普罗布考抑制冠状动脉损伤后Ⅰ型胶原和原癌基因c-myc表达

目的建立猪冠状动脉球囊损伤模型,观察普罗布考对损伤动脉内膜增生的影响及对Ⅰ型胶原和cmyc基因表达的影响。方法雌性大约克夏猪19只,随机分为对照组和普罗布考组,两组均行冠状动脉球囊扩张术,术后6周重复冠状动脉造影后处死动物。观察损伤动脉的形态学变化,计算损伤动脉内膜面积占有率。并检测管壁Ⅰ型胶原及原癌基因cmycmRNA的表达强度。结果对照组损伤动脉内膜呈偏心性增厚,内膜面积占有率为56.0%±17.8%,普罗布考组损伤动脉内膜面积占有率为30.3%±21.0%,普罗布考组较对照组内膜增厚程度明显减低(P<0.05)。普罗布考组Ⅰ型胶原表达强度较对照组明显减弱(0.22±0.06比0.41±0.06,P<0.05)。对照组cmycmRNA相对表达强度明显高于正常动脉(2.73±0.51比0.82±0.09,P<0.05),而普罗布考组(1.44±0.25)较对照组减弱(P<0.05),但仍高于正常动脉(P<0.05)。结论普罗布考具有抑制冠状动脉成形术后损伤血管内膜增生的作用,其机制可能与抑制冠状动脉球囊损伤后Ⅰ型胶原增生和原癌基因cmyc表达有关。     

苯妥英钠对大鼠颈总动脉球囊损伤后内膜增生的影响

目的研究苯妥英钠促进创伤修复的特殊药理学作用在大鼠颈总动脉球囊损伤后内膜修复过程中的影响。方法采用大鼠颈总动脉内膜球囊损伤模型,术后大鼠分为苯妥英钠组和损伤组。术后28天处死大鼠,取双侧颈总动脉,石蜡包埋、切片后进行血管病理学染色分析。结果术后28天,苯妥英钠组内膜面积(0.154±0.018mm2比0.204±0.054mm2,P<0.01)、内膜/中膜面积比(1.70±0.08比2.26±0.46,P<0.01)、再狭窄率(59.5%±3.2%比75.9%±13.3%,P<0.01)均小于损伤组,管腔面积(0.106±0.024mm2比0.063±0.034mm2,P<0.01)大于损伤组;内膜细胞密度(72.18±20.08/cm2比84.85±10.77/cm2,P<0.05)、增殖细胞核抗原阳性细胞数(9.89±7.63个/200倍视野比23.03±13.95个/200倍视野,P<0.01)和α-平滑肌肌动蛋白阳性细胞数(30.91±20.05/200倍视野比61.81±16.57个/200倍视野,P<0.01)均小于损伤组;新生内膜中有少量胶原组织增生,但组间血管胶原面积和密度均无统计学差异(P>0.05)。结论大鼠颈总动脉球囊损伤后28天,苯妥英钠可以抑制损伤血管内膜增生过程中的细胞增生,促进细胞外基质合成,对血管损伤后内膜增生和管腔狭窄具有抑制作用。     

