电针与西布曲明对肥胖大鼠脂肪细胞 产物影响的差异***★

背景：针灸与药物均是治疗单纯性肥胖病的有效方法，电针与常用减肥药西布曲明影响肥胖机体脂肪细胞产物是否存在差异？ 目的：观察电针与常用减肥药西布曲明影响肥胖大鼠脂肪细胞产物的差异，以探讨针灸减肥的机制。 设计：分层随机对照设计。 单位：南京中医药大学针药结合实验室。 材料：选用120只生后45 d雄性SD大鼠，由上海实验动物中心提供，实验过程中对动物的处置符合动物伦理学标准。盐酸西布曲明胶囊由太极集团涪陵制药厂生产，批号为国药准字X20010279；电针仪为韩氏LH402A穴位神经电刺激仪，由北京华卫产业开发公司生产。 方法：实验于2004-10/2006-11在南京中医药大学针药结合实验室和南京中医药大学实验动物中心完成。①高脂高能量饲料喂养100只SD雄性大鼠，选择食源性肥胖大鼠54只，分为电针组、药物组、肥胖组，每组18只，并以18只正常饲料大鼠为正常组。② 电针组大鼠均以2/15 Hz，4 mA的电针治疗，针刺穴位为同侧的“后三里”、“内庭”，每次针一侧2个穴位，隔日交替。以自制的束缚装置固定，治疗时大鼠处于清醒而不剧烈挣扎状态，治疗时间15 min/d，每6天休息1 d，共观察49 d，治疗42次；药物组采用0.2 g/L盐酸西布曲明溶液2.0 mg/（kg·d）灌胃；正常组及肥胖组与针刺组同样束缚而不针刺。 主要观察指标：①肥胖指标：检测各组大鼠体质量、体长、减重率及脂体比，生化比色法测定血清总胆固醇、高密度脂蛋白胆固醇及三酰甘油。②胰岛素敏感性指标：酶联免疫法测定空腹血清葡萄糖、胰岛素及胰岛素敏感指数。③脂肪细胞分泌调节物质水平：酶联免疫法测定血清抵抗素、瘦素、脂联素、肿瘤坏死因子α、白介素-6及其可溶性受体水平。 结果：纳入大鼠120只，食源性肥胖大鼠模型成功54只及正常组18只均进入结果分析。①肥胖组大鼠体质量、体脂量、胆固醇、三酰甘油明显高于正常组，差异有统计学意义(P < 0.01)。电针组大鼠体质量、体脂量、脂体比、胆固醇、三酰甘油低于肥胖组，差异有统计学意义(P < 0.01)。药物组大鼠三酰甘油低于肥胖组，差异有统计学意义(P < 0.01)。电针组减重率高于药物组，脂体比低于药物组，差异有显著性意义(P < 0.01)。②肥胖组大鼠血糖、血清胰岛素明显高于正常组，胰岛素敏感指数低于正常组，差异均有统计学意义(P < 0.01)。电针组及药物组血糖和胰岛素水平低于肥胖组，胰岛素敏感指数高于肥胖组，差异有统计学意义(P < 0.01)。③电针组大鼠脂联素水平高于肥胖组，差异有统计学意义(P < 0.01)。抵抗素、肿瘤坏死因子α水平均低于肥胖组，差异有统计学意义(P < 0.01)。药物组大鼠抵抗素水平低于肥胖组，差异有统计学意义(P < 0.01)。 结论：电针在改变肥胖大鼠脂肪组织异常分泌的产物方面的作用较西布曲明更为明显，这可能是针灸减肥和防治肥胖相关疾病的重要机制之一。     

