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Amyloid deposits in pancreatic islets, mainly formed by human islet amyloid polypeptide (hIAPP) aggregation, have been associated with loss of β-cell mass and function, and are a pathological hallmark of type 2 diabetes (T2D). Treatment with chaperones has been associated with a decrease in endoplasmic reticulum stress leading to improved glucose metabolism. The aim of this work was to investigate whether the chemical chaperone 4-phenylbutyrate (PBA) prevents glucose metabolism abnormalities and amyloid deposition in obese agouti viable yellow (A vy ) mice that overexpress hIAPP in β cells (A vy hIAPP mice), which exhibit overt diabetes. Oral PBA treatment started at 8 weeks of age, when A vy hIAPP mice already presented fasting hyperglycemia, glucose intolerance, and impaired insulin secretion. PBA treatment strongly reduced the severe hyperglycemia observed in obese A vy hIAPP mice in fasting and fed conditions throughout the study. This effect was paralleled by a decrease in hyperinsulinemia. Importantly, PBA treatment reduced the prevalence and the severity of islet amyloid deposition in A vy hIAPP mice. Collectively, these results show that PBA treatment elicits a marked reduction of hyperglycemia and reduces amyloid deposits in obese and diabetic mice, highlighting the potential of chaperones for T2D treatment.

The gastrointestinal tract maintains energy and glucose homeostasis, in part through nutrient-sensing and subsequent signaling to the brain and other tissues. In this review, we highlight the role of small intestinal nutrient-sensing in metabolic homeostasis, and link high-fat feeding, obesity, and diabetes with perturbations in these gut-brain signaling pathways. We identify how lipids, carbohydrates, and proteins, initiate gut peptide release from the enteroendocrine cells through small intestinal sensing pathways, and how these peptides regulate food intake, glucose tolerance, and hepatic glucose production. Lastly, we highlight how the gut microbiota impact small intestinal nutrient-sensing in normal physiology, and in disease, pharmacological and surgical settings. Emerging evidence indicates that the molecular mechanisms of small intestinal nutrient sensing in metabolic homeostasis have physiological and pathological impact as well as therapeutic potential in obesity and diabetes. The gastrointestinal tract participates in maintaining metabolic homeostasis in part through nutrient-sensing and subsequent gut-brain signalling. Here the authors review the role of small intestinal nutrient-sensing in regulation of energy intake and systemic glucose metabolism, and link high-fat diet, obesity and diabetes with perturbations in these pathways.

Activation of brown fat thermogenesis increases energy expenditure and alleviates obesity. Sympathetic nervous system (SNS) is important in brown/beige adipocyte thermogenesis. Here we discover a fat-derived “adipokine” neurotrophic factor neurotrophin 3 (NT-3) and its receptor Tropomyosin receptor kinase C (TRKC) as key regulators of SNS growth and innervation in adipose tissue. NT-3 is highly expressed in brown/beige adipocytes, and potently stimulates sympathetic neuron neurite growth. NT-3/TRKC regulates a plethora of pathways in neuronal axonal growth and elongation. Adipose tissue sympathetic innervation is significantly increased in mice with adipocyte-specific NT-3 overexpression, but profoundly reduced in mice with TRKC haploinsufficiency (TRKC +/−). Increasing NT-3 via pharmacological or genetic approach promotes beige adipocyte development, enhances cold-induced thermogenesis and protects against diet-induced obesity (DIO); whereas TRKC + /− or SNS TRKC deficient mice are cold intolerant and prone to DIO. Thus, NT-3 is a fat-derived neurotrophic factor that regulates SNS innervation, energy metabolism and obesity. Activation of brown adipose tissue thermogenesis increases energy expenditure and promotes weight loss in mice. Here the authors identify neurotrophic factor neurotrophin 3 (NT-3) as an adipokine that regulates sympathetic nervous system growth and innervation in adipose tissue and increases white adipose beiging.

