Otsuka Long-Evans Tokushima Fatty Research Articles

Carotid artery stenosis is exacerbated in spontaneously obese model rats with diabetes.

Population studies have shown obesity and diabetes to be risk factors for atherosclerosis. We assessed changes in the common carotid arteries in rat models of obesity and diabetes without hypertension. Twenty 30-week-old male spontaneously diabetic and obese model Otsuka Long-Evans Tokushima Fatty (OLETF) and 20 control Long-Evans Tokushima Otsuka (LETO) rats were used in the experiments. The animals were considered diabetic if the plasma glucose level peaked at >300 mg/dL and remained at >200 mg/dL for 120 minutes. Blood gas physiological parameters were continuously monitored under anesthesia, and the flow of the carotid artery was assessed with ultrasonography. All animals were sacrificed with an overdose of anesthesia at the end of the experiment. Sections of the middle portion of the internal carotid artery were cut and stained with hematoxylin and eosin to assess the overall morphology. All OLETF rats were diabetic, and all LETO rats were non-diabetic. The physiological parameters did not differ significantly between the control and model rats, whereas the carotid artery wall thickness (19.3 ± 3.2 vs. 6.1 ± 4.5 μm) was significantly different between the two groups. The blood flow velocity in the common carotid artery determined using ultrasonography and color Doppler sonography was significantly increased during systole in the model rats compared with that observed in the control rats (203 ± 20.3 vs. 55.3 ± 21.4 cm/sec). The OLETF rats were obese, and diabetes worsened the degree of carotid artery stenosis. These results indicate the possibility of new therapies for carotid artery stenosis in obese and diabetic patients.

Binge alcohol consumption aggravates oxidative stress and promotes pathogenesis of NASH from obesity-induced simple steatosis.

The pathogenesis of nonalcoholic steatohepatitis (NASH) is a two-stage process in which steatosis is the "first hit" and an unknown "second hit." We hypothesized that "a binge" could be a "second hit" to develop NASH from obesity-induced simple steatosis. Thirty-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) rats were administered 10 mL of 10% ethanol orally for 5, 3, 2, and 1 d/wk for 3 consecutive weeks. As control, male Otsuka Long-Evans Tokushima (OLET) rats were administered the same amount of alcohol. Various biochemical parameters of obesity, steatosis and NASH were monitored in serum and liver specimens in untreated and ethanol-treated rats. The liver sections were evaluated for histopathological alterations of NASH and stained for cytochrome P-4502E1 (CYP2E1) and 4-hydroxy-nonenal (4-HNE). Simple steatosis, hyperinsulinemia, hyperglycemia, insulin resistance, hypertriglycemia and marked increases in hepatic CYP2E1 and 4-HNE were present in 30-wk-old untreated OLETF rats. Massive steatohepatitis with hepatocyte ballooning was observed in the livers of all OLETF rats treated with ethanol. Serum and hepatic triglyceride levels as well as tumor necrosis factor (TNF)-α mRNA were markedly increased in all ethanol-treated OLETF rats. Staining for CYP2E1 and 4-NHE demonstrated marked increases in the hepatic tissue of all the groups of OLETF rats treated with ethanol compared with OLET rats. Our data demonstrated that "a binge" serves as a "second hit" for development of NASH from obesity-induced simple steatosis through aggravation of oxidative stress. The enhanced levels of CYP2E1 and increased oxidative stress in obesity play a significant role in this process.

Detailed localization of augmented angiotensinogen mRNA and protein in proximal tubule segments of diabetic kidneys in rats and humans.

