Type-2 Diabetic Rats Research Articles

The Effect of Interval Training on GCK Expression in Hepatocytes and Glucose Homeostasis in Type 2 Diabetes Rats

Objective: Hepatic glucose release plays a potential role in hyperglycemia in type 2 diabetes (T2D) patients. The aim of this experimental study was to determine the effect of 6 weeks of high-intensity interval training (HIIT) on fasting levels of glucose and insulin as well as glucokinase (GCK) expression in liver tissue in obese T2D rats.
 Materials and Methods: T2D was induced by a high-fat diet (HFD) and streptozotocin (STZ) intraperitoneal injection in 14 male wistar rats, then were randomly divided into HIIT (n=7) and control (n=7) groups. The HIIT group practiced 6-week HIIT (5 days/ weekly). Finally, 48 hours after the last session, fasting levels of glucose, insulin, and GCK expression in liver hepatocytes of both groups were measured and compared by independent T-test (SPSS, Version 22.0).
 Results: HIIT resulted in a significant decrease of fasting glucose compared to the control group (P< 0.0001). Compared with the control group, serum insulin (P: 0.018) and GCK expression in hepatocytes (P: 0.030) were significantly increased.
 Conclusion: Based on these findings, the improvement in glucose in response to HIIT may be rooted in increased insulin and GCK expression in hepatocytes. However, understanding the mechanisms responsible for the effect of exercise training on the processes affecting hepatic glucose release requires further studies.

MO615: The Lund Mets Rat, An Obese Type 2 Diabetic Preclinical Model, Develops Non-Alcoholic Steatohepatitis, Diabetic Nephropathy and Heart Failure with Preserved Ejection Fraction Under High Fat/Cholesterol/Fructose Diet

Abstract BACKGROUND AND AIMS Beyond the glucose control, anti-diabetic drugs need to demonstrate benefits on metabolic comorbidities. An animal model that recapitulates obesity and type 2 diabetes (T2D) comorbidities [i.e. non-alcoholic steato-hepatitis (NASH), nephropathy and heart failure with preserved ejection fraction (HFpEF)] is still needed for preclinical drug development. To overcome this limitation, we evaluated the effects of a high fat/cholesterol/fructose (HFCF) diet in the Lund MetS rat, a congenic BBDR.cg-lepr.cp model generated by introgression of the Koletsky leptin receptor mutation into the BioBreeding Diabetes Resistant (BBDR) rat. METHOD 17-week-old, male, lean control (ctrl) or Lund MetS obese T2D rats were fed a control chow (CC) diet or a HFCF diet, respectively for 8 weeks. Blood biochemistry was measured at 0, 4 and 8 weeks of diet. Kidney, heart and liver parameters were assessed at the end of the 8-week diet period. RESULTS Compared with ctrl, Lund MetS rats were obese (56% higher body weight) and diabetic with significantly higher %HbA1c (up to + 3%) and blood glucose levels (up to 3-fold higher) during the 8-week HFCF diet period. Significantly higher plasma insulin (up to 11-fold), total cholesterol (up to 5-fold), triglycerides (up to 8-fold), transaminases (up to 10-fold higher) levels were also observed in Lund MetS rats, as compared with ctrl. Hepatic total cholesterol, triglycerides and fatty acids levels were significantly higher in Lund Mets rats (14-, 7.3- and 6.7-fold higher as compared to ctrl, respectively). Liver histopathological scoring confirmed a NASH phenotype in Lund MetS rats fed the HFCF diet with strong liver steatosis, hepatic inflammation and portal to bridging fibrosis. Kidney function was substantially altered with a 60% decline in glomerular filtration rate and a 16-fold increase in urine albumin-to-creatinine ratio (both P < 0.0001 versus ctrl). Finally, echocardiography indicated diastolic dysfunction with significantly reduced E/A and greater E/e’ ratios, along with a preserved ejection fraction in Lund MetS rats, as compared with lean ctrl. CONCLUSION The present data demonstrate that the Lund MetS rat fed an HFCF diet that recapitulates the major metabolic comorbidities of obesity/T2D and may be a useful model for preclinical drug development.

