Des-acyl Ghrelin Research Articles

Oral administration of heat-killed Lactobacillus brevis SBC8803 elevates the ratio of acyl/des-acyl ghrelin in blood and increases short-term food intake

It is known that gastrointestinal microbiota, probiotics and heat-killed microbes can regulate intestinal immunity; however, their effect on the secretion of gastrointestinal hormones is unclear. The secretion of gastrointestinal hormones can be mediated by the elevation of intracellular Ca2+ concentration, suggesting that these hormones may act through common mechanisms. We have previously shown that heat-killed Lactobacillus brevis SBC8803 (hk-SBC8803) induced the secretion of serotonin and elevated intracellular Ca2+ concentration in serotonin-producing RIN-14B cells, suggesting that hk-SBC8803 could potentially cause the same effect on other gastrointestinal hormones, including hunger hormone ghrelin. Here, we tested this hypothesis by treating cultured cells and experimental animals with hk-SBC8803 and assessing ghrelin secretion, expression of ghrelin-related genes, and food intake. The results indicated that hk-SBC8803 treatment for 30 min significantly upregulated the secretion of acyl ghrelin (active form) (P=0.046) and mRNA expression of the Syt3 (synaptotagmin 3) gene related to ghrelin exocytosis (P<0.05) in primary mouse stomach cells. In addition, oral administration of 500 mg/kg hk-SBC8803 to rats tended to upregulate acyl ghrelin concentration (P=0.10) and significantly increased the ratio of acyl to des-acyl (inactive) ghrelin (P=0.027) in blood, which corresponded to a tendency of stimulating food intake (P=0.087) at 30 min post-treatment. However, when in order to minimise individual differences we normalised the data on food intake to those on one-day food intake prior to food deprivation, the resultant food intake ratio showed a significant increase (by 5% compared to control; P=0.032) at 30 min after hk-SBC8803 treatment, indicating that hk-SBC8803 administration stimulated rats to take more food during the first meal after fasting. These results suggest that hk-SBC8803 induces short-term ghrelin secretion and transiently increases appetite, which is an important effect for individuals with low energy intake.

Meal-Related Acyl and Des-Acyl Ghrelin and Other Appetite-Related Hormones in People with Obesity and Binge Eating.

Potential mechanisms of abnormal food intake, such as dysregulation of meal-related appetite hormones, including acyl ghrelin (AG) and des-acyl ghrelin (DAG), were investigated among men and women with obesity, with and without binge eating (BE). Participants (n=42: 19 female, 23 male) were assigned to a liquid meal and water condition in counterbalanced order, and blood samples for measuring hormones were obtained before and after these conditions. Participants with BE had significantly lower fasting and postingestive AG concentrations than participants without BE in both conditions. During the meal condition, postprandial decreases in AG concentrations were significantly smaller for the BE group than for the non-BE group. There were no significant differences in DAG by BE group. Leptin increased significantly less after meals for those with BE compared with those without BE. There were no differences in other hormones by BE group. Fasting and postmeal hunger ratings were significantly higher for those with BE than for those without BE. In individuals with BE, lower fasting AG may be due to downregulation by habitual overeating, and a smaller postmeal decline in AG may contribute to overeating. Lower postmeal leptin concentrations may also contribute to overeating.

Acylated Ghrelin Supports the Ovarian Transcriptome and Follicles in the Mouse: Implications for Fertility.

Ghrelin, an orexigenic gut-derived peptide, is gaining increasing attention due to its multifaceted role in a number of physiological functions, including reproduction. Ghrelin exists in circulation primarily as des-acylated and acylated ghrelin. Des-acyl ghrelin, until recently considered to be an inactive form of ghrelin, is now known to have independent physiological functionality. However, the relative contribution of acyl and des-acyl ghrelin to reproductive development and function is currently unknown. Here we used ghrelin-O-acyltransferase (GOAT) knockout (KO) mice that have no measurable levels of endogenous acyl ghrelin and chronically high levels of des-acyl ghrelin, to characterize how the developmental and life-long absence of acyl ghrelin affects ovarian development and reproductive capacity. We combined the assessment of markers of reproductive maturity and the capacity to breed with measures of ovarian morphometry, as well as with ovarian RNA sequencing analysis. Our data show that while GOAT KO mice retain the capacity to breed in young adulthood, there is a diminished number of ovarian follicles (per mm3) in the juvenile and adult ovaries, due to a significant reduction in the number of small follicles, particularly the primordial follicles. We also show pronounced specific changes in the ovarian transcriptome in the juvenile GOAT KO ovary, indicative of a potential for premature ovarian development. Collectively, these findings indicate that an absence of acyl ghrelin does not prevent reproductive success but that appropriate levels of acyl and des-acyl ghrelin may be necessary for optimal ovarian maturation.

