Mouse models and the genetics of diabetes: is there evidence for genetic overlap between type 1 and type 2 diabetes?

Ganoderma lucidum Modulates Glucose, Lipid Peroxidation and Hepatic Metabolism in Streptozotocin-Induced Diabetic Pregnant Rats

The consumption of functional foods, such as mushrooms, apparently influences Gestational Diabetes Mellitus (GDM), and brings benefits to maternal-fetal health. Ganoderma lucidum contains a variety of bioactive compounds, such as polysaccharides, proteins and polyphenols that are able to control blood glucose and be used in anti-cancer therapy. We aimed to evaluate the effects of the consumption of Ganoderma lucidum (Gl) on maternal-fetal outcomes in streptozotocin-induced GDM (GDM-STZ). Pregnant rats were exposed to Gl (100 mg/kg/day) before and after the induction of GDM-STZ (single dose 40 mg/kg) on the eighth pregnancy day. Biochemical and oxidative stress parameters, reproductive performance and morphometry of fetuses were assessed. Gl reduced the glycemic response in the oral glucose tolerance test. Moreover, Gl decreased AST and ALT activities. GDM increased lipid peroxidation, which was reverted by Gl. Catalase and glutathione peroxidase activities were decreased in GDM and the administered Gl after the fetus implantation increased catalase activity. Measurements of the fetal head, thorax, craniocaudal and tail showed greater values in fetuses from rats exposed to Gl compared to GDM. Ganoderma lucidum has an encouraging nutritional and medicinal potential against GDM, since it modifies glucose metabolism, reduces lipid peroxidation, and has protective effects in fetuses born from GDM dams.

A Brief History of Use of Animals in Biomedical Research and Perspective on Non-Animal Alternatives

Animals have been closely observed by humans for at least 17 000 years to gain critical knowledge for human and later animal survival. Routine scientific observations of animals as human surrogates began in the late 19th century driven by increases in new compounds resulting from synthetic chemistry and requiring characterization for potential therapeutic utility and safety. Statistics collected by the United States Department of Agriculture's Animal and Plant Health Inspection Service and United Kingdom Home Office show that animal usage in biomedical research and teaching activities peaked after the mid-20th century and thereafter fell precipitously until the early 21st century, when annual increases (in the UK) were again observed, this time driven by expansion of genetically modified animal technologies. The statistics also show a dramatic transfer of research burden in the 20th and 21st centuries away from traditional larger and more publicly sensitive species (dogs, cats, non-human primates, etc) towards smaller, less publicly sensitive mice, rats, and fish. These data show that new technology can produce multi-faceted outcomes to reduce and/or to increase annual animal usage and to redistribute species burden in biomedical research. From these data, it is estimated that annual total vertebrate animal usage in biomedical research and teaching in the United States was 15 to 25 million per year during 2001-2018. Finally, whereas identification and incorporation of non-animal alternatives are products of, but not an integral component of, the animal research cycle, they replace further use of animals for specific research and product development purposes and create their own scientific research cycles, but are not necessarily a substitute for animals or humans for discovery, acquisition, and application of new (eg, previously unknown and/or unsuspected) knowledge critical to further advance human and veterinary medicine and global species survival.

The ubiquitin E3 ligase Nedd4-2 relieves mechanical allodynia through the ubiquitination of TRPA1 channel in db/db mice

Neural precursor cell-expressed developmentally downregulated protein 4-2 (Nedd4-2) is a member of the E3 ubiquitin ligase family that is highly expressed in sensory neurons and involved in pain modulation via downregulation of ion channels in excitable membranes. Ubiquitination involving Nedd4-2 is regulated by adenosine monophosphate-activated protein kinase (AMPK), which is impaired in the dorsal root ganglion (DRG) neurons of db/db mice. AMPK negatively regulates the expression of transient receptor potential ankyrin 1 (TRPA1), a recognised pain sensor expressed on the membrane of DRG neurons, consequently relieving mechanical allodynia in db/db mice. Herein, we studied the involvement of Nedd4-2 in painful diabetic neuropathy and observed that Nedd4-2 negatively regulated diabetic mechanical allodynia. Nedd4-2 was co-expressed with TRPA1 in mouse DRG neurons. Nedd4-2 was involved in TRPA1 ubiquitination, this ubiquitination, as well as Nedd4-2-TRPA1 interaction, was decreased in db/db mice. Moreover, Nedd4-2 levels were decreased in db/db mice, while an abnormal intracellular distribution was observed in short-term high glucose-cultured DRG neurons. AMPK activators not only restored Nedd4-2 distribution but also increased Nedd4-2 expression. These findings demonstrate that Nedd4-2 is a potent regulator of TRPA1 and that the abnormal expression of Nedd4-2 in DRG neurons contributes to diabetic neuropathic pain.

