The Potential Mechanism of Remission in Type 2 Diabetes Mellitus After Vertical Sleeve Gastrectomy

In recent years, there has been a gradual increase in the prevalence of obesity and type 2 diabetes mellitus (T2DM), with bariatric surgery remaining the most effective treatment strategy for these conditions. Vertical sleeve gastrectomy (VSG) has emerged as the most popular surgical procedure for bariatric/metabolic surgeries, effectively promoting weight loss and improving or curing T2DM. The alterations in the gastrointestinal tract following VSG may improve insulin secretion and resistance by increasing incretin secretion (especially GLP-1), modifying the gut microbiota composition, and through mechanisms dependent on weight loss. This review focuses on the potential mechanisms through which the enhanced action of incretin and metabolic changes in the digestive system after VSG may contribute to the remission of T2DM.

Negative emotional eating patterns in general Chinese adults: A replication and expansion study examining group differences in eating disorder symptomatology, psychosocial impairment, and emotion regulation difficulties

Previous research identified four patterns of negative emotional eating in American and Chinese university students and proposed future directions (e.g., exploring potential differences in emotion regulation across patterns and replicating the patterns in a general, non-student population). Furthermore, prior research has not explored group differences in muscularity-oriented eating disorder symptomatology or psychosocial impairment. Therefore, the present study addressed these gaps in a sample of general Chinese adults, further testing group differences in typical and muscularity-oriented eating disorder symptomatology, psychosocial impairment, and emotion regulation difficulties across patterns of negative emotional eating. A total of 600 Chinese adults were recruited. Latent class analysis (LCA) was used. Results replicated the four patterns of negative emotional eating in previous research, including non-emotional eating (non-EE), emotional over- and under-eating (EOE-EUE), emotional over-eating (EOE), and emotional under-eating (EUE). Significant class differences were identified in eating disorder symptomatology, psychosocial impairment, and emotion regulation difficulties. Specifically, individuals with EOE and EOE-EUE patterns exhibited higher eating disorder symptomatology, higher psychosocial impairment, and more emotion regulation difficulties than those with non-EE and EUE patterns. Therefore, these two classes (i.e., EOE and EOE-EUE), especially the poorly researched EOE-EUE group, should be further examined to elucidate research and clinical applications. Furthermore, findings underscore the role of emotion regulation difficulties in further describing the differences across these negative emotional eating patterns, which can be considered in future interventions for reducing negative emotional eating.

New Lessons from the gut: Studies of the role of gut peptides in weight loss and diabetes resolution after gastric bypass and sleeve gastrectomy

It has been known since 2005 that the secretion of several gut hormones changes radically after gastric bypass operations and, although more moderately, after sleeve gastrectomy but not after gastric banding. It has therefore been speculated that increased secretion of particularly GLP-1 and Peptide YY (PYY), which both inhibit appetite and food intake, may be involved in the weight loss effects of surgery and for improvements in glucose tolerance. Experiments involving inhibition of hormone secretion with somatostatin, blockade of their actions with antagonists, or blockade of hormone formation/activation support this notion. However, differences between results of bypass and sleeve operations indicate that distinct mechanisms may also be involved. Although the reductions in ghrelin secretion after sleeve gastrectomy would seem to provide an obvious explanation, experiments with restoration of ghrelin levels pointed towards effects on insulin secretion and glucose tolerance rather than on food intake. It seems clear that changes in GLP-1 secretion are important for insulin secretion after bypass and appear to be responsible for postbariatric hypoglycemia in glucose-tolerant individuals; however, with time the improvements in insulin sensitivity, which in turn are secondary to the weight loss, may be more important. Changes in bile acid metabolism do not seem to be of particular importance in humans.

Bardet-Biedl syndrome: A focus on genetics, mechanisms and metabolic dysfunction

Bardet-Biedl syndrome (BBS) is a rare, monogenic, multisystem disorder characterized by retinal dystrophy, renal abnormalities, polydactyly, learning disabilities, as well as metabolic dysfunction, including obesity and an increased risk of type 2 diabetes. It is a primary ciliopathy, and causative mutations in more than 25 different genes have been described. Multiple cellular mechanisms contribute to the development of the metabolic phenotype associated with BBS, including hyperphagia as a consequence of altered hypothalamic appetite signalling as well as alterations in adipocyte biology promoting adipocyte proliferation and adipogenesis. Within this review, we describe in detail the metabolic phenotype associated with BBS and discuss the mechanisms that drive its evolution. In addition, we review current approaches to the metabolic management of patients with BBS, including the use of weight loss medications and bariatric surgery. Finally, we evaluate the potential of targeting hypothalamic appetite signalling to limit hyperphagia and induce clinically significant weight loss.

Sequence-based prediction of the intrinsic solubility of peptides containing non-natural amino acids

Non-natural amino acids are increasingly used as building blocks in the development of peptide-based drugs as they expand the available chemical space to tailor function, half-life and other key properties. However, while the chemical space of modified amino acids (mAAs) such as residues containing post-translational modifications (PTMs) is potentially vast, experimental methods for measuring the developability properties of mAA-containing peptides are expensive and time consuming. To facilitate developability programs through computational methods, we present CamSol-PTM, a method that enables the fast and reliable sequence-based prediction of the intrinsic solubility of mAA-containing peptides in aqueous solution at room temperature. From a computational screening of 50,000 mAA-containing variants of three peptides, we selected five different small-size mAAs for a total number of 37 peptide variants for experimental validation. We demonstrate the accuracy of the predictions by comparing the calculated and experimental solubility values. Our results indicate that the computational screening of mAA-containing peptides can extend by over four orders of magnitude the ability to explore the solubility chemical space of peptides and confirm that our method can accurately assess the solubility of peptides containing mAAs. This method is available as a web server at https://www-cohsoftware.ch.cam.ac.uk/index.php/camsolptm .

Physical Exercise and Appetite Regulation: New Insights

Physical exercise is considered an important physiological intervention able to prevent cardiovascular diseases, obesity, and obesity-related cardiometabolic imbalance. Nevertheless, basic molecular mechanisms that govern the metabolic benefits of physical exercise are poorly understood. Recent data unveil new mechanisms that potentially explain the link between exercise, feeding suppression, and obesity.

Discordance between assessments of food cue responsiveness: Implications for assessment in youth with overweight/obesity

Food cue responsiveness (FCR), broadly defined as behavioral, cognitive, emotional and/or physiological responses to external appetitive cues outside of physiological need, contributes to overeating and obesity among youth and adults. A variety of measures purportedly assess this construct, ranging from youth- or parent-report surveys to objective eating tasks. However, little research has assessed their convergence. It is especially important to evaluate this in children with overweight/obesity (OW/OB), as reliable and valid assessments of FCR are essential to better understand the role of this critical mechanism in behavioral interventions. The present study examined the relationship between five measures of FCR in a sample of 111 children with OW/OB (mean age = 10.6, mean BMI percentile = 96.4; 70% female; 68% white; 23% Latinx). Assessments included: objectively measured eating in the absence of hunger (EAH), parasympathetic activity when exposed to food, parent reported food responsiveness subscale from the Child Eating Behavior Questionnaire (CEBQ-FR), child self-reported Power of Food total score (C-PFS), and child self-reported Food Cravings Questionnaire total score (FCQ-T). Statistically significant spearman correlations were found between EAH and CEBQ-FR (ρ = 0.19, p < 0.05) and parasympathetic reactivity to food cues with both C-PFS (ρ = -0.32, p = 0.002) and FCQ-T (ρ = -0.34, p < 0.001). No other associations were statistically significant. These relationships remained significant in subsequent linear regression models controlling for child age and gender. The lack of concordance between measures assessing highly conceptually related constructs is of concern. Future studies should seek to elucidate a clear operationalization of FCR, examine the associations between FCR assessments in children and adolescents with a range of weight statuses, and evaluate how to best revise these measures to accurately reflect the latent construct being assessed.

