Ghrelin, the peripheral hunger hormone

An insoluble cellulose nanofiber with robust expansion capacity protects against obesity

An imbalance between energy intake and energy expenditure predisposes obesity and its related metabolic diseases. Soluble dietary fiber has been shown to improve metabolic homeostasis mainly via microbiota reshaping. However, the application and metabolic effects of insoluble fiber are less understood. Herein, we employed nanotechnology to design citric acid-crosslinked carboxymethyl cellulose nanofibers (CL-CNF) with a robust capacity of expansion upon swelling. Supplementation with CL-CNF reduced food intake and delayed digestion rate in mice by occupying stomach. Besides, CL-CNF treatment mitigated diet-induced obesity and insulin resistance in mice with enhanced energy expenditure, as well as ameliorated inflammation in adipose tissue, intestine and liver and reduced hepatic steatosis, without any discernible signs of toxicity. Additionally, CL-CNF supplementation resulted in enrichment of probiotics such as Bifidobacterium and decreased in the relative abundances of deleterious microbiota expressing bile salt hydrolase, which led to increased levels of conjugated bile acids and inhibited intestinal FXR signaling to stimulate the release of GLP-1. Taken together, our findings demonstrate that CL-CNF administration protects mice from diet-induced obesity and metabolic dysfunction by reducing food intake, enhancing energy expenditure and remodeling gut microbiota, making it a potential therapeutic strategy against metabolic diseases.

Overview of the therapeutic efficacy of marine fish oil in managing obesity and associated metabolic disorders

In the present scenario, obesity is a challenging health problem and its prevalence along with comorbidities are on the rise around the world. Ingestion of fish becomes trendy in daily meals. Recent research has shown that marine fish oil (FO) (found in tuna, sardines, and mackerel) may offer an alternative method for reducing obesity and problems associated with it. Marine FO rich in long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) and long-chain omega-6 polyunsaturated fatty acids (LC n-6 PUFA) plays an important role in reducing abnormalities associated with the metabolic syndrome and has a variety of disease-fighting properties, including cardioprotective activity, anti-atherosclerotic, anti-obesity, anti-cancer, anti-inflammatory activity. Studies in rodents and humans have indicated that LC n-3 PUFA potentially elicit a number of effects which might be useful for reducing obesity, including suppression of appetite, improvements in circulation, enhanced fat oxidation, energy expenditure, and reduced fat deposition. This review discusses the interplay between inflammation and obesity, and their subsequent regulation via the beneficial role of marine FO, suggesting an alternative dietary strategy to ameliorate obesity and obesity-associated chronic diseases.

A bird's-eye overview of molecular mechanisms regulating feed intake in chickens-with mammalian comparisons

In recent decades, a lot of research has been conducted to explore poultry feeding behavior. However, up to now, the processes behind poultry feeding behavior remain poorly understood. The review generalizes modern expertise about the hormonal regulation of feeding behavior in chickens, focusing on signaling pathways mediated by insulin, leptin, and ghrelin and regulatory pathways with a cross-reference to mammals. This overview also summarizes state-of-the-art research devoted to hypothalamic neuropeptides that control feed intake and are prime candidates for predictors of feeding efficiency. Comparative analysis of the signaling pathways that mediate the feed intake regulation allowed us to conclude that there are major differences in the processes by which hormones influence specific neuropeptides and their contrasting roles in feed intake control between two vertebrate clades.

Changes in food preferences and ingestive behaviors after glucagon-like peptide-1 analog treatment: techniques and opportunities

BACKGROUND

Glucagon-like peptide-1 (GLP-1) analogs are approved for the treatment of obesity in adults and adolescents. Reports have emerged that the weight loss effect of these medications may be related to changes in food preferences and ingestive behaviors following the treatment. Understanding the mechanisms which impact ingestive behavior could expand opportunities to develop more refined and personalized treatment options for obesity.

METHODS

Recent studies investigating the relationship between GLP-1 analogs and ingestive behaviors were retrieved from PubMed using the search terms: "obesity," "food preference," "taste," "ingestive behavior," "weight loss medication," "anti-obesity medication," "GLP-1 analog," "tirzepatide," "liraglutide," "semaglutide." Measurement tools were studied to compare variables used to assess food intake behavior. The main outcomes from each study were analyzed to evaluate the current standing and future directions of appetitive, ingestive, and consummatory behaviors and their association with GLP-1 analogs.

RESULTS

Thus far, studies have primarily explored the weight loss phase and report decreased short-term appetite and food intake upon treatment. However, research during the weight maintenance phase and objective measurements of food intake are notably sparse. Additionally, verbal reports have been primarily used to examine food intake, which can be susceptible to subjectivity.

CONCLUSIONS

Elucidating the relationship between GLP-1 analogs and ingestive behavior could reveal additional parameters which contribute to their anti-obesity effects. To better understand these mechanisms, it is imperative to consider objective measurements of food intake in future studies. Several measurement tools have been adapted to measure variables of food behavior in humans, and each must be carefully considered with their strengths and limitations to develop optimal investigations.

GHRL as a prognostic biomarker correlated with immune infiltrates and progression of precancerous lesions in gastric cancer

Objective

Ghrelin is a protein that regulate appetite and energy balance in the human body, which is encoded by the ghrelin prepropeptide gene (GHRL). GHRL is linked with carcinogenesis and immune regulation. However, the correlation of GHRL to prognosis and tumor-infiltrating lymphocytes in gastric cancer (GC) remains unclear.

Methods

In this study, we assessed the transcriptional expression, prognosis, and different clinicopathological features about GHRL and the correlation between GHRL and tumor infiltration immune cells in GC patients based on the data published in the following databases: TIMER, GEPIA, GEO, STRING, UALCAN, TISIDB, and Kaplan-Meier Plotter. Furthermore, R software analysis for GC Correa' cascade was also provided. Finally, GHRL expression in GC tissues was assayed using quantitative real-time polymerase chain reaction and immunohistochemistry.

Results

We found that GHRL expression in GC samples was lower than in normal samples and verified by quantitative PCR (qPCR) and immunohistochemistry. However, sample type, cancer stage, and worse survival were correlated to high GHRL expression. We also found that the expression of GHRL in dysplasia was significantly lower than that in CNAG and in GC. High GHRL expression was connected with immunomodulators, chemokines, and infiltrating levels of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells in GC.

Conclusions

GHRL is a prognostic biomarker for GC patients, and it is correlated with progression of precancerous lesions in GC. It might lead to poor prognosis by regulating tumor immune microenvironment. Studies are important to explore therapeutic targeting GHRL in the future.

Food addiction, hormones and blood biomarkers in humans: A systematic literature review

BACKGROUND

Food addiction may play a role in rising obesity rates in connection with obesogenic environments and processed food availability, however the concept of food addiction remains controversial. While animal studies show evidence for addictive processes in relation to processed foods, most human studies are psychologically focussed and there is a need to better understand evidence for biological mechanisms of food addiction in humans. Several key hormones are implicated in models of food addiction, due to their key roles in feeding, energy metabolism, stress and addictive behaviours. This systematic literature review examines evidence for relationships between food addiction, hormones and other blood biomarkers.

METHODS

A series of literature searches was performed in Scopus, PsychInfo, MedLine, ProQuest, CINAHL and Web of Science. A total of 3111 articles were found, of which 1045 were duplicates. Articles were included if they contained a psychometric measurement of food addiction, such as the Yale Food Addiction Scale, as well as addressed the association between FA and hormones or blood biomarkers in humans. Articles were assessed for eligibility by two independent reviewers.

