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Introduction: Rate-limiting enzymes (RLEs) are innate slow points in metabolic pathways, and many function in bio-processes related to nutrient sensing. Many RLEs carry causal mutations relevant to inherited metabolic disorders. Because the activity of RLEs in cardiovascular health is poorly characterized, our objective was to assess their involvement in cardiometabolic health and disease and where altered biophysical and biochemical functions can promote disease. Methods: A dataset of 380 human RLEs was compared to protein and gene datasets for factors likely to contribute to cardiometabolic disease, including proteins showing significant age-related altered expression in blood and genetic loci with variants that associate with common cardiometabolic phenotypes. The biochemical reactions catalyzed by RLEs were evaluated for metabolites enriched in RLE subsets associating with various cardiometabolic phenotypes. Most significance tests were based on Z-score enrichment converted to p values with a normal distribution function. Results: Of 380 RLEs analyzed, 112 function in mitochondria, and 53 are assigned to inherited metabolic disorders. There was a depletion of RLE proteins known as aging biomarkers. At the gene level, RLEs were assessed for common genetic variants that associated with important cardiometabolic traits of LDL-cholesterol or any of the five outcomes pertinent to metabolic syndrome. This revealed several RLEs with links to cardiometabolic traits, from a minimum of 26 for HDL-cholesterol to a maximum of 45 for plasma glucose. Analysis of these GWAS-linked RLEs for enrichment of the molecular constituents of the catalyzed reactions disclosed a number of significant phenotype-metabolite links. These included blood pressure with acetate (p = 2.2 × 10−4) and NADP+ (p = 0.0091), plasma HDL-cholesterol and triglyceride with diacylglycerol (p = 2.6 × 10−5, 6.4 × 10−5, respectively) and diolein (p = 2.2 × 10−6, 5.9 × 10−6), and waist circumference with d-glucosamine-6-phosphate (p = 1.8 × 10−4). Conclusion: In the context of cardiometabolic health, aging, and disease, these results highlight key diet-derived metabolites that are central to specific rate-limited processes that are linked to cardiometabolic health. These metabolites include acetate and diacylglycerol, pertinent to blood pressure and triglycerides, respectively, as well as diacylglycerol and HDL-cholesterol.

Abstract Background α-Humulene is a plant-derived monocyclic sesquiterpenoid with multiple pharmacological activities, and far-reaching potential for the development of new drugs. Currently, the production of α-humulene is typically achieved via plant extraction, which is not sustainable and limited by low yields. The oleaginous yeast Candida tropicalis has recently emerged as a valuable host for producing high-value-added chemicals. However, the potential of C. tropicalis for terpenoid production has not been exploited. Results In this study, C. tropicalis was engineered for de novo synthesis of α-humulene from glucose. To improve α-humulene production, the codon-optimised α-humulene synthase gene and the entire endogenous farnesyl diphosphate synthesis pathway were co-overexpressed. Furthermore, bottlenecks in the α-humulene synthase pathway were identified and relieved by overexpressing α-humulene synthase, acetoacetyl-CoA thiolase and NADH-dependent HMG-CoA reductase. Combined with fermentation medium optimisation, the engineered strain produced 195.31 mg/L of α-humulene in shake flasks and 4115.42 mg/L in a bioreactor through fed-batch fermentation, a 253- and 5345-fold increase over the initial production, respectively. Conclusions This study demonstrates the potential of C. tropicalis for α-humulene production, and presents a platform for the biosynthesis of other terpenoids.

