Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate

The development of formulas estimating glomerular filtration rate (eGFR) from serum creatinine and cystatin C and accounting for certain variables affecting the production rate of these biomarkers, including ethnicity, gender and age, has led to the current scheme of diagnosing and staging chronic kidney disease (CKD), which is based on eGFR values and albuminuria. This scheme has been applied extensively in various populations and has led to the current estimates of prevalence of CKD. In addition, this scheme is applied in clinical studies evaluating the risks of CKD and the efficacy of various interventions directed towards improving its course. Disagreements between creatinine-based and cystatin-based eGFR values and between eGFR values and measured GFR have been reported in various cohorts. These disagreements are the consequence of variations in the rate of production and in factors, other than GFR, affecting the rate of removal of creatinine and cystatin C. The disagreements create limitations for all eGFR formulas developed so far. The main limitations are low sensitivity in detecting early CKD in several subjects, e.g., those with hyperfiltration, and poor prediction of the course of CKD. Research efforts in CKD are currently directed towards identification of biomarkers that are better indices of GFR than the current biomarkers and, particularly, biomarkers of early renal tissue injury.

Hospital admissions in elderly patients on chronic hemodialysis

BACKGROUND

The purpose of this study was to determine whether number of hospital admissions per patient per year (n/[pt-yr]) and hospital days per patient per year (d/[pt-yr]) differ between elderly and younger patients on chronic hemodialysis (HD).

PATIENTS AND METHODS

In a retrospective cohort analysis of incident HD patients in one dialysis unit over 15 years, we compared 166 HD patients older than 70 years (77.1 ± 4.7 yrs) at the onset of HD (group A) and 216 patients younger than 70 years both at onset (57.1 ± 7.6 yrs) and at the end of the HD period (group B). Eighty (48.2%) of group A and 141 (65.3%) patients of group B had diabetes mellitus.

RESULTS

No differences were noted in the overall hospitalization rate, presented as mean, {95% Confidence interval} (group A 2.40 {2.04-2.75}, group B 2.03 {1.89-2.16} n[pt-yr]) and days/[pt-year] (group A 33.6 {25.3-41.8}, group B 24.1 {18.9-29.23}). Group A had higher number of hospitalization days (P = 0.012) for surgery or trauma and higher rate (P = 0.045) and days (P = 0.041) of hospitalization for miscellaneous causes, primarily pulmonary disease, or malignancy. Among diabetic patients, group A had only a greater number of hospital days for cardiac disease (P = 0.050). Among patients without diabetes, group A had a higher number for hospital days for surgery or trauma (P = 0.027). All other univariate comparisons were not significant. Multiple linear regression identified comorbidity, quantified by the Charlson index, Caucasian race and poor compliance with the HD schedule as predictors of admission rate and days per year for vascular access issues and comorbidity, poor compliance, and advanced age at onset of HD as predictors of admission for causes other than vascular access related.

CONCLUSION

Hospitalizations, which affect quality of life, differ little between elderly and younger patients on HD. Therefore, hospitalizations do not constitute an argument for restricting access to HD to elderly patients.

Activation of caspase-3 in the skeletal muscle during haemodialysis

BACKGROUND AND OBJECTIVE

Muscle atrophy in end-stage renal disease (ESRD) may be due to the activation of apoptotic and proteolytic pathways. We hypothesized that activation of caspase-3 in the skeletal muscle mediates apoptosis and proteolysis during haemodialysis (HD).

MATERIALS AND METHODS

Eight ESRD patients were studied before (pre-HD) and during HD and the findings were compared with those from six healthy volunteers. Protein kinetics was determined by primed constant infusion of L-(ring (13)C(6) ) Phenylalanine.

RESULTS

Caspase-3 activity in the skeletal muscle was higher in ESRD patients pre-HD than in controls (24966·0 ± 4023·9 vs. 15293·3 ± 2120·0 units, P<0·01) and increased further during HD (end-HD) (37666·6 ± 4208·3 units) (P<0·001). Actin fragments (14 kDa) generated by caspase-3 mediated cleavage of actomyosin was higher in the skeletal muscle pre-HD (68%) and during HD (164%) compared with controls. The abundance of ubiquitinized carboxy-terminal actin fragment was also significantly increased during HD. Skeletal muscle biopsies obtained at the end of HD exhibited augmented apoptosis, which was higher than that observed in pre-HD and control samples (P<0·001). IL-6 content in the soluble fraction of the muscle skeletal muscle was increased significantly during HD. Protein kinetic studies showed that catabolism was higher in ESRD patients during HD compared with pre-HD and control subjects. Muscle protein catabolism was positively associated with caspase-3 activity and skeletal muscle IL-6 content.

CONCLUSION

Muscle atrophy in ESRD may be due to IL-6 induced activation of caspase-3 resulting in apoptosis as well as muscle proteolysis during HD.

Beyond genetics: epigenetic code in chronic kidney disease

Epigenetics refers to a heritable change in the pattern of gene expression that is mediated by a mechanism specifically not due to alterations in the primary nucleotide sequence. Well-known epigenetic mechanisms encompass DNA methylation, chromatin remodeling (histone modifications), and RNA interference. Functionally, epigenetics provides an extra layer of transcriptional control and plays a crucial role in normal physiological development, as well as in pathological conditions. Aberrant DNA methylation is implicated in immune dysfunction, inflammation, and insulin resistance. Epigenetic changes may be responsible for 'metabolic memory' and development of micro- and macrovascular complications of diabetes. MicroRNAs are critical in the maintenance of glomerular homeostasis and hence RNA interference may be important in the progression of renal disease. Recent studies have shown that epigenetic modifications orchestrate the epithelial-mesenchymal transition and eventually fibrosis of the renal tissue. Oxidative stress, inflammation, hyperhomocysteinemia, and uremic toxins could induce epimutations in chronic kidney disease. Epigenetic alterations are associated with inflammation and cardiovascular disease in patients with chronic kidney disease. Reversible nature of the epigenetic changes gives a unique opportunity to halt or even reverse the disease process through targeted therapeutic strategies.

Abnormalities of serum potassium concentration in dialysis-associated hyperglycemia and their correction with insulin: review of published reports

The main difference between dialysis-associated hyperglycemia (DH) and diabetic ketoacidosis (DKA) or nonketotic hyperglycemia (NKH) occurring in patients with preserved renal function is the absence of osmotic diuresis in DH, which eliminates the need for large fluid and solute (including potassium) replacement. We analyzed published reports of serum potassium (K(+)) abnormalities and their treatment in DH. Hyperkalemia was often present at presentation of DH with higher frequency and severity than in hyperglycemic syndromes in patients with preserved renal function. The frequency and severity of hyperkalemia were higher in DH episodes with DKA than those with NKH in both hemodialysis and peritoneal dialysis. For DKA, the frequency and severity of hyperkalemia were similar in hemodialysis and peritoneal dialysis. For NKH, hyperkalemia was more severe and frequent in hemodialysis than in peritoneal dialysis. Insulin infusion corrected the hyperkalemia of DH in most cases. Additional measures for the management of hyperkalemia or modest potassium infusions for hypokalemia were needed in a few DH episodes. The predictors of the decrease in serum K(+) during treatment of DH with insulin included the starting serum K(+) level, the decreases in serum values of glucose concentration and tonicity, and the increase in serum total carbon dioxide level. DH represents a risk factor for hyperkalemia. Insulin infusion is the only treatment for hyperkalemia usually required.

