Publications by authors named "Ryuichi Tozawa"

Article Synopsis
  • Mutations in the human peptide-glycanase gene cause a rare genetic disorder that leads to severe developmental issues or even death in rodent models due to unknown mechanisms.
  • Deleting the gene responsible for a ubiquitin ligase subunit can prevent these lethal defects in mutant mice, indicating a potential rescue strategy.
  • The study identifies that the overproduction of a specific protein (FBS2) inhibits proteasome activity and leads to the harmful accumulation of improperly tagged proteins, mainly NRF1, which contributes to the health problems seen in patients with NGLY1 deficiency.
View Article and Find Full Text PDF

N-glycanase 1 (NGLY1) deficiency is a rare inherited disorder characterized by developmental delay, hypolacrima or alacrima, seizure, intellectual disability, motor deficits, and other neurological symptoms. The underlying mechanisms of the NGLY1 phenotype are poorly understood, and no effective therapy is currently available. Similar to human patients, the rat model of NGLY1 deficiency, Ngly1-/-, shows developmental delay, movement disorder, somatosensory impairment, scoliosis, and learning disability.

View Article and Find Full Text PDF

N-Glycanase 1 (NGLY1) deficiency is a congenital disorder caused by mutations in the NGLY1 gene. Because systemic Ngly1 mice with a C57BL/6 (B6) background are embryonically lethal, studies on the mechanism of NGLY1 deficiency using mice have been problematic. In this study, B6-Ngly1 mice were crossed with Japanese wild mice-originated Japanese fancy mouse 1 (JF1) mice to produce viable F Ngly1 mice from (JF1×B6)F Ngly1 mice.

View Article and Find Full Text PDF

N-glycanase 1 (NGLY1) deficiency, an autosomal recessive disease caused by mutations in the NGLY1 gene, is characterized by developmental delay, hypolacrima or alacrima, seizure, intellectual disability, movement disorders and other neurological phenotypes. Because of few animal models that recapitulate these clinical signatures, the mechanisms of the onset of the disease and its progression are poorly understood, and the development of therapies is hindered. In this study, we generated the systemic Ngly1-deficient rodent model, Ngly1-/- rats, which showed developmental delay, movement disorder, somatosensory impairment and scoliosis.

View Article and Find Full Text PDF

Dysferlinopathies, which are muscular diseases caused by mutations in the dysferlin gene, remain serious medical problems due to the lack of therapeutic agents. Herein, we report the design, synthesis, and structure-activity relationships of a 2,6-disubstituted 3-imidazo[4,5-]pyridine series, which was identified from the phenotypic screening of chemicals that increase the level of dysferlin in myocytes differentiated from patient-derived induced pluripotent stem cells (iPSCs). Optimization studies with cell-based phenotypic assay led to the identification of a highly potent compound, , with dysferlin elevation effects at double-digit nanomolar concentrations.

View Article and Find Full Text PDF

Dysferlinopathy is a progressive muscle disorder that includes limb-girdle muscular dystrophy type 2B and Miyoshi myopathy (MM). It is caused by mutations in the dysferlin (DYSF) gene, whose function is to reseal the muscular membrane. Treatment with proteasome inhibitor MG-132 has been shown to increase misfolded dysferlin in fibroblasts, allowing them to recover their membrane resealing function.

View Article and Find Full Text PDF

We attempted to clarify the therapeutic capability of antagonists of the farnesoid X receptor (FXR), a nuclear receptor that regulates lipid and bile acid metabolism. Herein, we report the antidyslipidemic effects of a novel synthesized FXR antagonist, compound-T1, utilizing a dyslipidemic hamster model. Compound-T1 selectively inhibited chenodeoxycholic acid-induced FXR activation (IC , 2.

View Article and Find Full Text PDF

Background: The effects of farnesoid X receptor (FXR) antagonists on plasma lipid profile in mice have not been investigated thus far. The aim of this study was to investigate the antidyslipidemic effects of an FXR antagonist in dyslipidemic mice, and to clarify the mechanisms underlying the lipid modulatory effect.

