BioBreeding Rats Research Articles

Secoisolariciresinol Diglucoside (SDG) from flaxseed in the prevention and treatment of diabetes mellitus

This review focuses on the role of reactive oxygen species (ROS) on the development of type 1 and type 2 diabetes and its treatment with secoisolariciresinol diglucoside (SDG) isolated from flaxseed which is an antioxidant and suppresses phosphoenolpyruvate carboxykinase (PEPCK) gene expression, a ratelimiting enzyme in the gluconeogenesis in the liver. Role of ROS in the development of type 1 diabetes [diabetic prone Bio Breeding (BBdp) rats and streptozotocin-induced diabetic (STZ) rats and type 2 diabetes (Zucker diabetic fatty female rats, ZDF rats)] has been discussed. Oxidative stress has been assessed by measuring serum and pancreatic malondialdehyde (MDA), pancreatic chemiluminescence (pancreatic-CL) and oxygen radical producing activity of white blood cells (WBCCL). Diagnosis of diabetes was made by hyperglycaemia and glucosuria. Incidence of diabetes was 100 % in SDZ rats, 72 % in BBdp rats and 100 % in ZDF rats by the age of 72 days. Development of diabetes was associated with increases in the serum and pancreatic MDA, WBC-CL and pancreatic-CL and glycated haemoglobin (HbA1 c). SDG prevented the development of diabetes by 75 % in STZ rats, by 71 % in BBdp rats and by 20 % at 72 days of age in ZDF rats. However, 80 % of the rats which did not develop diabetes by 72 days of age, developed diabetes later on, suggesting that SDG treatment delays the development of diabetes in ZDF rats. Treatment with SDG decreased the levels of serum and pancreatic MDA, WBC-CL and pancreatic-CL. In conclusion, development of type 1 and type 2 diabetes is mediated through oxidative stress and the prevention or delay in the development of diabetes with SDG could be due to its antioxidant activity and its suppressant effect on PEPCK enzyme. Lignan complex which contains 34 % to 38 % of SDG is effective in lowering serum glucose and HbA1 c in type 2 diabetes in humans.

Lactiplantibacillus plantarum 299v supplementation modulates β-cell ER stress and antioxidative defense pathways and prevents type 1 diabetes in gluten-free BioBreeding rats

ABSTRACT The increasing incidence of Type 1 diabetes has coincided with the emergence of the low-fiber, high-gluten Western diet and other environmental factors linked to dysbiosis. Since Lactiplantibacillus plantarum 299 v (Lp299v) supplementation improves gut barrier function and reduces systemic inflammation, we studied its effects in spontaneously diabetic DRlyp/lyp rats provided a normal cereal diet (ND) or a gluten-free hydrolyzed casein diet (HCD). All rats provided ND developed diabetes (62.5±7.7 days); combining ND with Lp299v did not improve survival. Diabetes was delayed by HCD (72.2±9.4 days, p = .01) and further delayed by HCD+Lp299v (84.9±14.3 days, p < .001). HCD+Lp299v pups exhibited increased plasma propionate and butyrate levels, which correlated with enriched fecal Bifidobacteriaceae and Clostridiales taxa. Islet transcriptomic and histologic analyses at 40-days of age revealed that rats fed HCD expressed an autophagy profile, while those provided HCD+Lp299v expressed ER-associated protein degradation (ERAD) and antioxidative defense pathways, including Nrf2. Exposing insulinoma cells to propionate and butyrate promoted the antioxidative defense response but did not recapitulate the HCD+Lp299v islet ERAD transcriptomic profile. Here, both diet and microbiota influenced diabetes susceptibility. Moreover, Lp299v supplement modulated antioxidative defense and ER stress responses in β-cells, potentially offering a new therapeutic direction to thwart diabetes progression and preserve insulin secretion.

Ramipril Reduces Acylcarnitines and Distinctly Increases Angiotensin-Converting Enzyme 2 Expression in Lungs of Rats.

