HBO1/KAT7/MYST2 HAT complex regulates human adenovirus replicative cycle

Human adenoviruses (HAdV) belong to a small DNA tumor virus family that continues as valuable models in understanding the viral strategies of usurping cell growth regulation. A number of HAdV type 2/5 early viral gene products interact with a variety of cellular proteins to build a conducive environment that promotes viral replication. Here we show that HBO1 (Histone Acetyltransferase Binding to ORC1), a member of the MYST histone acetyltransferase (HAT) complex (also known as KAT7 and MYST2) that acetylates most of the histone H3 lysine 14, is essential for HAdV5 growth. HBO1/MYST2/KAT7 HAT complexes are critical for a variety of cellular processes including control of cell proliferation. In HBO1 downregulated human cells, HAdV5 infection results in reduced expression of E1A and other viral early genes, virus growth is also reduced significantly. Importantly, HBO1 downregulation reduced H3 lysine 14 acetylation at viral promoters during productive infection, likely driving reduced viral gene expression. HBO1 was also associated with viral promoters during infection and co-localized with viral replication centers in the nuclei of infected cells. In transiently transfected cells, overexpression of E1A along with HBO1 stimulated histone acetyltransferase activity of HBO1. E1A also co-immunoprecipitated with HBO1 in transiently transfected cells. In summary, our results demonstrate that HAdV recruits the HBO1 HAT complex to aid in viral replication.

The Prebiotic Effects of Oats on Blood Lipids, Gut Microbiota, and Short-Chain Fatty Acids in Mildly Hypercholesterolemic Subjects Compared With Rice: A Randomized, Controlled Trial

Phytochemicals derived from oats are reported to possess a beneficial effect on modulating dyslipidemia, specifically on lowering total and LDL cholesterol. However, deeper insights into its mechanism remain unclear. In this randomized controlled study, we assigned 210 mildly hypercholesterolemic subjects from three study centers across China (Beijing, Nanjing, and Shanghai) to consume 80 g of oats or rice daily for 45 days. Plasma lipid profiles, short chain fatty acids (SCFAs), and fecal microbiota were measured. The results showed that total cholesterol (TC) and non-high-density lipoprotein cholesterol (non-HDL-C) decreased significantly with both oats and rice intake after 30 and 45 days. The reduction in TC and non-HDL-C was greater in the participants consuming oats compared with rice at day 45 (p = 0.011 and 0.049, respectively). Oat consumption significantly increased the abundance of Akkermansia muciniphila and Roseburia, and the relative abundance of Dialister, Butyrivibrio, and Paraprevotella, and decreased unclassified f-Sutterellaceae. In the oat group, Bifidobacterium abundance was negatively correlated with LDL-C (p = 0.01, r = −0.31) and, TC and LDL-C were negatively correlated to Faecalibacterium prausnitzii (p = 0.02, r = −0.29; p = 0.03, r = −0.27, respectively). Enterobacteriaceae, Roseburia, and Faecalibacterium prausnitzii were positively correlated with plasma butyric acid and valeric acid concentrations and negatively correlated to isobutyric acid. HDL-C was negatively correlated with valeric acid (p = 0.02, r = −0.25) and total triglyceride (TG) was positively correlated to isovaleric acid (p = 0.03, r = 0.23). Taken together, oats consumption significantly reduced TC and LDL-C, and also mediated a prebiotic effect on gut microbiome. Akkermansia muciniphila, Roseburia, Bifidobacterium, and Faecalibacterium prausnitzii, and plasma SCFA correlated with oat-induced changes in plasma lipids, suggesting prebiotic activity of oats to modulate gut microbiome could contribute towards its cholesterol-lowering effect.

The effect of cereal Β-glucan on body weight and adiposity: A review of efficacy and mechanism of action

The current review examines the totality of the evidence to determine if there exists a relationship between β-glucan and body weight and adiposity and whether such a relationship is a consistent, causal and plausible one. Observational studies suggest an association between oat (i.e., β-glucan) intake and reduced body weight, waist circumference and adiposity. High and moderate quality randomized controlled trials that were specifically designed to evaluate the efficacy of β-glucan on anthropometric outcomes were given the highest weight. Several of these studies indicated a causal relationship between β-glucan consumption and reduction in body weight, BMI, and at least one measure of body fat within diets that were not calorie-restricted. A review of additional animal and human evidence suggests multiple plausible mechanisms by which β-glucan may impact satiety perception, gastric emptying, gut hormones, gut microbiota and short chain fatty acids in the complex interplay of appetite and energy regulation.

