Low-dose Streptozotocin-induced Diabetic Rats Research Articles

Abietic acid ameliorates nephropathy progression via mitigating renal oxidative stress, inflammation, fibrosis and apoptosis in high fat diet and low dose streptozotocin-induced diabetic rats

BackgroundAbietic acid (AA) has been reported to exhibit anti-inflammatory activity, however its protective effect against inflammation and its trigger factor i.e., oxidative stress and the related sequelae i.e., apoptosis and fibrosis in the kidney in diabetes mellitus (DM) is unknown. PurposeTo identify the ability of AA to mitigate the inflammatory and inflammation-related insults to the kidney in DM. Methods & Study designAdult male rats were induced type-2 DM by feeding with a high-fat diet for twelve weeks followed by injection with a single dose of streptozotocin (STZ) (30 mg/kg/bw) intraperitoneally at twelve weeks. Following DM confirmation, AA (10 and 20 mg/kg/day) was given orally for another four weeks. Then the fasting blood glucose (FBG) and renal profile were determined and oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) tests were performed. A day after the last treatment, rats were sacrificed and kidneys were harvested and subjected for histopathological and molecular biological analysis. ResultsAA treatment was found to reduce the FBG, serum urea and creatinine levels (p < 0.05) while improving the OGTT and ITT (p < 0.05) in diabetic rats. Besides, AA treatment also mitigated kidney histopathological changes, reduces kidney oxidative stress as reflected by reduced levels of RAGE and Keap1 but increased levels of kidney antioxidants Nrf2, SOD, CAT, GPX, HO-1 & NQO-1 (p < 0.05). Additionally, AA treatment also decreases kidney inflammation (NF-kB p65, IL-1β, IL-6, TNF-α and iNOS) and fibrosis (TGF-β1 and GSK-3β) (p < 0/05). Kidney apoptosis decreased as reflected by decreased levels of Bax, caspase-3 and caspase-9 while its anti-apoptosis Bcl-2 protein levels increased (p < 0.05). ConclusionAA helps to mitigate nephropathy development in DM via counteracting oxidative stress, inflammation and apoptosis.

Anti-diabetic effect of Stachytarpheta jamaicensis on low dose streptozotocin-induced diabetic rats fed on a high-fat diet

IntroductionThis study evaluates the anti-diabetic effect of ethanol extract of Stachytarpheta jamaicensis leaf on streptozotocin (STZ) - induced diabetic rats fed on high-fat diet (HFD).MethodsSets of male albino rats of the Wistar strain weighing between 180 and 250 g were exposed to high fat diet (margarine and oil from vegetable sources in a ratio of 2:1 w/v) for 3 weeks. Then the animals were fasted overnight; hyperglycemic state was induced using reduced dose of streptozotocin (35 mg/kg) and animals were randomly divided into five groups (n = 7); group A received the HFD + STZ (35 mg/kg i.p.); group B received HFD + STZ + gliberclamide (10 mg/kg; i.p); groups C, D and E were administered the HFD + streptozotocin with different doses of the ethanol extract (30, 35 and 100 mg/kg p.o., respectively).ResultsResults showed significant (p < 0.05) decrease in blood glucose concentration of the rats treated with different doses of S. jamaicensis extract and those treated with gliberclamide compared to the untreated diabetic rats (negative control). Significant (p < 0.05) reductions in activities of serum AST, ALP, total protein and bilirubin were noticed in the groups in contrast to the control. Levels of urea, creatinine, potassium and chloride were considerably (p < 0.05) low while sodium and bicarbonate levels were high in the groups except the control. Lipid profile revealed significant (p < 0.05) reduction in total cholesterol, triacylglycerol, LDL, VLDL while HDL levels were high in the groups compared to the control. The extract significantly (p < 0.05) ameliorated weight loss. Histopathology of the liver, kidney and pancreas showed ameliorative effect of the extract against the deleterious changes occasioned by the HFD and STZ induced diabetic state.ConclusionThese findings have provided scientific basis for the use of S. jamaicensis in the treatment of diabetes mellitus in ethnomedicinal practices in Nigeria.

