Depletion of plasma thymidine results in growth retardation and mitochondrial myopathy in mice overexpressing human thymidine phosphorylase.

Plasma thymidine levels in rodents are higher than in other mammals including humans, possibly due to a different pattern and lower level of thymidine phosphorylase expression. Here, we generated a novel knock-in (KI) mouse line with high systemic expression of human thymidine phosphorylase to investigate this difference in nucleotide metabolism in rodents. The KI mice showed growth retardation around weaning and died by 4 weeks of age with a decrease in plasma thymidine level compared with the litter-control WT mice. These phenotypes were completely or partially rescued by administration of the thymidine phosphorylase inhibitor 5-chloro-6-(2-iminopyrrolidin-1-yl) methyl-2,4(1H,3H)-pyrimidinedione hydrochloride or thymidine, respectively. Interestingly, when thymidine phosphorylase inhibitor administration was discontinued in adult animals, KI mice showed deteriorated grip strength and locomotor activity, decreased bodyweight, and subsequent hind-limb paralysis. Upon histological analyses, we observed axonal degeneration in the spinal cord, muscular atrophy with morphologically abnormal mitochondria in quadriceps, retinal degeneration, and abnormality in the exocrine pancreas. Moreover, we detected mitochondrial DNA depletion in multiple tissues of KI mice. These results indicate that the KI mouse represents a new animal model for mitochondrial diseases and should be applicable for the study of differences in nucleotide metabolism between humans and mice.

Genome editing of Nf1, Pten, and Trp53 in neonatal mice induces glioblastomas positive for oligodendrocyte lineage transcription factor 2.

To generate a mouse glioblastoma model by genome editing, we introduced Cas9 protein and guide RNAs specific for Nf1, Pten, and Trp53 into the neonatal mouse forebrain by electroporation. We found a high incidence (approximately 90%) of glial tumor development, including glioblastomas, 15 weeks later. The histological features of the tumors were similar to those of diffuse gliomas and, in some cases, similar to human glioblastomas, with microvascular proliferation (glomeruloid structure). In addition, unlike glial fibrillary acidic protein (GFAP)-positive glioblastomas generated using a similar method in a previous model, the majority of tumor cells were positive for oligodendrocyte lineage transcription factor 2, but negative for GFAP and neurofilaments. One base pair insertions identical to those seen in a previous model were found around the target sequences in Nf1, Pten, and Trp53, and additional deletions were found only in Pten. Considering that the histological characteristics were different from those seen in the previous model, our new model provides an additional research tool to investigate the early stages of glioblastoma development.

Spontaneous thymoma in a 10-week-old sprague-dawley rat.

Spontaneous thymoma was found in the left lobe of the thymus of a male 10-week-old Sprague-Dawley (SD) rat. Microscopically, the thymic mass showed a sheet of dark area with multiple pale foci. The dark area mainly consisted of densely compacted small lymphoid cells with sporadic large epithelioid cells and mitotic figures. The epithelioid cells and mitotic figures were more frequent than those of the normal thymic cortex in this animal. The multiple pale foci were similar to the normal thymic medulla and occasionally had Hassall's corpuscles; thus, they were regarded as medullary differentiation areas. Furthermore, some perivascular spaces recognized as characteristics of thymoma were present in the center of the mass. Immunohistochemically, the epithelioid cells in the dark area were positive for cytokeratin. Ultrastructurally, desmosomes and tonofilaments were observed in the epithelioid cells. Thus, this tumor was diagnosed as a thymoma. This is a rare case of thymoma occurring spontaneously in young adult SD rat.

Comparison of biochemical data, blood pressure and physical activity between longevity and non-longevity districts in Japan.

BACKGROUND: There is controversy about longevity-associated factors, including environmental and genetic factors. Clinical and epidemiological studies suggest that multiple risk factors decrease life-span, but there has not been a definitive report regarding the association of risk factors with longevity. The ultimate aim of the present study was to prevent the overwhelming increase in life-style-related diseases by evaluating this association in 2 districts in Japan. METHODS AND RESULTS: Plasma glucose levels, hemoglobin (Hb) A1c, lipids, dehydroepiandrosterone-sulfate, adiponectin and physical activity were examined in 133 subjects (M/F 47/86, 67+/-1 years) in Kokufu, a longevity district (mean life span: 80.4 years according to 2000 Japanese census) and 69 subjects (M/F 29/40, 62+/-1 years) in Miyama, a non-longevity district (mean life span 77.4 years, 2000 census). There were significant differences in systolic and diastolic blood pressures (BPs, p < 0.001), exercise capacity (p < 0.0001) and plasma adiponectin levels (p < 0.04) between the districts. Plasma adiponectin level was significantly correlated with high-density lipoprotein-cholesterol (HDL-C) (r = 0.333, p < 0.0001), triglyceride (TG) (r = -0.161, p < 0.04), HbA1c (r = -0.163, p < 0.03) and HOMA-R (r = -0.163, p < 0.03). CONCLUSION: Life-style-related factors such as BP, exercise capacity and plasma adiponectin levels might play an important role in longevity, and those of HDL-C and TG, as well as glucose tolerance, might be associated with adiponectin levels.

