Are adipokines related to COVID-19 and its severity? A systematic review and meta-analysis.

Introduction: The relationship between several adipokines and COVID-19 severity has lately been evaluated, results being inconclusive. Therefore, we aimed to assess the association between adipokines in COVID-19 and its severity.
Methods: A search was performed in PubMed, Scopus, and Embase using predefined keywords. The Newcastle of Ottawa Scale (NOS) was used for the quality assessment of included studies. The main summary outcome was the mean difference (MD) in adipokine levels.
Results: A total of 8 studies involving 473 individuals were included. A significant MD in serum adiponectin levels was demonstrated in mild vs. severe COVID-19 patients (-5.734 [95% CI -11.215 - -0.252]), with no significant MD in mild vs. moderate (-7.117 [95% CI -19.546 - 5.313]), or moderate vs. severe COVID-19 (-1.846 [95% CI -4.516 - 0.824]). Moreover, no significant MD was found in adiponectin and leptin levels when comparing COVID-19 patients vs. controls (-12.675 [95% CI -36.159 - 10.808]) and (8.034 [95% CI -10.403 - 26.471]), respectively.
Conclusion: Adiponectin levels were significantly increased in patients with severe compared to mild COVID-19. However, no significant MD was found in adiponectin levels in mild vs. moderate and moderate vs. severe COVID-19 patients, nor in adiponectin and leptin levels in COVID-19 patients vs. controls.