Functional Amino Acids and Autophagy: Diverse Signal Transduction and Application

Claudin-4 Modulates Autophagy via SLC1A5/LAT1 as a Mechanism to Regulate Micronuclei

Genome instability is a hallmark of cancer crucial for tumor heterogeneity and is often a result of defects in cell division and DNA damage repair. Tumors tolerate genomic instability, but the accumulation of genetic aberrations is regulated to avoid catastrophic chromosomal alterations and cell death. In ovarian cancer tumors, claudin-4 is frequently upregulated and closely associated with genome instability and worse patient outcomes. However, its biological association with regulating genomic instability is poorly understood. Here, we used CRISPR interference and a claudin mimic peptide to modulate the claudin-4 expression and its function in vitro and in vivo. We found that claudin-4 promotes a tolerance mechanism for genomic instability through micronuclei generation in tumor cells. Disruption of claudin-4 increased autophagy and was associated with the engulfment of cytoplasm-localized DNA. Mechanistically, we observed that claudin-4 establishes a biological axis with the amino acid transporters SLC1A5 and LAT1, which regulate autophagy upstream of mTOR. Furthermore, the claudin-4/SLC1A5/LAT1 axis was linked to the transport of amino acids across the plasma membrane as one of the potential cellular processes that significantly decreased survival in ovarian cancer patients. Together, our results show that the upregulation of claudin-4 contributes to increasing the threshold of tolerance for genomic instability in ovarian tumor cells by limiting its accumulation through autophagy.

SIGNIFICANCE

Autophagy regulation via claudin-4/SLC1A5/LAT1 has the potential to be a targetable mechanism to interfere with genomic instability in ovarian tumor cells.

The Janus face of HIF-1α in ischemic stroke and the possible associated pathways

Stroke is the most devastating disease, causing paralysis and eventually death. Many clinical and experimental trials have been done in search of a new safe and efficient medicine; nevertheless, scientists have yet to discover successful remedies that are also free of adverse effects. This is owing to the variability in intensity, localization, medication routes, and each patient's immune system reaction. HIF-1α represents the modern tool employed to treat stroke diseases due to its functions: downstream genes such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Its role can be achieved via two downstream EPO and VEGF strongly related to apoptosis and antioxidant processes. Recently, scientists paid more attention to drugs dealing with the HIF-1 pathway. This review focuses on medicines used for ischemia treatment and their potential HIF-1α pathways. Furthermore, we discussed the interaction between HIF-1α and other biological pathways such as oxidative stress; however, a spotlight has been focused on certain potential signalling contributed to the HIF-1α pathway. HIF-1α is an essential regulator of oxygen balance within cells which affects and controls the expression of thousands of genes related to sustaining homeostasis as oxygen levels fluctuate. HIF-1α's role in ischemic stroke strongly depends on the duration and severity of brain damage after onset. HIF-1α remains difficult to investigate, particularly in ischemic stroke, due to alterations in the acute and chronic phases of the disease, as well as discrepancies between the penumbra and ischemic core. This review emphasizes these contrasts and analyzes the future of this intriguing and demanding field.

Study on the effects of rapamycin and the mTORC1/2 dual inhibitor OSI-027 on the metabolism of colon cancer cells based on UPLC-MS/MS metabolomics

mTORC1/2 dual inhibitors may be more effective than mTORC1 inhibitor rapamycin. However, their metabolic impacts on colon cancer cells remain unexplored. We conducted a comparative analysis of the anti-proliferative effects of rapamycin and the novel OSI-027 in colon cancer cells HCT-116, evaluating their metabolic influences through ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Our results demonstrate that OSI-027 more effectively inhibits colon cancer cell proliferation than rapamycin. Additionally, we identified nearly 600 metabolites from the spectra, revealing significant differences in metabolic patterns between cells treated with OSI-027 and rapamycin. Through VIP value screening, we pinpointed crucial metabolites contributing to these distinctions. For inhibiting glycolysis and reducing glucose consumption, OSI-027 was likely to be more potent than rapamycin. For amino acids metabolism, although OSI-027 has a broad effect as rapamycin, their effects in degrees were not exactly the same. These findings address the knowledge gap regarding mTORC1/2 dual inhibitors and lay a foundation for their further development and research.

