β-thalassaemia (β-TH) is the most common autosomal recessive blood disorder caused by mutations in the β-globin gene located on chromosome 11 [1]. Approximately 60,000 newborns are affected annually worldwide, predominantly in developing countries, accounting for about 1.5% of the global population (80–90 million people) [2].
Hemolysis is a hallmark of β-TH, resulting from an imbalance in the production of β-globin chains (decreased or absent) and normal alpha chains, leading to the precipitation of alpha chains and red cell damage. Ineffective erythropoiesis further increases erythroferrone production, suppresses hepcidin, and consequently enhances iron absorption and disrupts bone metabolism [3].
Hemolysis leads to the excretion of large amounts of bilirubin into the intestines. Bilirubin, historically regarded as a waste product of heme catabolism [4], plays a significant role in the pathophysiology of β-TH as a hemolytic disease [5]. The rupture of erythrocytes in β-TH increases serum levels of total and unconjugated bilirubin due to the oxidation of free hemoglobin's heme moiety [6]. Normally, bilirubin is conjugated to glucuronic acid, forming a soluble compound excreted as urobilinogen [7]. However, patients with β-TH have impaired liver function, reducing their ability to metabolize bilirubin, resulting in increased intestinal concentrations [8,9].
Intestinal bacteria degrade bilirubin to urobilinogen; half of these entities are reabsorbed into the circulation via the portal system for renal excretion, while the remainder is converted to stercobilinogen for fecal excretion [10]. The catabolism of bilirubin to urobilinoids regulates specific gut bacteria, maintaining homeostasis [11].
Fecal microbiota transplantation (FMT) has emerged as a prominent research area in recent years [12,13]. We hypothesized that FMT could standardize gut microbiota in Th3/+ mice and controls, thereby highlighting β-TH's impact on gut microbiota. Studying the effect of intestinal flora on the phenotype may provide novel treatments for β-TH.
Limited research exists on the gut microbiota in β-TH, and the mechanistic link between gut microbiota alterations and β-TH pathogenesis remains unclear. Given that various circulating metabolites act as intermediaries between the gut microbiome and host biology [14,15], integrated analyses of microbial metabolites, gut microbiome, and host phenotype may offer promising strategies to elucidate β-TH's development mechanisms.
In this study, we performed integrative metagenomic and metabolomic analyses to identify potential links between gut microbial composition and clinical phenotypes in β-TH. Our dual-omics analysis indicates that dysfunctional bilirubin metabolism, characterized by excess bilirubin, stercobilin, and biliverdin, along with disturbances in gut microbial ecology, is associated with β-TH anemia.