Significant lowering of plasma ghrelin but not des-acyl ghrelin in response to acute exercise in men

Systematic Review: Does Exercise Training Influence Ghrelin Levels?

Ghrelin, a gastric-derived peptide, regulates appetite, food intake, and energy homeostasis. Body weight plays a crucial role in modulating circulating ghrelin levels. Since exercise training is one of the most valuable tools for controlling body weight, it is relevant to consider whether exercise can influence total ghrelin secretion. This study aims to perform a systematic review of the effect of acute/chronic exercise on plasma ghrelin levels. An extensive literature search was carried out on various databases, including PubMed, ScienceDirect, and Google Scholar. The search was conducted using English keywords such as acute-exercise, transient-exercise, exercise, chronic-exercise, training, physical-activity, physical-training, exercise training, and total-ghrelin, ghrelin, appetite-related-peptides, gastrointestinal-peptides, gastrointestinal-hormones, and appetite-regulating-hormone. Initially, 2104 studies were identified. After evaluating study quality, data from 61 relevant studies were extracted for inclusion in this review. Most studies indicated that short-term acute aerobic exercise did not affect total ghrelin levels regardless of exercise intensity, characteristics, or growth hormone (GH) secretion. However, long and very-long aerobic/chronic exercise increased total ghrelin levels, mainly in overweight/obese individuals. Acute/chronic exercise may differentially influence total ghrelin secretion. Short-term acute aerobic exercise induces stable plasma ghrelin concentrations, independent of GH secretion. Long-term aerobic training increased its levels mainly in overweight/obese individuals through body composition and oxidative stress reduction. Additionally, total ghrelin secretion is more sensitive to exercise/training duration than exercise/training intensity.

Environmental enrichment attenuates reinstatement of heroin seeking and reverses heroin-induced upregulation of mesolimbic ghrelin receptors

We have shown that environmental enrichment (EE) can effectively reduce reinstatement and facilitate true abstinence in animal models of drug use. Here, we investigated whether EE is effective against reinstatement of heroin seeking in long access (LA) model, which has been argued to capture the compulsive features of human drug addiction. We also explored the neurobiology by which EE produces its anti-drug addiction effects. In particular, we focused here on the ghrelin system, which is known for its involvement in reward-motivated behaviors and upregulation following intravenous drug self-administration. Following LA to heroin, rats were housed in either non-EE or EE conditions. During extinction and cue-induced reinstatement test, EE rats showed a significant reduction in active lever responding compared to non-EE rats, suggesting that EE facilitates extinction of drug seeking and reduces the capacity of drug-associated stimuli to elicit and maintain drug seeking. Using Western Blotting, we found that rats with LA to heroin IVSA showed a significant increase in ghrelin receptor (GHS-R1a) expression in the ventral tegmental area and nucleus accumbens, the brain regions implicated in resumption of drug use . Exposure to EE attenuated heroin-induced upregulation of GHS-R1a receptor in these regions but produced no significant changes other brain regions. Our findings suggest that EE can be an effective behavioral approach to diminish drug seeking even following LA to heroin. Compulsive drug taking and seeking seem to be correlated with an upregulation of GHS-R1a expression in the limbic regions, and EE can reverse these neuroadaptations, potentially contributing to a reduction in drug seeking.

Acute effects of exercise intensity on butyrylcholinesterase and ghrelin in young men: A randomized controlled study

Background/objectives

Butyrylcholinesterase (BChE), a liver-derived enzyme that hydrolyzes acylated ghrelin to des-acylated ghrelin, may trigger a potential mechanism responsible for the acute exercise-induced suppression of acylated ghrelin. However, studies examining the effects of an acute bout of high-intensity exercise on BChE and acylated ghrelin have yielded inconsistent findings. This study aimed to examine the acute effects of exercise intensity on BChE, acylated ghrelin and des-acylated ghrelin concentrations in humans.

Methods

Fifteen young men (aged 22.7 ± 1.8 years, mean ± standard deviation) completed three, half-day laboratory-based trials (i.e., high-intensity exercise, low-intensity exercise and control), in a random order. In the exercise trials, the participants ran for 60 min (from 09:30 to 10:30) at a speed eliciting 70 % (high-intensity) or 40 % (low-intensity) of their maximum oxygen uptake and then rested for 90 min. In the control trial, participants sat on a chair for the entire trial (from 09:30 to 12:00). Venous blood samples were collected at 09:30, 10:00, 10:30, 11:00, 11:30 and 12:00.

Results

The BChE concentration was not altered over time among the three trials. Total acylated and des-acylated ghrelin area under the curve during the first 60 min (i.e., from 0 min to 60 min) of the main trial were lower in the high-intensity exercise trial than in the control (acylated ghrelin, mean difference: 62.6 pg/mL, p < 0.001; des-acylated ghrelin, mean difference: 31.4 pg/mL, p = 0.035) and the low-intensity exercise trial (acylated ghrelin, mean difference: 87.7 pg/mL, p < 0.001; des-acylated ghrelin, mean difference: 43.0 pg/mL, p = 0.042).

