Mechanisms In Diabetic Rats Research Articles

Effect of Pimpinella tirupatiensis Extract on Brain Free Radical Toxicity in STZ Induced Diabetic Rats

The objective of this study was to investigate the effects of Pimpinella tirupatiensis on oxidative stress markers in different regions of the brain (cerebral cortex, cerebellum, hippocampus, and Pons medulla) in rats with diabetes. Diabetes was induced in wistar rats by injecting them with STZ (40 mg/kg). The rats were then administered Pimpinella tirupatiensis aqueous extract (750 mg/kg / b.w. /day) and glibenclamide (Glb) (20 mg/ kg / b.w. /day) orally for 30 days. After 4 weeks of high blood sugar, the activity of antioxidant enzymes was measured in both the diabetic and control groups. Diabetes can worsen nerve damage and cause oxidative damage due to high blood sugar levels. The diabetic rats displayed a significant decrease in levels of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase) and reduced glutathione. However, when ginger was administered orally, it enhanced the activity of antioxidant enzymes in the diabetic rats. This suggests that Pimpinella tirupatiensis has a protective effect on the brain by enhancing antioxidant defense mechanisms in diabetic rats. Furthermore, it has a neuroprotective effect by enhancing the brain's antioxidant defense mechanisms and thereby attenuating the progression of hyperglycemia and some complications caused by diabetes in the rat brain.

Cadmium exposure exacerbates kidney damage by inhibiting autophagy in diabetic rats

The incidence of diabetes mellitus (DM) is gradually increasing, making it a widespread global health concern. Cadmium (Cd) is a common toxic heavy metal in the environment, and cadmium exposure may be associated with diabetic nephropathy (DN). However, the mechanism of Cd-induced DN remains unclear. In this study, we aimed to determine the effect of cadmium on diabetic kidney injury and the underlying mechanism in diabetic rats and a renal tubular epithelial cell line (NRK-52E cells). Our results could provide novel insights on the nephrotoxic mechanism of cadmium. HE, PAS, and Masson staining were used to observe pathological renal injury. COL-I, COL-IV, CTSB, and CTSD protein levels were detected by immunohistochemistry and western blotting. Immunofluorescence was used to detect the fluorescence intensity of p62 and LC3 proteins in kidney tissue. TEM was used to observe the ultrastructure of mitochondria and number of autophagosomes. After cadmium exposure, DM rats showed a dramatic decrease in body weight compared to the unexposed DM group. Relative kidney weight showed a contrasting trend after cadmium exposure. Urinary microalbumin/creatinine significantly increased in normal and DM rats after cadmium exposure. However, the trend was clearer in the DM groups than in the control groups. Endogenous creatinine clearance exhibited a contrasting trend. After cadmium exposure in DM rats, MDA content significantly increased and GSH, CAT, SOD, and GSH-PX activation reduced compared to normal controls. Pathological damage was more pronounced, and the expression of autophagy related proteins and apoptosis and fibrosis proteins was significantly higher in vivo and vitro in the cadmium-exposed groups than in unexposed controls. Further, lysosomal protein levels were lower, and ROS content and autophagosome count significantly higher in the cadmium exposed groups compared to the unexposed controls. Therefore, Cadmium exposure aggravates diabetic kidney injury via autophagy inhibition.

Dangua Fang regulating tricarboxylic acid cycle and respiratory chain and its mechanism in diabetic rats.

