Grant: Travel Awards - Institute Community Support

There is evidence that a high concentration of serum High-density lipoprotein (HDL) and a low concentration of serum triglycerides (TG) are associated with reduced risk of heart disease. Surprisingly, some studies have found negative associations between high HDL and low TG, and bone mineral density (BMD). Several mechanism have been proposed for such relationships, however the exact mechanism is not clear. It is possible that these unexpected associations are due to confounding factors that were not adjusted in previous studies. The objective of our study was to examine the associations between serum lipids and bone metabolism in aging men after adjusting for potential confounding factors using cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 1999-2002 cycles. NHANES is a population-based survey that provides extensive data on laboratory tests, medical conditions, use of prescription medication and dietary supplements, and various lifestyle factors. The two bone turnover makers measured in this survey are: serum bone-specific alkaline phosphatase (BAP, a biomarker of bone formation) and urinary N-Telopeptides/Creatinine (uNTx/Cr, a biomarker of bone resorption). In our unadjusted analysis, we found a negative association between HDL and BAP and positive associations between TG, and BAP. There were no associations between serum lipids and uNTx/Cr. Given that in aging men decreased bone-formation can be detrimental to bone health; our findings are in accordance with other studies that found that high HDL and low TG are associated with poorer bone health outcomes. However, after adjusting for insulin levels these relationships disappeared for HDL and the strength of relationship was reduced for TG. Therefore, the possible mechanism for the unexpected associations between HDL and TG, and bone health may be due to the confounding effect of high insulin levels.