L-carnitine ameliorates peripheral neuropathy in diabetic mice with a corresponding increase in insulin-like growth factor-1 level

Diabetic peripheral neuropathy (DPN) is one of the common complications in diabetes, affecting more than half of patients with diabetes. L-carnitine (LC) was recently demonstrated to serve a positive role in ameliorating DPN. Therefore, the aim of the present study was to investigate the underlying mechanisms of LC in ameliorating DPN. Male Kunming mice were randomly assigned into five groups, including the control group, diabetes mellitus group, pre-treatment group, treatment group and post-treatment group. Type 2 diabetes was induced in mice using a combination of high-fat diet and streptozotocin injection. Subsequently, peripheral neuropathy was measured and the levels of LC, insulin and insulin-like growth factor-1 (IGF-1) were detected. When diabetic mice were treated with LC, the levels of IGF-1 in the plasma and pancreas were increased. In addition, hyperalgesia, as determined by the tail-flick test as well as food intake, body weight and blood glucose levels were decreased. An amelioration of demyelination, axonal atrophy and mitochondria swelling in the nerve fibres of diabetic mice was also observed. The present study demonstrated that LC ameliorated peripheral neuropathy in type 2 diabetic mice and the effect of LC may in part be mediated by an increase in local and circulatory IGF-1 levels.