Diurnal rhythms of leptin and ghrelin in the systemic circulation and in the gastric mucosa are related to food intake in rats

We investigated diurnal changes in leptin and ghrelin levels in the stomach and in the systemic circulation and their relation to food intake rhythms in Wistar rats housed at 22 °C with a 12-h light/dark cycle and free access to food and water. Animals were sacrificed every 3 h over a 24-h period. Leptin and ghrelin levels in serum and in the gastric mucosa were analysed by immunoassay. Leptin mRNA levels were determined in the gastric mucosa by RT-PCR and in different adipose tissue depots (epididymal, retroperitoneal and mesenteric) by Northern blot. Ghrelin mRNA levels were determined by Northern blot. Gastric and serum leptin levels displayed similar diurnal rhythms, rising during the dark phase and decreasing gradually during the light phase. Leptin expression in the different adipose tissue depots correlated positively with circulating leptin levels (P<0.05), although there were some depot-associated differences. Leptin mRNA levels in the mesenteric depot correlated positively with food intake (P<0.05). In blood, ghrelin levels rose sharply just before the onset of the dark phase and dropped suddenly just after. In the stomach, ghrelin levels were high during the fasting period of light and low during the night, and correlated inversely with food intake, gastric contents and serum leptin levels (P<0.05). Leptin and ghrelin in the stomach and in the systemic circulation thus show diurnal variations that are influenced by food intake rhythms. The results agree with a role for ghrelin as a stimulant of meal initiation.     

Gastric capacity, test meal intake, and appetitive hormones in binge eating disorder

Binge eating disorder (BED), characterized by ingestion of very large meals without purging afterwards, is found in a subset of obese individuals. We showed previously that stomach capacity is greater in obese than in lean subjects, and in this study, we investigated capacity in obese individuals with BED. We also determined ad-libitum intake of a test meal until extremely full. Furthermore, we measured various appetitive hormones (insulin, leptin, glucagon, CCK, ghrelin) and glucose before a fixed meal and for 120 min afterwards. An acetaminophen tracer was used to assess gastric emptying rate. We compared three groups of overweight women: 11 BED, 13 BE (subthreshold BED), and 13 non-binge-eating normals. The BED individuals had the largest stomach capacity as assessed by either maximum volume tolerated (P=.05) or by gastric compliance to pressure (P=.02) using an intragastric balloon. Although test meal intake did not differ between groups, it correlated (P=.03) with gastric capacity. The BED group showed a tendency (P=.06) to have greater area under the curve (AUC) and had higher values at 5 and 60 min (P<.05) for insulin compared to normals. Moreover, the BED subjects had lower ghrelin baselines premeal, and lower AUC for ghrelin, which then declined less postmeal than for the normals (P<.05). None of the other blood values differed, including glucose, leptin glucagon, and CCK, as well as acetaminophen, reflecting gastric emptying. The lower ghrelin in BED, although contrary to what was expected, is consistent with lower ghrelin in obesity, and suggests down-regulation of ghrelin by overeating. The lack of differences in CCK is consistent with the lack of differences in gastric emptying rate, given that CCK is released when nutrients reach the intestine. The results show that BED subjects have a large gastric capacity as well as abnormalities in meal-related ghrelin and insulin patterns that may be factors in binge eating.     

脑肠肽Ghrelin对血管紧张素Ⅱ诱导的大鼠脑主动脉血管平滑肌细胞胞内钙浓度上升的影响

目的研究脑肠肽Ghrelin对血管紧张素Ⅱ（AngⅡ）诱导的大鼠胸主动脉血管平滑肌细胞（VSMCs）胞内钙离子浓度上升的作用,并初步探讨其机制。方法采用细胞培养的方法获得大鼠胸主动脉VSMCs,经Fluo-4-AM染色后,采用激光共聚焦显微镜技术分别检测加入AngⅡ后,1×10^-7mol·L^-1和1×10^-5mol·L^-1的Ghrelin对胞内钙荧光强度（FI）的影响,以及腺苷酸环化酶抑制剂Sq22536对Ghrelin作用的影响。结果①2×10^-8mol·L^-1的AngⅡ可以使得VSMCs胞内钙FI上升到静息状态的（165±76）％;②随后加入1×10^-7mol·L^-1的Ghrelin可以使FI下降到（117±34）％（P〈0．01vs①）;③加入1×10^-5mol·L^-1的Ghrelin可以使FI下降到（87±22）％（P〈0．01vs①,P〈0．05vs②）;④预先以1×10^-5mol·L^-1的Sq22536孵育,再加入2×10^-8mol·L^-1AngⅡ和1×10^-7mol·L^-1的Ghrelin,胞内FI为原来的（143±24）％（P〈0．01vs②）。结论Ghrelin能够降低AngⅡ引起的大鼠胸主动脉VSMCs胞内钙离子升高作用,其机制可能与激活胞内cAMP／PKA信号通路有关。     

Ghrelin基因Arg51Gln、Leu72Met多态性与甘肃回族2型糖尿病及血脂的关系

目的 探讨Ghrelin基因Arg51Gl(G-A)和Leu72Met(C-A)多态性与甘肃回族2型糖尿病及血脂的关系.方法 采用聚合酶链反应-限制性片段长度多态性方法检测甘肃回族人251例(2型糖尿病138例,对照组113例),Ghrelin基因Arg51Gln和Leu72Met各基因型,并测定其相关临床、生化指标....     

