Alterations in energy expenditure in Roux-en-Y gastric bypass rats persist at thermoneutrality.

BACKGROUND: The compensatory decrease in energy expenditure (EE) in response to body weight loss is attenuated by Roux-en-Y gastric bypass (RYGB) surgery in rats. The thermoneutral zone (TNZ) is at higher temperatures in rodents than in humans. Consequently, rodents may be under moderate cold stress if EE is measured at room temperature, leading to increased EE due to adaptive thermogenesis. We speculated that the reported alterations in EE of RYGB rats at room temperature are caused by higher adaptive thermogenesis and are therefore not present at thermoneutrality. METHODS: Male Wistar rats were randomized for RYGB or sham surgery. Some sham rats were body weight matched (BWM) to the RYGB rats by food restriction, the others received ad libitum access to food (AL). EE, body temperature, physical activity and food intake were measured at ambient temperatures between 22 and 32 °C to determine the TNZ. Adaptive thermogenesis requires ß3-adrenergic receptor-mediated uncoupling protein-1 (UCP-1) expression in brown adipose tissue (BAT). The in vivo thermogenic capacity of BAT was determined by administering the ß3-adrenergic agonist CL316,243, and UCP-1 protein expression was measured at room temperature. RESULTS: The TNZ was between 28 and 30 °C for AL and RYGB and between 30 and 32 °C for BWM rats, respectively. In contrast to AL and BWM rats, EE was not significantly higher at room temperature than at thermoneutrality in RYGB rats, reflecting a lack of adaptive thermogenesis. Consistently, both the thermogenic capacity of BAT and UCP-1 expression were decreased in RYGB compared with AL rats at room temperature. CONCLUSIONS: Our data confirm that the decrease in EE after body weight loss is attenuated by RYGB surgery and show that this effect persists at thermoneutrality. Contrary to our hypothesis, we found that adaptive thermogenesis at room temperature is reduced in RYGB rats.

Influence of Roux-en-Y gastric bypass on plasma bile acid profiles: a comparative study between rats, pigs and humans.

BACKGROUND: Roux-en-Y gastric bypass (RYGBP) is the most widely used bariatric surgery procedure, which induces profound metabolic and physiological effects, such as substantial improvements in obesity, type 2 diabetes and their comorbidities. Increasing evidence identifies bile acids (BAs) as signaling molecules that contribute to the metabolic improvement after RYGBP. However, how and to what extent BAs mediate the metabolic effects of RYGBP still remains unclear and requires mechanism of action studies using preclinical models. In this study, we compared plasma BA profiles before and after RYGBP in two animal models, rats and pigs, with humans to evaluate their translational potential. METHODS: Plasma BAs were profiled in rats, pigs and humans by liquid chromatography coupled with tandem mass spectrometry before and after RYGBP. RESULTS: RYGBP increased baseline plasma total BA concentrations in humans and in the two animal models to a similar extent (∼3-fold increase), despite differences in presurgery BA levels and profiles between the models. However, qualitatively, RYGBP differently affected individual plasma BA species, with similar increases in some free species (cholic acid (CA), chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA)), different increases in glyco-conjugated species depending on the model and globally no increase in tauro-conjugated species whatever the model. CONCLUSIONS: The tested animal models share similar quantitative RYGBP-induced increases in peripheral blood BAs as humans, which render them useful for mechanistic studies. However, they also present qualitative differences in BA profiles, which may result in different signaling responses. Such differences need to be taken into account when translating results to humans.

Exocrine Pancreas in Cats With Diabetes Mellitus.

