Influence of aldosterone on sodium, water and potassium metabolism in chronic renal disease

Dynamic pathology and pathogen distribution of the yeast Metschnikowia bicuspidata in the Chinese mitten crab (Eriocheir sinensis)

In this study, the "milky disease" model of Eriocheir sinhensis was constructed via intramuscular injection with the pathogenic yeast Metschnikowia bicuspidata. The dynamic pathological changes of E. sinensis after injection were elucidated with two staining methods (haemotoxylin-eosin and alcian blue periodic acid-Schiff) and fluorescence in situ hybridization technology. Anatomical observation revealed three stages of the "milky disease": no clinical signs (1-4 days after infection), the appearance of signs of disease (5-7 days), and significant liquefaction (10 days). Histological observation also revealed three stages of the disease: yeast diffusion (1-2 days after infection), yeast slow development (3-4 days), and yeast rapid proliferation (5 days). And FISH technique was suitable for the early detection of infection with M. bicuspidata in E. sinensis. We found that M. bicuspidata spread to the whole body of the crab through the haemolymph and developed into fungal septicaemia. These results elucidate the systemic pathological characteristics of "milky disease" in E. sinensis and suggest the pathogenic mechanism of M. bicuspidata.

Metabolomic and metagenomic analyses of the Chinese mitten crab Eriocheir sinensis after challenge with Metschnikowia bicuspidata

Milky disease caused by Metschnikowia bicuspidata fungus has significantly harmed the Chinese mitten crab Eriocheir sinensis aquaculture industry. However, the effect of M. bicuspidata infection on the metabolism and intestinal flora of the crab remains unclear. In this study, we aimed to explore the changes in the metabolism and intestinal flora E. sinensis after 48 h of infection with M. bicuspidata, using metabolomic and metagenomic analyses. Metabolomic analysis results revealed 420 significantly different metabolites between the infected and control groups, and these metabolites were enriched in 58 metabolic pathways. M. bicuspidata infection decreased the levels of metabolites related to amino acid biosynthesis, the tricarboxylic acid cycle, as well as lysine, histidine, linolenic, arachidonic, and linoleic acid metabolism. These results indicated that M. bicuspidata infection significantly affected the energy metabolism, growth, and immunity of E. sinensis. The results of metagenomic analysis showed that the anaerobes and ascomycetes populations significantly increased and decreased, respectively, after M. bicuspidata infection. These changes in intestinal flora significantly upregulated metabolic and synthetic pathways while downregulating immunity-related pathways. The results of integrated metabolomic and metagenomic analyses showed that 55 differentially expressed genes and 28 operational taxonomic units were correlated with 420 differential metabolites. Thus, the intestinal flora changes caused by M. bicuspidata infection also affected the metabolites. This study provides novel insights into the metabolic-and intestinal microflora-based effects of M. bicuspidata infection in E. sinensis, as well as a theoretical basis for the interaction between fungi and crustaceans.

Racial and Ethnic Differences in Mortality Associated with Serum Potassium in Incident Peritoneal Dialysis Patients

BACKGROUND

Abnormalities in serum potassium are risk factors for sudden cardiac death and arrhythmias among dialysis patients. Although a previous study in hemodialysis patients has shown that race/ethnicity may impact the relationship between serum potassium and mortality, the relationship remains unclear among peritoneal dialysis (PD) patients where the dynamics of serum potassium is more stable.

METHODS

Among 17,664 patients who started PD between January 1, 2007 and December 31, 2011 in a large US dialysis organization, we evaluated the association of serum potassium levels with all-cause and arrhythmia-related deaths across race/ethnicity using time-dependent Cox models with adjustments for demographics. We also used restricted cubic spline functions for serum potassium levels to explore non-linear associations.

RESULTS

Baseline serum potassium levels were the highest among Hispanics (4.2 ± 0.7 mEq/L) and lowest among non-Hispanic blacks (4.0 ± 0.7 mEq/L). Among 2,949 deaths during the follow-up of median 2.2 (interquartile ranges 1.3-3.2) years, 683 (23%) were arrhythmia-related deaths. Overall, both hyperkalemia and hypokalemia (i.e., serum potassium levels >5.0 and <3.5 mEq/L, respectively) were associated with higher all-cause and arrhythmia-related mortality. In a stratified analysis according to race/ethnicity, the association of hypokalemia with all-cause and arrhythmia-related mortality was consistent with an attenuation for arrhythmia-related mortality in non-Hispanic blacks. Hyperkalemia was associated with all-cause and arrhythmia-related mortality in non-Hispanic whites and non-Hispanic blacks, but no association was observed in Hispanics.

