Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent because it kills cancer cells while sparing normal cells. However, many cancers, including pancreatic ductal adenocarcinoma (PDAC), exhibit intrinsic or acquired resistance to TRAIL, and the molecular mechanisms underlying TRAIL resistance in cancers, particularly in PDAC, remain unclear.   In this study, we demonstrated that glutamine (Gln) endows PDAC cells with resistance to TRAIL through KDM4C-mediated epigenetic regulation of cFLIP. Inhibition of glutaminolysis significantly reduced the cFLIP level, leading to TRAIL-mediated formation of death-inducing signaling complexes. Overexpression of cFLIP dramatically rescued PDAC cells from TRAIL/Gln deprivation-induced apoptosis.   Alpha-Ketoglutarate (aKG) supplementation significantly reversed the decrease in the cFLIP level induced by glutaminolysis inhibition and rescued PDAC cells from TRAIL/Gln deprivation-induced apoptosis. Knockdown of glutamic-oxaloacetic transaminase 2, which facilitates the conversion of oxaloacetate and glutamate into aspartate and aKG, decreased aKG production and the cFLIP level and activated TRAIL-induced apoptosis.   AKG-mediated epigenetic regulation was necessary for maintaining a high level of cFLIP. Glutaminolysis inhibition increased the abundance of H3K9me3 in the cFLIP promoter, indicating that Gln-derived aKG production is important for Jumonji-domain histone demethylase (JHDM)-mediated cFLIP regulation. The JHDM KDM4C regulated cFLIP expression by binding to its promoter, and KDM4C knockdown sensitized PDAC cells to TRAIL-induced apoptosis.   The present findings suggest that Gln-derived aKG production is required for KDM4C-mediated epigenetic regulation of cFLIP, which leads to resistance to TRAIL.

Extensive industrial activities and anthropogenic agricultural practices have led to substantial ammonia release to the environment. Although croplands can act as ammonia sinks, reduced crop production under high concentrations of ammonium has been documented. Alpha-ketoglutarate (AKG) is a critical carbon source, displaying pleiotropic physiological functions. The objective of the present study is to disclose the potential of AKG to enhance ammonium assimilation in poplars.   It showed that AKG application substantially boosted the height, biomass, and photosynthesis activity of poplars exposed to excessive ammonium. AKG also enhanced the activities of key enzymes involved in nitrogen assimilation: glutamine synthetase (GS) and glutamate synthase (GOGAT), elevating the content of amino acids, sucrose, and the tricarboxylic acid cycle (TCA) metabolites.   Furthermore, AKG positively modulated key genes tied to glucose metabolism and ATP synthesis, while suppressing ATP-depleting genes. Correspondingly, both H+-ATPase activity and ATP content increased. These findings demonstrate that exogenously applying AKG improves poplar growth under a high level of ammonium treatment.   AKG might function through sufficient carbon investment, which enhances the carbon-nitrogen balance and energy stability in poplars, promoting ammonium assimilation at high doses of ammonium. Our study provides novel insight into AKG's role in improving poplar growth in response to excess ammonia exposure.

ecently, α-ketoglutaric acid (AKG) has gained importance as an antioxidant. Its dietary supplementation in animals and humans has proved beneficial. Moreover, an extensive group of studies on in ovo feeding has proved that it produces better day-old chicks and overall performance.   Combining the two, we hypothesized that in ovo feeding of AKG could improve the antioxidant status in addition to chick quality and broiler performance. At 17.5 days of incubation, eggs were divided into one of five groups: eggs that received (i) no injection (U-CON), (ii) distilled water (DDW) only (0 AKG), (iii) 0.5% AKG dissolved in DDW (0.5 AKG), (iv) 1.0% AKG dissolved in DDW (1.0 AKG), or (v) 1.5% AKG dissolved in DDW (1.5 AKG).   Chicks were raised until 21 days of age. Biological samples were collected on day 0 and day 21. Body weight (p = 0.020), average daily gain (p = 0.025), and average daily feed intake (p = 0.036) were found to quadratically increase with the amount of AKG during the grower phase. At day 0, the absolute (p = 0.040) and relative weight (p = 0.035) of the liver increased linearly with an increasing amount of AKG. The 0.5 AKG group had significantly higher plasma protein (p = 0.025), absolute and relative heart indices at day 0 (p = 0.006). An in ovo feeding of AKG improved the plasma antioxidant capacity of chicks at day 0 as compared to 0 AKG. AKG effect was seen on the plasma antioxidant balance, which increased linearly with the increasing dose of in ovo AKG.   Furthermore, 1.0 AKG and 1.5 AKG showed a significant (p = 0.002) upregulation of the hepatic mRNA expression of nuclear factor erythroid 2-related factor (NRF2) in comparison to 0 AKG. The results imply that without negatively affecting hatchability performance, in ovo feeding of AKG has beneficial effects on the antioxidant status of broilers.