针刺2型糖尿病大鼠脂肪细胞因子的变化*☆

背景：脂肪细胞因子在2型糖尿病发病中的作用尚未明确;针灸治疗2型糖尿病早中期具有良好的疗效,那么针刺对脂肪细胞因子是否也有影响呢？ 目的：验证脂肪细胞因子与2型糖尿病的关系以及针刺对2型糖尿病机体脂肪细胞因子的影响。 设计、时间及地点：随机对照动物实验,于2006-08/2007-01在南京中医药大学动物实验中心完成。 材料：刚断乳的SD雄性大鼠100只,平均体质量50 g左右,随机分为普通饲料组20只,高脂饲料组80只,高脂饲料组大鼠体质量高于普通饲料组平均体质量20%为食源性肥胖大鼠。 方法：给40只食源性肥胖大鼠腹腔注射小剂量链脲霉素,成功造成2型糖尿病模型27只,随机分为模型组、针刺组(针刺后三里、内庭和胰俞,1次/d)及优降糖组[格列本脲片1.6 mg/kg给药,1次/d],每组各9只,处理4周,与随机抽取的9只正常饲料大鼠做对照。 主要观察指标：以快速血糖仪检测空腹血糖、放免法检测空腹胰岛素、ELISA法检测血清脂联素、抵抗素和肿瘤坏死因子α质量浓度。 结果：模型组空腹血糖、空腹胰岛素、肿瘤坏死因子α明显高于正常组(P < 0.05或0.01);针刺组与模型组比较,空腹血糖、空腹胰岛素、肿瘤坏死因子α明显下降(P < 0.05或0.01),接近正常组水平;优降糖组与模型组比较,空腹血糖明显下降(P < 0.01),接近正常组水平,空腹胰岛素和肿瘤坏死因子α有所下降,和正常组仍有差异;模型组、正常组、针刺组、优降糖组血清脂联素和抵抗素水平差异无显著性意义(P > 0.05)。 结论：血清脂联素和抵抗素水平与2型糖尿病的发病无明显关系,血清肿瘤坏死因子α可能参与了2型糖尿病的发病机制;针刺和优降糖均具有明显的降血糖、改善胰岛素抵抗、抑制血清肿瘤坏死因子α作用,针刺作用优于优降糖。     

药源性肥胖患者血清瘦素和脂联素水平检测

目的:探讨抗精神病药药源性肥胖患者血清瘦素和脂联素的水平及相关性.方法:选择21例药源性肥胖的住院患者(A组),20例首发精神分裂症患者(B组),20名健康体检人员作为对照组(C组),采用放射免疫法检测各组血清瘦素和脂联素水平,并分析各组血清瘦素及脂联素与体质量指数(BMI)相关性.结果:A组血清瘦素水平(13.3±8...     

神经肽Y Y5受体基因反义寡核苷酸脑室给药对伴糖尿病缺血再灌注大鼠血清瘦素与TNF-α的影响

目的观察神经肽Y Y5(NPY Y5)受体基因反义寡核苷酸脑室给药对伴糖尿病缺血再灌注大鼠血清瘦素、胰岛素与TNF—α的影响。方法链脲佐菌素空腹腹腔注射制备糖尿病大鼠模型，线栓法闭塞大脑中动脉制作脑缺血再灌注大鼠模型；治疗组经导管向脑室注入50μg(5U／μl)NPY Y5受体基因反义寡核苷酸，每天3次给药，连续应用3天；采用ELISA双抗体夹心法测定血清TNF-α与瘦素含量，放射免疫法测定胰岛素含量。结果缺血再灌注损伤后，大鼠血清瘦素、胰岛素、TNF—α水平较对照组显著升高；NPY Y5受体基因反义脱氧核苷酸侧脑室注射干预后，其血清瘦素、胰岛素水平明显下降，TNF—α水平显著降低。结论神经肽Y Y5受体基因反义寡核苷酸侧脑室给药可降低伴糖尿病缺血再灌注大鼠的血清瘦素、TNF—α与胰岛素水平，改善外周瘦素抵抗与胰岛素抵抗，促进脑梗死恢复。     

