BACKGROUND:Transient receptor potential channel C6 (TRPC6) is a new and important slit diaphragm-associated protein in podocytes involved in regulating glomerular filter function. Glomerular TRPC6 expression is closely associated with proteinuria in diabetic kidney disease. OBJECTIVE: To investigate the expression of canonical TRPC6 in mouse podocytes induced by high glucose, and to explore the possible mechanism of diabetic kidney disease. METHODS:Mouse podocyte cels were cultured and divided into normal glucose group (5.6 mmol/L D-glucose), normal control group (5.6 mmol/L D-glucose+25 mmol/L mannitol) and experimental groups which were in the environment of high glucose (30 mmol/L). The experimental groups included high glucose group, valsartan treatment groups (10-5 mol/L) and U73122 control group (10μmol/L U73122). After 48 hours, the expressions of mRNA and proteins of TRPC6, nephrin and angiotensin II (AngII) were detected respectively by real-time quantitative PCR and western blot analysis. RESULTS AND CONCLUSION:Compared with the normal control group, the expressions of mRNA and proteins of TRPC6 and angiotensin II were markedly elevated in the high glucose group (P < 0.01), while the expressions of mRNA and proteins of nephrin were decreased (P < 0.01). The mRNA and proteins of TRPC6 and angiotensin II expressions were significantly down-regulated by valsartan (P < 0.05,P < 0.01), while the mRNA and protein expressions of nephrin were effectively up-regulated (P < 0.05). Compared with the high glucose group, the expressions of mRNA and proteins of TRPC6 and angiotensin II were ameliorated in the U73122 control group. The expressions of mRNA and proteins of TRPC6, nephrin and angiotensin II had no statistical significance between the normal control group and normal glucose group (P > 0.05). Angiotensin II-TRPC6 signaling pathway may mediate high glucose-induced podocyte injury, meanwhile it provides a new theoretical basis for the treatment of diabetic kidney disease, by which the angiotensin receptor blockers can protect podocytes in diabetic kidney disease.

ObjectiveTo validate the alleviating effect of Gegen Qinliantang （GGQLT） on insulin resistance in db/db diabetic mice by regulating the silent information regulator 1 （SIRT1）/forkhead transcription factor O1 （FoxO1） autophagy pathway. MethodSeventy-five SPF-grade spontaneous type 2 diabetic db/db mice and 15 control db/m mice were selected and maintained on regular feed for one week before measuring blood glucose. They were randomly divided into six groups， with 15 mice in each group. The groups included a normal group （physiological saline， 0.2 g·kg^-1）， a metformin group （0.2 g·kg^-1）， high-， medium-， and low-dose GGQLT groups （31.9， 19.1， 6.9 g·kg^-1）， and a model group （physiological saline， 0.2 g·kg^-1）. They were orally treated with corresponding drugs for eight weeks， once daily. Fasting blood glucose （FBG） was measured using a Roche glucometer. Serum levels of high-density lipoprotein cholesterol （HDL-C）， low-density lipoprotein cholesterol （LDL-C）， triglyceride （TG）， and total cholesterol （TC） were measured using an automated biochemical analyzer. Fasting serum insulin （INS） levels were determined using enzyme-linked immunosorbent assay （ELISA）， and the homeostasis model assessment of insulin resistance （HOMA-IR） was calculated. Western blot was used to detect the expression of Beclin-1， microtubule-associated protein 1 light chain 3 （LC3）， and SIRT1/FoxO1 autophagy pathway-related proteins in liver tissues. Immunohistochemistry was performed to assess the expression of SIRT1， FoxO1， Beclin-1， and LC3B proteins in liver tissues. Transmission electron microscopy was used to observe the formation of autophagosomes in the liver. ResultCompared with the normal group， the model group showed significant increases in FBG， FINS， HOMA-IR， TC， TG， LDL-C， and HDL-C levels （P<0.01）， and significant increases in the expression of SIRT1， Beclin-1， LC3， and FoxO1 proteins in liver tissues （P<0.01）. Transmission electron microscopy revealed the highest number of autophagosomes in the model group. Compared with the model group， the metformin group and the low-， medium-， and high-dose GGQLT groups showed significant decreases in serum FBG， FINS， HOMA-IR， TC， TG， LDL-C， and HDL-C levels （P<0.05， P<0.01）， significant decreases in the expression of SIRT1， Beclin-1， LC3 （P<0.05， P<0.01）， and up-regulated FoxO1 protein （P<0.01）. Transmission electron microscopy showed a reduction in the degree of autophagy in the treatment groups. Compared with the metformin group， the medium- and high-dose GGQLT groups showed significant decreases in FBG， FINS， and TG levels （P<0.01）， significant decreases in the expression of SIRT1， Beclin-1， and LC3 in liver tissues （P<0.05， P<0.01）， and reduced FoxO1 protein （P<0.01）. The high-dose GGQLT group showed reduced HOMA-IR， TC， LDL-C， and HDL-C levels （P<0.05， P<0.01）. Transmission electron microscopy revealed a significant reduction in autophagosomes in the medium- and high-dose GGQLT groups. ConclusionGGQLT can significantly improve glucose and lipid metabolism disorders， alleviate insulin resistance in db/db mice， and prevent and treat type 2 diabetes by activating the SIRT1/FoxO1 autophagy pathway.