Evans Tokushima Fatty Rats Research Articles

OLETF 당뇨모델동물을 이용한 맥문동 추출물(LP9M80-H)의 당뇨질환에 대한 효능

LP9M80-H는 맥문동(<TEX>$Liriope$</TEX> <TEX>$platyphylla$</TEX>)으로부터 메탄올과 헥산을 이용하여 추출한 새로운 추출물로서 ICR 마우스에서 인슐린분비를 촉진하며, 간과 뇌 조직에서 인슐린 신호경로를 활성화시키는 것으로 알려져 있다. 본 연구에서는 LP9M80-H가 당뇨와 비만의 치료에 미치는 효과를 조사하기 위하여, OLETF 모델동물에 LP9M80-H를 2주간 투여한 후 당뇨와 비만과 관련된 주요인자의 변화를 관찰하였다. 비록 체중은 두 집단간에 차이가 없었으나 복부 지방량은 vehicle 투여군보다 LP9M80-H 투여군에서 적었다. 또한, 혈중 포도당농도는 LP9M80-H를 투여한 OLETF 랫드가 대조군에 비하여 약간 낮았으나 인슐린의 농도는 유의적으로 크게 증가하였다. 혈청 내 3가지 주요 지질의 농도는 LP9M80-H를 투여한 OLETF 랫드에서 유의적으로 감소하였고, 지방의 산화를 촉진하는 아디포넥틴의 농도도 LP9M80-H를 투여한 OLETF 랫드에서 감소하였다. 더불어, 체내에 분비된 인슐린이 표적장기에 미치는 영향을 관찰하기 위하여 간조직에서 인슐린 수용체와 인슐린 수용체기질(iRS)의 발현을 관찰하였으며, 이러한 2가지 단백질은 LP9M80-H를 투여한 OLETF 랫드에서 vehicle 투여군에 비해 유의미하게 감소하였다. 또한, 인슐린 신호 경로의 다운스트림에 위치하는 포도당 수송체 중에서 Glut-2와 Glut-3 발현은 LP9M80-H를 투여한 OLETF 랫드에서 유의미하게 감소하는 반면에, Glut-4 발현은 일정하게 유지되었다. 따라서 이러한 결과는 LP9M80-H는 포도당 항상성과 지질농도의 조절을 통하여 당뇨와 비만의 증상을 완화시키는데 기여할 것으로 사료된다. It was reported that the novel compounds (LP9M80-H) of <TEX>$Liriope$</TEX> <TEX>$platyphylla$</TEX> regulate glucose transporter (Glut) biosynthesis by activating the insulin-signaling pathway in the liver and brain of ICR mice. To investigate the therapeutic effects of LP9M80-H on the pathology of diabetes and obesity, alterations of key factors related to symptoms were analyzed in the Otsuka Long Evans Tokushima Fatty (OLETF) rats treated with LP9M80-H for 2 weeks. The abdominal fat masses in the LP9M80-H-treated group were lower than the vehicle-treated group, although there was no difference in body weight between the two groups. Additionally, when compared to the vehicle-treated group, LP9M80-H treatment induced a significant decrease in glucose levels and an increase in the insulin concentration in the blood of OLETF rats. A high level of insulin protein was also detected in pancreatic <TEX>${\beta}$</TEX> cells of LP9M80-H-treated OLETF rats. A significant reduction in the concentration of lipids and adiponectin was detected only in LP9M80-H-treated OLETF rats. Furthermore, the expression of insulin receptor <TEX>${\beta}$</TEX> and the insulin receptor substrate (IRS) was dramatically decreased in LP9M80-H-treated OLETF rats compared to the vehicle-treated group. Of the glucose transporters located downstream of the insulin-signaling pathway, glucose transporters (Glut) -2 and -3 were significantly decreased in LP9M80-H-treated OLETF rats, while the level of Glut-4 was maintained under all conditions. Therefore, these results suggest that LP9M80-H may contribute to relieving symptoms of diabetes and obesity through glucose homeostasis and regulation of lipid concentration.