α-ketoglutarate (AKG) is a valuable dicarboxylic acid with multiple applications in the food, pharmaceutical, and chemical industries. Its chemical synthesis is associated with toxic by-products, low specificity, and high energy input. To create a more environmentally friendly and sustainable alternative, a microbial production process for AKG was developed.   Four potential producer strains were generated by metabolic engineering of Corynebacteriumglutamicum and characterized on defined glucose/sucrose media as well as molasses, a side stream from sugar beet processing. While strain C.glutamicum PO6-iolT1Δgdh ΔgltB mscCG' ΔodhA was not able to grow on defined media it outperformed all predecessor variants on molasses. Successful scale-up into a fed-batch bioreactor process with molasses yielded 96.2g AKG with a conversion yield of 0.64gg-1.   Finally, downstream processing by liquid-liquid extraction with ethyl acetate enabled product purification with an extraction efficiency of 87 % and an AKG purity of > 93 %.  

Alpha-ketoglutarate (AKG) is a key intermediate of various metabolic pathways including tricarboxylic acid (TCA) cycle, anabolic and catabolic reactions of amino acids, and collagen biosynthesis. Meanwhile, AKG also participates in multiple signaling pathways related to cellular redox regulation, epigenetic processes, and inflammation response. Emerging evidence has shown that kidney diseases like diabetic nephropathy and renal ischemia/reperfusion injury are associated with metabolic disorders. In consistence with metabolic role of AKG, further metabolomics study demonstrated a dysregulated AKG level in kidney diseases. Intriguingly, earlier studies during the years of 1980s and 1990s indicated that AKG may benefit wound healing and surgery recovery. Recently, interests on AKG are arising again due to its protective roles on healthy ageing, which may shed light on developing novel therapeutic strategies against age-related diseases including renal diseases. This review will summarize the physiological and pathological properties of AKG, as well as the underlying molecular mechanisms, with a special emphasis on kidney diseases.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent because it kills cancer cells while sparing normal cells. However, many cancers, including pancreatic ductal adenocarcinoma (PDAC), exhibit intrinsic or acquired resistance to TRAIL, and the molecular mechanisms underlying TRAIL resistance in cancers, particularly in PDAC, remain unclear.   In this study, we demonstrated that glutamine (Gln) endows PDAC cells with resistance to TRAIL through KDM4C-mediated epigenetic regulation of cFLIP. Inhibition of glutaminolysis significantly reduced the cFLIP level, leading to TRAIL-mediated formation of death-inducing signaling complexes. Overexpression of cFLIP dramatically rescued PDAC cells from TRAIL/Gln deprivation-induced apoptosis.   Alpha-Ketoglutarate (aKG) supplementation significantly reversed the decrease in the cFLIP level induced by glutaminolysis inhibition and rescued PDAC cells from TRAIL/Gln deprivation-induced apoptosis. Knockdown of glutamic-oxaloacetic transaminase 2, which facilitates the conversion of oxaloacetate and glutamate into aspartate and aKG, decreased aKG production and the cFLIP level and activated TRAIL-induced apoptosis.   AKG-mediated epigenetic regulation was necessary for maintaining a high level of cFLIP. Glutaminolysis inhibition increased the abundance of H3K9me3 in the cFLIP promoter, indicating that Gln-derived aKG production is important for Jumonji-domain histone demethylase (JHDM)-mediated cFLIP regulation. The JHDM KDM4C regulated cFLIP expression by binding to its promoter, and KDM4C knockdown sensitized PDAC cells to TRAIL-induced apoptosis.   The present findings suggest that Gln-derived aKG production is required for KDM4C-mediated epigenetic regulation of cFLIP, which leads to resistance to TRAIL.

