Diabetes is a disease characterized by a relative or absolute lack of insulin, leading to hyperglycaemia. There are two main types of diabetes: type 1 diabetes and type 2 diabetes. Type 1 diabetes is due to an autoimmune destruction of the insulin-producing pancreatic beta cells, and type 2 diabetes is caused by insulin resistance coupled by a failure of the beta cell to compensate. Animal models for type 1 diabetes range from animals with spontaneously developing autoimmune diabetes to chemical ablation of the pancreatic beta cells. Type 2 diabetes is modelled in both obese and non-obese animal models with varying degrees of insulin resistance and beta cell failure. This review outlines some of the models currently used in diabetes research. In addition, the use of transgenic and knock-out mouse models is discussed. Ideally, more than one animal model should be used to represent the diversity seen in human diabetic patients.

LINKED ARTICLES

Animal Models

This paper is the latest in a series of publications on the use of animal models in pharmacology research. Readers might be interested in the previous papers.

Robinson V (2009). Less is more: reducing the reliance on animal models for nausea and vomiting research.

Holmes AM, Rudd JA, Tattersall FD, Aziz Q, Andrews PLR (2009). Opportunities for the replacement of animals in the study of nausea and vomiting.

Giacomotto J and Segalat L (2010). High-throughput screening and small animal models, where are we?

McGrath JC, Drummond GB, McLachlan EM, Kilkenny C, Wainwright CL (2010). Guidelines for reporting experiments involving animals: the ARRIVE guidelines.

Kilkenny C, Browne W, Cuthill IC, Emerson M, Altman DG (2010). The ARRIVE guidelines.

Emerson M (2010). Refinement, reduction and replacement approaches to in vivo cardiovascular research.

Berge O-G (2011). Predictive validity of behavioural animal models for chronic pain.

Vickers SP, Jackson HC and Cheetham SC (2011). The utility of animal models to evaluate novel anti-obesity agents.

Percie du Sert N, Holmes AM, Wallis R, Andrews PLR (2012). Predicting the emetic liability of novel chemical entities: a comparative study.

The complete series including future publications, as they occur, can be found at http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1476-5381/homepage/animal_models.htm.

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1476-5381.2012.01911.x

The use of animal models in diabetes research

The design of the present study of the kinetics of insulin in man combines experimental features which obviate two of the major problems in previous insulin studies. (a) The use of radioiodinated insulin as a tracer has been shown to be inappropriate since its metabolism differs markedly from that of the native hormone. Therefore porcine insulin was administered by procedures which raised insulin levels in arterial plasma into the upper physiologic range. Hypoglycemia was prevented by adjusting the rate of an intravenous infusion of glucose in order to control the blood glucose concentration (the glucose-clamp technique). (b) Estimation of a single biological half-time of insulin after pulse injection of the hormone has been shown to be inappropriate since plasma insulin disappearance curves are multiexponential. Therefore the SAAM 25 computer program was used in order to define the parameters of a three compartment insulin model.

The combined insulin mass of the three compartments (expressed as plasma equivalent volume) is equal to inulin space (15.7% body wt). Compartment 1 is apparently the plasma space (4.5%). The other two compartments are extra-vascular; compartment 2 is small (1.7%) and equilibrates rapidly with plasma, and compartment 3 is large (9.5%) and equilibrates slowly with plasma.

The SAAM 25 program can simulate the buildup and decay of insulin in compartments 2 and 3 which cannot be assayed directly. Insulin in compartment 3 was found to correlate remarkably with the time-course of the servo-controlled glucose infusion. Under conditions of a steady-state arterial glucose level, glucose infusion is a measure of glucose utilization. We conclude that compartment 3 insulin (rather than plasma insulin) is a more direct determinant of glucose utilization.

We suggest that the combined use of glucose-clamp and kinetic-modeling techniques should aid in the delineation of pathophysiologic states affecting glucose and insulin metabolism.

/pdf/a-model-of-the-kinetics-of-insulin-in-man-2ow0mvmy5b.pdf

A Model of the Kinetics of Insulin in Man

Concentrations of insulin, proinsulin, and C-peptide were measured in portal and peripheral venous blood in six nondiabetic, nonobese subjects. Portal vein samples were obtained by umbilical vein catheterization. Three subjects were studied with intravenous infusion of 25 g glucose, and three with 30 g arginine. Insulin and proinsulin were determined in the insulin immunoassay after separation by gel filtration, and C-peptide was measured by direct immunoassay. With both glucose and arginine stimulation, portal vein levels of all three peptides peaked at 90-120 s after the onset of the stimulus. Relative increases in insulin concentration were greater than those of proinsulin or C-peptide. In peripheral venous blood, maximal levels of the three peptides were observed later (2-5 min), and the increase in insulin relative toproinsulin and C-peptide was not as great. At the time of peak secretion, portal vein insulin and C-peptide approached equimolar concentrations, and proinsulin, as measured against an insulin standard, comprised approximately 2.5% of the total immunoreactive insulin. After stimulation by glucose or arginine, portal insulin, proinsulin and C-peptide levels were not correlated with the concentrations measured in simultaneously drawn peripheral samples. At all sampling times, however, significant correlation was found between insulin and C-peptide in both peripheral and portal blood. The results indicate that under the conditions studied, insulin and C-peptide are secreted in equimolar concentrations in man, and that proinsulin is secreted in the same proportion to insulin as found in the pancreas. Consideration of the relative secretory and metabolic rates of the three beta cell peptides explains their peripheral concentrations. The data further support the use of plasma C-peptide as an indicator of beta cell secretory function.

