Feeding Response to Mercaptoacetate in Osborne-Mendel and S5B/PL Rats

SINGER, LORI K, DAVID A YORK, GEORGE A BRAY. Feeding response to mercaptoacetate in Osborne-Mendel and S5B/PL Rats. The purpose of this experiment was to determine if Osborne-Mendel (OM) rats, which are susceptible to dietary-induced obesity, and S5B/PL (S5B) rats, which are resistant to dietary-induced obesity, differ in their feeding responses to mercaptoacetate (MA), which blocks fatty acid oxidation, or 2-deoxy-D-glucose (2DG), which blocks glucose utilization. 2DG (100 mg/kg or 200 mg/ kg) increased food intake in both strains of rats on a high-fat diet (56% energy from fat). Mercaptoacetate (600 umol/kg) increased food intake in OM but not S5B rats on a high-fat diet. When maintained on a low-fat diet (10% energy from fat), MA (400 umol/kg or 600 umol/kg) stimulated food intake in OM rats, whereas S5B rats increased food intake only after the highest dose of MA (600 umol/kg). MA stimulated carbohydrate and protein intake in OM rats maintained on a macro-nutrient selection diet, whereas S5B rats maintained on this diet did not significantly increase intake of any mac-ronutrient after MA. These results demonstrate that OM and S5B rats have a similar food intake response to 2DG but a dissimilar response to MA. The variable response to MA in these strains may be due to a difference in peripheral or central signaling systems related to fatty acid oxidation or a difference in metabolic environments between the strains, which in turn affects the feeding response to MA. These studies suggest that a difference in control of fatty acid oxidation may account for the difference in susceptibility to obesity when eating a high-fat diet.     

高脂饮食和地塞米松联合诱导胰岛素抵抗大鼠模型

目的用高脂饲料＋地塞米松（dexamethasone,DEX）隔日腹腔注射建立实验性胰岛素抵抗大鼠模型,研究该模型糖代谢、脂代谢和激素水平等方面的变化。方法采用Wistar雄性大鼠,分为正常对照组、高脂组、DEX组（1mg/kg,i.p.）和高脂＋DEX组（1mg/kg,i.p.）,连续观察8周,每周测定大鼠空腹血糖,分别于造模第2周和第8周测糖耐量,8周后处死大鼠,测定胸腺、脾脏、肝脏等脏器重量。结果高脂饲料能加重腹腔注射DEX造成的空腹血糖升高,造模第8周空腹血糖（7.7±0.7）较空白组（6.5±0.6）显著升高。使模型动物糖耐量明显异常,肝糖原、肌糖原含量显著增加,血浆胰岛素及游离脂肪酸水平显著升高,各脏器指数明显增加。结论高脂＋DEX隔日腹腔注射能成功诱导胰岛素抵抗大鼠模型,这种造模方法较单纯注射DEX或单纯高脂饲养成模率高,造模周期短。     

Metabolic Differences in Response to a High-Fat vs. a High-Carbohydrate Diet

Energy expenditure was measured in a group of 7 subjects who received two isocaloric isonitrogenous diets for a period of 9–21 days with a 4–10-day break between diets. Diet 1 was a high-fat diet (83.5 ± 3.6% of total energy). Diet 2 was a high carbohydrate diet (83.1 ± 3.7% of total energy). Resting and postprandial resting metabolic rate were measured by open circuit indirect calorimetry 2–4 times during each metabolic period. Total energy expenditure (TEE) was measured by the doubly labeled water method over an 8–13-day period. The respiratory quotient was measured 2–4 hours after a meal during each metabolic period for the calculation of total energy expenditure by the doubly labeled water method. Levels of total T₃ (TT₃), T₃ uptake, free thyroid index and T₄ were measured at the end of each metabolic period. No significant changes in resting metabolic rate (RMR) were apparent on the two diets (1567 ± 426 kcal/d high-fat diet and 1503 ± 412 kcal/d high-carbohydrate diet n=7, p<0.15). Total energy expenditure measured in 5 subjects was significantly higher during the high-carbohydrate phase of the diet (2443 ± 422 vs. 2078 ± 482 kcal/d p<0.05). Activity estimated from TEE/RMR was greater on the high-carbohydrate diet but only approached statistical significance (p<0.06). Total T₃ was significantly lower and free thyroid index and T₃ uptake were significantly higher at the end of the high fat diet in comparison to the high-carbohydrate diet. These data suggest that individual tolerance to a high-fat diet varies considerably and may significantly lower TEE by changing levels of physical activity. The explanation for changes in thyroid hormone levels independent of changes in metabolic rate remains unclear.     