Gut Molecules in Cardiometabolic Diseases: The Mechanisms behind the Story

Atherosclerotic cardiovascular disease is the most common cause of morbidity and mortality worldwide. Diabetes mellitus increases cardiovascular risk. Heart failure and atrial fibrillation are associated comorbidities that share the main cardiovascular risk factors. The use of incretin-based therapies promoted the idea that activation of alternative signaling pathways is effective in reducing the risk of atherosclerosis and heart failure. Gut-derived molecules, gut hormones, and gut microbiota metabolites showed both positive and detrimental effects in cardiometabolic disorders. Although inflammation plays a key role in cardiometabolic disorders, additional intracellular signaling pathways are involved and could explain the observed effects. Revealing the involved molecular mechanisms could provide novel therapeutic strategies and a better understanding of the relationship between the gut, metabolic syndrome, and cardiovascular diseases.

Association Between Gut Hormones and Weight Change After Bariatric Arterial Embolization: Results from the BEAT Obesity Trial

PURPOSE

To evaluate associations of ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY 3-36 (PYY3-36) with weight change after bariatric arterial embolization (BAE).

MATERIALS AND METHODS

Subgroup analysis of data collected during the BEAT Obesity Trial involving 7 participants with BMI > 40 who were embolized with 300- to 500-μm Embosphere Microspheres. Three participants were characterized as "responders" (top tertile of weight loss at each visit) and 4 as "non-responders" (bottom tertile of weight loss at each visit). Mean ± standard deviation participant age was 44 ± 11 years, and 6 of 7 participants were women. Participants were evaluated at baseline, 2 weeks, and 1, 3, 6, and 12 months after BAE. After fasting, participants consumed a mixed meal test at each visit; blood samples were collected at 0, 15, 30, 60, 120, 180, and 240 min. Study outcome measures were changes in weight from baseline and plasma serum hormone levels.

RESULTS

Percentage change in ghrelin decreased significantly in non-responders at 60 and 120 min at 1 and 12 months (estimated difference between 60 vs. 0 min at 1 month: 69% [95% CI - 126%, - 13%]; estimated difference between 120 vs. 0 min at 12 months: - 131% (95% CI - 239%, - 23%]). Responders had significantly lower ghrelin and greater weight loss than non-responders at 6 and 12 months. GLP-1 and PYY3-36 levels did not differ between groups.

CONCLUSION

Participants with consistent weight loss throughout follow-up had lower ghrelin than non-responders, supporting decreased ghrelin as a mechanism underlying BAE-induced weight loss.

LEVEL OF EVIDENCE I

High-quality randomized trial or prospective study; testing of previously developed diagnostic criteria on consecutive patients; sensible costs and alternatives; values obtained from many studies with multiway sensitivity analyses; systematic review of Level I RCTs and Level I studies.

Influence of water-based exercise on energy intake, appetite, and appetite-related hormones in adults: A systematic review and meta-analysis

Single bouts of land-based exercise suppress appetite and do not typically alter energy intake in the short-term, whereas it has been suggested that water-based exercise may evoke orexigenic effects. The primary aim was to systematically review the available literature investigating the influence of water-based exercise on energy intake in adults (PROSPERO ID number CRD42022314349). PubMed, Medline, Sport-Discus, Academic Search Complete, CINAHL and Public Health Database were searched for peer-reviewed articles published in English from 1900 to May 2022. Included studies implemented a water-based exercise intervention versus a control or comparator. Risk of bias was assessed using the revised Cochrane 'Risk of bias tool for randomised trials' (RoB 2.0). We identified eight acute (same day) exercise studies which met the inclusion criteria. Meta-analysis was performed using a fixed effects generic inverse variance method on energy intake (8 studies (water versus control), 5 studies (water versus land) and 2 studies (water at two different temperatures)). Appetite and appetite-related hormones are also examined but high heterogeneity did not allow a meta-analysis of these outcome measures. We identified one chronic exercise training study which met the inclusion criteria with findings discussed narratively. Meta-analysis revealed that a single bout of exercise in water increased ad-libitum energy intake compared to a non-exercise control (mean difference [95% CI]: 330 [118, 542] kJ, P = 0.002). No difference in ad libitum energy intake was identified between water and land-based exercise (78 [-176, 334] kJ, P = 0.55). Exercising in cold water (18-20 °C) increased energy intake to a greater extent than neutral water (27-33 °C) temperature (719 [222, 1215] kJ; P < 0.005). The one eligible 12-week study did not assess whether water-based exercise influenced energy intake but did find that cycling and swimming did not alter fasting plasma concentrations of total ghrelin, insulin, leptin or total PYY but contributed to body mass loss 87.3 (5.2) to 85.9 (5.0) kg and 88.9 (4.9) to 86.4 (4.5) kg (P < 0.05) respectively. To conclude, if body mass management is a person's primary focus, they should be mindful of the tendency to eat more in the hours after a water-based exercise session, particularly when the water temperature is cold (18-20 °C).

Hypertension Related to Obesity: Pathogenesis, Characteristics and Factors for Control

The World Health Organization (WHO) refers to obesity as abnormal or excessive fat accumulation that presents a health risk. Obesity was first designated as a disease in 2012 and since then the cost and the burden of the disease have witnessed a worrisome increase. Obesity and hypertension are closely interrelated as abdominal obesity interferes with the endocrine and immune systems and carries a greater risk for insulin resistance, diabetes, hypertension, and cardiovascular disease. Many factors are at the interplay between obesity and hypertension. They include hemodynamic alterations, oxidative stress, renal injury, hyperinsulinemia, and insulin resistance, sleep apnea syndrome and the leptin-melanocortin pathway. Genetics, epigenetics, and mitochondrial factors also play a major role. The measurement of blood pressure in obese patients requires an adapted cuff and the search for other secondary causes is necessary at higher thresholds than the general population. Lifestyle modifications such as diet and exercise are often not enough to control obesity, and so far, bariatric surgery constitutes the most reliable method to achieve weight loss. Nonetheless, the emergence of new agents such as Semaglutide and Tirzepatide offers promising alternatives. Finally, several molecular pathways are actively being explored, and they should significantly extend the treatment options available.

Glucagon and other proglucagon-derived peptides in the pathogenesis of obesity

Because of differential processing of the hormone precursor, proglucagon, numerous peptide products are released from the pancreatic alpha cells and the intestinal L-cells in which the (pro)glucagon gene is expressed. Of particular interest in relation to obesity are glucagon from the pancreas and oxyntomodulin and GLP-1 from the gut, all of which inhibit food intake, but the other products are also briefly discussed, because knowledge about these is required for selection and evaluation of the methods for measurement of the hormones. The distal intestinal L-cells also secrete the appetite-inhibiting hormone PYY. Characteristics of the secretion of the pancreatic and intestinal products are described, and causes of the hypersecretion of glucagon in obesity and type 2 diabetes are discussed. In contrast, the secretion of the products of the L-cells is generally impaired in obesity, raising questions about their role in the development of obesity. It is concluded that the impairment probably is secondary to obesity, but the lower plasma levels may contribute to the development.

