Long-term dietary nitrite and nitrate deficiency causes the metabolic syndrome, endothelial dysfunction and cardiovascular death in mice

Abstract

Aims/hypothesis Nitric oxide (NO) is synthesised not only from L-arginine by NO synthases (NOSs), but also from its inert metabolites, nitrite and nitrate. Green leafy vegetables are abundant in nitrate, but whether or not a deficiency in dietary nitrite/nitrate spontaneously causes disease remains to be clarified. In this study, we tested our hypothesis that long-term dietary nitrite/nitrate deficiency would induce the metabolic syndrome in mice. Methods To this end, we prepared a low-nitrite/nitrate diet (LND) consisting of an amino acid-based low-nitrite/nitrate chow, in which the contents of L-arginine, fat, carbohydrates, protein and energy were identical with a regular chow, and potable ultrapure water. Nitrite and nitrate were undetectable in both the chow and the water. Results Three months of the LND did not affect food or water intake in wild-type C57BL/6J mice compared with a regular diet (RD). However, in comparison with the RD, 3 months of the LND significantly elicited visceral adiposity, dyslipidaemia and glucose intolerance. Eighteen months of the LND significantly provoked increased body weight, hypertension, insulin resistance and impaired endothelium-dependent relaxations to acetylcholine, while 22 months of the LND significantly led to death mainly due to cardiovascular disease, including acute Mika Kina-Tanada and Mayuko Sakanashi contributed equally to this work.

Mechanisms underlying blood pressure reduction by dietary inorganic nitrate

“…Even though other components in the fruit and vegetable juice could have contributed to the observed effects, plasma nitrate and nitrite increased to levels similar to those found in treatment studies with inorganic nitrate alone. Conversely, the effects of long‐term nitrate/nitrite deficiency in mice were investigated and after 18 months on a diet more or less free of nitrate and nitrite the mice developed severe cardiovascular and metabolic disturbances, including hypertension and this was associated with dysbiosis of the gut microbiota . Indeed, more studies are clearly needed to establish if and how inorganic nitrate may affect the gut microbiome and if so how this might be coupled to beneficial effects on cardiovascular and metabolic function.…”

Supplementation with nitrate only modestly affects lipid and glucose metabolism in genetic and dietary-induced murine models of obesity

“…In contrast, significant alterations were often reported in animals fed a complete NOx-free diet. (21,41) We found an increase in the blood content of nitrate/nitrite with increasing nitrate feeding, except for the highest supplemental nitrate group in db/db mice. Changes in serum nitrate, nitrite and NOx levels are a controversial issue, and elevated, (29) unchanged, (20,42) or even decreased levels have been reported in response to dietary nitrate.…”

“…Additionally, no significant differences in food intake or circulating concentrations of glucose, TG, and various inflammatory markers were detected in mice after 1.5 months of feeding a low-nitrate diet compared to a nitrate-supplemented diet. (21) In the same study, however, beneficial effects became evident after 3 months of nitrate feeding. Furthermore, a long-term dietary nitrite deficiency caused metabolic syndrome, endothelial dysfunction and death from cardiovascular failure in mice.…”

“…Long-term dietary nitrate/nitrite deficiency also led to the development of metabolic syndrome in mice, including endothelial dysfunction and cardiovascular death. (21) Furthermore, the generation of NO by inducible Nos (iNos) in response to proinflammatory cytokines and endotoxins plays a critical role in protecting against pathogens and uncontrolled inflammation, e.g., via activation of macrophages or the modulation of the epithelial barrier function. (22)(23)(24) The expression of iNos is increased in the skeletal muscle and adipose tissue of both genetic and diet-induced models of obesity, (5) whereas inorganic nitrite has been shown to reduce mRNA levels of iNos as well as superoxide anion free radical production in activated macrophages.…”

Astrofood, Priorities and Pandemics: Reflections of an Ultra-Processed Breakfast Program and Contemporary Dysbiotic Drift

“…With a good degree of consistency, researchers have shown general losses in microbial diversity in association with westernization and industrialization [109,110]. The loss of microbial diversity as a result of what Astrofood represents-that is, an ultra-processed, reassembled food supply deficient in fiber and phytochemicals-may have long-term consequences [111,112] and even extend over generations [113]. As in the larger world of natural environments, loss of microbial diversity generally equates to a loss of functional benefits and threat to a healthy ecosystem.…”