Longitudinal Arm of the 24-hour Intermittent Fasting Study
Background: Intermittent fasting is the most popular dietary strategy in the United States and can reduce cardiovascular risk factors. However, the effect of intermittent fasting on arterial stiffness, a vascular impairment strongly associated with cardiovascular disease and mortality, is incompletely understood. Methods: Wild-type (lean) and genetically obese (obese) mice were randomized to an acute fasting protocol such that terminal data was collected during either ad-libitum feeding, immediately after a 24-hour fast, one day after refeeding, or one week after refeeding. Another cohort of lean and obese mice were randomized to an 11-week protocol to receive either an ad libitum control diet or a once-weekly 24-hour fast. In both cohorts, arterial stiffness was measured via pulse wave velocity, gut microbial composition was assessed via 16s rRNA amplicon sequencing, splenocytes were identified via spectral flow cytometry, and plasma cytokines/chemokines were quantified via multiplex immunoassays. Results: A 24-hour fast increased pulse wave velocity in lean mice while impacting interactions between the gut microbiota and immune system. However, the worsening in arterial stiffness and alterations to gut microbe-immune relationships were largely reverted after 24 hours of refeeding. The acute fasting-refeeding cycle also impacted gut microbe-immune system interactions in obese mice. Still, it did not affect pulse wave velocity. 11 weeks of once-weekly 24-hour IF attenuated arterial stiffness only in obese mice. Improvements in obesity-associated arterial stiffness were not associated with changes in body weight or food intake but were accompanied by profound changes to the gut microbiota, which regulated endothelial chemokine production, leukocyte numbers in the vascular wall, and aberrant vascular smooth cell function. Conclusions: Our results suggest that a “gut-immune-vascular” axis is implicated in obesity-associated arterial stiffness. Furthermore, repeated bouts of intermittent fasting can reduce obesity-associated arterial stiffness by potentially altering crosstalk between the gut microbiota, immune system, and vasculature.