Central ghrelin acts as an anti-dipsogenic peptide in chicks

The aim of this study was to look at whether ghrelin has an anti-dipsogenic effect, as seen in the eel, when administered centrally in neonatal chicks. Intracerebroventricular (ICV) injection of chicken ghrelin inhibited water intake (WI) in chicks under both ad libitum and 17-h water-deprived drinking conditions at doses ranging from 0.01 to 0.1 nmol/chick. This inhibitory effect was observed when 0.1 nmol of rat ghrelin was injected. On the other hand, 0.1 nmol des-acyl rat ghrelin did not reduce WI. To examine the mechanism underlying the effect of ghrelin on WI, chicken B-type (or brain) natriuretic peptide (BNP), an anti-dipsogenic peptide in mammals, was injected at doses ranging from 0.1 to 1 nmol/chick. BNP did not affect WI in chicks under both normal and water-deprived drinking conditions. These findings indicate that ghrelin acts as an anti-dipsogenic peptide through the GHS receptor in the chicken.     

The role of GABAergic system on the inhibitory effect of ghrelin on food intake in neonatal chicks

Ghrelin is a gut-brain peptide that has a stimulatory effect on food intake in mammals. In contrast, this peptide decreases food intake in neonatal chicks when injected intracerebroventricularly (ICV). In mammals, neuropeptide Y (NPY) mediates the orexigenic effect of ghrelin whereas in chicks it appears that corticotrophin releasing factor (CRF) is partially involved in the inhibitory effect of ghrelin on food intake. Gamma aminobutyric acid (GABA) has a stimulatory effect on food intake in mammals and birds. In this study we investigated whether the anorectic effect of ghrelin is mediated by the GABAergic system. In Experiment 1, 3 h-fasted chicks were given an ICV injection of chicken ghrelin and picrotoxin, a GABA_A receptors antagonist. Picrotoxin decreased food intake compared to the control chicks indicating a stimulatory effect of GABA_A receptors on food intake. However, picrotoxin did not alter the inhibitory effect of ghrelin on food intake. In Experiment 2, THIP hydrochloride, a GABA_A receptor agonist, was used in place of picrotoxin. THIP hydrochloride appeared to partially attenuate the decrease in food intake induced by ghrelin at 30 min postinjection. In Experiment 3, the effect of ICV injection of chicken ghrelin on gene expression of glutamate decarboxylase (GAD)₁ and GAD₂, GABA synthesis enzymes in the brain stem including hypothalamus, was investigated. The ICV injection of chicken ghrelin significantly reduced GAD₂ gene expression. These findings suggest that ghrelin may decrease food intake in neonatal chicks by reducing GABA synthesis and thereby GABA release within brain feeding centers.     

Gamma(2)-melanocyte stimulating hormone decreases food intake in chicks

The role of gamma melanocyte stimulating hormone (γ-MSH) in appetite regulation is controversial in mammals and to our knowledge unreported within the avian class. Thus, the present study was designed to determine the effects of intracerebroventricularly (ICV) administered γ2-MSH on food intake using Cobb-500 chicks as models. In Experiment 1, chicks that received ICV γ2-MSH decreased their food intake throughout the 180 min observation period and plasma glucose concentration was not affected. Water intake was also decreased in ICV γ2-MSH-treated chicks, but only from 30 to 90 min post-injection. In Experiment 2, food pecking efficiency was decreased in ICV γ2-MSH-treated chicks and the amount of time spent sitting was increased. Other behaviors were not significantly affected by ICV γ2-MSH including distance traveled, the number of jumps, escape attempts, defecations, food pecks, exploratory pecks, and the amount of time spent standing, preening, perching, or in deep rest. These data suggest that γ2-MSH is associated with anorexigenic effects and because of γ-MSH's selectivity, implicates the melanocortin 3 receptor in appetite regulation.     