Extensive industrial activities and anthropogenic agricultural practices have led to substantial ammonia release to the environment. Although croplands can act as ammonia sinks, reduced crop production under high concentrations of ammonium has been documented. Alpha-ketoglutarate (AKG) is a critical carbon source, displaying pleiotropic physiological functions. The objective of the present study is to disclose the potential of AKG to enhance ammonium assimilation in poplars.   It showed that AKG application substantially boosted the height, biomass, and photosynthesis activity of poplars exposed to excessive ammonium. AKG also enhanced the activities of key enzymes involved in nitrogen assimilation: glutamine synthetase (GS) and glutamate synthase (GOGAT), elevating the content of amino acids, sucrose, and the tricarboxylic acid cycle (TCA) metabolites.   Furthermore, AKG positively modulated key genes tied to glucose metabolism and ATP synthesis, while suppressing ATP-depleting genes. Correspondingly, both H+-ATPase activity and ATP content increased. These findings demonstrate that exogenously applying AKG improves poplar growth under a high level of ammonium treatment.   AKG might function through sufficient carbon investment, which enhances the carbon-nitrogen balance and energy stability in poplars, promoting ammonium assimilation at high doses of ammonium. Our study provides novel insight into AKG's role in improving poplar growth in response to excess ammonia exposure.

ecently, α-ketoglutaric acid (AKG) has gained importance as an antioxidant. Its dietary supplementation in animals and humans has proved beneficial. Moreover, an extensive group of studies on in ovo feeding has proved that it produces better day-old chicks and overall performance.   Combining the two, we hypothesized that in ovo feeding of AKG could improve the antioxidant status in addition to chick quality and broiler performance. At 17.5 days of incubation, eggs were divided into one of five groups: eggs that received (i) no injection (U-CON), (ii) distilled water (DDW) only (0 AKG), (iii) 0.5% AKG dissolved in DDW (0.5 AKG), (iv) 1.0% AKG dissolved in DDW (1.0 AKG), or (v) 1.5% AKG dissolved in DDW (1.5 AKG).   Chicks were raised until 21 days of age. Biological samples were collected on day 0 and day 21. Body weight (p = 0.020), average daily gain (p = 0.025), and average daily feed intake (p = 0.036) were found to quadratically increase with the amount of AKG during the grower phase. At day 0, the absolute (p = 0.040) and relative weight (p = 0.035) of the liver increased linearly with an increasing amount of AKG. The 0.5 AKG group had significantly higher plasma protein (p = 0.025), absolute and relative heart indices at day 0 (p = 0.006). An in ovo feeding of AKG improved the plasma antioxidant capacity of chicks at day 0 as compared to 0 AKG. AKG effect was seen on the plasma antioxidant balance, which increased linearly with the increasing dose of in ovo AKG.   Furthermore, 1.0 AKG and 1.5 AKG showed a significant (p = 0.002) upregulation of the hepatic mRNA expression of nuclear factor erythroid 2-related factor (NRF2) in comparison to 0 AKG. The results imply that without negatively affecting hatchability performance, in ovo feeding of AKG has beneficial effects on the antioxidant status of broilers.

α-ketoglutarate (AKG) is a valuable dicarboxylic acid with multiple applications in the food, pharmaceutical, and chemical industries. Its chemical synthesis is associated with toxic by-products, low specificity, and high energy input. To create a more environmentally friendly and sustainable alternative, a microbial production process for AKG was developed.   Four potential producer strains were generated by metabolic engineering of Corynebacteriumglutamicum and characterized on defined glucose/sucrose media as well as molasses, a side stream from sugar beet processing. While strain C.glutamicum PO6-iolT1Δgdh ΔgltB mscCG' ΔodhA was not able to grow on defined media it outperformed all predecessor variants on molasses. Successful scale-up into a fed-batch bioreactor process with molasses yielded 96.2g AKG with a conversion yield of 0.64gg-1.   Finally, downstream processing by liquid-liquid extraction with ethyl acetate enabled product purification with an extraction efficiency of 87 % and an AKG purity of > 93 %.  