RESULTS

Sixteen studies were identified that examined relationships between food addiction and blood biomarkers, published between 2015 and 2021. Significant findings were reported for leptin, ghrelin, cortisol, insulin and glucose, oxytocin, cholesterol, plasma dopamine, thyroid stimulating hormone (TSH), haemoglobin A1c (HbA1c), triglyceride (TG), amylin, tumour necrosis factor alpha (TNF- α) and cholecystokinin (CCK). Methodological issues included small sample sizes and variation in obesity status, sex and mental health-related comorbidities. Due to methodological limitations, definite connections between FA, hormones and other blood biomarkers cannot yet be determined.

CONCLUSION

This systematic review identified preliminary evidence linking FA symptoms to hormones and other blood biomarkers related to feeding, addiction, and stress. However, due to the small number of studies and methodological limitations, further research is needed to evaluate biopsychosocial models of FA and to resolve controversies.

Molecular cloning and analysis of the ghrelin/GHSR system in Xenopus tropicalis

Ghrelin is a gut-derived peptide with several physiological functions, including feeding, gastrointestinal motility, and hormonal secretion. Recently, a host defense peptide, liver-expressed antimicrobial peptide-2 (LEAP2), was reported as an endogenous antagonist of growth hormone secretagogue receptor (GHS-R). The physiological relevance of the molecular LEAP2-GHS-R interaction in mammals has been explored; however, studies on non-mammals are limited. Here, we report the identification and functional characterization of ghrelin and its related molecules in Western clawed frog (Xenopus tropicalis), a known model organism. We first identified cDNA encoding X. tropicalis ghrelin and GHS-R. RT-qPCR revealed that ghrelin mRNA expression was most abundant in the stomach. GHS-R mRNA was widely distributed in the brain and peripheral tissues, and a relatively strong signal was observed in the stomach and intestine. In addition, LEAP2 was mainly expressed in intestinal tissues at higher levels than in the liver. In functional analysis, X. tropicalis ghrelin and human ghrelin induced intracellular Ca²⁺ mobilization with EC₅₀ values in the low nanomolar range in CHO-K1 cells expressing X. tropicalis GHS-R. Furthermore, ghrelin-induced GHS-R activation was antagonized with IC₅₀ values in the nanomolar range by heterologous human LEAP2. We also validated the expression of ghrelin and feeding-related factors under fasting conditions. After 2 days of fasting, no changes in ghrelin mRNA levels were observed in the stomach, but GHS-R mRNA levels were significantly increased, associated with significant downregulation of nucb2. In addition, LEAP2 upregulation was observed in the duodenum. These results provide the first evidence that LEAP2 functions as an antagonist of GHS-R in the anuran amphibian X. tropicalis. It has also been suggested that the ghrelin/GHS-R/LEAP2 system may be involved in energy homeostasis in X. tropicalis.

Body fatness associations with cancer: evidence from recent epidemiological studies and future directions

This narrative review highlights current evidence linking greater body fatness to risk of various cancers, with focus on evidence from recent large cohort studies and pooled analyses of cohort studies as well as Mendelian randomization studies (which utilized genetic variants associated with body mass index to debrief the causal effect of higher body fatness on cancer risk). This review also provides insights into the biological mechanisms underpinning the associations. Data from both observational and Mendelian randomization studies support the associations of higher body mass index with increased risk of many cancers with the strongest evidence for digestive system cancers, including esophageal, stomach, colorectal, liver, gallbladder, and pancreatic cancer, as well as kidney, endometrial, and ovarian (weak association) cancer. Evidence from observational studies suggests that greater body fatness has contrasting effects on breast cancer risk depending on menopausal status and on prostate cancer risk depending on disease stage. Experimental and Mendelian randomization studies indicate that adiponectin, insulin, and sex hormone pathways play an important role in mediating the link between body fatness and cancer risk. The possible role of specific factors and pathways, such as other adipocytokines and hormones and the gut microbiome in mediating the associations between greater body fatness and cancer risk is yet uncertain and needs investigation in future studies. With rising prevalence of overweight and obesity worldwide, the proportion of cancer caused by excess body fatness is expected to increase. There is thus an urgent need to identify efficient ways at the individual and societal level to improve diet and physical activity patterns to reduce the burden of obesity and accompanying comorbidities, including cancer.

The movement ecology of fishes

Movement of fishes in the aquatic realm is fundamental to their ecology and survival. Movement can be driven by a variety of biological, physiological and environmental factors occurring across all spatial and temporal scales. The intrinsic capacity of movement to impact fish individually (e.g., foraging) with potential knock-on effects throughout the ecosystem (e.g., food web dynamics) has garnered considerable interest in the field of movement ecology. The advancement of technology in recent decades, in combination with ever-growing threats to freshwater and marine systems, has further spurred empirical research and theoretical considerations. Given the rapid expansion within the field of movement ecology and its significant role in informing management and conservation efforts, a contemporary and multidisciplinary review about the various components influencing movement is outstanding. Using an established conceptual framework for movement ecology as a guide (i.e., Nathan et al., 2008: 19052), we synthesized the environmental and individual factors that affect the movement of fishes. Specifically, internal (e.g., energy acquisition, endocrinology, and homeostasis) and external (biotic and abiotic) environmental elements are discussed, as well as the different processes that influence individual-level (or population) decisions, such as navigation cues, motion capacity, propagation characteristics and group behaviours. In addition to environmental drivers and individual movement factors, we also explored how associated strategies help survival by optimizing physiological and other biological states. Next, we identified how movement ecology is increasingly being incorporated into management and conservation by highlighting the inherent benefits that spatio-temporal fish behaviour imbues into policy, regulatory, and remediation planning. Finally, we considered the future of movement ecology by evaluating ongoing technological innovations and both the challenges and opportunities that these advancements create for scientists and managers. As aquatic ecosystems continue to face alarming climate (and other human-driven) issues that impact animal movements, the comprehensive and multidisciplinary assessment of movement ecology will be instrumental in developing plans to guide research and promote sustainability measures for aquatic resources.

Mapping brain activity of gut-brain signaling to appetite and satiety in healthy adults: A systematic review and functional neuroimaging meta-analysis

Understanding how neurohormonal gut-brain signaling regulates appetite and satiety is vital for the development of therapies for obesity and altered eating behavior. However, reported brain areas associated with appetite or satiety regulators show inconsistency across functional neuroimaging studies. The aim of this study was to systematically assess the convergence of brain regions modulated by appetite and satiety regulators. Twenty-five studies were considered for qualitative synthesis, and 14 independent studies (20-experiments) found eligible for coordinate-based neuroimaging meta-analyses across 212 participants and 123 foci. We employed two different meta-analysis approaches. The results from the systematic review revealed the modulation of insula, amygdala, hippocampus, and orbitofrontal cortex (OFC) with appetite regulators, where satiety regulators were more associated with caudate nucleus, hypothalamus, thalamus, putamen, anterior cingulate cortex in addition to the insula and OFC. The two neuroimaging meta-analyses methods identified the caudate nucleus as a key area associated with satiety regulators. Our results provide quantitative brain activation maps of neurohormonal gut-brain signaling in heathy-weight adults that can be used to define alterations with eating behavior.

