BACKGROUNDInsulin treatment plays a key role in management of diabetes mellitus. Clinical researches showed that extra improvements in restoration of insulin secretion of pancreatic beta cells were found in patients with newly diagnosed type 2 diabetes. The purpose of this study was to investigate the effects of early insulin treatment on insulin mRNA expression and morphological alterations of beta cells in a Sprague Dawley (SD) rat model of type 2 diabetes.

METHODSA rat model of type 2 diabetes mellitus (T2DM) was induced by a high fat diet (high energy, HE) and low doses of streptozotoxin (STZ, 40 mg/kg). A group of diabetic rats was then injected with protamine zinc insulin [PZI, 1 - 2 U x kg(-1) x d(-1)] for one week. Insulin mRNA expression, morphological features of pancreatic islets, and metabolic parameters were examined in rats using reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry, and other techniques.

RESULTSIn insulin-treated diabetic rats, insulin mRNA levels prominently increased by 81.3% (P < 0.05), as compared with untreated diabetic rats. Moreover, timely insulin treatment noticeably improved the insulin content of beta cells, with an increase of 10.2% (P < 0.05), despite a slight reduction in fasting blood glucose (FBG), triglyceride (TG), and free fatty acid (FFA) levels, as compared to an untreated diabetic group.

CONCLUSIONInsulin treatment at the onset of T2DM effectively improves insulin synthesis, as confirmed by morphological changes to beta cells in a rat model of type 2 diabetes.