Arsenic disturbs the gut microbiome of individuals in a disadvantaged community in Nepal

Abstract

Arsenic is ubiquitous in nature, highly toxic, and is particularly abundant in Southern Asia. While many studies have focused on areas like Bangladesh and West Bengal, India, disadvantaged regions within Nepal have also suffered from arsenic contamination levels, with wells and other water sources possessing arsenic contamination over the recommended WHO and EPA limit of 10 μg/L, some wells reporting levels as high as 500 μg/L. Despite the region's pronounced arsenic concentrations within community water sources, few investigations have been conducted to understand the impact of arsenic contamination on host gut microbiota health. This study aims to examine differential arsenic exposure on the gut microbiome structure within two disadvantaged communities in southern Nepal. Fecal samples (n ¼ 42) were collected from members of the Mahuawa (n ¼ 20) and Ghanashyampur (n ¼ 22) communities in southern Nepal. The 16S rRNA gene was amplified from fecal samples using Illumina-tag PCR and subject to high-throughput sequencing to generate the bacterial community structure of each sample. Bioinformatics analysis and multivariate statistics were conducted to identify if specific fecal bacterial assemblages and predicted functions were correlated with urine arsenic concentration. Our results revealed unique assemblages of arsenic volatilizing and pathogenic bacteria positively correlated with increased arsenic concentration in individuals within the two respective communities. Additionally, we observed that commensal gut bacteria negatively correlated with increased arsenic concentration in the two respective communities. Our study has revealed that arsenic poses a broader human health risk than was previously known. It is influential in shaping the gut microbiome through its enrichment of arsenic volatilizing and pathogenic bacteria and subsequent depletion of gut commensals. This aspect of arsenic has the potential to debilitate healthy humans by contributing to disorders like heart and liver cancers and diabetes, and it has already been shown to contribute to serious diseases and disorders, including skin lesions, gangrene and several types of skin, renal, lung, and liver cancers in disadvantaged areas of the world like Nepal.

Impact of Environmental Pollutants on Gut Microbiome and Mental Health via the Gut–Brain Axis

“…Chronic inflammation, increased gut permeability, the proliferation of opportunistic microbes, increased metal uptake and increased BBB dysfunction are all promoted by decreased SCFA production [ 118 , 119 ]. Brabec et al found that As exposure altered the gut microbiota composition of Nepalese people by enriching As volatilizing and pathogenic bacteria while depleting gut commensals [ 73 ] ( Table 1 ). Furthermore, metabolomics profiling demonstrated a concomitant impact, with several gut microflora-related metabolites disrupted in a variety of biological matrices.…”

Role-Playing Between Environmental Pollutants and Human Gut Microbiota: A Complex Bidirectional Interaction

“…It can be found in water and soil, as both the organic and inorganic structures. It has been demonstrated to shape the GM depleting gut commensals and enriching pathogenic bacteria ( 98 ). In children exposed to As the GM alteration resulted in an abundance of Proteobacteria , highlighting changes in genes involved in multidrug resistance ( 67 ).…”

Influence of toxic metal exposure on the gut microbiota (Review)

“…Lower levels of As were associated with intestinal commensal bacteria. The authors stated that As plays a role in the GM shaping through the enrichment of pathogens and the weakening of commensal bacteria (34).…”