Hepatic Oxidation Research Articles

Effects of Acute Hypoxic Stress on Physiological and Hepatic Metabolic Responses of Triploid Rainbow Trout (Oncorhynchus mykiss).

This experiment simulated the hypoxic environment caused by actual production operations in fish farming (i.e., catching, gathering, transferring, and weighting) to study the effects of acute hypoxic conditions on the physiological and metabolic responses of triploid rainbow trout (O. mykiss). Two groups of fish weighting 590 g were sampled in the normoxia group (dissolved oxygen above 7 mg/L) and hypoxia group (dissolved oxygen ranged from 2 to 5 mg/L for 10 min). The results showed that 1) regarding stress response, hypoxia increased plasma levels of cortisol, heat shock protein 70 (HSP-70), lysozyme, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatine phosphokinase (CPK); induced the expression of hepatic genes encoding nuclear factor erythroid 2 related factor 2 (Nrf2), interferon γ (IFN-γ) and interleukin-1β (IL-1β). 2) Regarding metabolism response, hypoxia increased plasma levels of globulin (GLOB), glucose (GLU), triglyceride (TG) and lactate dehydrogenase (LDH); upregulated the hepatic gene expression of phosphoenolpyruvate carboxykinase, (PEPCK), pyruvate dehydrogenase kinase (PDK1), acetyl-CoA carboxylase (ACC) and acetyl-CoA oxidase (ACO); downregulated the hepatic gene expression of carnitine palmitoyl transferase 1 (CPT1); and unchanged the expression of hepatic genes in glycolysis and autophagy. 3) In response to hypoxia-inducible factors (HIFs), the hepatic HIF-2α gene was activated in the hypoxia group, but HIF-1α gene expression remained unchanged. Thus, during acute hypoxic stress, triploid rainbow trout were in a defensive state, with an enhanced immune response and altered antioxidant status. Additionally, the hepatic mitochondrial oxidation of glucose- and lipid-derived carbon in trout was suppressed, and hepatic gluconeogenesis and lipid synthesis were activated, which might be regulated by the HIF-2α pathway.

Reprint of: Evidence for the Participation of Cytochrome b5 in Hepatic Microsomal Mixed-Function Oxidation Reactions

Reprint of: Evidence for the Participation of Cytochrome b5 in Hepatic Microsomal Mixed-Function Oxidation Reactions

Regulation of Hepatic Lipid and Glucose Metabolism by INSP3R1.

With the rising epidemics of obesity and nonalcoholic fatty liver disease (NAFLD) and its downstream consequences including steatohepatitis, cirrhosis, and type 2 diabetes in the U.S. and worldwide, new therapeutic approaches are urgently needed to treat these devastating conditions. Glucagon, known for a century to be a glucose-raising hormone and clearly demonstrated to contribute to fasting and postprandial hyperglycemia in both type 1 and type 2 diabetes, represents an unlikely target to improve health in those with metabolic syndrome. However, recent work from our group and others' identifies an unexpected role for glucagon as a potential means of treating NAFLD, improving insulin sensitivity, and improving the lipid profile. We propose a unifying, calcium-dependent mechanism for glucagon's effects both to stimulate hepatic gluconeogenesis and to enhance hepatic mitochondrial oxidation: signaling through the inositol 1,4,5-trisphosphate receptor type 1 (INSP3R1), glucagon activates phospholipase C (PKC)/protein kinase A (PKA) signaling to enhance adipose triglyceride lipase (ATGL)-dependent intrahepatic lipolysis and, in turn, increase cytosolic gluconeogenesis by allosteric activation of pyruvate carboxylase. Simultaneously in the mitochondria, calcium transferred through mitochondria-associated membranes activates several dehydrogenases in the tricarboxylic acid cycle, correlated with an increase in mitochondrial energy expenditure and reduction in ectopic lipid. This model suggests that short-term, cyclic treatment with glucagon or other INSP3R1 antagonists could hold promise as a means to reset lipid homeostasis in patients with NAFLD.