Prediction of Atorvastatin Pharmacokinetics in High-Fat Diet and Low-Dose Streptozotocin-Induced Diabetic Rats Using a Semiphysiologically Based Pharmacokinetic Model Involving Both Enzymes and Transporters.

Atorvastatin is a substrate of cytochrome P450 3a (CYP3a), organic anion-transporting polypeptides (OATPs), breast cancer-resistance protein (BCRP), and P-glycoprotein (P-gp). We aimed to develop a semiphysiologically based pharmacokinetic (semi-PBPK) model involving both enzyme and transporters for predicting the contributions of altered function and expression of CYP3a and transporters to atorvastatin transport in diabetic rats by combining high-fat diet feeding and low-dose streptozotocin injection. Atorvastatin metabolism and transport parameters comes from in situ intestinal perfusion, primary hepatocytes, and intestinal or hepatic microsomes. We estimated the expressions and functions of these proteins and their contributions. Diabetes increased the expression of hepatic CYP3a, OATP1b2, and P-gp but decreased the expression of intestinal CYP3a, OATP1a5, and P-gp. The expression and function of intestinal BCRP were significantly decreased in 10-day diabetic rats but increased in 22-day diabetic rats. Based on alterations in CYP3a and transporters by diabetes, the developed semi-PBPK model was successfully used to predict atorvastatin pharmacokinetics after oral and intravenous doses to rats. Contributions to oral atorvastatin PK were intestinal OATP1a5 < intestinal P-gp < intestinal CYP3a < hepatic CYP3a < hepatic OATP1b2 < intestinal BRCP. Contributions of decreased expression and function of intestinal CYP3a and P-gp by diabetes to oral atorvastatin plasma exposure were almost attenuated by increased expression and function of hepatic CYP3a and OATP1b2. Opposite alterations in oral plasma atorvastatin exposure in 10- and 22-day diabetic rats may be explained by altered intestinal BCRP. In conclusion, the altered atorvastatin pharmacokinetics by diabetes was the synergistic effects of altered intestinal or hepatic CYP3a and transporters and could be predicted using the developed semi-PBPK.

Polyherbal Ayurvedic Powder Effectively Reduces Blood Sugar in Streptozotocin-induced Diabetic Rats

The polyherbal formulation Madhumehantak churna was studied for its efficacy at two doses using the hyperglycemia animal model of low dose streptozotocin-induced diabetic rats. The low dose Madhumehantak churna group of 1080 mg/kg/day was extrapolated from the typical 4 g thrice daily human dose used in Ayurveda. The high dose Madhumehantak churna group was 3× the low dose, equivalent to 36 g daily in humans. These groups were compared to a negative control group (non-streptozotocin-induced, non-treated), a positive control group (streptozotocin-induced, oral hypoglycemic agent-treated) and a diabetic control group (streptozotocin-induced, non-treated). Rats were fed for 28 consecutive days and monitored for plasma blood glucose. Results showed that rats with severe plasma glucose (438 and 325 mg/dl) in both low-dose Madhumehantak churna and high-dose Madhumehantak churna group re-attained almost-normal plasma glucose levels (118 and 128 mg/dl) in 28 d, reaching similar levels as the positive control, gold-standard treated group (120 mg/dl). Madhumehantak churna presents itself as a viable option for reversing hyperglycemia, as shown in this in vivo animal experimental study, and as a potentially more practical option for patients than oral hypoglycemic agents.

