Effects of 3-day fasting on secretory IgA concentration in the saliva and lymphotoxin alpha expression in healthy volunteers: a proof of concept study

Abstract

Background: animal studies have shown that enteral stimuli play an important role in modulating gut-associated lymphoid tissue thus fasting may exert detrimental effects on such. Objective: the main objectives of this study were: 1) to evaluate the effect of 3-day fasting on secretory immunoglobulin A (S-IgA) in parotid saliva; and 2) to determine the levels of lymphotoxin (LT) transcription in peripheral blood mononuclear cells (PBMNC) from healthy volunteers as a proxy for studying GALT health. Methods: these adult volunteers had fasted for 3 days as part of a cultural ritual. Eleven volunteers (seven men and four women) with a median age of 43 (40-56) were included. Parotid saliva and blood samples were collected on day 0 (no fasting) and 3 days after fasting. Parotid saliva was obtained using a modified on-Crittenden device, and S-IgA was quantified using ELISA. Total RNA was isolated from peripheral blood mononuclear cells, and the level of lymphotoxin (LT) mRNA expression was determined by RT-PCR. Lipopolysaccharide (LPS), IL-10 (interleukin), tumor necrosis factor (TNF)α, body composition and other metabolic indicators were measured. Results: median BMI was 27.3 kg/m2 (24.9-29.1). After 3 days of fasting, there were no significant differences in S-IgA concentrations (p = 0.657), LT expression (p = 0.063), LPS (p = 0.182), nor IL-10 (p = 0.110). We found a statistical difference in TNFα levels (13.5 vs 11.3 pg/mL; p = 0.005) between the 0 and 3-day samples; TNFα decreased after fasting. Conclusion: further studies are needed to clarify the role of LT in the production of S-IgA and its relationship with nutritional status and inflammatory factors.