Pancreatitis has been described in cats with diabetes mellitus, although the number of studies currently available is very limited. In addition, ketoacidosis has been hypothesized to be associated with pancreatitis in diabetic cats. The aims of the present study were to investigate whether diabetic cats have pancreatitis and to determine if pancreatitis is more frequent with ketoacidosis. Samples of pancreas were collected postmortem from 37 diabetic cats, including 15 with ketoacidosis, and 20 control cats matched for age, sex, breed, and body weight. Sections were stained with hematoxylin and eosin, double-labeled for insulin/CD3, insulin/CD20, insulin/myeloperoxidase, insulin/PCNA, and glucagon/Ki67, and single-labeled for Iba1. A previously proposed semiquantitative score was used to characterize pancreatitis, along with counts of inflammatory cells. Scores of pancreatitis and the number of neutrophils, macrophages, and lymphocytes in the exocrine pancreas did not differ between diabetic and control cats or between diabetic cats with and without ketoacidosis. Of note, PCNA-positive acinar cells were increased (P = .002) in diabetic cats, particularly near islets (P < .001). Ki67-positive acinar cells were increased only near islets (P = .038). Ketoacidosis was not linked to proliferation. The results suggest that histopathologic evidence of pancreatitis may not be more frequent in diabetic cats and that ketoacidosis may not be associated with it at the time of death. Augmented PCNA-positive acinar cells might indicate increased proliferation due to chronic pancreatitis. The reason behind the prevalent proliferation of acinar cells surrounding pancreatic islets deserves further investigation.

Endocrine Pancreas in Cats With Diabetes Mellitus.

Pancreatic amyloidosis and loss of α and ß cells have been shown to occur in cats with diabetes mellitus, although the number of studies currently available is very limited. Furthermore, it is not known whether pancreatic islet inflammation is a common feature. The aims of the present study were to characterize islet lesions and to investigate whether diabetic cats have inflammation of the pancreatic islets. Samples of pancreas were collected postmortem from 37 diabetic and 20 control cats matched for age, sex, breed, and body weight. Histologic sections were stained with hematoxylin and eosin and Congo red; double labeled for insulin/CD3, insulin/CD20, insulin/myeloperoxidase, insulin/proliferating cell nuclear antigen, and glucagon/Ki67; and single labeled for amylin and Iba1. Mean insulin-positive cross-sectional area was approximately 65% lower in diabetic than control cats (P = .009), while that of amylin and glucagon was similar. Surprisingly, amyloid deposition was similar between groups (P = .408). Proliferation of insulin- and glucagon-positive cells and the number of neutrophils, macrophages, and T (CD3) and B (CD20) lymphocytes in the islets did not differ. The presence of T and B lymphocytes combined tended to be more frequent in diabetic cats (n = 8 of 37; 21.6%) than control cats (n = 1 of 20; 5.0%). The results confirm previous observations that loss of ß cells but not α cells occurs in diabetic cats. Islet amyloidosis was present in diabetic cats but was not greater than in controls. A subset of diabetic cats had lymphocytic infiltration of the islets, which might be associated with ß-cell loss.

Renal morphology in cats with diabetes mellitus.

In humans, diabetes mellitus (DM) is an important cause of renal damage, with glomerular lesions being predominant. In cats, although diabetes is a common endocrinopathy, it is yet unknown whether it leads to renal damage. The aim of the study was to compare renal histologic features and parameters of renal function in diabetic cats against a control population matched for age, gender, breed, and body weight. Thirty-two diabetic and 20 control cats were included. Kidney sections from paraffin-embedded kidney samples were stained and examined with optical microscopy to identify glomerular, tubulointerstitial, and vascular lesions and to assess their frequency and severity. Serum creatinine and urea concentrations were also compared. Glomerular lesions were observed in 29 cats overall, with mesangial matrix increase being more common (19 cats). Tubulointerstitial lesions were observed in 42 cats, including lymphocytic infiltration (29), fibrosis (22), or tubular necrosis (21). Vascular lesions were observed in 5 cases. The frequency and severity of histologic lesions did not differ between diabetic and control cats; however, among diabetics, those that survived longer after diagnosis had more glomerular and vascular lesions. Serum creatinine and urea concentrations were similar between groups; in diabetic cats median creatinine was 109 µmol/l (range, 51-1200) and urea was 12 mmol/l (range, 4-63), and in controls creatinine was 126 µmol/l (range, 50-875) and urea 11 mmol/l (range, 3-80). The results suggest that DM in cats does not lead to microscopically detectable kidney lesions or clinically relevant renal dysfunction. The authors hypothesize that the short life expectancy of diabetic cats may be the main reason for the difference from human diabetics.