/pdf/proinsulin-insulin-and-c-peptide-concentrations-in-human-421yodgxgo.pdf

Proinsulin, insulin, and C-peptide concentrations in human portal and peripheral blood.

The aim of this prospective phase II study was to evaluate the tumor response of neuroendocrine tumors to high-dose targeted irradiation with 7.4 GBq/m2 of the radiolabeled somatostatin analog 90Y-1,4,7,10-tetra-azacyclododecan-4,7,10-tricarboxy-methyl-1-yl-acetyl-d-Phe-Tyr3-octreotide (DOTATOC). In addition, we investigated the clinical benefit of 90Y-DOTATOC regarding the malignant carcinoid syndrome and tumor-associated pain. Methods: Thirty-nine patients (mean age, 55 y) with progressive neuroendocrine gastroenteropancreatic and bronchial tumors were included. The treatment consisted of 4 equal intravenous injections of a total of 7.4 GBq/m290Y-DOTATOC, administered at intervals of 6 wk. After each treatment cycle, a standardized clinical benefit assessment using the National Cancer Institute grading criteria (NCI-CTC) was performed. Results: The objective response rate according to World Health Organization (WHO) criteria was 23%. For endocrine pancreatic tumors (13 patients), the objective response rate was 38%. Complete remissions were found in 5% (2/39), partial remissions in 18% (7/39), stable disease in 69% (27/39), and progressive disease in 8% (3/39). A significant reduction of clinical symptoms could be found in 83% of patients with diarrhea, in 46% of patients with flush, in 63% of patients with wheezing, and in 75% of patients with pellagra. The overall clinical benefit was 63%. All responses (both clinical benefit and WHO response) were ongoing for the duration of follow-up (median, 6 mo; range, 2–12 mo). Side effects were grade 3 or 4 (NCI-CTC) lymphocytopenia in 23%, grade 3 anemia in 3%, and grade 2 renal insufficiency in 3%. Conclusion: High-dose targeted radiotherapy with 7.4 GBq/m290Y-DOTATOC is a well-tolerated treatment for neuroendocrine tumors, with remarkable clinical benefit and objective response.

https://jnm.snmjournals.org/content/jnumed/43/5/610.full.pdf

Tumor response and clinical benefit in neuroendocrine tumors after 7.4 GBq (90)Y-DOTATOC.

Spontaneous hyperglycemia, hyperinsulinemia and obesity are common features for at least one period of the lifetime in some strains of mice. Both genetic and environmental factors are involved in the pathogenesis of the diabetes-like syndrome, making these strains excellent models for studies in both obesity and diabetes-like states. The metabolic peculiarities can be due to a dominant gene, as for the yellow obese, or a single recessive gene, as in the obese and the diabetes mouse; or they can be of polygenic origin, as for the KK and the NZO mouse. However, the severity of the metabolic disorder is due to the interaction of the mutant genes iwth modifiers in the bat genes themselves. Studies on the pathophysiology and biochemistry of these animals have revealed interstrain differences, different patterns of development of the metabolic disorder, and different degrees of severity of the diabetes-like syndrome. Although the primary causes of the syndrome remain unclear in some strains, an involvement of hypothalamic feeding centers has been implicated.

Laboratory animals exhibiting obesity and diabetes syndromes

Since hypometabolism and hypercholesterolemia are common to both hypothyroidism and nephrosis, it was postulated that thyroid activity was subnormal in nephrotic patients. However, Epstein found that remarkably large doses of thyroid hormone could be given to nephrotic patients without inducing hypermetabolism (1). Such tolerance to thyroid medication is unusual among patients with true hypothyroidism. It has therefore been suggested that the hypometabolism and increased serum cholesterol in nephrosis are due not to decreased thyroid function but to other causes, as yet unknown (2). The recent demonstration that the concentration of protein-bound iodine in the serum is reduced in nephrosis (3) has once more raised the question of whether thyroid function is impaired in this syndrome. The present study is an attempt to answer this question.

