Tsutomu Shimada

Monosodium glutamate (MSG): a villain and promoter of liver inflammation and dysplasia.

Chronic inflammation is a common theme in a variety of disease pathways, including autoimmune diseases. The pathways of chronic inflammation are well illustrated by nonalcoholic steatohepatitis (NASH), which is of a serious concern due to its increasing prevalence in the westernized world and its direct correlation with lifestyle factors, particularly diet. Importantly, NASH may ultimately lead to the development of hepatocellular carcinoma. We previously reported that injection of monosodium glutamate (MSG) in ICR mice leads to the development of significant inflammation, central obesity, and type 2 diabetes. To directly address the long-term consequences of MSG on inflammation, we have performed serial analysis of MSG-injected mice and focused in particular on liver pathology. By 6 and 12 months of age, all MSG-treated mice developed NAFLD and NASH-like histology, respectively. In particular, the murine steatohepatitis at 12 months was virtually undistinguishable from human NASH. Further, dysplastic nodular lesions were detected in some cases within the fibrotic liver parenchyma. We submit that MSG treatment of mice induces obesity and diabetes with steatosis and steatohepatitis resembling human NAFLD and NASH with pre-neoplastic lesions. These results take on considerable significance in light of the widespread usage of dietary MSG and we suggest that MSG should have its safety profile re-examined and be potentially withdrawn from the food chain.

Newborn screening and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are caused by deficiency of lysosomal enzyme activities needed to degrade glycosaminoglycans (GAGs), which are long unbranched polysaccharides consisting of repeating disaccharides. GAGs include: chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and hyaluronan. Their catabolism may be blocked singly or in combination depending on the specific enzyme deficiency. There are 11 known enzyme deficiencies, resulting in seven distinct forms of MPS with a collective incidence of higher than 1 in 25,000 live births. Accumulation of undegraded metabolites in lysosomes gives rise to distinct clinical syndromes. Generally, the clinical conditions progress if untreated, leading to developmental delay, systemic skeletal deformities, and early death. MPS disorders are potentially treatable with enzyme replacement therapy or hematopoietic stem cell transplantation. For maximum benefit of available therapies, early detection and intervention are critical. We recently developed a novel high-throughput multiplex method to assay DS, HS, and KS simultaneously in blood samples by using high performance liquid chromatography/tandem mass spectrometry for MPS. The overall performance metrics of HS and DS values on MPS I, II, and VII patients vs. healthy controls at newborns were as follows using a given set of cut-off values: sensitivity, 100%; specificity, 98.5-99.4%; positive predictive value, 54.5-75%; false positive rate, 0.62-1.54%; and false negative rate, 0%. These findings show that the combined measurements of these three GAGs are sensitive and specific for detecting all types of MPS with acceptable false negative/positive rates. In addition, this method will also be used for monitoring therapeutic efficacy. We review the history of GAG assay and application to diagnosis for MPS.

Pathogenesis of Morquio A syndrome: An autopsied case reveals systemic storage disorder

Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is a lysosomal storage disorder caused by deficiency of N-acetylgalactosamine-6-sulfate sulfatase, which results in systemic accumulation of glycosaminoglycans (GAGs), keratan sulfate and chondroitin-6-sulfate. Accumulation of these GAGs causes characteristic features as disproportionate dwarfism associated with skeletal deformities, genu valgum, pigeon chest, joint laxity, and kyphoscoliosis. However, the pathological mechanism of systemic skeletal dysplasia and involvement of other tissues remain unanswered in the paucity of availability of an autopsied case and successive systemic analyses of multiple tissues. We report here a 20-year-old male autopsied case with MPS IVA, who developed characteristic skeletal features by the age of 1.5 years and died of acute respiratory distress syndrome five days later after occipito-C1-C2 cervical fusion. We pathohistologically analyzed postmortem tissues including trachea, lung, thyroid, humerus, aorta, heart, liver, spleen, kidney, testes, bone marrow, and lumbar vertebrae. The postmortem tissues relevant with clinical findings demonstrated 1) systemic storage materials in multiple tissues beyond cartilage, 2) severely vacuolated and ballooned chondrocytes in trachea, humerus, vertebrae, and thyroid cartilage with disorganized extracellular matrix and poor ossification, 3) appearance of foam cells and macrophages in lung, aorta, heart valves, heart muscle, trachea, visceral organs, and bone marrow, and 4) storage of chondrotin-6-sulfate in aorta. This is the first autopsied case with MPS IVA whose multiple tissues have been analyzed pathohistologically and these pathological findings should provide a new insight into pathogenesis of MPS IVA.