Understanding the Effects of Antipsychotics on Appetite Control

Antipsychotic drugs (APDs) represent a cornerstone in the treatment of schizophrenia and other psychoses. The effectiveness of the first generation (typical) APDs are hampered by so-called extrapyramidal side effects, and they have gradually been replaced by second (atypical) and third-generation APDs, with less extrapyramidal side effects and, in some cases, improved efficacy. However, the use of many of the current APDs has been limited due to their propensity to stimulate appetite, weight gain, and increased risk for developing type 2 diabetes and cardiovascular disease in this patient group. The mechanisms behind the appetite-stimulating effects of the various APDs are not fully elucidated, partly because their diverse receptor binding profiles may affect different downstream pathways. It is critical to identify the molecular mechanisms underlying drug-induced hyperphagia, both because this may lead to the development of new APDs, with lower appetite-stimulating effects but also because such insight may provide new knowledge about appetite regulation in general. Hence, in this review, we discuss the receptor binding profile of various APDs in relation to the potential mechanisms by which they affect appetite.

Resistant starch wheat increases PYY and decreases GIP but has no effect on self-reported perceptions of satiety

Dietary fiber has numerous health benefits, such as increasing satiety, and is regularly included in healthy dietary recommendations. However, different types and sources of fiber vary in their chemical properties and biological effects. This double-blind, randomized, placebo-controlled, crossover study investigated the effects of resistant starch type 2 (RS2) from wheat on self-reported perceptions of satiety and associated gut hormones in 30 healthy adults ages 40-65 years of age. Participants consumed rolls made using either RS2-enriched wheat flour or a wild-type flour for one week before a test day during which they ate a mixed meal containing the same roll type. Both self-reported perceptions of satiety and plasma concentrations of gut hormones were measured following the meal to assess whether the RS2-enriched wheat enhanced satiety and suppressed hunger for a longer period than the control wheat. Exploratory analysis indicated that fasting and peak concentration of peptide YY_3-36 (PYY_3-36; q_fast = 0.02, q_peak = 0.02) increased, while peak concentration and iAUC of glucose-dependent insulinotropic peptide (GIP; q_peak < 0.001, q_iAUC < 0.001) decreased after ingesting RS2-enriched wheat. However, self-reported perceptions of hunger or fullness using visual analog scales (VAS) did not differ following the test meal.

Viral Infection Drives the Regulation of Feeding Behavior Related Genes in Salmo salar

The feeding behavior in fish is a complex activity that relies on the ability of the brain to integrate multiple signals to produce appropriate responses in terms of food intake, energy expenditure, and metabolic activity. Upon stress cues including viral infection or mediators such as the proinflammatory cytokines, prostaglandins, and cortisol, both Pomc and Npy/Agrp neurons from the hypothalamus are stimulated, thus triggering a response that controls both energy storage and expenditure. However, how appetite modulators or neuro-immune cues link pathogenesis and energy homeostasis in fish remains poorly understood. Here, we provide the first evidence of a molecular linkage between inflammation and food intake in Salmon salar. We show that in vivo viral challenge with infectious pancreatic necrosis virus (IPNV) impacts food consumption by activating anorexic genes such as mc4r, crf, and pomcb and 5-HT in the brain of S. salar. At the molecular level, viral infection induces an overall reduction in lipid content in the liver, favoring the production of AA and EPA associated with the increment of elovl2 gene. In addition, infection upregulates leptin signaling and inhibits insulin signaling. These changes are accompanied by a robust inflammatory response represented by the increment of Il-1b, Il-6, Tnfa, and Pge2 as well as an increased cortisol level in vivo. Thus, we propose a model in which hypothalamic neurons respond to inflammatory cytokines and stress-related molecules and interact with appetite induction/inhibition. These findings provide evidence of crosstalk between pathogenesis-driven inflammation and hypothalamic-pituitary-adrenocortical axes in stress-induced food intake behavior in fish.

Physiology of Taste Processing in the Tongue, Gut, and Brain

The gustatory system detects and informs us about the nature of various chemicals we put in our mouth. Some of these have nutritive value (sugars, amino acids, salts, and fats) and are appetitive and avidly ingested, whereas others (atropine, quinine, nicotine) are aversive and rapidly rejected. However, the gustatory system is mainly responsible for evoking the perception of a limited number of qualities that humans taste as sweet, umami, bitter, sour, salty, and perhaps fat [free fatty acids (FFA)] and starch (malto-oligosaccharides). The complex flavors and mouthfeel that we experience while eating food result from the integration of taste, odor, texture, pungency, and temperature. The latter three arise primarily from the somatosensory (trigeminal) system. The sensory organs used for detecting and transducing many chemicals are found in taste buds (TBs) located throughout the tongue, soft palate esophagus, and epiglottis. In parallel with the taste system, the trigeminal nerve innervates the peri-gemmal epithelium to transmit temperature, mechanical stimuli, and painful or cooling sensations such as those produced by changes in temperature as well as from chemicals like capsaicin and menthol, respectively. This article gives an overview of the current knowledge about these TB cells' anatomy and physiology and their trigeminal induced sensations. We then discuss how taste is represented across gustatory cortices using an intermingled and spatially distributed population code. Finally, we review postingestion processing (interoception) and central integration of the tongue-gut-brain interaction, ultimately determining our sensations as well as preferences toward the wholesomeness of nutritious foods. © 2021 American Physiological Society. Compr Physiol 11:1-35, 2021.

Identification of the Ghrelin and Cannabinoid CB2 Receptor Heteromer Functionality and Marked Upregulation in Striatal Neurons from Offspring of Mice under a High-Fat Diet

Cannabinoids have been reported as orexigenic, i.e., as promoting food intake that, among others, is controlled by the so-called “hunger” hormone, ghrelin. The aim of this paper was to look for functional and/or molecular interactions between ghrelin GHSR1a and cannabinoid CB₂ receptors at the central nervous system (CNS) level. In a heterologous system we identified CB₂-GHSR1a receptor complexes with a particular heteromer print consisting of impairment of CB₂ receptor/G_i-mediated signaling. The blockade was due to allosteric interactions within the heteromeric complex as it was reverted by antagonists of the GHSR1a receptor. Cannabinoids acting on the CB₂ receptor did not affect cytosolic increases of calcium ions induced by ghrelin acting on the GHSR1a receptor. In situ proximity ligation imaging assays confirmed the expression of CB₂-GHSR1a receptor complexes in both heterologous cells and primary striatal neurons. We tested heteromer expression in neurons from offspring of high-fat-diet mouse mothers as they have more risk to be obese. Interestingly, there was a marked upregulation of those complexes in striatal neurons from siblings of pregnant female mice under a high-fat diet.

Effects of Short-Term Fasting on mRNA Expression of Ghrelin and the Peptide Transporters PepT1 and 2 in Atlantic Salmon (Salmo salar)

Food intake is a vital process that supplies necessary energy and essential nutrients to the body. Information regarding luminal composition in the gastrointestinal tract (GIT) collected through mechanical and nutrient sensing mechanisms are generally conveyed, in both mammals and fish, to the hypothalamic neurocircuits. In this context, ghrelin, the only known hormone with an orexigenic action, and the intestinal peptide transporters 1 and 2, involved in absorption of dietary di- and tripeptides, exert important and also integrated roles for the nutrient uptake. Together, both are potentially involved in signaling pathways that control food intake originating from different segments of the GIT. However, little is known about the role of different paralogs and their response to fasting. Therefore, after 3 weeks of acclimatization, 12 Atlantic salmon (Salmo salar) post-smolt were fasted for 4 days to explore the gastrointestinal response in comparison with fed control (n = 12). The analysis covered morphometric (weight, length, condition factor, and wet content/weight fish %), molecular (gene expression variations), and correlation analyses. Such short-term fasting is a common and recommended practice used prior to any handling in commercial culture of the species. There were no statistical differences in length and weight but a significant lower condition factor in the fasted group. Transcriptional analysis along the gastrointestinal segments revealed a tendency of downregulation for both paralogous genes slc15a1a and slc15a1b and with significant lowered levels in the pyloric ceca for slc15a1a and in the pyloric ceca and midgut for slc15a1b. No differences were found for slc15a2a and slc15a2b (except a higher expression of the fasted group in the anterior midgut), supporting different roles for slc15 paralogs. This represents the first report on the effects of fasting on slc15a2 expressed in GIT in teleosts. Transcriptional analysis of ghrelin splicing variants (ghrl-1 and ghrl-2) showed no difference between treatments. However, correlation analysis showed that the mRNA expression for all genes (restricted to segment with the highest levels) were affected by the residual luminal content. Overall, the results show minimal effects of 4 days of induced fasting in Atlantic salmon, suggesting that more time is needed to initiate a large GIT response.

