Insulin Resistance In Obese Rats Research Articles

The Influence of Catechin on Adiponectin and Insulin Resistance in Obese Rats

Obesity represented as an abnormal accumulation of visceral fat. The synthesis of adiponectin has been linked to visceral fat accumulation. Obesity, and cardiovascular disease have all been linked to decreased levels of adiponectin. This study included the effect of catechin administration for 30 days on lipid profile, glucose, adiponectin and insulin serum levels as well as IR of obese female rats. Twenty female rats were conducted to the experiment where divide to four equal groups as; negative normal group received normal diet for all experiment time (60 days); positive obese control group received high fat diet (HFD) for (60 days); GTC-fed group fed HFD; ATV-fed group this group received ATV as cholesterol lowering drug. The significant differences considered at (p < 0.05 with 95% CI). The study revealed that the levels of Total-Ch, triglycerides and glucose were significantly higher in positive than negative control group. Additionally, a significant decreased Total-Ch, triglycerides and glucose level of Catechin treatment group than positive control group. Moreover, a significant reduction of adiponectin means levels obtained in positive control group compared to negative control and Catechin treatment groups. Furthermore, a significant difference of IR obtained between means of positive control group with Catechin treatment group. HDL-C levels were also differed significantly between positive control groups and Catechin treatment group. In conclusion this study exposed a positive influence of catechin administration on obesity lethal factors such as cholesterol, hyperglycemia, IR and the serum concentration of adiponectin in obese female rats.

Combined Sleeve Gastrectomy and Omentoplasty Improves Inflammation and Insulin Resistance in Obese Rats with Type II Diabetes Mellitus: A Randomized Controlled Trials

BACKGROUND: Diabetes mellitus (DM) is often associated with obesity, which can lead to chronic inflammation. Sleeve gastrectomy (SG) is a common treatment for obesity. Combining SG with omentoplasty, might help reducing inflammation in pancreatic beta cells. However, there is limited research regarding the combined effects of SG and omentoplasty in type 2 DM (T2DM). This study was conducted to fill this gap by evaluating the impact on body weight, insulin resistance, glucagon expression, and levels of interleukins (IL)-1, IL-6, and IL-10 in obese rats with type II DM.METHODS: An experimental study was conducted on 18 obese Wistar rats with DM that were randomized into: control, T1 (SG), and T2 (SG + omentoplasty). SG involved the surgical removal of a portion of the stomach to reduce its size, while omentoplasty utilized the omentum to target inflammation in pancreatic beta cells. Venous blood samples were taken from subjects one day before and ten days after the intervention to measure the biomedical parameters with various methods. Data was statistically analyzed using paired t-tests for pre-test and post-test differences, and Post Hoc tests or Mann-Whitney tests for hypothesis testing.RESULTS: All rats were confirmed to have obesity and DM according to the Lee index and blood glucose levels. T2 group exhibited a significant decrease in body weight, homeostatic model assessment of insulin resistance (HOMA-IR) values were lower, and glucagon expression, IL-1, IL-6, and IL-10 levels were significantly greater compared to both control and T1 groups.CONCLUSION: The combination of SG and omentoplasty significantly improves inflammation and insulin resistance in obese rats with T2DM.KEYWORDS: diabetes mellitus, sleeve gastrectomy, omentoplasty, inflammation, obesity

Activation of mitoKATP channels induces penile vasodilation and inhibits mitochondrial respiration and ROS production: Role of NO

ObjectiveMitochondrial ATP-sensitive K+ (mitoKATP) channels are involved in neuronal and cardiac protection from ischemia and oxidative stress. Penile erection is a neurovascular event mediated by relaxation of the erectile tissue via nitric oxide (NO) released from nerves and endothelium. In the present study, we investigated whether mitoKATP channels play a role in the control of penile vascular tone and mitochondrial dynamics, and the involvement of NO. MethodsThe effect of the selective mitoKATP activator BMS191095 was examined on vascular tone, on mitochondrial bioenergetics by real-time measurements with Agilent Seahorse and on ROS production by MitoSOX fluorescence in freshly isolated microarteries. ResultsBMS191095 and diazoxide relaxed penile arteries, BMS191095 being one order of magnitude more potent. BMS191095-induced relaxations were reduced by mechanical endothelium removal and by inhibitors of the nitric oxide synthase (NOS) and PI3K enzymes. The NO-dependent component of the relaxation to BMS191095 was impaired in penile arteries from insulin resistant obese rats. The blockers of mitoKATP channel 5-HD, sarcolemma KATP (sarcKATP) channel glibenclamide, and large conductance Ca2+-activated K+ (BKCa) channel iberiotoxin, inhibited relaxations to BMS191095 and to the NO donor SNAP. BMS191095 reduced the mitochondrial bioenergetic profile of penile arteries and attenuated mitochondrial ROS production. Blockade of endogenous NO impaired and exogenous NO mimicked, respectively, the inhibitory effects of BMS191095 on basal respiration and oxygen consumed for ATP synthesis. Exogenous NO exhibited dual inhibitory/stimulatory effects on mitochondrial respiration. ConclusionsThese results demonstrate that selective activation of mitoKATP channels causes penile vasodilation, attenuates ROS production and inhibits mitochondrial respiration in part by releasing endothelial NO. These mechanisms couple blood flow and metabolism in penile arterial wall and suggest that activation of vascular mitoKATP channels may protect erectile tissue against ischemic injury.