BackgroundAmong breast cancers, the triple-negative breast cancer (TNBC) subtype has the worst prognosis with no approved targeted therapies and only standard chemotherapy as the backbone of systemic therapy. Unique metabolic changes in cancer progression provide innovative therapeutic opportunities. The receptor tyrosine kinases (RTKs) epidermal growth factor receptor (EGFR), and MET receptor are highly expressed in TNBC, making both promising therapeutic targets. RTK signaling profoundly alters cellular metabolism by increasing glucose consumption and subsequently diverting glucose carbon sources into metabolic pathways necessary to support the tumorigenesis. Therefore, detailed metabolic profiles of TNBC subtypes and their response to tyrosine kinase inhibitors may identify therapeutic sensitivities.MethodsWe quantified the metabolic profiles of TNBC cell lines representing multiple TNBC subtypes using gas chromatography mass spectrometry. In addition, we subjected MDA-MB-231, MDA-MB-468, Hs578T, and HCC70 cell lines to metabolic flux analysis of basal and maximal glycolytic and mitochondrial oxidative rates. Metabolic pool size and flux measurements were performed in the presence and absence of the MET inhibitor, INC280/capmatinib, and the EGFR inhibitor, erlotinib. Further, the sensitivities of these cells to modulators of core metabolic pathways were determined. In addition, we annotated a rate-limiting metabolic enzymes library and performed a siRNA screen in combination with MET or EGFR inhibitors to validate synergistic effects.ResultsTNBC cell line models displayed significant metabolic heterogeneity with respect to basal and maximal metabolic rates and responses to RTK and metabolic pathway inhibitors. Comprehensive systems biology analysis of metabolic perturbations, combined siRNA and tyrosine kinase inhibitor screens identified a core set of TCA cycle and fatty acid pathways whose perturbation sensitizes TNBC cells to small molecule targeting of receptor tyrosine kinases.ConclusionsSimilar to the genomic heterogeneity observed in TNBC, our results reveal metabolic heterogeneity among TNBC subtypes and demonstrate that understanding metabolic profiles and drug responses may prove valuable in targeting TNBC subtypes and identifying therapeutic susceptibilities in TNBC patients. Perturbation of metabolic pathways sensitizes TNBC to inhibition of receptor tyrosine kinases. Such metabolic vulnerabilities offer promise for effective therapeutic targeting for TNBC patients.

The kidding traits of goats are an important index of production. However, the molecular regulatory mechanisms of kidding traits in goats have not been fully elucidated. This study aimed to investigate the molecular regulatory network of kidding traits in goats. Multi-omics revealed the enrichment of 10 signaling pathways, with fatty acid biosynthesis, biosynthesis of unsaturated fatty acids, and steroid hormone biosynthesis pathways being closely related to reproduction. Interestingly, the key rate-limiting enzymes, fatty acid synthase (FASN), stearoyl-CoA desaturase 5 (SCD5), fatty acid desaturase 1 (FADS1), 3β-hydroxysteroid dehydrogenase/isomerase (3BHSD), and steroidogenic acute regulatory protein (STAR) enriched in these pathways regulate changes in reproduction-related metabolites. In interference experiments, it was observed that suppressing these key rate-limiting enzymes inhibited the expression of CYP19A1, ESR2, and FSHR. Furthermore, interference inhibited granulosa cell proliferation, caused cell cycle arrest, and promoted apoptosis. Thus, these results suggest that the specific markers of nanny goats with multiple kids are the key rate-limiting enzymes FASN, SCD5, FADS1, 3BHSD, and STAR. These findings may greatly enhance the understanding of regulatory mechanisms that govern goat parturition., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Squalene is a medically valuable bioactive compound that can be used as a raw material for fuels. Microbial fermentation is the preferred method for the squalene production. In this study, we employed several metabolic engineering strategies to increase squalene yield in Rhodopseudomonas palustris. A 57% increase in squalene titer was achieved by blocking the carotenoid pathway, thus directing more FPP into the squalene biosynthetic pathway. In order to cut down the conversion of squalene to haponoids, a recombinant strain R. palustris [Δshc, ΔcrtB] in which both carotenoid and haponoid pathways were blocked was then constructed, resulting in a 50‐fold increase in squalene titer. Based on the expression of rate‐limiting enzymes involved in the squalene pathway, the final squalene content reached 23.3 mg/g DCW, which was 178‐times higher than that of the wild‐type strain. In this study, several methods effective in improving squalene yield have been described and the potential of R. palustris for producing squalene has been demonstrated. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a classic autoimmune disease characterized by uncontrolled synovial proliferation, pannus formation, cartilage injury, and bone destruction. The specific pathogenesis of RA, a chronic inflammatory disease, remains unclear. However, both key glycolysis rate-limiting enzymes, hexokinase-II (HK-II), phosphofructokinase-1 (PFK-1), and pyruvate kinase M2 (PKM2), as well as indirect rate-limiting enzymes, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), are thought to participate in the pathogenesis of RA. In here, we review the latest literature on the pathogenesis of RA, introduce the pathophysiological characteristics of HK-II, PFK-1/PFKFB3, and PKM2 and their expression characteristics in this autoimmune disease, and systematically assess the association between the glycolytic rate-limiting enzymes and RA from a molecular level. Moreover, we highlight HK-II, PFK-1/PFKFB3, and PKM2 as potential targets for the clinical treatment of RA. There is great potential to develop new anti-rheumatic therapies through safe inhibition or overexpression of glycolysis rate-limiting enzymes. [ABSTRACT FROM AUTHOR]

