Ghrelin and the short- and long-term regulation of appetite and body weight

Thyrotropin-Releasing Hormone and Food Intake in Mammals: An Update

Thyrotropin-releasing hormone (TRH; pGlu-His-Pro-NH2) is an intercellular signal produced mainly by neurons. Among the multiple pharmacological effects of TRH, that on food intake is not well understood. We review studies demonstrating that peripheral injection of TRH generally produces a transient anorexic effect, discuss the pathways that might initiate this effect, and explain its short half-life. In addition, central administration of TRH can produce anorexic or orexigenic effects, depending on the site of injection, that are likely due to interaction with TRH receptor 1. Anorexic effects are most notable when TRH is injected into the hypothalamus and the nucleus accumbens, while the orexigenic effect has only been detected by injection into the brain stem. Functional evidence points to TRH neurons that are prime candidate vectors for TRH action on food intake. These include the caudal raphe nuclei projecting to the dorsal motor nucleus of the vagus, and possibly TRH neurons from the tuberal lateral hypothalamus projecting to the tuberomammillary nuclei. For other TRH neurons, the anatomical or physiological context and impact of TRH in each synaptic domain are still poorly understood. The manipulation of TRH expression in well-defined neuron types will facilitate the discovery of its role in food intake control in each anatomical scene.

Pre-prandial plasma liver-expressed antimicrobial peptide 2 (LEAP2) concentration in humans is inversely associated with hunger sensation in a ghrelin independent manner

PURPOSE

The liver-expressed antimicrobial peptide 2 (LEAP2) is a newly recognized peptide hormone that acts via the growth hormone secretagogue receptor (GHSR) blunting the effects of ghrelin and displaying ghrelin-independent actions. Since the implications of LEAP2 are beginning to be elucidated, we investigated if plasma LEAP2 concentration varies with feeding status or sex and whether it is associated with glucose metabolism and appetite sensations.

METHODS

We performed a single test meal study, in which plasma concentrations of LEAP2, ghrelin, insulin and glucose as well as visual analogue scales for hunger, desire to eat, prospective food consumption, fullness were assessed before and 60 min after breakfast in 44 participants (n = 21 females) with normal weight (NW) or overweight/obesity (OW/OB).

RESULTS

Pre-prandial plasma LEAP2 concentration was ~ 1.6-fold higher whereas ghrelin was ~ 2.0-fold lower in individuals with OW/OB (p < 0.001) independently of sex. After adjusting for body mass index (BMI) and sex, pre-prandial plasma LEAP2 concentration displayed a direct relationship with BMI (β: 0.09; 95%CI: 0.05, 0.13; p < 0.001), fat mass (β: 0.05; 95%CI: 0.01, 0.09; p = 0.010) and glycemia (β: 0.24; 95%CI: 0.05, 0.43; p = 0.021), whereas plasma ghrelin concentration displayed an inverse relationship with BMI and fat mass but not with glycemia. Postprandial plasma LEAP2 concentration increased ~ 58% in females with OW/OB (p = 0.045) but not in females with NW or in males. Pre-prandial plasma LEAP2 concentration displayed an inverse relationship with hunger score (β: - 11.16; 95% CI: - 18.52, - 3.79; p = 0.004), in a BMI-, sex- and ghrelin-independent manner.

CONCLUSIONS

LEAP2 emerges as a key hormone implicated in the regulation of metabolism and appetite in humans.

TRIAL REGISTRATION

The study was retrospectively registered in clinicaltrials.gov (April 2023).

CLINICALTRIALS

gov Identifier: NCT05815641.

The Orexin/Hypocretin System, the Peptidergic Regulator of Vigilance, Orchestrates Adaptation to Stress

The orexin/hypocretin neuropeptide family has emerged as a focal point of neuroscientific research following the discovery that this family plays a crucial role in a variety of physiological and behavioral processes. These neuropeptides serve as powerful neuromodulators, intricately shaping autonomic, endocrine, and behavioral responses across species. Notably, they serve as master regulators of vigilance and stress responses; however, their roles in food intake, metabolism, and thermoregulation appear complementary and warrant further investigation. This narrative review provides a journey through the evolution of our understanding of the orexin system, from its initial discovery to the promising progress made in developing orexin derivatives. It goes beyond conventional boundaries, striving to synthesize the multifaceted activities of orexins. Special emphasis is placed on domains such as stress response, fear, anxiety, and learning, in which the authors have contributed to the literature with original publications. This paper also overviews the advancement of orexin pharmacology, which has already yielded some promising successes, particularly in the treatment of sleep disorders.

Efficacy of spironolactone as adjunctive therapy to sodium valproate in bipolar-I disorder: A double-blind, randomized, placebo-controlled clinical trial

INTRODUCTION

Treatment of mood and cognitive symptoms of patients with bipolar disorder is associated with many complications and is generally not associated with therapeutic satisfaction. In this clinical trial, we evaluated the effectiveness of spironolactone in controlling mood and cognitive symptoms, sleep quality, appetite, and body mass index in patients with bipolar disorder in manic episodes.

METHODS

Sixty inpatients with bipolar disorder in manic episodes were treated with spironolactone/placebo in an 8-week randomized, double-blind, placebo-controlled clinical trial. They were evaluated using the Young Mania Rating Scale (YMRS), mini-mental state examination (MMSE), Pittsburgh sleep quality index, Simplified Nutritional Appetite Questionnaire, and body mass index in weeks 1, 4, and 8.

RESULTS

For cognitive impairment (MMSE), there were significant interaction effects of group and time at week 8 (B = -1.60, SE = 0.69, t = -2.33, p = .021) such that individuals in the spironolactone group experienced more improvement in their cognitive performance. For manic symptoms (YMRS), there were no significant interaction effects of group and time at week 8 (B = -2.53, SE = 1.46, t = -1.73, p = .085).

CONCLUSIONS

Considering the promising findings in this clinical trial, further study of spironolactone as adjunctive therapy in bipolar disorder in manic episodes with larger sample sizes, multicenter settings, and longer follow-ups are recommended.

Ghrelin hormone a new molecular modulator between obesity and glomerular damage

The incidence of glomerular diseases is increasing worldwide due to increased prevalence of obesity which is a major risk factor for type-2 diabetes mellitus and cardiovascular disorders.Ghrelin, an orexigenic peptide hormone, has been implicated in obesity, and its impact on the pathology and function of the kidneys was found to be significant. Ghrelin known to regulate energy homeostasis and growth hormone release, has been shown to modulate critical signaling pathways involved in the health and survival of podocytes. These derangements directly affect glomerular function and manifest as impaired glomerular filtration barrier and leakage of albumin into urine. Although the pathological features of the above-mentioned disorders are different, they interestingly lead to similar clinical features of glomerular damage. The pathological events are majorly initiated by endocrine imbalance leading to abnormal activation of downstream signaling pathways involved in the development of glomerulosclerosis. In fact, obesity increases the risk of developing chronic kidney disease by altering the secretion of pro-inflammatory cytokines and adipokines, activating the renin-angiotensin-aldosterone system (RAAS), promoting lipotoxicity, oxidative stress and fibrosis within the kidneys. Whilst these bioregulators are well described, their direct involvement in renal homeostasis is still mostly elusive. This review summarized previous and recent evidence on the endocrine properties of ghrelin and perivascular adipose tissue involved in modulating kidney physiology.

Investigatıon of the effect of weight loss after laparoscopic sleeve gastrectomy on cobb angle, waist and back pain: a prospective study

BACKGROUND

In many studies, it has been stated that obesity causes severe increases in the risks of disc degeneration, vertebral fracture, low back, and back pain. One of the most effective treatment options for obesity is bariatric surgery.

OBJECTIVES

In this study, the effect of weight loss on these parameters was investigated by evaluating the Cobb angle, low back, and back pain.

SETTING

University Hospital METHODS: A total of 89 patients were included in the study. Laparoscopic sleeve gastrectomy (SG) was performed on all patients. In addition, Cobb angle, height, weight, and body mass index (BMI) measurements were recorded at each visit. Investigating the quality and quantity of low back pain and the loss of function caused by the patients; visual analog scale (VAS), Oswestry Low Back Pain Disability Questionnaire (OLBPDQ), Roland-Morris Disability Questionnaire (RMDQ), and SF-36 Quality of Life Questionnaire (SF36) were administered.

RESULTS

According to the preoperative Cobb angles, the decrease in the 6th month (P = .029) and 12th month (P = .007) measurements after the operation was found to be statistically significant (P < .05), but it was found to be clinically insignificant. When the changes in RMDQ, OLBPDQ, VAS, and SF-36 scores were examined, the decrease in the 6th month (P = .001) and 12th month (P = .001) scores after the operation was found to be significant compared to the preoperative scores (P < .01).

CONCLUSIONS

In this study, weight loss after SG improved for patients with chronic low back and back pain and significantly improved their quality of life.

