Cytokines of the IL-6 family, adiponectin and leptin levels in patients with metabolic syndrome during the post-COVID period

COVID-19 is a multisystem disease, but the extent of its consequences is currently poorly understood, especially in the persons with metabolic disorders. The aim of the present study was to evaluate the special changes in the cytokines of IL-6 family (IL-6 and sIL-6, LIF and sLIFr), adiponectin and leptin within 360 days after SARS-CoV-2 infection in the patients with metabolic syndrome (MetS), to discern features of immunopathogenesis depending on previous vaccination against COVID-19. We have classified the patients in two groups: (1) patients with MetS who underwent COVID-19 6-12 months after full-course vaccination with a vector vaccine (n = 32); (2) patients with MetS who underwent COVID-19 without story of vaccination (n = 29). Control group included conditionally healthy individuals without MetS: (3) vaccinated, and (4) non-vaccinated, who also had COVID-19. The levels of IL-6 and sIL-6, LIF and sLIFr, leptin and adiponectin, NO, ADMA, SDMA were determined by ELISA technique. In patients with MetS, changes in cytokine regulation towards proinflammatory reactions were revealed (an increase in blood IL-6 and leptin levels), which was most pronounced in MetS within first 30 days post-COVID, but with a number of changes which remained for 12 months (e.g., increased leptin concentration in blood). Vaccination against COVID-19 reduced the severity of pro-inflammatory changes in the sIL- 6r/ IL-6 and leptin/adiponectin systems towards protective adiponectin. However, the persistent increase in leptin was not canceled. When interpreting these results, no negative differences were revealed in the group of once vaccinated individuals with MetS, concerning the mentioned cytokine regulations of MetS over 1 year after COVID-19. The univariate, and then multifactorial correlation analysis between serum contents of sIL- 6r/ IL- 6, LIF/ sLIFr, adiponectin and leptin and the levels of vasoactive substances (NO, ADMA and SDMA), glycated hemoglobin, LDL has shown that the increased ratio of sIL-6r/IL-6 is an independent factor for the NO reduction of (r = 0.74, p 0.01); an increase in sLIFr positively correlates with increase in glycated hemoglobin (r = 0.69, p 0.01), and an association with increase of ADMA (r = 0.82, p 0.001), leptin (in this model) are shown to be an independent factor of LDL increase (r = 0.69, p 0.05). Influence of pre-COVID modifiable factors, in particular, vaccination, is relevant in terms of reducing the likelihood of progression of pre-existing chronic diseases (hypertension, atherosclerosis, diabetes mellitus) in the persons with MetS after COVID-19 and has prospects for implementation into clinical practice.