Emerging evidences demonstrate that metabolic reprogramming is a hallmark of malignancies, including gastric cancer (GC). Abnormal expression of metabolic rate-limiting enzymes, as the executive medium of energy metabolism, drives the occurrence and development of cancer. However, a comprehensive model of metabolic rate-limiting enzymes associated with the development and progression of GC remains unclear. In this research, we identified a rate-limiting enzyme, sterol O-acyltransferase 1 (SOAT1), was highly expressed in cancerous tissues, which was associated with advanced tumor stage and lymph node metastasis, leading to the poor prognosis of GC. It was shown that knockdown of SOAT1 or pharmacological inhibition of SOAT1 by avasimibe could suppress GC cell proliferation, cholesterol ester synthesis, and lymphangiogenesis. However, overexpression of SOAT1 promoted these biological processes. Mechanistically, SOAT1 regulated the expression of cholesterol metabolism genes SREBP1 and SREBP2, which could induce lymphangiogenesis via increasing the expression of VEGF-C. In conclusion, our results indicated that SOAT1 promotes gastric cancer lymph node metastasis through lipid synthesis, which suggested that it may be a promising prognostic biomarker for guiding clinical management and treatment decisions. [ABSTRACT FROM AUTHOR]

Objectives: Abnormal expression of metabolic rate‐limiting enzymes drives the occurrence and progression of hepatocellular carcinoma (HCC). This study aimed to elucidate the comprehensive model of metabolic rate‐limiting enzymes associated with the prognosis of HCC. Materials and Methods: HCC animal model and TCGA project were used to screen out differentially expressed metabolic rate‐limiting enzyme. Cox regression, least absolute shrinkage and selection operation (LASSO) and experimentally verification were performed to identify metabolic rate‐limiting enzyme signature. The area under the receiver operating characteristic curve (AUC) and prognostic nomogram were used to assess the efficacy of the signature in the three HCC cohorts (TCGA training cohort, internal cohort and an independent validation cohort). Results: A classifier based on three rate‐limiting enzymes (RRM1, UCK2 and G6PD) was conducted and serves as independent prognostic factor. This effect was further confirmed in an independent cohort, which indicated that the AUC at year 5 was 0.715 (95% CI: 0.653‐0.777) for clinical risk score, whereas it was significantly increased to 0.852 (95% CI: 0.798‐0.906) when combination of the clinical with signature risk score. Moreover, a comprehensive nomogram including the signature and clinicopathological aspects resulted in significantly predict the individual outcomes. Conclusions: Our results highlighted the prognostic value of rate‐limiting enzymes in HCC, which may be useful for accurate risk assessment in guiding clinical management and treatment decisions. [ABSTRACT FROM AUTHOR]

Emerging evidences demonstrate that metabolic reprogramming is a hallmark of malignancies, including gastric cancer (GC). Abnormal expression of metabolic rate-limiting enzymes, as the executive medium of energy metabolism, drives the occurrence and development of cancer. However, a comprehensive model of metabolic rate-limiting enzymes associated with the development and progression of GC remains unclear. In this research, we identified a rate-limiting enzyme, sterol O-acyltransferase 1 (SOAT1), was highly expressed in cancerous tissues, which was associated with advanced tumor stage and lymph node metastasis, leading to the poor prognosis of GC. It was shown that knockdown of SOAT1 or pharmacological inhibition of SOAT1 by avasimibe could suppress GC cell proliferation, cholesterol ester synthesis, and lymphangiogenesis. However, overexpression of SOAT1 promoted these biological processes. Mechanistically, SOAT1 regulated the expression of cholesterol metabolism genes SREBP1 and SREBP2, which could induce lymphangiogenesis via increasing the expression of VEGF-C. In conclusion, our results indicated that SOAT1 promotes gastric cancer lymph node metastasis through lipid synthesis, which suggested that it may be a promising prognostic biomarker for guiding clinical management and treatment decisions.

