Associations of plasma PAPP-A2 and genetic variations with salt sensitivity, blood pressure changes and hypertension incidence in Chinese adults.

OBJECTIVE: Pregnancy-associated plasma protein-A2 (PAPP-A2) is the homolog of PAPP-A in the vertebrate genome and its role in protecting against salt-induced hypertension in salt-sensitive rats has been confirmed. We sought to examine the associations of plasma PAPP-A2 levels and its genetic variants with salt sensitivity, blood pressure (BP) changes and hypertension incidence in humans. METHODS: Eighty participants (18-65 years old) sequentially consuming a usual diet, a 7-day low-salt diet (3.0 g/day) and a 7-day high-salt diet (18 g/day). In addition, we studied participants of the original Baoji Salt-Sensitive Study, recruited from 124 families in Northern China in 2004 who received the same salt intake intervention, and evaluated them for the development of hypertension over 14 years. RESULTS: The plasma PAPPA2 levels significantly decreased with the change from baseline to a low-salt diet and decreased further when converting from the low-salt to high-salt diet. SNP rs12042763 in the PAPP-A2 gene was significantly associated with systolic BP responses to both low-salt and high-salt diet while SNP rs2861813 showed a significant association with the changes in SBP and pulse pressure at 14-year follow-up. Additionally, SNPs rs2294654 and rs718067 demonstrated a significant association with the incidence of hypertension over the 14-year follow-up. Finally, the gene-based analysis found that Pappa2 was significantly associated with longitudinal SBP changes and the incidence of hypertension over the 14-year follow-up. CONCLUSIONS: This study shows that dietary salt intake affects plasma PAPP-A2 levels and that PAPP-A2 may play a role in salt sensitivity, BP progression and development of hypertension in the Chinese populations.

Optimal level of 25-(OH)D in children in Nanjing (32°N Lat) during winter.

BACKGROUND: The optimal serum level of 25-hydroxyvitamin D (25-(OH)D) for bone health is still unclear, especially in children. Hypovitaminosis D is also re-emerging in developed and developing countries. The purpose of the present study was therefore to determine optimal serum 25-(OH)D level and preliminarily identify the vitamin D nutritional status in Nanjing children. METHODS: All subjects (76 healthy, 66 suffering from infectious diseases) aged 0-10 years were recruited during the period December 2007-March 2008. Venous blood samples were collected before breakfast and the levels of serum 25-(OH)D, parathyroid hormone (PTH), bone-specific alkaline phosphatase (BAP), calcium (Ca), phosphorus (P) were determined. The optimal level of serum 25-(OH)D was explored using the three response curves of 25-(OH)D versus PTH, 25-(OH)D versus BAP, and 25-(OH)D versus Ca×P product. RESULTS: For 25-(OH)D ≤ 50 nmol/L, PTH and BAP were both inversely correlated with 25-(OH)D (PTH, r=-0.864, P < 0.01; BAP, r=-0.856, P < 0.01). For 25-(OH)D > 50-60 nmol/L, levels of PTH and BAP remained steady. With regard to the Ca×P product, for 25-(OH)D ≤ 50 nmol/L, Ca×P product increased as 25-(OH)D increased (r= 0.037, P > 0.05). For 25-(OH)D > 50-60 nmol/L, Ca×P product remained steady. The mean serum level of 25-(OH)D was 80.5 ± 29.3 nmol/L (mean ± SD) in the healthy children, and 65.7 ± 32.3 nmol/L in the sick children. CONCLUSION: The optimal 25-(OH)D level may be 50-60 nmol/L for bone health in Nanjing children. The vitamin D nutritional status of Nanjing children is relatively good in winter.