大鼠脑干DVC区注射ghrelin对弓状核NPY mRNA及AgRP mRNA表达的影响

目的 探讨脑干迷走神经复合体(DVC)区微量注射ghrelin对摄食的影响及其可能机制.方法 72只雄性SD大鼠随机分成给药组和正常对照组,每组36只大鼠,行DVC区埋管手术,术后恢复7 d.7 d后给药组大鼠DVC区微量注射20 pmol的ghrelin,正常对照组大鼠DVC区微量注射等体积生理盐水.两组分别于给药后1、2、3 h取大鼠下丘脑提取RNA,应用荧光定量PCR方法检测大鼠下丘脑弓状核神经肽Y(NPY)及刺鼠色蛋白相关蛋白(AgRP)mRNA的表达情况.结果 给药组大鼠给药后1、2、3 h下丘脑NPY mRNA和AgRP mRNA的表达水平均明显高于正常对照组,差异有显著性(t=2.79～9.12,P<0.05).给药组大鼠给药后2 h下丘脑NPY mRNA和AgRP mRNA的表达水平明显高于给药后1 h及3 h组(F=16.55、10.45,q=3.89～4.45,P<0.05),但给药后1 h与3 h下丘脑NPY mRNA和AgRP mRNA的表达水平比较差异无显著性(P>0.05).结论 作用于大鼠DVC区的ghrelin可能通过下丘脑弓状核NPY、AgRP神经通路促进摄食活动.     

糖尿病大鼠不同阶段Ghrelin变化与胃排空关系的研究

目的：观察不同阶段糖尿病大鼠Ghrelin的变化情况与胃运动异常之间的联系,了解在糖尿病的不同阶段Ghrelin对胃排空的影响。方法66只Wistar大鼠随机分为2周糖尿病组(DM-2w)及对照组（NC-2w）、8周糖尿病组(DM-8w)及对照组(NC-8w)、20周糖尿病组(DM-20w)和对照病组(NC-20w)。高脂料喂养诱导胰岛素抵抗后以小剂量链脲佐菌素(STZ,30 mg/kg)腹腔注射,制作2型糖尿病大鼠模型。造模成功后第2周、第8周、第20周进行核素法胃排空测定胃半排时间、50 min胃内核素残留率;酶联免疫法测定血浆Ghrelin水平,免疫组化方法观察胃组织Ghrelin免疫阳性细胞密度。结果(1) DM-2w组半排时间为(22.99±2.53) min,与NC-2w组(48.76±22.06) min比较胃排空明显加快,差异有统计学意义(P<0.01)。DM-8w组半排时间为(35.24±11.00) min,与NC-8w组(43.59±13.79) min比较差异无统计学意义(P>0.05)。DM-20w组半排空时间为(84.02±27.54) min,与NC-20w组(47.79±13.22) min比较胃排空时间延长,差异有统计学意义(P<0.01)。各对照组之间比较差异无统计学意义(P>0.05)。(2) DM-2w组大鼠血浆Ghrelin水平显著升高,与NC-2w组比较差异有统计学意义(P<0.05)。DM-8w组大鼠血浆Ghrelin水平与NC-8W组比较差异无统计学意义(P>0.05)。DM-20w组大鼠血浆Ghrelin水平与NC-20w组及DM-2w组比较差异有统计学意义(P<0.05)。各对照组之间差异无统计学意义(P>0.05)。(3)血浆Ghrelin水平与胃半排空时间呈负的直线相关。结论(1)糖尿病的不同阶段胃动力的变化有着不同的形式,在早期以胃动力加速为主;随着糖尿病病程的进展,胃排空逐渐减慢延迟。(2)在胃动力变化的过程中,血浆Ghrelin也呈现出与胃动力变化类似的变化趋势。(3)血浆Ghrelin水平与胃半排空时间呈负相关。     

