Furthermore, we excluded 52 men

who had and/or were receiving treatment for a disease that could influence bone metabolism (osteoporosis, rheumatoid arthritis, hyper- or hypothyroidism, hyper- or hypoparathyroidism, diabetes mellitus, renal dysfunction, or corticosteroid use); one man was excluded because of incomplete data. As a result, 193 men were included in the present study. None had a history of vertebral fractures. The protocol of this study was approved by the Institutional Review Board of the Tohoku University Graduate School of Medicine. Fig. 1 Flow chart of the sample selection process AGEs, advanced glycation end-products Skin autofluorescence AGE accumulation in skin tissue was assessed on the basis of skin AF, using an AF reader (AGE Reader; DiagnOptics, Groningen, PP2 The Netherlands), as described previously [16]. The AGE Reader consists

of a tabletop box equipped IACS-10759 price with an excitation light source. Each MK 8931 measurement took approximately 30 s to complete and was performed by an independent observer. Excitation light of 300–420-nm wavelength was projected onto the skin surface through a 1-cm2 hole. The intensity of light emitted from the skin at wavelengths between 420 and 600 nm was measured with a spectrometer via a glass fiber. Skin AF was calculated by dividing the mean value of the emitted light intensity per nanometer between 420 and 600 nm by the mean value of the excitation light intensity per nm between 300 and 420 nm; the result was expressed in arbitrary unit (AU) and multiplied by 100 for easier evaluation. The intra- and inter-assay coefficients of variation for AGE reader measurement were 2.9–1.8%, respectively. All AF measurements were

performed at room temperature on the volar side of the lower right arm, approximately 10–15 cm below the elbow fold, with the participants in a seated position. Care was taken to perform the measurement at a normal skin site without visible vessels, scars, lichenification, or other skin abnormalities. The arm of each subject was covered with a black cloth to avoid any influence of external light during the measurement. Because creams and sunscreens can affect skin AF measurement [20], we asked each participant whether they applied creams or sunscreens on their arms when skin AF was measured. No participants applied any creams or sunscreens. Since Microtubule Associated inhibitor skin pigmentation influences AF measurements, particularly when skin reflection is below 10%, AF values were not used if the skin reflection was below 10% [21]. Quantitative ultrasound assessment of the calcaneus Quantitative ultrasound assessment of the calcaneus was performed using an ultrasound system (AOS-100; Aloka Co. Ltd., Tokyo, Japan). The AOS-100 measured the speed of sound (SOS) as an index of bone density and the transmission index (TI) as an index of bone structure. The osteo-sono assessment index (OSI) was calculated using the following formula: OSI = TI × SOS2.