Independent of mitochondrial respiratory function, dietary nitrate attenuates HFD-induced lipid accumulation and mitochondrial ROS emission within the liver

Salivary-Gland-Mediated Nitrate Recirculation as a Modulator for Cardiovascular Diseases

Cardiovascular diseases (CVDs), which include multiple disorders of the heart and blood vessels, are the leading causes of death. Nitric oxide (NO) is a vasodilator that regulates vascular tension. Endogenous NO is produced via the L-arginine-nitric oxide synthase (NOS) pathway. In conditions of cardiovascular dysfunction, NOS activity is impaired, leading to NO deficiency. In turn, the reduction in NO bioactivity exacerbates the pathogenesis of CVDs. Exogenous intake of inorganic nitrate supplements endogenous production via the nitrate-nitrite-NO pathway to maintain the NO supply. Salivary glands play an essential role in the conversion of nitrate to NO, with approximately 25% of circulating nitrate being absorbed and secreted into saliva. As a result, salivary nitrate concentrations can exceed that in the blood by more than tenfold. This recycled nitrate in saliva serves as a reservoir for NO and performs NO-like functions when endogenous NO production is insufficient. In this review, we summarize the emerging benefits of dietary nitrate in CVDs, with a particular focus on salivary-gland-mediated nitrate recirculation in maintaining NO bioavailability and cardiovascular homeostasis. Salivary-gland-mediated nitrate recirculation provides a novel perspective for potential intervention of CVDs.

The Nitrate-Nitrite-Nitric Oxide Pathway: Potential Role in Mitigating Oxidative Stress in Hypertensive Disorders of Pregnancy

Hypertensive diseases of pregnancy (HDPs) represent a global clinical challenge, affecting 5-10% of women and leading to complications for both maternal well-being and fetal development. At the heart of these complications is endothelial dysfunction, with oxidative stress emerging as a pivotal causative factor. The reduction in nitric oxide (NO) bioavailability is a vital indicator of this dysfunction, culminating in blood pressure dysregulation. In the therapeutic context, although antihypertensive medications are commonly used, they come with inherent concerns related to maternal-fetal safety, and a percentage of women do not respond to these therapies. Therefore, alternative strategies that directly address the pathophysiology of HDPs are required. This article focuses on the potential of the nitrate-nitrite-NO pathway, abundantly present in dark leafy greens and beetroot, as an alternative approach to treating HDPs. The objective of this review is to discuss the prospective antioxidant role of nitrate. We hope our discussion paves the way for using nitrate to improve endothelial dysfunction and control oxidative stress, offering a potential therapy for managing HDPs.

Positive feedback loop between dietary nitrate intake and oral health

Nitrate was once thought to be an inert end-product of endothelial-derived nitric oxide (NO) heme oxidation; however, this view has been radically revised over the past few decades. Following the clarification of the nitrate-nitrite-NO pathway, accumulated evidence has shown that nitrate derived from the diet is a supplementary source of endogenous NO generation, playing important roles in a variety of pathological and physiological conditions. However, the beneficial effects of nitrate are closely related with oral health, and oral dysfunction has an adverse effect on nitrate metabolism and further impacts overall systemic health. Moreover, an interesting positive feedback loop has been identified between dietary nitrate intake and oral health. Dietary nitrate's beneficial effect on oral health may further improve its bioavailability and promote overall systemic well-being. This review aims to provide a detailed description of the functions of dietary nitrate, with an emphasis on the key role oral health plays in nitrate bioavailability. This review also provides recommendations for a new paradigm that includes nitrate therapy in the treatment of oral diseases.

Independent, but not co-supplementation, with nitrate and resveratrol improves glucose tolerance and reduces markers of cellular stress in high-fat-fed male mice

Independent supplementation with nitrate (NIT) and resveratrol (RSV) enriches various aspects of mitochondrial biology in key metabolic tissues. Although RSV is known to activate Sirt1 and initiate mitochondrial biogenesis, the metabolic benefits elicited by dietary nitrate appear to be dependent on 5'-adenosine monophosphate-activated protein kinase (AMPK)-mediated signaling events, a process also linked to the activation of Sirt1. Although the benefits of individual supplementation with these compounds have been characterized, it is unknown if co-supplementation may produce superior metabolic adaptations. Thus, we aimed to determine if treatment with combined +NIT and +RSV (+RN) could additively alter metabolic adaptations in the presence of a high-fat diet (HFD). Both +RSV and +NIT improved glucose tolerance compared with HFD (P < 0.05); however, this response was attenuated following combined +RN supplementation. Within skeletal muscle, all supplements increased mitochondrial ADP sensitivity compared with HFD (P < 0.05), without altering mitochondrial content. Although +RSV and +NIT decreased hepatic lipid deposition compared with HFD (P < 0.05), this effect was abolished with +RN, which aligned with significant reductions in Sirt1 protein content (P < 0.05) after combined treatment, in the absence of changes to mitochondrial content or function. Within epididymal white adipose tissue (eWAT), all supplements reduced crown-like structure accumulation compared with HFD (P < 0.0001) and mitochondrial reactive oxygen species (ROS) emission (P < 0.05), alongside reduced adipocyte cross-sectional area (CSA) (P < 0.05), with the greatest effect observed after +RN treatment (P = 0.0001). Although the present data suggest additive changes in adipose tissue metabolism after +RN treatment, concomitant impairments in hepatic lipid homeostasis appear to prevent improvements in whole body glucose homeostasis observed with independent treatment, which may be Sirt1 dependent.

