A human antibody against pathologic IAPP aggregates protects beta cells in type 2 diabetes models.

In patients with type 2 diabetes, pancreatic beta cells progressively degenerate and gradually lose their ability to produce insulin and regulate blood glucose. Beta cell dysfunction and loss is associated with an accumulation of aggregated forms of islet amyloid polypeptide (IAPP) consisting of soluble prefibrillar IAPP oligomers as well as insoluble IAPP fibrils in pancreatic islets. Here, we describe a human monoclonal antibody selectively targeting IAPP oligomers and neutralizing IAPP aggregate toxicity by preventing membrane disruption and apoptosis in vitro. Antibody treatment in male rats and mice transgenic for human IAPP, and human islet-engrafted mouse models of type 2 diabetes triggers clearance of IAPP oligomers resulting in beta cell protection and improved glucose control. These results provide new evidence for the pathological role of IAPP oligomers and suggest that antibody-mediated removal of IAPP oligomers could be a pharmaceutical strategy to support beta cell function in type 2 diabetes.

Diabetic cats have decreased gut microbial diversity and a lack of butyrate producing bacteria.

Obesity and inactivity are major risk factors of feline diabetes mellitus (FDM) and human type II diabetes mellitus (T2DM). In recent years, changes in the gut microbiota have been suggested as a contributing factor to T2DM. Whether the gut microbiota (GM) composition plays a role in FDM remains unknown. The aim of the current study was firstly a cross-sectional comparison of the GM of diabetic cats, to that of lean, and of obese/overweight non-diabetic cats of a similar age. Specifically, fecal samples from 82 privately-owned cats from Denmark and Switzerland were sequenced using 16S rRNA gene amplicon metabarcoding. Secondly dietary intervention data was generated, by obtaining additional samples from a subset of cats after placing them on a high-protein diet for four weeks. The GM diversity of diabetic cats was lower than that of lean cats in the cross-sectional study, and lower compared to lean and to overweight/obese cats after diet intervention. Diabetic cats also exhibited fewer Anaerotruncus, Dialister, and unknown Ruminococcaceae than lean cats. Serum fructosamine levels correlated negatively with Prevotellaceae abundance and positively with Enterobacteriaceae abundance. In summary the intestinal microbiota of diabetic cats was characterized by decreased GM diversity and loss of butyrate producing bacterial genera.

Translational value of animal models of obesity-Focus on dogs and cats.

A prolonged imbalance between a relative increase in energy intake over a decrease in energy expenditure results in the development of obesity; extended periods of a positive energy balance eventually lead to the accumulation of abnormally high amounts of fat in adipose tissue but also in other organs. Obesity is considered a clinical state of impaired general heath in which the excessive increase in adipose tissue mass may be associated with metabolic disorders such as type 2 diabetes mellitus, hyperlipidemia, hypertension and cardiovascular diseases. This review discusses briefly the use of animal models for the study of obesity and its comorbidities. Generally, most studies are performed with rodents, such as diet induced obesity and genetic models. Here, we focus specifically on two different species, namely dogs and cats. Obese dogs and cats show many features of human obesity. Interestingly, however, dogs and cats differ from each other in certain aspects because even though obese dogs may become insulin resistant, this does not result in the development of diabetes mellitus. In fact, diabetes in dogs is typically not associated with obesity because dogs present a type 1 diabetes-like syndrome. On the other hand, obese cats often develop diabetes mellitus which shares many features with human type 2 diabetes; feline and human diabetes are similar in respect to their pathophysiology, underlying risk factors and treatment strategies. Our review discusses genetic and endocrine factors in obesity, discusses obesity induced changes in lipid metabolism and includes some recent findings on the role of gut microbiota in obesity. Compared to research in rodent models, the array of available techniques and tools is unfortunately still rather limited in dogs and cats. Hence, even though physiological and pathophysiological phenomena are well described in dogs and cats, the underlying mechanisms are often not known and studies investigating causality specifically are scarce.

Roux-en-Y gastric bypass surgery in rats alters gut microbiota profile along the intestine.

Roux-en-Y gastric bypass (RYGB) surgery might modify the gut microbiota composition differently in the three distinct anatomical sections of the small intestine compared to sham surgery. We showed that RYGB induced changes in the microbiota of the alimentary limb and the common channel resembling those seen after prebiotic treatment or weight loss by dieting. These changes may be associated with altered production of intestinal hormones known to control energy balance. Postsurgical modulation of gut microbiota may significantly contribute to the beneficial metabolic effects of RYGB surgery.

