膳食钙降低饮食诱导肥胖大鼠体重的机制

目的 研究膳食钙对饮食诱导肥胖大鼠的治疗作用及其机制。方法 以雄性Wistar大鼠为实验对象，用高脂饮食诱导大鼠肥胖模型。将肥胖大鼠按体重随机分为4组：A组为基础饲料组，B组为高脂低钙组(含0．25％钙)，C组为高脂正常钙组(含0．5％钙)，D组为高脂高钙组(含1％钙)。于第10周末处死动物，计算脂／体比，测定血糖、血脂和激素水平。结果 高钙膳食降低饮食诱导肥胖大鼠的体重和体脂含量，改善血脂代谢紊乱状态和胰岛素抵抗；膳食高钙通过促进瘦素分泌，降低神经肽Y分泌，升高血中游离T3和生长激素水平，起到降低饮食诱导肥胖大鼠体重和体脂含量的作用。结论 高钙膳食可以影响血中瘦素、神经肽Y、T3和生长激的水平，从而降低饮食诱导肥胖大鼠的体重。     

饮食诱导肥胖抵抗和肥胖大鼠血中激素水平的比较

目的　研究饮食诱导肥胖抵抗 (DIO R)和肥胖 (DIO)大鼠血中胰岛素、瘦素 (leptin)和神经肽Y(NPY)水平的差别。方法　采用 5 0只健康雄性SD大鼠 ,随机分为基础组和高脂组 ,分别用基础饲料和高脂饲料喂养 13周 ,然后根据体重筛选出DIO R和DIO组 ,观察体重、摄食量和体脂含量的变化 ,放免法测血清胰岛素、leptin和血浆NPY含量。结果　DIO R大鼠体重、摄食量和体脂含量均明显低于DIO大鼠 (P <0 0 5 ) ;血清胰岛素、血浆NPY含量显著低于DIO大鼠 (P <0 0 5 ) ;高脂饲料使大鼠血清leptin水平明显增加 (P <0 0 5 ) ,但DIO R与DIO大鼠间无明显差别 (P >0 0 5 )。结论　高脂饲料能够诱导SD大鼠发生肥胖和肥胖抵抗 ,胰岛素 leptin NPY反馈环的平衡在肥胖抵抗的发生中起重要作用。     

肥胖和肥胖抵抗大鼠神经肽Y及其受体基因表达的研究

目的:探讨高脂饲料对大鼠下丘脑神经肽Y(NPY)及其受体Y1、Y2、Y5基因表达的影响及大鼠肥胖易感性差异的机制。方法:36只雌性SD大鼠,按体重随机分为高脂组和对照组,分别给予高脂饲料和基础饲料13w。实验结束时,根据体重将高脂组分为饮食诱导肥胖(DIO)和肥胖抵抗(DIO-R)大鼠,观察各组大鼠体重、内脏脂肪湿重、脂体比、热能摄入量及能量利用率的差异;RT-PCR法测定下丘脑NPY及其受体Y1、Y2、Y5mRNA的表达水平。结果:DIO大鼠体重、内脏脂肪湿重、脂体比、热能摄入量及能量利用率显著高于对照组和DIO-R大鼠,而DIO-R大鼠与对照组相比未见显著性差异;DIO大鼠下丘脑NPY及其受体Y1、Y2、Y5mRNA的表达水平显著高于对照组和DIO-R大鼠,而DIO-R大鼠与对照组相比,除Y2受体mRNA的表达水平显著下降外,其余指标均无显著性差异。结论:高脂饲料诱导下,SD大鼠表现为明显的肥胖易感性差异,下丘脑NPY及其受体的高水平表达可能是导致DIO大鼠热能摄入过多的内在机制之一。     

膳食诱导肥胖抵抗大鼠下丘脑NPY mRNA及蛋白的表达

目的研究膳食诱导肥胖(DIO)及肥胖抵抗(DIO-R)大鼠下丘脑弓状核神经肽Y mRNA及蛋白表达情况,探讨神经肽Y与肥胖抵抗的关系。方法高脂饮食建立DIO与DIO-R大鼠模型,分别于2周、12周末处死,采用原位杂交和免疫组化方法检测下丘脑弓状核神经肽Y的mRNA和蛋白表达情况。结果实验2周末,DIO大鼠神经肽Y mRNA和蛋白阳性面积分别为(0.563 8±0.100 5),(0.610 9±0.143 4)mm2,高于DIO-R(0.411 5±0.085 1),(0.523 1±0.096 3)mm2和对照组大鼠(0.400 4±0.062 2),(0.445 3±0.157 8)mm2;神经肽Y mRNA和蛋白积分光密度分别为9 025.48±2 192.32,7 786.39±1 423.02,高于DIO-R(7 651.79±2 279.21,5 447.16±3 207.09)和对照组大鼠(6 499.24±2 342.94,5 530.83±841.13)。结论神经肽Y mRNA和蛋白表达降低且保持敏感性可能与肥胖抵抗有关。     