Associations of thiocyanate, nitrate, and perchlorate exposure with dyslipidemia: a cross-sectional, population-based analysis

The aim of this study was to assess the associations of urinary thiocyanate, nitrate, and perchlorate concentrations with dyslipidemia, individually and in combination, which has not previously been studied. Data from the 2001-2002 and 2005-2016 National Health and Nutrition Examination Surveys (NHANES) were analyzed in this cross-sectional study. The dependent variables were continuous serum lipid variables (triglycerides [TG], total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], non-HDL-C, and apolipoprotein B [Apo B]) and binary serum lipid variables, with the latter reflecting dyslipidemia (elevated TG, ≥ 150 mg/dL; elevated TC, ≥ 200 mg/dL; elevated LDL-C, ≥ 130 mg/dL; lowered HDL-C, < 40 mg/dL in men and < 5 0 mg/dL in women; elevated non-HDL-C, ≥ 160 mg/dL; and elevated Apo B, ≥ 130 mg/dL). Multivariate logistic, linear, and weighted quantile sum (WQS) regression analyses were used to explore the associations of thiocyanate, nitrate, and perchlorate with the continuous and binary serum lipid variables. The linearity of the associations with the binary serum lipid variables was assessed using restricted cubic spline (RCS) regression. A total of 15,563 adults were included in the analysis. The multivariate linear and logistic regression analyses showed that thiocyanate was positively associated with multiple continuous (TG, TC, LDL-C, non-HDL-C, and Apo B, but not HDL-C) and binary (elevated TG, TC, LDL-C, and non-HDL-C) serum lipid variables, whereas perchlorate was negatively associated with elevated LDL-C. Multivariate RCS logistic regression revealed a linear dose-response relationship between thiocyanate and elevated TG, TC, LDL-C, non-HDL-C, and Apo B, but a nonlinear relationship with lowered HDL-C (inflection point = 1.622 mg/L). WQS regression showed that a mixture of thiocyanate, nitrate, and perchlorate was positively associated with all binary serum lipid variables except for Apo B. Our findings indicate that urinary thiocyanate, nitrate, and perchlorate concentrations, individually and in combination, were associated with dyslipidemia.

Efficacy and Variability in Plasma Nitrite Levels during Long-Term Supplementation with Nitrate Containing Beetroot Juice

Long-term consumption of beetroot juice on efficacy of converting dietary nitrate to plasma nitrate and nitrite was investigated. Adults were randomized to consume either beetroot juice with 380 mg of nitrate (BR) or a beetroot juice placebo (PL) for 12-weeks. Plasma nitrate and nitrite were measured before and 90-minutes after consuming their intervention beverage. Percent change in nitrite across the 90 min was greater in BR (273.2 ± 39.9%) vs. PL (4.9 ± 36.9%). Long-term consumption of nitrate containing beetroot juice increased fasting nitrate and nitrite plasma levels compared to baseline.

Depletion of Gut Microbiota Inhibits Hepatic Lipid Accumulation in High-Fat Diet-Fed Mice

Dysregulated lipid metabolism is a key pathology in metabolic diseases and the liver is a critical organ for lipid metabolism. The gut microbiota has been shown to regulate hepatic lipid metabolism in the host. However, the underlying mechanism by which the gut microbiota influences hepatic lipid metabolism has not been elucidated. Here, a gut microbiota depletion mouse model was constructed with an antibiotics cocktail (Abx) to study the mechanism through which intestinal microbiota regulates hepatic lipid metabolism in high-fat diet (HFD)-fed mice. Our results showed that the Abx treatment effectively eradicated the gut microbiota in these mice. Microbiota depletion reduced the body weight and fat deposition both in white adipose tissue and liver. In addition, microbiota depletion reduced serum levels of glucose, total cholesterol (TC), low-density lipoproteins (LDL), insulin, and leptin in HFD-fed mice. Importantly, the depletion of gut microbiota in HFD-fed mice inhibited excessive hepatic lipid accumulation. Mechanistically, RNA-seq results revealed that gut microbiota depletion changed the expression of hepatic genes involved in cholesterol and fatty acid metabolism, such as Cd36, Mogat1, Cyp39a1, Abcc3, and Gpat3. Moreover, gut microbiota depletion reduced the abundance of bacteria associated with abnormal metabolism and inflammation, including Lachnospiraceae, Coriobacteriaceae_UCG-002, Enterorhabdus, Faecalibaculum, and Desulfovibrio. Correlation analysis showed that there was strong association between the altered gut microbiota abundance and the serum cholesterol level. This study indicates that gut microbiota ameliorates HFD-induced hepatic lipid metabolic dysfunction, which might be associated with genes participating in cholesterol and fatty acid metabolism in the liver.