The interaction of amylin with other hormones in the control of eating.

Twenty years of research established amylin as an important control of energy homeostasis. Amylin controls nutrient and energy fluxes by reducing energy intake, by modulating nutrient utilization via an inhibition of postprandial glucagon secretion and by increasing energy disposal via a prevention of compensatory decreases of energy expenditure in weight reduced individuals. Like many other gastrointestinal hormones, amylin is secreted in response to meals and it reduces eating by promoting meal-ending satiation. Not surprisingly, amylin interacts with many of these hormones to control eating. These interactions seem to occur at different levels because amylin seems to mediate the eating inhibitory effect of some of these gastrointestinal hormones, and the combination of some of these hormones seems to lead to a stronger reduction in eating than single hormones alone. Amylin's effect on eating is thought to be mediated by a stimulation of specific amylin receptors in the area postrema. Secondary brain sites that were defined to mediate amylin action - and hence potential additional sites of interaction with other hormones - include the nucleus of the solitary tract, the lateral parabrachial nucleus, the lateral hypothalamic area and other hypothalamic nuclei. The focus of this review is to summarize the current knowledge of amylin interactions in the control of eating. In most cases, these interactions have only been studied at a descriptive rather than a mechanistic level and despite the clear knowledge on primary sites of amylin action, the interaction sites between amylin and other hormones are often unknown.

Diabetes from humans to cats.

Diabetes mellitus is a common endocrinopathy in humans and in cats. The general prevalence of diabetes mellitus, and in particular of type 2 diabetes, has risen dramatically in recent years. This increase has often been linked to the rise in the obesity pandemic because obesity and the ensuing metabolic consequences constitute major risk factors for human type 2 and for feline diabetes. Feline diabetes shares many features of human type 2 diabetes in respect to its pathophysiology, underlying risk factors and treatment strategies. This review will briefly summarize major characteristics in the human and the feline disease and where available, point out the current knowledge on similarities and differences.

Mechanisms underlying the efficacy of a rodent model of vertical sleeve gastrectomy - A focus on energy expenditure.

OBJECTIVE: Bariatric surgery remains the only effective and durable treatment option for morbid obesity. Vertical Sleeve Gastrectomy (VSG) is currently the most widely performed of these surgeries primarily because of its proven efficacy in generating rapid onset weight loss, improved glucose regulation and reduced mortality compared with other invasive procedures. VSG is associated with reduced appetite, however, the relative importance of energy expenditure to VSG-induced weight loss and changes in glucose regulation, particularly that in brown adipose tissue (BAT), remains unclear. The aim of this study was to investigate the role of BAT thermogenesis in the efficacy of VSG in a rodent model. METHODS: Diet-induced obese male Sprague-Dawley rats were either sham-operated, underwent VSG surgery or were pair-fed to the food consumed by the VSG group. Rats were also implanted with biotelemetry devices between the interscapular lobes of BAT to assess local changes in BAT temperature as a surrogate measure of thermogenic activity. Metabolic parameters including food intake, body weight and changes in body composition were assessed. To further elucidate the contribution of energy expenditure via BAT thermogenesis to VSG-induced weight loss, a separate cohort of chow-fed rats underwent complete excision of the interscapular BAT (iBAT lipectomy) or chemical denervation using 6-hydroxydopamine (6-OHDA). To localize glucose uptake in specific tissues, an oral glucose tolerance test was combined with an intraperitoneal injection of 14C-2-deoxy-d-glucose (14C-2DG). Transneuronal viral tracing was used to identify 1) sensory neurons directed to the stomach or small intestine (H129-RFP) or 2) chains of polysynaptically linked neurons directed to BAT (PRV-GFP) in the same animals. RESULTS: Following VSG, there was a rapid reduction in body weight that was associated with reduced food intake, elevated BAT temperature and improved glucose regulation. Rats that underwent VSG had elevated glucose uptake into BAT compared to sham operated animals as well as elevated gene markers related to increased BAT activity (Ucp1, Dio2, Cpt1b, Cox8b, Ppargc) and markers of increased browning of white fat (Ucp1, Dio2, Cited1, Tbx1, Tnfrs9). Both iBAT lipectomy and 6-OHDA treatment significantly attenuated the impact of VSG on changes in body weight and adiposity in chow-fed animals. In addition, surgical excision of iBAT following VSG significantly reversed VSG-mediated improvements in glucose tolerance, an effect that was independent of circulating insulin levels. Viral tracing studies highlighted a patent neural link between the gut and BAT that included groups of premotor BAT-directed neurons in the dorsal raphe and raphe pallidus. CONCLUSIONS: Collectively, these data support a role for BAT in mediating the metabolic sequelae following VSG surgery, particularly the improvement in glucose regulation, and highlight the need to better understand the contribution from this tissue in human patients.