Hypoglycemic effect of ethyl acetate fraction of methanol extract from Campylandra aurantiaca rhizome on high-fat diet and low-dose streptozotocin-induced diabetic rats

Background: Campylandra aurantiaca (Asparagaceae), commonly known as Nakima in Sikkimese Tibetan, is a plant grown in South-Central China and Northeast India. Objective: To evaluate the hypoglycemic activity of ethyl acetate fraction of methanol extract from C. aurantiaca rhizome (EFCA) in high-fat diet (HFD) and low-dose streptozotocin (STZ)-induced diabetic Wistar rats. Materials and Methods: In rats fed with HFD for 4 weeks, hyperglycemia was induced by single intraperitoneal injection of STZ (35 mg/kg body weight). Seven days after STZ induction, the hyperglycemic rats were treated with EFCA orally at the doses of 100 and 200 mg/kg b.w. daily for 28 days. Glibenclamide (0.5 mg/kg, orally) was used as reference drug. The fasting blood glucose levels were measured on every 7th day during the 28 days of treatment. Serum and hepatorenal biochemical parameters were estimated. Histological study of the pancreas was also performed. Results: EFCA at the doses of 100 and 200 mg/kg orally significantly (P Abbreviations used: IDDM: Insulin-dependent diabetes mellitus, T2DM: Type 2 diabetes mellitus, NIDDM: Noninsulin-dependent diabetes mellitus, T1DM: Type 1 diabetes mellitus, IDF: International Diabetes Federation, STZ: Streptozotocin, EFCA: Ethyl acetate fraction of methanol extract from Campylandra aurantiaca rhizome, OGTT: Oral glucose tolerance test, HFD: High-fat diet, FBG: Fasting blood glucose, HDL: High-density lipoprotein cholesterol, HbA1c: Glycosylated hemoglobin, AST: Aspartate transaminase, ALT: Alanine transaminase, ALP: Alkaline phosphatase, LPO: Lipid peroxidation, GSH: Reduced glutathione, SOD: Superoxide dismutase, CAT: Catalase, SEM: Standard error of mean, ANOVA: Analysis of variance, HPLC: High-performance liquid chromatography.

In silico, in vitro and in vivo analyses of dipeptidyl peptidase IV inhibitory activity and the antidiabetic effect of sodium caseinate hydrolysate.

The frequency (A), a novel in silico parameter, was developed by calculating the ratio of the number of truncated peptides with Xaa-proline and Xaa-alanine to all peptide fragments from a protein hydrolyzed with a specific protease. The highest in vitro DPP-IV inhibitory activity (72.7%) was observed in the hydrolysate of sodium caseinate by bromelain (Cas/BRO), and the constituent proteins of bovine casein also had relatively high A values (0.10-0.17) with BRO hydrolysis. 1CBR (the <1 kDa fraction of Cas/BRO) showed the greatest in vitro DPP-IV inhibitory activity of 77.5% and was used for in vivo test by high-fat diet-fed and low-dose streptozotocin-induced diabetic rats. The daily administration of 1CBR for 6 weeks was effective to improve glycaemic control in diabetic rats. The results indicate that the novel in silico method has the potential as a screening tool to predict dietary proteins to generate DPP-IV inhibitory and antidiabetic peptides.

Alterations in gut microbiota during remission and recurrence of diabetes after duodenal-jejunal bypass in rats.

