Gut Microbiome, Functional Food, Atherosclerosis, and Vascular Calcifications-Is There a Missing Link?

Food to Prevent Vascular Calcification in Chronic Kidney Disease

Vascular calcification (VC) is a consequence of chronic kidney disease (CKD) which is of paramount importance regarding the survival of CKD patients. VC is far from being controlled with actual medication; as a result, in recent years, diet modulation has become more compelling. The concept of medical nutritional therapy points out the idea that food may prevent or treat diseases. The aim of this review was to evaluate the influence of food habits and nutritional intervention in the occurrence and progression of VC in CKD. Evidence reports the harmfulness of ultra-processed food, food additives, and animal-based proteins due to the increased intake of high absorbable phosphorus, the scarcity of fibers, and the increased production of uremic toxins. Available data are more supportive of a plant-dominant diet, especially for the impact on gut microbiota composition, which varies significantly depending on VC presence. Magnesium has been shown to prevent VC but only in experimental and small clinical studies. Vitamin K has drawn considerable attention due to its activation of VC inhibitors. There are positive studies; unfortunately, recent trials failed to prove its efficacy in preventing VC. Future research is needed and should aim to transform food into a medical intervention to eliminate VC danger in CKD.

Reactive Carbonyl Species and Protein Lipoxidation in Atherogenesis

Atherosclerosis is a multifactorial disease of medium and large arteries, characterized by the presence of lipid-rich plaques lining the intima over time. It is the main cause of cardiovascular diseases and death worldwide. Redox imbalance and lipid peroxidation could play key roles in atherosclerosis by promoting a bundle of responses, including endothelial activation, inflammation, and foam cell formation. The oxidation of polyunsaturated fatty acids generates various lipid oxidation products such as reactive carbonyl species (RCS), including 4-hydroxy alkenals, malondialdehyde, and acrolein. RCS covalently bind to nucleophilic groups of nucleic acids, phospholipids, and proteins, modifying their structure and activity and leading to their progressive dysfunction. Protein lipoxidation is the non-enzymatic post-translational modification of proteins by RCS. Low-density lipoprotein (LDL) oxidation and apolipoprotein B (apoB) modification by RCS play a major role in foam cell formation. Moreover, oxidized LDLs are a source of RCS, which form adducts on a huge number of proteins, depending on oxidative stress intensity, the nature of targets, and the availability of detoxifying systems. Many systems are affected by lipoxidation, including extracellular matrix components, membranes, cytoplasmic and cytoskeletal proteins, transcription factors, and other components. The mechanisms involved in lipoxidation-induced vascular dysfunction are not fully elucidated. In this review, we focus on protein lipoxidation during atherogenesis.

Gut microbes in metabolic disturbances. Promising role for therapeutic manipulations?

The prevalence of overweight, obesity, type 2 diabetes, metabolic syndrome and steatotic liver disease is rapidly increasing worldwide with a huge economic burden in terms of morbidity and mortality. Several genetic and environmental factors are involved in the onset and development of metabolic disorders and related complications. A critical role also exists for the gut microbiota, a complex polymicrobial ecology at the interface of the internal and external environment. The gut microbiota contributes to food digestion and transformation, caloric intake, and immune response of the host, keeping the homeostatic control in health. Mechanisms of disease include enhanced energy extraction from the non-digestible dietary carbohydrates, increased gut permeability and translocation of bacterial metabolites which activate a chronic low-grade systemic inflammation and insulin resistance, as precursors of tangible metabolic disorders involving glucose and lipid homeostasis. The ultimate causative role of gut microbiota in this respect remains to be elucidated, as well as the therapeutic value of manipulating the gut microbiota by diet, pre- and pro- synbiotics, or fecal microbial transplantation.

