Long-Evans Tokushima Otsuka Rats Research Articles

Alteration of Sweet and Bitter Taste Sensitivity with Development of Glucose Intolerance in Non-insulin-Dependent Diabetes Mellitus Model OLETF Rats.

Patients with diabetes exhibit altered taste sensitivity, but its details have not been clarified yet. Here, we examined alteration of sweet taste sensitivity with development of glucose intolerance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats as a model of non-insulin-dependent diabetes mellitus. Compared to the cases of Long Evans Tokushima Otsuka (LETO) rats as a control, glucose tolerance of OLETF rats decreased with aging, resulting in development of diabetes at 36-weeks-old. In brief-access tests with a mixture of sucrose and quinine hydrochloride, OLETF rats at 25 or more-weeks-old seemed to exhibit lower sweet taste sensitivity than age-matched LETO ones, but the lick ratios of LETO, but not OLETF, rats for the mixture and quinine hydrochloride solutions decreased and increased, respectively, aging-dependently. Expression of sweet taste receptors, T1R2 and T1R3, in circumvallate papillae (CP) was almost the same in LETO and OLETF rats at 10- and 40-weeks-old, while expression levels of a bitter taste receptor, T2R16, were greater in 40-weeks-old rats than in 10-weeks-old ones in both strains. There was no apparent morphological alteration in taste buds in CP between 10- and 40-weeks-old LETO and OLETF rats. Metagenomic analysis of gut microbiota revealed strain- and aging-dependent alteration of mucus layer-regulatory microbiota. Collectively, we concluded that the apparent higher sweet taste sensitivity in 25 or more-weeks-old OLETF rats than in age-matched LETO rats was due to the aging-dependent increase of bitter taste sensitivity in LETO rats with alteration of the gut microbiota.

Effect of Anagliptin on Vascular Injury in the Femoral Artery of Type 2 Diabetic Rats.

Patients with diabetes mellitus (DM) often experience complications such as peripheral arterial disease (PAD), which is thought to be caused by vascular damage resulting from increased oxidative stress. Dipeptidyl peptidase-4 inhibitors have been reported to reduce oxidative stress, although the exact mechanism remains unclear. This study aimed to investigate the impact of long-term (6 weeks) anagliptin treatment at a dose of 200 mg/kg/d against oxidative stress in the femoral artery of Otsuka Long-Evans Tokushima Fatty (OLETF) rats using a well-established animal model for type 2 DM. Serum toxic advanced glycation end-products concentrations and blood glucose levels after glucose loading were significantly elevated in OLETF rats compared to Long-Evans Tokushima Otsuka (LETO) rats but were significantly suppressed by anagliptin administration. Plasma glucagon-like peptide-1 concentrations after glucose loading were significantly increased in anagliptin-treated rats. Superoxide production and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in femoral arteries were significantly increased in OLETF rats compared to LETO rats but were significantly decreased by anagliptin administration. The expressions of NADPH oxidase components (p22phox in the intima region and p22phox and gp91phox in the media region) in the femoral artery were significantly increased in OLETF rats compared to LETO rats but were significantly suppressed by anagliptin administration. Furthermore, the femoral artery showed increased wall thickness in OLETF rats compared to LETO rats, but anagliptin administration reduced the thickening. This study suggests that long-term anagliptin administration can reduce oxidative stress in femoral arteries and improve vascular injury.

Pseudocannabinoid H4CBD improves glucose response during advanced metabolic syndrome in OLETF rats independent of increase in insulin signaling proteins.

Cannabidiol (CBD) use has grown exponentially more popular in the last two decades, particularly among older adults (>55 yr), though very little is known about the effects of CBD use during age-associated metabolic dysfunction. In addition, synthetic analogues of CBD have generated great interest because they can offer a chemically pure product, which is free of plant-associated contaminants. To assess the effects of a synthetic analogue of CBD (H4CBD) on advanced metabolic dysfunction, a cohort of 41-wk-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats were administered 200 mg H4CBD/kg by oral gavage for 4 wk. Animals were fed ad libitum and monitored alongside vehicle-treated OLETF and Long-Evans Tokushima Otsuka (LETO) rats, the lean-strain controls. An oral glucose-tolerance test (oGTT) was performed after 4 wk of treatment. When compared with vehicle-treated, OLETF rats, H4CBD decreased body mass (BM) by 15%, which was attributed to a significant loss in abdominal fat. H4CBD reduced glucose response (AUCglucose) by 29% (P < 0.001) and insulin resistance index (IRI) by 25% (P < 0.05) compared with OLETF rats. However, H4CBD did not statically reduce fasting blood glucose or plasma insulin, despite compensatory increases in skeletal muscle native insulin receptor (IR) protein expression (54%; P < 0.05). H4CBD reduced circulating adiponectin (40%; P < 0.05) and leptin (47%; P < 0.05) and increased ghrelin (75%; P < 0.01) compared with OLETF. Taken together, a chronic, high dose of H4CBD may improve glucose response, independent of static changes in insulin signaling, and these effects are likely a benefit of the profound loss of visceral adiposity.NEW & NOTEWORTHY Cannabis product use has grown in the last two decades despite the lack of research on Cannabidiol (CBD)-mediated effects on metabolism. Here, we provide seminal data on CBD effects during age-associated metabolic dysfunction. We gave 41-wk-old OLETF rats 200 mg H4CBD/kg by mouth for 4 wk and noted a high dose of H4CBD may improve glucose response, independent of static changes in insulin signaling, and these effects are likely a benefit of loss of visceral adiposity.