The angiotensin-converting enzyme 2 (ACE2) receptor has been identified as the entry receptor for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that is abundantly expressed in many organs. With respect to the role of circulating ACE2 and its receptor expression in the pathogenesis of the SARS-CoV-2 infection, it is still debated whether diseases such as hypertension or pharmacotherapies, including ACE inhibitors and angiotensin receptor blockers that affect ACE2 receptor expression, may modulate the severity and outcome of the coronavirus disease 2019 (COVID-19). We therefore tested the hypothesis that treatment with the ACE inhibitor Ramipril affects organ-specific ACE2 receptor mRNA and protein expression as well as the serum metabolome in BioBreeding (BB) rats. Twelve male BioBreeding rats were randomly divided into a Ramipril (10 mg/kg body weight) treatment group or a control group (N = 12; n = 6 per group) over a period of seven days. Ramipril treatment resulted in the reduction of acylcarnitines (C3–C6) out of 64 metabolites. Among the different organs studied, only in the lungs did Ramipril treatment significantly increase both Ace2 mRNA and ACE2 receptor membrane protein levels. Increased ACE2 receptor lung expression after Ramipril treatment was not associated with differences in ACE2 serum concentrations between experimental groups. Our data provide experimental in vivo evidence that the ACE inhibitor Ramipril selectively increases pulmonary ACE2 receptor mRNA and protein levels and reduces acylcarnitines.

Probiotic Supplementation with Lactobacillus plantarum 299v Lowers Systemic Inflammation, Reduces Islet ER Stress and Prevents Type 1 Diabetes in BioBreeding Rats

Type 1 diabetes (T1D) is an autoimmune disease characterized by destruction of the pancreatic β-cells. T1D pathogenesis has a strong genetic basis. However, in recent decades, the prevalence of high-risk HLA haplotypes among new diagnoses has declined, the age of onset has decreased, and T1D incidence has increased. These changes are consistent with increased environmental pressure and coincide with introduction of the Western diet, widespread antibiotic use and reduced breast feeding. These factors are thought to drive intestinal dysbiosis, increased gut permeability and systemic inflammation. Notably, our studies of T1D families and the BioBreeding (BB) rat have identified a peripheral inflammatory state associated with diabetes susceptibility that is consistent with microbial antigen exposure and pattern recognition receptor ligation. Lactobacillus plantarum 299v (Lp299v), a probiotic strain, is reported to increase plasma and stool levels of anti-inflammatory short chain fatty acids (SCFA) and promote IL-10 signaling in colonic derived macrophages and T-cells. Here we investigated the effect of Lp299v supplement on T1D progression and inflammatory phenotypes in diabetes prone BB DRlyp/lyp rats. Rats were weaned at 21 days onto a normal cereal diet (ND) or a gluten-free hydrolyzed casein diet (HCD), with and without daily Lp299v supplementation. All DRlyp/lyp ND rats developed T1D by day 83 (mean time to onset of 62.8+/-7.9 days). DRlyp/lyp ND+Lp299v rats exhibited an insignificant delay in T1D onset (62.6+/-6.5 days), however 8% remained diabetes-free to day 130. Providing DRlyp/lyp rats HCD prevented T1D in 17% of rats (to age 130 days) and significantly delayed onset (mean time to onset 72.8+/-7.3 days, p<0.001). Providing DRlyp/lyp rats HCD+Lp299v prevented T1D in 25% of rats and more robustly delayed onset (mean time to onset 84.9 +/-14.3 days, p<0.001). While multiplex ELISA failed to detect significantly altered plasma cytokine/chemokine levels at 40 days of life, plasma induced transcription revealed the greatest normalization of systemic inflammation in the HCD+Lp299v group. Plasma SCFA levels (propionate and butyrate, p<0.01) were elevated in the HCD+Lp299v group compared to the ND group. Global gene expression analysis of pancreatic islets was conducted at 40 days, prior to insulitis. Endoplasmic reticulum (ER) stress has been implicated in the formation of islet neoantigens that may underlie the initial loss of immune tolerance in T1D. Under one or both diets, Lp299v favorably modulated islet expression levels of pathways and transcripts related to inflammation and innate immunity (Cxcl9, Cxcl10), oxidative stress (Gsta1, Gsta4, Gstp1, Gstk1), as well as ER stress and unfolded protein response (Cirbp, Edem1, Hspa1a, Atf4). These ongoing studies add to a growing understanding that inherited susceptibility can be modulated by diet and microbiota.

Extending the Enterovirus Lead: Could a Related Picornavirus be Responsible for Diabetes in Humans?

