AC/FC ratio correlated significantly with the FPG and FFA, but not with the TKB. These results suggest tha t the combination of IGT with simple obesity may trigger the accelerat ion of hepatic ketogenesis in conjunction with an elevated SCAC and an increased AC/FC ratio. In addition, the data also imply that, in pati ents with mild NIDDM, factors other than the carnitines may play a gre ater role in enhancing ketonemia.