MP74-03 LONG-TERM ADMINISTRATION OF A PDE-5 INHIBITOR PREVENTS THE DEVELOPMENT OF BLADDER EPITHELIAL ATP INCREASE AND DECREASED DETRUSOR CONTRACTILITY IN TYPE 2 DIABETIC RATS

You have accessJournal of UrologyCME1 Apr 2023MP74-03 LONG-TERM ADMINISTRATION OF A PDE-5 INHIBITOR PREVENTS THE DEVELOPMENT OF BLADDER EPITHELIAL ATP INCREASE AND DECREASED DETRUSOR CONTRACTILITY IN TYPE 2 DIABETIC RATS Kabuto Takafumi, So Inamura, Hisato Kobayashi, Xinmin Zha, Keiko Nagase, Minekatsu Taga, Masaya Seki, Nobuki Tanaka, Yoshinaga Okumura, Osamu Yokoyama, and Naoki Tearada Kabuto TakafumiKabuto Takafumi More articles by this author , So InamuraSo Inamura More articles by this author , Hisato KobayashiHisato Kobayashi More articles by this author , Xinmin ZhaXinmin Zha More articles by this author , Keiko NagaseKeiko Nagase More articles by this author , Minekatsu TagaMinekatsu Taga More articles by this author , Masaya SekiMasaya Seki More articles by this author , Nobuki TanakaNobuki Tanaka More articles by this author , Yoshinaga OkumuraYoshinaga Okumura More articles by this author , Osamu YokoyamaOsamu Yokoyama More articles by this author , and Naoki TearadaNaoki Tearada More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003348.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: We examined a series of pathological conditions of bladder wall in a type 2 diabetes mellitus (T2DM) model (Otsuka Long-Evans Tokushima Fatty [OLEFT] rats) and evaluated the effects of a long-term administration of the PDE-5 inhibitor tadalafil (TA) on these conditions. METHODS: Male OLETF and Long-Evans Tokushima Otsuka (LETO) rats were used as T2DM and control groups, respectively. TA was orally administered for 12 weeks (wks) from the age of 36 wks. Bladder blood flow and ATP, prostaglandin E2 (PGE2), and nerve growth factor (NGF) released from the bladder epithelium were measured at 36 and 48 wks of age. Vesicular nucleotide transporter (VNUT), hypoxia-inducible factor-1 alpha (HIF-1α), 8-hydroxy-2′-deoxyguanosine (HIF-1α), the oxidative stress marker 8-OHdG, and the mRNA and protein of pro-inflammatory cytokines and growth factors in the bladder wall were measured by RT-PCRs and ELISAs. Bladder strip contractions to KCl and carbachol were monitored in the OLETF rat bladder. RESULTS: The bladder blood flow in the OLETF rats was decreased at 48 wks compared to 36 wks. TA increased the bladder blood flow. Epithelial ATP was significantly increased in OLETF compared to LETO and decreased by TA in both LETO and OLETF. The bladder VNUT expression was significantly elevated in OLETF versus LETO at 36 wks; it was further enhanced at 48 wks, but a significant decrease occurred with TA in both rat strains. HIF-1α and 8-OHdG of OLETF were upregulated at 48 wks and decreased by TA. In OLETF, the expressions of IL-6, IL-8, bFGF, TNF-α, TGF-β, IGF-1, and IGF1R were increased at 48 wks versus 36 wks. TA decreased IL-6, TNF-α, IGF-1 and IGF1R. In OLETF, the contractile response of bladder strips to KCl and carbachol decreased at 48 wks versus 36 wks, but it recovered after TA administration. CONCLUSIONS: These data suggest that impaired bladder blood flow resulted in increased expressions of HIF-1α, 8-OhdG, and various pro-inflammatory cytokines and growth factors In T2DM. As a result, the bladder epithelial ATP release was enhanced, possibly via VNUT upregulation. A long-term administration of a PDE-5 inhibitor could prevent the development of storage and voiding dysfunction associated with T2DM. This study is the first to suggest that epithelium-derived ATP may be involved in urine storage dysfunction in T2DM and tadalafil inhibits ATP release and improves bladder contraction. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e1069 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Kabuto Takafumi More articles by this author So Inamura More articles by this author Hisato Kobayashi More articles by this author Xinmin Zha More articles by this author Keiko Nagase More articles by this author Minekatsu Taga More articles by this author Masaya Seki More articles by this author Nobuki Tanaka More articles by this author Yoshinaga Okumura More articles by this author Osamu Yokoyama More articles by this author Naoki Tearada More articles by this author Expand All Advertisement PDF downloadLoading ...