Involvement of gut microbiota in the development of low-grade inflammation and type 2 diabetes associated with obesity.

Obesity is associated with metabolic alterations related to glucose homeostasis and cardiovascular risk factors. These metabolic alterations are associated with low-grade inflammation that contributes to the onset of these diseases. We and others have provided evidence that gut microbiota participates in whole-body metabolism by affecting energy balance, glucose metabolism, and low-grade inflammation associated with obesity and related metabolic disorders. Recently, we defined gut microbiota-derived lipopolysaccharide (LPS) (and metabolic endotoxemia) as a factor involved in the onset and progression of inflammation and metabolic diseases. In this review, we discuss mechanisms involved in the development of metabolic endotoxemia such as the gut permeability. We also discuss our latest discoveries demonstrating a link between the gut microbiota, endocannabinoid system tone, leptin resistance, gut peptides (glucagon-like peptide-1 and -2), and metabolic features. Finally, we will introduce the role of the gut microbiota in specific dietary treatments (prebiotics and probiotics) and surgical interventions (gastric bypass).

Feline pancreatic islet-like clusters and insulin producing cells express functional Toll-like receptors (TLRs).

Toll-like receptors (TLRs) are cellular receptors that recognize molecules derived from pathogens, endogenous molecules generated after cellular stress, and free fatty acids. TLR activation leads to a proinflammatory reaction that is fundamental in the initiation of an innate immune response and subsequent adaptive responses but also can damage tissues. TLRs are not only expressed within the immune system, but also in most other organ systems including the pancreas. TLR4 is expressed in pancreatic ß-cells of rodents and humans and its stimulation affects insulin secretion in response to glucose. A low-grade inflammation is often associated with disturbed performance of ß-cells and insulin resistance, the cardinal metabolic event of type-2 diabetes. Feline diabetes mellitus shares many similarities with type-2 diabetes in humans. Our objective was to elucidate the role of TLRs in feline pancreatic islets and islet-like clusters (ILC) that consist of islets with their adjacent tissue. We tested whether TLRs are triggered by their agonists and lead to the expression of inflammatory cytokines. We confirmed the expression of all known feline TLRs in pancreas and ILC. Furthermore, stimulation with TLR agonists increased IL-6 mRNA and protein content and the expression of other proinflammatory cytokines indicating a clear proinflammatory response. The reactivity to TLR ligands was stronger in ß-cell enriched populations obtained after sorting by FACS indicating that inflammatory stimuli can also be generated within ß-cells. We conclude that the microenvironment of feline ß-cells harbor the potential for inflammatory reactions, that can be initiated by molecules released from bacteria or viruses or other molecules recognized by TLRs. Therefore infections associated with bacteriemia and viremia can induce inflammation in islets and damage the endocrine pancreatic tissue.

Hyperglycaemia but not hyperlipidaemia decreases serum amylase and increases neutrophils in the exocrine pancreas of cats.

The goal of the study was to determine whether hyperglycaemia or hyperlipidaemia causes pancreatitis in cats and to assess the effect of excess serum glucose and lipids on amylase and lipase activity. Ten-day hyperglycaemic and hyperlipidaemic clamps were carried out in five and six healthy cats, respectively. Ten healthy cats received saline and served as controls. The activity of amylase was below the normal range in 4 of 5 hyperglycaemic cats by day 10. The activity of lipase did not vary in any of the cats. Samples of exocrine pancreas were normal on histological examination, but the number of tissue neutrophils was increased in hyperglycaemic cats (P<0.05). In a retrospective study 14 of 40 (35%) cats with naturally occurring diabetes mellitus had amylase activities below the reference range at the time of admission. Amylase activities normalised within 1 week of insulin therapy and subsequent glycaemic control. Lipase activity was increased in 26 of 40 (65%) diabetic cats and remained elevated despite glycaemic control. In conclusion, hyperglycaemia, but not hyperlipidaemia, increases pancreatic neutrophils in cats. However, because the histological morphology of the exocrine pancreas was normal, hyperglycaemia may play only a minor role in the pathogenesis of pancreatitis. Low amylase activities in diabetic cats may reflect an imbalance in glucose metabolism rather than pancreatitis.

