Giardiasis, which is caused by Giardia lamblia infection, is a relevant cause of morbidity and mortality worldwide. Because no vaccines are currently available to treat giardiasis, chemotherapeutic drugs are the main options for controlling infection. Evidence has shown that the nitro drug nitazoxanide (NTZ) is a commonly prescribed treatment for giardiasis; however, the mechanisms underlying NTZ’s antigiardial activity are not well-understood. Herein, we identified the glucose-6-phosphate::6-phosphogluconate dehydrogenase (GlG6PD::6PGL) fused enzyme as a nitazoxanide target, as NTZ behaves as a GlG6PD::6PGL catalytic inhibitor. Furthermore, fluorescence assays suggest alterations in the stability of GlG6PD::6PGL protein, whereas the results indicate a loss of catalytic activity due to conformational and folding changes. Molecular docking and dynamic simulation studies suggest a model of NTZ binding on the active site of the G6PD domain and near the structural NADP⁺ binding site. The findings of this study provide a novel mechanistic basis and strategy for the antigiardial activity of the NTZ drug.

Metabolic diseases are strongly associated with chronic systemic inflammation and oxidative stress, which disrupt the microbiota–gut–brain (MGB) axis and promote neuroinflammation. Dysbiosis favors the release of proinflammatory metabolites, reactive oxygen species (ROS), and lipopolysaccharides (LPS), increasing intestinal permeability and triggering systemic immune responses that reach the central nervous system (CNS) through a weakened blood–brain barrier (BBB). This review summarizes current knowledge on the pathophysiological mechanisms linking the MGB axis, metabolic disorders, and neuroinflammation, as well as the therapeutic potential of antioxidants. A literature search was conducted in PubMed, Web of Science, Scopus, and ScienceDirect and included original research articles, reviews, clinical trials, and meta-analyses related to microbiota, neuroinflammation, oxidative stress, and antioxidant interventions. Evidence indicates that dysbiosis exacerbates metabolic dysfunction by activating the nuclear factor kappa B (NF-κB) and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome pathways, while excessive ROS production impairs mitochondrial function, neuronal survival, and cognitive processes. Antioxidant strategies, including polyphenols, omega-3 fatty acids, curcumin, vitamins C and E, and probiotics, can restore microbial diversity, reinforce intestinal and BBB integrity, and modulate oxidative and inflammatory signaling. In conclusion, supplements and bacteria with antioxidant properties show promising therapeutic effects by targeting oxidative stress mechanisms involved in metabolic diseases and their pathological consequences, such as dysbiosis and neuroinflammation.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a widespread enzymopathy affecting approximately 500 million individuals that represents a significant global health issue. Among the more than 230 identified mutations in the G6PD gene, six class A variants—G6PD Utrecht (Pro409Ser), G6PD Suwalki (Pro409Arg), G6PD Merlo (Pro409Gln), G6PD Kawasaki (Gly410Ala), G6PD Shinagawa (Gly410Asp), and G6PD Riverside (Gly410Cys)—are located in the beta-loop near the NADP⁺ binding site. These mutations are of particular interest due to their association with severe hematologic phenotypes, including chronic hemolytic anemia, as well as their proposed role in the allosteric regulation of G6PD multimerization. This study presents a comprehensive biochemical and functional characterization of these clinically relevant G6PD variants. The variant enzymes were cloned, expressed, and purified for characterization. Kinetic parameters and thermal stability assays, complemented by molecular dynamics simulations (MDS), were employed to elucidate the structural impacts of the mutations. Our results demonstrate that these mutations significantly impair protein function, characterized by reduced affinity for glucose-6-phosphate (G6P) and NADP⁺, as well as altered thermal stability compared with wild-type G6PD. MDS revealed that point mutations in the βN- and βM-sheets in the NADP⁺_s region propagate subtle conformational changes, ultimately affecting the NADP⁺c region and the G6P binding cavity. Furthermore, secondary structure element analyses of the simulation data showed that Pro409 and Gly410 point mutations propagate several changes around residues 195–210 (G6P binding site) and 380–400 (NADP⁺_s), explaining their effect on overall catalytic performance. These findings enhance our understanding of the molecular mechanisms underlying G6PD deficiency and its clinical implications, providing a foundation for future therapeutic strategies aimed at mitigating the effects of these variants.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an enzymopathy that affects approximately 500 million people worldwide. A great number of mutations in the G6PD gene have been described. However, three class A G6PD variants known as G6PD Tomah (C385R), G6PD Kangnam (C385G), and G6PD Madrid (C385W) have been reported to be clinically important due to their associations with severe clinical manifestations such as hemolytic anemia. Therefore, this work aimed to perform, for the first time, biochemical and functional characterizations of these variants. The G6PD variants were cloned and purified for this purpose, followed by analyses of their kinetic parameters and thermal stability, as well as in silico studies. The results showed that the mutations induced changes in the proteins. Regarding the kinetic parameters, it was observed that the three variants showed lower affinities for G6P and NADP⁺, as well as lower thermal stability compared to WT-G6PD. Molecular dynamics simulations showed that C385 mutations induced changes around neighboring amino acids. Metadynamics simulations showed that most remarkable changes account for the binding pocket volumes, particularly in the structural NADP⁺ binding site, with a concomitant loss of affinity for catalytic processes.

Autophagy is a cellular catabolic mechanism that facilitates the degradation of cytoplasmic components, thereby restoring energy homeostasis and mitigating cellular damage. This process functions as a housekeeping system, essential for maintaining organismal viability under stressful conditions. Numerous studies have highlighted the role of autophagy in regulating various physiological processes, including metabolic pathways. Notably, certain autophagy-related genes may play a relevant role in metabolic disorders, extending beyond their involvement in the autophagic process, and may offer potential therapeutic avenues for treating energy-related metabolic diseases. This review summarizes the roles of various components of each autophagic complex and the regulators involved in the autophagic process. In particular, it explores the intricate relationship between autophagy and several metabolic diseases, including type 2 diabetes mellitus (T2DM), obesity, and non-alcoholic fatty liver disease (NAFLD).

Giardiasis remains a significant global health issue, and its treatment is increasingly hampered by the emergence of drug resistance and cross-resistance between nitroimidazoles and nitazoxanide. In this study, we evaluated the in vitro antigiardial activity, cytotoxicity, and potential mechanisms of action of seven structural analogs (CLB 1–7) derived from a hybrid structure combining nitazoxanide and clofibric acid. Among them, compounds CLB-3 and CLB-5 emerged as the most potent candidates, demonstrating exceptional efficacy against a nitazoxanide-resistant (NTZr) strain of Giardia lamblia, with potencies up to 43 and 60 times higher than that of the reference drug, respectively. Furthermore, both compounds demonstrated high selectivity for the parasite, exhibiting low cytotoxicity in human Caco-2 cells. To investigate the mechanism of action, functional biochemical assays revealed that treatment with these derivatives significantly reduced the intracellular ATP levels and altered the ADP/ATP ratio, indicating a direct impact on the parasite’s energy metabolism. These functional findings correlate closely with RT-qPCR transcriptional analyses and in silico molecular dynamics simulations; collectively, the data suggest a multi-target mechanism of action that may involve the disruption of energy homeostasis and the possible inhibition of key enzymes in the glycolytic pathway (PFOR, G6PD::6PGL, PK, and PPDK). In summary, these results identify compounds CLB-3 and CLB-5 as highly promising chemotherapeutic candidates for combating refractory giardiasis.