Hyung Jin Choi

A graphene-based electrochemical device with thermoresponsive microneedles for diabetes monitoring and therapy

Owing to its high carrier mobility, conductivity, flexibility and optical transparency, graphene is a versatile material in micro- and macroelectronics. However, the low density of electrochemically active defects in graphene synthesized by chemical vapour deposition limits its application in biosensing. Here, we show that graphene doped with gold and combined with a gold mesh has improved electrochemical activity over bare graphene, sufficient to form a wearable patch for sweat-based diabetes monitoring and feedback therapy. The stretchable device features a serpentine bilayer of gold mesh and gold-doped graphene that forms an efficient electrochemical interface for the stable transfer of electrical signals. The patch consists of a heater, temperature, humidity, glucose and pH sensors and polymeric microneedles that can be thermally activated to deliver drugs transcutaneously. We show that the patch can be thermally actuated to deliver Metformin and reduce blood glucose levels in diabetic mice.

Prevalence and risk factors of osteoporosis in Korea: A community-based cohort study with lumbar spine and hip bone mineral density

PURPOSE To investigate bone mineral density (BMD) profiles, osteoporosis prevalence and risk factors in a community-based cohort in Korea. METHODS The present study is a cross-sectional study. The study population consisted of 1,547 men and 1991 women aged 40 years and older with BMD measurements using central dual energy X-ray absorptiometry from a prospective community-based cohort. The data were compared with other ethnic groups. Risk factors related to osteoporosis were analyzed. RESULTS Crude prevalence of osteoporosis in the whole subjects (40-79 years old) was 13.1% for men and 24.3% for women by WHO criteria, at any site among lumbar spine, femoral neck or total hip. Standardized prevalence of osteoporosis between age of 50 and 79 at lumbar spine, femoral neck and total hip was 12.9%, 1.3% and 0.7% in men and 24.0%, 5.7% and 5.6% in women, respectively. The mean BMD of studied female subjects after age of 50 was not significantly different from that of Chinese but significantly lower than that of Japanese, non-Hispanic whites, non-Hispanic blacks and Mexican Americans. Risk of osteoporosis was significantly associated with the presence of past fracture history (OR, 1.45; 95% CI, 1.08-1.94), smoking> or =1 pack/day (OR, 1.63; 95% CI, 1.01-2.62), menarche after age of 16 (OR, 1.46; 95% CI, 1.14-1.87), last delivery after age of 30 (OR, 1.58; 95% CI, 1.20-2.09), more than three offspring (OR, 1.42; 95% CI, 1.07-1.89), post-menopause status (OR, 7.32; 95% CI, 3.05-17.6), more than 17 years since menopause (OR, 1.53; 95% CI, 1.10-2.14), regular exercise of two to three times per week (OR, 0.40; 95% CI, 0.18-0.89), monthly income above 500,000 won per household (OR, 0.64; 95% CI, 0.45-0.92), college graduate (OR, 0.29; 95% CI, 0.13-0.63) and calcium intake> or =627.5 mg/day (OR, 0.65; 95% CI, 0.43-0.98) after adjusting for age and BMI. CONCLUSION The BMD and osteoporosis prevalence of Koreans are presented. Risk of osteoporosis was significantly associated with fracture history, smoking, reproductive history, regular exercise, income level, education background and calcium intake.

Trabecular Bone Score as an Indicator for Skeletal Deterioration in Diabetes

CONTEXT Trabecular bone score (TBS) is a novel texture index that evaluates the pixel gray-level variations in lumbar spine dual-energy X-ray absorptiometry images and is related to bone microarchitecture independent of bone mineral density (BMD). OBJECTIVE We investigated lumbar spine TBS as an indicator for skeletal deterioration in diabetes. DESIGN AND SETTING Cross-sectional data were collected from subjects participating in an ongoing prospective, community-based, cohort study from 2009 to 2010. PARTICIPANTS We included 1229 men and 1529 postmenopausal women older than 50 years in the Ansung cohort. OUTCOME MEASURES Biochemical parameters, lumbar spine TBS, and BMD from dual-energy X-ray absorptiometry images were measured. RESULTS Lumbar spine TBS was lower in men with diabetes than in nondiabetic men (1.287 ± 0.005 vs 1.316 ± 0.003, P < .001), whereas lumbar spine BMD was higher in men with diabetes (1.135 ± 0.010 vs 1.088 ± 0.006 g/cm(2)). Lumbar spine TBS was lower in women with diabetes than in nondiabetic women only in an unadjusted model (1.333 ± 0.004 vs 1.353 ± 0.003). However, women younger than 65 years (n = 707) with diabetes had a lower TBS than those without diabetes, even after adjusted for covariates (P < .001). Diabetes was not associated with BMD at femur sites in both genders. TBS was negatively correlated with glycated hemoglobin, fasting plasma glucose, fasting insulin, and homeostasis model assessment for insulin resistance but not with homeostasis model assessment for β-cell function in both genders. CONCLUSIONS The inverse association between lumbar spine TBS and insulin resistance may make it an indicator for determining skeletal deterioration in diabetic patients who have high BMD.

