TNF and chronic kidney disease: The median of TNF-α was slightly, but not significantly, increased in patients who did not take β-blockers compared to patients on β-blocker therapy (p = 0.406); see Figure 3B. The median level of Cu/Zn SOD, which is a recognized marker of oxidative stress in the population of CKD patients [30,31], was similar in all study groups and amounted to 56 (24–86) ng/mL in the controls, 56 (28–262) ng/mL in the patients treated with β-blockers, and 63 (24–196) ng/mL in the patients who did not take β-blockers (Figure 3C).