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Physiological Reviews Oct 2021A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and... (Review)
Review
A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.
Topics: Acclimatization; Animals; Body Temperature Regulation; Exercise; Heat Stress Disorders; Heat-Shock Response; Hot Temperature; Humans; Psychomotor Performance; Sweating; Water; Water Loss, Insensible
PubMed: 33829868
DOI: 10.1152/physrev.00038.2020 -
Endocrine Reviews Sep 2023Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most... (Review)
Review
Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.
Topics: Humans; Hyponatremia; Inappropriate ADH Syndrome; Water-Electrolyte Balance; Neoplasms
PubMed: 36974717
DOI: 10.1210/endrev/bnad010 -
American Journal of Physiology. Renal... Jan 2020The kidney is the central organ involved in maintaining water and sodium balance. In human kidneys, nine aquaporins (AQPs), including AQP1-8 and AQP11, have been found... (Review)
Review
The kidney is the central organ involved in maintaining water and sodium balance. In human kidneys, nine aquaporins (AQPs), including AQP1-8 and AQP11, have been found and are differentially expressed along the renal tubules and collecting ducts with distinct and critical roles in the regulation of body water homeostasis and urine concentration. Dysfunction and dysregulation of these AQPs result in various water balance disorders. This review summarizes current understanding of physiological and pathophysiological roles of AQPs in the kidney, with a focus on recent progress on AQP2 regulation by the nuclear receptor transcriptional factors. This review also provides an overview of AQPs as clinical biomarkers and therapeutic targets for renal diseases.
Topics: Animals; Aquaporins; Homeostasis; Humans; Kidney; Kidney Diseases; Water-Electrolyte Balance
PubMed: 31682170
DOI: 10.1152/ajprenal.00304.2019 -
Psychiatria Polska Oct 2019Refeeding syndrome (RS) is one of the serious complications during treatment of anorexia nervosa. It includes hormonal and metabolic changes that occur during the... (Review)
Review
Refeeding syndrome (RS) is one of the serious complications during treatment of anorexia nervosa. It includes hormonal and metabolic changes that occur during the process of refeeding in chronically malnourished patient when nutrition is introduced in an excessive and improper amount. RS manifests in water-electrolyte imbalances, including hypophosphatemia (the mostimportant diagnosticmarker), hypokalemia, hyponatremia, hypomagnesaemia, fluid retention, vitamin deficiency and metabolic acidosis. It applies to either oral and parenteral supplementation. In the treatment of malnourished patients with anorexia nervosa, it is essential to establish an initial caloric amount that will stimulate weight gain from the beginning of treatment, increase its effectiveness while minimizing the risk of RS. Recent research suggests that the current recommendations may be too stringent in this respect and require further updating. Awareness of the risks associated with RS, including significant mortality, appears to be currently insufficient also among physicians. There is a need for far more specialized multidisciplinary centers for patients with anorexia nervosa and also appropriate algorithms and standards of care for that population. The aim of this paper is to systematize the current knowledge about RS and RS prevention, to increase awareness of its occurrence and present the results of the latest research on safe resupplementation of patients suffering from anorexia nervosa.
Topics: Anorexia Nervosa; Feeding Methods; Humans; Refeeding Syndrome; Water-Electrolyte Balance; Weight Gain
PubMed: 31955189
DOI: 10.12740/PP/OnlineFirst/90275 -
American Journal of Hypertension Feb 2021Aldosterone is a mineralocorticoid hormone that controls body fluid and electrolyte balance. Excess aldosterone is associated with cardiovascular and metabolic diseases.... (Review)
Review
Aldosterone is a mineralocorticoid hormone that controls body fluid and electrolyte balance. Excess aldosterone is associated with cardiovascular and metabolic diseases. Inflammation plays a critical role on vascular damage promoted by aldosterone and aggravates vascular abnormalities, including endothelial dysfunction, vascular remodeling, fibrosis and oxidative stress, and other manifestations of end-organ damage that are associated with hypertension, other forms of cardiovascular disease, and diabetes mellitus and the metabolic syndrome. Over the past few years, many studies have consistently shown that aldosterone activates cells of the innate and adaptive immune systems. Macrophages and T cells accumulate in the kidneys, heart, and vasculature in response to aldosterone, and infiltration of immune cells contributes to end-organ damage in cardiovascular and metabolic diseases. Aldosterone activates various subsets of innate immune cells such as dendritic cells and monocytes/macrophages, as well as adaptive immune cells such as T lymphocytes, and, by activation of mineralocorticoid receptors stimulates proinflammatory transcription factors and the production of adhesion molecules and inflammatory cytokines and chemokines. This review will briefly highlight some of the studies on the involvement of aldosterone in activation of innate and adaptive immune cells and its impact on the cardiovascular system. Since aldosterone plays a key role in many cardiovascular and metabolic diseases, these data will open up promising perspectives for the identification of novel biomarkers and therapeutic targets for prevention and treatment of diseases associated with increased levels of aldosterone, such as arterial hypertension, obesity, the metabolic syndrome, and heart failure.