Comparison of Sitagliptin with Vildagliptin's effects on Mitochondrial Activity, Heart Rate Variability, and Cardiac Performance in Obese Insulin-Resistant Rats

Context and Objective: It has been demonstrated that a prolonged high-fat diet (HFD) can lead to insulin resistance, which is typified by hyperinsulinemia and metabolic inflexibility. Heart failure, cardiac mitochondrial dysfunction, and cardiac sympathovagal imbalance are all linked to insulin resistance. Oral anti-diabetic medications called sitagliptin and vildagliptin, which block dipeptidyl peptidase-4 (DPP-4), are frequently administered to individuals suffering from cardiovascular disease. Thus, using a mouse model of insulin resistance, we aimed to investigate the effects of sitagliptin and vildagliptin in this work. Method of Experimentation: Male For a period of 12 weeks, 180–200 g Wistar rats were fed either an HFD (59% energy from fat) or a regular diet (20% energy from fat). After that, these rats were split up into three subgroups and given either vehicle for an additional 21 days, sitagliptin (30 mg/kg/day-1), vildagliptin (3 mg/kg−1 day−1), or both days. Heart rate variability (HRV), cardiac function, oxidative stress, metabolic parameters, and cardiac mitochondrial function were all measured Important Findings: In rats fed a high-fat diet (HFD), they developed insulin resistance, which was manifested as a decrease in high-density lipoprotein (HDL) and an increase in body weight, plasma insulin, total cholesterol, and oxidative stress levels. Furthermore, HFD rats showed evidence of cardiac dysfunction, decreased HRV, cardiac mitochondrial dysfunction, and alterations in cardiac mitochondrial morphology. Vildagliptin and sitagliptin both raised HDL levels while lowering plasma insulin, total cholesterol, and oxidative stress. Additionally, sitagliptin and vildagliptin fully restored HRV and reduced cardiac dysfunction as well as cardiac mitochondrial dysfunction Conclusions and Significance: In obese insulin-resistant rats, vildagliptin and sitagliptin both had comparable cardioprotective effects.

Protective effects of copper nanoparticles green-formulated by Ginkgo biloba leaf extract on cardiac function in obese insulin-resistant rats

Ginkgo biloba has been revealed to have cardioprotective and antioxidant potentials. But, the efficacy of the copper nanoparticles green-formulated by Ginkgo biloba on the cardiac mitochondria, heart rate variability, and cardiac function are poorly defined. Initially, the plan, Ginkgo biloba extract was coated on the surface of graphene oxide. The as-prepared nanoparticles were analyzed using transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–Vis), field emission-scanning electron microscopy (FE-SEM), and fourier-transform infrared spectroscopy (FT-IR) analysis. It has been shown that the Cu NPs with spherical shape and uniform size were dispersed on the NPs surface. In the animal part, 60 % of energy from fat was used for inducing obesity. Then, the animals were divided to four groups: control rats were fed with the usual diet, untreated rats were fed with high-fat-diet, and treated rats were fed with high-fat-diet + Cu NPs@Ginkgo biloba (30 and 60 µg/kg/day). In this study, the cardiac mitochondrial function, cardiac function, heart rate variability (HRV), and metabolic parameters were determined. The levels of oxidative stress, total cholesterol, plasma insulin levels, visceral fat, and body weight increased and cardiac mitochondrial dysfunction and HRV reduced in the untreated group. Treatment with Cu NPs@Ginkgo biloba reduced oxidative stress, homeostasis model assessment index, total cholesterol, and plasma insulin and regulated cardiac mitochondrial function and HRV in rats. The above results confirm the cardioprotective effects of Cu NPs@Ginkgo biloba. According to the above findings, the recent nanoparticles may be used as a cardioprotective drug or supplement for the treatment of cardiovascular diseases after doing the clinical trial studies in humans.

Cyclosorus Terminans Extract Alleviates Neuroinflammation in Insulin Resistant Rats.