Shp2 suppresses fat accumulation in white adipose tissue by activating Wnt/β‑catenin signaling following vertical sleeve gastrectomy in obese rats with type‑2 diabetes

Adipogenesis and fat accumulation are closely associated with the development of obesity. Sleeve gastrectomy (SG) is an effective treatment for obesity and associated metabolic disorders. Leptin is downregulated after SG and Src homology phosphatase 2 (Shp2) has an important role in leptin signaling. The role of Shp2 in SG and the mechanisms of fat reduction following SG were further investigated in the current study. Sham and SG operations were performed on obese type-2 diabetes model Sprague-Dawley rats. Primary pre-adipocytes were isolated from the inguinal white adipose tissue (ingWAT) of the rats. Shp2 expression in ingWAT pre-adipocytes was silenced using small interfering RNA transfection. Shp2 function was inhibited using the specific inhibitor, SHP099. In addition, Shp2 was overexpressed using lentivirus. Gene and protein expression analysis was performed after adipocyte differentiation. Furthermore, Shp2-overexpressing ingWAT pre-adipocytes treated with the β-catenin inhibitor, PNU-74654, were also used for gene and protein expression analysis. Adipogenic markers, including triglycerides, peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (Cebpα), adiponectin, fatty acid-binding protein 4 and leptin, were examined. Compared with the sham, triglyceride, leptin, PPARγ and Cebpα levels were significantly reduced in the ingWAT from the SG group. Shp2 expression levels were reduced following leptin treatment. Moreover, genetic analysis demonstrated depot-specific adipogenesis following Shp2 silencing or inhibition in ingWAT pre-adipocytes. Conversely, Shp2 overexpression decreased the expression of adipogenic markers by enhancing β-catenin expression. PNU-74654 treatment abolished the downregulation of adipogenic markers caused by Shp2 overexpression. SG decreased leptin levels in ingWAT, which in turn upregulated Shp2, and Shp2 suppressed fat accumulation and adipogenic differentiation by activating the Wnt/β-catenin signaling pathway. Overall, this may represent a potential mechanism of fat reduction in SG, and Shp2 may serve as a potential therapeutic target for the treatment of obesity and type-2 diabetes.

Consistent gut bacterial and short-chain fatty acid signatures in hypoabsorptive bariatric surgeries correlate with metabolic benefits in rats

OBJECTIVE

The study aimed at comparing how changes in the gut microbiota are associated to the beneficial effects of the most clinically efficient hypoabsorptive bariatric procedures, namely Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD-DS) and single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S).

METHODS

Diet-induced obese (DIO) male Wistar rats were divided into seven groups. In addition to the groups subjected to RYGB, BPD-DS and SADI-S, the following four control groups were included: SHAM-operated rats fed a high-fat diet (SHAM HF), SHAM fed a low-fat diet (SHAM LF), SHAM HF-pair-weighed to BPD-DS (SHAM HF-PW) and sleeve-gastrectomy (SG) rats. Body weight, food intake, glucose tolerance, insulin sensitivity/resistance, and L-cell secretion were assessed. The gut microbiota (16 S ribosomal RNA gene sequencing) as well as the fecal and cæcal contents of short-chain fatty acids (SCFAs) were also analyzed prior to, and after the surgeries.

RESULTS

The present study demonstrates the beneficial effect of RYGB, BPD-DS and SADI-S on fat mass gain and glucose metabolism in DIO rats. These benefits were proportional to the effect of the surgeries on food digestibility (BPD-DS > SADI-S > RYGB). Notably, hypoabsorptive surgeries led to consonant microbial signatures characterized by decreased abundance of the Ruminococcaceae (Oscillospira and Ruminococcus), Oscillospiraceae (Oscillibacter) and Christensenellaceae, and increased abundance of the Clostridiaceae (Clostridium), Sutterellaceae (Sutterella) and Enterobacteriaceae. The gut bacteria following hypoabsorptive surgeries were associated with higher fecal levels of propionate, butyrate, isobutyrate and isovalerate. Increases in the fecal SCFAs were in turn positively and strongly correlated with the levels of peptide tyrosine-tyrosine (PYY) and with the beneficial effects of the surgery.

CONCLUSION

The present study emphasizes the consistency with which the three major hypoabsorptive bariatric procedures RYGB, BPD-DS and SADI-S create a gut microbial environment capable of producing a SCFA profile favorable to the secretion of PYY and to beneficial metabolic effects.

Potential Therapeutic Targeting Neurotransmitter Receptors in Diabetes

Neurotransmitters are signaling molecules secreted by neurons to coordinate communication and proper function among different sections in the central neural system (CNS) by binding with different receptors. Some neurotransmitters as well as their receptors are found in pancreatic islets and are involved in the regulation of glucose homeostasis. Neurotransmitters can act with their receptors in pancreatic islets to stimulate or inhibit the secretion of insulin (β cell), glucagon (α cell) or somatostatin (δ cell). Neurotransmitter receptors are either G-protein coupled receptors or ligand-gated channels, their effects on blood glucose are mainly decided by the number and location of them in islets. Dysfunction of neurotransmitters receptors in islets is involved in the development of β cell dysfunction and type 2 diabetes (T2D).Therapies targeting different transmitter systems have great potential in the prevention and treatment of T2D and other metabolic diseases.

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.

Multifactorial Basis and Therapeutic Strategies in Metabolism-Related Diseases

Throughout the 20th and 21st centuries, the incidence of non-communicable diseases (NCDs), also known as chronic diseases, has been increasing worldwide. Changes in dietary and physical activity patterns, along with genetic conditions, are the main factors that modulate the metabolism of individuals, leading to the development of NCDs. Obesity, diabetes, metabolic associated fatty liver disease (MAFLD), and cardiovascular diseases (CVDs) are classified in this group of chronic diseases. Therefore, understanding the underlying molecular mechanisms of these diseases leads us to develop more accurate and effective treatments to reduce or mitigate their prevalence in the population. Given the global relevance of NCDs and ongoing research progress, this article reviews the current understanding about NCDs and their related risk factors, with a focus on obesity, diabetes, MAFLD, and CVDs, summarizing the knowledge about their pathophysiology and highlighting the currently available and emerging therapeutic strategies, especially pharmacological interventions. All of these diseases play an important role in the contamination by the SARS-CoV-2 virus, as well as in the progression and severity of the symptoms of the coronavirus disease 2019 (COVID-19). Therefore, we briefly explore the relationship between NCDs and COVID-19.

Clamping Cortisol and Testosterone Mitigates the Development of Insulin Resistance during Sleep Restriction in Men

CONTEXT

Sleep loss in men increases cortisol and decreases testosterone, and sleep restriction by 3 to 4 hours/night induces insulin resistance.

OBJECTIVE

We clamped cortisol and testosterone and determined the effect on insulin resistance.

METHODS

This was a randomized double-blind, in-laboratory crossover study in which 34 healthy young men underwent 4 nights of sleep restriction of 4 hours/night under 2 treatment conditions in random order: dual hormone clamp (cortisol and testosterone fixed), or matching placebo (cortisol and testosterone not fixed). Fasting blood samples, and an additional 23 samples for a 3-hour oral glucose tolerance test (OGTT), were collected before and after sleep restriction under both treatment conditions. Cytokines and hormones were measured from the fasting samples. Overall insulin sensitivity was determined from the OGTT by combining complementary measures: homeostasis model assessment of insulin resistance of the fasting state; Matsuda index of the absorptive state; and minimal model of both fasting and absorptive states.

