Growing evidence suggests a distinction between water intake necessary for maintaining a euhydrated state, and water intake considered to be adequate from a perspective of long-term health. Previously, we have proposed that maintaining a 24-h urine osmolality (UOsm) of ⩽500 mOsm/kg is a desirable target for urine concentration to ensure sufficient urinary output to reduce renal health risk and circulating vasopressin. In clinical practice and field monitoring, the measurement of UOsm is not practical. In this analysis, we calculate criterion values for urine-specific gravity (USG) and urine color (UCol), two measures which have broad applicability in clinical and field settings. A receiver operating characteristic curve analysis performed on 817 urine samples demonstrates that a USG ⩾1.013 detects UOsm>500 mOsm/kg with very high accuracy (AUC 0.984), whereas a subject-assessed UCol⩾4 offers high sensitivity and moderate specificity (AUC 0.831) for detecting UOsm >500 m Osm/kg.
Probiotic microorganisms have historically been used to rebalance disturbed intestinal microbiota and to diminish gastrointestinal disorders, such as diarrhea or inflammatory bowel diseases (e.g., Crohn's disease and ulcerative colitis). Recent studies explore the potential for expanded uses of probiotics on medical disorders that increase the risk of developing cardiovascular diseases and diabetes, such as obesity, hypercholesterolemia, arterial hypertension, and metabolic disturbances such as hyperhomocysteinemia and oxidative stress. This review aims at summarizing the proposed molecular and cellular mechanisms involved in probiotic-host interactions and to identify the nature of the resulting beneficial effects. Specific probiotic strains can act by modulating immune response, by producing particular molecules or releasing biopeptides, and by modulating nervous system activity. To date, the majority of studies have been conducted in animal models. New investigations on the related mechanisms in humans need to be carried out to better enable targeted and effective use of the broad variety of probiotic strains.
PurposeInter-individual variation in median plasma copeptin is associated with incident type 2 diabetes mellitus, progression of chronic kidney disease, and cardiovascular events. In this study, we examined whether 24-h urine osmolality was associated with plasma copeptin and whether increasing daily water intake could impact circulating plasma copeptin.MethodsThis trial was a prospective study conducted at a single investigating center. Eighty-two healthy adults (age 23.6 ± 2.9 years, BMI 22.2 ± 1.5 kg/m2, 50% female) were stratified based upon habitual daily fluid intake volumes: arm A (50–80% of EFSA dietary reference values), arm B (81–120%), and arm C (121–200%). Following a baseline visit, arms A and B increased their water intake to match arm C for a period of 6 consecutive weeks.ResultsAt baseline, plasma copeptin was positively and significantly associated with 24-h urine osmolality (p = 0.002) and 24-h urine specific gravity (p = 0.003) but not with plasma osmolality (p = 0.18), 24-h urine creatinine (p = 0.09), and total fluid intake (p = 0.52). Over the 6-week follow-up, copeptin decreased significantly from 5.18 (3.3;7.4) to 3.90 (2.7;5.7) pmol/L (p = 0.012), while urine osmolality and urine specific gravity decreased from 591 ± 206 to 364 ± 117 mOsm/kg (p < 0.001) and from 1.016 ± 0.005 to 1.010 ± 0.004 (p < 0.001), respectively.ConclusionsAt baseline, circulating levels of copeptin were positively associated with 24-h urine concentration in healthy young subjects with various fluid intakes. Moreover, this study shows, for the first time, that increased water intake over 6 weeks results in an attenuation of circulating copeptin.Clinical Trial Registration Number NCT02044679.
