The Effect of Body Weight on Vitamin D Metabolism
Λέξεις-κλειδιά
Αφηρημένη
Περιγραφή
Part 1: Measurement of vitamin D and metabolites (adults and children) Circulating levels of vitamin D metabolites are influenced by calcium intake, so participants will be asked to complete a seven day diet diary before the first vitamin D measurement. Measured vitamin D is influenced by vitamin D binding protein, lipids and inflammatory cytokines, so the investigators will include and correct for these measurements.
Visit 1 Consent Height and weight Diet diary instructions Urine collection instructions
Visit 2 Return of 24h urine collection for calcium and creatinine Return of diet diary Fasting blood sample for vitamin D, binding protein and metabolites C reactive protein (CRP), lipids and creatine kinase (CK), PTH, insulin-like growth factor -1 (IGF-1), creatinine, calcium, albumin, phosphate
Part 2: Measurement of vitamin D clearance rate (adults only) Kinetic studies will be perturbed by acute changes in vitamin D (most likely to be caused by sunlight exposure on a sunny day), and so the studies will all be conducted in the autumn, winter, and early spring when sunlight in Sheffield will not be strong enough to deliver large doses of vitamin D.
The administration and sampling protocol for the kinetics study has been developed by statisticians at the Sheffield School of Health and Related Research (ScHaRR) in collaboration with the Medical Research Council Human Nutrition Unit, based on modelling from their previous use of the stable isotope tracer method.
Visit 2 Oral administration of stable vitamin D isotope
Visit 3 (5-7 days after visit 2) Blood sample for tracer and vitamin D metabolites
Visit 4 (9 days ± 2 after visit 2) Blood sample for tracer and vitamin D metabolites
Visit 5 (27 days ± 2 after visit 2) Blood sample for tracer and vitamin D metabolites
Visit 6 (30 days ± 2 after visit 2) Blood sample for tracer and vitamin D metabolites Height and weight
The effect of obesity on vitamin D metabolites will be determined by regression models of BMI and vitamin D measurements corrected for age and gender.
The effects of obesity on vitamin D kinetics will be determined by modelling metabolic clearance rate on age, gender and BMI.
Subjects' previous data from the 'Effects of obesity on bone structure and strength'study (STH 15688) and the 'Body weight and bone' study (STH16199) will be used to evaluate relationships between vitamin D metabolism and body fat distribution, bone density and structure, and bone biochemistry.
Ημερομηνίες
| Τελευταία επαλήθευση: | 11/30/2015 |
| Πρώτα υποβλήθηκε: | 12/06/2015 |
| Υποβλήθηκε εκτιμώμενη εγγραφή: | 12/08/2015 |
| Δημοσιεύτηκε για πρώτη φορά: | 12/13/2015 |
| Υποβλήθηκε τελευταία ενημέρωση: | 12/08/2015 |
| Δημοσιεύτηκε η τελευταία ενημέρωση: | 12/13/2015 |
| Ημερομηνία έναρξης της πραγματικής μελέτης: | 09/30/2012 |
| Εκτιμώμενη κύρια ημερομηνία ολοκλήρωσης: | 03/31/2013 |
| Εκτιμώμενη ημερομηνία ολοκλήρωσης μελέτης: | 03/31/2013 |
Κατάσταση ή ασθένεια
Φάση
Ομάδες βραχιόνων
| Μπράτσο | Παρέμβαση / θεραπεία |
|---|---|
| normal weight Healthy men and women ages 25-40 and 55-75. BMI 18.5 to 25.0 | |
| overweight Healthy men and women ages 25-40 and 55-75. BMI 25.0 to 30.0 | |
| obese Healthy men and women ages 25-40 and 55-75. BMI over 30 |
Κριτήρια καταλληλότητας
| Επιλέξιμες ηλικίες για μελέτη | 8 Years Προς την 8 Years |
| Φύλα επιλέξιμα για μελέτη | All |
| Μέθοδος δειγματοληψίας | Non-Probability Sample |
| Δέχεται υγιείς εθελοντές | Ναί |
| Κριτήρια | Inclusion Criteria: Caucasian BMI of 18.5 kg/m2 or above for adults, 2nd-91st centile or above 98th centile for children Ages 8 to 15 (children), 16 to 42 years (and premenopausal if female) or 55 to 77 years (and postmenopausal (at least 5 years since last menstrual period (LMP) if female) Able and willing to participate in the study and provide written informed consent Completed either STH15688 or STH16199 and gave consent to be approached about future studies Exclusion Criteria: History of any long term immobilization (duration greater than three months) Current confirmed or possible pregnancy (urinary pregnancy test if LMP >28 days) Previously-diagnosed diabetes mellitus History of or current conditions known to affect bone metabolism, including - Diagnosed skeletal disease - Chronic renal disease - Malabsorption syndromes - Diagnosed endocrine disorders - Hypocalcemia or hypercalcemia - Diagnosed restrictive eating disorder Use of medications or treatment known to affect bone metabolism, including - Depot medroxyprogesterone or the combined oral contraceptive pill Alcohol intake of greater than 21 units per week Competitive athlete, defined as participating in competitive sport at amateur or professional level Holiday with significant sunlight exposure in the last six weeks |
Αποτέλεσμα
Πρωτεύοντα αποτελέσματα
1. difference in serum 25OHD between groups [one measurement at study entry (cross-sectional study)]
Δευτερεύοντα αποτελέσματα
1. difference in 25OHD half-life between groups using the stable isotope tracer method [one measurement at study entry (cross-sectional study)]
2. difference in mean sunlight exposure score between groups (questionnaire) [one measurement at study entry (cross-sectional study)]
3. difference in mean dietary vitamin D intake between groups (diet diary) [one measurement at study entry (cross-sectional study)]
4. difference in mean of other serum vitamin D metabolites and measures between groups [one measurement at study entry (cross-sectional study)]
