Male Otsuka Long-Evans Tokushima Fatty Research Articles

Detraining after short-term exercise induces hyperphagia and obesity with fatty liver and brown adipose tissue whitening in young male OLETF rats.

This study examined the effects of exercise and detraining at a young age on fat accumulation in various organs. Four-week-old male Otsuka Long-Evans Tokushima Fatty (OLETF) rats were assigned to either the non-exercise sedentary (OLETF Sed) or exercise groups. The exercise group was subdivided into two groups: exercise between 4 and 12 weeks of age (OLETF Ex) and exercise between 4 and 6 weeks of age followed by non-exercise between 6 and 12 weeks of age (OLETF DT). Body weight was significantly lower in the OLETF Ex group than in the OLETF Sed group at 12 weeks of age. Fat accumulation in the epididymal white adipose tissue, liver, and brown adipose tissue was suppressed in the OLETF Ex group. During the exercise period, body weight and food intake in the OLETF DT group were significantly lower than those in the OLETF Sed group. However, food intake was significantly higher in the OLETF DT group than in the OLETF Sed group after exercise cessation, resulting in extreme obesity with fatty liver and brown adipose tissue whitening. Detraining after early-onset exercise promotes hyperphagia, causing extreme obesity. Overeating should be avoided during detraining periods in cases of exercise cessation at a young age.

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.

Correcting imbalance of sex hormones by a phosphodiesterase 5 inhibitor improves copulatory dysfunction in male rats with type 2 diabetes

IntroductionSexual dysfunction is a common complication in men with type 2 diabetes and is often refractory to treatment. This study investigated the long-term influence of the phosphodiesterase 5 inhibitor (PDE5I)...

SAT-173 Antiproliferative Effect of Teneligliptin on Atherosclerosis in Vascular Smooth Muscle Cell

Background and aims: In vivo and in vitro studies revealed that sitagliptin, linagliptin treatment suppressed proliferation of vascular smooth muscle cells (VSMCs). However, data are lacking regarding the effects of teneligliptin. Here, we demonstrate the effects of teneligliptin on VSMC proliferation and migration according to fluctuating glucose levels. Materials and methods: Primary cultures of male Otsuka Long-Evans Tokushima fatty (OLETF) rat VSMCs were obtained from enzymatically dissociated rat thoracic aorta. VSMCs with teneligliptin (100 μM) were incubated for 72 h with alternating normal (5.5 mmol/L) and high glucose (25 mmol/L) media every 12 h. The proliferation of VSMCs, proliferative and apoptotic molecular pathway and the migration of VSMC were analyzed with teneligliptin. Results: In MTT assay, teneligliptin attenuated the increase in cells pretreated with 100-μM teneligliptin 72 h prior to glucose fluctuation (F+T group) in comparison with fluctuation group (F group) (p-value, 0.005). The protein levels of phospho-MEK1/2 and phospho-ERK1/2 were significantly reduced in F+T group compared with F group (phospho-MEK1/2, p-value, 0.016; phospho-ERK1/2, p-value, 0.001). However no changes in the protein levels of caspase 3, Bcl-2, and phospho-Bad, Bax, Bcl-xL, were observed. In wound healing assay, migrated cell percentage was attenuated in F+T group (p-value, 0.043). phospho-BMK protein levels was also reduced in F+T group (p-value, 0.017). Conclusion: This study has demonstrated that teneligliptin significantly reduces the proliferation and migration of VSMCs in intermittent hyperglycemic condition.

Soy Protein Isolate Suppresses Bone Resorption and Improves Trabecular Microarchitecture in Spontaneously Hyperphagic, Rapidly Growing Male OLETF Rats