219-LB: The Mitochondrial Calcium Uniporter Regulates Hepatic Lipid Accumulation and Mitochondrial Oxidation

The mitochondrial calcium uniporter (MCU) facilitates mitochondrial calcium influx, and several enzymes that catalyze key steps of the tricarboxylic acid (TCA) cycle require calcium for their activation. As such, it is generally accepted that rates of mitochondrial oxidation correlate with mitochondrial calcium activity. Decreased rates of hepatic mitochondrial oxidation are associated with metabolic dysfunction and ectopic lipid accumulation as seen with type 2 diabetes and nonalcoholic fatty liver disease. Despite this, a role for MCU and mitochondrial calcium in regulating hepatic mitochondrial oxidation is still unclear. To address this question, we generated a liver-specific MCU knockout (MCU KO) mouse model which displayed significantly reduced mitochondrial calcium ([Ca2+]mt, p<0.05) and increased cytosolic calcium ([Ca2+]cyt, p<0.01) in isolated hepatocytes. Despite decreased [Ca2+]mt, we found that deletion of hepatic MCU resulted in increased rates of isocitrate dehydrogenase flux (VIDH, p<0.01) , α-ketoglutarate dehydrogenase flux (VOGDH, p<0.01) , and succinate dehydrogenase flux (VSDH, p<0.05) , using a novel in vivo [13C5]glutamine tracer technique. Further, we report that rates of [14C16]palmitate oxidation (p<0.01) and intrahepatic lipolysis (p<0.05) were significantly increased in precision-cut liver slices collected from MCU KO mice compared to WT, consistent with [Ca2+]cyt activation of CAMKII (p<0.01) and ATGL (p<0.001) in MCU KO mice, and were associated with reductions in hepatic triacylglycerol content in vivo (p<0.01) . Taken together, these data demonstrate that hepatic mitochondrial activity can be dissociated from mitochondrial calcium concentrations and reveal a key role for cytosolic calcium and mitochondrial anaplerosis in the regulation of hepatic mitochondrial fat oxidation. Disclosure T. E. Lamoia: n/a. B. T. Hubbard: None. M. Guerra: None. R. Goodman: None. M. H. Nathanson: None. V. Mootha: Advisory Panel; 5AM Ventures, LLC, Janssen Research & Development, LLC. G. I. Shulman: Advisory Panel; 89bio, Inc., AstraZeneca, Equator Therapeutics, Inc., Janssen Research & Development, LLC, Merck & Co., Inc., Consultant; DiCerna Pharmaceuticals, Inc. , Novo Nordisk, Other Relationship; Generian Pharmaceuticals, iMetabolic Biopharma Corporation, Maze Therapeutics, The Liver Company, Stock/Shareholder; Levels Health, Inc. . Funding F31 DK126362/DK/NIDDK NIH HHST32 GM007324/GM/NIGMS NIH HHS

532-P: Voluntary Exercise during Food Restriction Promotes a Sustained Increase in Hepatic Oxidative Metabolism

Exercise is an important lifestyle intervention for the prevention and treatment of NAFLD. Importantly, exercise can reduce hepatic steatosis independent of changes in body mass, which may stem from increased oxidative demand in liver during exercise. Increased hepatic gluconeogenesis (GNG) and tricarboxylic acid (TCA) cycle flux have been observed during exercise in rodents, but it is unclear whether this adaptation is chronically maintained outside of the exercise window. Liver metabolism is also altered by nutritional status. Fasting promotes hepatic fat oxidation, ketogenesis and GNG, while feeding promotes glycogen storage and fat synthesis. Hence, fasting and exercise may have a positive interaction, whereas exogenous nutrient intake or glucose infusion is known to reduce the induction of GNG during exercise. Here, we tested whether nutritional status impacts exercise induced hepatic metabolic adaptations. Sprague-Dawley rats were kept sedentary or provided voluntary wheel running (VWR) for 4 weeks in the presence or absence of food restriction during the dark phase when rats spontaneously run. Experiments were conducted one day following the last exercise bout. Hepatic metabolic flux was examined by in vivo stable isotope infusions of [U-13C3]propionate, [3,4-13C2]glucose and 2H2O in rats using mass spectrometry and computational analysis. Chronic VWR in the fed state had no effect on basal hepatic fluxes outside of the exercise window. However, exercise during food restriction chronically induced a 2-fold induction of TCA cycle turnover, increase in GNG from glycerol and lowered ketogenesis outside of the exercise window. Thus, VWR during food restriction triggered an increase in hepatic energy demand that was sustained for at least 24 hours, while the effects of exercise in the fed state dissipated by 24 hours. These data suggest that acute nutritional state may be an important factor in the long-term programming of liver metabolism by exercise. Disclosure S.Deja: None. B.Kucejova: None. A.Maurer: None. M.N.Mizerska: None. X.Fu: None. J.P.Thyfault: None. S.C.Burgess: n/a. Funding National Institutes of Health (R01DK121497, R01DK078184, P41EB015908)

