Ryo Okazaki

Association between activating mutations of calcium-sensing receptor and Bartter's syndrome

Bartters syndrome is a heterogeneous disorder characterised by deficient renal reabsorption of sodium and chloride, and hypokalaemic metabolic alkalosis with hyper-reninaemia and hyperaldosteronaemia. Mutations in several ion transporters and channels have been associated with the pathogenesis of Bartters syndrome. We describe two hypocalcaemic patients with deficient parathyroid hormone secretion who also showed characteristics of Bartters syndrome. We found activating mutations of the gene for the calcium-sensing receptor (CASR) in both patients. Activation of this calcium-sensing receptor inhibits the activity of a renal outer-medullary potassium channel that is mutated in type 2 Bartters syndrome. We therefore suggest that some activating mutations of CASR could provide new mechanisms for the development of Bartters syndrome.

Estrogen Promotes Early Osteoblast Differentiation and Inhibits Adipocyte Differentiation in Mouse Bone Marrow Stromal Cell Lines that Express Estrogen Receptor (ER) α or β

Although cells of the osteoblast lineage express functional ERs, direct effects of estrogen on bone formation remain obscure. In the present study, we have investigated estrogen effects on osteoblastic and adipocytic differentiation from a mouse bone marrow stromal cell line, ST-2, which had been manipulated to overexpress either human ER (ST2ER )o r ER (ST2ER). Treatment with bone morphogenetic protein-2 increased alkaline phosphatase activity as well as the number of Oil Red O-positive adipocytes, indicating that bone morphogenetic protein-2 stimulated both osteoblastic and adipocytic differentiation from these bipotential cells. In both ST2ER and ST2ER cells, cotreatment with E2 caused enhancement of alkaline phosphatase activity and suppression of lipid accumulation. These effects were completely reversed by an ER antagonist, ICI182780. Therefore, the estrogen regulation occurred in an ER-specific manner but without ER subtype specificity. Moreover, dose response curves of the opposing effects of estrogen on osteoblastogenesis and adipogenesis formed an apparent mirror image, consistent with a reciprocal regulation of differentiation into the two cell lineages. These results demonstrate that estrogen directly modulates differentiation of bipotential stromal cells into the osteoblast and adipocyte lineages, causing a lineage shift toward the osteoblast. Such effects would lead to direct stimulation of bone formation and thereby contribute to the protective effects of estrogen on bone. (Endocrinology 143: 2349 –2356, 2002)

Thiazolidinediones inhibit osteoclast-like cell formation and bone resorption in vitro.

Osteoblasts and adipocytes are derived from common bone marrow stromal cells that play crucial roles in the generation of osteoclasts. Activation of peroxisome proliferator-activated receptor-gamma (PPARgamma) induces adipogenic differentiation of stromal cells; however, whether this would affect osteoblast/osteoclast differentiation is unknown. Thus, we examined the effects of the thiazolidinedione (TZD) class of antidiabetic agents that activate PPARgamma on osteoblast/osteoclast differentiation using mouse whole bone marrow cell culture. As reported, all TZDs we tested (troglitazone, pioglitazone, and BRL 49653) markedly increased the number of Oil Red O-positive adipocytes and the expression of adipsin and PPARgamma 2. 1alpha,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] did not affect adipogenic differentiation induced by TZDs. TZDs did not affect alkaline phosphatase activity, an early marker of osteoblastic differentiation, despite their marked adipogenic effects. TZDs decreased the number of tartrate-resistant acid phosphatase-positive multinucleated osteoclast-like cells induced by 1,25-(OH)2D3 or PTH. Troglitazone dose dependently inhibited basal and 1,25-(OH)2D3- and PTH-induced bone resorption as assessed by pit formation assay. Interleukin-11 blocked the induction by troglitazone of adipogenesis, but had no effect on the inhibition of osteoclast-like cell formation. These results indicate that TZDs are potent inhibitors of bone resorption in vitro. Inhibitory effects of TZDs on osteoclastic bone resorption was not osteotropic factor specific and did not appear to be related to their adipogenic effects. Thus, TZDs may suppress bone resorption in diabetic patients and prevent bone loss.