Roux-en-Y gastric bypass in rats increases sucrose taste-related motivated behavior independent of pharmacological GLP-1-receptor modulation.

Roux-en-Y gastric bypass (RYGB) surgery has been shown to decrease consummatory responsiveness of rats to high sucrose concentrations, and genetic deletion of glucagon-like peptide-1 receptors (GLP-1R) has been shown to decrease consummatory responsiveness of mice to low-sucrose concentrations. Here we assessed the effects of RYGB and pharmacological GLP-1R modulation on sucrose licking by chow-fed rats in a brief-access test that assessed consummatory and appetitive behaviors. Rats were tested while fasted presurgically and postsurgically and while nondeprived postsurgically and 5 h after intraperitoneal injections with the GLP-1R antagonist exendin-3(9-39) (30 µg/kg), agonist exendin-4 (1 µg/kg), and vehicle in 30-min sessions during which a sucrose concentration series (0.01-1.0 M) was presented in 10-s trials. Other rats were tested postsurgically or 15 min after peptide or vehicle injection while fasted and while nondeprived. Independent of food-deprivation state, sucrose experience, or GLP-1R modulation, RYGB rats took 1.5-3× as many trials as sham-operated rats, indicating increased appetitive behavior. Under nondeprived conditions, RYGB rats with presurgical sucrose experience licked more to sucrose relative to water compared with sham-operated rats. Exendin-4 and exendin-3(9-39) impacted 0.3 M sucrose intake in a one-bottle test, but never interacted with surgical group to affect brief-access responding. Unlike prior reports in both clearly obese and relatively leaner rats given RYGB and in GLP-1R knockout mice, we found that neither RYGB nor GLP-1R blockade decreased consummatory responsiveness to sucrose in our less obese chow-fed rats. Collectively, these results highlight the fact that changes in taste-driven motivated behavior to sucrose after RYGB and/or GLP-1R modulation are very model and measure dependent.

Effect of tetra-hydroxylated bile acid on size and insulin sensitivity of subcutaneous adipocytes in healthy lean cats.

