👤 Hitoshi Kitamura

Prosaposin (PSAP) is a highly conserved glycoprotein in vertebrates. It is known to be transported into lysosomes and facilitates lysosomal hydrolysis. In addition, PSAP is secreted in various body fluids, including serum. Extracellular PSAP is known to function as a trophic factor for neurons, and recent studies have revealed that PSAP plays a pivotal role in dopaminergic neuron homeostasis. This study examined PSAP expression in the mouse pituitary gland, which is one of the principal sources of circulating hormones innervated by dopaminergic neurons. In situ hybridization showed that PSAP mRNA expression was high in the intermediate lobe (IL), whereas the expression was relatively low and sparse in the anterior (AL) and posterior lobes (PL). Immunohistochemical analyses showed that PSAP immunoreactivity was detected as fine, granular structures in the AL and IL. PSAP immunoreactivity was also observed in glial cells and the Herring bodies of the PL. The IL is innervated by axons from dopaminergic neurons in the periventricular hypothalamic area, and neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), are known to be highly expressed in the IL, where they support these neurons. The results of this study indicate that PSAP plays a pivotal role in the pituitary gland, particularly within the IL. Show less

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) confer cardio-renal protection, and recent work implicates enhanced branched-chain amino acid (BCAA) catabolism as a potential mechanism in the heart. Whether SGLT2i also promotes renal BCAA catabolism is largely unknown. We hypothesized that SGLT2i enhances renal BCAA catabolism independently of glycemic effects. We conducted a prospective, single-center, open-label, nonrandomized, controlled clinical study in patients with type 2 diabetes stably treated with insulin, who were assigned to dapagliflozin (5 mg/day with dose-reduced insulin; n=8/9 completed) or insulin dose-up (n=5/8 completed). At 12 weeks, changes in urinary and plasma metabolites and short-chain acylcarnitines related to BCAA catabolism were quantified. To explore mechanisms, 10-week-old db/db mice received luseogliflozin (10 mg/kg/day, p.o.) or insulin glargine (10 U/day, s.c.) for 4 weeks; renal histology, mRNA and protein expression of key enzymes involved in BCAA catabolism, including branched-chain aminotransferase 2 (BCAT2), branched-chain ketoacid dehydrogenase (BCKDH), and BCKD kinase (BCKDK), were assessed. Dapagliflozin treatment induced greater increases in urinary excretion of three BCAA-derived metabolites-3-hydroxypropionic acid, C5-OH carnitine, and 3-hydroxybutyric acid-compared with insulin at comparable glycemic levels. In contrast, C4 carnitine (an earlier metabolite in valine catabolism) rose more with insulin. No corresponding between-group differences were detected in plasma metabolites. In db/db mice, luseogliflozin attenuated glomerular mesangial expansion and tubular epithelial atrophy, and reduced Col1a1 mRNA and TGF-β1 protein, compared with glargine at comparable glycemic levels. Luseogliflozin decreased the phosphorylated (inactive) form of the BCKDH E1α subunit (p-BCKDHA/BCKDHA) and lowered BCKDK protein. mRNA expression of amino acid transporters and BCAT2 expression was unchanged. Across complementary human and mouse studies, SGLT2 inhibition was suggested to enhance renal BCAA catabolism compared with insulin at comparable glycemic levels. In humans, increases in urinary BCAA-derived downstream metabolites without corresponding changes in plasma support a kidney-localized metabolic effect. In mice, SGLT2 inhibitor improved renal histopathology, and reduced phosphorylation-mediated inactivation of BCKDH. These findings provide mechanistic, translational evidence that SGLT2i modulate BCAA flux independently of glucose lowering, suggesting BCAA catabolism as a therapeutic axis in diabetic kidney disease. https://rctportal.mhlw.go.jp/en/detail?trial_id=UMIN000052955, identifier UMIN000052955. Show less

Ectopic fat deposition refers to lipid accumulation that affects metabolic function and tissue characteristics. Japanese Black cattle are distinguished by their high intramuscular fat content, which contributes to their distinctive character. However, the genetic mechanisms underlying these traits remain unclear. This study compared gene expression patterns in different muscle regions to identify genes associated with intramuscular fat accumulation. First, we conducted RNA sequencing to analyze differences in gene expression profiles among the sternocleidomastoid, pectoralis minor, and pectoralis major muscles. In addition, single-cell nuclear RNA sequencing was conducted to investigate the cellular composition of these muscle tissues. Distinct gene expression patterns were observed among the different muscles. In the pectoralis, which contains a high proportion of intramuscular fat, adipocyte-related genes such as This study provides novel insight into the genetic regulation of intramuscular fat accumulation. It improves our understanding of the molecular mechanisms underlying their distinctive meat characteristics. Show less