Effects of Bioactive Peptides from Atlantic Salmon Processing By-Products on Oxyntopeptic and Enteroendocrine Cells of the Gastric Mucosa of European Seabass and Gilthead Seabream

The present study was designed to evaluate the effects of dietary levels of bioactive peptides (BPs) derived from salmon processing by-products on the presence and distribution of peptic cells (oxyntopeptic cells, OPs) and enteric endocrine cells (EECs) that contain GHR, NPY and SOM in the gastric mucosa of European seabass and gilthead seabream. In this study, 27 seabass and 27 seabreams were divided into three experimental groups: a control group (CTR) fed a control diet and two groups fed different levels of BP to replace fishmeal: 5% BP (BP5%) and 10% BP (BP10%). The stomach of each fish was sampled and processed for immunohistochemistry. Some SOM, NPY and GHR-IR cells exhibited alternating "open type" and "closed type" EECs morphologies. The BP10% group (16.8 ± 7.5) showed an increase in the number of NPY-IR cells compared to CTR (CTR 8.5 ± 4.8) and BP5% (BP10% vs. CTR p ≤ 0.01; BP10% vs. BP5% p ≤ 0.05) in the seabream gastric mucosa. In addition, in seabream gastric tissue, SOM-IR cells in the BP 10% diet (16.8 ± 3.5) were different from those in CTR (12.5 ± 5) (CTR vs. BP 10% p ≤ 0.05) and BP 5% (12.9 ± 2.5) (BP 5% vs. BP 10% p ≤ 0.01). EEC SOM-IR cells increased at 10% BP (5.3 ± 0.7) compared to 5% BP (4.4 ± 0.8) (5% BP vs. 10% BP p ≤ 0.05) in seabass. The results obtained may provide a good basis for a better understanding of the potential of salmon BPs as feed ingredients for seabass and seabream.

Inhibition of ghrelin activity by the receptor antagonist [D-Lys3]-GHRP-6 enhances hepatic fatty acid oxidation and gluconeogenesis in a growing pig model

Despite its central role in regulating energy intake and metabolism, ghrelin is little understood when it comes to its effects on hepatic lipid and glucose metabolism. Growing pigs were intravenously injected with ghrelin receptor antagonist [D-Lys3]-GHRP-6 (DLys; 6 mg/kg body weight) for seven days to determine whether ghrelin plays a role in glucose and lipid metabolism. DLys treatment significantly reduced body weight gain and adipose histopathology found that DLys treatment dramatically reduced adipocyte size. DLys treatment significantly increased serum NEFA and insulin levels, hepatic glucose level and HOMA-IR, and significantly decreased serum TBA level of growing pigs after fasting. Moreover, DLys treatment changed the dynamics of serum metabolic parameters, including glucose, NEFA, TBA, insulin, GH, leptin, and cortisol. Liver transcriptome showed that DLys treatment affected the metabolism-related pathways. Compared with the control group, adipose tissue lipolysis (the adipose triglyceride lipase level was significantly increased), hepatic gluconeogenesis (the G6PC protein level was significantly increased) and fatty acid oxidation (the CPT1A protein level was significantly increased) were promoted in the DLys group. DLys treatment expanded degrees of oxidative phosphorylation in the liver, coming about in a higher NAD+ /NADH proportion and enactment of the SIRT1 signaling pathway. Additionally, the liver protein levels of the DLys group were significantly higher than those of the control group for GHSR, PPAR alpha, and PGC-1. To summarize, inhibition of ghrelin activity can significantly affect metabolism and alter energy levels by enhancing fat mobilization, hepatic fatty acid oxidation and gluconeogenesis without affecting fatty acid uptake and synthesis in the liver.

Ghrelin and glucagon-like peptide-1 according to body adiposity and glucose homeostasis

Objective

We investigated the biological behavior of ghrelin and glucagon-like peptide-1 (GLP-1) after a standard liquid meal according to body adiposity and glucose homeostasis.

Subjects and methods

This cross-sectional study included 41 individuals (92.7% women; aged 38.3 ± 7.8 years; BMI 32.2 ± 5.5 kg/m2) allocated into three groups according to body adiposity and glucose homeostasis, as follows: normoglycemic eutrophic controls (CON, n = 11), normoglycemic with obesity (NOB, n = 15), and dysglycemic with obesity (DOB, n = 15). They were tested at fasting and 30 and 60 min after the ingestion of a standard liquid meal in which we measured active ghrelin, active GLP-1, insulin, and plasma glucose levels.

Results

As expected, DOB exhibited the worst metabolic status (glucose, insulin, HOMA-IR, HbA1c) and an inflammatory status (TNF-α) at fasting, besides a more significant increase in glucose than postprandial NOB (p ≤ 0.05). At fasting, no differences between groups were detected in lipid profile, ghrelin, and GLP-1 (p ≥ 0.06). After the standard meal, all groups exhibited a reduction in ghrelin levels between fasting vs. 60 min (p ≤ 0.02). Additionally, we noticed that GLP-1 and insulin increased equally in all groups after the standard meal (fasting vs. 30 and 60 min). Although glucose levels increased in all groups after meal intake, these changes were significantly more significant in DOB vs. CON and NOB at 30 and 60 min post-meal (p ≤ 0.05).

Conclusion

Time course of ghrelin and GLP-1 levels during the postprandial period was not influenced by body adiposity or glucose homeostasis. Similar behaviors occurred in controls and patients with obesity, independently of glucose homeostasis.

Ghrelin proteolysis increases in plasma of men, but not women, with obesity

AIMS

Since plasma ghrelin can undergo des-acylation and proteolysis, the aim of this study was to investigate the extent to which an enhancement of these reactions is associated to the decrease of ghrelin in plasma after food intake or in individuals with obesity.

MAIN METHODS

we performed an intervention cross-sectional study, in which levels of ghrelin, desacyl-ghrelin (DAG), glucose, insulin, ghrelin des-acylation and ghrelin proteolysis were assessed in plasma before and after a test meal in 40 people (n = 21 males) with normal weight (NW, n = 20) or overweight/obesity (OW/OB, n = 20).

KEY FINDINGS

Preprandial ghrelin and DAG levels were lower, whereas preprandial ghrelin proteolysis was ∼4.6-fold higher in plasma of males with OW/OB. In males, ghrelin proteolysis positively correlated with glycemia. Ghrelin and DAG levels were also lower in females with OW/OB, but preprandial ghrelin proteolysis was not different between females with NW or OW/OB. Ghrelin and DAG levels decreased postprandially in males and females, independently of BMI, and ghrelin proteolysis increased postprandially ∼2 folds only in individuals with NW. Ghrelin des-acylation remained unaffected by BMI or feeding status in both sexes.

SIGNIFICANCE

Current study shows that ghrelin proteolysis increases in males with obesity as well as after meal in lean individuals. Therefore, ghrelin proteolysis may be an important checkpoint and, consequently, a putative pharmacological target to control circulating ghrelin levels in humans.

Ghrelin, not corticosterone, is associated with transitioning of phenotypic states in a migratory Galliform

In both captive and free-living birds, the emergence of the migratory phenotype is signalled by rapid and marked increases in food intake and fuelling, as well as changes in amount of nocturnality or migratory restlessness. The metabolic hormone corticosterone and, as more recently suggested, the gut-derived hormone ghrelin have been suggested to play a role in mediating such phenomenal phenotypic flexibility given that they both regulate fuel metabolism and locomotion across vertebrate taxa. Here, using the Common quail (Coturnix coturnix) as our study species, we induced autumn migration followed by a non-migratory wintering phase through controlled changes in daylight. We thus compared plasma corticosterone and ghrelin concentrations between the two sampling phases and assessed whether these hormones might reflect the migratory state. While we found no differences in plasma corticosterone between the two sampling phases and no link of this hormone with changes in body mass, levels of food intake or migratory restlessness, the migratory birds had substantially higher levels of plasma ghrelin relative to the non-migratory birds. Furthermore, while ghrelin did not correlate with the gain in body mass over the entire pre-migratory fuelling phase (over an average of nine weeks preceding blood sampling), plasma ghrelin did positively correlate with the gain in body mass observed during the final fattening stages (over an average of three weeks preceding blood sampling). Again, variation in plasma ghrelin also reflected the amount of body mass depleted over both the long- and short-time frame as birds returned to their non-migratory baseline - lower levels of plasma ghrelin consistently correlated with larger losses in body mass. Thus, while our data do not highlight a role of the hormone corticosterone in sustaining pre-migratory fattening as shown in other bird species, they do add evidence for a potential role of ghrelin in mediating migratory behaviour and further suggest that this hormone might be important in regulating the transitioning of migratory states, possibly by promoting fuel mobilisation and usage.