Two weeks of exercise training intensity on appetite regulation in obese adults with prediabetes.

No short-term exercise data exist testing whether training intensity modifies hormonal and perceived appetite in obese adults with prediabetes. Therefore, we compared the effects of short-term moderate-continuous (CONT) vs. high-intensity interval (INT) training on appetite regulation. Twenty-eight obese adults [age: 61.3 ± 1.5 yr; body mass index (BMI): 33.2 ± 1.1 kg/m2] with prediabetes were randomized to work-matched CONT ( n = 14) or INT ( n = 14) training for 2 wk. Plasma acylated ghrelin (AG), des-acylated ghrelin (dAG), active glucagon-like peptide-1 (GLP-1), and insulin were measured at 0, 30, and 60 min of a 75-g oral glucose tolerance test (OGTT) before and after training. Visual analog scales were administered at 0 and 120 min during the OGTT to examine perceived appetite. Three-day food logs were collected before and after testing to assess ad libitum diet. CONT and INT increased peak oxygen consumption ( P < 0.01) and decreased BMI ( P < 0.01). Although neither intervention altered fasting levels of AG ( P = 0.94), dAG ( P = 0.36), or insulin ( P = 0.67), CONT raised GLP-1 compared with INT ( P = 0.05). Exercise training did not affect postprandial suppression of AG ( P = 0.81) and dAG ( P = 0.67) or stimulation of GLP-1 ( P = 0.67) and insulin ( P = 0.32). Both interventions tended to decrease total energy and protein intake ( P = 0.09 and P = 0.05, respectively), despite no change in fasting hunger ( P = 0.88) and reduced perceived fullness at 120 min during the OGTT ( P = 0.05). We conclude that 2 wk of exercise training intensity does not modulate appetite-regulatory hormones in obese adults with prediabetes. Although perceived fullness to the OGTT was reduced after exercise, CONT and INT decreased energy intake, suggesting that exercise does not elicit compensatory appetite behavior to gain weight. NEW & NOTEWORTHY Adults with prediabetes are at risk for appetite dysregulation. Although exercise promotes weight management, it is unclear whether moderate-continuous or high-intensity interval training is more beneficial for appetite regulation. We show that 2 wk of exercise, independent of intensity, does not alter postprandial appetite hormones or hunger, despite slight reductions in food intake and weight. These data support exercise as an effective method to induce negative energy balance without compensatory weight gain.

DESACYLATED GHRELIN AND LEPTIN IN THE CORD BLOOD OF SMALL-FOR-GESTATIONAL-AGE NEWBORNS WITH INTRAUTERINE GROWTH RESTRICTION.

Ghrelin, in both its acylated and desacylated forms, and leptin can modulate fetal energy balance and development. The aim of our study is to assess desacylated ghrelin (DAG) and leptin values and influence on intrauterine and postnatal growth in infants with intrauterine growth restriction. We performed a prospective study on 39 infants recruited over five months, 20 appropriate - for - gestational - age (AGA) infants and 19 small-for-gestational-age (SGA) infants, in which we measured DAG and leptin in the umbilical cord blood and we compared their respective values between the two groups, along with auxological parameters at birth and at 10 months of postnatal age. Our results show that both DAG and leptin have lower values in SGA infants and correlate with most of the anthropometrical parameters at birth. Both hormones correlate with weight at 10 months in SGA infants, but this correlation lacks in AGA infants. Whereas DAG in the cord blood can be considered a predictor for weight at 10 months (β=0.207, p=0.001), the same cannot be stated about leptin (β=0.078, p=0.195). DAG and leptin are involved in both intrauterine and postnatal development, but the extent of their role is still to be determined.