BackgroundTraditionally, milk proteins have been recommended for skeletal health; recently, soy proteins have emerged as popular alternatives. Excess adiposity appears detrimental to skeletal health, as obese adolescents have increased fracture rates compared with healthy controls. However, soy protein effects on skeletal health during excess adiposity remain unknown. ObjectiveThe study objective was to examine the effects of isocaloric diets containing milk protein isolate (MPI), soy protein isolate (SPI), or a 50/50 combination (MIX) as the sole protein source on metabolic health indicators and bone outcomes in rapidly growing, hyperphagic, male Otsuka Long Evans Tokushima Fatty (OLETF) rats. MethodsOLETF rats, aged 4 wk, were randomly assigned to 3 treatment groups (MPI, SPI, or MIX, n = 20 per group) and provided with access to experimental diets ad libitum for 16 wk. ResultsBody mass did not differ between the groups, but SPI had lower percentage body fat than MPI (P = 0.026). Insulin was lower in MPI than in MIX (P = 0.033) or SPI (P = 0.044), but fasting blood glucose was not different between the groups. SPI significantly reduced serum cholesterol compared with MPI (P = 0.001) and MIX (P = 0.002). N-terminal propeptide of type I collagen (P1NP) was higher in MIX than MPI (P = 0.05); C-terminal telopeptide of type 1 collagen (CTx) was higher in MPI than SPI (P < 0.001) and MIX (P < 0.001); the P1NP to CTx ratio was significantly higher in SPI and MIX than in MPI (P < 0.001). Trabecular separation was reduced in SPI compared with MPI (P = 0.030) and MIX (P = 0.008); trabecular number was increased in SPI compared with MIX (P = 0.038). No differences were seen in cortical geometry and biomechanical properties. ConclusionsIn the context of excess adiposity, soy- and milk-based proteins have comparable effects on cortical bone geometry and biomechanical properties, whereas soy-based proteins favorably affect the trabecular microarchitecture, and the combination of both proteins may offer additional benefits to bone remodeling in rapidly growing male OLETF rats.

Exercise initiated after the onset of insulin resistance improves trabecular microarchitecture and cortical bone biomechanics of the tibia in hyperphagic Otsuka Long Evans Tokushima Fatty rats

The present study extends our previous findings that exercise, which prevents the onset of insulin resistance and type 2 diabetes (T2D), also prevents the detrimental effects of T2D on whole-bone and tissue-level strength. Our objective was to determine whether exercise improves bone's structural and material properties if insulin resistance is already present in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. The OLETF rat is hyperphagic due to a loss-of-function mutation in cholecystokinin-1 receptor (CCK-1 receptor), which leads to progressive obesity, insulin resistance and T2D after the majority of skeletal growth is complete. Because exercise reduces body mass, which is a significant determinant of bone strength, we used a body-mass-matched caloric-restricted control to isolate body-mass-independent effects of exercise on bone. Eight-wk old, male OLETF rats were fed ad libitum until onset of hyperglycemia (20weeks of age), at which time they were randomly assigned to three groups: ad libitum fed, sedentary (O-SED); ad libitum fed, treadmill running (O-EX); or, sedentary, mild caloric restriction to match body mass of O-EX (O-CR). Long-Evans Tokushima Otsuka rats served as the normophagic, normoglycemic controls (L-SED). At 32weeks of age, O-SED rats had T2D as evidenced by hyperglycemia and a significant reduction in fasting insulin compared to OLETFs at 20weeks of age. O-SED rats also had reduced total body bone mineral content (BMC), increased C-terminal telopeptide of type I collagen (CTx)/tartrate resistant acid phosphatase isoform 5b (TRAP5b), decreased N-terminal propeptide of type I procollagen (P1NP), reduced percent cancellous bone volume (BV/TV), trabecular number (Tb.N) and increased trabecular separation (Tb.Sp) and structural model index (SMI) of the proximal tibia compared to L-SED. T2D also adversely affected biomechanical properties of the tibial diaphysis, and serum sclerostin was increased and β-catenin, runt-related transcription factor 2 (Runx2) and insulin-like growth factor-I (IGF-I) protein expression in bone were reduced in O-SED vs. L-SED. O-EX or O-CR had greater total body bone mineral density (BMD) and BMC, and BV/TV, Tb.N, Tb.Sp, and SMI compared to O-SED. O-EX had lower CTx and CR greater P1NP relative to O-SED. O-EX, not O-CR, had greater cortical thickness and area, and improved whole-bone and tissue-level biomechanical properties associated with a 4-fold increase in cortical bone β-catenin protein expression vs. O-SED. In summary, EX or CR initiated after the onset of insulin resistance preserved cancellous bone volume and structure, and EX elicited additional benefits in cortical bone.

