The human GLP-1 analogs liraglutide and semaglutide: absence of histopathological effects on the pancreas in nonhuman primates.

Increased pancreas mass and glucagon-positive adenomas have been suggested to be a risk associated with sitagliptin or exenatide therapy in humans. Novo Nordisk has conducted extensive toxicology studies, including data on pancreas weight and histology, in Cynomolgus monkeys dosed with two different human glucagon-like peptide-1 (GLP-1) receptor agonists. In a 52-week study with liraglutide, a dose-related increase in absolute pancreas weight was observed in female monkeys only. Such dose-related increase was not found in studies of 4, 13, or 87 weeks' duration. No treatment-related histopathological abnormalities were observed in any of the studies. Quantitative histology of the pancreas from the 52-week study showed an increase in the exocrine cell mass in liraglutide-dosed animals, with normal composition of endocrine and exocrine cellular compartments. Proliferation rate of the exocrine tissue was low and comparable between groups. Endocrine cell mass and proliferation rates were unaltered by liraglutide treatment. Semaglutide showed no increase in pancreas weight and no treatment-related histopathological findings in the pancreas after 13 or 52 weeks' dosing. Overall, results in 138 nonhuman primates showed no histopathological changes in the pancreas associated with liraglutide or semaglutide, two structurally different GLP-1 receptor agonists.

Laboratory animals as surrogate models of human obesity.

Obesity and obesity-related metabolic diseases represent a growing socioeconomic problem throughout the world. Great emphasis has been put on establishing treatments for this condition, including pharmacological intervention. However, there are many obstacles and pitfalls in the development process from pre-clinical research to the pharmacy counter, and there is no certainty that what has been observed pre-clinically will translate into an improvement in human health. Hence, it is important to test potential new drugs in a valid translational model early in their development. In the current mini-review, a number of monogenetic and polygenic models of obesity will be discussed in view of their translational character.

Secretion and dipeptidyl peptidase-4-mediated metabolism of incretin hormones after a mixed meal or glucose ingestion in obese compared to lean, nondiabetic men.

CONTEXT: Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are cleaved by dipeptidyl peptidase-4 (DPP-4); plasma activity of DPP-4 may be increased in obesity. The impact of this increase on incretin hormone secretion and metabolism is not known. OBJECTIVE: The aim of the study was to assess incretin hormone secretion and degradation in lean and obese nondiabetic subjects. DESIGN, SETTINGS, AND PARTICIPANTS: We studied the ingestion of a mixed meal (560 kcal) or oral glucose (2 g/kg) in healthy lean (n = 12; body mass index, 20-25 kg/m(2)) or obese (n = 13; body mass index, 30-35 kg/m(2)) males at a University Clinical Research Unit. MAIN OUTCOME MEASURES: We measured the area under the curve of plasma intact (i) and total (t) GIP and GLP-1 after meal ingestion and oral glucose. RESULTS: Plasma DPP-4 activity was higher in the obese subjects (38.5 +/- 3.0 vs. 26.7 +/- 1.6 mmol/min . microl; P = 0.002). Although GIP secretion (AUC(tGIP)) was not reduced in obese subjects after meal ingestion or oral glucose, AUC(iGIP) was lower in obese subjects (8.5 +/- 0.6 vs. 12.7 +/- 0.9 nmol/liter x 300 min; P < 0.001) after meal ingestion. GLP-1 secretion (AUC(tGLP-1)) was reduced in obese subjects after both meal ingestion (7.3 +/- 0.9 vs. 10.0 +/- 0.6 nmol/liter x 300 min; P = 0.022) and oral glucose (6.6 +/- 0.8 vs. 9.6 +/- 1.1 nmol/liter x 180 min; P = 0.035). iGLP-1 was reduced in parallel to tGLP-1. CONCLUSIONS: 1) Release and degradation of the two incretin hormones show dissociated changes in obesity: GLP-1 but not GIP secretion is lower after meal ingestion and oral glucose, whereas GIP but not GLP-1 metabolism is increased after meal ingestion. 2) Increased plasma DPP-4 activity in obesity is not associated with a generalized augmented incretin hormone metabolism.

Beta-cell function and mass in type 2 diabetes.

