Cold environment regulates ischemic stroke through modulation of gut microbiota

Abstract

Many diseases are influenced by environmental temperature, and recent studies have confirmed that cold exposure increases the risk of conditions such as ischemic stroke (IS). However, direct evidence supporting this hypothesis is lacking, and the molecular mechanisms through which cold exposure affects IS remain unclear. In this study, we found that chronic cold exposure increased platelet aggregation and the levels of certain inflammatory factors in high-risk stroke patients (HR), thereby increasing the risk of IS. Furthermore, before and after a cold wave, we observed gut microbiota dysbiosis in the HR group, including reduced relative abundance differences in Lachnospiraceae and Ruminococcaceae. The relative abundances of the Prevotella_9 and Catenibacterium genera increased, whereas that of Anaerostipes decreased. Notably, the results of fecal microbiota transplantation (FMT) indicated that cold-adapted microbiota transplantation partially replicated the microbiota characteristics of each donor subject and replicated the effects of cold exposure in C57BL/6J mice. Cold exposure impaired intestinal barrier function and interfered with microbial functions, such as increased lipid metabolism and LPS production, particularly by increasing the levels of TMAO derived from the gut microbiota. Our findings identify the significant role of abnormal gut microbiota-derived metabolites in cold exposure-related IS and highlight the potential opportunity to prevent or treat cold-related IS through the modulation of the gut microbiota.

Keywords: Cold temperature; Ischemic stroke; Microbiota; TMAO.

Fig. 1

The flowchart for the study.

Fig. 2

Temperature changes during the study period.

Fig. 3

Changes in primary outcomes after experiencing a cold wave. (A) Effects of cold waves on ADP-induced PARs. (B) Effects of cold waves on ICAM-3. (C) Effect of cold waves on VEGF. (D) Effect of cold waves on SII. (E) Effect of cold waves on sTNFR2. (F) Effects of cold waves on the Lp-PLA2S.

Fig. 4

(A, B) Alpha diversity of the HR and LR group. (C) Principal coordinate analysis (PCoA) plot based on the Bray‒Curtis distance matrix depicting patterns of beta diversity from the gut microbial communities at the ASV level. (D, E), Based on the beta diversity distance among samples within each group, we analyzed the differences in sample distances at different times within the HR and LR groups to compare differences in community structure between groups. (F) Figure showing the 10 differential genera among HR group (Kruskal–Wallis test with Dunn’s post-hoc test, and FDR correction for multiple comparisons was applied, with a significance threshold of 0.05).

Fig. 5

Cold exposure promotes platelet activation. (A) Cold exposure promotes platelet aggregation induced by different agonists. At 37 °C, different concentrations of ADP (5 μM, n = 6), thrombin (0.02 U/mL, n = 5), and collagen (1 μg/mL, n = 5) were used to stimulate washed platelets in mice. A Chrono-log lumi-aggregometer and AggRAM™ are used to record platelet aggregation continuously for 180 s. (B) Cold exposure promotes the clot retraction ability of platelets. Clot retraction of washed platelets from the NT and CE groups triggered by 0.1 U/mL thrombin (n = 6). Photographs were taken at the indicated times. The sizes of the clots were quantified via ImageJ software.

Fig. 6

Immunohistochemical staining and quantification of Occludin and ZO-1 in colon tissue samples from the NTHR (n = 5) and CEHR (n = 5) groups.

Fig. 7

The gut microbiome composition of the NTHR and CEHR groups. (A) PCoA plot based on the Bray‒Curtis distance of the genus-level relative abundance profile (p = 0.003). Bar chart showing the phylum-level composition of the gut microbiome. (C) Bar chart showing the genus-level composition of the gut microbiome (D). The difference in genus-level relative abundance according to LEfSe (p < 0.05 and LDA > 2). E.Differences in species-level relative abundance according to LEfSe (p < 0.05 and LDA > 2).

Fig. 8

(A) PCoA plot based on the Bray‒Curtis distance of gene-family abundance (p = 0.003). (B) Differences in metabolic pathway abundance according to LEfSe (p < 0.05 and LDA > 2). (C, D) Comparison of the main KEGG functions (LEfSe, p < 0.05 and LDA > 2).

Fig. 9

(A) Levels of fecal LPS; (B) Effect of in vitro LPS incubation on platelet aggregation; (C) Effect of in vitro LPS incubation on platelet retraction. ns, not significant; *P < 0.05; **P < 0.01.