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

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 ϭ 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 Ͻ 0.001). This was associated with sevenfold higher insulin and glucagon responses compared with fat ingestion (both P Ͻ 0.001). After protein, the early GIP, but not GLP-1, responses correlated to insulin (r 2 ϭ 0.86; P ϭ 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.insulin; glucagon; glucagon-like peptide-1; glucose-dependent insulinotropic polypeptide; incretins; man THE INTEGRATED ENDOCRINE RESPONSES TO FOOD INGESTION are dependent on both the size and the composition of a meal and include the postprandial release of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and the islet hormones insulin and glucagon (3,5,21,32). Most studies have focused on responses to an oral glucose tolerance test, after which levels of GIP, GLP-1, and insulin rise, whereas glucagon levels are suppressed (4,18,20, 24). It is also known that fat and protein ingestion stimulate GLP-1 and GIP secretion (10,14,20,27). Less is known, however, regarding relationships between the incretin responses and changes in insulin and glucagon levels after meal or noncarbohydrate macronutrient ingestions.GLP-1 and GIP are rapidly degraded by dipeptidyl peptidase-4 (DPP-4), which cleaves the two NH 2 -terminal amino acids of the peptides, making them largely inactive (9). Accurate estimation of the relationship between incretin hormone secretion and islet hormones therefore requires measurement of both the total and the active intact forms of the two incretins. How this is related to macronutrient ingestion is not known. Indeed, we recently showed in mice that protein ingestion increased intact incretin hormone levels compared with carbohydrate ingestion, and this was associated with reduced intestinal DPP-4...

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.

Intermediate NIA doses induced moderate changes of glucose tolerance [glucose area under the curve increased from 940 Ϯ 175 to 1,598 Ϯ 462 mM ⅐ min, P Ͻ 0.001 (100 mg/kg) and from 890 Ϯ 109 to 1,669 Ϯ 691 mM ⅐ min, P ϭ 0.003 (67 mg/kg)] with reduced insulin secretion [1,248 Ϯ 602 pM ⅐ min after 16 days and 1,566 Ϯ 190 pM ⅐ min after 60 days vs. 3,251 Ϯ 804 pM ⅐ min in normal animals (P Ͻ 0.001)] and ␤-cell mass [5.5 Ϯ 1.4 mg/kg after 27 days and 7.9 Ϯ 4.1 mg/kg after 60 days vs. 17.7 Ϯ 4.7 mg/kg in normal animals (P ϭ 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 ␤-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.in vivo pharmacology; large-animal model; glucose tolerance; ␤-cell reduction; glucose-stimulated insulin secretion.THE STUDY OF THE PATHOPHYSIOLOGY and treatment of diabetes requires well characterized animal models that resemble aspects of the disease in humans. Various forms of diabetes occur spontaneously or can be induced in several species of animals. Most of the available models are based on rodents; however, nonrodent models of diabetes are urgently needed as a valuable supplement to rodents for both practical and physiological reasons.The pig is useful as a model for human physiology and pathophysiology, because many organ systems resemble those of the human. Of special interest for the study of diabetes is the similarities to humans found in the clinical chemistry (7,10,12,14,24,26,55), nutrition and gastrointestinal tract (4,8,11,20,35,40,51), pancreas development and morphology (21,36,37,44,49,54), and metabolism (3, 35). These characteristics make swine an interesting species for studies of metabolic abnormalities in diabetes. The Göttingen minipig is especially suitable for long-term studies because of its small size and ease of handling, even at full maturity (6).Pancreatectomy has been investigated as a method of inducing diabetes in pigs (33,34,50,55). However, high rates of mortality have been observed postoperatively (50, 55), meaning that this technique should be used with great caution, and alternatives should be considered because of welfare considerations. Chemical induction of diabetes offers the advantage of preservation of both exocrine and endocrine cell populations other than ␤-cells, thus resembling the situation in human diabetes (55). Several stable models have been established for overt type 1 diabetes in the pig by the use of pharmacological induction of ␤-cell damage with streptozotocin (STZ), either as single or repeated injections (2, 15, 16, 27-29, 46, 55). Substantially increased fasting plasma glucose (FPG) levels and decreased insulin secretion in response to glucose stimuli have been obtained as well as increases in plasma triglycerides and total cholesterol (27,29). Late complications typical of diabetes, such...