MYD88 p.L265P mutation occurs in over 90% of Waldenström's macroglobulinemia (WM), which is characterized by lymphoplasmacytic lymphoma (LPL) with monoclonal IgM. WM requires careful diagnosis due to overlapping features with other B-cell malignancies. Bing-Neel syndrome (BNS), a rare complication of WM, involves central nervous system (CNS) invasion. This report describes two cases of morphologically low-grade B-cell lymphoma in the bone marrow accompanied by the presence of a large B-cell lymphoma in the brain and a common MYD88 p.L265P mutation, which were eventually established as BNS mimickers. Although the two components in these cases showed the same identical light-chain restriction, different immunoglobulin heavy-chain rearrangement peaks indicated distinct lymphoma stem cells for CNS and bone marrow lesions. These clinical cases emphasize the challenges in diagnosing BNS. Based on the findings, biopsy is recommended for accurate identification of the clonal relationship and MYD88 mutation status. Show less

Dysregulation of glucagon is associated with the pathophysiology of type 2 diabetes. We previously reported that postprandial hyperglucagonemia is more obvious than fasting hyperglucagonemia in type 2 diabetes patients. However, which nutrient stimulates glucagon secretion in the diabetic state and the underlying mechanism after nutrient intake are unclear. To answer these questions, we measured plasma glucagon levels in diabetic mice after oral administration of various nutrients. The effects of nutrients on glucagon secretion were assessed using islets isolated from diabetic mice and palmitate-treated islets. In addition, we analyzed the expression levels of branched chain amino acid (BCAA) catabolism-related enzymes and their metabolites in diabetic islets. We found that protein, but not carbohydrate or lipid, increased plasma glucagon levels in diabetic mice. Among amino acids, BCAAs, but not the other essential or nonessential amino acids, increased plasma glucagon levels. BCAAs also directly increased the intracellular calcium concentration in α cells. When BCAAs transport was suppressed by an inhibitor of system L-amino acid transporters, glucagon secretion was reduced even in the presence of BCAAs. We also found that the expression levels of BCAA catabolism-related enzymes and their metabolite contents were altered in diabetic islets and palmitate-treated islets compared to control islets, indicating disordered BCAA catabolism in diabetic islets. Furthermore, BCKDK inhibitor BT2 suppressed BCAA-induced hypersecretion of glucagon in diabetic islets and palmitate-treated islets. Taken together, postprandial hypersecretion of glucagon in the diabetic state is attributable to disordered BCAA catabolism in pancreatic islet cells. Show less

Biomarkers of Alzheimer's disease (AD) that can easily be measured in routine health checkups are desirable. Urine is a source of biomarkers that can be collected easily and noninvasively. We previously reported on the comprehensive profile of the urinary proteome of AD patients and identified proteins estimated to be significantly increased or decreased in AD patients by a label-free quantification method. The present study aimed to validate urinary levels of proteins that significantly differed between AD and control samples from our proteomics study (i.e., apolipoprotein C3 [ApoC3], insulin-like growth factor-binding protein 3 [Igfbp3], and apolipoprotein D [ApoD]). Enzyme-linked immunosorbent assays (ELISAs) were performed using urine samples from the same patient and control groups analyzed in the previous proteomics study (18 AD and 18 controls, set 1) and urine samples from an independent group of AD patients and controls (13 AD, 5 mild cognitive impairment [MCI], and 32 controls) from the National Center for Geriatrics and Gerontology Biobank (set 2). In set 1, the crude urinary levels of ApoD, Igfbp3, and creatinine-adjusted ApoD were significantly higher in the AD group relative to the control group ( ApoC3 may be a potential biomarker for AD, as validated by ELISA. Further analysis of ApoC3 as a urinary biomarker for AD is warranted. Show less

Brahma-related gene 1 (BRG1), an ATPase subunit of the SWItch/sucrose non-fermentable (SWI/SNF) chromatin remodeling complex controls multipotent neural crest formation by regulating epithelial-mesenchymal transition (EMT)-related genes with adenosine triphosphate-dependent chromodomain-helicase DNA-binding protein 7 (CHD7). The expression of BRG1 engages in pre-mRNA splicing through interacting RNPs in cancers; however, the detailed molecular pathology of how BRG1and CHD7 relate to cancer development remains largely unveiled. This study demonstrated novel post-transcriptional regulation of BRG1 in EMT and relationship with FIRΔexon2, which is a splicing variant of the far-upstream element-binding protein (FUBP) 1-interacting repressor (FIR) lacking exon 2, which fails to repress c-myc transcription in cancers. Previously, we have reported that FIR complete knockout mice (FIR Show less

