Je Ho Han

Association of Oxidative Stress with Postmenopausal Osteoporosis and the Effects of Hydrogen Peroxide on Osteoclast Formation in Human Bone Marrow Cell Cultures

It has been suggested that oxidative stress is associated with the pathogenesis of osteoporosis. The objective of this study was to explore the association between a marker of oxidative stress and either bone turnover markers or bone mineral density (BMD) in postmenopausal women. In addition, the effects of oxidative stress on the formation of osteoclasts in human bone marrow cell culture were examined. We performed a cross-sectional analysis in healthy postmenopausal women aged 60–78xa0years (nxa0=xa0135, 68.2xa0±xa04.9). Oxidative stress was evaluated in the serum by measuring 8-hydroxy-2′-deoxyguanosine (8-OH-dG) levels. The biochemical markers of bone turnover and areal BMD were measured in all participants. Multivariate linear regression analysis revealed a negative association between 8-OH-dG levels and BMD of the lumbar spine, total hip, femoral neck, and trochanter and positive association with type I collagen C-telopeptide (ICTP) levels. The odds ratio of 8-OH-dG for osteoporosis was 1.54 (1.14–2.31, Pxa0=xa00.003). In cultures of primary human marrow cells, H2O2 caused concentration-dependent activation of TRAP-positive multinucleated giant cells. H2O2 also increased the area of pits per osteoclast activity assay substrate. RT-PCR showed that H2O2 stimulated the expression of M-CSF and RANKL and increased the RANKL/OPG ratio. The data support the view that oxidative stress is associated with increased bone resorption and low bone mass in otherwise healthy women. In addition, RANKL and M-CSF stimulation induced by oxidative stress may participate in osteoclastogenesis in human bone.

The Effect of Simvastatin on the Proliferation and Differentiation of Human Bone Marrow Stromal Cells

Statins have been postulated to affect the bone metabolism. Recent experimental and epidemiologic studies have suggested that statins may also have bone protective effects. This study assessed the effects of simvastatin on the proliferation and differentiation of human bone marrow stromal cells (BMSCs) in an ex vivo culture. The bone marrow was obtained from healthy donors. Mononuclear cells were isolated and cultured to osteoblastic lineage. In the primary culture, 10-6 M simvastatin diminished the mean size of the colony forming units-fibroblastic (CFU-Fs) and enhanced matrix calcification. At near confluence, the cells were sub-cultured. Thereafter, the alkaline phosphatase (ALP) activities of each group were measured by the time course of the secondary culture. Simvastatin increased the ALP activity in a dose dependent manner, and this stimulatory effect was more evident during the early period of culture. A 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay was performed during the secondary culture in order to estimate the effect of simvastatin on the proliferation of human BMSCs. When compared to the control group, simvastatin significantly decreased the proliferation of cells of each culture well. 10-6 M of simvastatin also significantly enhanced the osteocalcin mRNA expression level. This study shows that simvastatin has a stimulatory effect on bone formation through osteoblastic differentiation, and has an inhibitory effect on the proliferative potential of human BMSCs

Association Between Low Serum Free Thyroxine Concentrations and Coronary Artery Calcification in Healthy Euthyroid Subjects

BACKGROUNDnConsiderable evidence suggests that hypothyroidism could promote atherosclerotic vascular changes. We planned this study to investigate whether serum free thyroxine (FT4) or thyroid-stimulating hormone (TSH) levels are associated with coronary artery calcification measured in healthy euthyroid subjects.nnnMETHODSnA cross-sectional analysis was performed among subjects who visited our hospital for a health checkup. Among 1849 subjects, 669 (mean age 55.3±8.8 years; 392 men) with FT4 and TSH in the normal ranges were included after excluding those with diabetes, a history of current smoking and cardiovascular disease (CVD), or the use of drugs for hypertension, antithyroid drugs, or thyroid hormone preparations. Coronary artery calcium scores (CACS) were measured by multi-detector computed tomography.nnnRESULTSnSubjects with a CACS >100 had lower FT4 levels than those with a lower CACS (p=0.017), whereas no difference was observed in the TSH levels among CACS categories. FT4 levels had an odds ratio of 0.06 for high CACS (95% confidence interval=0.01-0.74; p=0.028) after the adjustment for CVD risk factors. In multivariate regression analysis, CACS was negatively correlated with FT4 levels (β=-0.823, p=0.032), and the inverse association between FT4 and CACS remained significant only in men (p=0.011).nnnCONCLUSIONnFT4 levels were inversely associated with coronary artery calcification in euthyroid healthy subjects, especially in men independent of conventional CVD risk factors. Further studies are needed to validate whether subjects with decreased FT4 levels within the normal reference range are at a high CVD risk and have poor cardiovascular outcomes.

