S-44-4: POST-STROKE SUPPLEMENTATION WITH SHORT-CHAIN FATTY ACIDS ACCELERATES RECOVERY IN MICE VIA THE G-PROTEIN COUPLED RECEPTORS

Abstract

Objective: Dietary fibre intake is negatively associated with stroke and overall mortality. A plausible hypothesis is that this happens via the gut microbiota, producing metabolites known as short-chain fatty acids (SCFAs) during fibre fermentation. Indeed, our unpublished data showed that low-fibre (LF) intake worsens stroke outcomes while high-fibre (HF) intake ameliorates it. Thus, we aimed to investigate whether switching from a LF diet pre-stroke to either a HF diet or supplementation with SCFAs post-stroke can improve functional and histological outcomes. We also aimed to determine if this effect is dependent on SCFAs-sensing G-protein coupled receptors GPR41, GPR43, and GPR109A. Design and methods: Male C57BL/6J mice (8–9 weeks, n = 8/group) were randomized and treated with a LF diet for 4-weeks prior to photothrombotic stroke surgery. Post-stroke, the mice were either fed with LF, HF or SCFAs for 7-days. Results: Using MRI, we observed no difference in the infarct volume at day 1 (D1) post-stroke. However, a HF diet and SCFAs supplementation reduced infarct volume at day 7 (D7) (mean brain infarct volume ± SEM; LF:13.52 ± 2.43 mm3 vs HF:7.71 ± 1.12 mm3 vs SCFAs:5.25 ± 1.18 mm3, P = 0.007), and improved brain recovery rate (LF:64.93 ± 2.94% vs HF:78.06 ± 1.98% vs SCFAs:85.05 ± 2.45%, P < 0.001). High-fibre and SCFAs supplementation improved wire-hanging grip strength and coordination at D7, which measures motor function (mean % improvement ± SEM; LF:12.59 ± 2.66% vs HF:69.77 ± 8.44% vs SCFAs:97.42 ± 1.54%, P < 0.001). Immunofluorescence was performed to access gut barrier integrity, immune cell infiltration and neurogenesis in the brain at D7. HF and SCFAs improved gut barrier integrity (ZO-1, P < 0.001). Moreover, SCFAs-treated mice had fewer neutrophils (MPO+, P = 0.017) and more neuroblasts (DCX+/Tuj1+, P < 0.001) in the infarct core, with a positive correlation between DCX+/Tuj1+ and recovery rate post-stroke (R2 = 0.50, P < 0.001). To identify the receptors by which SCFAs improve stroke recovery, wild-type (WT) and GPR41/43/109a-/- mice (8–9 weeks, n = 8/group) were fed a HF diet pre- and post-stroke. GPR41/43/109a-/- mice showed worse stroke outcomes with larger brain infarct volume at D1 (P = 0.048) and D7 (P = 0.008), and worse recovery rate (P = 0.002). Consistent with this, wire-hanging grip strength was reduced (P < 0.001) at D7. In addition, compared to WT mice, GPR41/43/109a-/- mice had a leaky gut (P < 0.001), more neutrophils (P = 0.007) and very few neuroblasts (P = 0.011) in the infarct core. Conclusions: A high-fibre diet, resulting in the production of SCFAs, targets GPR41/43/109a signalling to reduce stroke-induced brain injury and improve functional recovery post-stroke. This improvement is likely to occur via neurogenesis and the suppression of the inflammatory response in the ischaemic brain.