THE COURSE OF CHRONIC KIDNEY DISEASE (CHRONIC PYELONEPHRITIS) IN PATIENTS WITH NON-ALCOHOLIC FATTY LIVER DISEASE AND OBESITY.

The aim of the research: to investigate the features of the comorbid course of chronic kidney disease (CKD) (chronic pyelonephritis), non-alcoholic fatty liver disease and obesity, depending on the stage of CKD. – stage II – CKD stage III – 45 subgroups: CKD stage I – CKD stage II – 31 patients, CKD stage III – 27 17.5% in patients without NASH), and in 4.9% of patients with comorbidity – no functional reserve of the kidneys (p > 0.05), indicating irreversible changes in the functional state of the kidneys.


Introduction/Вступ
According to various authors, the current problem of modern internal medicine is chronic kidney disease (CKD). As of January 1, 2015, about 500 thousand people with stage I-V CKD were registered in Ukraine. CKD is defined as an independent factor in the growth of cardiovascular risk and the equivalent of coronary heart disease [1][2][3].
As cited in literature, chronic kidney disease (CKD) goes with an increase of the nitrogen metabolism products in the systemic circulation on the background of hypoalbuminemia, hyper-and dyslipidemia, activation of oxidative and nitrositive stress on the background of significant suppression of antioxidant defense, activation of connective tissue system, inhibition of erythropoiesis, endothelial dysfunction, significant disorders of peripheral and organ (liver, kidney, myocardium) blood circulation [1][2][3][4]. All these components of the CKD pathogenesis can also be pathogenic components of non-alcoholic fatty liver disease (NAFLD), especially if they are caused by the development of chronic pyelonephritis, the influence of metabolic syndrome with hyperuricemia syndrome.
The frequency of comorbid course of NAFLD associated with obesity reaches 70-95%, the frequency of comorbidity of CKD associated with obesity is 25-30%, and in the background of hyperuricemia and kidney stone disease (KSD) it reaches 50-60% [3,4,5]. At the same time, the clinical features of the comorbid course of NAFLD with CKD and obesity are currently unknown, and the mechanisms of their mutual burdening have not been established.
The аim of research: to investigate the features of the comorbid course of chronic kidney disease (CKD) (chronic pyelonephritis), non-alcoholic fatty liver disease (NAFLD) and obesity, depending on the stage of CKD.
Material and methods. To achieve this goal, 250 patients with CKD (chronic bilateral pyelonephritis) stage I-III were examined, of which 160 patients had concomitant nonalcoholic steatohepatitis (NASH) and class 1 obesity (group 1) and 90 people had CKD stage I-III without NASH and obesity (group 2). Depending on the stage of CKD, patients of group 1 were divided into 3 subgroups: with CKD stage I -63 patients, with CKD stage II -52 patients, and with CKD stage III -45 patients. Patients of group 2 were also divided into 3 subgroups: with CKD stage I -32 patients, with CKD stage II -31 patients, and with CKD stage III -27 patients.
The control group included 30 apparently healthy individuals (AHIs). An average age of patients was 49.8 ± 5.8 years. The study did not include patients with CKD stage I-III with nephrotic syndrome and patients with chronic uncomplicated pyelonephritis in the phase of exacerbation.
The diagnosis of nonalcoholic steatohepatitis was established in accordance with the Before testing the statistical hypotheses, the analysis of the normality of the distribution of values in randomized samples was performed by determining the coefficients of asymmetry and excess using the Khan-Shapiro-Wilkie test. The probability of the difference of the arithmetic mean and its error between the study groups was determined using the bilateral odd Student's t-test. The difference was considered significant at a significance level of p < 0.05. Student's t-test was used only in the case of a normal distribution of equality of the general variances of the compared samples, which was verified using Fisher's F-test. In other cases, a nonparametric Mann-Whitney rank test was used to compare the results. The probability of changes in the dynamics of treatment in the case of normal distribution in the samples was determined by Student's paired test, in other casesby non-parametric paired T-test of Wilcoxon. For statistical analysis of the obtained results we used Statistica for Windows version 8.0 (Stat Soft Inc., USA), Microsoft Excel 2007 (Microsoft, USA) software packages.
