The Protective Effect of Calcitriol on Diabetic Neuropathy in STZ-induced Diabetic Rats

Diabetic peripheral neuropathy (DPN) is one of the diabetic complications that have a complex etiology and even with good glycemic control can have severe consequences. To date, there is no effective treatment for DPN. The current work aimed to investigate the possible protective effects of calcitriol on DPN by using streptozotocin-induced diabetic rats. Male rats were assigned into 5 equal groups: Normal control, diabetic untreated, diabetic treated with NPH Insulin, diabetic treated with calcitriol, diabetic received both insulin and calcitriol. Induction of diabetes mellitus was done by injection of a single dose of streptozotocin (30 mg/kg, intraperitonael). After 4 consecutive weeks, rats were subjected to tail flick latency test and blood samples were collected for biochemical assay of serum glucose, insulin, advanced glycation end products (AGEs). Sciatic nerves were dissected out for histopathological studies and estimation of tumor necrosis factor-α (TNF-α), superoxide dismutase (SOD) and malondialdhyde (MDA). Diabetes induced hyperalgesia, elevated levels of blood glucose, AGEs, TNF-α and MDA, decrease level of insulin and SOD together with marked structural changes in sciatic nerve. Minor to moderate improvement was recorded in either insulin- or calcitriol- treated diabetic subgroups. However, good amelioration was recorded in combination of insulin and calcitriol treatment. It is concluded that calcitriol improved the biochemical and histological changes induced by diabetes. Thus it may provide neural protection against DPN.