To observe the alterations in gut microbiota in high-fat diet (HFD)-induced diabetes recurrence after duodenal-jejunal bypass (DJB) in rats. We assigned HDF- and low-dose streptozotocin-induced diabetic rats into two major groups to receive DJB and sham operation respectively. When the DJB was completed, we used HFD to induce diabetes recurrence. Then, we grouped the DJB-operated rats by blood glucose level into the DJB-remission (DJB-RM) group and the DJB-recurrence (DJB-RC) group. At a sequence of time points after operations, we compared calorie content in the food intake (calorie intake), oral glucose tolerance test, homeostasis model assessment of insulin resistance (HOMA-IR), concentrations of glucagon-like peptide 1 (GLP-1), serum insulin, total bile acids (TBAs) and lipopolysaccharide (LPS) and alterations in colonic microbiota. The relative abundance of Firmicutes in the control (58.06% ± 11.12%; P < 0.05 vs sham; P < 0.05 vs DJB-RC) and DJB-RM (55.58% ± 6.16%; P < 0.05 vs sham; P < 0.05 vs DJB-RC) groups was higher than that in the sham (29.04% ± 1.36%) and DJB-RC (27.44% ± 2.17%) groups; but the relative abundance of Bacteroidetes was lower (control group: 33.46% ± 10.52%, P < 0.05 vs sham 46.88% ± 2.34%, P < 0.05 vs DJB-RC 47.41% ± 5.67%. DJB-RM group: 34.63% ± 3.37%, P < 0.05 vs sham; P < 0.05 vs DJB-RC). Escherichia coli was higher in the sham (15.72% ± 1.67%, P < 0.05 vs control, P < 0.05 vs DJB-RM) and DJB-RC (16.42% ± 3.00%; P < 0.05 vs control; P < 0.05 vs DJB-RM) groups than in the control (3.58% ± 3.67%) and DJB-RM (4.15% ± 2.76%) groups. Improved HOMA-IR (2.82 ± 0.73, P < 0.05 vs DJB-RC 4.23 ± 0.72), increased TBAs (27803.17 ± 4673.42 ng/mL; P < 0.05 vs DJB-RC 18744.00 ± 3047.26 ng/mL) and decreased LPS (0.12 ± 0.04 ng/mL, P < 0.05 vs DJB-RC 0.19 ± 0.03 ng/mL) were observed the in DJB-RM group; however, these improvements were reversed in the DJB-RC group, with the exception of GLP-1 (DJB-RM vs DJB-RC P > 0.05). Alterations in gut microbiota may be responsible for the diabetes remission and recurrence after DJB, possibly by influencing serum LPS and TBAs.

Improvements of Glucose and Lipid Metabolism After Jejuno-ileal Circuit Procedure in a Non-obese Diabetic Rat Model.

In a recent study, we showed a jejuno-ileal circuit (JIC) procedure that effectively improved glucose homeostasis, but the intrinsic mechanism requires further studies. Furthermore, the role of JIC in lipid metabolism is also unknown. Given that adiposity aggravates insulin sensitivity, we hypothesize that the JIC procedure improves fat metabolism and thus further contributes to diabetic remission. The aim of this study was to investigate the effects of JIC surgery on lipid metabolism and glucose homeostasis in a non-obese diabetic rat model. Fourteen high-fat diet and low-dose streptozotocin-induced diabetic rats were randomly divided into JIC and sham-JIC groups. Body weight, food intake, glucose tolerance, insulin resistance, serum lipid parameters, glucagon-like peptide 1 (GLP-1), and adipose-derived hormones were measured. At 12weeks postoperatively, the expressions of hepatic fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) were measured by Western blot. The lipid content of liver was assessed by hematoxylin-eosin staining and Oil Red O staining. The enteroendocrine cells in the distal ileum were examined by immunohistochemical staining. Relative to the sham group, the JIC rats exhibited significant improvements in glucose tolerance, insulin resistance, and dyslipidemia without weight loss, showing increased GLP-1 and adiponectin and decreased leptin. JIC also reduced the expression of FAS and ACC in the liver, exhibited improved hepatic fat content, and raised the levels of GLP-1 and chromogranin A in the distal gut. JIC alleviated lipometabolic disorders in hyperglycemic rats, which may contribute to the amelioration of insulin sensitivity and glycemic control.

Effects of exenatide therapy on insulin resistance in the skeletal muscles of high-fat diet and low-dose streptozotocin-induced diabetic rats