慢性肾脏病患者血清瘦素水平与颈动脉内膜-中层厚度的关系

目的 探讨慢性肾脏病患者血清瘦素水平与颈动脉内膜-中层厚度的关系.方法 选择79例慢性肾脏病非透析患者和15例健康对照者,采用放射免疫法测定血清瘦素水平,用高分辨二维颈动脉超声技术测定颈动脉内膜一中层厚度及粥样硬化斑块.结果 慢性肾脏病患者血清瘦素水平、平均颈动脉内膜-中层厚度和动脉粥样斑块检出率明显高于健康对照组(P<0.01).慢性肾脏病伴颈动硬化组(颈动脉内膜-中层厚度≥1.0mm,和/或颈动脉斑块)较无颈动脉硬化组血清瘦素(17.06±1.061ng/L比14.27±0.70ng/L)和C.反应蛋白(3.32±0.19mg/L比2.55±0.17mg/L)水平明显升高(P<0.01);慢性肾脏病患者血清瘦素与尿素氮、肌酐、C-反应蛋白、体质指数呈显著正相关(r=0.293,P<0.01;r=0.324,P<0.01;r=0.539,P<0.01;r=0.312,P<0.05);与肾小球滤过率、血红蛋白、白蛋白呈显著负相关(r=-0.389,P<0.01;r=-0.454,P<0.01;r=-0.246,P<0.05).瘦素(β=1.527,P<0.05)是慢性肾脏病患者并发动脉粥样硬化的独立危险因素.结论 慢性肾脏病患者存在高瘦素血症,高瘦素血症与颈动脉内膜-中层厚度的关系,其可能参与了慢性肾脏病患者动脉粥样硬化的发生和发展.     

ERK抑制剂对1型糖尿病模型小鼠血管内损伤后内膜增生的抑制作用

目的探讨细胞外信号调节激酶(ERK)特异性抑制剂PD98059对1型糖尿病模型血管内损伤后内膜增生的抑制作用。方法将实验动物分为3组,假手术组,1型糖尿病模型血管内损伤组,PD98059干预组。各组小鼠于颈动脉损伤后第28天处死并取右颈总动脉,检测颈动脉管腔面积、内膜面积、中膜面积及内膜/中膜面积比(I/M)。免疫组化检测内膜抗磷酸压ERK(p-ERK)、基质金属蛋白酶-9(MMP-9)表达水平。结果与假手术组相比,1型糖尿病模型血管内损伤组术后28 d,管腔面积明显缩小,内膜面积、中膜面积及I/M明显增加,差异有统计学意义(P0.01),颈动脉血管内膜p-ERK及MMP-9水平也明显增强(P0.01)。PD98059干预组术后28 d,与1型糖尿病模型血管内损伤组相比,管腔面积明显增加,内膜面积、中膜面积及I/M明显降低(P0.01),颈动脉内膜MMP-9表达明显减低,血脂及血糖水平无统计学意义。结论 ERK抑制剂可能通过抑制MMP-9减轻1型糖尿病高胆固醇饮食模型颈动脉血管内损伤后内膜增生。     

超高场强小动物磁共振成像活体观察小鼠颈动脉内膜损伤后的动态变化

目的 磁共振成像(MRI)活体观察内膜损伤后小鼠颈动脉管腔狭窄和管壁增厚的动态过程.方法 金属丝损伤法建立小鼠颈动脉内膜损伤模型,术后不同的时间点行MRI扫描,动态观察损伤血管的表现,包括管腔内径和面积、管壁的厚度和面积.结果 MRI能够清晰地观察小鼠颈动脉内膜损伤后的变化以及血管周围软组织的表现.小鼠颈动脉内膜损伤前、损伤后1、5、10d和15d管腔内径分别为(0.57±0.07)、(0.41±0.19)、(0.44±0.10)、(0.43±0.10)mm和(0.47±0.11)mm.管腔面积分别为:(0.30±0.06)、(0.18±0.11)、(0.18±0.06)、(0.18±0.06)mm2和(0.22±0.07)mm2.术后第15天患侧血管壁厚度为(0.23±0.12)mm,管壁面积为(0.35±0.24)mm2.结论 MRI可以在活体观察小鼠颈动脉内膜损伤后管腔狭窄和管壁增厚的动态变化过程.     

