Basic and clinical research for Endocrine and Metabolic disorders by a clinician

In our country, the management of lifestyle-related diseases and muscloskeletal disorders in becoming more important with the rapidly advancing aging society. I have conducted both basic and clinical research that could contribute to the amelioration of these diseases from the point of view of a clinician. Specifically, I have identified that skeletal muscle differentiation and developmental abnormalities in vitamin D receptor knockout mice, activated calcium-sensing receptor knock-in mice showed various metabolic abnormalities, regulation of stem cell differentiation by IL-11 and so on. We also conducted nationwide survey of fibroblast growth factor 23-related hypophosphatemic diseases to clarify the prevalence and the clinical presentations of the disorders. In this review, I show an overview of my research works, also including the relation to the latest findings

Osteoporosis : from pathophysiology to therapeutic approach

Osteoporosis is defined as a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Men as well as women are affected by osteoporosis, a disease that can be prevented and treated. In Japan, around １３ milion people already have osteoporosis or are high risk due to low bone mass. Hip and spine fractures are linked with increased mortality, and all fractures may lead to disability and reduced quality of life. Antiresorptive agents for osteoporosis are a cornerstone of therapy, and anabolic drugs have recently increased our options. Treatment of osteoporosis most commonly involves lifestyle changes and medications and aims to maximise bone density and reduce the risk of bone fracture

Compensatory Thrombopoietin Production from the Liver and Bone Marrow Stimulates Thrombopoiesis of Living Rat Megakaryocytes in Chronic Renal Failure

Background/Aims: Decreased thrombopoiesis has been ascribed a role in the pathogenesis of uremic bleeding in chronic renal failure (CRF). However, serum thrombopoietin (TPO) levels are usually elevated in CRF patients, suggesting increased thrombopoiesis. The aim of this study was to determine the thrombopoietic activity in CRF. Methods: Male Sprague-Dawley rats that underwent 5/6 nephrectomy were used as the model of CRF. Age-matched sham-operated rats were used as controls. Single megakaryocytes were isolated from the rat bone marrow, and their size distribution was examined. Megakaryocyte membrane invaginations were monitored by confocal imaging of di-8-ANEPPS staining, and patch clamp whole-cell recordings of membrane capacitance. TPO gene expression was assessed in various tissues. Results: Circulating platelet counts and the number of large megakaryocytes were increased in the bone marrow of CRF rats. Massive di-8-ANEPPS staining and increased membrane capacitance in large megakaryocytes demonstrated increased membrane invaginations. Unaffected Kv1.3-channel currents per cell surface area demonstrated unaltered channel densities. TPO transcription was decreased in the renal cortex but increased in the liver and bone marrow of CRF rats. Conclusion: Increased thrombopoiesis in CRF was thought to be a reactive mechanism to platelet dysfunction. Increased TPO production from the liver and bone marrow compensated for decreased production from damaged kidneys

Skeletal FGFR1 signaling is necessary for regulation of serum phosphate level by FGF23 and normal life span

Fibroblast growth factor (FGF) 23 produced by the bone is the principal hormone to regulate serum phosphate level. Serum FGF23 needs to be tightly regulated to maintain serum phosphate in a narrow range. Thus, we hypothesized that the bone has some phosphate-sensing mechanism to regulate the production of FGF23. Previously we showed that extracellular phosphate induces the phosphorylation of FGF receptor 1 (FGFR1) and FGFR1 signaling regulates the expression of Galnt3, whose product works to increase FGF23 production in vitro. In this study, we show the significance of FGFR1 in the regulated FGF23 production and serum phosphate level in vivo. We generated late-osteoblast/osteocyte-specific Fgfr1-knockout mice (Fgfr1fl/fl; OcnCre/+) by crossing the Ocn-Cre and the floxed Fgfr1 mouse lines. We evaluated serum phosphate and FGF23 levels, the expression of Galnt3 in the bone, the body weight and life span. A selective ablation of Fgfr1 aborted the increase of serum active full-length FGF23 and the enhanced expression of Galnt3 in the bone by a high phosphate diet. These mice showed more pronounced hyperphosphatemia compared with control mice. In addition, these mice fed with a control diet showed body weight loss after 23 weeks of age and shorter life span. These results reveal a novel significance of FGFR1 signaling in the phosphate metabolism and normal life span

A case of isolated ACTH deficiency that required 6 months for the diagnosis from onset