To investigate the influence and possible targets of Dangua Fang on tricarboxylic acid (TCA) cycle and respiratory chain to enrich the prescription's mechanism of effective intervention on glycolipid metabolic diseases such as type 2 diabetes. After interventional rats were fed with high glucose and high fat diet ad libitum for 4 weeks, intraperitoneally injected streptozotocin to induce diabetic model. According to blood glucose level,28 diabetic rats were selected and continued to be fed with high glucose and high fat diet, were stratified by body weight, and divided randomly by blood glucose into Model group (was given sterile water by gastric perfusion and injected aquae pro injection intraperitoneally), Dangua group [Dangua liquor 20.5 g·kg-1·d-1 by perfusion and aquae pro injection intraperitoneally], Inhibitor group [sterile water by perfusion and nicotinamide phosphoribosyl transferase (Nampt) specific blocker GEN-617 1.25 mg/kg intraperitoneally], DanInhit group (Dangua liquor and GEN-617 synchronously). Control group were continuously fed with ordinary diet. The intervention was last for 10 weeks. Body weight (BW), liver index (LI), glycosylated hemoglobin (HbA1c), TC, TG, free fatty acids (FFA), creatinine (Cr), and A-ketoglutarate (α-KG), Iso-citric acid (ICA), oxaloacetic acid (OAA) were tested. The cytochrome C oxidase (COX) and Succinate dehydrogenase (SDH) were evaluated by Colorimetry; Nampt protein, Adenosine triphosphate (ATP) synthase (ATPs), Nicotinamide adenine dinucleotide (NAD+)and its reduced (NADH) in liver were measured by enzyme linked immunosorbent assay. The expressions of Nampt and mitochondrialnadhdehydrogenase-1 (mt-ND1) gene in liver was assessed by real-time polymerase chain reaction. Hepatic tissue staining was also completed. The levels of BW, ICA, α-KG and Nampt-mRNA in the Model group are lower than that in the Normal group (P < 0.05), conversely, liver weight, LI, TC, HbA1c, SDH and ATPs, mt-ND1-mRNA, and Nampt protein in the Model group are higher (P < 0.01, P < 0.05). Compared with Model group, the levels of ICA, Nampt-mRNA and Nampt in Dangua group are significantly increased, and FFA obviously raised (P < 0.01 and P < 0.05); liver weight, BW, SDH are obviously lower, and HbA1c decreased significantly (P < 0.01, P < 0.05). TG, FFA and Nampt protein increased in the DanInhit group, TC, TG, BW obviously increased in the Inhibitor group, but SDH is decreased in both the two groups (P < 0.05, P < 0.01). Compared with Dangua group, DanInhib group has the lower levels of ICA, mt-ND1-mRNA, Nampt-mRNA, and the higher level of BW, LI and HbA1c. In the Inhibitor group, ICA and Nampt protein decreased, BW and LI, HbA1c and TG increased (P < 0.01 or P < 0.05). Tissue staining display that, in the model group there is obvious pathologic changes ie: fibrosis, steatosis and inflammatory cell infiltration. Lesions in the Dangua group are mild, and those of Inhibitor group are more obvious than the Model group, and DanInhit group is intermediately affected compared to Dangua group and Inhibitor group. Dangua Fang increases the metabolic flux of TCA cycle and optimizes respiratory chain function by up-regulating Nampt expression.

Vascular Protective Effects of Malus toringoides (Rehd.) Hughes Extracts and their Mechanism in Diabetic Rats and HUVECs.

Malus toringoides (Rehd.) Hughes (Rosaceae) is used as a traditional folk medicine in the Tibet autonomous region of China to treat hypertension, hyperglycemia, and hyperlipidemia. However, few modern pharmacological data on the use of this plant against diabetic syndrome are available. In this study, we examined the vascular protection provided by a 70% ethanol extract of M. toringoides (EMT) in human umbilical vein endothelial cells (HUVECs) grown in high-glucose medium and in a high-fat diet/streptozotocin-induced rat diabetes model. EMT significantly suppressed the expression of cell adhesion molecules in both HUVECs and diabetic rats. EMT also inhibited activation of the CX3CL1/CX3CR1 axis and the nuclear factor kappa B (NF-κB) signaling pathway in vivo and in vitro. The results provide a significant information on the vasoprotective properties of M. toringoides that may contribute to the development and application of related herbal medicines.

Berberine combined with stachyose improves glycometabolism and gut microbiota through regulating colonic microRNA and gene expression in diabetic rats

AimsBerberine is effective for type 2 diabetes mellitus (T2DM), but has limited use in clinic. This study aims to evaluate the effect of berberine combined with stachyose on glycolipid metabolism and gut microbiota and to explore the underlying mechanisms in diabetic rats. Main methodsZucker diabetic fatty (ZDF) rats were orally administered berberine, stachyose and berberine combined with stachyose once daily for 69 days. The oral glucose tolerance and levels of blood glucose, insulin, triglyceride and total cholesterol were determined. The gut microbial profile, colonic miRNA and gene expression were assayed using Illumina sequencing. The quantitative polymerase chain reaction was used to verify the expression of differentially expressed miRNAs and genes. Key findingsRepeated treatments with berberine alone and combined with stachyose significantly reduced the blood glucose, improved the impaired glucose tolerance, and increased the abundance of beneficial Akkermansiaceae, decreased that of pathogenic Enterobacteriaceae in ZDF rats. Furthermore, combined treatment remarkably decreased the abundances of Desulfovibrionaceae and Proteobacteria in comparison to berberine. Combined treatment evidently decreased the expression of intestinal early growth response protein 1 (Egr1) and heparin-binding EGF-like growth factor (Hbegf), and significantly increased the expression of miR-10a-5p, but berberine alone not. SignificanceBerberine combined with stachyose significantly improved glucose metabolism and reshaped gut microbiota in ZDF rats, especially decreased the abundance of pathogenic Desulfovibrionaceae and Proteobacteria compared to berberine alone, providing a novel strategy for treating T2DM. The underlying mechanisms may be associated with regulating the expression of intestinal Egr1, Hbegf and miR-10a-5p, but remains further elucidation.