CONCLUSION

Among incident PD patients, hypokalemia was consistently associated with all-cause and arrhythmia-related deaths irrespective of race/ethnicity. However, while hyperkalemia was associated with both death outcomes in non-Hispanic blacks and whites, it was not associated with either death outcome in Hispanic patients. Further studies are needed to demonstrate whether different strategies should be followed for the management of serum potassium levels according to race/ethnicity.

Analysis of baseline parameters in the HALT polycystic kidney disease trials

HALT PKD consists of two ongoing randomized trials with the largest cohort of systematically studied patients with autosomal dominant polycystic kidney disease to date. Study A will compare combined treatment with an angiotensin-converting inhibitor and receptor blocker to inhibitor alone and standard compared with low blood pressure targets in 558 early-stage disease patients with an eGFR over 60 ml/min per 1.73 m(2). Study B will compare inhibitor-blocker treatment to the inhibitor alone in 486 late-stage patients with eGFR 25-60 ml/min per 1.73 m(2). We used correlation and multiple regression cross-sectional analyses to determine associations of baseline parameters with total kidney, liver, or liver cyst volumes measured by MRI in Study A and eGFR in both studies. Lower eGFR and higher natural log-transformed urine albumin excretion were independently associated with a larger natural log-transformed total kidney volume adjusted for height (ln(HtTKV)). Higher body surface area was independently associated with a higher ln(HtTKV) and lower eGFR. Men had larger height-adjusted total kidney volume and smaller liver cyst volumes than women. A weak correlation was found between the ln(HtTKV) and natural log-transformed total liver volume adjusted for height or natural log liver cyst volume in women only. Women had higher urine aldosterone excretion and lower plasma potassium. Thus, our analysis (1) confirms a strong association between renal volume and functional parameters, (2) shows that gender and other factors differentially affect the development of polycystic disease in the kidney and liver, and (3) suggests an association between anthropomorphic measures reflecting prenatal and/or postnatal growth and disease severity.

Diagnostic value of urinary sodium, chloride, urea, and flow

Up to 30% of hospitalized critically ill patients may have a rise in serum creatinine concentration. In addition to history and physical examination, there is diagnostic value in assessing urinary electrolytes, solute excretion, and urine flow in these patients. The correct interpretation of these urinary parameters can avoid unnecessary volume overload and mechanical ventilation, risk factors for increased mortality in patients with rising serum creatinine. The present article also discusses the role of arterial underfilling in causing prerenal azotemia in the presence of an increase in total body sodium and extracellular fluid expansion. As with extracellular fluid volume depletion, arterial underfilling secondary to impaired cardiac function or primary arterial vasodilation can delay or prevent recovery from ischemic or toxic acute tubular necrosis. The present brief review discusses the various aspects of the correct interpretation of urinary electrolytes, solute excretion, and urine flow in the setting of a rising serum creatinine concentration.

Dietary potassium intake and mortality in long-term hemodialysis patients

BACKGROUND

Hyperkalemia has been associated with higher mortality in long-term hemodialysis (HD) patients. There are few data concerning the relationship between dietary potassium intake and outcome.

STUDY DESIGN

The mortality predictability of dietary potassium intake from reported food items estimated using the Block Food Frequency Questionnaire (FFQ) at the start of the cohort was examined in a 5-year (2001-2006) cohort of 224 HD patients in Southern California using Cox proportional hazards regression.

SETTING & PARTICIPANTS

224 long-term HD patients from 8 DaVita dialysis clinics.

PREDICTORS

Dietary potassium intake ranking using the Block FFQ.

OUTCOMES

5-year survival.

