Less known pathophysiological mechanisms of anemia in patients with diabetic nephropathy

Diabetes mellitus (DM) is currently considered a modern global epidemic, and diabetic nephropathy (DN) is the most common cause of chronic kidney disease (CKD). Anemia is one of the most significant complications of CKD, and it is mainly attributed to insufficient erythropoietin (EPO) production. However, anemia develops earlier in the course of CKD among patients with DM, and the severity of anemia tends to be more marked in these patients compared to nondiabetic subjects, regardless of the stage of CKD. In this review, we focus on the "less known" complex interacting mechanisms which are involved in the pathophysiology of anemia associated with DN. Although the major cause of anemia in DN is considered to be an inappropriate response of the plasma EPO concentration to anemia, several other possible mechanisms have been suggested. Glomerular hyperfiltration, proteinuria, renal tubular dysfunction and interstitial fibrosis are among the main culprits. On the other hand, systemic effects such as chronic inflammation, autonomic neuropathy and the renin-angiotensin system are also involved. Finally, several medications are considered to aggravate anemia associated with DN. Since anemia is an important predictor of quality of life and is implicated in the increased burden of cardiovascular morbidity and mortality, further research is required to elucidate its pathogenesis in diabetic patients.

Individual Renal Function in Polycystic Kidney Disease

PURPOSE

This study was undertaken to determine individual renal function in patients with autosomal dominant polycystic kidney disease (ADPKD).

MATERIALS AND METHODS

The authors initially examined (study t1) 25 patients with ADPKD (12 female, 13 male; ages 18 to 68 years). The serum creatinine concentration and glomerular filtration rate, measured by Tc-99m DTPA, were 1.5 +/- 0.56 mg/dl and 65.7 +/- 31 ml.minute-1.1.73 m2, respectively. Thirteen patients had a follow-up study (t2) 2 years after their initial evaluations. Individual renal function was assessed on Tc-99m DMSA renal scans.

RESULTS

The mean (+/- SD) difference between left kidney DMSA (DMSA-L) and right kidney DMSA (DMSA-R) was 7.04 % +/- 16.48%. In 20 patients (80%), the left kidney had a lower percentage contribution to the total renal function compared with the right kidney. When the results of the two studies were compared, deterioration in renal function was noted. In the t1 study, the mean serum creatinine concentration and glomerular filtration rate were 1.7 mg/dl and 67.02 ml.minute-1.1.73 m2 respectively, and in the t2 study these values were 2.01 mg/dl and 57.15 ml.minute-1.1.73 m2, respectively. No difference, however, was found in individual renal function in the two studies.

CONCLUSIONS

In patients with ADPKD, the percentage contribution of each kidney to total renal function is not equal and remains stable during the progression of renal failure.

Effect of L-carnitine supplementation on lipid parameters in hemodialysis patients

It has been reported that cumulative carnitine losses through dialysis membranes may worsen hyperlipidemia during long-term hemodialysis. However, carnitine supplementation has not shown a consistent beneficial response. We undertook the present study to determine if there is any hypolipidemic effect of L-carnitine on Greek dialysis patients in concert with the dialysate buffer composition (acetate or bicarbonate). A total of 28 patients (16 male, 12 female), mean age 43 years (range 21-61), with end-stage renal disease on maintenance hemodialysis for a mean period of 25 months (range 7-84) were studied. The dialysis schedule was 4 h, 3 times/week using cuprophane hollow-fiber dialyzers and acetate (n = 14) or bicarbonate (n = 14) dialysate. In all patients L-carnitine (5 mg/kg body weight) was infused intravenously 3 times/week at the end of each hemodialysis session. Blood samples for carnitine and lipid determinations were obtained before treatment, and 3 and 6 months following treatment. Even though L-carnitine did not modify most of the serum lipid levels, a significant decrease in serum triglycerides was evident in the whole group of patients (from 225 +/- 76 to 201 +/- 75 mg/dl, p = 0.03). Furthermore, L-carnitine could decrease serum triglycerides only in hypertriglyceridemic patients (from 260 +/- 64 to 226 +/- 82 mg/dl, p < 0.05). L-Carnitine resulted in a reduction of serum triglycerides in both patients on bicarbonate and on acetate dialysis, while there were no significant differences in the changes of lipid parameters after L-carnitine between the two groups of hemodialysis patients. We conclude that relatively low doses of L-carnitine supplementation could contribute to the management of some hypertriglyceridemic hemodialysis patients.