Naringenin attenuates cerebral Ischemia-Reperfusion injury through Inhibiting oxidative stress and Inflammation in Diabetic Rats

Aim: Ischemic stroke is one of the important complications of diabetes. Diabetes exacerbate cerebral injury after ischemia and reperfusion. This study was designed to investigate whether the naringenin has a cerebroprotective action against the ischemic reperfusion injury via anti-oxidant and anti-inflammatory mechanisms in diabetic rats. Diabetes was induced by Streptozocine (50mg/kg) intraperitoneal injection at once. Medial carotid artery occlusion (30 min) and reperfusion (3 hr) was employed to induce cerebral infarction in diabetic rats. The animals were divided in to groups as: normal, sham, ischemia-reperfusion and naringenin treated (50, 100, 150 and 200mg/kg). These were used for evaluation of percentage of cerebral infarction. Further, 200mg/kg dose was selected for the estimation of inflammatory biomarkers such as Tumor necrosis factor-α, Interlukin-6, Interlukin-10 and oxidative stress biomarkers such as malondialdehyde, superoxide dismutase, and catalase were estimated and histopathological changes were studied. Dose dependent reduction in percentage of cerebral infarction was observed in narigenin treated groups. With Naringenin 200mg/kg dose, inflammatory and oxidative stress markers like Tumor necrosis factor-α, Interlukin-6, myeloperoxidase and malondialdehyde levels were distinctively reduced and there was a remarkable increased levels of anti-inflammatory and anti-oxidant markers like Interlukin-10, catalase, and superoxide dismutase. Conclusion: Collectively, these findings demonstrate that the mechanism (s) responsible for a cerebroprotective effect of naringenin against the ischemic reperfusion injury in the diabetic rats involves anti-oxidant and anti-inflammatory actions.

The Effect of Endurance Training with Crocin Consumption on the Levels of AMPK and NRF1 Gene Expression in the Soleus Muscles of Diabetic Rats

Background: Exercise training and crocin, as a herbal antioxidant, help improve metabolism and insulin sensitivity in type 2 diabetes mellitus (T2D). AMP-activated protein kinase (AMPK) and nuclear respiratory factor 1 (NRF1) involve in the mitochondrial biogenesis pathway and diabetes control. Objective: This study aimed to investigate the effects of high-intensity interval training (HIIT), and low intensity continued training (LICT) in combination with crocin consumption on AMPK and NRF1 gene expression in the muscle tissue of diabetic rats. Methods: In this experimental study, 56 adult rats were divided into eight groups (n = 7), including diabetic (crocin utilization, HIIT, LICT, HIIT with crocin, LICT with crocin, control, sham groups) and healthy control group. The HIIT and LICT groups performed five sessions of training per week for eight weeks, and the crocin consumption groups received 25 mg/kg of crocin daily for eight weeks. Moreover, AMPK and NRF1 genes expression levels were evaluated in different groups using real-time polymerase chain reaction (RT-PCR). Results: According to our results, while induction of diabetes significantly decreased the levels of NRF1 and AMPK gene expression (P ≤ 0.05), training and crocin consumption significantly increased the levels of AMPK and NRF1 gene expression (P ≤ 0.05). Conclusions: It appears that crocin consumption along with HIIT improves diabetes symptoms through AMPK and NRF1 mechanism in diabetic rats.

Protective effect of Chrysin as Antioxidant, Anti-inflammatory and Anti apoptotic agent in Transient global cerebral Ischemia - Reperfusion injury among diabetic rats

Aim: Oxidative stress, inflammation and apoptosis have been implicated as pathological conditions in ischemic stroke, further these conditions worsen in the presence of diabetes. This study was designed to investigate whether the chrysin has protective role against ischemia reperfusion injury through anti-oxidant, anti-inflammatory and anti-apoptosis mechanisms in diabetic rats. Methods: Streptozocine (50mg/kg) intraperitonially given at once to induce the diabetes. Common carotid artery occlusion (30 min) and reperfusion (4 hr) was employed to induce cerebral infarction in diabetic rats. The animals were divided in to groups as: normal, sham, ischemia-reperfusion and chrysin treated (10, 20, 30 and 40mg/kg). These were used for estimation of percentage of cerebral infarction. 30mg/kg dose was used for further estimation of inflammatory markers like TNF-α, IL-6, IL-10 and oxidative stress markers (xanthine oxidase, glutathione, NADPH, malondialdehyde, superoxide dismutase and catalase), apotosis markers (Bcl2, BAX and Hsp90) were estimated and also glutamate and aspartate levels were measured in brain tissues. Results: Dose dependent reduction in percentage of cerebral infarction was observed in chrysin treated groups. With chyrsin 30mg/kg the apoptosis, inflammatory and oxidative stress markers like BAX, Hsp90, TNF-α, IL-6, myeloperoxidase, malondialdehyde, NADPH and xanthine oxidase levels were reduced and there was a significant increase in anti-apoptosis, anti-inflammatory and anti-oxidant markers like Bcl2, IL-10 levels and glutathione, catalase, superoxide dismutase which was also accompanied with elevated glutamate and aspartate levels. Conclusion: Collectively, these results show that chrysin possess a cerebroprotective effect against ischemic reperfusion injury in the diabetic rats.