Rheumatoid arthritis (RA) is a classic autoimmune disease characterized by uncontrolled synovial proliferation, pannus formation, cartilage injury, and bone destruction. The specific pathogenesis of RA, a chronic inflammatory disease, remains unclear. However, both key glycolysis rate-limiting enzymes, hexokinase-II (HK-II), phosphofructokinase-1 (PFK-1), and pyruvate kinase M2 (PKM2), as well as indirect rate-limiting enzymes, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), are thought to participate in the pathogenesis of RA. In here, we review the latest literature on the pathogenesis of RA, introduce the pathophysiological characteristics of HK-II, PFK-1/PFKFB3, and PKM2 and their expression characteristics in this autoimmune disease, and systematically assess the association between the glycolytic rate-limiting enzymes and RA from a molecular level. Moreover, we highlight HK-II, PFK-1/PFKFB3, and PKM2 as potential targets for the clinical treatment of RA. There is great potential to develop new anti-rheumatic therapies through safe inhibition or overexpression of glycolysis rate-limiting enzymes.

Coenzyme Q10 (CoQ10), a strong antioxidant, is used extensively in food, cosmetic and medicine industries. A natural producer, Rhodopseudomonas palustris, was engineered to overproduce CoQ10. For increasing the CoQ10 content, crtB gene was deleted to block the carotenoid pathway. crtB gene deletion led to 33% improvement of CoQ10 content over the wild type strain. However, it was found that the yield of hopanoids was also increased by competing for the precursors from carotenoid pathway with CoQ10 pathway. To further increase the CoQ10 content, hopanoid pathway was blocked by deleting shc gene, resulting in R. palustris [Δshc, ΔcrtB] to produce 4·7 mg g−1 DCW CoQ10, which was 1·2 times higher than the CoQ10 content in the wild type strain. The common strategy of co‐expression of rate‐limiting enzymes (DXS, DPS and UbiA) was combined with the pathway blocking method resulted in 8·2 mg g−1 DCW of CoQ10, which was 2·9 times higher than that of wild type strain. The results suggested a synergistic effect among different metabolic engineering strategies. This study demonstrates the potential of R. palustris for CoQ10 production and provides viable strategies to increase CoQ10 titer. [ABSTRACT FROM AUTHOR]

Abstract Background Squalene is currently used widely in the food, cosmetics, and medicine industries. It could also replace petroleum as a raw material for fuels. Microbial fermentation processes for squalene production have been emerging over recent years. In this study, to study the squalene-producing potential of Escherichia coli (E. coli), we employed several increasing strategies for systematic metabolic engineering. These include the expression of human truncated squalene synthase, the overexpression of rate-limiting enzymes in isoprenoid pathway, the modification of isoprenoid-feeding module and the blocking of menaquinone pathway. Results Herein, human truncated squalene synthase was engineered in Escherichia coli to create a squalene-producing bacterial strain. To increase squalene yield, we employed several metabolic engineering strategies. A fivefold squalene titer increase was achieved by expressing rate-limiting enzymes (IDI, DXS, and FPS) involved in the isoprenoid pathway. Pyridine nucleotide transhydrogenase (UdhA) was then expressed to improve the cellular NADPH/NADP+ ratio, resulting in a 59% increase in squalene titer. The Embden–Meyerhof pathway (EMP) was replaced with the Entner–Doudoroff pathway (EDP) and pentose phosphate pathway (PPP) to feed the isoprenoid pathway, along with the overexpression of zwf and pgl genes which encode rate-limiting enzymes in the EDP and PPP, leading to a 104% squalene content increase. Based on the blocking of menaquinone pathway, a further 17.7% increase in squalene content was achieved. Squalene content reached a final 28.5 mg/g DCW and 52.1 mg/L. Conclusions This study provided novel strategies for improving squalene yield and demonstrated the potential of producing squalene by E. coli.