Blocking lysophosphatidic acid receptor 1 signaling inhibits diabetic nephropathy in db/db mice

Lysophosphatidic acid (LPA) is known to regulate various biological responses by binding to LPA receptors. The serum level of LPA is elevated in diabetes, but the involvement of LPA in the development of diabetes and its complications remains unknown. Therefore, we studied LPA signaling in diabetic nephropathy and the molecular mechanisms involved. The expression of autotaxin, an LPA synthesis enzyme, and LPA receptor 1 was significantly increased in both mesangial cells (SV40 MES13) maintained in high-glucose media and the kidney cortex of diabetic db/db mice. Increased urinary albumin excretion, increased glomerular tuft area and volume, and mesangial matrix expansion were observed in db/db mice and reduced by treatment with ki16425, a LPA receptor 1/3 antagonist. Transforming growth factor (TGF)β expression and Smad-2/3 phosphorylation were upregulated in SV40 MES13 cells by LPA stimulation or in the kidney cortex of db/db mice, and this was blocked by ki16425 treatment. LPA receptor 1 siRNA treatment inhibited LPA-induced TGFβ expression, whereas cells overexpressing LPA receptor 1 showed enhanced LPA-induced TGFβ expression. LPA treatment of SV40 MES13 cells increased phosphorylated glycogen synthase kinase (GSK)3β at Ser9 and induced translocation of sterol regulatory element-binding protein (SREBP)1 into the nucleus. Blocking GSK3β phosphorylation inhibited SREBP1 activation and consequently blocked LPA-induced TGFβ expression in SV40 MES13 cells. Phosphorylated GSK3β and nuclear SREBP1 accumulation were increased in the kidney cortex of db/db mice and ki16425 treatment blocked these pathways. Thus, LPA receptor 1 signaling increased TGFβ expression via GSK3β phosphorylation and SREBP1 activation, contributing to the development of diabetic nephropathy.

Twins and endocrinology

Twins are two independent babies delivered during the same pregnancy and are divided as monozygotic or dizygotic based on their origin. Dizygotic twins are similar to two siblings and have different genetic information. In contrary, monozygotic twins have a similar genetic identity and provide a unique opportunity to evaluate the contribution of genetic and environmental factors of the disease. The endocrine and metabolic disorders affect a large number of the population including the twins. Diabetes, obesity, and autoimmune thyroid disease are the most common endocrine disorders in general practice. It is essential to understand the genetic basis of endocrine disorders for therapy, prognostication and risk assessment for future generations. In this article, we review the endocrine disorders in relation to their occurrence in monozygotic twins to highlight the genetic and environmental contribution.

Antidiabetic effect and mode of action of cytopiloyne

Cytopiloyne was identified as a novel polyacetylenic compound. However, its antidiabetic properties are poorly understood. The aim of the present study was to investigate the anti-diabetic effect and mode of action of cytopiloyne on type 2 diabetes (T2D). We first evaluated the therapeutic effect of cytopiloyne on T2D in db/db mice. We found that one dose of cytopiloyne reduced postprandial glucose levels while increasing blood insulin levels. Accordingly, long-term treatment with cytopiloyne reduced postprandial blood glucose levels, increased blood insulin, improved glucose tolerance, suppressed the level of glycosylated hemoglobin A_1c (HbA_1c), and protected pancreatic islets in db/db mice. Next, we studied the anti-diabetic mechanism of action of cytopiloyne. We showed that cytopiloyne failed to decrease blood glucose in streptozocin- (STZ-)treated mice whose β cells were already destroyed. Additionally, cytopiloyne dose dependently increased insulin secretion and expression in β cells. The increase of insulin secretion/expression of cytopiloyne was regulated by protein kinase Cα (PKCα) and its activators, calcium, and diacylglycerol (DAG). Overall, our data suggest that cytopiloyne treats T2D via regulation of insulin production involving the calcium/DAG/PKCα cascade in β cells. These data thus identify the molecular mechanism of action of cytopiloyne and prove its therapeutic potential in T2D.

A systems biology approach identifies inflammatory abnormalities between mouse strains prior to development of metabolic disease

OBJECTIVE

Type 2 diabetes and obesity are increasingly affecting human populations around the world. Our goal was to identify early molecular signatures predicting genetic risk to these metabolic diseases using two strains of mice that differ greatly in disease susceptibility.

