ABSTRACT
BACKGROUND: Osteoporosis and osteopenia are characterized by reduced bone mineral density (BMD) and increased fracture risk. Although the risk of fractures is higher in underweight people than in overweight people, the accumulation of body fat (especially abdominal fat) can increase the risk of bone loss. This study aimed to evaluate the association between body fat percentage and BMD in normal-weight middle-aged Koreans. METHODS: This study included 1,992 adults (mean age, 48.7 years; 52.9% women). BMD and body fat were measured using dual-energy X-ray absorptiometry. Multiple linear regression analyses and analysis of covariance were used to assess the association between BMD and body fat. Body fat percentage was grouped by cut-off values. The cut-off values were 20.6% and 25.7% for men with a body mass index of 18.5-22.9 kg/m2 , while the cut-off values were 33.4% and 36% for women. RESULTS: Body fat percentage tended to be negatively associated with BMD. Increased body fat percentage was associated with reduced BMD in normal-weight middle-aged adults. The effects of body fat percentage on BMD in normal-weight individuals were more pronounced in men than in women. CONCLUSION: There was a negative correlation between BMD and body fat percentage in middle-aged Korean men and women with normal body weight. This association was stronger in men than in women.
ABSTRACT
Variation in baseline ploidy is seen throughout the tree of life, yet the factors that determine why one ploidy level is maintained over another remain poorly understood. Experimental evolution studies using asexual fungal microbes with manipulated ploidy levels intriguingly reveals a propensity to return to the historical baseline ploidy, a phenomenon that we term "ploidy drive." We evolved haploid, diploid, and polyploid strains of the human fungal pathogen Candida albicans under three different nutrient limitation environments to test whether these conditions, hypothesized to select for low ploidy levels, could counteract ploidy drive. Strains generally maintained or acquired smaller genome sizes (measured as total nuclear DNA through flow cytometry) in minimal medium and under phosphorus depletion compared to in a complete medium, while mostly maintained or acquired increased genome sizes under nitrogen depletion. Improvements in fitness often ran counter to changes in genome size; in a number of scenarios lines that maintained their original genome size often increased in fitness more than lines that converged toward diploidy (the baseline ploidy of C. albicans). Combined, this work demonstrates a role for both the environment and genotype in determination of the rate of ploidy drive, and highlights questions that remain about the force(s) that cause genome size variation.