肥胖抵抗大鼠的食欲调节

目的　探讨肥胖抵抗大鼠摄食量减少的原因。方法　采用 50只健康雄性SD大鼠,分为对照组 10只和高脂组 40只,分别用基础饲料和高脂饲料喂养 13周,然后根据体重和能量摄入量筛选出饮食诱导肥胖抵抗(DIO-R)大鼠 9只和饮食诱导肥胖(DIO)大鼠 10只,观察总摄食量的变化,放免法测定血清瘦素和血浆神经肽Y水平,免疫印迹法测定大鼠脑组织中黑色素皮质激素受体 4(MCR- 4)蛋白含量。结果　DIO- R大鼠总摄食量为(1 679 .1±146. 8)g,明显低于DIO大鼠的总摄食量(1 818 .4±148 .9)g;DIO R大鼠血浆神经肽Y含量为 ( 795. 24±83 .59 )ng/L,显著低于DIO大鼠(1 007. 14±172. 83)ng/L;基础组大鼠血清瘦素含量为 ( 4 .80±0. 75 )μg/L,DIO R组为 ( 9 .17±1 .19)μg/L,DIO组为(9 .32±1 .04)μg/L,提示高脂饲料使大鼠血清瘦素水平明显增加,但DIO- R与DIO大鼠间无明显差别;基础组大鼠脑组织中MCR 4含量峰面积分析表明基础组为(342±31)mm2,DIO R组为(455±33)mm2,DIO组为(355±30)mm2,说明高脂饲料使DIO R大鼠脑组织中MCR- 4含量增加。结论　DIO- R大鼠通过增加ob基因的表达降低神经肽Y途径活性并激活MCR 4途径来减少进食量,从而抑制体重的增加。     

不同药物对肥胖大鼠进食量、体重及体脂等的影响

目的观察西布曲明、非诺贝特、二甲双胍对高脂饮食诱导肥胖Wistar大鼠体重、体脂、空腹血糖、血脂、胰岛素的影响。方法将27只肥胖大鼠按照体重分为4组,在高脂饲料喂养的基础上分别给予空白干预和西布曲明、非诺贝特、二甲双胍三种药物干预;8w后处死大鼠,并测定体重、体脂,取血测血脂、血糖、胰岛素。结果西布曲明和二甲双胍对大鼠的进食量无显著影响,而非诺贝特可显著减少大鼠的进食量;西布曲明和非诺贝特均可减轻肥胖大鼠的体重和体脂,而二甲双胍仅可以降低肥胖大鼠体重。结论西布曲明及非诺贝特可显著降低肥胖大鼠体内的脂肪含量。非诺贝特的减轻体重作用可能部分地与其食欲抑制作用有关;而西布曲明和二甲双胍的减轻体重机制可能并不完全依赖于其食欲抑制作用。     

饮食对下丘脑神经肽Y基因表达及肥胖影响

目的探讨高脂饮食对大鼠神经肽Y(NPY)基因表达及分泌的影响及大鼠肥胖易感性差异的机制.方法36只雌性SD大鼠按体重随机分为高脂实验组和基础对照组,分别给予高脂饲料和基础饲料喂养13周.据13周末体重从高脂饲料组选出体重最重和体重最轻者各9只为饮食诱导肥胖(DIO)和饮食诱导肥胖抵抗(DIR)组,比较各组大鼠能量摄入水平、血浆和下丘脑匀浆NPY及下丘脑NPY mRNA表达的差异.结果DIO组大鼠能量摄入量、下丘脑和血浆NPY水平之比显著高于DIR组和对照组(P＜0.01),DIO组大鼠下丘脑NPYmRNA表达显著高于DIR及对照组,而上述各指标DIR与对照组问差异均无统计学意义(P＞0.05).结论高脂饮食喂养条件下,SD大鼠表现为明显的肥胖易感性差异,这种差异与大鼠的能量摄入水平有关,下丘脑NPY高水平表达和分泌可能是导致肥胖易感大鼠多食和热能摄入过多的内在机制之一.     