Scar free healing of full thickness diabetic wounds: A unique combination of silver nanoparticles as antimicrobial agent, calcium alginate nanoparticles as hemostatic agent, fresh blood as nutrient/growth factor supplier and chitosan as base matrix

Healing of diabetic wounds present a big challenge due to insufficient vascular supply and bacterial infection. We developed chitosan based biodegradable polymeric hydrogel containing silver nanoparticles (AgNPs) as antimicrobial agent and calcium alginate nanoparticles (Ca-AlgNps) as hemostatic agent to address this problem. The prepared Chitosan/Ca-AlgNps/AgNPs hydrogel showed broad spectrum antimicrobial properties against both Gram negative (E. coli, P. aeruginosa) and Gram positive (B. subtilis, S. aureus) bacteria. Taken into account the blood as a vital material containing various circulatory fibrocytes, growth factors, cytokines, platelets and macrophages etc., we incorporated the fresh blood of the same animal to the prepared Chitosan/Ca-Alg Nps/AgNPs hydrogel. In-vivo animal studies of Chitosan/Ca-AlgNps/AgNPs hydrogel and blood mixed Chitosan/Ca-AlgNps/AgNPs hydrogel exhibit 83.5 ± 4.4% and 99.8 ± 2.0% closure of wound respectively, on day 15 as compared to 41.5 ± 3.2% in diabetic control and 60.3 ± 2.2% in commercially available wound healing cream, Silverex Heal. The incorporation of fresh blood to the prepared hydrogel has advantage in terms of supplying growth factors, platelets, circulatory fibrocytes and cytokines which further enhanced the wound healing mechanism in diabetic rats. This work opens a novel idea to formulate hydrogels based dressings for diabetic wound healing.

Putative Mechanisms Responsible for the Antihyperglycemic Action of Lactobacillus paracasei HII01 in Experimental Type 2 Diabetic Rats.

Despite the updated knowledge of the impact of gut dysbiosis on diabetes, investigations into the beneficial effects of individual bacteria are still required. This study evaluates the antihyperglycemic efficacy of Lactobacillus paracasei HII01 and its possible mechanisms in diabetic rats. Diabetic rats were assigned to receive vehicle, L. paracasei HII01 (108 CFU/day), metformin 30 (mg/kg) or a combination of L. paracasei HII01 and metformin. Normal rats given vehicle and L. paracasei HII01 were included. Metabolic parameters, including in vitro hemi-diaphragm glucose uptake, skeletal insulin-signaling proteins, plasma lipopolysaccharide (LPS), gut permeability, composition of gut microbiota and its metabolites, as well as short-chain fatty acids (SCFAs), were assessed after 12 weeks of experiment. The results clearly demonstrated that L. paracasei HII01 improved glycemic parameters, glucose uptake, insulin-signaling proteins including pAktSer473, glucose transporter 4 (GLUT4) and phosphorylation of AMP-activated protein kinase (pAMPKThr172), tumor necrosis factor (TNF-α) and nuclear factor-κB (NF-kB) in diabetic rats. Modulation of gut microbiota was found together with improvement in leaky gut, endotoxemia and SCFAs in diabetic rats administered L. paracasei HII01. In conclusion, L. paracasei HII01 alleviated hyperglycemia in diabetic rats primarily by modulating gut microbiota along with lessening leaky gut, leading to improvement in endotoxemia and inflammation-disturbed insulin signaling, which was mediated partly by PI3K/Akt signaling and AMPK activation.

Launaea taraxacifolia leaf partitions ameliorate alloxan-induced pathophysiological complications via antioxidant mechanisms in diabetic rats

Launaea taraxacifolia (Wild.) Amin ex. Jeffery belongs to family Asteracaea. The plant is used for treatment of diseases and eaten as vegetable in Nigeria. This study investigated the ameliorative potentials of L. taraxacifolia leaf partitions in alloxan induced diabetic complications. Male Albino rats were divided into eleven groups of five rats each. Diabetes was induced following intraperitoneal administration of 150 mg/kg alloxan monohydrate and was treated with 200 and 300 mg/kg of each partitioned fractions. Hyperglycemia was reversed in all treated rats within seven days of treatments. Rats treated with the partitions showed significant increase in hematological parameters compared with diabetic control. N-hexane fraction had the best overall effect against oxidative stress particularly on heart and pancreas reduced glutathione (GSH), superoxide dismutase (SOD) and kidney glutathione S-transferase (GST) activities. The various degrees of degeneration observed in the kidney, liver, pancreas and heart of the untreated diabetic rats were milder in rats treated with partitions. The results therefore revealed the ameliorative potentials of the partitioned fractions of L. taraxacifolia leaf extract against diabetes mellitus complications via activation of the antioxidant enzymes.