Safety considerations of chloroquine in the treatment of patients with diabetes and COVID-19

Patients with underlying diseases and coronavirus disease 2019 (COVID-19) are at increased risk of death. Using the recommended anti-COVID-19 drug, chloroquine phosphate (CQ), to treat patients with severe cases and type 2 diabetes (T2D) could potentially cause harm. We aimed to understand the safety of CQ in patients with T2D by administrating the recommended dose (63 mg/kg twice daily for 7 days) and a high dose (126 mg/kg twice daily for 7 days) of CQ in T2D rats. We found that CQ increased the total mortality of the T2D rats from 27.3% to 72.7% in the recommended and high-dose groups during the whole period. CQ also induced hematotoxicity of T2D rats in the high-dose group; the hepatic enzymes in T2D rats were significantly elevated. CQ also changed the electrocardiograms, prolonged the QTc intervals, and produced urinary leukocytes and proteins in the T2D rats. Histopathological observations revealed that CQ caused severe damage to the rats’ heart, jejunum, liver, kidneys, spleen, and retinas. Furthermore, CQ significantly decreased the serum IL-1β and IL-6 levels. In conclusion, the CQ dosage and regimen used to treat COVID-19 induced adverse effects in diabetic rats, suggesting the need to reevaluate the effective dose of CQ in humans.

IDF21-0176 Spatial memory impairment in type 2 diabetic rats is associated with adiposity and altered glucose metabolism

Background: Cognitive decline is a concerning complication for people with advanced stage type 2 diabetes (T2D). Consumption of high-fat, high-sugar western style diets is a risk factor for obesity, T2D and cognitive impairment. Our lab and others have established that cafeteria diet exposure impairs hippocampal dependent spatial memory. However, no previous studies appear to have tested spatial memory in T2D rats after cafeteria diet feeding and examined whether physiological and cognitive measures correlate.

IDF21-0412 Phyto-Pharmacological Benefits of Ethanol Extract of Guava Leaves on Streptozotocin Induced Type-2 Diabetic Model Rats

IDF21-0412 Phyto-Pharmacological Benefits of Ethanol Extract of Guava Leaves on Streptozotocin Induced Type-2 Diabetic Model Rats

The Comparative Effects of Aqueous Extracts of Green Tea and Catechin on Inflammation, Apoptosis and Oxidative Stress in the Testicular Tissue of Diabetic Rats

Diabetes mellitus causes damage to testicular tissue through inflammation and oxidative stress. Catechin has been reported to have anti-oxidant and anti-inflammatory properties. This study was performed to compare the effects of aqueous extracts of green tea and catechin on inflammation, apoptosis and oxidative stress in the testicular tissue of type-1 diabetic rats. In this experimental study, 48 male Wistar rats were divided into control group, and diabetic rats treated with aqueous extract of green tea (100 and 200 mg/kg) and diabetic rats treated with catechin (100 and 200 mg/kg) (n = 6/each group) for 4 weeks. Diabetes was induced by an intraperitoneal injection of 240 mg/kg Aloxan. Levels of glucose, CRP, TNF-α, IL-1β and IL-6, SOD, CAT, GPX, MDA, Bax and Bcl-2 were measured by Elisa in testicular tissue. Histomorphometric changes in testicular tissue were evaluated using E&H staining method. Treatment with aqueous extract of green tea (200 mg/kg) and catechin (100 and 200 mg/kg) resulted in a significant increase in Bcl-2, SOD, CAT, GPX levels and a significant decrease in serum glucose, Hs-CRP, TNF-α, IL-1β, IL-6, Bax and MDA levels, and significantly increased seminiferous tubules diameter and germinal cells count in testicular tissue compared to the diabetic control group. Treatment of diabetic rats with catechin had more improving effects on blood glucose, apoptosis, inflammation, lipid peroxidation, antioxidant enzymes, and histological structure of testis than green tea aqueous extract.

