TMAO: The Culprit Behind Demyelination in Hypertension

Published on August 22, 2022

Imagine you have a leaky faucet in your house. Over time, the constant dripping of water can cause damage to the surrounding area, leading to decay and weakening. Similarly, trimethylamine N-oxide (TMAO), a metabolite produced by the bacteria in our intestines, has been found to be the culprit behind the demyelination of white matter in individuals with hypertension. This demyelination, characterized by damage to the protective covering of nerve fibers in the brain, is a result of TMAO promoting the pyroptosis of oligodendrocytes, the cells responsible for producing myelin. Pyroptosis is like an explosion inside cells, causing inflammatory death and releasing harmful substances. As TMAO increases, it enhances ROS/NLRP3 inflammasome signaling and impairs mitochondrial function within oligodendrocytes, ultimately leading to demyelination. This study demonstrates that TMAO levels are not only linked to cardiovascular and aging diseases but may also serve as a diagnostic marker for white matter lesions in individuals with hypertension. To learn more about this fascinating research, check out the article linked below!

BackgroundHypertension is a leading risk factor for cerebral small vessel disease (CSVD), a brain microvessels dysfunction accompanied by white matter lesions (WML). Trimethylamine N-oxide (TMAO), a metabolite of intestinal flora, is correlated with cardiovascular and aging diseases. Here, we explored the effect of TMAO on the demyelination of WML.MethodsSpontaneous hypertension rats (SHRs) and primary oligodendrocytes were used to explore the effect of TMAO on demyelination in vivo and in vitro. T2-weighted magnetic resonance imaging (MRI) was applied to characterize the white matter hyperintensities (WMH) in rats. TMAO level was evaluated using LC-MS/MS assay. The histopathological changes of corpus callosum were measured by hematoxylin-eosin and luxol fast blue staining. And the related markers were detected by IHC, IF and western blot assay. Mito Tracker Red probe, DCFH-DA assay, flow cytometry based on JC-1 staining and Annexin V-FITC/PI double staining were conducted to evaluate the mitochondrial function, intracellular ROS levels and cell apoptosis.ResultsSHRs exhibited stronger WMH signals and a higher TMAO level than age-matched normotensive Wistar-kyoto rats (WKY). The corpus callosum region of SHR showed decreased volumes and enhanced demyelination when treated with TMAO. Furthermore, TMAO significantly elevated ROS production and induced NLRP3 inflammasome and impairment of mitochondrial function of oligodendrocytes. More importantly, TMAO enhanced the pyroptosis-related inflammatory death of oligodendrocytes.ConclusionTMAO could cross the blood-brain barrier (BBB) and promote oligodendrocytes pyroptosis via ROS/NLRP3 inflammasome signaling and mitochondrial dysfunction to promote demyelination, revealing a new diagnostic marker for WML under hypertension.

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