Acetylcholine and insulin‐mediated vasodilation in feed arteries and arterioles of rat skeletal muscle of different fiber type composition

Obese, insulin resistant Otsuka Long Evans Tokushima Fatty rats (age 20 wk) were randomly assigned to sedentary (SED), endurance exercise training (EET), interval exercise training (IET), metformin, EET+MET, or IET+MET; and age‐matched Long‐ Evans Tokushima Otsuka rats were assigned to SED or MET. At sacrifice (age 30–32 wk), feed arteries from slow‐twitch soleus (SFA) and fast‐twitch gastrocnemius (GFA) muscles, and second order arterioles from red (G2aR) and white (G2aW) portions of the gastrocnemius muscle were isolated for in vitro assessment of vasomotor responses to acetylcholine (ACh, 10‐9‐10‐4 M), insulin (1–1000 μIU/mL), and sodium nitroprusside (SNP, 10‐9‐10‐4 M). Collapsing across all groups (total n=21), ACh and insulin‐mediated vasodilation in the SFA and G2aR were greater compared to the GFA and G2aW, respectively (all p&lt;0.05). Conversely, SNP‐mediated vasodilation in the GFA was greater compared to the SFA (p&lt;0.05), while G2aR and G2aW exhibited similar responses. Using a heterogeneous group of animals, these data suggest that ACh and insulin‐induced vasodilation is greater in skeletal muscle feed arteries and arterioles perfusing slow‐twitch oxidative muscle fibers than in feed arteries and arterioles perfusing fast‐twitch low oxidative muscle fibers. Support: NIH RO1HL036088, VA CDA‐2 IK2BX001299‐01, AHA 11POST5080002

Enriched Cholesterol Diet Increases Expression of Renal Epithelial Na+ Channel Gamma Subunit in Rats

The epithelial Na+ channel (ENaC) is a trimeric transmembrane channel expressed in multiple secretory organs. ENaC is responsible for regulation of Na+ transport and balance in the kidney with the gamma subunit (γENaC) primarily responsible for regulation. However, the impact of enriched cholesterol diet on the regulation of ENaC during insulin resistance is not well described. To examine the effects of enriched cholesterol diet and activation of the angiotensin receptor on renal ENaC protein during insulin resistance, Otsuka Long Evans Tokushima Fatty (OLETF) rats and their lean, non‐insulin resistant controls, Long Evans Tokushima Otsuka (LETO) rats were supplemented with an enriched cholesterol diet (ECD; 2% + 0.5% cholic acid) and/ or treated with an angiotensin receptor blocker (ARB; 10 mg olmesartan/kg/d) for 16 weeks. The renal ENaC alpha and gamma subunits were measured by Western blot. The results suggest that elevated dietary cholesterol is associated with a quicker increase in blood pressure and expression of the ENaC γ loop. The ENaC γ loop was suppressed in the 24‐week‐old OLETFs, further implicating that the cleavage of ENaC γ loop is involved in renal uptake of Na+ resulting in volume‐dependent hypertension.

Effects of Endurance Exercise Training, Metformin, and Their Combination on Adipose Tissue Cytokine Secretion in a Rat Model of Type 2 Diabetes (T2D)

Otsuka Long Evans Tokushima Fatty (OLETF) rats are a hyperphagic and obese rodent model of T2D. We randomly assigned OLETF rats (age 20 wks, the onset of insulin resistance) to sedentary (SED), endurance exercise training (TR; 20 m/min, 60 min/d, 5 d/wk running), metformin (MET; 300 mg/kg/d in drinking water), or TR + MET groups. Age‐matched SED Long‐Evans Tokushima Otsuka (LETO) rats served as controls. At sacrifice (age 30–32 wks), retroperitoneal (RP) fat pads were harvested and incubated in Krebs solution for 60 min at 37°C. RP fat‐conditioned buffers were assayed for interleukin‐6 (IL‐6), leptin, monocyte chemoattractant protein‐1 (MCP‐1), and tumor necrosis factor‐α (TNF‐α). Compared to LETO RP fat, sedentary OLETF RP fat secreted ~30%, ~200%, ~15%, and ~50% more IL‐6, leptin, MCP‐1, and TNF‐α, respectively. Preliminary analysis of treatment effects revealed that: (i) MET alone or TR + MET, but not TR alone, normalized differences between OLETF and LETO groups in IL‐6 and TNF‐α secretion; (ii) only MET, but neither TR nor TR + MET, normalized MCP‐1 secretion; (iii) TR and TR + MET, but not MET alone, normalized leptin secretion. Leptin levels in RP fat‐conditioned buffer correlated with plasma leptin across all groups (r2 = 0.78, P &lt; 0.01). These data suggest that MET decreases adipose tissue inflammatory cytokine release and that TR decreases adipose tissue leptin secretion in T2D.