Studies on testicular ultrastructural and hormonal changes in type-2 diabetic rats treated with highly active antiretroviral therapy conjugated silver nanoparticles

AimThis study investigated the impact of highly active antiretroviral therapy (HAART) loaded silver nanoparticles (AgNPs) as HAART-AgNPs on the sperm count, viability, serum hormonal profile, insulin-like growth factor I (IGF-1), and testicular ultrastructure. MethodsThirty-six adult male Sprague-Dawley rats were allocated into diabetic and non-diabetic groups (n = 18). The rats in the diabetic group were induced experimental type 2 diabetes using fructose and streptozotocin (frt-STZ). Animals in both groups were subdivided into three groups each, A-C and DF (n = 6), and received distilled water, HAART, and HAART-AgNP, respectively. FindingsTreatment with HAART-AgNP displayed a significant increase (p < 0.05) in serum gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testicular IGF-1 in diabetic rats. Also, electron microscopy revealed ameliorated testicular ultrastructure upon administration of HAART-AgNP in diabetic rats that were previously marked with architectural and cellular alterations. In addition, treatment with HAART-AgNP significantly reduced (p < 0.05) the blood glucose levels of diabetic rats. In contrast, the treatment of non-diabetic rats with HAART caused a significant decrease (p < 0.05) in the sperm count, serum GnRH, and testicular IGF-1, however, this treatment induced ultrastructural changes and a significant increase (p < 0.05) in serum testosterone levels in diabetic and non-diabetic rats. SignificanceThis study has demonstrated the beneficial impact of HAART-AgNP on the hypothalamic-pituitary-gonadal axis, IGF-1, and testicular architecture in male frt-STZ induced diabetic rats. This nanoconjugate could be a potential nano-drug candidate to cater for testicular dysfunction and metabolic derangements while managing HIV-infected male individuals.

Advancing combination treatment with cilostazol and caffeine for Alzheimer's disease in high fat-high fructose-STZ induced model of amnesia

Several studies have suggested that phosphodiesterase (PDE) inhibitors may be a disease-modifying for Alzheimer’s disease (AD). Cilostazol (CSZ) has been shown to be a new treatment for cognitive impairment with limited efficacy. Our aim was to investigate the effect of caffeine on the efficacy of CSZ against STZ-induced type 2 diabetes (T2D)-related cognitive impairment in high fat/high fructose fed rats. The efficacy of low doses of caffeine, CSZ, and CSZ plus caffeine against abnormal behavioral, biochemical, histological, or genetic changes of animal models of AD was examined. Eight weeks treatment with CSZ plus caffeine was more effective than CSZ or caffeine in improving impaired behavioral tests for cognition and memory. Histological examination exhibited a significant augmentation in the efficacy of CSZ by caffeine in protecting neurons from damage in T2D rats. Importantly, CSZ and caffeine normalized the accumulation of Amyloid beta (Aβ-42) and phosphorylated tau protein (p-tau) positive cells in the brain of T2D rats. CSZ or CSZ plus caffeine reversed low glutamate gene expression, elevated cholinesterase level, and elevated caspase-3 activity in T2D rats. Furthermore, CSZ plus caffeine was significantly more effective than CSZ or caffeine in inhibiting the increase in malondialdehyde (MDA) level, total oxidative stress, pro-inflammatory cytokines and glucogen synthase kinase-3 beta (GSK-3β) in the hippocampus of T2D rats. Also, CSZ plus caffeine was more effective than CSZ or caffeine in alleviating insulin resistance and hypercholesterolemia in T2D rats. Our findings suggest the possibility of effective treatment of AD by enhancing the therapeutic potential of CSZ through combined treatment with lower doses of caffeine. The enhancement of CSZ effect by caffeine is attributed to the increased inhibitory effect of CSZ on insulin resistance, GSK-3β activity, hypercholesterolemia, oxidative stress and pro-inflammatory cytokines.

1,8 cineole protects type 2 diabetic rats against diabetic nephropathy via inducing the activity of glyoxalase-I and lowering the level of transforming growth factor-1β.