Conclusion

The findings suggest that BChE may not be involved in the modulation of ghrelin even though lowered acylated ghrelin concentration was observed after high-intensity exercise.

The effects of peripheral hormone responses to exercise on adult hippocampal neurogenesis

Over the last decade, a considerable amount of new data have revealed the beneficial effects of exercise on hippocampal neurogenesis and the maintenance or improvement of cognitive function. Investigations with animal models, as well as human studies, have yielded novel understanding of the mechanisms through which endocrine signaling can stimulate neurogenesis, as well as the effects of exercise on acute and/or chronic levels of these circulating hormones. Considering the effects of aging on the decline of specific endocrine factors that affect brain health, insights in this area of research are particularly important. In this review, we discuss how different forms of exercise influence the peripheral production of specific endocrine factors, with particular emphasis on brain-derived neurotrophic factor, growth hormone, insulin-like growth factor-1, ghrelin, estrogen, testosterone, irisin, vascular endothelial growth factor, erythropoietin, and cortisol. We also describe mechanisms through which these endocrine responses to exercise induce cellular changes that increase hippocampal neurogenesis and improve cognitive function.

The Effects of Exercise on Appetite-Regulating Hormone Concentrations over a 36-h Fast in Healthy Young Adults: A Randomized Crossover Study

Hunger and satiety are controlled by several physiological mechanisms, including pancreatic and gastrointestinal hormones. While the influence of exercise and fasting have been described individually, in relation to these hormones, there is a paucity of work showing the effects of the two modalities (fasting and exercise) combined. Twenty healthy adults (11 males, 9 females) completed both conditions of this study, each consisting of a 36-h water-only fast. One of the fasts began with treadmill exercise, and the differences between the conditions on various appetite hormones were measured every 12 h. The difference in the area under the curve between conditions for ghrelin was 211.8 ± 73.1 pg/mL (F = 8.40, p < 0.0105), and, for GLP-1, it was -1867.9 ± 850.4 pg/mL (F = 4.82, p < 0.0422). No significant differences were noted for areas under the curve between conditions for leptin, PP, PYY, insulin, or GIP. Initiating a fast with exercise lowers ghrelin concentrations and elevates GLP-1 concentrations. Given that ghrelin elicits feelings of hunger and GLP-1 signals feelings of satiety, adding exercise to the beginning of a fast may reduce some of the biological drive of hunger, which could make fasting more tolerable, leading to better adherence and more significant health outcomes.

Does butyrylcholinesterase mediate exercise-induced and meal-induced suppression in acylated ghrelin?

Ample evidence supports the notion that an acute bout of aerobic exercise and meal consumption reduces acylated ghrelin concentration. However, the mechanisms by which this exercise- and meal-induced suppression of acylated ghrelin occurs in humans is unknown. This study aimed to examine the concentration of butyrylcholinesterase (BChE), an enzyme responsible for hydrolysing ghrelin and other appetite-related hormones in response to a single bout of running and a standardised meal in young, healthy men. Thirty-three men (aged 23 ± 2 years, mean ± standard deviation) underwent two (exercise and meal conditions) 2-h laboratory-based experiments. In the exercise condition, all participants ran for 30 min at 70% of the maximum oxygen uptake (0930-1000) and rested until 1130. In the meal condition, participants reported to the laboratory at 0930 and rested until 1000. Subsequently, they consumed a standardised meal (1000-1015) and rested until 1130. Blood samples were collected at baseline (0930), 1000, 1030, 1100 and 1130. BChE concentration was not altered in both the exercise and meal conditions (p > 0.05). However, acylated ghrelin was suppressed after exercise (p < 0.05) and meal consumption (p < 0.05). There was no association between the change in BChE concentration and the change in acylated ghrelin before and after exercise (p = 0.571). Although des-acylated ghrelin concentration did not change during exercise (p > 0.05), it decreased after meal consumption (p < 0.05). These findings suggest that BChE may not be involved in the suppression of acylated ghrelin after exercise and meal consumption.

Appetite Is Suppressed After Full-Body Resistance Exercise Compared With Split-Body Resistance Exercise: The Potential Influence of Lactate and Autonomic Modulation

