Vitamin D Supplementation and Recurrence of Benign Paroxysmal Positional Vertigo.

Positional vertigo manifests as a spinning sensation triggered by changes in head position relative to gravity. Benign paroxysmal positional vertigo (BPPV) is an inner ear disorder characterized by recurrent episodes of positional vertigo. The connection between vitamin D insufficiency/deficiency and the onset and recurrence of BPPV is established. This study aims to assess vitamin D as a recurring factor in BPPV and the efficacy of vitamin D supplementation in preventing its recurrence. A comprehensive literature review on the relationship between vitamin D and BPPV recurrence was conducted, searching PubMed, Embase, Web of Science, and article reference lists for studies published from 2020 to 2023. A total of 79 articles were initially identified through the search, with 12 of them being utilized in the study. Recurrence rates for BPPV varied from 13.7% to 23% for studies with follow-up less than 1 year and 13.3% to 65% for studies with follow-up equal to or exceeding 2 years. Risk factors for BPPV recurrence include advanced age, female sex, hypertension, diabetes mellitus, hyperlipidemia, osteoporosis, and vitamin D deficiency. While earlier studies did not establish a link between low vitamin D levels and initial BPPV occurrence, they did associate recurrent episodes with low vitamin D levels. Recent research indicates that vitamin D supplementation in BPPV patients with deficiency or insufficiency decreases both the numbers of relapsing patients and relapses per patient. To validate these findings across diverse populations, further randomized controlled studies with larger cohorts and extended follow-up durations are essential.

Donor protection: Iron supplementation for frequent blood donors in Korea.

OBJECTIVE: This study aimed to evaluate the effect of oral iron supplementation in frequent donors in Korea, based solely on donation history. STUDY DESIGN: The hemoglobin (Hb) level, ferritin level, soluble transferrin receptor (sTfR), total iron binding capacity (TIBC), and transferrin saturation of frequent donors at high risk for iron deficiency were compared to those of first donors. The frequent donors took iron supplements for 4 weeks and the same tests were repeated after 2 and 4 weeks to evaluate their effects. RESULT: A total of 53 male and 57 female frequent donors were recruited. After 4-week iron supplementation, among the men, the prevalence of a: low Hb level (<13.0 g/dL) decreased from 25% to 2%; low ferritin level (<15.0 ng/mL) decreased from 58% to 4%; iron deficient erythropoiesis (IDE) (log(sTfR/ferritin) ≥ 2.07) decreased from 77% to 33%. Among the women, the percentage of a: low Hb level (<12.0 g/dL) decreased from 44% to 9%; low ferritin level decreased from 79% to 11%; IDE decreased from 95% to 47%. In total, 15 male (28.3%) and 29 female (56.9%) blood donors reported undesirable side effects related to iron supplementation. No serious adverse events were reported. CONCLUSION: Ferritin level, a reliable indicator of iron status, increased and IDE decreased significantly after four-week iron supplementation in the female, but not in the male, donor group, compared to those of control donors. Four-week oral iron supplement was not enough to restore iron storage level in the male donor group.

Selenium utilization in thioredoxin and catalytic advantage provided by selenocysteine.

Thioredoxin (Trx) is a major thiol-disulfide reductase that plays a role in many biological processes, including DNA replication and redox signaling. Although selenocysteine (Sec)-containing Trxs have been identified in certain bacteria, their enzymatic properties have not been characterized. In this study, we expressed a selenoprotein Trx from Treponema denticola, an oral spirochete, in Escherichia coli and characterized this selenoenzyme and its natural cysteine (Cys) homologue using E. coli Trx1 as a positive control. (75)Se metabolic labeling and mutation analyses showed that the SECIS (Sec insertion sequence) of T. denticola selenoprotein Trx is functional in the E. coli Sec insertion system with specific selenium incorporation into the Sec residue. The selenoprotein Trx exhibited approximately 10-fold higher catalytic activity than the Sec-to-Cys version and natural Cys homologue and E. coli Trx1, suggesting that Sec confers higher catalytic activity on this thiol-disulfide reductase. Kinetic analysis also showed that the selenoprotein Trx had a 30-fold higher Km than Cys-containing homologues, suggesting that this selenoenzyme is adapted to work efficiently with high concentrations of substrate. Collectively, the results of this study support the hypothesis that selenium utilization in oxidoreductase systems is primarily due to the catalytic advantage provided by the rare amino acid, Sec.