Diabetes leading to the production and circulation of glycation products along with the reduction of the activity of glyoxalase-I (GLO-I) contribute to diabetic nephropathy. Therefore, we studied the effect of 1,8 cineole (Cin) on the formation of diverse glycation products and the activity of GLO-I as well as renal histopathological alterations in the type-2 diabetic rat. Type 2 diabetes was induced in rats with a combination of streptozotocin and nicotinamide (55 + 200mg/kg). Two groups of rats, normal and diabetic, were treated intragastrically with Cin (200mg/kg) once daily for 2months. Fasting blood sugar, insulin resistance index, lipid profile, the activity of GLO-I, glycation products (Glycated albumin, Glycated LDL, Methylglyoxal, and advanced glycation end products), and oxidative stress (Advanced oxidation protein products, malondialdehyde, oxidized LDL, and reduced glutathione), inflammatory markers (Tumor necrosis factor-α and Transforming growth factor-1β), creatinine in the serum (Cre), and proteinuria (PU) in the urine of all rats was determined as well as renal histopathological alterations were investigated. Cin reduced biochemical (Cre and PU) and histopathological (glomerulosclerosis) indicators of renal dysfunction in the diabetic rat compared to untreated diabetic rats. Moreover, the treatment decreased different glycation, oxidative stress, and pro-inflammatory markers (p < 0.001).Further, Cin had an advantageous effect on glucose and lipid metabolism. Cin ameliorated diabetic nephropathy via reduction of TGF-1β following to decrease the formation of different glycation products, oxidative stress, and inflammatory process with the induction of the activity of glyoxalase-I in type 2 diabetic rats.

Effect of fucoidan on kidney injury in type 2 diabetic rats based on PI3K/AKT/Nrf2

Diabetic nephropathy (DN) is the most serious complication of diabetes mellitus. Although some studies have demonstrated that fucoidan can improve DN, the specific protective mechanism is not fully understood, so this study investigated the improvement effect and possible mechanism of fucoidan on renal function in type 2 diabetic (T2D) rats. The results showed that fucoidan could improve the general symptoms and disorders of glucolipid metabolism in T2D rats after 8 weeks of intervention. And it could alleviate the kidney damage in T2D rats. Meanwhile, fucoidan could reduce the oxidative stress levels in the blood and kidney of T2D rats, and significantly improved the expression levels of corresponding proteins (PI3K, AKT, Nrf2, HO-1, NQO1, TGF-β1) in the kidney tissues. The above results suggested that fucoidan could improve renal injury in T2D rats through antioxidant, and the mechanism may be related to the activation of PI3K/AKT/Nrf2.

In vitro and in vivo antihyperglycemic activity of the ethanol extract of Heritiera fomes bark and characterization of pharmacologically active phytomolecules.

This study aimed to demonstrate the mechanistic basis of Heritiera fomes, which has traditionally been used to treat diabetes. Clonal pancreatic β-cells and primary islets were used to measure insulin release. 3T3-L1 cells were used to analyse insulin action, and in vitro systems were used to measure further glucose-lowering activity. In vivo assessment was performed on streptozotocin (STZ)-induced type-2 diabetic rats and reversed-phase-HPLC followed by liquid chromatography mass spectrometry (LC-MS) to detect bioactive molecules. Ethanol extract of Heritiera fomes (EEHF) significantly increased insulin release with stimulatory effects comparable to 1 µM glucagon-like peptide 1, which were somewhat reduced by diazoxide, verapamil and calcium-free conditions. Insulin release was stimulated by tolbutamide, isobutyl methylxanthine and KCl. EEHF induced membrane depolarization and increased intracellular Ca2+ levels. EEHF enhanced glucose uptake in 3T3L1 cells and decreased protein glycation. EEHF significantly inhibited postprandial hyperglycaemia following sucrose loading and inversely elevated unabsorbed sucrose concentration in the gut. It suppressed glucose absorption during in situ gut perfusion. Furthermore, EEHF improved glucose tolerance, plasma insulin and gut motility, and decreased plasma dipeptidyl peptidase IV activity. Procyanidins, epicatechin and proanthocyanidins were some of the identified bioactive constituents that may involve in β-cell actions. This study provides some evidence to support the use of H. fomes as an antidiabetic traditional remedy.