We found an association between the abundance of rodents in the wild and onset of type 1 diabetes (T1D) in humans. A picornavirus named Ljungan virus (LV) was subsequently isolated from wild bank voles. Both picornavirus-like particles detected by electron microscopy and LV antigen visualized by immunohistochemistry was seen in islets of Langerhans in diabetic wild bank voles. LV antigen has also been found in islets of Langerhans in a patient with recent onset of T1D and in the commonly used Bio Breeding (BB) T1D rat model. We discuss the possibility of T1D and type 2 diabetes (T2D) as parts of a single disease entity. Antiviral compounds directed against picornavirus have been found to be an effective treatment of diabetes in BB rats. We propose using the same currently available antiviral compounds in clinical trials in humans. Antiviral treatment would have the potential to be both proof of concept for involvement of a picornavirus in diabetes pathogenesis and also present a first-generation therapy.

Effectiveness of Antivirals in a Type 1 Diabetes Model and the Move Toward Human Trials.

A Picornavirus (Ljungan virus [LV]) originally found in bank voles has been associated with type 1 diabetes (T1D) in its wild rodent reservoir, but also associated with T1D in a laboratory rat model for the disease, the diabetes prone (DP) Bio Breeding (BB) rat. Successful treatment of diabetes in this rat model, using experimental antiviral compounds directed against picornavirus, has been reported. In the present study we show significant clinical response in DP-BB rats using antiviral compounds available for human use (Pleconaril, Efavirenz, and Ribavirin). Presence of LV picornavirus antigen has been detected in islets of Langerhans from both human and the T1D rat model with clear morphological similarity. Based on these data it would be of interest to test antiviral treatment in patients with newly diagnosed T1D. Successful outcome will offer both proof of concept regarding the role of virus involvement in the disease and possibly a first generation treatment interrupting a persistent infection and stopping β-cell destruction.

Highly blood perfused, highly metabolically active pancreatic islets may be more susceptible for immune attack.

Differences in pancreatic islet susceptibility during type 1 diabetes development may be explained by interislet variations. This study aimed to investigate if heterogeneities in vascular support and metabolic activity in rat and human islets may explain why some islets are attacked earlier than other islets. In rats, highly blood perfused islets were identified by injection of microspheres into the ascending aorta, whereas a combination of anterograde and retrograde injections of microspheres into pancreas was used to determine the islet vascular drainage system. Highly blood perfused islets had superior function and lower glucose threshold for insulin release when compared with other islets. These islets had a preferential direct venous drainage to the portal vein, whereas other islets mainly were incorporated into the exocrine capillary system. In BioBreeding rats, the hypothesis that islets with high islet blood perfusion was more prone to immune cell infiltration was investigated. Indeed, highly blood perfused islets were the first affected by the immune attack. In human subjects, differences in glucose threshold for insulin (C‐peptide) secretion was evaluated in individuals recently diagnosed for type 1 diabetes and compared to control subjects. A preferential loss of capacity for insulin release in response to low glucose concentrations was observed at debut of type 1 diabetes. Our study indicates that highly blood perfused islets with direct venous drainage and lower glucose threshold for insulin release are of great importance for normal glucose homeostasis. At the same time, these highly metabolically active islets were the primary target of the immune system.

Diurnal Rhythmicity of Autophagy Is Impaired in the Diabetic Retina.

Retinal homeostasis is under both diurnal and circadian regulation. We sought to investigate the diurnal expression of autophagy proteins in normal rodent retina and to determine if this is impaired in diabetic retinopathy. C57BL/6J mice and Bio-Breeding Zucker (BBZ) rats were maintained under a 12h/12h light/dark cycle and eyes, enucleated over a 24 h period. Eyes were also collected from diabetic mice with two or nine-months duration of type 1 diabetes (T1D) and Bio-Breeding Zucker diabetic rat (BBZDR/wor rats with 4-months duration of type 2 diabetes (T2D). Immunohistochemistry was performed for the autophagy proteins Atg7, Atg9, LC3 and Beclin1. These autophagy proteins (Atgs) were abundantly expressed in neural retina and endothelial cells in both mice and rats. A differential staining pattern was observed across the retinas which demonstrated a distinctive diurnal rhythmicity. All Atgs showed localization to retinal blood vessels with Atg7 being the most highly expressed. Analysis of the immunostaining demonstrated distinctive diurnal rhythmicity, of which Atg9 and LC3 shared a biphasic expression cycle with the highest level at 8:15 am and 8:15 pm. In contrast, Beclin1 revealed a 24-h cycle with the highest level observed at midnight. Atg7 was also on a 24-h cycle with peak expression at 8:15 am, coinciding with the first peak expression of Atg9 and LC3. In diabetic animals, there was a dramatic reduction in all four Atgs and the distinctive diurnal rhythmicity of these autophagy proteins was significantly impaired and phase shifted in both T1D and T2D animals. Restoration of diurnal rhythmicity and facilitation of autophagy protein expression may provide new treatment strategies for diabetic retinopathy.