Differential effects of trimetazidine on vascular smooth muscle cell and endothelial cell in response to carotid artery balloon injury in diabetic rats

BackgroundTreatment with trimetazidine (TMZ), 1-[2,3,4-trimethoxybenzyl] piperazine, dihydrochloride, improves cardiac function and ameliorates endothelial dysfunction. However, its potential efficacy against restenosis after balloon injury has not been addressed. We investigated the effect of TMZ on reducing the occurrence of restenosis in the carotid artery in response to balloon injury and explored potential mechanisms for the effects. Material and methodsStreptozotocin (40mg/kg)-injected Sprague–Dawley rats and Otsuka Long–Evans Tokushima Fatty rats were used for type 1 and type 2 diabetes models, respectively. Both types of rats were divided into three groups: control and TMZ treatment 10 and 20mg/kg per day (n=10 per group). TMZ or normal saline was given orally from 2weeks before to 2weeks after carotid injury. ResultsFour weeks of TMZ treatment resulted in a significant and dose-dependent reduction in the intima-media ratio in diabetic rats. This effect was accompanied by decreased proliferation of vascular smooth muscle cells (VSMCs) and accelerated re-endothelialization after carotid balloon injury. In vitro study with VSMCs decreased proliferation and migration, while human umbilical vein endothelial cells (HUVECs) increased proliferation and decreased apoptosis after TMZ treatment. Antioxidative effects of TMZ were observed in both VSMCs and HUVECs. ConclusionsReduction of restenosis by TMZ treatment involved changes in antioxidative and anti-inflammatory properties, which are cell-specific effects on either survival or apoptosis. The specific actions and physiological effects of TMZ may contribute to better understanding of the pathogenesis of atherosclerosis, which is a major complication of diabetes mellitus.

Taurine ameliorates hyperglycemia and dyslipidemia by reducing insulin resistance and leptin level in Otsuka Long-Evans Tokushima fatty (OLETF) rats with long-term diabetes

This study aimed to determine whether taurine supplementation improves metabolic disturbances and diabetic complications in an animal model for type 2 diabetes. We investigated whether taurine has therapeutic effects on glucose metabolism, lipid metabolism, and diabetic complications in Otsuka Long-Evans Tokushima fatty (OLETF) rats with long-term duration of diabetes. Fourteen 50-week-old OLETF rats with chronic diabetes were fed a diet supplemented with taurine (2%) or a non-supplemented control diet for 12 weeks. Taurine reduced blood glucose levels over 12 weeks, and improved OGTT outcomes at 6 weeks after taurine supplementation, in OLETF rats. Taurine significantly reduced insulin resistance but did not improve β-cell function or islet mass. After 12 weeks, taurine significantly decreased serum levels of lipids such as triglyceride, cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol. Taurine significantly reduced serum leptin, but not adiponectin levels. However, taurine had no therapeutic effect on damaged tissues. Taurine ameliorated hyperglycemia and dyslipidemia, at least in part, by improving insulin sensitivity and leptin modulation in OLETF rats with long-term diabetes. Additional study is needed to investigate whether taurine has the same beneficial effects in human diabetic patients.

Regulation of hepatic lipid metabolism by adiponectin via IRS-2 phosphorylation in OLETF rats

To explore the effect and mechanism of adiponectin on hepatic lipid metabolism in Otsuka Long Evans Tokushima fatty (OLETF) rats. Twenty male OLETF rats and 10 male Long-Evans Tokushima (LETO) rats were sacrificed at 8, 32 or 40-week old to examine the fasting blood glucose, plasma insulin, adiponectin and blood lipid profile. The levels of triglyceride, cholesterol, adiponectin, phosphotyrosine of IRS-2, acetyl-coenzyme A carboxylase and sterol regulatory element-binding protein 1 (SREBP-1) mRNA in liver tissue were determined by chemical enzymatic assay, enzyme-linked immunosorbent assay (ELISA) or Western blot. Higher insulin level, lower insulin sensitivity index and deteriorated lipid metabolism was observed in OLETF rats since 32-week age. ACC (acetyl coenzyme A carboxylase) and SREBP-1 mRNA expression, lowered plasma adiponectin (OLETF vs LETO: 8 weeks age, 2.38 ± 0.23 vs 3.1 ± 0.17, P < 0.05; 32 weeks age, 1.51 ± 0.05 vs 2.84 ± 0.34, P < 0.01; 40 weeks age, 1.24 ± 0.04 vs 2.64 ± 0.49 ng/ml, P < 0.01) and liver tissue (8, 32 or 40 weeks age, 2.24 ± 0.18 vs 2.68 ± 0.13, 2.04 ± 0.19 vs 2.51 ± 0.14, 1.76 ± 0.12 vs 2.47 ± 0.21 µg/g respectively, P < 0.05) as well as elevated triglyceride (TG) (40 weeks age, TG 1.88 ± 0.11 vs 0.51 ± 0.07 mmol/L, P < 0.01) and cholesterol (40 weeks age, total cholesterol 0.94 ± 0.17 vs 0.69 ± 0.14 mmol/L, P < 0.01) and lowered IRS-1 (insulin receptor substrate 1) tyrosine phosphorylation in liver tissue in OLETF rats were observed. The hepatic adiponectin was positively correlated with the level of py-IRS2 and inversely with those of hepatic ACC, SREBP-1 mRNA, triglyceride and cholesterol (r = -0.431, -0.396, -0.353, -0.349, P < 0.05). Adiponectin may affect the signaling pathway of hepatic insulin via tyrosine phosphorylation of IRS-2. It is involved in the regulation of hepatic lipid metabolism.