血清瘦素与抗精神病药源性肥胖及糖尿病的相关性研究

目的　调查和探讨长期使用抗精神病药患者血瘦素水平及其与服用抗精神病药后体重 增加、肥胖及糖尿病之间的关系。方法　对符合入组标准的308例长期服用抗精神病药的精神分裂症 患者分为对照组、肥胖组、糖耐量减低组及糖尿病组,比较血清瘦素水平、胰岛素抵抗指数、血清甘油三 酯及总胆固醇水平。结果　(1)肥胖组、糖耐量减低组及糖尿病组患者的血清瘦素水平、胰岛素抵抗指 数、血清甘油三酯及总胆固醇水平均显著高于对照组(P<0.05)。(2)长期应用抗精神病药患者血瘦 素水平与体重指数、简易胰岛素抵抗指数、空腹血糖、血甘油三酯及胆固醇均呈极显著正相关(P<0.01 ～0.0001),而与餐后2h血糖水平及用药时间无相关性。结论　长期应用抗精神病药患者血瘦素水 平在肥胖、糖耐量降低及糖尿病患者中显著升高,且与体重指数、简易胰岛素抵抗指数、空腹血糖水平等 均呈显著正相关,提示高血清瘦素水平是长期应用抗精神病药所致的代谢紊乱综合征的重要指征之一。     

高频电刺激伏隔核壳部对肥胖大鼠摄食相关激素的影响

目的 探讨伏隔核壳部(NAc-sh)脑深部电刺激术(DBS)对肥胖大鼠摄食量和摄食相关激素分泌的影响.方法 取8周龄雄性SD大鼠60只,高脂饮食建立肥胖大鼠模型,6个月后取24只肥胖大鼠,采用随机数字表法随机分为NAc-sh高频DBS刺激组(简称刺激组)和假刺激组,每组12只.分别在双侧NAc-sh植入刺激电极固定装置.术后30 d大鼠进食完全恢复后,两组各选取进食量稳定的大鼠10只植入电极行刺激(电压3.0V,波宽100μs,频率180 ～ 200 Hz)或假刺激,并于刺激或假刺激前后断尾取血,放射免疫方法检测外周血胃促生长素、瘦素及神经肽Y(NPY)水平的变化.结果 刺激组大鼠刺激开始摄食量即较刺激前明显下降(P＜0.05),刺激后血清瘦素和神经肽Y的浓度较刺激前明显下降[瘦素:(20±10) pg/ml对比(32±10) pg/ml;神经肽Y:(926±299) pg/ml对比(1302±287)pg/ml,P值均＜0.05],胃促生长素的血清浓度较刺激前明显增加[(1 603±848) pg/ml对比(1 066 ±310) pg/ml,P＜0.05),而假刺激组刺激前后进食量及胃促生长素、瘦素、神经肽Y的变化差异均无统计学意义(P＞0.05).结论 NAc-sh高频电刺激能有效降低肥胖大鼠摄食量,外周血激素的变化可能与外侧丘脑的兴奋性改变有关.     

大鼠动脉硬化闭塞模型两种构建方法的比较

背景：由于动脉硬化闭塞症的发病机制还不明确，所以建立动脉硬化闭塞症的病理动物模型，对于探明动脉硬化闭塞症的病因、病理生理、发病机制及防治药物的研究与开发均具有重要的意义。 目的：比较单纯高脂饲料喂养及给予内膜损伤加高脂饲料喂养大鼠动脉硬化闭塞模型复制建立的方法。 设计、时间及地点：随机对照动物实验，2007-08/2008-03于中国医科大学实验动物中心完成。 材料：清洁级3.0~4.0月龄健康纯种Wistar雄性大白鼠60只，体质量200 g。高脂饲料:62.8%基础饲料+20%猪油+150 g/L胆固醇+20 g/L胆酸钠+2 g/L丙基硫氧嘧啶。 方法：将60只大鼠随机分成3组，每组20只。普通饲养组给予普通饲料喂养；高脂饲养组给予高脂饲料喂养；高脂饲养加内膜损伤组给予内膜损伤加高脂饲料喂养。后两组同时给予维生素D3，30万u/kg体质量，右后肢肌肉注射,1次/月。 主要观察指标：①于内膜损伤后术后30 d，各组大鼠取血检测血浆总胆固醇、三酰甘油、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇浓度变化。②于内膜损伤后术后7，30，90 d时，取大鼠左后肢股-腘动脉，行苏木精-伊红等染色，光镜下观察股-腘动脉的病理变化。 结果：高脂饮食组大鼠与正常饮食组大鼠相比，高脂饮食组大鼠血清胆固醇 ，三酰甘油和低密度脂蛋白胆固醇均明显升高。病理显示：7 d高脂饲养组内皮细胞少量脱落，高脂饲养加内膜损伤组内皮细胞完全脱落、弹力板松弛，平滑肌细胞排列紊乱。90 d高脂饲养组内皮细胞完全脱落、平滑肌和胶原纤维增多、增厚，为早期硬化改变。高脂饲养加内膜损伤组内膜增厚、大量吞噬脂质、类脂质细胞、管腔闭塞。 结论：单纯给予大鼠高脂、高胆固醇饲料喂养不易形成动脉硬化闭塞症病变，大鼠股-腘动脉内注入蒸馏水损伤内皮加高脂饲料喂养可较快形成与人动脉硬化闭塞症相似的、较成熟的大鼠动脉硬化闭塞模型。     