Insulin‐Stimulated Bone Blood Flow and Bone Biomechanical Properties Are Compromised in Obese, Type 2 Diabetic OLETF Rats

Type 2 diabetes (T2D) increases skeletal fragility and fracture risk; however, the underlying mechanisms remain to be identified. Impaired bone vascular function, in particular insulin‐stimulated vasodilation and blood flow is a potential, yet unexplored mechanism. The purpose of this study was to determine the effects of T2D on femoral biomechanical properties, trabecular microarchitecture, and insulin‐stimulated bone vasodilation by comparison of hyperphagic Otsuka Long‐Evans Tokushima Fatty (OLETF) rats with normoglycemic control OLETF rats. Four‐week old, male OLETF rats were randomized to two groups: type 2 diabetes (O‐T2D) or normoglycemic control (O‐CON). O‐T2D were allowed ad libitum access to a rodent chow diet and O‐CON underwent moderate caloric restriction (30% restriction relative to intake of O‐T2D) to maintain normal body weight (BW) and glycemia until 40 weeks of age. Hyperphagic O‐T2D rats had significantly greater BW, body fat, and blood glucose than O‐CON. Total cross‐sectional area (Tt.Ar), cortical area (Ct.Ar), Ct.Ar/Tt.Ar, and polar moment of inertia of the mid‐diaphyseal femur adjusted for BW were greater in O‐T2D rats versus O‐CON. Whole‐bone biomechanical properties of the femur assessed by torsional loading to failure did not differ between O‐T2D and O‐CON, but tissue‐level strength and stiffness adjusted for BW were reduced in O‐T2D relative to O‐CON. Micro–computed tomography (μCT) of the distal epiphysis showed that O‐T2D rats had reduced percent bone volume, trabecular number, and connectivity density, and greater trabecular spacing compared with O‐CON. Basal tibial blood flow assessed by microsphere infusion was similar in O‐T2D and O‐CON, but the blood flow response to insulin stimulation in both the proximal epiphysis and diaphyseal marrow was lesser in O‐T2D compared to O‐CON. In summary, impaired insulin‐stimulated bone blood flow is associated with deleterious changes in bone trabecular microarchitecture and cortical biomechanical properties in T2D, suggesting that vascular dysfunction might play a causal role in diabetic bone fragility. © 2017 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Soy compared with milk protein in a Western diet changes fecal microbiota and decreases hepatic steatosis in obese OLETF rats

Soy protein is effective at preventing hepatic steatosis; however, the mechanisms are poorly understood. We tested the hypothesis that soy vs. dairy protein-based diet would alter microbiota and attenuate hepatic steatosis in hyperphagic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Male OLETF rats were randomized to “Western” diets containing milk protein isolate (MPI), soy protein isolate (SPI) or 50:50 MPI/SPI (MS) (n=9–10/group; 21% kcal protein) for 16 weeks. SPI attenuated (P<.05) fat mass and percent fat by ~10% compared with MS, but not compared with MPI. Serum thiobarbituric acid reactive substance and total and low-density lipoprotein cholesterol concentrations were lower (P<.05) with dietary SPI vs. MPI and MS. Histological hepatic steatosis was lower (P<.05) in SPI compared with MPI or MS. Lipidomic analyses revealed reductions (P<.05) in hepatic diacylglycerols but not triacylglycerols in SPI compared with MPI, which was associated with lower hepatic de novo lipogenesis (ACC, FAS and SCD-1 protein content, and hepatic 16:1 n-7 and 18:1 n-7 PUFA concentrations) (P<.05) compared with MPI and MS; however, MPI displayed elevated hepatic mitochondrial function compared with SPI and MS. Fecal bacterial 16S rRNA analysis revealed SPI-intake elicited increases (P<.05) in Lactobacillus and decreases (P<.05) in Blautia and Lachnospiraceae suggesting decreases in fecal secondary bile acids in SPI rats. SPI and MS exhibited greater (P<.05) hepatic Fxr, Fgfr4, Hnf4a, HmgCoA reductase and synthase mRNA expression compared with MPI. Overall, dietary SPI compared with MPI decreased hepatic steatosis and diacylglycerols, changed microbiota populations and altered bile acid signaling and cholesterol homeostasis in a rodent model of obesity.

