Takashi Natori

Spontaneous long-term hyperglycemic rat with diabetic complications : otsuka long-evans tokushima fatty (OLETF) strain

A spontaneously diabetic rat with polyuria, polydipsia, and mild obesity was discovered in 1984 in an outbred colony of Long-Evans rats, which had been purchased from Charles River Canada (St. Constant, Quebec, Canada) in 1982. A strain of rats developed from this rat by selective breeding has since been maintained at the Tokushima Research Institute (Otsuka Pharmaceutical, Tokushima, Japan) and named OLETF. The characteristic features of OLETF rats are 1) late onset of hyperglycemia (after 18 wk of age); 2) a chronic course of disease; 3) mild obesity; 4) inheritance by males; 5) hyperplastic foci of pancreatic islets; and 6) renal complication (nodular lesions). Histologically, the changes of pancreatic islets can be classified into three stages: 7) an early stage (6–20 wk of age) of cellular infiltration and degeneration; 2) a hyperplastic stage (20–40 wk of age); and 3) a final stage (at >40 wk of age). These clinical and pathological features of disease in OLETF rats resemble those of human NIDDM.

OLETF (Otsuka Long-Evans Tokushima Fatty) rat: a new NIDDM rat strain

The characteristic features of OLETF rats are: (1) late onset of hyperglycemia (after 18 weeks of age); (2) a chronic course of disease; (3) mild obesity; (4) clinical onset of diabetes mellitus (DM) mostly in males; (5) hereditary trait: (a) multiple recessive genes are involved in the induction of DM; (b) rat MHC, RT1 has no diabetogenic effect; (c) control strain, LETO appears to share some of diabetogenic genes with OLETF rats; (d) female OLETF rats also carry diabetogenic genes; and (e) one of the diabetogenic genes, designated as odb-1, is transmitted linked with the X-chromosome of OLETF rats, however testosterone is an important factor involved in developing diabetes; (6) the changes of pancreatic islets can be classified into three stages: (1) an early stage (at less than 9 weeks of age) mild lymphocyte infiltration; (2) a hyperplastic stage (10-40 weeks of age); hyperplastic change and fibrosis in or around islets; (3) a final stage (at more than 40 weeks of age) showing atrophy of islets; (7) diabetic nephropathy; (a) diffuse glomerulosclerosis; (b) nodular lesion (thickening of basement membranes, mesangial proliferation, fibrin cap). These clinical and pathologic features of disease in OLETF rats resemble those of human NIDDM.

New Inbred Strain of Long-Evans Tokushima Lean Rats With IDDM Without Lymphopenia

Spontaneously diabetic rats with remarkable polyuria, polyphagia, and polydipsia werediscovered in 1983 in an outbred colony of Long-Evans rats purchased from Charles River Canada in 1982. They have since been maintained at the Tokushima Research Institute (OtsukaPharmaceutical, Tokushima, Japan). A strain of rats (Long-Evans Tokushima Lean [LETL]) with diabetes was bred from these rats. The characteristic features of the disease in LETL rats are 1) sudden onset of polyuria, polyphagia, hyperglycemia, andweight loss; 2) no sex differences in the rate of onset or severity; 3) lymphocyte infiltration into islets followed by destruction of β-cells and disappearance of lymphocytes at the onset of diabetes; 4) no significant T lymphopenia; 5) lymphocyte infiltration into the salivary glands and lacrimal glands; and 6) at least two recessive genes involved in the pathogenesis of insulitis, one of which is closely linked with RT1u. These characteristics closely resemble those of human insulin-dependent diabetes mellitus (IDDM). Results suggest that the LETL rat is a useful animal model for analysisof genetic and immunologic factors relating to the pathogenesis of human IDDM.

A diabetogenic gene (ODB-1) assigned to the X-chromosome in OLETF rats

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat develops hyperglycemia, hyperinsulinemia and mild obesity, features that closely resemble those in human non-insulin-dependent diabetes mellitus (NIDDM). Here, we report a gene involved in the development of diabetes in OLETF rats. Segregation studies using OLETF and an unrelated strain, F344 showed that no diabetes was observed in F1 progeny and less than 12.5% of the F2 progeny developed diabetes, suggesting that multiple recessive genes are involved in the disease. Interestingly, diabetes was observed in approximately 40% of (OLETF female x LETO male) F1 male rats, whereas less than 4% of males were diabetic in the reverse F1 mating. This suggested that the LETO rat which has been established from the same original colony as the OLETF rat shares some, but not all, diabetogenic genes with the OLETF, and that one of the responsible genes locates on the X-chromosome. Linkage study using (OLETF female x F344 male)F2 progeny has confirmed that one of the diabetogenic loci in the OLETF rats locates on the X-chromosome 14 cM distant from the AR gene (LOD = 2.598) and has been designated as ODB-1.