Effects of a High-Fat Diet and Strain on Hypothalamic Gene Expression in Rats

Objective: This study was designed to investigate whether dietary fat and genetic background might differentially alter the expression of hypothalamic genes involved in food intake. Research Methods and Procedures: Three-month-old Osborne-Mendel (OM) and S5B/Pl rats were fed either a high-fat or a low-fat diet for 14 days. mRNA for neuropeptide Y (NPY), corticotrophin-releasing hormone, NPY Y-1 receptor and Y-5 receptor, and serotonin 2c (5-HT2c) receptors were measured using Northern blotting or ribonuclease protection assays. Results: OM rats showed an increased expression of NPY and corticotrophin-releasing hormone compared with S5B/Pl rats. The expression of NPY-Y1 and -Y5 receptor mRNA was significantly higher in the hypothalamus of OM rats compared with S5B/Pl rats. The expression of 5HT-2c receptor mRNA was significantly reduced in both strains of rats eating a high-fat diet when compared with the animals eating the low-fat diet. Discussion: These data suggest that over activity of the NPY system may contribute to the development of obesity in OM rats and that expression of the 5HT-2c receptor gene may be modulated by dietary fat.     

Genetic Control of Obesity and Gut Microbiota Composition in Response to High-Fat,High-Sucrose Diet in Mice

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Highlights? Detailed analysis of diet-induced obesity in more than 100 inbred mouse strains ? Identification of 11 genetic loci associated with obesity and dietary responsiveness ? Significant overlap between mouse loci with human GWAS loci for obesity ? Strain-specific shifts in gut microbiota composition in response to dietary intervention     

Fructus Xanthii Attenuates Hepatic Steatosis in Rats Fed on High-Fat Diet

Fructus Xanthii (FX) has been widely used as a traditional herbal medicine for rhinitis, headache, cold, etc. Modern pharmacological studies revealed that FX possesses anti-inflammatory, anti-oxidative, and anti-hyperglycemic properties. The present study was designed to investigate the effects of FX on glucose and insulin tolerance, and hepatic lipid metabolism in rats fed on high-fat diet (HFD). Hepatic steatosis was induced by HFD feeding. Aqueous extraction fractions of FX or vehicle were orally administered by gavage for 6 weeks. Body weight and blood glucose were monitored. Glucose and insulin tolerance test were performed. Liver morphology was visualized by hematoxylin and eosin, and oil red O staining. Expression of liver lipogenic and lipolytic genes was measured by real-time PCR. We showed here that FX improved glucose tolerance and insulin sensitivity in HFD rats. FX significantly decreased the expression of lipogenic genes and increased the expression of lipolytic genes, ameliorated lipid accumulation and decreased the total liver triglyceride (TG) content, and thus attenuated HFD-induced hepatic steatosis. In conclusion, FX improves glucose tolerance and insulin sensitivity, decreases lipogenesis and increases lipid oxidation in the liver of HFD rats, implying a potential application in the treatment of non-alcoholic fatty liver disease.     