Diol-ginsenosides from Korean Red Ginseng delay the development of type 1 diabetes in diabetes-prone biobreeding rats

BackgroundThe effects of diol-ginsenoside fraction (Diol-GF) and triol-ginsenoside fraction (Triol-GF) from Korean Red Ginseng on the development of type 1 diabetes (T1D) were examined in diabetes-prone biobreeding (DP-BB) rats that spontaneously develop T1D through an autoimmune process. MethodsDP-BB female rats were treated with Diol-GF or Triol-GF daily from the age of 3–4 weeks up to 11–12 weeks (1 mg/g body weight). ResultsDiol-GF delayed the onset, and reduced the incidence, of T1D. Islets of Diol-GF–treated DP-BB rats showed significantly lower insulitis and preserved higher plasma and pancreatic insulin levels. Diol-GF failed to change the proportion of lymphocyte subsets such as T cells, natural killer cells, and macrophages in the spleen and blood. Diol-GF had no effect on the ability of DP-BB rat splenocytes to induce diabetes in recipients. Diol-GF and diol-ginsenoside Rb1 significantly decreased tumor necrosis factor α production, whereas diol-ginsenosides Rb1 and Rd decreased interleukin 1β production in RAW264.7 cells. Furthermore, mixed cytokine- and chemical-induced β-cell cytotoxicity was greatly inhibited by Diol-GF and diol-ginsenosides Rc and Rd in RIN5mF cells. However, nitric oxide production in RAW264.7 cells was unaffected by diol-ginsenosides. ConclusionDiol-GF, but not Triol-GF, significantly delayed the development of insulitis and T1D in DP-BB rats. The antidiabetogenic action of Diol-GF may result from the decrease in cytokine production and increase in β-cell resistance to cytokine/free radical–induced cytotoxicity.

Description of Paraclostridium bifermentans subsp. muricolitidis subsp. nov., emended description of Paraclostridium bifermentans (Sasi Jyothsna et al., 2016), and creation of Paraclostridium bifermentans subsp. bifermentans subsp. nov

Taxonomic studies of strain PAGU 1678T , an obligately anaerobic, gram-positive, spore-forming bacterium isolated from biobreeding rat feces, were performed. This strain has been demonstrated to have the ability to exacerbate pathosis in a mouse model of dextran sulfate sodium-induced ulcerative colitis. Phylogenetic analysis based on the 16S rRNA gene showed high homology with Paraclostridium bifermentans. To clarify the correct taxonomic position of strain PAGU 1678T , a comparative taxonomic study using P. bifermentans PAGU 2008T (═JCM 1386T ) and the closely related bacterial species P. benzoelyticum PAGU 2068T (═LMG 28745T ) was carried out. Despite the close similarity of 16S rRNA gene sequences, DNA-DNA hybridization between strain PAGU 1678T and P. bifermentans PAGU 2008T was 60.03% on average, average nucleotide identity was 96.17%, and it was shown to have different genomic sequences. Biochemically, strain PAGU 1678T could be differentiated from P. bifermentans PAGU 2008T by H2 S production. Furthermore, strain PAGU 1678T was characterized by the presence of two phospholipids with different polarity on polar lipid analysis. In addition, strain PAGU 1678T differed from P. bifermentans PAGU 2008T in findings on whole-cell protein analysis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. On the basis of these biochemical and genetic characteristics, a novel subspecies of P. bifermentans with the name Paraclostridium bifermentans subsp. muricolitidis subsp. nov. is here proposed, with PAGU 1678T (═CCUG 72489T ═NBRC 113386T ) as the type strain, which automatically creates P. bifermentans subsp. bifermentans subsp. nov. JCM 1386T (═ATCC 638T ═DSM 14991T ).