The effect of antecedent exercise on the acute stress response and subsequent food consumption: a preliminary investigation

Physical activity has been shown to be protective against many of the deleterious consequences of stress; however, the effects of exercise on stress-induced food consumption are unclear. This study examined the effect of an acute bout of exercise prior to exposure to an acute stressor on subsequent eating behavior, together with the physiological (e.g., heart rate, blood pressure, salivary cortisol) and psychological (e.g., mood, perceived stress) responses to stress. Twenty-three men and women completed four experimental conditions (control, exercise only, stress only, and exercise prior to stress) conducted in a counterbalanced order using a within-subjects repeated measures design. Ad libitum energy intake from a laboratory test meal was assessed at each trial, together with monitoring of physiological and psychological responses. No difference in total energy intake (p = 0.146) or energy intake from 'unhealthy' foods was noted between conditions (p = 0.783), despite lower circulating ghrelin when antecedent exercise was performed compared with stress alone (p < 0.05). Exposure to an acute stressor is not necessarily associated with alterations in subsequent food intake, nor does antecedent exercise prior to stress exposure affect food choices, despite transient alterations in the hunger hormone ghrelin.

Potential Therapeutic Effects of Exogenous Ketone Supplementation for Type 2 Diabetes: A Review

Type 2 diabetes (T2D) is among the most prevalent non-communicable lifestyle diseases. We propose that overnutrition and low levels of physical activity can contribute to a vicious cycle of hyperglycemia, inflammation and oxidative stress, insulin resistance, and pancreatic β-cell dysfunction. The pathophysiological manifestations of T2D have a particular impact on the vasculature and individuals with T2D are at high risk of cardiovascular disease. Targeting aspects of the vicious cycle represent therapeutic approaches for improving T2D and protecting against cardiovascular complications. The recent advent of exogenous oral ketone supplements represents a novel, non-pharmacological approach to improving T2D pathophysiology and potentially protecting against cardiovascular disease risk. Herein, we review the emerging literature regarding the effects of exogenous ketone supplementation on metabolic control, inflammation, oxidative stress, and cardiovascular function in humans and highlight the potential application for breaking the vicious cycle of T2D pathophysiology.

The physiology of movement

Movement, from foraging to migration, is known to be under the influence of the environment. The translation of environmental cues to individual movement decision making is determined by an individual's internal state and anticipated to balance costs and benefits. General body condition, metabolic and hormonal physiology mechanistically underpin this internal state. These physiological determinants are tightly, and often genetically linked with each other and hence central to a mechanistic understanding of movement. We here synthesise the available evidence of the physiological drivers and signatures of movement and review (1) how physiological state as measured in its most coarse way by body condition correlates with movement decisions during foraging, migration and dispersal, (2) how hormonal changes underlie changes in these movement strategies and (3) how these can be linked to molecular pathways. We reveale that a high body condition facilitates the efficiency of routine foraging, dispersal and migration. Dispersal decision making is, however, in some cases stimulated by a decreased individual condition. Many of the biotic and abiotic stressors that induce movement initiate a physiological cascade in vertebrates through the production of stress hormones. Movement is therefore associated with hormone levels in vertebrates but also insects, often in interaction with factors related to body or social condition. The underlying molecular and physiological mechanisms are currently studied in few model species, and show -in congruence with our insights on the role of body condition- a central role of energy metabolism during glycolysis, and the coupling with timing processes during migration. Molecular insights into the physiological basis of movement remain, however, highly refractory. We finalise this review with a critical reflection on the importance of these physiological feedbacks for a better mechanistic understanding of movement and its effects on ecological dynamics at all levels of biological organization.

Serum ghrelin and esophageal and gastric cancer in two cohorts in China

Ghrelin is a hormone produced in the oxyntic glands of the stomach. Previous work by our group has suggested that serum ghrelin concentrations are inversely associated with gastric and esophageal cancer risk. We measured ghrelin concentrations in the Linxian General Population Nutrition Intervention Trial (NIT), and the Shanghai Women's Health Study (SWHS). In NIT, we analyzed serum samples from 298 esophageal squamous cell carcinoma (ESCC) cases, 518 gastric cardia adenocarcinoma (GCA) cases, 258 gastric noncardia adenocarcinoma (GNCA) cases and 770 subcohort controls (case-cohort). In SWHS, we measured ghrelin in plasma samples from 249 GNCA cases and 498 matched controls (nested case-control). Ghrelin was measured using radioimmunoassay. In NIT and SWHS, low ghrelin concentrations were associated with an increased risk of developing GNCA and GCA. The hazard ratio (HR _Q1:Q4 ) for GNCA in NIT was 1.35 (95% CI: 0.89-2.05; p-trend = 0.02); the odds ratio in SWHS was 1.66 (95% CI: 1.02-2.70; p-trend = 0.06). Low ghrelin was associated with a twofold increase of GCA (HR _Q1:Q4 = 2.00, 95% CI: 1.45-2.77; p-trend<0.001). In contrast, a lower risk of ESCC (NIT ESCC HR _Q1:Q4 = 0.65, 95% CI: 0.45-0.92; p-trend = 0.02) was found in NIT. Low baseline ghrelin concentrations were associated with an increased risk for GNCA and GCA in the NIT and the SWHS. In contrast, low ghrelin concentrations at baseline were associated with a reduced risk of developing ESCC in the NIT. Ghrelin may be an early marker of future cancer risk for developing upper gastrointestinal cancer in regions of high incidence.

Impact of Hunger, Satiety, and Oral Glucose on the Association Between Insulin and Resting-State Human Brain Activity

To study the interplay of metabolic state (hungry vs. satiated) and glucose administration (including hormonal modulation) on brain function, resting-state functional magnetic resonance imaging (rs-fMRI) and blood samples were obtained in 24 healthy normal-weight men in a repeated measurement design. Participants were measured twice: once after a 36 h fast (except water) and once under satiation (three meals/day for 36 h). During each session, rs-fMRI and hormone concentrations were recorded before and after a 75 g oral dose of glucose. We calculated the amplitude map from blood-oxygen-level-dependent (BOLD) signals by using the fractional amplitude of low-frequency fluctuation (fALFF) approach for each volunteer per condition. Using multiple linear regression analysis (MLRA) the interdependence of brain activity, plasma insulin and blood glucose was investigated. We observed a modulatory impact of fasting state on intrinsic brain activity in the posterior cingulate cortex (PCC). Strikingly, differences in plasma insulin levels between hunger and satiety states after glucose administration at the time of the scan were negatively related to brain activity in the posterior insula and superior frontal gyrus (SFG), while plasma glucose levels were positively associated with activity changes in the fusiform gyrus. Furthermore, we could show that changes in plasma insulin enhanced the connectivity between the posterior insula and SFG. Our results indicate that hormonal signals like insulin alleviate an acute hemostatic energy deficit by modifying the homeostatic and frontal circuitry of the human brain.