Aminoguanidine normalizes ET-1-induced aortic contraction in type 2 diabetic Otsuka Long–Evans Tokushima Fatty (OLETF) rats by suppressing Jab1-mediated increase in ETA-receptor expression

Circulating levels of endothelin (ET)-1 are increased in the diabetic state, as is endogenous ETA-receptor-mediated vasoconstriction. However, the responsible mechanisms remain unknown. We hypothesized that ET-1-induced vasoconstriction is augmented in type 2 diabetes with hyperglycemia through an increment in advanced glycation end-products (AGEs). So, we investigated whether treatment with aminoguanidine (AG), an inhibitor of AGEs, would normalize the ET-1-induced contraction induced by ET-1 in strips of thoracic aortas isolated from OLETF rats at the chronic stage of diabetes. In such aortas (vs. those from age-matched genetic control LETO rats): (1) the ET-1-induced contraction was enhanced, (2) the levels of HIF1α/ECE1/plasma ET-1 and plasma CML-AGEs were increased, (3) the ET-1-stimulated ERK phosphorylation mediated by ETA-R was increased, (4) the expression level of Jab1-modified ETA-R protein was reduced, and (5) the expression level of O-GlcNAcylated ETA-R protein was increased. Aortas isolated from such OLETF rats that had been treated with AG (50mg/kg/day for 10 weeks) exhibited reduced ET-1-induced contraction, suppressed ET-1-stimulated ERK phosphorylation accompanied by down-regulation of ETA-R, and increased modification of ETA-R by Jab1. Such AG-treated rats exhibited normalized plasma ET-1 and CML-AGE levels, and their aortas exhibited decreased HIF1α/ECE1 expression. However, such AG treatment did not alter the elevated levels of plasma glucose or insulin, or systolic blood pressure seen in OLETF rats. These data from the OLETF model suggest that within the timescale studied here, AG normalizes ET-1-induced aortic contraction by suppressing ETA-R/ERK activities and/or by normalizing the imbalance between Jab1 and O-GlcNAc in type 2 diabetes.

The combination of metallothionein and superoxide dismutase protects pancreatic β cells from oxidative damage

Reactive oxygen species are considered an important cause of the death of pancreatic β cells, thereby triggering the development of type 2 diabetes as well as failure of islet transplantation. The biological properties of metallothionein (MT) and superoxide dismutase (SOD) are likely to be related to their antioxidant and free-radical scavenging abilities, but their access across biological membranes is limited. We investigated whether Tat-MT and Tat-SOD fusion protein could be introduced into islets by a novel protein transduction technology and protect them from oxidative damage. We used 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and Annexin V/propidium iodide assays to analyse cell viability, and assessed expression of apoptosis marker proteins by Western blotting. We examined the protective effect of Tat-MT and Tat-SOD on the development of diabetes and on graft failure after syngeneic islet transplantation into Otsuka Long Evans Tokushima Fatty (OLETF) rats and Imprinting Control Region (ICR) mice, respectively. Tat-MT and Tat-SOD were successfully delivered into the rat islets, and reactive oxygen species, nitric oxide, glucolipotoxicity-induced cell death, cytokine injury, and DNA fragmentation due to ischaemia-reperfusion in pancreatic β cells were significantly reduced. In addition Tat-MT and Tat-SOD treatment protected OLETF rats from developing diabetes, and enhanced the survival of antioxidant-treated islets transplanted into the renal capsules of diabetic mice. Transduction of Tat-MT and Tat-SOD proteins offers a new strategy for protecting against the development of diabetes by relieving oxidative stress.

Anti-diabetic effect of standardized herbal formula PM021 consisting of Mori Folium and Aurantii Fructus on type II diabetic Otsuka Long–Evans Tokushima Fatty (OLETF) rats

PM021, which consists of two herbal components, Mori Folium and Aurantii Fructus, is routinely used to treat diabetes in Korea. In this study, the anti-diabetic effect of PM021 on an animal model of developing type 2 diabetes of Otsuka Long–Evans Tokushima Fatty (OLETF) rats was investigated. Eight weeks of age male OLETF rats were treated daily with PM021 or vehicle for five months. Specifically, changes in body weight, blood glucose, urine volume, food intake and oral glucose tolerance were measured in rats for five months. The rats in this study were divided into four groups: a Long–Evans Tokushima Otsuka (LETO) rat group, which is a genetic control group for OLETF, that received no treatment; a PM021 treatment group of LETO rats; OLETF rats that received no treatment; and OLETF rats that received PM021 treatment. The results showed that PM021 significantly prevented increases in body weight, blood glucose, and urine and food intake that resulted from the induction of obesity and diabetes. PM021 also improved glucose tolerance in OLETO rats. However, PM021 had no effect on LETO rats, a control group of OLETF rats. Taken together, these findings indicate that PM021 has distinct anti-diabetic effects without any adverse effects or toxicities.

