Porcine model of diabetic dyslipidemia: insulin and feed algorithms for mimicking diabetes mellitus in humans

A weakness of many animal models of diabetes mellitus is the failure to use insulin therapy, which typically results in severe body wasting. Data collected from such studies must be interpreted cautiously to separate the effects of hyperglycemia from those of starvation. We provide several algorithms that were used by us in two long-term (20-week) experiments in which hyperglycemia (300 to 400 mg/dl), dyslipidemia (cholesterol [280 to 405 mg/dl] and triglycerides [55 to 106 mg/dl] concentrations), and positive energy balance were maintained in swine. Yucatan miniature swine groups included control, alloxan-induced diabetes mellitus, diabetes mellitus plus diet-induced dyslipidemia, and exercise-trained diabetic dyslipidemic pigs. The algorithms were developed for the porcine model because of several similarities to humans, including: cardiac anatomy and physiology, propensity for sedentary behavior, and metabolism of dietary carbohydrates and lipids. Acute toxic effects of alloxan (hypoglycemia, hyperglycemia, nephrotoxicosis) were minimized by preventive fluid loading and by use of algorithms in which insulin, food, and fluid therapy were administered. Long-term insulin and food maintenance algorithms elicited normal body weight gain in all three diabetic groups (lean experiment) and threefold greater body weight gain in pigs of an obesity experiment. Exercise-trained pigs of both experiments manifested significantly increased work performance and did not experience medical complications. We conclude that these algorithms can be used in swine, or similar algorithms can be developed for other animal species to maintain hyperglycemia and/or dyslipidemia, while avoiding diabetes-induced wasting. Importantly, animal models of diabetes mellitus that maintain positive energy balance and poor glycemic control provide a marked improvement over other models by more closely mimicking the human presentation of diabetes mellitus.     

Clinical significance of cardiovascular dysmetabolic syndrome

Although diabetes mellitus is predominantly a metabolic disorder, recent data suggest that it is as much a vascular disorder. Cardiovascular complications are the leading cause of death and disability in patients with diabetes mellitus. A number of recent reports have emphasized that many patients already have atherosclerosis in progression by the time they are diagnosed with clinical evidence of diabetes mellitus. The increased risk of atherosclerosis and cardiovascular complications in diabetic patients is related to the frequently associated dyslipidemia, hypertension, hyperglycemia, hyperinsulinemia, and endothelial dysfunction. The evolving knowledge regarding the variety of metabolic, hormonal, and hemodynamic abnormalities in patients with diabetes mellitus has led to efforts designed for early identification of individuals at risk of subsequent disease. It has been suggested that insulin resistance, the key abnormality in type II diabetes, often precedes clinical features of diabetes by 5–6 years. Careful attention to the criteria described for the cardiovascular dysmetabolic syndrome should help identify those at risk at an early stage. The application of nonpharmacologic as well as newer emerging pharmacologic therapies can have beneficial effects in individuals with cardiovascular dysmetabolic syndrome and/or diabetes mellitus by improving insulin sensitivity and related abnormalities. Early identification and implementation of appropriate therapeutic strategies would be necessary to contain the emerging new epidemic of cardiovascular disease related to diabetes.     

Intraportal autotransplantation of cryopreserved porcine islets of Langerhans

Mechanically prepared isolated islets of Langerhans were cryopreserved in liquid nitrogen for a period of 4 days. Intraportal autotransplantation studies were performed on two groups of six pigs rendered diabetic by total pancreatectomy (group 2) or by partial pancreatectomy combined with streptozotocin (group 4) and compared with two control groups (groups 1 and 3, respectively). The pigs were assessed for survival, weight gain, glycosuria, polyuria, systemic blood sugar and insulin, and, in selected pigs, intravenous glucose tolerance tests. Results showed that partial pancreatectomy with streptozotocin was the better tolerated experimental diabetes. Variable control of hyperglycemia was obtained over an experimental period of 3 months. Random blood glucose returned to normal in one of six pigs in the totally pancreatectomized group and three of six pigs in the partial pancreatectomy and streptozotocin group. Despite these normal circulating glucose levels, imperfect glucose homeostasis was achieved as shown by the response to glucose tolerance testing. These results report blood glucose control after cryopreserved islet autotransplants in diabetic pigs but further study is still necessary to achieve consistency.     