营养变迁模型大鼠肾周脂肪神经肽Y与胰岛素抵抗的关系

目的观察能量限制后重新开放饮食的营养变迁模型大鼠肾周脂肪组织神经肽Y表达改变及其与胰岛素抵抗的关系。方法选取8周龄SPF级雄性SD大鼠按随机数字表法分为空白对照组和限食4周后重饲8周组,每组16只。限食4周期间喂饲量为对照组同体重大鼠进食量的60%,重饲8周期间喂饲量与体重匹配。于实验4周和12周末时每组分别取8只大鼠检测空腹血糖、空腹胰岛素和游离脂肪酸水平,高胰岛素-正糖钳夹实验检测第60～120 min平均葡萄糖输注率(average glucose infusion rate during 60～120 min, GIR_( 60-120)),实时定量PCR检测肾周脂肪组织神经肽Y基因mRNA表达水平。采用Spearman相关分析检测肾周脂肪组织神经肽Y基因表达与胰岛素抵抗的关系。结果能量限制4周时大鼠体重明显低于对照组(P0.01),肾周脂肪组织神经肽Y基因mRNA表达水平和游离脂肪酸水平显著高于对照组(P0.01),空腹血糖、空腹胰岛素水平轻度下降,GIR_( 60-120)轻度升高,与对照组相比差异无统计学意义(P0.05)。开放饮食8周后,体重虽大幅提升但仍低于对照组(P0.05),神经肽Y基因mRNA表达水平仍呈轻度上升趋势,明显高于对照组(P0.01),空腹胰岛素、游离脂肪酸水平显著升高,GIR_( 60-120)显著降低,与对照组相比差异均有统计学意义(P0.01),空腹血糖变化不明显。逐步回归分析结果显示,肾周脂肪组织神经肽Y基因mRNA表达水平与GIR_( 60-120)、空腹胰岛素密切相关,r值分别为-0.816和0.789(R~2=0.892,P0.01)。相关结果显示,限食4周时,肾周脂肪组织神经肽Y基因mRNA表达水平与GIR_( 60-120)、空腹胰岛素、游离脂肪酸密切相关,r值分别为-0.765、0.716和0.657(P0.01);重饲8周后,肾周脂肪组织神经肽Y基因mRNA表达水平与GIR_( 60-120)、空腹胰岛素、游离脂肪酸密切相关,r值分别为-0.853、0.622和0.608(P0.01)。结论营养变迁模型中肾周脂肪组织神经肽Y基因mRNA表达与胰岛素抵抗指标密切相关,是影响胰岛素敏感性的重要因素。     

反义RNA和反义硫代寡核苷酸抗HBV转基因小鼠病毒疗效的比较

目的　比较人工合成的反义硫代寡核苷酸 (asODN )和反义RNA真核表达质粒 (PCEP4-ac)在乙型肝炎(HBV)病毒转基因小鼠体内的抗病毒作用。　方法　设计合成针对HBV -pre -c/c基因的反义硫代寡核苷酸 5‘ -CAT GCCCCAAAGCCAC -3’。构建HBV -c区反义RNA真核表达质粒 (PCEP4-ac) ,并以半乳糖 -多聚赖氨酸 (Gal15 -PLL)作肝靶向载体。将 2 0只HBV转基因小鼠分为反义寡核苷酸、反义RNA真核质粒表达、生理盐水组。靶向反义硫代寡核苷酸以每只体重 15 0ug剂量 ,反义RNA真核质粒每只 10 0ug剂量 ,尾静脉注射给药 ,对照组用同样体积生理盐水同样方法给药。　结果　注射asODN和PCEP4-aC后 7d血清HBsAg已有所下降 (P <0 .0 5 ) ;14d时显著下降 (P <0 .0 1) ,且血清HBV -DNA转阴率分别为 66.7% ( 4 /6)和 62 .5 % ( 5 /8) ,而生理盐水组无明显变化。　结论　反义硫代寡核苷酸和反义RNA真核表达质粒均能在乙肝转基因小鼠体内抑制HBV复制和表达 ,且两者在抑制作用上无明显差异性。     