Serum ghrelin and obestatin levels in patients with acne vulgaris: are they important for the severity?

IntroductionAcne vulgaris (AV) is a chronic, inflammatory disease of the pilosebaceous unit. Recently, three peptide-structured hormones, products of a single gene, have been discovered. These hormones are acylated ghrelin, des-acyl ghrelin and obestatin.AimTo demonstrate the association of serum acylated ghrelin, des-acyl ghrelin, and obestatin levels with acne severity.Material and methodsA total of 63 patients grouped as mild (n = 22), moderate (n = 21) and severe (n = 20) acne according to the Global Acne Grading System and 20 medically healthy volunteers were included in the study. Serum ghrelin and obestatin levels obtained from the participants were examined.ResultsWhen mean ghrelin, des-acyl-ghrelin and obestatin values of the acne-group (AG) were compared with the control group (CG), they were found be lower in the AG, but were not statistically significant. Among the patient groups, while acylated ghrelin values were highest in the severe AG, des-acyl ghrelin values were highest in mild severe AG and mean obestatin values were highest in moderate severe AG (p > 0.05). When the groups were compared for obestatin values; the highest average value was detected in the CG. However, it was not significant when the groups were compared.ConclusionsIt has been suggested that there may be a link between acne and the levels of acylated ghrelin, des-acyl ghrelin and obestatin which are decreased in the serum of acne patients. Because of the decrease observed in the levels of these hormones which have antimicrobial features, we suggest that inflammation in acne cannot be suppressed and the reproduction of the microorganisms that play a role in the aetiology of the disease cannot be prevented. The replacement of these hormones at physiologic concentrations may contribute to the acne treatment.

Association between adiposity and fasting serum levels of appetite-regulating peptides: Leptin, neuropeptide Y, desacyl ghrelin, peptide YY(1-36), obestatin, cocaine and amphetamine-regulated transcript, and agouti-related protein in nonobese participants

The objective of this study was to evaluate the association between adiposity parameters and fasting serum levels of appetite-regulating peptides: leptin, neuropeptide Y (NPY), desacyl ghrelin, peptide YY(1-36), obestatin, cocaine- and amphetamine-regulated transcript (CART), and agouti-related protein in 30 healthy, non-obese subjects. Thirty European Caucasian adult participants were included in the study (17 men and 13 women). Body composition (body fat and lean body mass) was determined using bioelectrical impedance analysis. Concentrations of peptides in serum were assessed using the enzyme-linked immunosorbent assay. Women had higher level of leptin (P < 0.001), with no other differences for analyzed peptides. We have found a significant correlation between serum concentrations of CART and NPY (P < 0.001). Fasting leptin level was associated with age (P = 0.002), waist circumference (P < 0.001), and lean body mass (P < 0.001). Levels of ghrelin were lower in participants with dyslipidemia (P = 0.009). Levels of obestatin (P = 0.008) and leptin (P = 0.02) were higher in participants with insulin resistance. Associations between body fat and appetite-regulating peptides are more complex than simple feedback loops. Leptin is probably the first signal in the pathway that regulates body fat content, as of all analyzed peptides leptin was the only one that was associated with body composition or anthropometric measurements.

Intake of a Japanese-Style Healthy Lunch Has Possibilities of Contributing to the Normalization of Serum Lipids and Adipokines: A Non-Randomized Controlled Trial Pilot Study

