Nickel-resistant gut microbiota: a missing link between environmental exposure and metabolic disease.

Environmental factors are emerging as important modulators of the gut microbiome, with significant implications for metabolic health. Among these, nickel-a ubiquitous dietary metal traditionally regarded as an allergen-is gaining recognition as a systemic immune-metabolic modulator. Chronic nickel exposure has been linked to overweight and metabolic alterations, particularly in nickel-allergic individuals, suggesting that environmental nickel may represent an underrecognized contributor to metabolic dysfunction in susceptible populations. Recent studies have identified nickel-resistant bacteria within the gut microbiota of affected individuals, providing a biologically plausible framework linking environmental metal exposure to microbial ecology. These microorganisms contribute to nickel detoxification and may influence host physiology through interactions with microbial metabolism, energy balance, and immune signaling. Under conditions of chronic exposure, ecological selection of nickel-resistant communities may contribute to dysbiosis and altered host-microbiome interactions. By integrating clinical observations with emerging microbiological evidence, this Perspective explores the hypothesis that nickel-resistant gut microbiota may represent candidate mediators at the intersection of environmental exposure, immunity, and metabolism. Understanding how dietary metals shape microbial ecosystems may provide new insights into metabolic disease and highlights metal-microbiota interactions as a promising area for future investigation.