RESEARCH DESIGN AND METHODS

We integrated metabolic characterization, gene expression, protein-protein interaction networks, RT-PCR, and flow cytometry analyses of adipose, skeletal muscle, and liver tissue of diabetes-prone C57BL/6NTac (B6) mice and diabetes-resistant 129S6/SvEvTac (129) mice at 6 weeks and 6 months of age.

RESULTS

At 6 weeks of age, B6 mice were metabolically indistinguishable from 129 mice, however, adipose tissue showed a consistent gene expression signature that differentiated between the strains. In particular, immune system gene networks and inflammatory biomarkers were upregulated in adipose tissue of B6 mice, despite a low normal fat mass. This was accompanied by increased T-cell and macrophage infiltration. The expression of the same networks and biomarkers, particularly those related to T-cells, further increased in adipose tissue of B6 mice, but only minimally in 129 mice, in response to weight gain promoted by age or high-fat diet, further exacerbating the differences between strains.

CONCLUSIONS

Insulin resistance in mice with differential susceptibility to diabetes and metabolic syndrome is preceded by differences in the inflammatory response of adipose tissue. This phenomenon may serve as an early indicator of disease and contribute to disease susceptibility and progression.

Immune cell-derived c3 is required for autoimmune diabetes induced by multiple low doses of streptozotocin

OBJECTIVE

The complement system contributes to autoimmune injury, but its involvement in promoting the development of autoimmune diabetes is unknown. In this study, our goal was to ascertain the role of complement C3 in autoimmune diabetes.

RESEARCH DESIGN AND METHODS

Susceptibility to diabetes development after multiple low-dose streptozotocin treatment in wild-type (WT) and C3-deficient mice was analyzed. Bone marrow chimeras, luminex, and quantitative reverse transcription PCR assays were performed to evaluate the phenotypic and immunologic impact of C3 in the development of this diabetes model.

RESULTS

Coincident with the induced elevations in blood glucose levels, we documented alternative pathway complement component gene expression within the islets of the diabetic WT mice. When we repeated the experiments with C3-deficient mice, we observed complete resistance to disease, as assessed by the absence of histologic insulitis and the absence of T-cell reactivity to islet antigens. Studies of WT chimeras bearing C3-deficient bone marrow cells showed that bone marrow cell-derived C3, and not serum C3, is involved in the induction of diabetes in this model.

CONCLUSIONS

The data reveal a key role for immune cell-derived C3 in the pathogenesis of murine multiple low-dose streptozotocin-induced diabetes and support the concept that immune cell mediated diabetes is in part complement-dependent.

Early progression of the autonomic dysfunction observed in pediatric type 1 diabetes mellitus

To focus on early cardiac and vascular autonomic dysfunction that might complicate type 1 diabetes mellitus in children, we planned an observational, cross-sectional study in a population of 93 young patients, under insulin treatment, subdivided in 2 age subgroups (children: 11.5+/-0.4 years; adolescents: 19.3+/-0.2 years). Time and frequency domain analysis of RR interval and systolic arterial pressure variability provided quantitative indices of the sympatho-vagal balance regulating the heart period, of the gain of cardiac baroreflex, and of the sympathetic vasomotor control. Sixty-eight children of comparable age served as a reference group. At rest, systolic arterial pressure and the power of its low-frequency component were greater in patients than in controls, particularly in children (14.0+/-2.3 versus 3.1+/-0.3 mm Hg2). Moreover, baroreflex gain was significantly reduced in both subgroups of patients. Standing induced similar changes in the autonomic profiles of controls and patients. A repeat study after 1 year showed a progression in low-frequency oscillations of arterial pressure and a shift toward low frequency in RR variability. Data in young patients with type 1 diabetes mellitus show a significant increase in arterial pressure, a reduced gain of the baroreflex regulation of the heart period, and an increase of the low-frequency component of systolic arterial pressure variability, suggestive of simultaneous impairment of vagal cardiac control and increases of sympathetic vasomotor regulation. A repeat study after 1 year shows a further increase of sympathetic cardiac and vascular modulation, suggesting early progression of the autonomic dysfunction.