The aim of the work described here was to improve our understanding of beta-cell function (BCF) and beta-cell mass (BCM) and their relationship in vivo using the minipig as a model for some of the aspects of human type 2 diabetes (T2DM). More specifically, the aim was to evaluate the following questions: How is BCF, especially high frequency pulsatile insulin secretion, affected by a primary reduction in BCM or by primary obesity or a combination of the two in the minipig? Can evaluation of BCF in vivo be used as a surrogate measure to predict BCM in minipigs over a range of BCM and body weight? We first developed a minipig model of reduced BCM and mild diabetes using administration of a combination of streptozotocin (STZ) and nicotinamide (NIA) as a tool to study effects of a primary reduction of BCM on BCF. The model was characterized using a mixed-meal oral glucose tolerance test and intravenous stimulation with glucose and arginine as well as by histology of the pancreas after euthanasia. It was shown that stable, moderate diabetes can be induced and that the model is characterized by fasting and postprandial hyperglycemia, reduced insulin secretion and reduced BCM. Several defects in insulin secretion are well documented in human T2DM; however, the role in the pathogenesis and the possible clinical relevance of high frequency (rapid) pulsatile insulin secretion is still debated. We therefore investigated this phenomenon in normal minipigs and found easily detectable pulses in peripheral vein plasma samples that were shown to be correlated with pulses found in portal vein plasma. Furthermore, the rapid kinetics of insulin in the minipig strongly facilitates pulse detection. These characteristics make the minipig particularly suitable for studying the occurrence of disturbed pulsatility in relation to T2DM. Disturbances of rapid pulsatile insulin secretion have been reported to be a very early event in the development of T2DM and include disorderliness of pulses and reduced ability to entrain pulses with glucose. However, the role of reduced BCM and/or obesity in the development of these defects in humans is unknown. Therefore, the investigations were extended to include lean NIA/STZ minipigs where it was shown that a primary reduction of BCM leads to reduced insulin pulse mass but does not change periodicity of the pulses or the ability of glucose to entrain pulses. In contrast, obesity was found to be associated with reduced pulsatile insulin secretion and improved orderliness of glucose entrained pulses in the minipig. Furthermore obesity was associated with pancreatic lipid accumulation and increased beta-cell volume, although BCM relative to body weight was not changed. Finally, a combination of obesity and reduced BCM resulted in severely disturbed insulin secretion and severe morphological changes. Thus, results from NIA/STZ minipigs suggest that not all of the defects of rapid pulsatile insulin secretion seen in human T2DM can be explained by a primary reduction of BCM mass or up to 2 weeks of mild hyperglycemia. Furthermore, based on the results from obese minipigs, obesity in itself induces small defects in rapid pulsatile insulin secretion and the combination of obesity and reduced BCM leads to further deterioration of BCF. Another major characteristic of human diabetes is thought to be reduction of BCM and the ability to follow this parameter over time would greatly improve our understanding of disease progression and allow evaluation of pharmacological methods to increase BCM. BCM cannot, at present, be measured in vivo in humans. We therefore set out to further validate data from smaller studies in lean non-human primates and minipigs showing a correlation between measures of BCF in vivo and BCM. In a large study in lean minipigs with a range of BCM, we found that a strong stimulation of insulin secretion with a combination of glucose and arginine resulted in the best correlation to BCM, as determined using stereology. A similar relationship was also shown in a group of both lean and obese animals, thereby supporting the application of similar methods to estimate BCM in humans over a range of body weights. Since changes in rapid pulsatile insulin secretion are detectable early in the development of diabetes and in obesity, we hypothesized that this parameter could also be highly correlated to BCM as it has been shown in smaller studies in lean minipigs. However, rapid pulsatile insulin secretion did not show a better correlation to BCM than combined stimulation with glucose and arginine, and thus analysis of pulses does not provide a better surrogate marker for BCM in the minipig. To evaluate the weaker correlation of glucose stimulation compared to combined glucose and arginine stimulation in vivo with BCM, we further investigated BCF in lean, beta-cell reduced minipigs by studying BCF in vitro after isolation and perfusion of their pancreases to investigate the ability of the remaining beta-cells to compensate for the loss of BCM by increasing insulin secretion per BCM. The perfused pancreas was chosen in order to allow direct measurement of the insulin secretion without the effects of peripheral tissues. During the perfusion, it was shown that the remaining beta-cells were indeed able to compensate for the loss of BCM to a large extent in response to stimulation with glucose and glucagon-like peptide-1 but not in response to arginine. This shows that the type of stimulus applied is important for the ability to compensate for reduced BCM from the remaining population of beta-cells, and further supports the use of combined stimulation with glucose and arginine for estimation of BCM in vivo. In conclusion, an animal model of reduced BCM and mild diabetes has been developed and characterized. The model has been used to evaluate effects of a primary reduction of BCM, showing a reduced rapid insulin pulse mass but normal periodicity and entrainability of the pulses, whereas obesity was associated with reduced rapid pulsatile insulin secretion. Thus, based on these data, the disturbed rapid pulsatile insulin secretion seen in T2DM humans may not directly be explained by the reduced BCM in diabetes, whereas obesity may be related to the reduced pulsatility. Furthermore, the model has been used to establish a correlation between extensive stimulation of insulin secretion in vivo and BCM obtained by stereology in both lean and obese animals. The ability to estimate BCM based on in vivo experiments in the minipig would allow longitudinal studies on changes in this parameter over time in the intact animal and support application of similar methods in humans. Such methods could be useful for the diagnosis and the measurement of the effectiveness of treatment of diabetes in humans in the future.