骨髓间充质干细胞对球囊损伤的大鼠颈总动脉内皮修复的影响

目的 研究骨髓间充质干细胞对球囊损伤的大鼠颈总动脉内皮修复的影响.方法 球囊损伤24只SD大鼠颈总动脉,建立动脉内皮损伤模型,随机分为:(1)治疗组12只SD大鼠,球囊损伤颈总动脉即刻注射1 mL骨髓间充质干细胞溶液;(2)对照组12只SD大鼠,球囊损伤颈总动脉即刻注射1 mL磷酸盐缓冲液.14 d及28 d后,取颈总动脉标本作组织病理切片,行苏木精伊红及血管内皮生长因子受体2、α-平滑肌肌动蛋白免疫组化染色.结果 用苏木精伊红染色观察新生内膜的厚度,14 d及28 d治疗组血管内膜增生均较对照组轻(14 d时0.57±0.06 cm比1.09±0.06 cm,P<0.05;28 d时0.43±0.09 cm比4.72±0.15 cm,P<0.05);用血管内皮生长因子受体-2免疫组化染色观察内皮化程度,治疗组血管内皮细胞覆盖程度高于对照组(14 d时70.8%±1.3%比20.4%±1.1%,P<0.05;28 d时90.2%±1.3%比10.7%±0.4%,P<0.05),治疗组可见血管内皮生长因子受体-2/5-溴脱氧尿核苷双阳性细胞约占血管内皮生长因子受体-2单阳性细胞的50%.α-平滑肌肌动蛋白免疫组化染色观察平滑肌细胞浸润积分,14 d时治疗组平滑肌细胞浸润1.5分,对照组2分;28 d时两组分别为1分和3分.结论 骨髓间充质干细胞可减轻新生内膜增生,加快损伤血管的内皮化进程,减少平滑肌细胞浸润,从而促进球囊损伤的大鼠颈总动脉内皮完整性修复.     

泛素及大鼠蛋白酶体第三亚基在大鼠颈总动脉球囊损伤后的表达

目的 研究泛素(ubiquitin)、大鼠蛋白酶体第三亚基(rat component 3 of proteasome,Re3)在大鼠颈总动脉球囊损伤后的动态表达及在内膜增生中的作用.方法 雄性SD大鼠56只,随机分为假手术组(8只)、单纯球囊损伤组(48只,包括1、4、7、14、21、28 d组),建立大鼠颈总动脉球囊损伤模型,苏木素-伊红(HE)染色光镜下观察血管内膜增生情况;应用逆转录聚合酶链反应(RTPCR)观察泛紊、RC3 mRNA表达情况,免疫组化方法 观察泛素蛋白表达情况.结果 球囊损伤后血管内膜增生明显,第28天内膜与中膜(Intima/Media,I/M)厚度比值最高[(2.31 ±0.43)比对照组(0.02±0.005),P＜0.01];泛素、RC3 mRNA表达升高,泛紊第7天达高峰[(1.33±0.26)比对照组(0.21±0.04),P＜0.01],RC3第14天达高峰[(1.35±0.26)比对照组0.31 ±0.06,P＜0.01];球囊损伤后泛素蛋白表达升高,第14天达高峰[(21.53±4.09)比对照组(4.21±0.78),P＜0.01].相关分析显示泛素蛋白表达与血管内膜增生呈正相关(r=0.827,P＜0.05).结论 大鼠颈总动脉球囊损伤后内膜增生明显,泛素、RC3 mRNA及泛素蛋白表达增高,球囊损伤后泛素蛋白表达与血管内膜增生呈正相关.     

罗格列酮减轻大鼠自体颈静脉移植后内膜增生

目的 观察过氧化体增殖物激活型受体γ激动剂对大鼠移植静脉内膜增生的影响.方法 建立大鼠颈静脉移植血管模型,16只大鼠被随机分为罗格列酮组和模型组,每组8只,饲养6周.罗格列酮组应用罗格列酮.6周后观察大鼠的体重变化、内膜增生程度,RT-PCR检测移植静脉过氧化体增殖物激活型受体γ mRNA表达.结果 术后饲养6周,模型组大鼠体重(521.6±22.3 g)较罗格列酮组(457.3±25.3 g)明显增加,差异有显著性 (P<0.05).与正常静脉相比,罗格列酮组(内膜厚度25.99±3.31 μm)和模型组(内膜厚度35.28±5.76 μm)的移植静脉出现了明显内膜增生,但罗格列酮组内膜增生比模型组明显减轻(P<0.05).RT-PCR检测发现罗格列酮组移植静脉过氧化体增殖物激活型受体γ mRNA表达显著高于模型组(1.12±0.28比0.68±0.20,P<0.05).结论 过氧化体增殖物激活型受体γ激动剂罗格列酮对大鼠移植静脉内膜增生有减轻作用.     