Obesity leads to insulin resistance and is a major risk factor for the development of diabetes mellitus in cats. Prevention of obesity and obesity-induced insulin resistance is difficult, and reliable long-term strategies are currently lacking. Retinoid-related orphan receptor gamma (RORγ) was recently identified as an important transcription factor in the development of large insulin-resistant adipocytes in mice and humans. RORγ negatively affects adipocyte differentiation through expression of its target gene matrix metalloproteinase 3 (MMP3) and promotes the development of large insulin-resistant adipocytes. Preliminary studies in mice showed that RORγ can be inhibited by its ligand tetra-hydroxylated bile acid (THBA). In the present study, serum THBA levels were determined in healthy and diabetic cats. Moreover, potential side effects and the effects of THBA supplementation on adipocyte size, mRNA expression of RORγ, MMP3, interleukin 6, tumor necrosis factor α, adiponectin and leptin in feline subcutaneous adipocytes and insulin sensitivity were investigated in healthy normal weight cats. Thirteen healthy and 13 diabetic cats were used for determination of serum THBA level, and six healthy normal-weight cats were included in a feeding trial. Similar THBA levels were determined in serum of healthy and diabetic cats. Supplementation of 5 mg/kg THBA for 8 wk did not cause any negative effect on feeding behavior, general condition and blood parameters of tested cats. It significantly reduced adipocyte size and mRNA expression of MMP3, interleukin 6, and tumor necrosis factor α in adipocytes, while mRNA expression of adiponectin significantly increased and mRNA expression of RORγ and leptin remained unchanged. Administration of THBA did not influence fasting blood glucose levels or the response of cats to acute insulin administration. Based on these results, THBA is palatable and is considered safe for use in cats. It reduces expression of MMP3 and promotes the development of small adipocytes with increased expression of adiponectin and reduced expression of interleukin 6 and tumor necrosis factor α. Further studies are recommended to evaluate the effect of THBA on adipocyte size and insulin sensitivity in obese cats.

[Diabetes remission in cats: a review]. / Diabetes-Remission bei der Katze: Ein Überblick.

Remission from diabetes is seen in 25 - 50 % of cats during the first months of therapy. The likelihood of remission is higher in old cats and cats with normal cholesterol than in young cats and cats with increased cholesterol. The results of an ongoing study indicate that initial intravenous insulin therapy has positive effects on remission rates and quality of metabolic control.

Toll-like receptor 2-deficient mice are protected from insulin resistance and beta cell dysfunction induced by a high-fat diet.

AIMS/HYPOTHESIS: Inflammation contributes to both insulin resistance and pancreatic beta cell failure in human type 2 diabetes. Toll-like receptors (TLRs) are highly conserved pattern recognition receptors that coordinate the innate inflammatory response to numerous substances, including NEFAs. Here we investigated a potential contribution of TLR2 to the metabolic dysregulation induced by high-fat diet (HFD) feeding in mice. METHODS: Male and female littermate Tlr2(+/+) and Tlr2(-/-) mice were analysed with respect to glucose tolerance, insulin sensitivity, insulin secretion and energy metabolism on chow and HFD. Adipose, liver, muscle and islet pathology and inflammation were examined using molecular approaches. Macrophages and dendritic immune cells, in addition to pancreatic islets were investigated in vitro with respect to NEFA-induced cytokine production. RESULTS: While not showing any differences in glucose homeostasis on chow diet, both male and female Tlr2(-/-) mice were protected from the adverse effects of HFD compared with Tlr2(+/+) littermate controls. Female Tlr2(-/-) mice showed pronounced improvements in glucose tolerance, insulin sensitivity, and insulin secretion following 20 weeks of HFD feeding. These effects were associated with an increased capacity of Tlr2(-/-) mice to preferentially burn fat, combined with reduced tissue inflammation. Bone-marrow-derived dendritic cells and pancreatic islets from Tlr2(-/-) mice did not increase IL-1beta expression in response to a NEFA mixture, whereas Tlr2(+/+) control tissues did. CONCLUSION/INTERPRETATION: These data suggest that TLR2 is a molecular link between increased dietary lipid intake and the regulation of glucose homeostasis, via regulation of energy substrate utilisation and tissue inflammation.

10-day hyperlipidemic clamp in cats: effects on insulin sensitivity, inflammation, and glucose metabolism-related genes.