RESULTS

Sleep restriction alone induced hyperinsulinemia, hyperglycemia, and overall insulin resistance (P < 0.001 for each). Clamping cortisol and testosterone alleviated the development of overall insulin resistance (P = 0.046) and hyperinsulinemia (P = 0.014) by 50%. Interleukin-6, high-sensitivity C-reactive protein, peptide YY, and ghrelin did not change, whereas tumor necrosis factor-α and leptin changed in directions that would have mitigated insulin resistance with sleep restriction alone.

CONCLUSION

Fixing cortisol-testosterone exposure mitigates the development of insulin resistance and hyperinsulinemia, but not hyperglycemia, from sustained sleep restriction in men. The interplay between cortisol and testosterone may be important as a mechanism by which sleep restriction impairs metabolic health.

Rational Development of Stable PYY3-36 Peptide Y2 Receptor Agonists

PURPOSE

The anorectic effect of PYY_3-36 makes it a potential pharmacological weight loss treatment. Modifications of the endogenous peptide to obtain commercially attractive pharmacological and biophysical stability properties are examined.

METHODS

Half-life extended PYY_3-36 analogues were prepared and examined regarding Y₂-receptor potency as well as biophysical and stability properties.

RESULTS

Deamidation of asparagine in position 18 and 29 was observed upon incubation at 37°C. Asparagine in position 18 - but not position 29 - could be substituted to glutamine without detrimental effects on Y₂-receptor potency. Covalent dimers were formed via the phenol impurity benzoquinone reacting with two N-terminal residues (Isoleucine-Lysine). Both residues had to be modified to suppress dimerization, which could be done without negatively affecting Y₂-receptor potency or other stability/biophysical properties. Introduction of half-life extending modifications in position 30 and 35 eliminated aggregation at 37°C without negatively affecting other stability properties. Placement of a protracting moiety (fatty acid) in the receptor-binding C-terminal region reduced Y₂-receptor potency substantially, whereas only minor effects of protractor position were observed on structural, biophysical or stability properties. Lipidated PYY_3-36 analogues formed oligomers of various sizes depending on primary structure and solution conditions.

CONCLUSIONS

By rational design, a chemically and physically stable Y₂-receptor selective, half-life extended PYY_3-36 peptide has been developed.

Mechanism of bariatric and metabolic surgery: beyond surgeons, gastroenterologists and endocrinologists

Bariatric-metabolic surgery is the safest, most effective and long-lasting treatment for obesity and its associated co-morbidities, whether they be metabolic (type 2 diabetes, hyperlipidemia non-alcoholic fatty liver disease) or cardiovascular (myocardial infarction, stroke). Due to the obesity pandemic, bariatric-metabolic surgery is the second most frequent intra-abdominal procedure and the gastroenterologist and the surgeon must be aware of the physiologic changes caused by the anatomic reconfiguration following surgery. Among the mechanisms of action, independent of the loss of weight and fat tissue, surgery leads to the release of gut hormones related to carbohydrate metabolism (the rapid and continuous release of insulin), appetite and degree of satiety (glucagon-like peptide 1, peptide Y-Y, grhelin). As a result, indications for surgery have been extended to earlier disease stages. Apart from the neurohormonal effects, changes in the metabolism of biliary acids and the microbiota have also been reported. The aim of this review is to describe the physiologic changes caused by bariatric-metabolic surgery.

The Function of Gastrointestinal Hormones in Obesity-Implications for the Regulation of Energy Intake

The global burden of obesity and the challenges of prevention prompted researchers to investigate the mechanisms that control food intake. Food ingestion triggers several physiological responses in the digestive system, including the release of gastrointestinal hormones from enteroendocrine cells that are involved in appetite signalling. Disturbed regulation of gut hormone release may affect energy homeostasis and contribute to obesity. In this review, we summarize the changes that occur in the gut hormone balance during the pre- and postprandial state in obesity and the alterations in the diurnal dynamics of their plasma levels. We further discuss how obesity may affect nutrient sensors on enteroendocrine cells that sense the luminal content and provoke alterations in their secretory profile. Gastric bypass surgery elicits one of the most favorable metabolic outcomes in obese patients. We summarize the effect of different strategies to induce weight loss on gut enteroendocrine function. Although the mechanisms underlying obesity are not fully understood, restoring the gut hormone balance in obesity by targeting nutrient sensors or by combination therapy with gut peptide mimetics represents a novel strategy to ameliorate obesity.

Could the Gut Microbiota Serve as a Therapeutic Target in Ischemic Stroke?

The brain-gut axis is a relatively recent discovery of a two-way regulation system between the gut and brain, suggesting that the gut microbiota may be a promising targeted prevention and treatment strategy for patients with a high risk of acute cerebral ischemia/reperfusion injury. There are many risk factors for ischemic stroke, and many studies have shown that the gut microbiota affects the absorption and metabolism of the body, as well as the risk factors of stroke, such as blood pressure, blood glucose, blood lipids, and atherosclerosis, either directly or indirectly. Furthermore, the gut microbiota can affect the occurrence and prognosis of ischemic stroke by regulating risk factors or immune responses. Therefore, this study aimed to collect evidence of the interaction between gut microbiota and ischemic stroke, summarize the interaction mechanism between the two, and explore the gut microbiota as a new targeted prevention and treatment strategy for patients with high ischemic risk.

β Cell GHS-R Regulates Insulin Secretion and Sensitivity

Growth hormone secretagogue receptor (GHS-R) is widely known to regulate food intake and adiposity, but its role in glucose homeostasis is unclear. In this study, we investigated the expression of GHS-R in mouse pancreatic islets and its role in glycemic regulation. We used Ghsr-IRES-tauGFP mice, with Green Fluorescent Protein (GFP) as a surrogate for GHS-R, to demonstrate the GFP co-localization with insulin and glucagon expression in pancreatic islets, confirming GHS-R expression in β and α cells. We then generated β-cell-specific GHSR-deleted mice with MIP-Cre/ERT and validated that GHS-R suppression was restricted to the pancreatic islets. MIP-Cre/ERT;Ghsr^f/f mice showed normal energy homeostasis with similar body weight, body composition, and indirect calorimetry profile. Interestingly, MIP-Cre/ERT;Ghsr^f/f mice exhibited an impressive phenotype in glucose homeostasis. Compared to controls, MIP-Cre/ERT;Ghsr^f/f mice showed lower fasting blood glucose and insulin; reduced first-phase insulin secretion during a glucose tolerance test (GTT) and glucose-stimulated insulin secretion (GSIS) test in vivo. The isolated pancreatic islets of MIP-Cre/ERT;Ghsr^f/f mice also showed reduced insulin secretion during GSIS ex vivo. Further, MIP-Cre/ERT;Ghsr^f/f mice exhibited improved insulin sensitivity during insulin tolerance tests (ITT). Overall, our results confirmed GHS-R expression in pancreatic β and α cells; GHS-R cell-autonomously regulated GSIS and modulated systemic insulin sensitivity. In conclusion, β cell GHS-R was an important regulator of glucose homeostasis, and GHS-R antagonists may have therapeutic potential for Type 2 Diabetes.