Topics: Aldosterone; Blood Pressure; Cardiometabolic Risk Factors; Humans; Hypertension; Immunity; Water-Electrolyte Balance
PubMed: 32820797
DOI: 10.1093/ajh/hpaa137 -
Anaesthesiology Intensive Therapy 2021Critically ill patients are often presumed to be in a state of "constant dehydration" or in need of fluid, thereby justifying a continuous infusion with some form of... (Review)
Review
Critically ill patients are often presumed to be in a state of "constant dehydration" or in need of fluid, thereby justifying a continuous infusion with some form of intravenous (IV) fluid, despite their clinical data suggesting otherwise. Overzealous fluid administration and subsequent fluid accumulation and overload are associated with poorer outcomes. Fluids are drugs, and their use should be tailored to meet the patient's individualized needs; fluids should never be given as routine maintenance unless indicated. Before prescribing any fluids, the physician should consider the patient's characteristics and the nature of the illness, and assess the risks and benefits of fluid therapy. Decisions regarding fluid therapy present a daily challenge in many hospital departments: emergency rooms, regular wards, operating rooms, and intensive care units. Traditional fluid prescription is full of paradigms and unnecessary routines as well as malpractice in the form of choosing the wrong solutions for maintenance or not meeting daily requirements. Prescribing maintenance fluids for patients on oral intake will lead to fluid creep and fluid overload. Fluid overload, defined as a 10% increase in cumulative fluid balance from baseline weight, is an independent predictor for morbidity and mortality, and thus hospital cost. In the last decade, increasing evidence has emerged supporting a restrictive fluid approach. In this manuscript, we aim to provide a pragmatic description of novel concepts related to the use of IV fluids in critically ill patients, with emphasis on the different indications and common clinical scenarios. We also discuss active deresuscitation, or the timely cessation of fluid administration, with the intention of achieving a zero cumulative fluid balance.
Topics: Critical Illness; Fluid Therapy; Humans; Intensive Care Units; Pharmaceutical Preparations; Water-Electrolyte Balance
PubMed: 34006046
DOI: 10.5114/ait.2021.105252 -
The Journal of Investigative Dermatology Sep 2020Human skin acts as a barrier to protect our bodies from UV rays and external pathogens and to prevent water loss. Phenotypes of aging, or natural aging due to chronic... (Review)
Review
Human skin acts as a barrier to protect our bodies from UV rays and external pathogens and to prevent water loss. Phenotypes of aging, or natural aging due to chronic damage, include wrinkles and the reduction of skin thickness that occur because of a loss of skin cell function. The dysregulation of autophagy, a lysosome-related degradation pathway, can lead to cell senescence, cancer, and various human diseases due to abnormal cellular homeostasis. Here, we discuss the roles and molecular mechanisms of autophagy involved in the anti-aging effects of autophagy and the relationship between autophagy and aging in skin cells.
Topics: Adult Stem Cells; Autophagy; Cellular Senescence; Fibroblasts; Humans; Keratinocytes; Melanocytes; Skin; Skin Aging; Skin Diseases; Ultraviolet Rays; Water Loss, Insensible
PubMed: 32800183
DOI: 10.1016/j.jid.2019.11.023 -
Sports Medicine (Auckland, N.Z.) Feb 2022Body-fluid loss during prolonged continuous exercise can impair cardiovascular function, harming performance. Delta percent plasma volume (dPV) represents the change in... (Meta-Analysis)
Meta-Analysis
The Hydrating Effects of Hypertonic, Isotonic and Hypotonic Sports Drinks and Waters on Central Hydration During Continuous Exercise: A Systematic Meta-Analysis and Perspective.
BACKGROUND
Body-fluid loss during prolonged continuous exercise can impair cardiovascular function, harming performance. Delta percent plasma volume (dPV) represents the change in central and circulatory body-water volume and therefore hydration during exercise; however, the effect of carbohydrate-electrolyte drinks and water on the dPV response is unclear.
OBJECTIVE
To determine by meta-analysis the effects of ingested hypertonic (> 300 mOsmol kg), isotonic (275-300 mOsmol kg) and hypotonic (< 275 mOsmol kg) drinks containing carbohydrate and electrolyte ([Na] < 50 mmol L), and non-carbohydrate drinks/water (< 40 mOsmol kg) on dPV during continuous exercise.
METHODS
A systematic review produced 28 qualifying studies and 68 drink treatment effects. Random-effects meta-analyses with repeated measures provided estimates of effects and probability of superiority (p) during 0-180 min of exercise, adjusted for drink osmolality, ingestion rate, metabolic rate and a weakly informative Bayesian prior.