Micro-opioid receptor agonist diminishes POMC gene expression and anorexia by central insulin in neonatal chicks

Pro-opiomelanocortin (POMC) neurons in the hypothalamus are direct targets of peripheral satiety signals, such as leptin and insulin in mammals. The stimulation of these signals activates hypothalamic POMC neurons and elevates POMC-derived melanocortin peptides that inhibit food intake in mammals. On the other hand, it has been recognized that beta-endorphin, a post-translational processing of POMC, acts in an autoreceptor manner to the micro-opioid receptor (MOR) on POMC neurons, diminishing POMC neuronal activity in mammals. Recently, we found that central insulin functions as an anorexic peptide in chicks. Thus, the present study was done to elucidate whether beta-endorphin affects the activation of POMC neurons by insulin in neonatal chicks. Consequently, quantitative real-time PCR analysis shows that intracerebroventricular (ICV) injection of insulin with beta-endorphin significantly decreases brain POMC mRNA expression when compared with insulin alone. In addition, co-injection of MOR agonist (beta-endorphin or [d-Ala2, N-MePhe4, Gly5-ol]-enkephalin (DAMGO)) significantly attenuates insulin-induced hypophagia in chicks. These data suggest that beta-endorphin regulates the activity of the central melanocortin system, and its activation may provide an inhibitory feedback mechanism in the brain of neonatal chicks.     

Effects of prenatal exposure to antithyroid drugs on imprinting behavior in chicks

Thyroid hormones play important roles in vertebrate brain development. However, there is little understanding of the direct effects of fetal thyroid dysfunction, i.e., not acquired through the mother, on learning ability. In the present study, we use a chick embryo as a fetal model to investigate the effects of prenatal exposure to antithyroid drugs on imprinting behavior in hatched chicks. Methimazole (MMI) at 20 µmol/egg or 5 µmol/egg of propylthiouracil (PTU) was administered to eggs on day 14 while the control was given only a vehicle. An imprinting test was conducted after the chicks hatched. Day-old chicks were exposed to a rotating training object for 150 min. The next day, the trained chicks were exposed to the training object and a novel object. The imprinting preference was represented as a preference score (PS) calculated as the rate of following the training object to following the training and novel objects. In the MMI-treated chicks, the PS was 0.68 ± 0.06 (range, 0.38-0.88), which was significantly lower than that in the control chicks (0.86 ± 0.04, p < 0.01). In the PTU-treated chicks, the PS was 0.69 ± 0.04 (range, 0.52-0.89), which was also significantly lower than that in the control (0.88 ± 0.02, p < 0.001). The present findings suggested that fetal thyroid dysfunction inhibited brain development, leading to impaired learning and memory. Our chick model can be considered useful for investigating the direct effects of prenatal exposure to antithyroid drugs or substances in the environment on learning ability after birth.     

Consumption of a high-fat diet induces central insulin resistance independent of adiposity

Plasma insulin enters the CNS where it interacts with insulin receptors in areas that are related to energy homeostasis and elicits a decrease of food intake and body weight. Here, we demonstrate that consumption of a high-fat (HF) diet impairs the central actions of insulin. Male Long-Evans rats were given chronic (70-day) or acute (3-day) ad libitum access to HF, low-fat (LF), or chow diets. Insulin administered into the 3rd-cerebral ventricle (i3vt) decreased food intake and body weight of LF and chow rats but had no effect on HF rats in either the chronic or the acute experiment. Rats chronically pair-fed the HF diet to match the caloric intake of LF rats, and with body weights and adiposity levels comparable to those of LF rats, were also unresponsive to i3vt insulin when returned to ad libitum food whereas rats pair-fed the LF diet had reduced food intake and body weight when administered i3vt insulin. Insulin's inability to reduce food intake in the presence of the high-fat diet was associated with a reduced ability of insulin to activate its signaling cascade, as measured by pAKT. Finally, i3vt administration of insulin increased hypothalamic expression of POMC mRNA in the LF- but not the HF-fed rats. We conclude that consumption of a HF diet leads to central insulin resistance following short exposure to the diet, and as demonstrated by reductions in insulin signaling and insulin-induced hypothalamic expression of POMC mRNA.     

