Statin resistance in Candida glabrata

Effect of Ginkgo biloba extract on pharmacology and pharmacokinetics of atorvastatin in rats with hyperlipidaemia

Ginkgo biloba extract (GBE) is a common dietary supplement used by people with dyslipidaemia worldwide to reduce the risk of cardiovascular disease. Many studies have found that GBE itself has a variety of pharmacological activities. However, the role of GBE as an adjunct to conventional therapy with chemical drugs remains controversial. Therefore, this study explored the additional benefits of GBE in the treatment of hyperlipidaemia with statins in terms of both pharmacodynamics and pharmacokinetics. A hyperlipidaemia model was established by feeding rats a high-fat diet for a long time. The animals were treated with atorvastatin only, GBE only, or a combination of atorvastatin and GBE. The results showed that statins combined with GBE could significantly improve the blood lipid parameters, reduce the liver fat content, and reduce the size of adipocytes in abdominal fat. The effect was superior to statin therapy alone. In addition, the combination has shown additional liver protection against possible pathological liver injury or statin-induced liver injury. A lipidomic study showed that GBE could regulate the abnormal lipid metabolism of the liver in hyperlipemia. When statins are combined with GBE, this callback effect introduced by GBE on endogenous metabolism has important implications for resistance to disease progression and statin resistance. Finally, in the presence of GBE, there was a significant increase in plasma statin exposure. These results all confirmed that GBE has incremental benefits as a dietary supplement of statin therapy for dyslipidaemia.

Antifungal Activity of Fibrate-Based Compounds and Substituted Pyrroles That Inhibit the Enzyme 3-Hydroxy-methyl-glutaryl-CoA Reductase of Candida glabrata (CgHMGR), Thus Decreasing Yeast Viability and Ergosterol Synthesis

Due to the emergence of multidrug-resistant strains of yeasts belonging to the Candida genus, there is an urgent need to discover antifungal agents directed at alternative molecular targets. The aim of the current study was to evaluate the capacity of three different series of synthetic compounds to inhibit the Candida glabrata enzyme denominated 3-hydroxy-methyl-glutaryl-CoA reductase and thus affect ergosterol synthesis and yeast viability. Compounds 1c (α-asarone-related) and 5b (with a pyrrolic core) were selected as the best antifungal candidates among over 20 synthetic compounds studied. Both inhibited the growth of fluconazole-resistant and fluconazole-susceptible C. glabrata strains. A yeast growth rescue experiment based on the addition of exogenous ergosterol showed that the compounds act by inhibiting the mevalonate synthesis pathway. A greater recovery of yeast growth occurred for the C. glabrata 43 fluconazole-resistant (versus fluconazole-susceptible) strain and after treatment with 1c (versus 5b). Given that the compounds decreased the concentration of ergosterol in the yeast strains, they probably target ergosterol synthesis. According to the docking analysis, the inhibitory effect of 1c and 5b could possibly be mediated by their interaction with the amino acid residues of the catalytic site of the enzyme. Since 1c displayed higher binding energy than α-asarone and 5b, it is the best candidate for further research, which should include structural modifications to increase its specificity and potency. The derivatives could then be examined with in vivo animal models using a therapeutic dose. IMPORTANCE Within the context of the COVID-19 pandemic, there is currently an epidemiological alert in health care services due to outbreaks of Candida auris, Candida glabrata, and other fungal species multiresistant to conventional antifungals. Therefore, it is important to propose alternative molecular targets, as well as new antifungals. The three series of synthetic compounds herein designed and synthesized are inhibitors of ergosterol synthesis in yeasts. Of the more than 20 compounds studied, two were selected as the best antifungal candidates. These compounds were able to inhibit the growth and synthesis of ergosterol in C. glabrata strains, whether susceptible or resistant to fluconazole. The rational design of antifungal compounds derived from clinical drugs (statins, fibrates, etc.) has many advantages. Future studies are needed to modify the structure of the two present test compounds to obtain safer and less toxic antifungals. Moreover, it is important to carry out a more in-depth mechanistic approach.

Point mutations in Candida glabrata 3-hydroxy-3-methylglutaryl-coenzyme A reductase (CgHMGR) decrease enzymatic activity and substrate/inhibitor affinity

3-Hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) is a crucial enzyme in the ergosterol biosynthesis pathway. The aim of this study was to obtain, purify, characterize, and overexpress five point mutations in highly conserved regions of the catalytic domain of Candida glabrata HMGR (CgHMGR) to explore the function of key amino acid residues in enzymatic activity. Glutamic acid (Glu) was substituted by glutamine in the E680Q mutant (at the dimerization site), Glu by glutamine in E711Q (at the substrate binding site), aspartic acid by alanine in D805A, and methionine by arginine in M807R (the latter two at the cofactor binding site). A double mutation, E680Q-M807R, was included. Regarding recombinant and wild-type CgHMGR, in vitro enzymatic activity was significantly lower for the former, as was the in silico binding energy of simvastatin, alpha-asarone and the HMG-CoA substrate. E711Q displayed the lowest enzymatic activity and binding energy, suggesting the importance of Glu711 (in the substrate binding site). The double mutant CgHMGR E680Q-M807R exhibited the second lowest enzymatic activity. Based on the values of the kinetic parameters KM and Vmax, the mutated amino acids appear to participate in binding. The current findings provide insights into the role of residues in the catalytic site of CgHMGR.