Incretin and islet hormonal responses to fat and protein ingestion in healthy men.

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) regulate islet function after carbohydrate ingestion. Whether incretin hormones are of importance for islet function after ingestion of noncarbohydrate macronutrients is not known. This study therefore examined integrated incretin and islet hormone responses to ingestion of pure fat (oleic acid; 0.88 g/kg) or protein (milk and egg protein; 2 g/kg) over 5 h in healthy men, aged 20-25 yr (n=12); plain water ingestion served as control. Both intact (active) and total GLP-1 and GIP levels were determined as was plasma activity of dipeptidyl peptidase-4 (DPP-4). Following water ingestion, glucose, insulin, glucagon, GLP-1, and GIP levels and DPP-4 activity were stable during the 5-h study period. Both fat and protein ingestion increased insulin, glucagon, GIP, and GLP-1 levels without affecting glucose levels or DPP-4 activity. The GLP-1 responses were similar after protein and fat, whereas the early (30 min) GIP response was higher after protein than after fat ingestion (P<0.001). This was associated with sevenfold higher insulin and glucagon responses compared with fat ingestion (both P<0.001). After protein, the early GIP, but not GLP-1, responses correlated to insulin (r(2)=0.86; P=0.0001) but not glucagon responses. In contrast, after fat ingestion, GLP-1 and GIP did not correlate to islet hormones. We conclude that, whereas protein and fat release both incretin and islet hormones, the early GIP secretion after protein ingestion may be of primary importance to islet hormone secretion.

A novel glucagon receptor antagonist, NNC 25-0926, blunts hepatic glucose production in the conscious dog.

Elevated glucagon is associated with fasting hyperglycemia in type 2 diabetes. We assessed the effects of the glucagon receptor antagonist (2R)-N-[4-({4-(1-cyclohexen-1-yl)[(3,5-dichloroanilino)carbonyl]anilino}methyl)benzoyl]-2-hydroxy-b-alanine (NNC 25-0926) on hepatic glucose production (HPG) in vivo, using arteriovenous difference and tracer techniques in conscious dogs. The experiments consisted of equilibration (-140 to -40 min), control (40-0 min), and experimental [0-180 min, divided into P1 (0-60 min) and P2 (60-180 min)] periods. In P1, NNC 25-0926 was given intragastrically at 0 (veh), 10, 20, 40, or 100 mg/kg, and euglycemia was maintained. In P2, somatostatin, basal intraportal insulin, and 5-fold basal intraportal glucagon (2.5 ng/kg/min) were infused. Arterial plasma insulin levels remained basal throughout the study in all groups. Arterial plasma glucagon levels remained basal during the control period and P1 and then increased to approximately 70 pg/ml in P2 in all groups. Arterial plasma glucose levels were basal in the control period and P1 in all groups. In P2, the arterial glucose level increased to 245+/-22 and 172+/-15 mg/dl in the veh and 10 mg/kg groups, respectively, whereas in the 20, 40, and 100 mg/kg groups, there was no rise in glucose. Net hepatic glucose output was approximately 2 mg/kg/min in all groups during the control period. In P2, it increased by 9.4+/-2 mg/kg/min in the veh group. In the 10, 20, 40, and 100 mg/kg groups, the rise was only 4.1+/-0.9, 1.6+/-0.6, 2.4+/-0.7, and 1.5+/-0.3 mg/kg/min, respectively, due to inhibition of glycogenolysis. In conclusion, NNC 25-0926 effectively blocked the ability of glucagon to increase HGP in the dog.