PS-B03-8: ORAL CANNABIDIOL REDUCES ARTERIAL BLOOD PRESSURE DURING EARLY PHASE METABOLIC SYNDROME IN OLETF RATS

Objective: Cardiovascular disease (CVD) is the leading cause of death in the U.S. and a primary outcome of metabolic syndrome (MetS). MetS is diagnosed by the presentation of at least 3 of the 6 conditions including abdominal obesity, elevated arterial pressure, and glucose intolerance ± insulin resistance. Identifying the root cause of these conditions individually is difficult but developing new treatments, which can ameliorate the multiple conditions of MetS has greater potential to reduce later-onset CVD. The benefits of cannabidiol (CBD) is widely recognized for potent anti-inflammatory and antioxidative properties, which may be cardioprotective during isolated risk factor conditions. However, these effects have not been examined during MetS conditions. Design: A cohort of 14-week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats were administered 175 mg CBD/kg by oral gavage for 5 weeks (CBD; n = 8). Animals were fed ad libitum and monitored alongside vehicle-treated OLETF (OLETF; n = 8) and vehicle-treated Long-Evans Tokushima Otsuka (LETO) rats, the lean-strain controls (LETO; n = 8). Rats were implanted with biotelemeters to chronically measure arterial pressure [DSI; HD-S10]. An oral glucose tolerance test (oGTT) was performed after 5 weeks of treatment. Results: CBD reduced arterial pressure within the first week of dosing (6 ± 1.4 mmHg or 4.1%; p &lt; 0.05) and, after 5 weeks, by 9.7 ± 1.7 mmHg (6.5%; p &lt; 0.05) from baseline. CBD blunted body mass gain and reduced abdominal adiposity by 39% (p &lt; 0.0001) compared to untreated OLETF. Additionally, glucose absorption (AUCglucose 10 minutes after glucose bolus) was reduced 21% (p &lt; 0.01) and enhanced uptake (slope 60 minutes to 120 minutes after glucose bolus) by 160% (p &lt; 0.05). However, neither glucose response overall nor static fasting blood glucose were improved. On the other hand, insulin response (AUCinsulin) was reduced 77% (p &lt; 0.0001) compared to OLETF, which ultimately reduced calculated insulin resistance index (IRI) of 79% (p &lt; 0.0001). Moreover, CBD treatment reduced fasting plasma insulin by 76% compared to OLETF (p &lt; 0.001). CBD decreased adiposity by 59% (p &lt; 0.0001) associated with reduced plasma leptin. Conclusions: A chronic, high dose of CBD reduced the MetS-associated hypertension and other cluster factors. The renin-angiotensin-aldosterone system is a known driver of hypertension in humans with MetS and in the OLETF rat model and could be directly or indirectly modulated by CBD (analysis on-going). Collectively, CBD could be a novel and effective intervention strategy for early-stage hypertension and other metabolic risk factors associated with MetS.

Exercise training improves obesity-induced inflammatory signaling in rat brown adipose tissue

Chronic inflammation is considered as an etiology of obesity and type 2 diabetes. Brown adipose tissue (BAT) of obese animals shows increased inflammation. Regular exercise has anti-inflammatory effects; however, the effects of exercise training on BAT inflammation in obese animals remain unclear. Thus, this study aimed to investigate the effects of exercise training on inflammation-related signaling in the BAT of obese and diabetic rats. Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an obese/diabetic rodent model, were randomly divided into either sedentary (n = 11) or exercise training (n = 8) groups. Long-Evans Tokushima Otsuka (LETO; n = 9) rats were used as the nondiabetic sedentary controls. Exercise training using a treadmill was conducted 4 days per week for 20 weeks, starting at 5 weeks old. As a result, exercise training attenuated the phosphorylation levels of p65 and mitogen-activated protein kinases in the BAT of OLETF rats, concurrently with the improvement of obesity and systemic glucose tolerance. Moreover, exercise training decreased oxidative stress and increased the antioxidant and anti-inflammatory protein levels in the BAT. Conversely, exercise training did not alter the expression levels of uncoupling protein-1 and oxidative phosphorylation-related proteins in the BAT, which were lower in the OLETF rats than the LETO rats. In conclusion, our data suggest that exercise training prevents the activation of inflammatory signaling in the BAT of obese/diabetic rats.