Type-2 diabetic rat heart: The effect of kolaviron on mTOR-1, P70S60K, PKC-α, NF-kB, SOD-2, NRF-2, eNOS, AKT-1, ACE, and P38 MAPK gene expression profile

It has been established that genetic factors partially contribute to type-2 diabetes and vascular disease development. This study determined the effect of kolaviron on the expression profile of genes associated with the insulin signaling pathway and involved in regulating glucose and lipid metabolism, oxidative stress, inflammation, vascular functions, pro-survival and the apoptosis pathway in the heart of type-2 diabetic rats. After induction and confirmation of type-2 diabetes seven days after, the rats were treated with kolaviron for twenty-eight days before being euthanized. Organs were harvested and stored at − 80 °C in a biofreezer. Total RNA was extracted from the ventricle, reverse transcribed to cDNA followed by a real-time quantitative polymerase chain reaction (RT-qPCR) analysis of the expression of mTOR-1, P70S60K, PKC-α, NF-kB, SOD-2, NRF-2, eNOS, AKT-1, ACE, p38 MAPK and the reference gene (GAPDH), after which they were normalized/standardized. The results show an increase in the relative mRNA expression of mTOR/P70S60K/PKCα /P38MAPK/NF-KB/ACE and a decrease in the relative mRNA expression of NRF2/SOD/AKT/eNOS in the heart of the diabetic rats. Nevertheless, kolaviron modulated the expression profile of these genes, which suggest a therapeutic effect and target for vascular dysfunction and complications in type-2 diabetes through the activation of the NRF-2/AKT-1/eNOS signaling pathway and suppression of the NF-kB/PKC signaling pathway.

The vascular impact of dapagliflozin, liraglutide, and atorvastatin alone or in combinations in type 2 diabetic rat model.

Diabetic dyslipidemia is a significant contributor in the pathogenesis of type 2 diabetes (T2D). The study aimed at comparing the effect of dapagliflozin, liraglutide, and atorvastatin alone or their combinations on lipids and inflammatory markers and their vascular impact in T2D rats. There were 56 male albino rats included in the study and divided into two main groups. Group A (8 rats) served as normal control. Group B (48 rats) were streptozotocin-nicotinamide-induced diabetic rats. Subgroups (B-1, B-2, B-3, B-4, B-5, and B-6) received (no medications, dapagliflozin, liraglutide, atorvastatin, dapagliflozin + atorvastatin, and liraglutide + atorvastatin), respectively. Urine albumin/creatinine ratio (UACR), glycosylated hemoglobin (HBA1c), fasting serum glucose (FSG), serum low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), TGs, lipoprotein(a) Lp (a), serum thyrotropin (TSH), highly sensitive C-reactive protein (hs-CRP) and advanced glycation end products (AGEs), were assessed. Qualitative and quantitative histological examination of kidneys focused on renal corpuscles. Dapagliflozin improved the studied parameters but with statistically insignificant increase in LDL-C, Lp (a) and significant increase in UACR. Atorvastatin improved the studied parameters but with statistically insignificant increase in FSG and HbA1C. Liraglutide and the combination groups significantly improved all studied parameters. Histologically, liraglutide and atorvastatin produced therapeutic effect, while dapagliflozin depicted nephrotoxic effect. Combination groups resulted in better effects with normalization of most of renal corpuscles. There were positive correlations between LDL-C and hs-CRP, AGEs, TSH and mesangial expansion. Combination of atorvastatin with liraglutide can improve its vasculoprotective effect. Moreover, combination of atorvastatin with dapagliflozin can ameliorate its possible nephrotoxic effect.

Role of CK1ε-regulated PERIOD2 in STZ-induced diabetic myocardial injury.

