Ghi Su Kim

Effects of vitamin B12 on cell proliferation and cellular alkaline phosphatase activity in human bone marrow stromal osteoprogenitor cells and UMR106 osteoblastic cells

Pernicious anemia has recently been recognized as one of the risk factors for osteoporosis and bone fractures, but the underlying pathophysiologic mechanism is still unknown. To determine whether vitamin B12 has any direct effect on osteoblasts, we studied the effects of vitamin B12 on the proliferation and alkaline phosphatase activity in human bone marrow stromal osteoprogenitor cells (hBMSC) and UMR106 osteoblastic cells. Vitamin B12 at concentrations as low as 10(-12) mol/L significantly stimulated [3H]-thymidine incorporation in both types of cells, but concentrations higher than 10(-12) mol/L did not produce a greater effect. Vitamin B12 in the concentration range from 10(-12) to 10(-8) mol/L concentration-dependently increased alkaline phosphatase activity in both hBMSC and UMR106 cells. Based on these results, we suggest that a suppressed activity of osteoblasts may contribute to osteoporosis and fractures in patients with vitamin B12 deficiency.

α‐Lipoic Acid Inhibits TNF‐α‐Induced Apoptosis in Human Bone Marrow Stromal Cells

TNF‐α is an important mediator of bone loss. In the HS‐5 hBMSC, TNF‐α and H2O2 increased intracellular ROS levels and induced cell apoptosis through activation of caspases, JNK and NF‐κB. α‐Lipoic acid prevented these changes induced by TNF‐α and H2O2, suggesting its potential therapeutic applications in attenuating bone loss.

Low normal TSH levels are associated with low bone mineral density in healthy postmenopausal women.

Objective  Hyperthyroidism is accompanied by low bone mass. Because the reference range of TSH levels is defined statistically, some individuals with low normal TSH levels may have mild hyperthyroidism and reduced bone mass. We therefore determined whether serum TSH levels correlate with bone mineral density (BMD).

European bone mineral density loci are also associated with BMD in East-Asian populations

Most genome-wide association (GWA) studies have focused on populations of European ancestry with limited assessment of the influence of the sequence variants on populations of other ethnicities. To determine whether markers that we have recently shown to associate with Bone Mineral Density (BMD) in Europeans also associate with BMD in East-Asians we analysed 50 markers from 23 genomic loci in samples from Korea (n = 1,397) and two Chinese Hong Kong sample sets (n = 3,869 and n = 785). Through this effort we identified fourteen loci that associated with BMD in East-Asian samples using a false discovery rate (FDR) of 0.05; 1p36 (ZBTB40, P = 4.3×10−9), 1p31 (GPR177, P = 0.00012), 3p22 (CTNNB1, P = 0.00013), 4q22 (MEPE, P = 0.0026), 5q14 (MEF2C, P = 1.3×10−5), 6q25 (ESR1, P = 0.0011), 7p14 (STARD3NL, P = 0.00025), 7q21 (FLJ42280, P = 0.00017), 8q24 (TNFRSF11B, P = 3.4×10−5), 11p15 (SOX6, P = 0.00033), 11q13 (LRP5, P = 0.0033), 13q14 (TNFSF11, P = 7.5×10−5), 16q24 (FOXL1, P = 0.0010) and 17q21 (SOST, P = 0.015). Our study marks an early effort towards the challenge of cataloguing bone density variants shared by many ethnicities by testing BMD variants that have been established in Europeans, in East-Asians.

Association between Bone Mineral Density and LDL Receptor-Related Protein 5 Gene Polymorphisms in Young Korean Men

Recently, It has been reported that the LDL receptor-related protein 5 (LRP5) regulates bone formation, and that mutations of the gene cause osteoporosis-pseudoglioma syndrome or high bone mass phenotypes. However, the mutations cannot explain a genetic trait for osteoporosis in the general population because of their rarity. From 219 Korean men aged 20-34 yr, we looked for six known polymorphisms causing amino acid changes in the LRP5 coding region, and investigated their association with bone mineral density (BMD) at the following anatomical sites: lumbar spine (L2-L4) and the left proximal femur (femoral neck, Wards triangle, trochanter and shaft). We found that the Q89R polymorphism was significantly associated with BMD at the femoral neck and Wards triangle (p=0.004 and <0.001, respectively). However, after adjusting for age, weight and height, a statistically significant association only occurred at the Wards triangle (p=0.043), and a marginal association was observed at the femoral neck (p=0.098). No A400V, V667M, R1036Q and A1525V polymorphisms were found, and no statistically significant association was found between the A1330V polymorphism and BMD at any sites. Although we failed to demonstrate a clear association between the LRP5 polymorphism and peak bone mass in young men, the present study suggests that larger-scale studies on the Q89R polymorphism need to be performed.