血管去内皮损伤后平滑肌细胞凋亡的实验观察

目的 了解血管去内皮损伤后新内膜形成及平滑肌细胞(SMCs)凋亡的时相变化。方法用氮气干燥剥脱大鼠颈动脉内皮复制血管损伤模型,HE染色光镜形态计量内膜/中膜比(I/M),末端脱氧核苷酸转移酶(TdT)介导的荧光素d-uTP缺口末端标记(TRNEL)方法观察不同时间新内膜形成(I/M)及VSMC凋亡。结果 血管去内皮后四天,在SMCs增生形成的新内膜中有TUNEL法证实的细胞凋亡,I/M加比,凋亡指数(TUNELI)分别为0.12±0.06,2.4±1.98。在七天,内膜明显增厚(I/M为0.6±0.15,与四天比,P<0.05),TUNELI达到最大值(为9.3±3.8,与四天比,P<0.05)。到第14天,内膜明显增厚约为中膜的1.25倍(I/M比1.25±0.14,与七天比,P<0.05),TUNELI逐渐减小(为8.75±4.01;与七天比,P>0.05)。损伤后21天,内膜开始变薄(I/M比为0.98±0.41,与14天比,P<0.05),凋亡水平进一步下降(TUNELI为6.58±3.97,但差异无显著性,P=NS)。结论 血管壁对损伤刺激诱发增生反应的同时激活凋亡机制。凋亡调节血管壁细胞数和内膜增厚演变。细胞凋亡的平衡失调可能是动脉粥样硬化(AS)、再狭窄(RS)等血管疾病发生的机制之一。     

瞬时受体电位香草酸亚型1在小鼠心肌梗死后炎症中的保护作用

目的 研究瞬时受体电位香草酸亚型1(TRPV1)在心肌梗死(MI)后炎症中的保护作用.方法 在TRPV1基因敲除(TRPV1-/-)小鼠和野生型(WT)小鼠建立MI模型,监测梗死后第3天的梗死面积、炎症细胞渗透、炎症因子和趋化因子的表达水平、心功能和第7天的生存率.结果 TRPV1-/-小鼠MI后7 d内的生存率低于野生型小鼠(62.5%比82.1%,P<0.05).MI后第3天:TRPV1-/-小鼠的梗死面积(INF)大于野生型小鼠[INF/危险区面积(AAR):69.5%±3.1%比40.1%±2.6%,P<0.05];TBPV1-/-小鼠的血浆心肌钙蛋白Ⅰ水平[(0.98±0.16)ng/ml比(0.58±0.15)ng/ml,P<0.001]、中性粒细胞[(1142±112)/mm2比(779±50)/mm2,P<0.05]和巨噬细胞渗透[(1098±58)/mm2比(664±49)/mm2,P<0.01]均高于野生型小鼠.TRPV1-/-小鼠的肿瘤坏死因子(TNF)-α、白细胞介素(IL)-1β、IL-6、巨噬细胞趋化蛋白(MCP)-1和巨噬细胞炎症蛋白(MIP)-2表达也明显高于野生型小鼠(均P<0.05).此外,与野生型小鼠比较,TRPV1-/-小鼠梗死后收缩末期和舒张末期内径进一步扩大,收缩功能恶化.结论 TRPV1基因缺失导致MI后生存率下降,炎症反应增强,心功能恶化,提示TRPV1可能通过抑制炎症和保存心功能而防止梗死扩散和心脏损伤.     