On ‘Evidence for the participation of cytochrome b5 in hepatic microsomal mixed-function oxidation reactions’ by Alfred Hildebrandt and Ronald W. Estabrook

This paper by Alfred G. Hildebrandt and Ronald W. Estabrook at the University of Texas (Southwestern) Medical School, led to the concept of cytochrome b5 (b5) as an auxiliary protein facilitating some cytochrome P450 (P450) reactions in the liver and other tissues. The gist of the paper is that DPNH (now known as NADH) enhanced rates of TPNH (now NADPH)-supported N-demethylation of O-ethylmorphine in rat liver microsomes. The conclusion was that b5 was providing an electron to the ferrous-oxy form of P450 (Fe2+O2), which was supported by some spectral observations on the oxidation state of b5 in the microsomes in the steady state. This observation led to a flurry of activity, which is still in progress. This paper has been cited 678 times in Google (558 in Clarivate), and I have often cited it myself. A PubMed search for the terms P450 andb5 yielded 2244 results.

Folic Acid Homeostasis and Its Pathways Related to Hepatic Oxidation in Adolescent Rats Exposed to Binge Drinking.

Chronic ethanol consumption and liver disease are intimately related to folic acid (FA) homeostasis. Despite the fact that FA decreases lipid oxidation, its mechanisms are not yet well elucidated. Lately, adolescents have been practising binge drinking (BD), consisting of the intake of a high amount of alcohol in a short time; this is a particularly pro-oxidant form of consumption. The aim of this study is to examine, for the first time, FA homeostasis in BD adolescent rats and its antioxidant properties in the liver. We used adolescent rats, including control rats and rats exposed to an intermittent intraperitoneal BD model, supplemented with or without FA. Renal FA reabsorption and renal FA deposits were increased in BD rats; hepatic deposits were decreased, and heart and serum levels remained unaffected. This depletion in the liver was accompanied by higher transaminase levels; an imbalance in the antioxidant endogenous enzymatic system; lipid and protein oxidation; a decrease in glutathione (GSH) levels; hyper-homocysteinemia (HHcy); an increase in NADPH oxidase (NOX) 1 and NOX4 enzymes; an increase in caspase 9 and 3; and a decrease in the anti-apoptotic metallopeptidase inhibitor 1. Furthermore, BD exposure increased the expression of uncoupled endothelial nitric oxide synthase (eNOS) by increasing reactive nitrogen species generation and the nitration of tyrosine proteins. When FA was administered, hepatic FA levels returned to normal levels; transaminase and lipid and protein oxidation also decreased. Its antioxidant activity was due, in part, to the modulation of superoxide dismutase activity, GSH synthesis and NOX1, NOX4 and caspase expression. FA reduced HHcy and increased the expression of coupled eNOS by increasing tetrahydrobiopterin expression, avoiding nitrosative stress. In conclusion, FA homeostasis and its antioxidant properties are affected in BD adolescent rats, making it clear that this vitamin plays an important role in the oxidative, nitrosative and apoptotic hepatic damage generated by acute ethanol exposure. For this, FA supplementation becomes a potential BD therapy for adolescents, preventing future acute alcohol-related harms.

Effect of dietary incorporation of Chlorella vulgaris and CAZyme supplementation on the hepatic proteome of finishing pigs

The combination of several factors, including an increase in world population and living standards in developing countries and world dependency on conventional crop imports drive a search for alternative feedstuffs for poultry and pig diets. This would reduce the environmental impact associated with the foreseeable increase in the demand for animal products. One of such alternatives are microalgae, a diverse group of aquatic organisms with interesting nutritional properties. Chlorella vulgaris is a green microalga with a crude protein content comparable to that of soybean meal. However, its recalcitrant cell wall prevents it from being used as a nutrient source in monogastric diets. CAZyme supplementation is a putative strategy to increase its nutritional value, aiming at disrupting the cell wall and make intracellular nutrients available for digestion. The impact of these dietary strategies on the hepatic metabolism is currently unknown. The objective of this study was to evaluate the hepatic proteome of pigs fed with 5% C. vulgaris with or without CAZyme supplementation. Microalga inclusion has affected lipid metabolism and oxidative stress. CAZyme supplementation has caused higher oxidative stress in the liver, possibly caused by the higher digestive availability and consequent hepatic oxidation of fatty acids. SignificanceC. vulgaris, a microalga, is a novel feedstuff that is an alternative to conventional crops such as maize and soybean meal. Its recalcitrant cell wall may cause antinutritional effects when included in monogastric diets. This can be prevented by using exogenous enzyme supplementation, namely CAZymes, aimed at degrading this cell wall during digestion. Liver proteomics was used to identify the impact of these diets in finishing pig metabolism.

