Tittle: Six-month Physical Activity versus Sclerostin and Interleukin 6 Concentration in Patients Receiving Renal Replacement Therapy by Hemodialysis – pilot study

Abstract: Background and Objectives: Chronic kidney disease and renal replacement therapy are associated with reduced physical activity, which may result in the presence of mineralbone disorders and an increase in inflammation markers. The aim of the study was to assess the relationship between the performance of daily physical activity, expressed in the number of steps performed by patients undergoing hemodialysis and the concentration of selected biochemical parameters (SCL, IL-6). Materials and Methods: The study involved 33 patients aged 59.8 ± 9.8 years from the dialysis station at the Department of Nephrology, Transplantology and Internal Medicine PUM. Group C consisted of 30 people aged 54.9 (9.37), with GFR over 60 mL/min/1.73m. The study group was divided into S-N and N-S. Participants of the S-N group were assigned the task of performing the appropriate daily number of steps, and the N-S group was to perform spontaneous physical activity. The tasks were replaced after the third month of the research project. Physical activity was measured with pedometers. Anthropometric and biochemical parameters were assessed at baseline, after the third and sixth month of the study. Descriptive statistics, intergroup comparisons using Mann-Whitney U or Kruskal-Wallis tests and Spearman correlation analysis were performed. The level of significance was set at p≤0.005. Results: Patients from the S-N and N-S groups compared to group C performed significantly fewer steps in the 0-3 month and 4-6 month periods. In the S-N group, with an increase in steps performed in the period of 4-6 months, sclerostin levels dropped in the 6 month. In group C, the concentration of SCL and IL-6 decreased with the increase in the number of steps taken. Only in group C the waist circumference decreased with the increase of the number of steps performed. Conclusions: Patients receiving renal replacement therapy by hemodialysis showed significantly lower physical activity compared to people without kidney disease. Performing bigger number of steps can lower sclerostin levels in hemodialysis patients. Background and Objectives: Chronic kidney disease and renal replacement therapy are associated with reduced physical activity, which may result in the presence of mineralbone disorders and an increase in inflammation markers. The aim of the study was to assess the relationship between the performance of daily physical activity, expressed in the number of steps performed by patients undergoing hemodialysis and the concentration of selected biochemical parameters (SCL, IL-6). Materials and Methods: The study involved 33 patients aged 59.8 ± 9.8 years from the dialysis station at the Department of Nephrology, Transplantology and Internal Medicine PUM. Group C consisted of 30 people aged 54.9 (9.37), with GFR over 60 mL/min/1.73m. The study group was divided into S-N and N-S. Participants of the S-N group were assigned the task of performing the appropriate daily number of steps, and the N-S group was to perform spontaneous physical activity. The tasks were replaced after the third month of the research project. Physical activity was measured with pedometers. Anthropometric and biochemical parameters were assessed at baseline, after the third and sixth month of the study. Descriptive statistics, intergroup comparisons using Mann-Whitney U or Kruskal-Wallis tests and Spearman correlation analysis were performed. The level of significance was set at p≤0.005. Results: Patients from the S-N and N-S groups compared to group C performed significantly fewer steps in the 0-3 month and 4-6 month periods. In the S-N group, with an increase in steps performed in the period of 4-6 months, sclerostin levels dropped in the 6 month. In group C, the concentration of SCL and IL-6 decreased with the increase in the number of steps taken. Only in group C the waist circumference decreased with the increase of the number of steps performed. Conclusions: Patients receiving renal replacement therapy by hemodialysis showed significantly lower physical activity compared to people without kidney disease. Performing bigger number of steps can lower sclerostin levels in hemodialysis patients.


