K. Trocha1,2,3, P. Kip1,3, M. MacArthur2, M. Tao1, J. R. Mitchell2, K. Ozaki1 1Brigham And Women’s Hospital,Vascular Surgery,Boston, MA, USA 2Harvard School Of Public Health,Genetics & Complex Diseases,Boston, MA, USA 3Leiden University Medical Center,Surgery,Leiden, , Netherlands
Introduction: Short-term pre-operative dietary restriction holds promise as a translatable approach to mitigate surgical complications. One of the regulators responsible for these benefits is hydrogen sulfide (H2S), an anti-inflammatory gaseous signaling molecule produced endogenously by the enzyme cystathionine γ-lyase (CGL). Recently we have shown that short-term methionine (MR) and protein restriction (PR) upregulates H2S production reducing ischemia-reperfusion damage and attenuating the surgical stress response, showing great potential for clinical translation. However, short-term restriction of protein or amino acids could potentially impair wound healing in surgical patients, we therefore hypothesized that short-term pre-operative protein restriction (PR) or methionine restriction (MR) would not impair wound healing and by genetically upregulating H2S, mimicking PR and MR that this gaseous transmitter would protect against ischemia reperfusion injury.
Methods: Surgical outcomes were tested using a bilateral 35-minute renal ischemia-reperfusion model and a Mcfarlane wound healing model, where a pedicle flap measuring 2.5 x 1.25cm with a silicone flap placed inferior to flap to prevent angiogenesis from bellow was performed on the dorsum of the mouse and wound healing was observed for 7 days post operatively. Dietary interventions included 7 days of either an isocaloric protein restricted (0%) diet or 3 weeks of an isocaloric methionine restricted diet. A CGL transgenic overexpressing mouse model (10-12 weeks, C57BL/6 background) of increased endogenous H2S production was used to test the potential of increased endogenous H2S to protect from a severe 35-minute renal ischemia.
Results: PR mice revealed a trend towards accelerated wound healing, with no difference in percentage of viable skin 7 days after surgery (Figure A). MR mice displayed accelerated wound healing 1-4 days after surgery compared to controls while after 7 days, as with PR mice, no difference in percentage viable skin was observed (Figure B). Also, 75% of CGLtg mice survived at post operative day 3 following bilateral renal ischemia, compared to a 100% mortality of littermate controls (p<0.05,Figure C), thereby elucidating the benefits of H2S upregulation on ischemia-reperfusion damage and survival.
Conclusion: Reducing protein intake or specific amino acids prior to surgery without reducing calories in pre-clinical models protects against ischemia-reperfusion injury and may protect against surgical stress. Improving mortality via the reduction of ischemia reperfusion damage using a CGLtg mouse we elaborate on our previous work that these dietary benefits are largely secondary to upregulation of endogenous H2S. Here we show that such brief dietary-manipulations stand as simple strategies toward improving the host response to surgical injury and they do not inhibit or impair wound healing in mice, thereby further enhancing clinical applicability.