Contribution of ghrelin to functional gastrointestinal disorders’ pathogenesis

Functional gastrointestinal disorders (FGID) are heterogeneous disorders with a variety of clinical manifestations, primarily defined by signs and symptoms rather than a definite underlying cause. Their pathophysiology remains obscure and, although it is expected to differ according to the specific FGID, disruptions in the brain-gut axis are now thought to be a common denominator in their pathogenesis. The hormone ghrelin is an important component of this axis, exerting a wide repertoire of physiological actions, including regulation of gastrointestinal motility and protection of mucosal tissue. Ghrelin’s gene shows genetic polymorphism, while its protein product undergoes complex regulation and metabolism in the human body. Numerous studies have studied ghrelin’s relation to the emergence of FGIDs, its potential value as an index of disease severity and as a predictive marker for symptom relief during attempted treatment. Despite the mixed results currently available in scientific literature, the plethora of statistically significant findings shows that disruptions in ghrelin genetics and expression are plausibly related to FGID pathogenesis. The aim of this paper is to review current literature studying these associations, in an effort to uncover certain patterns of alterations in both genetics and expression, which could delineate its true contribution to FGID emergence, either as a causative agent or as a pathogenetic intermediate.

Fasting Upregulates npy, agrp, and ghsr Without Increasing Ghrelin Levels in Zebrafish (Danio rerio) Larvae

Food intake in fish and mammals is orchestrated by hypothalamic crosstalk between orexigenic (food intake stimulation) and anorexigenic (food intake inhibition) signals. Some of these signals are released by peripheral tissues that are associated with energy homeostasis or nutrient availability. During the fish larva stage, orexigenic stimulation plays a critical role in individual viability. The goal of this study was to assess the mRNA levels of the main neuropeptides involved in food intake regulation (npy, agrp, carppt, and pomc), in concert with the mRNA levels and peptide levels of ghrelin, under a fasting intervention at the larval stage in zebrafish (Danio rerio). Prior to the fasting intervention, the zebrafish larva cohort was reared for 20 days post fertilization (dpf) and then randomly divided into two groups of 20 individuals. One group was subjected to a fasting intervention for 5 days (fasted group), and the other group was fed normally (fed group); this experimental protocol was performed twice independently. At the end of the fasting period, individuals from each experimental group were divided into different analysis groups, for evaluations such as relative gene expression, immunohistochemistry, and liquid chromatography coupled to nano high-resolution mass spectrometry (nLC-HRMS) analyses. The relative expression levels of the following genes were assessed: neuropeptide Y (npy), agouti-related peptide (agrp), proopiomelanocortin (pomc), cocaine and amphetamine-regulated transcript (cartpt), ghrelin (ghrl), ghrelin O-acyltransferase (mboat4), growth hormone secretagogue receptor (ghsr), and glucokinase (gck). In the fasted group, significant upregulation of orexigenic peptides (npy - agrp) and ghsr was observed, which was associated with significant downregulation of gck. The anorexigenic peptides (pomc and cartpt) did not show any significant modulation between the groups, similar to mboat4. Contrary to what was expected, the relative mRNA upregulation of the orexigenic peptides observed in the fasted experimental group could not be associated with significant ghrelin modulation as assessed by three different approaches: qPCR (relative gene expression of ghrelin), nLC-HRMS (des-acyl-ghrelin levels), and immunohistochemistry (integrated optical density of prepropeptides in intestinal and hepatopancreas tissues). Our results demonstrate that zebrafish larvae at 25 dpf exhibit suitable modulation of the relative mRNA levels of orexigenic peptides (npy and agrp) in response to fasting intervention; nevertheless, ghrelin was not coregulated by fasting. Therefore, it can be suggested that ghrelin is not an essential peptide for an increase in appetite in the zebrafish larva stage. These results give rise to new questions about food intake regulation factors in the early stages of fish.

Neuroanatomical Framework of the Metabolic Control of Reproduction

A minimum amount of energy is required for basic physiological processes, such as protein biosynthesis, thermoregulation, locomotion, cardiovascular function, and digestion. However, for reproductive function and survival of the species, extra energy stores are necessary. Production of sex hormones and gametes, pubertal development, pregnancy, lactation, and parental care all require energy reserves. Thus the physiological systems that control energy homeostasis and reproductive function coevolved in mammals to support both individual health and species subsistence. In this review, we aim to gather scientific knowledge produced by laboratories around the world on the role of the brain in integrating metabolism and reproduction. We describe essential neuronal networks, highlighting key nodes and potential downstream targets. Novel animal models and genetic tools have produced substantial advances, but critical gaps remain. In times of soaring worldwide obesity and metabolic dysfunction, understanding the mechanisms by which metabolic stress alters reproductive physiology has become crucial for human health.

Adiposity and gastrointestinal cancers: epidemiology, mechanisms and future directions

Excess adiposity is a risk factor for several cancers of the gastrointestinal system, specifically oesophageal adenocarcinoma and colorectal, small intestine, pancreatic, liver, gallbladder and stomach cancers. With the increasing prevalence of obesity in nearly all regions of the world, this relationship could represent a growing source of cancers of the digestive system. Experimental and molecular epidemiological studies indicate important roles for alterations in insulin signalling, adipose tissue-derived inflammation and sex hormone pathways in mediating the association between adiposity and gastrointestinal cancer. The intestinal microbiome, gut hormones and non alcoholic fatty liver disease (NAFLD) also have possible roles. However, important gaps remain in our knowledge. For instance, our understanding of how adiposity throughout the life course is related to the risk of gastrointestinal cancer development and of how obesity influences gastrointestinal cancer prognosis and survival is limited. Nonetheless, the increasing use of state-of-the-art analytical methods (such as omics technologies, Mendelian randomization and MRI) in large-scale epidemiological studies offers exciting opportunities to advance our understanding of the complex relationship between adiposity and gastrointestinal cancers. Here, we examine the epidemiology of associations between obesity and gastrointestinal cancer, explore potential mechanisms underlying these relationships and highlight important unanswered research questions.

Serum ghrelin and obestatin levels in HIV-infected patients: Effect of 36 weeks of antiretroviral treatment

INTRODUCTION

Patients with HIV+ often present lipid disturbances. The role of ghrelin and obestatin in these lipid disturbances is not clear. The effect of antiretroviral (ART) drugs on those molecules is also unknown. This study measured ghrelin and obestatin levels, as well as metabolic markers, in patients with HIV+ before and after 36 weeks of ART.

MATERIAL AND METHODS

Twenty HIV-positive, ART-naïve patients who started a scheme consisting of tenofovir/emtricitabine+lopinavir/ritonavir were enrolled. Plasma samples were collected before and after 36 weeks of treatment. Serum ghrelin and obestatin levels were quantitated by ELISA; glucose, cholesterol, and triglyceride levels were measured by colorimetric and enzymatic methods, and cardiovascular risk was calculated by the atherogenic index of plasma (AIP).

RESULTS

All patients completed 36 weeks of ART. Total cholesterol (p<0.001), LDL-C (p=0.019), HDL-C (p=0.003), VLDL-C (p=0.002), and triglyceride levels (p=0.021) significantly increased after treatment. AIP revealed increased cardiovascular risk at baseline, which remained high after treatment. There was a statistically significant increase in obestatin level in the unpaired and paired analyses, while ghrelin levels only showed a trend to increase. Changes in ghrelin and obestatin levels positively correlated, but no correlation was seen with any metabolic parameter.

CONCLUSION

After 36 weeks of ART, patients showed an altered lipid profile, but there were no significant changes in cardiovascular risk. Ghrelin and obestatin levels increased after 36 weeks of ART, but the increase was only significant for obestatin. Changes in ghrelin and obestatin positively correlate.