In the intrarenal renin-angiotensin system, angiotensinogen levels are well known to be increased in diabetes, and these enhanced intrarenal angiotensinogen levels may initiate the development and accelerate the progression of diabetic nephropathy. However, the specific localization of the augmented angiotensinogen in proximal tubule segments in diabetes is still unknown. We investigated the detailed localization of angiotensinogen in 3 proximal tubule segments in the diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats and the control Long-Evans Tokushima Otsuka (LETO) rats. We also prepared OLETF rats treated with angiotensin II type 1 receptor blocker, olmesartan or with a combination of vasodilator agents. Moreover, biopsied samples of human kidney cortex were used to confirm the results of animal studies. We examined the co-localization of angiotensinogen with segment-specific markers by double staining using fluorescence in situ hybridization and/or immunofluorescence. Angiotensinogen mRNA expression was barely detectable in segment 1. In segment 3, the area of angiotensinogen mRNA expression was augmented in the OLETF rats compared with the LETO rats. Angiotensinogen protein expression areas in segments 1 and 3 were also increased in the OLETF rats compared with the LETO rats. Chronic treatment with olmesartan ameliorated these areas of augmented angiotensinogen expression. Biopsied human kidney samples showed similar results. These data suggest that the augmented angiotensinogen mRNA levels in segment 3 and angiotensinogen protein levels in segments 1 and 3 may contribute to the progression of diabetic nephropathy.

Vascular Aldosterone Production at the Pre-Diabetic Stage of Young Otsuka Long-Evans Tokushima Fatty (OLETF) Rats, Compared with Long-Evans Tokushima Otsuka (LETO) Rats

We examined the ability of aortic smooth muscle cells (AoSMC) prepared from spontaneously diabetic rats to produce aldosterone (Aldo) and the regulatory mechanism that controls their Aldo production. AoSMC of 6 week-old Long-Evans Tokushima Otsuka (LETO: the control group) and 6 week-old Otsuka Long-Evans Tokushima Fatty (OLETF: the type 2 diabetes group) rats were used in the present experiments. CYP11B2 (Aldo synthetase) mRNA expression was detected in both the LETO and OLETF AoSMC. Basal Aldo production was significantly greater (4–5 fold higher) in the OLETF AoSMC culture medium than in the LETO AoSMC culture medium. When AoSMC were co-incubated with high-density lipoproteins (HDL), supplying cholesterol as a substrate for steroidogenesis in rats, angiotensin II (AII) significantly increased greater Aldo production in the OLETF AoSMC than in the LETO AoSMC. The present data suggested that future onset of diabetic vascular dysfunction is partly caused by excess Aldo production by AoSMC in young OLETF rats. Concomitant stimulation by HDL and AII resulted in elevated Aldo production in the OLETF and the LETO AoSMC, and also demonstrated that AII-induced Aldo production is greatly enhanced by HDL in OLETF, rather than in LETO. In conclusion, our data clearly demonstrated that Aldo production in the OLETF AoSMC was significantly higher than in the LETO AoSMC, suggesting possible future onset of vascular dysfunction in diabetes, induced by local Aldo production in the AoSMC.

Impaired Survival of Autologous Fat Grafts by Diabetes Mellitus in an Animal Model: A Pilot Study

Many surgeons are reluctant to perform fat grafting in patients with diabetes because soft-tissue healing is impaired, but no previous study has reported data-driven outcomes of fat grafting in subjects with diabetes. The authors investigate whether diabetes affected survival and complication rates of autologous fat grafting (AFG) in Sprague-Dawley (SD) and Otsuka Long-Evans Tokushima Fatty (OLETF) rats. In total, 16 male SD and 16 male OLETF rats were prepared for AFG. Fat tissue was harvested from the inguinal fat pad and cut into 1-g (800-1250 mg) sections. Each rat received fat in a subcutaneous pocket in the paraspinal area. The grafted fat tissue was measured by ultrasonography at 30, 60, and 90 days after implantation and evaluated by histological analyses. Ultrasonographic analysis indicated that compared with the SD group, the AFG survival rate was lower in OLETF rats (40.52% vs 53.38%), and the failure rate was higher in OLETF rats (31.25% vs 6.25%). The histological analysis indicated that compared with the OLETF group, adipocytes were more dense (3.18 vs 2.33; P = .025), cyst formation occurred less frequently (3.00 vs 3.61; P = .030), and more capillaries were formed (2.31/field vs 1.61/field; P = .001) in the SD rat group. Diabetes causes marked deterioration in the survival and quality of AFG in the diabetic rat model.