伴糖尿病大鼠脑缺血再灌注损伤后血清抵抗素及瘦素与TNF-α的相互作用

目的观察血清抵抗素、瘦素与TNF-α在伴糖尿病大鼠缺血再灌注损伤中的作用。方法链脲佐菌素空腹腹腔注射缺血糖尿病大鼠模型,线栓法闭塞大脑中动脉制作脑缺血再灌注大鼠模型;采用ELISA双抗体夹心法测定血清TNF-α、瘦素与抵抗素含量。结果糖尿病大鼠血清TNF-α、瘦素与抵抗素水平均高于正常对照组,缺血再灌注损伤后,大鼠血TNF-α、瘦素水平较对照组显著升高,而血清抵抗素水平降低。结论抵抗素、瘦素和TNF-α参与了糖尿病与缺血再灌注的损伤发病过程,TNF-α抵抗素的负调节因子,能下调抵抗素表达。TNF-α与瘦素相互作用,导致瘦素抵抗,血清瘦素水平增高。     

幼鼠骨骼发育中高脂饮食的影响*○

背景：高脂饮食能引起肥胖,成年人肥胖能增加骨密度,对健康有一定的正面作用,而高脂饮食对生长快速的儿童骨骼发育的影响并不十分明确。 目的：观察高脂饮食对雌性幼鼠骨胳发育的影响。 方法：取12只4周龄雌性CD1小鼠,分别给予高脂饮食和正常饮食,喂养10周后用双能X射线骨密度仪扫描全身;用三点弯曲实验检测骨生物力学特征;用酶联免疫分析法检测血清中骨转换标志物;股骨组织切片苏木精-伊红染色观察骨小梁变化和骨髓的脂肪化程度。 结果与结论：高脂饮食组小鼠的体质量、体脂含量均显著高于正常饮食组,但全身的骨密度、骨矿物质含量、骨面积和肌肉组织含量与正常饮食组无显著差异,但腰椎的骨密度、骨矿物质含量和骨面积都显著低于正常饮食组,而股骨的骨密度、骨矿物质含量和骨面积都显著高于正常饮食组,经体质量或体脂含量校正后虽然无显著统计学差异,但高脂饮食组全身和股骨的骨密度、骨矿物质含量和骨面积都呈现了低于正常饮食组的趋势;两组在骨生物力学特性方面的比较没有显著差异;高脂饮食组的血清骨转换标志物浓度较正常饮食组低;组织切片可见高脂饮食组的骨髓腔中有大量脂肪浸润和骨小梁宽度和面积减小。提示肥胖对生长旺盛阶段的幼鼠骨骼发育有不良影响,椎骨的骨矿物化程度下降,承重部位骨量的增加不能充分代偿体质量的增加。     