Duality of Branched-Chain Amino Acids in Chronic Cardiovascular Disease: Potential Biomarkers versus Active Pathophysiological Promoters

Branched-chain amino acids (BCAAs), comprising leucine (Leu), isoleucine (Ile), and valine (Val), are essential nutrients vital for protein synthesis and metabolic regulation via specialized signaling networks. Their association with cardiovascular diseases (CVDs) has become a focal point of scientific debate, with emerging evidence suggesting both beneficial and detrimental roles. This review aims to dissect the multifaceted relationship between BCAAs and cardiovascular health, exploring the molecular mechanisms and clinical implications. Elevated BCAA levels have also been linked to insulin resistance (IR), type 2 diabetes mellitus (T2DM), inflammation, and dyslipidemia, which are well-established risk factors for CVD. Central to these processes are key pathways such as mammalian target of rapamycin (mTOR) signaling, nuclear factor kappa-light-chain-enhancer of activate B cells (NF-κB)-mediated inflammation, and oxidative stress. Additionally, the interplay between BCAA metabolism and gut microbiota, particularly the production of metabolites like trimethylamine-N-oxide (TMAO), adds another layer of complexity. Contrarily, some studies propose that BCAAs may have cardioprotective effects under certain conditions, contributing to muscle maintenance and metabolic health. This review critically evaluates the evidence, addressing the biological basis and signal transduction mechanism, and also discusses the potential for BCAAs to act as biomarkers versus active mediators of cardiovascular pathology. By presenting a balanced analysis, this review seeks to clarify the contentious roles of BCAAs in CVD, providing a foundation for future research and therapeutic strategies required because of the rising prevalence, incidence, and total burden of CVDs.

The SLC38A9-mTOR axis is involved in autophagy in the juvenile yellow catfish (Pelteobagrus fulvidraco) under ammonia stress

The primary objective of this study was to examine the effect of acute ammonia stress on hepatic physiological alterations in yellow catfish by performing a comprehensive analysis of the metabolome and transcriptome. The present study showed that ammonia stress led to liver metabolic disruption, functional incapacitation, and oxidative damage. Transcriptomic and metabolomic analyses revealed transcriptional and metabolic differences in the liver of yellow catfish under control and high ammonia stress conditions. After 96 h of acute exposure to ammonia, the mRNA levels of 596 liver genes were upregulated, whereas those of 603 genes were downregulated. Enrichment analysis of the differentially expressed genes identified multiple signalling pathways associated with autophagy, including the endocytosis, autophagy-animal, and mammalian target of rapamycin signalling pathways. A total of 186 upregulated and 117 downregulated metabolites, primarily associated with amino acid biosynthesis pathways, were identified. Multi-omics integration revealed the solute carrier family 38 member 9 (SLC38A9)-mammalian target of rapamycin axis as a signalling nexus for amino acid-mediated modulation of autophagy flux, and q-PCR was used to assess the expression of autophagy-related genes (LC3a and sqstm1), revealing an initial inhibition followed by the restoration of autophagic flux during ammonia stress. Subsequent utilisation of arginine as a specific SLC38A9 activator during ammonia stress demonstrated that augmented SLC38A9 expression hindered autophagy, exacerbated ammonia toxicity, and caused a physiological decline (total cholesterol, total triglyceride, acid phosphatase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase levels were significantly increased), oxidative stress, and apoptosis. Autophagy activation may be an adaptive mechanism to resist ammonia stress.

Dysregulation of acyl carnitines, pentose phosphate pathway and arginine and ornithine metabolism are associated with decline in intrinsic capacity in Chinese older adults

BACKGROUND

Intrinsic capacity is the combination of individual physical and mental abilities, reflecting the aging degree of the older adults. However, the mechanisms and metabolic characteristics of the decline in intrinsic capacity are still unclear.

AIMS

To identify metabolic signatures and associated pathways of decline in intrinsic capacity based on the metabolite features.

METHODS

We recruited 70 participants aged 77.19 ± 8.31 years. The five domains of intrinsic capacity were assessed by Short Physical Performance Battery (for mobility), Montreal cognition assessment (for cognition), 30-Item Geriatric Depression Scale (for psychology), self-reported hearing/visual impairment (for sensory) and Nutritional risk screening (for vitality), respectively. The serum samples of participants were analyzed by liquid chromatography-mass spectrometry-based metabolomics, followed by metabolite set enrichment analysis and metabolic pathway analysis.

RESULTS

There were 50 participants with a decline in intrinsic capacity in at least one of the domains. A total of 349 metabolites were identified from their serum samples. Overall, 24 differential metabolites, 5 metabolite sets and 13 pathways were associated with the decline in intrinsic capacity.