Changes in insulin, glucagon and ER stress precede immune activation in type 1 diabetes.

It is unknown whether there is a gene signature in pancreas which is associated with type 1 diabetes (T1D). We performed partial pancreatectomies on 30-day preinsulitic, diabetes-prone BioBreeding (BBdp) rats to prospectively identify factors involved in early prediabetes. Microarrays of the biopsies revealed downregulation of endoplasmic reticulum (ER) stress, metabolism and apoptosis. Based on these results, additional investigations compared gene expression in control (BBc) and BBdp rats age ~8, 30 and 60 days using RT-qPCR. Neonates had increased ER stress gene expression in pancreas. This was associated with decreased insulin, cleaved caspase-3 and Ins1 whereas Gcg and Pcsk2 were increased. The increase in ER stress was not sustained at 30 days and decreased by 60 days. In parallel, the liver gene profile showed a similar signature in neonates but with an early decrease of the unfolded protein response (UPR) at 30 days. This suggested that changes in the liver precede those in the pancreas. Tnf and Il1b expression was increased in BBdp pancreas in association with increased caspase-1, cleaved caspase-3 and decreased proinsulin area. Glucagon area was increased in both 30-day and 60-day BBdp rats. Increased colocalization of BIP and proinsulin was observed at 60 days in the pancreas, suggesting insulin-related ER dysfunction. We propose that dysregulated metabolism leads to ER stress in neonatal rats long before insulitis, creating a microenvironment in both pancreas and liver that promotes autoimmunity.

Hyperglycaemia correlates with skeletal muscle capillary regression and is associated with alterations in the murine double minute-2/forkhead box O1/thrombospondin-1 pathway in type 1 diabetic BioBreeding rats.

Type 1 diabetes can have deleterious effects on skeletal muscle and its microvasculature. Our laboratory has recently identified murine double minute-2 as a master regulator of muscle microvasculature by controlling expression levels of two key molecular actors of the angio-adaptive process: the pro-angiogenic vascular endothelial growth factor-A and the anti-angiogenic thrombospondin-1. Here, we show for the first time that in the soleus and plantaris muscles of the diabetes-prone BioBreeding rats, a rodent model of autoimmune type 1 diabetes, murine double minute-2 protein levels are significantly decreased, coinciding with elevated protein levels of thrombospondin-1 and its transcription factor forkhead box O1. Significant capillary regression was observed to similar extent in soleus and plantaris muscles of type 1 diabetic rats. Elevated blood glucose levels were correlated with the loss of capillaries, the reduction in murine double minute-2 expression and with the elevations in thrombospondin-1. Vascular endothelial growth factor-A protein levels were unaltered or even increased in diabetic animals, yet type 1 diabetic animals had less vascular endothelial growth factor receptor-2 abundance. The vascular endothelial growth factor-A/thrombospondin-1 ratio, a good indicator of skeletal muscle angio-adaptive environment, was decreased in type 1 diabetic muscle. Our results suggest that the murine double minute-2-forkhead box O1-thrombospondin-1 pathway plays an important role in angio-regulation of the skeletal muscle in the pathophysiological context of type 1 diabetes.

Modulation of the diet and gastrointestinal microbiota normalizes systemic inflammation and β-cell chemokine expression associated with autoimmune diabetes susceptibility.

Environmental changes associated with modern lifestyles may underlie the rising incidence of Type 1 diabetes (T1D). Our previous studies of T1D families and the BioBreeding (BB) rat model have identified a peripheral inflammatory state that is associated with diabetes susceptibility, consistent with pattern recognition receptor ligation, but is independent of disease progression. Here, compared to control strains, islets of spontaneously diabetic BB DRlyp/lyp and diabetes inducible BB DR+/+ weanlings provided a standard cereal diet expressed a robust proinflammatory transcriptional program consistent with microbial antigen exposure that included numerous cytokines/chemokines. The dependence of this phenotype on diet and gastrointestinal microbiota was investigated by transitioning DR+/+ weanlings to a gluten-free hydrolyzed casein diet (HCD) or treating them with antibiotics to alter/reduce pattern recognition receptor ligand exposure. Bacterial 16S rRNA gene sequencing revealed that these treatments altered the ileal and cecal microbiota, increasing the Firmicutes:Bacteriodetes ratio and the relative abundances of lactobacilli and butyrate producing taxa. While these conditions did not normalize the inherent hyper-responsiveness of DR+/+ rat leukocytes to ex vivo TLR stimulation, they normalized plasma cytokine levels, plasma TLR4 activity levels, the proinflammatory islet transcriptome, and β-cell chemokine expression. In lymphopenic DRlyp/lyp rats, HCD reduced T1D incidence, and the introduction of gluten to this diet induced islet chemokine expression and abrogated protection from diabetes. Overall, these studies link BB rat islet-level immunocyte recruiting potential, as measured by β-cell chemokine expression, to a genetically controlled immune hyper-responsiveness and innate inflammatory state that can be modulated by diet and the intestinal microbiota.