食源性肥胖大鼠2型糖尿病模型的建立

背景：高脂饮食加小剂量链脲佐菌素是目前国内最常用的2型糖尿病大鼠造模方式，但高脂饮食仅能诱导50%大鼠发生胰岛素抵抗，因此还需寻找更理想的2型糖尿病大鼠建模方法。 目的：选择食源性肥胖大鼠进行小剂量链脲佐菌素腹腔注射，建立更理想的2型糖尿病动物模型。 方法：将SD大鼠随机分成对照组和高脂饮食组。4周后，据大鼠体质量将高脂饮食组分为食源性肥胖组和食源性肥胖抵抗组。8周后，所有大鼠均给予小剂量链脲佐菌素(30 mg/kg)腹腔注射，将注射10 d后空腹血糖> 7.8 mmol/L且稳定2周以上者纳为2型糖尿病大鼠模型。检测各组大鼠的空腹血糖、血脂、胰岛素；评价各组大鼠的胰岛素抵抗程度；比较各组大鼠的2型糖尿病成模率。 结果与结论：与对照组及食源性肥胖抵抗组相比，食源性肥胖组大鼠出现明显的体质量增加、高血脂、高胰岛素血症及胰岛素抵抗(P < 0.01)。注射链脲佐菌素后食源性肥胖组2型糖尿病成模率高达100%，食源性肥胖抵抗组成模率仅为12.5%。由结果可知选择食源性肥胖组大鼠作为2型糖尿病造模对象，是2型糖尿病造模方法的成功改良。     

Altered hypothalamic c-Fos-like immunoreactivity in diet-induced obese mice

High-fat diet can induce obesity. However, it is not known if the neural activity of the hypothalamus is altered under high-fat diet. The aim of the present study is to search for the altered hypothalamic neuronal activity in C57BI/6J mice fed a high-fat diet for 15 weeks. Hypothalamic c-Fos-like immunoreactivity (FLI) and serum leptin were measured after mice were fed a high-fat diet for 15 weeks. Our results demonstrate that increased body weight and serum leptin are accompanied by an elevated neuronal c-Fos-like immunoreactivity in the lateral hypothalamus, the lateral part of the dorsomedial hypothalamic and perifornical nuclei of diet-induced obese mice. Fasting increases FLI neurons in the arcuate hypothalamic nucleus and decreases FLI neurons in the lateral hypothalamic area and dorsomedial hypothalamic nucleus of both diet-induced obese and lean mice. The current data suggest that constantly activated status of these neurons in the hypothalamus may be responsible for differences in body weight and serum leptin between obese and lean mice.     

Localization of leptin receptor immunoreactivity in the lean and obese Zucker rat brain

Leptin, a product of the obese (ob) gene, is secreted by adipocytes and appears to act as a hormone to regulate food intake, metabolism and body weight. Subcutaneous administration of leptin causes reductions in food intake and body and fat-depot weights in both lean and genetically obese (ob/ob) mice, and leptin infusion into the lateral cerebral ventricles decreases feeding with short latency, suggesting a central site of action. A gene defect in the Zucker obese rat causes an amino acid substitution in the leptin receptor and reduced leptin binding at the cell surface. An antiserum to a portion of the mouse leptin receptor (AA 877–894) located within the intracellular domain was used to label Zucker lean (Fa/?) and obese (fa/fa) rat brain sections. At optimal dilution (1:8000), only cells in the basal forebrain, preoptic area, hypothalamus and brainstem were moderately or intensely labeled. The most intensely-labeled nuclei, the anterior commissural, magnocellular paraventricular, supraoptic, circularis in the anterior hypothalamus and fornical in the lateral hypothalamus contain large neurons that synthesize and secrete vasopressin or oxytocin and their respective neurophysins. Diminished leptin transport into the central nervous system or defective signal transduction in Zucker obese rats may sufficiently compromise leptin regulation of the HPA axis, NPY-immunoreactive neurons or other hypothalamic elements to cause obesity.     

Nutritional regulation of hypothalamic leptin receptor gene expression is defective in diet-induced obesity

Leptin action in the hypothalamus plays a critical role in maintaining normal food intake and body weight. Hyperleptinaemia is associated with obesity in humans and animal models, suggesting a state of leptin resistance. Although the mechanism of leptin resistance is not clearly understood, alterations in leptin receptor (Ob-R) gene expression have been proposed as a potential mechanism mediating modifications in leptin action in obesity and during changes in nutritional status (fed/fasted). The current study examined the effects of diet-induced obesity (DIO) made by feeding rats a high fat diet for 9 weeks, and nutritional status on levels of long form (Ob-Rb) and total (Ob-Rtot) Ob-R mRNA expression in the hypothalamus. In the fed state, hypothalamic Ob-Rb mRNA and Ob-Rtot mRNA levels were similar in DIO and control standard chow fed rats (SC) despite hyperleptinaemia in DIO rats. However, although an overnight fast moderately increased hypothalamic Ob-Rb mRNA levels in SC rats, fasting did not increase Ob-Rb mRNA levels in DIO rats. To address the possibility that elevated leptin concentration in DIO rats may mediate an alteration in OB-R mRNA levels, we examined the effects of adenovirus-mediated hyperleptinaemia on Ob-R gene expression in SC rats. Despite substantially elevated plasma and cerebrospinal fluid concentrations of leptin, hypothalamic Ob-R mRNA levels were similar in both groups. In conclusion, the current study demonstrates that DIO is associated with a loss of nutritional regulation of hypothalamic Ob-R mRNA levels, and that hyperleptinaemia is not sufficient to alter Ob-R mRNA expression.     