Quantitative real-time PCR detection of insulin signalling-related genes in pancreatic islets isolated from healthy cats.

The cat has recently been proposed as a valuable model for type 2 diabetes mellitus (T2DM), because feline diabetes shares several similarities with the disease in humans. Impaired beta-cell function, decreased beta-cell mass, insulin resistance that is often related to obesity, and pancreatic amyloid deposition, are among these common features. In this study, and to further develop the cat as a model of T2DM, feline pancreatic islets were isolated and real-time PCR quantification of mRNA transcripts of genes central to beta-cell function and survival established. In particular, mRNA quantification systems were determined for insulin, the insulin enhancer pancreatic duodenal homeobox-1 (PDX-1), the insulin suppressor CCAAT/enhancer binding protein-beta (C/EBPbeta), glucose transporter isoform 2 (GLUT2), Fas receptor, the caspase-8 inhibitor FLIP (FLICE [caspase-8]-inhibitory protein) and two chemokines, interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1). Pancreatic islets were isolated by collagenase digestion from healthy cat donors. Partial feline mRNA sequences were determined for PDX-1, C/EBPbeta, GLUT2 and FLIP using primers identified from conserved regions of human, dog and rat mRNA. These novel and the previously available sequences (insulin, Fas receptor, IL-8 and MCP-1) were used to design feline-specific primers suitable for real-time PCR in isolated pancreatic islets. The adopted protocol of collagenase digestion yielded pancreatic islets that were frequently surrounded by acinar cells. Quantification of mRNA transcripts was simple and reproducible in healthy cats. Characterisation of genes related to insulin signalling in cats will prove useful to better understand the pathogenesis of feline diabetes and possibly of human T2DM.

Assessment of six different collagenase-based methods to isolate feline pancreatic islets.

Isolation of pancreatic islets is necessary to study the molecular mechanisms underlying beta-cell demise in diabetic cats. Six collagenase-based methods of isolation were compared in 10 cat pancreata, including single and double course of collagenase, followed or not by Ficoll centrifugation or accutase, and collagenase plus accutase. Morphometric analysis was performed to measure the relative area of islet and exocrine tissue. Islet specific mRNA transcripts were quantified in isolates by real-time PCR. The single and double course of collagenase digestion was successful in each cat and provided similar islet-to-exocrine tissue ratio. Quantities of insulin mRNA did not differ between the two methods. However, on histological examination either method yielded only approximately 2% of pure islets. The other methods provided disrupted islets or insufficient samples in 1-7 cats. Although pancreas digestion with single and double course of collagenase was superior, further studies are needed to improve islet isolation in cats.

Vaccination against GIP for the treatment of obesity.

BACKGROUND: According to the WHO, more than 1 billion people worldwide are overweight and at risk of developing chronic illnesses, including cardiovascular disease, type 2 diabetes, hypertension and stroke. Current therapies show limited efficacy and are often associated with unpleasant side-effect profiles, hence there is a medical need for new therapeutic interventions in the field of obesity. Gastric inhibitory peptide (GIP, also known as glucose-dependent insulinotropic polypeptide) has recently been postulated to link over-nutrition with obesity. In fact GIP receptor-deficient mice (GIPR(-/-)) were shown to be completely protected from diet-induced obesity. Thus, disrupting GIP signaling represents a promising novel therapeutic strategy for the treatment of obesity. METHODOLOGY/PRINCIPAL FINDINGS: In order to block GIP signaling we chose an active vaccination approach using GIP peptides covalently attached to virus-like particles (VLP-GIP). Vaccination of mice with VLP-GIP induced high titers of specific antibodies and efficiently reduced body weight gain in animals fed a high fat diet. The reduction in body weight gain could be attributed to reduced accumulation of fat. Moreover, increased weight loss was observed in obese mice vaccinated with VLP-GIP. Importantly, despite the incretin action of GIP, VLP-GIP-treated mice did not show signs of glucose intolerance. CONCLUSIONS/SIGNIFICANCE: This study shows that vaccination against GIP was safe and effective. Thus active vaccination may represent a novel, long-lasting treatment for obesity. However further preclinical safety/toxicology studies will be required before the therapeutic concept can be addressed in humans.