To date, the incidence of metabolic syndrome has been increasing continuously worldwide; and recently, low vegetable consumption has become a major issue of concern in Japan. Furthermore, Japan is facing a shortfall in places offering food that can help prevent metabolic syndrome. Our study was designed to determine the influence of an on-going healthy lunch on metabolic syndrome outcomes (blood pressure, serum TNF-alpha, IL-6, serum lipids) in adult middle-aged office male workers, in Japan. We conducted a non-randomized controlled trial among 38 middle-aged office male workers (control group: 7 males, intervention group: 31 males) with mostly low levels of physical activity, by providing a Japanese-style healthy lunch for 3 months (intervention group) at a workplace cafeteria. The control group consumed their habitual lunches without restriction and only the nutrient contents were assessed. Furthermore, the intervention group was divided into two (non-metabolic [non-MS] and metabolic syndrome [MS] groups) for analysis. Overall 38 males with a mean age of 47.2 ± 7.9 years were included. Abdominal circumference level (p<0.05), systolic and diastolic (p<0.05) blood pressure (p<0.01), as well as serum low-density lipoprotein (LDL-Chol), serum tumor necrosis factor (TNF-α) (p<0.001) and interleukin (IL-6) (p<0.01) decreased significantly after intervention compared with the baseline in the intervention/non-MS group and intervention/MS groups. Furthermore, ghrelin (p<0.001) and desacyl ghrelin (p<0.05) increased significantly after intervention compared with the baseline in the intervention/non-MS group and intervention/MS groups. These showed an effective outcome, demonstrated by the ongoing intake of a Japanese-style healthy lunch, of decreased blood pressure, serum TNF-α, IL-6, serum LDL-Chol and total cholesterol. This study presents new empirical data based on an original intervention program showing that the consumption of a Japanese-style healthy lunch containing many vegetables can help prevent and/or improve metabolic syndrome. The findings of this study could also lead to the opportunity for participants to practice following healthy menus at home. We therefore consider that this is valuable in promoting improvement in diet in the food environment at the workplace.

Sleep Deprivation Selectively Upregulates an Amygdala-Hypothalamic Circuit Involved in Food Reward.

Sleep loss is associated with increased obesity risk, as demonstrated by correlations between sleep duration and change in body mass index or body fat percentage. Whereas previous studies linked this weight gain to disturbed endocrine parameters after sleep deprivation or restriction, neuroimaging studies revealed upregulated neural processing of food rewards after sleep loss in reward-processing areas such as the anterior cingulate cortex, ventral striatum, and insula. To address this ongoing debate between hormonal versus hedonic factors underlying sleep-loss-associated weight gain, we rigorously tested the association between sleep deprivation and food cue processing using high-resolution fMRI and assessment of hormones. After taking blood samples from 32 lean, healthy, human male participants, they underwent fMRI while performing a neuroeconomic, value-based decision-making task with snack food and trinket rewards following a full night of habitual sleep and a night of sleep deprivation in a repeated-measures crossover design. We found that des-acyl ghrelin concentrations were increased after sleep deprivation compared with habitual sleep. Despite similar hunger ratings due to fasting in both conditions, participants were willing to spend more money on food items only after sleep deprivation. Furthermore, fMRI data paralleled this behavioral finding, revealing a food-reward-specific upregulation of hypothalamic valuation signals and amygdala-hypothalamic coupling after a single night of sleep deprivation. Behavioral and fMRI results were not significantly correlated with changes in acyl, des-acyl, or total ghrelin concentrations. Our results suggest that increased food valuation after sleep loss might be due to hedonic rather than hormonal mechanisms.SIGNIFICANCE STATEMENT Epidemiological studies suggest an association between overweight and reduced nocturnal sleep, but the relative contributions of hedonic and hormonal factors to overeating after sleep loss are a matter of ongoing controversy. Here, we tested the association between sleep deprivation and food cue processing in a repeated-measures crossover design using fMRI. We found that willingness to pay increased for food items only after sleep deprivation. fMRI data paralleled this behavioral finding, revealing a food-reward-specific upregulation of hypothalamic valuation signals and amygdala-hypothalamic coupling after a single night of sleep deprivation. However, there was no evidence for hormonal modulations of behavioral or fMRI findings. Our results suggest that increased food valuation after sleep loss is due to hedonic rather than hormonal mechanisms.