The Leading Role of Peptide Tyrosine Tyrosine in Glycemic Control After Roux-en-Y Gastric Bypass in Rats

AIMS

Roux-en-Y gastric bypass (RYGB) is one of the most effective surgical therapies for the rapid resolution of type 2 diabetes. However, the mechanisms underlying the entero-hormonal response after surgery and the role of peptide tyrosine tyrosine (PYY) in the restoration of normoglycemia are still not clear.

METHODS

We reproduced the RYGB technique in Wistar and Goto-Kakizaki rats and performed serum hormonal, histological, and hormonal-infusion test.

RESULTS

Using the diabetic Goto-Kakizaki (GK) rat model, we demonstrated that PYY plasma levels showed a remarkable peak approximately 30 min earlier than GLP-1 or GIP after mixed-meal administration in RYGB-operated rats with PYY. The GLP-1 and GIP areas under the curve (AUCs) increased after RYGB in GK rats. Additionally, the findings suggested that PYY (3-36) infusion led to increased GLP-1 and GIP plasma levels close to those obtained after a meal. Finally, the number of GLP-1-positive cells appeared to increase in the three segments of the small intestine in GK-RYGB-operated rats beyond the early presence of nutrient stimulation in the ileum. Nevertheless, PYY-positive cell numbers appeared to increase only in the ileum.

CONCLUSION

At least in rats, these data demonstrate an earlier essential role for PYY in gut hormone regulation after RYGB. We understand that PYY contributes to GLP-1 and GIP release and there must be the existence of enteroendocrine communication routes between the distal and proximal small intestine.

Current Aspects of the Role of Autoantibodies Directed Against Appetite-Regulating Hormones and the Gut Microbiome in Eating Disorders

The equilibrium and reciprocal actions among appetite-stimulating (orexigenic) and appetite-suppressing (anorexigenic) signals synthesized in the gut, brain, microbiome and adipose tissue (AT), seems to play a pivotal role in the regulation of food intake and feeding behavior, anxiety, and depression. A dysregulation of mechanisms controlling the energy balance may result in eating disorders such as anorexia nervosa (AN) and bulimia nervosa (BN). AN is a psychiatric disease defined by chronic self-induced extreme dietary restriction leading to an extremely low body weight and adiposity. BN is defined as out-of-control binge eating, which is compensated by self-induced vomiting, fasting, or excessive exercise. Certain gut microbiota-related compounds, like bacterial chaperone protein Escherichia coli caseinolytic protease B (ClpB) and food-derived antigens were recently described to trigger the production of autoantibodies cross-reacting with appetite-regulating hormones and neurotransmitters. Gut microbiome may be a potential manipulator for AT and energy homeostasis. Thus, the regulation of appetite, emotion, mood, and nutritional status is also under the control of neuroimmunoendocrine mechanisms by secretion of autoantibodies directed against neuropeptides, neuroactive metabolites, and peptides. In AN and BN, altered cholinergic, dopaminergic, adrenergic, and serotonergic relays may lead to abnormal AT, gut, and brain hormone secretion. The present review summarizes updated knowledge regarding the gut dysbiosis, gut-barrier permeability, short-chain fatty acids (SCFA), fecal microbial transplantation (FMT), blood-brain barrier permeability, and autoantibodies within the ghrelin and melanocortin systems in eating disorders. We expect that the new knowledge may be used for the development of a novel preventive and therapeutic approach for treatment of AN and BN.

Effects of resistant starch on glycaemic control: a systematic review and meta-analysis

The effects of resistant starch on glycaemic control are controversial. In this study, a systematic review and meta-analysis of results from nineteen randomised controlled trials (RCT) was performed to illustrate the effects of resistant starch on glycaemic control. A literature search was conducted on PubMed, Scopus and Cochrane electronic databases for related publications from inception to 6 April 2020. Key inclusion criteria were: RCT; resistant starch as intervention substances and reporting glucose- and insulin-related endpoints. Exclusion criteria were: using type I resistant starch or a mixture of resistant starch and other functional food ingredients as intervention; using substances other than digestible starch as controls. The effect of resistant starch on fasting plasma glucose was significant (effect size (ES) –0·09 (95 % CI –0·13, −0·04) mmol/l, P = 0·001) compared with digestible starch. Subgroup analyses revealed that the ES was larger when the dosage of resistant starch was more than 28 g/d (ES –0·16 (95 % CI –0·24, –0·08) mmol/l, P < 0·001) or the intervention period was more than 8 weeks (ES –0·12 (95 % CI –0·18, –0·06) mmol/l, P < 0·001). The effect on homoeostatic model assessment (HOMA)-insulin resistance (IR) was significant (ES –0·33 (95 % CI –0·51, –0·14), P = 0·001). However, the effects on other insulin-related endpoints were not significant, including fasting plasma insulin, four endpoints from the frequently sampled intravenous glucose tolerance test (insulin sensitivity index, acute insulin response, disposition index and glucose effectiveness) and HOMA-β. The current study indicated moderate effects of resistant starch on improving glycaemic control.

The Implication of Gut Hormones in the Regulation of Energy Homeostasis and Their Role in the Pathophysiology of Obesity

PURPOSE OF REVIEW

This review provides an update on the role of gut hormones and their interactions in the regulation of energy homeostasis, describes gut hormone adaptations in obesity and in response to weight loss, and summarizes the current evidence on the role of gut hormone-based therapies for obesity treatment.

RECENT FINDINGS

Gut hormones play a key role in regulating eating behaviour, energy and glucose homeostasis. Dysregulated gut hormone responses have been proposed to be pathogenetically involved in the development and perpetuation of obesity. Summarizing the major gut hormone changes in obesity, obese individuals are characterized by blunted postprandial ghrelin suppression, loss of premeal ghrelin peaks, impaired diurnal ghrelin variability and reduced fasting and postprandial levels of anorexigenic peptides. Adaptive alterations of gut hormone levels are implicated in weight regain, thus complicating hypocaloric dietary interventions, and can further explain the profound weight loss and metabolic improvement following bariatric surgery. A plethora of compounds mimicking gut hormone changes after bariatric surgery are currently under investigation, introducing a new era in the pharmacotherapy of obesity. The current trend is to combine different gut hormone receptor agonists and target multiple systems simultaneously, in order to replicate as closely as possible the gut hormone milieu after bariatric surgery and circumvent the counter-regulatory adaptive changes associated with dietary energy restriction. An increasing number of preclinical and early-phase clinical trials reveal the additive benefits obtained with dual or triple gut peptide receptor agonists in reducing body weight and improving glycaemia. Gut hormones act as potent regulators of energy and glucose homeostasis. Therapeutic strategies targeting their levels or receptors emerge as a promising approach to treat patients with obesity and hyperglycaemia.

Peptide YY3-36 concentration in acute- and long-term recovered anorexia nervosa

Purpose

The gut–brain axis could be a possible key factor in the pathophysiology of anorexia nervosa. The neuropeptide peptide YY_3–36, secreted by endocrine L cells of the gastrointestinal tract, is a known regulator of appetite and food intake. The objective of this study was to investigate peptide YY_3–36 plasma concentrations at different stages of anorexia nervosa in a combined cross-sectional and longitudinal design to differentiate between effects of acute undernutrition and more enduring characteristics.

Methods

We measured fasting plasma peptide YY_3–36 concentrations in young patients with acute anorexia nervosa (n = 47) and long-term recovered patients (n = 35) cross-sectionally in comparison to healthy control participants (n = 58), and longitudinally over the course of inpatient treatment. Physical activity was controlled as it may modulate peptide YY secretion.