Continuous-cropping leads to obstacles in crop productivity by the accumulation of p-hydroxybenzoic acid (PHBA) and ferulic acid (FA). In this study, a strain CFA of Pseudomonas was shown to have a higher PHBA- and FA-degrading ability in media and soil and the mechanisms underlying this were explored. Optimal conditions for PHBA and FA degradation by CFA were 0.2 g/l of PHBA and FA, 37°C, and pH 6.56. Using transcriptome analysis, complete pathways that converted PHBA and FA to acetyl coenzyme A were proposed in CFA. When CFA was provided with PHBA and FA, we observed upregulation of genes in the pathways and detected intermediate metabolites including vanillin, vanillic acid, and protocatechuic acid. Moreover, 4-hydroxybenzoate 3-monooxygenase and vanillate O-demethylase were rate-limiting enzymes by gene overexpression. Knockouts of small non-coding RNA (sRNA) genes, including sRNA 11, sRNA 14, sRNA 20, and sRNA 60, improved the degradation of PHBA and FA. When applied to cucumber-planted soil supplemented with PHBA and FA, CFA decreased PHBA and FA in soil. Furthermore, a reduction of superoxide radical, hydrogen peroxide, and malondialdehyde in cucumber was observed by activating superoxide dismutase, catalase, glutathione peroxidase, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase in seedlings, increasing the reduced glutathione and ascorbate in leaves, and inducing catalase, urease, and phosphatase in the rhizosphere. CFA has potential to mitigate PHBA and FA stresses in cucumber and alleviate continuous-cropping obstacles.

Continuous-cropping leads to obstacles in crop productivity by the accumulation of p -hydroxybenzoic acid (PHBA) and ferulic acid (FA). In this study, a strain CFA of Pseudomonas was shown to have a higher PHBA- and FA-degrading ability in media and soil and the mechanisms underlying this were explored. Optimal conditions for PHBA and FA degradation by CFA were 0.2 g/l of PHBA and FA, 37°C, and pH 6.56. Using transcriptome analysis, complete pathways that converted PHBA and FA to acetyl coenzyme A were proposed in CFA. When CFA was provided with PHBA and FA, we observed upregulation of genes in the pathways and detected intermediate metabolites including vanillin, vanillic acid, and protocatechuic acid. Moreover, 4-hydroxybenzoate 3-monooxygenase and vanillate O -demethylase were rate-limiting enzymes by gene overexpression. Knockouts of small non-coding RNA (sRNA) genes, including sRNA 11 , sRNA 14 , sRNA 20 , and sRNA 60 , improved the degradation of PHBA and FA. When applied to cucumber-planted soil supplemented with PHBA and FA, CFA decreased PHBA and FA in soil. Furthermore, a reduction of superoxide radical, hydrogen peroxide, and malondialdehyde in cucumber was observed by activating superoxide dismutase, catalase, glutathione peroxidase, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase in seedlings, increasing the reduced glutathione and ascorbate in leaves, and inducing catalase, urease, and phosphatase in the rhizosphere. CFA has potential to mitigate PHBA and FA stresses in cucumber and alleviate continuous-cropping obstacles. [ABSTRACT FROM AUTHOR]