Central and peripheral dysregulation of melanin-concentrating hormone in obese Zucker rats

Melanin concentrating hormone (MCH) is a peptide synthesized in the lateral hypothalamus which stimulates food ingestion and leptin secretion in rodents. In this experiment, we measured the expressions of MCH as well as of its receptor (SLC-1) in the hypothalamus of obese hyperphagic and lean Zucker rats by quantitative real time RT-PCR. MCH mRNA expression in the obese rats was significantly increased by a factor of five (P<0.01) whereas expression of SLC-1 was decreased by more than 50% (P<0.05). Circulating levels of leptin and MCH were increased in the plasma of obese Zucker rats when compared to lean rats (38-fold and 1.7-fold, respectively, P<0.001 and P<0.01). However, individual MCH levels were not directly correlated to leptin levels in the lean (functional leptin receptor) or in the obese (non-functional leptin receptor) Zucker rats. These results indicate that the absence of leptin signaling in rats is associated with an increased hypothalamic expression and circulating release of MCH, contributing to their obesity syndrome.     

Immunohistochemical characterization of localization of long-form leptin receptor (OB-Rb) in neurochemically defined cells in the ovine hypothalamus

Leptin, a hormone secreted from the adipose tissue, is involved in the regulation of food intake and neuroendocrine function, by modulation of the expression and/or function of various neuropeptides in the hypothalamus. The long isoform (OB-Rb) is the major signaling form of the leptin receptor in the hypothalamus. We have used double-labeling immunohistochemistry to examine the extent of OB-Rb expression in neurochemically defined cell types in the ovine hypothalamus. OB-Rb-like immunoreactivity was widespread within cells localized to the periventricular, paraventricular, supraoptic, dorsomedial hypothalamic, ventromedial hypothalamic and arcuate nuclei, as well as the median eminence, perifornical, anterior hypothalamic and lateral hypothalamic areas and the zona incerta. Double-labeling showed expression of OB-Rb in 59.6±6.0% neuropeptide Y-containing cells, 60.8±4.7% galanin-containing cells, 89.8±2.65% pro-opiomelanocortin-containing cells, 73.4±3.5% tyrosine hydroxylase-containing cells and 31.8±2.8% corticotropin-releasing factor-containing cells. Interestingly 100% of melanin-concentrating hormone and orexin positive cells were also OB-Rb immunoreactive. These data provide semi-quantitative information on the extent to which various cell types express OB-Rb in the hypothalamus. Expression of OB-Rb within specific neuropeptidergic neurons provides evidence for the direct action of leptin upon the various neurochemical systems that regulate food intake, neuroendocrine and autonomic function in the brain.     

Expression of complement messenger RNAs by human endothelial cells

Reduction in the adiposity or dietary restriction increases plasma growth hormone (GH) concentrations, and in sheep this appears to be due, at least in part, to a reduction in the concentrations of somatostatin (SRIF) in hypophyseal portal blood. Leptin is a hormone secreted by the adipocytes and it is possible that the effects of altered adiposity or fasting on GH secretion could be due to regulation of SRIF neurons by leptin. To ascertain the extent to which leptin may act on these neurons, we have used immunohistochemistry to examine co-localization of long-form of the leptin receptor (OB-Rb) and SRIF in the sheep hypothalamus. In the hypothalamic periventricular area (PeriV), 44.5±10% of SRIF cells were found to co-stain for OB-Rb. In the dorsomedial hypothalamic, ventromedial hypothalamic and arcuate nuclei, 100% of SRIF immunoreactive neurons expressed OB-Rb. These findings provide a basis for the direct action of leptin on SRIF neurons. Thus, it is possible that leptin stimulates the secretion of SRIF in relatively obese individuals. The significance of the lower number of SRIF cells in the PeriV co-localizing OB-Rb expression is not clear at present.     

