Plant-Based Diets, the Gut Microbiota, and Trimethylamine N-Oxide Production in Chronic Kidney Disease: Therapeutic Potential and Methodological Considerations

Dietary Phosphorus Levels Influence Protein-Derived Uremic Toxin Production in Nephrectomized Male Rats

Gut microbiota-derived uremic toxins (UT) accumulate in patients with chronic kidney disease (CKD). Dietary phosphorus and protein restriction are common in CKD treatment, but the relationship between dietary phosphorus, a key nutrient for the gut microbiota, and protein-derived UT is poorly studied. Thus, we explored the relationship between dietary phosphorus and serum UT in CKD rats. For this exploratory study, we used serum samples from a larger study on the effects of dietary phosphorus on intestinal phosphorus absorption in nephrectomized (Nx, n = 22) or sham-operated (sham, n = 18) male Sprague Dawley rats. Rats were randomized to diet treatment groups of low or high phosphorus (0.1% or 1.2% w/w, respectively) for 1 week, with serum trimethylamine oxide (TMAO), indoxyl sulfate (IS), and p-cresol sulfate (pCS) analyzed by LC-MS. Nx rats had significantly higher levels of serum TMAO, IS, and pCS compared to sham rats (all p < 0.0001). IS showed a significant interaction between diet and CKD status, where serum IS was higher with the high-phosphorus diet in both Nx and sham rats, but to a greater extent in the Nx rats. Serum TMAO (p = 0.24) and pCS (p = 0.34) were not affected by dietary phosphorus levels. High dietary phosphorus intake for 1 week results in higher serum IS in both Nx and sham rats. The results of this exploratory study indicate that reducing dietary phosphorus intake in CKD may have beneficial effects on UT accumulation.

Rapid and Direct Detection of Trimethylamine N-oxide Using an Off-Chip Capacitance Biosensor with Readout SoC for Early-Stage Thrombosis and Cardiovascular Disease

A demonstration of an off-chip capacitance array sensor with a limit of detection of 1 μM trimethylamine N-oxide (TMAO) to diagnose a chronic metabolism disease in urine is presented. The improved Cole-Cole model is employed to determine the parameters of R_catalyzed, C_catalyzed, and Rp_catalyzed, enabling the prediction of the catalytic resistance of enzyme, reduction effects of the analyte, and characterize the small signal alternating current properties of ionic strength caused by catalysis. Based on the standard solutions, we investigate the effects of pixel geometry parameters, driving electrode width, and sensing electrode width on the electrical field change of the off-chip capacitance sensor; the proposed off-chip sensor with readout system-on-chip exhibits a high sensitivity of 21 analog-to-digital converter counts/μM TMAO (or 2.5 mV/μM TMAO), response time of 1 s, repetition of 98.9%, and drift over time of 0.5 mV. The proposed off-chip sensor effectively discriminates TMAO in a phosphate-buffered saline solution based on minute changes in capacitance induced by the TorA enzyme, resulting in a discernible 2.15% distinction. These measurements have been successfully corroborated using the conventional cyclic voltammetry method, demonstrating a mere 0.024% variance. The off-chip sensor is crafted with a specific focus on detecting TMAO, achieved by excluding any reduction reactions between the TMAO-specific enzyme TorA and the compounds creatine and creatinine present in urine. This deliberate omission ensures that the sensor's attention remains solely on TMAO, thereby enhancing its precision in achieving accurate and reliable TMAO detection.

Dieta de la Milpa: A Culturally-Concordant Plant-Based Dietary Pattern for Hispanic/Latine People with Chronic Kidney Disease

Chronic kidney disease (CKD) disproportionately affects minorities in the United States, including the Hispanic/Latine population, and is a public health concern in Latin American countries. An emphasis on healthy dietary patterns, including the Mediterranean and the Dietary Approaches to Stop Hypertension (DASH) diets, has been suggested as they are associated with a lower incidence of CKD, slower CKD progression, and lower mortality in kidney failure. However, their applicability may be limited in people from Latin America. The Dieta de la Milpa (Diet of the Cornfield) was recently described as the dietary pattern of choice for people from Mesoamerica (Central Mexico and Central America). This dietary pattern highlights the intake of four plant-based staple foods from this geographical region, corn/maize, common beans, pumpkins/squashes, and chilies, complemented with seasonal and local intake of plant-based foods and a lower intake of animal-based foods, collectively classified into ten food groups. Limited preclinical and clinical studies suggest several health benefits, including cardiometabolic health, but there is currently no data concerning CKD. In this narrative review, we describe and highlight the potential benefits of the Dieta de la Milpa in CKD, including acid-base balance, protein source, potassium and phosphorus management, impact on the gut microbiota, inflammation, and cultural appropriateness. Despite these potential benefits, this dietary pattern has not been tested in people with CKD. Therefore, we suggest key research questions targeting measurement of adherence, feasibility, and effectiveness of the Dieta de la Milpa in people with CKD.

