Jia-Wei-Jiao-Tai-Wan ameliorates type 2 diabetes by improving β cell function and reducing insulin resistance in diabetic rats

Abstract

Background: Jia-Wei-Jiao-Tai-Wan (JWJTW), composed of Jiao-Tai-Wan (Cinnamomum cassia and Rhizoma coptidis) and other antidiabetic herbs, including Astragalus membranaceus, Herba Gynostemmatis, Radix Puerariae Lobatae, Folium Mori and Semen Trigonellae, is widely used to treat diabetes and has demonstrated a curative effect in the clinic, but the potential mechanism is unknown. This study aimed to explore the effects of JWJTW on diabetic rats and to clarify the underlying mechanism.

Methods: JWJTW was prepared, and the main components contained in the formula were identified by high-performance liquid chromatography (HPLC) fingerprint analysis. Diabetic rats induced by streptozotocin (STZ) and a high-sucrose-high-fat diet were treated with two concentrations of JWJTW (1.025 and 2.05 g/kg/d) for 100 days. The oral glucose tolerance test (OGTT), insulin release test (IRT) and insulin tolerance test (ITT) were performed to measure the glycometabolism of the diabetic rats at the end of the treatment period. Blood was collected to determine the serum lipid levels of the diabetic rats. Nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) were detected in pancreas homogenates to analyze the oxidative stress in the pancreata of diabetic rats, and the expression levels of pancreatic and duodenal homeobox 1 (PDX-1) and insulin in the pancreas were tested by Western blot to measure pancreatic islet function. In addition, Western blots were used to measure the expression of proteins related to the insulin signaling pathway in skeletal muscle of the diabetic rats.

Results: The results showed that the administration of JWJTW could ameliorate impairments in glucose tolerance, insulin release function and insulin tolerance in diabetic rats. JWJTW could also dose-dependently reduce serum lipid levels in diabetic rats. JWJTW restrained oxidative stress by decreasing the expression of NO and MDA and increasing the expression of SOD and GSH-px. JWJTW improved the function of pancreatic β cells by increasing PDX-1 and insulin expression. In addition, JWJTW restored the impaired insulin signaling; upregulated phospho-insulin receptor (pInsR) expression, insulin receptor substrate (IRS) tyrosine phosphorylation, phosphatidylinositol 3-kinase (PI3K) (p85), and glucose transporter 4 (GLUT4) expression; and downregulated the serine phosphorylation of IRS.

Conclusions: This study suggests that JWJTW can ameliorate type 2 diabetes by improving β cell function and reducing insulin resistance in diabetic rats.

Keywords: Insulin resistance; Jia-Wei-Jiao-Tai-Wan (JWJTW); Oxidative stress; Pancreatic β cell; Type 2 diabetes mellitus.

Fig. 1

Preparation procedure for JWJTW

Fig. 2

HPLC fingerprint of the extract. HPLC fingerprint chromatograms of extracts of the reference standards (a) and JWJTW (b). In the chromatograms: (1) trigonelline (PubChem CID:5570); (2) puerarin (PubChem CID: 5,281,807); (3) coptisine (PubChem CID: 72,322); (4) jateorhizine (PubChem CID:72,323); (5) berberine (PubChem CID: 2353); (6) palmatine (PubChem CID: 19,009); (7) cinnamic acid (PubChem CID:444,539)

Fig. 3

Effects of JWJTW on glucose tolerance, insulin release and insulin tolerance in diabetic rats. a GTT of diabetic rats; b IRT of diabetic rats; c ITT of diabetic rats. Normal: normal group rats without streptozotocin (STZ) or high-sucrose-high-fat diet; Diabetic: diabetic rats induced by STZ and a high-sucrose-high-fat diet; 1.025 g/kg/d JWJTW: diabetic rats treated with 1.025 g/kg/d Jia-Wei-Jiao-Tai-Wan; 2.05 g/kg/d JWJTW: diabetic rats treated with 2.05 g/kg/d Jia-Wei-Jiao-Tai-Wan. GTT and IRT: Oral glucose tolerance test and insulin release test, respectively, performed on diabetic rats that were orally administered 2.2 g of glucose per kg after 12 h of fasting (n = 10). ITT: insulin tolerance test performed on diabetic rats injected with 0.4 U insulin per kg after 4 h of fasting (n = 10)

Fig. 4

Effects of JWJTW on lipid metabolic parameters of diabetic rats. TC: total cholesterol, TG: triglyceride, LDL: low-density lipoprotein, FFA: free fatty acids. ^* p < 0.05, ^** p < 0.01 (n = 10)

Fig. 5

Effects of JWJTW on SOD and GSH-px activity, MDA and NO content of pancreatic islets in diabetic rats. NO: nitric oxide, SOD: superoxide dismutase, GSH-px: glutathione peroxidase, MDA: malondialdehyde. a Homogenates of the pancreas were analyzed for NO and MDA. b Homogenates of the pancreas were analyzed for SOD and GSH-px. ^* p < 0.05, ^** p < 0.01 (n = 10)

Fig. 6

Effects of JWJTW on pancreatic islet number and structure in diabetic rats. a Representative hematoxylin and eosin staining of pancreatic islets, 4×. b Representative hematoxylin and eosin staining of pancreatic islets, 40 ×

Fig. 7

Effects of JWJTW on insulin and PDX-1 protein expression in pancreatic islets of rats. a Western blot analysis of insulin and PDX-1 expression in pancreatic islets. b Bar graph of the signals for insulin and PDX-1. ^* p < 0.05, ^** p < 0.01 (n = 5)

Fig. 8

Effect of JWJTW on insulin signaling in skeletal muscle of diabetic rats. Western blot analysis of phospho-InsR-β^Tyr1361(a), phospho-IRS-1^Tyr612 and phospho-IRS-1^Ser307 (b), PI3K (p85) (c) and GLUT4 (d). ^* p < 0.05, ^** p < 0.01, ^*** p < 0.001 (n = 5)