The gastrointestinal tract plays a role in the development and treatment of metabolic diseases. During a meal, the gut provides crucial information to the brain regarding incoming nutrients to allow proper maintenance of energy and glucose homeostasis. This gut–brain communication is regulated by various peptides or hormones that are secreted from the gut in response to nutrients; these signaling molecules can enter the circulation and act directly on the brain, or they can act indirectly via paracrine action on local vagal and spinal afferent neurons that innervate the gut. In addition, the enteric nervous system can act as a relay from the gut to the brain. The current review will outline the different gut–brain signaling mechanisms that contribute to metabolic homeostasis, highlighting the recent advances in understanding these complex hormonal and neural pathways. Furthermore, the impact of the gut microbiota on various components of the gut–brain axis that regulates energy and glucose homeostasis will be discussed. A better understanding of the gut–brain axis and its complex relationship with the gut microbiome is crucial for the development of successful pharmacological therapies to combat obesity and diabetes. Gut–brain communication: Role in energy and glucose metabolism Signaling between the gut and the brain involves a complex mix of nutrients, peptides, and microbes that could be targeted as therapies for obesity and diabetes. Our bodies regulate food intake and energy expenditure via cells in the intestinal wall that sense certain nutrients, then release peptides which activate neurons. A review by Frank Duca and graduate students Hallie Wachsmuth and Savanna Weninger at the University of Arizona, Tucson, USA, reveals a more complicated picture, with many different interacting neural and hormonal signals, with increasing evidence for the vital role played by the microbes in the gastrointestinal tract. In particular, the gut microbiome impacts food intake, fat formation, endogenous glucose production, and insulin sensitivity. Novel metabolic therapies could target specific signaling pathways between the microbes, gut, and brain.

Key Points Type 2 diabetes is characterized by elevated blood glucose levels and insulin resistance. Current diabetes drugs can lower blood glucose but often have side effects, and the most widely used drug — metformin — does not have a clear mechanism of action. Targeting glucose and glycogen metabolism in the liver is a strategy for type 2 diabetes treatment, as it can decrease hepatic glucose output, but this approach has not been fully explored. Gluconeogenic and glycogenolytic enzymes or their regulators present numerous drug targets that are currently being investigated or have the potential to be developed. Transcriptional co-activators and transcription factors are emerging diabetes drug targets with the ability to control entire gene programmes involved in glucose and glycogen metabolism. It may be possible to specifically target these transcriptional regulators by modulating their protein–protein interactions or post-translational modifications. Novel diabetes drugs would most probably be used in combination with existing therapies to enable sustained blood glucose suppression, and so that each drug could be used at a lower concentration to limit side effects. Drugs decreasing hepatic glucose output may be most effectively used with drugs that work by other mechanisms, such as thiazolidinediones or sodium-glucose co-transporter 2 (SGLT2) inhibitors. Challenges of inhibiting hepatic glucose output include preventing hypoglycaemia, enabling tissue-specific targeting, analysing the possible effects of redirecting carbons to triglyceride or cholesterol synthesis, and avoiding lactic acidosis. Although the liver has a key role in maintaining blood glucose homeostasis, few existing type 2 diabetes therapies directly target this organ. Here, Puigserver et al . provide an overview of the molecular mechanisms controlling hepatic gluconeogenesis and glycogen storage, focusing on emerging strategies to target hepatic glucose metabolism for the treatment of diabetes. Type 2 diabetes mellitus is characterized by the dysregulation of glucose homeostasis, resulting in hyperglycaemia. Although current diabetes treatments have exhibited some success in lowering blood glucose levels, their effect is not always sustained and their use may be associated with undesirable side effects, such as hypoglycaemia. Novel antidiabetic drugs, which may be used in combination with existing therapies, are therefore needed. The potential of specifically targeting the liver to normalize blood glucose levels has not been fully exploited. Here, we review the molecular mechanisms controlling hepatic gluconeogenesis and glycogen storage, and assess the prospect of therapeutically targeting associated pathways to treat type 2 diabetes.