The Impact of Job-Demand-Control-Support on Leptin and Ghrelin as Biomarkers of Stress in Emergency Healthcare Workers

Despite the available literature on the consequences of night shiftwork on stress and food intake, its impact on leptin and ghrelin has never been studied. We previously demonstrated that leptin and ghrelin were biomarkers related to stress, and acute stress-induced a decrease in leptin levels and an increase in ghrelin levels. We performed a prospective observational study to assess the influence of night work, nutrition, and stress on the levels of ghrelin and leptin among emergency healthcare workers (HCWs). We took salivary samples at the beginning of a day shift and/or at the end of a night shift. We also monitored stress using the job demand-control-support model of Karasek. We recorded 24-h food intake during the day shift and the consecutive night shift and during night work and the day before. We included 161 emergency HCWs. Emergency HCWs had a tendency for decreased levels of leptin following the night shift compared to before the dayshift (p = 0.067). Furthermore, the main factors explaining the decrease in leptin levels were an increase in job-demand (coefficient -54.1, 95 CI -99.0 to -0.92) and a decrease in job control (-24.9, -49.5 to -0.29). Despite no significant changes in ghrelin levels between shifts, social support was the main factor explaining the increase in ghrelin (6.12, 0.74 to 11.5). Food intake (kcal) also had a negative impact on leptin levels, in addition to age. Ghrelin levels also decreased with body mass index, while age had the opposite effect. In conclusion, we confirmed that ghrelin and leptin as biomarkers of stress were directly linked to the job demand-control-support model of Karasek, when the main cofounders were considered.

Heat stress in pigs and broilers: role of gut dysbiosis in the impairment of the gut-liver axis and restoration of these effects by probiotics, prebiotics and synbiotics

Heat stress is one of the most challenging stressors for animal production due to high economic losses resulting from impaired animal’s productivity, health and welfare. Despite the fact that all farm animal species are susceptible to heat stress, birds and pigs are particularly sensitive to heat stress due to either lacking or non-functional sweat glands. Convincing evidence in the literature exists that gut dysbiosis, a term used to describe a perturbation of commensal gut microbiota, develops in broilers and pigs under heat stress. Owing to the protective role of commensal bacteria for the gut barrier, gut dysbiosis causes a disruption of the gut barrier leading to endotoxemia, which contributes to the typical characteristics of heat stressed broilers and growing and growing-finishing pigs, such as reduced feed intake, decreased growth and reduced lean carcass weight. A substantial number of studies have shown that feeding of probiotics, prebiotics and synbiotics is an efficacious strategy to protect broilers from heat stress-induced gut barrier disruption through altering the gut microbiota and promoting all decisive structural, biochemical, and immunological elements of the intestinal barrier. In most of the available studies in heat stressed broilers, the alterations of gut microbiota and improvements of gut barrier function induced by feeding of either probiotics, prebiotics or synbiotics were accompanied by an improved productivity, health and/or welfare when compared to non-supplemented broilers exposed to heat stress. These findings indicate that the restoration of gut homeostasis and function is a key target for dietary interventions aiming to provide at least partial protection of broilers from the detrimental impact of heat stress conditions. Despite the fact that the number of studies dealing with the same feeding strategy in heat stressed pigs is limited, the available few studies suggest that feeding of probiotics might also be a suitable approach to enhance productivity, health and welfare in pigs kept under heat stress conditions. 

Postprandial Glucose and Gastrointestinal Hormone Responses of Healthy Subjects to Wheat Biscuits Enriched with L-Arginine or Branched-Chain Amino Acids of Plant Origin

The study investigates the effects of wheat biscuits supplemented with plant flours originating from legumes/seeds enriched either in L-arginine (L-arg) or branched-chain amino acids (BCAAs) on postprandial glucose response of healthy subjects. Gastrointestinal hormone and amino acid responses as well as subjective appetite sensations are also evaluated. Subjects consumed wheat-based biscuits, enriched either in L-arg (ArgB) or BCAAs (BCAAsB) or a conventional wheat biscuit (CB) or a glucose solution (GS) in an acute randomized crossover design. Responses of glucose, insulin, ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and glicentin, as well as those of L-arginine, L-leucine, L-isoleucine and L-valine, were evaluated over 180 min. Consumption of ArgB and BCAAsB elicited lower glucose iAUC compared to GS (p < 0.05). A lower iAUC for insulin was observed after consumption of BCAAsB (p < 0.05 compared to CB and ArgB), while ArgB elicited higher iAUC for GLP-1 accompanied by higher glicentin response (p < 0.05 compared to CB). BCAAsB and ArgB increased postprandial amino acid concentrations and caused stronger satiety effects compared to CB. Increasing protein content of wheat biscuits with supplementation of plant flours originating from legumes/seeds decreases postprandial glycemia and provides with healthier snack alternatives which can easily be incorporated into diet.

Ghrelin May Inhibit Inflammatory Response and Apoptosis During Ischemia-Reperfusion Injury

BACKGROUND

Ghrelin, a novel growth hormone-releasing peptide, has both anti-inflammatory and anti-apoptotic effects on human endothelial cells. We evaluated the protective effects of ghrelin against ischemia-reperfusion injury (IRI) in a murine heterotopic cervical heart transplantation model.

METHODS

Donor hearts from C57BL/6J wild-type mice, which were kept in cold saline for 60 minutes, were heterotopically transplanted into C57BL/6J wild-type recipients. A day prior to heterotopic cervical heart transplantation, donor animals received either ghrelin (300 nmol/kg) or saline (0.3 mL) intraperitoneally. Upon reperfusion and postoperative day 1, ghrelin or saline was administered to the recipients. Donor hearts were procured on day 2.

RESULTS

Ghrelin injection did not result in any adverse effects in donors or recipients. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were significantly decreased in the ghrelin group (0.38% ± 0.21% vs 5.74% ± 3.68%; P < .001). Both cleaved caspase-3 activity and Bcl-2/Bax ratio from the ghrelin group were significantly reduced compared to those in the control. Furthermore, the phosphorylated Akt/Akt ratio was higher in the ghrelin group (0.44 ± 0.21 vs 0.14 ± 0.03; P = .043). Nuclear factor-kappa B p65 nuclear translocation was reduced in the ghrelin hearts compared to the controls (3.17% ± 1.84% vs 19.28% ± 13.14%; P = .009). Vascular cell adhesion molecule-1, intracellular adhesion molecule-1, nuclear factor-kappa B, and tumor necrosis factor alpha levels were also significantly reduced in the ghrelin-treated group. No significant difference was observed in 8-isoprostane production between groups.

CONCLUSION

Ghrelin inhibits the inflammatory response and apoptosis during transplant-related IRI. This study demonstrates the protective effects of ghrelin against IRI.

The physiology of experimental overfeeding in animals

BACKGROUND

Body weight is defended by strong homeostatic forces. Several of the key biological mechanisms that counteract weight loss have been unraveled over the last decades. In contrast, the mechanisms that protect body weight and fat mass from becoming too high remain largely unknown. Understanding this aspect of energy balance regulation holds great promise for curbing the obesity epidemic. Decoding the physiological and molecular pathways that defend against weight gain can be achieved by an intervention referred to as 'experimental overfeeding'.

SCOPE OF THE REVIEW

In this review, we define experimental overfeeding and summarize the studies that have been conducted on animals. This field of research shows that experimental overfeeding induces a potent and prolonged hypophagic response that seems to be conserved across species and mediated by unidentified endocrine factors. In addition, the literature shows that experimental overfeeding can be used to model the development of non-alcoholic steatohepatitis and that forced intragastric infusion of surplus calories lowers survival from infections. Finally, we highlight studies indicating that experimental overfeeding can be employed to study the transgenerational effects of a positive energy balance and how dietary composition and macronutrient content might impact energy homeostasis and obesity development in animals.

MAJOR CONCLUSIONS

Experimental overfeeding of animals is a powerful yet underappreciated method to investigate the defense mechanisms against weight gain. This intervention also represents an alternative approach for studying the pathophysiology of metabolic liver diseases and the links between energy balance and infection biology. Future research in this field could help uncover why humans respond differently to an obesogenic environment and reveal novel pathways with therapeutic potential against obesity and cardiometabolic disorders.

Opioid receptor μ, not δ and κ modulate food intake induced by ghrelin in laying chickens

Evidence from animal studies suggests that opioidergic system and gherlin have a regulatory role in food intake, but their interaction(s) have not been studied in laying chickens. So in this study, 4 experiments (each included 4 groups) were designed. The first experiment was performed to evaluate the effect of ghrelin on the cumulative food intake. Experiments 2 to 4 were designed to investigate the possibility of μ, δ, or κ opioid receptors mediating ghrelin-induced hypophagia. All drugs were injected intracerebroventricularly (ICV) at 5 days of age. The results of this study showed that the ICV injection of 1.5 nmol ghrelin did not affect cumulative food intake. But ICV injection of ghrelin with doses of 3 and 6 nmol significantly reduced the cumulative food intake (p<0.05). However, co-injection of ghrelin with NTI, and nor-BNI did not show a significant change in decreased food intake compared to ghrelin. Also, opioid μ receptor gene expression significantly increased (p<0.05), but δ and κ opioid receptors gene expression did not significantly change. These results indicated the opioidergic system is involved in developing ghrelin-induced hypophagic effects in laying chickens. Accordingly, this effect of ghrelin to modify the nutritional behavior is possibly mediated by opioid μ receptor.