A Diet Containing Soy Protein Isolate is Not Detrimental to Skeletal Development in Spontaneously Hyperphagic, Adolescent Male OLETF Rats

Obesity and its associated metabolic dysfunction are associated with increased fracture risk in children and adolescents, suggesting excess adiposity negatively impacts skeletal development. Although the consumption of milk‐based proteins has been recommended for normal skeletal development, soy‐based proteins have emerged as popular plant‐based dairy alternatives. However, the effect of soy protein on bone health during adolescent skeletal development has not been studied. The purpose of this study was to examine the effects of isocaloric diets containing milk protein isolate (MPI), soy protein isolate (SPI), or a 50/50 combination of the two (MIX) on metabolic health indicators and bone outcomes in adolescent, hyperphagic, male Otsuka Long Evans Tokushima Fatty (OLETF) rats. At 4 weeks of age, rats were randomized to three treatment groups (MPI, SPI, and MIX) and provided ad libitum access to the diets until 20 weeks of age, at which time animals were fasted overnight, euthanized, and blood and hind limbs collected. Fasting glucose, insulin, lipids, and bone formation (N‐terminal propeptide of type 1 procollagen, P1NP) and resorption (C‐terminal telopeptide of type I collagen, CTx) markers were measured using commercially available ELISA kits. Tibial trabecular microarchitecture and cortical geometry were measured by micro‐computed tomography (μCT); and, biomechanical properties were measured by torsional loading to failure. Femoral calcium and phosphorus content were measured using Inductive Coupled Plasma‐Optical Emission Spectroscopy. One‐way ANOVA was used to test for significant differences among groups for metabolic outcomes and bone turnover markers. One‐way ANCOVA, with final body weight as a covariate, was used to determine differences among groups for all bone outcomes. At 20 weeks of age, there were no group differences in body weight or body fat. Animals in all groups were insulin resistant based on fasting glucose and insulin. MPI reduced fasting insulin compared to MIX and SPI. SPI reduced total serum cholesterol compared to MPI and MIX. P1NP was greater in MIX than MPI, but CTx was not different among groups. Trabecular spacing was reduced in SPI compared to MIX, while cortical geometry and biomechanical properties were not different among groups. MPI had higher calcium and phosphorus content than MIX. In conclusion, these results suggest that a diet containing soy protein is not detrimental to skeletal development in spontaneously hyperphagic, adolescent male OLETFs rats, and may benefit trabecular microarchitecture. In addition, these results suggest that a diet containing a combination of milk‐ and plant‐based proteins might promote bone formation during skeletal growth.Support or Funding InformationSupport: DuPont Nutrition &amp; Health, NIH R01DK088940 (JPT) and VHA‐CDA2 IK2BX001299 (RSR).

Combined long-term caffeine intake and exercise inhibits the development of diabetic nephropathy in OLETF rats.