Plasma oxyphytosterols most likely originate from hepatic oxidation and subsequent spill-over in the circulation

We evaluated oxyphytosterol (OPS) concentrations in plasma and various tissues of two genetically modified mouse models with either increased cholesterol (apoE KO mice) or increased cholesterol and plant sterol (PS) concentrations (apoExABCG8 dKO mice). Sixteen female apoE KO and 16 dKO mice followed the same standard, low OPS-chow diet. Animals were euthanized at 36 weeks to measure PS and OPS concentrations in plasma, brain, liver and aortic tissue. Cholesterol and oxysterol (OS) concentrations were analyzed as reference for sterol oxidation in general. Plasma campesterol (24.1 ± 4.3 vs. 11.8 ± 3.0 mg/dL) and sitosterol (67.4 ± 12.7 vs. 4.9 ± 1.1 mg/dL) concentrations were severely elevated in the dKO compared to the apoE KO mice (p < 0.001). Also, in aortic and brain tissue, PS levels were significantly elevated in dKO. However, plasma, aortic and brain OPS concentrations were comparable or even lower in the dKO mice. In contrast, in liver tissue, both PS and OPS concentrations were severely elevated in the dKO compared to apoE KO mice (sum OPS: 7.4 ± 1.6 vs. 4.1 ± 0.8 ng/mg, p < 0.001). OS concentrations followed cholesterol concentrations in plasma and all tissues suggesting ubiquitous oxidation. Despite severely elevated PS concentrations, OPS concentrations were only elevated in liver tissue, suggesting that OPS are primarily formed in the liver and plasma concentrations originate from hepatic spill-over into the circulation.

Longitudinal liver proteome profiling in dairy cows during the transition from gestation to lactation: Investigating metabolic adaptations and their interactions with fatty acids supplementation via repeated measurements ANOVA-simultaneous component analysis

Repeated measurements analysis of variance – simultaneous component analysis (ASCA) has been developed to handle complex longitudinal omics datasets and combine novel information with existing data. Herein, we aimed at applying ASCA to 64 liver proteomes collected at 4-time points (day −21, +1, +28, and + 63 relative to parturition) from 16 Holstein cows treated from 9 wk. antepartum to 9 wk. postpartum (PP) with coconut oil (CTRL) or a mixture of essential fatty acids (EFA) and conjugated linoleic acid (CLA) (EFA + CLA). The ASCA modeled 116, 43, and 97 differentially abundant proteins (DAP) during the transition to lactation, between CTRL and EFA + CLA, and their interaction, respectively. Time-dependent DAP were annotated to pathways related to the metabolism of carbohydrates, FA, and amino acid in the PP period. The DAP between FA and the interaction effect were annotated to the metabolism of xenobiotics by cytochrome P450, drug metabolism - cytochrome P450, retinol metabolism, and steroid hormone biosynthesis. Collectively, ASCA provided novel information on molecular markers of metabolic adaptations and their interactions with EFA + CLA supplementation. Bioinformatics analysis suggested that supplemental EFA + CLA amplified hepatic FA oxidation; cytochrome P450 was enriched to maintain metabolic homeostasis by oxidation/detoxification of endogenous compounds and xenobiotics. SignificanceThis report is among the first ones applying repeated measurement analysis of variance–simultaneous component analysis (ASCA) to deal with longitudinal proteomics results. ASCA separately identified differentially abundant proteins (DAP) in ‘transition time’, ‘between fatty acid treatments’, and ‘their interaction’. We first identified the molecular signature of hepatic metabolic adaptations during postpartum negative energy balance; the enriched pathways were well-known pathways related to mobilizing fatty acids (FA) and amino acids to support continuous energy production through fatty acid oxidation, TCA cycle, and gluconeogenesis. Some of the DAP were not previously reported in transition dairy cows. Secondly, we provide novel information on the mechanisms by which supplemented essential FA and conjugated linoleic acids interact with hepatic metabolism. In this regard, FA amplified hepatic detoxifying and oxidation capacity through ligand activation of nuclear receptors. Finally, we briefly compared the strengths and weaknesses of the ASCA model with PLS-DA and outlined why these methods are complementary.

Gardeniae Fructus Attenuates Thioacetamide-Induced Liver Fibrosis in Mice via Both AMPK/SIRT1/NF-κB Pathway and Nrf2 Signaling.