Close Relationship of Abnormal Glucose Tolerance With Endothelial Dysfunction in Hypertension

Hypertension is frequently accompanied by left ventricular hypertrophy, endothelial dysfunction, and abnormal glucose metabolism. However, no study has examined the relative pathological significance of left ventricular hypertrophy and abnormal glucose metabolism on endothelial dysfunction in hypertension. This study was conducted to evaluate whether abnormal glucose tolerance assessed by 75-g oral glucose tolerance test or left ventricular hypertrophy is more closely associated with endothelial dysfunction in never-treated hypertensive patients without elevated fasting blood glucose. We studied 107 unmedicated hypertensive patients (mean age, 54+/-10 years) whose fasting blood glucose was <7.0 mmol/L. Endothelial function was assessed by change in brachial artery diameter in response to reactive hyperemia, and left ventricular mass index was determined by ultrasonography. Simple linear regression analysis demonstrated that endothelial function significantly correlated with left ventricular mass index and 2-hour blood glucose in 75-g oral glucose tolerance test, but not with fasting blood glucose. Multiple linear regression analysis revealed that endothelial function significantly correlated with 2-hour blood glucose (beta=-2.68, P<0.05) after we controlled for other clinical variables. Patients were divided into 3 groups according to 2-hour blood glucose levels. Endothelial function was more impaired in patients with diabetes (n=12; 4.7+/-1.8%) and in those with impaired glucose tolerance (n=31; 6.3+/-2.9%) than in those with normal glucose tolerance (n=64; 8.4+/-4.5%) (P<0.05), but left ventricular mass index was similar in these 3 groups. Abnormal glucose tolerance assessed by 75-g oral glucose tolerance test, rather than left ventricular hypertrophy, may have direct pathophysiological relevance to endothelial dysfunction in borderline to moderate hypertensive patients.

Inactivating mutations of calcium-sensing receptor results in parathyroid lipohyperplasia.

Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominant disease characterized by mild hypercalcemia, an inappropriately high parathyroid hormone level, and absence of hypercalciuria. Heterozygous inactivating mutations of calcium-sensing receptor (CaSR) are found in about two thirds of patients with FHH. Histologic examination of parathyroid glands in FHH is reported to show normal histology or chief cell hyperplasia. Thus, histologic features of the parathyroid glands in FHH vary, and there is no clear histologic criterion that indicates FHH. The authors have encountered three hypercalcemic patients with characteristic histologic features of enlarged parathyroid glands. Clusters of parenchymal cells were mixed with fat cells, and the area of fat cells was 33% to 49% of the total area. These features are similar to those described as parathyroid lipohyperplasia. Postoperative evaluation showed that fractional excretion of calcium was low in these patients. Direct sequencing of the polymerase chain reaction product showed that the first patient was heterozygous for an already reported inactivating mutation of CaSR (P55L). The second patient was also heterozygous for a novel inactivating mutation (R220W). The third was homozygous for an inactivating mutation (Q27R). These results indicate that histologic features of parathyroid lipohyperplasia suggest the presence of inactivating mutations of CaSR.

Ethanol Stimulates Glycogenolysis and Inhibits both Glycogenesis via Gluconeogenesis and from Exogenous Glucose in Perfused Rat Liver

Aims: Although it is commonly recognized that ethanol suppresses gluconeogenesis, the influence of alcohol intake on blood glucose levels remains controversial. Ethanol may act on both glucose production and glucose consumption in the liver. Thus, we studied each effect of ethanol on glucose oxidation, gluconeogenesis, glycogenesis and glycogenolysis in the liver. Methods: The rat liver was isolated and cyclically perfused with a medium containing 50 mmol/l ethanol. Results: Ethanol enhanced 14C-glucose oxidation in the liver from 1.09 ± 0.11 to 1.41 ± 0.14 µmol for 20 min (p < 0.05). Gluconeogenesis from 14C-lactate was markedly reduced by ethanol from 8.0 ± 1.3 to 1.5 ± 0.6 µmol for 12 min (p < 0.01). Ethanol increased glycogenolysis (net hepatic glucose output, 0.47 ± 0.10 vs. 0.22 ± 0.04 mmol/30 min, p < 0.01), and then decreased hepatic glycogen content (179 ± 38 vs. 273 ± 39 mg in the presence of 1 mU/ml insulin after 30 min of perfusion, p < 0.05). Ethanol decreased the direct glycogenesis from 14C-glucose from 0.55 ± 0.08 to 0.33 ± 0.05 µmol per 100 mg glycogen for 30 min (p < 0.01). Ethanol inhibited the indirect glycogenesis from 14C-lactate from 0.21 ± 0.04 to 0.09 ± 0.01 µmol per 100 mg glycogen for 30 min (p < 0.01). Discussion: The influence of ethanol on the blood glucose regulation by the liver seems to be different between fasted and fed states. Namely, ethanol has both the hypoglycemic effects through decreased gluconeogenesis and increased glucose oxidation and the hyperglycemic effects through decreased glycogenesis and increased glycogenolysis.