This study was performed to examine the effects of long-term caffeine-intake, with and without exercise, on the progression of diabetic nephropathy (DN) in an obese diabetic rat model. Thirty-two male Otsuka Long-Evans Tokushima fatty (OLETF) rats were assigned to sedentary (OLETF-Sed), exercise (OLETF-Ex), caffeine-intake (OLETF-Caf), and combined (OLETF-Caf + Ex) groups. Caffeine-intake groups were fed rat chow containing caffeine (90.7 ± 4.7 mg/kg/day). The OLETF-Ex and OLETF-Caf + Ex groups were able to run voluntarily at any time using a rotatory wheel. Body weight (BW) and blood pressure (BP) were measured weekly from 24 to 29 wk of age. Pre- and posttreatment serum glucose, insulin, and creatinine concentrations were measured, and a 24 h urine sample was collected for measurement of creatinine clearance (Ccr) and albumin excretion (UEAlb). After treatment, the kidneys were removed for morphological analysis. The OLETF-Caf and OLETF-Caf + Ex groups exhibited no BP increase during the study. Both the caffeine-intake groups exhibited a significant increase in urine volume (UV), electrolyte excretion, and Ccr, and decreased UEAlb, following treatment. Furthermore, no structural damage was observed in the kidneys of rats from either caffeine-intake group, whereas the OLETF-Sed and OLETF-Ex groups exhibited DN progression. This study demonstrates that caffeine-intake alone and/or combined with exercise significantly decreases BW and improves glucose intolerance, without the progression of DN. Further research should be performed to examine whether the quantities of caffeine contained in a normal human daily intake also have a protective effect against kidney damage.NEW & NOTEWORTHY The present study showed that caffeine administration alone and/or combined with exercise results in an improvement of diabetic nephropathy (DN), including an increase in creatinine clearance and urinary Na excretion, a decrease in urinary protein excretion, and in renal morphological findings. To our knowledge, there are no other studies showing that caffeine administration inhibits DN progression.

Compound K attenuates glucose intolerance and hepatic steatosis through AMPK-dependent pathways in type 2 diabetic OLETF rats

Background/AimsNon-alcoholic fatty liver disease is associated with insulin resistance. Compound K (CK) is the final metabolite of panaxadiol ginsenosides that have been shown to exert antidiabetic effects. However, the molecular mechanism of the antidiabetic effects in the liver have not been elucidated; further, whether CK has beneficial effects in hepatosteatosis remains unclear. Therefore, we evaluated the effect of CK on hepatosteatosis as well as its mechanism in high-fat diet (HFD)-fed type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats.MethodsTwenty-four-week-old male OLETF rats were assigned to four groups: control (saline), CK 10 mg/kg, CK 25 mg/kg, or metformin 300 mg/kg (positive control); all treatments were administered orally for 12 weeks.ResultsFasting glucose levels of the CK25 group were significantly lower than those of the control group during the 12 weeks. The results of the oral glucose tolerance test showed that both the glucose concentration after glucose loading and the fasting insulin levels of the CK25 group were significantly lower than those of the control. Hepatosteatosis was significantly improved by CK25. CK25 and metformin significantly increased the phosphorylation of hepatic adenosine monophosphate-activated protein kinase (AMPK). CK25 significantly inhibited the expression of sterol regulatory element-binding protein-1c and fatty acid synthase, while upregulating that of peroxisome proliferator-activated receptor-α and carnitine palmitoyltransferase-1.ConclusionsCK improved glucose intolerance and hepatosteatosis in HFD-fed OLETF rats through AMPK activation, which has dual mode of action that involves decreasing the synthesis of fatty acids and increasing fatty acid oxidation.

A return to ad libitum feeding following caloric restriction promotes hepatic steatosis in hyperphagic OLETF rats.

Hyperphagic Otsuka Long-Evans Tokushima fatty (OLETF) rats develop obesity, insulin resistance, and nonalcoholic fatty liver disease (NAFLD), but lifestyle modifications, such as caloric restriction (CR), can prevent these conditions. We sought to determine if prior CR had protective effects on metabolic health and NAFLD development following a 4-wk return to ad libitum (AL) feeding. Four-week-old male OLETF rats (n = 8-10/group) were fed AL for 16 wk (O-AL), CR for 16 wk (O-CR; ∼70% kcal of O-AL), or CR for 12 wk followed by 4 wk of AL feeding (O-AL4wk). CR-induced benefit in prevention of NAFLD, including reduced hepatic steatosis, inflammation, and markers of Kupffer cell activation/number, was largely lost in AL4wk rats. These findings occurred in conjunction with a partial loss of CR-induced beneficial effects on obesity and serum triglycerides in O-AL4wk rats, but in the absence of changes in serum glucose or insulin. CR-induced increases in hepatic mitochondrial respiration remained significantly elevated (P < 0.01) in O-AL4wk compared with O-AL rats, while mitochondrial [1-(14)C]palmitate oxidation, citrate synthase activity, and β-hydroxyacyl-CoA dehydrogenase activity did not differ among OLETF groups. NAFLD development in O-AL4wk rats was accompanied by increases in the protein content of the de novo lipogenesis markers fatty acid synthase and stearoyl-CoA desaturase-1 and decreases in phosphorylated acetyl-CoA carboxylase (pACC)/ACC compared with O-CR rats (P < 0.05 for each). The beneficial effects of chronic CR on NAFLD development were largely lost with 4 wk of AL feeding in the hyperphagic OLETF rat, highlighting the importance of maintaining energy balance in the prevention of NAFLD.