瘦素和神经肽Y mRNA与肥胖抵抗的关系

目的　研究膳食诱导肥胖 (DIO)及膳食诱导肥胖抵抗 (DIO -R)大鼠血清瘦素水平及下丘脑弓状核神经肽YmRNA(NPYmRNA)的表达情况 ,探讨瘦素、神经肽YmRNA与肥胖抵抗的关系。方法　采用放射免疫方法检测血清瘦素水平 ,原位杂交方法检测神经肽YmRNA表达。结果　 2周末 ,DIO -R大鼠神经肽YmRNA水平显著低于DIO大鼠 (P <0 0 5 ) ,而瘦素水平高于DIO和对照组大鼠 (P <0 0 5 ) ;12周末 ,DIO -R大鼠瘦素水平低于DIO大鼠 (P <0 0 5 ) ,高于对照组大鼠 (P <0 0 5 )。结论　保持瘦素敏感性和神经肽YmRNA下降可能与肥胖抵抗有关。     

Altered hypothalamic signaling and responses to food deprivation in rats fed a low-carbohydrate diet

OBJECTIVE: To model how consuming a low-carbohydrate (LC) diet influences food intake and body weight. RESEARCH METHODS AND PROCEDURES: Food intake and body weight were monitored in rats with access to chow (CH), LC-high-fat (HF), or HF diets. After 8 weeks, rats received intracerebroventricular injections of a melanocortin agonist (melanotan-II) and antagonist (SHU9119), and feeding responses were measured. At sacrifice, plasma hormones and hypothalamic expression of mRNA for proopiomelanocortin (POMC), melanocortin-4 receptor, neuropeptide Y (NPY), and agouti related protein (AgRP) were assessed. A second set of rats had access to diet (chow or LC-HF) for 4 weeks followed by 24 h food deprivation on two occasions, after which food intake and hypothalamic POMC, NPY, and AgRP mRNA expression were measured. RESULTS: HF rats consumed more food and gained more weight than rats on CH or LC-HF diets. Despite similar intakes and weight gains, LC-HF rats had increased adiposity relative to CH rats. LC-HF rats were more sensitive to melanotan-II and less sensitive to SHU9119. LC-HF rats had increased plasma leptin and ghrelin levels and decreased insulin levels, and patterns of NPY and POMC mRNA expression were consistent with those of food-deprived rats. LC-HF rats did not show rebound hyperphagia after food deprivation, and levels NPY, POMC, and AgRP mRNA expression were not affected by deprivation. DISCUSSION: Our results demonstrate that an LC diet influences multiple systems involved in the controls of food intake and body weight. These data also suggest that maintenance on an LC-HF diet affects food intake by reducing compensatory responses to food deprivation.     

Responsiveness of obese Zucker rats to [D-Trp34]-NPY supports the targeting of Y5 receptor for obesity treatment

The increased synthesis and release of neuropeptide Y (NPY) in the hypothalamus participate in the development of overeating and obesity in the Zucker fa/fa rat. The orexigenic effects of NPY are mediated through the Y1 and Y5 receptors. The substitution of [D-Trp34] in the NPY amino-acid sequence increases selectivity without lowering potency at the Y5 receptor. In the present study, to address the role of the NPY Y5 receptor in obesity, we investigated the acute effect of [D-Trp 34]-NPY in lean and obese Zucker rats. Obese rats were markedly hyperphagic (27.1 +/- 0.6 vs. 18.7 +/- 0.4 (lean) g/day; p < 0.01). Injection of [D-Trp34]-NPY in the lateral brain ventricle at a dose of 16 microg stimulated food intake to the same extent in both lean (p < 0.01) and obese (p < 0.01) rats 1 h after injection. This effect was still observed after 6 h (p < 0.01). These results indicate, therefore, that the obese rats are responsive to [D-Trp34]-NPY. They support the role of the neuropeptide Y5 receptor in the regulation of food intake and suggest that NPY Y5 antagonism might be useful for treating obesity.     

Responsiveness of obese Zucker rats to [D-Trp34]-NPY supports the targeting of Y5 receptor for obesity treatment

The increased synthesis and release of neuropeptide Y (NPY) in the hypothalamus participate in the development of overeating and obesity in the Zucker fa/fa rat. The orexigenic effects of NPY are mediated through the Y1 and Y5 receptors. The substitution of [D-Trp³⁴] in the NPY amino-acid sequence increases selectivity without lowering potency at the Y5 receptor. In the present study, to address the role of the NPY Y5 receptor in obesity, we investigated the acute effect of [D-Trp³⁴]-NPY in lean and obese Zucker rats. Obese rats were markedly hyperphagic (27.1 ± 0.6 vs. 18.7 ± 0.4 (lean) g/day; p < 0.01). Injection of [D-Trp³⁴]-NPY in the lateral brain ventricle at a dose of 16 μg stimulated food intake to the same extent in both lean (p < 0.01) and obese (p < 0.01) rats 1 h after injection. This effect was still observed after 6 h (p < 0.01). These results indicate, therefore, that the obese rats are responsive to [D-Trp³⁴]-NPY. They support the role of the neuropeptide Y5 receptor in the regulation of food intake and suggest that NPY Y5 antagonism might be useful for treating obesity.     