Modulation of mdr1a and CYP3A gene expression in the intestine and liver as possible cause of changes in the cyclosporin A disposition kinetics by dexamethasone

We investigated the effect of dexamethasone (DEX) on the disposition kinetics of cyclosporin A (CyA) and the mechanism of this drug interaction. Rats were treated with DEX (1 or 75mg/kg per day, i.p.) once a day for 1-7 days, and the blood concentration of CyA was measured after an i.v. or p.o. dose of CyA (10mg/kg) at 1.5hr after the last DEX treatment. In rats treated with a low dose of DEX (1mg/kg), the blood concentration of CyA after i.v. administration was unchanged compared with that of untreated rats, whereas the blood concentration after oral administration was significantly decreased, and this decrease was dependent on the duration of DEX administration. The total clearance (CL(tot)) of CyA was unchanged, but the bioavailability was significantly decreased to about one-third of that in DEX-untreated rats after 7 days of DEX treatment. At this time, the expression of mdr1a mRNA and P-gp in the liver and intestine was increased, whereas CYP3A2 was unaffected at both the mRNA and protein levels. In rats treated with a high dose of DEX (75mg/kg), the blood concentration of CyA was significantly decreased after both i.v. and p.o. administrations compared with those of untreated rats. The bioavailability of CyA was decreased, and the CL(tot) was significantly increased. The P-gp and CYP3A2 in the liver and intestine were increased at both the mRNA and protein levels. Our results indicate that the drug interaction between CyA and DEX is a consequence of modulation of P-gp and CYP3A2 gene expression by DEX, with differential dose-dependence.

Dose dependent development of diabetes mellitus and non-alcoholic steatohepatitis in monosodium glutamate-induced obese mice.

AIMS We have recently reported that monosodium glutamate (MSG) induces severe obesity with diabetes mellitus and/or non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) in Crj:CD-1(ICR) neonatal mice. In this study, we investigated the effects of varying the dose of MSG on the resulting obesity and diabetes mellitus. MAIN METHODS Crj:CD-1(ICR) neonatal mice were administered MSG in one of several courses: once-daily subcutaneous injections of 2mg/g for 5 consecutive days (2 mg/g x 5 group), a single subcutaneous injection of 4 mg/g (4 mg/g x 1 group) and once-daily subcutaneous injections of 4 mg/g for 5 consecutive days (4 mg/g x 5 group). KEY FINDINGS In all the MSG treatment groups, severe obesity developed by 29 weeks of age. The onset of diabetes mellitus and liver lesions (resembling those of human NAFLD/NASH) were observed before 54 weeks of age. The obesity, diabetes mellitus and liver lesions were most severe in the 4 mg/g x 1 group. In the 4 mg/g x 5 group, increases in body weight and body length were inhibited by MSGs severe toxicity. SIGNIFICANCE A single 4 mg/g dose of MSG is the most suitable as the obese model and induces not only severe obesity and diabetes mellitus, but also liver changes resembling human NAFLD/NASH. A small amount of MSG in the newborn develops obesity and the other complications without hyperphagia after a long term.

Skin fragility in obese diabetic mice: possible involvement of elevated oxidative stress and upregulation of matrix metalloproteinases

Abstract:  The purpose of this study was to test the hypothesis that obese diabetic mice exhibit marked skin fragility, which is caused by increased oxidative stress and increased matrix metalloproteinase (MMP) gene expression in the subcutaneous adipose tissue. Scanning electron microscopy of skin samples from Tsumura‐Suzuki obese diabetic (TSOD) mice revealed thinner collagen bundles, and decreased density and convolution of the collagen fibres. Furthermore, skin tensile strength measurements confirmed that the dorsal skin of TSOD mice was more fragile to tensile force than that of non‐obese mice. The mRNA expressions of heme oxygenase 1 (Hmox1), a marker of oxidative stress, Mmp2 and Mmp14 were increased in the adipose tissue of TSOD mice. Antioxidant experiments were subsequently performed to determine whether the changes in collagen fibres and skin fragility were caused by oxidative stress. Strikingly, oral administration of the antioxidant dl‐α‐tocopherol acetate (vitamin E) decreased Hmox1, Mmp2 and Mmp14 mRNA expressions, and improved the skin tensile strength and structure of collagen fibres in TSOD mice. These findings suggest that the skin fragility in TSOD mice is associated with dermal collagen damage and weakened tensile strength, and that oxidative stress and MMP overexpression in the subcutaneous adipose tissue may, at least in part, affect dermal fragility via a paracrine pathway. These observations may contribute to novel clinical interventions, such as dietary supplementation with antioxidants or application of skin cream containing antioxidants, which may overcome skin fragility in obese patients with diabetes.