Summary: The plastidial methylerythritol phosphate (MEP) pathway is an essential route for plants as the source of precursors for all plastidial isoprenoids, many of which are of medical and biotechnological importance. The MEP pathway is highly sensitive to environmental cues as many of these compounds are linked to photosynthesis and growth and light is one of the main regulatory factors. However, the mechanisms coordinating the MEP pathway with light cues are not fully understood. Here we demonstrate that by a differential direct transcriptional modulation, via the key‐master integrators of light signal transduction HY5 and PIFs which target the genes that encode the rate‐controlling DXS1,DXR and HDR enzymes, light imposes a direct, rapid and potentially multi‐faceted response that leads to unique protein dynamics of this pathway, resulting in a significant difference in the protein levels. For DXS1, PIF1/HY5 act as a direct activation/suppression module. In contrast, DXR accumulation in response to light results from HY5 induction with minor contribution of de‐repression by PIF1. Finally, HDR transcription increases in the light exclusively by suppression of the PIFs repression. This is an example of how light signaling components can differentially multi‐target the initial steps of a pathway whose products branch downstream to all chloroplastic isoprenoids. These findings demonstrate the diversity and flexibility of light signaling components that optimize key biochemical pathways essential for plant growth. Significance Statement: Light imposes a direct, rapid and potentially multi‐faceted effect that leads to unique protein dynamics to the main flux‐limiting steps of the MEP pathway, a key route essential for plants. Through differential direct transcriptional interaction, the key‐master integrators of light signals HY5 and PIFs, target the main flux‐limiting steps of the pathway. Our work illustrates how light signals can impose contrasting dynamics over a key pathway whose products multi‐branch downstream to all chloroplastic isoprenoids. [ABSTRACT FROM AUTHOR]

Twenty-four endophytic fungal isolates recovered from Podocarpus gracilior were screened for Taxol biosynthetic potency. Among these endophytes, three isolates of Aspergillus terreus EFB108, EFB59, EFB14 recovered from P. gracilior cork, leaves and twigs, respectively, were reported as potent Taxol producers. The chemical identity of A. terreus extracted Taxol was verified from the HPLC, NMR and FTIR analyses, with strong cytotoxic activity for HEPG2 and MCF7 cell lines (IC 50 4.5–6.5 nM). Upon nutritional of A. terreus EFB108 (MF377552), the maximum yield of Taxol (265 μg/L) was obtained by growing the fungus on MID medium of initial pH 8.0, with 0.6% asparagine and 2.4% xylose, incubated for 21 days. Taxol yield of A. terreus was increased by ∼2.4 folds (432 μg/L) upon addition of surface sterilized P. gracilior leaves. The yield of Taxol by A. terreus was not affected by the dichloromethane plant extract negating the presence of direct signals inducing Taxol biosynthesis. So, the intimate physical interaction of endogenous endophytes of P. gracilior with the fungus, could be essential for triggering the biosynthesis of Taxol by A. terreus. This is the first report describing the feasibility of A. terreus , endophytes of P. gracilior, for Taxol production that could be a good industrial platform. [ABSTRACT FROM AUTHOR]

Introduction: Rate-limiting enzymes (RLEs) are innate slow points in metabolic pathways, and many function in bio-processes related to nutrient sensing. Many RLEs carry causal mutations relevant to inherited metabolic disorders. Because the activity of RLEs in cardiovascular health is poorly characterized, our objective was to assess their involvement in cardiometabolic health and disease and where altered biophysical and biochemical functions can promote disease., Methods: A dataset of 380 human RLEs was compared to protein and gene datasets for factors likely to contribute to cardiometabolic disease, including proteins showing significant age-related altered expression in blood and genetic loci with variants that associate with common cardiometabolic phenotypes. The biochemical reactions catalyzed by RLEs were evaluated for metabolites enriched in RLE subsets associating with various cardiometabolic phenotypes. Most significance tests were based on Z-score enrichment converted to p values with a normal distribution function., Results: Of 380 RLEs analyzed, 112 function in mitochondria, and 53 are assigned to inherited metabolic disorders. There was a depletion of RLE proteins known as aging biomarkers. At the gene level, RLEs were assessed for common genetic variants that associated with important cardiometabolic traits of LDL-cholesterol or any of the five outcomes pertinent to metabolic syndrome. This revealed several RLEs with links to cardiometabolic traits, from a minimum of 26 for HDL-cholesterol to a maximum of 45 for plasma glucose. Analysis of these GWAS-linked RLEs for enrichment of the molecular constituents of the catalyzed reactions disclosed a number of significant phenotype-metabolite links. These included blood pressure with acetate (p = 2.2 × 10-4) and NADP+ (p = 0.0091), plasma HDL-cholesterol and triglyceride with diacylglycerol (p = 2.6 × 10-5, 6.4 × 10-5, respectively) and diolein (p = 2.2 × 10-6, 5.9 × 10-6), and waist circumference with d-glucosamine-6-phosphate (p = 1.8 × 10-4)., Conclusion: In the context of cardiometabolic health, aging, and disease, these results highlight key diet-derived metabolites that are central to specific rate-limited processes that are linked to cardiometabolic health. These metabolites include acetate and diacylglycerol, pertinent to blood pressure and triglycerides, respectively, as well as diacylglycerol and HDL-cholesterol., (© 2023 The Author(s). Published by S. Karger AG, Basel.)