Animal models of catheter-induced intimal hyperplasia in type 1 and type 2 diabetes and the effects of pharmacologic intervention

Diabetes is a complex disorder characterized by impaired insulin formation, release or action (insulin resistance), elevated blood glucose, and multiple long-term complications. It is a common endocrine disorder of humans and is associated with abnormalities of carbohydrate and lipid metabolism. There are two forms of diabetes, classified as type 1 and type 2. In type 1 diabetes, hyperglycemia is due to an absolute lack of insulin, whereas in type 2 diabetes, hyperglycemia is due to a relative lack of insulin and insulin resistance. More than 90% of people with diabetes have type 2 with varied degrees of insulin resistance. Insulin resistance is often associated with impaired insulin secretion, and hyperglycemia is a common feature in both types of diabetes, but failure to make a distinction between the types of diabetes in different animal models has led to confusion in the literature. This is particularly true in relation to cardiovascular disease in the presence of diabetes and especially the response to vascular injury, in which there are major differences between the two types of diabetes. Animal models do not completely mimic the clinical disease seen in humans. Animal models are at best analogies of the pathologic process they are designed to represent. The focus of this review is an analysis of intimal hyperplasia following catheter-induced vascular injury, including factors that may complicate comparisons between different animal models or between in vitro and in vivo studies. We examine the variables, pitfalls, and caveats that follow from the manner of induction of the injury and the diabetic state of the animal. The efficacy of selected antidiabetic drugs in inhibiting the development of the hyperplastic response is also discussed.

Selecting the "right" mouse model for metabolic syndrome and type 2 diabetes research

This is not a "Methods" chapter in the traditional sense. Rather, it is an essay designed to help address one of the most frequently asked questions by investigators about to embark on a study requiring an animal model of diabetes - what is the "right" model for the reader's specific research application. Because genetic heterogeneity and the requirement for complex gene-environment interaction characterize the various mouse models of Type 2 diabetes as well as the human disease manifestations, the readers may come to share the author's conclusion that more than one model is required if the investigator is interested in knowing how broadly effective a given compound with putative therapeutic efficacy might be.

Association of small ubiquitin-like modifier 4 (SUMO4) variant, located in IDDM5 locus, with type 2 diabetes in the Japanese population

CONTEXT

Despite distinct differences in the pathogenesis, epidemiological data have indicated familial clustering of type 1 and type 2 diabetes, suggesting a common genetic basis between these two types of diabetes. Few shared susceptibility genes, however, have been reported to date.

OBJECTIVE

Small ubiquitin-like modifier 4 (SUMO4) has been identified as a candidate gene for the IDDM5 locus and suggested to have possible involvement in immune responses, such as autoimmunity and inflammation. Recent reports demonstrated that a polymorphism with an amino acid substitution (Met55Val) in SUMO4 was associated with type 1 diabetes in Asian populations, although no association was reproduced in subjects of Caucasian descent. The present study aimed to clarify the contribution of SUMO4 to type 2 diabetes susceptibility in the Japanese population.

SUBJECTS

The 753 subjects included 355 cases and 398 control subjects.

METHODS

The SUMO4 Met55Val (rs237025) and 001Msp (rs577001) polymorphisms were genotyped.

RESULTS

Strong linkage disequilibrium (D': 1.0 in each pair of single-nucleotide polymorphisms) across the MAP3K7IP2/SUMO4 region was shown in the Japanese population. The frequency of genotypes with the G allele of the SUMO4 Met55Val polymorphism was significantly higher in patients with type 2 diabetes [odds ratio, 1.46; 95% confidence interval (CI), 1.08-1.93; P = 0.01, chi(2) test]. The association was concentrated in patients without insulin therapy (odds ratio, 1.56; 95% CI, 1.13-2.15; P = 0.0072), but not in those with insulin (odds ratio, 1.24; 95% CI, 0.81-1.89; not significant).

CONCLUSIONS

These data, together with previous reports, suggest the contribution of the SUMO4 Met55Val polymorphism to both type 1 and type 2 diabetes susceptibility in the Japanese population.

"Type 1 on type 2" diabetes mellitus: autoimmune type 1 diabetes superimposed on established type 2 diabetes

OBJECTIVE

To investigate clinical features and pathophysiology of a rare form of new-onset type 1 diabetes mellitus that was superimposed on established type 2 diabetes.

PATIENTS AND METHODS

We retrospectively analyzed 126 consecutive type 2 diabetic patients, who were admitted to the hospital 2 or more times from July 2000 to December 2005 and had been repeatedly examined for islet-associated autoantibodies and insulin secretory capacity over a period of years.

RESULTS

We experienced 2 patients in whom autoantibodies including ICA, GADAb, and IA-2Ab were initially all negative, but in whom at least 1 of these antibodies later became positive, whose endogenous insulin secretion decreased, and who eventually reached an insulin-dependent stage. At the time of seroconversion of antibodies, the patients had 15 to 23 years' history of diabetes, and had microvascular complications specific to diabetes mellitus, and before seroconversion insulin secretory capacities were preserved. The patients had HLA types associated with susceptibility to Japanese type 1 diabetes mellitus.

CONCLUSIONS

Our findings suggest that autoimmune type 1 diabetes mellitus may be superimposed on well-established type 2 diabetes.