High-fat diet consumption for an extended period causes obesity, systemic metabolic disturbance, and brain insulin resistance, resulting in neuroinflammation. Although the beneficial effect of Cyclosorus terminans extract on obesity-related insulin resistance has been demonstrated, little is known about how it affects neuroinflammation and brain insulin resistance in obese rats. Male Wistar rats were given either a normal diet (ND, n = 6) or a high-fat diet (HFD, n = 24) for a total of 14 weeks. At the beginning of the week, 13 rats in the ND group were given vehicle orally for 2 weeks, while rats on HFD diets were randomized to one of four groups and given either vehicle, 100 mg/kg/day of Cyclosorus terminans extract, 200 mg/kg/day of Cyclosorus terminans extract, or 20 mg/kg/day of pioglitazone orally for 2 weeks. After the experimental period, blood and brain samples were taken to assess metabolic and brain parameters. HFD-fed rats had obesity, systemic and brain insulin resistance, brain inflammation, microglial and astrocyte hyperactivity, and brain necroptosis. Treatment with 200 mg/kg/day of Cyclosorus terminans extract and pioglitazone equally attenuated obesity, insulin resistance, brain insulin dysfunction, and neuroinflammation in insulin resistant rats. Our findings suggest that Cyclosorus terminans extract may hold promise as a therapeutic agent for insulin resistance and neuroinflammation in obese conditions.

Preparation and formulation of Ag NPs for the anticancer activities and its protective effects on cardiac function, heart rate variability, and cardiac mitochondria in obese insulin-resistant rats

Panax ginseng as an ethnomedicinal plant has many therapeutic effects in the traditional medicine. This medicinal plant, having antioxidant substances, can protect body cells from various damages and prevent cancer. Also, folic acid in this plant helps the body to produce new cells and reduces the possibility of heart disease and colon cancer. In the recent years, the silver nanoparticles green-mediated by ethno medicinal plants have been used for the treatment of several kinds of cancers and heart disease. Now, we investigated the silver nanoparticles green-synthesized according to green chemistry rules using the aqueous extract of Panax ginseng leaf for the treatment of lung carcinoma and protective effects on cardiac function, heart rate variability, and cardiac mitochondria in obese insulin-resistant rats. The green-synthesized silver nanoparticles were characterized using different techniques such as FE-SEM, UV–Vis, XRD, and TEM. The FE-SEM and TEM results confirm spherical morphology for the nanoparticles with size of 12.11 to 43.33 nm. The IC50 of the silver nanoparticles was 311, 293, 375, and 250 against EKVX, HOP-62, A549 and NCI-H460, respectively. In the in vivo part of this study, after treating 12 weeks with high-fat-diet, then 28 days with Ag NPs (20 and 40 µg/kg/day, respectively), the metabolic parameters, heart rate variability (HRV), cardiac function, and cardiac mitochondrial function were determined. Silver nanoparticles at both concentrations significantly decreased the plasma insulin, total cholesterol, homeostasis model assessment index, and oxidative stress levels and restored the HRV, cardiac function, and cardiac mitochondrial function. We concluded that silver nanoparticles at both concentrations exerted cardioprotective effects against mitochondrial dysfunction and cardiac dysfunction in obese insulin-resistant rats.

Resistant starch from black rice, Oryza sativa L. var. ameliorates renal inflammation, fibrosis and injury in insulin resistant rats.

It has recently been reported that black rice (BR) extract has anti-obesity, anti-diabetic, and anti-osteoporosis effects. It has been shown to reduce obese-related kidney dysfunction in animal models. This study aimed to investigate the effect of resistant starch from BR (RS) on renal inflammation, oxidative stress, and apoptosis in obese insulin resistant rats. Male Wistar rats were divided into six groups: normal diet (ND), ND treated with 150 mg of RS (NDRS150), high-fat (HF) diet, HF treated with 100 and 150 mg of RS (HFRS100), (HFRS150), and HF treated with metformin as a positive control. Insulin resistance was shown in the HF rats by glucose intolerance, increased insulin, total area under the curve of glucose and homeostasis model assessment of insulin resistance and dyslipidemia. The resulting metabolic disturbance in the HF rats caused renal inflammation, fibrosis and apoptosis progressing to kidney injury and dysfunction. Prebiotic RS including anthocyanin from BR at doses of 100 and 150 mg ameliorated insulin resistance, dyslipidemia and liver injury. Treatment with RS reduced TGF-β fibrotic and apoptotic pathways by inhibition of NF-κB and inflammatory cytokines which potentially restore kidney damage and dysfunction. In conclusion, prebiotic RS from BR ameliorated obesity induced renal injury and dysfunction by attenuating inflammatory, fibrotic, and apoptotic pathways in insulin resistant rats induced by HF.