Adipokines and Bacterial Metabolites: A Pivotal Molecular Bridge Linking Obesity and Gut Microbiota Dysbiosis to Target

Adipokines are essential mediators produced by adipose tissue and exert multiple biological functions. In particular, adiponectin, leptin, resistin, IL-6, MCP-1 and PAI-1 play specific roles in the crosstalk between adipose tissue and other organs involved in metabolic, immune and vascular health. During obesity, adipokine imbalance occurs and leads to a low-grade pro-inflammatory status, promoting insulin resistance-related diabetes and its vascular complications. A causal link between obesity and gut microbiota dysbiosis has been demonstrated. The deregulation of gut bacteria communities characterizing this dysbiosis influences the synthesis of bacterial substances including lipopolysaccharides and specific metabolites, generated via the degradation of dietary components, such as short-chain fatty acids, trimethylamine metabolized into trimethylamine-oxide in the liver and indole derivatives. Emerging evidence suggests that these bacterial metabolites modulate signaling pathways involved in adipokine production and action. This review summarizes the current knowledge about the molecular links between gut bacteria-derived metabolites and adipokine imbalance in obesity, and emphasizes their roles in key pathological mechanisms related to oxidative stress, inflammation, insulin resistance and vascular disorder. Given this interaction between adipokines and bacterial metabolites, the review highlights their relevance (i) as complementary clinical biomarkers to better explore the metabolic, inflammatory and vascular complications during obesity and gut microbiota dysbiosis, and (ii) as targets for new antioxidant, anti-inflammatory and prebiotic triple action strategies.

The role of the gut microbiota in health and cardiovascular diseases

The gut microbiota is critical to human health, such as digesting nutrients, forming the intestinal epithelial barrier, regulating immune function, producing vitamins and hormones, and producing metabolites to interact with the host. Meanwhile, increasing evidence indicates that the gut microbiota has a strong correlation with the occurrence, progression and treatment of cardiovascular diseases (CVDs). In patients with CVDs and corresponding risk factors, the composition and ratio of gut microbiota have significant differences compared with their healthy counterparts. Therefore, gut microbiota dysbiosis, gut microbiota-generated metabolites, and the related signaling pathway may serve as explanations for some of the mechanisms about the occurrence and development of CVDs. Several studies have also demonstrated that many traditional and latest therapeutic treatments of CVDs are associated with the gut microbiota and its generated metabolites and related signaling pathways. Given that information, we summarized the latest advances in the current research regarding the effect of gut microbiota on health, the main cardiovascular risk factors, and CVDs, highlighted the roles and mechanisms of several metabolites, and introduced corresponding promising treatments for CVDs regarding the gut microbiota. Therefore, this review mainly focuses on exploring the role of gut microbiota related metabolites and their therapeutic potential in CVDs, which may eventually provide better solutions in the development of therapeutic treatment as well as the prevention of CVDs.

The role of microbiota in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most frequent liver disease worldwide. Gut microbiota can play a role in the pathogenesis of NAFLD since dysbiosis is associated with reduced bacterial diversity, altered Firmicutes/Bacteroidetes ratio, a relative abundance of alcohol-producing bacteria, or other specific genera. Changes can promote disrupted intestinal barrier and hyperpermeability, filtration of bacterial products, activation of the immune system, and pro-inflammatory changes in the intestine, in the liver, and at a systemic level. Microbiota-derived molecules can contribute to the steatogenic effects. The link between gut dysbiosis and NAFLD, however, is confused by several factors which include age, BMI, comorbidities, dietary components, and lifestyle. The role of toxic chemicals in food and water requires further studies in both gut dysbiosis and NAFLD. We can anticipate that gut microbiota manipulation will represent a potential therapeutic tool to delay or reverse the progression of NAFLD, paving the way to primary prevention measures.

Association between trimethylamine N-oxide and prognosis of patients with acute myocardial infarction and heart failure

AIMS

This study aimed to investigate the association between trimethylamine N-oxide (TMAO) and the prognosis and association between high-sensitivity C-reactive protein (hsCRP) and TMAO-associated cardiovascular risk in patients with acute myocardial infarction (AMI) complicated by heart failure (HF).