Sources of variation in estimates of lean body mass by creatinine kinetics and by methods based on body water or body mass index in patients on continuous peritoneal dialysis

OBJECTIVE

We identified factors that account for differences between lean body mass computed from creatinine kinetics (LBM(cr)) and from either body water (LBM(V)) or body mass index (LBM(BMI)) in patients on continuous peritoneal dialysis (CPD).

DESIGN

We compared the LBM(cr) and LBM(V) or LBM(BMI) in hypothetical subjects and actual CPD patients.

PATIENTS

We studied 439 CPD patients in Albuquerque, Pittsburgh, and Toronto, with 925 clearance studies.

INTERVENTION

Creatinine production was estimated using formulas derived in CPD patients. Body water (V) was estimated from anthropometric formulas. We calculated LBM(BMI) from a formula that estimates body composition based on body mass index. In hypothetical subjects, LBM values were calculated by varying the determinants of body composition (gender, diabetic status, age, weight, and height) one at a time, while the other determinants were kept constant. In actual CPD patients, multiple linear regression and logistic regression were used to identify factors associated with differences in the estimates of LBM (LBM(cr)<LBM(V), or LBM(cr)<LBM(BMI)).

MAIN OUTCOME MEASURE

We sought predictors of the differences LBM(V) - LBM(cr) and LBM(BMI) - LBM(cr).

RESULTS

Both LBM(V) (regardless of formula used to estimate V) and LBM(BMI) exceeded LBM(cr) in hypothetical subjects with average body compositions. The sources of differences between LBM estimates in this group involved differences in the coefficients assigned to gender, age, height, weight, presence or absence of diabetes, and serum creatinine concentration. In CPD patients, mean LBM(V) or LBM(BMI) exceeded mean LBM(cr) by 6.2 to 6.9 kg. For example, the LBM(V) obtained from one anthropometric formula was 50.4+/-10.4 kg and the LBM(cr) was 44.1+/-13.6 kg (P < .001), whereas among the 925 clearance studies, only 216 (23.3%) had LBM(cr)>LBM(V). The differences in determinants of body composition between groups with high versus low LBM(cr) were similar in hypothetical and actual CPD patients. Multivariate analysis in actual CPD patients identified serum creatinine, height, age, gender, weight, and body mass index as predictors of the differences LBM(V)-LBM(cr) and LBM(BMI)-LBM(cr).

CONCLUSIONS

Overhydration is not the sole factor accounting for the differences between LBM(cr) and either LBM(V) or LBM(BMI) in CPD patients. These differences also stem from the coefficients assigned to major determinants of body composition by the formulas estimating LBM.

Soluble CD14 levels, interleukin 6, and mortality among prevalent hemodialysis patients

BACKGROUND

CD14 is a pattern-recognition receptor that has a central immunomodulatory role in proinflammatory signaling in response to a variety of ligands, including endotoxin. CD14 protein is present in 2 forms: soluble (sCD14) and membrane bound. Here, we studied the implications of increased sCD14 levels in hemodialysis patients. We hypothesized that sCD14 level increase may link to cytokine activation and protein-energy wasting, predisposing to increased mortality risk.

STUDY DESIGN

Prospective observational study of prevalent hemodialysis patients.

SETTING & PARTICIPANTS

211 prevalent hemodialysis patients, median age of 65 years, with 29 months of vintage dialysis time followed up for mortality for a median of 31 months.

PREDICTORS

Tertiles of baseline circulating sCD14 levels corresponding to less than 2.84, 2.85 to 3.62, and greater than 3.63 microg/mL.

OUTCOME

The major outcome of interest was all-cause mortality.

MEASUREMENTS

sCD14 and endotoxin, together with other markers of inflammation and protein-energy wasting.

RESULTS

Median sCD14 level was 3.2 microg/mL (25th to 75th percentile, 2.7 to 3.9). sCD14 level correlated positively with C-reactive protein, interleukin 6, endotoxin, and pentraxin 3 levels and negatively with serum albumin level, muscle mass, and handgrip strength. Patients with increased sCD14 levels had lower body mass index and increased prevalence of muscle atrophy. Patients within the highest sCD14 tertile had a crude morality hazard ratio of 1.94 (95% confidence interval, 1.13 to 3.32) that persisted after adjustment for multiple confounders (hazard ratio, 3.11; 95% confidence interval, 1.49 to 6.46). In patients with persistent inflammation, the presence of a concurrent sCD14 level increase gradually increased mortality risk, but this effect was less than multiplicative and failed to show a statistical interaction.

LIMITATIONS

Those inherent to an observational study.

CONCLUSIONS

sCD14 level is associated with inflammation and protein-energy wasting in hemodialysis patients. It is a strong and independent predictor of mortality that warrants further assessment in the clinical setting regarding its usefulness as a complementary prognosticator to other general inflammatory markers.

Association of soluble endotoxin receptor CD14 and mortality among patients undergoing hemodialysis

BACKGROUND

CD14 is a key molecule in innate immunity that mediates cell activation and signaling in response to endotoxin and other bacterial wall-derived components. CD14 protein exists in soluble (sCD14) and membrane-bound forms. The correlates of sCD14 in persons undergoing long-term hemodialysis (HD) therapy are not known. We hypothesized that increased sCD14 levels in HD patients are associated with proinflammatory cytokine activation and increased mortality.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

310 long-term HD patients who participated in the Nutritional and Inflammatory Evaluation in Dialysis (NIED) Study, a cohort derived from a pool of more than 3,000 HD outpatients during 5 years in 8 DaVita maintenance dialysis facilities in the South Bay Los Angeles, CA, area.

PREDICTORS

sCD14 levels in serum.

OUTCOMES

33-month mortality.

RESULTS

Mean sCD14 level was 7.24 +/- 2.45 microg/mL. Tumor necrosis factor alpha level was the strongest correlate of sCD14 level (r = +0.24; P < 0.001), followed by interleukin 6 level (r = +0.18; P = 0.002), serum ferritin level (r = +0.21; P < 0.001), total iron-binding capacity (r = -0.19; P < 0.001), body mass index (r = -0.15; P = 0.008), vintage (r = +0.14; P = 0.01), low-density lipoprotein cholesterol level (r = +0.13; P = 0.03), and body fat (r = -0.11; P = 0.06). During the 33-month follow-up, 71 (23%) patients died. Multivariable Cox proportional analysis adjusted for case-mix and other nutritional and inflammatory confounders, including serum tumor necrosis factor alpha, C-reactive protein, and interleukin 6 levels, showed that compared with the lowest sCD14 tertile, sCD14 levels in the third tertile (>7.8 microg/mL) were associated with greater death risk (hazard ratio, 1.94; 95% confidence interval, 1.01 to 3.75; P = 0.04).

LIMITATIONS

Survivor bias in combined incident/prevalent studies.

CONCLUSIONS

Increased sCD14 level is related positively to markers of inflammation and negatively to nutritional status and is an independent predictor of mortality in long-term HD patients. Additional studies are needed to examine the usefulness of sCD14 level in risk stratification and the clinical decision-making process in HD patients.