Transplantation of Mesenchymal Stem Cells Overexpressing RANK-Fc or CXCR4 Prevents Bone Loss in Ovariectomized Mice

Osteoporosis is a systemic skeletal disorder characterized by reduced bone mineral density (BMD) and increased risk of fracture. We studied the effects of transplantation of mesenchymal stem cells (MSCs) overexpressing receptor activator of nuclear factor-kappaB (RANK)-Fc and CXC chemokine receptor-4 (CXCR4) using retrovirus on ovariectomy (OVX)-induced bone loss in mice. Ten-week-old adult female C57BL/6 mice were divided into six groups as follows: Sham-operated mice treated with phosphate-buffered saline (PBS) (Sham-op + PBS); OVX mice intravenously transplanted with syngeneic MSCs overexpressing RANK-Fc-DsRED and CXCR4-GFP (RANK-Fc + CXCR4); RANK-Fc-DsRED and GFP (RANK-Fc + GFP); CXCR4-GFP and DsRED (CXCR4 + RED); DsRED and GFP (RED + GFP); or treated with PBS only (OVX + PBS). Measurement of BMD showed that introduction of RANK-Fc resulted in significant protection against OVX-induced bone loss compared to treatment with PBS (-0.1% versus -6.2%, P < 0.05) at 8 weeks after cell infusion. CXCR4 + RED group also significantly prevented bone loss compared to OVX + PBS group (2.7% versus -6.2%, P < 0.05). Notably, the effect of RANK-Fc + CXCR4 was greater than that of RANK-Fc + GFP (4.4% versus -0.1%, P < 0.05) while it was not significantly different from that in CXCR4 + RFP group (4.4% versus 2.7%, P = 0.055) at 8 weeks. Transplantation of MSCs with control virus (RED + GFP group) also resulted in amelioration of bone loss compared to OVX + PBS group (-1.7% versus -6.2%, P < 0.05). Fluorescence-activated cell sorting (FACS) and real-time quantitative PCR (qPCR) analysis for GFP from bone tissue revealed enhanced cell trafficking to bone by co-overexpression of CXCR4. In conclusion, we have demonstrated that intravenous transplantation of syngeneic MSCs overexpressing CXCR4 could promote increased in vivo cell trafficking to bone in OVX mice, which could in itself protect against bone loss but also enhance the therapeutic effects of RANK-Fc.

Vitamin K2 Supplementation Improves Insulin Sensitivity via Osteocalcin Metabolism: A Placebo-Controlled Trial

Undercarboxylated osteocalcin (ucOC) is reported to function as an endocrine hormone, affecting glucose metabolism in mice (1,2). Vitamin K, which converts ucOC to carboxylated osteocalcin (cOC), has been suggested to regulate glucose metabolism by modulating osteocalcin and/or proinflammatory pathway (3–5). We studied whether modulation of ucOC via vitamin K2 supplementation for 4 weeks affects β-cell function and/or insulin sensitivity in healthy young male subjects. Forty-two healthy young male volunteers received vitamin K2 (menatetrenone; 30 mg; Eisai Co., Japan) or placebo t.i.d. for 4 weeks. Frequently sampled intravenous glucose tolerance test was performed to determine insulin sensitivity index ( S i), acute insulin response to glucose (AIRg), and disposition index (DI) before and after treatment. Adiponectin, interleukin (IL)-6, C-reactive protein (CRP), ucOC, and cOC …

