Biology subjects

Ortiz, S. R.

Publications and source records attributed to Ortiz, S. R..

4 recordsLinked to original sources

bioRxiv2023

C2C12 muscle myotubes, but not kidney proximal tubule HK-2 cells, elevate erythritol synthesis in response to oxidative stress

BackgroundAs a biomarker, elevated serum erythritol predicts type 2 diabetes and cardiovascular disease onset. Erythritol was recently shown to be a product of human glucose metabolism through the pentose phosphate pathway. The regulation of erythritol synthesis from glucose has been explored in cancer cells, but not in non-transformed cells. ObjectiveThe kidneys and skeletal muscle have increased erythritol content in response to dietary sucrose, which suggests that they may significantly contribute to circulating erythritol levels. In the present study, we evaluated if conditions that promote erythritol synthesis in cancer cells are consistent in skeletal muscle and kidney cells. MethodsC2C12 myotubules were used as a model for skeletal muscle and HK-2 human proximal tubule cells were used to model kidney. C2C12 cells were exposed to high-or low-glucose conditions. Both C2C12 and HK-2 cells were exposed to the free radical generator menadione, then intracellular reactive oxygen species (ROS) and erythritol were measured. Intracellular sorbitol levels were also measured because increased polyol flux is also observed after exposure to excess glucose and oxidative stress. ResultsIntracellular erythritol was significantly elevated in C2C12 cells following both high glucose and menadione treatment. In contrast, HK-2 cells did not increase erythritol synthesis in response to oxidative stress. Generation of ROS through hydrogen peroxide (H2O2) exposure elevated sorbitol levels in both C2C12 and HK-2 cells, whereas generation of radicals with menadione treatment did not affect sorbitol production in either cell type. ConclusionsThese findings highlight that the factors contributing to elevated erythritol synthesis vary between cell types. More specifically, these studies demonstrate that muscle cells increase erythritol synthesis in response to both high glucose in culture medium and oxidative stress, whereas kidney cells increase erythritol synthesis only in response to high glucose.

biochemistry↗

bioRxiv2022

Elevated plasma and urinary erythritol is a biomarker of excess simple carbohydrate intake in mice

BackgroundElevated serum erythritol is a predictive biomarker of diabetes and cardiovascular incidence and complications. Erythritol is synthesized endogenously from glucose, but little is known regarding the origin of elevated circulating erythritol in vivo. ObjectiveIn vitro evidence indicates that intracellular erythritol is elevated by high-glucose cell culture conditions and that final step of erythritol synthesis is catalyzed by the enzymes SORD and ADH1. The purpose of this study was to determine if dietary intake and/or diet-induced obesity (DIO) affect erythritol synthesis in mice, and if this relationship is modified by loss of the enzymes SORD or ADH1. MethodsFirst, 8-week-old, male Sord+/+, Sord-/-, Adh1+/+, and Adh1-/- mice were fed either low-fat diet (LFD) with 10% fat-derived calories or DIO high-fat diet (HFD) with 60% fat-derived calories for 8 weeks. Plasma and tissue erythritol were measured using GC-MS. Second, wild-type 8-week-old C57BL/6J mice were fed LFD or HFD with plain drinking water or 30% sucrose water for 8 weeks. Blood glucose and plasma and urinary erythritol were measured in non-fasted and fasted samples. Tissue erythritol was measured following sacrifice. Finally, Sord+/+ and Sord-/- mice were fed LFD with 30% sucrose water for two weeks, then non-fasted plasma, urine, and tissue erythritol were quantified. ResultsPlasma and tissue erythritol were not impacted by loss of Sord or Adh1 on LFD or HFD. In wild-type mice, consumption of 30% sucrose water significantly elevated plasma and urinary erythritol on both LFD and HFD compared to plain water. Sord genotype did not affect plasma or urinary erythritol in response to sucrose feeding, but Sord-/- mice had reduced kidney erythritol content compared to wildtype littermates in response to sucrose. ConclusionsSucrose intake, not high-fat diet, elevates erythritol synthesis and excretion in mice. Loss of ADH1 or SORD does not significantly impact erythritol levels in mice.

biochemistry↗

bioRxiv2022

Erythritol synthesis in human cells is elevated in response to oxidative stress and regulated by the non-oxidative pentose phosphate pathway

Erythritol is a predictive biomarker of cardiometabolic diseases and is produced from glucose metabolism through the pentose phosphate pathway (PPP). Little is known regarding the regulation of endogenous erythritol synthesis in humans. In the present study, we investigated the stimuli that promote erythritol synthesis in human cells and characterized potential points of regulation along the PPP. Human A549 lung carcinoma cells were chosen for their known ability to synthesize erythritol. A549 cells were treated with potential substrates for erythritol production, including glucose, fructose, and glycerol. Using siRNA knockdown, we assessed the necessity of enzymes G6PD, TKT, TALDO, and SORD for erythritol synthesis. We also used position-specific 13C-glucose tracers to determine whether the carbons for erythritol synthesis are derived directly from glycolysis or through the oxidative PPP. Finally, we assessed if erythritol synthesis responds to oxidative stress using chemical and genetic models. Intracellular erythritol was directly associated with media glucose concentration. In addition, siRNA knockdown of TKT or SORD inhibited erythritol synthesis, whereas siG6PD did not. Both chemically induced oxidative stress and constitutive activation of the antioxidant response transcription factor NRF2 elevated intracellular erythritol. Our findings indicate that erythritol synthesis is proportional to flux through the PPP and is regulated by non-oxidative PPP enzymes.

biochemistry↗

bioRxiv2021

Chronic dietary erythritol exposure elevates fasting plasma erythritol levels but does not cause weight gain or modify glucose homeostasis in mice

ObjectiveErythritol is both a common non-nutritive sweetener (NNS) and an endogenous product of glucose metabolism. Recent reports indicate that elevated plasma erythritol is a predictive biomarker of cardiometabolic disease onset and complications. Although short-term erythritol consumption has been evaluated, the effect of chronically elevated circulating erythritol on adiposity and glucose metabolism has not. This study investigated the effect of longer-term erythritol consumption on weight gain and glucose tolerance, and the interaction between dietary composition and erythritol supplementation on these parameters. Methods8-week-old and 20-week-old C57BL/6J mice were randomized to consume low-fat diet (LFD), high-fat diet (HFD), LFD with 40g/kg erythritol (LFD+ERY), and HFD with 40g/kg erythritol (HFD+ERY) groups. After 8 weeks, plasma erythritol, body weight and composition, food intake, glucose tolerance, and brown adipose tissue (BAT) uncoupling protein 1 (UCP1) expression were measured. ResultsPlasma erythritol was elevated 40-fold in mice consuming LFD+ERY or HFD+ERY relative to mice consuming LFD or HFD, respectively. Liver and kidney tissue contained higher levels of erythritol than adipose. Unexpectedly, there was no effect of erythritol supplementation on body weight or glucose tolerance in 8- or 20-week-old mice fed LFD+ERY, or in 8-week-old mice fed HFD+ERY. In 20-week-old mice fed HFD+ERY, there was a significant interaction between erythritol and body weight (p<0.0001) compared to controls, but the main effect of diet was not significant. We also found no effect of chronic erythritol consumption on BAT UCP1 expression. ConclusionProlonged erythritol consumption did not significantly impact body weight, composition, or glucose tolerance. This suggests that dietary erythritol does not contribute to the development of cardiometabolic disease.

biochemistry↗