Pathophysiology and management of fluid and electrolyte disturbances in patients on chronic dialysis with severe hyperglycemia

The mechanisms of fluid and solute abnormalities that should be considered in any patient with severe hyperglycemia include changes in the total amount of extracellular solute, osmotic diuresis, intake of water driven by thirst, and influences from associated conditions. The absence of osmotic diuresis distinguishes dialysis-associated hyperglycemia (DH) from hyperglycemia with preserved renal function (HPRF). Mainly because of this absence, comparable degrees of hyperglycemia tend to produce less hypertonicity and less severe intracellular volume contraction in DH than in HPRF, while extracellular volume is expanded in DH but contracted in HPRF. Ketoacidosis can develop in both DH and HPRF. Among DH patients, hyperkalemia appears to be more frequent when ketoacidosis is present than when nonketotic hyperglycemia is present. Among HPRF patients, the frequency of hyperkalemia appears to be similar whether ketoacidosis or nonketotic hyperglycemia is present. Usually patients with severe DH have no symptoms or may exhibit a thirst. Infrequent clinical manifestations of DH include coma and seizures from hypertonicity or ketoacidosis and pulmonary edema from extracellular expansion. Insulin infusion is usually the only treatment required to correct the biochemical abnormalities and reverse the clinical manifestations of DH. Monitoring of the clinical manifestations and biochemical parameters during treatment of DH with insulin is needed to determine whether additional measures, such as administration of saline, free water, or potassium salts, as well as emergency hemodialysis (HD) are needed. Emergency HD carries the risk of excessively rapid decline in tonicity; its benefits in the treatment of DH have not been established.

Mitochondrial function in physically active elders with sarcopenia

Physical activity is reported to protect against sarcopenia and preserve mitochondrial function. Healthy normal lean (NL: n=15) and sarcopenic (SS: n=9) participants were recruited based on body composition (DXA, Lunar DPX), age, and physical activity. Gastrocnemius mitochondrial function was assessed by (31)P MRS using steady-state exercise in a 4T Bruker Biospin. Total work (429.3+/-160.2J vs. 851.0+/-211.7J, p<0.001) and muscle volume (p=0.006) were lower in SS, although these variables were not correlated (NL r=-0.31, p=0.33, SS r=(0.03, p=0.93). In the SS resting ATP/ADP was lower (p=0.03) and ATP hydrolysis higher (p=0.02) at rest. Free energy ATP hydrolysis was greater at the end of exercise (p=0.02) and [ADP] relative to total work output was higher in SS (ANCOVA, p=0.005). [PCr] recovery kinetics were not different between the groups. Adjusting these parameters for differences in total work output and muscle volume did not explain these findings. These data suggest that aerobic metabolism in physically active older adults with sarcopenia is mildly impaired at rest and during modest levels of exercise where acidosis was avoided. Muscle energetics is coordinated at multiple cellular levels and further studies are needed to determine the loci/locus of energy instability in sarcopenia.

Hospitalizations in patients treated sequentially by chronic hemodialysis and continuous peritoneal dialysis

It is not established whether hospitalizations are more frequent or longer in patients on peritoneal dialysis (PD) or chronic in-center hemodialysis (HD). Comorbidity is a major factor affecting the comparison of hospitalizations. To account for comorbidity, we compared hospitalizations between the PD and HD periods in 16 patients, 8 of whom were treated by PD first (group A), and 8, by HD first (group B). In group A, causes of renal failure were diabetes (n = 3), primary renal disease (n = 2), systemic disease (n = 2), and hereditary nephropathy (n = 1). Age at onset of PD was 53 +/- 11 years; duration of PD, 31 +/- 17 months; and duration of HD, 40 +/- 33 months. This group had 52 hospitalizations in the PD period and 80 hospitalizations in the HD period. Hospitalization rate (n/ patient-year) was 2.5 +/- 2.0 during PD and 3.0 +/- 3.0 during HD (nonsignificant), and duration of hospitalization (days/patient-year) was 19.6 +/- 15.5 during PD and 21.9 +/- 17.7 during HD (nonsignificant). The three most common causes of hospitalization were peritonitis (27%), other infections (21%), and cardiovascular disease (14%) in the PD period, and HD access problems (35%), infections (16%), and cardiovascular disease (12%) in the HD period. In group B, causes of renal failure were diabetes (n = 4), primary renal disease (n = 3), and hypertension (n = 1). Age at onset of HD was 56 +/- 10 years; duration of HD, 41 +/- 19 months; and duration of PD, 60 +/- 24 months. This group had 82 hospitalizations in the HD period and 76 hospitalizations in the PD period. Hospitalization rate was 3.0 +/- 2.4 during HD and 1.9 +/- 2.8 during PD (nonsignificant), and duration of hospitalization was 17.3 +/- 25.1 during HD and 12.7 +/- 21.3 during PD (nonsignificant). The three most common causes of hospitalization were HD access problems (40%), cardiovascular disease (19%), and infections (12%) in the HD period, and other infections (36%), cardiovascular disease (19%), and peritonitis (21%) in the PD period. In patients changing dialysis modalities, rate and duration of hospitalizations did not vary between HD and PD. The causes of hospitalization were similar in the HD and PD periods regardless of which modality was applied first.

Body fluid abnormalities in severe hyperglycemia in patients on chronic dialysis: review of published reports

Reports of dialysis-associated hyperglycemia (DH) were compared to reports of diabetic ketoacidosis (DKA) and nonketotic hyperglycemia (NKH) in patients with preserved renal function. Average serum values in DH (491 observations), DKA (1036 observations), and NKH (403 observations) were as follows, respectively: glucose, 772, 649, and 961 mg/dl; sodium, 127, 134, and 149, mmol/l; and tonicity, 298, 304, and 355 mOsm/kg. Assuming that euglycemic (serum glucose, 90 mg/dl) values were the same (sodium, 140 mmol/l; tonicity, 285 mOsm/kg) for all three states, the hyperglycemic rise in the average serum tonicity value per 100-mg/dl rise in serum glucose concentration was 1.9 mOsm/kg in DH, 3.5 mOsm/kg in DKA, and 8.1 mOsm/kg in NKH. Neurological manifestations in DH patients were caused by coexisting conditions (ketoacidosis, sepsis, and neurological disease) in most instances, and by severe hypertonicity (>320 mOsm/kg), with clearing after insulin administration, in a few instances. In 148 episodes of DH corrected with insulin only, the mean increase in serum sodium per 100-mg/dl decrease in serum glucose (Delta[Na]/Delta[Glu]) was -1.61 mmol/l. In agreement with theoretical predictions, Delta[Na]/Delta[Glu] was numerically smaller in patients with edema than in those with euvolemia. The average hyperglycemic increase in extracellular volume, calculated from changes in serum sodium concentration during correction of DH using insulin alone, was 0.013 l/l per 100-mg/dl increase in serum glucose concentration. A small number of DH patients presented with pulmonary edema rectified by insulin alone. DH causes modest hypertonicity, with few patients having neurological manifestations caused usually by other coexisting conditions. In contrast to DKA or NKH, which usually presents with hypovolemia, DH causes hypervolemia manifested occasionally by pulmonary edema. Insulin is adequate treatment for DH.