Fat mass is negatively associated with bone mineral content in Koreans

SummaryAlthough obesity and osteoporosis are important public health problems, the effect of fat mass on bone mass remains controversial. This study demonstrated that fat mass was inversely related to bone mineral content, and abdominal obesity was significantly associated with bone mineral content independent of total fat mass.IntroductionObesity and osteoporosis, two disorders of body composition, have become increasingly important public health problems throughout the world. However, the effect of fat mass on bone mass remains controversial. This study investigates the effect of fat mass and regional fat distribution on bone mass within a community-dwelling cohort.MethodsA total of 3,042 subjects (1,284 men, 362 premenopausal women, and 1,396 postmenopausal women) were studied. Fat mass, percent fat mass, lean mass, percent lean mass, and bone mineral content (BMC) were measured by dual energy X-ray absorptiometry.ResultsFat mass and percent fat mass decreased significantly across increasing tertiles of BMC in all three subgroups (men, premenopausal and postmenopausal women). In contrast, lean mass and percent lean mass increased significantly across tertiles of BMC in men, and a similar trend was also identified in postmenopausal women. Interestingly, although correlation analysis showed a positive association between fat mass and BMC (p < 0.05), this association became negative after controlling for age and weight (p < 0.05). Finally, in premenopausal and postmenopausal women, subjects with the lowest waist circumference (WC) had the highest BMC in the higher three quartiles of percent fat mass after adjusting for age and weight (p < 0.05), indicating that abdominal obesity is associated with BMC independent of total fat mass.ConclusionThis study demonstrated that fat mass was inversely related to BMC after removing the mechanical loading effect in Korean men and women. Moreover, abdominal obesity as measured by WC was significantly associated with BMC independent of total fat mass.

Wnt inhibitory factor (WIF)-1 inhibits osteoblastic differentiation in mouse embryonic mesenchymal cells

Wnt inhibitory factor (WIF)-1 belongs to the members of secreted modulators of Wnt proteins. Secreted frizzled-related proteins (sFRPs), another member of Wnt modulators, have been shown to play differential roles in Wnt signaling depending on the subtypes and cell models. This study was undertaken to investigate the functional role of WIF-1 in osteoblastic differentiation of mouse mesenchymal C3H10T1/2 cells. C3H10T1/2 cells express endogenous WIF-1 and its expression level decreases during osteoblastogenesis. Treatment of C3H10T1/2 cells with WIF-1 significantly reduced alkaline phosphatase (ALP) activities induced by either osteogenic medium (OM, ascorbic acid and beta-glycerophosphate) or Wnt-3a conditioned medium (CM) in a dose-dependent manner. In contrast, the expression level of endogenous WIF-1 increased during adipogenesis and WIF-1 treatment resulted in increased adipogenesis. C3H10T1/2 cells transduced with WIF-1 retrovirus also exhibited reduced ALP activity and decreased mRNA expression of Runx2, collagen type 1, ALP and osteocalcin during osteoblastic differentiation compared to empty virus-transduced cells. Moreover, treatment with WIF-1 dose-dependently attenuates beta-catenin/T-cell factor (TCF) transcriptional activity in this cell line. Finally, knockdown of WIF-1 in C3H10T1/2 cells by RNA interference leads to increase in ALP activities. Collectively, these results indicate that WIF-1 plays as a negative regulator of osteoblastic differentiation in mouse mesenchymal C3H10T1/2 cells in vitro.

Changes of microRNA profile and microRNA-mRNA regulatory network in bones of ovariectomized mice.

Growing evidence shows the possibility of a role of microRNAs (miRNA) in regulating bone mass. We investigated the change of miRNAs and mRNA expression profiles in bone tissue in an ovariectomized mice model and evaluated the regulatory mechanism of bone mass mediated by miRNAs in an estrogen‐deficiency state. Eight‐week‐old female C3H/HeJ mice underwent ovariectomy (OVX) or sham operation (Sham‐op), and their femur and tibia were harvested to extract total bone RNAs after 4 weeks for microarray analysis. Eight miRNAs (miR‐127, ‐133a, ‐133a*, ‐133b, ‐136, ‐206, ‐378, ‐378*) were identified to be upregulated after OVX, whereas one miRNA (miR‐204) was downregulated. Concomitant analysis of mRNA microarray revealed that 658 genes were differentially expressed between OVX and Sham‐op mice. Target prediction of differentially expressed miRNAs identified potential targets, and integrative analysis using the mRNA microarray results showed that PPARγ and CREB pathways are activated in skeletal tissues after ovariectomy. Among the potential candidates of miRNA, we further studied the role of miR‐127 in vitro, which exhibited the greatest changes after OVX. We also studied the effects of miR‐136, which has not been studied in the context of bone mass regulation. Transfection of miR‐127 inhibitor has enhanced osteoblastic differentiation in UAMS‐32 cells as measured by alkaline phosphatase activities and mRNA expression of osteoblast‐specific genes, whereas miR‐136 precursor has inhibited osteoblastic differentiation. Furthermore, transfection of both miR‐127 and miR‐136 inhibitors enhanced the osteocyte‐like morphological changes and survival in MLO‐Y4 cells, whereas precursors of miR‐127 and ‐136 have aggravated dexamethasone‐induced cell death. Both of the precursors enhanced osteoclastic differentiation in bone marrow macrophages, indicating that both miR‐127 and ‐136 are negatively regulating bone mass. Taken together, these results suggest a novel insight into the association between distinct miRNAs expression and their possible role through regulatory network with mRNAs in the pathogenesis of estrogen deficiency–induced osteoporosis.