RESULTS

HD patients with higher potassium intake had greater dietary energy, protein, and phosphorus intakes and higher predialysis serum potassium and phosphorus levels. Greater dietary potassium intake was associated with significantly increased death HRs in unadjusted models and after incremental adjustments for case-mix, nutritional factors (including 3-month averaged predialysis serum creatinine, potassium, and phosphorus levels; body mass index; normalized protein nitrogen appearance; and energy, protein, and phosphorus intake) and inflammatory marker levels. HRs for death across the 3 higher quartiles of dietary potassium intake in the fully adjusted model (compared with the lowest quartile) were 1.4 (95% CI, 0.6-3.0), 2.2 (95% CI, 0.9-5.4), and 2.4 (95% CI, 1.1-7.5), respectively (P for trend = 0.03). Restricted cubic spline analyses confirmed the incremental mortality predictability of higher potassium intake.

LIMITATIONS

FFQs may underestimate individual potassium intake and should be used to rank dietary intake across the population.

CONCLUSIONS

Higher dietary potassium intake is associated with increased death risk in long-term HD patients, even after adjustments for serum potassium level; dietary protein; energy, and phosphorus intake; and nutritional and inflammatory marker levels. The potential role of dietary potassium in the high mortality rate of HD patients warrants clinical trials.

Serum and Dialysate Potassium Concentrations and Survival in Hemodialysis Patients

BACKGROUND AND OBJECTIVES

Controlling serum potassium is an important goal in maintenance hemodialysis patients. We examined the achievement of potassium balance through hemodialysis treatments and the associated fluctuations in serum potassium.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A 3-yr (July 2001 to June 2004) cohort of 81,013 maintenance hemodialysis patients from all DaVita dialysis clinics across the United States were studied. Nine quarterly-averaged serum potassium groups (< 4.0, > or = 6.3 mEq/L and seven increments in-between) and four dialysate potassium concentration groups were created in each of the 12 calendar quarters. The death risk associated with predialysis potassium level and dialysate potassium concentration was examined using unadjusted, case-mix adjusted, and malnutrition-inflammation-adjusted time-dependent survival models.

RESULTS

Serum potassium correlated with nutritional markers. Serum potassium between 4.6 and 5.3 mEq/L was associated with the greatest survival, whereas potassium < 4.0 or > or = 5.6 mEq/L was associated with increased mortality. The death risk of serum potassium > or = 5.6 mEq/L remained consistent after adjustments. Higher dialysate potassium concentration was associated with increased mortality in hyperkalemic patients with predialysis serum potassium > or = 5.0 mEq/L.

CONCLUSIONS

A predialysis serum potassium of 4.6 to 5.3 mEq/L is associated with the greatest survival in maintenance hemodialysis patients. Hyperkalemic patients who undergo maintenance hemodialysis against lower dialysate bath may have better survival. Limitations of observational studies including confounding by indication should be considered when interpreting these results.

Reduced 11beta-hydroxysteroid dehydrogenase activity in the remaining kidney following nephrectomy

Intracellular access of steroids to gluco- and mineralocorticoid receptors is regulated by reduced 11beta-hydroxysteroid dehydrogenase (OHSD) 1 and 2. These enzymes convert active 11beta-OH-steroids into inactive 11-keto-steroids. The purpose of the present study was to establish whether the 11beta-OHSD1 and 11beta-OHSD2 are modulated in the remnant kidney 24 h or 14 days after uninephrectomy (UNX) in rats. Overall, 11beta-OHSD activity was analyzed by measuring the ratio of the exogenous 11beta-OH-steroid prednisolone to its 11-keto metabolite prednisone in vivo in kidney tissue using high performance liquid chromatography. To determine which isoenzyme accounts for the changed activity 24 h after UNX, the oxidation and reduction attributable to 11beta-OHSD1 and oxidation to 11beta-OHSD2 were analyzed in total renal extracts and in isolated glomeruli, proximal convoluted tubules (PCT), cortical ascending limbs, and cortical convoluted tubules (CCT). The messenger RNA content of 11beta-OHSD1 and 11beta-OHSD2 was measured by RT-PCR in renal tissues and single segments, using glyceraldehyde-3-phosphate-dehydrogenase as an internal standard. Protein amounts of 11beta-OHSD1 and 11beta-OHSD2 were assessed by Western blot. The prednisolone/prednisone ratio increased 24 h after UNX in 9 out of 10 animals (P < or = 0.0011), and was unchanged 14 days after UNX. 11Beta-OHSD1 oxidation (P < or = 0.032) and reduction activity (P < or = 0.002) declined 24 h after UNX in total extracts. 11Beta-OHSD1 oxidase activity was more than 3 times higher in PCT than in glomeruli, cortical ascending limbs, and CCT, and declined by 50% after UNX (P < or = 0.001). The reductase activity did not change following UNX in PCT. 11Beta-OHSD2 activity was 5-15 times higher in CCT than in the other segments, and decreased significantly after UNX (P < or = 0.008). UNX did not affect messenger RNA and protein levels of both enzymes in total renal extracts. In conclusion, 11beta-OHSD1 and 11beta-OHSD2 are predominantly expressed in PCT and CCT, respectively, and their corresponding oxidative activities decline after UNX. Thus, the access of 11beta-glucocorticosteroids to gluco- and mineralocorticoid receptors in the remaining kidney is facilitated after UNX.