Effectiveness and metabolic effects of perindopril and diuretics combination in primary hypertension

The effectiveness as well as the metabolic effects of the combination of diuretics [hydrochlorothiazide (HCT) vs indapamide (IND)] and perindopril (P) in 14 patients (7 male, 7 female) aged 37-62 years with mild idiopathic hypertension were studied. Following a 4-week wash-out period and a 4-week period of monotherapy with P (4 mg/daily), IND (2.5 mg/daily) or HCT (25 mg/daily) was added for 4 weeks. Selection of the diuretic agent was random. Following a 4-week wash-out period from the diuretic, in which only P was given, the alternative diuretic was administered for another period of 4 weeks. P decreased blood pressure levels significantly. However, the drug was more efficacious in patients with higher plasma renin activity (PRA). Combination treatment induced an additional decrease in the blood pressure levels, mainly in patients with lower PRA. The combination of P + HCT was more effective than the combination P + IND. The addition of either HCT or IND evoked a small but statistically significant increase in serum glucose levels while fasting as well as during the 75 g oral glucose challenge. However, insulin levels did not change significantly during the study. Small but not statistically significant changes in serum electrolytes and lipid parameters were observed during the various phases of the study, while a statistically significant increase in the serum uric acid was noticed when the combination P + HCT was given. We conclude: (1) P in small doses is an effective and safe antihypertensive agent, (2) PRA has a predictive value in determining the effectiveness of P treatment, (3) the combination of P with small doses of HCT or IND is more efficacious than P alone, (4) the combination treatment has adverse effects in the carbohydrate tolerance, while there are not significant changes in serum electrolyte and lipid parameters.

Peritoneal membrane transport for low molecular weight substances with the use of one bag dialysate collection

The 24-hour collection of dialysate provides an accurate method for evaluation of both adequacy of dialysis and peritoneal membrane transport characteristics in patients on chronic ambulatory peritoneal dialysis. However, this test requires 24 hours to complete and therefore it is inconvenient for both patients and nurses in the every day practice. We determined the peritoneal membrane transport characteristics for low molecular weight substances of ten patients by using the dialysate collection of only one bag. Dialysate/plasma creatinine ratios were calculated for each of the 4 bags (DATT1, DATT2, DATT3, DATT4) as well as for the 24 hour dialysate (DATTo). We found a very good correlation between DATTo and the four DATTs. We therefore propose that the evaluation of the peritoneal membrane transport, at least for creatinine could be determined with the use of one bag dialysate collection.

Absence of HCV viraemia in anti-HCV-negative haemodialysis patients

BACKGROUND

Immunologic alterations have been reported in chronic haemodialysis (HD) patients. Some HD patients may have, therefore, an inability to produce detectable amounts of serum antibodies to hepatitis C virus (anti-HCV). Previous studies have shown the presence of HCV viraemia in anti-HCV-negative HD patients (ranging from 1 to 15%). However, the universal epidemiologic impact of these cases remains uncertain since there are conflicting results. In this context, we conducted a study in an attempt to investigate the presence of HCV viraemia among anti-HCV-negative HD patients in a well-defined geographic area of the northwestern part of Greece.

METHODS

During a 6 month period, 81 anti-HCV-negative HD patients were tested twice for the presence of HCV RNA, using the reverse transcriptase polymerase chain reaction (RT-PCR) combined with a DNA enzyme immunoassay (DEIA). At the same time, periodic testing for anti-HCV by two commercially available third generation assays was done. In addition, 15 anti-HCV-positive HD patients and 20 non-HD patients with well established chronic HCV infection used as internal controls were tested for the presence of HCV RNA and anti-HCV.

RESULTS

None of the anti-HCV-negative HD patients were shown to be viraemic by the combined RT-PCR and DEIA method. During the same time period, all remained anti-HCV negative by the third generation assays. By contrast, all the patients with known HCV-infection were positive by the two enzyme immunoassays, whereas 13 anti-HCV-positive HD patients (86.7%) and 18 non-HD patients (90%) were viraemic by RT-PCR.

CONCLUSIONS

This study demonstrated that routine HCV RNA testing in anti-HCV-negative HD patients appears not to be necessary particularly when third generation assays are used for the detection of anti-HCV.