Rumination in anorexia nervosa: Cognitive-affective and neuroendocrinological aspects

Rumination about body weight/figure as well as food is common in patients with Anorexia Nervosa (AN) and may be a maintenance factor of the disorder. While rumination can generally be considered as a cognitive-affective process, food-related rumination may be driven primarily by a physiological response to undernutrition. In the current longitudinal study, we integrate ecological momentary assessment of rumination and affect and, as a biological marker of undernutrition, plasma leptin levels collected from 33 AN patients. At the very acute stage and again after short-term weight-restoration patients answered short questionnaires six times per day over two weeks. Analyses via hierarchical linear modelling confirmed that rumination is closely linked to affect in AN before and after weight-restoration. Rumination about food decreased during weight-restoration and was correlated with leptin levels. In contrast, rumination about body weight/figure was not linked to leptin, persisted after weight gain, and showed stronger connections with affect. This suggests that rumination about body weight/figure seems to be a cognitive-affective aspect of the disorder, but food-related rumination may need to be considered from a physiological perspective. It is possible that food-related ruminative thoughts reflect a physiological symptom induced by undernutrition, similar to well-described leptin-associated changes in physical activity.

Serum ghrelin is associated with risk of colorectal adenocarcinomas in the ATBC study

BACKGROUND

Colorectal cancers are the third most common cancers in women and men in the USA. While dietary and lifestyle factors such as Western diet, physical inactivity and obesity have been linked to an increased risk of this malignancy, the mechanisms for these associations are unclear. GI hormones, including ghrelin, are involved in energy balance by mediating appetite and metabolism; however, the association between ghrelin and colorectal cancer has not been studied.

METHODS

We conducted a case-control study nested within the all-male Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study of Finnish smokers (aged 50-69 years) to examine serum ghrelin concentration and colorectal cancer risk. Data from 284 colon and 239 rectal cancers and 523 controls (matched on age, date of blood draw and serum availability) were analysed. ORs and 95% CIs were calculated using multivariable (conditional) logistic regression.

RESULTS

Overall, low-serum ghrelin was significantly associated with increased risk of colorectal cancer (Q1 vs Q4: OR:1.57, 95% CI 1.05 to 2.34). For individuals developing tumours within 10 years of blood draw, those in the lowest quartile of serum ghrelin concentrations were statistically significantly more likely to develop colorectal cancers than those with higher serum ghrelin concentrations (OR: 10.86, 95% CI 5.01 to 23.55). However, for individuals with tumours developing more than 20 years after blood draw, low-serum ghrelin concentrations were associated with a decreased risk of colorectal cancer relative to those with the highest serum ghrelin concentrations (OR: 0.26, 95% CI 0.11 to 0.64).

CONCLUSION

Low-serum ghrelin was associated with an increased colorectal cancer risk within 10 years of blood draw with a decreased risk for developing colorectal cancer more than 20 years after blood draw. These results suggest that ghrelin concentrations may vary across the carcinogenic process.

Food Cues and Obesity: Overpowering Hormones and Energy Balance Regulation

PURPOSE OF REVIEW

In the modern obesogenic environment, food cues play a crucial role in the development of obesity by disrupting hormone and energy balance mechanisms. Thus, it is critical to understand the neurobiology of feeding behaviors and obesity in the context of ubiquitous food cues. The current paper reviews the physiology of feeding, hormonal regulation of energy balance, and food cue responses and discusses their contributions to obesity.

RECENT FINDINGS

Food cues have strong impact on human physiology. Obese individuals have altered food cue-elicited responses in the brain and periphery, overpowering hormone and energy balance regulation. Disrupted homeostasis during food cue exposure leads to continued food intake, unsuccessful weight management, and poor treatment outcomes, which further contributes to obesity epidemic. Findings from the review emphasize the crucial role of food cues in obesity epidemic, which necessitates multidimensional approaches to the prevention and treatment of obesity, including psychosocial interventions to reduce food cue reactivity, along with conventional treatment.

Peripherally injected ghrelin and leptin reduce food hoarding and mass gain in the coal tit (Periparus ater)

In birds little is known about the hormonal signals that communicate nutritional state to the brain and regulate appetitive behaviours. In mammals, the peptide hormones ghrelin and leptin elevate and inhibit consumption and food hoarding, respectively. But in birds, administration of both ghrelin and leptin inhibit food consumption. The role of these hormones in the regulation of food hoarding in avian species has not been examined. To investigate this, we injected wild caught coal tits (Periparus ater) with leptin, high-dose ghrelin, low-dose ghrelin and a saline control in the laboratory. We then measured food hoarding and mass gain, as a proxy of food consumption, every 20 min for 2 h post-injection. Both high-dose ghrelin and leptin injections significantly reduced hoarding and mass gain compared with controls. Our results provide the first evidence that hoarding behaviour can be reduced by both leptin and ghrelin in a wild bird. These findings add to evidence that the hormonal control of food consumption and hoarding in avian species differs from that in mammals. Food hoarding and consumptive behaviours consistently show the same response to peripheral signals of nutritional state, suggesting that the hormonal regulation of food hoarding has evolved from the consumption regulatory system.

Influences of Hunger, Satiety and Oral Glucose on Functional Brain Connectivity: A Multimethod Resting-State fMRI Study

A major regulatory task of the organism is to keep brain functions relatively constant in spite of metabolic changes (e.g., hunger vs. satiety) or availability of energy (e.g., glucose administration). Resting-state functional magnetic resonance imaging (rs-fMRI) can reveal resulting changes in brain function but previous studies have focused mostly on the hypothalamus. Therefore, we took a whole-brain approach and examined 24 healthy normal-weight men once after 36 h of fasting and once in a satiated state (six meals over the course of 36 h). At the end of each treatment, rs-fMRI was recorded before and after the oral administration of 75 g of glucose. We calculated local connectivity (regional homogeneity [ReHo]), global connectivity (degree of centrality [DC]), and amplitude (fractional amplitude of low-frequency fluctuation [fALFF]) maps from the rs-fMRI data. We found that glucose administration reduced all measures selectively in the left supplementary motor area and increased ReHo and fALFF in the right middle and superior frontal gyri. For fALFF, we observed a significant interaction between metabolic states and glucose in the left thalamus. This interaction was driven by a fALFF increase after glucose treatment in the hunger relative to the satiety condition. Our results indicate that fALFF analysis is the most sensitive measure to detect effects of metabolic states on resting-state brain activity. Moreover, we show that multimethod rs-fMRI provides an unbiased approach to identify spontaneous brain activity associated with changes in homeostasis and caloric intake.

A Role for Exercise in Attenuating Unhealthy Food Consumption in Response to Stress

It is well established that both acute and chronic stress can be detrimental to health and wellbeing by directly increasing the risk of several chronic diseases and related health problems. In addition, stress may contribute to ill-health indirectly via its downstream effects on individuals’ health-related behaviour, such as promoting the intake of unhealthy palatable foods high in fat and sugar content. This paper reviews (a) the research literature on stress-models; (b) recent research investigating stress-induced eating and (c) the potential physiological and psychological pathways contributing to stress-induced eating. Particular attention is given to (d) the role of physical exercise in attenuating acute stress, with exploration of potential mechanisms through which exercise may reduce unhealthy food and drink consumption subsequent to stressor exposure. Finally, exercise motivation is discussed as an important psychological influence over the capacity for physical exercise to attenuate unhealthy food and drink consumption after exposure to stressors. This paper aims to provide a better understanding of how physical exercise might alleviate stress-induced unhealthy food choices.