Introduction
Chronic Kidney Disease (CKD) is a major public health problem associated with reduced motor activity. This may result in the occurrence of mineral and bone disorders and an increase in the concentration of inflammation markers [1].
The key role in regulating bone mass and inhibiting anabolic processes of bone formation plays, among others sclerostina glycoprotein encoded within chromosome 17 (region 17q12-q21) in the proximity of the SOST gene [2,3,4]. Mechanical stress is a key regulator that controls bone formation and remodelling involving osteocytes. An increase in concentration of sclerostin (SCL) has been observed from stage 3 of CKD. In patients with end stage renal disease, it is several times higher compared to the population with normal renal function [5][6][7][8][9][10].
The occurrence of inflammation and reduced muscle clearance is associated, among others with an increase in the concentration of interleukin 6 (IL-6)a pleiotropic cytokine (a 26 kDa protein) encoded by a gene located on the short arm of chromosome 7 (7p15-p21) [11][12][13]. The increase in IL-6 concentration occurs already in the early stages of CKD, and reaches a significantly higher level in patients treated with hemodialysis [14,15].
Deterioration of health, malaise and treatment with hemodialysis makes it difficult for patients to perform physical exertion. In addition, the group of patients treated with renal replacement therapy usually has a negative attitude towards physical exertion and cooperation with them in this aspect is extremely difficult. It is important to encourage patients undergoing hemodialysis to physical therapy and modification of their lifestyle by increasing the attractiveness of exercise, monitoring physical activity and highlighting the benefits of regular exercise [16][17][18][19].
The available literature lacks comparative studies on the relationship between regular physical activity and the value of interleukin 6 and sclerostin concentration in patients treated with hemodialysis. Therefore, it is justified to supplement these reports. The topic requires indepth research and a comprehensive approach to the problem.
The aim of the study was to assess the effect of regular six-month physical activity measured by the number of steps on the plasma concentration of sclerostin and interleukin 6 and selected anthropometric parameters in the group of patients receiving renal replacement therapy by hemodialysis.

Group characteristics
The study included 34 patients treated with renal replacement therapy by hemodialysis, with complete absence of diuresis for at least three months, and with a frequency of three hemodialysis sessions a week. The mean duration of a single hemodialysis session was 242.6 ± 25.2 min (X ± SD), and the average duration of hemodialysis treatment was 56 months. Patients with renal replacement therapy by hemodialysis (29 men, 14 women) were qualified for the study (Figure 1), 11 people (5 women and 6 men) did not agree to participate in the research project, justifying this decision with their reluctance to perform physical activity.
Three people (1 man, 2 women) died during the research project, one man had a kidney transplant, and 5 people (1 man, 4 women) resigned from the participation in the study.
Eventually, 33 people (20 men and 13 women) completed the study. Patients were randomly divided into groups S-N (n=16) and N-S (n=17) depending on the intervention given Table 1.
The control group was also selected based on the inclusion and exclusion criteria for the research project. The inclusion criteria were: consent to participate in the study, age over eighteen, normal renal function. The exclusion criteria were the same as in the study group.
78 people (41 men, 37 women) volunteered to participate in the research project ( Figure 1).
Eventually, 30 people (15 men, 15 women) were randomly qualified for the study. There were no statistically significant differences in the mean values of systolic and diastolic pressure and pulse between the groups. Patients selected for the study did not declare any other chronic diseases. No statistically significant differences were observed between groups B and C in terms of gender, age, body weight, BMI and waist circumferences ( Table 2).
The number of hospitalizations was significantly higher in the study group than in the control group.  Range -(minimum-maximum); P-valuestatistical significance; *statistically significant parameter.

The course of the study
The study subjects were given Beurer AS 50 pedometers. Data such as date, time, body weight, step length have been entered into the patient's device and sensitivity of the device was set (in the study group S-N and N-S on a day without hemodialysis).
Participants in both study and control group were asked to perform only physical activity, which can be measured with a pedometer 3 months before the start of the research project and during its duration.
The subjects belonging to the S-N, N-S and C groups were trained to use the pedometer.
Participants in the research program were required to wear the device all the time in one place (on a belt, on a chain or in a pocket), throughout the whole duration of the study, excluding sleep and bath time. Depending on the assignment to a given group (N-S, S-N, K), the subjects were given an intervention (Table 3).

Statistical Analysis
All statistical calculations were performed using the statistical package STATISTICA (data analysis software system version 12.0).
Quantitative variables were characterized by the arithmetic mean, standard deviation, median, minimum and maximum values. Qualitative variables were presented by absolute counts and percentages. Normal distribution was tested using the Shapiro Wilk test. The Mann-Whitney U test was used to assess the significance of differences between the two groups. The significance of differences between more than two groups was verified by the Kruskal-Wallis test. In the event of statistically significant differences between the groups, post hoc tests were used (Dunn's test). Correlation analysis by calculating correlation coefficients or Spearman's rank coefficients was performed to determine the relationship of strength and direction between variables. In all calculations, the level of significance was set at p≤0.05.