Ocular findings in Zucker Diabetic Fatty rats emphasize the key role of neuroglia degeneration in diabetic retinopathy pathophysiology.

Ocular findings in Zucker Diabetic Fatty rats emphasize the key role of neuroglia degeneration in diabetic retinopathy pathophysiology.

Housing influences tissue cytokine levels and the fecal bacterial community structure in rats

Immune measures and the fecal bacterial community were examined in female Biobreeding rats housed in wire bottom cages (wire) or in solid bottom cages containing hardwood chips (bedding). Housing did not affect food intake, weight gain, fecal output or fibre content, serum liver enzymes, or spleen and mesenteric lymph node immune cell populations. Bedding-housed rat feces were enriched in phylotypes aligning within the phylum Firmicutes (families Lactobacillaceae and Erysipelotrichaceae) and had a 2-fold lower content of phylotypes aligning within the phylum Bacteroidetes. Feces from bedding-housed rats also contained significantly more acetic acid and less propionic, isobutyric, valeric and isovaleric acids than those housed on wire. Bedding-housed rats had significantly higher splenic concentrations of interleukin-4 (P < 0.001). These results demonstrate that bedding can indirectly influence systemic and mucosal immune measures, potentially adding additional complexities and confounding results to nutrition studies investigating the health effects of dietary fibres.

Development of the Nonobese Diabetic Mouse and Contribution of Animal Models for Understanding Type 1 Diabetes.

In 1974, the discovery of a mouse and a rat that spontaneously developed hyperglycemia led to the development of 2 autoimmune diabetes models: nonobese diabetic (NOD) mouse and Bio-Breeding rat. These models have contributed to our understanding of autoimmune diabetes, provided tools to dissect autoimmune islet damage, and facilitated development of early detection, prevention, and treatment of type 1 diabetes. The genetic characterization, monoclonal antibodies, and congenic strains have made NOD mice especially useful.Although the establishment of the inbred NOD mouse strain was documented by Makino et al (Jikken Dobutsu. 1980;29:1–13), this review will focus on the not-as-well-known history leading to the discovery of a glycosuric female mouse by Yoshihiro Tochino. This discovery was spearheaded by years of effort by Japanese scientists from different disciplines and dedicated animal care personnel and by the support of the Shionogi Pharmaceutical Company, Osaka, Japan. The history is based on the early literature, mostly written in Japanese, and personal communications especially with Dr Tochino, who was involved in diabetes animal model development and who contributed to the release of NOD mice to the international scientific community. This article also reviews the scientific contributions made by the Bio-Breeding rat to autoimmune diabetes.

Longitudinal analysis of hepatic transcriptome and serum metabolome demonstrates altered lipid metabolism following the onset of hyperglycemia in spontaneously diabetic biobreeding rats.

Type 1 diabetes is associated with abberations of fat metabolism before and after the clinical onset of disease. It has been hypothesized that the absence of the effect of insulin in the liver contributes to reduced hepatic fat synthesis. We measured hepatic gene expression and serum metabolites before and after the onset of hyperglycemia in a BioBreeding rat model of type 1 diabetes. Functional pathway annotation identified that lipid metabolism was differentially expressed in hyperglycemic rats and that these pathways significantly overlapped with genes regulated by insulin. 17 serum metabolites significantly changed in concentration. All but 2 of the identified metabolites had previously been reported in type 1 diabetes, and carbohydrates were overall the most upregulated class of metabolites. We conclude that lack of insulin in the liver contributes to the changes in fat metabolism observed in type 1 diabetes. Further studies are needed to understand the clinical consequences of a lack of insulin in the liver in patients with type 1 diabetes.