Effect of COVID-19 Pandemic-Induced Dietary and Lifestyle Changes and Their Associations with Perceived Health Status and Self-Reported Body Weight Changes in India: A Cross-Sectional Survey

Home confinement during the COVID-19 pandemic is accompanied by dramatic changes in lifestyle and dietary behaviors that can significantly influence health. We conducted an online cross-sectional survey to assess COVID-19 pandemic-induced dietary and lifestyle changes and their association with perceived health status and self-reported body weight changes among 1000 Indian adults in early 2021. Positive improvements in dietary habits, e.g., eating more nutritious (85% of participants) and home-cooked food (89%) and an increase in overall nutrition intake (79%), were observed. Sixty-five percent of participants self-reported increased oat consumption to support immunity. There were some negative changes, e.g., more binge eating (69%), eating more in between meals (67%), and increasing meal portion size (72%). Two-thirds of participants reported no change in lifestyles, whereas 21 and 23% reported an increase, and 13 and 10% reported a decrease in physical activity and sleep, respectively. Overall, 64 and 65% of participants reported an improvement in perceived health and an increase in body weight during the COVID-19 period compared to pre-COVID-19, respectively. The top motivations for improving dietary habits included improving physical and mental health and building immunity. In conclusion, the overall perceived health was improved and there was an increase in self-reported body weight in most participants during COVID-19. Diet emerged as the most crucial determinant for these changes.

Serum Metabolomics Reveals Underlying Mechanisms of Cholesterol-Lowering Effects of Oat Consumption: A Randomized Controlled Trial in a Mildly Hypercholesterolemic Population

INTRODUCTION

The purpose of this study is to examine the effects of oat supplementation on serum lipid in a population of adults with mild hypercholesterolemia and reveal the underlying mechanisms with serum untargeted metabolomics.

METHODS AND RESULTS

In this placebo-controlled trial, 62 participants from Nanjing, China, with mild elevations in cholesterol are randomly assigned to receive 80 g oats (containing 3 g beta-glucan) or rice daily for 45 days. Fasting blood samples are collected at the beginning, middle, and end of the trial. Compared with the rice group, oat consumption significantly decreases serum total cholesterol (TC) (-8.41%, p = 0.005), low-density lipoprotein cholesterol (LDL-c) (-13.93%, p = 0.001), and non high-density lipoprotein cholesterol (non-HDL-c) (-10.93%, p = 0.017) levels. There are no significant between-group differences in serum triglyceride (TG), apolipoprotein B (Apo B), glycated albumin, or fasting blood glucose levels. An orthogonal partial least squares discriminant analysis (OPLS-DA) suggests a clear separation in metabolic profiles between the groups after the intervention. Twenty-one metabolites in the oat group are significantly different from those in the rice group, among which 14 metabolites show a decreased trend. In comparison, seven metabolites show an increased trend. Correlations analysis from both groups indicate that most metabolites [e.g., sphinganine and phosphatidylcholine (PC)(20:5(5Z,8Z,11Z,14Z,17Z)/20:1(11Z))] have positive correlations with serum cholesterol levels. Kyoto Encyclopedia of Gene and Genomes pathway analysis suggests that oat consumption regulated glycerophospholipid, alanine, aspartate and glutamate, sphingolipid, and retinol metabolism.

CONCLUSION

Oat consumption has beneficial effects on serum lipids profiles. The underlying mechanisms involve glycerophospholipid, alanine, aspartate and glutamate, sphingolipid, and retinol metabolism in adults.

