Abstract: Objective To investigate the effects of ligustrazine (TMP) on the ratio of urine microalbumin to urinary creatinine (UACR), renal pathological changes, PI3K / Akt / mTOR signaling pathway and autophagosome marker protein LC3B in diabetic nephropathy (DN) rats. Methods The DN rat model was established by streptozotoein (STZ) peritoneal injection. DN model rats were randomly divided into model group, the low, middle and high dose of TMP groups, and irbesartan group. In addition, the normal rats were served as the normal group (n=12 for each group). After 8 weeks of intervention respectively, urine creatinine was determined by enzymatic method, urinary microalbumin was determined by immunoturbidimetry, and UACR was calculated. Kidney tissues were fixed with formaldehyde, hematoxylin-eosin (HE) and periodic acid-schiff (PAS) staining were performed. The protein expressions of p-PI3K, PI3K, p-Akt, Akt, p-mTOR, mTOR, and LC3B in the kidney tissues were detected by Western blot assay and immunohistochemistry (n=6 for each group). Results Compared with the model group, the increase of UACR was inhibited and the pathological changes in kidney were significantly ameliorated after treatment with TMP, especially in the middle and high dose groups, UACR were significantly lower than that of model group (P＜0.05). There was no significant difference in UACR between the middle and high dose groups and irbesartan group (P＞0.05). Moreover, the protein levels of p-PI3K, p-Akt and p-mTOR were decreased, while the expression of LC3B and the ratio of LC3B - Ⅱ/LC3B - Ⅰ were increased in TMP groups than those of model group. Conclusion TMP can reduce the increase of UACR and improve the pathological changes of kidney in DN rats. The molecular mechanisms that drive the therapeutic effects of TMP may involve in the inhibition of PI3K/Akt/mTOR signaling pathway to consequently promote renal autophagy.

Key words: Tetramethylpyrazine, diabetic nephropathies, autophagy, PI3K/Akt/mTOR pathway, irbesartan, LC3B