Robert Kowalski

The effects of P2X receptor agonists on renal sodium and water excretion in anaesthetized rats.

Aim:  To investigate in vivo effects of P2X receptor activation on sodium and water excretion in urine.

Harmonization of urine albumin/creatinine ratio (ACR) results: a study based on an external quality assessment program in Polish laboratories

Abstract Background: The ratio of albumin to creatinine (ACR) is an important parameter used for detection of albuminuria in patients with early kidney damage. The aim of the study was to evaluate the harmonization of ACR results among Polish participants in an international external quality assessment (EQA) program, and to evaluate the impact of albumin and creatinine analytical performance on the harmonization of ACR results. Methods: We analyzed 182 results of albumin, 202 of creatinine, and 180 of ACR obtained from Polish laboratories in an EQA program organized by Labquality. The dispersion of the results in surveys and percentage differences between the results and target values were calculated. Moreover, differences between method groups were assessed. Results: The inter-laboratory coefficient of variation (CV) for ACR was 36%. Only 74% of results of Polish laboratories were within the target limits; for 11% of the results, an incorrect albuminuria category would have been reported. The inter-laboratory CV for albumin was 20%, 2.6-fold higher than for creatinine. Significant differences between method groups for albumin determination have been observed, even when the same measurement technique was used. The greatest difference between two groups was 23%, 2.5-fold greater in comparison to creatinine. Conclusions: There is an insufficient harmonization of ACR values among Polish laboratories, caused mainly by urine albumin analytical performance. Given the important role of ACR in the classification, monitoring and treatment of kidney damage, the harmonization of albumin measurements is crucial and urgently needed.

Progression of Chronic Kidney Disease Affects HDL Impact on Lipoprotein Lipase (LPL)-Mediated VLDL Lipolysis Efficiency

Background/Aims: Hypertriglyceridaemia (HTG) and reduction and dysfunction of high density lipoprotein (HDL) are common lipid disturbances in chronic kidney disease (CKD). HTG in CKD is caused mainly by the decreased efficiency of lipoprotein lipase (LPL)-mediated very low density lipoprotein triglyceride (VLDL-TG) lipolysis. It has not been clarified whether HDL dysfunction in CKD contributes directly to HTG development; thus, the aim of this study was to assess the impact of CKD progression on the ability of HDL to enhance LPL-mediated VLDL-TG lipolysis efficiency. Methods: VLDL was isolated from non-dialysis patients in CKD stages 3 and 4 and from non-CKD patients. The VLDL was incubated with LPL at the constant LPL:VLDL-TG ratio, in the absence or presence of HDL. After incubation, the VLDL was separated and the percentage (%) of hydrolyzed TG was calculated. Results: HDL presence increased the lipolysis efficiency of VLDL isolated from CKD and non-CKD patients, for the VLDL-TG> 50 mg/dl. Its effect was dependent on the VLDL-TG and HDL-cholesterol concentrations in the reaction mixtures: the higher the concentrations of VLDL-TG and HDL-cholesterol, the greater the effect. The positive impact of HDL on VLDL lipolysis was modified by CKD progression: the percentage of lipolyzed VLDL-TG in the presence of HDL decreased with a reduction in eGFR (r=0.43, p=0.009), and for patients with stage 4 CKD, no positive impact of HDL on lipolysis was observed. The percentage of lipolyzed TG correlated negatively with apoE and apoCs content in VLDL, and positively with HDL-apoCII, as well as with VLDL and HDL apoCII/ apoCIII ratios. The progression of CKD was associated with unfavourable changes in VLDL and HDL composition; apoE and apoCs levels increased in VLDL with a decrease in eGFR whereas the HDL-cholesterol level decreased. Conclusion: The progression of CKD affects lipoprotein composition and properties, and modulates the positive impact of HDL on VLDL lipolysis efficiency. In CKD patients, HDL deficiency and dysfunction can directly affect hypertriglyceridaemia development.

Cardioprotective effect of N-methylnicotinamide salt of pyruvate in experimental model of cardiac hypoxia

BACKGROUND Pyruvate improves contractility of normal, hypoxic, and post-ischemic myocardium. However, sodium overload is a major problem with its therapeutic application if sodium pyruvate is used. Development of alternative forms such as N-1-methylnicotinamide (MNA) pyruvate may help to overcome this problem. The aim of the study was to investigate the effect of MNA pyruvate in a murine model of cardiac ischemia. METHODS Seven month old male ApoE-/-LDLr-/- mice that develop myocardial infarction when exposed to hypoxic stress, were used in this study. Hypoxia (8% O2 in inspired air) was maintained for 8min and was followed by reoxygenation (21% O2 in inspired air). Four groups of mice were treated 10min before the hypoxic event by intravenous injection of MNA, MNA pyruvate, sodium pyruvate, and saline as control. The myocardial ischemia and damage was recorded by ECG. Four hours following the hypoxic episode serum troponin T and creatine kinase activity were measured. RESULTS Significant hypernatremia was found in the sodium pyruvate group. During hypoxia, control and MNA group developed profound STU depressions on ECG while no changes were observed in MNA pyruvate and sodium pyruvate group. Creatine kinase activity and troponin T content in the mice plasma were significantly higher in the control and MNA group as compared to the MNA pyruvate and sodium pyruvate group. CONCLUSIONS This study demonstrated that administration of MNA pyruvate prior to a hypoxia-induced cardiac event was cardioprotective. This intervention did not cause hypernatremia in contrast to sodium pyruvate.

Thiopurine S-Methyltransferase Phenotype and Genotype in Pediatric Patients with Inflammatory Bowel Disease; Implication for AzathioprineTreatment

Inflammatory Bowel Disease (IBD) is more prevalent in children than adults, and the incidence is increasing. IBD is treated with thiopurines, metabolized by thiopurine S-methyltransferase (TPMT) and inter-individual variability in activity of TPMT affecting therapy efficiency and drug toxicity arises from genetic polymorphisms, mainly TPMT*2, *3A, and *3C. The aim was to investigate the frequency distribution of TPMT activity, determine the penetration rate of TPMT*2, *3A, and *3C alleles in children, and compare TPMT activity in children and adults with IBD. The study included 85 children, 45% with Crohn’s disease (CD) and 55% with ulcerative colitis (UC), and 31 adults with IBD. TPMT activity was measured with radiochemistry. TPMT*2, *3A, and *3C alleles were investigated with PCR and restriction fragment length polymorphism analyses. Children showed median TPMT activities of 13.12 and 13.19 U/ml RBC in CD and UC, respectively, with 4.8-fold variability (range, 4.74 - 22.56 U/ml RBC). TPMT activity was similar in children and adults; ranges: 5.56-21.34 vs. 9.61-17.84 U/ml RBC, respectively, in CD; and 4.74-22.56 vs. 5.19-21.98 U/ml RBC, respectively, in UC. Patients with CD and UC treated with azathioprine displayed similar TPMT activities, similar adverse event frequencies, and similar numbers of non-responders. One out of 85 patients (1.18%) was heterozygous with TPMT*1/TPMT*2 (TPMT activity: 5.19 ± 0.05 U/ml RBC). Individuals with low-intermediate TPMT activity (<8 U/ ml RBC) did not carry mutant alleles *3A or *3C. TPMT phenotypes were similar in children and adults with inflammatory bowel disease.