1114 THE EFFECT OF ETHANOL INTAKE ON RHO-KINASE SIGNALING PATHWAY IN TYPE 2 DM RATS

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Basic Research1 Apr 20111114 THE EFFECT OF ETHANOL INTAKE ON RHO-KINASE SIGNALING PATHWAY IN TYPE 2 DM RATS Soo Jin Kim, Woong Jin Bae, Jin Hee Han, Sung Hoo Hong, Sae Woong Kim, Tae-Kon Hwang, Dae Jin Kim, and Ji Youl Lee Soo Jin KimSoo Jin Kim Seoul, Korea, Republic of More articles by this author , Woong Jin BaeWoong Jin Bae Seoul, Korea, Republic of More articles by this author , Jin Hee HanJin Hee Han Seoul, Korea, Republic of More articles by this author , Sung Hoo HongSung Hoo Hong Seoul, Korea, Republic of More articles by this author , Sae Woong KimSae Woong Kim Seoul, Korea, Republic of More articles by this author , Tae-Kon HwangTae-Kon Hwang Seoul, Korea, Republic of More articles by this author , Dae Jin KimDae Jin Kim Seoul, Korea, Republic of More articles by this author , and Ji Youl LeeJi Youl Lee Seoul, Korea, Republic of More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.711AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Cavernosal smooth muscle relaxation plays a major role in erectile function, which is regulated by the Rho-Kinase signaling pathway and NO/cGMP pathways. Therefore we investigated the effect of ethanol intake on Rho kinase signal pathway in corpus cavernosum of type 2 DM rat. METHODS Otsuka Long Evans Tokushima Fatty (OLETF) rats (n=28) and Long Evans Tokushima Otsuka (LETO, n=28) rats were used. LETO is a normal control of OLETF. The animals were assigned to 4 groups: LC group, LETO rats were fed with isocaloric diets (n=14); LE group, LETO rats were fed with 36 % ethanol, 7g/kg/day for 10 weeks (n=14); OC group, OLETF rats were fed with isocaloric diets (n=14); OE group, OLETF rats were fed with 36 % ethanol, 7g/kg/day for 10 weeks (n=14). During the experiment, body weights and fasting glucose levels were check in all animals. After 10 weeks, RT-PCR for 3 RhoGEFs (PDZ-RhoGEF, LARG, p115-RhoGEF) and western blot for RhoA, Rho Kinase-¥á, Rho Kinase-¥â were performed in corpus cavernosum. The expression of endothelial NO synthase (eNOS) and nervous NO synthase (nNOS) in corpus cavernosum were evaluated by immunohistochemistry. RESULTS In non-alcoholic group, RhoGEFs (PDZ-RhoGEF, LARG, p115-RhoGEF) gene and RhoA/Rho-kinase protein expression in OLETF rats were significantly increased compared to LETO rats (P <0.05). After alcohol oral administration, the increased RhoGEFs/RhoA/Rho-Kinase expression in OLETF rats was obviously decreased (P <0.05). The expression of eNOS and nNOS in corpus cavernosum of alcoholic group were higher than non-alcoholic group. The expression of eNOS and nNOS were decreased in OC group compared with LC, LE and OE groups. CONCLUSIONS This study suggested oral administration of ethanol down-regulated Rho-Kinase signal pathway in corpus cavernosum of type 2 DM rat. These results showed that ethanol intake may have positive effect on erectile function in DM rat through Rho kinase pathway. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e448 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Soo Jin Kim Seoul, Korea, Republic of More articles by this author Woong Jin Bae Seoul, Korea, Republic of More articles by this author Jin Hee Han Seoul, Korea, Republic of More articles by this author Sung Hoo Hong Seoul, Korea, Republic of More articles by this author Sae Woong Kim Seoul, Korea, Republic of More articles by this author Tae-Kon Hwang Seoul, Korea, Republic of More articles by this author Dae Jin Kim Seoul, Korea, Republic of More articles by this author Ji Youl Lee Seoul, Korea, Republic of More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Increased expression of three-repeat isoforms of tau contributes to tau pathology in a rat model of chronic type 2 diabetes