Double leptin and melanocortin-4 receptor gene mutations have an additive effect on fat mass and are associated with reduced effects of leptin on weight loss and food intake

Melanocortin-4 receptors (MC4Rs) are involved in the regulation of food intake, sympathetic nervous activity, and adrenal and thyroid function by leptin. The role of MC4Rs in regulating energy balance by leptin was investigated using double heterozygote or homozygous leptin (Lep(ob)) and Mc4r gene mutant mice. Double heterozygous or homozygous mutants were generated by crossing MC4R knockout (Mc4r-/-) mice, backcrossed onto C57BL/6J, with B6.V-Lep(ob) mice. Energy expenditure was measured using indirect calorimetry. The effect of leptin on food intake, weight loss, insulin, and corticosterone was compared for Lep(ob)/Lep(ob)Mc4r-/- mice and Lep(ob)/Lep(ob) mice. Double heterozygous and homozygous mutants exhibited an additive effect on fat mass. The 2-fold increase in body weight associated with severe obesity of Lep(ob)/Lep(ob) mice was associated with a significantly higher 24 h total and resting energy expenditure. The effect of obesity on energy expenditure was attenuated by 50% in Lep(ob)/Lep(ob) Mc4r+/- and Lep(ob)/Lep(ob) Mc4r-/- mice. Loss of MC4Rs did not affect basal food intake of Lep(ob)/Lep(ob) mice but was associated with partial leptin resistance in terms of food intake and weight loss. Leptin suppression of insulin and corticosterone in Lep(ob)/Lep(ob) mice were not significantly affected by Mc4r genotype. These results suggest a complex interaction between the Lep and Mc4r genes in energy homeostasis and suggest that MC4Rs retain significant anti-obesity function in the obese leptin-deficient state. Increased adiposity with double mutations may involve a reduction in energy expenditure. MC4Rs might have a modest role in the regulation of energy balance by exogenously administered leptin, primarily effecting food intake.     

Control of blood pressure, appetite, and glucose by leptin in mice lacking leptin receptors in proopiomelanocortin neurons

Although the central nervous system melanocortin system is an important regulator of energy balance, the role of proopiomelanocortin (POMC) neurons in mediating the chronic effects of leptin on appetite, blood pressure, and glucose regulation is unknown. Using Cre/loxP technology we tested whether leptin receptor deletion in POMC neurons (LepR(flox/flox)/POMC-Cre mice) attenuates the chronic effects of leptin to increase mean arterial pressure (MAP), enhance glucose use and oxygen consumption, and reduce appetite. LepR(flox/flox)/POMC-Cre, wild-type, LepR(flox/flox), and POMC-Cre mice were instrumented for MAP and heart rate measurement by telemetry and venous catheters for infusions. LepR(flox/flox)/POMC-Cre mice were heavier, hyperglycemic, hyperinsulinemic, and hyperleptinemic compared with wild-type, LepR(flox/flox), and POMC-Cre mice. Despite exhibiting features of metabolic syndrome, LepR(flox/flox)/POMC-Cre mice had normal MAP and heart rate compared with LepR(flox/flox) but lower MAP and heart rate compared with wild-type mice. After a 5-day control period, leptin was infused (2 μg/kg per minute, IV) for 7 days. In control mice, leptin increased MAP by ≈5 mm Hg despite decreasing food intake by ≈35%. In contrast, leptin infusion in LepR(flox/flox)/POMC-Cre mice reduced MAP by ≈3 mm Hg and food intake by ≈28%. Leptin significantly decreased insulin and glucose levels in control mice but not in LepR(flox/flox)/POMC-Cre mice. Leptin increased oxygen consumption in LepR(flox/flox)/POMC-Cre and wild-type mice. Activation of POMC neurons is necessary for the chronic effects of leptin to raise MAP and reduce insulin and glucose levels, whereas leptin receptors in other areas of the brain other than POMC neurons appear to play a key role in mediating the chronic effects of leptin on appetite and oxygen consumption.     