Obesity is associated with a disturbed adipose tissue (AT) function characterized by adipocyte hypertrophy, an impaired lipolysis and pro-inflammatory phenotype, which contributes to insulin resistance (IR). We investigated whether AT phenotype in different AT depots of obese individuals with and without type 2 diabetes mellitus (T2DM) is associated with whole-body IR. Subcutaneous (SC) and visceral (V) AT biopsies from 18 lean, 17 obese and 8 obese T2DM men were collected. AT phenotype was characterized by ex vivo measurement of basal and stimulated lipolysis (mature adipocytes), adipocyte size distribution (AT tissue sections) and AT immune cells (flow cytometry). In VAT, mean adipocyte size, CD45 + leukocytes and M1 macrophages were significantly increased in both obese groups compared to lean individuals. In SCAT, despite adipocyte hypertrophy, no significant differences in immune cell populations between groups were found. In SCAT, multiple linear regression analysis showed that none of the AT phenotype markers independently contributed to HOMA-IR while in VAT, mean adipocyte size was significantly related to HOMA-IR. In conclusion, beside adipocyte hypertrophy in VAT, M1 macrophage- or B-cell-mediated inflammation, may contribute to IR, while inflammation in hypertrophic SCAT does not seem to play a major role in IR.

Visceral adipose tissue (VAT)—fat stored around the internal organs—has been suggested as an independent risk factor for cardiovascular and metabolic disease1–3, as well as all-cause, cardiovascular-specific and cancer-specific mortality4,5. Yet, the contribution of genetics to VAT, as well as its disease-related effects, are largely unexplored due to the requirement for advanced imaging technologies to accurately measure VAT. Here, we develop sex-stratified, nonlinear prediction models (coefficient of determination = 0.76; typical 95% confidence interval (CI) = 0.74–0.78) for VAT mass using the UK Biobank cohort. We performed a genome-wide association study for predicted VAT mass and identified 102 novel visceral adiposity loci. Predicted VAT mass was associated with increased risk of hypertension, heart attack/angina, type 2 diabetes and hyperlipidemia, and Mendelian randomization analysis showed visceral fat to be a causal risk factor for all four diseases. In particular, a large difference in causal effect between the sexes was found for type 2 diabetes, with an odds ratio of 7.34 (95% CI = 4.48–12.0) in females and an odds ratio of 2.50 (95% CI = 1.98–3.14) in males. Our findings bolster the role of visceral adiposity as a potentially independent risk factor, in particular for type 2 diabetes in Caucasian females. Independent validation in other cohorts is necessary to determine whether the findings can translate to other ethnicities, or outside the UK.

Key Points Chronic kidney disease (CKD) affects ∼50% of patients with type 2 diabetes mellitus (T2DM), and changes in the epidemiology of T2DM are driving changes in the epidemiology of T2DM-associated CKD Demographic transition resulting in population ageing has contributed not only to an increased prevalence of T2DM but also to an increased prevalence of co-morbid CKD Young and/or obese patients with T2DM have an increased risk of diabetic complications, including CKD The greatest increase in T2DM prevalence has occurred in low-to-middle income countries where risk of CKD is also high; these regions are least able to manage the disease burden Although the incidence of cardiovascular disease in patients with T2DM has improved, this effect has not been associated with any substantial reduction in T2DM-associated renal impairment In the absence of new and effective renoprotective interventions, the increasing global prevalence of T2DM will inevitably be associated with an increase in the prevalence of CKD Chronic kidney disease (CKD) is a common comorbidity in patients with type 2 diabetes mellitus (T2DM). In this Review, Paul Zimmet and colleagues discuss the changing epidemiology of T2DM and the effect of these changes on the prevalence of CKD. They indicate how the decreasing prevalence of cardiovascular disease in T2DM has resulted in an increased prevalence of CKD, outline differences in the prevalence and disease burden of T2DM and CKD in various populations worldwide, and describe the financial, societal, and clinical impact of these diseases. Chronic kidney disease (CKD) is a common comorbidity in patients with type 2 diabetes mellitus (T2DM) and both conditions are increasing in prevalence. CKD is estimated to affect ∼50% patients with T2DM globally, and its presence and severity markedly influences disease prognosis. CKD is more common in certain patient populations, including the elderly, those with youth-onset diabetes mellitus, those who are obese, certain ethnic groups, and disadvantaged populations. These same settings have also seen the greatest increase in the prevalence of T2DM, as exemplified by the increasing prevalence of T2DM in low-to- middle income countries. Patients from low-to-middle income countries are often the least able to deal with the burden of T2DM and CKD and the health-care facilities of these countries least able to deal with the demand for equitable access to renal replacement therapies. The increasing prevalence of younger individuals with T2DM, in whom an accelerated course of complications can be observed, further adds to the global burden of CKD. Paradoxically, improvements in cardiovascular survival in patients with T2DM have contributed to patients surviving longer, allowing sufficient time to develop renal impairment. This Review explores how the changing epidemiology of T2DM has influenced the prevalence and incidence of associated CKD across different populations and clinical settings.