Mouse Cardiac Pde1C Is a Direct Transcriptional Target of Pparα

Phosphodiesterase 1C (PDE1C) is expressed in mammalian heart and regulates cardiac functions by controlling levels of second messenger cyclic AMP and cyclic GMP (cAMP and cGMP, respectively). However, molecular mechanisms of cardiac Pde1c regulation are currently unknown. In this study, we demonstrate that treatment of wild type mice and H9c2 myoblasts with Wy-14,643, a potent ligand of nuclear receptor peroxisome-proliferator activated receptor alpha (PPARα), leads to elevated cardiac Pde1C mRNA and cardiac PDE1C protein, which correlate with reduced levels of cAMP. Furthermore, using mice lacking either Pparα or cardiomyocyte-specific Med1, the major subunit of Mediator complex, we show that Wy-14,643-mediated Pde1C induction fails to occur in the absence of Pparα and Med1 in the heart. Finally, using chromatin immunoprecipitation assays we demonstrate that PPARα binds to the upstream Pde1C promoter sequence on two sites, one of which is a palindrome sequence (agcTAGGttatcttaacctagc) that shows a robust binding. Based on these observations, we conclude that cardiac Pde1C is a direct transcriptional target of PPARα and that Med1 may be required for the PPARα mediated transcriptional activation of cardiac Pde1C.

Cardiomyocyte-Specific Ablation of Med1 Subunit of the Mediator Complex Causes Lethal Dilated Cardiomyopathy in Mice

Mediator, an evolutionarily conserved multi-protein complex consisting of about 30 subunits, is a key component of the polymerase II mediated gene transcription. Germline deletion of the Mediator subunit 1 (Med1) of the Mediator in mice results in mid-gestational embryonic lethality with developmental impairment of multiple organs including heart. Here we show that cardiomyocyte-specific deletion of Med1 in mice (csMed1-/-) during late gestational and early postnatal development by intercrossing Med1fl/fl mice to α-MyHC-Cre transgenic mice results in lethality within 10 days after weaning due to dilated cardiomyopathy-related ventricular dilation and heart failure. The csMed1-/- mouse heart manifests mitochondrial damage, increased apoptosis and interstitial fibrosis. Global gene expression analysis revealed that loss of Med1 in heart down-regulates more than 200 genes including Acadm, Cacna1s, Atp2a2, Ryr2, Pde1c, Pln, PGC1α, and PGC1β that are critical for calcium signaling, cardiac muscle contraction, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy and peroxisome proliferator-activated receptor regulated energy metabolism. Many genes essential for oxidative phosphorylation and proper mitochondrial function such as genes coding for the succinate dehydrogenase subunits of the mitochondrial complex II are also down-regulated in csMed1-/- heart contributing to myocardial injury. Data also showed up-regulation of about 180 genes including Tgfb2, Ace, Atf3, Ctgf, Angpt14, Col9a2, Wisp2, Nppa, Nppb, and Actn1 that are linked to cardiac muscle contraction, cardiac hypertrophy, cardiac fibrosis and myocardial injury. Furthermore, we demonstrate that cardiac specific deletion of Med1 in adult mice using tamoxifen-inducible Cre approach (TmcsMed1-/-), results in rapid development of cardiomyopathy and death within 4 weeks. We found that the key findings of the csMed1-/- studies described above are highly reproducible in TmcsMed1-/- mouse heart. Collectively, these observations suggest that Med1 plays a critical role in the maintenance of heart function impacting on multiple metabolic, compensatory and reparative pathways with a likely therapeutic potential in the management of heart failure.

High Preformed Vitamin A Intake during Pregnancy Prevents Embryonic Accumulation of Intact β-Carotene from the Maternal Circulation in Mice

BACKGROUND

The vitamin A precursor β-carotene (BC) promotes mammalian embryonic development by serving as a source of retinoids (vitamin A derivatives) to the developing tissues. In the Western world, increased consumption of dietary supplements, including vitamin A and BC, is common; however, the consequences of maternal high preformed vitamin A intake on embryonic uptake and metabolism of BC are poorly understood.

OBJECTIVE

This study investigated vitamin A and BC metabolism in developing mouse tissues after a single BC administration to pregnant wild-type (WT) mice fed purified diets with different vitamin A concentrations.

METHODS

WT dams fed a sufficient vitamin A (VA-S; 4.2 μg of retinol/g of diet), high vitamin A (VA-H; 33 μg of retinol/g of diet), or excess vitamin A (VA-E; 66 μg of retinol/g of diet) diet throughout gestation were intraperitoneally injected with BC or vehicle at 13.5 d postcoitum (dpc). At 14.5 dpc, retinoid and BC concentrations in maternal serum and liver, placenta, and embryo were quantified by HPLC; expressions of genes controlling retinoid and BC homeostasis were analyzed by quantitative polymerase chain reaction. Maternal lipoprotein BC concentrations were analyzed by density gradient ultracentrifugation followed by HPLC.