Prokineticin-2 and ghrelin robustly influence the sexual and ingestive behaviors of female Syrian hamsters

Prokineticins are involved in many physiological processes including circadian rhythms, neurogenesis, angiogenesis, and cancer. Recently, they have been found to play a role in regulating food intake. Historically, proteins that increase feeding behavior in mammals decrease reproductive behavior to prevent pregnancy and lactation when food is scarce. In the current study, prokineticin-2 (PK2) had pronounced effects on reproductive and ingestive behaviors when given to female Syrian hamsters. Administration of PK2 prevented ingestive behaviors induced by food restriction, such as the amount of time spent with food and eating. Hamsters given PK2 preferred to engage in reproductive behaviors, including spending time with a male and lordosis. Furthermore, analysis of blood plasma revealed that changes to behavior persisted despite similar levels of des-acyl ghrelin (DAG) and reduced glucose concentrations in the blood. Additionally, administering 10 mg/kg of acyl ghrelin (AG) to a different cohort of animals significantly decreased the amount of time females spent with a potential mating partner, increased the amount of time females spent with food, decreased the duration of lordosis, and increased the duration of eating. Results from the current study support the need for further research investigating the reproductive and ingestive roles of PK2 and ghrelin.

Gender Differences in Plasma Ghrelin Levels in Hemodialysis Patients.

Ghrelin is an orexigenic hormone mainly secreted by the stomach, and it decreases according to the severity of gastric atrophy. Ghrelin has multiple favorable functions, including protein anabolism enhancement, anti-inflammatory activity, and cardiovascular protection, and is associated with survival in hemodialysis (HD) patients. Although the plasma level and role of ghrelin may be different depending on gender, they have not been completely assessed in HD patients. We enrolled 80 (male/female: 51/29) maintenance HD patients. An upper gastrointestinal endoscopic examination was performed for all patients to determine the severity of gastric mucosal atrophy and Helicobacter pylori infection. We measured plasma acyl and desacyl ghrelin levels and assessed the association between ghrelin levels and relevant clinical parameters, including nutrition, inflammation, atherosclerosis, and bone metabolism, by gender. Both acyl and desacyl ghrelin levels in female HD patients were significantly higher than those in male HD patients. When stratified by gastric mucosal atrophy, these gender differences were observed only in patients without gastric atrophy. In female patients, acyl ghrelin level was negatively correlated with age. In male patients, both acyl and desacyl ghrelin levels were positively correlated with bone mineral density. Multiple regression analysis showed significant positive correlations between both ghrelin levels and female gender after adjusting for confounding factors. Plasma ghrelin levels were higher in female HD patients than in male HD patients. The gender difference was more evident in patients without gastric atrophy.

Ghrelin cascade changes in the peripheral blood of Japanese patients with Alzheimer's disease

The neuroprotective effect of ghrelin has recently been reported in Alzheimer's disease (AD). Ghrelin is converted from des-acyl ghrelin to the activated form, acyl ghrelin, by membrane bound o-acyltransferase 4 (MBOAT4), and then binds to growth hormone secretagogue receptor (GHS-R). We examined the levels of plasma acyl/des-acyl ghrelin in 75 AD subjects and age- and sex-matched controls, as well as the DNA methylation and mRNA expression of MBOAT4 and GHS-R in peripheral leukocytes. The acyl ghrelin concentration was significantly higher in AD subjects than in controls (2.18 ± 1.25 vs. 1.49 ± 2.3, p = 0.001). The methylation rate of MBOAT4 CpG 2 was significantly lower in AD subjects than in controls (4.0 ± 0.9 vs. 4.7 ± 1.2, p < 0.001). The mRNA expression levels of MBOAT4 and GHS-R1b were significantly higher in AD subjects than in controls (MBOAT4: 1.10 ± 0.48 vs. 1.0 ± 0.55, p = 0.049; GHS-R1b: 1.76 ± 3.18 vs. 1.0 ± 1.56, p = 0.030). These changes in the ghrelin cascade in peripheral blood may reflect those in the brain, and may be a neuroprotective biomarker in AD.