Association between Lower Normal Free Thyroxine Concentrations and Obesity Phenotype in Healthy Euthyroid Subjects

We investigated whether thyroid function could identify obesity phenotype in euthyroid subjects. A cross-sectional analysis was performed among nondiabetic, euthyroid subjects. We stratified subjects into four groups by BMI and insulin resistance (IR). Of 6241 subjects, 33.8% were overweight or obese (OW/OB) and 66.2% were normal weight (NW). Free thyroxine (FT4) levels were negatively associated with body mass index, waist circumference, triglyceride, c-reactive protein, and HOMA-IR and positively with high-density lipoprotein cholesterol in both genders. In multivariate regression analysis, FT4 level, a continuous measurement, was negatively correlated with HOMA-IR (β = −0.155, P < 0.001 in men; β = −0.175, P < 0.001 in women). After adjustment for age, sex, metabolic, and life style factors, subjects in the lowest FT4 quartile had an odds ratio (OR) for IR of 1.99 (95% confidence interval 1.61–2.46), as compared to those in the highest quartile. The association between low FT4 and IR remained significant in both NW and OW/OB subgroups. In conclusion, low normal FT4 levels were independently related to IR in NW and OW/OB euthyroid subjects. Further studies are needed to investigate the mechanisms by which low FT4 levels are linked to high IR in euthyroid ranges.

A novel neurofibromatosis type 1 ( NF1 ) mutation in a patient with NF1 and pheochromocytoma

pISSN 1226-3303 eISSN 2005-6648 http://www.kjim.org Copyright

Association of serum calcium concentrations with fibrinogen and homocysteine in nondiabetic Korean subjects.

AbstractConsiderable evidence shows that increased serum calcium levels are associated with metabolic disorders, cardiovascular disease, and increased mortality. This study investigated whether serum calcium, within a normal range, is significantly associated with serum fibrinogen and homocysteine, markers of increased cardiovascular disease risk in nondiabetic Korean subjects.A cross-sectional analysis was performed on 1096 subjects (mean age, 55.1u200a±u200a11.1 years; 36.1% women) undergoing a general health checkup. Serum biochemistry was analyzed including serum albumin-corrected calcium (Cac), insulin resistance (IR, using homeostasis model assessment [HOMA]), fibrinogen, and homocysteine.Compared with patients within the lowest Cac quartile, those with higher Cac levels had increased fibrinogen and homocysteine levels as well as an increased proportion of smoking, dyslipidemia, and HOMA-IR. Correlation analyses revealed linear relationships for Cac with fibrinogen and homocysteine in both genders. After adjustment for confounding factors, serum Cac was significantly associated with high fibrinogen (odds ratio [OR] for the highest vs the lowest quartile = 1.76, 95% confidence interval [CI] = 1.09–2.83, P = 0.02) and homocysteine (OR = 1.83, 95% CI = 1.07–3.11, P = 0.027). Multivariate regression models showed that Cac was linearly associated with fibrinogen (standardized &bgr; = 0.14, Pu200a<u200a0.001) and homocysteine (standardized &bgr; = 0.07, P = 0.009).High normal calcium concentrations were independently associated with increased levels of fibrinogen and homocysteine. Further investigation is needed to validate whether slightly increased calcium levels within the normal range indicate a higher risk of cardiovascular disease.

Identification and functional analysis of a novel CaSR mutation in a family with familial hypocalciuric hypercalcemia.