Combining metformin and aerobic exercise training in the treatment of type 2 diabetes and NAFLD in OLETF rats

Here, we sought to compare the efficacy of combining exercise and metformin for the treatment of type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) in hyperphagic, obese, type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. OLETF rats (age: 20 wk, hyperglycemic and hyperinsulinemic; n = 10/group) were randomly assigned to sedentary (O-SED), SED plus metformin (O-SED + M; 300 mg·kg(-1)·day(-1)), moderate-intensity exercise training (O-EndEx; 20 m/min, 60 min/day, 5 days/wk treadmill running), or O-EndEx + M groups for 12 wk. Long-Evans Tokushima Otsuka (L-SED) rats served as nonhyperphagic controls. O-SED + M, O-EndEx, and O-EndEx + M were effective in the management of type 2 diabetes, and all three treatments lowered hepatic steatosis and serum markers of liver injury; however, O-EndEx lowered liver triglyceride content and fasting hyperglycemia more than O-SED + M. In addition, exercise elicited greater improvements compared with metformin alone on postchallenge glycemic control, liver diacylglycerol content, hepatic mitochondrial palmitate oxidation, citrate synthase, and β-HAD activities and in the attenuation of markers of hepatic fatty acid uptake and de novo fatty acid synthesis. Surprisingly, combining metformin and aerobic exercise training offered little added benefit to these outcomes, and in fact, metformin actually blunted exercise-induced increases in complete mitochondrial palmitate oxidation and β-HAD activity. In conclusion, aerobic exercise training was more effective than metformin administration in the management of type 2 diabetes and NAFLD outcomes in obese hyperphagic OLETF rats. Combining therapies offered little additional benefit beyond exercise alone, and findings suggest that metformin potentially impairs exercise-induced hepatic mitochondrial adaptations.

Inhibition of Postprandial Hyperglycemia by Either an Insulin-Dependent or -Independent Drug Reduces the Expression of Genes Related to Inflammation in Peripheral Leukocytes of OLETF Rats

Treatment with the dipeptidyl peptidase-4 inhibitor, anagliptin, or with the α-glucosidase inhibitor, miglitol, reduced the oral sucrose load-inducible expression of interleukin (IL)-1β, IL-18, tumor necrosis factor-α, S100a8, S100a9, S100a11, IL-1R2, IL-1Rn and tumor necrosis factor receptor 2 genes in peripheral leukocytes of Otsuka Long-Evans Tokushima fatty (OLETF) rats at the stage of impaired glucose tolerance. Inhibiting postprandial hyperglycemia reduced the expression of genes related to inflammation in peripheral leukocytes of OLETF rats.

Decreased perivascular CGRP-containing nerves in Otsuka Long–Evans Tokushima Fatty rats with insulin resistance and hypertension

We previously reported that chronic hyperinsulinemia induced by drinking fructose elicited an abnormal neuronal regulation of vascular tone, which contributed to the development of hypertension. This study was designed to elucidate the possible mechanisms underlying the dysfunctional neuronal regulation of vascular tone induced by chronic hyperinsulinemia by comparing isolated mesenteric vascular beds from Otsuka Long-Evans Tokushima Fatty (OLETF) rats with those of control Long-Evans Tokushima Otsuka rat (LETO) rats. Insulin, triglyceride and total cholesterol levels in plasma, blood glucose concentrations, a glucose-insulin index, systolic blood pressure and perivascular innervations were assessed using biochemical and immunohistochemical methods. Mesenteric vascular beds isolated from OLETF and LETO rats were perfused with a Krebs solution containing methoxamine, and changes in perfusion pressure in response to periarterial nerve stimulation (PNS) and the perfusion of vasoactive agents were measured. OLETF rats (8-25 weeks old) showed age-related increases in insulin, triglycerides, total cholesterol, blood glucose, the glucose-insulin index (homeostasis model assessment ratio (HOMA-IR)) and systolic blood pressure compared with LETO rats. In perfused mesenteric vascular beds, the PNS-induced adrenergic nerve-mediated vasoconstrictor responses in OLETF rats were significantly greater than those in LETO rats, whereas the PNS-induced calcitonin gene-related peptide (CGRP) nerve-mediated vasodilator responses in OLETF rats were significantly smaller than those in LETO rats. In immunohistochemical experiments, the density of CGRP-immunopositive nerves in the mesenteric arteries of OLETF rats decreased significantly with age. The present findings suggest that the abnormal innervation of perivascular nerves in mesenteric resistance arteries induced by chronic hyperinsulinemia disturbs the neuronal regulation of vascular tone and may cause hypertension in OLETF rats.