Results

There was no group difference in peptide YY_3–36 concentration among young acutely underweight anorexia nervosa patients, long-term recovered anorexia nervosa patients, and healthy control participants. Longitudinally, there was no change in peptide YY_3–36 concentration after short-term weight rehabilitation. For acute anorexia nervosa patients at admission to treatment, there was a negative correlation between peptide YY_3–36 concentration and body mass index.

Conclusions

The current study provides additional evidence for a normal basal PYY_3–36 concentration in AN. Future studies should study multiple appetite-regulating peptides and their complex interplay and also use research designs including a food challenge.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02210-7) contains supplementary material, which is available to authorized users.

Increases in PYY and uncoupling of bone turnover are associated with loss of bone mass after gastric bypass surgery

CONTEXT

The gut hormones peptide YY (PYY) and ghrelin mediate in part the metabolic benefits of Roux-en-Y gastric bypass (RYGB) surgery. However, preclinical data suggest these hormones also affect the skeleton and could contribute to postoperative bone loss.

OBJECTIVE

We investigated whether changes in fasting serum total PYY and ghrelin were associated with bone turnover marker levels and loss of bone mineral density (BMD) after RYGB.

DESIGN, SETTING, PARTICIPANTS

Prospective cohort of adults undergoing RYGB (n=44) at San Francisco academic hospitals.

MAIN OUTCOME MEASURES

We analyzed 6-month changes in PYY, ghrelin, bone turnover markers, and BMD by dual-energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT). We calculated the uncoupling index (UI), reflecting the relative balance of bone resorption and formation.

RESULTS

Postoperatively, there was a trend for an increase in PYY (+25pg/mL, p=0.07) and a significant increase in ghrelin (+192pg/mL, p<0.01). PYY changes negatively correlated with changes in spine BMD by QCT (r=-0.36, p=0.02) and bone formation marker P1NP (r=-0.30, p=0.05). Relationships were significant after adjustments for age, sex, and weight loss. No consistent relationships were found between ghrelin and skeletal outcomes. Mean 6-month UI was -3.3; UI correlated with spine BMD loss by QCT (r=0.40, p=0.01).

CONCLUSIONS

Postoperative PYY increases were associated with attenuated increases in P1NP and greater declines in spine BMD by QCT. Uncoupling of bone turnover correlated with BMD loss. These findings suggest a role for PYY in loss of bone mass after RYGB and highlight the relationship between intestinal and skeletal metabolism.

The Chemical Methods of Disulfide Bond Formation and Their Applications to Drug Conjugates

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The disulfide bond possesses unique chemical and biophysical properties which distinguish it as one of the key structural elements of bioactive proteins and peptides, important drugs and other materials. The chemo-selective synthesis of these structures and the exploration of their function have been of longstanding interest to the chemistry community. The past decades have witnessed significant progress in both areas. This review will summarize the historically established and recently developed chemical methods in disulfide bond formation. The discussion will also be extended to the use of the disulfide linkers in small molecules, and peptide- and protein-drug conjugates. It is hoped that the combined overview of the fundamental chemistries and applications to drug discovery will inspire creative thinking and stimulate future novel uses of these versatile chemistries.

Gut Peptide Agonism in the Treatment of Obesity and Diabetes

Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.

Global transcriptome analysis of rat hypothalamic arcuate nucleus demonstrates reversal of hypothalamic gliosis following surgically and diet induced weight loss

The central mechanisms underlying the marked beneficial metabolic effects of bariatric surgery are unclear. Here, we characterized global gene expression in the hypothalamic arcuate nucleus (Arc) in diet-induced obese (DIO) rats following Roux-en-Y gastric bypass (RYGB). 60 days post-RYGB, the Arc was isolated by laser-capture microdissection and global gene expression was assessed by RNA sequencing. RYGB lowered body weight and adiposity as compared to sham-operated DIO rats. Discrete transcriptome changes were observed in the Arc following RYGB, including differential expression of genes associated with inflammation and neuropeptide signaling. RYGB reduced gene expression of glial cell markers, including Gfap, Aif1 and Timp1, confirmed by a lower number of GFAP immunopositive astrocyte profiles in the Arc. Sham-operated weight-matched rats demonstrated a similar glial gene expression signature, suggesting that RYGB and dietary restriction have common effects on hypothalamic gliosis. Considering that RYGB surgery also led to increased orexigenic and decreased anorexigenic gene expression, this may signify increased hunger-associated signaling at the level of the Arc. Hence, induction of counterregulatory molecular mechanisms downstream from the Arc may play an important role in RYGB-induced weight loss.

A randomized crossover trial assessing the effects of acute exercise on appetite, circulating ghrelin concentrations, and butyrylcholinesterase activity in normal-weight males with variants of the obesity-linked FTO rs9939609 polymorphism

BACKGROUND

The fat mass and obesity-associated gene (FTO) rs9939609 A-allele is associated with higher acyl-ghrelin (AG) concentrations, higher energy intake, and obesity, although exercise may mitigate rs9939609 A-allele-linked obesity risk. Butyrylcholinesterase (BChE) hydrolyzes AG to des-acyl-ghrelin (DAG), potentially decreasing appetite. However, the effects of the FTO rs9939609 genotype and exercise on BChE activity, AG, DAG, and energy intake are unknown.

OBJECTIVE

We hypothesized that individuals homozygous for the obesity-risk A-allele (AAs) would exhibit higher postprandial AG and energy intake than individuals homozygous for the low obesity-risk T-allele (TTs), but that exercise would increase BChE activity and diminish these differences.

METHODS

Twelve AA and 12 TT normal-weight males completed a control (8 h rest) and an exercise (1 h of exercise at 70% peak oxygen uptake, 7 h rest) trial in a randomized crossover design. A fixed meal was consumed at 1.5 h and an ad libitum buffet meal at 6.5 h. Appetite, appetite-related hormones, BChE activity, and energy intake were assessed.

RESULTS

AAs displayed lower baseline BChE activity, higher baseline AG:DAG ratio, attenuated AG suppression after a fixed meal, and higher ad libitum energy intake compared with TTs [effect sizes (ESs) ≥ 0.72, P ≤ 0.049]. Exercise increased Δ BChE activity in both genotypes (ESs = 0.37, P = 0.004); however, exercise lowered AG and the AG:DAG ratio to a greater extent in AAs (P ≤ 0.023), offsetting the higher AG profile observed in AAs during the control trial (ESs ≥ 1.25, P ≤ 0.048). Exercise did not elevate energy intake in either genotype (P = 0.282).

CONCLUSIONS

Exercise increases BChE activity, suppresses AG and the AG:DAG ratio, and corrects the higher AG profile observed in obesity-risk AA individuals. These findings suggest that exercise or other methods targeting BChE activity may offer a preventative and/or therapeutic strategy for AA individuals. This trial was registered at clinicaltrials.gov as NCT03025347.

Implementation of a novel self-induced promoter for the expression of pharmaceutical peptides in Escherichia coli: YY(3-36) peptide

Background

Increasing the expression rate of recombinant mammalian hormones in Escherichia coli by combining efficient promoters and signal sequences is a never ending process. A self-induced promoter will have some beneficial gains compared to the classical T7 promoter or its variants with isopropyl β-D-1-thiogalactopyranoside (IPTG) as the inducer. Obesity is the prime suspect in widespread frequency of diabetes type II and cardiovascular diseases worldwide. YY (tyrosine-tyrosine) peptide is a local acting hormone, controlling appetite. Excitingly, it was has been shown that a truncated version of the YY peptide, YY(3-36) peptide, has potential as a worthy biopharmaceutical agent in the fight against obesity.