Cardioprotective effects of erythropoietin in diabetic rats determined by CD34 and vascular endothelial growth factor levels

IntroductionIn this study, the effects of diabetes mellitus on the cardiovascular system were investigated by assessing the stem cell levels in serum and heart and compared with the normal population. Additionally, efficacy of erythropoietin, which is known to increase stem cells, was studied in diabetic rats.Material and methodsTwenty-five male Sprague Dawley rats were divided into three groups as a control group (group 1), diabetic group (group 2) and erythropoietin induced diabetic group (group 3). A diabetes model was created with streptozocin. In group 3 rats received 3000 U/kg of erythropoietin. At the end of 1 month blood reticulocyte levels, degree of tissue fibrosis and immunohistochemical assessment of reliable stem cell markers, CD34 and vascular endothelial growth factor (VEGF), were analyzed.ResultsThe increase in the blood glucose levels resulted in a significant decrease in reticulocyte levels in group 2. The increase in blood glucose levels resulted in a statistically significant increase in tissue level of fibrosis, CD34 and VEGF. When the rats in groups 1 and 2 were compared, the fibrosis, CD34 and VEGF levels were found to increase significantly. When group 2 and group 3 were compared, the amount of fibrosis was lower and the levels of CD34 and VEGF were significantly higher in group 3 than group 2.ConclusionsThe results of our study indicated that the amount of CD34 and VEGF which function in cellular protection and tissue regeneration may be enhanced with safely applicable erythropoietin leading to increase in reticulocyte levels in serum, and CD34 and VEGF levels in right atrium, right ventricle, left atrium, and left ventricle as a protective mechanism in diabetic rats.

A Possible Mechanism of Metformin in Improving Insulin Resistance in Diabetic Rat Models.

Background Type 2 diabetes has become one of the most common diseases worldwide, causing a serious social burden. As a first-line treatment for diabetes, metformin can effectively improve insulin resistance. It has been reported that 12α-hydroxylated BA (mainly CA) is associated with insulin resistance. The purpose of this study was to analyze the changes in CA and possible signaling mechanisms in diabetic rats after metformin intervention. Methods HepG2 cells were cultured after adding different concentrations of metformin. The cell viability was measured using CCK8 kit, and the expression of FXR, MAFG, and CYP8B1 in cells was detected by WB. The rat models of type 2 diabetes were induced by low-dose streptozotocin by feeding a high-fat diet, and the control rats (CON) were fed on normal food; the diabetic rats (DM) were given a high-fat diet without supplementation with metformin, while the metformin-treated diabetic rats (DM + MET) were given a high-fat diet and supplemented with metformin. Biochemical parameters were detected at the end of the test. Expression levels of FXR, CYP8B1, and MAFG were assessed by WB. Serum CA were measured using an enzyme-linked immunosorbent assay (ELISA). Results In HepG2 cells, metformin dose-dependently enhanced the transcriptional activity of FXR and MAFG and inhibited the expression of CYP8B1. Metformin-treated DM rats showed improved glucose and bile acid metabolism. In addition, significantly increased FXR and MAFG and decreased CYP8B1 were observed in DM + MET rats. At the same time, the CA content of metformin-treated rats was lower than that of diabetic rats. Conclusion Changes in CA synthesis after metformin treatment may be associated with inhibition of CYP8B1. These results may play an important role in improving insulin sensitivity after metformin treatment.

Impairment of Intestinal Monocarboxylate Transporter 6 Function and Expression in Diabetic Rats Induced by Combination of High-Fat Diet and Low Dose of Streptozocin: Involvement of Butyrate-Peroxisome Proliferator-Activated Receptor-γ Activation.