ABSTRACT

Conrado de Freitas, M, Ricci-Vitor, AL, de Oliveira, JVNS, Quizzini, GH, Vanderlei, LCM, Silva, BSA, Zanchi, NE, Cholewa, JM, Lira, FS, and Rossi, FE. Appetite is suppressed after full-body resistance exercise compared with split-body resistance exercise: the potential influence of lactate and autonomic modulation. J Strength Cond Res 35(9): 2532-2540, 2021-The purposes of this study were to investigate the effects of full- vs. split-body resistance training on appetite and leptin response and to verify the potential involvement of lactate and autonomic modulation during this response in trained men. Twelve recreationally resistance-trained men (age = 26.1 ± 5.5 years) performed 3 randomized trials in 3 conditions: upper body (UB), lower body (LB), and full body (FB). The subjective rating of hunger was obtained through a visual analog scale. Leptin and lactate concentration were evaluated at rest, immediately after exercise, and during recovery. Heart rate variability in the time and frequency domains was recorded at baseline and during recovery (until 60 minutes after exercise) to assess autonomic modulation. The FB condition induced lower subjective hunger ratings than the UB at Post-1 hour (p < 0.05) and a significant difference in the area under the curve between conditions (p = 0.028) with lower hunger sensation for FB in relation to UB (p = 0.041). The FB presented greater lactate concentration and induced slower heart rate variability recovery in relation to UB and LB conditions (p < 0.05), and heart rate variability remained lower until 60 minutes after exercise compared with rest only in the FB condition. There was a significant negative correlation between subjective hunger ratings and lactate concentration only for the FB condition (r = -0.72, p = 0.028). Full-body resistance exercise induced lower subjective hunger ratings after exercise in relation to UB resistance exercise. The FB also induced higher lactate production and slower recovery of autonomic modulation compared with the UB and LB conditions. Future research is necessary to investigate a mechanistic relationship between lactate concentrations and hunger suppression after resistance exercise.

Ghrelin Response to Acute and Chronic Exercise: Insights and Implications from a Systematic Review of the Literature

BACKGROUND

Ghrelin is a peptide hormone predominantly produced by the stomach. It exerts a wide range of functions including stimulating growth hormone release and regulating appetite, food intake, and glucose and lipid metabolism. Since physical exercise affects all these aspects, a particular interest is accorded to the relationship between ghrelin and exercise. This systematic review aimed to summarize the current available data on the topic for a better understanding of the relationship.

METHODS

An extensive computerized search was performed in the PubMed and SPORTDiscus databases for retrieving relevant articles. The search contained the following keywords: ghrelin, appetite-related peptides, gastrointestinal peptides, gastrointestinal hormones, exercise, acute exercise, chronic exercise, training, and physical activity. Studies investigating the effects of acute/chronic exercise on circulating forms of ghrelin were included.

RESULTS

The initial search identified 840 articles. After screening, 80 articles were included. Despite a heterogeneity of studies and a variability of the findings, the review suggests that acute exercise suppresses acyl ghrelin production regardless of the participants and the exercise characteristics. Long- and very long-term exercise training programs mostly resulted in increased total and des-acyl ghrelin production. The increase is more noticeable in overweight/obese individuals, and is most likely due to weight loss resulting from the training program.

CONCLUSION

The review suggests that exercise may impact ghrelin production. While the precise mechanisms are unclear, the effects are likely due to blood flow redistribution and weight loss for acute and chronic exercise, respectively. These changes are expected to be metabolically beneficial. Further research is needed for a better understanding of the relationship between ghrelin and exercise.

Unexpected Association of Desacyl-Ghrelin with Physical Activity and Chronic Food Restriction: A Translational Study on Anorexia Nervosa

Anorexia nervosa (AN) is a severe metabopsychiatric disorder characterised by caloric intake restriction and often excessive physical exercise. Our aim is to assess in female AN patients and in a rodent model, the co-evolution of physical activity and potential dysregulation of acyl—(AG) and desacyl—(DAG) ghrelin plasma concentrations during denutrition and weight recovery. AN inpatients were evaluated at inclusion (T0, n = 29), half—(T1) and total (T2) weight recovery, and one month after discharge (T3, n = 13). C57/Bl6 mice with access to a running wheel, were fed ad libitum or submitted to short—(15 days) or long—(50 days) term quantitative food restriction, followed by refeeding (20 days). In AN patients, AG and DAG rapidly decreased during weight recovery (T0 to T2), AG increased significantly one-month post discharge (T3), but only DAG plasma concentrations at T3 correlated negatively with BMI and positively with physical activity. In mice, AG and DAG both increased during short- and long-term food restriction. After 20 days of ad libitum feeding, DAG was associated to persistence of exercise alteration. The positive association of DAG with physical activity during caloric restriction and after weight recovery questions its role in the adaptation mechanisms to energy deprivation that need to be considered in recovery process in AN.

A phase II, open-label clinical trial on the combination therapy with medium-chain triglycerides and ghrelin in patients with chronic obstructive pulmonary disease

The aim of this study was to investigate the effect of activated ghrelin with dietary octanoic acids or medium-chain triglyceride (MCT) administration to underweight patient with chronic obstructive pulmonary disease (COPD). Eleven severe and very severe COPD patients received a 5-day treatment with edible MCT. Sequentially, 10 patients received a 3-week combination treatment with MCT and intravenous acyl ghrelin. Five-day MCT treatment increased endogenous acyl ghrelin (p = 0.0049), but the total ghrelin level was unchanged. MCT-ghrelin combination treatment improved the peak oxygen uptake (p = 0.0120) during whole treatment course. This effect was attributed to the resultant improvements in cardiac function by O2 pulse, and to the difference between inspired and expired oxygen concentration rather than minute ventilation. Addition of dietary MCT to ghrelin treatment improved the aerobic capacity of underweight COPD patients, likely by mechanisms of increased O2 delivery through improvements in primary cardiocirculatory and muscular crosstalk.