Obesity and hyperlipidemia are associated with impaired insulin sensitivity in human type 2 diabetes mellitus, possibly due to activation of a mild inflammatory response. Because obesity-induced insulin resistance predisposes cats to diabetes and because hyperlipidemia is a frequent concurrent finding, excess lipids may also impair insulin sensitivity in cats. Healthy cats (n=6) were infused with lipids (Lipovenoes 10%) for 10 days to clamp blood triglycerides at the approximate concentration of untreated feline diabetes (3-7 mmol/l). Controls received saline (n=5). On day 10, plasma adiponectin and proinflammatory markers were measured. Whole-body insulin sensitivity was calculated following an intravenous glucose tolerance test. Tissue mRNAs of glucose metabolism-related genes were quantified in subcutaneous and visceral fat, liver, and skeletal muscles. Accumulation of lipids was assessed in liver. At the termination of infusion, whole-body insulin sensitivity did not differ between groups. Compared to saline, cats infused with lipids had 50% higher plasma adiponectin and 2-3 times higher alpha(1)-acid glycoprotein and monocyte chemoattractant protein-1. Unexpectedly, lipid-infused cats had increased glucose transporter-4 (GLUT4) mRNA in the visceral fat, and increased peroxisome proliferative activated receptor-gamma2 (PPARgamma2) in subcutaneous fat; adiponectin expression was not affected in any tissue. Lipid-infused cats developed hepatic steatosis. Although hyperlipidemia induced systemic inflammation, whole-body insulin sensitivity was not impaired after 10 day infusion. Increased circulating adiponectin may have contributed to prevent insulin resistance, possibly by increasing GLUT4 and PPARgamma2 transcripts in fat depots.

Predictors of clinical remission in cats with diabetes mellitus.

BACKGROUND: Clinical remission is frequent in cats with well-controlled diabetes mellitus, but few studies explored predictors of this phenomenon. HYPOTHESIS: Data retrieved from medical records at admission might be valuable to identify likelihood of remission and its duration in diabetic cats. ANIMALS: Ninety cats with newly diagnosed diabetes, followed-up until death or remission. METHODS: Retrospective cohort study. Data were collected from records at admission, including history, signalment, physical examination, haematology, and biochemical profile, and the occurrence and duration of remission, defined as normoglycemia without insulin for ≥4 weeks. Predictors of remission were studied with univariate and multivariate logistic regression. Factors associated with remission duration were analyzed with Kaplan-Meier and Cox proportional hazard models. RESULTS: Forty-five (50%) cats achieved remission, after a median time of 48 days (range: 8-216). By study end, median remission duration was 114 days (range: 30-3,370) in cats that died and 151 days (range: 28-1,180) in alive cats. Remission was more likely with higher age (OR: 1.23, 95% CI: 1.04-1.46; P=.01) and less likely with increased serum cholesterol (OR: 0.36, 95% CI: 0.11-0.87; P=.04). Remission was longer with higher body weight (HR: 0.65, 95% CI: 0.42-0.99; P=.04) and shorter with higher blood glucose (HR: 1.01, 95% CI: 1.00-1.02; P=.02). CONCLUSIONS AND CLINICAL IMPORTANCE: Age, body weight, cholesterol, and glucose levels are suggested for prediction of remission or its duration in diabetic cats. Older cats developing diabetes may have a better outcome, possibly suggesting a slower disease progression.

Evaluation of a novel real-time continuous glucose-monitoring system for use in cats.

BACKGROUND: The Guardian REAL-Time is a continuous glucose-monitoring system (CGMS) recently developed to provide instantaneous interstitial glucose concentrations; the system does not require a monitor being fixed to the animal. HYPOTHESIS: The CGMS provides accurate and reproducible real-time readings of glucose concentration in cats. ANIMALS: Thirty-two diabetic cats, 2 cats with suspected insulinoma, and 5 healthy cats. METHODS: Prospective, observational study. CGMS accuracy was compared with a reference glucose meter at normal, high, and low blood glucose concentrations using error grid analysis. Reading variability of 2 simultaneously used CGMS was determined in diabetic cats by calculating correlation and percentage of concordance of paired data at different glycemic ranges. The time interval between increasing glycemia and a rise in interstitial fluid glucose measured by the CGMS was assessed in healthy cats receiving glucose IV; the time point of maximal increase in interstitial glucose concentrations was calculated. RESULTS: The CGMS was 100, 96.1, and 91.0% accurate at normal, high, and low blood glucose concentrations. Measurements deviated from reference by -12.7 +/- 70.5 mg/dL at normal, -12.1 +/- 141.5 mg/dL at high, and -1.9 +/- 40.9 mg/dL at low glucose concentrations. Overall, paired CGMS readings correlated significantly (r = 0.95, P < .0001) and concordance was 95.7%. The median delay after IV administration of glucose to an increase in interstitial glucose was 11.4 minutes (range: 8.8-19.7 minutes). CONCLUSIONS AND CLINICAL IMPORTANCE: Although some readings substantially deviated from reference values, the CGMS yields reproducible results, is clinically accurate in cats with hyperglycemia and euglycemia, and is slightly less accurate if blood glucose concentrations are low. Rapidly increasing interstitial glucose after a glycemic rise suggests that the CGMS is suitable for real-time measurement under clinical conditions.