血管紧张素转化酶抑制剂对兔腹主动脉球囊损伤后的影响

目的:研究血管紧张素转化酶抑制剂(ACEI)对兔腹主动脉球囊损伤后的影响及作用机制。方法:雄性新西兰大白兔随机分为ACEI组和对照组,每组10只。球囊损伤腹主动脉后,ACEI组给予福辛普利5mg.kg-1.d-1,对照组不给予药物处理。实验4周后,取腹主动脉标本,使用计算机辅助形态分析系统比较2组新生内膜、中膜及管腔面积,测定血清、组织肝细胞生长因子(HGF)浓度以及与新生内膜面积的相关关系。结果:ACEI组新生内膜面积显著低于对照组[(0.048±0.011)mm2∶(0.124±0.021)mm2,P<0.001];管腔面积对照组显著低于ACEI组[(1.920±0.140)mm2∶(2.290±0.260)mm2,P=0.001];血管中膜面积2组差异无统计学意义[(0.890±0.130)mm2∶(0.990±0.120)mm2,P>0.05]。2组血浆HGF浓度差异无统计学意义[(485±84)ng/L∶(507±106)ng/L,P>0.05],组织HGF浓度ACEI组显著高于对照组[(49.9±5.5)ng/g∶(32.7±4.5)ng/g,P<0.001];单因素相关分析发现新生内膜面积与组织HGF浓度呈负相关(r=-0.943,P<0.001)。结论:ACEI可以减轻兔腹主动脉球囊损伤后新生内膜的形成,增加管腔面积,升高组织HGF浓度而对血浆HGF浓度无影响。ACEI减轻血管球囊损伤后的新生内膜形成部分通过升高组织HGF发挥作用。     

Restoration of fertility in young obese (Lep(ob) Lep(ob)) male mice with low dose recombinant mouse leptin treatment

OBJECTIVE: We investigated the effects of low-dose leptin treatment on restoration of fertility in young adult male leptin deficient obese mice. EXPERIMENTAL DESIGN AND RESULTS: MMTV-TGF-alpha Lep(ob) Lep(ob) mice (8--10 weeks old) were treated with recombinant mouse leptin. In experiment 1, four mice (5 microg/g body weight leptin followed by 2.5 microg/g) lost weight and impregnated females (number of pregnancies/number of females, 3/6, 5/6, 5/10, 4/10). In experiment 2, Leptin-Obese (2.5 microg/g) and Control-Lean mice weighed significantly less than Control-Obese mice. Epididymal pad weights of Control-Obese mice were the heaviest, followed by those of Leptin-Obese mice, and Control-Lean mice were the lightest. Testes weight was greater in Control-Lean vs Control-Obese mice. Leptin-Obese mice had testes weight not significantly different from either control group. Four of five Leptin-Obese mice impregnated females (4/10, 5/10, 2/10, 5/12, 0/10). CONCLUSIONS: These results indicate that low-dosage mouse recombinant leptin treatment restored fertility to young Lep(ob) Lep(ob) male mice. Although body weights of Leptin-Obese mice were similar to those of lean age-matched mice, epididymal fat pad weights were heavier. International Journal of Obesity (2001) 25, 95-97     

Counterintuitive effects of double-heterozygous null melanocortin-4 receptor and leptin genes on diet-induced obesity and insulin resistance in C57BL/6J mice