DISCUSSION

Our results indicated that decline in intrinsic capacity had unique metabolomic profiles.

CONCLUSION

The specific change of acyl carnitines was observed to be a feature of decline in intrinsic capacity. Dysregulation of the pentose phosphate pathway and of arginine and ornithine metabolism was strongly associated with the decline in intrinsic capacity.

Empagliflozin ameliorates diabetic cardiomyopathy via regulated branched-chain amino acid metabolism and mTOR/p-ULK1 signaling pathway-mediated autophagy

BACKGROUND

Empagliflozin, a sodium-glucose co-transporter 2 inhibitor (SGLT2i), has been reported to significantly reduce the risk of heart failure in multiple clinical studies. However, the underlying mechanisms remain elusive. This study aimed to investigate the effect of empagliflozin on branched-chain amino acid (BCAA) metabolism in diabetic cardiomyopathy.

METHODS

Thirty male 8-week KK Cg-Ay/J mice were used to study diabetic cardiomyopathy; here, 15 were used as the model group, and the remaining 15 were administered empagliflozin (3.75 mg/kg/day) by gavage daily for 16 weeks. The control group consisted of fifteen male 8-week C57BL/6J mice, whose blood glucose and body weight were measured simultaneously with the diabetic mice until 16 weeks without additional intervention. Echocardiography and histopathology were performed to evaluate cardiac structure and function. Proteomic sequencing and biogenic analysis were performed on mouse hearts. Parallel Reaction Monitoring and western blotting were performed to validate the expression levels of differentially expressed proteins.

RESULTS

The results showed that empagliflozin improved ventricular dilatation and ejection fraction reduction in diabetic hearts, as well as the elevation of myocardial injury biomarkers hs-cTnT and NT-proBNP. At the same time, empagliflozin alleviates myocardial inflammatory infiltration, calcification foci deposition, and fibrosis caused by diabetes. The results of the proteomics assay showed that empagliflozin could improve the metabolism of various substances, especially promoting the BCAA metabolism of diabetic hearts by up-regulating PP2Cm. Furthermore, empagliflozin could affect the mTOR/p-ULK1 signaling pathway by reducing the concentration of BCAA in diabetic hearts. When mTOR/p-ULK1 protein was inhibited, ULK1, the autophagy initiation molecule, increased. Moreover, autophagy substrate p62 and autophagy marker LC3B were significantly reduced, indicating that the autophagy activity of diabetes inhibition was reactivated.

CONCLUSIONS

Empagliflozin may attenuate diabetic cardiomyopathy-related myocardial injury by promoting the catabolism of BCAA and inhibiting mTOR/p-ULK1 to enhance autophagy. These findings suggest that empagliflozin could be a potential candidate drug against BCAA increase and could be used for other cardiovascular diseases with a metabolic disorder of BCAA.

Comparison of dual mTORC1/2 inhibitor AZD8055 and mTORC1 inhibitor rapamycin on the metabolism of breast cancer cells using proton nuclear magnetic resonance spectroscopy metabolomics

Dual mTORC1/2 inhibitors may be more effective than mTORC1 inhibitor rapamycin. Nevertheless, their metabolic effects on breast cancer cells have not been reported. We compared the anti-proliferative capacity of rapamycin and a novel mTORC1/2 dual inhibitor (AZD8055) in two breast cancer cell lines (MDA-MB-231 and MDA-MB-453) and analyzed their metabolic effects using proton nuclear magnetic resonance (¹H NMR) spectroscopy-based metabolomics. We found that AZD8055 more strongly inhibited breast cancer cell proliferation than rapamycin. The half-inhibitory concentration of AZD8055 in breast cancer cells was almost one-tenth that of rapamycin. We identified 22 and 23 metabolites from the ¹H NMR spectra of MDA-MB-231 and MDA-MB-453 cells. The patterns of AZD8055- and rapamycin-treated breast cancer cells differed significantly; we then selected the metabolites that contributed to these differences. For inhibiting glycolysis and reducing glucose consumption, AZD8055 was likely to be more potent than rapamycin. For amino acids metabolism, although AZD8055 has a broad effect as rapamycin, their effects in degrees were not exactly the same. AZD8055 and rapamycin displayed cell-specific metabolic effects on breast cancer cells, a finding that deserves further study. These findings help fill the knowledge gap concerning dual mTORC1/2 inhibitors and provide a theoretical basis for their development.