Results
The research involved an analysis comparing the study groups and control group in terms of the number of steps performed (Table 4). It was observed that all groups showed statistical significance between the number of steps performed, both during 0-3 and 4-6 months. Post-hoc analysis also showed the relationship between individual groups in the analysis of the tested parameter.  The correlation between the number of steps in the study and control groups and the concentration of sclerostin and interleukin was examined after 3 and 6 months. It was shown that in the control group both SCL and IL-6 levels negatively correlated with the number of steps both after 0-3 months and after 4-6 months. Analyzing the study groups, it was shown that SCL concentration negatively correlated with the number of steps after 4-6 months, but this correlation was observed only in the S-N group (Table 5).  Correlations between the number of steps in the study and control groups were also analyzed in terms of age, body weight, BMI (Table 6). It was shown that in the control group waist circumference and age of patients negatively correlated with the number of steps both after 0-3 and 4-6 months.

Discussion
The literature describes many benefits of exercising and increasing regular physical activity for the health and well-being of patients with chronic kidney disease [22][23][24][25]. Despite this fact, the level of physical activity in this group of patients is significantly lower compared to people with normal renal function [26.27]. The presented work showed that despite the introduced intervention, the total number of steps performed was significantly lower in periods of 0-3 and 4-6 months in groups S-N and N-S compared to C. Similar relationships have been found in publications of other authors [28,29]. This could be influenced by complications associated with chronic kidney disease and renal replacement therapy, as well as by a lack of motivation to exercise [30][31][32][33].
There are many works in which, similarly to the conducted research project, pedometers or accelerometers were used in AF studies as well as tools for monitoring and motivating of renal replacement patients to exercise [34][35][36][37]. It is important that in the presented studies out of 53 patients qualified by a nephrologist only 43 persons entered the study. In the study group there were no patients who stopped performing the intervention. The only exception resulting in cessation of physical activity were independent factors, such as kidney transplantation to a patient treated with renal replacement therapy or death. Prescribed physical exercise performed by hemodialysis patients was completely safe and did not adversely affect their health.
Mechanical stress is a key regulator that controls bone formation and remodelling involving Lack or reduced physical activity may result in an increase in inflammation among people with chronic kidney disease [43]. In turn, regular exercise is particularly important in people with chronic kidney disease because it has anti-inflammatory effects [44].
Many studies have been published on the relationship between physical activity and IL The study showed that there is a negative correlation between the total number of steps performed and waist circumference in the control group. Research by Huang et al. showed that people who exercise systematically have a lower waist circumference [53].
There are few publications assessing the impact of exercise on anthropometric parameters in hemodialysis patients, such as BMI and body weight [54], which may be due to problems arising from the overhydration of patients in the period between dialysis.
Regular physical activity positively affects the physical and mental functioning of a person.
Studies have shown that with age deterioration of the body's cognitive functions, sarcopenia or a decrease in bone mineral density may occur. Age is a good predictor of health condition.
However, there is a large individual variability showing that some elderly people are in good health, while others are weak or disabled [55]. In this study, a negative correlation between age and physical activity, expressed in the number of steps was confirmed only in the control group.
The absence of these relationships among the participants of the study group may be due to their chronic kidney disease, conducted renal replacement therapy or post-dialysis complications, such as fatigue.

Conclusions
The studies showed that intensified, regular physical activity expressed in the number of steps may have an impact on lowering the concentration of the biochemical parameters tested (sclerostin, interleukin 6), but it does not affect the BMI, body weight, waist circumferences in the group of patients treated with hemodialysis. In turn, in the group of patients without endstage kidney disease, a bigger number of steps performed is associated with lower values of both interleukin 6 and sclerostin levels. The key factor is to encourage patients with end-stage renal disease who are being treated with hemodialysis to exercise regularly, as they show significantly lower physical activity compared to patients with normal renal function.

Limitations
The obtained results were influenced by the worsening condition of patients with CKD, renal replacement therapy and the occurrence of various comorbidities. In the study of patients with chronic kidney disease treated with hemodialysis, it was difficult to find people willing to participate in the project assessing their AF. It was also necessary to choose physical activity in a way, which allowed the participants to be able to perform the recommended intervention. The size of the study group during the research project decreased for independent reasons, such as kidney transplants and deaths among project participants. In the study, the psychological aspect of having a pedometer could have made the hemodialysis patients more willing to perform physical activity, even when they did not have the recommended intervention. This could have been an independent factor influencing the course of the study. In the continuation of research, it is necessary to increase the size of the study group, which would allow a more accurate analysis of these relationships.