The calcium-sensing receptor (CaSR) is a G-protein-coupled receptor that plays an essential role in maintaining calcium homeostasis. In the present study, we analyzed the CaSR gene in a Korean family with familial hypocalciuric hypercalcemia (FHH). Genetic studies were performed by direct sequence analysis of the CaSR gene in genomic DNA obtained from peripheral leukocytes. A novel heterozygous G to T substitution at nucleotide position 1711 in exon 6, resulting in the G571W mutation, was identified in the CaSR gene in a 26-year-old female with asymptomatic hypercalcemia, a low calcium/creatinine clearance ratio, and normal intact parathyroid hormone. To study CaSR expression, the mutation was introduced by site-directed mutagenesis into a wild-type (WT) CaSR-expressing pCR3.1 vector, and COS-7 cells were transfected with either the WT or mutant CaSR-containing vector. Transfected cells loaded with Fura-2/AM, a fluorescent indicator of Ca2+, were assessed for CaSR function by the change in intracellular calcium [as measured by the 340xa0nm/380xa0nm fluorescence intensity ratio (F340/F380)] made in response to challenge with extracellular Ca2+. Both WT and G571W cells had equivalent amounts of CaSR protein in the cell membrane. However, after challenge with extracellular Ca2+, cells transfected with G571W CaSR responded with a lower F340/F380 ratio than those transfected with WT CaSR and showed decreased sensitivity to extracellular Ca2+ concentrations. The G571W mutation had therefore impaired the CaSR function. In conclusion, we identified a novel loss-of-function mutation, G571W, in the CaSR gene in a Korean family with FHH.

Serum gamma-glutamyltransferase is not associated with subclinical atherosclerosis in patients with type 2 diabetes.

BackgroundThis study investigated the association between serum gamma-glutamyltransferase (GGT) level and subclinical atherosclerosis in patients with type 2 diabetes.MethodsThis cross-sectional study involved 1024 patients with type 2 diabetes mellitus. Measurement of brachial-ankle pulse wave velocity (baPWV; as a marker of arterial stiffness) and an ultrasound assessment of carotid atherosclerosis were performed. Subclinical atherosclerosis was defined by the presence of a high baPWV (≥1720xa0cm/s), carotid atherosclerosis (intima-media thicknessxa0>0.8xa0mm or the presence of plaques), and carotid stenosis (≥50xa0% of luminal narrowing). The subjects were stratified into quartiles according to GGT level, and the relationship between GGT level and subclinical atherosclerosis was analysed.ResultsSerum GGT levels were closely associated with obesity, atherogenic dyslipidemia, and metabolic syndrome. However, serum GGT levels did not show a linear association with baPWV, carotid intima-media thickness, or plaque grade. The prevalence of high baPWV, carotid atherosclerosis, and carotid stenosis did not differ between the quartiles in men and women. Multivariate logistic regression analyses revealed no association between GGT level and high baPWV, carotid atherosclerosis, and carotid stenosis, either as continuous variables or quartiles.ConclusionsSerum GGT levels were significantly associated with obesity, atherogenic dyslipidaemia, and metabolic syndrome, but not with the early and late stages of atherosclerotic vascular changes, in patients with type 2 diabetes. Serum GGT level may not be a reliable marker of subclinical atherosclerosis in type 2 diabetes.

Serum bilirubin levels are inversely associated with PAI-1 and fibrinogen in Korean subjects.

OBJECTIVESnOxidative stress may contribute to atherosclerosis and increased activation of the coagulation pathway. Bilirubin may reduce activation of the hemostatic system to inhibit oxidative stress, which would explain its cardioprotective properties shown in many epidemiological studies. This study investigated the association of serum bilirubin with fibrinogen and plasminogen activator inhibitor-1 (PAI-1), respectively.nnnMETHODSnA cross-sectional analysis was performed on 968 subjects (mean age, 56.0 ± 11.2 years; 61.1% men) undergoing a general health checkup. Serum biochemistry was analyzed including bilirubin subtypes, insulin resistance (using homeostasis model of assessment [HOMA]), C-reactive protein (CRP), fibrinogen, and PAI-1.nnnRESULTSnCompared with subjects with a total bilirubin (TB) concentration of <10.0 μmol/L, those with a TB concentration of >17.1 μmol/L had a smaller waist circumference, a lower triglyceride level, a lower prevalence of metabolic syndrome, and decreased HOMA-IR and CRP levels. Correlation analysis revealed linear relationships of fibrinogen with TB and direct bilirubin (DB), whereas PAI-1 was correlated with DB. After adjustment for confounding factors, bilirubin levels were inversely associated with fibrinogen and PAI-1 levels, respectively. Multivariate regression models showed a negative linear relationship between all types of bilirubin and fibrinogen, whereas there was a significant linear relationship between PAI-1 and DB.nnnCONCLUSIONSnHigh bilirubin concentrations were independently associated with low levels of fibrinogen and PAI-1, respectively. The association between TB and PAI-1 was confined to the highest TB concentration category whereas DB showed a linear association with PAI-1. Bilirubin may protect against the development of atherothrombosis by reducing the hemostatic response.