Varying relationship between 25-hydroxy-vitamin D, high density lipoprotein cholesterol, and serum 7-dehydrocholesterol reductase with sunlight exposure.
BACKGROUND
Cholesterol and cholecalciferol are synthesized from a common substrate 7-dehydrocholesterol. 7-dehydrocholesterol is converted to cholesterol by 7-dehydrocholesterol reductase enzyme (DHCR7) and to cholecalciferol by ultraviolet B radiation from sunlight.


OBJECTIVE
To examine the effect of sunlight exposure and serum DHCR7 levels on cholecalciferol and cholesterol levels and studying any interrelationship.


METHODS
In a cross-sectional observational study, 307 apparently healthy men (aged 40-60 years) were assessed for sunlight exposure, lipid levels, serum DHCR7, 25 hydroxyvitamin D (25(OH)D), body composition, and dietary milk calcium intake.


RESULTS
Vitamin D deficiency (25(OH)D <20 ng/mL, 1 ng/mL = 2.496 nmols/L) was found in 56% of subjects. Serum 25(OH)D concentrations increased significantly with increasing duration of sunlight exposure (P < .05). At lower sunlight exposure (<1 h/d), serum 25(OH)D levels were positively associated with high-density lipoprotein cholesterol (HDL-C) levels (P < .05) but at moderate sunlight exposure (1-2 h/d), there was no significant association. However, with higher sunlight exposure (>2 h/d), serum 25(OH)D concentrations were significantly negatively associated with HDL-C (P < .05). At moderate and higher sunlight exposure, an inverse significant relationship was observed between 25(OH)D and serum DHCR7 (P < .05); however, at lower sunlight exposure, no significant relationship was seen.


CONCLUSIONS
25(OH)D seems to show a varying relationship with HDL-C and serum DHCR7 at different durations of sunlight exposure.
Growth and Endocrine Unit, Hirabai Cowasji Jehangir Medical Research Institute, Jehangir Hospital, Pune, India.
Vivek G
VG
Patwardhan
Growth and Endocrine Unit, Hirabai Cowasji Jehangir Medical Research Institute, Jehangir Hospital, Pune, India. Electronic address: anuradhavkhadilkar@gmail.com.
Anuradha V
AV
Khadilkar
Growth and Endocrine Unit, Hirabai Cowasji Jehangir Medical Research Institute, Jehangir Hospital, Pune, India.
Shashi A
SA
Chiplonkar
Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Manchester, UK.
Zulf M
ZM
Mughal
Growth and Endocrine Unit, Hirabai Cowasji Jehangir Medical Research Institute, Jehangir Hospital, Pune, India.
Vaman V
VV
Khadilkar
D000328:Adult; D008076:Cholesterol, HDL / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000097:blood*; D000069079:Radiation Exposure / Q000706:statistics & numerical data*; D013997:Time Factors; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
D008076:Cholesterol, HDL; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019995:7-dehydrocholesterol reductase
25(OH)D; Cholecaciferol; HDL-cholesterol; Serum DHCR7; Sunlight; Vitamin D