Abstract: Ruminant animals depend mainly on hepatic gluconeogenesis pathway to maintain glucose homeostasis. Effects of diets with different ingredients on gene expression profile related to bovine hepatic glucose metabolism are unknown. Objective of this study was to examine gene expression coding for rate-limiting enzymes in hepatic glucose metabolism in response to two different diets. In this study, two kinds of isoenergetic and isonitrogenous diets were designed. Group I diets consisted mainly of corn straw (37.1%), corn (33.5%) and soybean meal (23.6%). Group II diets consisted mainly of alfalfa hay (28.4%), corn silage (26.5%) and corn (22.8%). After 30-day experimental period, biopsy section of liver and blood samples were obtained before feeding. Expression of 28 genes coding for rate-limiting enzymes in hepatic gluconeogenesis pathway, pentose phosphate pathway, glycogen synthesis pathway, glycogen decomposition pathway, glycolysis pathway, glucose aerobic oxidation pathway, and glucose transporters was detected with reverse transcription quantitative PCR (RT-qPCR). Results showed that Group II led to marked up-regulation of phosphoenolpyruvate carboxykinase (PEPCK) and marked up-regulation tendency of glucose-6-phosphatase (G6P), both involved in hepatic gluconeogenesis pathway (P<0.05). No significant differences were observed in mRNA expression of genes involved in other glucose metabolism pathways. Higher relative percentage mRNA abundance of G6P (22.6%), representing the important gluconeogenic enzyme and also catalyzing the last step in glycogenolysis, underscored its importance for ruminant hepatic glucose metabolism. It was concluded that different dietary ingredients could change gene expression of hepatic gluconeogenesis pathway, especially PEPCK and G6P. Dietary ingredients had little effect on other bovine hepatic glucose metabolism pathways and glucose transporter protein. Results indicate that in order to respond to different diet ingredients, genes involved in gluconeogenesis pathway play an important role. [Copyright &y& Elsevier]

Coenzyme Q 10 (CoQ 10 ), a strong antioxidant, is used extensively in food, cosmetic and medicine industries. A natural producer, Rhodopseudomonas palustris, was engineered to overproduce CoQ 10 . For increasing the CoQ 10 content, crtB gene was deleted to block the carotenoid pathway. crtB gene deletion led to 33% improvement of CoQ 10 content over the wild type strain. However, it was found that the yield of hopanoids was also increased by competing for the precursors from carotenoid pathway with CoQ 10 pathway. To further increase the CoQ 10 content, hopanoid pathway was blocked by deleting shc gene, resulting in R. palustris [Δshc, ΔcrtB] to produce 4·7 mg g -1 DCW CoQ 10 , which was 1·2 times higher than the CoQ 10 content in the wild type strain. The common strategy of co-expression of rate-limiting enzymes (DXS, DPS and UbiA) was combined with the pathway blocking method resulted in 8·2 mg g -1 DCW of CoQ 10 , which was 2·9 times higher than that of wild type strain. The results suggested a synergistic effect among different metabolic engineering strategies. This study demonstrates the potential of R. palustris for CoQ 10 production and provides viable strategies to increase CoQ 10 titer., (© 2021 The Society for Applied Microbiology.)