Neuroendocrine Regulation of Food Intake in Polycystic Ovary Syndrome

Several peripheral and central signals are involved in the sophisticated regulation of food intake. Women with polycystic ovary syndrome (PCOS) are prone to consume a diet higher in saturated fat and foods with high glycemic index and show impaired appetite regulation and measures of satiety. As a consequence, obesity, mostly of the central type, is prevalent in the syndrome and worsens the endocrine and metabolic profile of the affected patients. This review article briefly analyzes the current knowledge about the neuroendocrine mechanisms underlying the interplay between feeding behavior, obesity, and reproductive abnormalities in PCOS.

Ghrelin affects stopover decisions and food intake in a long-distance migrant

Billions of birds migrate long distances to either reach breeding areas or to spend the winter at more benign places. On migration, most passerines frequently stop over to rest and replenish their fuel reserves. To date, we know little regarding how they decide that they are ready to continue their journey. What physiological signals tell a bird's brain that its fuel reserves are sufficient to resume migration? A network of hormones regulates food intake and body mass in vertebrates, including the recently discovered peptide hormone, ghrelin. Here, we show that ghrelin reflects body condition and influences migratory behavior of wild birds. We measured ghrelin levels of wild garden warblers (Sylvia borin) captured at a stopover site. Further, we manipulated blood concentrations of ghrelin to test its effects on food intake and migratory restlessness. We found that acylated ghrelin concentrations of garden warblers with larger fat scores were higher than those of birds without fat stores. Further, injections of unacylated ghrelin decreased food intake and increased migratory restlessness. These results represent experimental evidence that appetite-regulating hormones control migratory behavior. Our study lays a milestone in migration physiology because it provides the missing link between ecologically dependent factors such as condition and timing of migration. In addition, it offers insights in the regulation of the hormonal system controlling food intake and energy stores in vertebrates, whose disruption causes eating disorders and obesity.

AMPKα2 in Kiss1 Neurons Is Required for Reproductive Adaptations to Acute Metabolic Challenges in Adult Female Mice

A temporary and reversible inhibition of the hypothalamo-pituitary-gonadal axis is adaptive when energy reserves are diminished, allowing individual survival and energy accumulation for eventual reproduction. The AMP-activated protein kinase (AMPK) works as a cellular sensor of the AMP to ATP ratio and ultimately of energy availability. Activation of AMPK suppresses ATP-consuming processes and stimulates ATP-producing pathways. The AMPK α2 catalytic subunit is expressed in multiple hypothalamic nuclei including those associated with reproductive control, ie, the anteroventral periventricular nucleus and the arcuate nucleus. Subsets of kisspeptin neurons in the anteroventral periventricular nucleus (20% in females) and arcuate nucleus (45% in males and 65% in females) coexpress AMPKα2 mRNA. Using the Cre-loxP approach, we assessed whether AMPKα2 in Kiss1 cells is required for body weight and reproductive function. The AMPKα2-deleted mice show no difference in body weight and time for sexual maturation compared with controls. Males and females are fertile and have normal litter size. The AMPKα2-deleted and control females have similar estradiol feedback responses and show no difference in Kiss1 mRNA expression after ovariectomy or ovariectomy plus estradiol replacement. In males, acute fasting decreased Kiss1 mRNA expression in both groups, but no effect was observed in females. However, after an acute fasting, control mice displayed prolonged diestrous phase, but AMPKα2-deleted females showed no disruption of estrous cycles. Our findings demonstrate that the AMPKα2 catalytic subunit in Kiss1 cells is dispensable for body weight and reproductive function in mice but is necessary for the reproductive adaptations to conditions of acute metabolic distress.

The Neuroendocrine Regulation of Food Intake in Fish: A Review of Current Knowledge

Fish are the most diversified group of vertebrates and, although progress has been made in the past years, only relatively few fish species have been examined to date, with regards to the endocrine regulation of feeding in fish. In fish, as in mammals, feeding behavior is ultimately regulated by central effectors within feeding centers of the brain, which receive and process information from endocrine signals from both brain and peripheral tissues. Although basic endocrine mechanisms regulating feeding appear to be conserved among vertebrates, major physiological differences between fish and mammals and the diversity of fish, in particular in regard to feeding habits, digestive tract anatomy and physiology, suggest the existence of fish- and species-specific regulating mechanisms. This review provides an overview of hormones known to regulate food intake in fish, emphasizing on major hormones and the main fish groups studied to date.

Ghrelin is a possible new predictor associated with executive function in patients with type 2 diabetes mellitus

AIMS/INTRODUCTION

The aim of the present research was to study the ghrelin level, executive function and their possible association in patients with type 2 diabetes mellitus.

MATERIALS AND METHODS

A total of 370 people were recruited between March 2015 and March 2016 in this study. Among them, 212 participants were patients with type 2 diabetes mellitus and 158 participants were included as the control group. Their blood sample was analyzed for the level of ghrelin and other clinical indexes. Cognitive function was measured by the Montreal Cognitive Assessment, and executive function was evaluated by the Wisconsin Card Sorting Test.

RESULTS

In the type 2 diabetes mellitus group, age, years of education, duration of diabetes, fasting blood glucose, glycated hemoglobin, hypertension and waist-to-hip ratio were correlated with total Montreal Cognitive Assessment scores. No association was found between ghrelin level and total Montreal Cognitive Assessment score in patients with type 2 diabetes mellitus. However, ghrelin was found to be a significant predictor for executive function impairment measured by the Wisconsin Card Sorting Test in patients with type 2 diabetes mellitus.

CONCLUSIONS

The level of serum ghrelin might be a biomarker of executive function and become a strong predictor of executive function impairment in patients with type 2 diabetes mellitus. Ghrelin might have a potential protective effect against cognitive function impairment in type 2 diabetes patients.

Obesity in MENX Rats Is Accompanied by High Circulating Levels of Ghrelin and Improved Insulin Sensitivity

Ghrelin, the natural ligand of the growth hormone secretagogue receptor type 1a (GHS-R1a), is mainly secreted from the stomach and regulates food intake and energy homeostasis. p27 regulates cell cycle progression in many cell types. Here, we report that rats affected by the multiple endocrine neoplasia syndrome MENX, caused by a p27 mutation, develop pancreatic islet hyperplasia containing elevated numbers of ghrelin-producing ε-cells. The metabolic phenotype of MENX-affected rats featured high endogenous acylated and unacylated plasma ghrelin levels. Supporting increased ghrelin action, MENX rats show increased food intake, enhanced body fat mass, and elevated plasma levels of triglycerides and cholesterol. Ghrelin effect on food intake was confirmed by treating MENX rats with a GHS-R1a antagonist. At 7.5 months, MENX-affected rats show decreased mRNA levels of hypothalamic GHS-R1a, neuropeptide Y (NPY), and agouti-related protein (AgRP), suggesting that prolonged hyperghrelinemia may lead to decreased ghrelin efficacy. In line with ghrelin's proposed role in glucose metabolism, we find decreased glucose-stimulated insulin secretion in MENX rats, while insulin sensitivity is improved. In summary, we provide a novel nontransgenic rat model with high endogenous ghrelin plasma levels and, interestingly, improved glucose tolerance. This model might aid in identifying new therapeutic approaches for obesity and obesity-related diseases, including type 2 diabetes.