Relationship between Immunological Abnormalities in Rat Models of Diabetes Mellitus and the Amplification Circuits for Diabetes.

A better understanding of pathogenic mechanisms is required in order to treat diseases. However, the mechanisms of diabetes mellitus and diabetic complications are extremely complex. Immune reactions are involved in the pathogenesis of diabetes and its complications, while diabetes influences immune reactions. Furthermore, both diabetes and immune reactions are influenced by genetic and environmental factors. To address these issues, animal models are useful tools. So far, various animal models of diabetes have been developed in rats, which have advantages over mice models in terms of the larger volume of tissue samples and the variety of type 2 diabetes models. In this review, we introduce rat models of diabetes and summarize the immune reactions in diabetic rat models. Finally, we speculate on the relationship between immune reactions and diabetic episodes. For example, diabetes-prone Biobreeding rats, type 1 diabetes model rats, exhibit increased autoreactive cellular and inflammatory immune reactions, while Goto-Kakizaki rats, type 2 diabetes model rats, exhibit increased Th2 reactions and attenuation of phagocytic activity. Investigation of immunological abnormalities in various diabetic rat models is useful for elucidating complicated mechanisms in the pathophysiology of diabetes. Studying immunological alterations, such as predominance of Th1/17 or Th2 cells, humoral immunity, and innate immune reactions, may improve understanding the structure of amplification circuits for diabetes in future studies.

Diabetes Prevention Through Antiviral Treatment in Biobreeding Rats.

A picornavirus (Ljungan virus) has been associated with diabetes in its wild rodent reservoir and in diabetes-prone biobreeding (DP-BB) rats. We attempted to alter the development of diabetes in DP-BB rats using two anti-picornavirus compounds (pleconaril and APO-N039), singly or in combination. Antiviral therapy was initiated 2 weeks before expected onset of diabetes. Pleconaril or APO-N039 alone did not affect the debut of diabetes. However, animals receiving a combination of both compounds were protected for at least the entire period of treatment (4 weeks after expected time of diabetes onset). Immunohistochemistry demonstrated that the presence and distribution of virus antigen in the pancreatic islets coincided with the clinical status of the animal. Data indicate that a treatable picornavirus can be involved in the cellular assault resulting in diabetes and in these cases the disease mechanism appears to involve a virus present in the pancreatic beta cell mass itself.

The Immune Pathogenesis of Type 1 Diabetes: Not Only Thinking Outside the Cell but Also Outside the Islet and Out of the Box.

Around 1960, observations of lymphocytic insulitis and the presence of islet cell autoantibodies in patients with type 1 diabetes led to the concept of type 1 diabetes being an organ-specific autoimmune disease. Much work has since been done to unravel the mechanisms behind the aberrant self-directed immune response and to predict disease progression, as it appeared that the autoimmune reaction preceded clinical diabetes, often for many years. Research focused on the identification of the primary autoantigen(s) to which the antibodies were directed. Important targets, such as insulin, GAD65, and IA-2, were discovered. However, research into the pathogenic mechanisms was hampered because the pancreas tissue of patients in the initial phases was rarely available. For that reason, animal models, such as the NOD mouse and the diabetes-prone BioBreeding (BBDP) rat, that developed autoimmune diabetes spontaneously were used to study prestages of the disease and to test therapeutic interventions. Studies in these animal models have mainly focused on autoreactive T-cell–mediated inflammatory destructive reactions to the islets of Langerhans, and balances between a multitude of regulatory and effector mechanisms became gradually apparent (1). However, translation of these animal data to the human disease was a controversial issue. Nevertheless, from all this work the view developed that the central pathogenic mechanism is an antigen-driven T lymphocyte–mediated inflammatory reaction of the islets, which specifically affects the β-cells disappearing in the reaction. This excessive reaction is allowed by defective tolerance mechanisms, and particular emphasis has been on the population of thymus-derived CD4+CD25+FOXP3+ T regulatory cells (excellently reviewed in ref. 1). However, many questions remained (1), among which were, “What are the initiating factors?” and “How are innate immune responses involved?” A consortium of research groups (Network for Pancreatic Organ Donors with Diabetes [nPOD]) embarked on collecting relevant tissues from organ donors …