Exendin-4 antagonizes the metabolic action of acylated ghrelinergic signaling in the hypothalamic paraventricular nucleus

In the current study we investigated the interaction of hypothalamic paraventricular nucleus (PVN) glucagon-like peptide-1 (GLP-1) and ghrelin signaling in the control of metabolic function. We first demonstrated that acylated ghrelin injected directly into the PVN reliably altered the respiratory exchange ratio (RER) of adult male Sprague Dawley rats. All testing was carried out during the initial 2 h of the nocturnal cycle using an indirect open circuit calorimeter. Results indicated that acylated ghrelin induced a robust increase in RER representing a shift toward enhanced carbohydrate oxidation and reduced lipid utilization. In contrast, treatment with comparable dosing of des-acyl ghrelin failed to significantly impact metabolic activity. In separate groups of rats we subsequently investigated the ability of exendin-4 (Ex-4), a GLP-1 analogue, to alter acylated ghrelin’s metabolic effects. Rodents were treated with either systemic or direct PVN Ex-4 followed by acyl ghrelin microinjection. While our results showed that both systemic and PVN administration of Ex-4 significantly reduced RER, importantly, Ex-4 pretreatment itself reliably inhibited the impact of ghrelin on RER. Overall, these findings provide increasingly compelling evidence that GLP-1 and ghrelin signaling interact in the neural control of metabolic function within the PVN.

Eradication Therapy for Helicobacter pylori Improves Nutrition Status Depended on Severity of Gastric Mucosal Atrophy and Plasma Ghrelin Level in Japanese Hemodialysis Patients

Introduction: The state of metabolic and nutritional derangement, called protein—energy wasting (PEW), has a major impact on mortality in hemodialysis (HD) patients. Ghrelin has multiple favorable functions and associates with the pathogenesis of PEW in HD patients. Plasma and gastric ghrelin levels are affected in H pylori status. Here, we investigated relationships among nutrition status, ghrelin level, H. pylori and severity of atrophy in HD patients and investigated the efficacy of H. pylori eradication therapy for improvement of nutrition status related with ghrelin in H. pylori—positive HD patients. Methods: H. pylori&#x2014;IgG and pepsinogen levels of 500 HD patients at 8 dialysis centers were measured. We classified H. pylori infectionstatus into three groups: present infection, past infection and non—infection. Plasma ghrelin levels were measured and we investigated above relationship among three groups. H. pylori—positives underwent endoscopy for evaluation of the severity of atrophy, and eradicated by PPI, amoxocollin and clarithromycin for 7days. We evaluated nutrition markers and ghrelin levels before and 1 year after eradication. Results: Acyl— and desacyl—ghrelin levels were 29.7±21.3 fmol/mland 279.2±168.5 fmol/ml, respectively. Acyl—ghrelin in the non—infection group was significantly higher than in the present and past infection groups. Acyl—ghrelin level was positively correlated with serum PG I level and PG I/II ratio and was significantly lower in patients with severe atrophy than in those with no atrophy (20.9±14.6and 40.4±21.9, p<0.001). Cholinesterase level was significantly increased after eradication compared with before eradication (303.2±76.0 vs. 287.3±68.1, p=0.029). In particular, cholesterol(before, 196.6±23.2; after, 206.1±25.9, p=0.042) and cholinesterase levels(before, 296.9±70.8; after, 316.4±73.8, p=0.049) increased more strongly in patients with mild-moderate atrophy than those with severe atrophy. Conclusion: Plasma ghrelin level was associated with endoscopic and serological severity of atrophy related with H. pylori infection in HD patients. Eradication improved nutrition status by increasing serum cholinesterase and cholesterol levels, especially those with mild and moderate gastric mucosal atrophy. In HD patients, eradication therapy may contribute to an improvement in prognosis associated with PEW.

Ghrelin transport across the blood–brain barrier can occur independently of the growth hormone secretagogue receptor