Neuropeptide Y fails to normalize food intake in zinc-deficient rats

Zinc deprivation results in decreased and cyclic food intake in rats. We determined the response of zinc-deprived rats to neuropeptide Y (NPY). In a preliminary experiment, rats were fed a low (-Zn; <1 mg/kg) or adequate zinc diet (+Zn; 100 mg/kg) for 4 days. NPY (5 or 10 microg) was then administered via an intracerebroventricular (ICV) cannula and food intake measured for 4 h. NPY stimulated food intake in all rats, but the difference in food intake due to zinc deprivation persisted. In a subsequent experiment, rats were fed the low zinc and adequate zinc diets for 4, 5 or 6 days. Food intake was suppressed in rats fed the low zinc compared to the adequate zinc diet on all of these days. When NPY (10 microg) was administered at the onset of the light cycle, the food intake was approximately 2.5-fold greater regardless of dietary zinc status, but the amount of food consumed by rats fed low zinc was approximately one-half the quantity consumed by NPY-stimulated zinc-adequate rats. NPY administered at the onset of dark failed to stimulate food intake in either dietary group although the total intake difference due to zinc status persisted. ICV administration of 5 nmol of zinc prior to NPY injection failed to correct the food intake response of the zinc-deficient rats. We conclude that the basis of the reduced food intake of zinc-deficient rats does not relate to NPY quantity or release, or to impairment of its signal transduction. There appears to be another undefined factor that limits food intake in zinc deficiency.     

Effect of topiramate on body weight and body composition of osborne-mendel rats fed a high-fat diet: alterations in hormones, neuropeptide, and uncoupling-protein mRNAs

The effects of topiramate on food intake and body composition were investigated in rats fed a high-fat diet and compared with rats that were pair fed or treated with D-fenfluramine. Topiramate (40 mg. kg. d for 80 d) reduced body-weight gain in a manner similar to that of pair-fed rats and D-fenfluramine-treated rats. The reduction in body fat accounted for all the weight reduction after topiramate treatment but not after pair feeding or D-fenfluramine treatment. Topiramate reduced food intake acutely and increased metabolic rate. There were also significant reductions in leptin, insulin, and corticosterone. In the hypothalamus, topiramate increased mRNA for neuropeptide Y, reduced mRNA for neuropeptide-Y Y1 and Y5 receptors, corticotropin-releasing hormone (CRH), and type II glucocorticoid receptors but had no effect on mRNA levels for the short or long form of the leptin receptor. In peripheral tissues, topiramate reduced leptin mRNA in adipose tissue, had no effect on uncoupling protein 1 mRNA in brown adipose tissue but had tissue-selective effects on uncoupling proteins 2 and 3 mRNA levels in white and brown adipose tissues and muscle. In conclusion, topiramate is an effective inhibitor of weight gain in rats on a high-fat diet, but the mechanism through which the change in energy balance is achieved is unclear.     

Sibutramine decreases body weight gain and increases energy expenditure in obese Zucker rats without changes in NPY and orexins

The aim of the present work was to describe the effects of sibutramine on body weight and adiposity and to establish the potential involvement of neuropeptide Y (NPY) and orexins in the anorectic action of this drug. Male obese Zucker rats were daily administered with sibutramine (10 mg/kg, intraperitoneal) for two weeks. Carcass composition was assessed using the official methods of the Association of Official Analytical Chemists. Total body oxygen consumption was measured daily for 60 min before sibutramine or saline injection and for 30 min (from 60 to 90 min) after drug or saline injection. Hypothalamic arcuate and paraventricular nuclei, and the lateral hypothalamic area were immunostained for NPY, orexin A and orexin B. Commercial kits were used for serum determinations. Reductions in body weight and adipose tissue weights were observed after sibutramine treatment in obese Zucker rats. No changes in NPY immunostaining in the arcuate and paraventricular nuclei were found. Orexin A and orexin B immunostaining was not modified in the lateral hypothalamic area in treated rats. The reduction in body weight and adiposity induced by sibutramine was achieved by both a reduction in food intake and an increase in energy expenditure. NPY and orexins do not seem to be involved in the anorectic effect of sibutramine.