Circulating levels of leptin correlate with food intake and adiposity. A decline in serum leptin associated with calorie restriction instigates behavioral and metabolic adaptation, increasing appetite and conserving energy. Brain melanocortin-4 receptors (Mc4rs) are important mediators of leptin's effects on appetite and energy expenditure. Because subtle changes in function associated with heterozygous null mutations for either the Leptin (Lep-HET) or Mc4r genes (Mc4r-HET) increase adiposity, we tested the hypothesis that combined heterozygous mutations (Dbl-HET) would severely exacerbate diet-induced obesity (DIO) and insulin resistance in C57BL/6J mice. Serum leptin levels were lower as a function of adiposity in heterozygous Leptin mutants (Lep-HET, Dbl-HET) matched with mice homozygous for the wild-type (WT) Lep gene (Mc4r-HET). Evidence for an additive interaction on adiposity in Dbl-HET mice maintained on a low-fat diet was observed at 10 wk of age. Male but not female mice developed DIO and insulin resistance on a high-fat diet. Compared with WT mice, DIO was more severe in Mc4r-HET but not Lep-HET mice, regardless of sex. However, the response of male and female Dbl-HET mice was different, with males being less and females being more responsive relative to Mc4r-HET. Glucose tolerance of Dbl-HET mice was not significantly different from WT mice in either sex. These results show a complex interaction between the Leptin and Mc4r genes that is influenced by age, gender, and diet. Remarkably, while heterozygous Lep mutations initially exacerbate obesity, in situations of severe obesity, reduced leptin levels may act oppositely and have beneficial effects on energy homeostasis.     

Minor gene effect of leptin receptor variant on the body weight in KK/Ta mice

OBJECTIVE: Leptin is an adipocyte-derived hormone involved in body weight regulation that acts through the leptin receptor. Previous studies exploring potential association between the leptin receptor (Lepr) variant and obesity have reported conflicting results. The objectives of the present study are to evaluate (1) whether the Lepr variant contributes to type 2 diabetes and its related disorders such as obesity and (2) whether the gene interaction between Lepr and Zn-alpha(2) glycoprotein1 (Azgp1) genes is recognized using genetically homogeneous type 2 diabetic KK/Ta mice. METHODS: The levels of leptin (Lep) and Lepr mRNA in adipose tissues and brain were measured by relative quantitative RT-PCR. The levels of leptin protein in sera were measured by enzyme-linked immunosorbent assay. Genotyping of backcross mice was performed using a mismatch primer. RESULTS: Leptin protein and its mRNA levels were increased in KK/Ta mice. Lepr mRNA levels of KK/Ta mice did not differ from those of BALB/c mice. Sequence analysis revealed that the coding region of Lep in KK/Ta mice was identical to that in BALB/c mice. Six nucleotide polymorphisms were observed in the coding region of Lepr. In KK/Ta x (BALB/c x KK/Ta) F1 backcross mice, the Lepr variant of KK/Ta mice failed to alter any of the variables of obesity except for body weight at 20 weeks of age. However, it enhanced the effect of Azgp1 on body weight. CONCLUSION: It is concluded that the Lepr variant contributes to obesity to some degree in KK/Ta mice.     

Effects of leptin receptor mutation on Agrp gene expression in fed and fasted lean and obese (LA/N-faf) rats

Agouti-related protein provides an orexigenic signal, probably through interaction with central melanocortin receptors. Expression of Agrp is markedly increased in the hypothalamus of mice deficient in leptin (Lep(ob)/Lep(ob)) or its receptor (Lepr(db)/Lepr(db)), suggesting that leptin mediates signals suppressing Agouti-related protein production. The regulation of Agrp expression in the rat hypothalamus has not been reported. We, therefore, analyzed the expression of Agrp in the medial basal hypothalamus of lean (+/+, +/fa(f)) and obese leptin receptor-deficient (fa(f)/fa(f)) LA/N rats. Using a sensitive solution hybridization/S1 nuclease protection assay, we found no significant difference in Agrp messenger RNA (mRNA) levels (pg/microg total RNA +/- SEM) in obese rats (n = 5), compared with lean controls (n = 5): 0.46 +/- 0.06 vs. 0.47 +/- 0.06 (P = 0.9). Similarly, no difference in Agrp expression was found using in situ hybridization or semiquantitative RT-PCR. In contrast to Agrp, Pomc mRNA levels were significantly suppressed in the obese, compared with the lean, rats (P = 0.001). Thus, the ratio of Pomc to Agrp mRNA is decreased in the obese rats and may be an important modulator of food intake. To assess the physiological regulation of Agrp in rats, we examined the effect of food deprivation in lean Sprague Dawley (SD) rats. There was a 273% increase in medial basal hypothalamus Agrp mRNA in SD rats fasted for 48 h (n = 8), compared with rats fed ad libitum (n = 8): 0.82 +/- 0.23 vs. 0.30 +/- 0.08 (P = 0.0001). Lean LA/N rats (n = 7) fasted for 48 h also showed a 231% increase in Agrp expression, compared with fed lean controls (n = 8): 0.74 +/- 0.11 vs. 0.32 +/- 0.03 (P = 0.002), whereas Pomc expression was decreased by 32% in fasted animals from the same experiment (0.34 +/- 0.05 vs. 0.50 +/- 0.07; P = 0.03). There were no significant differences in Agrp or Pomc mRNA levels between fasted and fed obese LA/N-fa(f) rats. These results suggest that, in the rat, the Agrp response to fasting may involve leptin-mediated phenomena, but factors in addition to leptin must also be involved in the regulation of Agrp gene expression.     