Adenoviral insulin gene therapy prolongs survival of IDDM model BB rats by improving hyperlipidemia.

Diabetes is frequently associated with hyperlipidemia, which results in atherogenic complications. Insulin-dependent diabetes mellitus (IDDM) model BB/Wor//Tky (BB) rats exhibit both hyperglycemia and hyperlipidemia and die within 3 weeks after the onset of diabetes unless insulin therapy is given. We performed insulin gene therapy in BB rats with adenovirus vectors through the tail vein. After infusion, plasma triglyceride levels dropped quickly and maintained low levels for 1 week, whereas blood glucose levels showed a slight decrease. The survival period of diabetic BB rats was prolonged to up to 75 days by infusing insulin gene-expressing adenoviral vectors. We suggest that the control of hyperlipidemia can be a life-saving measure when combined with hyperglycemia control in the treatment of diabetes.     

Hyperglycemia-induced insulin resistance in diabetic dyslipidemic Yucatan swine

Hyperglycemia, dyslipidemia, and associated insulin resistance are hallmarks of diabetes mellitus. Purposes of the study reported here were to develop practical methods for assessment of in vivo insulin sensitivity and determine contributions of hyperglycemia and dyslipidemia to insulin resistance in the porcine model of alloxan-induced diabetes mellitus and dyslipidemia. Male Yucatan swine groups were treated for 20 weeks: control (C), high fat-fed (2% cholesterol) hyperlipidemic (H), alloxan-induced diabetic normolipidemic (D), diabetic high fat-fed (diabetic dyslipidemic, DD), and diabetic dyslipidemic treated with the lipid-lowering agent atorvastatin (DDA). Plasma cholesterol concentration increased sixfold in animals of groups H, DD, and DDA, whereas triglyceride concentration increased threefold in animals of group DD only. Diabetics had decreases in glucose tolerance and pancreatic immunostaining for insulin. Use of the gold standard hyperinsulinemic euglycemic clamp procedure indicated that maximal insulin-stimulated glucose uptake was similar to that in humans, but this method was not practical for use in pigs. Instead, a more convenient and valid insulin sensitivity test involving suppression of insulin secretion with somatostatin and a single insulin injection was used. Insulin sensitivity was greatly impaired by anesthesia with isoflurane, but was not affected by use of the anxiolytic agent diazepam. Insulin sensitivity decreased by 75% in diabetics (groups D, DD, DDA), compared with animals of groups C and H, and was inversely related to fasting blood glucose concentration (r = -0.72). Insulin treatment to restore blood glucose values of diabetics (> 250 mg/dl) to near control values (< 100 mg/dl) promptly restored insulin sensitivity to control values. We conclude that hyperglycemia is a major cause of insulin resistance in the porcine model of alloxan-induced diabetes mellitus and dyslipidemia.     

Dominant-negative mutant hepatocyte nuclear factor 1α induces diabetes in transgenic-cloned pigs

Pigs have been recognized as an excellent biomedical model for investigating a variety of human health issues. We developed genetically modified pigs that exhibit the apparent symptoms of diabetes. Transgenic cloned pigs carrying a mutant human hepatocyte nuclear factor 1α gene, which is known to cause the type 3 form of maturity-onset diabetes of the young, were produced using a combined technology of intracytoplasmic sperm injection-mediated gene transfer and somatic cell nuclear transfer. Although most of the 22 cloned offspring obtained died before weaning, four pigs that lived for 20–196 days were diagnosed as diabetes mellitus with nonfasting blood glucose levels greater than 200 mg/dl. Oral glucose tolerance test on a cloned pig also revealed a significant increase of blood glucose level after glucose loading. Histochemical analysis of pancreas tissue from the cloned pigs showed small and irregularly formed Langerhans Islets, in which poor insulin secretion was detected.     