The prescription of peritoneal dialysis

In addition to the maintenance of normal extracellular electrolyte composition, the prescription of continuous peritoneal dialysis (CPD) should address four other specific issues: (i) prevention of uremia by achievement of adequate clearance of azotemic substances, (ii) prevention of progressive expansion of the extracellular volume by adequate peritoneal ultrafiltration, (iii) prevention of loss of residual renal function, and (iv) prevention of deterioration of the peritoneal membrane structure and function. Urea clearance, in the form of Kt/V(Urea), is the index of removal of azotemic substances proposed by current guidelines. The target total (renal plus peritoneal) Kt/V(Urea) is >or=1.7 weekly. To provide the desired peritoneal Kt/V(Urea) (K(p)t/V(Urea)), the prescription of peritoneal dialysis must provide a daily drain volume (Dv) defined by the clearance equations as Dv = V x (K(p)t/V(Urea))/(D/P(Urea)), where V is body water obtained from published anthropometric formulas, K(p)t/V(Urea) = (1.7 - renal Kt/V(Urea))/7 and D/P(Urea) is the dialysate-to-plasma urea concentration ratio at the dwell time prescribed. Computer programs obtain the relevant D/P(Urea) values from formal studies of peritoneal transport. In the absence of these studies (for example, at initiation of CPD), D/P(Urea) values can be obtained from published studies with similar dwell times. Body size, indicated by V, is the major determinant of the K(p)t/V(Urea) limit provided by a given CPD schedule. Other obstacles to achievement of adequate urea clearance are created by poor patient compliance, inaccuracies of the anthropometric formulas estimating V, and mechanical complications of CPD that lead to retention of dialysate in the body. The main requirements for the prescription of adequate ultrafiltration are knowledge of the individual peritoneal transport characteristics, monitoring of urinary volume, and restriction of dietary sodium intake. Excessive dietary sodium intake is the major cause of extracellular volume expansion in CPD. Ideally, sodium intake should be kept at the level of total (peritoneal plus renal) sodium removal. Preventing the loss of residual renal function involves avoidance of nephrotoxic influences in the form of medications, radiocontrast agents, urinary obstruction and infection, and possibly other influences, such an elevated calcium-phosphorus product and anemia. Use of the lowest dialysate dextrose concentration that will allow adequate ultrafiltration is currently the most widespread practical measure of prevention of peritoneal membrane deterioration. Formulation of biocompatible dialysate is a major ongoing research effort and may greatly enhance the success of CPD in the future.

Body fluid abnormalities in severe hyperglycemia in patients on chronic dialysis: review of published reports

Reports of dialysis-associated hyperglycemia (DH) were compared to reports of diabetic ketoacidosis (DKA) and nonketotic hyperglycemia (NKH) in patients with preserved renal function. Average serum values in DH (491 observations), DKA (1036 observations), and NKH (403 observations) were as follows, respectively: glucose, 772, 649, and 961 mg/dl; sodium, 127, 134, and 149, mmol/l; and tonicity, 298, 304, and 355 mOsm/kg. Assuming that euglycemic (serum glucose, 90 mg/dl) values were the same (sodium, 140 mmol/l; tonicity, 285 mOsm/kg) for all three states, the hyperglycemic rise in the average serum tonicity value per 100-mg/dl rise in serum glucose concentration was 1.9 mOsm/kg in DH, 3.5 mOsm/kg in DKA, and 8.1 mOsm/kg in NKH. Neurological manifestations in DH patients were caused by coexisting conditions (ketoacidosis, sepsis, and neurological disease) in most instances, and by severe hypertonicity (>320 mOsm/kg), with clearing after insulin administration, in a few instances. In 148 episodes of DH corrected with insulin only, the mean increase in serum sodium per 100-mg/dl decrease in serum glucose (Delta[Na]/Delta[Glu]) was -1.61 mmol/l. In agreement with theoretical predictions, Delta[Na]/Delta[Glu] was numerically smaller in patients with edema than in those with euvolemia. The average hyperglycemic increase in extracellular volume, calculated from changes in serum sodium concentration during correction of DH using insulin alone, was 0.013 l/l per 100-mg/dl increase in serum glucose concentration. A small number of DH patients presented with pulmonary edema rectified by insulin alone. DH causes modest hypertonicity, with few patients having neurological manifestations caused usually by other coexisting conditions. In contrast to DKA or NKH, which usually presents with hypovolemia, DH causes hypervolemia manifested occasionally by pulmonary edema. Insulin is adequate treatment for DH.

Body fluid abnormalities in severe hyperglycemia in patients on chronic dialysis: theoretical analysis

Hyperglycemic syndromes cause disturbances in the tonicity of body fluids, the distribution of body water between major body fluid compartments, and the external balance of body solute and water. The unique feature of dialysis-associated hyperglycemia (DH) is that, during its development, it can cause changes exclusively in the internal balance of body solute (hypertonicity) and fluids (intracellular volume contraction and extracellular volume expansion) without affecting the external balance of water or solute. This makes DH the proper substrate for studying predictions of the changes in tonicity and extracellular volume caused by hyperglycemia because these predictions fail, by and large, to account for changes in the external balance of sodium, potassium, and water observed in hyperglycemic syndromes occurring in patients with preserved renal function. The predictions suggest that the baseline state of extracellular volume and the degree of hyperglycemia are major factors influencing the magnitude of abnormalities in the tonicity and extracellular volume resulting from DH, while transfers of solute between the intracellular compartment and the extracellular compartment have relatively smaller effects. Edematous patients are at risk for greater hypertonicity and larger increases in their extracellular volume than euvolemic -- or, even less, hypovolemic -- patients with the same degree of hyperglycemia. Studies reporting the treatment of DH with only insulin therapy can be used to test these theoretical predictions and to analyze the relationship between solute and fluid abnormalities and clinical manifestations.

Haemodialysis induces mitochondrial dysfunction and apoptosis

BACKGROUND

Mitochondria play a crucial role in the regulation of the endogenous pathways of apoptosis activated by oxidant stress. Nuclear factor-kappaB (NF-kappaB) is a central integration site for pro-inflammatory signals and oxidative stress.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from eight end-stage renal disease (ESRD) patients before haemodialysis (Pre-HD) and during the last 10 min of HD (End-HD). A new polysulfone membrane (F70, Fresenius) was used for dialysis. Intracellular generation of reactive oxygen species (ROS), mitochondrial redox potential (Deltapsim) and PBMC apoptosis were determined by flow-cytometry.

RESULTS

Plasma levels of interleukin-6 (IL-6) (24.9+/-7.0 vs. 17.4+/-5.5 pg dL(-1), P<0.05), IL-6 soluble receptor (52.2+/-4.9 vs. 37.6+/-3.2 ng dL(-1), P<0.02) and IL-6 gp130 (405.7+/-41.0 vs. 235.1+/-38.4 ng dL(-1), P<0.02) were higher end-HD compared to pre-HD. IL-6 secretion by the isolated PBMC (24.0+/-2.3 vs. 19.3+/-3.5 pg dL(-1), P<0.02) increased end-HD. Percentage of lymphocytes exhibiting collapse of mitochondrial membrane potential (43.4+/-4.6% vs. 32.6+/-2.9%, P<0.01), apoptosis (33.4+/-7.1% vs. 23.7+/-7.7%, P<0.01), and generation of superoxide (20.7+/-5.2% vs. 12.5+/-2.9%, P<0.02) and hydrogen peroxide (51.1+/-7.8% vs.38.2+/-5.9%, P<0.04) were higher at end-HD than pre-HD. NF-kappaB activation (3144.1+/-208.1 vs. 2033.4+/-454.6 pg well(-1), P<0.02), expression of B-cell lymphoma protein-2 (6494.6+/-1461 vs. 3501.5+/-796.5 ng mL(-1), P<0.03) and heat shock protein-70 (9.81+/-1.47 vs. 6.38+/-1.0 ng mL(-1), P<0.05) increased during HD.