Serotonergic receptor upregulation in cerebral cortex and down regulation in brainstem of streptozotocin induced diabetic rats: Antagonism by pyridoxine and insulin

Insulin secretion and glucose homeostasis is implicated through serotonergic function. Pyridoxine is involved in decarboxylation step in synthesis of serotonin. The present study was carried out to find the role of insulin in combination with pyridoxine on the concentrations of 5-HT and 5-HIAA, 5-HT receptor binding, 5-HTT gene expression and immunohistochemistry studies in the cerebral cortex and brainstem of streptozotocin induced diabetic rats. 5-HT content showed a significant decrease with a significant increase in 5-HIAA in cerebral cortex (p < 0.01) and brain stem (p < 0.001) in diabetic rats. 5-HT receptor binding parameters, B_max and K_d, showed a significant decrease (p < 0.001) in diabetic rats in cerebral cortex whereas in brainstem it showed a significant increase (p < 0.001) compared to control. Gene expression studies of 5-HTT in cerebral cortex showed a significant down regulation (p < 0.001) and in brainstem an upregulation (p < 0.001) in diabetic rats compared to control. Insulin and pyridoxine treatment to diabetic rats reversed the 5-HT content, B_max, K_d and gene expression of 5-HTT confirmed by immunohistochemistry studies in cerebral cortex and brainstem to near control. Thus our results suggest that pyridoxine along with insulin has a role in the regulation of insulin synthesis and release through serotonergic function which has clinical significance in the management of diabetes.     

Chronic prenatal lead exposure impairs long-term memory in day old chicks

Environmental exposure to lead during developmental stages has been established as a potential cause of intellectual deficits. The high susceptibility of rapidly developing fetal and infant brains to external factors suggests that impairment of later cognitive functions may arise from relatively minor prenatal exposure to environmental lead levels. In this study, we used the one-trial passive avoidance learning paradigm with day old chicks to evaluate memory function and memory consolidation in response to prenatal lead exposure. Lead acetate (5.5 mg/kg, 11 mg/kg, 16.5 mg/kg) was administered daily from E9 to E16 via direct injection into the airspace in chick eggs. Higher doses of lead acetate (11 mg/kg, 16.5 mg/kg) administration had significant effects on the hatching success (23.4 and 17, respectively) and hatch weight (∼10% decrease) of chicks when compared to equivalent treatments of sodium acetate (11 mg/kg, 16.5 mg/kg) (p < 0.001). Low doses of lead acetate (5.5 mg/kg) did not significantly affect chick hatching, weight or morphology compared to equivalent sodium acetate treatments (5.5 mg/kg) and controls. However, lead acetate (5.5 mg/kg) was found to significantly impair long-term memory after 120 min following training in the one-trial passive avoidance learning task (p < 0.05). These findings add to a growing body of evidence that suggests lead toxicity during fetal development leads to impairment in cognitive and memory processes.     

罗格列酮对多囊卵巢综合征患者卵巢黄素化颗粒细胞胰岛素受体底物1和2蛋白表达及酪氨酸磷酸化的影响

目的： 研究罗格列酮对多囊卵巢综合征(PCOS)患者卵巢黄素化颗粒细胞胰岛素受体底物-1(IRS-1)和IRS-2蛋白表达及酪氨酸磷酸化的影响。探讨罗格列酮改善PCOS卵巢局部胰岛素抵抗的作用。方法: 收集行IVF-ET治疗的11例PCOS患者（PCOS组）和15例排卵正常患输卵管性不孕患者（对照组）促排卵后黄素化颗粒细胞行体外培养，分别用不同浓度罗格列酮（0、1、10、100、1 000、10 000 nmol/L）处理细胞48 h，采用RT-PCR、免疫印迹（Western blotting）及免疫沉淀法分别检测卵巢黄素化颗粒细胞IRS-1和IRS-2mRNA的表达、蛋白含量及酪氨酸磷酸化水平。结果: （1）与对照比较，PCOS组黄素化颗粒细胞IRS-1mRNA表达及蛋白含量显著增加（P<0.05），IRS-2mRNA表达及蛋白含量显著降低（P<0.05），IRS-1和IRS-2酪氨酸磷酸化水平均显著降低（P<0.05，P<0.05）；（2）不同浓度罗格列酮作用后，PCOS组黄素化颗粒细胞IRS-1mRNA及蛋白表达显著降低，IRS-2mRNA及蛋白表达显著增加，同时IRS-1和IRS-2酪氨酸磷酸化水平也显著增加，而正常对照组黄素化颗粒细胞IRS表达及酪氨酸磷酸化水平无显著变化。结论: PCOS患者卵巢局部存在胰岛素抵抗，其原因可能与IRS-1和IRS-2蛋白表达及酪氨酸磷酸化异常有关；罗格列酮可以通过调整IRS-1和IRS-2表达失衡，提高IRS-1和IRS-2酪氨酸磷酸化水平，改善PCOS患者卵巢局部胰岛素抵抗。     