Materials and methods

To develop an economical expression system for the large scale production of the peptide in Gram-negative bacteria, we introduced a promoter sequence upstream of a chimeric gene for the extracellular expression of this peptide with the assistance of a signal sequence of asparaginase II from E. coli. This system has the advantage of producing a complete sequence of a truncated YY peptide, YY(3-36), without any extra tags that would require further removal with the assistance of expensive specific proteases and reduced the downstream steps, significantly.

Results

Recombinant production of YY(3-36) peptide under a self-induced promoter proves the efficacy of the asparaginase II signal sequence as a communicator of foreign peptides and proteins into the extracellular space of E. coli.

Conclusions

The application of fusion protein expression of biopharmaceuticals, especially mammalian hormones, in prokaryotic systems with the help of native signal sequences makes some common tags with expensive proteases for the removal of the attached protein Tag redundant.

Bile Diversion Improves Metabolic Phenotype Dependent on Farnesoid X Receptor (FXR)

OBJECTIVE

The current study investigated whether bile diversion (BD) improves metabolic phenotype under farnesoid X receptor (FXR) deficiency.

METHODS

BD was performed in high-fat diet (HFD)-fed FXR knockout (FXRko) and wild-type (WT) animals. Metabolic phenotypes, circulating enteroendocrine hormones, total bile acids (BAs) and BA composition, and cecal gut microbiota were analyzed.

RESULTS

FXR-deficient mice were resistant to HFD-induced obesity; however, FXR-deficient mice also developed hyperglycemia and exhibited increased liver weight, liver steatosis, and circulating triglycerides. BD increased circulating total BAs and taurine-b-muricholic acid, which were in line with normalized hyperglycemia and improved glucose tolerance in HFD-fed WT mice. FXR deficiency also increased total BAs and taurine-b-muricholic acid, but these animals remained hyperglycemic. While BD improved metabolic phenotype in HFD-fed FXRko mice, these improvements were not as effective as in WT mice. BD increased liver expression of fibroblast growth factor 21 and peroxisome proliferator-activated receptor γ coactivator-1β and elevated circulating glucagon-like peptide-1 levels in WT mice but not in FXRko mice. FXR deficiency altered gut microbiota composition with a specific increase in phylum Proteobacteria that may act as a possible microbial signature of some diseases. These cellular and molecular changes in FXRko mice may contribute to resistance toward improved metabolism.

CONCLUSIONS

FXR signaling plays a pivotal role in improved metabolic phenotype following BD surgery.

Gut Hormones and Their Effect on Bone Metabolism. Potential Drug Therapies in Future Osteoporosis Treatment

Bone homeostasis displays a circadian rhythm with increased resorption during the night time as compared to day time, a difference that seems-at least partly-to be caused by food intake during the day. Thus, ingestion of a meal results in a decrease in bone resorption, but people suffering from short bowel syndrome lack this response. Gut hormones, released in response to a meal, contribute to this link between the gut and bone metabolism. The responsible hormones appear to include glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), known as incretin hormones due to their role in regulating glucose homeostasis by enhancing insulin release in response to food intake. They interact with their cognate receptors (GIPR and GLP-1R), which are both members of the class B G protein-coupled receptors (GPCRs), and already recognized as targets for treatment of metabolic diseases, such as type 2 diabetes mellitus (T2DM) and obesity. Glucagon-like peptide-2 (GLP-2), secreted concomitantly with GLP-1, acting via another class B receptor (GLP-2R), is also part of this gut-bone axis. Several studies, including human studies, have indicated that these three hormones inhibit bone resorption and, moreover, that GIP increases bone formation. Another hormone, peptide YY (PYY), is also secreted from the enteroendocrine L-cells (together with GLP-1 and GLP-2), and acts mainly via interaction with the class A GPCR NPY-R2. PYY is best known for its effect on appetite regulation, but recent studies have also shown an effect of PYY on bone metabolism. The aim of this review is to summarize the current knowledge of the actions of GIP, GLP-1, GLP-2, and PYY on bone metabolism, and to discuss future therapies targeting these receptors for the treatment of osteoporosis.

Intestinal Sensing by Gut Microbiota: Targeting Gut Peptides

There are more than 2 billion overweight and obese individuals worldwide, surpassing for the first time, the number of people affected by undernutrition. Obesity and its comorbidities inflict a heavy burden on the global economies and have become a serious threat to individuals' wellbeing with no immediate cure available. The causes of obesity are manifold, involving several factors including physiological, metabolic, neural, psychosocial, economic, genetics and the environment, among others. Recent advances in genome sequencing and metagenomic profiling have added another dimension to this complexity by implicating the gut microbiota as an important player in energy regulation and the development of obesity. As such, accumulating evidence demonstrate the impact of the gut microbiota on body weight, adiposity, glucose, lipid metabolism, and metabolic syndrome. This also includes the role of microbiota as a modulatory signal either directly or through its bioactive metabolites on intestinal lumen by releasing chemosensing factors known to have a major role in controlling food intake and regulating body weight. The importance of gut signaling by microbiota signaling is further highlighted by the presence of taste and nutrient receptors on the intestinal epithelium activated by the microbial degradation products as well as their role in release of peptides hormones controlling appetite and energy homeostasis. This review present evidence on how gut microbiota interacts with intestinal chemosensing and modulates the release and activity of gut peptides, particularly GLP-1 and PYY.

Metformin-induced glucagon-like peptide-1 secretion contributes to the actions of metformin in type 2 diabetes

BACKGROUND

Metformin reduces plasma glucose and has been shown to increase glucagon-like peptide 1 (GLP-1) secretion. Whether this is a direct action of metformin on GLP-1 release, and whether some of the glucose-lowering effect of metformin occurs due to GLP-1 release, is unknown. The current study investigated metformin-induced GLP-1 secretion and its contribution to the overall glucose-lowering effect of metformin and underlying mechanisms in patients with type 2 diabetes.

METHODS

Twelve patients with type 2 diabetes were included in this placebo-controlled, double-blinded study. On 4 separate days, the patients received metformin (1,500 mg) or placebo suspended in a liquid meal, with subsequent i.v. infusion of the GLP-1 receptor antagonist exendin9-39 (Ex9-39) or saline. During 240 minutes, blood was sampled. The direct effect of metformin on GLP-1 secretion was tested ex vivo in human ileal and colonic tissue with and without dorsomorphin-induced inhibiting of the AMPK activity.

RESULTS

Metformin increased postprandial GLP-1 secretion compared with placebo (P = 0.014), and the postprandial glucose excursions were significantly smaller after metformin + saline compared with metformin + Ex9-39 (P = 0.004). Ex vivo metformin acutely increased GLP-1 secretion (colonic tissue, P < 0.01; ileal tissue, P < 0.05), but the effect was abolished by inhibition of AMPK activity.

CONCLUSIONS

Metformin has a direct and AMPK-dependent effect on GLP-1-secreting L cells and increases postprandial GLP-1 secretion, which seems to contribute to metformin's glucose-lowering effect and mode of action.

TRIAL REGISTRATION

NCT02050074 (https://clinicaltrials.gov/ct2/show/NCT02050074).