RESULTS

Intact BC was undetectable only in embryos from VA-E + BC dams. Relative to the VA-S + vehicle group, placentas from VA-S + BC dams showed 39% downregulation of LDL-receptor-related protein 1 (Lrp1 ); 35% downregulation of VLDL receptor (Vldlr); 56% reduced mRNA expression of β-carotene 15,15'-oxygenase (Bco1); and 80% upregulation of β-carotene 9',10'-oxygenase (Bco2). Placental cytochrome P450, family 26, subfamily A, polypeptide 1 (Cyp26A1) was upregulated 2-fold in the VA-E group compared with the VA-S group, regardless of maternal treatment.

CONCLUSIONS

In mice, transfer of intact BC to the embryo is attenuated by high tissue vitamin A concentrations. Maternal vitamin A intake and BC availability activate a placental transcriptional response to protect the embryo from retinoid and carotenoid excess.

Soluble apoE/Aβ complex: mechanism and therapeutic target for APOE4-induced AD risk

The APOE4 allele of apolipoprotein E (apoE) is the greatest genetic risk factor for Alzheimer's disease (AD) compared to APOE2 and APOE3. Amyloid-β (Aβ), particularly in a soluble oligomeric form (oAβ), is considered a proximal cause of neurodegeneration in AD. Emerging data indicate that levels of soluble oAβ are increased with APOE4, providing a potential mechanism of APOE4-induced AD risk. However, the pathway(s) by which apoE4 may increase oAβ levels are unclear and the subject of continued inquiry. In this editorial review, we present the hypothesis that apoE isoform-specific interactions with Aβ, namely apoE/Aβ complex, modulate Aβ levels. Specifically, we propose that compared to apoE3, apoE4-containing lipoproteins are less lipidated, leading to less stable apoE4/Aβ complexes, resulting in reduced apoE4/Aβ levels and increased accumulation, particularly of oAβ. Evidence that support or counter this argument, as well as the therapeutic significance of this pathway to neurodegeneration, are discussed.

Mammalian metabolism of β-carotene: gaps in knowledge

β-carotene is the most abundant provitamin A carotenoid in human diet and tissues. It exerts a number of beneficial functions in mammals, including humans, owing to its ability to generate vitamin A as well as to emerging crucial signaling functions of its metabolites. Even though β-carotene is generally considered a safer form of vitamin A due to its highly regulated intestinal absorption, detrimental effects have also been ascribed to its intake, at least under specific circumstances. A better understanding of the metabolism of β-carotene is still needed to unequivocally discriminate the conditions under which it may exert beneficial or detrimental effects on human health and thus to enable the formulation of dietary recommendations adequate for different groups of individuals and populations worldwide. Here we provide a general overview of the metabolism of this vitamin A precursor in mammals with the aim of identifying the gaps in knowledge that call for immediate attention. We highlight the main questions that remain to be answered in regards to the cleavage, uptake, extracellular and intracellular transport of β-carotene as well as the interactions between the metabolism of β-carotene and that of other macronutrients such as lipids.

β-Carotene supplementation decreases placental transcription of LDL receptor-related protein 1 in wild-type mice and stimulates placental β-carotene uptake in marginally vitamin A-deficient mice

The human diet contains β-carotene as the most abundant precursor of vitamin A, an essential nutrient for embryogenesis. Our laboratory previously showed the importance of β-carotene metabolism via β-carotene-15,15'-oxygenase (CMOI) to support mouse embryonic development. However, the mechanisms regulating embryonic acquisition and utilization of β-carotene from the maternal circulation via placenta remain unknown. We used wild-type (WT) and Lrat(-/-)Rbp(-/-) (L(-/-)R(-/-)) mice, the latter being a model of marginal vitamin A deficiency. Pregnant dams, fed a nonpurified diet sufficient in vitamin A throughout life, were i.p. supplemented with β-carotene or vehicle at 13.5 d postcoitum (dpc). Effects of this acute maternal supplementation on retinoid and β-carotene metabolism in maternal (serum, liver) and developing tissues (placenta, yolk sac, embryo) were investigated at 14.5 dpc. We showed that, upon supplementation, placental β-carotene concentrations were greater in L(-/-)R(-/-) than in WT mice. However, the retinoid (retinol and retinyl ester) concentrations remained unchanged in placenta (and in all other tissues analyzed) of both genotypes upon β-carotene administration. We also showed that upon a single i.p. β-carotene supplementation, placental LDL receptor-related protein (Lrp1) mRNA expression was lower in WT mice, and embryonic CmoI mRNA expression was greater in L(-/-)R(-/-) mice. Together, these data suggest a potential role of LRP1 in mediating the uptake of β-carotene across the placenta and that even a marginally impaired maternal vitamin A status may influence uptake and utilization of β-carotene by the placenta and the embryo.