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.

Insulin Pump Therapy - Influence on Body Fat Redistribution, Skeletal Muscle Mass and Ghrelin, Leptin Changes in T1D Patients

BACKGROUND

To report changes in body composition and biochemical parameters in patients with type 1 diabetes mellitus (T1D) after switching from multiple daily injection (MDI) to continuous subcutaneous insulin infusion (CSII).

METHODS

31 patients switched over from MDI to CSII. Body composition, biochemical parameters, glycaemic variability (GV) and level of physical activity were evaluated before and 6 months on CSII.

RESULTS

In both sexes, we found an increase in skeletal muscle mass (SMM), (p = 0.008; 0.008). In men, there was mainly a decrease in visceral fat area (VFA), (p = 0.028) and in women there was decrease of total body fat (TBF), (p = 0.020) and non-significant decrease of VFA (p = 0.098). SMM inversely correlated with VFA in men (p = -0.001) and with TBF in women (p = -0.005 ). GV was decreased generally and correlated inversely with TBF in men only (p = -0.026). Physical activity was increased and correlated inversely with VFA in men (p = -0.002) and in women (p = -0.006).

CONCLUSIONS

Using CSII in T1D leads to a significant increase of SMM in both sexes to a decrease of VFA in men and to a non-significant decrease of VFA in women. Changes in adipose tissue and SMM were also related to increased physical activity and to decreased GV.

Potential involvement of lactate and interleukin-6 in the appetite-regulatory hormonal response to an acute exercise bout

This study examines the involvement of two potential mechanisms (lactate and IL-6) that may explain the intensity-dependent effects of acute exercise on appetite-related parameters. Our findings support a clear intensity-dependent paradigm for appetite-regulation following exercise, as highlighted by the change in acylated ghrelin and the suppression of appetite and energy intake after vigorous exercise (continuous and intermittent). Further, our findings extend previous work in animal/cell models by providing evidence for the potential role of lactate and IL-6 in mediating changes in appetite-related parameters following exercise in humans.

High-intensity exercise suppresses appetite partly through changes in peripheral appetite-regulating hormones. Lactate and IL-6 mediate the release of these hormones in animal/cell models and may provide a mechanistic link between exercise intensity and appetite regulation. The current study examined changes in appetite-regulating hormones, lactate, and IL-6 after different intensities of running. Eight males completed four experimental sessions: 1) moderate-intensity continuous training (MICT; 65% V̇o_2max); 2) vigorous-intensity continuous training (VICT; 85% V̇o_2max); 3) sprint interval training (SIT; repeated “all-out” sprints); and 4) Control (CTRL; no exercise). Acylated ghrelin, active glucagon-like peptide-1 (GLP-1), total peptide YY (PYY), lactate, IL-6, and appetite perceptions were measured pre-, immediately postexercise, 30 min postexercise, and 90 min postexercise. Energy intake was recorded over 3 days. VICT and SIT suppressed ghrelin (P < 0.001), although SIT elicited a greater (P = 0.016 vs. MICT) and more prolonged (P < 0.001 vs. all sessions) response. GLP-1 increased immediately after MICT (P < 0.001) and 30 min after VICT (P < 0.001) and SIT (P < 0.002), while VICT elicited a greater postexercise increase in PYY vs. MICT (P = 0.027). Postexercise changes in blood lactate and IL-6 correlated with the area under the curve values for ghrelin (r = −0.60, P < 0.001) and GLP-1 (r = 0.42, P = 0.017), respectively. Appetite was suppressed after exercise (P < 0.001), although more so after VICT (P < 0.027) and SIT (P < 0.001) vs. MICT, and energy intake was reduced on the day after VICT (P < 0.017 vs. MICT and CTRL) and SIT (P = 0.049 vs. MICT). These findings support an intensity-dependent paradigm for appetite regulation following exercise and highlight the potential involvement of lactate and IL-6.

NEW & NOTEWORTHY This study examines the involvement of two potential mechanisms (lactate and IL-6) that may explain the intensity-dependent effects of acute exercise on appetite-related parameters. Our findings support a clear intensity-dependent paradigm for appetite regulation following exercise, as highlighted by the change in acylated ghrelin and the suppression of appetite and energy intake after vigorous exercise (continuous and intermittent). Further, our findings extend previous work in animal/cell models by providing evidence for the potential role of lactate and IL-6 in mediating changes in appetite-related parameters following exercise in humans.