Daytime modulation of cortical spreading depression according to blood glucose levels

The aim of this study was to investigate the effects of daytime and blood glucose levels on the propagation of cortical spreading depression (SD). Thirty-nine male Wistar rats were used. Animals were housed 5 per cage with a 12-h, light–dark cycle (lights on at 0600 h). Food and water were available ad libitum, and animals were fasted the night before the experiments. Cortical SD was recorded continuously for 3 h using Ag–AgCl agar-Ringer electrodes placed on the parietal cortex. Every 20 min, SD was elicited by 2% KCl stimulation of the frontal cortex for 1 min. After 1 h of SD-recording, blood glucose levels were measured, and animals were injected intravenously either with glucose (40% solution, 1 mL), insulin (0.3 U/100 g of body weight), or mannitol (20% solution, 1 mL). In the middle of the light period, which corresponds to zeitgeber time (ZT)5, 8 animals received glucose, 7 received insulin, and 6 received mannitol. In another experimental set, glucose or insulin was administered at ZT12 (at the end of the light period); 12 rats received glucose, and 6 received insulin. All the animals that received glucose were hyperglycaemic (P < 0.01), and the hyperglycaemia was less pronounced in the ZT12 group (P < 0.05; Student's t-test). Insulin induced acute hypoglycaemia in animals of both groups (ZT5, P < 0.02; ZT12, P < 0.05; Student's t-test). Glucose injection at ZT5 reduced SD, whereas the insulin ZT5 group showed increased SD propagation (ANOVA, P < 0.05 and 0.01, respectively). Neither glucose nor insulin injection changed SD velocity at ZT12. We concluded that blood glucose levels change the velocity of SD propagation and that these effects are influenced by the daytime. Dark periods seemed to produce a resistance to cortical SD propagation.     

Effect of dietary vitamin E on plasma oxidative stress in broiler chicks infected with Eimeria tenella

The aim of the present experiment was to study the alterations in plasma oxidative stress parameters in broiler chicks fed with graded dietary vitamin E whilst infected with Eimeria tenella. Ninety six new-born chicks were assigned into three treatment groups by adding 0, 316 or 562?ppm of vitamin E premix to their regular diet. On day?21, half of the experimental birds were inoculated with 4?×?10⁴ sporulated oocysts of E. tenella per bird; whereas the remaining chicks served as non-infected controls. Blood samples were taken and assayed for total antioxidant activity (TAA), lipid peroxidation level and vitamin E content. Oocyst shedding was also examined in all treatments. Results showed that TAA and vitamin E levels in plasma were not affected by dietary treatment (p?>?0.05). The lowest level of plasma lipid peroxidation (p?<?0.001) was noticed in the chicks treated with 562?ppm of dietary vitamin E, but the difference between the chicks fed a regular diet or 316?ppm dietary vitamin E was not significant (p?>?0.05). The oocyst shedding was the lowest in the chicks treated with 316?ppm dietary vitamin E (p?<?0.001), but there was no significant difference between the other two dietary treatments (p?>?0.05). In conclusion, the addition of vitamin E at a rate of 316?ppm to broiler basal diet can improve cellular defence system against E. tenella infection without any effect on the plasma antioxidant status, but at higher values it may have an adverse effect.     

Effects of ghrelin on Kisspeptin mRNA expression in the hypothalamic medial preoptic area and pulsatile luteinising hormone secretion in the female rat