A model of postprandial hyperinsulinemia in miniature swine

This report describes a new animal model of postprandial hyperinsulinemia (PPH) in adult miniature swine that consume a diet simulating that of affluent Western societies. Two progressive levels of PPH were induced experimentally by injecting subcutaneously low and high doses of purified porcine insulin without causing acute detrimental clinical effects or significant biological effects on total serum cholesterol, sodium and potassium concentrations, mean arterial blood pressure, or heart rate. Physiologic postprandial increments in total serum triglyceride concentrations were inhibited by experimentally-induced PPH. With this model, the in vivo effects of homologous PPH can be studied in a dose-responsive manner. Areas of potential research use of this model include study of the chronic effects of PPH on lipoprotein metabolism, the development of atherosclerosis and diabetes mellitus, and the association with regional body fat distribution and metabolism.     

Generation of insulin-deficient piglets by disrupting <Emphasis Type="Italic">INS</Emphasis> gene using CRISPR/Cas9 system

Diabetes mellitus is a chronic disease with accompanying severe complications. Various animal models, mostly rodents due to availability of genetically modified lines, have been used to investigate the pathophysiology of diabetes. Using pigs for diabetic research can be beneficial because of their similarity in size, pathogenesis pathway, physiology, and metabolism with human. However, the use of pigs for diabetes research has been hampered due to only few pig models presenting diabetes symptoms. In this study, we have successfully generated insulin-deficient pigs by generating the indels of the porcine INS gene in somatic cells using CRISPR/Cas9 system followed by somatic cell nuclear transfer. First, somatic cells carrying a modified INS gene were generated using CRISPR/Cas9 system and their genotypes were confirmed by T7E1 assay; targeting efficiency was 40.4% (21/52). After embryo transfer, three live and five stillborn piglets were born. As expected, INS knockout piglets presented high blood glucose levels and glucose was detected in the urine. The level of insulin and c-peptide in the blood serum of INS knockout piglets were constant after feeding and the expression of insulin in the pancreas was absent in those piglets. This study demonstrates effectiveness of CRISPR/Cas9 system in generating novel pig models. We expect that these insulin-deficient pigs can be used in diabetes research to test the efficacy and safety of new drugs and the recipient of islet transplantation to investigate optimal transplantation strategies.     

Increased atherosclerosis in diabetic dyslipidemic swine: protection by atorvastatin involves decreased VLDL triglycerides but minimal effects on the lipoprotein profile

Male Yucatan swine were allocated to four groups (n = 5-6 pigs per group): low fat (3%) fed control, high fat/2% cholesterol (CH) fed (HF), high fat/CH fed with alloxan-induced diabetes (DF) and DF pigs that were treated with atorvastatin (80 mg/day; DF+A). Pigs were fed two meals per day and daily insulin injections were used in diabetic pigs to maintain plasma glucose between 250 and 350 mg/dl. Diabetic dyslipidemic (DF) pigs exhibited greater coronary atherosclerosis and increased collagen deposition in internal mammary artery compared with normoglycemic hyperlipidemic pigs. Although total and LDL CH concentrations did not differ, triglyceride (TG) were increased in DF pigs and FPLC analysis indicated that the LDL/HDL CH ratio was significantly increased in DF compared with HF pigs. The LDL fraction of DF pigs contained larger, lipid enriched particles resembling IDL. Consumption of the high fat/CH diet caused a moderate increase in the percentage of 14:0 fatty acids in plasma lipids and this was compensated by small-moderate declines in several unsaturated fatty acids. There was a significant increase in phospholipid arachidonic acid in DF compared with HF pigs. Atorvastatin protected diabetic pigs from atherosclerosis and decreased total and VLDL TG, but exerted minimal effects on the FPLC lipoprotein and plasma fatty acid profiles and plasma concentrations of total and LDL CH, vitamin A, vitamin E, and lysophosphatidylcholine. Across all groups the plasma CH concentration was positively correlated with hepatic CH concentration. These findings suggest that atorvastatin's protection against coronary artery atherosclerosis in diabetes may involve effects on plasma VLDL TG concentration. Lack of major effects on other lipid parameters, including the LDL/HDL ratio, suggests that atorvastatin may have yet other anti-atherogenic effects, possibly directly in the vessel wall.     