血清Ghrelin和瘦素水平与幽门螺杆菌感染的关系研究

目的 探讨血清Ghrelin和瘦素水平与幽门螺杆菌(Hp)感染的关系,进一步明确其临床意义.方法 选取2009年4-7月于北京大学第三医院进行胃镜检查的患者116例,于胃镜检查前抽血检测血清Ghrelin和瘦素水平,同时检测血清Hp抗体.所有患者进行胃镜检查时于胃窦和胃体至少分别钳取一块组织进行Warthin-Starry染色,判定Hp感染情况.血清Ghrelin、瘦素和Hp抗体检测采用ELISA法.结果 Hp阳性患者血清Ghrelin水平低于Hp阴性患者(291.03 pg/ml vs.374.77 pg/ml),Hp阳性患者血清瘦素水平亦低于Hp阴性患者(4.34 ng/ml vs.4.37 ng/ml),但差异均无统计学意义(P值分别为0.288、0.550).男性患者血清Ghrelin水平低于女性患者(232.28 pg/ml vs.403.09 pg/ml),差异有统计学意义(P=0.000);男性患者血清瘦素水平亦低于女性患者(4.24 ng/ml vs.4.46 ng/ml),但差异无统计学意义(P=0.671).男性患者Hp阳性组与Hp阴性组血清Ghrelin水平间差异无统计学意义(243.87 pg/ml vs.205.67 pg/ml,P=0.950),血清瘦素水平间差异亦无统计学意义(4.16 ng/ml vs.4.42 ng/ml,P=0.297).女性患者Hp阳性组与Hp阴性组血清Ghrelin水平间差异无统计学意义(342.12 pg/ml vs.494.54 pg/ml,P=0.330),血清瘦素水平间差异亦无统计学意义(4.54 ng/ml vs.4.34 ng/ml,P=0.856).体质指数(BMI)＜24.0 kg/m2组与BMI≥24.0 kg/m2组血清Ghrelin水平间差异有统计学意义(362.28 pg/ml vs.238.40 pg/ml,P=0.003),血清瘦素水平间差异亦有统计学意义(3.83 ng/ml vs.5.39 ng/ml,P=0.000).BMI＜24.0 kg/m2时,Hp阳性组与Hp阴性组血清Ghrelin水平间差异无统计学意义(303.85 pg/ml vs.483.81 pg/ml,P=0.107),血清瘦素水平间差异亦无统计学意义(3.79 ng/ml vs.3.91 ng/ml,P=0.387).BMI≥24.0 kg/m2时,Hp阳性组与Hp阴性组血清Ghrelin水平间差异无统计学意义(262.06 pg/ml vs.204.39 pg/ml,P=0.621),血清瘦素水平间差异亦无统计学意义(5.59 ng/ml vs.5.10 ng/ml,P=0.388).结论 Hp感染与否对血清Ghrelin及瘦素水平没有影响,性别对血清Ghrelin水平可能有影响,BMI对血清Ghrelin及瘦素水平可能有影响.     

Total and active ghrelin in developing rats during hypoxia

Hypoxia is well known to decrease appetite and weight gain in growing rats, and to induce weight loss in humans. It has been hypothesized that this is mediated by a change in ghrelin, an orexigenic peptide synthesized and released primarily from the stomach. Rats were exposed to hypoxia for 7 d as neonates (birth-7 d of age), weanlings (28–35 d of age), and juveniles (49–56 d of age). Hypoxia had no effect on total or active plasma ghrelin. There was a significant decrease in active ghrelin in weaned rats (0.8±0.1 ng/mL) compared to nursing pups at 7 d of age (2.3±0.2 ng/mL). The proportion of total ghrelin that was active decreased significantly between 7 and 35 d of age. We conclude that the anorexia and weight loss associated with hypoxia is probably not mediated by ghrelin. There appear to be changes in active ghrelin levels in plasma during early development in the rat.     

The negative association between plasma ghrelin and IGF-I is modified by obesity, insulin resistance and type 2 diabetes

Aims/hypothesis Ghrelin is a natural growth hormone-releasing peptide thought to be involved in the regulation of energy metabolism. The recent studies concerning the association between ghrelin and insulin-like growth factor-I (IGF-I) concentrations have shown either negative correlation or no correlation at all. The aims of this study were to clarify the association between ghrelin and IGF-I concentrations in a large cohort and to characterize whether obesity, insulin resistance and type 2 diabetes affect this association.Methods We analysed fasting plasma ghrelin and IGF-I concentrations of 1,004 middle-aged subjects of the population-based OPERA study. Insulin resistance was estimated using QUICKI.Results IGF-I concentrations were negatively associated with ghrelin concentrations in the analysis of all subjects before (=–0.32, p<0.001) and after adjustments for BMI, insulin levels, sex and age (=–0.40, p<0.001). The association was particularly strong in males and in the higher BMI tertiles. The degree of association varied in relation to the glycaemic status: no insulin resistance: r²=6.5% (p<0.001), insulin resistance without type 2 diabetes: r²=21.0% (p<0.001), type 2 diabetes: r²=25.4 (p<0.001). IGF-I levels explained larger proportion (r²=9.8%) of the variation in ghrelin concentrations compared to fasting insulin concentration (r²=3.0%) and BMI (r²=1.5%).Conclusions/interpretation There is a negative and independent association between ghrelin and IGF-I concentrations in middle-aged subjects. The interaction between IGF-I and ghrelin is modified by obesity, IR and type 2 diabetes. Further studies are warranted to elucidate the role of ghrelin in the development of these states.