Increased acyl ghrelin but decreased total ghrelin and unacyl ghrelin in Chinese Han people with impaired fasting glucose combined with impaired glucose tolerance

We assessed the plasma acyl ghrelin (AG), unacyl ghrelin (UAG), and total ghrelin (TGhr) levels in Chinese adults with pre-diabetes and newly diagnosed diabetes mellitus (NDDM) after an oral glucose tolerance test (OGTT), and abdominal subcutaneous fat area and visceral fat area (VFA) were measured. Fasting AG level was increased in the impaired fasting glucose (IFG) combined with impaired glucose tolerance (IFG+IGT) and NDDM groups. AG, UAG, and TGhr levels were significantly decreased post-OGTT, and the decrements of 30-min AG, UAG, and TGhr post-OGTT were not significantly different among groups. UAG and TGhr levels did not differ significantly among the normal glucose tolerance (NGT), IFG and NDDM groups, but they decreased obviously in the IFG+IGT and impaired glucose tolerance (IGT) groups. The NDDM group had larger VFA than the NGT, IGT, and IFG+IGT groups, even after adjustment for height, it was still larger than the NGT group. The factors such as dyslipidemia and obesity which are prone to develop insulin resistance (IR) and decrease insulin sensitivity (IS) were negatively correlated with UAG and TGhr, positively with AG/UAG, while no correlations with AG. In terms of evaluating IS and IR, AG/UAG ratio may be superior in AG concentration. Our findings suggest that relative sufficiency of AG, the deficiency of TGhr and UAG are already present in IFG+IGT patients. We speculate that there is UAG resistance in severe hyperglycemia (diabetic state), which could produce elevated TGhr and UAG compared to IFG+IGT group. In the development of T2D, increase of VFA could be the initiating factor, leading elevated AG, reduced UAG, IR, decreased IS, and finally hyperglycemia.

A predictive model of the dynamics of body weight and food intake in rats submitted to caloric restrictions

Dynamics of body weight and food intake can be studied by temporally perturbing food availability. This perturbation can be obtained by modifying the amount of available food over time while keeping the overall food quantity constant. To describe food intake dynamics, we developed a mathematical model that describes body weight, fat mass, fat-free mass, energy expenditure and food intake dynamics in rats. In addition, the model considers regulation of food intake by leptin, ghrelin and glucose. We tested our model on rats experiencing temporally variable food availability. Our model is able to predict body weight and food intake variations by taking into account energy expenditure dynamics based on a memory of the previous food intake. This model allowed us to estimate this memory lag to approximately 8 days. It also explains how important variations in food availability during periods longer than these 8 days can induce body weight gains.

Estradiol modulates Kiss1 neuronal response to ghrelin

Ghrelin is a metabolic signal regulating energy homeostasis. Circulating ghrelin levels rise during starvation and fall after a meal, and therefore, ghrelin may function as a signal of negative energy balance. Ghrelin may also act as a modulator of reproductive physiology, as acute ghrelin administration suppresses gonadotropin secretion and inhibits the neuroendocrine reproductive axis. Interestingly, ghrelin's effect in female metabolism varies according to the estrogen milieu predicting an interaction between ghrelin and estrogens, likely at the hypothalamic level. Here, we show that ghrelin receptor (GHSR) and estrogen receptor-α (ERα) are coexpressed in several hypothalamic sites. Higher levels of circulating estradiol increased the expression of GHSR mRNA and the coexpression of GHSR mRNA and ERα selectively in the arcuate nucleus (ARC). Subsets of preoptic and ARC Kiss1 neurons coexpressed GHSR. Increased colocalization was observed in ARC Kiss1 neurons of ovariectomized estradiol-treated (OVX + E₂; 80%) compared with ovariectomized oil-treated (OVX; 25%) mice. Acute actions of ghrelin on ARC Kiss1 neurons were also modulated by estradiol; 75 and 22% of Kiss1 neurons of OVX + E₂ and OVX mice, respectively, depolarized in response to ghrelin. Our findings indicate that ghrelin and estradiol may interact in several hypothalamic sites. In the ARC, high levels of E₂ increase GHSR mRNA expression, modifying the colocalization rate with ERα and Kiss1 and the proportion of Kiss1 neurons acutely responding to ghrelin. Our findings indicate that E₂ alters the responsiveness of kisspeptin neurons to metabolic signals, potentially acting as a critical player in the metabolic control of the reproductive physiology.

Changes in ghrelin and obestatin levels before and after a meal in children with simple obesity and anorexia

BACKGROUND

Obestatin and ghrelin both have effects on the hypothalamus which controls food intake. We hypothesize that the circulating levels of obestatin and ghrelin may change after a meal and might be different between obesity and anorexia, which might be relevant to anorexia or obesity.

METHOD

Fifteen children with obesity, 25 children with anorexia and 17 normal-weight healthy controls were enrolled in the study. The preprandial and postprandial glucose, insulin, total ghrelin and obestatin tests were completed in the three groups. The values of these indices were compared.

RESULTS

The obesity group had the highest values for BMI and fasting glucose (p < 0.001), while the anorexia group had the highest values for obestatin and ghrelin, followed by the control and obesity groups. No differences in ratios of ghrelin to obestatin were found between the anorexia and obesity groups (p > 0.05), but both were higher than that of the control group (p < 0.05). BMI was negatively correlated with preprandial obestatin (r = -0.8413, p < 0.001) and ghrelin (r = -0.7400, p < 0.001), but showed no significant correlations with the ghrelin-to-obestatin ratio.

CONCLUSION

Although there is still controversy between the present and previous studies, the present study show that levels of obestatin and ghrelin are inversely correlated with BMI.

Associations of diabetes mellitus, insulin, leptin, and ghrelin with gastroesophageal reflux and Barrett's esophagus

BACKGROUND & AIMS

Insulin and leptin have proliferative and anti-apoptotic effects. Ghrelin promotes gastric emptying and secretion of growth hormone and inhibits inflammation. We assessed whether diabetes mellitus and serum levels of insulin, leptin, and ghrelin are associated with gastroesophageal reflux disease (GERD) and Barrett's esophagus.

METHODS

We conducted a case-control study in 822 men undergoing colorectal cancer screening who were recruited to also undergo upper endoscopy. We identified 70 with Barrett's esophagus; 80 additional men with Barrett's esophagus were recruited shortly after their clinical diagnoses. Serum levels of insulin, leptin, and ghrelin were assayed in all 104 fasting men with Barrett's esophagus without diabetes and 271 without diabetes or Barrett's esophagus. Logistic regression was used to estimate the effects of diabetes and levels of insulin, leptin, and ghrelin on GERD and Barrett's esophagus.

RESULTS

Among men with GERD, diabetes was inversely associated with Barrett's esophagus (adjusted odds ratio [OR] = 0.383; 95% confidence interval [CI]: 0.179-0.821). Among nondiabetics, hyperinsulinemia was positively associated with Barrett's esophagus, but the association was attenuated by adjustment for leptin and ghrelin. Leptin was positively associated with Barrett's esophagus, adjusting for obesity, GERD, and levels of insulin and ghrelin (OR for 3(rd) vs 1(st) tertile = 3.25; 95% CI: 1.29-8.17); this association was stronger in men with GERD (P = .01 for OR heterogeneity). Ghrelin was positively associated with Barrett's esophagus (OR for an increment of 400 pg/mL = 1.39; 95% CI: 1.09-1.76), but inversely associated with GERD (OR for 3(rd) vs 1(st) tertile = 0.364; 95% CI: 0.195-0.680).

CONCLUSIONS

Based on a case-control study, leptin was associated with Barrett's esophagus, particularly in men with GERD. Serum insulin level was associated with Barrett's esophagus, but might be mediated by leptin. Serum ghrelin was inversely associated with GERD, as hypothesized, but positively associated with Barrett's esophagus, contrary to our hypothesis. Additional studies are needed in men and women to replicate these findings.

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.