Research results. According to the results of our study, it was found that the content of creatinine in the plasma of patients of groups 1 and 2 with stage I chronic kidney disease was significantly different, namely in patients of group 1 the value exceeded the data in healthy individuals by 1.6 times (p < 0.05), in group 2by 1.4 times (p < 0.05) ( Table 1); in patients with stage II chronic kidney disease in group 1 the creatinine content exceeded the value in healthy individuals by 1.6 times vs. 1.4 times in group 2 (p < 0.05). Accordingly, in patients with stage III CKD, the content of creatinine in group 1 exceeded the data in AHIs by 2.3 times (p < 0.05), in group 2by 1.9 times (p < 0.05), in all cases the difference between the groups was significant (p < 0.05) ( Table 1).

Table 1 -Indicators of renal function in patients with comorbid non-alcoholic steatosis of the liver and steatohepatitis and chronic kidney disease (M ± m)
Indicators, units Thus, concomitant non-alcoholic fatty liver disease significantly affects the functional parameters of the kidneys, in particular, their nitrogen-releasing function. This position is confirmed by the obtained data on the content of urea in the blood in a comparative aspect between the groups (Table 1). Thus, the content of urea in the blood of patients with CKD stage I exceeded the values in AHIs in groups 1 and 2 by 2.5 and 2.3 times, respectively, (p < 0.05). In patients with CKD stage II in group 1, the urea content exceeded the values in AHIs by 2.6 times vs. 2.5 times in group 2 (p < 0.05). In patients with CKD stage III, the content of urea in the blood of patients in group 1 exceeded the data in AHIs by 2.9 times (p < 0.05), in group 2by 2.5 times (p < 0.05), given a significant intergroup difference (p < 0.05).
We found that the rate of albumin in the blood of patients with CKD stage І was lower than in AHIs in groups 1 and 2 by 1.4 and 1.3 times (p < 0.05), respectively. In particular, in patients with CKD stage II in group 1, the albumin content was 1.5 times lower than in AHIs vs. 1.4 times in group 2 (p < 0.05). Accordingly, in patients with CKD stage III the content of albumin in the blood of patients in group 1 was 1.5 times lower than normal values (p < 0.05), in group 2by 1.4 times (p < 0.05). In consequence of these changes, there was a significant decrease in the glomerular filtration rate (GFR) according to the Cockcroft-Gault creatinine clearance calculated by CKD-EPI (Table 1). Thus, the creatinine clearance index according to the Cockcroft-Gault formula in patients with CKD stage I was lower than in AHIs only in patients of group 1 (by 11.8%) (p < 0.05), in patients of group 2 changes were not statistically significant and a significant difference between groups was not found (p > 0.05). In patients with CKD stage II in group 1, the creatinine clearance was lower than in AHIs by 39.2% vs. a decrease of 25.5% in group 2 (p <0.05) with a statistically significant difference between the groups (p <0.05). At the same time, in patients with stage III CKD, the creatinine clearance in patients of group 1 was lower than normal values by 55.9% (p < 0.05), in group 2by 44.1% (p < 0.05), with a significant difference between patients with combined NASH and CKD in comparison with patients with CKD without comorbid diseases (p < 0.05). The calculation of GFR by SKD-EPI indicated a higher accuracy of GFR estimation, as the values differed significantly between comparison groups, indicating the probability of our working hypothesis. Thus, the GFR in patients with stage I CKD was lower than in AHIs in patients of group 1 by 1.5 times (p < 0.05), in patients of group 2by 1.3 times (p < 0.05) with confirmation of a statistically significant difference between the groups (p < 0.05). In patients with CKD stage II in group 1, GFR was lower than in AHIs by 1.9 times vs. a decrease by 1.6 times in group 2 (p < 0.05) with confirmation of a statistically significant difference between groups (p < 0.05). At the same time, in patients with CKD stage III, GFR in patients of group 1 was 2.7 times lower than normal values (p < 0.05), in group 2by 2.2 times (p < 0.05), with a significant difference between patients with comorbid NASH and CKD stage II and III in comparison with patients with isolated CKD of the corresponding stage (p < 0.05). Thus, in patients with comorbid CKD and nonalcoholic steatohepatitis, GFR was significantly reduced compared to patients with CKD without comorbidity.
