Masafumi Kurajoh

Utility of serum tartrate‐resistant acid phosphatase (TRACP5b) as a bone resorption marker in patients with chronic kidney disease: independence from renal dysfunction

Background  Serum tartrate‐resistant acid phosphatase (TRACP) 5b levels were assessed in predialysis patients with chronic kidney disease (CKD). The aim of the study was to establish the usefulness of a new assay for TRACP5b in assessing bone turnover in these patients.

Receptor for advanced glycation end products regulates adipocyte hypertrophy and insulin sensitivity in mice: involvement of Toll-like receptor 2.

Receptor for advanced glycation end products (RAGE) has been shown to be involved in adiposity as well as atherosclerosis even in nondiabetic conditions. In this study, we examined mechanisms underlying how RAGE regulates adiposity and insulin sensitivity. RAGE overexpression in 3T3-L1 preadipocytes using adenoviral gene transfer accelerated adipocyte hypertrophy, whereas inhibitions of RAGE by small interfering RNA significantly decrease adipocyte hypertrophy. Furthermore, double knockdown of high mobility group box-1 and S100b, both of which are RAGE ligands endogenously expressed in 3T3-L1 cells, also canceled RAGE-medicated adipocyte hypertrophy, implicating a fundamental role of ligands–RAGE ligation. Adipocyte hypertrophy induced by RAGE overexpression is associated with suppression of glucose transporter type 4 and adiponectin mRNA expression, attenuated insulin-stimulated glucose uptake, and insulin-stimulated signaling. Toll-like receptor (Tlr)2 mRNA, but not Tlr4 mRNA, is rapidly upregulated by RAGE overexpression, and inhibition of Tlr2 almost completely abrogates RAGE-mediated adipocyte hypertrophy. Finally, RAGE−/− mice exhibited significantly less body weight, epididymal fat weight, epididymal adipocyte size, higher serum adiponectin levels, and higher insulin sensitivity than wild-type mice. RAGE deficiency is associated with early suppression of Tlr2 mRNA expression in adipose tissues. Thus, RAGE appears to be involved in mouse adipocyte hypertrophy and insulin sensitivity, whereas Tlr2 regulation may partly play a role.

Biochemistry of uridine in plasma.

Uridine is a pyrimidine nucleoside that plays a crucial role in synthesis of RNA, glycogen, and biomembrane. In humans, uridine is present in plasma in considerably higher quantities than other purine and pyrimidine nucleosides, thus it may be utilized for endogenous pyrimidine synthesis. Uridine has a number of biological effects on a variety of organs with or without disease, such as the reproductive organs, central and peripheral nervous systems, and liver. In addition, it is used in clinical situations as a rescue agent to protect against the adverse effects of 5-fluorouracil. Since the biological actions of uridine may be related to its plasma concentration, it is important to examine factors that have effects on that concentration. Factors associated with an increase in plasma concentration of uridine include enhanced ATP consumption, enhanced uridine diphosphate (UDP)-glucose consumption via glycogenesis, inhibited uridine uptake by cells via the nucleoside transport pathway, increased intestinal absorption, and increased 5-phosphribosyl-1-pyrophosphate and urea synthesis. In contrast, factors that decrease the plasma concentration of uridine are associated with accelerated uridine uptake by cells via the nucleoside transport pathway and decreased pyrimidine synthesis.

Plasma brain-derived neurotrophic factor and reverse dipping pattern of nocturnal blood pressure in patients with cardiovascular risk factors.

Context Basic studies have shown that brain-derived neurotrophic factor (BDNF) has critical roles in the survival, growth, maintenance, and death of central and peripheral neurons, while it is also involved in regulation of the autonomic nervous system. Furthermore, recent clinical studies have suggested potential role of plasma BDNF in the circulatory system. Objective We investigated the mutual relationships among plasma BDNF, patterns of nocturnal blood pressure changes (dippers, non-dippers, extra-dippers, and reverse-dippers), and cardiac autonomic function as determined by heart rate variability (HRV). Design This was a cross-sectional study of patients registered in the Hyogo Sleep Cardio-Autonomic Atherosclerosis (HSCAA) Study from October 2010 to November 2012. Patients Two-hundred fifty patients with 1 or more cardiovascular risk factor(s) (obesity, smoking, presence of cardiovascular event history, hypertension, dyslipidemia, diabetes mellitus, chronic kidney disease) were enrolled. Results Plasma BDNF levels (natural logarithm transformed) were significantly (p = 0.001) lower in reverse-dipper patients (7.18±0.69 pg/ml, mean ± SD, n = 36) as compared to dippers (7.86±0.86 pg/ml, n = 100). Multiple logistic regression analysis showed that BDNF (odds ratios: 0.417, 95% confidence interval: 0.228–0.762, P = 0.004) was the sole factor significantly and independently associated with the reverse-dippers as compared with dippers. Furthermore, plasma BDNF level was significantly and positively correlated with the time-domain (SDNN, SDANN5, CVRR) and frequency-domain (LF) of HRV parameters. Finally, multiple logistic regression analyses showed that the relationship between plasma BDNF and the reverse-dippers was weakened, yet remained significant or borderline significant even after adjusting for HRV parameters. Conclusions Low plasma BDNF was independently associated with patients showing a reverse-dipper pattern of nocturnal blood pressure, in which an imbalance of cardiac autonomic function may be partly involved.