Refeeding after prolonged food restriction differentially affects hypothalamic and adipose tissue leptin gene expression

Rat adipose tissue is the principal site of leptin synthesis, however, leptin gene expression has been demonstrated in many rat tissues. Some data indicate that leptin produced by human brain and adipose tissue could cooperate in the regulation of food intake. In this case the regulation of leptin gene expression in hypothalamus and in adipose tissue should be coordinately regulated. Food restriction is often undertaken by many humans trying to lose body weight. Thus, the current study was aimed to analyze whether leptin gene expression in rat hypothalamus and in adipose tissue is regulated synchronously by prolonged food restriction and prolonged food restriction/refeeding.We demonstrate here that although leptin gene is expressed at very low level in rat hypothalamus, its expression in hypothalamus was down-regulated by prolonged food restriction similarly as in the white adipose tissue. Refeeding after prolonged food restriction caused both an increase of leptin gene expression in white adipose tissue and the increase in serum leptin concentration. In contrast, no significant effect of prolonged food restriction/refeeding on hypothalamic leptin gene expression was observed. The reduction of leptin gene expression in both hypothalamus and white adipose tissue by prolonged food restriction was associated with a significant increase of NPY gene (a target of leptin signaling) expression in hypothalamus. Refeeding after prolonged food restriction caused the decrease of NPY gene expression in hypothalamus, however NPY mRNA level remained higher than in controls.The results presented in this paper indicate that prolonged food restriction/refeeding differentially affects leptin gene expression in adipose tissue and in hypothalamus. Moreover, obtained data suggest that in rats leptin synthesized in hypothalamus exerts marginal effect on NPY gene expression and on serum leptin concentration.     

Effect of nicotine on the expression of leptin and forebrain leptin receptors in the rat

We have previously reported that chronic nicotine administration (4.0 mg/kg/day by i.p. injection over 14 days) up-regulates orexin/hypocretin and neuropeptide Y (NPY) mRNA expression and peptide levels within the hypothalamus. Since there exists a coregulation between these neuropeptides and the protein leptin, the present study was undertaken to determine whether nicotine has a regulatory effect on leptin signaling. Under the same experimental regimen used previously, we found that nicotine down-regulates plasma leptin concentration by 48.8% (P<0.001) and leptin RNA level by 11.4% and 12.4%, respectively, in the perirenal and epididymal white adipose tissue (PWAT, EWAT) compared to the saline controls. We also measured an approximately 20% decrease in white and brown adipose tissue (BAT) by weight in nicotine-treated animals relative to saline controls (P<0.05). On the other hand, we found that chronic nicotine administration increased the expression levels of OB-Rb mRNA by 12% and OB-R mRNA by 25% in the medial basal hypothalamus compared to control rats. Subsequent radioligand binding assays indicated that nicotine also significantly increased leptin binding in ventromedial hypothalamic area (VMA), medial basal hypothalamic area (MBA), arcuate nucleus/median eminence, paraventricular nuclei and piriform cortex. Taken together, our results revealed that nicotine is involved in the regulation of leptin signaling, suggesting that leptin and its receptor play a role in the anorectic effects of nicotine on food intake and body weight in rats.     

Disruption in neuropeptide Y and leptin signaling in obese ventromedial hypothalamic-lesioned rats

