Structural and pharmacological characterization of novel potent and selective monoclonal antibody antagonists of glucose-dependent insulinotropic polypeptide receptor.

Glucose-dependent insulinotropic polypeptide (GIP) is an endogenous hormonal factor (incretin) that, upon binding to its receptor (GIPr; a class B G-protein-coupled receptor), stimulates insulin secretion by beta cells in the pancreas. There has been a lack of potent inhibitors of the GIPr with prolonged in vivo exposure to support studies on GIP biology. Here we describe the generation of an antagonizing antibody to the GIPr, using phage and ribosome display libraries. Gipg013 is a specific competitive antagonist with equally high potencies to mouse, rat, dog, and human GIP receptors with a Ki of 7 nm for the human GIPr. Gipg013 antagonizes the GIP receptor and inhibits GIP-induced insulin secretion in vitro and in vivo. A crystal structure of Gipg013 Fab in complex with the human GIPr extracellular domain (ECD) shows that the antibody binds through a series of hydrogen bonds from the complementarity-determining regions of Gipg013 Fab to the N-terminal α-helix of GIPr ECD as well as to residues around its highly conserved glucagon receptor subfamily recognition fold. The antibody epitope overlaps with the GIP binding site on the GIPr ECD, ensuring competitive antagonism of the receptor. This well characterized antagonizing antibody to the GIPr will be useful as a tool to further understand the biological roles of GIP.

Forced and voluntary exercise counteract insulin resistance in rats: the role of coping style.

There are large individual differences in the success rates of exercise intervention programs aimed at the prevention and treatment of obesity-related disorders. In the present study, we tested the hypothesis that differences in coping style may impact the success rates of these intervention programs. We tested insulin responses before and after voluntary wheel running in both passive (insulin resistant) Roman Low Avoidance (RLA) and proactive (insulin sensitive) Roman High Avoidance (RHA) rats using intravenous glucose tolerance tests (IVGTTs). To control for a potential difference between voluntary and forced exercise, we also included RLA and RHA rats that were subjected to forced running. We found the following: 1) when given the opportunity to run voluntarily in a running wheel, passive RLA rats run more than proactively than RHA rats; 2) voluntary exercise leads to a normalization of insulin responses during an IVGTTs in RLA rats; and 3) there were no behavioral and physiological differences in efficacy between voluntary and forced running. We conclude that exercise, both forced and voluntary, is a successful lifestyle intervention for the treatment of hyperinsulinemia, especially in individuals with a passive coping style.

Beneficial effects of a plant-fish oil, slow carbohydrate diet on cardio-metabolic health exceed the correcting effects of metformin-pioglitazone in diabetic pigs fed a fast-food diet.

BACKGROUND: Lifestyle influences endocrine, metabolic and cardiovascular homeostasis. This study investigated the impact of diet and oral anti-diabetic medication on cardio-metabolic health in human-sized diabetic pigs. METHODS: After a growing pre-phase from ~30 to ~69 kg during which domestic pigs were fed either a low fat, low sucrose diet (group A) or a fast food-type diet elevated in lard (15%) and sucrose (40%) (group B), the pigs were subdivided in 5 groups (n = 7-8 pigs per group). Group 1, normal pigs from group A on a low fat, low sugar (L) pig diet and group 2, normal pigs from group B on a high lard (25%), sucrose-fructose (40%), cholesterol (1%) fast food-type (F) diet. Diabetes (D) was induced in group B pigs by streptozotocin and group 3 received the F diet (DF), group 4 received the F diet with Anti-diabetic medication metformin (2 g.day-1)-pioglitazone (40 mg.day-1) (DFA) and group 5 switched to a Plant-Fish oil (25%), Slowly digestible starch (40%) diet (DPFS). The F and PFS diets were identical for fat, carbohydrate and protein content but only differed in fat and carbohydrate composition. The 5 pig groups were followed up for 7 weeks until reaching ~120 kg. RESULTS: In normal pigs, the F diet predisposed to several abnormalities related to metabolic syndrome. Diabetes amplified the inflammatory and cardiometabolic abnormalities of the F diet, but both oral FA medication and the PFS diet partially corrected these abnormalities (mean±SEM) as follows: Fasting plasma TNF-ɑ (pg.ml-1) and NEFA (mmol.l-1) concentrations were high (p<0.02) in DF (193±55 and 0.79±0.16), intermediate in DFA (136±40 and 0.57±012) and low in DPFS pigs (107±31 and 0.48±0.19). Meal intolerance (response over fasting) for glucose and triglycerides (area under the curve, mmol.h-1) and for lactate (3-h postprandial, mmol.l-1) was high (p<0.03) in DF (489±131, 8.6±4.8 and 2.2±0.6), intermediate in DFA (276±145, 1.4±1.1 and 1.6±0.4) and low in DPFS (184±62, 0.7±1.8 and 0.1±0.1). Insulin-mediated glucose disposal (mg.kg-1.min-1) showed a numerical trend (p = NS): low in DF (6.9±2.2), intermediate in DFA (8.2±1.3) and high in DPFS pigs (10.4±2.7). Liver weight (g.kg-1 body weight) and liver triglyceride concentration (g.kg-1 liver) were high (p<0.001) in DF (23.8±2.0 and 69±14), intermediate in DFA (21.1±2.0 and 49±15) and low in DPFS pigs (16.4±0.7 and 13±2.0). Aorta fatty streaks were high (p<0.01) in DF (16.4±5.7%), intermediate in DFA (7.4±4.5%) and low in DPFS pigs (0.05±0.02%). CONCLUSION: This translational study using pigs with induced type 2 diabetes provides evidence that a change in nutritional life style from fast food to a plant-fish oil, slowly digestible starch diet can be more effective than sole anti-diabetic medication.