Hangry in the field: An experience sampling study on the impact of hunger on anger, irritability, and affect

The colloquial term “hangry” refers to the notion that people become angry when hungry, but very little research has directly determined the extent to which the relationship between hunger and negative emotions is robust. Here, we examined associations between everyday experiences of hunger and negative emotions using an experience sampling method. Sixty-four participants from Central Europe completed a 21-day experience sampling phase in which they reported their hunger, anger, irritability, pleasure, and arousal at five time-points each day (total = 9,142 responses). Results indicated that greater levels of self-reported hunger were associated with greater feelings of anger and irritability, and with lower pleasure. These findings remained significant after accounting for participant sex, age, body mass index, dietary behaviours, and trait anger. In contrast, associations with arousal were not significant. These results provide evidence that everyday levels of hunger are associated with negative emotionality and supports the notion of being “hangry”.

Gut peptide regulation of food intake - evidence for the modulation of hedonic feeding

The number of people living with obesity has tripled worldwide since 1975 with serious implications for public health, as obesity is linked to a significantly higher chance of early death from associated comorbidities (metabolic syndrome, type 2 diabetes, cardiovascular disease and cancer). As obesity is a consequence of food intake exceeding the demands of energy expenditure, efforts are being made to better understand the homeostatic and hedonic mechanisms governing food intake. Gastrointestinal peptides are secreted from enteroendocrine cells in response to nutrient and energy intake, and modulate food intake either via afferent nerves, including the vagus nerve, or directly within the central nervous system, predominantly gaining access at circumventricular organs. Enteroendocrine hormones modulate homeostatic control centres at hypothalamic nuclei and the dorso-vagal complex. Additional roles of these peptides in modulating hedonic food intake and/or preference via the neural systems of reward are starting to be elucidated, with both peripheral and central peptide sources potentially contributing to central receptor activation. Pharmacological interventions and gastric bypass surgery for the treatment of type 2 diabetes and obesity elevate enteroendocrine hormone levels and also alter food preference. Hence, understanding of the hedonic mechanisms mediated by gut peptide action could advance development of potential therapeutic strategies for the treatment of obesity and its comorbidities.

Body mass index is associated with Helicobacter pylori infection and increased oxidative DNA damage in an obese population

Objective

To determine the prevalence of Helicobacter pylori infection in a Saudi Arabian population and its association with the body mass index (BMI) and serum 8-hydroxy deoxyguanine (8-OHdG) levels as biomarker for oxidative stress.

Methods

This cross-sectional study enrolled patients that had experienced epigastric discomfort or dyspepsia for > 1 month and had undergone diagnostic upper endoscopy. Patients with a body mass index (BMI) ≥30 kg/m² were defined as obese. The presence of anti-H. pylori antibodies was confirmed using an H. pylori immunoglobulin G (IgG) antibody enzyme-linked immunosorbent assay. The levels of 8-OHdG were measured using a competitive inhibition enzyme immunoassay.

Results

A total of 298 patients were enrolled in the study. Of these, 186 (62.4%) patients were H. pylori-positive and 112 (37.6%) patients were H. pylori-negative. The mean ± SD age of the overall study cohort was 47.17 ± 9.27 years. The H. pylori-positive patients had significantly higher levels of H. pylori IgG antibodies than H. pylori-negative patients. H. pylori prevalence linearly correlated with BMI quantile. The 8-OHdG levels were strongly associated with the BMI of the patients in the H. pylori-positive group.

Conclusion

Obese individuals exhibited higher H. pylori prevalence than individuals with a lean BMI (BMI < 25.00 kg/m²).

Diet-induced Fasting Ghrelin Elevation Reflects the Recovery of Insulin Sensitivity and Visceral Adiposity Regression

CONTEXT

Lower fasting ghrelin levels (FGL) are associated with obesity and metabolic syndrome.

OBJECTIVE

We aimed to explore the dynamics of FGL during weight loss and its metabolic and adiposity-related manifestations beyond weight loss.

METHODS

This was a secondary analysis of a clinical trial that randomized participants with abdominal obesity/dyslipidemia to 1 of 3 diets: healthy dietary guidelines (HDG), Mediterranean diet (MED), or green-MED diet, all combined with physical activity (PA). Both MED diets were similarly hypocaloric and included 28 g/day walnuts. The green-MED group further consumed green tea (3-4 cups/day) and a Wolffia globosa (Mankai) plant green shake. We measured FGL and quantified body fat depots by magnetic resonance imaging at baseline and after 18 months.

RESULTS

Among 294 participants (body mass index = 31.3 kg/m2; FGL = 504 ± 208 pg/mL; retention rate = 89.8%), lower FGL was associated with unfavorable cardiometabolic parameters such as higher visceral adipose tissue (VAT), intrahepatic fat, leptin, and blood pressure (P < 0.05 for all; multivariate models). The ∆FGL18-month differed between men (+7.3 ± 26.6%) and women (-9.2% ± 21.3%; P = 0.001). After 18 months of moderate and similar weight loss among the MED groups, FGL increased by 1.3%, 5.4%, and 10.5% in HDG, MED, and green-MED groups, respectively (P = 0.03 for green-MED vs HDG); sex-stratified analysis revealed similar changes in men only. Among men, FGL18-month elevation was associated with favorable changes in insulin resistance profile and VAT regression, after adjusting for relative weight loss (HbA1c: r = -0.216; homeostatic model of insulin resistance: r = -0.154; HDL-c: r = 0.147; VAT: r = -0.221; P < 0.05 for all). Insulin resistance and VAT remained inversely related with FGL elevation beyond that explained by weight loss (residual regression analyses; P < 0.05).

CONCLUSION

Diet-induced FGL elevation may reflect insulin sensitivity recovery and VAT regression beyond weight loss, specifically among men. Green-MED diet is associated with greater FGL elevation.

An evolving view on food viscosity regulating gastric emptying

Viscosity is a property of most foods. The consumption of the high-viscosity food is associated with a variety of physiological responses, one of which is their ability to regulate gastric emptying and modulate postprandial glycemic response. Gastric emptying has been proven to be a key step affecting the digestion and absorption of food, whereas, the relationship between viscosity and gastric emptying is still far away from being understood. Here, we reviewed the factors that influence food viscosity and food viscosity changes during digestion. Besides, the effect of food viscosity on gastric emptying and food-viscosity-physiological response were highlighted. Finally, "quantitative relationship" of viscosity and gastric emptying was discussed. This review can contribute to the understanding that how food viscosity affects gastric emptying, and help for developing foods that could control satiety and manage body weight for the specific populations.

Why We Eat Too Much, Have an Easier Time Gaining Than Losing Weight, and Expend Too Little Energy: Suggestions for Counteracting or Mitigating These Problems

The intent of this review is to survey physiological, psychological, and societal obstacles to the control of eating and body weight maintenance and offer some evidence-based solutions. Physiological obstacles are genetic and therefore not amenable to direct abatement. They include an absence of feedback control against gaining weight; a non-homeostatic relationship between motivations to be physically active and weight gain; dependence of hunger and satiation on the volume of food ingested by mouth and processed by the gastrointestinal tract and not on circulating metabolites and putative hunger or satiation hormones. Further, stomach size increases from overeating and binging, and there is difficulty in maintaining weight reductions due to a decline in resting metabolism, increased hunger, and enhanced efficiency of energy storage. Finally, we bear the evolutionary burden of extraordinary human capacity to store body fat. Of the psychological barriers, human craving for palatable food, tendency to overeat in company of others, and gullibility to overeat when offered large portions, can be overcome consciously. The tendency to eat an unnecessary number of meals during the wakeful period can be mitigated by time-restricted feeding to a 6-10 hour period. Social barriers of replacing individual physical work by labor-saving appliances, designing built environments more suitable for car than active transportation; government food macronutrient advice that increases insulin resistance; overabundance of inexpensive food; and profit-driven efforts by the food industry to market energy-dense and nutritionally compromised food are best overcome by informed individual macronutrient choices and appropriate timing of exercise with respect to meals, both of which can decrease insulin resistance. The best defense against overeating, weight gain, and inactivity is the understanding of factors eliciting them and of strategies that can avoid and mitigate them.

