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Lipoic acid increases glucose uptake by skeletal muscles of obese-diabetic ob/ob mice

Authors



Dr C. J. Bailey, Department of Pharmaceutical Sciences, School of Pharmacy, Aston University, Birmingham B4 7ET, UK.

Abstract

Aim: Alpha-lipoic acid has been reported to increase glucose disposal in diabetic states. This study has examined the effect of α-lipoic acid on glucose uptake by cultured L6 muscle cells and different types of skeletal muscles in normal lean (+/+) and severely insulin-resistant, obese-diabetic (ob/ob) mice.

Methods: Glucose uptake was measured in L6 muscle cells using the non-metabolized glucose analogue 2-deoxy-d-glucose (2DG), and in isolated muscles by glucose disappearance from the incubation medium.

Results: In L6 muscle cells, short-term incubations (2–12 h) with 10−3 mα-lipoic acid increased glucose uptake by 40–80%, approximately the same extent as 10−6 m insulin. Combination of the two agents produced a slightly greater increase (120% at 12 h) than either alone. Red quadriceps (mainly type 1 fibres), diaphragm (similar proportions of type 1 and 2 fibres) and abdominal muscle (mainly type 2 fibres) from normal mice incubated with 10−3 mα-lipoic acid showed increased glucose uptake to a similar extent as 10−6 m insulin in each of the three muscles. Muscles from ob/ob mice, which showed little response to insulin, showed a substantial increase (approximately 300%, p < 0.05–0.01) in glucose uptake when 10−3 mα-lipoic acid was added in the presence of insulin. The α-lipoic acid also increased glucose uptake in red quadriceps (approximately 300%, p < 0.01) from ob/ob mice without added insulin.

Conclusion: The results suggest that α-lipoic acid can increase glucose uptake by a range of normal muscle types and improve the response to insulin by insulin-resistant skeletal muscles of ob/ob mice.

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