Background: Squalene is currently used widely in the food, cosmetics, and medicine industries. It could also replace petroleum as a raw material for fuels. Microbial fermentation processes for squalene production have been emerging over recent years. In this study, to study the squalene-producing potential of Escherichia coli (E. coli), we employed several increasing strategies for systematic metabolic engineering. These include the expression of human truncated squalene synthase, the overexpression of rate-limiting enzymes in isoprenoid pathway, the modification of isoprenoid-feeding module and the blocking of menaquinone pathway. Results: Herein, human truncated squalene synthase was engineered in Escherichia coli to create a squalene-producing bacterial strain. To increase squalene yield, we employed several metabolic engineering strategies. A fivefold squalene titer increase was achieved by expressing rate-limiting enzymes (IDI, DXS, and FPS) involved in the isoprenoid pathway. Pyridine nucleotide transhydrogenase (UdhA) was then expressed to improve the cellular NADPH/NADP+ ratio, resulting in a 59% increase in squalene titer. The Embden–Meyerhof pathway (EMP) was replaced with the Entner–Doudoroff pathway (EDP) and pentose phosphate pathway (PPP) to feed the isoprenoid pathway, along with the overexpression of zwf and pgl genes which encode rate-limiting enzymes in the EDP and PPP, leading to a 104% squalene content increase. Based on the blocking of menaquinone pathway, a further 17.7% increase in squalene content was achieved. Squalene content reached a final 28.5 mg/g DCW and 52.1 mg/L. Conclusions: This study provided novel strategies for improving squalene yield and demonstrated the potential of producing squalene by E. coli. [ABSTRACT FROM AUTHOR]

Specific activities of the hepatic microsomal enzymes 3-hydroxy-3-methylglutaryl CoA (HMG CoA) reductase and cholesterol 7α-hydroxylase were studied in rats fed sterols and bile acids. The administration of bile acids (taurocholate, taurodeoxycholate, taurochenodeoxycholate) at a level of 1% of the diet for 1 wk reduced the activity of HMG CoA reductase. Taurocholate and taurodeoxycholate, but not taurochenodeoxycholate, inhibited cholesterol 7α-hydroxylase. Dietary sitosterol produced increases in the specific activity of HMG CoA reductase (3.6-fold) and cholesterol 7α-hydroxylase (1.4-fold), and biliary cholesterol concentrations in this group more than doubled. Compared with controls fed the stock diet, the simultaneous administration of sitosterol and taurochenodeoxycholate resulted in a 60% decrease of HMG CoA reductase activity and no change in cholesterol 7α-hydroxylase activity or biliary cholesterol concentration. Rats fed sitosterol plus taurocholate had nearly normal HMG CoA reductase activity, but cholesterol 7α-hydroxylase was inhibited and biliary cholesterol remained high. Bile acid secretion rates and biliary bile acid composition were similar in controls and sterol-fed animals. In all groups receiving bile acids, biliary secretion of bile acids was nearly doubled and bile acid composition was shifted in the direction of the administered bile acid. It is concluded that the composition of the bile acid pool influences the hepatic concentrations of the rate-controlling enzymes of bile acid synthesis.

Cellular metabolism of cancer cell is generally recognized to provide energy for facilitating tumor growth, but little is known about the aberrant metabolism in tumor progression and its prognostic value. Here, we applied integrated genomic approach to uncover the aberrant expression of metabolic enzymes in poorly-differentiated human hepatocellular carcinoma (HCC) for revealing targets against HCC malignancy. A total of 135 upregulated (22 are rate-limiting enzymes (RLEs)) and 362 down-regulated (77 are RLEs) metabolic genes were identified and associated with poor patient survival in large-cohorts of HCC patients in TCGA-LIHC and two other independent transcriptomic studies. Ten out of 22 upregulated RLEs in poorly-differentiated HCC are critical enzymes in pyrimidine metabolism pathways in association with stemness features by gene enrichment analysis and upregulated in ALDH1 + stem-like HCC subpopulations. By focusing on three RLEs including TK1, TYMS and DTYMK of dTTP biosynthesis pathway, expression of 3 RLEs in well-differentiated HCC cells increased ALDH1 + and spheroid stemness population but reversed by knockdown in poorly-differentiated HCC cells. Up-regulated 3 RLEs in HCC were associated with poor patient survival in multiple cohorts. Together, we identified aberrant pyrimidine pathway in poorly-differentiated HCC promotes cancer stemness served as potential theranostic target for battling HCC tumor progression., Competing Interests: CONFLICTS OF INTEREST The authors declare no conflicts of interest.