Liver fibrosis, which means a sort of the excessive accumulation of extracellular matrices (ECMs) components through the liver tissue, is considered as tissue repair or wound-healing status. This pathological stage potentially leads to cirrhosis, if not controlled, it progressively results in hepatocellular carcinoma. Herein, we investigated the pharmacological properties and underlying mechanisms of Gardeniae Fructus (GF) against thioacetamide (TAA)-induced liver fibrosis of mice model. GF not only attenuated hepatic tissue oxidation but also improved hepatic inflammation. We further confirmed that GF led to ameliorating liver fibrosis by ECMs degradations. Regarding the possible underlying mechanism of GF, we observed GF regulated epigenetic regulator, Sirtuin 1 (SIRT1), in TAA-injected liver tissue. These alterations were well supported by SIRT1 related signaling pathways through regulations of its downstream proteins including, AMP-activated protein kinase (AMPK), p47phox, NADPH oxidase 2, nuclear factor erythroid 2–related factor 2 (Nrf2), and heme oxygenase-1, respectively. To validate the possible mechanism of GF, we used HepG2 cells with hydrogen peroxide treated oxidative stress and chronic exposure conditions via deteriorations of cellular SIRT1. Moreover, GF remarkably attenuated ECMs accumulations in transforming growth factor–β1-induced LX-2 cells relying on the SIRT1 existence. Taken together, GF attenuated liver fibrosis through AMPK/SIRT1 pathway as well as Nrf2 signaling cascades. Therefore, GF could be a clinical remedy for liver fibrosis patients in the future.

White meat proteins were more conducive to hepatic antioxidative status than soybean and red meat proteins.

Intake of protein-rich foods might induce oxidative stress in organs. This study investigated the impacts of protein sources including casein, soybean, fish, chicken, pork, and beef proteins on hepatic oxidation and antioxidation status in rats. It was shown that meat proteins produced higher reactive oxygen species in livers (from 64,868 to 87,153F/mgpro) than casein (54,045F/mgpro) and soybean protein (48,361F/mgpro, p<.05). Pork and soybean proteins induced higher hepatic oxidative stress than fish, chicken and beef proteins by increasing malondialdehyde production (>16%, p<.05). White meat (fish and chicken) proteins promoted hepatic superoxide dismutase activity and total antioxidant capacity compared to soybean and red meat (pork and beef) proteins (p<.05). Compared to red meat proteins, white meat proteins increased hepatic expressions of thioredoxin and glutaredoxin. Rats fed red meat proteins showed hepatic steatosis with small vacuoles. Therefore, white meat proteins were more conducive to hepatic antioxidative status than soybean and red meat proteins. PRACTICAL APPLICATIONS: Intake of protein-rich foods may induce oxidative stress response at both cell and organ levels. The objective of this study was to investigate the impacts of different protein sources including casein, soybean, fish, chicken, pork, and beef proteins on oxidation and antioxidation status in rat livers. It was shown that meat proteins induced higher production of reactive oxygen species than casein and soybean protein. However, white meat proteins showed higher antioxidant capacity than soybean and red meat proteins by increasing hepatic superoxide dismutase activity and total antioxidant capacity. Therefore, compared to soybean and red meat proteins, white meat proteins lowered hepatic oxidative stress by reducing malondialdehyde production. This study suggested that intake of moderate white meat proteins was more conducive to hepatic antioxidative status than intake of soybean and red meat proteins. This study would promote the understanding of healthy effects of different protein sources.

Pectic Oligogalacturonide Facilitates the Synthesis and Activation of Adiponectin to Improve Hepatic Lipid Oxidation.

Adiponectin (ADPN), a kind of adipokines, plays an important role in the regulation of lipid metabolism. The objective of this study is focused on the ADPN to investigate the functional mechanisms of pectin oligosaccharide (POS) from hawthorn fruit in the improvement of hepatic fatty acid oxidation. High-fat fed mice are used in this experiment. POS is administrated with the doses of 0.25, 0.75, and 1.5 g kg-1 diet, respectively. The results demonstrate that gene and protein expressions of ADPN synthesis regulators involved in PKA/ERK/CREB and C/EBPα/PPARγ pathways are upregulated by POS administration. POS also activates the AdiopR1/AMPKα/PGC1 and AdipoR2/PPARα signaling pathways to improve the fatty acid oxidation in the liver, which is further accelerated by the enhancement of mitochondrial functions. POS can act as an ADPN activator to improve lipid metabolism, leading it to the applications of biomedical and functional foods for ameliorating chronic liver diseases resulted from a high-energy diet.