Alpha-ketoglutarate (AKG) is a key intermediate of various metabolic pathways including tricarboxylic acid (TCA) cycle, anabolic and catabolic reactions of amino acids, and collagen biosynthesis. Meanwhile, AKG also participates in multiple signaling pathways related to cellular redox regulation, epigenetic processes, and inflammation response. Emerging evidence has shown that kidney diseases like diabetic nephropathy and renal ischemia/reperfusion injury are associated with metabolic disorders. In consistence with metabolic role of AKG, further metabolomics study demonstrated a dysregulated AKG level in kidney diseases. Intriguingly, earlier studies during the years of 1980s and 1990s indicated that AKG may benefit wound healing and surgery recovery. Recently, interests on AKG are arising again due to its protective roles on healthy ageing, which may shed light on developing novel therapeutic strategies against age-related diseases including renal diseases. This review will summarize the physiological and pathological properties of AKG, as well as the underlying molecular mechanisms, with a special emphasis on kidney diseases.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent because it kills cancer cells while sparing normal cells. However, many cancers, including pancreatic ductal adenocarcinoma (PDAC), exhibit intrinsic or acquired resistance to TRAIL, and the molecular mechanisms underlying TRAIL resistance in cancers, particularly in PDAC, remain unclear.   In this study, we demonstrated that glutamine (Gln) endows PDAC cells with resistance to TRAIL through KDM4C-mediated epigenetic regulation of cFLIP. Inhibition of glutaminolysis significantly reduced the cFLIP level, leading to TRAIL-mediated formation of death-inducing signaling complexes. Overexpression of cFLIP dramatically rescued PDAC cells from TRAIL/Gln deprivation-induced apoptosis.   Alpha-Ketoglutarate (aKG) supplementation significantly reversed the decrease in the cFLIP level induced by glutaminolysis inhibition and rescued PDAC cells from TRAIL/Gln deprivation-induced apoptosis. Knockdown of glutamic-oxaloacetic transaminase 2, which facilitates the conversion of oxaloacetate and glutamate into aspartate and aKG, decreased aKG production and the cFLIP level and activated TRAIL-induced apoptosis.   AKG-mediated epigenetic regulation was necessary for maintaining a high level of cFLIP. Glutaminolysis inhibition increased the abundance of H3K9me3 in the cFLIP promoter, indicating that Gln-derived aKG production is important for Jumonji-domain histone demethylase (JHDM)-mediated cFLIP regulation. The JHDM KDM4C regulated cFLIP expression by binding to its promoter, and KDM4C knockdown sensitized PDAC cells to TRAIL-induced apoptosis.   The present findings suggest that Gln-derived aKG production is required for KDM4C-mediated epigenetic regulation of cFLIP, which leads to resistance to TRAIL.

Extensive industrial activities and anthropogenic agricultural practices have led to substantial ammonia release to the environment. Although croplands can act as ammonia sinks, reduced crop production under high concentrations of ammonium has been documented. Alpha-ketoglutarate (AKG) is a critical carbon source, displaying pleiotropic physiological functions. The objective of the present study is to disclose the potential of AKG to enhance ammonium assimilation in poplars.   It showed that AKG application substantially boosted the height, biomass, and photosynthesis activity of poplars exposed to excessive ammonium. AKG also enhanced the activities of key enzymes involved in nitrogen assimilation: glutamine synthetase (GS) and glutamate synthase (GOGAT), elevating the content of amino acids, sucrose, and the tricarboxylic acid cycle (TCA) metabolites.   Furthermore, AKG positively modulated key genes tied to glucose metabolism and ATP synthesis, while suppressing ATP-depleting genes. Correspondingly, both H+-ATPase activity and ATP content increased. These findings demonstrate that exogenously applying AKG improves poplar growth under a high level of ammonium treatment.   AKG might function through sufficient carbon investment, which enhances the carbon-nitrogen balance and energy stability in poplars, promoting ammonium assimilation at high doses of ammonium. Our study provides novel insight into AKG's role in improving poplar growth in response to excess ammonia exposure.