Effects of Rosa roxburghii on insulin resistance in obese rats and its mechanisms

Objective: To investigate the effects of Rosa roxburghii on insulin resistance in obese rats and the regulation of phosphatidylinositol 3-kinase (PI3K)/ protein kinase Bβ(PKBβ/Akt2)/ glucose transporter 4(GLUT4) signaling pathway. Methods: Five-week-old male SD rats were randomly divided into normal control group (NC), model group (M), positive control group (PC), low-dose rosa roxburghii group (LD) and high-dose rosa roxburghii group (HD), with 10 rats in each group. The rats in the NC group were fed with normal diet, while those in the M, PC, LD and HD groups were fed with high-fat diet. From the 13th week, according to the dose standard of 6 ml/kg, rats in the LD group were intragastrically administered with 100 mg/kg Rosa roxburghii Tratt, the HD group were treated with 300 mg/kg Rosa roxburghii Tratt, the PC group were treated with 0.11 g/kg Chiglitazar sodium, and the NC and M groups were intragastrically administered with the same volume of normal saline. The body weight was measured every week until 20 weeks. The rats were sacrificed 24 h after the last experiment. Blood and skeletal muscle were collected. Serum total cholesterol (TC) and triglyceride (TG) contents were detected by colorimetric method, serum superoxide dismutase (SOD) activity was detected by xanthine oxidase method, serum malondialdehyde (MDA) content was detected by thiobarbituric acid method, blood glucose (FBG) value was detected by glucose oxidase method, insulin (FINS) content was detected by ELISA, and PI3K, Akt2, and GLUT4 protein and gene expressions were detected by Western blot and reverse transcription-polymerase chain reaction (RT-PCR). Results: Compared with the NC group, the body weight, serum MDA, TG, TC, FBG, FINS, HOMA-IR levels in the M group were significantly increased (P＜0.01), while SOD activity, PI3K、Akt2、GLUT4 protein and mRNA expression levels were significantly increased(P＜ 0.01). Compared with group M, the body weight, serum MDA, TG, TC, FBG, FINS, and HOMA-IR were decreased significantly in LD group, HD group and PC group (P＜0.05 or P＜0.01), while SOD activity, PI3K, Akt2, GLUT4 protein and mRNA expression levels were increased significantly (P＜0.05 or P＜0.01). Conclusion: Rosa roxburghii can improve insulin resistance in obese rats by antioxidant stress and up-regulating the expressions of PI3K, Akt2, and GLUT4 proteins and genes, which may be related to the PI3K/Akt2/GLUT4 signaling pathway.

Naringin Ameliorates Skeletal Muscle Atrophy and Improves Insulin Resistance in High-Fat-Diet-Induced Insulin Resistance in Obese Rats.

Obesity causes progressive lipid accumulation and insulin resistance within muscle cells and affects skeletal muscle fibres and muscle mass that demonstrates atrophy and dysfunction. This study investigated the effects of naringin on the metabolic processes of skeletal muscle in obese rats. Male Sprague Dawley rats were divided into five groups: the control group with normal diet and the obese groups, which were induced with a high-fat diet (HFD) for the first 4 weeks and then treated with 40 mg/kg of simvastatin and 50 and 100 mg/kg of naringin from week 4 to 8. The naringin-treated group showed reduced body weight, biochemical parameters, and the mRNA expressions of protein degradation. Moreover, increased levels of antioxidant enzymes, glycogen, glucose uptake, the expression of the insulin receptor substrate 1 (IRS-1), the glucose transporter type 4 (GLUT4), and the mRNA expressions of protein synthesis led to improved muscle mass in the naringin-treated groups. The in vitro part showed the inhibitory effects of naringin on digestive enzymes related to lipid and glucose homeostasis. This study demonstrates the potential benefits of naringin as a supplement for treating muscle abnormalities in obese rats by modulating the antioxidative status, regulating protein metabolism, and improved insulin resistance in skeletal muscle of HFD-induced insulin resistance in obese rats.

N-Stearoylethanolamine Inhibits Integrin-Mediated Activation, Aggregation, and Adhesion of Human Platelets.