Paraquat-induced renal injury studied by 1H nuclear magnetic resonance spectroscopy of urine

The herbicide paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride; PQ), is a poison known to cause delayed mortality due to lung and kidney injuries. High-resolution proton nuclear magnetic resonance (1H NMR) spectroscopy has been extensively applied in evaluating nephrotoxicity by the characteristic perturbations in the excretion pattern of low molecular weight endogenous metabolites. The application of the method allows the rapid localization of the renal injury noninvasively. In this study, we report 1H NMR and conventional clinical chemistry urinalysis in two patients suffering from paraquat intoxication after overdose with suicidal intent. The alterations in the urine NMR spectrum suggest necrosis of the pars recta of the proximal renal tubules. The molecule of paraquat is also clearly detected in the same spectrum. In conclusion, the rapid screening of urine by NMR spectroscopy provides information about both the identity of the poison and the abnormal pattern of endogenous metabolites that characterize the location of the injury in renal tubules and reveals alterations in unusual metabolites that are not commonly measured.

The control of hyperphosphataemia in haemodialysis patients

Patients with chronic uraemia develop various metabolic abnormalities, the most significant being the low production of vitamin D [1.25(OH)2D3] by the kidneys (1-3), hyperphosphataemia, and hypocalcaemia (4). These abnormalities, occurring usually in combination, are responsible for the pathogenesis of secondary hyperparathyroidism (HPT) (5-11). Prevention and treatment of secondary HPT can be achieved by means of administration of vitamin D and calcium. However, the above treatment is conditional on a low serum phosphorus concentration.

Long-term effect of low molecular weight heparin on serum lipids in hypertriglyceridemic chronic hemodialysis patients

Although low-molecular-weight heparin (LMWH) has been reported to lower serum triglycerides and raise HDL in patients previously receiving classic heparin for hemodialysis by sparing lipoprotein lipase activation, this is not universally accepted. To evaluate this effect we studied 14 hypertriglyceridemic patients on hemodialysis for a median of 61 months (range 6-168 months); six were males and eight females, with a median age of 54 years (range 30-78). Eight patients were on bicarbonate and six on acetate HD. Eight were receiving EPO. All had been given conventional heparin, 102 +/- 5.8 IU/kg, at least for the last six months (control period) before switching to LMWH. Mean LMWH dose was 77 +/- 3.1 IU/kg. Fasting levels of total cholesterol (TC), triglycerides (TG) and HDL were measured monthly during the control period and every trimester for the next 36 months. Serum lipoproteins were measured at months 0 and 36 of the trial. TC, Lp alpha and beta showed no significant change. Serum TG and Lp pre-beta dropped significantly, to almost normal levels. EPO treatment, serum iPTH levels or dialysate buffer did not seem to influence this effect. HDL rose significantly higher in women than in men. It is concluded that LMWH substantially lowered the abnormally high serum TG and Lp pre-beta to almost normal and raised serum HDL in chronic hemodialysis patients.

Ambulatory blood pressure monitoring in hemodialysis patients

The aim of our study was the detection of blood pressure (BP) variability during a dialysis session and in the interdialytic period in normotensive and hypertensive hemodialysis (HD) patients using ambulatory blood pressure monitoring (ABPM). Twenty-two HD patients aged 54 (range, 33-78) years who were on HD for a mean of 17.7 (range, 1-70) months were studied. Twelve patients were hypertensives, while the remaining 10 were normotensives (BP < 140/90 mm Hg). In all patients ABPM was performed for a total of 48 h including an HD session. A significant decrease in systolic BP, diastolic BP and mean BP was observed at the end of a dialysis session in hypertensive HD patients. However, in only five patients a reduction of more than 5% In mean arterial BP was noticed. No significant differences were observed in the BP values between the first and the second day after the HD in hypertensive HD patients. Interdialytic BP (both systolic and diastolic) was significantly higher than the postdialysis BP measured either in the clinic or with the ABPM in these patients. Normotensive HD patients exhibited a normal diurnal variation of BP during the first day after the HD session (decrease in BP during the night). On the second day after the HD session an increase in BP (mainly of systolic BP), as well as a loss of diurnal variation were observed. On the contrary, hypertensive HD patients did not exhibit the normal diurnal variation of BP during the first or the second day after the HD session. Hypertensive HD patients exhibited increased daytime and night time BP loads. On the other hand, normotensive HD patients presented with BP loads within normal limits, even though a small increase in these loads was observed on the second day after dialysis. In conclusion, while hypertensive HD patients present a loss of the normal diurnal variation of BP, normotensive HD patients exhibit normal variation during the first day after the HD session. The loss of the diurnal variation during the second day in these patients suggests a volume-dependent state.