The Orexigenic Force of Olfactory Palatable Food Cues in Rats

Environmental cues recalling palatable foods motivate eating beyond metabolic need, yet the timing of this response and whether it can develop towards a less palatable but readily available food remain elusive. Increasing evidence indicates that external stimuli in the olfactory modality communicate with the major hub in the feeding neurocircuitry, namely the hypothalamic arcuate nucleus (Arc), but the neural substrates involved have been only partially uncovered. By means of a home-cage hidden palatable food paradigm, aiming to mimic ubiquitous exposure to olfactory food cues in Western societies, we investigated whether the latter could drive the overeating of plain chow in non-food-deprived male rats and explored the neural mechanisms involved, including the possible engagement of the orexigenic ghrelin system. The olfactory detection of a familiar, palatable food impacted upon meal patterns, by increasing meal frequency, to cause the persistent overconsumption of chow. In line with the orexigenic response observed, sensing the palatable food in the environment stimulated food-seeking and risk-taking behavior, which are intrinsic components of food acquisition, and caused active ghrelin release. Our results suggest that olfactory food cues recruited intermingled populations of cells embedded within the feeding circuitry within the Arc, including, notably, those containing the ghrelin receptor. These data demonstrate the leverage of ubiquitous food cues, not only for palatable food searching, but also to powerfully drive food consumption in ways that resonate with heightened hunger, for which the orexigenic ghrelin system is implicated.

Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Non-Alcoholic Fatty Liver Disease: A 12-Month Follow-Up Study with Paired Liver Biopsies

Roux-en-Y gastric bypass (RYGB) improves, and can sometimes resolve, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) but data based on histological assessment for the efficacy of sleeve gastrectomy (SG) in resolving NAFLD are sparse. Consequently, we aimed to compare the efficacy of RYGB vs. SG on NAFLD 12 months after surgery. In a prospective cohort study, 40 patients with obesity underwent bariatric surgery (16 RYGB and 24 SG). During surgery, a liver biopsy was taken and repeated 12 months later. NAFLD severity was evaluated using the NAFLD Activity Score (NAS) and Kleiner Fibrosis score. RYGB and SG patients were comparable at baseline. Mean (standard deviation, SD) NAS was 3.3 (0.9) in RYGB and 3.1 (1.4) in SG (p = 0.560) with similar degrees of steatosis, inflammation, and ballooning. Two RYGB patients, and six SG patients, had NASH (p = 0.439). Twelve months after surgery, NAS was significantly and comparably (p = 0.241) reduced in both RYGB (−3.00 (95% CI −3.79–−2.21), p < 0.001) and SG (−2.25 (95% CI −2.92–−1.59), p < 0.001) patients. RYGB patients had significantly more reduced (p = 0.007) liver steatosis (−0.91 (95% CI −1.47–−1.2) than SG patients (−0.33 (95% CI −0.54–−0.13) and greater improvement in the plasma lipid profile. Fibrosis declined non-significantly. NASH was resolved in seven of eight patients without a worsening of their fibrosis. RYGB and SG have similar beneficial effects on NAS and NASH without the worsening of fibrosis. RYGB is associated with a more pronounced reduction in liver steatosis.

Does kisspeptin act as a neuropeptide or as an adipokine in obese people?

Objectives

Obesity is a serious global issue with a massive impact on the health and life of people worldwide. Besides being a neuropeptide, kisspeptin is an important adipokine involved in regulating energy homeostasis and body weight. This study aims to clarify the underlying role of kisspeptin in obesity.

Methods

This case-control study included 110 obese individuals with BMI of 33.45 ± 0.36 kg/m² and 84 normal-weight individuals with BMI 21.35 ± 0.24 kg/m². The individuals' ages ranged from 21 to 45 years (31.56 ± 0.67 year). Kisspeptin, neutrophil epithelial activating peptide (ENA-78), and ghrelin were determined using the enzyme-linked immunosorbent assay (ELISA) technique. Lipid profile parameters were determined using the commercial colorimetric techniques.

Results

Plasma concentrations of kisspeptin and ENA-78 were significantly higher in obese subjects (kisspeptine of obese: 437.66 ± 34.96 pg/ml; kisspeptine of normal-weight: 250.10 ± 16.16 pg/ml, p< 0.0001; ENA-78 of obese: 144.80 ± 23.94 pg/ml; ENA-78 of normal-weight: 50.97 ± 3.91 pg/ml, p< 0.001). Ghrelin concentrations showed no significant difference between obese and normal-weight subjects. The lipid profile parameters significantly differed between obese and normal-weight subjects.

Conclusion

Kisspeptin is associated with obesity. An increased mass of adipose tissue could be responsible not only for increased kisspeptin secretion but also for the increased ENA-78 secretion. Kisspeptin may act as an adipokine more than a neuropeptide in obese population. Further studies on humans are required to establish the underlying role of kisspeptin in adipocyte differentiation and lipogenesis.

Post-weight loss changes in fasting appetite- and energy balance-related hormone concentrations and the effect of the macronutrient content of a weight maintenance diet: a randomised controlled trial

PURPOSE

We investigated the effects of the macronutrient composition of diets with differing satiety values on fasting appetite-related hormone concentrations after weight loss and examined whether the hormone secretion adapted to changes in body fat mass (FM) and fat-free mass (FFM) during the weight maintenance period (WM).

METHODS

Eighty-two men and women with obesity underwent a 7-week very-low-energy diet (VLED) and were then randomised to a higher-satiety food (HSF) group or a lower-satiety food (LSF) group during 24-weeks of the WM. The groups consumed isoenergetic foods with different satiety ratings and macronutrient compositions.

RESULTS

During the WM, the HSF group consumed more protein and dietary fibre and less fat than the LSF group, but the groups showed similar changes in body weight and fasting appetite-related hormones. In the whole study sample, VLED induced 12 kg (p < 0.001) weight loss. At the end of the WM, weight regain was 1.3 kg (p = 0.004), ghrelin concentration increased, whereas leptin, insulin, and glucose concentrations decreased compared to pre-VLED levels (p < 0.001 for all). Peptide YY did not differ from pre-VLED levels. Changes in ghrelin levels were inversely associated with changes in FFM during weeks 0-12 of the WM (p = 0.002), while changes in leptin and insulin levels were positively associated with changes in FM during weeks 0-12 (p = 0.015 and p = 0.038, respectively) and weeks 12-24 (p < 0.001 and p = 0.022) of the WM.

CONCLUSIONS

The macronutrient composition of an isoenergetic WM diet did not affect fasting appetite-related hormone concentrations. Leptin and insulin adjusted to the reduced FM, whereas ghrelin reflected FFM during the first months of the WM.

TRIAL REGISTRATION

isrctn.com, ID 67529475.

Comparison Between Laparoscopic Sleeve Gastrectomy and Laparoscopic Greater Curvature Plication Treatments for Obesity: an Updated Systematic Review and Meta-Analysis

Bariatric surgery has been widely performed to treat morbid obesity. Our meta-analysis aims to provide an updated comparison between laparoscopic sleeve gastrectomy (LSG) and laparoscopic greater curvature plication (LGCP). Medline, EMBASE, Scopus, and Cochrane Central were searched. Ongoing clinical trials were identified from the clinicaltrials.gov website. References of the chosen literatures were manually reviewed for additional relevant studies. As a result, a total of 18 studies involving 1329 patients were selected. We demonstrated a significant higher excess weight loss (%EWL) after LSG at the 1-, 3-, 6-, 12-, and 18-month follow-up time points. However, no significant difference was found at 36 months. Body Mass Index Loss (BMIL) was better after LSG than LGCP at 12 and 24 months. The difference in the improvement of comorbidities (i.e., T2-DM, hypertension, and sleep apnea) did not reach statistical significance. The complications (i.e., bleeding, stenosis, leak, and abdominal pain), operative time, and length of hospital stay were comparable. More patients undergoing LGCP experienced nausea and vomiting. We obtained some different and new results compared to the previously published meta-analysis. Our meta-analysis showed significantly higher %EWL at 24 months (Z=2.08, p=0.04), significantly higher BMIL at 36 months (Z=9.11, p <0.00001), and significantly higher costs (Z=2.87, p=0.004) in the LSG group. In addition, for the first time, complications (i.e., GERD, wound infection, port-site hernia, and mortality) and improvement of dyslipidemia were compared between the two techniques. According to our pooled data, no significant differences were found in any of the above aspects. In conclusion, LSG is superior to LGCP with regard to providing effective weight loss in the short- and mid-term. LSG has a lower rate of minor complications, but was less effective when considering cost. The two procedures are similar in terms of improvement of comorbidities, major complications, operative time, and length of stay.

Impact of the Hepatic Branch of the Vagus Nerve Transection in Laparoscopic Sleeve Gastrectomy for Patients with Obesity and Type 2 Diabetes Mellitus

BACKGROUND

An increase in gastroesophageal reflux disease (GERD) after laparoscopic sleeve gastrectomy (LSG) has been reported, and concomitant hiatal hernia repair (HHR) during LSG is expected to reduce the incidence of post-LSG GERD. In HHR, the hepatic branch of the vagus nerve is anatomically transected. Recent experimental animal models suggest that vagotomy may affect glycemic control and weight loss through a neuroendocrine response.