Water extract of Helicobacter pylori stimulates interleukin-8 secretion by a human gastric epithelial cell line (JR-St) through protein tyrosine phosphorylation

Background : Infection by Helicobacter pylori induces cytokine production in gastric mucosal cells. Production of interleukin‐8 (IL‐8) is known to be markedly increased and is believed to play an important role in gastric mucosal inflammation. The aim of this study was to elucidate the effects of soluble factors of H. pylori on IL‐8 production in a gastric epithelial cell line, JR‐St.

Skull metastasis of thyroid papillary carcinoma.

Skull metastasis of thyroid carcinoma is rare. The majority of skull metastases of thyroid carcinoma are of the follicular subtype, rather than thyroid papillary carcinoma. In this report, a 55-year-old woman with skull metastasis from thyroid papillary carcinoma is presented. The metastatic lesion of the skull was hypervascular and osteolytic, and the bleeding was profuse during resection. There have been only four reports of skull metastasis from thyroid papillary carcinoma. The mean period from the initial diagnosis of thyroid carcinoma until the detection of skull metastasis is 23.3 years, whereas in this patient, it was about 2 years. Therefore, in the clinical course of thyroid papillary carcinoma, skull metastasis should be considered, and the patient should be meticulously followed up.

Osteoporosis Associated with Chronic Obstructive Pulmonary Disease

Recent epidemiological studies have revealed that osteoporosis is closely associated with common chronic diseases including diabetes, hypertension, chronic kidney disorders, and chronic obstructive pulmonary disease (COPD). COPD is a chronic inflammatory airway disease but now well known to be associated with various systemic comorbidities including osteoporosis. Osteoporosis and osteoporotic fractures are extremely common in COPD patients, which have significant impacts on their quality of life (QOL), activities of daily life (ADL), respiratory function, and possibly their prognosis. COPD-associated osteoporosis is however extremely under-recognized, hence undertreated. Recent studies have suggested that both decreased bone mineral density (BMD) and impaired bone quality compromise bone strength causing fractures in COPD. In COPD patients, various general clinical risk factors for osteoporosis are present including smoking, older age, low body weight, and physical inactivity. In addition, disease-related risk factors such as decreased pulmonary function, inflammation, glucocorticoid use and vitamin D deficiency/insufficiency have been linked to the development of osteoporosis in COPD. Increased awareness of osteoporosis in COPD, especially that of high prevalence of vertebral fractures is called upon among general physicians as well as pulmonologists. Routine screening for osteoporosis and risk assessment of fractures will enable physicians to diagnose COPD patients with comorbid osteoporosis at an early stage. Timely prevention of developing osteoporosis together with appropriate treatment of established osteoporosis may improve QOL and ADL of the COPD patients, preserve their lung function and eventually result in better prognosis in these patients.

Pathogenesis and diagnostic criteria for rickets and osteomalacia—proposal by an expert panel supported by the Ministry of Health, Labour and Welfare, Japan, the Japanese Society for Bone and Mineral Research, and the Japan Endocrine Society

Rickets and osteomalacia are diseases characterized by impaired mineralization of bone matrix. Recent investigations have revealed that the causes of rickets and osteomalacia are quite variable. Although these diseases can severely impair the quality of life of affected patients, rickets and osteomalacia can be completely cured or at least respond to treatment when properly diagnosed and treated according to the specific causes. On the other hand, there are no standard criteria to diagnose rickets or osteomalacia nationally and internationally. Therefore, we summarize the definition and pathogenesis of rickets and osteomalacia, and propose diagnostic criteria and a flowchart for the differential diagnosis of various causes of these diseases. We hope that these criteria and the flowchart are clinically useful for the proper diagnosis and management of these diseases.