Generally, diabetes remarkably alters the expression and function of intestinal drug transporters. Nateglinide and bumetanide are substrates of monocarboxylate transporter 6 (MCT6). We investigated whether diabetes down-regulated the function and expression of intestinal MCT6 and the possible mechanism in diabetic rats induced by a combination of high-fat diet and low-dose streptozocin. Our results indicated that diabetes significantly decreased the oral plasma exposure of nateglinide. The plasma peak concentration and area under curve in diabetic rats were 16.9% and 28.2% of control rats, respectively. Diabetes significantly decreased the protein and mRNA expressions of intestinal MCT6 and oligopeptide transporter 1 (PEPT1) but up-regulated peroxisome proliferator-activated receptor γ (PPARγ) protein level. Single-pass intestinal perfusion demonstrated that diabetes prominently decreased the absorption of nateglinide and bumetanide. The MCT6 inhibitor bumetanide, but not PEPT1 inhibitor glycylsarcosine, significantly inhibited intestinal absorption of nateglinide in rats. Coadministration with bumetanide remarkably decreased the oral plasma exposure of nateglinide in rats. High concentrations of butyrate were detected in the intestine of diabetic rats. In Caco-2 cells (a human colorectal adenocarcinoma cell line), bumetanide and MCT6 knockdown remarkably inhibited the uptake of nateglinide. Butyrate down-regulated the function and expression of MCT6 in a concentration-dependent manner but increased PPARγ expression. The decreased expressions of MCT6 by PPARγ agonist troglitazone or butyrate were reversed by both PPARγ knockdown and PPARγ antagonist 2-chloro-5-nitro-N-phenylbenzamide (GW9662). Four weeks of butyrate treatment significantly decreased the oral plasma concentrations of nateglinide in rats, accompanied by significantly higher intestinal PPARγ and lower MCT6 protein levels. In conclusion, diabetes impaired the expression and function of intestinal MCT6 partly via butyrate-mediated PPARγ activation, decreasing the oral plasma exposure of nateglinide.

Neuroprotection of rhGLP‐1 in diabetic rats with cerebral ischemia/reperfusion injury via regulation of oxidative stress, EAAT2, and apoptosis

Preclinical Research & Development The purpose of the present study is to evaluate the neuroprotective effect of recombinant human glucagon-like peptide-1 (rhGLP-1) as well as to explore corresponding mechanisms in diabetic rats with cerebral ischemia/reperfusion injury induced by middle cerebral artery occlusion (MCAO). Diabetes mellitus was induced by intraperitoneal injection of streptozotocin. The rats were pretreated with rhGLP-1 (20 μg/kg intraperitoneally, thrice a day) for 14 days. Thereafter, the rats were subjected to MCAO 90 min/reperfusion 24 hr. At 2 and 24 hr of reperfusion, the rats were assessed for neurological deficits and subsequently executed for the evaluation of cerebral infarct volume, oxidative stress parameters, and the expression of excitatory amino acid transporter 2 (EAAT2) and apoptotic markers. Results indicate that rhGLP-1 significantly ameliorated neurological deficits and reduced cerebral infarct volume in diabetic MCAO rats. In addition, oxidative stress parameters in ischemic penumbra were significantly alleviated in rhGLP-1-pretreated diabetic MCAO rats. rhGLP-1 significantly upregulated the ratio of Bcl-2/Bax and EAAT2 expression and downregulated cleaved caspase-3 expression in ischemic penumbra of diabetic MCAO rats. Our results suggest that rhGLP-1 could significantly ameliorate neurological deficits and reduce cerebral infarct volume in diabetic MCAO rats, which may be due to the inhibition of oxidative stress and apoptosis and the promotion of EAAT2 expression.

Insulin treatment reverses the increase in atrogin-1 expression in atrophied skeletal muscles of diabetic rats with acute joint inflammation.

BackgroundThe aim of this study was to evaluate the changes in biomarkers of skeletal muscle proteolysis (atrogin-1, muscle RING finger-1 protein [MuRF-1]) and inflammation (nuclear factor kappa-B) in skeletal muscles of rats under two catabolic conditions, diabetes mellitus (DM) and acute joint inflammation, and the effects of insulin therapy.Materials and methodsMale Wistar rats were divided into groups without diabetes – normal (N), saline (NS), or ι-carrageenan (NCa) injection into the tibiotarsal joint – and groups with diabetes – diabetes (D), plus insulin (DI), saline (DS), or ι-carrageenan (DCa) injection into the tibiotarsal joint, or ι-carrageenan injection and treatment with insulin (DCaI). Three days after ι-carrageenan injection (17 days after diabetes induction), tibialis anterior (TA) and soleus (SO) skeletal muscles were used for analysis.ResultsDM alone caused a significant decrease in the mass of TA and SO muscles, even with low levels of atrogenes (atrogin-1, MuRF-1), which could be interpreted as an adaptive mechanism to spare muscle proteins under this catabolic condition. The loss of muscle mass was exacerbated when ι-carrageenan was administered in the joints of diabetic rats, in association with increased expression of atrogin-1, MuRF-1, and nuclear factor kappa-B. Treatment with insulin prevented the increase in atrogin-1 (TA, SO) and the loss of muscle mass (SO) in diabetic-carrageenan rats; in comparison with TA, SO muscle was more responsive to the anabolic actions of insulin.ConclusionAcute joint inflammation overcame the adaptive mechanism in diabetic rats to prevent excessive loss of muscle mass, worsening the catabolic state. The treatment of diabetic-carrageenan rats with insulin prevented the loss of skeletal muscle mass mainly via atrogin-1 inhibition. Under the condition of DM and inflammation, muscles with the prevalence of slow-twitch, type 1 fibers were more responsive to insulin treatment, recovering the ability to grow.