/pdf/thyroid-function-in-nephrosis-2iv0fivb8g.pdf

Thyroid function in nephrosis

The glucagonoma syndrome associated with alpha-2 cell tumors of the islets of Langerhans has emerged as a specific member of the apudoma tumor family. The first case was described in 1942, and the syndrome was well documented in 1966. There are now (including the 3 case reports presented herein) forty-seven cases in the literature, thirty appearing during the past three years. Major features of the syndrome are: (1) diabetes mellitus; (2) characteristic skin lesions (necrolytic migratory erythema); (3) glossitis; (4) normochromic, normocytic anemia; and (5) weight loss with associated elevation of the plasma level of immunoreactive glucagon. Of the patients, 59.6 per cent are female (28 of 47) aged twenty to seventy-three years. The tumors grow slowly, suggesting that early diagnosis and surgical excision can be curative; however 59.1 per cent (27 of 47) of the reported patients had extensive disease and/or hepatic metastases at the time of diagnosis. The primary tumor was located in the body or tail (30 patients) or head and neck (4), with the remaining being “extensive” (12) or not found (1). All patients on whom determinations were made (37) had elevated glucagon levels in the plasma or in the tumor, with plasma glucagon levels between 0.3 and 96 ng/ml (normal The three patients here reported are representative, one having a localized resectable tumor in the tail of the pancreas with complete reversal of symptoms and return of plasma glucagon to normal levels after operation, one having extensive metastases in the remote postresection period, and the third having an extensive nonresectable tumor. Increased awareness of the syndrome along with improved technics of diagnosis and localization have already produced a promising trend toward earlier diagnosis and treatment of this surgically curable type of diabetes.

The glucagonoma syndrome: Surgically curable diabetes

Because islet-cell tumors of the pancreas produce proinsulin-like material in vitro, the plasma of 11 patients with functioning insulinomas was studied to determine the immunoreactive insulin proportion contributed by circulating proinsulin-like material. The plasma of nine patients with insulinomas showed on gel filtration an increased proinsulin-like material (28 to 89 per cent) as compared to subjects of normal weight, those who were obese, and those with functional hypoglycemia (less than 20 per cent). Polyacrylamide-gel electrophoresis of serum showed material compatible with proinsulin, insulin and an intermediate component. Considering the data so far reported, any patient with hypoglycemia who shows an elevated percentage of proinsulin-like material should be suspected of having an insulinoma. In one patient, surgical removal of an islet-cell adenoma resulted in a fall of serum proinsulin-like material from 65 to 0 per cent. Determination of plasma proinsulin-like material may provide dia...

https://www.nejm.org/doi/pdf/10.1056/NEJM197105062841803?listPDF=true

Circulating proinsulin-like material in patients with functioning insulinomas.

Isolated rat islets of Langerhans were incubated for 60, 120, and 180 min and the incorporation of leucine-3H into proinsulin and insulin moieties was followed. Synthesis and release of these hormones could be followed by separate extractions of islets and incubation media.

Release of newly synthesized proinsulin and insulin occurred under the following conditions: (a) incubation for greater than 60 min; (b) glucose concentrations above 5.3 mmoles/liter; (c) incubation with 5 mM dibutyryl cyclic AMP or theophylline in 5.3 mM glucose (potentiated by 16 mM glucose); and (d) incubation with 5 mM tolbutamide and 16 mM glucose.

Synthesis of proinsulin and insulin was enhanced by time of incubation, high glucose concentrations, by dibutyryl cyclic AMP or theophylline, and by tolbutamide only at 16 mM glucose. Synthesis was totally inhibited by tolbutamide at 5.3 mM glucose.

https://dm5migu4zj3pb.cloudfront.net/manuscripts/106000/106357/JCI70106357.pdf

Synthesis and release of proinsulin and insulin by isolated rat islets of Langerhans

Immunoreactive glucagon (IRG) fractions from plasma of 8 normal subjects and 4 patients with glucagon secreting tumors were studied by gel filtration techniques on Bio Gel P-30 and Sephadex G-50 columns. The pancreatic glucagon specific anti serum (30K) of Unger was utilized to measure IRG. Columns were calibrated with labelled albumin, proinsulin, insulin and glucagon. Four peaks were defined in normal and tumor bearing patients: peak I (>20000 mol. wt.), peak II (primarily 9000 mol. wt.), peak III pancreatic glucagon (3500 mol. wt.) and peak IV small glucagon (<3500 mol. wt.). Glucagonoma patients differed from our normal and reported normal subjects in that peak II contained most of the circulating IRG. The percent of IRG associated with peak II was 9.5–31.5% in normals and 39.1–61.2% in glucagonomas. Glucagon-like biological activity in an isolated hepatocyte system was demonstrated for all peaks. However, relative to immunoreactivity, peak II showed reduced activity (25–33%). Immunoassay of dilutions of all peaks revealed the probability of immuno determinants identical with porcine pancreatic glucagon. The presence of heterogeneous IRG peaks with biological glucagon-like activity suggest that the larger molecules may be prohormones. Further, it is possible that specific elevation of peak II may be a diagnostic feature of glucagonomas.

/pdf/plasma-immunoreactive-glucagon-fractions-in-four-cases-of-4ugnhrld88.pdf

L. Recant

Papers

Thyroid function in nephrosis

The glucagonoma syndrome: Surgically curable diabetes

Circulating proinsulin-like material in patients with functioning insulinomas.

Synthesis and release of proinsulin and insulin by isolated rat islets of Langerhans

Plasma immunoreactive glucagon fractions in four cases of glucagonoma: Increased “Large glucagon — immunoreactivity”