Methods: Compound-T0 (1-100 mg/kg) was orally administered to C57BL/6J mice fed a Western-type diet or low-density lipoprotein receptor knockout (LDLR-/-) mice fed a Western-type diet for a week, and plasma lipid levels were investigated.

View Article and Find Full Text PDF

Sarcopenia and cachexia present characteristic features of a decrease in skeletal muscle mass and strength, anorexia, and lack of motivation. Treatments for these diseases have not yet been established, although selective androgen receptor modulators (SARMs) are considered as therapeutic targets. We previously reported that a novel SARM compound, SARM-2f, exhibits anabolic effect on muscles, with less stimulatory effect on prostate weight compared with testosterone, in rat Hershberger assays and cancer cachexia models.

View Article and Find Full Text PDF

Neuromedin U (NMU), a neuropeptide originally isolated from porcine spinal cord, has multiple physiological functions and is involved in obesity and inflammation. Excessive fat accumulation in the liver leads to non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), which is closely associated with obesity. NAFLD and NASH develop and progress via complex pathophysiological processes, and it remains unclear to what extend the NMU system contributes to the risk of obesity-related disorders such as NAFLD and NASH.

View Article and Find Full Text PDF

Although chronic kidney disease (CKD) is strongly associated with onsets of cardiovascular disease (CVD), the pathogenic mechanism between these diseases has not been fully understood. To develop and validate new therapeutic strategies for this complication, appropriate experimental models that reflect the complexity of the underlying pathophysiology are needed. The Osborne-Mendel (OM) rat was identified as an atherosclerosis-prone and a premature-death rat strain among 16 inbred rat strains when fed high-cholesterol containing diet.

View Article and Find Full Text PDF

Inositol hexakisphosphate kinase 3 (IP6K3) generates inositol pyrophosphates, which regulate diverse cellular functions. However, little is known about its own physiological role. Here, we show the roles of IP6K3 in metabolic regulation.

View Article and Find Full Text PDF

Aim: Low-density lipoprotein receptor knockout (LDLR-KO) mice fed a modified choline-deficient and amino acid-defined (mCDAA) diet show non-alcoholic steatohepatitis (NASH)-like pathophysiology. In order to pharmacologically benchmark this model, effects of pioglitazone (a thiazolidinedione) and candesartan cilexetil (an angiotensin II type 1 receptor blocker) on steatosis and liver fibrosis were examined.

Methods: Pioglitazone (10 mg/kg) and candesartan cilexetil (3 mg/kg) were given orally once daily to LDLR-KO mice under mCDAA diet for 7 weeks.

View Article and Find Full Text PDF

Aim: Experimental models of non-alcoholic steatohepatitis (NASH) are still required for understanding the pathophysiology of this disease. This study aimed to examine whether disease progression is accelerated by combining dyslipidemic genetic modification and dietary challenges and develop NASH-associated hepatic fibrosis, cirrhosis, and carcinoma in a short period.

Methods: Low-density lipoprotein receptor knockout mice were fed a modified choline-deficient amino acid-defined diet, including 1 w/w% cholesterol and 41 kcal% fat, and was comprehensively profiled over 1 year.

View Article and Find Full Text PDF

Nephropathy frequently co-occurs with metabolic syndrome in humans. Metabolic syndrome is a cluster of metabolic diseases including obesity, diabetes, hypertension, and dyslipidemia, and some previous studies revealed that dyslipidemia contributes to the progression of kidney dysfunction. To establish a new nephropathy model with metabolic syndrome, we produced human apolipoprotein B (apoB) transgenic (Tg.

View Article and Find Full Text PDF

Squalene synthase (SS) catalyzes the biosynthesis of squalene, the first specific intermediate in the cholesterol biosynthetic pathway. To test the feasibility of lowering plasma cholesterol by inhibiting hepatic SS, we generated mice in which SS is specifically knocked out in the liver (L-SSKO) using Cre-loxP technology. Hepatic SS activity of L-SSKO mice was reduced by >90%.