CONCLUSIONS

Intra-dialytic activation of cytokines, together with impaired mitochondrial function, promotes generation of ROS culminating in augmented PBMC apoptosis. There is concomitant activation of pathways aimed at attenuation of cell stress and apoptosis during HD.

Body fluid abnormalities in severe hyperglycemia in patients on chronic dialysis: theoretical analysis

Hyperglycemic syndromes cause disturbances in the tonicity of body fluids, the distribution of body water between major body fluid compartments, and the external balance of body solute and water. The unique feature of dialysis-associated hyperglycemia (DH) is that, during its development, it can cause changes exclusively in the internal balance of body solute (hypertonicity) and fluids (intracellular volume contraction and extracellular volume expansion) without affecting the external balance of water or solute. This makes DH the proper substrate for studying predictions of the changes in tonicity and extracellular volume caused by hyperglycemia because these predictions fail, by and large, to account for changes in the external balance of sodium, potassium, and water observed in hyperglycemic syndromes occurring in patients with preserved renal function. The predictions suggest that the baseline state of extracellular volume and the degree of hyperglycemia are major factors influencing the magnitude of abnormalities in the tonicity and extracellular volume resulting from DH, while transfers of solute between the intracellular compartment and the extracellular compartment have relatively smaller effects. Edematous patients are at risk for greater hypertonicity and larger increases in their extracellular volume than euvolemic -- or, even less, hypovolemic -- patients with the same degree of hyperglycemia. Studies reporting the treatment of DH with only insulin therapy can be used to test these theoretical predictions and to analyze the relationship between solute and fluid abnormalities and clinical manifestations.

Cytokine gene polymorphism and progression of renal and cardiovascular diseases

Cytokines are important modulators of inflammation. The balance between pro- and anti-inflammatory cytokines determines whether the intensity of inflammatory response is within physiological limits or in the pathological range. The cytokine network is highly complex, containing interactive cascades of gene activation and suppression. Both chronic kidney disease (CKD) and end-stage renal disease (ESRD) are characterized by elevated levels of proinflammatory cytokines and markers of inflammation. Cytokines may modulate the risk for progression of renal disease and the susceptibility to cardiovascular disease (CVD). Polymorphisms of cytokine genes may influence gene transcription and cytokine secretion and thereby modulate the risk of progression of renal and CVDs. The observed inconsistencies in the data regarding associations between single-nucleotide gene polymorphisms (SNPs) and their presumed phenotypic expression emphasize the need to recognize several conceptual and methodological aspects such as haplotypic rather than single SNP variations and the influence of pathway genes with synergistic or antagonistic effects that ultimately determine the phenotype. It is conceivable that when a patient with a high-risk cytokine genotype develops CKD, the risk for CVD is increased. Early interventions in CKD patients with high-risk genotypes may slow the progression of renal disease and also decrease CV mortality and morbidity.

Amino acid repletion does not decrease muscle protein catabolism during hemodialysis

Intradialytic protein catabolism is attributed to loss of amino acids in the dialysate. We investigated the effect of amino acid infusion during hemodialysis (HD) on muscle protein turnover and amino acid transport kinetics by using stable isotopes of phenylalanine, leucine, and lysine in eight patients with end-stage renal disease (ESRD). Subjects were studied at baseline (pre-HD), 2 h of HD without amino acid infusion (HD-O), and 2 h of HD with amino acid infusion (HD+AA). Amino acid depletion during HD-O augmented the outward transport of amino acids from muscle into the vein. Increased delivery of amino acids to the leg during HD+AA facilitated the transport of amino acids from the artery into the intracellular compartment. Increase in muscle protein breakdown was more than the increase in synthesis during HD-O (46.7 vs. 22.3%, P < 0.001). Net balance (nmol.min(-1).100 ml (-1)) was more negative during HD-O compared with pre-HD (-33.7 +/- 1.5 vs. -6.0 +/- 2.3, P < 0.001). Despite an abundant supply of amino acids, the net balance (-16.9 +/- 1.8) did not switch from net release to net uptake. HD+AA induced a proportional increase in muscle protein synthesis and catabolism. Branched chain amino acid catabolism increased significantly from baseline during HD-O and did not decrease during HD+AA. Protein synthesis efficiency, the fraction of amino acid in the intracellular pool that is utilized for muscle protein synthesis decreased from 42.1% pre-HD to 33.7 and 32.6% during HD-O and HD+AA, respectively (P < 0.01). Thus amino acid repletion during HD increased muscle protein synthesis but did not decrease muscle protein breakdown.

Computation of the dose of continuous peritoneal dialysis required for adequate peritoneal urea clearance without taking into account peritoneal transport indices

To test the feasibility of calculating, in the absence of peritoneal transport studies, the dose (daily drain volume) of continuous peritoneal dialysis (CPD) that will produce a high probability of adequate fractional peritoneal urea clearance (Kpt/Vurea), we randomly separated 619 clearance studies in patients on continuous ambulatory peritoneal dialysis (CAPD) with 4 daily exchanges into a derivation (n = 322) and a validation (n = 297) group. In the derivation group, the dialysate-to-plasma urea concentration ratio (D/Purea) was < or = 0.799 within the lowest 5% of the studies. By the urea clearance formula, a D/Purea value of 0.799 will produce weekly Kpt/Vurea values of 1.70 or better if the ratio of the daily drain volume to plasma water (Dv/V) is > or = 0.304 L/L. Among the 56 studies in the validation group with Dv/V values of 0.304 L/L or more, 52 (92.9%) had weekly Kpt/Vurea values of 1.70 or better. Assuming a suitable (low) D/Purea value for a given CPD treatment, it is possible to derive the dose of dialysis (the Dv/V ratio) that will provide adequate peritoneal urea clearance levels regardless of peritoneal transport characteristics. This method is applicable to the prescription of CPD for patients lacking studies of peritoneal transport. Anuric patients on CAPD with 4 daily exchanges require a Dv/V value of 0.304 L/L or better to have a > or = 0.9 probability of achieving a weekly Kpt/Vurea of 1.70 or better.

Hemodialysis modulates gene expression profile in skeletal muscle

BACKGROUND

Uremia alters diverse metabolic pathways involving multiple organ systems, including skeletal muscle. Skeletal muscle has an important role in nutrition, metabolism, oxidative stress, and inflammation. We hypothesized that hemodialysis (HD) will change the genomic fingerprinting associated with uremia and facilitate expression of a distinct set of genes.

METHODS

Five patients with end-stage renal disease (ESRD) were studied. Skeletal muscle biopsy specimens from the vastus lateralis were obtained before (pre-HD) and during the last 10 minutes of HD (post-HD). Oligonucleotide microarray (version 2, GeneChip arrays; Affymetrix U95A, Santa Clara, CA) was used to analyze global transcriptional modification in skeletal muscle by HD. Pre-HD data were compared with data from 3 subjects without renal failure.