ObjectiveThe blood–brain barrier (BBB) regulates the entry of substrates and peptides into the brain. Ghrelin is mainly produced in the stomach but exerts its actions in the central nervous system (CNS) by crossing the BBB. Once present in the CNS, ghrelin can act in the hypothalamus to regulate food intake, in the hippocampus to regulate neurogenesis, and in the olfactory bulb to regulate food-seeking behavior. The goal of this study was to determine whether the primary signaling receptor for ghrelin, the growth hormone secretagogue receptor (GHSR), mediates the transport of ghrelin from blood to brain. MethodsWe utilized the sensitive and quantitative multiple-time regression analysis technique to determine the transport rate of mouse and human acyl ghrelin (AG) and desacyl ghrelin (DAG) in wildtype and Ghsr null mice. We also measured the regional distribution of these ghrelin peptides throughout the brain. Lastly, we characterized the transport characteristics of human DAG by measuring the stability in serum and brain, saturability of transport, and the complete transfer across the brain endothelial cell. ResultsWe found the transport rate across the BBB of both forms of ghrelin, AG, and DAG, were not affected by the loss of GHSR. We did find differences in the transport rate between the two isoforms, with DAG being faster than AG; this was dependent on the species of ghrelin, human being faster than mouse. Lastly, based on the ubiquitous properties of ghrelin throughout the CNS, we looked at regional distribution of ghrelin uptake and found the highest levels of uptake in the olfactory bulb. ConclusionsThe data presented here suggest that ghrelin transport can occur independently of the GHSR, and ghrelin uptake varies regionally throughout the brain. These findings better our understanding of the gut-brain communication and may lead to new understandings of ghrelin physiology.

Ghrelin Reduces TNF-α-Induced Human Hepatocyte Apoptosis, Autophagy, and Pyroptosis: Role in Obesity-Associated NAFLD.

Human obesity is associated with increased circulating TNF-α, a proinflammatory cytokine that induces hepatocyte cell death. The potential beneficial effects of acylated and desacyl ghrelin in the progression of nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis in obesity via the inhibition of TNF-α-induced hepatocyte apoptosis, autophagic cell death, and pyroptosis were investigated. Plasma ghrelin isoforms and TNF-α were measured in 158 participants, and hepatocyte cell death was evaluated in liver biopsies from 76 patients with morbid obesity undergoing bariatric surgery with available liver echography and pathology analysis. The effect of acylated and desacyl ghrelin on basal and TNF-α-induced cell death was determined in vitro in human HepG2 hepatocytes. Circulating TNF-α and the acylated/desacyl ghrelin ratio were increased, whereas desacyl ghrelin levels were decreased in patients with obesity and NAFLD. Six months after bariatric surgery, decreased acylated/desacyl ghrelin levels, and improved hepatic function were found. Patients with obesity and type 2 diabetes showed increased hepatic ghrelin O-acyltransferase transcripts as well as an increased hepatic apoptosis, pyroptosis, and compromised autophagy. In HepG2 hepatocytes, acylated and desacyl ghrelin treatment reduced TNF-α-induced apoptosis, evidenced by lower caspase-8 and caspase-3 cleavage, as well as TUNEL-positive cells and pyroptosis, revealed by decreased caspase-1 activation and lower high-mobility group box 1 expression. Moreover, acylated ghrelin suppressed TNF-α-activated hepatocyte autophagy, as evidenced by a decreased LC3B-II/I ratio and increased p62 accumulation via AMPK/mTOR. Ghrelin constitutes a protective factor against hepatocyte cell death. The increased acylated/desacyl ghrelin ratio in patients with obesity and NAFLD might constitute a compensatory mechanism to overcome TNF-α-induced hepatocyte apoptosis, autophagy, and pyroptosis.

Acylated ghrelin suppresses the cytokine response to lipopolysaccharide and does so independently of the hypothalamic-pituitary-adrenal axis

Ghrelin, one of the major metabolic hormones involved in controlling energy balance, has recently been shown to have other properties including regulating the hypothalamic-pituitary-adrenal (HPA) axis response to psychological stress and being a potent anti-inflammatory agent. Ghrelin’s HPA axis and anti-inflammatory actions have previously been identified as principally due to the acylated form (AG). However, our recent work has also suggested a role for des-acylated ghrelin (DAG) in these functions. Here we hypothesized ghrelin’s anti-inflammatory activity is mediated by the HPA axis and this effect is differentially executed by AG and DAG. We gave adult male Wistar rats a concomitant injection of AG or DAG and lipopolysaccharide (LPS) and measured their effects on circulating cytokines, stress hormones and neuronal activation of the paraventricular nucleus of the hypothalamus (PVN). AG, but not DAG significantly suppressed the pro- and anti-inflammatory cytokine response induced by LPS in vivo. DAG also had no effects on any components of the HPA axis. AG, despite stimulating neuronal activation in the PVN in vivo and stimulating ACTH release from the pituitary in vitro, did not affect the HPA axis response to LPS. These findings suggest AG’s anti-inflammatory effects are independent of its actions on the HPA axis and have implications for the potential use of this peptide for treatment of inflammatory conditions without compromising HPA axis activity.