Histological Influences of Food Restriction on Brown Adipose Tissue in Young OLETF Rats

Whitening of brown adipose tissue (BAT) promotes obesity and causes obesity‐related health problems. It has been suggested that food restriction can prevent BAT whitening and inhibit the decline of BAT function with obesity. However, details of the histological feature remain unknown. The purpose of the present study was to investigate the influences of food restriction during childhood on histological features of BAT in Otsuka Long‐Evans Tokushima fatty (OLETF) rats.Male OLETF rats and Long‐Evans Tokushima Otsuka (LETO) rats were used as models of obesity and non‐obesity, respectively. OLETF rats were divided into the food restriction and ad libitum feeding groups. OLETF rats with food restriction were received the daily average amount of food consumed by same‐age LETO rats. The others were fed ad libitum with standard laboratory rodent chow from 4‐ to 20‐week‐old. At 20‐week‐old, the BAT was collected from the interscapular region and the sections were stained with hematoxylin and eosin for histological observation. This study was approved by the Institutional Animal Care and Use Committee of Hiroshima University (A19‐163) and conducted in accordance with the Hiroshima University Regulations for Animal Experimentation. All experiments complied with the National Institute of Health Guidelines for the Care and Use of Laboratory Animals.Body weight of OLETF rats ad libitum feeding was significantly higher than those of LETO rats and OLETF rats with food restriction at 20‐week‐old. Enlarged unilocular adipocytes were often located in the peripheral area of the adipose lobule, the number appeared to be higher in OLETF rats ad libitum feeding than in LETO rats. Although the number of whitened unilocular adipocytes located in the central area was significantly lower in OLETF rats with food restriction than in OLETF rats ad libitum feeding, the number of enlarged unilocular adipocytes located in the peripheral area was a bit less in OLETF rats with food restriction.These results suggest that BAT whitening in young OLETF rats is started from the peripheral area of the adipose lobule, adipocytes located in the central area of the lobule translate from multilocular to unilocular with the progression of hyperphagia‐induced obesity.

Aerobic exercise training-induced follistatin-like 1 secretion in the skeletal muscle is related to arterial stiffness via arterial NO production in obese rats.

Follistatin‐like 1 (FSTL1), which is mainly secreted from skeletal muscle and myocardium, upregulates protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) phosphorylation in vascular endothelial cells. It is unclear whether skeletal muscle‐ and myocardium‐derived FSTL1 secretion induced by aerobic exercise training is involved in the reduction of arterial stiffness via arterial NO production in obese rats. This study aimed to clarify whether aerobic exercise training‐induced FSTL1 secretion in myocardium and skeletal muscle is associated with a reduction in arterial stiffness via arterial Akt‐eNOS signaling pathway in obese rats. Sixteen Otsuka Long‐Evans Tokushima Fatty (OLETF) obese rats were randomly divided into two groups: sedentary control (OLETF‐CON) and eight‐week aerobic exercise training (treadmill for 60min at 25m/min, 5days/week, OLETF‐AT). Eight Long‐Evans Tokushima Otsuka (LETO) rats were used as a healthy sedentary control group. In OLETF‐CON, serum FSTL1, arterial Akt and eNOS phosphorylation, and arterial nitrite/nitrate (NOx) levels were significantly lower, and carotid‐femoral pulse wave velocity (cfPWV) was significantly greater than those in LETO. These parameters were improved in the OLETF‐AT compared to the OLETF‐CON. In the OLETF‐AT, FSTL1 levels in slow‐twitch fiber‐rich soleus muscle were significantly greater than those in the OLETF‐CON, but not in myocardium, fast‐twitch fiber‐rich tibialis anterior muscle, and adipose tissue. Serum FSTL1 levels were positively correlated with soleus FSTL1, arterial eNOS phosphorylation, and NOx levels and negatively correlated with cfPWV. Thus, aerobic exercise training‐induced FSTL1 secretion in slow‐twitch fiber‐rich muscles may be associated with a reduction in arterial stiffness via arterial NO production in obese rats.

Phosphodiesterase 5 inhibitor suppresses prostate weight increase in type 2 diabetic rats

Aims: Hyperinsulinemia is an important causative factor of prostate enlargement in type 2 diabetes (T2D), however, clinically prostate weight increases during hypoinsulinemic condition. To investigate the pathogenesis of prostate enlargement and effects of phosphodiesterase 5 inhibitor (PDE5i), male Otsuka Long-Evans Tokushima Fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) rats were used as T2D and control, respectively.Materials and Methods: OLETF and LETO rats were treated with oral tadalafil (100 μg/kg/day) or vehicle for 12 wks from at the age of 36 wks.Key findings: Prostate weight of OLETF rats was significantly higher than that of LETO at 36 wks, and increased at 48 wks. In OLETF rats, prostate blood flow was significantly lower at 48 wks versus 36 wks. Twelve-week-tadalafil treatment increased prostate blood flow and suppressed prostate weight increase in both strains. This change was inversely correlated with changes in prostate expressions of hypoxia-inducible factor-1 alpha (HIF-1α) and 8-hydroxy-2′-deoxyguanosine (8-OHdG). Increases with age were observed in mRNA and/or protein levels of cytokines interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha (TNF-α) and cell growth factors insulin-like growth factor-1 (IGF-1), basic fibroblast growth factor (bFGF), and transforming growth factor-beta (TGF-β); especially IL-6, TNF-α, IGF-1, bFGF and TGF-β increased with T2D. Tadalafil suppressed these cytokines and growth factors.Significance: These data suggest chronic ischemia caused by T2D leads to oxidative stress, resulting in prostate enlargement through upregulation of several cytokines and growth factors. Treatment with PDE5i improves prostate ischemia and might prevent enlargement via suppression of cytokines and growth factors in T2D.