RESULTS

In skeletal muscle of patients with ESRD, 83 genes were upregulated and 8 genes were downregulated pre-HD compared with controls. Pathway analysis linked 55 genes to 5 gene networks involved in the regulation of cell cycle, cell proliferation, cellular organization, apoptosis, and inflammation. During HD, expression of 22 genes increased and 1 (TOB1) decreased. Pathway analysis mapped 20 genes to 2 genetic networks involved in: (1) inflammation, cell proliferation, and cell signaling; and (2) apoptosis, cell function, protein synthesis, and tissue morphology. Reverse-transcription polymerase chain reaction confirmed increased expression of GADD45A, BTG2, PDE4B, and CEBPD and downregulation of TOB1 in skeletal muscle intradialysis.

CONCLUSION

In response to the uremic milieu, skeletal muscle goes through very active transcriptional and translational changes. HD activates a diverse, yet biologically linked, network of genes related to inflammation and apoptosis in skeletal muscle.

Amino Acid and protein kinetics in renal failure: an integrated approach

Even apparently healthy patients on dialysis have significant loss of lean body mass. Patients with chronic renal failure without coexisting metabolic acidosis or inflammation have decreased protein turnover, with balanced reduction in protein synthesis and breakdown. However, regional and whole-body protein kinetic studies indicate that hemodialysis (HD) induces net increase in protein breakdown. Whole-body protein turnover studies show that HD is associated with decreased protein synthesis, but proteolysis is not increased. Muscle protein kinetics studies, however, identify enhanced muscle protein breakdown with inadequate compensatory increases in synthesis as the cause of the catabolism. Transmembrane amino acid-transport kinetics studies show that the outward transport is increased more than the inward transport of amino acids during HD. Altered intracellular amino acid transport kinetics and protein turnover during HD could be caused by the loss of amino acids in the dialysate or cytokine activation. Cytokines may be released from peripheral blood mononuclear cells and skeletal muscle during HD. Preliminary evidence indicates that intradialytic increase in cytokines activates the ubiquitin-proteasome pathway. An intradialytic increase in albumin and fibrinogen synthesis is facilitated by interleukin-6 and the constant supply of amino acids derived from skeletal muscle catabolism. Protein anabolism can be induced in end-stage renal disease patients by repletion of amino acids, and perhaps treatment with recombinant human insulin-like growth factor.

Skeletal muscle, cytokines, and oxidative stress in end-stage renal disease

BACKGROUND

End-stage renal disease (ESRD) is a state of microinflammation, with increased activation of cytokines and augmented oxidative stress. While peripheral blood mononuclear cells are an established source of reactive oxygen species and inflammatory cytokines during hemodialysis (HD), skeletal muscle is also capable of generating these biomolecules.

METHODS

Femoral arterio-venous (A-V) balance of interleukin-1 (IL-1), IL-6, IL-10, tumor necrosis factor-alpha (TNF-alpha), malonyldialdehyde (MDA), and carbonyl protein (CP) were measured in 17 ESRD patients and 9 healthy volunteers. ESRD patients were studied before (pre-HD) and during HD. mRNA levels of cytokines, heme oxygenase-1 (HO-1), and suppressors of cytokine signaling-2 (SOCS-2) were quantitated in the skeletal muscle by real-time polymerase chain reaction (PCR).

RESULTS

Arterial concentration of MDA (pmol/mL) was higher pre-HD (325.5 +/- 19.6) compared to controls (267.7 +/- 14.7), but decreased intradialysis (248.8 +/- 16.1) (P < 0.01). Dialysis clearance of MDA was 16.9 +/- 3.1 mL/min. CP concentration (nmol/mg protein) in the artery was significantly higher pre-HD (2.29 +/- 0.09) than in controls (1.92 +/- 0.05), and remained stable during HD (2.23 +/- 0.07). Plasma cytokines increased to a variable degree in the artery and vein during HD. A-V balance studies demonstrated that the MDA (17.8%) and CP (5.1%) concentrations increased significantly in the vein intradialysis. Venous concentration of IL-6 was higher than that in the artery during dialysis (16.27 +/- 2.42 vs. 11.29 +/- 2.17 pg/dL, P < 0.01). mRNA levels of IL-6 (0.028 +/- 0.02 vs. 6.69 +/- 0.21), HO-1 (0.96 +/- 0.01 vs. 5.08 +/- 1.11), and SOCS-2 (0.63 +/- 0.12 vs. 0.82 +/- 0.14) in the muscle increased during HD (P < 0.01). Immunohistochemical studies confirmed the increase in IL-6 protein in the skeletal muscle during HD. The intradialytic increase in IL-1, IL-10, and TNF-alpha gene expression was not significant.

CONCLUSION

Skeletal muscle may also contribute to the circulating plasma IL-6 and increased oxidative stress during HD.

Does Hemodialysis Increase Protein Breakdown? Dissociation between Whole-Body Amino Acid Turnover and Regional Muscle Kinetics

Hemodialysis (HD) is a protein catabolic procedure. Whole-body amino acid turnover studies identify dialysate amino acid loss and reduced protein synthesis as the catabolic events; proteolysis is not increased. Regional amino acid kinetics, however, document enhanced muscle protein breakdown as the cause of the catabolism; muscle protein synthesis also increased but to a lesser magnitude than the increment in protein breakdown. This discordance between whole-body and regional kinetics is best explained by the contrasting physiology between the muscle and the liver. During HD, muscle releases amino acids, which then are taken up by the liver for de novo protein synthesis. There seems to be a somatic to visceral recycling of amino acids. Evidence supporting this concept includes the increased fractional synthesis of albumin and fibrinogen during HD. It should be emphasized that region- or organ-specific kinetics vary, and whole-body turnover is a composite of all of the visceral and somatic compartments taken together. Reduced whole-body protein synthesis may be a compensatory adaptation to dialysate amino acid loss with a consequent reduction in plasma amino acid concentration. Notwithstanding the protein catabolic nature of HD, evidence is accumulating that intradialytic nutritional supplementation may blunt its catabolic effect.

Glutamine kinetics and protein turnover in end-stage renal disease

Alanine and glutamine constitute the two most important nitrogen carriers released from the muscle. We studied the intracellular amino acid transport kinetics and protein turnover in nine end-stage renal disease (ESRD) patients and eight controls by use of stable isotopes of phenylalanine, alanine, and glutamine. The amino acid transport kinetics and protein turnover were calculated with a three-pool model from the amino acid concentrations and enrichment in the artery, vein, and muscle compartments. Muscle protein breakdown was more than synthesis (nmol.min(-1).100 ml leg(-1)) during hemodialysis (HD) (169.8 +/- 20.0 vs. 125.9 +/- 21.8, P < 0.05) and in controls (126.9 +/- 6.9 vs. 98.4 +/- 7.5, P < 0.05), but synthesis and catabolism were comparable pre-HD (100.7 +/- 15.7 vs. 103.4 +/- 14.8). Whole body protein catabolism decreased by 15% during HD. The intracellular appearance of alanine (399.0 +/- 47.1 vs. 243.0 +/- 34.689) and glutamine (369.7 +/- 40.6 vs. 235.6 +/- 27.5) from muscle protein breakdown increased during dialysis (nmol.min(-1).100 ml leg(-1), P < 0.01). However, the de novo synthesis of alanine (3,468.9 +/- 572.2 vs. 3,140.5 +/- 467.7) and glutamine (1,751.4 +/- 82.6 vs. 1,782.2 +/- 86.4) did not change significantly intradialysis (nmol.min(-1).100 ml leg(-1)). Branched-chain amino acid catabolism (191.8 +/- 63.4 vs. -59.1 +/- 42.9) and nonprotein glutamate disposal (347.0 +/- 46.3 vs. 222.3 +/- 43.6) increased intradialysis compared with pre-HD (nmol.min(-1).100 ml leg(-1), P < 0.01). The mRNA levels of glutamine synthase (1.45 +/- 0.14 vs. 0.33 +/- 0.08, P < 0.001) and branched-chain keto acid dehydrogenase-E2 (3.86 +/- 0.48 vs. 2.14 +/- 0.27, P < 0.05) in the muscle increased during HD. Thus intracellular concentrations of alanine and glutamine are maintained during HD by augmented release of the amino acids from muscle protein catabolism. Although muscle protein breakdown increased intradialysis, the whole body protein catabolism decreased, suggesting central utilization of amino acids released from skeletal muscle.