A 67-year-old female was referred to our hospital with a sternal fracture in March 2008. She received a diagnosis of multiple myeloma (MM) BJP-κ type (ISS stage III). G-banding karyotype revealed 46, XX, t(11;22)(q23.3;q11.2) (Hubacek, Gene 592:193-9, 2016), which was later confirmed to be congenital. After repeated rounds of chemotherapy with bortezomib and lenalidomide, she obtained a very good partial response in August 2014, and she was followed up with no treatment. However, she relapsed in February 2016. At that time, fluorescence in situ hybridization identified del(13q) and t(4;14)(p16;q32), which are associated with a poor prognosis. Furthermore, PCR analysis showed that the chromosome 11 breakpoint was at the APOA5/APOA4 locus at 11q23.3, which is associated with malignancy, and that the chromosome 22 breakpoint was at the SEPT5 intron 1 locus, which also plays a role in leukemogenesis through formation of a fusion gene with MLL. Although she was treated with three further lines of therapy, she died from disease progression in August 2017. Synergism between t(11;22) and t(4;14) may have induced the double-refractory phenotype to proteasome inhibitor and lenalidomide, at least during the chemorefractory phase. We present a biological analysis of this case and a review of the literature. Show less

Alzheimer's disease (AD) is the most common cause of dementia in elderly persons. Since the pathology of AD develops slowly from a preclinical or early phase into a fully expressed clinical syndrome, at the time of diagnosis the disease has been progressing for many years. To facilitate the early diagnosis of AD, we performed protein profiling of blood in patients with mild AD as defined by the Functional Assessment Staging (FAST) scale. Plasma samples from mild AD patients and healthy controls were analyzed using two-dimensional differential gel electrophoresis (2D-DIGE) combined with matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF/MS) followed by peptide mass fingerprinting. Three downregulated proteins were identified: apolipoprotein A-1, alpha-2-HS-glycoprotein, and afamin. Two proteins, including apolipoprotein A-4 and fibrinogen gamma chain, were upregulated in mild AD patients. Our results suggest that altered expression levels of these proteins in plasma may yield candidate biomarkers for the early diagnosis of AD. AD, Alzheimer's disease; FAST, Functional Assessment Staging; 2D-DIGE, two-dimensional differential gel electrophoresis; MALDI-TOF/TOF/MS, matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry; CSF, cerebrospinal fluid; Aβ, amyloid beta; MMSE, Mini Mental State Examination; MRI, magnetic resonance imaging; NINCDS-ADRDA, National Institute for Neurological Diseases and Stroke/Alzheimer's Disease and Related Disorders Association; CHAPS, 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate; DTT, dithiothreitol; SDS-PAGE, SDS-polyacrylamide gel electrophoresis; DIA, differential in-gel analysis; BVA, biological variation analysis; CBB, Coomassie brilliant blue; 2DE, two-dimensional gel electrophoresis; TFA, trifluoroacetic acid; ACTH, adrenocorticotropic hormone; Apo A-1, apolipoprotein A-1; AHSG, alpha-2-HS-glycoprotein; Apo A-4, apolipoprotein A-4; MCI, mild cognitive impairment. Show less

In liver, glucose utilization and lipid synthesis are inextricably intertwined. When glucose availability exceeds its utilization, lipogenesis increases, leading to increased intrahepatic lipid content and lipoprotein secretion. Although the fate of three-carbon metabolites is largely determined by flux rate through the relevant enzymes, insulin plays a permissive role in this process. But the mechanism integrating insulin receptor signaling to glucose utilization with lipogenesis is unknown. Forkhead box O1 (FoxO1), a downstream effector of insulin signaling, plays a central role in hepatic glucose metabolism through the regulation of hepatic glucose production. In this study, we investigated the mechanism by which FoxO1 integrates hepatic glucose utilization with lipid synthesis. We show that FoxO1 overexpression in hepatocytes reduces activity of carbohydrate response element binding protein (Chrebp), a key regulator of lipogenesis, by suppressing O-linked glycosylation and reducing the protein stability. FoxO1 inhibits high glucose- or O-GlcNAc transferase (OGT)-induced liver-pyruvate kinase (L-PK) promoter activity by decreasing Chrebp recruitment to the L-PK promoter. Conversely, FoxO1 ablation in liver leads to the enhanced O-glycosylation and increased protein level of Chrebp owing to decreased its ubiquitination. We propose that FoxO1 regulation of Chrebp O-glycosylation is a mechanism linking hepatic glucose utilization with lipid synthesis. Show less