Effect of fasting on PPARgamma and AMPK activity in adipocytes.

We investigated the effects of fasting on gene expression and intracellular signals regulating energy metabolism in adipose tissue. Following fasting for 15h or 39h, epididymal fat pads were isolated from Wistar rats. PPARgamma mRNA levels decreased in the adipose tissues isolated from rats fasted for 39h, whereas adipocyte lipid-binding protein (aP2) and lipoprotein lipase (LPL) mRNA levels increased. Overnight fasting increased the AMP/ATP ratio and AMP-activated protein kinase (AMPK) in adipose tissue, but not in muscle or liver tissue. In addition, the effect of 5-aminoimidazole-4-carboxyamide-ribonucleoside (AICAR) on PPARgamma expression in primary cultured adipocytes was investigated. AICAR reduced PPARgamma mRNA levels but increased aP2 and LPL mRNA levels. Thus, fasting-induced AMPK activation may affect on the regulation of gene expression in adipocytes.

Effect of dehydroepiandrosterone on insulin sensitivity in Otsuka Long-Evans Tokushima-fatty rats.

In order to clarify the effect of dehydroepiandrosterone (DHEA) on improvement of insulin resistance, we examined the effects of overexpression of wild-type protein kinase C-zeta (wt-PKCzeta)/3-phosphoinositide-dependent protein kinase-1 (wt-PDK1) and kinase-inactive PKCzeta/PDK1 (DeltaPKCzeta/DeltaPDK1) on DHEA-induced [(3)H]2-deoxyglucose (DOG) uptake using the electroporation method in rat adipocytes. Overexpression of wt-PKCzeta and wt-PDK1 significantly increased in DHEA-induced [(3)H]2-DOG uptake. Wortmannin completely suppressed DHEA-induced [(3)H]2-DOG uptake in wt-PKCzeta- and wt-PDK1-transfected adipocytes. Overexpression of neither DeltaPKCzeta nor DeltaPDK1 increased DHEA-induced [(3)H]2-DOG uptake. Otsuka Long-Evans fatty rats (OLETF), animal models of type 2 diabetes, and Long-Evans Tokushima rats (LETO) as control, were treated with 0.4% DHEA for 2 weeks. Insulin-induced [(3)H]2-DOG uptakes, activations of PI 3-kinase and PKCzeta of adipocytes were significantly increased in DHEA-treated OLETF rats. Moreover, plasma glucose levels in OLETF rats after treatment with DHEA for 2 weeks were significantly lower than treatment without DHEA, but not in LETO rats. These results indicate that DHEA treatment may improve glucose tolerance through a PI 3-kinase-PKCzeta pathway and downregulates adiposity in OLETF rats.

Platelet aggregation in obese and diabetic subjects: association with leptin level.

To clarify the relationship between serum leptin concentration and platelet aggregation mechanism, we investigated serum leptin concentration and agonist-induced platelet aggregation in eight obese subjects and eight non-obese and non-diabetic controls. In addition we also measured them in 15 type 2 diabetic subjects and 17 control subjects. Maximum platelets aggregation rate (MPAR) in control and diabetic subjects by adenosine diphosphate (ADP), collagen and thrombin were measured by aggregometer after pretreatment with 100 ng/ml leptin for 60 min. The MPAR by 0.15 U/ml thrombin stimulation in leptin-treated platelet in the controls was significantly increased compared with that in non-treated platelets, but not by ADP and collagen stimulation. Despite a significantly higher concentration of leptin in obese subjects, agonist-induced platelet aggregation in obese subjects was not different from that in controls. There were no significant differences in serum leptin concentration and MPAR by various agonists between diabetic and control subjects. When MPAR by ADP in the diabetic subjects was divided into two groups (high group: >50%, low group: <50%), the serum leptin concentration in the high group was significantly increased, compared with that in the low group. These results suggest that ADP-induced platelet aggregation may be associated with serum leptin concentration in diabetic subjects, and that leptin-associated platelet aggregation may affect the development of cardiovascular complications in obese and diabetic subjects.