Hypertension control with daily dialysis

Hypertension is present in 60-90% of patients on maintenance hemodialysis (HD) and it is an important cause of cardiovascular (CV) mortality and morbidity. Frequent and prolonged HD has been uniformly shown to control hypertension in end-stage renal disease (ESRD) patients more effectively than conventional HD. The etiology of hypertension is predominantly volume dependent, but in a subset of patients increased renin, sympathetic overactivity, and endothelial dysfunction may play a role. Intradialytic hypotension precludes attainment of dry weight and hence optimal control of hypertension in conventional HD is challenging. Frequent and prolonged dialysis with gentle and persistent ultrafiltration allows time for refilling of the intravascular compartment and permits normalization of extracellular volume. It is also possible that intensive dialysis enables removal of pressor molecules and improves endothelial function. Improved blood pressure control translates into regression of left ventricular hypertrophy in patients on daily HD. Thus prolonged and frequent dialysis permits better control of hypertension via volume and volume-independent mechanisms and also improves cardiac geometry.

Markers of inflammation, proteolysis, and apoptosis in ESRD

BACKGROUND

Hemodialysis (HD) is associated with protein catabolism and augmented apoptosis. Although the effect of metabolic acidosis and inflammatory cytokines on activation of the ubiquitin-proteasome pathway and branched-chain keto acid dehydrogenase (BCKAD) is well known, the effect of HD on these pathways remains unexplored.

METHODS

Twelve patients with end-stage renal disease were studied before and during HD. Eight controls also were studied. Plasma levels of complement components and cytokines, interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF-alpha) were measured. Messenger RNA (mRNA) levels of caspase-3, a mediator of apoptosis; ubiquitin, a marker of proteolysis; and BCKAD-E2, an enzyme regulating branched-chain amino acid oxidation, were estimated in skeletal muscle biopsy specimens by means of reverse-transcriptase polymerase chain reaction. Annexin-V expression was quantified by DNA array. Before the study, participants were placed on a 1.2-g/kg/d protein diet, and metabolic acidosis was corrected.

RESULTS

During HD, plasma IL-6 levels increased from 7.54 +/- 2.24 to 27.86 +/- 4.94 pg/dL (P < 0.001). Complement component, IL-1, and TNF-alpha levels did not change significantly during HD. mRNA levels of caspase-3 (0.50 +/- 0.01 versus 0.81 +/- 0.04), annexin-V (0.94 +/- 0.06 versus 1.48 +/- 0.05; P < 0.001), ubiquitin (1.10 +/- 0.03 versus 1.44 +/- 0.03), and BCKAD-E2 (0.47 +/- 0.01 versus 0.81 +/- 0.04) increased in muscle during HD compared with pre-HD values (P < 0.001). mRNA levels of ubiquitin (0.62 +/- 0.03) and BCKAD-E2 (0.58 +/- 0.02) were greater in controls than pre-HD values (P < 0.05). There were significant positive correlations between plasma IL-6 levels and expression of caspase-3, ubiquitin, and BCKAD-E2 genes.

CONCLUSION

HD causes activation of cytokines, which may mediate the increase in gene expression of caspase-3, ubiquitin, and BCKAD-E2 in skeletal muscles.

Advanced glycation end products and oxidative stress are increased in chronic allograft nephropathy

BACKGROUND

The histologic picture of chronic allograft nephropathy (CAN) resembles early arteriosclerotic lesion. Oxidative stress and advanced glycation end products (AGES) have been implicated in the pathogenesis of atherosclerosis and progression of renal disease.

METHODS

The authors serially measured the plasma malonyldialdehyde (MDA), carbonyl protein (CP), pentosidine, and argpyramidine levels in 11 postrenal transplant patients with normal renal function (KPT) and 10 patients with biopsy proven CAN at 1, 3, 6, 9 through 12, and 18 through 24 months posttransplant. Data were also obtained in 16 controls and 13 patients with chronic renal failure (CRF).

RESULTS

Although serum creatinine, MDA, CP, pentosidine, and argpyrimidine levels decreased during follow-up in KPT, it progressively increased in patients with CAN. The mean serum creatinine level was higher in patients with CRF (3.3 +/- 0.8 mg/dL [291.7 +/- 70.7 micromol/L]) and CAN (2.4 +/- 1.1 mg/dL [212.1 +/- 96.6 micromol/L]) than in controls (1.2 +/- 0.3 mg/dL [105.8 +/- 26.7 micromol/L]) and KPT patients (1.2 +/- 0.2 mg/dL [109.7 +/- 17.7 micromol/L]; P < 0.001). Markers of oxidative stress and AGEs measured at 18 to 24 months posttransplant in patients with CAN were higher than in KPT, controls, and CRF patients. MDA (nmol/mL) was significantly higher in patients with CAN (1.30 +/- 0.30) compared with controls (0.53 +/- 0.12), KPT (0.52 +/- 0.15), and CRF (0.74 +/- 0.27) groups (P < 0.001). Plasma CP (nmol/mg protein) in patients with CAN (4.3 +/- 1.00) was higher than in controls (1.90 +/- 0.69) and KPT (2.62 +/- 1.00) groups at the same time-point (P < 0.001), but comparable with CRF (2.69 +/- 1.20). Plasma pentosidine (pmol/micromol protein) level in patients with CAN (19.69 +/- 5.05) was higher compared with controls (2.49 +/- 0.86), CRF (13.10 +/- 3.68), and KPT (14.32 +/- 6.28) groups (P < 0.001). Plasma argpyrimidine (pmol/10 micromol protein) was higher in patients with CAN (123.8 +/- 17.9) compared with controls (4.81 +/- 1.91), CRF (56.92 +/- 29.67), and KPT (31.1 +/- 11.1; P < 0.001) groups.

CONCLUSION

Oxidative stress and AGEs are increased in patients with CAN, which cannot be explained by the decline in renal function alone. Oxidative stress and AGEs may be one among the nonimmune mediators of CAN.

