Browsing by Subject "Vitamin D"

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Development of a non-invasive clinical screening tool to asses 25-hydroxyvitamin D (25(OH)D) serum levels in long-term care older adults
(2020-05-06) Robbins, Ronna Nikole Osborn; Briley, Margaret E.; Davis, Jaimie; Hoelscher, Deanna M; Jolly, Christopher; Ranjit, Nalini; Sweitzer, Sara
The purpose of this study was to develop, test, and enhance a non-invasive clinical diagnostic screening tool for the identification of hypovitaminosis D, 25-hydroxyvitamin D [25(OH)D] serum levels <30 ng/mL, in older adults living in long-term care communities. The primary hypothesis of this study was that hypovitaminosis D could accurately be predicted in long-term care older adults through a series of healthrelated and demographic characteristics. This observational cross-sectional study recruited older adults >65 years from five long-term care communities in central Texas. A one-time venous blood draw measuring 25(OH)D serum level was obtained from each participant. Several multiple logistic regression models were tested to identify the best fitting model that described the relationship between categorical insufficient (<30 ng/mL) 25(OH)D serum levels and health-related conditions, demographics, and clinical characteristics. Inter-rater reliability was established using the test-retest method. The developed screening tool was administered to a randomized subset of participants (n=50), each of whom had the screener administered twice by blinded trained data collectors, resulting in two screeners per participant (n=100 screeners). Of the 180 participants recruited, 173 provided blood samples and had complete data sets. The mean age was 83.0 (+ 11) years, 107 (61.2%) were female, 159 (89%) were Caucasian, 65 (38%) were not prescribed a vitamin D supplement, and 94 (54%) participants had hypovitaminosis D (<30 ng/mL). Mean vitamin D supplementation rate was 1190 IU/d with mean 25(OH)D serum levels of 32.5 ng/mL. There were no significant differences between demographic characteristics (gender, age, BMI, etc.) in 25(OH)D serum levels and dose rate of vitamin D supplementation. Using only ten clinical variables, the screening tool significantly predicted hypovitaminosis D “insufficient” serum levels (p<0.001) and accounted for approximately 30.6% of the variance in 25(OH)D serum levels. The screening tool accurately predicted serum levels 74.16% of the time, with 53.85% of adequate (>30 ng/mL) serum levels correctly classified (specificity) and 90.00% of hypovitaminosis D correctly classified (sensitivity). Inter-reliability testing indicated that there was significant agreement between the two administered screeners (p<0.000). This study successfully developed a low cost, easy to administer, non-invasive diagnostic clinical screening tool that can identify hypovitaminosis D, 25(OH)D serum levels <30 ng/mL, in older adults living in long-term care communities.
Exploring the impact of inducible-whole body and tissue-specific removal of CYP24A1 on vitamin D metabolism in mice
(2023-05) Watkins, Natalie Madeleine; Fleet, James C.
CYP24A1 is an enzyme that initiates the catabolism of 1,25 Hydroxyvitamin D3 (1,25(OH)₂D₃ ;1,25D), the active hormonal form of Vitamin D that regulates bone and calcium homeostasis. In the following two experiments, we aim to elucidate the specific roles of whole-body versus intestinal CYP24A1 in the metabolism of 1,25(OH)₂D₃. We generated inducible-Cyp24a1 KO and HT (UBC [superscript Cre+/-] xCyp24a1 [superscript flox/flox]; UBC [superscript Cre+/-] xCyp24a1 [superscript flox/wt]) mice to understand the impact of CYP24A1 dose variation in healthy, adult mice. The Cyp24a1 KO, HT, and Control (Cyp24a1 [superscript flox/flox]) littermates were fed a standard Chow diet from weaning until 11-weeks of age. Following a series of intraperitoneal injections of 2.5ul/g(body weight) of Tamoxifen daily for 7 days to induce genetic recombination the mice were randomized to AIN93G diets (0.4% P, 200 IU/kg Vitamin D3) with either adequate (0.5%) or deficient (0.2%) calcium (Ca) levels (n=6/sex/group). At 12-weeks old, all mice were euthanized, and tissues collected and stored for RNA isolation. Duodenal (Dd) and renal (Kd) mRNA levels were quantified using qPCR. As expected, we observed a trend towards an allele-dependent suppression of Cyp27b1 regardless of diet compared to controls supporting alterations in 1,25D metabolism. Interestingly, there was no change to Trpv6 and s100g mRNA by diet or genotype, possibly due to balancing circulating 1,25D production through Cyp27b1 suppression. In the second study, control (Cyp24a1 [superscript flox/flox]) and intestinal-epithelial-cell-specific knock-out (Villin [superscript Cre+/-] x Cyp24a1 [superscript flox/flox], IEC KO) mice were fed a standard Chow diet from weaning until 11 weeks old, they were then randomized to AIN93G diets (0.4% P, 200 IU/kg Vitamin D3) with 0.5% or 0.2% Ca (n=5/sex/group). One week later, mice were euthanized, and tissues collected and stored for RNA isolation. Dd and Kd mRNA levels were quantified using qPCR. Surprisingly, while we saw trends of Cyp27b1 mRNA suppression and intestinal Trpv6 mRNA elevation, there were no significant changes to mRNA expression.
Serum concentration levels of 25(OH)D and injury reports in NCAA Division I football players
(2014-05) McGill, Lauren Elyse; Farrar, Roger P.
Vitamin D deficiency has been linked with many health problems. Early research demonstrated the importance of vitamin D for bone health, but it may also play a larger role than first reported in muscle health and function. Specifically, low vitamin D may hinder athletic performance, as such evaluation of serum vitamin D levels in high volume training athletes has merit. The purpose of this study was to evaluate serum levels of 25(OH)D in college athletes to determine how many had levels below the recommended values. Data from student-athletes who were attending a large university in the south included: serum vitamin D levels, demographics information, and injury reports. Mean serum vitamin D level for the group was 34.17 ng/mL ± 0.88. Average injury for the group was 1.3± 0.14. The mean value of serum vitamin D for Caucasian players was 38.3 ng/mL ± 1.33 with a range of 23-59 ng/mL. The mean value of serum vitamin D for African American players was 31.16 ng/mL ± 1.08 with a range of 16-52 ng/mL. African American players had significantly lower serum vitamin D levels (p<0.01) than Caucasian players. Players with one or more injury had significantly lower serum vitamin D values (p<0.05) than players who had zero injuries. Forty-eight players (44.4%) had insufficient levels of vitamin D (20-31.9ng/ml). 60 players (55.6%) had values within normal limits (>32 ng/ml). Players with one or more musculoskeletal injury or fracture had significantly lower serum vitamin D levels (p<0.05) compared to players that had zero injuries. African American players had significantly lower serum vitamin D levels (p<0.01) compared to Caucasian players. It is important for athletes to monitor serum vitamin D levels and adhere to a supplementation protocol when levels are insufficient.