Supplementary Material for: Expression of the Sodium/Calcium/Potassium Exchanger, NCKX4, in Ameloblasts

Transcellular calcium transport is an essential activity in mineralized tissue formation, including dental hard tissues. In many organ systems, this activity is regulated by membrane-bound sodium/calcium (Na⁺/Ca²⁺) exchangers, which include the NCX and NCKX [sodium/calcium-potassium (Na⁺/Ca²⁺-K⁺) exchanger] proteins. During enamel maturation, when crystals expand in thickness, Ca²⁺ requirements vastly increase but exactly how Ca²⁺ traffics through ameloblasts remains uncertain. Previous studies have shown that several NCX proteins are expressed in ameloblasts, although no significant shifts in expression were observed during maturation which pointed to the possible identification of other Ca²⁺ membrane transporters. NCKX proteins are encoded by members of the solute carrier gene family, Slc24a, which include 6 different proteins (NCKX1–6). NCKX are bidirectional electrogenic transporters regulating Ca²⁺ transport in and out of cells dependent on the transmembrane ion gradient. In this study we show that all NCKX mRNAs are expressed in dental tissues. Real-time PCR indicates that of all the members of the NCKX group, NCKX4 is the most highly expressed gene transcript during the late stages of amelogenesis. In situ hybridization and immunolocalization analyses clearly establish that in the enamel organ, NCKX4 is expressed primarily by ameloblasts during the maturation stage. Further, during the mid-late maturation stages of amelogenesis, the expression of NCKX4 in ameloblasts is most prominent at the apical poles and at the lateral membranes proximal to the apical ends. These data suggest that NCKX4 might be an important regulator of Ca²⁺ transport during amelogenesis

Supplementary Material for: The effect of social isolation on sarcopenia: a longitudinal study among the middle-aged and older population in China

Introduction: Although social isolation is associated with premature death and somatic and mental diseases, evidence of its long-term effect on sarcopenia is scarce. This study aimed to examine the longitudinal association between social isolation and possible sarcopenia. Methods: We extracted baseline and four-year follow-up data from the China Health and Retirement Longitudinal Study and included participants aged 45 years or above. Social isolation was measured by factors including living alone, marital status, frequency of contact with adult children and friends, and participation in social activity. The change in social isolation from baseline to follow-up was classified into stable, progressive, and regressive groups. Possible sarcopenia was detected using the handgrip strength and five-time chair stand test. Using mixed effects logistic regression, we studied the effect of baseline isolation and the change in isolation status on possible sarcopenia at a four-year follow-up. Results: A total of 5289 participants aged 45 to 90 years and without possible sarcopenia at baseline were included. After four years, possible sarcopenia was detected in 21.7% (1146/5289) of the participants. Compared with the low social isolation group, the middle (OR=1.53, 95% confidence interval [CI]=1.16~2.04, p=0.003) and high social isolation groups (OR=1.65, 95% CI=1.26~2.18, p<0.001) were associated with a higher risk of possible sarcopenia. Being not married/cohabiting (OR=1.58, 95% CI=1.19~2.10, p=0.002), lack of contact with children (OR=1.86, 95% CI=1.21~2.85, p=0.004), and lack of social activities (OR=1.26, 95% CI=1.04~1.53, p=0.019) were associated with an increased risk of possible sarcopenia. Compared with the stable social isolation group, the progressive group was associated with a greater risk of possible sarcopenia (OR=1.51, 95% CI=1.17~1.95, p=0.001). Conclusions: Social isolation is associated with an increased risk of possible sarcopenia. Progressive social isolation further elevates the risk. The most vulnerable groups are middle-aged and older people who live alone, are not socially active, and lack contact with their children