Macroangiopathy in adults and children with diabetes: from molecular mechanisms to vascular damage (part 1).

Type 2 diabetes mellitus (T2DM) is an increasing problem in childhood; however type 1 diabetes mellitus (T1DM) remains by far the most common type of diabetes in this age group. In this review we will focus on T1DM, because this will have the greatest implication for patients diagnosed in childhood. During the atherosclerotic process, several molecular, receptorial and cellular factors provide a continous mechanism of vascular damage. In diabetic children this state seems to be enhanced and facilitated so that accelerated atherosclerosis is associated with an increased risk of cardiovascular events in respect to the non diabetic population. Hyperglycemia PER SE and associated with diabetes is an important risk factor for atherosclerosis. At present a substantial part of children with diabetes do not reach satisfactory glycemic control. Other risk factors for the development and progression of atherosclerosis may be inherited or develop in the course of the disease: hypertension, dyslipidemia, insulin resistance, obesity, cigarette smoking, physical inactivity, disturbance of platelet function, coagulation and fibrinolysis. The development and progression of atherosclerosis should be blocked at an early age, if possible. Primary prevention to all risk factors for cardiovascular disease is important and intervention is indicated if necessary. At the moment the best therapeutic strategy is to maintain metabolic control at a physiologic level and perform screening and early intervention for vascular complications.     

Establishment of a Refined Oral Glucose Tolerance Test in Pigs,and Assessment of Insulin,Glucagon and Glucagon-Like Peptide-1 Responses

Diabetes mellitus is increasing worldwide and reliable animal models are important for progression of the research field. The pig is a commonly used large animal model in diabetes research and the present study aimed to refine a model for oral glucose tolerance test (OGTT) in young growing pigs, as well as describing intravenous glucose tolerance test (IVGTT) in the same age group. The refined porcine OGTT will reflect that used in children and adolescents. Eighteen pigs were obtained one week after weaning and trained for two weeks to bottle-feed glucose solution, mimicking the human OGTT. The pigs subsequently underwent OGTT (1.75 g/kg BW) and IVGTT (0.5 g/kg BW). Blood samples were collected from indwelling vein catheters for measurements of glucose and the diabetes related hormones insulin, glucagon and active glucagon-like peptide-1. The study confirmed that pigs can be trained to bottle-feed glucose dissolved in water and thereby undergo an OGTT more similar to the human standard OGTT than previously described methods in pigs. With the refined method for OGTT, oral intake only consists of glucose and water, which is an advantage over previously described methods in pigs where glucose is given together with feed which will affect glucose absorption. Patterns of hormonal secretion in response to oral and intravenous glucose were similar to those in humans; however, the pigs were more glucose tolerant with lower insulin levels than humans. In translational medicine, this refined OGTT and IVGTT methods provide important tools in diabetes research when pigs are used as models for children and adolescents in diabetes research.     

Mitochondria in the pathogenesis of diabetes: a proteomic view

Diabetes mellitus is a complex metabolic disorder characterized by chronic hyperglycemia due to absolute or relative lack of insulin. Though great efforts have been made to investigate the pathogenesis of diabetes, the underlying mechanism behind the development of diabetes and its complications remains unexplored. Cumulative evidence has linked mitochondrial modification to the pathogenesis of diabetes and its complications and they are also observed in various tissues affected by diabetes. Proteomics is an attractive tool for the study of diabetes since it allows researchers to compare normal and diabetic samples by identifying and quantifying the differentially expressed proteins in tissues, cells or organelles. Great progress has already been made in mitochondrial proteomics to elucidate the role of mitochondria in the pathogenesis of diabetes and its complications. Further studies on the changes of mitochondrial protein specifically post-translational modifications during the diabetic state using proteomic tools, would provide more information to better understand diabetes.     

