👤 Makoto Okawa

Cerebrotendinous xanthomatosis is a rare autosomal recessive lipid storage disorder involving bile acid biosynthesis. Reduced mitochondrial cytochrome P450 enzyme activity leads to abnormal lipid accumulation in various tissues, especially tendons, lenses, and the central and peripheral nervous systems. This condition manifests with systemic symptoms such as neurological disorders, atherosclerosis, tendon xanthomas, and cataracts. Cerebrotendinous xanthomatosis typically presents in individuals with homozygous or compound heterozygous mutations in the CYP27A1 gene because of its autosomal recessive inheritance pattern. However, the phenotypic expression in heterozygous carriers remains uncertain. We report a 53-year-old Japanese man who was clinically diagnosed with familial hypercholesterolemia. He presented with marked Achilles tendon xanthomas and refractory hyper-low-density-lipoprotein cholesterolemia. Initiation of intensified lipid-lowering therapy, including inclisiran, resulted in improvement of hyper-low-density-lipoprotein cholesterolemia. Genetic testing revealed heterozygous mutations in CYP27A1 (p.Arg405Gln) and apolipoprotein B (APOB) (p.Pro955Ser). He had no neurological symptoms, cataracts, or other features suggestive of cerebrotendinous xanthomatosis without Achilles tendon xanthomas. This case highlights a rare presentation of a potential CYP27A1 heterozygous mutation-related phenotype. The APOB (p.Pro955Ser) variant is associated with reduced low-density-lipoprotein receptor activity, contributing to hyper-low-density-lipoprotein cholesterolemia and Achilles tendon xanthomas. However, this patient's Achilles tendon xanthoma was thicker than those reported in previous cases with APOB (p.Pro955Ser) gene mutations, suggesting a potential contribution from the CYP27A1 mutation. Although the patient did not exhibit elevated serum cholestanol levels or other cerebrotendinous xanthomatosis features, the marked Achilles tendon thickening raises the possibility that the combination of a heterozygous CYP27A1 gene mutation and an APOB gene mutation contributed to the condition. Show less

Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus that is associated with long-term morbidity and mortality. Pathomorphological findings of LN are broadly divided into proliferative lupus nephritis (PLN) and membranous lupus nephritis (MLN). PLN is characterized by diffuse global or segmental proliferative glomerulonephritis with significant infiltration of inflammatory cells. Type 1 T-helper (Th1) cells, which predominate under inflammatory conditions, and NETosis, as the process of forming neutrophil extracellular traps (NETs), are key factors in the development of PLN. Meanwhile, MLN is characterized by diffuse membranous nephropathy (MN) with global granular subepithelial immune deposits. MLN patients usually experience massive proteinuria, and occasionally show an unfavorable renal prognosis despite aggressive treatment, similar to PLN patients. Intriguingly, in some instances, MLN patients do not show the general immunoserological characteristics of SLE, such as low serum complement and elevated anti-DNA antibody titers. Several reports have indicated an association between Th2 cell dominance and the development of MLN. Moreover, exostosin 1 (EXT1) and exostosin 2 (EXT2) on the glomerular basement membrane have recently been discovered as novel putative antigens for secondary MN, and have been shown to be up-regulated in patients with MLN. To date, many studies have focused on the dissimilarities between PLN and MLN. However, the reason for two polar morphological forms existing within the same disease is not completely clear. The present review addresses published observations on this topic in addition to providing our assertion regarding characteristic NETosis and glomerular EXT1/EXT2 expressions between PLN and MLN. Show less