D-allulose protects against diabetic nephropathy progression in Otsuka Long-Evans Tokushima Fatty rats with type 2 diabetes.

d-allulose is a rare sugar that has been reported to possess anti-hyperglycemic effects. In the present study, we hypothesized that d-allulose is effective in attenuating the progression of diabetic nephropathy in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat model of type 2 diabetes mellitus. Drinking water with or without 3% d-allulose was administered to OLETF rats for 13 weeks. Long-Evans Tokushima Otsuka rats that received drinking water without d-allulose were used as non-diabetic control rats. d-allulose significantly attenuated the increase in blood glucose levels and progressive mesangial expansion in the glomerulus, which is regarded as a characteristic of diabetic nephropathy, in OLETF rats. d-allulose also attenuated the significant increases in renal IL-6 and tumor necrosis factor-α mRNA levels in OLETF rats, which is a proinflammatory parameter. Additionally, we showed that d-allulose suppresses mesangial matrix expansion, but its correlation with suppressing renal inflammation in OLETF rats should be investigated further. Collectively, our results support the hypothesis that d-allulose can prevent diabetic nephropathy in rats.

Reductions in Intestinal Taurine-Conjugated Bile Acids and Short-Chain Fatty Acid-Producing Bacteria Might be Novel Mechanisms of Type 2 Diabetes Mellitus in Otsuka Long-Evans Tokushima Fatty Rats.

The pathogenesis of spontaneously diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats, among the best models for human type 2 diabetes mellitus (T2DM), remains poorly defined. Therefore, we investigated the dynamic changes in taurine-conjugated bile acids (T-BAs) and intestinal microbiota during T2DM development in OLETF rats. OLETF rats and corresponding diabetes-resistant Long Evans Tokushima Otsuka (LETO) rats were fed a normal baseline diet. The progress of T2DM was divided into four phases, including normal glycemia-normal insulinemia (baseline), normal glycemia-hyperinsulinemia, impaired glucose tolerance, and DM. Body weight, liver function, blood lipids, fasting plasma glucose, fasting plasma insulin, fasting plasma glucagon-like peptide (GLP)-1 and GLP-2, serum and fecal T-BAs, and gut microbiota were analyzed during the entire course of T2DM development. There were reductions in fecal T-BAs and short-chain fatty acids (SCFAs)-producing bacteria including Phascolarctobacterium and Lactobacillus in OLETF rats compared with those in LETO rats at baseline, and low levels of fecal T-BAs and SCFAs-producing bacteria were maintained throughout the whole course of the development of T2DM among OLETF rats compared with those in corresponding age-matched LETO rats. Fecal taurine-conjugated chenodeoxycholic acid correlated positively with Phascolarctobacterium. Fecal taurine-conjugated deoxycholic acid correlated positively with Lactobacillus and fasting plasma GLP-1 and inversely with fasting plasma glucose. The fecal BAs profiles and microbiota structure among OLETF rats were different from those of LETO rats during the entire course of T2DM development, indicating that reductions in intestinal T-BAs and specific SCFA-producing bacteria may be potential mechanisms of T2DM in OLETF rats.

Subproteomic profiling from renal cortices in OLETF rats reveals mutations of multiple novel genes in diabetic nephropathy.

Diabetic nephropathy (DN) is a serious threat to human health, but its pathogenesis is not fully understood. Otsuka Long-Evans Tokushima Fatty (OLETF) rats are very similar to human DN in many aspects such as pathological changes and processes, and are deemed to be an ideal rodent model. This study was aimed to explore the pathogenesis of DN by analyzing the protein expression profile from renal cortices in OLETF rats. Thirty-six-week-old diabetic OLETF rats and normal control Long-Evans Tokushima Otsuka (LETO) rats were nephrectomized, and the renal cortices were isolated. The proteins were separated by soluble and insoluble high-resolution subproteomics methods for the analysis and identification of differential proteins. Thirty-six differentially expressed proteins were found. Among them, 11 proteins had different isoelectric points and molecular weights between OLETF and LETO rats. Further sequencing identified point mutations in genes encoding eight of these proteins, which are involved in many biological processes closely related to DN, including oxidative stress and inflammation. Five of these eight proteins have not been reported in DN. This study reveals mutations of multiple novel genes in diabetic OLETF rats, providing some new potential targets for the pathogenesis of DN and helping to better understand the pathogenesis of DN.

Impact of Exercise and Detraining during Childhood on Brown Adipose Tissue Whitening in Obesity.