Evaluation of antifungal activity of mint, pomegranate and coriander on fluconazole-resistant Candida glabrata

Introduction:

Antifungal resistance shown by different species of Candida has affected the management of candidiasis drastically. This has led to the need for newer safer therapeutic alternatives for their management. Phytochemical agents have been long known to possess numerous medicinal activities.

Aim:

The aim of this study was to evaluate the efficacy and resistance of fluconazole and to compare the antifungal effects of Coriandrum sativum, Mentha piperita and Punica granatum in Candida glabrata.

Materials and Methods:

The organism was inoculated into a specific medium, and extracts are added at serial dilutions and incubated to evaluate the zone of inhibition.

Results:

All the three extracts showed statistically significant and superior antifungal activity to fluconazole in fluconazole-resistant C. glabrata.

Conclusion:

Although the extracts showed superior antifungal activity in resistant C. glabrata strains, further studies are needed to evaluate these extracts in patients to see if their efficacy is impeded by any systemic or local factors in the body.

Utilization of an Industry Byproduct, Corymbia maculata Leaves, by Aspergillus terreus to Produce Lovastatin

Due to its ability to lower cholesterol levels, simvastatin is a leading drug for the prevention of strokes and heart disease: it also lowers the incidence of neurodegenerative diseases. Simvastatin is made from lovastatin, a precursor produced by the industrial fungus, Aspergillus terreus. In this study, Corymbia maculata leaves were tested as a novel substrate for the growth of a new isolate of A. terreus and a lovastatin-resistant strain of A. terreus to produce lovastatin. Corymbia maculata (spotted gum) is well utilized by forest industries as a source of timber because of its high strength, durability and smooth texture. However, the leaves are a major waste product. Growth of A. terreus on Corymbia maculata leaves, in solid-state fermentation resulted in the production of lovastatin. Fermentation of media using fresh leaves of Corymbia maculata produced more lovastatin (4.9 mg g−1), than the sun-dried leaves (3.2 mg g−1). Levels of lovastatin were further increased by the lovastatin-resistant strain of A. terreus (Lvs-r), which produced twice the amount of the parental strain. The production of lovastatin was confirmed by HPLC and LC–MS/MS studies. The study suggests that the utilization of a cheap substrate for the production of lovastatin can have a potential economic benefit.

Antifungal effects of statins

Fungal infections are estimated to be responsible for 1.5 million deaths annually. Global anti-microbial resistance is also observed for fungal pathogens, and scientists are looking for new antifungal agents to address this challenge. One potential strategy is to evaluate currently available drugs for their possible antifungal activity. One of the suggested drug classes are statins, which are commonly used to decrease plasma cholesterol and reduce cardiovascular risk associated with low density lipoprotein cholesterol (LDL-c). Statins are postulated to possess pleiotropic effects beyond cholesterol lowering; improving endothelial function, modulating inflammation, and potentially exerting anti-microbial effects. In this study, we reviewed in-vitro and in-vivo studies, as well as clinical reports pertaining to the antifungal efficacy of statins. In addition, we have addressed various modulators of statin anti-fungal activity and the potential mechanisms responsible for their anti-fungal effects. In general, statins do possess anti-fungal activity, targeting a broad spectrum of fungal organisms including human opportunistic pathogens such as Candida spp. and Zygomycetes, Dermatophytes, alimentary toxigenic species such as Aspergillus spp., and fungi found in device implants such as Saccharomyces cerevisiae. Statins have been shown to augment a number of antifungal drug classes, for example, the azoles and polyenes. Synthetic statins are generally considered more potent than the first generation of fungal metabolites. Fluvastatin is considered the most effective statin with the broadest and most potent fungal inhibitory activity, including fungicidal and/or fungistatic properties. This has been demonstrated with plasma concentrations that can easily be achieved in a clinical setting. Additionally, statins can potentiate the efficacy of available antifungal drugs in a synergistic fashion. Although only a limited number of animal and human studies have been reported to date, observational cohort studies have confirmed that patients using statins have a reduced risk of candidemia-related complications. Further studies are warranted to confirm our findings and expand current knowledge of the anti-fungal effects of statins.