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Worldwide, chronic kidney disease (CKD) affects eight to sixteen percent of the population. It is a leading cause of morbidity and mortality, and this implies a high social burden . CKD greatly impairs individuals’ quality life, especially in those with the most advanced stages or who are on replacement therapy . Hemodialysis continues to be the most common form of replacement therapy [3]; despite its advantages, hemodialysis entails a reduced adherence to treatment, poor eating habits, and low physical activity , which in turn further impair the patient’s physical, functional, metabolic, social, and mental status . In addition, adverse therapeutic effects may complicate the clinical picture.
CKD progresses in different ways among individuals, and these differences might not be explained by clinical conditions in patients, suggesting that the genetic component is important . For these reasons, we assume that SNPs in genes involved in the inflammatory response influence CKD progression to some degree.This research aimed to identify both the inflammatory determinants based on the estimation of relevance and the effect of serum concentrations of cytokines IL-6 and IL-10 related to the SNPs IL-6 -572 G/C and IL-10 -1082 A/G on the associated morbidity in patients receiving hemodialysis.
The cross-sectional study was performed at the Hospital Regional No. 46 of the IMSS in Guadalajara, Jalisco. Inclusion criteria:It enrolled subjects from Western Mexico diagnosed with stage 5 CKD according to the KDIGO guidelines and who attended their morning or evening hemodialysis sessions during October 2022.
Exclusion criteria: Patients with active infectious diseases, immunodeficiencies, cancer, morbid obesity, or any neuropsychiatric disease were omitted.Those who did not complete the questionnaires or whose sample was lost were excluded.
Measures
Cytokine Serum Levels: A 4-mL peripheral blood sample was collected in EDTA vials through the hemodialysis vascular line at the beginning of the treatment session and was subsequently used to determine IL-10 and IL-6 levels..ELISA kits ( IL-10, IL-16) -The result of cytokine levels was expressed in picograms per milliliters (pg/mL).
Patient Health Questionnaire-9 (PHQ-9): Screening depressive symptoms and their severity. The PHQ-9 consists of 9 questions that are based on the 9 DSM-IV.Scores for each item on the PHQ-9 range between .0 (not at all) -1 (several days) .2 (more than half of the days). 3 (almost every day). The summed scores range from 0 to 27. Each score was classified as follows: 0 to 4 points, absence of depressive symptoms; 5 to 9 points, minimal symptoms .10 to 14 points, minor depressive symptoms .15 to 19 points, moderate major depress. >20 points, severe major depression according to the manual of the questionnaire.
Malnutrition Inflammation Score (MIS):Which consists of anthropometric measurements, biochemical data, and subjective global assessment (SGA) components, was used to assess nutritional status.The questionnaire consists of five sections: medical history, dietary intake, physical examination, body mass index (BMI), biochemical parameters, and total iron binding capacity (TIBC) or transferrin; each MIS component is assigned to one of four severity levels ranging from 0 (normal) to 3 (very severe). The total score is the sum of the 10 components assessed and ranges from 0 to 30.It was categorized as follows: normal nutritional status: 0, 1, and 2 points; Mild malnutrition: 3–5; Moderate malnutrition: 6–8; Severe malnutrition: from 9 points.
Genotypes:We extracted blood genomic DNA with the PureLink® Genomic DNA Mini Kit Cat. Number K1820-01 and NucleoSpin®Blood Mini Kit. DNA samples were stored at −80 °C until used to analyze the single nucleotide polymorphism (SNP) IL-6-572C/G (db SNP ID rs1800796) and IL-10-1082A/G (db SNP ID rs1800896). We searched these SNPs by coupling the polymerase chain reaction (PCR) with the restriction fragment length polymorphism (RFLP) technique.
Demographic and General Characteristics
Complete data were obtained from 85 individuals, including 47 (54%) men, with a mean age of 41 ± 15 years. About half of them (49.4%) perceived their health status as regular; renal hypoplasia was the leading cause of CKD (41.2%). The mean subject’s weight was 63.8 ± 17.3 kg and 48.2% of participants had normal weight by body mass index (BMI).
Serum Levels of IL-6 and IL-10.Serum levels of both cytokines were expressed as medians (interquartile range) and were classified into two groups (Table 2: out of range (quartiles 1 and 4) and in range (quartiles 2 and 3). IL-6 had a median of 37.33 (0.00–258.17) pg/mL with out-of-range values (44.0–269.8) in 75% of patients, while IL-10 had a median of 22.33 (0.00–141.50) pg/mL with out-of-range concentrations (22.3–141.5) in 71.8% of the patients.
Associated Morbidity. Based on the individuals’ responses to the MIS and PHQ-9 questionnaires, we categorized the variables malnutrition–inflammation and depressive symptomatology by the sum of the items. For the latter, the mean score was 6.7 ± 7.1. Table 3 shows the frequency of associated morbidities. According to MIS and PHQ-9 scores, 85.9% (73) of the subjects had some degree of malnutrition and 50.6% (43) reported minimal to severe depression. The frequency of the out-of-range levels for both cytokines and the most prevalent genotype for either SNP in each category of clinical outcome are also described.
Inflammatory Determinants.Using the CIBER method, we identified that the most relevant determinant of malnutrition–inflammation and depressive symptomatology was IL-10 with coefficients (R2) of 0.05 and 0.11, respectively .
Association of Genotypes and Cytokine Levels at Clinical OutcomeTo identify the association of genotypes with cytokine levels on malnutrition–inflammation severity and depressive symptomatology, we built a simple regression model between predictors (cytokines) and targets (MIS and PHQ-9 scores) where such genotypes were covariates.For depression symptom severity, the C allele of IL-6-572 G/C showed no effect on the PHQ-9 score (GC–GG, δ = 0.1), meanwhile the GG genotype of IL-10-1082 A/G exhibited a small effect on symptom severity (GG–AA, δ = −0.35).
The increased prevalence of malnutrition–inflammation and depressive symptomatology here observed agrees with the highly associated morbidity documented in individuals with CKD receiving hemodialysis. Moreover, we identified IL-10 as an inflammatory determinant for associated morbidity and that IL-6-572 G/C and IL-10-1082 A/G SNPs contribute to the severity of malnutrition–inflammation and depressive symptoms.Our findings support the claim that the interaction between traditional and non-traditional factors increases long-term morbidity and mortality in patients undergoing hemodialysis. Accordingly, we suggest a more extensive evaluation of nutritional, psychological, and neuroimmune parameters as well as the multidisciplinary management of CKD integrating behavioral interventions, targeted nutritional therapies, and an assessment of biomarkers of inflammation to prevent or delay the disease’s progression. Lastly, prospective studies that include more clinical, psychological, endocrine, and immunological parameters of CKD at various stages must refine the causal relationship between inflammation and associated morbidity in CKD.