This study aimed to investigate the influence of childhood exercise and detraining on brown adipose tissue (BAT) whitening in obesity. Four-week-old male Long-Evans Tokushima Otsuka (LETO) rats (n = 9) and Otsuka Long-Evans Tokushima Fatty (OLETF) rats (n = 24) were used as non-obese and obese animals, respectively. OLETF rats were divided into non-exercise sedentary (n = 9) and exercise groups. OLETF rats in the exercise group were further divided into subgroups according to the exercise period—exercise from 10- to 12-weeks-old (n = 6); and exercise from 4- to 6-weeks-old, and detraining from 6- to 12-weeks-old (n = 9). At 12-weeks-old, immediately after exercise period, BAT whitening in OLETF rats was inhibited by exercise despite the fact that hypertrophy was not caused in the plantaris muscle. However, the effectiveness was attenuated during the detraining period. Histological BAT whitening and downregulation of uncoupling protein-1 (UCP-1) were found in non-exercise sedentary OLETF rats at 12-weeks-old. The downregulation was not inhibited, even though exercise histologically inhibited BAT whitening in OLETF rats. Childhood exercise decreased BAT whitening in obesity. Detraining attenuated the inhibition of BAT whitening. These results suggest that regular exercise is needed to improve BAT whitening and downregulation of UCP-1 in obesity.

Medial prefrontal area reductions, altered expressions of cholecystokinin, parvalbumin, and activating transcription factor 4 in the corticolimbic system, and altered emotional behavior in a progressive rat model of type 2 diabetes.

Metabolic disorders are associated with a higher risk of psychiatric disorders. We previously reported that 20-week-old Otsuka Long-Evans Tokushima fatty (OLETF) rats, a model of progressive type 2 diabetes, showed increased anxiety-like behavior and regional area reductions and increased cholecystokinin-positive neurons in the corticolimbic system. However, in which stages of diabetes these alterations in OLETF rats occur remains unclear. We aimed to investigate anxiety-like behavior and its possible mechanisms at different stages of type 2 diabetes in OLETF rats. Eight- and 30-week-old OLETF rats were used as diabetic animal models at the prediabetic and progressive stages of type 2 diabetes respectively, and age-matched Long-Evans Tokushima Otsuka rats served as non-diabetic controls. In the open-field test, OLETF rats showed less locomotion in the center zone and longer latency to leave the center zone at 8 and 30 weeks old, respectively. The areas of the medial prefrontal cortex were smaller in the OLETF rats, regardless of age. The densities of cholecystokinin-positive neurons in OLETF rats were higher in the lateral and basolateral amygdala only at 8 weeks old and in the anterior cingulate and infralimbic cortices and hippocampal cornu ammonis area 3 at both ages. The densities of parvalbumin-positive neurons of OLETF rats were lower in the cornu ammonis area 2 at 8 weeks old and in the prelimbic and infralimbic cortices at both ages. No apoptotic cell death was detected in OLETF rats, but the percentage of neurons co-expressing activating transcription factor 4 and cholecystokinin and parvalbumin was higher in OLETF rats at both ages in the anterior cingulate cortex and basolateral amygdala, respectively. These results suggest that altered emotional behavior and related neurological changes in the corticolimbic system are already present in the prediabetic stage of OLETF rats.

Sevoflurane and isoflurane inhibit KCl-induced, Rho kinase-mediated, and PI3K-participated vasoconstriction in aged diabetic rat aortas

BackgroundThe mechanism of volatile anesthetics on vascular smooth muscle (VSM) contraction in the setting of diabetes mellitus (DM) remains unclear. The current study was designed to determine the effects of sevoflurane (SEVO) and isoflurane (ISO) on phosphoinositide 3-kinase (PI3K) and Rho kinase (ROCK) mediated KCl-induced vasoconstriction in aged type 2 diabetic rats.MethodsKCl-induced (60 mM) contractions were examined in endothelium-denuded aortic rings from aged T2DM Otsuka Long-Evans Tokushima Fatty (OLETF) rats (65–70 weeks old), control age-matched nondiabetic Long-Evans Tokushima Otsuka (LETO) rats and young Wistar rats (6–8 weeks old). The effects of SEVO or ISO (1–3 minimum alveolar concentration, MAC) on KCl-induced vasoconstriction, as well as those of LY294002 (PI3K inhibitor) and Y27632 (ROCK inhibitor) were measured in aortic rings from the three groups using an isometric force transducer.ResultsKCl induced rapid and continuous contraction of aortic smooth muscle in the three groups, and the contraction was more obvious in OLETF rats.SEVO and ISO inhibited KCl-induced vasoconstriction in a concentration-dependent manner and were suppressed by LY294002 (10 µM) and Y27632 (1 µM). SEVO had a stronger inhibitory effect on the aortas of young Wistar rats than ISO, especially at 2 MAC and 3 MAC (P < 0.05). In aged rats, the inhibitory effect of ISO was stronger than that of SEVO, especially OLETF rats. There was no significant difference in the effects of different concentrations of ISO on arterial contraction among the three groups (P > 0.05). The effects of 1 MAC SEVO on Wistar rats and 3 MAC SEVO on OLETF rats, however, were noticeably and significantly different (P < 0.05).Compared with the control condition, LY294002 and Y27632 had the most noticeable effect on the KCl-induced contraction of aortic rings in OLETF rats (P < 0.01).ConclusionSEVO (3 MAC), ISO (1, 2, 3 MAC), LY294002 and Y27632 have more significant inhibitory effect on the contraction of vascular smooth muscle in aged T2MD rats. The mechanism of SEVO and ISO in vascular tension in T2DM is partly due to changes in PI3K and/or Rho kinase activity.

