An Avocado Extract Enriched in Mannoheptulose Prevents the Negative Effects of a High-Fat Diet in Mice

Beginning at 16 weeks of age and continuing for 44 weeks, male C57BL/6J were fed either a control (CON) diet; a high-fat (HF) diet (60% unsaturated); or the HF diet containing an extract of unripe avocados (AvX) enriched in the 7-carbon sugar mannoheptulose (MH), designed to act as a glycolytic inhibitor (HF + MH). Compared to the CON diet, mice on the HF diet exhibited higher body weights; body fat; blood lipids; and leptin with reduced adiponectin levels, insulin sensitivity, VO2max, and falls from a rotarod. Mice on the HF + MH diet were completely protected against these changes in the absence of significant diet effects on food intake. Compared to the CON diet, oxidative stress was also increased by the HF diet indicated by higher levels of total reactive oxygen species, superoxide, and peroxynitrite measured in liver samples by electron paramagnetic resonance spectroscopy, whereas the HF + MH diet attenuated these changes. Compared to the CON, the HF diet increased signaling in the mechanistic target of the rapamycin (mTOR) pathway, and the addition of the MH-enriched AvX to this diet attenuated these changes. Beyond generating further interest in the health benefits of avocados, these results draw further new attention to the effects of this rare sugar, MH, as a botanical intervention for preventing obesity.

Mitochondria Metabolomics Reveals a Role of β-Nicotinamide Mononucleotide Metabolism in Mitochondrial DNA Replication

Summary Mitochondrial DNA (mtDNA) replication is tightly regulated and necessary for cellular homeostasis; however, its relationship with mitochondrial metabolism remains unclear. Advances in metabolomics integrated with the rapid isolation of mitochondria will allow for remarkable progress in analyzing mitochondrial metabolism. Here, we propose a novel methodology for mitochondria-targeted metabolomics, which employs a quick isolation procedure using a hemolytic toxin from Streptococcus pyogenes streptolysin O (SLO). SLO-isolation of mitochondria from cultured HEK293 cells is time- and labor-saving for simultaneous multi-sample processing and has been applied to various other cell lines in this study. Furthermore, our method can detect the time-dependent reduction in mitochondrial ATP in response to a glycolytic inhibitor 2-deoxyglucose, indicating the suitability to prepare metabolite analysis-competent mitochondria. Using this methodology, we searched for specific mitochondrial metabolites associated with mtDNA replication activation, and nucleotides and NAD+ were identified to be prominently altered. Most notably, treatment of β-Nicotinamide Mononucleotide (β-NMN), a precursor of NAD+, to HEK293 cells activated and improved the rate of mtDNA replication by increasing nucleotides in mitochondria and decreasing their degradation products: nucleosides. Our results suggest that β-NMN metabolism play a role in supporting mtDNA replication by maintaining the nucleotide pool balance in the mitochondria.

Glycolytic inhibitor 2-Deoxy-D-glucose attenuates SARS-CoV-2 multiplication in host cells and weakens the infective potential of progeny virions

The COVID-19 pandemic is an ongoing public health emergency of international concern. Millions of people lost their lives to this pandemic. While a lot of efforts are being invested in vaccinating the population, there is also an emergent requirement to find potential therapeutics to effectively counter this fast mutating SARS-CoV-2 virus-induced pathogenicity. Virus-infected host cells switch their metabolism to a more glycolytic phenotype. This switch induced by the virus is needed for faster production of ATP and higher levels of glycolytic intermediates, which are required for anabolic processes such as fatty acid synthesis and nucleotide generation for new virion synthesis and packaging. In this study, we used 2-Deoxy-D-glucose (2-DG) to target and inhibit the metabolic reprogramming induced by SARS-CoV-2 infection. Our results showed that virus infection induces glucose influx and glycolysis resulting in selective high accumulation of the fluorescent glucose/2-DG analogue, 2-NBDG in these cells. Subsequently, 2-DG reduces the virus multiplication and alleviates the cells from infection-induced cytopathic effect (CPE) and cell death. Herein, we demonstrate that progeny virions produced from 2-DG treated cells are defective with compromised infectivity potential. Further, it was also observed that mannose inhibits 2-NBDG uptake at a very low concentration, suggesting that 2-DG uptake in virus-infected cells might be exploiting the specific mannose transporter or high-affinity glucose transporter, GLUT3, which was found to be increased on SARS-CoV-2 infection. In conclusion, our findings suggest that 2-DG effectively inhibits the SARS-CoV-2 multiplication and can be used as a treatment regimen. Based on these preliminary in-vitro findings this molecule reached clinical trial in COVID patients.

Correction: The sensitive detection of single-cell secreted lactic acid for glycolytic inhibitor screening with a microdroplet biosensor

Correction for ‘The sensitive detection of single-cell secreted lactic acid for glycolytic inhibitor screening with a microdroplet biosensor’ by Xuyue Chen et al., Anal. Methods, 2020, 12, 3250–3259, DOI: 10.1039/D0AY00633E.

The sensitive detection of single-cell secreted lactic acid for glycolytic inhibitor screening with a microdroplet biosensor

Lactic acid (LA) plays an important role in the tumor metabolism and malignant progression of various cancers.