The Levels of Somatostatin Receptors in Causative Tumors of Oncogenic Osteomalacia Are Insufficient for Their Agonist to Normalize Serum Phosphate Levels

Oncogenic osteomalacia (OOM) is a rare disease characterized by renal phosphate wasting and osteomalacia and is caused by the secretion of fibroblast growth factor 23 (FGF-23) from causative tumors. Scintigraphy with octreotide, which binds to somatostatin receptors (SSTRs), is a useful way to locate causative tumors in OOM patients. However, the therapeutic effects of octreotide acetate are still controversial. Two OOM patients were administered octreotide acetate intramuscularly. Ten causative OOM tumors, including two resected from the patients participating in the octreotide administration study, were examined for expression of genes encoding SSTRs by quantitative real-time RT-PCR and immunohistochemistry. Octreotide therapy did not improve hypophosphatemia in either case, despite temporal decreases in FGF-23 levels in one patient. The mean expression levels of SSTR1, SSTR3, and SSTR5 were similar in the OOM and non-OOM tumors. Expression of SSTR2 was significantly higher in the OOM tumors than in the non-OOM tumors. Immunohistochemical examinations revealed the presence of SSTR2A, SSTR2B, and SSTR5 in both the OOM and non-OOM tumors. The expression of SSTR genes in OOM tumors contributes to positive imaging using octreotide scintigraphy. However, the levels of SSTRs seem to be insufficient for the octreotide therapy to improve hypophosphatemia. Further studies are needed to clarify the mechanisms by which FGF-23 secretion from OOM tumors is suppressed by octreotide acetate.

Serum CRP in patients with gout and effects of benzbromarone.

OBJECTIVE C-reactive protein (CRP) is associated with increased risk for myocardial infarction, atherosclerosis, and peripheral artery diseases, while increased serum uric acid level is suggested to be independently associated with an increased risk of cardiovascular mortality. Accordingly, to investigate whether hyperuricemia is associated with serum CRP, we compared serum CRP levels between healthy subjects and patients with gout. In addition, we also examined whether benzbromarone has effects on serum CRP levels in patients with gout and the expression of CRP messenger RNA of CRP in the hepatoma cell line HuH7. METHODS In the first experiment, 40 healthy males and 43 male patients with gout were enrolled, then blood samples were drawn from each after an overnight fast. In the second experiment, 42 male patients with gout were given uric acid-lowering therapy with benzbromarone. Blood samples were drawn after an overnight fast before and 1 year after beginning benzbromarone treatment. In the third experiment, the effects of benzbromarone on IL1beta-induced CRP expression were determined in HuH7 cells. RESULTS Log serum CRP levels were not significantly different between the patients with gout and healthy subjects, while log serum CRP levels were decreased by 11% after benzbromarone treatment, as compared to the values before treatment (p < 0.01). In addition, log serum adiponectin levels were elevated by 2% after treatment (p < 0.01). Furthermore, our in vitro findings demonstrated that benzbromarone down-regulated IL1beta-stimulated CRP gene expression. CONCLUSIONS These results suggest that hyperuricemia may not contribute to an increase in serum CRP level, while benzbromarone may have a favorable effect on CRP.