Pathophysiology of potassium absorption and secretion by the human intestine

When normal people ingest 90 mEq/day of K+ in their diet, they absorb about 90% of intake (81 mEq) and excrete an equivalent amount of K+ in the urine. Normal fecal K+ excretion averages about 9 mEq/day. The vast majority of intestinal K+ absorption occurs in the small intestine; the contribution of the normal colon to net K+ absorption and secretion is trivial. K+ is absorbed or secreted mainly by passive mechanisms; the rectum and perhaps the sigmoid colon have the capacity to actively secrete K+, but the quantitative and physiological significance of this active secretion is uncertain. Hyperaldosteronism increases fecal K+ excretion by about 3 mEq/day in people with otherwise normal intestinal tracts. Cation exchange resin by mouth can increase fecal K+ excretion to 40 mEq/day. The absorptive mechanisms of K+ are not disturbed by diarrhea per se, but fecal K+ losses are increased in diarrheal diseases by unabsorbed anions (which obligate K+), by electrochemical gradients secondary to active chloride secretion, and probably by secondary hyperaldosteronism. In diarrhea, total body K+ can be reduced by two mechanisms: loss of muscle mass because of malnutrition and reduced net absorption of K+; only the latter causes hypokalemia. Balance studies in patients with diarrhea are exceedingly rare, but available data emphasize an important role for dietary K+ intake, renal K+ excretion, and fecal K+ losses in determining whether or not a patient develops hypokalemia. The paradoxical negative K+ balance induced by ureterosigmoid anastomosis is described. The concept that fecal K+ excretion is markedly elevated in patients with uremia as an intestinal adaptation to prevent hyperkalemia is analyzed; we conclude that the data do not convincingly show the existence of a major intestinal adaptive response to chronic renal failure.

Normal renin-aldosterone-insulin and potassium interrelationship in FMF patients and amyloid nephropathy

The renin-aldosterone system and plasma insulin were studied in 19 patients with familial Mediterranean fever (FMF). Their relationships to serum potassium level at rest and before and after oral glucose loading are described. An interesting finding is the occurrence of hyperkalemia in the absence of oliguria, in the advanced stages of renal failure. No differences were found in the activity of the renin-angiotensin-aldosterone system to explain these variations in serum potassium found in some of the patients. The response of the renin-aldosterone system to glucose loading showed no abnormality, and the regular relationship between serum potassium, plasma renin activity (PRA), aldosterone, insulin, and plasma pH is maintained. Levels of insulin, potassium, and bicarbonate in serum or plasma pH were found similar in FMF patients with normal renal function with and without proteinuria. Further decrease in renal function due to the progression of the underlying disease is manifested by an increase in FENa+ and FEK+ and a hyperchloremic metabolic acidosis, as is the case in other patients with chronic renal failure.

Potassium tolerance

The maintenance of potassium homeostasis with an increased potassium intake or decreased renal function is dependent in part on the renal adaptation observed in 'potassium tolerance'. However other factors, including control of ingestion, and increased distal delivery of fluid, also play a role.