Circadian rhythms are fundamental to regulating metabolic processes and cardiovascular functions. Phosphorylated PERIOD2 (PER2) is a key factor in determining the period of the mammalian circadian clock. Moreover, casein kinase 1ε (CK1ε) primes the PER2 phosphoswitch and its stability. While diabetes contributes to the disorder of the circadian system, changes in PER2 forms and their regulatory mechanisms during diabetes remain unclear. In this study, we examined the impact of diabetes on PER2 and CK1ε signaling in the heart to determine the potential mechanism between them. A Type-1 diabetic rat model was established by intraperitoneally injecting rats with streptozotocin. General characteristics, cardiac function, histology, serum biochemistry, apoptosis index and circadian rhythm were analyzed in controls and diabetic rats treated with or without PF-670462 (a CK1ε inhibitor). A high-glucose model was created with H9c2 cells and treated with PF-670462 and PER2 siRNA. Cell viability, LDH release, dead/live rate and histology were determined to assess cellular injuries. RT-PCR and Western blot were used to evaluate the expression of PER2, CK1ε, phosphorylated PER2, and immunofluorescence (IF) was employed to determine PER2's location. STZ-induced diabetes prolonged PER's period and upregulated the expression of CK1ε and phosphorylated PER2 compared to the controls. Inhibiting CK1ε and PER2 with PF-670462 downregulated the phosphorylation at Ser662 and the nuclear entry of PER2 in high glucose conditions. In addition, pharmacologically or genetically suppressing PER2 mitigated high-glucose-instigated myocardial injury. Diabetes compromised PER2 in association with activated CK1ε signaling. Targeting CK1ε-regulated PER2 alleviates myocardial injuries in the presence of high glucose.

In vitro and in vivo evaluation of 3D printed sodium alginate/polyethylene glycol scaffolds for sublingual delivery of insulin: Preparation, characterization, and pharmacokinetics

Delivery of therapeutic peptides via sublingual administration is extremely desired and 3D printed scaffolds are potential candidates as carriers to enhance insulin delivery. 3D printed sublingual sodium alginate (SA)/polyethylene glycol (PEG) composite scaffolds were produced for enhancing insulin delivery by examining the chemical, morphological, mechanical, thermal, cytotoxic, and pharmacokinetic features. The tensile strength and flexibility of scaffolds increased after loading insulin due to the crystalline structure of insulin. Furthermore, insulin-loaded 9SA/3PEG scaffolds showed ultrafast wetting (<1 s), disintegration (<6 s), and also dissolution (<30 s) according to Hixson-Crowell kinetic model. The cell viability of L929 cells on 3D printed scaffolds was examined and these scaffolds could be safely applied on animals. Pharmacokinetic parameters and blood glucose level were evaluated following sublingual administration of scaffolds to type-1 diabetic rats. A single dose of scaffold presented a longer hypoglycemic effect, reducing ~60% of glycemia after 30 min and it lasted for 12 h by increasing the bioavailability of insulin. Scaffolds indicated a sustained profile for serum insulin levels, which continued to increase slightly after 3 h during the study. The polymeric scaffold with a high safety and efficacy holds a new promising delivery strategy for administering injectable insulin through the sublingual route.

Myricetin Increases Circulating Adropin Level after Activation of Glucagon-like Peptide 1 (GLP-1) Receptor in Type-1 Diabetic Rats.

Myricetin is a common plant-derived flavonoid, considered an agonist of glucagon-like peptide 1 (GLP-1) receptor. It improves glycemic control and helps reduce body weight in diabetic subjects. The potential mechanisms of action of myricetin in this context might be enhancing the secretion of β-endorphin (BER) to activate peripheral μ-opioid receptors. Moreover, adropin is a nutritionally regulated peptide hormone, which regulates energy metabolism, and plays a role in ameliorating diabetes. Because their mechanisms of insulin sensitivity are closely related, we hypothesized that myricetin may interact with adropin and plasma BER. The present study investigated the glucose-lowering effect of acute and chronic treatments of myricetin in type-1 diabetic rats. Plasma BER and adropin levels were determined by enzyme-linked immunosorbent assay (ELISA). The secretion of BER was measured in rats who received adrenalectomy. The changes in adropin gene (Enho) or mRNA level of GLP-1 receptor were measured using qPCR analysis. The results showed that myricetin dose-dependently increased plasma BER and adropin levels like the reduction of hyperglycemia after bolus injection as acute treatment. In addition, these effects of myricetin were inhibited by the antagonist of GLP-1 receptor. Moreover, in HepG2 cell line, myricetin induced GLP-1 receptor activation, which modulated the expression of adropin. In diabetic rats, the plasma adropin increased by myricetin is mainly through endogenous β-endorphin after activation of GLP-1 receptor via bolus injection as acute treatment. Additionally, chronic treatment with myricetin increased adropin secretion in diabetic rats. In conclusion, our results provide a new finding that activation of opioid μ-receptor in the liver may enhance circulating adropin in animals.

