The existence of an insulin-stimulated glucose and non-essential but not essential amino acid substrate interaction in diabetic pigs

Research Progress on the Experimental Animal Model of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) refers to different degrees of abnormal glucose metabolism during pregnancy, where blood glucose levels do not reach the level of overt diabetes, accounting for 80-90% of pregnancy with hyperglycemia. Hyperglycemia affects the pregnancy process, leading to a series of adverse maternal outcomes that have a profound impact on the future of the offspring. The establishing of an appropriate GDM model will provide theoretical basis for study GDM pathogenesis involves, the choice of resonable drugs and the observation the disease trends and outcomes. At present, there are many methods for establishing experimental GDM animal models and animal choices. This paper examines the different GDM models and their induction methods.

Porcine models for studying complications and organ crosstalk in diabetes mellitus

The worldwide prevalence of diabetes mellitus and obesity is rapidly increasing not only in adults but also in children and adolescents. Diabetes is associated with macrovascular complications increasing the risk for cardiovascular disease and stroke, as well as microvascular complications leading to diabetic nephropathy, retinopathy and neuropathy. Animal models are essential for studying disease mechanisms and for developing and testing diagnostic procedures and therapeutic strategies. Rodent models are most widely used but have limitations in translational research. Porcine models have the potential to bridge the gap between basic studies and clinical trials in human patients. This article provides an overview of concepts for the development of porcine models for diabetes and obesity research, with a focus on genetically engineered models. Diabetes-associated ocular, cardiovascular and renal alterations observed in diabetic pig models are summarized and their similarities with complications in diabetic patients are discussed. Systematic multi-organ biobanking of porcine models of diabetes and obesity and molecular profiling of representative tissue samples on different levels, e.g., on the transcriptome, proteome, or metabolome level, is proposed as a strategy for discovering tissue-specific pathomechanisms and their molecular key drivers using systems biology tools. This is exemplified by a recent study providing multi-omics insights into functional changes of the liver in a transgenic pig model for insulin-deficient diabetes mellitus. Collectively, these approaches will provide a better understanding of organ crosstalk in diabetes mellitus and eventually reveal new molecular targets for the prevention, early diagnosis and treatment of diabetes mellitus and its associated complications.

Amylase-Dependent Regulation of Glucose Metabolism and Insulin/Glucagon Secretion in the Streptozotocin-Induced Diabetic Pig Model and in a Rat Pancreatic Beta-Cell Line, BRIN-BD11

The current study was aimed at highlighting the role of blood pancreatic amylase in the regulation of glucose homeostasis and insulin secretion in a porcine model of streptozotocin- (STZ-) induced diabetes and in a rat pancreatic beta-cell line, BRIN-BD11. Blood glucose, plasma insulin, and glucagon levels were measured following a duodenal glucose tolerance test (IDGTT), in four pigs with STZ-induced type 2 diabetes (T2D pigs) and in four pigs with STZ-induced type 1 diabetes (T1D pigs). Four intact pigs were used as the control group. The effect of amylase supplementation on both acute and chronic insulin secretion was determined in a BRIN-BD11 cell line. The amylase infusion had no effect on the glucose utilization curve or glucagon levels in the healthy pigs. However, a significant lowering of insulin release was observed in healthy pigs treated with amylase. In the T2D pigs, the glucose utilization curve was significantly lowered in the presence of amylase, while the insulin response curve remained unchanged. Amylase also significantly increased glucagon release during the IDGTT in the T2D and T1D pigs, by between 2- and 4-fold. Amylase did not affect the glucose utilization curve in the T1D pigs. Amylase supplementation significantly decreased both acute and chronic insulin secretion in the BRIN-BD11 cells. These data confirm our previous observations and demonstrate the participation of pancreatic amylase in glucose absorption/utilization. Moreover, the present study clearly highlights the direct impact of pancreatic blood amylase on insulin secretion from pancreatic beta-cells and its interactions with insulin and glucagon secretion in a porcine model.

