The effects of peripheral administration of morphine on serum insulin, leptin, and TNF-α in diet-induced obese rats

Clinical lore has long suggested that opiates produce hyperglycemia in normal subjects but it has been shown that peripheral administration of morphine can decrease glucose levels in obese diabetic subjects. It has been shown recently that some adipose-derived peptides such as TNF-alpha and leptin are major factors in insulin resistance in obese diabetic subjects.

In this study we decided to determine the effect of peripheral administration of 10 mg/kg morphine on some of adipose derived factors (leptin, TNF- α) in 8 diet-induced obese rats (DIO rats). The control group were injected equal volume of saline.

Peripheral administration of morphine significantly increased serum insulin levels 30 minuets after injection (p< 0.05). Serum TNF-α levels were significantly suppressed 30 minutes after injection (p< 0.05) but leptin levels decreased 60 minutes after injection (p < 0.05). Serum level of free fatty acids significantly decreased up to 120 minutes after injection (p < 0.05). Serum glucose levels were not affected by morphine in comparison with controls.

It has recently been shown that sensitivity of α-2 adrenergic receptors are increased in peripheral tissues of obese patients. Since cAMP is the main regulatory factor of TNF- α, leptin and FFA production in adipocytes, morphine may decrease α – 2 adrenoceptor sensitivity in adipose tissue and increase cAMP levels in adipocytes.