Contribution of the distal tubule to potassium excretion in experimental glomerulonephritis

The renal adaptations that maintain potassium homeostasis in diffuse forms of glomerular disease are not well defined. Thus, handling of potassium by superficial nephron segments was examined in a rat model of antiglomerular basement membrane nephritis. Sampling the same nephron successively from the end and beginning of the distal tubule and the end of the proximal tubule allowed a segmental analysis. Despite a 40% reduction in GFR, potassium excretion in the glomerulonephritis animals was normal due to an increase in FEK. The proximal tubule and loop segment did not contribute to the enhanced FEK seen in these animals. In contrast, potassium entry along the distal tubule was significantly greater in the experimental group averaging 13.7 +/- 4.3 pmol/min compared to 1.2 +/- 1.7 pmol/min in controls (P less than 0.01). Multiple linear regression analysis showed that distal tubule potassium entry at any level of flow was enhanced in glomerulonephritis compared to controls (P less than 0.0001). Plasma aldosterone levels were similar in both groups of animals. Thus, the adaptation to potassium excretion seen in glomerulonephritis is partly achieved by the distal tubule through flow-rate independent mechanisms and appears to be independent of plasma aldosterone levels.

Mechanism of intestinal adaptation in rats with acute renal failure

Acute renal failure (ARF) was experimentally induced in rats and the specific activity of mucosal Na-K-ATPase activity in segments of the small intestine and colon was measured. Bilateral nephrectomy (BN) resulted in a significant evaluation of the enzyme activity in all segments examined. With an additional procedure of adrenalectomy (BN + Ax), the enzyme activity failed to show any increase in ARF rats produced by BN. However, a supplementation of a maintenance dose of dexamethasone to adrenalectomized ARF rats (BN + Ax + DM 10) resulted in a significant resumption of the activity in all intestinal segments, although its increase was insignificant in the duodenum. Addition of a high dose of DOCA (BN + Ax + DOCA 500) was effective in increasing the enzyme activity only in the colon but not in the small intestine. With a high dose of DM or a maintenance dose of DM plus a high dose of DOCA (BN + Ax + DM 30 or BN + Ax + DM 10 + DOCA 500), there was an increase in the enzyme activity of all intestinal segments. In ARF rats induced by bilateral lower ureteral ligation (BLUL), the enzyme activity did not show any increase at all. Addition of a high dose of DOCA to this animal model (BLUL + DOCA 500) brought about the increase of the enzyme activity in the intestinal segments but for the jejunum.(ABSTRACT TRUNCATED AT 250 WORDS)

Interpreting the fractional excretion of sodium

In most normal subjects, the fractional excretion of sodium is usually less than 1 percent but may be raised with an increase in salt intake. In acutely azotemic patients, a low fractional excretion of sodium usually indicates a prerenal process that is responsive to volume repletion. However, such a low fractional excretion of sodium also can be seen with azotemia due to hepatic or cardiac failure, as well as acute glomerulonephritis, pigment nephropathy, contrast nephrotoxicity, polyuric renal failure associated with burns, acute obstruction, renal transplant rejection, and occasionally non-oliguric acute renal failure, none of which is a volume-responsive process. A fractional excretion greater than 1 percent in acutely azotemic patients usually indicates intrinsic renal injury, but is consistent with volume depletion in patients receiving diuretics or in some patients with chronic renal insufficiency. Similarly, a low quotient in acute renal parenchymal injury is usually interpreted to indicate widespread tubular integrity, but is consistent with several different pathophysiologic processes. The fractional excretion of sodium must be interpreted in light of the specific clinical setting and other laboratory data to be useful in patient management.

Disorders of body fluids, sodium and potassium in chronic renal failure

A stable volume and composition of extracellular fluid are essential for normal functioning of the body. Since the kidney is primarily responsible for regulating extracellular fluid, loss of kidney function should have catastrophic consequences. Fortunately, even with loss of more than 90 percent of renal function, a remarkable capacity to regulate body fluid volumes and sodium and potassium persists. Nevertheless, this capacity is limited to chronic renal disease and this has important consequences for clinical management of these patients. How can sodium and potassium homeostasis be assessed? Methods for evaluating the steady-state regulation of sodium include measurement of body fluids and their distribution in different compartments and measurement of exchangeable and intracellular sodium. Short-term regulation of body sodium can be assessed from measurement of sodium balance during changes in dietary salt. Potassium is predominantly contained within cells and thus the assessment of its regulation requires special emphasis on measurement of steady-state body stores and potassium distribution across cell membranes. However, the methods used to make all of these measurements require assumptions that may not hold in the altered state of uremia. This raises problems in interpretation requiring critical analysis before conclusions can be made regarding sodium and potassium homeostasis in patients with chronic renal failure. This review focuses on abnormalities of body fluids, sodium and potassium in patients with creatinine clearances of less than 20 ml/min due to chronic renal failure and the impact of conservative therapy, dialysis and renal transplantation on these patients.