Impact of enzyme replacement therapy and hematopoietic stem cell transplantation in patients with Morquio A syndrome

Patients with mucopolysaccharidosis IVA (MPS IVA) can present with systemic skeletal dysplasia, leading to a need for multiple orthopedic surgical procedures, and often become wheelchair bound in their teenage years. Studies on patients with MPS IVA treated by enzyme replacement therapy (ERT) showed a sharp reduction on urinary keratan sulfate, but only modest improvement based on a 6-minute walk test and no significant improvement on a 3-minute climb-up test and lung function test compared with the placebo group, at least in the short-term. Surgical remnants from ERT-treated patients did not show reduction of storage materials in chondrocytes. The impact of ERT on bone lesions in patients with MPS IVA remains limited. ERT seems to be enhanced in a mouse model of MPS IVA by a novel form of the enzyme tagged with a bone-targeting moiety. The tagged enzyme remained in the circulation much longer than untagged native enzyme and was delivered to and retained in bone. Three-month-old MPS IVA mice treated with 23 weekly infusions of tagged enzyme showed marked clearance of the storage materials in bone, bone marrow, and heart valves. When treatment was initiated at birth, reduction of storage materials in tissues was even greater. These findings indicate that specific targeting of the enzyme to bone at an early stage may improve efficacy of ERT for MPS IVA. Recombinant N-acetylgalactosamine-6-sulfate sulfatase (GALNS) in Escherichia coli BL21 (DE3) (erGALNS) and in the methylotrophic yeast Pichia pastoris (prGALNS) has been produced as an alternative to the conventional production in Chinese hamster ovary cells. Recombinant GALNS produced in microorganisms may help to reduce the high cost of ERT and the introduction of modifications to enhance targeting. Although only a limited number of patients with MPS IVA have been treated with hematopoietic stem cell transplantation (HSCT), beneficial effects have been reported. A wheelchair-bound patient with a severe form of MPS IVA was treated with HSCT at 15 years of age and followed up for 10 years. Radiographs showed that the figures of major and minor trochanter appeared. Loud snoring and apnea disappeared. In all, 1 year after bone marrow transplantation, bone mineral density at L2–L4 was increased from 0.372 g/cm2 to 0.548 g/cm2 and was maintained at a level of 0.48±0.054 for the following 9 years. Pulmonary vital capacity increased approximately 20% from a baseline of 1.08 L to around 1.31 L over the first 2 years and was maintained thereafter. Activity of daily living was improved similar to the normal control group. After bilateral osteotomies, a patient can walk over 400 m using hip–knee–ankle–foot orthoses. This long-term observation of a patient shows that this treatment can produce clinical improvements although bone deformity remained unchanged. In conclusion, ERT is a therapeutic option for MPS IVA patients, and there are some indications that HSCT may be an alternative to treat this disease. However, as neither seems to be a curative therapy, at least for the skeletal dysplasia in MPS IVA patients, new approaches are investigated to enhance efficacy and reduce costs to benefit MPS IVA patients.

Pharmacokinetic advantage of intraperitoneal injection of docetaxel in the treatment for peritoneal dissemination of cancer in mice