N-stearoylethanolamine (NSE), a lipid mediator that belongs to the N-acylethanolamine (NAE) family, has anti-inflammatory, antioxidant, and membranoprotective actions. In contrast to other NAEs, NSE does not interact with cannabinoid receptors. The exact mechanism of its action remains unclear. The aim of this study is to evaluate the action of NSE on activation, aggregation, and adhesion of platelets that were chosen as a model of cellular response. Aggregation of platelets was measured to analyze the action of NSE (10^-6-10^-10 M) on platelet reactivity. Changes in granularity and shape of resting platelets and platelets stimulated with ADP in the presence of NSE were monitored by flow cytometry, and platelet deganulation was monitored by spectrofluorimetry. In vivo studies were performed using obese insulin-resistant rats. Binding of fibrinogen to the GPIIb/IIIa receptor was estimated using indirect ELISA and a scanning electron microscopy (SEM). It was found that NSE inhibits the activation and aggregation of human platelets. Our results suggest that NSE may decrease the activation and subsequent aggregation of platelets induced by ristocetin, epinephrine, and low doses of ADP. NSE also reduced the binding of fibrinogen to GPIIb/IIIa on activated platelets. These effects could be explained by the inhibition of platelet activation mediated by integrin receptors: the GPIb-IX-V complex for ristocetin-induced activation and GPIIb/IIIa when epinephrine and low doses of ADP were applied. The anti-platelet effect of NSE complements its anti-inflammatory effect and allows us to prioritize studies of NSE as a potent anti-thrombotic agent. SIGNIFICANCE STATEMENT: N-stearoylethanolamine (NSE) was shown to possess inhibitory action on platelet activation, adhesion, and aggregation. The mechanism of inhibition possibly involves integrin receptors. This finding complements the known anti-inflammatory effects of NSE.

Bacillus natto ameliorates obesity by regulating PI3K/AKT pathways in rats

Obesity has become the second leading cause of death globally after smoking. Probiotic Bacillus has noticeable weight-loss effects. This study aimed to investigate the mechanism of Bacillus natto (B. natto) on insulin resistance in obese rats. The obese rat model was established with a HFD for 8 weeks, and then, B. natto was orally administered at different dosed for 8 weeks. The results showed that B. natto significantly reduced the body weight, epididymis fat weight, total cholesterol, triglyceride, low-density lipoprotein while increasing the level of high-density lipoprotein in HFD rats. B. natto intervention improved liver injury by reducing alanine aminotransferase and aspartate transaminase levels. B. natto intervention was also beneficial for the inhibition of hepatic steatosis and inflammation factors in HFD rats by inhibiting the mRNA expression level of SREBP-1 gene. Moreover, B. natto improved insulin resistance homeostasis by activating PI3K/AKT signaling pathway. Therefore, B. natto could be used as a potential probiotic supplement to provided new strategy for the prevention and treatment of metabolic diseases such as obesity.

Combination of Aerobic Training and Cocoa Flavanols as Effective Therapies to Reduce Metabolic and Inflammatory Disruptions in Insulin-Resistant Rats: The Exercise, Cocoa, and Diabetes Study.

We aimed to investigate the combined effects of aerobic exercise (EXE) and cocoa flavanol (COCOA) supplementation on performance, metabolic parameters, and inflammatory and lipid profiles in obese insulin-resistant rats. Therefore, 32 male Wistar rats (230-250g) were fed a high-fat diet and a fructose-rich beverage for 30days to induce insulin resistance. Next, the rats were randomized into four groups, orally administered placebo solution or COCOA supplementation (45mg·kg-1), and either remained sedentary or were subjected to EXE on a treadmill at 60% peak velocity for 30min, for 8 weeks. Blood samples and peripheral tissues were collected and processed to analyze metabolic and inflammatory parameters, lipid profiles, and morphological parameters. Supplementation with COCOA and EXE improved physical performance and attenuated body mass gain, adipose index, and adipocyte area. When analyzed as individual interventions, supplementation with COCOA and EXE improved glucose intolerance and the lipid profile reduced the concentrations of leptin, glucose, and insulin, and reduced homeostasis assessment index (all effects were p < .001 for both interventions), while ameliorated some inflammatory mediators in examined tissues. In skeletal muscles, both COCOA supplementation and EXE increased the expression of glucose transporter (p < .001 and p < .001), and combined intervention showed additive effects (p < .001 vs. COCOA alone or EXE alone). Thus, combining COCOA with EXE represents an effective nonpharmacological strategy to treat insulin resistance; it could prevent Type 2 diabetes mellitus by improving physical performance, glucose metabolism, neuroendocrine control, and lipid and inflammatory mediators in the liver, pancreas, adipose tissue, and skeletal muscle in obese male insulin-resistant rats.

Adrenomedullin ameliorates palmitic acid-induced insulin resistance through PI3K/Akt pathway in adipocytes.

