Abstract Body: Introduction: Aged individuals have a decreased ability to excrete sodium and an increased susceptibility to kidney disease. Factors that contribute to this include age-induced structural changes and functional decline. Time-restricted feeding (TRF) has been linked to improved cardiovascular and renal health.
Hypothesis: This study tests the hypothesis that time-restricted feeding will improve the high-salt-induced inflammatory response in the kidneys of aged male mice.
Methods: Six-month-old male Young (Y) C57BL/6 mice were placed on a high salt (4.0% NaCl) diet and used for comparison. Eighteen-month-old male mice were placed on a high salt diet for 4 weeks with ad-libitum (AL) access or time-restricted feeding (TRF) where food was restricted to 8 hours during the midpoint of their active periods. Kidneys were harvested at the beginning of the inactive period for assessment of cytokine levels via multiplex immunoassays and immune cell populations via flow cytometry. One-way ANOVA was used for statistical comparison unless otherwise noted.
Results: There was no difference in 24-hour food intake in TRF aged mice compared to ad libitum (T-test P=NS; AL: 13.3 ± 0.7; TRF: 12.6 ± 1.2 pellets; N=5). The pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) increased with age in the kidney but was not altered with TRF in aged mice (P=0.02; Y: 0.9 ± 0.1; AL: 1.5 ± 0.2; TRF: 1.3 ± 0.1 pg/mL/protein; N=5). The chemokine monocytic chemotactic protein 1 (MCP-1) increased with age in the kidney but did not change with TRF in aged mice (P=0.005; Y: 3.0 ± 0.2; AL: 8.6 ± 1.2; TRF: 7.9 ± 1.3 pg/mL/protein; N=5). There was no difference in renal CD45+ immune cells in aged mice or following TRF (P=NS; N=5).
Conclusions: In conclusion, aging led to increased inflammation in the kidneys of mice on a high salt diet. Contrary to our hypothesis, TRF did not appear to have an anti-inflammatory effect in aged mice on a high salt diet. Future studies will determine if the age of the mouse or type of diet consumed changes this outcome. These data suggest that more studies examining TRF need to include aged populations.