A 53-year-old man noticed anorexia, nausea, and arthralgia of the upper limbs in April, 201X. Since these symptoms persisted, he visited general hospital and clinic and was examined for blood chemistry, ECG, echocardiography and so on. However, he did not get a definitive diagnosis and was followed up with drip infusion of saline. The symptoms did not subside and fatigue and syncope with hypotension developed. Furthermore, he also suffered weight loss of 10 kg in few months and was referred to our hospital for more detailed examinations in October, 201X. Upon the initial examination, all his symptoms matched those of adrenal insufficiency and notable decreases of both plasma ACTH and serum cortisol level were observed. Prompt glucocorticoid supplementation improved his symptoms and the abnormal laboratory data immediately. He was diagnosed adrenal insufficiency due to isolated ACTH deficiency from the results of CRH loading test and insulin tolerance test. Since most of the symptoms and laboratory findings are non-specific, diagnosis of adrenal insufficiency is often delayed. However, adrenal insufficiency could worsen when the patient is under stress (e.g. infection) and often be life-threatening. Glucocorticoid replacement therapy should be initiated as soon as the diagnosis is confirmed. Furthermore, educating patients and his families plays a very important role in the management of chronic adrenal insufficiency, in particular to the prevention of adrenal crisis

Basal insulin ratio of type 1 diabetes

Aims/Introduction: To investigate the basal insulin requirement in patients with type 1 diabetes who are on multiple daily injections (MDI) and to assess the patient characteristics that affect the percent of total daily basal insulin dose to the total daily insulin dose (%TBD/TDD). Materials and Methods: The subjects of this study were 67 inpatients with type 1 diabetes who were served diabetic meals of 25–30 kcal/kg standard body weight during several weeks of hospitalization. The basal insulin requirement was adjusted to keep the blood glucose level from bedtime to before breakfast within a 30 mg/dL difference. The bolus insulin dose before the meal was adjusted to keep the blood glucose level below 140 and 200 mg/dL before and 2 h after each meal, respectively. The total daily insulin dose (TDD), the percent of total daily basal insulin dose (TBD) to TDD (%TBD/TDD), and clinical characteristics were collected. Results: The median (Q1, Q3) of TDD was 33.0 (26.0, 49.0) units, and the %TBD/TDD was 24.1 ± 9.8%. The %TBD/TDD was positively correlated with the body mass index (BMI) and negatively correlated with the age at the onset and at the examination according to a univariate analysis. However, the %TBD/TDD was dependent on the BMI (β = 0.340, P = 0.004) and the age at examination (β = −0.288, P = 0.012) according to the multiple regression analysis. Conclusions: The average %TBD/TDD in patients with type 1 diabetes on MDI was approximately 24% under inpatient conditions. The basal insulin requirement was dependent on the BMI and the age at examination

Mechanical Stress Activates Smad Pathway through PKCδ to Enhance Interleukin-11 Gene Transcription in Osteoblasts

BACKGROUND: Mechanical stress rapidly induces ΔFosB expression in osteoblasts, which binds to interleukin (IL)-11 gene promoter to enhance IL-11 expression, and IL-11 enhances osteoblast differentiation. Because bone morphogenetic proteins (BMPs) also stimulate IL-11 expression in osteoblasts, there is a possibility that BMP-Smad signaling is involved in the enhancement of osteoblast differentiation by mechanical stress. The present study was undertaken to clarify whether mechanical stress affects BMP-Smad signaling, and if so, to elucidate the role of Smad signaling in mechanical stress-induced enhancement of IL-11 gene transcription. METHODOLOGY/PRINCIPAL FINDINGS: Mechanical loading by fluid shear stress (FSS) induced phosphorylation of BMP-specific receptor-regulated Smads (BR-Smads), Smad1/5, in murine primary osteoblasts (mPOBs). FSS rapidly phosphorylated Y311 of protein kinase C (PKC)δ, and phosphorylated PKCδ interacted with BR-Smads to phosphorylate BR-Smads. Transfection of PKCδ siRNA or Y311F mutant PKCδ abrogated BR-Smads phosphorylation and suppressed IL-11 gene transcription enhanced by FSS. Activated BR-Smads bound to the Smad-binding element (SBE) of IL-11 gene promoter and formed complex with ΔFosB/JunD heterodimer via binding to the C-terminal region of JunD. Site-directed mutagenesis in the SBE and the AP-1 site revealed that both SBE and AP-1 sites were required for full activation of IL-11 gene promoter by FSS. CONCLUSIONS/SIGNIFICANCE: These results demonstrate that PKCδ-BR-Smads pathway plays an important role in the intracellular signaling in response to mechanical stress, and that a cross-talk between PKCδ-BR-Smads and ΔFosB/JunD pathways synergistically stimulates IL-11 gene transcription in response to mechanical stress

Adult onset IgAV

Immunoglobulin A vasculitis (IgAV), formerly known as Henoch-Schönlein purpura, primarily occurs during childhood between the ages of 3 and 15 years and is the most common form of systemic vasculitis in children ; its occurrence in adults has been rarely reported. Such low incidence could be attributable to either under-diagnosis or misdiagnosis. Thus, not only pediatricians but also physicians should be able to diagnose IgAV accurately to manage the patients appropriately and avoid its associated complications. In addition, treatment of adult onset IgAV with renal involvement has not been fully established yet. We describe here a case of adult onset IgAV complicated by proteinuria and pharyngitis, which was cured by no specific treatment