Iron overload accelerates bone loss in healthy postmenopausal women and middle‐aged men: A 3‐year retrospective longitudinal study

Despite extensive experimental and animal evidence about the detrimental effects of iron and its overload on bone metabolism, there have been no clinical studies relating iron stores to bone loss, especially in nonpathologic conditions. In the present study, we performed a large longitudinal study to evaluate serum ferritin concentrations in relation to annualized changes in bone mineral density (BMD) in healthy Koreans. A total of 1729 subjects (940 postmenopausal women and 789 middle‐aged men) aged 40 years or older who had undergone comprehensive routine health examinations with an average 3 years of follow‐up were enrolled. BMD in proximal femur sites (ie, the total femur, femur neck, and trochanter) was measured with dual‐energy X‐ray absorptiometry using the same equipment at baseline and follow‐up. The mean age of women and men in this study was 55.8 ± 6.0 years and 55.5 ± 7.8 years, respectively, and serum ferritin levels were significantly higher in men than in women (p < 0.001). The overall mean annualized rates of bone loss in the total femur, femur neck, and trochanter were −1.14%/year, −1.17%/year, and −1.51%/year, respectively, in women, and −0.27%/year, −0.34%/year, and −0.41%/year, respectively, in men. After adjustment for potential confounders, the rates of bone loss in all proximal femur sites in both genders were significantly accelerated in a dose‐response fashion across increasing ferritin quartile categories (p for trend = 0.043 to <0.001). Consistently, compared with subjects in the lowest ferritin quartile category, those in the third and/or highest ferritin quartile category showed significantly faster bone loss in the total femur and femur neck in both genders (p = 0.023 to <0.001). In conclusion, these data provide the first clinical evidence that increased total body iron stores could be an independent risk factor for accelerated bone loss, even in healthy populations.

Prevalence and Associated Features of Albuminuria in Koreans with NIDDM

OBJECTIVE To determine the prevalence and the associated features of microalbuminuria and overt proteinuria in Korean subjects with non-insulin-dependent diabetes mellitus (NIDDM) attending a hospital clinic. RESEARCH DESIGN AND METHODS A total of 631 Korean outpatients with NIDDM were studied cross-sectionally for the presence of albuminuria and other micro- and macrovascular complications. Urinary albumin excretion rate (AER) was determined in timed overnight urine samples. Subjects were divided into three groups: no nephropathy (AER <20 μg/min), microalbuminuria (AER 20–200 μg/min), and overt proteinuria (AER >200 μg/min). RESULTS Increased AER was present in 34% of our patients: 20% had microalbuminuria and 14% had overt proteinuria. Of patients with diabetes duration ≥ 15 years, 35% had overt proteinuria. Most (82%) patients with overt proteinuria had retinopathy. Although the prevalence of microalbuminuria as a whole did not differ according to diabetes duration, the prevalence of microalbuminuria in the patients with retinopathy increased with diabetes duration. The microalbuminuric patients without retinopathy (diabetes duration < 5 years) were characterized by higher prevalence of hypertension and previous obesity, higher plasma triglyceride level, and lower plasma high-density lipoprotein cholesterol level. CONCLUSIONS The prevalence of overt proteinuria in Korean NIDDM patients with a long diabetes duration was higher than that reported in Caucasians. Our data also suggest that the clinical meaning of microalbuminuria may be different based on the presence or the absence of retinopathy. Microalbuminuria in patients with retinopathy most probably would reflect diabetic nephropathy. In contrast, some recent-onset NIDDM patients with microalbuminuria in the absence of retinopathy had features of syndrome X.

Relationship between serum hsCRP concentration and biochemical bone turnover markers in healthy pre- and postmenopausal women.