In the study of values of inflammatory process activity in patients with CKD plus NASH in comparison with the isolated course of CKD, the following data were obtained (Table 2). Thus, in patients with stage I CKD in group 1, the rate increased by 6.9 times compared with AHIs (p < 0.05), and in group 2by 5.7 times (p < 0.05) ( Table 2). In patients with CKD stage II in group 1, the number of leukocytes in 1 ml exceeded normal values by 7.9 times vs. 6.8 times in group 2 (p < 0.05). In patients with CKD stage III, the content of leukocytes in patients of group 1 exceeded the normal values by 11.1 times (p < 0.05), in group 2by 8.2 times (p < 0.05), with a significant intergroup difference (p < 0.05). When comparing the number of erythrocytes by urine analysis according to Nechiporenko, it was found that in patients with stage I CKD, the indicator exceeded the data in AHIs by 5.7 times (p < 0.05), and in group 2by 4.6 times (p < 0.05) ( Table 2). In patients with CKD II stage in group 1, the number of erythrocytes in 1 ml exceeded the normal values by 6.9 times vs. an increase of 5.6 times in group 2 (p < 0.05). In patients with CKD stage III the content of erythrocytes in the urine of patients in group 1 exceeded the normal values by 7.4 times (p < 0.05), in group 2by 6.0 times (p < 0.05), in all cases with a significant difference between the groups (p < 0.05).
We found the following results on cylindruria when comparing data in patients of groups 1 and 2 with CKD stage I: increase by 4.9 and 3.6 times (p < 0.05), with CKD stage II 232 This work is licensed under Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/ by 6.3 and 3.6 times (p < 0.05), and with CKD stage IIIan increase by 7.8 and 6.9 times (p < 0.05), with a significant difference between groups (p < 0.05). Analysis of the presence of bacteria in the urine also showed a significant intergroup difference in the values in patients with CKD with NASH and without concomitant pathology (p < 0.05) ( Table 2).   The significant impact on GFR of indicators that contribute to the endothelial dysfunction and its direct biochemical markers should be pointed out. In particular, there was a significant impact of hydrogen sulfide deficiency, hyperhomociteinemia, overproduction of the endothelin-1 and increased expression of iNOS on GFR, which led to the hyperproduction and impaired excretion of nitric oxide metabolites with activation of nitrositic distress and redistributive vascular tone abnormality, that have also impacted the decrease of GFR on patients with CKD and NASH (p < 0.05). The obtained data significantly complement the concept of the pathogenesis of the mutual burden of CKD and NASH, obesity, and contribute to the search for new, previously unknown mechanisms of their progression.

Table 2 -Indicators of the inflammatory process in patients with comorbid non-alcoholic steatosis of the liver and steatohepatitis and chronic kidney disease
The decrease in GFR depends on two groups of reasons: a decrease in the number of functioning nephrons, which can occur in pathology of the kidneys after their death; this is a temporary decrease in GFR in functioning nephrons due to systemic or local hemodynamic changes. The present shows that the estimated GFR required to establish the GFR stage does not indicate renal reserve capacity in response to stimuli, or may change under certain circumstances, conditions, and comorbidity with other somatic pathologies. GFR parameters recorded at the state of functional rest are not sufficient to conclude on the number of functioning nephrons and the functional capabilities of the active ones. In this regard, it is important to study the indicator of functional renal reserve (FRR). The fact of increasing GFR in response to a certain stimulus indicates the presence of a reserve of filtration capacity of the kidneys. The quantitative measure of the reserve is 233 This work is licensed under Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/ the difference between the maximally stimulated GFR and its basal level. Depending on the change in GFR in response to stimuli, there are: preserved FRR, ie the ability of the kidneys to increase GFR by more than 10%, decreased FRRwith an increase in GFR in response to the stimulus by 5-10%; no filtration reservewith an increase in GFR of less than 5%. In healthy individuals, the increase in GFR in response to functional stimulation ranges 10-60%, which reflects the preservation of FRR and the normal level of pressure in the renal capillaries. The absence of FRR indicates that the level of GFR, in which the kidney works, is extremely high and is considered the equivalent of hyperfiltration.
The clinic often uses a water-salt load of 0.5% sodium chloride solution with a volume of 0.5% of the patient's body weight. In nephrologically healthy individuals, GFR increases after salt load due to the inclusion of FRR, which averages 50%. Studies conducted in patients with CKD stage I and stage II showed that despite the signs of kidney damage, FRR not only did not decrease, but on the contrary, it increased within 20-30% [8][9]. That is, in the initial stages of CKD, there is damage to the nephrons, but their number does not decrease. This is evidence of the possibility of pathogenetically justified influence on the course of CKD. Therefore, the working hypothesis of our study is to test the presence and degree of FRR in patients with CKD for comorbidity with NASH and obesity and on the basis of the results, to assess the development of pathogenetic methods for the correction of established disorders. At present, the features of the functional state of the kidneys with the study of FRR for comorbidity of CKD with NASH were not evaluated. Thus, the aim of the next stage of our study was to establish changes in the functional reserve of the kidneys depending on the stage of chronic kidney disease (pyelonephritis) in comorbidity with NASH and obesity.