Allopurinol ameliorates high fructose diet induced hepatic steatosis in diabetic rats through modulation of lipid metabolism, inflammation, and ER stress pathway

Excess fructose consumption contributes to development obesity, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD). Uric acid (UA), a metabolite of fructose metabolism, may have a direct role in development of NAFLD, with unclear mechanism. This study aimed to evaluate role of fructose and UA in NAFLD and explore mechanisms of allopurinol (Allo, a UA lowering medication) on NAFLD in Otsuka Long-Evans Tokushima Fatty (OLETF) rats fed a high fructose diet (HFrD), with Long-Evans Tokushima Otsuka (LETO) rats used as a control. There were six groups: LETO, LETO-Allo, OLETF, OLETF-Allo, OLETF-HFrD, and OLETF-HFrD-Allo. HFrD significantly increased body weight, epididymal fat weight, and serum concentrations of UA, cholesterol, triglyceride, HbA1c, hepatic enzymes, HOMA-IR, fasting insulin, and two hour-glucose after intraperitoneal glucose tolerance tests, as well as NAFLD activity score of liver, compared to the OLETF group. Allopurinol treatment significantly reduced hepatic steatosis, epididymal fat, serum UA, HOMA-IR, hepatic enzyme levels, and cholesterol in the OLETF-HFrD-Allo group. Additionally, allopurinol significantly downregulated expression of lipogenic genes, upregulated lipid oxidation genes, downregulated hepatic pro-inflammatory cytokine genes, and decreased ER-stress induced protein expression, in comparison with the OLETF-HFrD group. In conclusion, allopurinol ameliorates HFrD-induced hepatic steatosis through modulation of hepatic lipid metabolism, inflammation, and ER stress pathway. UA may have a direct role in development of fructose-induced hepatic steatosis, and allopurinol could be a candidate for prevention or treatment of NAFLD.

Influences of exercise and detraining during childhood on brown adipose tissue in OLETF rats

Brown adipose tissue (BAT) oxidizes lipids to fuel thermogenesis. However, the activity declines in obesity due to brown-to-white conversion in BAT. Because the properties of adipose tissue are determined before adult, childhood exercise could prevent brown-to-white conversion and maintain metabolic activity of BAT in future. The purpose of the present study was to investigate histological influences of childhood exercise and detraining in BAT of genetic predisposition to obesity. Four-week-old male Long-Evans Tokushima Otsuka (LETO) rats and age-matched male Otsuka Long-Evans Tokushima fatty (OLETF) rats were used as non-obesity animals and spontaneous obesity animals, respectively. OLETF rats were divided into the non-exercise sedentary (OLETF Sed) or exercise groups. OLETF rats in the exercise group were further divided into subgroups according to exercise age. OLETF rats in the exercise groups were placed in the cages with a running wheel for 12 h (20:00 to 8:00) daily from 4 to 6 (OLETF Ex 4-6 w) or 10 to 12 (OLETF Ex 10-12 w) weeks of age (i.e. the OLETF Ex 4-6 w group: exercise from 4 to 6-week-old, detraining from 6 to 12-week-old; the OLETF Ex 10-12 w group: non-exercise from 4 to 10-week-old, exercise from 10 to 12-week-old). Food and water were provided ad libitum. At 12-week-old, transverse sections were obtained from interscapular BAT and stained with hematoxylin and eosin for histological observation. The results at 12-week-old were shown below. The wet weights of interscapular BAT were significantly higher in the OLETF Sed group than in LETO rats. The values were significantly lower in the OLETF Ex 10-12 w group than in the OLETF Sed group. There were no significant differences for the weights between the OLETF Ex 4-6 w and OLETF Sed groups. Histological observation revealed conversion of brown adipocytes to white-like unilocular cells in both LETO and OLETF rats. In LETO rats, the white-like unilocular cells were located uniformly in the fat lobule. In OLETF rats, enlarged white-like unilocular cells were also observed in the peripheral zone of the lobule. There were no significant differences for the diameters of white-like unilocular cells located in the central zone of the lobule among the experimental groups. The densities of white-like unilocular cells located in the central zone of the lobule were significantly lower in the OLETF Ex 10-12 w group than in the other groups. There were no significant differences for the densities among LETO rats, the OLETF Sed, and OLETF Ex 4-6 w groups. Childhood Exercise immediately inhibited brown-to-white conversion in the BAT and decreased the mass. However, the effectiveness did not be maintained for a long time. These results suggested that chronic exercise is required to maintain adipose tissue browning in genetic predisposition to obesity.

