Gut-Derived Metabolite Indole-3-Propionic Acid Modulates Mitochondrial Function in Cardiomyocytes and Alters Cardiac Function

Abstract

Background: The gut microbiome has been linked to the onset of cardiometabolic diseases, in part facilitated through gut microbiota-dependent metabolites such as trimethylamine-N-oxide. However, molecular pathways associated to heart failure mediated by microbial metabolites remain largely elusive. Mitochondria play a pivotal role in cellular energy metabolism and mitochondrial dysfunction has been associated to heart failure pathogenesis. Aim of the current study was to evaluate the impact of gut-derived metabolites on mitochondrial function in cardiomyocytes via an in vitro screening approach.Methods: Based on a systematic Medline research, 25 microbial metabolites were identified and screened for their metabolic impact with a focus on mitochondrial respiration in HL-1 cardiomyocytes. Oxygen consumption rate in response to different modulators of the respiratory chain were measured by a live-cell metabolic assay platform. For one of the identified metabolites, indole-3-propionic acid, studies on specific mitochondrial complexes, cytochrome c, fatty acid oxidation, mitochondrial membrane potential, and reactive oxygen species production were performed. Mitochondrial function in response to this metabolite was further tested in human hepatic and endothelial cells. Additionally, the effect of indole-3-propionic acid on cardiac function was studied in isolated perfused hearts of C57BL/6J mice.Results: Among the metabolites examined, microbial tryptophan derivative indole-3-propionic acid could be identified as a modulator of mitochondrial function in cardiomyocytes. While acute treatment induced enhancement of maximal mitochondrial respiration (+21.5 ± 7.8%, p < 0.05), chronic exposure led to mitochondrial dysfunction (−18.9 ± 9.1%; p < 0.001) in cardiomyocytes. The latter effect of indole-3-propionic acids could also be observed in human hepatic and endothelial cells. In isolated perfused mouse hearts, indole-3-propionic acid was dose-dependently able to improve cardiac contractility from +26.8 ± 11.6% (p < 0.05) at 1 μM up to +93.6 ± 14.4% (p < 0.001) at 100 μM. Our mechanistic studies on indole-3-propionic acids suggest potential involvement of fatty acid oxidation in HL-1 cardiomyocytes.Conclusion: Our data indicate a direct impact of microbial metabolites on cardiac physiology. Gut-derived metabolite indole-3-propionic acid was identified as mitochondrial modulator in cardiomyocytes and altered cardiac function in an ex vivo mouse model.

Biological Effects of Indole-3-Propionic Acid, a Gut Microbiota-Derived Metabolite, and Its Precursor Tryptophan in Mammals’ Health and Disease

“…Initially endogenous metabolites of tryptophan were suspected to be accountable for tryptophan's cardiovascular actions [166]. Recently, it has been established that IPA itself can also affect cardiovascular system [19,167]. Additionally, its synthesis can change in presence of cardiovascular-related diseases (Table 1).…”

“…The scientific literature indicates that IPA is also involved in blood pressure regulation in mammals [19]. Using the Langendorff heart model in mice, an IPA-dependent increase in myocardial contractility was demonstrated [167]. Additionally, this metabolite causes vasoconstriction of the endothelium-denuded mesenteric resistance arteries [19] and diminishes vasodilatation associated with pre-treatment with sodium nitroprusside [189] and acetylcholine [19].…”

Indole-3-Propionic Acid, a Gut-Derived Tryptophan Metabolite, Associates with Hepatic Fibrosis

“…Under physiological conditions, serum IPA concentrations range from 1–10 μM in humans [ 19 , 38 ]. In most of the in vitro studies testing the efficacy of IPA, 100 μM and higher doses have been used [ 15 , 20 , 40 , 41 ]. Since we have no knowledge about the tissue concentrations in humans, we decided to use commonly used 100 μM concentration with cells.…”

“…Since we have no knowledge about the tissue concentrations in humans, we decided to use commonly used 100 μM concentration with cells. A recent study also reports contrasting acute and chronic effect of IPA on mitochondrial function in human cardiomyocytes [ 40 ] which also indicates that detailed mechanistic actions have to be investigated before proceeding to clinical studies in humans.…”

“…Whereas, after 48 h, both 1 and 2 mM reduced cell viability significantly. Therefore, IPA doses of 1, 10, and 100 μM were selected for the actual experiments, which were the highest non-toxic concentrations, close to the physiological range [ 19 , 38 ] and which have been previously used [ 15 , 40 , 41 ].…”