Intracerebroventricular injection of ghrelin decreases wheel running activity in rats

There is an increasing interest in elucidating the molecular mechanisms by which voluntary exercise is regulated. In this study, we examined how the central nervous system regulates exercise. We used SPORTS rats, which were established in our laboratory as a highly voluntary murine exercise model. SPORTS rats showed lower levels of serum ghrelin compared with those of the parental line of Wistar rats. Intracerebroventricular and intraperitoneal injection of ghrelin decreased wheel-running activity in SPORTS rats. In addition, daily injection of the ghrelin inhibitor JMV3002 into the lateral ventricles of Wistar rats increased wheel-running activity. Co-administration of obestatin inhibited ghrelin-induced increases in food intake but did not inhibit ghrelin-induced suppression of voluntary exercise in rats. Growth hormone secretagogue receptor (GHSR) in the hypothalamus and hippocampus of SPORTS rats was not difference that in control rats. We created an arcuate nucleus destruction model by administering monosodium glutamate (MSG) to neonatal SPORTS rats. Injection of ghrelin into MSG-treated rats decreased voluntary exercise but did not increase food intake, suggesting that wheel-running activity is not controlled by the arcuate nucleus neurons that regulate feeding. These results provide new insights into the mechanism by which ghrelin regulates voluntary activity independent of arcuate nucleus neurons.

The Effect of a 20 km Run on Appetite Regulation in Long Distance Runners

The purpose of the present study was to investigate appetite-related hormonal responses and energy intake after a 20 km run in trained long distance runners. Twenty-three male long-distance runners completed two trials: either an exercise trial consisting of a 20 km outdoor run (EX) or a control trial with an identical period of rest (CON). Blood samples were collected to determine plasma acylated ghrelin, peptide YY_3-36 (PYY_3-36) and other hormonal and metabolite concentrations. Energy intake during a buffet test meal was also measured 30 min after the exercise or rest periods. Although plasma acylated ghrelin concentrations were significantly decreased after the 20 km run (p < 0.05), plasma PYY_3-36 did not change significantly following exercise. Absolute energy intake during the buffet test meal in EX (1325 ± 55 kcal) was significantly lower than that in CON (1529 ± 55 kcal), and there was a relatively large degree of individual variability for exercise-induced changes in energy intake (−40.2% to 12.8%). However, exercise-induced changes in energy intake were not associated with plasma acylated ghrelin or PYY_3-36 responses. The results demonstrated that a 20 km run significantly decreased plasma acylated ghrelin concentrations and absolute energy intake among well-trained long distance runners.

Effect of heat exposure and exercise on food intake regulation: A randomized crossover study in young healthy men

OBJECTIVE

The effect of physical activity on food intake regulation may be moderated by environmental temperature. The aim of the study was to determine the single and combined effects of metabolic activity and temperature on energy intake and its hormonal regulation.

METHODS

A randomized crossover study was conducted in the laboratory. Ten healthy and physically active young Afro-Caribbean men participated in four experimental sessions (rest at 22°C and 31°C and cycling at 60% of their maximal oxygen uptake at 22°C and 31°C, all for 40 min). Each test period was followed by a 30-min recovery period and then an ad libitum meal. The main outcome measures were energy balance, subjective appetite, and plasma pancreatic polypeptide (PP), cholecystokinin (CCK) and ghrelin concentrations.

RESULTS

Relative energy intake was significantly decreased whereas plasma PP was increased in the exercise conditions (p=0.004 and p=0.002, respectively). Postprandial levels of CCK were elevated only in the rest conditions. Exposure to heat induced a decrease in plasma ghrelin (p=0.031).

CONCLUSIONS

Exercise induced a short-term energy deficit. However, modifications in the hormonal regulation of food intake in response to short-term heat or heat and exercise exposure seem to be minor and did not induce changes in energy intake. This trial was registered at clinicaltrials.gov as NCT02157233.

A New Strategy Using Rikkunshito to Treat Anorexia and Gastrointestinal Dysfunction

Because the clinical condition of gastrointestinal dysfunction, including functional dyspepsia, involves tangled combinations of pathologies, there are some cases of insufficient curative efficacy. Thus, traditional herbal medicines (Kampo medicines) uniquely developed in Japan are thought to contribute to medical treatment for upper gastrointestinal symptoms. Rikkunshito is a Kampo medicine often used to treat dyspeptic symptoms. Over the past few years, several studies have investigated the efficacy of rikkunshito for dysmotility, for example, upper abdominal complaints, in animals and humans. Rikkunshito ameliorated the decrease in gastric motility and anorexia in cisplatin-treated rats, stress-loaded mice, and selective serotonin reuptake inhibitor-treated rats by enhancing plasma ghrelin levels via serotonin2B/2C receptor antagonism. In addition, rikkunshito ameliorated the decrease in food intake in aged mice and stress-loaded decreased gastric motility via enhanced ghrelin receptor signaling. Several clinical studies revealed that rikkunshito was effective in ameliorating upper gastrointestinal symptoms, including dyspepsia, epigastric pain, and postprandial fullness. In this review, we discuss these studies and propose additional evidence-based research that may promote the clinical use of Kampo medicines, particularly rikkunshito, for treating anorexia and gastrointestinal dysfunction.