METHODS AND RESULTS

A total of 985 patients presenting with AMI and HF were consecutively enrolled at the Fuwai Hospital between March 2017 and January 2020. Patients were stratified into groups according to tertiles of TMAO levels and the median hsCRP levels. The primary endpoint was major adverse cardiac events (MACE), including all-cause death, recurrence of myocardial infarction, and rehospitalization due to HF. During a median follow-up of 716 days, 138 (14.0%) patients experienced MACE. Cox regression analyses showed that the adjusted hazard ratio (HR) for MACE was higher in patients in tertile 3 [TMAO > 9.52 μmol/L, HR: 1.85, 95% confidence interval (CI): 1.18-2.89; P = 0.007] than in tertile 1 (TMAO < 4.74 μmol/L), whereas no significant differences were detected between the patients in tertiles 1 and 2 (TMAO = 4.74-9.52 μmol/L, HR: 0.96, 95% CI: 0.59-1.58; P = 0.874). Restricted cubic spline regression depicted an S-shaped association between TMAO and MACE (P for nonlinearity = 0.012). In the setting of hsCRP above the median level (6.68 mg/L), per unit increase of TMAO was associated with a 20% increase of MACE risk (HR: 1.20, 95% CI: 1.05-1.37, P = 0.009); increasing tertiles of TMAO were significantly associated with a higher risk of MACE (adjusted P = 0.007 for interaction; P < 0.001 for trend across tertiles). The Kaplan-Meier analysis indicated that patients in tertile 3 had a significantly lower event-free survival (P = 0.001) when the hsCRP level was above the median level. No similar association between TMAO and MACE was observed when the hsCRP level was below the median level.

CONCLUSIONS

High plasma TMAO levels were independently correlated with poor prognosis in patients with AMI complicated by HF, especially in those with higher hsCRP levels. There was an S-shaped relationship between TMAO and HR for MACE.

The Interplay Between Gut Microbiota and miRNAs in Cardiovascular Diseases

The human microbiota contains microorganisms found on the skin, mucosal surfaces and in other tissues. The major component, the gut microbiota, can be influenced by diet, genetics, and environmental factors. Any change in its composition results in pathophysiological changes that can further influence the evolution of different conditions, including cardiovascular diseases (CVDs). The microbiome is a complex ecosystem and can be considered the metagenome of the microbiota. MicroRNAs (miRNAs) are speculated to interact with the intestinal microbiota for modulating gene expressions of the host. miRNAs represent a category of small non-coding RNAs, consisting of approximately 22 nucleotides, which can regulate gene expression at post-transcriptional level, by influencing the degradation of mRNA and modifying protein amounts. miRNAs display a multitude of roles, being able to influence the pathogenesis and progression of various diseases. Circulating miRNAs are stable against degradation, due to their enclosure into extracellular vesicles (EVs). This review aims to assess the current knowledge of the possible interactions between gut microbiota, miRNAs, and CVDs. As more scientific research is conducted, it can be speculated that personalized patient care in the future may include the management of gut microbiota composition and the targeted treatment against certain expression of miRNAs.

Intestinal Barrier and Permeability in Health, Obesity and NAFLD

The largest surface of the human body exposed to the external environment is the gut. At this level, the intestinal barrier includes luminal microbes, the mucin layer, gastrointestinal motility and secretion, enterocytes, immune cells, gut vascular barrier, and liver barrier. A healthy intestinal barrier is characterized by the selective permeability of nutrients, metabolites, water, and bacterial products, and processes are governed by cellular, neural, immune, and hormonal factors. Disrupted gut permeability (leaky gut syndrome) can represent a predisposing or aggravating condition in obesity and the metabolically associated liver steatosis (nonalcoholic fatty liver disease, NAFLD). In what follows, we describe the morphological-functional features of the intestinal barrier, the role of major modifiers of the intestinal barrier, and discuss the recent evidence pointing to the key role of intestinal permeability in obesity/NAFLD.