Hepatic-portal oleic acid inhibits feeding more potently than hepatic-portal caprylic acid in rats.

In several human and animal studies, medium-chain triglycerides decreased food intake more than did long-chain triglycerides. It is possible that faster uptake and metabolism of medium-chain fatty acids in the liver is responsible for this difference. To test this hypothesis we compared the feeding effects of hepatic portal vein (HPV) infusion of the medium-chain fatty acid caprylic acid (CA) with those of the long-chain fatty acid oleic acid (OA). Contrary to our expectation, six-h HPV infusion of 14 microg/min (50 nmol/min) OA robustly inhibited feeding, whereas infusion of 22 or 220 microg/min (150 and 1500 nmol/min) CA failed to have any effect on feeding. Only a much larger dose of CA, 1100 microg/min (7500 nmol/min) inhibited feeding similarly to 14 microg/min OA. The increased feeding-inhibitory potency of OA did not appear to be due to differences in stimulation of hepatic fatty acid oxidation because equimolar (50 nmol/min) doses of OA (14 microg/min) and CA (7 microg/min) did not differentially affect post-infusion levels of beta-hydroxybutyrate. Stress, inflammation, acute hepatotoxicity or oxidative stress also do not appear to account for the increased feeding-inhibitory potency of HPV OA because plasma concentrations of the stress hormones corticosterone and epinephrine, the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-alpha, the liver enzymes gamma-glutamyl transferase and alanine aminotransferase and as well as hepatic levels of malondialdehyde and glutathione were all similar after HPV infusion of saline or of 50 nmol/min OA or CA.

Effects of a novel potent melanin-concentrating hormone receptor 1 antagonist, AZD1979, on body weight homeostasis in mice and dogs.

BACKGROUND AND PURPOSE: Melanin-concentrating hormone (MCH) is an orexigen, and while rodents express one MCH receptor (MCH1 receptor), humans, non-human primates and dogs express two MCH receptors (MCH1 and MCH2 ). MCH1 receptor antagonists have been developed for the treatment of obesity and lower body weight in rodents. However, the mechanisms for the body weight loss and whether MCH1 receptor antagonism can lower body weight in species expressing both MCH receptors are not fully understood. EXPERIMENTAL APPROACH: A novel recently identified potent MCH1 receptor antagonist, AZD1979, was studied in wild type and Mchr1 knockout (KO) mice and by using pair-feeding and indirect calorimetry in diet-induced obese (DIO) mice. The effect of AZD1979 on body weight was also studied in beagle dogs. KEY RESULTS: AZD1979 bound to MCH1 receptors in the CNS and dose-dependently reduced body weight in DIO mice leading to improved homeostasis model assessment-index of insulin sensitivity. AZD1979 did not affect food intake or body weight in Mchr1 KO mice demonstrating specificity for the MCH1 receptor mechanism. In DIO mice, initial AZD1979-mediated body weight loss was driven by decreased food intake, but an additional component of preserved energy expenditure was apparent in pair-feeding and indirect calorimetry studies. AZD1979 also dose-dependently reduced body weight in dogs. CONCLUSION AND IMPLICATIONS: AZD1979 is a novel potent MCH1 receptor antagonist that affects both food intake and energy expenditure. That AZD1979 also lowers body weight in a species expressing both MCH receptors holds promise for the use of MCH1 receptor antagonists for the treatment of human obesity.