Non-invasive detection of renal disease biomarkers through breath analysis

Breath biomarkers are substances found in exhaled breath that can be used for non-invasive diagnosis and monitoring of medical conditions, including kidney disease. Detection techniques include mass spectrometry (MS), gas chromatography (GC), and electrochemical sensors. Biosensors, such as GC-MS or electronic nose (e-nose) devices, can be used to detect volatile organic compounds (VOCs) in exhaled breath associated with metabolic changes in the body, including the kidneys. E-nose devices could provide an early indication of potential kidney problems through the detection of VOCs associated with kidney dysfunction. This review discusses the sources of breath biomarkers for monitoring renal disease during dialysis and different biosensor approaches for detecting exhaled breath biomarkers. The future of using various types of biosensor-based real-time breathing diagnosis for renal failure is also discussed.

Trimethylamine N-oxide and kidney diseases: what do we know?

In the human gut, there is a metabolically active microbiome whose metabolic products reach various organs and are used in the physiological activities of the body. When dysbiosis of intestinal microbial homeostasis occurs, pathogenic metabolites may increase and one of them is trimethyl amine-N-oxide (TMAO). TMAO is thought to have a role in the pathogenesis of insulin resistance, diabetes, hyperlipidemia, atherosclerotic heart diseases, and cerebrovascular events. TMAO level is also associated with renal inflammation, fibrosis, acute kidney injury, diabetic kidney disease, and chronic kidney disease. In this review, the effect of TMAO on various kidney diseases is discussed.

The dietary source of trimethylamine N-oxide and clinical outcomes: an unexpected liaison

The profile of gut microbiota can vary according to host genetic and dietary characteristics, and be influenced by disease state and environmental stressors. The uremic dysbiosis results in a loss of biodiversity and overgrowth of microorganisms that may cause elevation of metabolic solutes such as trimethylamine N-oxide (TMAO), inducing pathogenic effects on its host. In patients with chronic kidney disease (CKD), TMAO levels are elevated because of a decreased clearance and an increased production from the uremic gut dysbiosis with a disrupted intestinal barrier and elevated enzymatic hepatic activity. Dietary precursors of TMAO are abundant in animal-derived foods such as red meat, egg yolk and other full-fat dietary products. TMAO is also found naturally in fish and certain types of seafood, with the TMAO content highly variable according to the depth of the sea where the fish is caught, as well as processing and storage. Although evidence points towards TMAO as being an important link to vascular damage and adverse cardiovascular outcomes, the evidence in CKD patients has not been consistent. In this review we discuss the potential dietary sources of TMAO and its actions on the intestinal microbiome as an explanation for the divergent results. We further highlight the potential of a healthy diet as one feasible therapeutic opportunity to prevent gut dysbiosis and reduce uremic toxin levels in patients with CKD.

Targeting the Gut Microbiota in Kidney Disease: The Future in Renal Nutrition and Metabolism

There is increasing interest in the therapeutic potential of manipulating the gut microbiome of patients with chronic kidney disease (CKD). This is because there is a substantial deviation from a balanced gut microbiota profile in CKD, with many deleterious downstream effects. Nutritional interventions such as plant-based diets with reduced animal protein intake and the use of probiotics, prebiotics, and synbiotics may alter the microbiome. This article aims to briefly describe what is known about the gut microbiome in patients with CKD, factors contributing to gut dysbiosis, and outline important evidence gaps. Future potential therapies, including restoring the microbiota with food and microbiota-based and metabolomic-based therapies, are also discussed.

Microbiota of the gastrointestinal tract: Friend or foe?

The gut microbiota is currently considered an external organ of the human body that provides important mechanisms of metabolic regulation and protection. The gut microbiota encodes over 3 million genes, which is approximately 150 times more than the total number of genes present in the human genome. Changes in the qualitative and quantitative composition of the microbiome lead to disruption in the synthesis of key bacterial metabolites, changes in intestinal barrier function, and inflammation and can cause the development of a wide variety of diseases, such as diabetes, obesity, gastrointestinal disorders, cardiovascular issues, neurological disorders and oncological concerns. In this review, I consider issues related to the role of the microbiome in the regulation of intestinal barrier function, its influence on physiological and pathological processes occurring in the body, and potential new therapeutic strategies aimed at restoring the gut microbiome. Herewith, it is important to understand that the gut microbiota and human body should be considered as a single biological system, where change of one element will inevitably affect its other components. Thus, the study of the impact of the intestinal microbiota on health should be considered only taking into account numerous factors, the role of which has not yet been fully elucidated.