Combination of a peroxisome proliferator-activated receptor-gamma agonist and an angiotensinII receptor blocker attenuates myocardial fibrosis and dysfunction in type2 diabetic rats.

We aimed to examine the effect of an angiotensinII receptor blocker (ARB), a peroxisome proliferator-activated receptor (PPAR)-gamma agonist, and their combination on myocardial fibrosis and function in type2 diabetic rats. Five male Long-Evans Tokushima Otsuka (LETO) rats and 20 male Otsuka Long-Evans Tokushima Fatty (OLETF) rats were used. OLETF rats were assigned to four groups (n=5 per group) at 28weeks-of-age: untreated, losartan-treated, rosiglitazone-treated and combination-treated. The ARB, losartan, was administered at a dose of 5mg/kg/day, and the PPAR-gamma agonist, rosiglitazone, was administered at a dose of 3mg/kg/day by oral gavage for 12weeks. Urine and blood samples were collected, and two-dimensional echocardiograms and strain rate imaging were obtained at 28 and 40weeks. Cytokines were evaluated by reverse transcriptase polymerase chain reaction, and histological analysis was carried out at 40weeks. At 40weeks, the global radial strains of the losartan-treated (55.7±4.5%, P=0.021) and combination-treated groups (59.3±6.7%, P=0.001) were significantly higher compared with the untreated OLETFs (44.3±10.5%). No difference was observed when compared with LETO rats. Although the rosiglitazone-treated group showed a better metabolic profile than the untreated OLETF group, there was no difference in the global radial strain (49.8±6.0 vs 44.3±10.5, P=0.402). The expression of pro-inflammatory cytokines, and collagen typeI and III were consistently attenuated in the losartan-treated and combination-treated OLETF groups, but not in the rosiglitazone-treated group. A combination of rosiglitazone and losartan attenuates myocardial fibrosis and dysfunction in type2 diabetic rats.

Resistant starch improves insulin resistance and reduces adipose tissue weight and CD11c expression in rat OLETF adipose tissue

ObjectiveCD11s/CD18 dimers induce monocyte/macrophage infiltration into many tissues, including adipose tissues. In particular, it was reported that β2-integrin CD11c-positive macrophages in adipose tissues are closely associated with the development of insulin resistance. The aim of this study was to determine whether intake of resistant starch (RS) reduces macrophage accumulation in adipose tissues and inhibits the development of insulin resistance at an early stage in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. MethodsTwenty-two-wk-old male OLETF rats were fed a control diet (55% α-corn starch) or an RS diet (55% RS) for 5 wk. An oral glucose tolerance test was performed after 4 wk of feeding; tissues (mesenteric and epididymal adipose tissues, and liver) and tail vein blood were collected after 5 wk of feeding the test diets. ResultsFeeding the RS diet to OLETF rats for 5 wk improved insulin resistance, reduced the mesenteric adipose tissue weight, and enhanced the number of small adipocytes. CD68 expression, a macrophage infiltration marker, was not changed by the RS diet, whereas the gene expression levels of integrins such as CD11c, CD11d, and CD18, but not CD11a, and CD11b, were significantly reduced. CD11c protein expression was reduced by the RS diet. ConclusionThese findings suggest that part of the mechanism for the improved insulin resistance by the RS diet involves a reduction of CD11c expression in adipose tissues.

