Epigenetic Chronotherapy For Hypertension: Sleep-time Supplementation Of 1,3-butanediol Confers Better Protection Against Hypertension Via Enhanced Histone -hydroxybutyrylation

The leading global contributor to cardiovascular disease and early death is hypertension. Previously, we demonstrated that the ketone body, β-hydroxybutyrate (BHB), is a potent antihypertensive metabolite. BHB is newly recognized to epigenetically modify histones by β-hydroxybutyrylation (BHBylation). As it is known that BHB is predominantly synthesized when there is a lack of food and blood pressure (BP) is lower while animals are sleeping, we hypothesized that an increased histone BHBylation occurs during sleep-time to promote ketosis and lower hypertension. To test this hypothesis, we examined the epigenetic effect of enhancing systemic BHB on BP of the Dahl Salt-Sensitive (S) rat. Methods: Male S rats that were six weeks old and fed on a high salt diet were divided into two groups. They were gavaged daily for nine weeks at two different time points, 2 pm/sleep-time (n=6) and 2 am/awake-time (n=5) with 5g/kg/day of a precursor of BHB, 1, 3-butanediol (1,3-BD). BP was monitored by radiotelemetry until euthanasia when tissues were harvested for further analyses. Results: The sleep-time chronotherapy group had significantly lower mean arterial BP over the course of twenty-four hours than the awake-time chronotherapy group (130±4 mmHg vs. 138±8 mmHg, p<0.0001). Renal histone3lysine9 (H3K9) BHBylation examined by western blotting was elevated in the sleep-time compared to the awake-time chronotherapy group. Ketosis, as monitored by the expression of the lipid metabolism genes, Hmgcs2, Acaa1b, Cyp2d4, and Cyp2e1, was significantly higher in the sleep-time compared to the awake-time chronotherapy group. Further, the expression of renal injury and inflammation markers KIM1, MCP1, IL-18, IL-16, and TGF-β were significantly lowered in the sleep-time compared to the awake-time chronotherapy group. Conclusion: This is the first study to demonstrate that enhanced renal epigenetic histone BHBylation is mechanistically linked to better antihypertensive outcomes during sleep-time compared to awake-time chronotherapy with 1,3-BD.