Serum Macro TSH Level is Associated with Sleep Quality in Patients with Cardiovascular Risks – HSCAA Study

Macro thyroid-stimulating hormone (TSH) has been reported to be associated with seasonality and regulated by changes in day length in rodents, different from free TSH. In the present study, we investigated structural differences between macro TSH and free TSH levels in human serum, as well as the association of macro TSH with sleep quality. We enrolled 314 patients registered in the Hyogo Sleep Cardio-Autonomic Atherosclerosis (HSCAA) study. Sleep quality shown by actigraphy, sleep physical activity, and percent sleep in all and TSH closely matched subjects were significantly associated with high macro TSH levels. Macro and free TSH were similarly increased following thyrotropin-releasing hormone (TRH) stimulation, while circadian changes associated with those were distinct. To further analyze the structure of macro TSH, serum samples were separated by gel filtration chromatography. Although treatment with glycosidase did not affect morbidity, the macro TSH fraction had a markedly low affinity to the Con A column as compared with free TSH, indicating a distinct glycosylation structure. In conclusion, an increase in serum macro TSH is associated with low sleep quality and regulated in a manner distinct from free TSH, potentially due to an altered glycosylation structure.

Associations of Sleep Quality and Awake Physical Activity with Fluctuations in Nocturnal Blood Pressure in Patients with Cardiovascular Risk Factors

Background Sleep quality and awake physical activity are important behavioral factors involved in the occurrence of cardiovascular diseases, potentially through nocturnal blood pressure (BP) changes. However, the impacts of quantitatively measured sleep quality and awake physical activity on BP fluctuation, and their relationships with several candidate causal factors for nocturnal hypertension are not well elucidated. Methods This cross-sectional study included 303 patients registered in the HSCAA study. Measurements included quantitatively determined sleep quality parameters and awake physical activity obtained by actigraph, nocturnal systolic BP (SBP) fall [100 × (1- sleep SBP/awake SBP ratio)], apnea hypopnea index, urinary sodium and cortisol secretion, plasma aldosterone concentration and renin activity, insulin resistance index, parameters of heart rate variability (HRV), and plasma brain-derived neurotrophic factor (BDNF). Results Simple regression analysis showed that time awake after sleep onset (r = -0.150), a parameter of sleep quality, and awake physical activity (r = 0.164) were significantly correlated with nocturnal SBP fall. Among those, time awake after sleep onset (β = -0.179) and awake physical activity (β = 0.190) were significantly and independently associated with nocturnal SBP fall in multiple regression analysis. In a subgroup of patients without taking anti-hypertensive medications, both time awake after sleep onset (β = -0.336) and awake physical activity (β = 0.489) were more strongly and independently associated with nocturnal SBP falls. Conclusion Sleep quality and awake physical activity were found to be significantly associated with nocturnal SBP fall, and that relationship was not necessarily confounded by candidate causal factors for nocturnal hypertension.

Evaluation of bone markers in hypophosphatemic rickets/osteomalacia

N-terminal propeptide of type I procollagen (PINP) is a marker of newly formed type I collagen. However, its role in hypophosphatemic rickets/osteomalacia has not yet been established. Metabolic bone markers were examined in patients with oncogenic osteomalacia (OOM) and X-linked hypophosphatemic rickets (XLH), and in healthy controls. OOM and XLH patients were found to have hypophosphatemia secondary to elevated levels of serum fibroblast growth factor 23 (FGF-23). OOM patients had reduced levels of 1,25-dihydroxy vitamin D (1,25D) compared with XLH patients and healthy controls, despite attenuation of the reduction in these levels in the XLH patients secondary to active vitamin D supplementation. In contrast to patients with XLH, OOM patients showed a significant increase in serum PINP, which is suggestive of accelerated bone matrix formation. Bone alkaline phosphatase (BAP) and the BAP/PINP ratio were also increased in OOM but not in XLH patients, suggesting the presence of a disturbance in bone mineralization in OOM. Long-term supplementation of active form vitamin D and inorganic phosphate (IP) may have attenuated the defect in bone mineralization in the XLH patients, resulting in the normalization of PINP, BAP, and the BAP/PINP ratio. The present results suggest that, as with BAP, PINP is an appropriate metabolic bone marker in the assessment of hypophosphatemic rickets/osteomalacia.

Partial HPRT Deficiency with a Novel Mutation of the HPRT Gene in Combination with Four Previously Reported Variants Associated with Hyperuricemia

A 15-year-old boy was referred to our department due to gout. The laboratory findings showed hyperuricemia with a decreased erythrocyte hypoxanthine phosphoribosyl transferase (HPRT) activity. The HPRT cDNA sequence was revealed to be 206A>T, which has not been previously reported. In addition, direct sequencing of genomic DNA showed the patient to possess four variants reported to be associated with hyperuricemia. This is the first case report of partial HPRT deficiency due to a novel HPRT mutation accompanied by variants associated with hyperuricemia. Combination treatment consisting of benzbromarone and febuxostat had a significant effect in reducing the urate level in our patient.