Potassium homeostasis

Potassium balance is regulated by appropriate changes in potassium excretion in the distal portion of the nephron. By contrast, potassium intake, absorption and proximal renal reabsorption do not show regulatory variation. Extracellular potassium concentration, which is a critical factor in membrane polarization, may at times vary in a direction opposite to total body content, because of altered distribution across cell membranes. Alterations in acid-base status frequently disturb homeostasis by altering potassium movement into cells, while insulin has an important regulatory effect on distribution. In general, the multiple renal and extra-renal mechanisms which prevent potassium overload are highly developed, while conservation is relatively ineffective. Consequently, depletion occurs more easily than spontaneous potassium overload. Homeostasis can be disturbed by renal impairment, excessive tissue breakdown, disturbances of acid-base balance, abnormal routes of loss, mineralocorticoid abnormalities and aberrations of sodium balance.

Reversibility of the "salt-losing" tendency of chronic renal failure

We examined the salt-losing tendency of chronic renal failure in five patients with glomerular filtration rates varying from 5.2 to 16.0 ml per minute. When the studies began, patients were in sodium balance on metabolic diets containing 58 to 342 meq of sodium daily. The sodium content of the diet was then reduced in stages at intervals of at least one week over four to 14 weeks with careful clinical and laboratory monitoring. In four of the patients a salt-losing tendency developed, temporarily requiring intravenous salt replacement in two. At the completion of the studies all the patients remained in sodium balance while ingesting a mean (+/- S.D.) of 5.0 +/- 2.9 meq of sodium per day. There was no change in renal function. Thus, the salt-losing tendency of chronic renal failure is reversible and appears to be a manifestation of the long-term adaptation for sodium excretion.

Pathologic hypofunction of the renin-angiotensin-aldosterone system

The literature now contains reports of many cases of aldosterone deficiency. Usually, the presenting features are persistent hyperkalemia and tendencies to serious urinary sodium loss and hypotension. A classification of defects leading to pathologic hypofunction of the renin-angiotensin-aldosterone system (RAAS hypofunction) is presented, with emphasis on idiopathic hyporeninemia (probably the most common). Criteria for diagnosis are (1) normal adrenal glucocorticoid function, (2) low aldosterone excretion under basal and stimulated conditions, and (3) renal tubular responsiveness to exogenous mineralocorticoid. The condition is effectively managed with mineralocorticoid replacement therapy and should be considered in the presence of unexplained persistent hyperkalemia, hyponatremia, or postural hypotension.

Relationships of the renin-angiotensin-aldosterone system and sodium balance to blood pressure regulation in chronic renal failure of polycystic kidney disease

In 5 patients with polycystic kidney disease and creatinine clearances ranging from 4 to 40 ml/min, relationships between changes in blood pressure, sodium balance, body fluid compartments, plasma renin activity (PRA), urinary aldosterone excretion, and plasma aldosterone concentrations were studied during periods of low, medium, and high sodium intake. Total body water (TBW), total exchangeable body sodium (TEBS), and extracellular volume (ECV) were measured by isotope dilution techniques, plasma volume with Evan's blue dye, and PRA and aldosterone by radioimmunoassay. Low sodium intake reduced kidney function, blood pressure, and serum sodium, while PRA reached its highest levels. Subsequent increases in sodium intake improved kidney function and increased blood pressure. Plasma volume increased slightly and ECV markedly, while PRA dropped to 15 percent of the value noted after the low sodium intake. TBW and TEBS showed inconsistent changes. Aldosterone changes correlated closely with PRA. Blood pressure showed a negative correlation with PRA, but a positive one with body weight and cumulative sodium balance, and with plasma and extracellular volumes.it is suggested that whereas renin and aldosterone are involved in the maintenance of circulatory homeostasis during sodium loss, sodium retention causes an increase in blood pressure by concomitant changes in body fluids.