Feeding and Growth Response of Roach, Rutilus rutilus, to Alarm Substance

Feeding and growth responses of roach from three size classes to alarm substance (Schreckstoff) were quantified in laboratory experiments. Larger fish (60.0–80.0 mm in length) reacted stronger to treatment than two smaller sized groups (35.0–45.0 and 46.0–55.0 mm) lowering feeding rate by 80 and 40 and 50%, respectively. The reduction in feeding rate of larger fish caused decrease in growth rate in length and weight, while the lowered consumption of smaller fish caused only reduction in growth rate in weight. Condition factor of exposed to alarm substance small sized roach was lower than that of the control individuals and roach from other two size classes, both, treated and untreated. The difference in growth response to a danger of predation has its roots probably in different metabolism and growth rates of small and large fish. Small fish have higher metabolic rate and less lipid reserves than larger ones, therefore they are probably forced to feed to be able to grow. Also, small sized roach is more vulnerable to predation than large sized fish, thus growing fast seem to be crucial for survival in a risky environment. Study shows that small roach trade off their safety against food, feeding in risky environment to sustain fast growth. This ability of fast outgrowing of a dangerous, vulnerable to predators, size increases survival of juveniles in dangerous environment.     

Measuring Glutathione-induced Feeding Response in Hydra

Hydra is among the most primitive organisms possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey. The movement of prey organisms causes mechanosensory discharge of the stinging cells called nematocysts from hydra, which are inserted into the prey. The feeding response in hydra, which includes curling of the tentacles to bring the prey towards the mouth, opening of the mouth and consequent engulfing of the prey, is triggered by GSH present in the fluid released from the injured prey. To be able to identify the molecular mechanism of the feeding response in hydra which is unknown to date, it is necessary to establish an assay to measure the feeding response. Here, we describe a simple method for the quantitation of the feeding response in which the distance between the apical end of the tentacle and mouth of hydra is measured and the ratio of such distance before and after the addition of GSH is determined. The ratio, called the relative tentacle spread, was found to give a measure of the feeding response. This assay was validated using a starvation model in which starved hydra show an enhanced feeding response in comparison with daily fed hydra.     

Dll4蛋白在高脂饮食喂养大鼠脂肪组织炎症中的作用

目的 探讨Delta-like ligand 4（Dll4）蛋白在高脂饮食喂养大鼠脂肪组织中的表达及其与脂肪组织炎症的关系.方法 将20只SPF级雄性Sprague-Dawley大鼠随机分为正常饮食组（SD,n=10）和高脂饮食组（HFD,n=10）喂养16w后,应用免疫组化及Western blot方法检测脂肪组织中Dll4及炎症通路NF-κB磷酸化、IL-6的表达.结果 免疫组化结果显示,HFD组Dll4表达量显著升高（P〈0.001）;Western blot结果与免疫组化结果相一致,Dll4蛋白表达量是SD组的1.34倍（P〈0.01）;磷酸化核转录因子NF-κB表达水平升高,HFD组为SD组的2.03倍（P〈0.01）;HFD组炎症细胞因子IL-6水平明显升高,为SD组的3.02倍（P〈0.01）.结论 高脂饮食可增加脂肪组织中Dll4蛋白表达,促进了脂肪组织中炎症的发生.     

Growth of Zinc-Deficient Rats During Intra-Gastric Tube Feeding

The main aim of the study was to determine the role of cerium in the amelioration of calcium-deficiency effects in spinach plants. Spinach plants were cultivated in Hoagland’s solution. They were subjected to calcium-deficiency and to cerium chloride administered in the calcium-present Hoagland’s media and calcium-deficient Hoagland’s media. Within 3weeks, young leaves developed distinct calcium-deficient symptoms, and plant growth significantly inhibited to calcium deprivation as would be expected; cerium-treated groups grown in the same conditions did not develop calcium-deficient symptoms; fresh weight, dry weight and chlorophyll content of spinach plants were increased by 35.9, 45 and 64.05% compared to those of plants cultivated in calcium-deficient media. In addition, calcium deprivation in spinach plants caused the reduction of photosynthetic rate, oxygen evolution rate and ribulose-1,5-bisphosphate carboxylase/oxygenase activity. The reduction of activities of nitrate reductase, glutamate dehydrogenase, glutamate synthase and glutamic-pyruvic transaminase was observed under calcium-deficient media. However, cerium treatment under calcium-deficient media could significantly improve photosynthesis and nitrogen metabolism of spinach plants. This is viewed as evidence that cerium added to calcium-deficient media in the spinach plants could substitute for calcium and improve spinach growth.     