The imbalance between three-repeat (3R) and four-repeat (4R) tau isoforms produced by the alternative splicing of tau exon 10 leads to neuronal instability and eventual neurodegeneration in tauopathy. However, the role of altered 3R/4R tau ratio in Alzheimer's disease (AD) remains controversial. It has been shown that the expression of 3R tau is modulated by peptide amyloid β (Aβ) and that 3R tau levels increase with the progression of AD. The incidence of AD increases in patients with type 2 diabetes mellitus (T2DM), and the comorbidity of these disorders is closely associated with both aging and disease duration. To investigate whether changes in 3R and 4R tau isoforms are involved in AD pathology pertaining to age-related T2DM, the expression of tau isoforms and their relationship with AD-like tau pathology were examined in a spontaneous T2DM model using aged Otsuka Long–Evans Tokushima Fatty (OLETF) rats with obesity. An AD-like pathology consisting of increased aggregates in the neuronal cytoplasm and a loss of synaptic proteins was observed in these rats. The aggregates were reactive with a 3R tau-specific, but not 4R tau-specific, antibody. In contrast to 4R tau, the level of 3R tau profoundly increased and the proteins were prone to taking toxic phosphorylated and truncated forms. Taken together, these findings suggest that increased 3R tau may contribute to AD-like tau pathology in a chronic T2DM model. Thus, the restoration of normal 3R tau expression should be considered as an important therapeutic strategy in the treatment of AD.

Daily physical activity enhances reactivity to insulin in skeletal muscle arterioles of hyperphagic Otsuka Long-Evans Tokushima Fatty rats.

Insulin-mediated glucose disposal is dependent on the vasodilator effects of insulin. In type 2 diabetes, insulin-stimulated vasodilation is impaired as a result of an imbalance in NO and ET-1 production. We tested the hypothesis that chronic voluntary wheel running (RUN) prevents impairments in insulin-stimulated vasodilation associated with obesity and type 2 diabetes independent of the effects of RUN on adiposity by randomizing Otsuka Long Evans Tokushima Fatty (OLETF) rats, a model of hyperphagia-induced obesity and type 2 diabetes, to 1) RUN, 2) caloric restriction (CR; diet adjusted to match body weights of RUN group), or 3) sedentary control (SED) groups (n = 8/group) at 4 wk. At 40 wk, NO- and ET-1-mediated vasoreactivity to insulin (1-1,000 μIU/ml) was assessed in the presence of a nonselective ET-1 receptor blocker (tezosentan) or a NO synthase (NOS) inhibitor [N(G)-nitro-L-arginine methyl ester (L-NAME)], respectively, in second-order arterioles isolated from the white portion of the gastrocnemius muscle. Body weight, fasting plasma glucose, and hemoglobin A1c were lower in RUN and CR than SED (P < 0.05); however, the glucose area under the curve (AUC) following the intraperitoneal glucose tolerance test was lower only in the RUN group (P < 0.05). Vasodilator responses to all doses of insulin were greater in RUN than SED or CR in the presence of a tezosentan (P < 0.05), but group differences in vasoreactivity to insulin with coadministration of L-NAME were not observed. We conclude daily wheel running prevents obesity and type 2 diabetes-associated declines in insulin-stimulated vasodilation in skeletal muscle arterioles through mechanisms that appear to be NO mediated and independent of attenuating excess adiposity in hyperphagic rats.

Involvement of cholecystokinin in baseline and post-prandial whole body insulin sensitivity in rats

The objective of the study was to investigate the role of cholecystokinin (CCK) on the food-induced insulin sensitization phenomenon in healthy Long Evans Tokushima Otsuka (LETO) and Otsuka Long Evans Tokushima Fatty (OLETF) rats. Whole body insulin sensitivity determined by hyperinsulinaemic euglycaemic glucose clamping and the rapid insulin sensitivity test served as endpoints. Determinations were done in both fasted and re-fed animals. The involvement of CCK in post-prandial insulin sensitization was assessed by using proglumide, a CCK receptor blocker, by assessment of hypothalamic CCK-1/CCK-2 receptor expression by rt-PCR technique and by plasma insulin immunoreactivity determinations by means of radioimmunoassay as pharmacological, genetic and analytical approaches, respectively. The body weight of the OLETF rats and the amount of food consumed much exceeded those seen with LETO rats. The post-prandial increase in insulin sensitivity was marked in LETO, but not in OLETF rats. Intravenous proglumide attenuated post-prandial insulin sensitivity in LETO rats, with no effect in OLETF rats. Nevertheless, baseline insulin sensitivity was much lower in OLETF than in LETO rats. Treatment with rosiglitazone increased baseline insulin sensitivity of OLETF rats and evoked an increase in CCK-1 receptor gene expression in LETO rats. The results provide evidence for the involvement of CCK receptors in adjustment of both fasting and post-prandial insulin sensitivity. The data obtained with OLETF rats strongly suggest the predominant role of CCK-1 receptors.