Purpose: The glucagon-like peptide (GLP)-1 agonist exenatide shows the same multiple effects on glucose homeostasis as native GLP-1, which can reduce blood glucose levels in individuals with type-2 diabetes mellitus (T2DM). However, its underlying action mechanism on glucose metabolism in the skeletal muscle of T2DM cases is unknown. We investigated the effects and action mechanisms of exenatide on insulin resistance (IR) in the skeletal muscle of high-fat diet and low-dose streptozotocin-induced T2DM rats. Methods: Four groups of Sprague–Dawley rats were studied: non-T2DM (control, C); non-T2DM + exenatide (C + E); T2DM (D); and T2DM + exenatide (D + E). After eight weeks, isotope-tracer methodology was applied to measure the total rate of appearance (Ra) of glucose and glucose infusion rate (GIR) using a hyperinsulinemic–euglycemic clamp with 3-3H-glucose infusion. Glucose uptake in gastrocnemius muscles was determined by measuring 2-deoxy-D-14C-glucose radioactivity. Simultaneously, ultrastructural changes in the cells of gastrocnemius muscles were studied. Results: In the D + E group, body weight and levels of fasting plasma glucose, triglyceride, total cholesterol, low-density lipoprotein and insulin were decreased significantly (p < 0.01) compared with the D group. The Ra of glucose (94.70 ± 13.46 versus 121.07 ± 16.55 μmol/kg/min) was decreased (p < 0.01), whereas the exogenous GIR (144.68 ± 11.03 versus 114.50 ± 9.40 μmol/kg/min) and glucose uptake in muscle (0.24 ± 0.02 versus 0.17 ± 0.02 μmol/g/min) were increased markedly (p < 0.01). Ultrastructural observations revealed that exenatide attenuated the effect of swollen mitochondrial and endoplasmic reticulum within the cells of the skeletal muscle of T2DM rats. Conclusions: These data suggest that exenatide can significantly improve insulin sensitivity in skeletal muscle by increasing glucose uptake in T2DM rats.

Curcumin pretreatment mediates antidiabetogenesis via functional regulation of adrenergic receptor subtypes in the pancreas of multiple low-dose streptozotocin-induced diabetic rats

Lifestyle modification pivoting on nutritional management holds tremendous potential to meet the challenge of management of diabetes. The current study hypothesizes that regular uptake of curcumin lowers the incidence of diabetes by functional regulation of pancreatic adrenergic receptor subtypes. The specific objective of the study was to identify the regulatory pathways implicated in the antidiabetogenesis effect of curcumin in multiple low-dose streptozotocin (MLD-STZ)-induced diabetic Wistar rats. Administration of MLD-STZ to curcumin-pretreated rats induced a prediabetic condition. Scatchard analysis, real-time polymerase chain reaction, and confocal microscopic studies confirmed a significant increase in α2-adrenergic receptor expression in the pancreas of diabetic rats. Pretreatment with curcumin significantly decreased α2-adrenergic receptor expression. The diabetic group showed a significant decrease in the expression of β-adrenergic receptors when compared with control. Pretreatment significantly increased β-adrenergic receptor expression to near control. When compared with the diabetic rats, a significant up-regulation of CREB, phospholipase C, insulin receptor, and glucose transporter 2 were observed in the pretreated group. Curcumin pretreatment was also able to maintain near control levels of cyclic adenosine monophosphate, cyclic guanosine monophosphate, and inositol triphosphate. These results indicate that a marked decline in α2-adrenergic receptor function relents sympathetic inhibition of insulin release. It also follows that escalated signaling through β-adrenergic receptors mediates neuronal stimulation of hyperglycemia-induced β-cell compensatory response. Curcumin-mediated functional regulation of adrenergic receptors and modulation of key cell signaling molecules improve pancreatic glucose sensing, insulin gene expression, and insulin secretion.

Renoprotective effects of berberine and its possible molecular mechanisms in combination of high-fat diet and low-dose streptozotocin-induced diabetic rats

Berberine (BBR), an effective compound of Chinese traditional herbal medicine, has preventive effects on diabetes and its complications. In this study, we investigated the therapeutic effects and underlying molecular mechanisms of BBR in rats with high-fat diet and streptozotocin (STZ)-induced diabetic nephropathy model. BBR (50, 100, 200 mg/kg/d) were orally administered to male Sprague-Dawley rats after STZ injection and conducted for 8 weeks. Renal damage was evaluated by kidney weight to body weight ratio (KW/BW), urine microalbumin (UMAlb), urine protein for 24 h (UP24 h), urine creatinine (UCr), and histological examination. Type IV collagen and transforming growth factor-beta1 (TGF-β1) were detected by immunohistochemistry and ultrastructure of glomeruli was observed. Fasting blood glucose (FBG),serum creatinine (SCr), blood urea nitrogen (BUN), total cholesterol (TC), triglyceride (TG), high-density lipoprotein-cholesterol (HDL-c), low-density lipoprotein-cholesterol (LDL-c) in serum and G protein-coupled receptor kinases (GRKs), cAMP in kidney were measured. Remarkable renal damage, hyperglycemia and hyperlipidemia were observed in DN rats. BBR could restore renal functional parameters, suppress alterations in histological and ultrastructural changes in the kidney tissues, improve glucose and lipid metabolism disorders, and increase cAMP levels compared with those of DN model group. Furthermore, BBR down-regulated total protein expression of GRK2, GRK3 and up-regulated expression of GRK6 of renal cortex in DN rats, but had a slight effects on GRK4 and GRK5. These studies demonstrate, for the first time, that BBR exerts renoprotection in high-fat diet and STZ-induced DN rats by modulating the proteins expression of GRKs in G protein- AC-cAMP signaling pathway.