Islet-like cell clusters: viability, cell types, and subretinal transplantation in pancreatectomized cats

We investigated a method for isolating sufficient feline islets of Langerhans to restore normoglycaemia following transplantation into the subretinal space of pancreatectomized cats. Collagenase digestate of feline pancreas was maintained in serum-free tissue culture medium for 1-9 days. Viability of islet-like cell clusters (ICC) was assessed with ethidium bromide and fluorescein diacetate staining; cell types were identified immunohistochemically. After nine days, the ICC were transplanted. We estimated viable ICC in tissue culture at nine days as 3800 +/- 2000 (mean +/- SD) per pancreas. While numbers of beta cells decreased over time in culture, ductal cells increased. Bromodeoxyuridine labelling showed no proliferation of beta cells but extensive proliferation of ductal cells. Subretinal transplants of cultured ICC in the diabetic cats maintained normoglycaemia for up to 12 days, while they provoked massive lymphocyte infiltration indicating rejection. Islet transplantation into the feline subretinal space temporarily restored normoglycaemia. Our current method of culture achieved sufficient reduction of acinar cells but an insufficient yield of insulin-producing cells.     

STZ诱导恒河猴糖尿病动物模型的建立

目的复制稳定的链脲佐菌素诱导糖尿病恒河猴动物模型。方法健康恒河猴5只,小剂量（30mg/kg）多次静脉注射链脲佐菌素,分别在注射后2、3个月进行葡萄糖耐量实验并连续观察血糖、胰岛素、C肽的变化。连续观察12个月。结果随着时间推移,动物出现典型的糖尿病症状。3只动物的血糖静脉注射1次后持续10周稳定,另外2只分别进行了第2、3次注射。动物血糖在12个月内平稳上升、胰岛素、C肽分泌持续下降。2个月时葡萄糖耐量减低明显（P〈0.01）。结论小剂量多次注射STZ后恒河猴可出现持续、稳定的糖尿病表现,可作为相关研究的动物模型。     

Myeloid lineage cell-restricted insulin resistance protects apolipoproteinE-deficient mice against atherosclerosis

Inflammatory processes play an important role in the pathogenesis of vascular diseases, and insulin-resistant diabetes mellitus type 2 represents an important risk factor for the development of atherosclerosis. To directly address the role of insulin resistance in myeloid lineage cells in the development of atherosclerosis, we have created mice with myeloid lineage-specific inactivation of the insulin receptor gene. On an ApoE-deficient background, MphIRKO mice developed smaller atherosclerotic lesions. There was a dramatic decrease in LPS-stimulated IL-6 and IL-1beta expression in the presence of macrophage autonomous insulin resistance. Consistently, while insulin-resistant IRS-2-deficient mice on an ApoE-deficient background display aggravated atherosclerosis, fetal liver cell transplantation of IRS-2(-/-) ApoE(-/-) cells ameliorated atherosclerosis in Apo-E-deficient mice. Thus, systemic versus myeloid cell-restricted insulin resistance has opposing effects on the development of atherosclerosis, providing direct evidence that myeloid lineage autonomous insulin signaling provides proinflammatory signals predisposing to the development of atherosclerosis.     

The potential usefulness of taurine on diabetes mellitus and its complications

Taurine (2-aminoethanesulfonic acid) is a free amino acid found ubiquitously in millimolar concentrations in all mammalian tissues. Taurine exerts a variety of biological actions, including antioxidation, modulation of ion movement, osmoregulation, modulation of neurotransmitters, and conjugation of bile acids, which may maintain physiological homeostasis. Recently, data is accumulating that show the effectiveness of taurine against diabetes mellitus, insulin resistance and its complications, including retinopathy, nephropathy, neuropathy, atherosclerosis and cardiomyopathy, independent of hypoglycemic effect in several animal models. The useful effects appear due to the multiple actions of taurine on cellular functions. This review summarizes the beneficial effects of taurine supplementation on diabetes mellitus and the molecular mechanisms underlying its effectiveness.     