Decreased Muscle‐derived Musclin by Chronic Resistance Exercise is Associated with Improved Insulin Resistance in Rats with Type 2 Diabetes

Introduction Chronic resistance exercise induces improved hyperglycemia in patients with type 2 diabetes mellitus. Musclin, a muscle-derived secretory factor, is involved in the induction of insulin resistance via the downregulation of the glucose transporter-4 (GLUT-4) signaling pathway in skeletal muscles. However, whether musclin affects the mechanism of resistance exercise remains unclear. This study aimed to test the hypothesis that decreased muscle-derived musclin secretion in chronic resistance exercise is involved in improvement of insulin resistance via the GLUT-4 signaling pathway in rats with type 2 diabetes. Methods Male, 20-week-old, Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type 2 diabetes model, were randomly divided into two groups: sedentary control (OLETF-Con) and chronic resistance exercise (OLETF-RT; climbing a ladder three times a week on alternate days for 8 weeks), whereas Long-Evans Tokushima Otsuka (LETO) rats were used as the nondiabetic sedentary control group. Results OLETF-Con rats showed increased fasting glucose levels, decreased insulin sensitivity index (QUICKI), muscle GLUT-4 translocation, and protein kinase B (Akt) phosphorylation, and concomitantly increased muscle musclin expression as compared with LETO rats (P < 0.01). In contrast, OLETF-RT rats significantly reduced muscle musclin expression, improved fasting glucose levels, and QUICKI through an accelerated muscle GLUT-4/Akt signaling pathway as compared with OLETF-Con rats (P < 0.01). Moreover, musclin protein levels in skeletal muscle were positively correlated with fasting blood glucose (r = 0.717, P < 0.01), and negatively correlated with QUICKI (r = -0.491, P < 0.05), muscle Akt phosphorylation (r = -0.475, P < 0.05), and GLUT-4 translocation levels (r = -0.643, P < 0.01). Conclusions These findings suggest that the reduction in muscle-derived musclin production by chronic resistance exercise may be involved in improved insulin resistance in rats with type 2 diabetes.

Effects of exercise on browning of adipose tissue in OLETF rat

Browning of subcutaneous white adipose tissue (WAT) is induced by stimulation of β3 adrenergic receptor agonist with cold exposure and exercise training. However, it is remained unknown whether browning of adipose tissue equally inducing between obesity and non-obesity. The purpose of the present study was to investigate the effects of exercise on browning of adipose tissue in obesity. Male Otsuka Long-Evans Tokushima fatty (OLETF) rats and Long-Evans Tokushima Otsuka (LETO) rats were used as models of obesity and non-obesity, respectively. The rats were divided into exercise and sedentary groups. The rats of exercise groups were placed in the cages with a running wheel for 12 h (20:00 to 8:00 h) daily from 19 to 21 weeks of age. Food and water were provided ad libitum. There were no significant differences in the amount of voluntary wheel running between animal strains. Although there were no significant differences in the expression level of uncoupling protein 1 (UCP1) of brown adipose tissue (BAT) between the exercise and sedentary groups of LETO rats, the expression levels were significantly higher in the exercise group than the sedentary group of OLETF rats. In the inguinal WAT, the expression levels of UCP1 were below the minimum detectable threshold among all groups in both strains. These results suggest differential sensitivity of activation of UCP1 in BAT between obesity and non-obesity. In addition, one of the reasons for undetectable exercise-induced UCP1 expression in the WAT could be due to the low intensity by voluntary wheel running. This study was approved by the Institutional Animal Care and Use Committee of Hiroshima University (A19-163) and conducted in accordance with the Hiroshima University Regulations for Animal Experimentation. All experiments complied with the National Institute of Health Guidelines for the Care and Use of Laboratory Animals.

Decreased muscle-derived musclin by chronic resistance exercise is associated with improved insulin resistance in rats with type 2 diabetes.

Chronic resistance exercise induces improved hyperglycemia in patients with type 2 diabetes mellitus. Musclin, a muscle‐derived secretory factor, is involved in the induction of insulin resistance via the downregulation of the glucose transporter‐4 (GLUT‐4) signaling pathway in skeletal muscles. However, whether musclin affects the mechanism of resistance exercise remains unclear. This study aimed to clarify whether decreased muscle‐derived musclin secretion in chronic resistance exercise is involved in the improvement of insulin resistance via the GLUT‐4 signaling pathway in rats with type 2 diabetes. Male, 20‐week‐old, Otsuka Long‐Evans Tokushima Fatty (OLETF) rats, a type 2 diabetes model, were randomly divided into two groups: sedentary control (OLETF‐Con) and chronic resistance exercise (OLETF‐RT; climbing a ladder three times a week on alternate days for 8 weeks), whereas Long‐Evans Tokushima Otsuka rats were used as the nondiabetic sedentary control group. OLETF‐Con rats showed increased fasting glucose levels, decreased insulin sensitivity index (QUICKI), muscle GLUT‐4 translocation, and protein kinase B (Akt) phosphorylation, and concomitantly increased muscle musclin expression. In contrast, OLETF‐RT rats significantly reduced muscle musclin expression, improved hyperglycemia, and QUICKI through an accelerated muscle GLUT‐4/Akt signaling pathway. Moreover, chronic resistance exercise‐induced reduction of muscle musclin was correlated with changes in fasting glucose, QUICKI, GLUT‐4 translocation, and Akt phosphorylation. These findings suggest that the reduction in muscle‐derived musclin production by chronic resistance exercise may be involved in improved insulin resistance in rats with type 2 diabetes.