713c Dietary Fat Increases Intestinal Fructose Conversion to Glycerate that Accumlates in Circulation, Driving Glucose Intolerance

The development of type II diabetes mellitus (T2DM) is strongly associated with consuming a western diet, high in sugars and fats. Metabolites from both dietary fats and carbohydrates can regulate each other through transcriptional regulators like carbohydrate response element-binding protein (ChREBP) and sterol regulatory element-binding protein-1c (SREBP-1c), complicating the potential mechanisms driving the development of T2D. Both excess sugar and excess fat consumption can drive obesity independently, but combinatorial feeding studies show that fructose, but not glucose, exaggerates liver stenosis and ectopic fat deposition caused by dietary fat. Models describing this interaction have focused on hepatic fructose oxidation fueling de novo triglycerides synthesis or depleting local adenosine triphosphate (ATP), although the relevance of both models to the development of insulin resistance is unclear.

Prevention of Teratogenesis in Pregnancies of Obese Rats by Vitamin E Supplementation.

Congenital malformations are a common adverse outcome in pregnancies complicated by pregestational obesity, although the underlying mechanisms are still unrevealed. Our aim was to study the effect of oxidative stress in obesity-induced teratogenesis. Wistar rats were fed a high-fat diet for 13 weeks, with (OE group) or without (O group) vitamin E supplementation. Then, rats were mated and sacrificed at day 11.5 of gestation. Embryos from O dams presented a 25.9 ± 3.5% rate of malformations (vs. 8.7 ± 3.4% in C rats), which was reduced in the OE group (11.5 ± 2.3%). Pregestational obesity induced hepatic protein and DNA oxidation and a decline in antioxidant enzymes. Importantly, glutathione content was also decreased, limiting the availability of this antioxidant in the embryos. Vitamin E supplementation efficiently maintained glutathione levels in the obese mothers, which could be used in their embryos to prevent oxidation-induced malformations. To test the effect of decreasing glutathione levels alone in a cell culture model of neuroepithelium, murine embryonic stem cells (ESC) were induced to form neuronal precursors and glutathione synthesis was inhibited with the gamma–glutamylcysteine synthesis inhibitor, buthionine sulfoximine (BSO). BSO inhibited the expression of Pax3, a gene required for neural tube closure that is also inhibited by oxidative stress. Taken together, our data indicate that obesity causes malformations through the depletion of maternal glutathione, thereby decreasing glutathione-dependent free radical scavenging in embryos, which can be prevented by vitamin E supplementation.

The effect of 1,25-dihydroxyvitamin D3 on liver damage, oxidative stress, and advanced glycation end products in experimental nonalcoholic- and alcoholic- fatty liver disease

Background/aim Oxidative stress and advanced glycation end products (AGEs) formation are proposed as effective mechanisms in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD). 1,25(OH)2D3 was proposed to have antioxidant, antiinflammatory and antiglycation properties. In this study, the effect of 1,25(OH)2D3 treatment on oxidative stress parameters and AGEs levels together with hepatic histopathology was investigated in high fructose (HFr) or ethanol (EtOH)-treated rats. Materials and methods Rats were treated with fructose (30%) or ethanol (5-20%) in drinking water with and without 1,25(OH)2D3 treatment (5 µg/kg two times a week) for 8 weeks. Insulin resistance (IR), oxidative stress parameters, AGEs, triglyceride (TG), and hydroxyproline (Hyp) levels together with histopathology were investigated in the liver. Results1,25(OH)2D3 decreased hepatic reactive oxygen species, lipid and protein oxidation products together with histopathological improvements in HFr- and EtOH-treated rats. 1,25(OH)2D3 treatment was observed to decrease significantly serum and hepatic AGEs in HFr group, and hepatic AGEs in EtOH group.Conclusion Our results clearly show that 1,25(OH)2 D3 treatment may be useful in the alleviation of hepatic lesions by decreasing glycooxidant stress in both NAFLD and ALD models created by HFr- and EtOH-treated rats, respectively.

Fetal Programming Is Deeply Related to Maternal Selenium Status and Oxidative Balance; Experimental Offspring Health Repercussions.