Glucose-induced incretin hormone release and inactivation are differently modulated by oral fat and protein in mice.

Monounsaturated fatty acids, such as oleic acid (OA), and certain milk proteins, especially whey protein (WP), have insulinotropic effects and can reduce postprandial glycemia. This effect may involve the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). To explore this, we examined the release and inactivation of GIP and GLP-1 after administration of glucose with or without OA or WP through gastric gavage in anesthetized C57BL/6J mice. Insulin responses to glucose (75 mg) were 3-fold augmented by addition of WP (75 mg; P < 0.01), which was associated with enhanced oral glucose tolerance (P < 0.01). The insulin response to glucose was also augmented by addition of OA (34 mg; P < 0.05) although only 1.5-fold and with no associated increase in glucose elimination. The slope of the glucose-insulin curve was increased by OA (1.7-fold; P < 0.05) and by WP (4-fold; P < 0.01) compared with glucose alone, suggesting potentiation of glucose-stimulated insulin release. WP increased GLP-1 secretion (P < 0.01), whereas GIP secretion was unaffected. OA did not affect GIP or GLP-1 secretion. Nevertheless, WP increased the levels of both intact GIP and intact GLP-1 (both P < 0.01), and OA increased the levels of intact GLP-1 (P < 0.05). WP inhibited dipeptidyl peptidase IV activity in the proximal small intestine by 50% (P < 0.05), suggesting that luminal degradation of WP generates small fragments, which are substrates for dipeptidyl peptidase IV and act as competitive inhibitors. We therefore conclude that fat and protein may serve as exogenous regulators of secretion and inactivation of the incretin hormones with beneficial influences on glucose metabolism.

Measurements of insulin responses as predictive markers of pancreatic beta-cell mass in normal and beta-cell-reduced lean and obese Göttingen minipigs in vivo.

At present, the best available estimators of beta-cell mass in humans are those based on measurement of insulin levels or appearance rates in the circulation. In several animal models, these estimators have been validated against beta-cell mass in lean animals. However, as many diabetic humans are obese, a correlation between in vivo tests and beta-cell mass must be evaluated over a range of body weights to include different levels of insulin sensitivity. For this purpose, obese (n = 10) and lean (n = 25) Göttingen minipigs were studied. Beta-cell mass had been reduced (n = 16 lean, n = 5 obese) with a combination of nicotinamide (67 mg/kg) and streptozotocin (125 mg/kg), acute insulin response (AIR) to intravenous glucose and/or arginine was tested, pulsatile insulin secretion was evaluated by deconvolution (n = 30), and beta-cell mass was determined histologically. AIR to 0.3 (r(2) = 0.4502, P < 0.0001) or 0.6 g/kg glucose (r(2) = 0.6806, P < 0.0001), 67 mg/kg arginine (r(2) = 0.5730, P < 0.001), and maximum insulin concentration (r(2) = 0.7726, P < 0.0001) were all correlated to beta-cell mass when evaluated across study groups, and regression lines were not different between lean and obese groups except for AIR to 0.3 g/kg glucose. Baseline pulse mass was not significantly correlated to beta-cell mass across the study groups (r(2) = 0.1036, NS), whereas entrained pulse mass did show a correlation across groups (r(2) = 0.4049, P < 0.001). This study supports the use of in vivo tests of insulin responses to evaluate beta-cell mass over a range of body weights in the minipig. Extensive stimulation of insulin secretion by a combination of glucose and arginine seems to give the best correlation to beta-cell mass.

Use of the Göttingen minipig as a model of diabetes, with special focus on type 1 diabetes research.

