Introduction
Chronic Kidney Disease (CKD), is a syndrome characterized by the
progressive and irreversible loss of nephrons due to various diseases
[1,2]. CKD has not only significantly increased morbidity and
mortality, but also decreases quality of life. The risk of mortality in
hemodialysis (HD) patients is about 10 to 20 times higher than in the
general population [3]. In these patients, many molecules (e.g.
uremic toxins) accumulate in the body which contributes to uremic
symptoms and increases mortality [4]. High level of uremic toxins
lead to increased oxidative stress in several tissues. Furthermore,
increased oxidative stress has negative effects on macromolecules such
as lipids, proteins, and nucleic acids [5].
It is well known that oxidative balance is disrupted due to
overproduction of free radicals and insufficient antioxidant system in
HD patients. Therefore, there are many studies analyzing oxidative
stress levels in HD patients [6-8]. Enzymatic and non-enzymatic
defense mechanisms against the harmful effects of free radicals are
known to exist. One of these antioxidant mechanisms is the presence of
thiol-containing compounds. Thiols, also called mercaptans, are
sulfhydryl group-containing (-SH) compounds. The main target of free
radicals is thiol groups in the sulfur-containing amino acids of
proteins. Thiol groups interact with free radicals to form reversible
disulfide bonds it then reduced back to thiol groups by several
antioxidants. Thus, dynamic thiol-disulfide balance is achieved [9].
Dynamic thiol-disulfide balance has a vital role in the organism and is
important to maintain this balance. Thiol-disulfide balance has been
measured in only one direction since 1979, but henceforth with novel
automated method developed by Erel et al., the level of both variables
can be measured distinctly and collectively [10]. In the literature,
there are studies related to analysis of thiol levels in CKD patients,
but yet there is no study showing the effect of dynamic thiol-disulfide
balance and hemodialysis on thioredoxin reductase enzyme levels.
Thioredoxin reductase (TrxR) is a homodimeric flavoenzyme responsible
for the catalysis of thioredoxins. TrxR is also of vital importance in
controlling intracellular redox medium, cell growth, and apoptosis
[11]. Thus, TrxR plays a pivotal role in the pathophysiology of
chronic diseases. The sulfhydryl groups of thioredoxins are involved in
cellular regulation of various biochemical mechanisms with different
functions and the regeneration of inactive proteins as a result of
oxidative stress [12]. In this study, we addressed to indicate the
relationship between the dynamic thiol-disulfide balance, systemic
oxidative stress parameters and TrxR enzyme levels in CKD (stage 3-5)
and HD patients.