Effects of Sleeve Gastrectomy on Serum 12α-Hydroxylated Bile Acids in a Diabetic Rat Model.

Diabetes mellitus is a prevalent disease that endangers human health. Bariatric surgery can effectively relieve insulin resistance with elevated serum bile acids (BAs). 12α-Hydroxylated BAs were previously reported to be associated with insulin resistance. The aim of this study was to analyze changes in 12α-hydroxylated BA composition and possible associated mechanisms in diabetic rats following sleeve gastrectomy (SG). SG and sham operations were performed in diabetic rats induced by high-fat diet feeding and streptozotocin. Body weight, food intake, oral glucose tolerance test (OGTT), insulin tolerance test (ITT), and serum BAs were analyzed at corresponding time points. Cholesterol 12α-hydroxylase (CYP8B1) and transcription factor V-Maf Avian Musculoaponeurotic Fibrosarcoma Oncogene Homolog G (MAFG) expression levels were assessed by RT-PCR and western blotting. Compared with the SHAM group, the SG group displayed significant weight loss from 6weeks postoperatively, accompanied by decreased food intake from 4weeks after the operation. At 2 and 12weeks postoperatively, the areas under the curve of OGTT and ITT were significantly decreased in the SG group. At 12weeks post-operation, the SG group displayed elevated serum BAs, but the percentage of 12α-hydroxylated BAs was reduced. Furthermore, SG rats exhibited higher MAFG and lower CYP8B1 protein and mRNA levels in the liver (P<0.05). The percentage of 12α-hydroxylated bile acids was reduced after SG, which was relevant with the inhibition of CYP8B1 and overexpression of MAFG. These outcomes may play an important role in the improvement of insulin sensitivity following SG.

Paeoniflorin ameliorates cognitive dysfunction via regulating SOCS2/IRS-1 pathway in diabetic rats

Paeoniflorin is a natural monoterpene glycoside in Paeonia lactiflora pall with various biological properties including promising anti-inflammatory activity. Current evidences support that inflammatory reaction, oxidative stress, as well as abnormal insulin signaling in the hippocampus are potential causes of tau hyperphosphorylation and finally induce cognitive dysfunction. The present study aims to explore the effects of paeoniflorin on the cognitive deficits and investigate the underlying mechanisms in diabetic rats induced by a high-sucrose, high-fat diet and low dose of streptozotocin (STZ). Paeoniflorin treatment effectively improved the performance of diabetic rats in the Morris water maze test via decreasing escape latency and increasing the spent time in the target quadrant. Immunohistochemistry staining also had shown that tau hyperphosphorylation in the hippocampus was prevented after paeoniflorin administration. This function was correlated with its abilities of reducing the brain inflammatory cytokines (IL-1β and TNF-α), decreasing suppressor of cytokine signaling 2 (SOCS2) expressions and promoting insulin receptor substrate-1 (IRS-1) activity. Additionally, we also found paeoniflorin administration significantly promoted the phosphorylation levels of protein kinase B (Akt) and glycogen synthase kinase-3β (GSK-3β). Together, these results showed that paeoniflorin had beneficial effects on relieving diabetes-associated cognitive deficits via regulating SOCS2/IRS-1 pathway and might provide a feasible method for the treatment of diabetes-associated cognitive dysfunction.

Hydrogen sulfide reduced renal tissue fibrosis by regulating autophagy in diabetic rats.