Maternal-fetal transfer and metabolism of vitamin A and its precursor β-carotene in the developing tissues

The requirement of the developing mammalian embryo for retinoic acid is well established. Retinoic acid, the active form of vitamin A, can be generated from retinol and retinyl ester obtained from food of animal origin, and from carotenoids, mainly β-carotene, from vegetables and fruits. The mammalian embryo relies on retinol, retinyl ester and β-carotene circulating in the maternal bloodstream for its supply of vitamin A. The maternal-fetal transfer of retinoids and carotenoids, as well as the metabolism of these compounds in the developing tissues are still poorly understood. The existing knowledge in this field has been summarized in this review in reference to our basic understanding of the transport and metabolism of retinoids and carotenoids in adult tissues. The need for future research on the metabolism of these essential lipophilic nutrients during development is highlighted. This article is part of a Special Issue entitled: Retinoid and Lipid Metabolism.

Identification of amino acids critical for the cytotoxicity of Shiga toxin 1 and 2 in Saccharomyces cerevisiae

Shiga toxins (Stx1 and Stx2) are produced by E. coli O157:H7, which is a leading cause of foodborne illness. The A subunits of Stx1 (Stx1A) and Stx2 (Stx2A) are ribosome inactivating proteins (RIPs) that inhibit translation by removing an adenine from the highly conserved α-sarcin ricin loop (SRL) of the large rRNA. Here, we used mutagenesis in Saccharomyces cerevisiae to identify residues critical for cytotoxicity of Stx1A and Stx2A. The A subunits depurinated the SRL, inhibited translation and caused apoptotic-like cell death in yeast. Single mutations in Asn75, Tyr77, Glu167 and Arg176 reduced the cytotoxicity of both toxins around 10-fold. However, Asn75 and Tyr77 were more critical for the depurination activity of Stx2A, while Arg176 was more critical for the depurination activity of Stx1A. The crystal structures of the two proteins lack electron density for some surface loops, including one which is adjacent to the active site in both molecules. Modeling these loops changed neither the secondary nor the tertiary structures of the rest of the protein. Analysis of solvent accessible surface areas indicated that Asn75 and Tyr77 are more exposed in Stx2A, while Arg176 is more exposed in Stx1A, indicating that residues with higher surface exposure were more critical for enzymatic activity. Double mutations at Glu167 and Arg176 eliminated the depurination activity and cytotoxicity of both toxins. C-terminal deletions of A chains eliminated cytotoxicity of both toxins, but showed functional differences. Unlike Stx1A, cytotoxicity of Stx2A was lost before its ability to depurinate ribosomes. These results identify residues that affect enzymatic activity and cytotoxicity of Stx1A and Stx2A differently and demonstrate that the function of these residues can be differentiated in yeast. The extent of ribosome depurination and translation inhibition did not correlate with the extent of cell death, indicating that depurination of the SRL and inhibition of translation are not entirely responsible for cell death.

Serum retinol-binding protein 4 (RBP4) and retinol in a cohort of borderline obese women with and without gestational diabetes

OBJECTIVES

To evaluate whether serum RBP4 correlates with gestational diabetes mellitus (GDM) in a cohort of borderline obese (BMI>30) pregnant women.

DESIGN AND METHODS

Serum RBP4 and retinol were measured in pregnant women with (n=12) and without (n=10) GDM.

RESULTS

RBP4, retinol and RBP4:retinol molar ratio were not different between the groups and were not associated with markers of insulin resistance.

CONCLUSIONS

GDM is not associated with RBP4 or retinol among borderline obese pregnant women.