Differential vasomotor effects of insulin on gastrocnemius and soleus feed arteries in the OLETF rat model: role of endothelin‐1

The vascular actions of insulin are complex, because it can stimulate both nitric oxide-mediated dilatation and endothelin (ET)-1-mediated constriction. We examined vasoreactivity to insulin in isolated feed arteries of the gastrocnemius (GFA) and soleus muscles (SFA) of 32-week-old Long-Evans Tokushima Otsuka (LETO) and Otsuka Long-Evans Tokushima fatty (OLETF) rats, a hyperphagic rodent model of obesity and insulin resistance. The insulin-induced vasoreactivity of SFA and GFA was similar in LETO (healthy) and OLETF (obese/insulin-resistant) rats. However, examination of between-vessel effects revealed a number of novel insights into the heterogeneous vascular effects of insulin. Soleus feed arteries dilated more than GFA in LETO at 100 and 1000 μIU ml(-1) insulin (23 versus 6 and 28 versus 0%, respectively; P < 0.05 for between-vessel differences). Likewise, in OLETF rats there was significantly greater dilatation in SFA than GFA at 10, 100 and 1000 μIU ml(-1) insulin (28 versus 3, 30 versus 0 and 34 versus 0%, respectively; all P < 0.05). In the presence of 3 μm tezosentan, a non-specific endothelin-1 receptor blocker, insulin-induced dilatation of the GFA was enhanced such that differences between vessels were largely abolished in both groups. Furthermore, acetylecholine-induced dilatation was significantly greater in SFA than GFA within each group, whereas sodium nitroprusside-induced dilatory responses were greater in the GFA compared with the SFA. Overall, our findings indicate that the insulin/endothelin-1 vasoconstrictor pathway is more active in GFA than in SFA, independent of obesity in the OLETF rat model.

G-CSF Prevents Progression of Diabetic Nephropathy in Rat

BackgroundThe protective effects of granulocyte colony-stimulating factor (G-CSF) have been demonstrated in a variety of renal disease models. However, the influence of G-CSF on diabetic nephropathy (DN) remains to be examined. In this study, we investigated the effect of G-CSF on DN and its possible mechanisms in a rat model.MethodsOtsuka Long-Evans Tokushima Fatty (OLETF) rats with early DN were administered G-CSF or saline intraperitoneally. Urine albumin creatinine ratio (UACR), creatinine clearance, mesangial matrix expansion, glomerular basement membrane (GBM) thickness, and podocyte foot process width (FPW) were measured. The levels of interleukin (IL)-1β, transforming growth factor (TGF)-β1, and type IV collagen genes expression in kidney tissue were also evaluated. To elucidate the mechanisms underlying G-CSF effects, we also assessed the expression of G-CSF receptor (G-CSFR) in glomeruli as well as mobilization of bone marrow (BM) cells to glomeruli using sex-mismatched BM transplantation.ResultsAfter four weeks of treatment, UACR was lower in the G-CSF treatment group than in the saline group (p<0.05), as were mesangial matrix expansion, GBM thickness, and FPW (p<0.05). In addition, the expression of TGF-β1 and type IV collagen and IL-1β levels was lower in the G-CSF treatment group (p<0.05). G-CSFR was not present in glomerular cells, and G-CSF treatment increased the number of BM-derived cells in glomeruli (p<0.05).ConclusionsG-CSF can prevent the progression of DN in OLETF rats and its effects may be due to mobilization of BM cells rather than being a direct effect.