View Article and Find Full Text PDF

Aims: We previously reported anti-dyslipidemic effects of a farnesoid X receptor antagonist in monkeys. In this study, we compared the cholesterol-lowering effects of single and combined administration of a farnesoid X receptor antagonist, compound-T8, and the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor atorvastatin in a guinea pig model.

Main Methods: Plasma levels of 7α-hydroxy-4-cholesten-3-one, a marker of hepatic cholesterol 7α-hydroxylase activity, were measured after a single administration of compound-T8.

View Article and Find Full Text PDF

Aims: We investigated antidyslipidemic effects of a farnesoid X receptor antagonist compound-T3 in non-human primates as a novel treatment approach for dyslipidemia.

Main Methods: Cynomolgus monkeys were fed a high-fat diet over 3 weeks. Drugs were administered to the monkeys for a week, and their plasma and fecal lipid parameters were measured.

View Article and Find Full Text PDF

We aimed to elucidate the mechanism underlying the anti-dyslipidemic effect of compound-T3, a farnesoid X receptor antagonist, by investigating its effects on hepatic lipid metabolism in non-human primates. We administered lipid-lowering drugs for 7 days to cynomolgus monkeys receiving a high-fat diet, and subsequently measured the levels of lipid parameters in plasma, feces, and hepatic tissue fluids. Compound-T3 (0.

View Article and Find Full Text PDF

Age-related decrease of testosterone levels in blood and brain is believed to be associated with neurodegenerative diseases such as Alzheimer's disease. However, the effect of testosterone on brain function is not well understood. Therefore, we investigated the impact of testosterone deprivation on mitochondrial gene expression in the brain of male gonadectomized (GDX) rats.

View Article and Find Full Text PDF

Inhibitor of apoptosis proteins (IAP), which are key regulators of apoptosis, are inhibited by second mitochondria-derived activator of caspase (SMAC). Small-molecule IAP antagonists have recently been reported as novel therapeutic treatments for cancer. In this study, we showed that the octahydro-pyrrolo[1,2-a]pyrazine derivative, T-3256336, is a novel and orally available small-molecule IAP antagonist.

View Article and Find Full Text PDF

To establish low density lipoprotein receptor (LDLR) mutant rats as a hypercholesterolemia and atherosclerosis model, we screened the rat LDLR gene for mutations using an N-ethyl-N-nitrosourea mutagenesis archive of rat gene data, and identified five mutations in its introns and one missense mutation (478T>A) in exon 4. The C160S mutation was located in the ligand binding domain of LDLR and was revealed to be equivalent to mutations (C160Y/G) identified in human familial hypercholesterolemia (FH) patients. The wild type, heterozygous, and homozygous mutant rats were fed a normal chow diet or a high fat high cholesterol (HFHC) diet from the age of 10 weeks for 16 weeks.

View Article and Find Full Text PDF

Deposition of amyloid β peptide (Aβ) into the brain causes cognitive impairment. We investigated whether prescription pre-administration of n-3 fatty acids improves cognitive learning ability in young rats and whether it protects against learning ability impairments in an animal model of Alzheimer's disease that was prepared by infusion of Aβ(1-40) into the cerebral ventricles of rats. Pre-administration of TAK-085 (highly purified and concentrated n-3 fatty acids containing eicosapentaenoic acid ethyl ester and docosahexaenoic acid ethyl ester) at 300 mg kg(-1) day(-1) for 12 weeks significantly reduced the number of reference memory errors in an 8-arm radial maze, suggesting that long-term administration of TAK-085 improves cognitive leaning ability in rats.

View Article and Find Full Text PDF

High-dose statin treatment has been recommended as a primary strategy for aggressive reduction of LDL cholesterol levels and protection against coronary artery disease. The effectiveness of high-dose statins may be limited by their potential for myotoxic side effects. There is currently little known about the molecular mechanisms of statin-induced myotoxicity.

View Article and Find Full Text PDF