FUNDING

This study received grants from the A.P. Møller Foundation, the Novo Nordisk Foundation, the Danish Medical Association research grant, the Australian Research Council, the National Health and Medical Research Council, and Pfizer Inc.

Acute and Chronic Effects of Exercise on Appetite, Energy Intake, and Appetite-Related Hormones: The Modulating Effect of Adiposity, Sex, and Habitual Physical Activity

Exercise facilitates weight control, partly through effects on appetite regulation. Single bouts of exercise induce a short-term energy deficit without stimulating compensatory effects on appetite, whilst limited evidence suggests that exercise training may modify subjective and homeostatic mediators of appetite in directions associated with enhanced meal-induced satiety. However, a large variability in responses exists between individuals. This article reviews the evidence relating to how adiposity, sex, and habitual physical activity modulate exercise-induced appetite, energy intake, and appetite-related hormone responses. The balance of evidence suggests that adiposity and sex do not modify appetite or energy intake responses to acute or chronic exercise interventions, but individuals with higher habitual physical activity levels may better adjust energy intake in response to energy balance perturbations. The effect of these individual characteristics and behaviours on appetite-related hormone responses to exercise remains equivocal. These findings support the continued promotion of exercise as a strategy for inducing short-term energy deficits irrespective of adiposity and sex, as well as the ability of exercise to positively influence energy balance over the longer term. Future well-controlled studies are required to further ascertain the potential mediators of appetite responses to exercise.

Defining G protein-coupled receptor peptide ligand expressomes and signalomes in human and mouse islets

INTRODUCTION

Islets synthesise and secrete numerous peptides, some of which are known to be important regulators of islet function and glucose homeostasis. In this study, we quantified mRNAs encoding all peptide ligands of islet G protein-coupled receptors (GPCRs) in isolated human and mouse islets and carried out in vitro islet hormone secretion studies to provide functional confirmation for the species-specific role of peptide YY (PYY) in mouse islets.

MATERIALS AND METHODS

GPCR peptide ligand mRNAs in human and mouse islets were quantified by quantitative real-time PCR relative to the reference genes ACTB, GAPDH, PPIA, TBP and TFRC. The pathways connecting GPCR peptide ligands with their receptors were identified by manual searches in the PubMed, IUPHAR and Ingenuity databases. Distribution of PYY protein in mouse and human islets was determined by immunohistochemistry. Insulin, glucagon and somatostatin secretion from islets was measured by radioimmunoassay.

RESULTS

We have quantified GPCR peptide ligand mRNA expression in human and mouse islets and created specific signalomes mapping the pathways by which islet peptide ligands regulate human and mouse GPCR signalling. We also identified species-specific islet expression of several GPCR ligands. In particular, PYY mRNA levels were ~ 40,000-fold higher in mouse than human islets, suggesting a more important role of locally secreted Pyy in mouse islets. This was confirmed by IHC and functional experiments measuring insulin, glucagon and somatostatin secretion.

DISCUSSION

The detailed human and mouse islet GPCR peptide ligand atlases will allow accurate translation of mouse islet functional studies for the identification of GPCR/peptide signalling pathways relevant for human physiology, which may lead to novel treatment modalities of diabetes and metabolic disease.

Ablation of somatostatin cells leads to impaired pancreatic islet function and neonatal death in rodents

The somatostatin (SST)-secreting cells were mainly distributed in the pancreatic islets, brain, stomach and intestine in mammals and have many physiological functions. In particular, the SST-secreting δ cell is the third most common cell type in the islets of Langerhans. Recent studies have suggested that dysregulation of paracrine interaction between the pancreatic δ cells and β cells results in impaired glucose homeostasis and contributes to diabetes development. However, direct evidence of the functional importance of SST cells in glucose homeostasis control is still lacking. In the present study, we specifically ablated SST-secreting cells by crossing Sst-cre transgenic mice with R26 ^DTA mice (Sst ^Cre R26 ^DTA ). The Sst ^Cre R26 ^DTA mice exhibited neonatal death. The life spans of these mice with severe hypoglycemia were extended by glucose supplementation. Moreover, we observed that SST cells deficiency led to increased insulin content and excessive insulin release, which might contribute to the observed hypoglycemia. Unexpectedly, although SST is critical for the regulation of insulin content, factors other than SST that are produced by pancreatic δ cells via their endogenous corticotropin-releasing hormone receptor 2 (CRHR2) activity play the main roles in maintaining normal insulin release, as well as neonatal glucose homeostasis in the resting state. Taken together, our results identified that the SST cells in neonatal mouse played critical role in control of insulin release and normal islet function. Moreover, we provided direct in vivo evidence of the functional importance of the SST cells, which are essential for neonatal survival and the maintenance of glucose homeostasis.

Anorectic response to the trichothecene T-2 toxin correspond to plasma elevations of the satiety hormone glucose-dependent insulinotropic polypeptide and peptide YY3-36

T-2 toxin, a potent type A trichothecene mycotoxin, is produced by various Fusarium species and can negatively impact animal and human health. Although anorexia induction is a common hallmark of T-2 toxin-induced toxicity, the underlying mechanisms for this adverse effect are not fully understood. The goal of this study was to determine the roles of two gut satiety hormones, glucose-dependent insulinotropic polypeptide (GIP) and Peptide YY_3-36 (PYY_3-36) in anorexia induction by T-2 toxin. Elevations of plasma GIP and PYY_3-36 markedly corresponded to anorexia induction following oral exposure to T-2 toxin using a nocturnal mouse anorexia model. Direct administration of exogenous GIP and PYY_3-36 similarly induced anorectic responses. Furthermore, the GIP receptor antagonist Pro3GIP dose-dependently attenuated both GIP- and T-2 toxin-induced anorectic responses. Pretreatment with NPY2 receptor antagonist JNJ-31020028 induced a dose-dependent attenuation of both PYY_3-36- and T-2 toxin-induced anorectic responses. To summarize, these findings suggest that both GIP and PYY_3-36 might be critical mediators of anorexia induction by T-2 toxin.

Obesity, body weight regulation and the brain: insights from fMRI

Obesity constitutes a major global health threat. Despite the success of bariatric surgery in delivering sustainable weight loss and improvement in obesity-related morbidity, effective non-surgical treatments are urgently needed, necessitating an increased understanding of body weight regulation. Neuroimaging studies undertaken in people with healthy weight, overweight, obesity and following bariatric surgery have contributed to identifying the neurophysiological changes seen in obesity and help increase our understanding of the mechanisms driving the favourable eating behaviour changes and sustained weight loss engendered by bariatric surgery. These studies have revealed a key interplay between peripheral metabolic signals, homeostatic and hedonic brain regions and genetics. Findings from brain functional magnetic resonance imaging (fMRI) studies have consistently associated obesity with an increased motivational drive to eat, increased reward responses to food cues and impaired food-related self-control processes. Interestingly, new data link these obesity-associated changes with structural and connectivity changes within the central nervous system. Moreover, emerging data suggest that bariatric surgery leads to neuroplastic recovery. A greater understanding of the interactions between peripheral signals of energy balance, the neural substrates that regulate eating behaviour, the environment and genetics will be key for the development of novel therapeutic strategies for obesity. This review provides an overview of our current understanding of the pathoaetiology of obesity with a focus upon the role that fMRI studies have played in enhancing our understanding of the central regulation of eating behaviour and energy homeostasis.