Abstract
1486 Carnitine (β-hydroxy-ã-trimethylaminobutyric acid) is essential for transport of long chain fatty acids across the inner mitochondrial compartment for β-oxydation to provide energy. It is now known that exercise has a differential impact on glucose and insulin levels when performed in the fed vs the fasted state. The decrement observed in insulin levels allows an increment in plasma free fatty acids, who is the major substrate for energy via lipolysis. Thus, carnitine play an important role while controlling the transport of free fatty acids throught mitochondra during exercise. PURPOSE: To compare the influence of 60 minutes of exercise performed at 60% of VO2 peak on plasma total carnitine, free carnitine and acyl carnitine levels, in the fasted state or 2 hours after a standardized meal in subjects with type 2 diabetes. METHODS: Ten sedentary men (55 ± 5 yrs) with type 2 diabetes treated with oral hypoglycemic agents and/or diet were tested on 2 occasions (fasted and fed state) in a random order. Subjects exercised in the fasted state and 2 hours after a 395-kcal standardized breakfast (49% carbohydrate, 34% fat, 17% protein). Blood samples were obtained at rest, at 15-min intervals during exercise, and at 15 and 30 min during the recovery period. RESULTS: Total carnitine level was higher in the fasted state compared to the fed state after the exercise period (60 minutes; P = 0.03). At the end of the exercise carried out in the fasted state, there was a significant (P<0.001) rise in total carnitine concentrations compared to baseline (−15 min). Free carnitine was significantly higher in the fed state than in the fasted state at baseline (−15 and 0 min). However, after exercise, free carnitine were much lower in the fed state (P = 0.02) compared to baseline. Acyl carnitine was statistically different (P = 0.007) between both conditions after 60 min of exercise. At the end of the exercise carried out in the fasted state, there was a significant (P<0.001) increment in acyl carnitine compared to baseline (−15 min). CONCLUSIONS: Exercise induced an increase in total carnitine and acyl carnitine level in the fasted state due to the increase of the use of plasma free fatty acids to provide energy for exercise. In contrast, in the fed state, there was a reduction of free carnitine levels during exercice due to the utilisation of glucose as a primary substrate.
Published Version
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