Anxiety-like behavior and locomotion in CCK 1 knockout rats as a function of strain, sex and early maternal environment

CCK is a peptide broadly distributed in the brain that is involved in the regulation of emotional behaviors through its binding to CCK 1 and CCK 2 receptors. Research has shown altered emotional and activity phenotypes in (male) Otsuka Long Evans Tokushima Fatty (OLETF) rats that lack CCK 1 receptors. In the present study, we examined anxiety-like behaviors, locomotion and corticosterone levels in OLETF and control (Long Evans Tokushima Otsuka (LETO)) strains (Experiment 1), and after cross-fostering and in-fostering conditions (Experiment 2), in males and females. The aim was to examine the early maternal contribution to the offspring's behaviors as examined in the elevated plus-maze and open-field paradigms. The results suggest a genetic/prenatal predisposition to moderate anxiety-like behaviors in the OLETF strain, especially in the males. Cross-fostering OLETF females to LETO dams significantly improved their performance both in the open field and the elevated plus maze. Hypo-locomotion was evident in OLETF rats of both sexes and remained unchanged regardless of the rearing conditions. LETO rats’ behavior was not affected by cross-fostering. Basal corticosterone levels remained similar among all groups at weaning and adulthood. The improvement in the OLETF strain's overall performance after adoption suggests a maternal contribution to the altered phenotype of these rats. The findings demonstrated the contribution of genetics, sex and early maternal environment to anxiety-like behaviors and locomotion in CCK 1 knockout rats, suggesting in addition to locomotion-reduction, the mutation may predispose the animals (rather than directly induce) to a moderate anxious phenotype.

Altered orosensory sensitivity to oils in CCK-1 receptor deficient rats

CCK-1 receptor deficient Otsuka Long Evans Tokushima Fatty (OLETF) rats are hyperphagic, which leads to subsequent obesity and diabetes. Additionally, they have increased sham intake and enhanced preference for sucrose solutions relative to control, Long Evans Tokushima Otsuka (LETO) rats. To determine the effects of oil on ingestion, we first measured real feeding of various concentrations of oil emulsions (12.5, 25, 50, 75, and 100%) in rats that were fed ad libitum. Secondly, to isolate the orosensory compontent of oils from post-ingestive consequences, as well as determine the contribution of energy status, we measured sham feeding in OLETF and LETO rats using one-bottle acceptance tests while non-deprived and overnight food deprived. Finally, to assess the orosensory effects of nutritive and non-nutritive oils, we used two-bottle preference tests in sham fed OLETF and LETO rats. We found that real feeding resulted in increased intake of high oil concentrations for OLETF rats relative to LETO rats. Similarly, OLETF rats consumed significantly more of higher concentration corn oils than LETO while non-deprived sham feeding. Conversely, OLETF rats overconsumed low concentration corn oil compared to LETO during overnight deprived sham-feeding tests. In two-bottle sham-feeding preference tests, both non-deprived OLETF and LETO rats preferred corn to mineral oil. Collectively, these results show that increased oil intake in OLETF rats is driven by both peripheral deficits to satiation and altered orosensory sensitivity.

The α-glucosidase inhibitor miglitol delays the development of diabetes and dysfunctional insulin secretion in pancreatic β-cells in OLETF rats

The Otsuka Long–Evans Tokushima Fatty (OLETF) rat, an animal model of type 2 diabetes, exhibits obesity, hyperglycemia and hyperlipidemia, with late onset of chronic and slowly progressive hyperinsulinemia. In this study, we examined effects of long-term dietary supplementation with the α-glucosidase inhibitor miglitol on the development of diabetes and the reduction of β-cells in the pancreas of OLETF rats. The OLETF rats were fed a control diet or a diet containing 800 ppm miglitol (miglitol diet) for 65 weeks from pre-onset stage (5 weeks old). The non-fasting blood glucose concentrations gradually increased in OLETF rats fed the control diet and, at week 64, were significantly higher than those in OLETF rats fed the miglitol diet and age-matched Long–Evans Tokushima Otsuka (LETO) rats, which are control, non-diabetic, non-obese rats of the same strain. Oral glucose tolerance tests revealed that OLETF rats fed the control diet showed pronounced impaired glucose tolerance, but those fed the miglitol diet did not. Furthermore, insulin concentrations after glucose-loading were significantly lower in OLETF rats fed the control diet than in those fed the miglitol diet. The islets of 65-week-old OLETF rats fed the control diet showed significant fibrosis and loss of β-cells, while those of age-matched control LETO rats had a normal appearance. Feeding OLETF rats a miglitol diet reduced fibrosis and the loss of β-cells. Our results suggest that dietary supplementation with miglitol from pre-onset stage in OLETF rats delays the onset and development of diabetes and preserves the insulin secretory function of pancreatic islets.