RESULTS
Mean drink effects on dPV were: hypertonic - 7.4% [90% compatibility limits (CL) - 8.5, - 6.3], isotonic - 8.7% (90% CL - 10.1, - 7.4), hypotonic - 6.3% (90% CL - 7.4, - 5.3) and water - 7.5% (90% CL - 8.5, - 6.4). Posterior contrast estimates relative to the smallest important effect (dPV = 0.75%) were: hypertonic-isotonic 1.2% (90% CL - 0.1, 2.6; p = 0.74), hypotonic-isotonic 2.3% (90% CL 1.1, 3.5; p = 0.984), water-isotonic 1.3% (90% CL 0.0, 2.5; p = 0.76), hypotonic-hypertonic 1.1% (90% CL 0.1, 2.1; p = 0.71), hypertonic-water 0.1% (90% CL - 0.8, 1.0; p = 0.12) and hypotonic-water 1.1% (90% CL 0.1, 2.0; p = 0.72). Thus, hypotonic drinks were very likely superior to isotonic and likely superior to hypertonic and water. Metabolic rate, ingestion rate, carbohydrate characteristics and electrolyte concentration were generally substantial modifiers of dPV.
CONCLUSION
Hypotonic carbohydrate-electrolyte drinks ingested continuously during exercise provide the greatest benefit to hydration.
Topics: Bayes Theorem; Dehydration; Exercise; Humans; Osmolar Concentration; Sodium; Water-Electrolyte Balance
PubMed: 34716905
DOI: 10.1007/s40279-021-01558-y -
Skin Pharmacology and Physiology 2023The anatomic layers of the skin are well-defined, and a functional model of the skin barrier has recently been described. Barrier disruption plays a key role in several... (Review)
Review
BACKGROUND
The anatomic layers of the skin are well-defined, and a functional model of the skin barrier has recently been described. Barrier disruption plays a key role in several skin conditions, and moisturization is recommended as an initial treatment in conditions such as atopic dermatitis. This review aimed to analyze the skin barrier in the context of the function model, with a focus on the mechanisms by which moisturizers support each of the functional layers of the skin barrier to promote homeostasis and repair.
SUMMARY
The skin barrier is comprised of four interdependent layers - physical, chemical, microbiologic, and immunologic - which maintain barrier structure and function. Moisturizers target disruption affecting each of these four layers through several mechanisms and were shown to improve transepidermal water loss in several studies. Occlusives, humectants, and emollients occlude the surface of the stratum corneum (SC), draw water from the dermis into the epidermis, and assimilate into the SC, respectively, in order to strengthen the physical skin barrier. Acidic moisturizers bolster the chemical skin barrier by supporting optimal enzymatic function, increasing ceramide production, and facilitating ideal conditions for commensal microorganisms. Regular moisturization may strengthen the immunologic skin barrier by reducing permeability and subsequent allergen penetration and sensitization.
KEY MESSAGES
The physical, chemical, microbiologic, and immunologic layers of the skin barrier are each uniquely impacted in states of skin barrier disruption. Moisturizers target each of the layers of the skin barrier to maintain homeostasis and facilitate repair.
Topics: Humans; Skin; Dermatitis, Atopic; Epidermis; Emollients; Water; Water Loss, Insensible
PubMed: 37717558
DOI: 10.1159/000534136 -
International Journal of Sport... Sep 2021Beer is used to socialize postexercise, celebrate sport victory, and commiserate postdefeat. Rich in polyphenols, beer has antioxidant effects when consumed in...
Beer is used to socialize postexercise, celebrate sport victory, and commiserate postdefeat. Rich in polyphenols, beer has antioxidant effects when consumed in moderation, but its alcohol content may confer some negative effects. Despite beer's popularity, no review has explored its effects on exercise performance, recovery, and adaptation. Thus, a systematic literature search of three databases (PubMed, SPORTDiscus, and Web of Science) was conducted by two reviewers. The search resulted in 16 studies that were appraised and reviewed. The mean PEDro score was 5.1. When individuals are looking to rehydrate postexercise, a low-alcohol beer (<4%) may be more effective. If choosing a beer higher in alcoholic content (>4%), it is advised to pair this with a nonalcoholic option to limit diuresis, particularly when relatively large volumes of fluid (>700 ml) are consumed. Adding Na+ to alcoholic beer may improve rehydration by decreasing fluid losses, but palatability may decrease. These conclusions are largely based on studies that standardized beverage volume, and the results may not apply equally to situations where people ingest fluids and food ad libitum. Ingesting nonalcoholic, polyphenol-rich beer could be an effective strategy for preventing respiratory infections during heavy training. If consumed in moderation, body composition and strength qualities seem largely unaffected by beer. Mixed results that limit sweeping conclusions are owed to variations in study design (i.e., hydration and exercise protocols). Future research should incorporate exercise protocols with higher ecological validity, recruit more women, prioritize chronic study designs, and use ad libitum fluid replacement protocols for more robust conclusions.
Topics: Alcohol Drinking; Beer; Dehydration; Exercise; Female; Fluid Therapy; Humans; Water-Electrolyte Balance
PubMed: 34284350
DOI: 10.1123/ijsnem.2021-0064