OBJECTIVES

To examine whether LSG with/without hepatic branch vagotomy (HV) has a clinical impact on glycemic control in patients with obesity and type 2 diabetes mellitus (T2DM). Furthermore, the impact on weight loss and post-LSG GERD were evaluated.

METHODS

A total of 204 Japanese patients with obesity and T2DM, who underwent LSG and completed 1-year follow-up, were retrospectively analyzed. Operative outcomes, weight loss, glycemic, and GERD-related parameters were compared between the LSG/HHR/HV group (n = 89) and the LSG group (n = 115).

RESULTS

There was no significant difference in the background factors in terms of anthropometric and T2DM-related parameters between the groups. The median operation times in the LSG/HHR/HV and LSG groups were 133 and 124 minutes, respectively (p = 0.236). At 1 year, the diabetes remission rate, HbA1c, fasting glucose, and C-peptide levels were all comparable between the groups. The weight loss effect was also comparable. The patients in the LSG/HHR/HV group achieved significant improvement and prevention of GERD and hiatus hernia (p < 0.001).

CONCLUSION

HV does not appear to have a clinical impact on glycemic control and weight loss. Concomitant HHR with LSG serves to reduce post-LSG GERD.

Unacylated ghrelin, leptin, and appetite display diurnal rhythmicity in lean adults

Constant routine and forced desynchrony protocols typically remove the effects of behavioral/environmental cues to examine endogenous circadian rhythms, yet this may not reflect rhythms of appetite regulation in the real world. It is therefore important to understand these rhythms within the same subjects under controlled diurnal conditions of light, sleep, and feeding. Ten healthy adults (9 M/1 F, means ±SD: age, 30 ± 10 yr; body mass index, 24.1 ± 2.7 kg·m^-2) rested supine in the laboratory for 37 h. All data were collected during the final 24 h of this period (i.e., 0800-0800 h). Participants were fed hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 2200 to 0700 h. Hourly blood samples were collected throughout the 24-h period. Dim light melatonin onset occurred at 2318 ± 46 min. A diurnal rhythm in mean plasma unacylated ghrelin concentration was identified (P = 0.04), with the acrophase occurring shortly after waking (0819), falling to a nadir in the evening with a relative amplitude of 9%. Plasma leptin concentration also exhibited a diurnal rhythm (P < 0.01), with the acrophase occurring shortly after lights-out (0032 h) and the lowest concentrations at midday. The amplitude for this rhythm was 25%. Diurnal rhythms were established in all dimensions of appetite except for sweet preference (P = 0.29), with both hunger (2103 h) and prospective food consumption (1955 h) reaching their peak in the evening before falling to their nadir shortly after waking. Under controlled diurnal conditions, simultaneous measurement of leptin, unacylated ghrelin, and subjective appetite over a 24-h period revealed rhythmicity in appetite regulation in lean, healthy humans.NEW & NOTEWORTHY Simultaneous assessment of subjective appetite, unacylated ghrelin, and leptin was carried out over a continuous 37-h protocol for the first time under conditions of controlled light, sleep, and feeding in healthy, lean adults. Rhythms were observed in unacylated ghrelin, leptin, and components of subjective appetite, such as hunger, prospective consumption, and fullness. Concurrent measurement of rhythms in these variables is important to fully understand the temporal relationships between components of appetite as well as the influence of diurnal factors such as sleep, light, and feeding.

Ghrelin-Mediated Regeneration and Plasticity After Nervous System Injury

The nervous system is highly vulnerable to different factors which may cause injury followed by an acute or chronic neurodegeneration. Injury involves a loss of extracellular matrix integrity, neuronal circuitry disintegration, and impairment of synaptic activity and plasticity. Application of pleiotropic molecules initiating extracellular matrix reorganization and stimulating neuronal plasticity could prevent propagation of the degeneration into the tissue surrounding the injury. To find an omnipotent therapeutic molecule, however, seems to be a fairly ambitious task, given the complex demands of the regenerating nervous system that need to be fulfilled. Among the vast number of candidates examined so far, the neuropeptide and hormone ghrelin holds within a very promising therapeutic potential with its ability to cross the blood-brain barrier, to balance metabolic processes, and to stimulate neurorepair and neuroactivity. Compared with its well-established systemic effects in treatment of metabolism-related disorders, the therapeutic potential of ghrelin on neuroregeneration upon injury has received lesser appreciation though. Here, we discuss emerging concepts of ghrelin as an omnipotent player unleashing developmentally related molecular cues and morphogenic cascades, which could attenuate and/or counteract acute and chronic neurodegeneration.

Weight loss-induced increase in fasting ghrelin concentration is a predictor of weight regain: Evidence from the Diabetes Remission Clinical Trial (DiRECT)

AIM

To investigate whether appetite-related hormones were predictors of weight regain in the Diabetes Remission Clinical Trial (DiRECT).

MATERIALS AND METHODS

DiRECT is a cluster-randomized clinical trial, designed to assess the effect of weight loss on type 2 diabetes remission. For this post hoc analysis, data were available for 253 (147 interventions, 106 controls) individuals with type 2 diabetes (age 53.6 ± 7.5 years, body mass index 34.7 ± 4.4 kg/m2 , 59% men). Intervention participants received a 24-month weight management programme, and controls remained on usual diabetes care. Fasting plasma concentrations of leptin, ghrelin, glucagon-like peptide-1 and peptide YY were measured at baseline, 12 months and 24 months in all participants, and at 5 months in a subset of participants in the intervention (n = 56) and control groups (n = 22). Potential predictors were examined using multivariable linear regression models.

RESULTS

The intervention group lost 14.3 ± 6.0% body weight at 5 months but regained weight over time, with weight losses of 10.0 ± 7.5% at 12 months and 7.6 ± 6.3% at 24 months. Weight loss in controls was 1.1 ± 3.7% and 2.1 ± 5.0% at 12 and 24 months, respectively. Body weight increased by 2.3% (95% confidence interval [CI] 0.4, 4.1; P = 0.019) between 12 and 24 months for every 1-ng/mL increase in ghrelin between baseline and 12 months, and weight regain between 12 and 24 months was increased by 1.1% (95% CI 0.2, 2.0; P = 0.023) body weight for every 1-ng/mL increase in ghrelin at 12 months.

CONCLUSION

The rise in ghrelin (but not any other measured hormone) during diet-induced weight loss was a predictor of weight regain during follow-up, and concentrations remained elevated over time, suggesting a small but significant compensatory drive to regain weight. Attenuating the effects of ghrelin may improve weight-loss maintenance.

Ghrelin as a Biomarker of Stress: A Systematic Review and Meta-Analysis

Introduction: Ghrelin is an orexigenic hormone which favors food-seeking behavior and has been postulated to be a biomarker of stress. We conducted a systematic review and meta-analysis on the evolution of ghrelin levels following acute stress. Methods: The PubMed, Cochrane Library, Embase, and ScienceDirect databases were searched for studies reporting ghrelin levels before and after acute stress in humans. Results: We included ten studies for a total of 348 patients. Acute stress (intervention) was always in a laboratory. Acute stress was psychological (Trier Social Stress Test), physical, or mixed (cold pressure test). The overall meta-analysis demonstrated an increase in ghrelin after the stress intervention (ES = 0.21, 95CI 0.09 to 0.34) compared with baseline levels. Stratification by time demonstrated an acute increase in ghrelin levels in the five minutes immediately following the initiation of stress (0.29, 0.10 to 0.48) but without any difference after. Obese individuals had a more significant (ES = 0.51, 95CI 0.18 to 0.84) and prolonged increase in ghrelin levels for up to 45 min compared with non-obese individuals who had a significant increase only five minutes after stress. Moreover, the ghrelin levels increased in response to stress with BMI (coefficient 0.028, 0.01 to 0.49; p = 0.013) and decreased with the time after the stress intervention (coefficient -0.007, −0.014 to −0.001; p = 0.025). Conclusion: Ghrelin is a biomarker of stress, with a short-term increase following acute stress. Obese individuals have both a higher and prolonged response, emphasizing the link between obesity and stress.