Nutrients consumed by mothers during pregnancy and lactation can exert permanent effects upon infant developing tissues, which could represent an important risk factor for diseases during adulthood. One of the important nutrients that contributes to regulating the cell cycle and tissue development and functionality is the trace element selenium (Se). Maternal Se requirements increase during gestation and lactation. Se performs its biological action by forming part of 25 selenoproteins, most of which have antioxidant properties, such as glutathione peroxidases (GPxs) and selenoprotein P (SELENOP). These are also related to endocrine regulation, appetite, growth and energy homeostasis. In experimental studies, it has been found that low dietary maternal Se supply leads to an important oxidative disruption in dams and in their progeny. This oxidative stress deeply affects gestational parameters, and leads to intrauterine growth retardation and abnormal development of tissues, which is related to endocrine metabolic imbalance. Childhood pathologies related to oxidative stress during pregnancy and/or lactation, leading to metabolic programing disorders like fetal alcohol spectrum disorders (FASD), have been associated with a low maternal Se status and intrauterine growth retardation. In this context, Se supplementation therapy to alcoholic dams avoids growth retardation, hepatic oxidation and improves gestational and breastfeeding parameters in FASD pups. This review is focused on the important role that Se plays during intrauterine and breastfeeding development, in order to highlight it as a marker and/or a nutritional strategy to avoid diverse fetal programming disorders related to oxidative stress.

Impact of Dietary Crude Protein Level on Hepatic Lipid Metabolism in Weaned Female Piglets.

Simple SummaryIt has been reported that a high crude protein diet could reverse the diet-induced lipid accumulation in the liver of mice and rodents. However, in vivo data supporting a functional role of a high crude protein diet on hepatic lipid metabolism-associated genes and proteins in weaned piglets is not available. In the present study, we aimed to provide a mechanistic insight into alterations in the hepatic lipid lipogenesis, lipolysis, oxidation, and gluconeogenesis in response to different dietary crude protein levels. Our results demonstrated that dietary crude protein could regulate hepatic lipid metabolism through regulating hepatic lipid lipogenesis, lipolysis, oxidation, and gluconeogenesis. The result indicated an important role of dietary crude protein in regulating hepatic lipid metabolism in weaned piglets.Amino acids serve not only as building blocks for proteins, but also as substrates for the synthesis of low-molecular-weight substances involved in hepatic lipid metabolism. In the present study, eighteen weaned female piglets at 35 days of age were fed a corn- and soybean meal-based diet containing 20%, 17%, or 14% crude protein (CP), respectively. We found that 17% or 20% CP administration reduced the triglyceride and cholesterol concentrations, while enhanced high-density lipoprotein cholesterol (HDL-C) concentration in serum. Western blot analysis showed that piglets in the 20% CP group had higher protein abundance of hormone-sensitive triglyceride lipase (HSL) and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), as compared with other groups. Moreover, the mRNA expression of sterol regulatory element binding transcription factor 1 (SREBPF1), fatty acid synthase (FASN), and stearoyl-CoA desaturase (SCD) were lower in the 17% or 20% CP group, compared with those of the piglets administered with 14% CP. Of note, the mRNA level of acetyl-CoA carboxylase alpha (ACACα) was lower in the 17% CP group, compared with other groups. Additionally, the mRNA level of lipoprotein lipase (LPL), peroxisome proliferator-activated receptor alpha α (PPARα), glucose-6-phosphatase catalytic subunit (G6PC), and phosphoenolpyruvate carboxykinase 1 (PKC1) in the liver of piglets in the 20% CP group were higher than those of the 14% CP group. Collectively, our results demonstrated that dietary CP could regulate hepatic lipid metabolism through altering hepatic lipid lipogenesis, lipolysis, oxidation, and gluconeogenesis.

282-OR: The Effect of Glucagon on Rates of Hepatic Mitochondrial Oxidation and Pyruvate Carboxylase Flux in Man Assessed by Positional Isotopomer NMR Tracer Analysis (PINTA)