Animal models of type 1 diabetes remain essential tools for investigation of the etiology and pathogenesis of the disease and, importantly, for the development of effective new treatments. Although a range of well-characterized and widely used models of type 1 diabetes in rodents are currently available, large animal models are a valuable complement to rodent models for both physiological and practical reasons. The pig is very useful in many aspects as a model for human physiology and pathophysiology because many organ systems of this species, as well as physiological and pathophysiological responses, resemble those of the human. The Göttingen minipig is particularly suitable for long-term studies because of its inherent small size and ease of handling, even at full maturity. Of particular relevance to the field of type 1 diabetes are the many similarities evident between humans and pigs with regard to pharmacokinetics of compounds after subcutaneous administration, structure and function of the gastrointestinal tract, morphology of the pancreas, and the overall metabolic status of the two species. Because spontaneous type 1-like diabetes is very rare in pigs, a model of the condition must be induced experimentally, either surgically or chemically. This process is discussed, and the use of the pig as a model in islet transplantation and diabetic complications is briefly summarized.

Measurements of insulin secretory capacity and glucose tolerance to predict pancreatic beta-cell mass in vivo in the nicotinamide/streptozotocin Göttingen minipig, a model of moderate insulin deficiency and diabetes.

Knowledge about beta-cell mass and/or function could be of importance for the early diagnosis and treatment of diabetes. However, measurement of beta-cell function as an estimate of beta-cell mass is currently the only method possible in humans. The present study was performed to investigate different functional tests as predictors of beta-cell mass in the Göttingen minipig. beta-cell mass was reduced in the Göttingen minipig with a combination of nicotinamide (100 [n = 6], 67 [n = 25], 20 [n = 2], or 0 mg/kg [n = 4]) and streptozotocin (125 mg/kg). Six normal pigs were included. An oral glucose tolerance test (OGTT) (n = 43) and insulin secretion test (n = 30) were performed and pancreata obtained for stereological determination of beta-cell mass. During OGTT, fasting glucose (r(2) = 0.1744, P < 0.01), area under the curve for glucose (r(2) = 0.2706, P < 0.001), maximum insulin secretion (r(2) = 0.2160, P < 0.01), and maximum C-peptide secretion (r(2) = 0.1992, P < 0.01) correlated with beta-cell mass. During the insulin secretion test, acute insulin response to 0.3 g/kg (r(2) = 0.6155, P < 0.0001) and 0.6 g/kg glucose (r(2) = 0.7321, P < 0.0001) and arginine (67 mg/kg) (r(2) = 0.7732, P < 0.0001) and maximum insulin secretion (r(2) = 0.8192, P < 0.0001) correlated with beta-cell mass. This study supports the use of functional tests to evaluate beta-cell mass in vivo and has established a validated basis for developing a mathematical method for estimation of beta-cell mass in vivo in the Göttingen minipig.

NN2211: a long-acting glucagon-like peptide-1 derivative with anti-diabetic effects in glucose-intolerant pigs.

Glucagon-like peptide-1 (GLP-1) is an effective anti-diabetic agent, but its metabolic instability makes it therapeutically unsuitable. This study investigated the pharmacodynamics of a long-acting GLP-1 derivative (NN2211: (Arg(34)Lys(26)-(N- epsilon -(gamma-Glu(N-alpha-hexadecanoyl)))-GLP-1(7-37)), after acute and chronic treatment in hyperglycaemic minipigs. During hyperglycaemic glucose clamps, NN2211 (2 micrograms kg(-1) i.v.) treated pigs required more (P < 0.005) glucose than control animals (5.8 +/- 2.1 vs. 2.9 +/- 1.8 mg kg(-1) min(-1)). Insulin excursions were higher (P < 0.01) after NN2211 (15,367 +/- 5,438 vs. 9,014 +/- 2,952 pmol l(-1) min), and glucagon levels were suppressed (P < 0.05). Once-daily injections of NN2211 (3.3 micrograms kg(-1) s.c.) reduced the glucose excursion during an oral glucose tolerance test, to 59 +/- 15% of pre-treatment values by 4 weeks (P < 0.05), without measurable changes in insulin responses. Fructosamine concentrations were unaltered by vehicle, but decreased (from 366 +/- 187 to 302 +/- 114 micromol l(-1), P = 0.14) after 4 weeks of NN2211. Gastric emptying was reduced (P < 0.05) by NN2211. NN2211 acutely increases glucose utilization during a hyperglycaemic glucose clamp and chronic treatment results in better daily metabolic control. Therefore, NN2211, a GLP-1 derivative that can be administered once daily, holds promise as a new anti-diabetic drug with a minimal risk of hypoglycaemia.