The Torpid State: Recent Advances in Metabolic Adaptations and Protective Mechanisms†

Torpor and hibernation are powerful strategies enabling animals to survive periods of low resource availability. The state of torpor results from an active and drastic reduction of an individual's metabolic rate (MR) associated with a relatively pronounced decrease in body temperature. To date, several forms of torpor have been described in all three mammalian subclasses, i.e., monotremes, marsupials, and placentals, as well as in a few avian orders. This review highlights some of the characteristics, from the whole organism down to cellular and molecular aspects, associated with the torpor phenotype. The first part of this review focuses on the specific metabolic adaptations of torpor, as it is used by many species from temperate zones. This notably includes the endocrine changes involved in fat- and food-storing hibernating species, explaining biomedical implications of MR depression. We further compare adaptive mechanisms occurring in opportunistic vs. seasonal heterotherms, such as tropical and sub-tropical species. Such comparisons bring new insights into the metabolic origins of hibernation among tropical species, including resistance mechanisms to oxidative stress. The second section of this review emphasizes the mechanisms enabling heterotherms to protect their key organs against potential threats, such as reactive oxygen species, associated with the torpid state. We notably address the mechanisms of cellular rehabilitation and protection during torpor and hibernation, with an emphasis on the brain, a central organ requiring protection during torpor and recovery. Also, a special focus is given to the role of an ubiquitous and readily-diffusing molecule, hydrogen sulfide (H2S), in protecting against ischemia-reperfusion damage in various organs over the torpor-arousal cycle and during the torpid state. We conclude that (i) the flexibility of torpor use as an adaptive strategy enables different heterothermic species to substantially suppress their energy needs during periods of severely reduced food availability, (ii) the torpor phenotype implies marked metabolic adaptations from the whole organism down to cellular and molecular levels, and (iii) the torpid state is associated with highly efficient rehabilitation and protective mechanisms ensuring the continuity of proper bodily functions. Comparison of mechanisms in monotremes and marsupials is warranted for understanding the origin and evolution of mammalian torpor.

The ups and downs of growth hormone secretagogue receptor signaling

The growth hormone secretagogue receptor (GHSR) has emerged as one of the most fascinating molecules from the perspective of neuroendocrine control. GHSR is mainly expressed in the pituitary and the brain, and plays key roles regulating not only growth hormone secretion but also food intake, adiposity, body weight, glucose homeostasis and other complex functions. Quite atypically, GHSR signaling displays a basal constitutive activity that can be up- or downregulated by two digestive system-derived hormones: the octanoylated-peptide ghrelin and the liver-expressed antimicrobial peptide 2 (LEAP2), which was recently recognized as an endogenous GHSR ligand. The existence of two ligands with contrary actions indicates that GHSR activity can be tightly regulated and that the receptor displays the capability to integrate such opposing inputs in order to provide a balanced intracellular signal. This article provides a summary of the current understanding of the biology of ghrelin, LEAP2 and GHSR and discusses the reconceptualization of the cellular and physiological implications of the ligand-regulated GHSR signaling, based on the latest findings.

A mathematical model of food intake

The metabolic, hormonal and psychological determinants of the feeding behavior in humans are numerous and complex. A plausible model of the initiation, continuation and cessation of meals taking into account the most relevant such determinants would be very useful in simulating food intake over hours to days, thus providing input into existing models of nutrient absorption and metabolism. In the present work, a meal model is proposed, incorporating stomach distension, glycemic variations, ghrelin dynamics, cultural habits and influences on the initiation and continuation of meals, reflecting a combination of hedonic and appetite components. Given a set of parameter values (portraying a single subject), the timing and size of meals are stochastic. The model parameters are calibrated so as to reflect established medical knowledge on data of food intake from the National Health and Nutrition Examination Survey (NHANES) database during years 2015 and 2016.

Vagotomy increases alcohol intake in female rats in diet dependent manner: Implications for increased alcohol use disorder after roux-en-y gastric bypass surgery

A variety of weight loss surgeries have been developed to fight the obesity epidemic, with Roux-en-Y gastric bypass (RYGB) being one of the most effective and popular procedures. However, the underlying mechanisms behind its efficacy are still not well understood. Furthermore, growing clinical evidence suggests that RYGB may result in increased risk for development of alcohol use disorder (AUD). The vagus nerve is a potentially critical contributor to increased risk of AUD following RYGB due to the potential for significant damage to the vagus during surgery, which has been confirmed in rodent studies. Studies aiming at the mechanisms underlying development of alcohol or substance use disorders following the surgery have exclusively used male rats, despite the majority of RYGB patients being female. Thus, the current study had two objectives: 1) to investigate the effect of RYGB on ethanol (EtOH) intake in female rats using a protocol previously established in male rats, and 2) to test the effect of vagal damage and high fat diet (HFD) on EtOH intake in female rats. In the first study, 22 female rats were maintained on HFD for four weeks and then split into two surgical groups, RYGB (n = 10) and Sham (n = 12). All rats then underwent a two-bottle choice test of increasing EtOH concentrations: 2%, 4%, 6%, 8%. Rats were then forced to abstain from EtOH for two weeks, after which access to 8% EtOH was reinstated. The RYGB female rats significantly increased their intake for low concentrations of EtOH (2% and 4%) and during the reinstatement period for 8%. These results mirror those seen in male rats, and thus, confirms RYGB in female rats as an equally viable model to males. In the second study, 40 female rats were separated into four groups: HFD/Sham, HFD/Vagotomy, normal diet (ND)/Sham, and ND/Vagotomy. All rats then were subjected to the same two-bottle choice test protocol as in the previous study. Rats in the vagotomy condition had significantly greater preference for 2% and 4% EtOH compared with Sham-operated controls. EtOH intake, either in ml or adjusted for body weight, was greater in rats maintained on ND compared with rats maintained on HFD. These data suggest that vagal damage may, at least in part, contribute to increased preference for EtOH. Furthermore, this increase in EtOH preference is counter to the blunting effect of HFD. In conclusion, the data presented here suggest a role for vagal damage in risk of AUD after weight loss surgery.

Mechanism of Action of Acupuncture in Obesity: A Perspective From the Hypothalamus

Obesity is a prevalent metabolic disease caused by an imbalance in food intake and energy expenditure. Although acupuncture is widely used in the treatment of obesity in a clinical setting, its mechanism has not been adequately elucidated. As the key pivot of appetite signals, the hypothalamus receives afferent and efferent signals from the brainstem and peripheral tissue, leading to the formation of a complex appetite regulation circuit, thereby effectively regulating food intake and energy homeostasis. This review mainly discusses the relationship between the hypothalamic nuclei, related neuropeptides, brainstem, peripheral signals, and obesity, as well as mechanisms of acupuncture on obesity from the perspective of the hypothalamus, exploring the current evidence and therapeutic targets for mechanism of action of acupuncture in obesity.

Is there a hypothalamic basis for anorexia nervosa?

The hypothalamus has long been known to control food intake and energy metabolism through a complex network of primary and secondary neurons and glial cells. Anorexia nervosa being a complex disorder characterized by abnormal feeding behavior and food aversion, it is thus quite surprising that not much is known concerning potential hypothalamic modifications in this disorder. In this chapter, we review the recent advances in the fields of genetics, epigenetics, structural and functional imaging, and brain connectivity, as well as neuroendocrine findings and emerging animal models, which have begun to unravel the importance of hypothalamic adaptive processes to our understanding of the pathology of eating disorders.

A Focused Review of the Metabolic Side-Effects of Clozapine

The second generation antipsychotic drug clozapine represents the most effective pharmacotherapy for treatment-resistant psychosis. It is also associated with low rates of extrapyramidal symptoms and hyperprolactinemia compared to other antipsychotic drugs. However, clozapine tends to be underutilized in clinical practice due to a number of disabling and serious side-effects. These are characterized by a constellation of metabolic side-effects which include dysregulation of glucose, insulin, plasma lipids and body fat. Many patients treated with clozapine go on to develop metabolic syndrome at a higher rate than the general population, which predisposes them for Type 2 diabetes mellitus and cardiovascular disease. Treatments for the metabolic side-effects of clozapine vary in their efficacy. There is also a lack of knowledge about the underlying physiology of how clozapine exerts its metabolic effects in humans. In the current review, we focus on key studies which describe how clozapine affects each of the main symptoms of the metabolic syndrome, and cover some of the treatment options. The clinical data are then discussed in the context of preclinical studies that have been conducted to identify the key biological substrates involved, in order to provide a better integrated overview. Suggestions are provided about key areas for future research to better understand how clozapine causes metabolic dysregulation.

Bifidobacterium longum counters the effects of obesity: Partial successful translation from rodent to human

Background

The human gut microbiota has emerged as a key factor in the development of obesity. Certain probiotic strains have shown anti-obesity effects. The objective of this study was to investigate whether Bifidobacterium longum APC1472 has anti-obesity effects in high-fat diet (HFD)-induced obese mice and whether B. longum APC1472 supplementation reduces body-mass index (BMI) in healthy overweight/obese individuals as the primary outcome. B. longum APC1472 effects on waist-to-hip ratio (W/H ratio) and on obesity-associated plasma biomarkers were analysed as secondary outcomes.