White adipose tissue (WAT) dysfunction has been associated with adipose tissue low-grade inflammation and oxidative stress leading to insulin resistance (IR). Adrenomedullin (ADM), an endogenous active peptide considered as an adipokine, is associated with adipocytes function. We evaluated the protective effects of ADM against IR in 3T3-L1 adipocytes treated by palmitic acid (PA) and in visceral white adipose tissue (vWAT) of obese rats fed with high-fat diet. We found that endogenous protein expressions of ADM and its receptor in PA-treated adipocytes were markedly increased. PA significantly induced impaired insulin signaling by affecting phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) axis and glucose transporter-4 (GLUT-4) levels, whereas ADM pretreatment enhanced insulin signaling PI3K/Akt and GLUT-4 membrane protein levels, decreased pro-inflammatory cytokines tumor necrosis factor α (TNFα), interleukin-1β (IL-1β) and IL-6 levels, and improved oxidative stress accompanied with reduced reactive oxygen species (ROS) levels and increased anti-oxidant enzymes manganese superoxide dismutase 2 (SOD2), glutathione peroxidase (GPx1) and catalase (CAT) protein expressions. Furthermore, ADM treatment not only improved IR in obese rats, but also effectively restored insulin signaling, and reduced inflammation and oxidative stress in vWAT of obese rats. This study demonstrates a prevention potential of ADM against obesity-related metabolic disorders, due to its protective effects against IR, inflammation and oxidative stress in adipocytes.

Blocking myeloid differentiation factor 2 improves cognitive function via reducing microglia activation, neuroinflammation, brain mitochondrial dysfunction and dendritic spine loss in obese insulin‐resistant rats

Chronic high fat diet (HFD) consumption induces not only low-grade systemic inflammation and obese-insulin resistance, but also initiates neuroinflammation via activating myeloid differentiation factor 2 (MD-2)/toll-like receptor 4 (TLR4) complex, resulting in brain pathologies and cognitive impairment. Recently, MD-2 inhibitor (L6H21) has been shown to alleviate systemic inflammation. However, the effect of L6H21 on the cognitive function and brain pathologies of HFD-induced obese insulin-resistant condition has not been investigated. Male Wistar rats were fed either a normal diet (ND; n=8) or HFD (n=40) for 16 weeks. After 12th week of dietary periods, HFD-fed rats were divided into 5 groups (n=8/group). Each group was orally administered either vehicle, 10 mg/kg/day of L6H21, 20 mg/kg/day of L6H21, 40 mg/kg/day of L6H21, or 300 mg/kg/day of metformin for 4 weeks. For ND-fed rats, animals were orally administered vehicle for 4 weeks. At the end of experimental protocol, the novel object location (NOL) test was examined in each animal. Then, blood was collected before animals were sacrificed. Brains were rapidly removed to determine microglial activity, dendritic spine density, inflammatory cytokines, mitochondrial function, and insulin signaling. HFD-fed rats showed peripheral and brain insulin resistance, as indicated by impaired glucose tolerance and reduced brain insulin receptor substrate (IRS) level. In addition, HFD-fed rats developed brain pathologies, and cognitive impairment, as indicated by increased brain TNF-α level, increased microglial hyperactivity, increased mitochondrial reactive oxygen species (ROS), increased Bax/Bcl2 level, reduced dendritic spine density, and reduced preference indexes of NOL phase. Although L6H21 (20mg/kg/day, 40 mg/kg/day) and metformin alleviated HFD-induced brain pathologies and cognitive impairment, L6H21 at 40mg/kg/day and metformin had the highest efficacy for the neuroprotection in obese insulin-resistant rats through inhibiting neuroinflammation, oxidative stress, microglial activation, neuronal apoptosis and improving dendritic spine density, resulting in restoring cognitive function (p<0.05, Figure 1). These findings suggest that MD-2 inhibitor may be the other drug of choice for improving brain function in the obese-insulin resistant condition.

Abstract 15180: Myeloid Differentiation Factor 2 Inhibitor Improves Left Ventricular Function And Heart Rate Variability Via Attenuating Cardiac Mitochondrial Dysfunction In Pre-diabetic Rats