The present study aimed to explore the effect of hydrogen sulfide (H2S) on renal tissue fibrosis and its mechanism in diabetic rats. Rats were randomly divided into four groups (n=13/group): Control group; induced diabetes mellitus group (STZ); induced diabetes mellitus treated with H2S group (STZ + H2S); normal rats treated with H2S group (H2S). The diabetic model was induced by intraperitoneal (i.p.) injections of 40 mg/kg body weight streptozotocin (STZ); the control group was treated with saline every day (i.p); NaHS (100 µmol/kg i.p.) was administered to rats of STZ + H2S group and H2S group. After 8 weeks, rat body weight and 24 h proteinuria levels were determined in each group, renal pathological morphology was analyzed by Masson's trichrome staining, collagen IV content was detected by immunohistochemistry, and periodic acid-Schiff (PAS) staining was performed on renal glomerular and tubular basement membranes. The expression levels of matrix metalloproteinase 9 (MMP9), MMP7, tissue inhibitor of metalloproteinase 1 (TIMP1), superoxide dismutase (SOD), serine/threonine kinase AKT, transforming growth factor (TGF)-β1, nuclear factor (NF)-κB and several autophagy related proteins were assessed by western blot analysis. Compared with the control group, renal tissue fibrosis was observed, collagen IV expression and the 24 h proteinuria quantity was markedly increased and the amount of PAS positive material in renal glomerular and tubular basement membranes was notably increased in STZ-treated rats. Furthermore, the expression levels of MMP9, MMP7, TIMP1, autophagy-associated proteins, AKT, TGF-β1 and NF-κB protein were significantly increased, and SOD expression levels were significantly decreased in the STZ group compared with the control (P<0.05). In the H2S+STZ group, renal tissue fibrosis and the expression of collagen IV were improved, 24 h proteinuria was decreased, the amount of PAS positive material in renal glomerular and tubular basement membranes was decreased, the expression levels MMP9, MMP7, TIMP1, autophagy-associated proteins, AKT, TGF-β1 and NF-κB protein were significantly decreased, and the expression levels of SOD were significantly increased compared with the STZ group (P<0.05). In conclusion, H2S may improve renal tissue fibrosis by inhibiting autophagy, upregulating SOD and downregulating AKT, TGF-β1 and NF-κB.

Protection of sericin to retinal microvessels and its mechanism in diabetic rats

Background Diabetic retinopathy (DR) is a chronic inflammatory disease, with pathological changes of retinal microvessels.Studies demonstrated that sericin has anti-inflammation and anti-oxidation effects, inferring that sericin might play a protective effect on diabetic microangiopathy. Objective This study was to investigate the effects of sericin on intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and Cx43 expressions in retina and explore the protection of sericin to retinal microangiopathy in diabetic rats. Methods Forty-eight specific pathogen free male SD rats were randomly divided into normal control group, diabetic model group, sericin-treated group and calcium dobesilate-treated group, with 12 rats for each group.The diabetic models were established by intraperitoneal injection of streptozotocin (STZ) for 3 consecutive days and feeding up with high lipid foods.Normal saline solution, 2.4 g/(kg·d) sericin solution and 0.2 g/(kg·d) calcium dobesilate were used by gavage administration in the rats of the diabetic model group, sericin-treated group and calcium dobesilate-treated for 3 months group, respectively.The rats were sacrificed and retinal sections were prepared, and the retinal morphology was examined by hematoxylin-eosin staining.The expressions of ICAM-1, VCAM-1 and Cx43 proteins and mRNA in retinas were detected by Western blot assay and reverse transcription PCR.The use and care of the rats complied with Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission and ARVO statement. Results The retinal structure was normal in the normal control group.The swell and rupture of inter limiting membrane (ILM), scatter vascular endothelial cell nuclei breakthrough ILM and decrease of retinal ganglion cells (RGCs) were displayed in the diabetic model group; while in the sericin-treated group and calcium dobesilate-treated group, the mild thickening of ILM and disorder of retinal cells were obtained.The relative expression levels of ICAM-1 and VCAM-1 were significantly raised and those of Cx43 were reduced in the diabetic model group, sericin-treated group and calcium dobesilate-treated group when compared with the normal control group (all at P<0.05). Compared with the diabetic model group, the expressions of ICAM-1 and VCAM-1 proteins and mRNA in the sericin-treated group were significantly reduced (ICAM-1 protein: 0.834 3±0.032 1 vs. 0.918 9±0.042 4; VCAM-1 protein: 0.726 4±0.011 2 vs. 1.235 0±0.078 9; ICAM-1 mRNA: 0.716 3±0.008 6 vs. 0.956 8±0.012 5; VCAM-1 mRNA: 0.393 7±0.035 0 vs.0.477 9±0.020 6) and those of Cx43 protein and mRNA were evidently elevated (Cx43 protein: 0.133 1±0.015 3 vs.0.039 2±0.002 0; Cx43 mRNA: 0.676 8±0.064 8 vs.0.430 8±0.111 3) (all at P<0.05). Conclusions Sericin can relieve retinal microangiopathy and protect retina against the pathogenesis and development of DR by down-regulating the expressions of ICAM-1, VCAM-1 and up-regulating the expression of Cx43 in retinas of diabetic rats. Key words: Sericins/pharmacology; Anti-inflammatory agents/pharmacology; Diabetic retinopathy/physiopathology; Gene expression; Intercellular adhesion molecule-1; Vascular cell adhesion molecule-1; Connexin 43; Retinal vessels/physiopathology; Rats, Sprague-Dawley