Intraperitoneal administration of docetaxel has been used to treat peritoneal dissemination of cancer, but its safety has not yet been confirmed. We have compared the pharmacokinetic behaviour of docetaxel after intravenous and intraperitoneal administration in CD‐1‐nu/nu mice bearing MKN‐45P, a gastric cancer variant line producing peritoneal dissemination. Docetaxel (8mg kg−1) was intravenously or intraperitoneally injected into the mice and at designated times the drug concentration was measured in plasma, ascites fluid, and abdominal tissues (liver, kidney, intestine and spleen, solid cancer, and suspended free cancer). The pharmacokinetic behaviour of docetaxel was similar in control mice and cancer‐bearing mice after administration via either route, except that the transfer of docetaxel from the abdominal cavity to systemic blood (plasma) was slower in cancer‐bearing mice than in control mice. As expected, the intraperitoneal drug concentration was much higher (approximately 100‐fold) and was maintained for a longer time in the intraperitoneal injection group than in the intravenous injection group. The drug concentrations in peritoneal solid cancer tissue and suspended free cancer cells were also significantly higher for a longer time in the intraperitoneal injection group than in the intravenous injection group. The values of the plasma area under concentration‐time curves (AUC) were similar for both administration routes. The ratio of AUC ascite/AUC plasma after intraperitoneal administration was higher than after intravenous administration. The drug concentration in abdominal organs after intraperitoneal injection was lower during the first 2 h, then became similar to those after intravenous injection. These results indicated that the intraperitoneal administration of docetaxel for peritoneal dissemination was likely to be an effective treatment method, without causing any increase in systemic toxicity.

Spontaneous onset of nonalcoholic steatohepatitis and hepatocellular carcinoma in a mouse model of metabolic syndrome

Metabolic syndrome is a worldwide healthcare issue and a dominant risk factor for the development of incurable diseases that affect the entire body. The hepatic manifestations of this syndrome include nonalcoholic fatty liver disease (NAFLD) and its progressive variant nonalcoholic steatohepatitis (NASH). The basic pathogenesis of NAFLD/NASH remains controversial because it is difficult to clarify the disease process of NASH on the basis of metabolic syndrome alone. To determine the pathogenesis and effective treatment, an excellent animal model of NASH is required. Tsumura Suzuki obese diabetes (TSOD) male mice spontaneously develop diabetes mellitus, obesity, glucosuria, hyperglycemia, and hyperinsulinemia without any special treatments such as gene manipulation. In this study, we examined the histopathological characteristics of visceral fat and liver of 56 male TSOD mice aged 4–17 months and 9 male Tsumura Suzuki non-obesity (control) mice aged 6–12 months. In the visceral fat, enlargement of adipocytes and perivascular and pericapsular CD8-positive lymphoid aggregation were observed in 4-month-old mice. Abnormal expression of tumor necrosis factor-α, interleukin-6, and lipid peroxidation endo products was observed in macrophages. In the liver, microvesicular steatosis, hepatocellular ballooning, and Mallory bodies were observed in 4-month-old mice, with severity worsening with increasing time. These pathological findings in the liver mimic those seen in patients with NASH. Interestingly, small liver nodules with high cellularity and absence of portal tracts were frequently observed after 12 months. Most of them showed nuclear and structural atypia, and mimicked human hepatocellular carcinoma. The degree of steatosis in the non-tumor portions of the liver improved when the liver nodules developed. These findings were not observed in control mice. Here, we report that TSOD male mice spontaneously developed NAFLD without any special treatment, and that these mice are a valuable model for assessing NASH and NASH carcinogenesis owing to metabolic syndrome.

Establishment of Glycosaminoglycan Assays for Mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by deficiency of the lysosomal enzymes essential for catabolism of glycosaminoglycans (GAGs). Accumulation of undegraded GAGs results in dysfunction of multiple organs, resulting in distinct clinical manifestations. A range of methods have been developed to measure specific GAGs in various human samples to investigate diagnosis, prognosis, pathogenesis, GAG interaction with other molecules, and monitoring therapeutic efficacy. We established ELISA, liquid chromatography tandem mass spectrometry (LC-MS/MS), and an automated high-throughput mass spectrometry (HT-MS/MS) system (RapidFire) to identify epitopes (ELISA) or disaccharides (MS/MS) derived from different GAGs (dermatan sulfate, heparan sulfate, keratan sulfate, and/or chondroitin sulfate). These methods have a high sensitivity and specificity in GAG analysis, applicable to the analysis of blood, urine, tissues, and cells. ELISA is feasible, sensitive, and reproducible with the standard equipment. HT-MS/MS yields higher throughput than conventional LC-MS/MS-based methods while the HT-MS/MS system does not have a chromatographic step and cannot distinguish GAGs with identical molecular weights, leading to a limitation of measurements for some specific GAGs. Here we review the advantages and disadvantages of these methods for measuring GAG levels in biological specimens. We also describe an unexpected secondary elevation of keratan sulfate in patients with MPS that is an indirect consequence of disruption of catabolism of other GAGs.