Chronic alcohol consumption, type 2 diabetes mellitus, insulin-like growth factor-I (IGF-I), and growth hormone (GH) in ethanol-treated diabetic rats

AimsAlcohol has deleterious influences on glucose metabolism which may contribute to the development of type 2 diabetes mellitus (T2DM). Insulin-like growth factor I (IGF-I) and growth hormone (GH), which interact with insulin to modulate metabolic control, have been shown to be related to impaired glucose tolerance. This study was conducted to assess the possibility that altered circulating IGF-I and GH levels contribute to the exacerbation of T2DM by alcohol use in type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats and non-diabetic Long-Evans Tokushima Otsuka (LETO) rats. Main methodOLETF rats were pair-fed a Lieber-DeCarli Regular Ethanol diet and LETO rats were pair-fed a control diet for 6weeks. At 6weeks, an Intraperitoneal Glucose Tolerance Test (IP-GTT) was performed and IGF-I and GH levels were evaluated. Key findingsPrior to an IP-GTT, OLETF-Ethanol (O-E) group had significantly a decrease in the mean glucose levels compared to OLETF-Control (O-C) group. At 120min post IP-GTT, the O-E group had significantly an increase in the mean glucose levels compared to O-C group. The serum IGF-I levels were significantly lower and the serum GH levels were significantly higher in the O-E group than in L-C group. SignificanceThese results suggest that IGF-I and GH are prominent in defining the risk and development of T2DM, and may be adversely affected by heavy alcohol use, possibly mediating its diabetogenic effects. Thus, the overall glucose intolerance in the setting of alcoholism may be attributable to inappropriate alteration of IGF-I and GH levels.

Investigation of the metabolic effects of chronic clozapine treatment on CCK-1 receptor deficient Otsuka Long Evans Tokushima Fatty (OLETF) rats

Clozapine increases meal size and meal duration, effects similar to the pharmacological blockade or congenital deficiency of CCK-1 receptor. We aimed to investigate the role of CCK-1 receptor in clozapine-induced weight gain and insulin sensitivity in CCK-1 receptor deficient, male Otsuka Long Evans Tokushima Fatty rats (OLETF). Long Evans Tokushima Otsuka (LETO) rats served as healthy control. Animals were orally treated with either clozapine (10mg/kg) or its vehicle over 25 days. Daily metabolic parameters were measured by metabolic cages. The insulin sensitivity was determined by hyperinsulinaemic euglycaemic glucose clamping (HEGC). Adiposity was determined by measuring the perirenal, intraabdominal and epididymal white adipose tissue fat pads. Hypothalamic mRNA expression of CCK-1 and CCK-2 receptor was measured by real-time PCR, plasma insulin by radioimmunoassay. Clozapine failed to increase weight gain or daily food intake, but it increased adiposity, 1st meal size and duration and decreased insulin sensitivity both in OLETF or LETO rats. The glucose infusion rate during the steady state of the HEGC was unaltered, but the metabolic clearance rate of insulin was reduced by the clozapine treatment. Hypothalamic mRNA of CCK-1 and CCK-2 receptor was elevated in LETO rats, but the mRNA of CCK-2 receptor was reduced by clozapine in OLETF rats. Our results suggest that the CCK-1 receptor has no direct role in the clozapine-induced adiposity and insulin resistance. We also demonstrated that atypical antipsychotic treatment can induce insulin resistance in the absence of manifest obesity in male rats.

Iron restriction prevents diabetic nephropathy in Otsuka Long-Evans Tokushima fatty rat

High body iron levels are found in type 2 diabetes mellitus (DM). Iron excess leads to tissue injury through free radical formation. We investigated the effect of iron restriction on renal damage in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type 2 DM. OLETF rats (n = 18) were divided into three groups at 10 weeks of age: high fat diet containing 8% NaCl (HFS, n = 6), HFS diet with iron restricted (HFS + IR, n = 6), and HFS with hydralazine (HFS + Hyd, n = 6). Long-Evans Tokushima (LETO) rats served as control. Iron restriction decreased hemoglobin levels, systolic blood pressure, and urinary excretion of protein and 8-hydroxy-2'-deoxyguanosine in the OLETF rats fed with HFS diet. Compared to the HFS group, the expression of desmin, renal glomerular injury marker and iron deposition in the renal tubules were attenuated in the HFS + IR group but not in the HFS + Hyd group at 26 weeks of age. Moreover, renal hypoxia (evaluated as pimonidazole adducts) was improved in the HFS + IR group compared to the HFS group in spite of anemia. Iron restriction prevented the production of reactive oxygen species and the development of early stage nephropathy in OLETF rats. Iron restriction may be beneficial in prevention of nephropathy in type 2 DM.