A once-monthly GLP-1 receptor agonist for treatment of diabetic cats.

There is growing evidence that peptidic glucagon-like peptide-1 receptor agonists (GLP-1RA), such as exenatide, may provide useful therapeutic options for treatment of feline diabetes. However, because such drugs are administered subcutaneously, it is desirable that they be long-acting and not require frequent injections. We have developed a chemically controlled delivery system to support half-life extension of peptidic therapeutics. Here, the peptide is covalently attached to hydrogel microspheres by a self-cleaving ß-eliminative linker; after subcutaneous injection of the microspheres, the peptide is slowly released from the depot to the systemic circulation. Using this technology, we developed a delivery system that supports once-monthly administration of a stable exenatide analog, [Gln28]exenatide, in rodents (Schneider, et al, ACS Chem Biol 12, 2107 to 2116, 2017). The purposes of the present study were a) to demonstrate pharmacokinetic and pharmacodynamic similarities of the deamidation-sensitive GLP-1RA exenatide and the closely related, more stable [Gln28]exenatide and b) to develop a long-acting GLP-1RA in cats. The results show that exenatide and [Gln28]exenatide injected intravenously or subcutaneously at 10 µg/kg have nearly identical pharmacokinetics in the cat-both having elimination half-lives of ∼40 min-but subcutaneously administered [Gln28]exenatide has superior bioavailability-93% for [Gln28]exenatide vs 52% for exenatide. The results also show that exenatide and [Gln28]exenatide have similar insulinotropic activities in the cat during a high-dose intravenous glucose tolerance test; they increased the area under the curve (AUC) for insulin to a similar extent but had no effect on glucose AUC. Finally, subcutaneous injection of a microsphere-[Gln28]exenatide conjugate containing an appropriate self-cleaving linker in the cat provides plasma [Gln28]exenatide with a half-life of about 40 d vs 40 min with the injected free peptide. Hence, the large body of information available for exenatide can be used to facilitate clinical development of [Gln28]exenatide as a treatment for feline diabetes, and the microsphere-[Gln28]exenatide conjugate is quite suitable for once-monthly subcutaneous administration of the peptide in the cat.

Hyperglycaemia but not hyperlipidaemia causes beta cell dysfunction and beta cell loss in the domestic cat.

AIMS/HYPOTHESIS: In vitro studies point to a toxic effect of high glucose and non-esterified fatty acids on beta cells. Whether elevated levels of glucose and lipids induce beta cell loss in vivo is less clear. The domestic cat has recently been proposed as a valuable animal model for human type 2 diabetes because feline diabetes shows several similarities with diabetes in humans, including obesity-induced insulin resistance, impaired beta cell function, decreased number of beta cells and pancreatic amyloid deposition. METHODS: We infused healthy cats with glucose or lipids for 10 days to clamp their blood concentrations at the approximate level found in untreated feline diabetes (glucose: 25-30 mmol/l; triacylglycerols: 3-7 mmol/l). RESULTS: Glucose and lipid levels were adequately targeted. Plasma non-esterified fatty acids were increased by lipid infusion 1.7-fold. A dramatic and progressive decline of plasma insulin levels was observed in glucose-infused cats beginning after 2 days of hyperglycaemic clamp. In contrast, plasma insulin concentration and glucose tolerance test were not affected by hyperlipidaemia. Compared with controls, glucose-infused cats had a 50% decrease in beta cells per pancreatic area. Apoptotic islet cells and cleaved caspase-3-positive beta cells were observed in glucose-infused cats only. CONCLUSIONS/INTERPRETATION: Sustained hyperglycaemia but not hyperlipidaemia induces early and severe beta cell dysfunction in cats, and excess glucose causes beta cell loss via apoptosis in vivo. Hyperglycaemic clamps in cats may provide a good model to study the pathogenesis of glucose toxicity in beta cells.