Electrolytic lesions placed in the ventromedial hypothalamus (VMH) of rats induce instant hyperphagia and excessive weight gain. Since neuropeptide Y (NPY) is a potent hypothalamic orexigenic signal, and leptin secreted by adipocytes regulates NPY output, we tested the hypothesis that altered NPYergic-leptin signaling may underlie hyperphagia in VMH-lesioned rats. VMH-lesioned rats exhibiting hyperphagia and excessive weight gain in a time-related fashion were sacrificed on days 2, 7, and 21 post-surgery. Quite unexpectedly, NPY concentrations in the hypothalamic paraventricular nucleus (PVN), a major site of NPY release for stimulation of feeding, and in other sites, such as the dorsomedial nucleus, lateral hypothalamic area and median eminence-arcuate nucleus decreased, with the earliest diminution occurring on day 2 in the PVN only. In vitro basal and K⁺-evoked NPY release from the PVN of VMH-lesioned rats was significantly lower than that of controls. Analysis of hypothalamic NPY gene expression showed that although the daily decrease in NPY mRNA from 0800 to 2200 h occurred as in control rats, NPY mRNA concentrations were markedly reduced at these times in the hypothalami of VMH-lesioned rats. Leptin synthesis in adipocytes as indicated by leptin mRNA levels was also profoundly altered in VMH-lesioned rats. The daily pattern of increase in adipocyte leptin mRNA at 2200 h from 0800 h seen in controls was abolished, higher levels of leptin gene expression at 2200 h were maintained at 0800 h. The pattern of increase in serum leptin and insulin levels diverged in VMH-lesioned rats. Serum insulin concentration increased to maximal on day 2 and remained at that level on day 21-post-lesion; serum leptin levels on the other hand, increased slowly in a time-related fashion during this period. These results demonstrate that hyperphagia and excessive weight gain in VMH-lesioned rats are associated with an overall decrease in hypothalamic NPY and augmented leptin signaling to the hypothalamus. The divergent time course of increases in serum leptin and insulin levels suggest independent mechanisms responsible for their augmented secretion, and neither these hormones nor VMH lesions altered the daily rhythm in NPY gene expression. These observations underscore the existence of an independent mechanism controlling the daily rhythm in hypothalamic NPY gene expression and suggest that leptin feedback action requires an intact VMH.     

Neuropeptide Y counteracts the anorectic and weight reducing effects of ciliary neurotropic factor

Ciliary neurotrophic factor (CNTF), a cytokine of the interleukin-6 superfamily, has been shown to induce hypophagia and weight loss. Neuropeptide Y (NPY) and orexin are potent orexigenic signals in the hypothalamus. Anorexia, normally seen in response to infection, injury and inflammation, may result from diminished hypothalamic orexigenic signalling caused by persistently elevated cytokines, including CNTF. To test this hypothesis, we first examined the effects of chronic intracerebroventricular (i.c.v.) infusion of CNTF for 6-7 days on food intake and body weight as well as hypothalamic NPY and orexin gene expression in male rats. Subsequently, the effectiveness of NPY replacement to counteract the effects of CNTF by coinfusion of NPY and CNTF was evaluated. Chronic i.c.v. infusion of CNTF (2.5 microg/day) reduced body weight (14.3% vs control) at the end of 7 days. Food intake remained suppressed for 5 days postinfusion and subsequently gradually returned to the control range by day 7. Serum leptin concentrations in these rats were in the same range seen in control rats. Chronic i.c.v. infusion of higher doses of CNTF (5.0 microg/day) produced sustained anorexia and body weight loss (29% vs controls) through the entire duration of the experiment. This severe anorexia was accompanied by markedly suppressed serum leptin concentrations. Furthermore, CNTF infusion alone significantly reduced hypothalamic NPY gene expression (P < 0. 05) without affecting orexin gene expression. As expected, in fusion of NPY alone (18 microg/day) augmented food intake (191.6% over the initial control, P < 0.05) and produced a 25.1% weight gain in conjunction with a 10-fold increase in serum leptin concentrations at the end of the 7-day period. Interestingly, coinfusion of this regimen of NPY with the highly effective anorectic and body reducing effects of CNTF (5.0 microg/day) not only prevented the CNTF-induced anorexia and weight loss, but also normalized serum leptin concentrations and hypothalamic NPY gene expression. These results demonstrate that chronic central infusion to produce a persistent elevation of the cytokine at pathophysiological levels (a situation that may normally manifest during infection, injury and inflammation) produced severe anorexia and weight loss in conjunction with reduction in both serum leptin concentrations and hypothalamic NPY gene expression. Reinstatement of hypothalamic NPY signalling by coinfusion of NPY counteracted these CNTF-induced responses.