Age-dependent increases in tau phosphorylation in the brains of type 2 diabetic rats correlate with a reduced expression of p62

Aging increases the co-incidence of Alzheimer's disease (AD) and type 2 diabetes (T2DM). However, the critical factors that contribute to the age-related increase in AD–T2DM comorbidity have yet to be clarified. In this study, aging effects and their relationship to AD-related pathology and T2DM as well as the underlying mechanisms of this process were investigated using obese rats with chronic T2DM. Tau pathology and its associated signaling pathways in the brain were compared between Otsuka Long–Evans Tokushima Fatty (OLETF) rats and corresponding non-diabetic controls at various ages. Tau phosphorylation at AD-related epitopes, including Thr212, Thr231, Ser262, and Ser396, increased with age in the soluble brain extracts of chronic OLETF rats and were accompanied by synaptic protein loss. There was also a marked age-dependent accumulation of polyubiquitinated substances in diabetic rats. Accordingly, tau proteins were highly polyubiquitinated in aged OLETF rats and a strong degree of co-localization existed between p-tau and ubiquitin in these neurons. In addition, the mRNA and protein levels of p62, a known cargo molecule that transports polyubiquitinated tau to proteasomal and autophagic degradation systems, decreased robustly with age in OLETF rats and there was an inverse correlation between protein levels of p62 and p-tau. The impaired degradation of polyubiquitinated p-tau due to age- and T2DM-dependent decreases in p62 transcription is a primary mechanism underlying increased AD-like pathology in a T2DM rat model as age increases. These results provide novel insight into the mechanisms supporting the age-related increase in AD–T2DM comorbidity.

Angiotensin receptor-mediated oxidative stress is associated with impaired cardiac redox signaling and mitochondrial function in insulin-resistant rats

Activation of angiotensin receptor type 1 (AT1) contributes to NADPH oxidase (Nox)-derived oxidative stress during metabolic syndrome. However, the specific role of AT1 in modulating redox signaling, mitochondrial function, and oxidative stress in the heart remains more elusive. To test the hypothesis that AT1 activation increases oxidative stress while impairing redox signaling and mitochondrial function in the heart during diet-induced insulin resistance in obese animals, Otsuka Long Evans Tokushima Fatty (OLETF) rats (n = 8/group) were treated with the AT1 blocker (ARB) olmesartan for 6 wk. Cardiac Nox2 protein expression increased 40% in OLETF compared with age-matched, lean, strain-control Long Evans Tokushima Otsuka (LETO) rats, while mRNA and protein expression of the H₂O₂-producing Nox4 increased 40-100%. ARB treatment prevented the increase in Nox2 without altering Nox4. ARB treatment also normalized the increased levels of protein and lipid oxidation (nitrotyrosine, 4-hydroxynonenal) and increased the redox-sensitive transcription factor Nrf2 by 30% and the activity of antioxidant enzymes (SOD, catalase, GPx) by 50-70%. Citrate synthase (CS) and succinate dehydrogenase (SDH) activities decreased 60-70%, whereas cardiac succinate levels decreased 35% in OLETF compared with LETO, suggesting that mitochondrial function in the heart is impaired during obesity-induced insulin resistance. ARB treatment normalized CS and SDH activities, as well as succinate levels, while increasing AMPK and normalizing Akt, suggesting that AT1 activation also impairs cellular metabolism in the diabetic heart. These data suggest that the cardiovascular complications associated with metabolic syndrome may result from AT1 receptor-mediated Nox2 activation leading to impaired redox signaling, mitochondrial activity, and dysregulation of cellular metabolism in the heart.