Inheritance of T helper immunodeficiency (thid) in LEC mutant rats

LEC rat was originally established at the Center for Experimental Plants and Animals, Hokkaido University, as a mutant strain that spontaneously develops hepatic injury and hepatocarcinoma. The gene responsible for these hepatic effects was designated as hts (Masuda et al. 1988). Thereafter, it was reported that LEC rats have another recessive mutational gene, Igsr-1, which causes decrease in serum IgG level but not in Igm or IgA level (Matsumoto et al. 1989). Most recently, we found a deficiency in CD4 + T-cells in LEC rats and demonstrated it is caused by an arrest of the maturation from CD4+8 + to CD4+8 cells in the thymus (Agui et al. 1990). In this study, we report the genetic characterization of CD4 + Tcells deficiency and its linkage relationship with Igsr-1 locus or other loci reorted already. LEC/Tj (RT1.A) and WKAH/Tj (RT1.A k) inbred rats have been bred in our laboratory under specific pathogen free conditions. BN/Kyo (RT1.A n) rats were kindly supplied by Dr. J. Yamada, University of Kyoto, Japan. LEC mutant rats used in this experiment were highly inbred (over 48 generations of brother and sister mating). LEC, WKAH, (WKAH x LEC)F 1 hybrids, and (WKAH x LEC)F 1 x LEC and (BN x LEC)F1 x LEC backcrosses animals were used in genetic analyses. CD4 + T-cells from thymuses and peripheral organs of 1-12 months old rats were analyzed by either singleor two-color flow cytometry (FACScan, Becton Dickinson, Mountain View, California) using fluorescein isothiocyanate (FITC)-conjugated W3/25 monoclonal antibody (mAb) or FITC-conjugated W3/25 and phycoerythrin (PE)-conjugated OX8 mAbs, respectively. Serum IgG levels of (WKAH x LEC)F1 x LEC one-month-old rats

Relationships between diet control and the development of spontaneous type II diabetes and diabetic nephropathy in OLETF rats

The effect of a 30% restricted diet on the development of diabetes and diabetic nephropathy was examined using the Otsuka Long Evans Tokushima Fatty (OLETF) rat which develops non-insulin-dependent diabetes mellitus (NIDDM) spontaneously after 25-30 weeks of age. The first experimental group that received 30% restricted feeding from six to 80 weeks old, showed complete suppression of spontaneous diabetes up to 40 weeks of age and showed milder histopathological change of pancreatic islets, that those of the control group. The second group which received 30% restricted feeding during 30-80 weeks, showed a gradual decrease in clinical diabetes with age, even though they had already developed diabetes at 25 weeks. In both groups, levels of urinary protein content appeared to decrease, compared with that in control rats, although a gradual increase of urinary protein was observed with age. Histopathologically, glomerular damages were slight to mild in both groups. However, no improvement in nephrotic complication was observed for the group which received a 30% restricted feeding after 70 weeks of age. These results clearly show that the balanced-control diet, given at a 30% restricted feeding level and at an early phase, is effective in the prevention or improvement of NIDDM and nephrotic complications. Diet therapy after 70 weeks of age, however, had little or no effect.

Pathological and laboratory findings in LEC/Otk rats that spontaneously develop hepatic injury

The LEC strain of rats that spontaneously develops hepatic injury has been introduced into specific pathogen‐free (SPF) conditions (SPF‐LEC/Otk). The present communication describes the clinical and pathological features of the SPF‐LEC/Otk rats. The characteristic features of these animals are as follows: (i) Jaundice develops in almost all rats with increase in the P‐GPT level; (ii) The animals show episodes of jaundice, a high P‐GPT level and liver cell necrosis, but only slight inflammatory cell infiltration; (iii) The liver cells show characteristic microvesicular fatty changes; (iv) The P‐GPT level shows increases, first at 18 weeks and then at 25 weeks of age; (v) The rats show immunological disorders, such as deficiency of immunoglobulins, especially IgG1, and of helper T cells; (vi) Infectious agents such as viruses do not seem to be involved, although this possibility cannot be absolutely excluded; (vii) The immunological disorders are not directly associated with the occurrence of liver cell necrosis; and (viii) The pattern of inheritance (autosomal single‐recessive trait) of the disease strongly suggests that it is due to a genetic metabolic disorder.

Neoplastic and Non-Neoplastic Lesions in Aging LEC/Otk Rats

We have previously reported that the SPF-conditioned LEC/Otk rat has characteristic pathological features. (1) Jaundice develops in almost all rats with increase in the plasma glutamic pyruvic transaminase (P-GPT) level. (2) The animals show episodes of jaundice, a high P-GPT level, and liver cell necrosis, but only slight inflammatory cell infiltration. (3) The liver cells show characteristic microvesicular fatty changes. (4) The P-GPT level shows increases, first at 18 weeks and then at 25 weeks of age. (5) The rats show immunological disorders, such as deficiency of immunoglobulins, especially IgG1, and of helper T cells [1].

Spontaneously diabetic rat “OLETF” as a model for NIDDM in humans

A spontaneous polyuria, polydipsia, and mild obesity was discovered in 1984 in an outbred colony of Long Evans (LE) rats, that had been purchased from Charles River Canada (St. Constant, Quebec, Canada) in 1982. A strain of rats was developed by selective breeding from this rat and designated OLETF (Otsuka Long-Evans Tokushima Fatty). The OLETF line has been maintained since then by brother-sister mating at the Tokushima Research Institute, Otsuka Pharmaceutical Co., Ltd.1,2 From the same LE colony stock, a line developing insulin-dependent diabetes mellitus (IDDM) has been isolated (LETL)3–4 and a control line, LETO, has also been established.

Pathological and Laboratory Findings of “LEC/Otk” Rats Maintained Under SPF Conditions

A mutant strain of rats, LEC, that develops spontaneous hepatic injury associated with severe jaundice was developed in 1987 [1]. In this LEC strain, isolated and established as an inbred strain by sibmating, almost 90% of the animals show hereditary hepatic injury in conventional conditions [2, 3]. Genetic analysis indicated that at least one autosomal recessive gene is responsible for this disease [4]. Thus, the LEC strain is a useful model for studies on liver cell injury and liver cancer. Hepatocellular carcinomas have been found in LEC rats surviving for a long time after recovery from jaundice [2, 5]. Hepatocellular carcinomas were also found in all cases in the present study, as will be reported in detail (Chap. III. p. 2).