The long-acting GLP-1 derivative NN2211 ameliorates glycemia and increases beta-cell mass in diabetic mice.

NN2211 is a long-acting, metabolically stable glucagon-like peptide-1 (GLP-1) derivative designed for once daily administration in humans. NN2211 dose dependently reduced the glycemic levels in ob/ob mice, with antihyperglycemic activity still evident 24 h postdose. Apart from an initial reduction in food intake, there were no significant differences between NN2211 and vehicle treatment, and body weight was not affected. Histological examination revealed that beta-cell proliferation and mass were not increased significantly in ob/ob mice with NN2211, although there was a strong tendency for increased proliferation. In db/db mice, exendin-4 and NN2211 decreased blood glucose compared with vehicle, but NN2211 had a longer duration of action. Food intake was lowered only on day 1 with both compounds, and body weight was unaffected. beta-Cell proliferation rate and mass were significantly increased with NN2211, but with exendin-4, only the beta-cell proliferation rate was significantly increased. In conclusion, NN2211 reduced blood glucose after acute and chronic treatment in ob/ob and db/db mice and was associated with increased beta-cell mass and proliferation in db/db mice. NN2211 is currently in phase 2 clinical development.

Chamber-dependent expression of brain natriuretic peptide and its mRNA in normal and diabetic pig heart.

Brain natriuretic peptide (BNP) is produced in cardiac myocytes, and increased secretion is closely associated with cardiac dysfunction. However, several fundamental aspects of BNP expression in the myocardium have not yet been resolved. In the present study, we report the presence of a precursor BNP mRNA transcript and a mature BNP mRNA transcript in normal porcine hearts. In normal pigs, the amount of precursor BNP mRNA was similar in atrial and ventricular myocardium, whereas the mature BNP transcript was 10- to 50-fold more abundant in atrial than in ventricular myocardium. Quantitation of proBNP in normal porcine hearts by radioimmunoassay disclosed abundant proBNP in the atria, whereas proBNP was undetectable in the ventricles. Laser confocal microscopy revealed proBNP in secretory granules of atrial but not in the ventricular myocardium of normal pigs. Mild streptozotocin-induced diabetes doubled the expression of BNP mRNA in porcine atrial myocardium (P=0.03), but was without effect on BNP mRNA in the ventricular myocardium. The data suggest that BNP mRNA processing and proBNP storage differ between the atrial and ventricular myocardium. The results also imply that diabetes increases cardiac BNP expression in a chamber-dependent manner.

Mild streptozotocin diabetes in the Göttingen minipig. A novel model of moderate insulin deficiency and diabetes.

Nonrodent models of diabetes are needed for practical and physiological reasons. Induction of mild insulin-deficient diabetes was investigated in male Göttingen minipigs by use of streptozotocin (STZ) alone (75, 100, and 125 mg/kg) or 125 mg/kg combined with pretreatment with nicotinamide (NIA; 0, 20, 67, 100, 150, and 230 mg/kg). Use of NIA resulted in a less steep slope of the regression line between fasting plasma glucose and changing doses compared with STZ [-7.0 +/- 1.4 vs. 29.7 +/- 7.0 mM. mg(-1). kg(-1), P < 0.0001]. Intermediate NIA doses induced moderate changes of glucose tolerance [glucose area under the curve increased from 940 +/- 175 to 1,598 +/- 462 mM. min, P < 0.001 (100 mg/kg) and from 890 +/- 109 to 1,669 +/- 691 mM. min, P = 0.003 (67 mg/kg)] with reduced insulin secretion [1,248 +/- 602 pM. min after 16 days and 1,566 +/- 190 pM. min after 60 days vs. 3,251 +/- 804 pM. min in normal animals (P < 0.001)] and beta-cell mass [5.5 +/- 1.4 mg/kg after 27 days and 7.9 +/- 4.1 mg/kg after 60 days vs. 17.7 +/- 4.7 mg/kg in normal animals (P = 0.009)]. The combination of NIA and STZ provided a model characterized by fasting and especially postprandial hyperglycemia and reduced, but maintained, insulin secretion and beta-cell mass. This model holds promise as an important tool for studying the pathophysiology of diabetes and development of new pharmacological agents for treatment of the disease.