Insulin resistance,lipotoxicity and endothelial dysfunction

The number of people with the insulin-resistant conditions of type 2 diabetes mellitus (T2DM) and obesity has reached epidemic proportions worldwide. Eighty percent of people with T2DM will die from the complications of cardiovascular atherosclerosis. Insulin resistance is characterised by endothelial dysfunction, which is a pivotal step in the initiation/progression of atherosclerosis. A hallmark of endothelial dysfunction is an unfavourable imbalance between the bioavailability of the antiatherosclerotic signalling molecule nitric oxide (NO) and proatherosclerotic reactive oxygen species. In this review we discuss the mechanisms linking insulin resistance to endothelial dysfunction, with a particular emphasis on a potential role for a toxic effect of free fatty acids on endothelial cell homeostasis.     

Experimental diabetes in cats induced by partial pancreatectomy alone or combined with local injection of alloxan

Experimental diabetes was produced in cats by partial pancreatectomy using a short and technically simple surgical procedure. Electrocautery was used to cauterize pancreatic blood vessels and seal free edges of remaining pancreatic tissue to prevent secretion of pancreatic enzymes into the peritoneal cavity. In a second group of animals, partial pancreatectomy was followed by local injection of alloxan into an arterial branch of the cranio-mesenteric artery. The combined procedure resulted in diabetes mellitus in 100% (8 of 8) animals as compared to only 70% (14 of 20) in those subjected to partial pancreatectomy alone. In addition, the alloxan-pancreatectomized cats had a reduced latency period prior to onset of chronic hyperglycemia (4.8 days compared to 19.3 days postoperatively in pancreatectomized cats). The diabetic cats were maintained in poor metabolic control (blood glucose approximately 300 mg/dl) by daily injections of low doses of long-acting insulin. Pancreatic enzyme supplementation was given by mouth. Weight changes and blood glucose levels were monitored carefully to maintain the health of the animals while keeping them in poor metabolic control.     

2型糖尿病合并下肢动脉粥样硬化的危险因素

下肢动脉粥样硬化是2型糖尿病(T2DM)患者最常见的大血管并发症之一。作为T2DM患者严重的慢并发症之一,下肢动脉粥样硬化可引起糖尿病足的发生,严重情况下可导致足坏疽。因此,阐明T2DM合并下肢动脉粥样硬化的危险因素,早期预防和治疗糖尿病合并下肢动脉粥样硬化症,不仅提高了患者的生活质量,而且减轻了家庭和社会的经济负担,具有较大的现实意义。影响T2DM患者下肢动脉粥样硬化的因素错综复杂,分为不可调控的和可调控的因素,不可调控的危险因素包括年龄、种族、遗传等,可调控的危险因素包括吸烟、高血糖、高血脂、高血压,以及近年提出的肥胖、胰岛素抵抗、高纤维蛋白血症、炎症等。本文就T2DM合并下肢动脉粥样硬化的危险因素做一综述。     

Comparison of therapeutic regimens in the amelioration of alterations in rat gastrointestinal mucosal DNA, RNA and protein induced by streptozotocin diabetes mellitus

Type 1 diabetes mellitus is characterized by hyperglycemia, insulinopenia, and secondary neural, renal and vascular complications. Clinical manifestations in the gastrointestinal tract range from initial mild complications to more severe complications as the disease progresses, but as of yet, are poorly understood. The current study has two main foci 1) to monitor the alterations in gastrointestinal DNA, RNA and protein content induced by streptozotocin diabetes and 2) to use these parameters to monitor the efficacy of intensive insulin treatment versus pancreatic islet transplantation in the amelioration of the diabetes induced alterations. Female Wistar Furth rats were rendered diabetic by streptozotocin injection and measured for alterations in gastrointestinal DNA, RNA and protein content. Similarly, animals which had streptozotocin-induced diabetes were also treated by intensive insulin therapy or pancreatic islet transplant and monitored for alterations in gastrointestinal DNA, RNA and protein content. In general, diabetes induced increases in stomach, duodenal, jejunal and colonic macromolecular content. With few exceptions, treatment with either intensive insulin or pancreatic islet transplantation returned each variable measured back to control levels. In every case, pancreatic islet transplantation was comparable to intensive insulin therapy. In the short term the treatments are comparable, but long term analyses are needed to determine if the treatments offer any difference in their ability to prevent the long term complications related to diabetes mellitus.