Analysis of the values indicating the functional reserve of the kidneys after water-salt load showed significant differences between the groups of comparison (Table 3). Plasma creatinine decreased after exercise in patients with CKD stage I in groups 1 and 2, but exceeded the values in AHIs by 1.5 and 1.3 times, respectively (p < 0.05). The calculated GFR and glomerular filtration by creatinine clearance in spontaneous diuresis did not differ ( Table 3).
Calculation of FRR after induced salt diuresis showed an increase in GFR in patients of both groups, but more significantly in patients without comorbidity with NASHby 36.6% vs. 31.1% in group 1 (p < 0.05), which indicated the presence of sufficient functional renal reserve in patients with CKD stage I and lower reserve capacity for comorbidity with liver pathology ( Table 3). The rate of urination under salt load in comparison with spontaneous diuresis significantly increased in patients of both groups (p < 0.05). An interesting pattern was shown by the results of a study of the functional state of the kidneys regarding the content of creatinine in urine, which increased in both groups of patients with CKD stage I by 1.8 and 1.6 times (p < 0.05), respectively. Indeed, the use of water-salt stimulation and determination of FRR makes it possible to assess the functional state of the urinary system, and also to develop tactics for the possibility of its correction through the use of polyelectrolyte mixtures and drugs of amino acid origin.
Similar trends were found in the results of the study of FRR in patients with CKD stage II, in particular, GFR increased in groups 1 and 2 by 19.3% and 28.9%, respectively, (p < 0.05) with a significant intergroup difference (p < 0.05) remaining lower than the normative indicators by 2.0 and 1.5 times, respectively (p < 0.05). Urine creatinine after stimulation also increased and exceeded the data in AHIs by 2.2 and 1.9 times (p < 0.05). On the background of diuresis increase mainly in patients of group 2, the rate of creatinine excretion was increasing more intensively in patients of group 2 and exceeded the data in AHIs by 2.1 times vs. 1.4 times in group 1 (p < 0,05). The increase of diuresis and urinary flow rate under water-salt load results from the increased filtration on the background of constant reabsorption.
FRR with water-salt load in patients with CKD stage I-II at both groups were positive and sufficient, when calculating it by detecting an increase in filtration, both by GFR and glomerular filtration by creatinine clearance (p < 0.05) ( Table  4)  0.028 ± 0.0001*/** 0.026 ± 0.0002*/** 0.020 ± 0.0001*/** Notes: * -changes are probable in comparison with the indicator in practical healthy person (p < 0.05); ** -changes are probable in comparison with the indicator in the group of patients with the corresponding stage of CKD with comorbid NASH and obesity (p < 0.05) In patients with CKD stage III in group 1, after water-salt load GFR increased by only 8.9% (p < 0.05), while in group 2by 17.5% (p < 0.05). This may be due to the presence of comorbid liver disease (NASH) and is regarded as decreased FRRan increase in GFR in response to stimulus in the range of 5-10%. In two patients of group 1 (4.9%), the increase in GFR was 3.2% and FRR was absent, which indicated significant renal damage under the influence of liver dysfunction and a decrease in functioning renal parenchyma, in particular due to their fibrosis.

Conclusions/Висновки
In patients with CKD stage I-II without comorbid NASH and obesity, we found a significantly higher renal functional reserve in response to water-electrolyte stimulation, which is sufficient in both groups of patients (increase in GFR by 28-37% vs. 19-31% for comorbidity with NASH). In patients with CKD stage III with nonalcoholic steatohepatitis we found a significantly reduced functional reserve of the kidneys (increase in GFR by 8.9% vs. 17.5% in patients without NASH), and in 4.9% of patients with comorbidityno functional reserve of the kidneys (p > 0.05), indicating irreversible changes in the functional state of the kidneys. There was a significant correlation between a decrease in glomerular filtration rate (GFR), an increase in the intensity of oxidative stress, a decrease in blood glutathione, hydrogen sulfide, hyperproduction of homocysteine, cytokeratin-18, connective tissue components (collagen, sialic acids).