The orexigenic gut peptide ghrelin negatively modulates the hypothalamic–pituitary–gonadal (HPG) axis. Hyperghrelinaemia results during negative energy balance, a state often associated with delayed puberty and disrupted fertility, whilst exogenous ghrelin suppresses pulsatile luteinising hormone (LH) secretion. The recent identification of kisspeptin (Kiss1) and its G protein-coupled receptor (GPR)54 (Kiss1r) as an essential component of the HPG axis controlling gonadotrophin secretion raises the possibility that kisspeptin-Kiss1r signalling may play a critical role in the transduction of ghrelin-induced suppression of LH. Ovariectomised oestrogen-replaced rats were implanted with intravenous catheters and blood samples collected for detection of LH pulses prior to and after intravenous administration of ghrelin (3 nM/250 μl) or saline (250 μl) during ad libitum feeding or after overnight fasting. Quantitative RT-PCR was used to determine Kiss1 and Kiss1r mRNA levels in brain punches of the key hypothalamic sites regulating gonadotrophin secretion, the medial preoptic area (mPOA) and arcuate nucleus (ARC), collected 6 h following administration of ghrelin. Ghrelin significantly lowered LH pulse frequency in fed rats, an effect significantly enhanced by food deprivation. Fasting, ghrelin or their combination down-regulated Kiss1, without affecting Kiss1r, expression in the mPOA, and affected the expression of neither in the ARC. Considering the pivotal role for kisspeptin signalling in the activation of the HPG axis, the ability of ghrelin to down-regulate Kiss1 expression in mPOA may be a contributing factor in ghrelin-related suppression of pulsatile LH secretion.     

Metabolic indicators of nutritional stress are not predictive of abnormal oral behavior in piglets

Belly nosing is an abnormal oral-nasal behavior that can develop to high levels in newly weaned piglets and may signal nutritional need. The effects of feed restriction on both behavior and metabolic serum parameters were examined in 128 weaned piglets. All pigs were fed ad libitum during week 1, and during week 2, half of all pens (N = 8) were restricted to 65% of ad libitum intake. Blood samples were collected on days 3 and 10 after weaning and behavior was observed from video recordings on days 5 and 12. Piglets were classified as early ‘nosers’ or early ‘non-nosers’ based on their behavior on day 5. Feed restriction resulted in elevated non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB) and both lower glucose and a NEFA/glucose ratio, but belly nosing was not affected. Piglets classified as ‘nosers’ did not have blood profiles indicating they were in greater nutritional need compared to ‘non-nosers’ in the first week of weaning, nor did they increase belly nosing or other piglet directed behaviors when restricted in week 2. Overall, no associations were found between blood parameters indicative of nutritional stress and belly nosing. This study identifies serum glucose, BHB and NEFA as well as the glucose/NEFA ratio as useful indicators of nutritional stress in newly weaned piglets.     

Autonomic function and change in insulin for exercising postmenopausal women

Purpose

Obesity, physical inactivity and altered estrogen metabolism play an integrated role contributing to the disease risk profiles of postmenopausal women. These same risk factors also affect modulation of the autonomic nervous system (ANS).

Methods

We examined 332 postmenopausal, overweight, previously sedentary women (mean ± SD; age, 57.6 ± 6.3 years; weight, 84.3 ± 11.9 kg; BMI, 31.7 ± 3.7 kg/m²) participating in a 6-month, moderate intensity, aerobic exercise training intervention to determine the relationship between heart rate variability (HRV) derived autonomic function and fasting insulin. We analyzed quartiles of change in time and frequency domain indices of ANS activity and changes in insulin for between and within group differences using ANCOVA and Tukey post hoc tests adjusted for age, ethnicity, randomization group, change in fitness, and change in weight.

Results

We observed at baseline that insulin was positively correlated with body anthropometry (body weight, r² = 0.34; BMI, r² = 0.39; waist circumference, r² = 0.29; all, P < 0.001), and inversely associated with rMSSD (r² = −0.12) and SDNN (r² = −0.18; all, P < 0.01). After the intervention, changes in rMSSD (r² = −0.21, P < 0.002) and SDNN r² −0.19, P < 0.0001) were inversely correlated to insulin change. Further ANCOVA analysis revealed that rMSSD and SDNN were both significant (P < 0.0001); however, only rMSSD exhibited a step-wise pattern of improvement when quartiles of rMSSD were compared to corresponding insulin reductions: Q1 (referent group, 8.41 ± 3.2 uIU/ml), Q2 (−3.30 ± −3.2 uIU/ml), Q3 (−5.66 ± −3.2 uIU/ml; P < 0.02), and Q4 (−9.60 ± −3.2 uIU/ml; P < 0.006).

Conclusion

Our study shows that changes in autonomic function are associated with changes in insulin and that exercise training may influence this relationship in postmenopausal women.