Influencing variables on total and free 25(OH)D levels in healthy population.

INTRODUCTION: Vitamin D plays a fundamental role in calcium homeostasis and bone metabolism. It mainly comes from cutaneous synthesis through the action of sunlight. Therefore, variations in exposure to this radiation modify serum levels. We studied two different analytes of vitamin D in the healthy Spanish population and the influence of seasonality, climate, and latitude on its levels. METHODS: This work is a cross-sectional, descriptive study. A total of 206 blood donors from Burgos and Valencia between 18-60 years of age were recruited during March-April and October-November 2018. Total and free serum 25-hydroxycholecalciferol (25(OH)D) were analyzed. RESULTS: After summer, total and free serum 25(OH)D medium levels were 24.31 ±â€¯5.25 ng/mL and 5.01 ±â€¯1.25 pg/mL in Burgos and 25.99 ±â€¯6.87 ng/mL and 8.97 ±â€¯2.82 pg/mL in Valencia. After winter, they were 17.66 ±â€¯5.04 ng/mL and 4.08 ±â€¯0.66 ng/mL in Burgos and 21.38 ±â€¯3.77 ng/mL and 7.23 ±â€¯2.44 ng/mL in Valencia. The seasonal changes were statistically significant for both components studied both in the sample as a whole and in the separate populations. The differences found between the two populations in total and free 25(OH)D levels were statistically significant except for total 25(OH)D after summer (24.07 ng/mL vs. 26.03 ng/mL; p = .408). Latitude was also shown to be a factor that influences concentrations of both analytes in summer and winter. CONCLUSIONS: Our study shows lower vitamin D levels than expected for a healthy Spanish population. Seasonality, climate, and latitude were demonstrated to influence total and free 25(OH)D levels.

[Cholesterol and phospholipids in high density lipoproteins and their subfractions in a population in its second decade of life. The Burgos study]. / Colesterol y fosfolípidos en lipoproteínas de alta densidad y sus subfracciones en una población en la segunda década de la vida. Estudio de Burgos.

Decreased levels of high-density lipoproteins (HDL) are related to a risk of ischaemic heart disease and are measured as HDL-cholesterol (HDLc), whereas little attention has been paid to HDL-phospholipids (HDLph). Regarding HDL subfractions (HDL2, HDL3) and risk of ischaemic heart disease, there are few studies in the literature and these are contradictory, especially those performed in subjects that were in their second decade of life. This study consisted of 322 healthy volunteers between 11 and 19 years of age. The HDL fractions and HDL3 subfractions were separated by precipitation with polyethylene glycol at defined pH and concentration. Concentrations of cholesterol and triglycerides were measured by enzymatic methods, except for HDL2c and HDL2ph, which were calculated by subtraction. Forty-two percent of the children with parental history of ischaemic heart disease, but only 26% of the children without parental history of heart disease, exhibited HDL3ph levels lower than 0.95 mmol/l (74 mg/dl). Levels of HDLc, HDL3c and HDL2c are relatively constant in girls after puberty and levels of HDLph and HDL3ph are increased; levels of HDLph are relatively constant in boys after puberty while levels of HDLc, HDL3c and HDL2c are decreased. Our results suggest that serum levels of HDL3ph are potential markers for a risk of ischaemic heart disease, together with other more classic risk factors.