The liberation of energy stores from adipocytes is critical to support survival in times of energy deficit; however, uncontrolled or chronic lipolysis associated with insulin resistance and/or insulin insufficiency disrupts metabolic homeostasis 1 , 2 . Coupled to lipolysis is the release of a recently identified hormone, fatty-acid-binding protein 4 (FABP4) 3 . Although circulating FABP4 levels have been strongly associated with cardiometabolic diseases in both preclinical models and humans 4 – 7 , no mechanism of action has yet been described 8 – 10 . Here we show that hormonal FABP4 forms a functional hormone complex with adenosine kinase (ADK) and nucleoside diphosphate kinase (NDPK) to regulate extracellular ATP and ADP levels. We identify a substantial effect of this hormone on beta cells and given the central role of beta-cell function in both the control of lipolysis and development of diabetes, postulate that hormonal FABP4 is a key regulator of an adipose–beta-cell endocrine axis. Antibody-mediated targeting of this hormone complex improves metabolic outcomes, enhances beta-cell function and preserves beta-cell integrity to prevent both type 1 and type 2 diabetes. Thus, the FABP4–ADK–NDPK complex, Fabkin, represents a previously unknown hormone and mechanism of action that integrates energy status with the function of metabolic organs, and represents a promising target against metabolic disease. Hormonal FABP4 is discovered to be a pivotal regulator of an adipose–beta-cell endocrine axis that coordinates energy status and metabolic organ function, and targeting this axis improved metabolic outcomes.

BackgroundHSG4112 is a clinical-stage drug candidate for the treatment of obesity. Here, we report its discovery and preclinical efficacy.MethodsIn high-fat diet (HFD)-induced obese male C57BL/6J mice, we tested the weight loss effect of synthetic compounds derived from a structure–activity relationship (SAR) study of glabridin, a natural compound known to reduce body weight and influence energy homeostasis. After selecting HSG4112 as our optimized compound from this discovery method, we characterized its pharmacological effects on parameters related to obesity through in vivo metabolic and biochemical measurements, histology and gene expression analysis, and indirect calorimetry.ResultsThrough the SAR study, we identified four novel components of glabridin pertinent for its anti-obesity activity, and found that HSG4112, an optimized structural analog of glabridin, markedly supersedes glabridin in weight reduction efficacy and chemical stability. Six-week administration of HSG4112 to HFD-induced obese mice led to dose-dependent normalization of obesity-related parameters, including body weight, muscle and adipose tissue weight, adipocyte size, and serum leptin/insulin/glucose levels. The weight reduction induced by HSG4112 was partially mediated by decreased food intake and mainly mediated by increased energy expenditure, with no change in physical activity. Accordingly, the pattern of transcriptional changes was aligned with increased energy expenditure in the liver and muscles. Following significant body weight reduction, robust amelioration of histopathology and blood markers of fatty liver were also observed.ConclusionsOur study demonstrates the key chemical components of glabridin pertinent to its weight loss effects and suggests HSG4112 as a promising novel drug candidate for the pharmacological treatment of obesity.