Osteoblast‐targeted overexpression of PPARγ inhibited bone mass gain in male mice and accelerated ovariectomy‐induced bone loss in female mice

PPARγ has critical role in the differentiation of mesenchymal stem cells into adipocytes while suppressing osteoblastic differentiation. We generated transgenic mice that overexpress PPARγ specifically in osteoblasts under the control of a 2.3‐kb procollagen type 1 promoter (Col.1‐PPARγ). Bone mineral density (BMD) of 6‐ to 14‐week‐old Col.1 − PPARγ male mice was 8% to 10% lower than that of their wild‐type littermates, whereas no difference was noticed in Col.1‐PPARγ female mice. Col.1‐PPARγ male mice exhibited decreased bone volume (45%), trabecular thickness (23%), and trabecular number (27%), with a reciprocal increase in trabecular spacing (51%). Dynamic histomorphometric analysis also revealed that bone‐formation rate (42%) and mineral apposition rate (32%) were suppressed significantly in Col.1‐PPARγ male mice compared with their wild‐type littermates. Interestingly, osteoclast number and surface also were decreased by 40% and 58%, respectively, in Col.1‐PPARγ male mice. In vitro whole‐marrow culture for osteoclastogenesis also showed a significant decrease in osteoclast formation (approximately 35%) with the cells from Col.1‐PPARγ male mice, and OPG/RANKL ratio was reduced in stromal cells from Col.1‐PPARγ male mice. Although there was no significant difference in BMD in Col.1‐PPARγ female mice up to 30 weeks, bone loss was accelerated after ovariectomy compared with wild‐type female mice (−3.9% versus −6.8% at 12 weeks after ovariectomy, p < .01), indicating that the effects of PPARγ overexpression becomes more evident in an estrogen‐deprived state in female mice. In conclusion, in vivo osteoblast‐specific overexpression of PPARγ negatively regulates bone mass in male mice and accelerates estrogen‐deficiency‐related bone loss in female mice.

Transgenic mice overexpressing secreted frizzled-related proteins (sFRP)4 under the control of serum amyloid P promoter exhibit low bone mass but did not result in disturbed phosphate homeostasis

Secreted frizzled-related protein-4 (sFRP4) is a member of secreted modulators of Wnt signaling pathways and has been recognized to play important role in the pathogenesis of oncogenic osteomalacia as a potential phosphatonin. To investigate the role of sFRP4 in bone biology and phosphorus homeostasis in postnatal life, we generated transgenic mice that overexpress sFRP4 under the control of the serum amyloid P promoter (SAP-sFRP4), which drives transgene expression postnatally. Serum phosphorus level and urinary phosphorus excretion were slightly lower and higher, respectively, in SAP-sFRP4 compared to wild-type (WT) littermate, but the difference did not reach statistical significance. However, renal Na(+/-)/Pi co-transporter (Npt) 2a and 1alpha-hydroxylase gene expression were up-regulated in SAP-sFRP4 mice. In addition, the level of serum 1,25-dihydroxyvitamin D(3) was higher in SAP-sFRP4 mice. At 5 weeks of age, bone mineral density (BMD) in SAP-sFRP4 was similar to that in WT. However, with advancing age, SAP-sFRP4 mice gained less BMD so that areal BMD of SAP-sFRP4 mice was significantly lower compared to WT at 15 weeks of age. Histomorphometric analysis of proximal tibia showed that trabecular bone volume (BV/TV) and thickness (Tb.Th) were significantly lower in SAP-sFRP4 mice. There was no evidence of osteomalacia in histological analysis. Our data do not support the role of sFRP4 per se as a phosphatonin but suggest that sFRP4 negatively regulates bone formation without disrupting phosphorus homeostasis.