Introduction: Systemic inflammation is known as a key mediator of left ventricular (LV) dysfunction in pre-diabetic models including obese-insulin resistance. In obese rats, lipopolysaccharide activates myeloid differentiation factor 2 (MD2)/toll-like receptor 4 complex, leading to systemic inflammation. Previously, MD2 inhibitor L6H21 (20 mg/kg) was shown to effectively reduce systemic inflammation in obese mice. However, its potential benefits on the heart and the underlying mechanisms in pre-diabetic obese-insulin resistant rats are unknown. Hypothesis: L6H21 exerts cardiometabolic protection in pre-diabetic rats by improving LV function and heart rate variability (HRV) via reducing cardiac mitochondrial dysfunction. Methods: Male Wistar rats were fed either a normal diet (n=8) or high-fat diet (HFD, n=40) for 12 weeks. In HFD group, rats were divided into 5 groups (n=8/group): 1) vehicle (1% Na-carboxymethyl cellulose), 2) metformin (300 mg/kg, positive control), 3-5) L6H21 at 10, 20, and 40 mg/kg. After 4 weeks of treatments, LV function and HRV were examined. Heart tissue was assessed for mitochondrial function. Results: Pre-diabetic rats had impaired glucose tolerance, depressed HRV, and decreased LV ejection fraction (LVEF), indicating cardiac autonomic imbalance and LV dysfunction. Cardiac mitochondrial dysfunction was also observed, shown by increased mitochondrial ROS levels, mitochondrial depolarization, and mitochondrial swelling. Although L6H21 at 20 and 40 mg/kg improved insulin sensitivity, cardiac autonomic balance, LV function, and mitochondrial function, L6H21 at 40 mg/kg exerted the highest cardioprotective effects, compared to metformin, in pre-diabetic rats by restoring LV function, HRV, and cardiac mitochondrial function (Fig) . Conclusions: L6H21 exerted cardiometabolic protection in pre-diabetic rats by improving insulin sensitivity and cardiac mitochondrial function, leading to restoring LV function.

Necroptosis inhibitor directly reduced left ventricular dysfunction in obese-insulin resistant rats, independent of the metabolic status

Abstract Background The number of obese people is increasing globally. Our previous studies showed that chronic high-fat diet (HFD) consumption led to obesity with peripheral insulin resistance, which was associated with left ventricular (LV) dysfunction. Mechanistically, cardiac mitochondrial dysfunction and cell death are proposed as an underlying mechanism for LV dysfunction in obese subjects. Recently, necroptosis was defined as a novel cell death pathway, which can be found in various types of cardiac diseases such as myocardial ischaemia and heart failure. Pharmacological inhibition of necroptosis by necrostatin 1 (nec-1) provided the favorable outcomes to those cardiac diseases. However, the roles of necroptosis and the effects of nec-1 on the heart of obese-insulin resistant rats have never been investigated. Purpose We hypothesized that nec-1 attenuates LV dysfunction by reducing cardiac mitochondrial dysfunction, necroptosis, and apoptosis in obese-insulin resistant rats. Methods Male rats (n=32) were fed with normal diet (ND) or HFD for 12 weeks to induce obese-insulin resistance. At weeks 13, HFD-fed rats were assigned into 3 interventional groups (n=8/group) as follows: 1) HFD-fed rats treated with saline, 2) HFD-fed rats treated with nec-1 (1.65 mg/kg/day, subcutaneous injection), 3) HFD-fed rats treated with metformin (300 mg/kg/day, oral gavage feeding, served as a positive control). ND rats were treated with saline. Rats received their assigned interventions for additional 7 weeks. Blood pressure (BP), cardiac sympathovagal balance, and LV function were determined. At the end, the heart was excised to determine cardiac mitochondrial function including mitochondrial respiration, reactive oxygen species (ROS) levels, membrane potential changes, swelling, as well as apoptosis and necroptosis protein levels. Results HFD-fed rats had increased body weight, visceral fat deposition, hyperinsulinemia with euglycemia, and dyslipidemia. Moreover, HFD-fed rats had increased systolic and diastolic BP, reduced cardiac sympathovagal balance, and %LV ejection fraction (LVEF) (Fig. 1A). For mitochondrial function, respiratory control ratio was decreased, ROS levels were increased, along with mitochondrial membrane depolarization and swelling (Fig. 1B). Both necroptosis and apoptosis were observed in HFD-fed rats. Treatment with nec-1 reduced systolic and diastolic BP, cardiac sympathovagal imbalance, and increased %LVEF (Fig. 1A). Necroptosis and apoptosis were reduced, and all mitochondrial function parameters were improved in nec-1 treated rats (Fig. 1B). However, the metabolic parameters were not modified by nec-1. Treatment with metformin had similar benefits as nec-1 (Fig. 1), with additional improvement in metabolic parameters in HFD-fed rats. Conclusion Nec-1 directly improves LV function in obese-insulin resistant rats via attenuating cardiac mitochondrial dysfunction and cell death, independent of metabolic parameters. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Science and Technology Development Agency, Thailand Research Fund (TRF)

Grape polyphenols and exercise training have distinct molecular effects on cardiac hypertrophy in a model of obese insulin-resistant rats