Control of food intake and energy expenditure by amylin-therapeutic implications.

Amylin is a pancreatic B-cell hormone that plays an important role in the control of nutrient fluxes because it reduces food intake, slows gastric emptying, and reduces postprandial glucagon secretion. These actions seem to depend on a direct effect on the area postrema (AP). Subsequent to area AP activation, the amylin signal is conveyed to the forebrain via distinct relay stations. Within the lateral hypothalamic area, amylin diminishes the expression of orexigenic neuropeptides. Recent studies suggest that amylin may also play a role as a long term, adiposity signal. Similar to leptin or insulin, an infusion of amylin into the brain resulted in lower body weight gain than in controls, irrespective of the starting body weight. Interestingly, preliminary data also suggest that rats fed an energy-dense diet develop resistance to central amylin. In addition to amylin's action to control meal termination and to act as a potential adiposity signal, amylin and its agonist salmon calcitonin have recently been shown to increase energy expenditure under certain conditions. In summary, amylin may be an interesting target as a body weight lowering drug. In fact, recent studies provide evidence that amylin, especially when combined with other anorectic hormones (for example, peptide YY and leptin) has beneficial long-term effects on body weight.

Increase in high molecular weight adiponectin by bariatric surgery-induced weight loss.

AIM: To determine the changes in adiponectin multimers upon marked weight loss. METHODS: Plasma samples were obtained preoperatively and 3, 6, 12 and 24 months after surgery from 12 obese subjects undergoing weight loss-inducing bariatric surgery. Seven non-operated obese subjects served as controls. Plasma levels of adiponectin multimers were determined by protease digestion and Enzyme-Linked ImmunoSorbent Assay (ELISA) detection. In addition, adiponectin multimers were assessed by western blotting. RESULTS: In patients with weight loss after surgery but not in controls, total adiponectin and high molecular weight (HMW) adiponectin steadily increased during the observation period. Twenty-four months after surgery, the increase in total and HMW adiponectin was 2.2 +/- 0.46 and 1.4 +/- 0.3 microg/ml, respectively. In contrast, plasma concentrations of middle and low molecular weight adiponectin remained unchanged. CONCLUSIONS: The increase in plasma adiponectin levels observed 24 months after bariatric surgery depended on continuous weight loss and was completely attributable to the HMW complex.

Establishment of a protocol for the isolation of feline pancreatic islets.

Diabetes mellitus is a common endocrinopathy in cats that is associated with pancreatic islets lesions. Research on isolated islets contributed to the understanding of the pathophysiology of human diabetes. Therefore, by improving the existing methods of isolation in cats, we aimed at increasing islet yield, purity and viability of feline isolated islets. Islet isolation was accomplished by pancreas perfusion with 80ml of Collagenase type IV through the pancreatic duct at the site of the major papilla. The enzymatic digestion was combined with mechanical disruption and controlled by dithizone staining. Purification was performed by filtration and handpicking. Purified islets were plated on extracellular matrix pre-coated plates and cultured for 48h. Feline islets with a high degree of viability and purity were isolated and cultured for the first time. Although the percentage of islet free from the acinar tissue relative to the total number of isolated islets was low compared to other species, the suggested protocol represents a promising progress in the procedure of islet isolation in cats.