Background: From the start of the COVID-19 pandemic, new SARS-CoV-2 variants have emerged that potentially affect transmissibility, severity, and immune evasion in infected individuals. In the present systematic review, the impact of different SARS-CoV-2 variants on clinical outcomes is analyzed. Methods: A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020. Two databases (PubMed and ScienceDirect) were searched for original articles published from 1 January 2020 to 23 November 2021. The articles that met the selection criteria were appraised according to the Newcastle–Ottawa Quality Assessment Scale. Results: Thirty-three articles were included, involving a total of 253,209 patients and 188,944 partial or complete SARS-CoV-2 sequences. The most reported SARS-CoV-2 variants showed changes in the spike protein, N protein, RdRp and NSP3. In 28 scenarios, SARS-CoV-2 variants were found to be associated with a mild to severe or even fatal clinical outcome, 15 articles reported such association to be statistically significant. Adjustments in eight of them were made for age, sex and other covariates. Conclusions: SARS-CoV-2 variants can potentially have an impact on clinical outcomes; future studies focused on this topic should consider several covariates that influence the clinical course of the disease.

Family history of type 2 diabetes mellitus (T2DM) is one of risk factors for that in future a subject can develop diabetes. Insulin resistance (IR) is important in the pathogenesis of T2DM. There is evidence that oxidative stress plays an important role in the etiology and/or progression of diabetes. Myeloperoxidase (MPO) participates in developing of inflammation. The objective was to investigate if MPO is associated with IR and inflammation in individuals with first-degree relatives of T2DM. Cross-sectional study in 84 overweight individuals with family history of T2DM divided in two groups according to IR, group with IR (homeostasis model assessment [HOMA] ≥2.5; n=43) and control group (CG; HOMA <2.5; n=41). Complete clinical history and a venous blood sample were collected for measuring glucose and lipids profile, insulin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), MPO, glutathione reductase (GRd), glutathione peroxidase, and superoxide dismutase. MPO, TNF-α, and IL-6 were higher in patients with IR than in CG (MPO: 308.35 [190.85 to 445.42] vs. 177.35 [104.50 to 279.85], P=0.0001; TNF-α: 13.46 [10.58 to 18.88] vs. 9.39 [7.53 to 11.25], P=0.0001; IL-6: 32.93 [24.93 to 38.27] vs. 15.60 [12.93 to 26.27]; P=0.0001, respectively). MPO was associated with IR (rho de Spearman=0.362, P=0.001). In the analysis of lineal regression, MPO predicts IR (β, 0.263; t, 2.520; P=0.014). In the univariate analysis, MPO had an odds ratio of 9.880 for risk of IR (95% confidence interval, 2.647 to 36.879). MPO had relation with IR and inflammation parameters in overweight subjects with first-degree relatives of T2DM. We need studies on a casual relationship and molecular mechanisms among the increased serum MPO levels, inflammation markers, and IR.

Knowledge about the immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, particularly regarding the function of eosinophils, has been steadily emerging recently. There exists controversy regarding the implications of eosinophils in the coronavirus disease 2019 (COVID-19)’s pathology. We report a retrospective cohort study including the comparison of leukocyte counts in COVID-19 patients, considering the outcomes of recovery (n = 59) and death (n = 60). Among the different types of leukocytes, the eosinophil counts were those that showed the greatest difference between recovered and deceased patients. Eosinopenia (eosinophil count < 0.01 × 10⁹/L) was more frequently observed in deceased than recovered patients (p = 0.0012). The eosinophil counts more rapidly increased and showed a greater proportion over the course of the disease in the recovered than deceased patients. Furthermore, the estimated survival rate was greater in patients without eosinopenia than in patients with eosinopenia (p = 0.0070) during hospitalization. Importantly, recovered but not deceased patients showed high negative correlations of the eosinophils with the neutrophil-to-lymphocyte ratio (NLR) and neutrophil counts at Day 9 of the onset of clinical symptoms (p ≤ 0.0220). Our analysis suggests that eosinopenia may be associated with unfavorable disease outcomes and that the eosinophils have a beneficial function in COVID-19 patients, probably contributing by controlling the exacerbated inflammation induced by neutrophils.