Angiotensin II Receptor Blocker Telmisartan Prevents New-Onset Diabetes in Pre-Diabetes OLETF Rats on a High-Fat Diet: Evidence of Anti-Diabetes Action

This study aims to investigate the effects of telmisartan, pioglitazone and metformin administration on the prevention of new-onset type 2 diabetes mellitus in pre-diabetes Otsuka Long-Evans Tokushima Fatty (OLETF) rats fed with a high-fat diet (HFD). OLETF rats 22 weeks of age were treated with pioglitazone (O-P), metformin (O-M), telmisartan (O-T) and low telmisartan starting from their pre-diabetes period. The weight, glucose tolerance and insulin sensitivity were measured. The lipid profiles were obtained. The abdominal subcutaneous (SC) and omental (OM) fat pads were dissected to measure the expression of mRNA and protein levels (adiponectin, proinflammatory cytokines, etc.). Telmisartan significantly reversed glucose tolerance and improved insulin resistance. The incidence rates of impaired glucose tolerance and type 2 diabetes in the O-P (χ(2)= 11.025, p=0.001) and O-T (χ(2)=5.495, p=0.019) groups were significantly reduced. The mRNA expression of proinflammatory cytokines was downregulated by telmisartan. The expression of adiponectin, PPARγ1 and γ2 was markedly improved by telmisartan and pioglitazone compared with the OLETF control (O-C) group. The correlation analysis showed that the systolic and diastolic blood pressures were not correlated with the homeostasis model assessment-insulin resistance (p>0.05). Telmisartan acts beneficially against diabetes-induced inflammation and improves insulin resistance in pre-diabetes OLETF rats fed with HFD. In view of this improved responsiveness to insulin sensitivity, telmisartan may prove to be a promising candidate for the intervention treatment of the pre-diabetes state.

Sulodexide improves renal function through reduction of vascular endothelial growth factor in type 2 diabetic rats

AimsSulodexide is a promising therapeutic drug for the management of diabetic nephropathy. Although sulodexide has demonstrated a renoprotective effect through its ability to restore glomerular ionic permselectivity, the exact mechanism is still not clear. We investigated the effects of long-term sulodexide treatment on diabetic nephropathy in Otsuka-Long–Evans-Tokushima-Fatty (OLETF) rats. Main methodsDiabetic rats were treated with or without sulodexide at 10mg/kg/day in the drinking water for nine months. Renal morphology and changes in VEGF and p38 mitogen-activated protein kinase (p38 MAPK), urinary levels of albumin (UAE) and urinary VEGF excretion were determined. To define the direct effects of sulodexide, we performed an in vitro experiment using podocytes. Key findingsUAE was significantly higher in OLETF rats than in control LETO rats, and the sulodexide group showed significantly decreased UAE after six months of treatment. Interestingly, urinary VEGF levels were also significantly decreased in the sulodexide-treated group. In accordance with UAE and urinary VEGF changes, the renal expression of profibrotic molecules was significantly decreased after sulodexide treatment. In addition, the activation of p38 MAPK, assessed by measuring the level of phospho-specific p38 MAPK, increased in diabetic renal tissues and was markedly suppressed by sulodexide treatment. In cultured podocytes, sulodexide treatment significantly decreased high glucose-induced p38 MAPK activation and VEGF synthesis. SignificanceSulodexide directly suppresses VEGF synthesis through the p38 MAPK pathway in podocytes, and these results suggest that sulodexide may provide renoprotection via suppression of renal VEGF synthesis independently of glomerular basement membrane ionic permselectivity in type 2 diabetic rats.

Mo1046 Effects of Iron Restriction on Hepatic Mitochondrial Iron Metabolism and Oxidative Stress in Nonalcoholic Fatty Liver Disease (NAFLD) in Otsuka Long-Evans Tokushima Fatty (OLETF) Rats

Mo1046 Effects of Iron Restriction on Hepatic Mitochondrial Iron Metabolism and Oxidative Stress in Nonalcoholic Fatty Liver Disease (NAFLD) in Otsuka Long-Evans Tokushima Fatty (OLETF) Rats