Our preliminary studies revealed that oncogenic KRAS (KRAS/V12) dramatically suppressed the growth of immortalized airway epithelial cells (NHBE-T, with viral antigen-inactivated p53 and RB proteins). This process appeared to be a novel event, different from the so-called premature senescence that is induced by either p53 or RB, suggesting the existence of a novel tumor suppressor that functions downstream of oncogenic KRAS. After a comprehensive search for genes whose expression levels were modulated by KRAS/V12, we focused on DUSP6, a pivotal negative feedback regulator of the RAS-ERK pathway. A dominant-negative DUSP6 mutant, however, failed to rescue KRAS/V12-induced growth suppression, but conferred a stronger anchorage-independent growth activity to the surviving subpopulation of cells generated from KRAS/V12-transduced NHBE-T. DUSP6 expression levels were found to be weaker in most lung cancer cell lines than in NHBE-T, and DUSP6 restoration suppressed cellular growth. In primary lung cancers, DUSP6 expression levels decreased as both growth activity and histological grade of the tumor increased. Loss of heterozygosity of the DUSP6 locus was found in 17.7% of cases and was associated with reduced expression levels. These results suggest that DUSP6 is a growth suppressor whose inactivation could promote the progression of lung cancer. We have here identified an important factor involved in carcinogenesis through a comprehensive search for downstream targets of oncogenic KRAS. Show less

COUP-TFII has an important role in regulating metabolism in vivo. We showed this previously by deleting COUP-TFII from pancreatic beta cells in heterozygous mutant mice, which led to abnormal insulin secretion. Here, we report that COUP-TFII expression is reduced in the pancreas and liver of mice refed with a carbohydrate-rich diet and in the pancreas and liver of hyperinsulinemic and hyperglycemic mice. In pancreatic beta cells, COUP-TFII gene expression is repressed by secreted insulin in response to glucose through Foxo1 signaling. Ex vivo COUP-TFII reduces insulin production and secretion. Our results suggest that beta cell insulin secretion is under the control of an autocrine positive feedback loop by alleviating COUP-TFII repression. In hepatocytes, both insulin, through Foxo1, and high glucose concentrations repress COUP-TFII expression. We demonstrate that this negative glucose effect involves ChREBP expression. We propose that COUP-TFII acts in a coordinate fashion to control insulin secretion and glucose metabolism. Show less

The onset of leukaemia caused by type C retroviruses (MLV) in mice is accelerated by the emergence of recombinant polytropic or mink cell focus-forming (MCF) viruses. Susceptibility to infection by polytropic/MCF and also by closely related xenotropic MLV has been mapped to Rmc1 on mouse chromosome 1 (refs 5-7). To identify this gene, we introduced an expression cDNA library prepared from mouse NIH3T3 fibroblasts into nonpermissive hamster cells and screened these cells for acquired susceptibility to MCF viruses encoding beta-galactosidase and G418 resistance. From hamster cell clones identified in the screen, we recovered a mouse cDNA that maps to Rmc1 and confers MCF MLV infection when expressed in nonpermissive cell lines. It encodes a membrane protein related to Syg1p (suppressor of yeast G alpha deletion; ref. 8). The receptor-binding domain of the MCF MLV envelope protein binds specifically to Xenopus laevis oocytes that express mouse Syg1, suggesting it functions as a receptor that mediates virus entry. We also obtained the cDNA encoding human SYG1. When expressed in hamster cells, it establishes infectivity by MCF MLV as well as xenotropic MLV, which do not infect laboratory mice. Show less

The c-kit protooncogene is a transmembrane tyrosine kinase receptor expressed during gametogenesis. Using the polymerase chain reaction (PCR), we have identified the c-kit receptor mRNA transcripts in the rat testis and studied their expression during postnatal development of the testis. Five different transcripts were identified using sets of primers encoding within the extracellular domain. Two transcripts were obtained from primer sets encoding regions within the cytoplasmic domain and the primer set encoding the entire length of the c-kit receptor. We have compared the levels of expression of these transcripts on different days during postnatal development. The level of expression of a particular transcript varied depending upon the developmental stage of the testis. In summary, our results suggest that multiple forms of mRNAs exist for the c-kit receptor in the rat testis, and they are regulated differentially during postnatal development. Show less