The effects of two different exercise programmes on adipose tissue hormones in sedentary middle-aged women

Adipokines play an important role in obesity and related inflammatory disorders. We aimed to determine the effects of exercise training on serum adipokines. Forty sedentary women were randomly assigned to two groups as aerobic (AE) and core exercise (CE). The exercise programmes were performed 4 days a week for 16 weeks. Blood samples were taken before and after the 8 and 16 weeks training period. Percent changes of each parameter were calculated. Sixteen weeks of exercise caused significant decrease in body weight and fat mass (p < 0.001), significant increase in adiponectin (16.1% in AE, 15.8% in CE group, p < 0.05) and resistin levels (21.1% in AE and 26.6% in CE group, p < 0.05) but had no effect on leptin and ghrelin levels. Eight weeks of exercise had no effect on adipokines except leptin. These data suggest that both exercise programmes have improving effects on body composition, adiponectin and resistin levels.

Effects of Cigarette Smoking on Plasma Concentration of the Appetite-Regulating Peptide Ghrelin

BACKGROUND

Weight gain is a common but only a partially understood consequence of smoking cessation. Existing data suggest modulating effects of the orexigenic peptide ghrelin on food intake. The aim of the present study was to investigate the effect of tobacco withdrawal on plasma concentration of acetylated and total ghrelin.

METHODS

Fifty four normal-weighted smokers and 30 non-smoking healthy controls were enrolled in our study. Concentrations of acetylated and total ghrelin were measured in blood plasma drawn two hours after a standardized meal and three hours after the smokers smoked their last cigarette. The severity of tobacco addiction was assessed based on cotinine plasma concentration, the Fagerström Test for Nicotine Dependence (FTND) and the number of cigarettes smoked per day.

RESULTS

The plasma concentration of acetylated ghrelin, but not total ghrelin, was significantly higher in smokers than in non-smokers. Moreover, we found significant negative correlations between acetylated ghrelin and all measures of the severity of nicotine dependence.

CONCLUSIONS

Early abstinence from tobacco smoking seems to be associated with increased plasma concentration of the orexigenic peptide acetylated ghrelin. This could be one reason for increased food craving during nicotine withdrawal and subsequent weight gain. Smokers might compensate these effects by increasing tobacco intake.

Food addiction: an evolving nonlinear science

The purpose of this review is to familiarize readers with the role that addiction plays in the formation and treatment of obesity, type 2 diabetes and disorders of eating. We will outline several useful models that integrate metabolism, addiction, and human relationship adaptations to eating. A special effort will be made to demonstrate how the use of simple and straightforward nonlinear models can and are being used to improve our knowledge and treatment of patients suffering from nutritional pathology. Moving forward, the reader should be able to incorporate some of the findings in this review into their own practice, research, teaching efforts or other interests in the fields of nutrition, diabetes, and/or bariatric (weight) management.

Seven transmembrane G protein-coupled receptor repertoire of gastric ghrelin cells

The molecular mechanisms regulating secretion of the orexigenic-glucoregulatory hormone ghrelin remain unclear. Based on qPCR analysis of FACS-purified gastric ghrelin cells, highly expressed and enriched 7TM receptors were comprehensively identified and functionally characterized using in vitro, ex vivo and in vivo methods. Five Gαs-coupled receptors efficiently stimulated ghrelin secretion: as expected the β1-adrenergic, the GIP and the secretin receptors but surprisingly also the composite receptor for the sensory neuropeptide CGRP and the melanocortin 4 receptor. A number of Gαi/o-coupled receptors inhibited ghrelin secretion including somatostatin receptors SSTR1, SSTR2 and SSTR3 and unexpectedly the highly enriched lactate receptor, GPR81. Three other metabolite receptors known to be both Gαi/o- and Gαq/11-coupled all inhibited ghrelin secretion through a pertussis toxin-sensitive Gαi/o pathway: FFAR2 (short chain fatty acid receptor; GPR43), FFAR4 (long chain fatty acid receptor; GPR120) and CasR (calcium sensing receptor). In addition to the common Gα subunits three non-common Gαi/o subunits were highly enriched in ghrelin cells: GαoA, GαoB and Gαz. Inhibition of Gαi/o signaling via ghrelin cell-selective pertussis toxin expression markedly enhanced circulating ghrelin. These 7TM receptors and associated Gα subunits constitute a major part of the molecular machinery directly mediating neuronal and endocrine stimulation versus metabolite and somatostatin inhibition of ghrelin secretion including a series of novel receptor targets not previously identified on the ghrelin cell.