Efficacy of Dietary Lipid Control in Healing High-Fat and High-Cholesterol Diet-Induced Fibrotic Steatohepatitis in Rats

Nonalcoholic steatohepatitis is related to lifestyle, particularly to dietary habits. We developed diet-induced fibrotic steatohepatitis model stroke-prone spontaneously hypertensive 5/Dmcr (SHRSP5/Dmcr) rats showing steatosis, hepatic inflammation, and severe fibrosis induced by high-fat and -cholesterol (HFC) diet feeding. We aimed to clarify the efficacy of dietary intervention on the disease before and after the appearance of fibrosis. Male SHRSP5/Dmcr rats were divided into 9 groups; of these, 6 groups were fed control or HFC diet for several weeks and the remaining 3 groups represented the dietary intervention groups, which were fed the control diet after HFC diet feeding for 2 (before the appearance of fibrosis) or 8 (after the appearance of fibrosis) weeks. Dietary intervention before the appearance of fibrosis significantly improved the steatosis and reset the increased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and serum total cholesterol (TC) levels. However, dietary intervention after the appearance of fibrosis was unable to reset the levels of hepatic TC, serum ALT, and fibrogenesis-related markers and had only a minor influence on hepatic fibrosis, although it reset the increased expression of transforming growth factor (TGF)-β1 and α-smooth muscle actin (SMA). It was noted that dietary intervention improved the increased AST levels; however, aggregated CD68-positive cells were still observed around the fibrosis area, which may be related to the findings of inflammatory cytokine mRNAs. Taken together, dietary intervention for fibrotic steatohepatitis improved steatosis, although it could not completely improve fibrosis.     

Vagal-Central Nervous System Interactions Modulate the Feeding Response to Peripheral Enterostatin

Enterostatin selectively inhibits the intake of dietary fat after both peripheral and central administration. We have investigated the role of the hepatic vagus nerve in modulating the peripheral response to enterostatin in Sprague-Dawley rats adapted to a high fat (HF) diet. Intraperitoneal (ip) enterostatin reduced intake of HF diet after overnight starvation. This response was abolished by selective vagal hepatic branch transection. Immunohistochemical techniques were used to identify the location of Fos protein in brain nuclei after ip enterostatin. Fos protein was evident in the nucleus tractus solitarius (NTS), parabrachial, paraventricular and supraoptic nuclei. The pattern of expression of Fos-like immunoreactivity differed from that induced by the lipoprivic agent β-mercaptoacetate. Transection of the hepatic vagus blocked the central Fos responses to ip enterostatin. We conclude that afferent hepatic vagal nerve activity is required for the feeding response to peripheral enterostatin.     

Mice Long-Term High-Fat Diet Feeding Recapitulates Human Cardiovascular Alterations: An Animal Model to Study the Early Phases of Diabetic Cardiomyopathy

Background/Aim

Hypercaloric diet ingestion and sedentary lifestyle result in obesity. Metabolic syndrome is a cluster of clinical features secondary to obesity, considered as a pre-diabetic condition and recognized as an independent risk factor for cardiovascular diseases. To better understand the relationship between obesity, metabolic syndrome and cardiovascular disease as well as for the development of novel therapeutic strategies, animal models that reproduce the etiology, course and outcomes of these pathologies are required. The aim of this work was to characterize the long-term effects of high-fat diet-induced obesity on the mice cardiovascular system, in order to make available a new animal model for diabetic cardiomyopathy.