Bone Geometry and Trabecular and Cortical Microarchitecture are Altered by Type 2 Diabetes, but not Insulin Resistance, in the Hyperphagic OLETF Rat

Recently, fragility fracture has been added to the list of type 2 diabetes (T2D) complications. The purpose of this study was to determine the effects of insulin resistance (IR) and T2D on bone outcomes using the hyperphagic Otsuka Long‐Evans Tokushima Fatty (OLETF) rat model of T2D. Long‐Evans Tokushima Otsuka (LETO) and calorically restricted (CR; ~30% reduction vs. OLETF) OLETF rats weight‐matched to the LETO controls were used as lean, normoglycemic controls. The skeletal effects of IR and T2D were evaluated in 20‐ and 40‐week old male OLETF rats. Femur geometry and trabecular and cortical microarchitecture were analyzed using mCT. Cortical bone strength was analyzed by torsional loading of the femur to failure. The effects of IR and T2D on bone outcomes were compared using a two‐way (group, age) ANOVA; body weight (BW) was included as a covariate for body‐size‐dependent outcomes. As expected, the hyperphagic OLETF rats had significantly greater BW than controls. Blood glucose and insulin confirmed that OLETF rats were hyperglycemic and hyperinsulinemic at 20 weeks and at 40 weeks were hypoinsulinemic due to β‐cell dysfunction. At 20 weeks, only the cortical‐to‐total area ratio (Ct.Ar/Tt.Ar) was greater in IR OLETF versus CR controls. However, at 40 weeks bone geometry, microarchitecture, and biomechanical properties differed between OLETF rats and LETO and CR controls. OLETF rats had significantly shorter femur length than LETO and CR controls. Total cross‐sectional area and cortical area were greater in T2D OLETF rats versus LETO and CR controls. Ct.Ar/Tt.Ar and polar moment of inertia were greater in OLETF compared with CR. OLETF rats showed a greater increase in trabecular spacing and greater decreases in connectivity density from 20 to 40 weeks compared with LETO and CR controls; at 40 weeks T2D OLETF rats had reduced percent bone volume. T2D OLETF rats did not show the age‐related decline in torsional stiffness (Ks) observed in controls. Relative to CR, OLETF rats had a greater decline in ultimate tensile strength (Su), and at 40 weeks OLETF rats had reduced shear modulus of elasticity (G). In summary, bone geometry, trabecular and cortical microarchitecture, and biomechanical properties are altered by T2D, but not IR, in the hyperphagic OLETF rat relative to lean controls. The results of this study suggest that early identification and treatment of T2D might reduce the skeletal complications associated with hyperglycemia and β‐cell dysfunction.Support or Funding InformationThis work was funded by the VA Career Development Award and the Department of Nutrition and Exercise Physiology at the University of Missouri.

Exercise Attenuates Ischemia-reperfusion Injury of Nonalcoholic Fatty Liver in OLETF Rat

