Context: Vitamin D status in the Korean population has not been adequately determined. Objective: To investigate the vitamin D status and the prevalence of vitamin D insufficiency in the Korean population, and also identify the predictors for vitamin D insufficiency in Korea. Design and Setting: The Fourth Korea National Health and Nutrition Examination Surveys (KNHANES IV) in the Korean population conducted in 2008. Participants: 3,047 males and 3,878 females aged 10 years and older selected in all the 16 administrative districts of South Korea. Main Outcome Measures: Serum 25-hydroxyvitamin D [25(OH)D] levels and the prevalence of vitamin D insufficiency defined as serum 25(OH)D level of less than 20 ng/ml. Results: Vitamin D insufficiency was found in 47.3% of males and 64.5% of females, whereas only 13.2% of male and 6.7% of female population had a serum 25(OH)D level of greater than 30 ng/ml. Vitamin D insufficiency was most prevalent in the age of 20–29, with a rate of 65.0% in males and 79.9% in females, and least prevalent in the age of 60–69 in males and 50–59 in females. Those who work usually indoors were more predisposed to vitamin D insufficiency. In the adult population, predictors for vitamin D insufficiency included young age groups, spring and winter seasons, living in an urban area, and indoor occupations. Conclusions: Vitamin D insufficiency is very common, and it is now a greater threat to the younger generation in Korea. Current recommendations for vitamin D intakes for Koreans are inadequate, especially for the youth.

Connexin 43 (Cx43) mediates osteocyte communication with other cells and with the extracellular milieu and regulates osteoblastic cell signaling and gene expression. We now report that mice lacking Cx43 in osteoblasts/osteocytes or only in osteocytes (Cx43^ΔOt mice) exhibit increased osteocyte apoptosis, endocortical resorption, and periosteal bone formation, resulting in higher marrow cavity and total tissue areas measured at the femoral mid‐diaphysis. Blockade of resorption reversed the increased marrow cavity but not total tissue area, demonstrating that endocortical resorption and periosteal apposition are independently regulated. Anatomical mapping of apoptotic osteocytes, osteocytic protein expression, and resorption and formation suggests that Cx43 controls osteoclast and osteoblast activity by regulating osteoprotegerin and sclerostin levels, respectively, in osteocytes located in specific areas of the cortex. Whereas empty lacunae and living osteocytes lacking osteoprotegerin were distributed throughout cortical bone in Cx43^ΔOt mice, apoptotic osteocytes were preferentially located in areas containing osteoclasts, suggesting that osteoclast recruitment requires active signaling from dying osteocytes. Furthermore, Cx43 deletion in cultured osteocytic cells resulted in increased apoptosis and decreased osteoprotegerin expression. Thus, Cx43 is essential in a cell‐autonomous fashion in vivo and in vitro for osteocyte survival and for controlling the expression of osteocytic genes that affect osteoclast and osteoblast function. © 2012 American Society for Bone and Mineral Research

The periosteal and endocortical surfaces of cortical bone dictate the geometry and overall mechanical properties of bone. Yet the cellular and molecular mechanisms that regulate activity on these surfaces are far from being understood. Parathyroid hormone (PTH) has profound effects in cortical bone, stimulating periosteal expansion and at the same time accelerating intracortical bone remodeling. We report herein that transgenic mice expressing a constitutive active PTH receptor in osteocytes (DMP1‐caPTHR1 mice) exhibit increased cortical bone area and an elevated rate of periosteal and endocortical bone formation. In addition, DMP1‐caPTHR1 mice display a marked increase in intracortical remodeling and cortical porosity. Crossing DMP1‐caPTHR1 mice with mice lacking the Wnt coreceptor, LDL‐related receptor 5 (LRP5), or with mice overexpressing the Wnt antagonist Sost in osteocytes (DMP1‐Sost mice) reduced or abolished, respectively, the increased cortical bone area, periosteal bone formation rate, and expression of osteoblast markers and Wnt target genes exhibited by the DMP1‐caPTHR1 mice. In addition, DMP1‐caPTHR1 lacking LRP5 or double transgenic DMP1‐caPTHR1;DMP1‐Sost mice exhibit exacerbated intracortical remodeling and increased osteoclast numbers, and markedly decreased expression of the RANK decoy receptor osteoprotegerin. Thus, whereas Sost downregulation and the consequent Wnt activation is required for the stimulatory effect of PTH receptor signaling on periosteal bone formation, the Wnt‐independent increase in osteoclastogenesis induced by PTH receptor activation in osteocytes overrides the effect on Sost. These findings demonstrate that PTH receptor signaling influences cortical bone through actions on osteocytes and defines the role of Wnt signaling in PTH receptor action. © 2011 American Society for Bone and Mineral Research.

The overarching goal of osteoporosis management is to prevent fractures. A goal-directed approach to long-term management of fracture risk helps ensure that the most appropriate initial treatment and treatment sequence is selected for individual patients. Goal-directed treatment decisions require assessment of clinical fracture history, vertebral fracture identification (using vertebral imaging as appropriate), measurement of bone mineral density (BMD), and consideration of other major clinical risk factors. Treatment targets should be tailored to each patient’s individual risk profile and based on the specific indication for beginning treatment, including recency, site, number and severity of prior fractures, and BMD levels at the total hip, femoral neck, and lumbar spine. Instead of first-line bisphosphonate treatment for all patients, selection of initial treatment should focus on reducing fracture risk rapidly for patients at very high and imminent risk, such as in those with recent fractures. Initial treatment selection should also consider the probability that a BMD treatment target can be attained within a reasonable period of time and the differential magnitude of fracture risk reduction and BMD impact with osteoanabolic versus antiresorptive therapy. This position statement of the ASBMR/BHOF Task Force on Goal-Directed Osteoporosis Treatment provides an overall summary of the major clinical recommendations about treatment targets and strategies to achieve those targets based on the best evidence available, derived primarily from studies in older postmenopausal women of European ancestry.