The impact of dietary nutrient intake on gut microbiota in the progression and complications of chronic kidney disease

Chronic kidney disease (CKD) has been associated with changes in the function and composition of the gut microbiota. The ecosystem of the human gut consists of trillions of microorganisms forming an authentic metabolically active organ that is fueled by nutrients to produce bioactive compounds. These microbiota-derived metabolites may be protective for kidney function (e.g. short-chain fatty acids from fermentation of dietary fibers) or deleterious (e.g. gut-derived uremic toxins such as trimethylamine N-oxide, p-cresyl sulfate, and indoxyl sulfate from fermentation of amino acids). Although diet is the cornerstone of the management of the patient with CKD, it remains a relatively underused component of the clinician's armamentarium. In this review, we describe the latest advances in understanding diet-microbiota crosstalk in a uremic context, and how this communication might contribute to CKD progression and complications. We then discuss how this knowledge could be harnessed for personalized nutrition strategies to prevent patients with CKD progressing to end-stage kidney disease and its detrimental consequences.

Ethnobotanical, pharmacological, phytochemical, and clinical investigations on Moroccan medicinal plants traditionally used for the management of renal dysfunctions

ETHNOPHARMACOLOGICAL RELEVANCE

Renal disease is a significant public health concern that affects people all over the world. The main limitations of conventional therapy are the adverse reaction on human health and the expensive cost of drugs. Indeed, it is necessary to develop new therapeutic strategies that are less expensive and have fewer side effects. As a consequence of their natural compounds, medicinal plants can be used as an alternative therapy to cure various ailments including kidney diseases.

OBJECTIVE

of the study: This review paper has two principal goals: (1) to inventory and describe the plants and their ancestral use by Moroccan society to cure renal problems, (2) to link traditional use with scientific confirmations (preclinical and clinical).

METHODS

To analyze pharmacological effects, phytochemical, and clinical trials of plants, selected for renal therapy, a bibliographical search was undertaken by examining ethnobotanical investigations conducted in Morocco between 1991 and 2019 and consulting peer-reviewed papers from all over the world.

RESULTS

Approximately 290 plant species, spanning 81 families and 218 genera have been reported as being utilized by Moroccans to manage renal illness. The most frequently mentioned species in Morocco were Herniaria hirsuta subsp. cinerea (DC.), Petroselinum crispum (Mill.) Fuss and Rosmarinus officinalis L. The leaves were the most frequently used plant parts, followed by the whole plant. Decoction and infusion were the most popular methods of preparation. A record of 71 plant species was studied in vitro and/or in vivo for their therapeutic efficacy against kidney disorders, including 10 plants attempting to make it to the clinical stage. Twenty compounds obtained from 15 plants have been studied for the treatment of kidney diseases.

CONCLUSION

Medicinal herbs could be a credible alternative therapy for renal illness. However, additional controlled trials are required to confirm their efficiency in patients with kidney failure. Overall, this work could be used as a database for future exploration.

Nephroprotective Plants: A Review on the Use in Pre-Renal and Post-Renal Diseases

Kidney diseases are expected to become the fifth leading cause of death by 2040. Several physiological failures classified as pre-, intra-, and post-renal factors induce kidney damage. Diabetes, liver pathologies, rhabdomyolysis, and intestinal microbiota have been identified as pre-renal factors, and lithiasis or blood clots in the ureters, prostate cancer, urethral obstructions, prostate elongation, and urinary tract infections are post-renal factors. Additionally, the nephrotoxicity of drugs has been highlighted as a crucial factor inducing kidney injuries. Due to the adverse effects of drugs, it is necessary to point to other alternatives to complement the treatment of these diseases, such as nephroprotective agents. Plants are a wide source of nephroprotective substances and can have beneficial effects in different levels of the physiological pathways which lead to kidney damage. In traditional medicines, plants are used as antioxidants, anti-inflammatories, diuretics, and anticancer agents, among other benefits. However, the mechanism of action of some plants empirically used remains unknown and scientific data are required to support their nephroprotective effects. The present work reviewed the plants with a beneficial effect on kidney diseases. The classification of nephroprotective plants according to the clinical definition of pre-renal, intrinsic, and post-renal factors is proposed to orient their use as complementary treatments.

Dyslipidemia in Chronic Kidney Disease: Contemporary Concepts and Future Therapeutic Perspectives

BACKGROUND

Chronic kidney disease (CKD) is an increasingly prevalent disease state met with great morbidity and mortality primarily resulting from the high incidence of adverse cardiovascular outcomes. Therapeutic strategies in this patient population aim at controlling modifiable cardiovascular risk factors, including dyslipidemia.

SUMMARY

In this review article, we first provide the latest pathophysiologic evidence regarding the altered dyslipidemia pattern in CKD, followed by its contemporary management according to the latest guidelines. Moreover, we present the current progress regarding the emerging therapeutic strategies. Key Messages: The presence of renal impairment leads to alterations in cholesterol structure, metabolism, and reverse transport paired with increased oxidative stress. Statins remain the cornerstone of dyslipidemia management in patients with kidney dysfunction who are at risk for cardiovascular events. However, their efficacy is debatable in end-stage renal disease under renal replacement therapy. Therefore, novel treatment approaches aiming at hypertriglyceridemia, proprotein convertase subtilisin/kexin type 9, and lipoprotein(a) are under rigorous investigation while the research of gut microbiome might provide additional mechanistic and therapeutic insight.