Tuning constitutive and pathological inflammation in the gut via the interaction of dietary nitrate and polyphenols with host microbiome

Chronic inflammation is currently recognized as a critical process in modern-era epidemics such as diabetes, obesity and neurodegeneration. However, little attention is paid to the constitutive inflammatory pathways that operate in the gut and that are mandatory for local welfare and the prevention of such multi-organic diseases. Hence, the digestive system, while posing as a barrier between the external environment and the host, is crucial for the balance between constitutive and pathological inflammatory events. Gut microbiome, a recently discovered organ, is now known to govern the interaction between exogenous agents and the host with ensued impact on local and systemic homeostasis. Whereas gut microbiota may be modulated by a myriad of factors, diet constitutes one of its major determinants. Thus, dietary compounds that influence microbial flora may thereby impact on inflammatory pathways. One such example is the redox environment in the gut lumen which is highly dependent on the local generation of nitric oxide along the nitrate-nitrite-nitric oxide pathway and that is further enhanced by simultaneous consumption of polyphenols. In this paper, different pathways encompassing the interaction of dietary nitrate and polyphenols with gut microbiota will be presented and discussed in connection with local and systemic inflammatory events. Furthermore, it will be discussed how these interactive cycles (nitrate-polyphenols-microbiome) may pose as novel strategies to tackle inflammatory diseases.