Background: Steatotic livers are increasingly used for liver transplantation and the strategy to minimize its disadvantage is required. We determined whether exercise could protect liver against ischemia-reperfusion (IR) injury in the anesthetized hyperphagic, Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an animal model of the metabolic syndrome. Methods: At 16 th week of age, male OLETF rats (n=7/group) were randomized to the groups of sedentary (OLETF-SED)-IR, exercise (OLETF-EX)-IR, and OLETF-non IR. Non-hyperphagic, control strain Long-Evans Tokushima Otsuka (LETO) rats were similarly assigned. Rats in the exercise groups were subjected to treadmill running 6 days a week for 5 weeks. Rats were anesthetized with intraperitoneal pentobarbital and subjected to partial liver ischemia (70%) for 30 min and subsequent reperfusion for 120 min. IR injury was evaluated by plasma alanine aminotransferase (ALT)concentration, bile flow rate, liver histopathology, and hepatic microcirculation of the left lateral lobe analyzed by laser Doppler flowmetry. Results: Increases in body and liver weight were attenuated in the OLETF-EX rats as compared with the OLETF-SED rats. The ALT levels after reperfusion in the OLETF-EX rats were smaller than that in the OLETF-SED rats, and were comparable to those in the LETOSED and -EX rats. Exercise attenuated the IR-induced reduction of liver blood flow and morphological hepatic damages as observed in the OLETF-SED group. In contrast, exercise provided no influences on the LETO rats. Conclusion: Exercise attenuated the liver steatosis and IRinduced disturbances of hepatic microcirculation and parenchymal injury in the hyperphagic, OLETF rats.

Combining metformin therapy with caloric restriction for the management of type 2 diabetes and nonalcoholic fatty liver disease in obese rats.

Weight loss is recommended for patients with nonalcoholic fatty liver disease (NAFLD), while metformin may lower liver enzymes in type 2 diabetics. Yet, the efficacy of the combination of weight loss and metformin in the treatment of NAFLD is unclear. We assessed the effects of metformin, caloric restriction, and their combination on NAFLD in diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Male OLETF rats (age 20 weeks; n = 6-8 per group) were fed ad libitum (AL), given metformin (300 mg·kg(-1)·day(-1); Met), calorically restricted (70% of AL; CR), or calorically restricted and given metformin (CR+Met) for 12 weeks. Met lowered adiposity compared with AL but not to the same magnitude as CR or CR+Met (p < 0.05). Although only CR improved fasting insulin and glucose, the combination of CR+Met was needed to improve post-challenge glucose tolerance. All treatments lowered hepatic triglycerides, but further improvements were observed in the CR groups (p < 0.05, Met vs. CR or CR+Met) and a further reduction in serum alanine aminotransferases was observed in CR+Met rats. CR lowered markers of hepatic de novo lipogenesis (fatty acid synthase, acetyl-CoA carboxylase (ACC), and stearoyl-CoA desaturase-1 (SCD-1)) and increased hepatic mitochondrial activity (palmitate oxidation and β-hydroxyacyl CoA dehydrogenase (β-HAD) activity). Changes were enhanced in the CR+Met group for ACC, SCD-1, β-HAD, and the mitophagy marker BNIP3. Met decreased total hepatic mTOR content and inhibited mTOR complex 1, which may have contributed to Met-induced reductions in de novo lipogenesis. These findings in the OLETF rat suggest that the combination of caloric restriction and metformin may provide a more optimal approach than either treatment alone in the management of type 2 diabetes and NAFLD.

Obesity-related changes in bone structural and material properties in hyperphagic OLETF rats and protection by voluntary wheel running

PurposeTo examine how the development of obesity and the associated insulin resistance affect bone structural and material properties, and bone formation and resorption markers in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat model. MethodsThis was a 36-week study of sedentary, hyperphagic, male OLETF rats (OLETF-SED), exercise-treated OLETF rats (OLETF-EX) and sedentary non-hyperphagic controls (LETO-SED) with data collection at 13, 20, and 40weeks of age (n=5–8 animals per group per timepoint). ResultsBody mass and fat (%) were significantly greater in OLETF-SED versus controls. OLETF-SED were insulin resistant at 13 and 20weeks, with overt diabetes by 40weeks. At 13weeks, OLETF-SED had lower total body BMC and BMD and serum P1NP compared with LETO-SED. Differences in total body BMC and BMD between OLETF-SED and LETO-SED persisted at 20weeks, with reductions in total and cortical BMD of the tibia. OLETF-SED also had lesser femur diameter, cross-sectional area, polar moment of area, and torque at fracture than LETO-SED. By 40weeks, OLETF-SED had elevated bone resorption and reduced intrinsic bone strength. OLETF-EX did not show the excessive weight gain, obesity, insulin resistance or diabetes observed in OLETF-SED. OLETF-EX had greater BMD than OLETF-SED, and structural and material properties of the femur were significantly increased in OLETF-EX relative to OLETF-SED and LETO-SED. ConclusionsThe negative skeletal effects of excessive adiposity and insulin resistance were evident early in the progressive obesity with lasting negative impacts on intrinsic and extrinsic bone strength. Exercise protected against obesity-associated skeletal changes with marked benefits on the biomechanical properties of bone.