Discovery of (3-(4-(2-Oxa-6-azaspiro[3.3]heptan-6-ylmethyl)phenoxy)azetidin-1-yl)(5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methanone (AZD1979), a Melanin Concentrating Hormone Receptor 1 (MCHr1) Antagonist with Favorable Physicochemical Properties.

A novel series of melanin concentrating hormone receptor 1 (MCHr1) antagonists were the starting point for a drug discovery program that culminated in the discovery of 103 (AZD1979). The lead optimization program was conducted with a focus on reducing lipophilicity and understanding the physicochemical properties governing CNS exposure and undesired off-target pharmacology such as hERG interactions. An integrated approach was taken where the key assay was ex vivo receptor occupancy in mice. The candidate compound 103 displayed appropriate lipophilicity for a CNS indication and showed excellent permeability with no efflux. Preclinical GLP toxicology and safety pharmacology studies were without major findings and 103 was taken into clinical trials.

Novel Zn2+ Modulated GPR39 Receptor Agonists Do Not Drive Acute Insulin Secretion in Rodents.

Type 2 diabetes (T2D) occurs when there is insufficient insulin release to control blood glucose, due to insulin resistance and impaired ß-cell function. The GPR39 receptor is expressed in metabolic tissues including pancreatic ß-cells and has been proposed as a T2D target. Specifically, GPR39 agonists might improve ß-cell function leading to more adequate and sustained insulin release and glucose control. The present study aimed to test the hypothesis that GPR39 agonism would improve glucose stimulated insulin secretion in vivo. A high throughput screen, followed by a medicinal chemistry program, identified three novel potent Zn2+ modulated GPR39 agonists. These agonists were evaluated in acute rodent glucose tolerance tests. The results showed a lack of glucose lowering and insulinotropic effects not only in lean mice, but also in diet-induced obese (DIO) mice and Zucker fatty rats. It is concluded that Zn2+ modulated GPR39 agonists do not acutely stimulate insulin release in rodents.

Neuroendocrinology of insulin resistance: metabolic and endocrine aspects of adiposity.

Abdominal obesity is a major risk factor to attract the insulin resistance syndrome. It is proposed that abdominal obesity exposes the liver to elevated levels of free fatty acids, which activate a neuroendocrine reflex, leading to increased circulating levels of glucocorticoids. Besides directly attenuating peripheral insulin signaling, glucocorticoids oppose the activity of central nervous regulatory systems that stimulate insulin action. Among the factors that promote insulin action is leptin. Leptin regulates peripheral fuel partitioning and insulin action mainly through hypothalamic neuronal networks, which in turn, regulate endocrine activity of adipose tissue in a way comparable to thiazolidinediones. These are a class of insulin-sensitizing drugs, which exert their antidiabetic effects through the gamma isoform of peroxisome proliferator-activated receptor (PPAR-gamma). Since glucocorticoids oppose leptin action at several levels of control (including the central nervous system, CNS), it is argued that subjects easily develop obesity and associated metabolic disorders.

Individual variation in the (patho)physiology of energy balance.

There are large individual differences in the susceptibility for metabolic disorders such as obesity, the metabolic syndrome and type 2 diabetes. Unfortunately, most animal studies in this field ignore the importance of individual variation which limits the face validity of these studies for translation to the human situation. We have performed a series of studies that were particularly focused on the individual differences in the (patho)physiology of energy balance. The studies were performed with passive and proactive individuals of two different rat strains: the Roman High and Low Avoidance rats and the Wild type Groningen rat. The data reveal that passive and proactive individuals differ significantly on several parameters, i.e. body composition, Hypothalamic-Pituitary-Adrenal (HPA) axis activity, plasma levels of insulin and leptin, intestinal transit time, systolic blood pressure and meal patterns. We also found that the selection line of the Roman Low Avoidance rat may be considered as a non-obese animal model for the metabolic syndrome, since these rats display, under sedentary conditions, many of the related symptoms such as hypertension, visceral adiposity and insulin resistance during an intravenous glucose tolerance test. These symptoms disappeared when the animals were allowed to exercise voluntarily in a running wheel. We conclude that experiments with passive and proactive individuals are highly relevant for studying the (patho)physiology and behavior of energy balance and the related metabolic disorders.

Personality, a key factor in personalized medicine?

