Metabolomics and microbiome profiling as biomarkers in obstructive sleep apnoea: a comprehensive review

Abstract

Introduction: Obstructive sleep apnoea (OSA) is a common sleep disorder with a high social and economic burden. Thus, early prediction and diagnosis of OSA are important. Changes in metabolism and the microbiome may serve as biomarkers for OSA. Herein, we review the literature on the metabolomic and microbiome changes associated with OSA, and identify the metabolites and microorganisms involved.

Methods: We searched the PUBMED and EMBASE electronic databases using the following terms: "obstructive sleep apnea", "OSA", "sleep disordered breathing", "SDB", "intermittent hypoxia", "sleep fragmentation", and either "metabolomics" or "microbiome". In total, 273 papers were identified, of which 28 were included in our study.

Results: Changes in the levels of certain metabolites related to fatty acid, carbohydrate and amino acid metabolism were associated with the incidence of OSA. The diversity and abundance of microflora, particularly Firmicutes and Bacteroidetes, were altered in humans and rodents with OSA.

Conclusions: Certain changes in metabolism and the microbiota play an integral role in the pathophysiology of OSA and OSA-induced cardiovascular complications. Metabolomic and microbiome biomarkers shed light on the pathogenesis of OSA, and facilitate early diagnosis and treatment.

FIGURE 1

Flowchart of selecting literature in a) metabolomics and b) microbiome.

FIGURE 2

a) Summary of metabolic alterations in obstructive sleep apnoea (OSA). The red arrows represent an increased level, while the green arrows represent a decreased level. IH: intermittent hypoxia; BCAAs: branch chain amino acids; TCA: tricarboxylic acid; NADH: nicotinamide adenine dinucleotide. b) Alterations of gut microbiota in OSA rodent models. Red represents an increase in relative abundance, while green represents a decrease. c) Alterations of gut microbiota in OSA-induced hypertension models. Red represents an increase in relative abundance. d) Cardiovascular, hepatic, pulmonary and cerebral complications caused by OSA and influenced by microbiota dysbiosis. The dotted arrows refer to the unclear mechanisms and pathophysiological pathways. SCFA: short-chain fatty acids; IL: interleukin; TGF: transforming growth factor; oxLDL: oxidised low-density lipoprotein; TMAO: trimethylamine oxide; PLA2: phospholipase A2; NO: nitric oxide.