The gut-brain axis and sodium appetite: Can inflammation-related signaling influence the control of sodium intake?

Sodium is the main cation present in the extracellular fluid. Sodium and water content in the body are responsible for volume and osmotic homeostasis through mechanisms involving sodium and water excretion and intake. When body sodium content decreases below the homeostatic threshold, a condition termed sodium deficiency, highly motivated sodium seeking, and intake occurs. This is termed sodium appetite. Classically, sodium and water intakes are controlled by a number of neuroendocrine mechanisms that include signaling molecules from the renin-angiotensin-aldosterone system acting in the central nervous system (CNS). However, recent findings have shown that sodium and water intakes can also be influenced by inflammatory agents and mediators acting in the CNS. For instance, central infusion of IL-1β or TNF-α can directly affect sodium and water consumption in animal models. Some dietary conditions, such as high salt intake, have been shown to change the intestinal microbiome composition, stimulating the immune branch of the gut-brain axis through the production of inflammatory cytokines, such as IL-17, which can stimulate the brain immune system. In this review, we address the latest findings supporting the hypothesis that immune signaling in the brain could produce a reduction in thirst and sodium appetite and, therefore, contribute to sodium intake control.

Socio-environmental and parasitological aspects of waste pickers in Minas Gerais, Brazil

The increase in the generation of Solid Urban Waste causes social, environmental problems and damages to the population's health. Professionals who work in the collection of recyclable waste are exposed to risks of contamination either by toxic elements or pathogenic organisms. The objective of the work was to estimate the types and prevalence of intestinal parasites in waste pickers. A field research was carried out from December 2017 to April 2018 with the voluntary participation of 26 waste pickers belonging to three associations in the municipality of Conselheiro Lafaiete, Minas Gerais, Brazil (CAAE: nº 79937817.7.0000.8122). In addition to the application a socio-environmental questionnaire, each volunteer provided a stool sample for laboratory testing the parasitological examination. Of the 26 survey participants, four (15.4%) had a positive result and were infected by the parasites Giardia lamblia, Entamoeba coli and Iodamoeba butschlii. Among the main factors that can contribute to the infection these waste pickers are the ingestion of untreated water for consumption in addition to reduced access to Personal Protective Equipment (PPE) during waste management. One way to control the presence of parasites would be through health and environmental education actions, periodic parasitological examinations and permanent use of PPE.

Swimming training improves cardiovascular autonomic dysfunctions and prevents renal damage in rats fed a high-sodium diet from weaning

NEW FINDINGS

What is the central question of this study? How does swimming exercise training impact hydro-electrolytic balance, renal function, sympathetic contribution to resting blood pressure and cerebrospinal fluid (CSF) [Na⁺ ] in rats fed a high-sodium diet from weaning? What is the main finding and its importance? An exercise-dependent reduction in blood pressure was associated with decreased CSF [Na⁺ ], sympathetically driven vasomotor tonus and renal fibrosis indicating that the anti-hypertensive effects of swimming training in rats fed a high-sodium diet might involve neurogenic mechanisms regulated by sodium levels in the CSF rather than changes in blood volume.

ABSTRACT

High sodium intake is an important factor associated with hypertension. High-sodium intake with exercise training can modify homeostatic hydro-electrolytic balance, but the effects of this association are mostly unknown. In this study, we sought to investigate the effects of swimming training (ST) on cerebrospinal fluid (CSF) Na⁺ concentration, sympathetic drive, blood pressure (BP) and renal function of rats fed a 0.9% Na⁺ (equivalent to 2% NaCl) diet with free access to water for 22 weeks after weaning. Male Wistar rats were assigned to two cohorts: (1) fed standard diet (SD) and (2) fed high-sodium (HS) diet. Each cohort was further divided into trained and sedentary groups. ST normalised BP levels of HS rats as well as the higher sympathetically related pressor activity assessed by pharmacological blockade of ganglionic transmission (hexamethonium). ST preserved the renal function and attenuated the glomerular shrinkage elicited by HS. No change in blood volume was found among the groups. CSF [Na⁺ ] levels were higher in sedentary HS rats but were reduced by ST. Our findings showed that ST effectively normalised BP of HS rats, independent of its effects on hydro-electrolytic balance, which might involve neurogenic mechanisms regulated by Na⁺ levels in the CSF as well as renal protection.