A exposição prolongada ao metilmercúrio e dieta rica em gordura induzem alterações na microbiota, barreira intestinal e metabolômica em camundongos

Abstract

Methylmercury (MeHg), a highly toxic organic form of mercury (Hg), poses a significant risk to human health, particularly when associated with obesity induced by high-fat diets (HFD). This study investigates the effects of MeHg and HFD (42% fat) on intestinal barrier integrity and microbiota composition in mice. Weanling mice were fed a HFD or a standard diet for 40 days. For the last 21 days, they received MeHg (20 mg/L) or drinking water only. Proximal intestinal, cecal, and hair samples were collected. Intestinal morphology was assessed by the number and area of villi, while intestinal barrier integrity was analyzed by counting cells positive for mucin-2 and lysozyme, as well as by the mRNA expression of ZO-1 and occludin, and by immunostaining for Iba-1 and NFκB. Functional intestinal permeability was assessed by quantifying blood radioactivity levels. The gut microbiota profile was obtained from DNA collected from fecal samples, and the metabolic profile of cecal contents was analyzed by gas chromatography-mass spectrometry (GC-MS). ZO-1 immunofluorescence was performed in the colon and proximal intestine. The results showed that HFD increased mucin-2 expression and reduced lysozyme(+) cell expression. The MeHg + HFD combination compromised the intestinal barrier, reducing ZO-1 and occludin transcription, decreasing villi area, and increasing intestinal permeability. Both MeHg and HFD alone increased immunostaining for Iba-1 and NFκB, but the MeHg + HFD combination reduced this immunostaining. The MeHg + HFD combination decreased microbiome alpha-diversity and led to the loss of colonic ZO-1 immunostaining compared to non-intoxicated mice fed a control diet. After MeHg intoxication, there was a significant depletion of the genera Streptococcus, Psychrobacter, Facklamia, and Corynebacterium, while other groups, such as Atopostipes and Jeotgalicoccus, were not affected alone but showed significant reduction with the MeHg + HFD combination. In the metabolic profile, MeHg intoxication resulted in significant increases in alanine, valine, benzoic acid, aspartate, leucine, isoleucine, and proline. However, the HFD and the MeHg + HFD combination did not show significant changes in metabolites. Our findings suggest that, although MeHg does not cause extensive intestinal dysbiosis, it compromises the integrity of the intestinal barrier. Furthermore, the synergistic effects of the MeHg + HFD combination on the mucosa-associated microbiota are more pronounced than the individual effects of each.