Fasting or systemic des-acyl ghrelin administration to rats facilitates thermoregulatory behavior in a cold environment

Fasted rats place their tails underneath their body trunks in the cold (tail-hiding behavior), which is a thermoregulatory behavior. The aim of the present study was to investigate the effect of fasting and des-acyl ghrelin, a hormone related to fasting, on tail-hiding behavior and neural activity in the cold. Wistar rats were divided into ‘fed’, ‘42-h fasting’ and des-acyl ghrelin groups. The rats received an intraperitoneal saline or 30-μg des-acyl ghrelin injection, and were then exposed to 27 °C or 15 °C for 2-h with continuous body temperature (Tb), tail skin temperature (Ttail), and tail-hiding behavior measurements. cFos immunoreactive (cFos-IR) cells in the insula, secondary somatosensory cortex, medial preoptic nucleus, parastrial nucleus, amygdala, and lateral parabrachial nucleus were counted in four segments: seg1, 2, 3, and 4 (bregma −0.36, −1.44, −2.64, and −9.00 mm), respectively. At 15 °C, Tb and Ttail were lower in the 42-h fasting group than in the fed and des-acyl ghrelin groups, and the duration of tail-hiding behavior was longer in the 42-h fasting and des-acyl ghrelin groups than in the fed group. The onset of tail-hiding behavior more advanced in the des-acyl ghrelin group than in the fed group at 15 °C. Only at the insula in seg3 at 15 °C, the number of cFos-IR cells was greater in the 42-h fasting group than in the fed group. Both the 42-h fasting and des-acyl ghrelin groups might modulate the tail-hiding behavior of rats in a cold, and a part of the insula might be involved this response during fasting.

High plasma levels of ghrelin and des-acyl ghrelin in responders to antiepileptic drugs.

To reconsider ghrelin and des-acyl ghrelin plasma levels in children with epilepsy in order to establish a possible relation with response to antiepileptic drugs (AEDs). We designed an observational study in which 114 patients with epilepsy were classified as responders (77) or nonresponders (37) and compared to 59 controls. In these patients, we measured ghrelin and des-acyl ghrelin by immunoassays in blood samples obtained after overnight fast. Ghrelin plasma levels were higher (+94%; p < 0.001, Dunn test) in responders compared to controls. Des-acyl ghrelin plasma levels were also higher in the same group (+55%; p < 0.001). In addition, both hormones were unmodified in nonresponders compared to controls. By comparing responders to nonresponders, ghrelin and des-acyl ghrelin, respectively, were +126% (p < 0.001) and +29% (p < 0.001) in patients with a positive response to AEDs. These results indicate that ghrelin and des-acyl ghrelin plasma levels are especially high in patients with epilepsy who positively respond to AEDs. In view of the anticonvulsant properties of ghrelin and des-acyl ghrelin, we propose that their higher levels could play a role in modulating the response to AEDs. Moreover, these peptides could be promising markers of response to AEDs.

Comment: Ghrelin and des-acyl ghrelin: Do they predict success of AED treatment?

Ghrelin and des-acyl ghrelin are gastric mucosa–secreted neuropeptide hormones whose primary function is energy homeostasis, with widespread actions on many tissues including the hypothalamus and hippocampus. Their role in sleep and pituitary function suggested an effect in epilepsy, and elevated ghrelin levels were found in adults with controlled epilepsy.1 But subsequent studies have had confusing results, with both higher and lower ghrelin levels in adults and children with epilepsy, including lower levels in the acute postictal period.2 Weight changes, pre/postpubertal status, sample timing, and valproate use may all be confounders. Generally animal studies support a neuroprotective and antiepilepsy effect of ghrelin.3