Parabrachial Coding of Sapid Sucrose:

Cumulative evidence in rats suggests that the pontine parabrachial nuclei (PBN) are necessary for assigning hedonic value to taste stimuli. In a series of studies, our laboratory has investigated the parabrachial coding of sapid sucrose in normal and obese rats. First, using chronic microdialysis, we demonstrated that sucrose intake increases dopamine release in the nucleus accumbens, an effect that is dependent on oral stimulation and on concentration. The dopamine response was independent of the thalamocortical gustatory system but was blunted substantially by lesions of the PBN. Similar lesions of the PBN but not the thalamic taste relay diminished cFos activation in the nucleus accumbens caused by sucrose ingestion. Recent single-neuron recording studies have demonstrated that processing of sucrose-evoked activity in the PBN is altered in Otsuka Long Evans Tokushima Fatty (OLETF) rats, which develop obesity due to chronic overeating and express increased avidity to sweet. Compared with lean controls, taste neurons in OLETF rats had reduced overall sensitivity to sucrose and altered concentration responses, with decreased responses to lower concentrations and augmented responses to higher concentrations. The decreased sensitivity to sucrose was specific to NaCl-best neurons that also responded to sucrose, but the concentration effects were carried by the sucrose-specific neurons. Collectively, these findings support the hypothesis that the PBN enables taste stimuli to engage the reward system and, in doing so, influences food intake and body weight regulation. Obesity, in turn, may further alter the gustatory code via forebrain connections to the taste relays or hormonal changes consequent to weight gain.

Cocaine- and amphetamine-regulated transcript peptide immunoreactivity in the brain of the CCK-1 receptor deficient obese OLETF rat

Cocaine- and amphetamine-regulated transcript (CART) peptide is expressed in brain areas involved in homeostatic regulation and reward. CART has been shown to reduce food intake, but the underlying mechanisms and the relevance of this effect on obesity yet remain unknown. Therefore, we used immunohistochemistry to investigate the expression of CART peptide in various brain regions of the obese Otsuka Long Evans Tokushima Fatty (OLETF) rats lacking the CCK-1 receptor. Analysis revealed that whereas the distribution of CART-peptide immunoreactive neurons and axonal networks was identical in OLETF rats and lean controls, the intensity of CART immunoreactivity was significantly reduced in the rostral part of the nucleus accumbens (p < 0.01), the basolateral complex of the amygdala (p < 0.05) and the rostro-medial nucleus of the solitary tract (p < 0.001) of the OLETF rats. These areas are involved in reward and integration of taste and viscerosensory information and have been previously associated with altered functions in this strain. The findings suggest that in addition to previously described deficits in peripheral satiety signals and augmented orexigenic regulation, the anorectic effect of CART peptide may also be diminished in OLETF rats.

Effects of combined olmesartan and pravastatin on glucose intolerance and cardiovascular remodeling in a metabolic-syndrome model

Hypertension and dyslipidemia frequently coexist in patients with progressive insulin resistance and thus constitute metabolic syndrome. We sought to determine the merits of combining an angiotensin II receptor blocker and a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor in treating this pathological condition. Five-week-old Otsuka Long-Evans Tokushima Fatty rats, a model of metabolic syndrome, were untreated or treated with olmesartan 3 mg kg(-1) per day, pravastatin 30 mg kg(-1) per day or their combination for 25 weeks. Long-Evans Tokushima Otsuka rats served as normal controls. The antihypertensive effect of olmesartan and the lipid-lowering properties of pravastatin were both augmented by the combination. The oral glucose tolerance test revealed that only the combined treatment significantly reduced the area under the time-glucose curve, which was accompanied by augmented adiponectin messenger RNA expression in epididymal adipose tissue. Although the total cardiac endothelial nitric oxide synthetase (eNOS) content did not significantly differ among the groups, the combined treatment significantly increased the content of dihydrofolate reductase, a key eNOS coupler. Dihydroethidium staining of the aorta showed that the combination most significantly attenuated superoxide production. Moreover, Azan-Mallory staining revealed that the combination most significantly limited the perivascular fibrosis and wall thickening of intramyocardial coronary arteries. In conclusion, the combination of olmesartan and pravastatin augmented adiponectin expression in white adipose tissue and improved glucose tolerance in a rat model of metabolic syndrome, which was associated with more significant ameliorations of cardiovascular redox state and remodeling than those by treatments with either agent alone.