ecently, α-ketoglutaric acid (AKG) has gained importance as an antioxidant. Its dietary supplementation in animals and humans has proved beneficial. Moreover, an extensive group of studies on in ovo feeding has proved that it produces better day-old chicks and overall performance.   Combining the two, we hypothesized that in ovo feeding of AKG could improve the antioxidant status in addition to chick quality and broiler performance. At 17.5 days of incubation, eggs were divided into one of five groups: eggs that received (i) no injection (U-CON), (ii) distilled water (DDW) only (0 AKG), (iii) 0.5% AKG dissolved in DDW (0.5 AKG), (iv) 1.0% AKG dissolved in DDW (1.0 AKG), or (v) 1.5% AKG dissolved in DDW (1.5 AKG).   Chicks were raised until 21 days of age. Biological samples were collected on day 0 and day 21. Body weight (p = 0.020), average daily gain (p = 0.025), and average daily feed intake (p = 0.036) were found to quadratically increase with the amount of AKG during the grower phase. At day 0, the absolute (p = 0.040) and relative weight (p = 0.035) of the liver increased linearly with an increasing amount of AKG. The 0.5 AKG group had significantly higher plasma protein (p = 0.025), absolute and relative heart indices at day 0 (p = 0.006). An in ovo feeding of AKG improved the plasma antioxidant capacity of chicks at day 0 as compared to 0 AKG. AKG effect was seen on the plasma antioxidant balance, which increased linearly with the increasing dose of in ovo AKG.   Furthermore, 1.0 AKG and 1.5 AKG showed a significant (p = 0.002) upregulation of the hepatic mRNA expression of nuclear factor erythroid 2-related factor (NRF2) in comparison to 0 AKG. The results imply that without negatively affecting hatchability performance, in ovo feeding of AKG has beneficial effects on the antioxidant status of broilers.

α-ketoglutarate (AKG) is a valuable dicarboxylic acid with multiple applications in the food, pharmaceutical, and chemical industries. Its chemical synthesis is associated with toxic by-products, low specificity, and high energy input. To create a more environmentally friendly and sustainable alternative, a microbial production process for AKG was developed.   Four potential producer strains were generated by metabolic engineering of Corynebacteriumglutamicum and characterized on defined glucose/sucrose media as well as molasses, a side stream from sugar beet processing. While strain C.glutamicum PO6-iolT1Δgdh ΔgltB mscCG' ΔodhA was not able to grow on defined media it outperformed all predecessor variants on molasses. Successful scale-up into a fed-batch bioreactor process with molasses yielded 96.2g AKG with a conversion yield of 0.64gg-1.   Finally, downstream processing by liquid-liquid extraction with ethyl acetate enabled product purification with an extraction efficiency of 87 % and an AKG purity of > 93 %.  

Alpha-ketoglutarate (AKG) is a key intermediate of various metabolic pathways including tricarboxylic acid (TCA) cycle, anabolic and catabolic reactions of amino acids, and collagen biosynthesis. Meanwhile, AKG also participates in multiple signaling pathways related to cellular redox regulation, epigenetic processes, and inflammation response. Emerging evidence has shown that kidney diseases like diabetic nephropathy and renal ischemia/reperfusion injury are associated with metabolic disorders. In consistence with metabolic role of AKG, further metabolomics study demonstrated a dysregulated AKG level in kidney diseases. Intriguingly, earlier studies during the years of 1980s and 1990s indicated that AKG may benefit wound healing and surgery recovery. Recently, interests on AKG are arising again due to its protective roles on healthy ageing, which may shed light on developing novel therapeutic strategies against age-related diseases including renal diseases. This review will summarize the physiological and pathological properties of AKG, as well as the underlying molecular mechanisms, with a special emphasis on kidney diseases.