Mitigation of streptozotocin-induced alterations by natural agents via upregulation of PDX1 and Ins1 genes in male rats.

Diabetes is the most common endocrine disorder contributing to high morbidity and mortality globally. Due to the side effects reported for anti-diabetic drugs, there is a rising interest in herbal medicine for diabetes mitigation. However, rare studies were performed to analyze the molecular effects of natural agents on diabetes. Therefore, this study is the first to assess the possible ameliorating effects of avocado and cinnamon extracts on streptozotocin (STZ)-induced disturbances in the gene expression of PDX1 and Ins1 in type-2 diabetic rats, in comparison to metformin. A total number of 50 male Albino rats were randomly divided into five groups; normal control, STZ-induced diabetic group (65mg/kg b.w divided into three doses 5days apart), three other STZ-diabetic groups were treated orally for 6weeks with metformin (500mg/kg b.w/day), an avocado fruit ethanolic extract (300mg/kg b.w/day), or a cinnamon aqueous extract (200mg/kg b.w/day). All rats were fasted overnight then euthanized, blood was collected, and serum was separated for biochemical analyses. The pancreas was processed for the evaluation of PDX1 and Ins1 gene expression by qRT-PCR. Oral administration of the avocado/cinnamon extract significantly improved the altered levels of blood glucose, insulin, lipid profile, and total antioxidant capacity (TAC) and upregulated the pancreatic expression of PDX1 and Ins1 genes. In conclusion, this study added another mechanism of anti-diabetic action for the plant extracts via upregulating the gene expression of PDX1 and Ins1 in STZ-diabetic rats. Metformin has a more profound effect than the plant extracts; however, cinnamon has a comparable effect. PRACTICAL APPLICATIONS: Diabetes is a worldwide chronic serious problem; therefore, different efficacious drug treatments are currently available. However, several side effects of these drugs also negatively affect patient welfare. Therefore, the present study provides an additive/adjunct biochemical rationale for further natural intervention strategy for type-2 diabetes through the introduction of plant-derived products that revealed a wide range of therapeutic effects without causing untoward actions. This study revealed that cinnamon and avocado extracts exhibited marked anti-diabetic and antioxidant effects in rats, as compared to the standard drug, metformin. These results augmented the previous ones and added a new molecular mechanism of action through upregulation of Ins1 and PDX1 in type-2 diabetic rats.

Effects of Pharmacological Inhibitors of NADPH Oxidase on Myogenic Contractility and Evoked Vasoactive Responses in Rat Resistance Arteries.

Reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide, are reported to contribute to the dynamic regulation of contractility in various arterial preparations, however, the situation in pressurized, myogenically active resistance arteries is much less clear. In the present study, we have utilized established pharmacological inhibitors of NADPH oxidase activity to examine the potential contribution of ROS to intrinsic myogenic contractility in adult Sprague–Dawley rat resistance arteries and responses to vasoactive agents acting via the endothelium (i.e., acetylcholine, SKA-31) or smooth muscle (i.e., sodium nitroprusside, phenylephrine). In cannulated and pressurized cremaster skeletal muscle and middle cerebral arteries, the NOX inhibitors 2-acetylphenothiazine (2-APT) and VAS2870, selective for NOX1 and NOX2, respectively, evoked concentration-dependent inhibition of basal myogenic tone in a reversible and irreversible manner, respectively, whereas the non-selective inhibitor apocynin augmented myogenic contractility. The vasodilatory actions of 2-APT and VAS2870 occurred primarily via the vascular endothelium and smooth muscle, respectively. Functional responses to established endothelium-dependent and –independent vasoactive agents were largely unaltered in the presence of either 2-APT or apocynin. In cremaster arteries from Type 2 Diabetic (T2D) Goto-Kakizaki rats with endothelial dysfunction, treatment with either 2-APT or apocynin did not modify stimulus-evoked vasoactive responses, but did affect basal myogenic tone. These same NOX inhibitors produced robust inhibition of total NADPH oxidase activity in aortic tissue homogenates from control and T2D rats, and NOX isozymes 1, 2 and 4, along with superoxide dismutase 1, were detected by qPCR in cremaster arteries and aorta from both species. Based on the diverse effects that we observed for established, chemically distinct NOX inhibitors, the functional contribution of vascular NADPH oxidase activity to stimulus-evoked vasoactive signaling in myogenically active, small resistance arteries remains unclear.