Acute aerobic exercise differentially alters acylated ghrelin and perceived fullness in normal-weight and obese individuals

Adiposity alters acylated ghrelin concentrations, but it is unknown whether adiposity alters the effect of exercise and feeding on acylated ghrelin responses. Therefore, the purpose of this study was to determine whether adiposity [normal-weight (NW) vs. obese (Ob)] influences the effect of exercise and feeding on acylated ghrelin, hunger, and fullness. Fourteen NW and 14 Ob individuals completed two trials in a randomized counterbalanced fashion, including a prior exercise trial (EX) and a no exercise trial (NoEX). During the EX trial, the participants performed 1 h of treadmill walking (55–60% peak O2 uptake) during the evening, 12 h before a 4-h standardized mixed meal test. Frequent blood samples were taken and analyzed for acylated ghrelin, and a visual analog scale was used to assess perceived hunger and fullness. In NW individuals, EX, compared with NoEX, reduced fasting acylated ghrelin concentrations by 18% ( P = 0.03), and, in response to feeding, the change in acylated ghrelin ( P = 0.02) was attenuated by 39%, but perceived hunger and fullness were unaltered. In Ob individuals, despite no changes in fasting or postprandial acylated ghrelin concentrations with EX, postprandial fullness was attenuated by 46% compared with NoEX ( P = 0.05). In summary, exercise performed the night before a meal suppresses acylated ghrelin concentrations in NW individuals without altering perceived hunger or fullness. In Ob individuals, despite no changes in acylated ghrelin concentrations, EX reduced the fullness response to the test meal. Acylated ghrelin and perceived fullness responses are differently altered by acute aerobic exercise in NW and Ob individuals.

Impaired postprandial fullness in Type 2 diabetic subjects is rescued by acute exercise independently of total and acylated ghrelin

Ghrelin levels are suppressed in obese subjects and subjects with Type 2 diabetes mellitus (T2DM). Exercise-stimulated decreases in plasma ghrelin are a proposed mediator of exercise-induced satiety in healthy subjects. However, exercise-induced satiety and the impact of impaired ghrelin levels in obesity-related disease are poorly understood. Therefore our objective was to investigate exercise-induced postprandial satiety and ghrelin responses in overweight subjects with T2DM ( N = 8) and healthy controls ( N = 7). Visual analog scale satiety questionnaires (assessing hunger, thirst, food that could be eaten, nausea, and fullness) and circulating levels of glucose, insulin, and total and acylated ghrelin were measured at baseline and in response to a 75 g oral glucose load, provided immediately after an aerobic exercise bout (1 h at 50% Wmax) or no exercise (rest trial), on two separate occasions. Baseline levels of total (284.4 ± 15.9 and 397.6 ± 35.2 pmol/l) and acylated ghrelin (7.9 ± 1.0 and 13.7 ± 1.2 pmol/l) were lower in subjects with T2DM compared with healthy subjects ( P < 0.05). In the rest trial, post- vs. preprandial feeling of fullness increased in healthy subjects but decreased in subjects with T2DM (healthy vs. T2DM; P < 0.05). Exercise increased postprandial fullness in the T2DM group ( P < 0.05), while plasma ghrelin levels were unaffected. Our data suggest that the presence of T2DM likely drives suppressed ghrelin levels and poor appetite regulation, but a single exercise bout is sufficient to restore oral glucose-induced fullness independently of ghrelin.

Prandial ghrelin attenuation provides evidence that des-acyl ghrelin may be an artifact of sample handling in human plasma

BACKGROUND

Plasma acyl and des-acyl ghrelin are thought of as components of total ghrelin, but this has never been validated using ex vivo spiking experiments, human sample collection comparisons and fit-for-purpose translatable assays.

RESULTS

Acyl ghrelin plasma stability was analyzed by LC-MS/MS and it revealed that acyl ghrelin is enzymatically and chemically converted to des-acyl ghrelin in the presence of active serine proteases and HCl. ELISAs with less than 30% total error were used to assess acyl ghrelin behavior in matched authentic human samples. Acyl and total ghrelin were not statistically different in 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride samples and acyl ghrelin losses in K(2)EDTA plasma were accounted for in des-acyl ghrelin formation.

CONCLUSION

Acyl ghrelin is total ghrelin and des-acyl ghrelin should not be detectible in healthy human plasma under optimal sample handling and assaying conditions.

Exercise and ghrelin. A narrative overview of research

Since its discovery in 1999, ghrelin has been implicated in a multiplicity of physiological activities. Most notably, ghrelin has an important influence on energy metabolism and after the identification of its potent appetite stimulating effects ghrelin has been termed the 'hunger hormone'. Exercise is a stimulus which has a significant impact on energy homeostasis and consequently a substantial body of research has investigated the interaction between exercise and ghrelin. This narrative review provides an overview of research relating to the acute and chronic effects of exercise on circulating ghrelin (acylated, unacylated and total). To enhance study comparability, the scope of this review is limited to research undertaken in adult humans and consequently studies involving children and animals are not discussed. Although there is significant ambiguity within much of the early research, our review suggests that acute exercise transiently interferes with the production of acylated ghrelin. Furthermore, the consensus of evidence indicates that exercise training does not influence circulating ghrelin independent of weight loss. Additional research is needed to verify and extend the available literature, particularly by uncovering the mechanisms governing acute exercise-related changes and characterising responses in other populations such as females, older adults, and the obese.

