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Open AccessArticle

Seasonal Antimicrobial Activity of the Airway: Post-Hoc Analysis of a Randomized Placebo-Controlled Double-Blind Trial

1
Department of Internal Medicine, Carver College of Medicine Iowa City, University of Iowa, Iowa City, IA 52242, USA
2
Department of Pediatrics, Carver College of Medicine Iowa City, University of Iowa, Iowa City, IA 52242, USA
*
Author to whom correspondence should be addressed.
Nutrients 2020, 12(9), 2602; https://doi.org/10.3390/nu12092602
Received: 10 July 2020 / Revised: 19 August 2020 / Accepted: 20 August 2020 / Published: 27 August 2020
(This article belongs to the Section Micronutrients and Human Health)
Background: It is widely unknown why respiratory infections follow a seasonal pattern. Variations in ultraviolet B (UVB) light during seasons affects cutaneous synthesis of vitamin D3. Serum vitamin D concentration influences the expression of airway surface liquid (ASL) antimicrobial peptides such as LL-37. Objective: We sought to determine the effect of seasons on serum vitamin D levels and ASL antimicrobial activity. Methods: Forty participants, 18–60 years old, were randomized 1:1 to receive 90 days of 1000 IU vitamin D3 or placebo. We collected ASL via bronchoscopy and measured serum 25(OH) vitamin D from participants before and after intervention across seasons. We measured ASL antimicrobial activity by challenging samples with bioluminescent Staphylococcus aureus and measured relative light units (RLUs) after four minutes. We also investigated the role of LL-37 using a monoclonal neutralizing antibody. Results: We found that participants, prior to any intervention, during summer–fall (n = 20) compared to winter–spring (n = 20) had (1) decreased live bacteria after challenge (5542 ± 175.2 vs. 6585 ± 279 RLU, p = 0.003) and (2) higher serum vitamin D (88.25 ± 24.25 vs. 67.5 ± 45.25 nmol/L, p = 0.026). Supplementation with vitamin D3 increased vitamin D levels and restored ASL antimicrobial activity only during the winter–spring. The increased ASL antimicrobial activity seen during the summer–fall was abrogated by adding the LL-37 neutralizing antibody. Conclusion: ASL kills bacteria more effectively during the summer–fall compared to the winter–spring. Supplementation of vitamin D during winter–spring restores ASL antimicrobial activity by increasing the expression of antimicrobial peptides including LL-37. View Full-Text
Keywords: humans; vitamin D; respiratory tract infections; peptides; antibacterial agents; double-blind method; seasons humans; vitamin D; respiratory tract infections; peptides; antibacterial agents; double-blind method; seasons
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MDPI and ACS Style

Vargas Buonfiglio, L.G.; Vanegas Calderon, O.G.; Cano, M.; Simmering, J.E.; Polgreen, P.M.; Zabner, J.; Gerke, A.K.; Comellas, A.P. Seasonal Antimicrobial Activity of the Airway: Post-Hoc Analysis of a Randomized Placebo-Controlled Double-Blind Trial. Nutrients 2020, 12, 2602. https://doi.org/10.3390/nu12092602

AMA Style

Vargas Buonfiglio LG, Vanegas Calderon OG, Cano M, Simmering JE, Polgreen PM, Zabner J, Gerke AK, Comellas AP. Seasonal Antimicrobial Activity of the Airway: Post-Hoc Analysis of a Randomized Placebo-Controlled Double-Blind Trial. Nutrients. 2020; 12(9):2602. https://doi.org/10.3390/nu12092602

Chicago/Turabian Style

Vargas Buonfiglio, Luis G.; Vanegas Calderon, Oriana G.; Cano, Marlene; Simmering, Jacob E.; Polgreen, Philip M.; Zabner, Joseph; Gerke, Alicia K.; Comellas, Alejandro P. 2020. "Seasonal Antimicrobial Activity of the Airway: Post-Hoc Analysis of a Randomized Placebo-Controlled Double-Blind Trial" Nutrients 12, no. 9: 2602. https://doi.org/10.3390/nu12092602

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