Exercise training prevents the development of cardiac dysfunction in the low-dose streptozotocin diabetic rats fed a high-fat diet

This study tested the hypothesis that exercise training would prevent the development of diabetes-induced cardiac dysfunction and altered expression of sarcoplasmic reticulum Ca(2 +)-transport proteins in the low-dose streptozotocin-induced diabetic rats fed a high-fat diet (HFD+STZ). Male Sprague-Dawley rats (4 weeks old; 125-150 g) were made diabetic using a high-fat diet (40% fat, w/w) and a low-dose of streptozotocin (35 mg·(kg body mass)(-1)) by intravenous injection. Diabetic animals were divided among a sedentary group (Sed+HFD+STZ) or an exercise-trained group (Ex+HFD+STZ) that accumulated 3554 ± 338 m·day(-1) of voluntary wheel running (mean ± SE). Sedentary animals fed a low-fat diet served as the control (Sed+LFD). Oral glucose tolerance was impaired in the sedentary diabetic group (1179 ± 29; area under the curve (a.u.c.)) compared with that in the sedentary control animals (1447 ± 42 a.u.c.). Although left ventricular systolic function was unchanged by diabetes, impaired E/A ratios (i.e., diastolic function) and rates of pressure decay (-dP/dt) indicated the presence of diastolic dysfunction. Diabetes also reduced SERCA2a protein content and maximal SERCA2a activity (V(max)) by 21% and 32%, respectively. In contrast, the change in each parameter was attenuated by exercise training. Based on these data, it appears that exercise training prevented the development of diabetic cardiomyopathy and the dysregulation of sarcoplasmic reticulum protein content in an inducible animal model of type 2 diabetes.

Amelioration of Obesity, Glucose Intolerance, and Oxidative Stress in High-Fat Diet and Low-Dose Streptozotocin-Induced Diabetic Rats by Combination Consisting of “Curcumin with Piperine and Quercetin”

Curcumin is an important nutraceutical that has enormous potential for a variety of diseases, but the medicinal properties of curcumin cannot be utilized due to its low in vivo bioavailability. Therefore, in view of the foregoing, there is an extensive need for combinatorial extract “curcumin with piperine and quercetin” which may enhance bioavailability of oral curcumin by inhibiting the enzymes responsible for the metabolism of curcumin. Thus, the present study investigated the effect of combinatorial extract of curcumin on obesity, glucose intolerance, and oxidative stress in high fat diet and low-dose streptozotocin-induced rats. Oral administration of combinatorial extract for 28 days significantly (P < 0.05) reduced PGL (64.84%), PTG (88.94%), LDL (26.38%) and PTC (50.23%) levels, respectively and improved glucose tolerance (P < 0.05) significantly to exogenously administered glucose (2 g/kg) at 60, 90, and 120 min interval on OGTT. The results for antioxidant potential indicate that at 100 mg/kg dose of combinatorial extract of curcumin significantly prevented the high-fat diet and low-dose streptozotocin-induced changes in the oxidative stress parameters (P < 0.01) which supports popular medicinal uses of this combinatorial extract as antihyperglycemic and hypolipidemic and is likely to bring this promising natural product to the forefront of therapeutic agents in the in the treatment of “metabolic syndrome”.