Reduced effects of L-carnitine on glucose and fatty acid metabolism in myocytes isolated from diabetic rats

Preventing organ-specific chemotherapy toxicity

Recent advances in treatment for pediatric cancers has increased overall survival rates. As more and more survive pediatric cancer, we continue to see the emergence of late effects of treatment within pediatric and the growing adult survivor population. The evaluation of late effects was initiated approximately two decades ago, and has become an extremely important facet of pediatric oncology. This review delves into several of the most serious organ-specific late effects of pediatric cancer treatment, outline what we know and what we do not currently understand about preventing or reducing them. Clinical and bench research are necessary to develop interventions that will avoid or mitigate late effects and improve the health of pediatric cancer survivors.

Effect of L-carnitine on plasma glycemic and lipidemic profile in patients with type II diabetes mellitus

OBJECTIVE

We designed this study to investigate the effects of oral L-carnitine administration on fasting plasma glucose (FPG), glycosylated hemoglobin (HbA1c) and lipid parameters in patients with diabetes mellitus type II.

PATIENTS AND METHODS

The effect of L-carnitine on FPG and lipid parameters was investigated in 22 male and 13 female type II diabetic patients; the mean age +/- s.d. was 51.3 +/- 3.7 y. The patients were randomly allocated to two groups (L-carnitine and placebo group) and 1 g of L-carnitine or of placebo was given orally three times a day for a period of 12 weeks.

RESULTS

FPG in the L-carnitine group decreased significantly from 143 +/- 35 to 130 +/- 33 mg/dl (P = 0.03), and we observed a significant increase of triglycerides (TG) from 196+/-61 to 233+/-12 mg/dl (P = 0.05), of Apo A1 from 94 +/- 20 to 103 +/- 23 mg/dl (P = 0.02), and of Apo B100 from 98 +/- 18 to 108 +/- 22 mg/dl (P = 0.02) after 12 weeks of treatment. There was no significant change in LDL-C, HDL-C, HbA1C, LP(a) or total cholesterol.

CONCLUSION

L-Carnitine significantly lowers FPG but increases fasting triglyceride in type II diabetic patients.

Insulin-like effects of a physiologic concentration of carnitine on cardiac metabolism

Pharmacologic (millimolar) levels of carnitine have been reported to increase myocardial glucose oxidation, but whether physiologically relevant concentrations of carnitine affect cardiac metabolism is not known. We employed the isolated, perfused rat heart to compare the effects of physiologic levels of carnitine (50 microM) and insulin (75 mU/l [0.5 nM]) on the following metabolic processes: (1) glycolysis (release of 3H2O from 5-3H-glucose); (2) oxidation of glucose and pyruvate (production of 14CO2 from U-14C-glucose, 1-14C-glucose, 3,4-14C-glucose, 1-14C-pyruvate, and 2-14C-pyruvate); and (3) oxidation of palmitate (release of 3H2O from 9,10-3H-palmitate). We found that addition of carnitine (50 microM) to a perfusate containing both glucose (10 mM) and palmitate (0.5 mM) stimulated glycolytic flux by 20%, nearly doubled the rate of glucose oxidation, and inhibited palmitate oxidation by 20%. These actions of carnitine were uniformly similar to those of insulin. When carnitine and insulin were administered together, their effects on the oxidation of glucose and palmitate, but not on glycolysis, were additive. When pyruvate (1 mM) was substituted for glucose, neither carnitine nor insulin influenced the rate of oxidation of pyruvate or palmitate. In combination, however, carnitine and insulin sharply suppressed pyruvate oxidation (75%) and doubled the rate of palmitate oxidation. None of the responses to carnitine or insulin was affected by varying the isotopic labeling of glucose or pyruvate. The results show that carnitine, at normal blood levels, exerts insulin-like effects on myocardial fuel utilization. They also suggest that plasma carnitine in vivo may interact with insulin both additively and permissively on the metabolism of carbohydrates and fatty acids.