Leptin is an endothelial-independent vasodilator in humans with coronary artery disease: Evidence for tissue specificity of leptin resistance.

AIMS: We sought to define the mechanisms and correlates of leptin's vascular actions in humans with coronary artery disease. METHODS AND RESULTS: In 131 patients (age 65.7+/-0.7 years mean+/-SEM), ex vivo vascular reactivity to leptin (10(-13)-10(-7) M) was assessed in saphenous vein (SV) rings. Leptin led to SV relaxation (maximal relaxation 24.5+/-1.6%). In separate experiments, relaxation to leptin was unaffected by L-NMMA (17.4+/-3.4 vs.17.8+/-3.3%, P = 0.9) or endothelial denudation (17.4+/-4.4 vs. 22.5+/-3.0%, P = 0.4). We explored the possibility that leptin's vascular effects are mediated via smooth muscle hyperpolarization. In the presence of KCl (30 mmol/L) to inhibit hyperpolarization, the vasodilator effect of leptin was completely blocked (0.08+/-4.1%, P < 0.001 vs. control). Similar results were demonstrated in internal mammary artery rings. The only independent correlate of leptin-mediated vasodilatation was plasma TNF-alpha (r = 0.25, P < 0.05). Neither body mass index nor waist circumference correlated with leptin-mediated vasorelaxation. This lack of a correlation with markers of total body fat/fat distribution suggests that leptin resistance may not extend to the vasculature. CONCLUSION: Leptin is a vasoactive peptide in human SV and internal mammary artery. Its action is not nitric oxide or endothelial-dependent. Markers of body fat did not correlate with leptin-mediated vasodilatation, raising the intriguing possibility of selective resistance to leptin's actions.     

Hypothalamic sites of leptin action linking metabolism and reproduction

A critical amount of energy reserve is necessary for puberty initiation, for normal sexual maturation and maintenance of cyclicity and fertility in females of most species. Therefore, the existence of circulating metabolic cues which directly modulate the hypothalamus-pituitary-gonad axis is predictable. The adipocyte-derived hormone leptin is one of these cues having been studied extensively in the context of regulating the reproductive physiology. Humans and mice lacking leptin (ob/ob) or leptin receptor (LepR, db/db) are infertile. Leptin administration to leptin-deficient subjects and ob/ob mice induces puberty and restores fertility. LepR is expressed in brain, pituitary gland and gonads, but studies using genetically engineered mouse models determined that the brain plays a major role. Recently, it has been made clear that leptin acts indirectly on gonadotropin-releasing hormone (GnRH)-secreting cells via actions on interneurons. However, the exact site(s) of leptin action has been difficult to determine. In this review, we discuss the recent advances in the field focused on the identification of potential site(s) or specific neuronal populations involved in leptin's effects in the neuroendocrine reproductive axis.