Methods/Results

Male C57BL/6 mice were fed with a standardized high-fat diet (obese) or regular diet (normal) for 16 months. Metabolic syndrome was evaluated testing plasma glucose, triglycerides, cholesterol, insulin, and glucose tolerance. Arterial pressure was measured using a sphygmomanometer (non invasive method) and by hemodynamic parameters (invasive method). Cardiac anatomy was described based on echocardiography and histological studies. Cardiac function was assessed by cardiac catheterization under a stress test. Cardiac remodelling and metabolic biomarkers were assessed by RT-qPCR and immunoblotting. As of month eight, the obese mice were overweight, hyperglycaemic, insulin resistant, hyperinsulinemic and hypercholesterolemic. At month 16, they also presented normal arterial pressure but altered vascular reactivity (vasoconstriction), and cardiac contractility reserve reduction, heart mass increase, cardiomyocyte hypertrophy, cardiac fibrosis, and heart metabolic compensations. By contrast, the normal mice remained healthy throughout the study.

Conclusions

Mice fed with a high-fat diet for prolonged time recapitulates the etiology, course and outcomes of the early phases of human diabetic cardiomyopathy.     

Fat Feeding of Rats During Pubertal Growth Leads to Neuroendocrine Alterations in Adulthood

Juvenile obesity is a rising epidemic due largely to consumption of caloric dense, fat-enriched foods. Nevertheless, literature on fat-induced neuroendocrine and metabolic disturbances during adolescence, preceding obesity, is limited. This study aimed to examine early events induced by a fat diet (45% calories from saturated fat) in male rats fed the diet during the pre- and post-pubertal period. The neuroendocrine endpoints studied were the levels of circulating leptin, insulin and corticosterone, as well as their receptors in the hypothalamus and hippocampus. Hormonal levels were determined by radioimmunoassay and receptors’ levels by western blot analysis. Leptinemia was increased in pubertal rats and in adult rats fed the fat diet from weaning to adulthood, but not in those fed from puberty to adulthood. Modifications in the developmental pattern from puberty to adulthood were observed for most of the brain receptors studied. In adult animals fed the fat diet from weaning onwards, the levels of leptin receptors in the hypothalamus and glucocorticoid receptors in the hippocampus were decreased compared to chow-fed controls. Switching from fat to normal chow at puberty onset restored the diet-induced alterations on circulating leptin, but not on its hypothalamic receptors. These data suggest that when a fat-enriched diet, resembling those consumed by many teenagers, provided in rats during pubertal growth, it can longitudinally influence the actions of leptin and corticosterone in the brain. The observed alterations at a preobese state may constitute early signs of the disturbed energy balance toward overweight and obesity.     

补料速度对工程菌生长和产物表达的影响研究

通过研究各培养阶段补料速度对温敏启动子控制的rIL-2工程菌E.coliK802(pLY-4)培养密度和rIL-2表达的影响,发现在各培养阶段控制不同的补料速度有利于提高菌密度和rIL-2表达,缩短培养周期。确定了rIL-2工程菌高密度培养方案,三批重复实验,平均菌密度为58OD_(600);菌干重18.0g/L,rIL-2表达水平为42.4％。     