Downregulation of transient receptor potential M6 channels as a cause of hypermagnesiuric hypomagnesemia in obese type 2 diabetic rats.

We assessed the expression profile of Mg(2+)-transporting molecules in obese diabetic rats as a cause of hypermagnesiuric hypomagnesemia, which is involved in the development of insulin resistance, hypertension, and coronary diseases. Kidneys were obtained from male Otsuka Long-Evans Tokushima fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) obese diabetic rats at the ages of 16, 24, and 34 wk. Expression profiles were studied by real-time PCR and immunohistochemistry together with measurements of urine Mg(2+) excretion. Urine Mg(2+) excretion was increased in 24-wk-old OLETF rats and hypomagnesemia was apparent in 34-wk-old OLETF rats but not in LETO rats (urine Mg(2+) excretion: 0.16 ± 0.01 μg·min(-1)·g body wt(-1) in 24-wk-old LETO rats and 0.28 ± 0.01 μg·min(-1)·g body wt(-1) in 24-wk-old OLETF rats). Gene expression of transient receptor potential (TRP)M6 was downregulated (85.5 ± 5.6% in 34-wk-old LETO rats and 63.0 ± 3.5% in 34-wk-old OLETF rats) concomitant with Na(+)-Cl(-) cotransporter downregulation, whereas the expression of claudin-16 in tight junctions of the thick ascending limb of Henle was not different. The results of the semiquantitative analysis of immunohistochemistry were consistent with these findings (TRPM6: 0.49 ± 0.04% in 16-wk-old LETO rats, 0.10 ± 0.01% in 16-wk-old OLETF rats, 0.52 ± 0.03% in 24-wk-old LETO rats, 0.10 ± 0.01% in 24-wk-old OLETF rats, 0.48 ± 0.02% in 34-wk-old LETO rats, and 0.12 ± 0.02% in 34-wk-old OLETF rats). Gene expression of fibrosis-related proinflammatory cytokines as well as histological changes showed that the hypermagnesiuria-related molecular changes and tubulointerstitial nephropathy developed independently. TRPM6, located principally in distal convoluted tubules, appears to be a susceptible molecule that causes hypermagnesiuric hypomagnesemia as a tubulointerstitial nephropathy-independent altered tubular function in diabetic nephropathy.

The Effect of Lithospermic Acid, an Antioxidant, on Development of Diabetic Retinopathy in Spontaneously Obese Diabetic Rats

BackgroundLithospermic acid B (LAB), an active component isolated from Salvia miltiorrhiza radix, has been reported to have antioxidant effects. We examined the effects of LAB on the prevention of diabetic retinopathy in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model of type 2 diabetes.Methods and FindingsLAB (10 or 20 mg/kg) or normal saline were given orally once daily to 24-week-old male OLETF rats for 52 weeks. At the end of treatment, fundoscopic findings, vascular endothelial growth factor (VEGF) expression in the eyeball, VEGF levels in the ocular fluid, and any structural abnormalities in the retina were assessed. Glucose metabolism, serum levels of high-sensitivity C-reactive protein (hsCRP), monocyte chemotactic protein-1 (MCP1), and tumor necrosis factor-alpha (TNFα) and urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels were also measured. Treatment with LAB prevented vascular leakage and basement membrane thickening in retinal capillaries in a dose-dependent manner. Insulin resistance and glucose intolerance were significantly improved by LAB treatment. The levels of serum hsCRP, MCP1, TNFα, and urinary 8-OHdG were lower in the LAB-treated OLETF rats than in the controls.ConclusionsTreatment with LAB had a preventive effect on the development of diabetic retinopathy in this animal model, probably because of its antioxidative effects and anti-inflammatory effects.

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.

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.