Coordinated increase in albumin, fibrinogen, and muscle protein synthesis during hemodialysis: role of cytokines

Serum albumin, fibrinogen levels, and lean body mass are important predictors of outcome in end-stage renal disease (ESRD). We estimated the fractional synthesis rates of albumin (FSR-A), fibrinogen (FSR-F), and muscle protein (FSR-M) in nine ESRD patients and eight controls, using primed constant infusion of l-[ring-(13)C(6)]phenylalanine. Cytokine profile and arteriovenous balance of amino acids were also measured. ESRD patients were studied before (Pre-HD) and during hemodialysis (HD). Plasma IL-6, IL-10, and C-reactive protein increased significantly during HD. Despite a decrease in the delivery of amino acids to the leg, the outflow of the amino acids increased during HD. The net balance of amino acids became more negative during HD, indicating release from the muscle. HD increased leg muscle protein synthesis (45%) and catabolism (108%) but decreased whole body proteolysis (15%). FSR-A during HD (9.7 +/- 0.9%/day) was higher than pre-HD (6.5 +/- 0.9%/day) and controls (5.8 +/- 0.5%/day, P < 0.01). FSR-F increased during HD (19.7 +/- 2.6%/day vs. 11.8 +/- 0.6%/day, P < 0.01), but it was not significantly different from that of controls (14.4 +/- 1.4%/day). FSR-M intradialysis (1.77 +/- 0.19%/day) was higher than pre-HD (1.21 +/- 0.25%/day) and controls (1.30 +/- 0.32%/day, P < 0.001). Pre-HD FSR-A, FSR-F, and FSR-M values were comparable to those of controls. There was a significant and positive correlation between plasma IL-6 and the FSRs. Thus, in ESRD patients without metabolic acidosis, the fractional synthesis rates of albumin, fibrinogen, and muscle protein are not decreased pre-HD. However, HD increases the synthesis of albumin, fibrinogen, and muscle protein. The coordinated increase in the FSRs is facilitated by constant delivery of amino acids derived from the muscle catabolism and intradialytic increase in IL-6.

Protein turnover and amino acid transport kinetics in end-stage renal disease

Protein and amino acid metabolism is abnormal in end-stage renal disease (ESRD). Protein turnover is influenced by transmembrane amino acid transport. The effect of ESRD and hemodialysis (HD) on intracellular amino acid transport kinetics is unknown. We studied intracellular amino acid transport kinetics and protein turnover by use of stable isotopes of phenylalanine, leucine, lysine, alanine, and glutamine before and during HD in six ESRD patients. Data obtained from amino acid concentrations and enrichment in the artery, vein, and muscle compartments were used to calculate intracellular amino acid transport and muscle protein synthesis and catabolism. Fractional muscle protein synthesis (FSR) was estimated by the precursor product approach. Despite a significant decrease in the plasma concentrations of amino acids in the artery and vein during HD, the intracellular concentrations remained stable. Outward transport of the amino acids was significantly higher than the inward transport during HD. FSR increased during HD (0.0521 +/- 0.0043 vs. 0.0772 +/- 0.0055%/h, P < 0.01). Results derived from compartmental modeling indicated that both protein synthesis (118.3 +/- 20.6 vs. 146.5 +/- 20.6 nmol.min-1.100 ml leg-1, P < 0.01) and catabolism (119.8 +/- 18.0 vs. 174.0 +/- 14.2 nmol.min-1.100 ml leg-1, P < 0.01) increased during HD. However, the intradialytic increase in catabolism exceeded that of synthesis (57.8 +/- 13.8 vs. 28.0 +/- 8.5%, P < 0.05). Thus HD alters amino acid transport kinetics and increases protein turnover, with net increase in protein catabolism.

Role of APD in compliance with therapy

Lack of compliance with prescribed treatment is an important cause of inadequate dialysis in patients on peritoneal dialysis (PD). The reported prevalence of noncompliance with treatment in PD varies from 5 to 38%. The predictors of noncompliance, its consequences, methods to identify and monitor compliance, differences in frequency between continuous ambulatory PD (CAPD) and automated PD (APD), and management are reviewed. The risk of noncompliance is greater in CAPD than in APD. Noncompliance should be managed by patient education and appropriate modification of therapy, including consideration of APD.

Hemodynamic changes during hemodialysis: role of nitric oxide and endothelin

BACKGROUND

Etiology of dialysis induced hypotension and hypertension remains speculative. There is mounting evidence that nitric oxide (NO) and endothelin (ET-1) may play a vital role in these hemodynamic changes. We examined the intradialytic dynamic changes in NO and ET-1 levels and their role in the pathogenesis of hypotension and rebound hypertension during hemodialysis (HD).

METHODS

The serum nitrate + nitrite (NT), fractional exhaled NO concentration (FENO), L-arginine (L-Arg), NGNG-dimethyl-L-arginine (ADMA) and endothelin (ET-1) profiles were studied in 27 end-stage renal disease (ESRD) patients on HD and 6 matched controls. The ESRD patients were grouped according to their hemodynamic profile; Group I patients had stable BP throughout HD, Group II had dialysis-induced hypotension, and Group III had intradialytic rebound hypertension.

RESULTS

Pre-dialysis FENO was significantly lower in the dialysis patients compared to controls (19.3 +/- 6.3 vs. 28.6 +/- 3.4 ppb, P < 0.002). Between the experimental groups, pre-dialysis FENO was significantly higher in Group II (24.1 +/- 6.7 ppb) compared to Group I (17.8 +/- 5.6 ppb) and Group III (16.1 +/- 4.2 ppb; P < 0.05). Post-dialysis, FENO increased significantly from the pre-dialysis values (19.3 +/- 6.3 vs. 22.6 +/- 7.9 ppb; P=0.001). Pre-dialysis NT (34.4 +/- 28.2 micromol/L/L) level was not significantly different from that of controls (30.2 +/- 12.3 micromol/L/L). Serum NT decreased from 34.4 +/- 28.2 micromol/L/L at initiation of dialysis to 10.0 +/- 7.4 micormol/L/L at end of dialysis (P < 0.001). NT concentration was comparable in all the three groups at all time points. Pre-dialysis L-Arg (105.3 +/- 25.2 vs. 93.7 +/- 6.0 micromol/L/L; P < 0.05) and ADMA levels were significantly higher in ESRD patients (4.0 +/- 1.8 vs. 0.9 +/- 0.2 micromol/L/L; P < 0.001) compared to controls. Dialysis resulted in significant reduction in L-Arg (105.3 +/- 25.2 vs. 86.8 +/- 19.8 micromol/L/L; P < 0.005) and ADMA (4.0 +/- 1.8 vs. 1.6 +/- 0.7 micromol/L/L; P < 0.001) concentrations. Pre-dialysis ET-1 levels were significantly higher in ESRD patients compared to the controls (8.0 +/- 1.9 vs. 12.7 +/- 4.1 pg/mL; P < 0.002), but were comparable in the three study groups. Post-dialysis ET-1 levels did not change significantly in Group I compared to pre-dialysis values (14.3 +/- 4.3 vs.15.0 +/- 2.4 pg/mL, P=NS). However, while the ET-1 concentration decreased significantly in Group II (12.0 +/- 4.0 vs. 8.7 +/- 1.8 pg/mL, P < 0.05), it increased in Group III from pre-dialysis levels (12.8 +/- 3.8 vs. 16.7 +/- 4.5 pg/mL, P=0.06).

CONCLUSION

Pre-dialysis FENO is elevated in patients with dialysis-induced hypotension and may be a more reliable than NT as a marker for endogenous NO activity in dialysis patients. Altered NO/ET-1 balance may be involved in the pathogenesis of rebound hypertension and hypotension during dialysis.