The incidence of health problems resulting from obesity is growing and obesity and its related diseases has become one of the main causes in death in industrialized societies. Environmental influences are crucial for the interactions between genetic, neurohormonal and metabolic factors that may be important in understanding individual differences in the development of obesity and metabolic diseases like type 2 diabetes. In particular the interactions between the personality of an individual and the environment play a key role in predicting the chance for successful treatment. Our experimental data clearly point out that the success of interventions designed to prevent or treat metabolic diseases could be considerably improved by adjusting the intervention to the personality of the individual. Furthermore, certain physiological and neuroendocrine characteristics of a personality are strong indicators for pathology development, both in experimental animals and humans. Future research should focus on the identification of easily measurable physiological and neuroendocrine markers indicative of the coping style or personality in humans.

Pharmacological treatment of hyperinsulineamia in rats depends on coping style.

Passive and proactive coping styles are associated with marked differences in behavioral and neuroendocrine responses. Previous studies revealed that the passive individuals are more prone to hyperinsulinemia. Likewise, we hypothesize that different coping styles may require different drugs to treat this. We tested this by treating passive and proactive rats (Roman Low Avoidance and Roman High Avoidance rats respectively) with either Rosiglitazone or with RU486. After eight days of treatment we performed and intravenous glucose tolerance test (IVGTT) and we compared the insulin and glucose levels with those measured during the IVGTT at baseline. Rosiglitazone improved insulin levels during an IVGTT in both passive and proactive coping styles. RU486, however, lowered insulin levels only in rats with a passive coping style. This study suggests that insight in the neuroendocrine differences between passive and proactive coping styles may provide an extra impulse to improve treatment of insulin resistance, since it allows the application of drugs targeted at the individual.

Coping style predicts the (in)sensitivity for developing hyperinsulinemia on a high fat diet in rats.

The aim of this study was to explore interactions between coping style and diet as risk factors for developing insulin resistance in rats. We hypothesized that rats characterized by a passive coping strategy are more susceptible for developing insulin resistance and visceral obesity than proactively coping rats, particularly on a high (45%) fat diet. This hypothesis was tested by comparing 1) insulin and glucose responses to an intravenous glucose tolerance test (IVGTT), and 2) body fat distribution, in two rat models for passive and proactive coping styles. We found that the most extremely passive rats are characterized by elevated insulin levels during a IVGTT, even on chow. Moderately passive rats display normal insulin responses under chow conditions, but develop insulin resistance on a high fat diet. Proactive rats are remarkably resistant to insulin resistance and visceral obesity, even when overfeeding on a high fat diet. Carcass analysis revealed that passive rats are characterized by increased epididymal fat deposition, which is in line with the observed differences in insulin resistance. We conclude that a passive personality is prone to develop insulin resistance and visceral obesity on a palatable fat diet and a proactive personality might be protected against the development of diet-induced insulin resistance.

Intestinal, adipose, and liver inflammation in diet-induced obese mice.

Chronic inflammation and increased visceral adipose tissue (VAT) are key elements of the metabolic syndrome. Both are considered to play a pathogenic role in the development of liver steatosis and insulin resistance. The aim of the present study was to investigate the hypothesis that an inflamed intestine, induced both by diet and chemical irritation, could induce persistent inflammation in VAT. Female C57BL/6JOlaHsd mice were used. In study I, groups of mice (n = 6 per group) were given an obesity-inducing cafeteria diet (diet-induced obesity) or regular chow only (control) for 14 weeks. In study II, colitis in mice (n = 8) was induced by 3% dextran sulfate sodium in tap water for 5 days followed by 21 days of tap water alone. Healthy control mice (n = 8) had tap water only. At the end of the studies, all mice were killed; and blood and tissues were sampled and processed for analysis. Body weight of diet-induced obese mice was greatly increased, with evidence of systemic inflammation, insulin resistance, and liver steatosis. Tissue inflammation indexed by proinflammatory cytokine expression was recorded in liver, mesenteric fat, and proximal colon/distal ileum, but not in subcutaneous or perigonadal fat. In dextran sulfate sodium-induced colitis mice, mesenteric fat was even more inflamed than the colon, whereas a much milder inflammation was seen in liver and subcutaneous fat. The studies showed both diet- and colitis-initiated inflammation in mesenteric fat. Fat depots contiguous with intestine and their capacity for exaggerated inflammatory responses to conditions of impaired gut barrier function may account for the particularly pathogenic role of VAT in obesity-induced metabolic disorders.