Objective   Although osteoporosis and atherosclerosis seem to be related, the mechanisms are not yet understood. We previously observed that women with higher serum concentrations of high sensitivity C‐reactive protein (hsCRP), a strong risk factor for atherosclerosis, had lower bone mineral density (BMD). However, the relationship of hsCRP level with bone turnover rate, an independent risk factor for osteoporotic fracture, is not known.

Association study of semaphorin 7a (sema7a) polymorphisms with bone mineral density and fracture risk in postmenopausal Korean women

AbstractBone mineral density (BMD), the major factor determining bone strength, is closely related to osteoporotic fracture risk and is determined largely by multiple genetic factors. Semaphorin 7a (SEMA7A), a recently described member of the semaphorin family, has been shown to play a critical role in the activation of monocyte/macrophages that share progenitors with bone-resorbing osteoclasts and thus might contribute to osteoclast development. In the present study, we directly sequenced theSEMA7A gene in 24 Korean individuals, and identified 15 sequence variants. Five polymorphisms (+15667G>A, +15775C>G, +16285C>T, +19317C>T, +22331A>G) were selected and genotyped in postmenopausal Korean women (n=560) together with measurement of the areal BMD (g/cm2) of the anterior-posterior lumbar spine and the non-dominant proximal femur using dual-energy X-ray absorptiometry. We found that polymorphisms of the SEMA7A gene were associated with the BMD of the lumbar spine and femoral neck. SEMA7A+15775C>G and SEMA7A+22331A>G were associated with low BMD of the femoral neck (P=0.02) and lumbar spine (P=0.04) in a recessive model. SEMA7A-ht4 also showed an association with risk of vertebral fracture (OR=1.87-1.93, P=0.02-0.03). Our results suggest that variations in SEMA7A may play a role in decreased BMD and risk of vertebral fracture.

Involvement of Different Second Messengers in Parathyroid Hormone– and Interleukin‐1–Induced Interleukin‐6 and Interleukin‐11 Production in Human Bone Marrow Stromal Cells

Previous studies have suggested that increased secretion of bone active cytokines, such as interleukin‐6 (IL‐6) and interleukin‐11 (IL‐11), from osteoblasts and stromal cells play a pivotal role in the activation of osteoclasts and the genesis of osteoporosis. Various systemic and local factors can stimulate IL‐6/IL‐11 production, but the intracellular mechanism for such stimulation is largely unknown. In this study, we characterized the second messenger signaling in parathyroid hormone (PTH)‐ and IL‐1–induced production of IL‐6/IL‐11 and studied the possible modulating effects of estrogen. rhPTH(1–34) and rhIL‐1α dose‐dependently stimulated IL‐6 and IL‐11 production from human bone marrow stromal cells (hBMSCs). Agonists for protein kinase A (PKA) (forskolin), and protein kinase C (PKC) (phorbol 12‐myristate 13‐acetate; PMA) also stimulated IL‐6/IL‐11 production. Rp‐diastereoisomer of adenosine cyclic 3′,5′‐phosphorothioate (Rp‐cAMPS) and H‐8, inhibitors of PKA, significantly inhibited PTH‐stimulated IL‐6/IL‐11 production, but did not inhibit IL‐1–stimulated IL‐6/IL‐11 production. In contrast, staurosporine and calphostin C, inhibitors of PKC, suppressed IL‐1–stimulated, but not PTH‐stimulated, IL‐6/IL‐11 production. Pretreatment of cells with 17β‐estradiol (17β‐E2) antagonized IL‐1–stimulated IL‐6 production. However, PTH‐stimulated IL‐6 production and IL‐1– and PTH‐stimulated IL‐11 production were not affected by 17β‐E2. Similarly, 17β‐E2 inhibited PMA‐stimulated IL‐6 production, whereas neither forskolin‐stimulated IL‐6/IL‐11 production nor PMA‐stimulated IL‐11 production was affected by 17β‐E2. These results indicate that different second messengers are involved in PTH‐ and IL‐1–induced IL‐6 and IL‐11 production by hBMSCs: PTH and IL‐1 stimulate IL‐6/IL‐11 production via a PKA‐dependent and PKC‐dependent pathway, respectively. Furthermore, our results suggest that regulation of cytokine production by estrogen in hBMSCs is selective; only the IL‐1–induced IL‐6 production, which is mediated by PKC pathway, is inhibited, but PTH‐induced IL‐6 production and PTH/IL‐1–induced IL‐11 production are not inhibited by estrogen.