Methods

B. longum APC1472 was administered to HFD-fed C57BL/6 mice in drinking water for 16 weeks. In the human intervention trial, participants received B. longum APC1472 or placebo supplementation for 12 weeks, during which primary and secondary outcomes were measured at the beginning and end of the intervention.

Findings

B. longum APC1472 supplementation was associated with decreased bodyweight, fat depots accumulation and increased glucose tolerance in HFD-fed mice. While, in healthy overweight/obese adults, the supplementation of B. longum APC1472 strain did not change primary outcomes of BMI (0.03, 95% CI [-0.4, 0.3]) or W/H ratio (0.003, 95% CI [-0.01, 0.01]), a positive effect on the secondary outcome of fasting blood glucose levels was found (-0.299, 95% CI [-0.44, -0.09]).

Interpretation

This study shows a positive translational effect of B. longum APC1472 on fasting blood glucose from a preclinical mouse model of obesity to a human intervention study in otherwise healthy overweight and obese individuals. This highlights the promising potential of B. longum APC1472 to be developed as a valuable supplement in reducing specific markers of obesity.

Funding

This research was funded in part by Science Foundation Ireland in the form of a Research Centre grant (SFI/12/RC/2273) to APC Microbiome Ireland and by a research grant from Cremo S.A.

Genetic variation in lean body mass, changes of appetite and weight loss in response to diet interventions: The POUNDS Lost trial

AIM

To investigate whether the genetic risk score (GRS) for lean body mass (LBM) modified the effects of weight-loss diets on changes in appetite and adiposity among overweight and obese individuals.

PARTICIPANTS AND METHODS

In the 2-year Preventing Overweight Using Novel Dietary Strategies (POUNDS Lost) trial, we included 692 adults who were randomly assigned to one of four diets varying in macronutrient intake. A GRS was calculated using five single nucleotide polymorphisms associated with LBM.

RESULTS

The LBM-GRS was not associated with the baseline LBM measured by dual-energy x-ray absorptiometry in a subgroup (50%) of the study population. We found that the LBM-GRS had significantly different associations with changes in appetite from baseline to 6 months according to low- or high-fat diet group (P-interaction < 0.001, 0.021, 0.005 and 0.024 for total appetite score, hunger, fullness and prospective consumption, respectively). Lower LBM-GRS (indicating a greater genetic predisposition to LBM) was associated with greater decreases in the total appetite score (P < 0.001), hunger (P = 0.01), fullness (P = 0.001) and prospective consumption (P = 0.019) in participants in the low-fat diet group, whereas no significant associations with these appetite measures were observed in the high-fat diet group. In addition, lower LBM-GRS was associated with greater reduction in body weight (P = 0.003) and waist circumference (P = 0.011) among participants in the low-fat diet group, while no associations were observed in the high-fat diet group. The interactions attenuated, along with weight regain, from 6 months to 2 years.

CONCLUSIONS

Our findings suggest that genetic variation in LBM may be differentially associated with appetite changes, and may subsequently be related to changes in body weight and waist circumference, according to dietary fat intake.

"A LEAP 2 conclusions? Targeting the ghrelin system to treat obesity and diabetes"

BACKGROUND

The hormone ghrelin stimulates food intake, promotes adiposity, increases body weight, and elevates blood glucose. Consequently, alterations in plasma ghrelin levels and the functioning of other components of the broader ghrelin system have been proposed as potential contributors to obesity and diabetes. Furthermore, targeting the ghrelin system has been proposed as a novel therapeutic strategy for obesity and diabetes.

SCOPE OF REVIEW

The current review focuses on the potential for targeting ghrelin and other proteins comprising the ghrelin system as a treatment for obesity and diabetes. The main components of the ghrelin system are introduced. Data supporting a role for the endogenous ghrelin system in the development of obesity and diabetes along with data that seemingly refute such a role are outlined. An argument for further research into the development of ghrelin system-targeted therapeutic agents is delineated. Also, an evidence-based discussion of potential factors and contexts that might influence the efficacy of this class of therapeutics is provided.

MAJOR CONCLUSIONS

It would not be a "leap to" conclusions to suggest that agents which target the ghrelin system - including those that lower acyl-ghrelin levels, raise LEAP2 levels, block GHSR activity, and/or raise desacyl-ghrelin signaling - could represent efficacious novel treatments for obesity and diabetes.

Potato Fibers Have Positive Effects on Subjective Appetite Sensations in Healthy Men, but Not on Fecal Fat Excretion: A Randomized Controlled Single-Blind Crossover Trial

Dietary fibers can affect appetite and gut metabolism, but the effect of the novel potato fibers FiberBind and rhamnogalacturonan I (RG-I) is unknown. We, therefore, aimed to investigate the effect of daily intake of FiberBind and RG-I on appetite sensations and fecal fat excretion. In a single-blinded, randomized, three-way crossover trial, wheat buns with FiberBind, RG-I, or low fiber (control) were consumed by 18 healthy men during a 21-day period. Appetite sensation and blood samples during a 3 h meal test, fecal fat content, and ad libitum energy intake were assessed after each period. Compared to RG-I and control, FiberBind caused a higher composite satiety score (6% ± 2% and 5% ± 2%), lower prospective food consumption (5% ± 2% and 6% ± 2%), and lower desire to eat (7% ± 3% and 6% ± 3%) (all p < 0.05). FiberBind also caused higher satiety (6% ± 2%) and fullness (9% ± 3%) compared to RG-I (all p < 0.01). No effects on fecal fat excretion or energy intake were found. The RG-I fiber caused higher postprandial glucose concentration compared to FiberBind (p < 0.05) and higher insulin concentration at 180 min compared to control (p < 0.05). Compared to the control, RG-I and FiberBind lowered peak insulin concentration (both p < 0.05) and delayed time to peak for glucose (both p < 0.05). In conclusion, FiberBind intake could be beneficial for appetite regulation, but neither FiberBind nor RG-I affected fecal fat excretion or energy intake.

The Effect of Supplementation with Low Doses of a Cod Protein Hydrolysate on Satiety Hormones and Inflammatory Biomarkers in Adults with Metabolic Syndrome: A Randomized, Double-Blind Study

Metabolic syndrome (MetS) is characterised by metabolic abnormalities that increase the risk of developing type 2 diabetes mellitus and cardiovascular disease. Altered levels of circulating ghrelin, several adipokines and inflammatory markers secreted from adipose tissue, such as leptin, adiponectin, tumor necrosis factor alpha, are observed in overweight and obese individuals. We assessed the effect of supplementation with low doses of a cod protein hydrolysate (CPH) on fasting and postprandial levels of acylated ghrelin, as well as fasting levels of adiponectin, leptin and inflammatory markers in subjects with MetS. A multicentre, double-blinded, randomized controlled trial with a parallel group design was conducted. Subjects received a daily supplement of CPH (4 g protein, n = 15) or placebo (0 g protein, n = 15). We observed no effect on fasting or postprandial levels of acylated ghrelin, fasting levels of adiponectin (p = 0.089) or leptin (p = 0.967) after supplementation with CPH, compared to placebo. Overall, our study showed that 8 weeks supplementation with a low dose of CPH in subjects with MetS had no effect on satiety hormones or most of the inflammatory markers, but the levels of high-sensitivity C-reactive protein were statistically significantly different in the CPH-group compared to placebo group. The robustness and clinical relevance of these findings should be explored in future studies with a larger sample size.

The Good, the Bad and the Unknown Aspects of Ghrelin in Stress Coping and Stress-Related Psychiatric Disorders

Ghrelin is a peptide hormone released by specialized X/A cells in the stomach and activated by acylation. Following its secretion, it binds to ghrelin receptors in the periphery to regulate energy balance, but it also acts on the central nervous system where it induces a potent orexigenic effect. Several types of stressors have been shown to stimulate ghrelin release in rodents, including nutritional stressors like food deprivation, but also physical and psychological stressors such as foot shocks, social defeat, forced immobilization or chronic unpredictable mild stress. The mechanism through which these stressors drive ghrelin release from the stomach lining remains unknown and, to date, the resulting consequences of ghrelin release for stress coping remain poorly understood. Indeed, ghrelin has been proposed to act as a stress hormone that reduces fear, anxiety- and depression-like behaviors in rodents but some studies suggest that ghrelin may - in contrast - promote such behaviors. In this review, we aim to provide a comprehensive overview of the literature on the role of the ghrelin system in stress coping. We discuss whether ghrelin release is more than a byproduct of disrupted energy homeostasis following stress exposure. Furthermore, we explore the notion that ghrelin receptor signaling in the brain may have effects independent of circulating ghrelin and in what way this might influence stress coping in rodents. Finally, we examine how the ghrelin system could be utilized as a therapeutic avenue in stress-related psychiatric disorders (with a focus on anxiety- and trauma-related disorders), for example to develop novel biomarkers for a better diagnosis or new interventions to tackle relapse or treatment resistance in patients.