Molecular mechanism of Gegen Qinlian Decoction in promoting differentiation of brown adipose tissue to improve glucose and lipid metabolism disorders in diabetic rats

This study explored the molecular mechanism underlying the Gegen Qinlian Decoction(GQD) promoting the differentiation of brown adipose tissue(BAT) to improve glucose and lipid metabolism disorders in diabetic rats. After the hypoglycemic effect of GQD on diabetic rats induced by high-fat diet combined with a low dose of streptozotocin was confirmed, the total RNA of rat BAT around scapula was extracted. Nuclear transcription genes Prdm16, Pparγc1α, Pparα, Pparγ and Sirt1, BAT marker genes Ucp1, Cidea and Dio2, energy expenditure gene Ampkα2 as well as BAT secretion factors Adpn, Fndc5, Angptl8, IL-6 and Rbp4 were detected by qPCR, then were analyzed by IPA software. Afterward, the total protein from rat BAT was extracted, and PRDM16, PGC1α, PPARγ, PPARα, SIRT1, ChREBP, AMPKα, UCP1, ADPN, NRG4, GLUT1 and GLUT4 were detected by Western blot. The mRNA expression levels of Pparγc1α, Pparα, Pparγ, Ucp1, Cidea, Ampkα2, Dio2, Fndc5, Rbp4 and Angptl8 were significantly increased(P<0.05) and those of Adpn and IL-6 were significantly decreased(P<0.05) in the GQD group compared with the diabetic group. In addition, Sirt1 showed a downward trend(P=0.104), whereas Prdm16 tended to be up-regulated(P=0.182) in the GQD group. IPA canonical pathway analysis and diseases-and-functions analysis suggested that GQD activated PPARα/RXRα and SIRT1 signaling pathways to promote the differentiation of BAT and reduce the excessive lipid accumulation. Moreover, the protein expression levels of PRDM16, PGC1α, PPARα, PPARγ, SIRT1, ChREBP, AMPKα, UCP1, GLUT1, GLUT4 and NRG4 were significantly decreased in the diabetic group(P<0.01), which were elevated after GQD intervention(P<0.05). Unexpectedly, the expression of ADPN protein in the diabetic group was up-regulated(P<0.01) as compared with the control group, which was down-regulated after the administration with GQD(P<0.01). This study indicated that GQD promoted BAT differentiation and maturity to increase energy consumption, which reduced the glucose and lipid metabolism disorders and thereby improved diabetes symptoms.