Considerations on pig models for appetite, metabolic syndrome and obese type 2 diabetes: From food intake to metabolic disease

(Mini)pigs have proven to be a valuable animal model in nutritional, metabolic and cardiovascular research and in some other biomedical research areas (toxicology, neurobiology). The large resemblance of (neuro)anatomy, the gastro-intestinal tract, body size, body composition, and the omnivorous food choice and appetite of the pig are additional reasons to select this large animal species for (preclinical) nutritional and pharmacological studies. Both humans and pigs are prone to the development of obesity and related cardiovascular diseases such as hypertension and atherosclerosis. Bad cholesterol (LDL) is high and good cholesterol (HDL) is low in pigs, like in humans. Disease-relevant pig models fill the gap between rodent models and primate species including humans. Diet-induced obese pigs show a phenotype related to the metabolic syndrome including high amounts of visceral fat, fatty organs, insulin resistance and high blood pressure. However, overt hyperglycaemia does not develop within 6 months after initiation of high sugar-fat feeding. Therefore, to accelerate the induction of obese type 2 diabetes, obese pigs can be titrated with streptozotocin, a chemical agent which selectively damages the insulin-producing pancreatic beta-cells. However, insulin is required to maintain obesity. With proper titration of streptozotocin, insulin secretion can be restrained at such a level that hyperglycaemia will be induced but lipolysis is still inhibited due to the fact that inhibition of lipolysis is more sensitive to insulin compared to stimulation of glucose uptake. This strategy may lead to a stable hyperglycaemic, non-ketotic obese pig model which remains anabolic with time without the necessity of exogenous insulin treatment.

Effects of acute exposure to increased plasma branched-chain amino acid concentrations on insulin-mediated plasma glucose turnover in healthy young subjects

BACKGROUND

Plasma branched-chain amino acids (BCAA) are inversely related to insulin sensitivity of glucose metabolism in humans. However, currently, it is not known whether there is a cause-and-effect relationship between increased plasma BCAA concentrations and decreased insulin sensitivity.

OBJECTIVE

To determine the effects of acute exposure to increased plasma BCAA concentrations on insulin-mediated plasma glucose turnover in humans.

METHODS

Ten healthy subjects were randomly assigned to an experiment where insulin was infused at 40 mU/m2/min (40U) during the second half of a 6-hour intravenous infusion of a BCAA mixture (i.e., BCAA; N = 5) to stimulate plasma glucose turnover or under the same conditions without BCAA infusion (Control; N = 5). In a separate experiment, seven healthy subjects were randomly assigned to receive insulin infusion at 80 mU/m2/min (80U) in association with the above BCAA infusion (N = 4) or under the same conditions without BCAA infusion (N = 3). Plasma glucose turnover was measured prior to and during insulin infusion.

RESULTS

Insulin infusion completely suppressed the endogenous glucose production (EGP) across all groups. The percent suppression of EGP was not different between Control and BCAA in either the 40U or 80U experiments (P > 0.05). Insulin infusion stimulated whole-body glucose disposal rate (GDR) across all groups. However, the increase (%) in GDR was not different [median (1st quartile - 3rd quartile)] between Control and BCAA in either the 40U ([199 (167-278) vs. 186 (94-308)] or 80 U ([491 (414-548) vs. 478 (409-857)] experiments (P > 0.05). Likewise, insulin stimulated the glucose metabolic clearance in all experiments (P < 0.05) with no differences between Control and BCAA in either of the experiments (P > 0.05).

CONCLUSION

Short-term exposure of young healthy subjects to increased plasma BCAA concentrations does not alter the insulin sensitivity of glucose metabolism.

Animal models of diabetes mellitus for islet transplantation

Due to current improvements in techniques for islet isolation and transplantation and protocols for immunosuppressants, islet transplantation has become an effective treatment for severe diabetes patients. Many diabetic animal models have contributed to such improvements. In this paper, we focus on 3 types of models with different mechanisms for inducing diabetes mellitus (DM): models induced by drugs including streptozotocin (STZ), pancreatomized models, and spontaneous models due to autoimmunity. STZ-induced diabetes is one of the most commonly used experimental diabetic models and is employed using many specimens including rodents, pigs or monkeys. The management of STZ models is well established for islet studies. Pancreatomized models reveal different aspects compared to STZ-induced models in terms of loss of function in the increase and decrease of blood glucose and therefore are useful for evaluating the condition in total pancreatomized patients. Spontaneous models are useful for preclinical studies including the assessment of immunosuppressants because such models involve the same mechanisms as type 1 DM in the clinical setting. In conclusion, islet researchers should select suitable diabetic animal models according to the aim of the study.