Aortic Response to Balloon Injury in Obese Zucker Rats

The small diameter of the carotid artery is not compatible with the evaluation of clinically available endovascular devices in the carotid balloon-injury (BI) model. We developed an endovascular BI model in the rat descending aorta, whose size is compatible with available endovascular instruments. We also tested the hypothesis that neointima formation is enhanced in the aorta of obese Zucker rats (OZR) compared with lean Zucker rats (LZR). Left external carotid arteriotomies and BI of the thoracic and abdominal aorta were performed by using a balloon catheter. Aortograms and aortic pathology were examined at 2, 4, and 10 wk after BI. At 10 wk after BI, the abdominal aorta in OZR had narrowed 8.3% ± 1.1% relative to baseline compared with an expansion of 2.4% ± 2.2% in LZR. Simultaneously, the thoracic aorta had expanded 9.5% ± 4.3% in LZR compared with stenosis of 2.8% ± 1.6% in OZR. Calculation of the intimal:medial thickness ratio revealed significantly increased neointimal formation in the OZR descending aorta compared with that in LNR. In conclusion, this minimally invasive BI model involving the rat descending aorta is compatible with available endovascular instruments. The descending aorta of OZR demonstrates enhanced neointimal formation and constrictive vascular remodeling after BI.Abbreviations: BI, balloon injury; LZR, lean Zucker rats; OZR, obese Zucker ratsMany endovascular interventions, either cardiovascular or neuro­vascular, involve balloon-angioplasty or stenting of stenosed or vasospastic arteries. Balloon injury (BI) to the arterial wall is well known to induce restenosis, with a typical decrease in lumen diameter as a result of intimal hyperplasia and vessel wall remodeling.^{4,5,6,15,17,18} Restenosis occurs more frequently in patients with additional cardiovascular risk factors including diabetes, dyslipidemia, obesity, and hypertension.^4,8,23 Zucker rats frequently are used as animal models of obesity, dyslipidemia, and type 2 diabetes.^16,20,24The rat common carotid artery BI model is widely applied to study molecular mechanisms and the role of smooth muscle cells in arterial disease and healing.¹⁷ Data on injury in other arteries and models are not extensive.⁵ From a clinical perspective, the rat carotid artery is too small to test available endovascular devices. Other sites that have been used in rat models include the infrarenal aorta and the common iliac artery.^{4,5,11,13,15,25} The aortic model requires an open laparotomy, whereas the common iliac artery is another small-caliber vessel. The goal of the present study was to create a minimally invasive BI model in the rat descending aorta that would be compatible with many endovascular instruments and implantable devices, such as stents, that are used currently in clinical practice.¹⁵     

Proteomic Response to Acupuncture Treatment in Spontaneously Hypertensive Rats

Previous animal and clinical studies have shown that acupuncture is an effective alternative treatment in the management of hypertension, but the mechanism is unclear. This study investigated the proteomic response in the nervous system to treatment at the Taichong (LR3) acupoint in spontaneously hypertensive rats (SHRs). Unanesthetized rats were subject to 5-min daily acupuncture treatment for 7 days. Blood pressure was monitored over 7 days. After euthanasia on the 7^th day, rat medullas were dissected, homogenized, and subject to 2D gel electrophoresis and MALDI-TOF analysis. The results indicate that blood pressure stabilized after the 5th day of acupuncture, and compared with non-acupoint treatment, Taichong-acupunctured rat’s systolic pressure was reduced significantly (P<0.01), though not enough to bring blood pressure down to normal levels. The different treatment groups also showed differential protein expression: the 2D images revealed 571±15 proteins in normal SD rats’ medulla, 576±31 proteins in SHR’s medulla, 597±44 proteins in medulla of SHR after acupuncturing Taichong, and 616±18 proteins in medulla of SHR after acupuncturing non-acupoint. In the medulla of Taichong group, compared with non-acupoint group, seven proteins were down-regulated: heat shock protein-90, synapsin-1, pyruvate kinase isozyme, NAD-dependent deacetylase sirtuin-2, protein kinase C inhibitor protein 1, ubiquitin hydrolase isozyme L1, and myelin basic protein. Six proteins were up-regulated: glutamate dehydrogenase 1, aldehyde dehydrogenase 2, glutathione S-transferase M5, Rho GDP dissociation inhibitor 1, DJ-1 protein and superoxide dismutase. The altered expression of several proteins by acupuncture has been confirmed by ELISA, Western blot and qRT-PCR assays. The results indicate an increase in antioxidant enzymes in the medulla of the SHRs subject to acupuncture, which may provide partial explanation for the antihypertensive effect of acupuncture. Further studies are warranted to investigate the role of oxidative stress modulation by acupuncture in the treatment of hypertension.