Background/Objectives:Urinary biomarkers of hydration (urine osmolality, UOsm; urine specific gravity, USG) follow circadian variations. For individuals, researchers and health-care professionals, there is value in identifying time frames during which spot values of UOsm and USG are representative of 24-h values in healthy young adults.Subjects/Methods:Eighty-two free-living adults (22.3±2.9 years, 22.2±1.5 kg/m2) collected individual urine voids over a 24-h period. UOsm and USG were measured on each void and on the pooled 24-h sample. To determine the time of day when a spot sample was likely to be equivalent to the 24-h value, daytime voids were binned by time and equivalence was tested for each 2-h window. Equivalence was a priori defined as being within 100 mOsm/kg (UOsm) and within 0.003 units (USG) of 24-h values.Results:For both UOsm and USG, voids between 1400 and 2000 hours produced values that were equivalent to the 24-h sample, whereas earlier voids tended to overestimate 24-h UOsm and USG. For windows 1401–1600 hours, 1601–1800 hours and 1801–2000 hours, the mean difference (95% confidence interval) between spot and 24-h UOsm (mOsm/kg) was −25 (−72; 22), 28 (−35; 92) and 12 (−41; 66), respectively, whereas for USG the difference was 0.0014 (−0.0028; −0.0001), 0.0001 (−0.0017; 0.0019) and 0.0005 (−0.0018; 0.0009), respectively.Conclusions:In free-living healthy French adults, 24-h urine concentration can be approximated from a mid- to late-afternoon spot urine sample. This finding suggests that an afternoon sample may be an accurate and practical tool for hydration monitoring, useful to individuals and health-care practitioners.
Objective Because elevated copeptin, a marker of vasopressin, is linked to low water intake and high diabetes risk, we tested the effect of water supplementation on copeptin and fasting glucose. Design, Setting, and Participants Thirty-one healthy adults with high copeptin (>10.7 pmol · L −1 in men and >6.1 pmol·L −1 in women) identified in a population-based survey from 2013 to 2015 and with a current 24-hour urine osmolality of >600 mOsm · kg −1 were included. Intervention Addition of 1.5 L water daily on top of habitual fluid intake for 6 weeks. Main outcome measure Pre- and postintervention fasting plasma copeptin concentrations. Results Reported mean water intake increased from 0.43 to 1.35 L · d −1 ( P < 0.001), with no other observed changes in diet. Median (interquartile range) urine osmolality was reduced from 879 (705, 996) to 384 (319, 502) mOsm · kg −1 ( P < 0.001); urine volume increased from 1.06 (0.90, 1.20) to 2.27 (1.52, 2.67) L · d −1 ( P < 0.001); and baseline copeptin decreased from 12.9 (7.4, 21.9) pmol · L −1 to 7.8 (4.6;11.3) pmol · L −1 ( P < 0.001). Water supplementation reduced fasting plasma glucose from a mean (SD) of 5.94 (0.44) to 5.74 (0.51) ( P = 0.04). The water-associated reduction of both fasting copeptin and glucose concentration in plasma was most pronounced in participants in the top tertile of baseline copeptin. Conclusions Water supplementation in persons with habitually low water consumption and high copeptin levels is effective in lowering copeptin. It appears a safe and promising intervention with the potential of lowering fasting plasma glucose and thus reducing diabetes risk. Further investigations are warranted to support these findings.
The plasma membrane (PM) is a key structure for the survival of cells during dehydration. In this study, we focused on the concomitant changes in survival and in the lateral organization of the PM in yeast strains during desiccation, a natural or technological environmental perturbation that involves transition from a liquid to a solid medium. To evaluate the role of the PM in survival during air-drying, a wild-type yeast strain and an osmotically fragile mutant (erg6Δ) were used. The lateral organization of the PM (microdomain distribution) was observed using a fluorescent marker related to a specific green fluorescent protein-labeled membrane protein (Sur7-GFP) after progressive or rapid desiccation. We also evaluated yeast behavior during a model dehydration experiment performed in liquid medium (osmotic stress). For both strains, we observed similar behavior after osmotic and desiccation stresses. In particular, the same lethal magnitude of dehydration and the same lethal kinetic effect were found for both dehydration methods. Thus, yeast survival after progressive air-drying was related to PM reorganization, suggesting the positive contribution of passive lateral rearrangements of the membrane components. This study also showed that the use of glycerol solutions is an efficient means to simulate air-drying desiccation.
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