Obesity and exercise lead to structural changes in heart such as cardiac hypertrophy. The underlying signaling pathways vary according to the source of the overload, be it physiological (exercise) or pathologic (obesity). The physiological pathway relies more on PI3K-Akt signaling while the pathologic pathway involves calcineurin-Nuclear factor of activated T-cells activation and fibrosis accumulation. Independently, exercise and polyphenols have demonstrated to prevent pathologic cardiac hypertrophy. Therefore, we investigated the molecular adaptations of the combination of exercise training and grape polyphenols supplementation (EXOPP) in obese high-fat fed rats on heart adaptation in comparison to exercise (EXO), polyphenols supplementation (PP) and high-fat fed rats (HF), alone. Exercised and PP rats presented a higher heart weight/body weight ratio compared to HF rats. EXO and EXOPP depicted an increase in cell-surface area, P-Akt/Akt, P-AMPK/AMPK ratios with a decreased fibrosis and calcineurin expression, illustrating an activation of the physiological pathway, but no additional benefit of the combination. In contrast, neither cell-surface area nor Akt signaling increased in PP rats; but markedly decreased fibrosis, calcineurin expression, systolic blood pressure, higher SERCA and P-Phospholamdan/Phospholamdan levels were observed. These data suggest that PP rats have a shift from pathologic toward physiological hypertrophy. Our study demonstrates that polyphenols supplementation has physical-activity-status-specific effects; it appears to be more protective in sedentary obese insulin-resistant rats than in the exercised ones. Exercise training improved metabolic and cardiac alterations without a synergistic effect of polyphenols supplementation. These data highlight a greater effect of exercise than polyphenols supplementation for the treatment of cardiac alterations in obese insulin-resistant rats.

PCSK9 inhibitor effectively attenuates cardiometabolic impairment in obese-insulin resistant rats

Long-term high-fat diet consumption causes obese-insulin resistance and cardiac mitochondrial dysfunction, leading to impaired left ventricular (LV) function. Atorvastatin effectively improved lipid profiles in obese patients. However, inadequate reduction in low density lipoprotein cholesterol (LDL-C) level was found. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor effectively reduced LDL-C levels. We hypothesized that this PCSK9 inhibitor has a greater efficacy in attenuating cardiometabolic impairments than atorvastatin in obese-insulin resistant rats. Female rats were fed with either a high fat or normal diet for 12 weeks. High fat diet fed rats (HFD) were then divided into 3 groups and were given vehicle, atorvastatin (40 mg/kg/day; s.c.), or PCSK9 inhibitor (4 mg/kg/day; s.c.) for additional 3 weeks. The metabolic parameters, cardiac and mitochondrial function and [Ca2+]i transients were determined. HFD rats developed obese-insulin resistance as indicated by increased plasma insulin and HOMA index. Although high-fat diet fed rats treated with vehicle (HFV) rats had markedly impaired LV function as indicated by reduced %LVFS, impaired cardiac mitochondrial function, and [Ca2+]i transient regulation, these impairments were attenuated in high-fat diet fed rats treated with atorvastatin (HFA) and high-fat diet fed rats treated with PCSK9 inhibitor (HFP) rats. However, these improvements were greater in HFP rats than HFA rats. Our findings indicated that the PCSK9 inhibitor exerted greater cardioprotection than atorvastatin through improved mitochondrial function in obese-insulin resistant rats.

Antioxidant Properties of Saffron Stigma and Petals: A Potential Therapeutic Approach for Insulin Resistance through an Insulin-Sensitizing Adipocytokine in High-Calorie Diet Rats.

Background:Oxidative stress and alteration of lipid profile due to obesity and overweight is a major risk factor for atherosclerotic plaque or coronary artery disease. Because of antioxidant and lipid lowering potential of saffron, this study investigated weight alteration, lipid profiles, and insulin resistance index in high-calorie diet rats treated with aqueous extract of saffron stigma and petal.Methods:Forty Sprague-Dawley male rats were randomly divided into 8 groups including healthy control, high-fat diet control, nicotinic acid treated, Anethum graveolens treated, and saffron stigma and petal treated groups. Rats received a high-calorie diet for 16 weeks. For treatment, aqueous extract of saffron stigma (40 and 80 mg/kg) and petal (50 and 100 mg/kg) was used once daily for 4 weeks. Afterward, lipid profile, oxidative stress status, and insulin and adiponectin levels were measured using desired kits.Results:There was a significant decrease in the mean weight of the groups receiving saffron stigma and petal compared to control group (P < 0.05). The increased level of insulin hormone in obese group was improved in treated groups especially in the case of saffron stigma. Also, the decreased level of adiponectin was recovered in treated groups. An improvement was seen in oxidative stress markers and lipid profiles in treated groups compared to obesity pair.Conclusions:In this study, a remarkable antioxidant and lipid lowering potential was detected for saffron stigma, which could improve insulin resistance in obese rats. Therapeutic and protective effect of saffron is mainly related to its richness in phenolic compounds. Saffron stigma compared with petal had more notable effect, which could and should be mentioned in pharmaceutical studies.