Effects of phytosterol supplementation on lipoprotein subfractions and LDL particle quality.

Phytosterols are natural components of plant-based foods used as supplements because of their known cholesterol-lowering effect. However, their effects on lipoprotein subfractions and the quality of the LDL particle have not been studied in greater detail. We aimed to evaluate the effects of phytosterols supplements on lipids, lipoproteins subfractions, and on the quality of LDL. A prospective, pilot-type, open label, cross-over study, randomized 23 males in primary prevention of hypercholesterolemia to receive diet or diet plus phytosterol (2.6 g in 2 doses, with meals) for 12 weeks, when treatments were switched for another 12 weeks. Lipoprotein subfractions were analyzed by electrophoresis in polyacrylamide gel (Lipoprint System®). The Sampson equation estimated the small and dense (sd) and large and buoyant (lb) LDL subfractions from the lipid profile. Quality of LDL particle was analyzed by Z-scan and UV-vis spectroscopy. Primary outcome was the comparison of diet vs. diet plus phytosterols. Secondary outcomes assessed differences between baseline, diet and diet plus phytosterol. Non-parametric statistics were performed with p < 0.05. There was a trend to reduction on HDL-7 (p = 0.05) in diet plus phytosterol arm, with no effects on the quality of LDL particles. Heatmap showed strong correlations (ρ > 0.7) between particle size by different methods with both interventions. Diet plus phytosterol reduced TC, increased HDL-c, and reduced IDL-B, whereas diet increased HDL7, and reduced IDL-B vs. baseline (p < 0.05, for all). Phytosterol supplementation demonstrated small beneficial effects on HDL-7 subfraction, compared with diet alone, without effects on the quality of LDL particles.This trial is registered in Clinical Trials (NCT06127732) and can be accessed at https://clinicaltrials.gov .

Necrotic activity of ExhC from Mammaliicoccus sciuri is mediated by specific amino acid residues.

Mammaliicoccus sciuri, a commensal and pathogenic bacterium of significant clinical and veterinary relevance, expresses exfoliative toxin C (ExhC), a specific glutamyl endopeptidase belonging to the chymotrypsin family as the principal virulence factor. However, unlike most members of this family, ETs are inactive against a wide range of substrates and possess exquisite specificity for desmoglein-1 (Dsg1), a cadherin-like adhesion molecule that is crucial to maintain tissue integrity, thereby preventing the separation of skin cells and the entry of pathogens. ExhC is of clinical importance since in addition to causing exfoliation in pigs and mice, it induces necrosis in multiple mammalian cell lines, a property not observed for other ETs. Previous experiments have implicated the ExhC79-128 fragment in causing necrosis. Site-directed mutagenesis of specific residues within this fragment were studied and led to the design of an ExhC variant containing four-point mutations (ExhCmut4) lacking necrotic potential but retaining nearly wild-type (wt) levels of enzymatic activity. Moreover, the determination of the ExhCwt and ExhCmut4 crystal structures identified the conformation in the necrosis-linked region. These results constitute an important step toward the understanding of the mechanisms underlying the necrotic and epidermolytic activity of ExhC.

Staphylococcus aureus Exfoliative Toxin E, Oligomeric State and Flip of P186: Implications for Its Action Mechanism.

Staphylococcal exfoliative toxins (ETs) are glutamyl endopeptidases that specifically cleave the Glu381-Gly382 bond in the ectodomains of desmoglein 1 (Dsg1) via complex action mechanisms. To date, four ETs have been identified in different Staphylococcus aureus strains and ETE is the most recently characterized. The unusual properties of ETs have been attributed to a unique structural feature, i.e., the 180° flip of the carbonyl oxygen (O) of the nonconserved residue 192/186 (ETA/ETE numbering), not conducive to the oxyanion hole formation. We report the crystal structure of ETE determined at 1.61 Å resolution, in which P186(O) adopts two conformations displaying a 180° rotation. This finding, together with free energy calculations, supports the existence of a dynamic transition between the conformations under the tested conditions. Moreover, enzymatic assays showed no significant differences in the esterolytic efficiency of ETE and ETE/P186G, a mutant predicted to possess a functional oxyanion hole, thus downplaying the influence of the flip on the activity. Finally, we observed the formation of ETE homodimers in solution and the predicted homodimeric structure revealed the participation of a characteristic nonconserved loop in the interface and the partial occlusion of the protein active site, suggesting that monomerization is required for enzymatic activity.