Effect of exercise on appetite-regulating hormones in overweight women

Over the past decade, our knowledge of how homeostatic systems regulate food intake and body weight has increased with the discovery of circulating peptides such as leptin, acyl ghrelin, des-acyl ghrelin and obestatin. These hormones regulate the appetite and food intake by sending signals to the brain regarding the body's nutritional status. The purpose of this study was to investigate the response of appetite-regulating hormones to exercise. Nine overweight women undertook two 2 h trials in a randomized crossover design. In the exercise trial, subjects ran for 60 min at 50% of maximal oxygen uptake followed by a 60 min rest period. In the control trial, subjects rested for 2 h. Obestatin, acyl ghrelin, des-acyl ghrelin and leptin concentrations were measured at baseline and at 20, 40, 60, 90 and 120 min after baseline. A two-way ANOVA revealed a significant (P < 0.05) interaction effect for leptin and acyl ghrelin. However, changes in obestatin and des-acyl ghrelin concentration were statistically insignificant (P > 0.05). The data indicated that although acute treadmill exercise resulted in a significant change in acyl ghrelin and leptin levels, it had no effect on plasma obestatin and des-acyl ghrelin levels.

Ghrelin - a pleiotropic hormone secreted from endocrine x/a-like cells of the stomach

The gastric X/A-like endocrine cell receives growing attention due to its peptide products with ghrelin being the best characterized. This peptide hormone was identified a decade ago as a stimulator of food intake and to date remains the only known peripherally produced and centrally acting orexigenic hormone. In addition, subsequent studies identified numerous other functions of this peptide including the stimulation of gastrointestinal motility, the maintenance of energy homeostasis and an impact on reproduction. Moreover, ghrelin is also involved in the response to stress and assumed to play a role in coping functions and exert a modulatory action on immune pathways. Our knowledge on the regulation of ghrelin has markedly advanced during the past years by the identification of the ghrelin acylating enzyme, ghrelin-O-acyltransferase, and by the description of changes in expression, activation, and release under different metabolic as well as physically and psychically challenging conditions. However, our insight on regulatory processes of ghrelin at the cellular and subcellular levels is still very limited and warrants further investigation.

Unacylated ghrelin is associated with changes in insulin sensitivity and lipid profile during an exercise intervention

OBJECTIVE

Ghrelin has been implicated in energy homeostasis, body weight regulation and glucose metabolism. Level of unacylated ghrelin (UAG), but not acylated ghrelin (AG), has been suggested to increase during long-term exercise. However, the association of the level of UAG with exercise-induced changes of insulin sensitivity and lipid metabolism has not been previously investigated. We hypothesized that an increase in UAG level in response to a long-term exercise programme improves insulin sensitivity and associated lipid profile, independently of weight loss.

DESIGN, PATIENTS AND MEASUREMENTS

A prospective study of 552 young men (mean age 19·3 and range 19-28 years) undergoing military service with structured 6-month exercise training programme. Exercise performance, clinical and biochemical measurements were obtained at baseline and follow-up. Association between UAG level and fasting glucose, insulin, insulin sensitivity and lipid levels were evaluated.

RESULTS

An overall increase in the level of UAG was observed during the 6-month follow-up (P < 0·001), which was largest among those with weight loss ≥ 2·5% or among those whose reduction in waist circumference was largest (P = 0·007 and P < 0·001, respectively). A change in UAG level correlated inversely with a change in fasting glucose and insulin levels, HOMA-IR, total cholesterol and total triglyceride levels (P < 0·001 for all). The association between change in the UAG level and the change in insulin sensitivity was independent of weight loss or reduction in waist circumference.

CONCLUSIONS

Increase in UAG level was associated with improved insulin sensitivity via mechanisms independent of weight loss during an intensive, long-term exercise intervention in young healthy men.

Stress-related alterations of acyl and desacyl ghrelin circulating levels: mechanisms and functional implications

Ghrelin is the only known peripherally produced and centrally acting peptide hormone that stimulates food intake and digestive functions. Ghrelin circulates as acylated and desacylated forms and recently the acylating enzyme, ghrelin-O-acyltransferase (GOAT) and the de-acylating enzyme, thioesterase 1/lysophospholipase 1 have been identified adding new layers of complexity to the regulation of ghrelin. Stress is known to alter gastrointestinal motility and food intake and was recently shown to modify circulating ghrelin and GOAT levels with differential responses related to the type of stressors including a reduction induced by physical stressors (abdominal surgery and immunological/endotoxin injection, exercise) and elevation by metabolic (cold exposure, acute fasting and caloric restriction) and psychological stressors. However, the pathways underlying the alterations of ghrelin under these various stress conditions are still largely to be defined and may relate to stress-associated autonomic changes. There is evidence that alterations of circulating ghrelin may contribute to the neuroendocrine and behavioral responses along with sustaining the energetic requirement needed upon repeated exposure to stressors. A better understanding of these mechanisms will allow targeting components of ghrelin signaling that may improve food intake and gastric motility alterations induced by stress.