Dual GLP-1/glucagon agonists are now in clinical trials for the treatment of T2D and NASH. In addition to promoting further reduction in food intake on top of GLP-1, the glucagon component of these dual agonists may also promote increased rates of hepatic mitochondrial fat oxidation. In order to investigate this possibility we assessed the glucagon-specific effects of a dual agonist on rates of hepatic mitochondrial oxidation (VCS) and pyruvate carboxylase flux (VPC) in humans by infusing glucagon to achieve a physiological increase in plasma glucagon concentrations in combination with a novel 13C PINTA method to assess rates of hepatic VCS and VPC in 15 healthy volunteers using a paired study design. Following an overnight fast a 3-h IV infusion of [3-13C]lactate (4.3 μmol/Kg-min) and [1,2,3,4,5,6,6-2H7]glucose (0.22 μmol/Kg-min) was begun and during the last 2 hours glucagon (GLG) was co-infused [6 ng/(Kg-min)] or no GLG (CON). The GLG infusion resulted in a ~2.4 fold increase in plasma GLG conc. (from 75±11 to 183±20 pg/mL; P&amp;lt;0.0001), which was associated with an ~20% increase in both plasma C-peptide (from 1.89±0.17 to 2.30±0.26 ng/mL; P=0.02) and plasma insulin conc. (from 9.9±2.0 to 12.0±2.4 μU/mL; P=0.06). Plasma glucose conc. increased from 4.90±0.16 to 5.64±0.19 mmol/L (P=0.0001) which was associated with a tendency for increased rates of glucose production (CON:1042±123 vs. GLG:1148±122 μmol/min; p=0.086) despite no change in rates of VPC flux (CON: 403±69 vs. GLG: 373±55 μmol/min; p=NS). In contrast, this physiological increase in plasma GLG concentrations caused an 85% increase in rates of hepatic VCS (P&amp;lt;0.05). Conclusion: Taken together these studies demonstrate that a physiological increase in plasma glucagon promotes increased rates of hepatic mitochondrial oxidation in humans, which may provide additional benefits to the anorexic effects of dual GLP-1/glucagon agonists to reduce hepatic steatosis. Disclosure K. Petersen: Advisory Panel; Spouse/Partner; AstraZeneca, iMetabolic Biopharma Corporation, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc., Consultant; Spouse/Partner; Aegerion Pharmaceuticals Inc., Novo Nordisk, Research Support; Self; Gilead Sciences, Inc., Merck &amp; Co., Inc. G. I. Shulman: Consultant; Self; 89bio, Inc., BridgeBio, Ionis Pharmaceuticals, Maze Therapeutics, Novo Nordisk, Other Relationship; Self; AstraZeneca, Esperion Therapeutics, Inc, Generian Pharmaceuticals, Inc., Gilead Sciences, Inc., iMetabolic Biopharma Corporation, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc., The Liver Company. Funding Merck &amp; Co., Inc. (MISP583402); National Institutes of Health (R01DK113984)

Chronic Dietary Branched-Chain Amino Acids Induced Lipid Oxidation and Blunted Insulin-Stimulated Glucose Production in Mice With NAFLD

Abstract Objectives Elevated circulating branched-chain amino acids (BCAAs) during insulin resistance are strong predictors of type 2 diabetes mellitus onset. Defects in BCAA degradation are evident in several tissues during insulin resistance and non-alcoholic fatty liver disease (NAFLD). Furthermore, alterations in BCAA metabolism are associated with changes in several aspects lipid metabolism, including lipogenesis, ketogenesis and mitochondrial TCA cycle activity. Considering the crosstalk between BCAAs and lipid metabolism, we hypothesized that chronic supplementation of BCAAs will modulate hepatic insulin resistance and mitochondrial lipid oxidation during NAFLD. Methods Mice (C57BL/6N) were reared on either a low-fat (LF; 10% fat kcal), high-fat (HF; 60% fat kcal or high-fat diet supplemented with BCAA (HFBA; 150% BCAA) for 24 weeks. Metabolic profiling was conducted under fed or overnight fasted (14–16 hrs) conditions. A subset of overnight fasted mice from the HF and HFBA groups were subjected to hyperinsulinemic euglycemic clamps, following implantation of jugular vein catheters. Results Feeding HF and HFBA diets resulted in NAFLD. Circulating BCAAs were higher in ‘fed’ mice consuming HFBA diet (e.g., Valine, µM ± SEM; 311 ± 38 in HF, 432 ± 34 in HFBA, P ≤ 0.05). Overnight fasting significantly reduced BCAA levels in all groups, but the fasting levels of BCAAs remained similar between groups. Fed-to-fasted fold changes in blood glucose, serum insulin and c-peptide were higher in HFBA mice (P ≤ 0.05). Insulin stimulated suppression of glucose production (% ± SEM; HF = 38 ± 11, HFBA = 16 ± 16) was blunted in HFBA mice. Furthermore, fed-to-fasted expression of hepatic genes involved in lipid oxidation, including LCAD, MCAD, PPARa and CPT1a were significantly higher (P ≤ 0.05) in the HFBA mice. Conclusions In summary, chronic BCAA supplementation induced hepatic lipid oxidation gene expression, without any apparent improvements in insulin sensitivity. In conclusion, while the induction of lipid oxidation by BCAAs could explain certain beneficial effects associated with their supplementation, the longer-term impact of the BCAAs on insulin sensitivity need to be further explored. Funding Sources National Institutes of Health (NIH) grant RO1-DK-112865