Beneficial effects of metformin supplementation in hypothalamic paraventricular nucleus and arcuate nucleus of type 2 diabetic rats

BackgroundOxidative stress and inflammation play important roles in the development of diabetes. Metformin (MET) is considered as the first-line therapy for patients with type 2 diabetes (T2D). Hypothalamic paraventricular nucleus (PVN) and hypothalamic arcuate nucleus (ARC) are vital in obesity and diabetes. However, there have been few studies on the effects of MET on inflammatory reaction and oxidative stress in the PVN and ARC of T2D diabetic rats.MethodsMale Sprague-Dawley (SD) rats were fed with high-fat diet (HFD), and intraperitoneally injected with low-dose streptozotocin (STZ, 30 mg/kg) at 6th week to induce T2D diabetes. After injection of STZ, they were fed with HFD continually. Starting from the 8th week of HFD feeding, T2D rats received intragastrical administration of MET (150 mg/kg/day) in addition to the HFD for another 8 weeks. At the end of the 15th week, the rats were anaesthetized to record the sympathetic nerve activity and collect blood and tissue samples.ResultsIn comparison with control rats, T2D diabetic rats had higher levels of pro-inflammatory cytokines (PICs) and excessive oxidative stress in the PVN and ARC, accompanied with more activated astrocytes. The renal sympathetic nerve activity (RSNA) and the plasma norepinephrine (NE) increased in T2D diabetic rats. The expression of tyrosine hydroxylase (TH) increased and the expression of 67-kDa isoform of glutamate decarboxylase (GAD67) decreased in T2D diabetic rats. Supplementation of MET decreased blood glucose, suppressed RSNA, decreased PICs (TNF-α, IL-1β and IL-6) in PVN and ARC, attenuated oxidative stress and activation of astrocytes in ARC and PVN of T2D diabetic rats, as well as restored the balance of neurotransmitter synthetase. The number of Fra-LI (chronic neuronal excitation marker) positive neurons in the ARC and PVN of T2D diabetic rats increased. Chronic supplementation of MET also decreased the number of Fra-LI positive neurons in the ARC and PVN of T2D diabetic rats.ConclusionThese findings suggest that the PVN and ARC participate in the beneficial effects of MET in T2D diabetic rats, which is possibly mediated via down-regulating of inflammatory molecules, attenuating oxidative stress and restoring the balance of neurotransmitter synthetase by MET in the PVN and ARC.

Effect of Type 2 Diabetes and Impaired Glucose Tolerance on Digestive Enzymes and Glucose Absorption in the Small Intestine of Young Rats.

The reactions of intestinal functional parameters to type 2 diabetes at a young age remain unclear. The study aimed to assess changes in the activity of intestinal enzymes, glucose absorption, transporter content (SGLT1, GLUT2) and intestinal structure in young Wistar rats with type 2 diabetes (T2D) and impaired glucose tolerance (IGT). To induce these conditions in the T2D (n = 4) and IGT (n = 6) rats, we used a high-fat diet and a low dose of streptozotocin. Rats fed a high-fat diet (HFD) (n = 6) or a standard diet (SCD) (n = 6) were used as controls. The results showed that in T2D rats, the ability of the small intestine to absorb glucose was higher in comparison to HFD rats (p < 0.05). This was accompanied by a tendency towards an increase in the number of enterocytes on the villi of the small intestine in the absence of changes in the content of SGLT1 and GLUT2 in the brush border membrane of the enterocytes. T2D rats also showed lower maltase and alkaline phosphatase (AP) activity in the jejunal mucosa compared to the IGT rats (p < 0.05) and lower AP activity in the colon contents compared to the HFD (p < 0.05) and IGT (p < 0.05) rats. Thus, this study provides insights into the adaptation of the functional and structural parameters of the small intestine in the development of type 2 diabetes and impaired glucose tolerance in young representatives.