Gastric inhibitory polypeptide (GIP) is an incretin secreted from the gastrointestinal tract after an ingestion of nutrients, and stimulates an insulin secretion from the pancreatic islets. Additionally, GIP has important roles in extrapancreatic tissues: fat accumulation in adipose tissue, neuroprotective effects in the central nervous system and an inhibition of bone resorption. In the current study, we investigated the effects of GIP signaling on the peripheral nervous system (PNS). First, the presence of the GIP receptor (GIPR) in mouse dorsal root ganglion (DRG) was evaluated utilizing immunohistochemical analysis, western blotting and reverse transcription polymerase chain reaction. DRG neurons of male wild-type mice (WT) were cultured with or without GIP, and their neurite lengths were quantified. Functions of the PNS were evaluated in GIPR-deficient mice (gipr-/-) and WT by using current perception thresholds (CPTs), Thermal Plantar Test (TPT), and motor (MNCV) and sensory nerve conduction velocity (SNCV, respectively). Sciatic nerve blood flow (SNBF) and plantar skin blood flow (PSBF) were also evaluated. We confirmed the expression of GIPR in DRG neurons. The neurite outgrowths of DRG neurons were promoted by the GIP administrations. The gipr-/- showed impaired perception functions in the examination of CPTs and TPT. Both MNCV and SNCV were delayed in gipr-/- compared with these in WT. There was no difference in SNBF and PSBF between WT and gipr-/-. Our findings show that the GIP signal could exert direct physiological roles in the PNS, which might be directly exerted on the PNS. Show less

Hypertrophic cardiomyopathy (HCM) is a primary myocardial disorder with an autosomal-dominant pattern of inheritance mainly caused by single heterozygous mutations in sarcomere genes. Although multiple gene mutations have recently been reported in Western countries, clinical implications of multiple mutations in Japanese subjects are not clear. A comprehensive genetic analysis of 5 sarcomere genes (cardiac β-myosin heavy chain gene [MYH7], cardiac myosin-binding protein C gene [MYBPC3], cardiac troponin T gene [TNNT2], α-tropomyosin gene [TPM1] and cardiac troponin I gene [TNNI3]) was performed in 93 unrelated patients and 14 mutations were identified in 28 patients. Twenty-six patients had single heterozygosity (20 in MYBPC3, 4 in MYH7, 1 in TNNT2, 1 in TNNI3), whereas 2 proband patients with familial HCM had double heterozygosity: 1 with P106fs in MYBPC3 and R869C in MYH7 and 1 with R945fs in MYBPC3 and E1049D in MYH7. From the results of the family survey and the previous literature on HCM mutations, P106fs, R945fs and R869C seemed to be pathological mutations and E1049D might be a rare polymorphism. The proband patient with P106fs and R869C double mutation was diagnosed as having HCM at an earlier age (28 years of age) than her relatives with single mutation, and had greater wall thickness with left ventricular outflow obstruction. One double mutation was identified in a Japanese cohort of HCM patients. Further studies are needed to clarify the clinical significance of multiple mutations including phenotypic severity. Show less

Mutations in the cardiac myosin-binding protein C gene (MYBPC3) have been reported to be associated with delayed expression of hypertrophic cardiomyopathy (HCM) and a relatively good prognosis. The aim of this study was to evaluate clinical manifestations in patients with familial HCM caused by a novel nonsense mutation, S297X, in MYBPC3. We analyzed the sarcomere protein genes in 93 probands with HCM. The nonsense mutation S297X in MYBPC3 was present in nine subjects from two unrelated families. Eight of those nine subjects with this mutation were found to be phenotype-positive and the remaining individual was not affected phenotypically. The age range at diagnosis was 9-75 years. There was no family history of sudden death in either family. At presentation, there were various left ventricular hypertrophy (LVH) patterns, including Maron type III hypertrophy from the LV base to apex, hypertrophy confined to the anterolateral wall at the basal LV wall. Two patients showed a significant LV outflow tract gradient and one patient showed intra-right-ventricular obstruction. During follow-up, one patient was repeatedly hospitalized for the treatment of heart failure after development of paroxysmal atrial fibrillation at the age of 86 years and the remaining eight subjects were in relatively stable condition and did not require hospitalization for the treatment of HCM-related events. The novel mutation S297X in MYBPC3 causes HCM in a broad range of ages and heterogeneous clinical manifestations, though the clinical course in patients with this mutation seems to be benign. Show less