Restaurant outlet density and the healthfulness of food purchases: evidence from FoodAPS.

Introduction: The average American household's diet and food purchasing patterns are out of sync with federal recommendations. Researchers have connected this with the large and growing rates of obesity, diabetes, and other diet-related ailments in the U.S. Restaurant food has been discussed a potential contributor to unhealthful diets, as it is often calorically dense. We investigate the association between household access to restaurants and diet quality using USDA FoodAPS data and NPD ReCount data. Methods: We define radii around households to measure restaurant outlet counts and apply a regression analysis incorporating household characteristics. Results: We find that neither restaurant counts nor openings share many statistically or economically significant associations with average dietary quality. Household characteristics and demographics are far more powerful in explaining variation in diet quality. Discussion: Our findings align with the large and growing body of empirical research that suggests that personal preferences and other household characteristics are more important than the food environment in explaining food choices and diet quality. Given the extant research on the importance of access to large supermarkets, our results suggest that access to food retailers is more important in explaining diet quality than access to restaurants.

Plasticity of thalamocortical axons is regulated by serotonin levels modulated by preterm birth.

Sensory inputs are conveyed to distinct primary areas of the neocortex through specific thalamocortical axons (TCA). While TCA have the ability to reorient postnatally to rescue embryonic mistargeting and target proper modality-specific areas, how this remarkable adaptive process is regulated remains largely unknown. Here, using a mutant mouse model with a shifted TCA trajectory during embryogenesis, we demonstrated that TCA rewiring occurs during a short postnatal time window, preceded by a prenatal apoptosis of thalamic neurons-two processes that together lead to the formation of properly innervated albeit reduced primary sensory areas. We furthermore showed that preterm birth, through serotonin modulation, impairs early postnatal TCA plasticity, as well as the subsequent delineation of cortical area boundary. Our study defines a birth and serotonin-sensitive period that enables concerted adaptations of TCA to primary cortical areas with major implications for our understanding of brain wiring in physiological and preterm conditions.

Remodelin Is a Cryptic Assay Interference Chemotype That Does Not Inhibit NAT10-Dependent Cytidine Acetylation.

Remodelin is a putative small molecule inhibitor of the RNA acetyltransferase NAT10 which has shown preclinical efficacy in models of the premature aging disease Hutchinson-Gilford Progeria Syndrome (HGPS). Here we evaluate remodelin's assay interference characteristics and effects on NAT10-catalyzed RNA cytidine acetylation. We find the remodelin chemotype constitutes a cryptic assay interference compound, which does not react with small molecule thiols but demonstrates protein reactivity in ALARM NMR and proteome-wide affinity profiling assays. Biophysical analyses find no direct evidence for interaction of remodelin with the NAT10 acetyltransferase active site. Cellular studies verify that N4-acetylcytidine (ac4C) is a nonredundant target of NAT10 activity in human cell lines and find that this RNA modification is not affected by remodelin treatment in several orthogonal assays. These studies display the potential for remodelin's chemotype to interact with multiple protein targets in cells and indicate remodelin should not be applied as a specific chemical inhibitor of NAT10-catalyzed RNA acetylation.

Acetylation of Cytidine in mRNA Promotes Translation Efficiency.

Generation of the "epitranscriptome" through post-transcriptional ribonucleoside modification embeds a layer of regulatory complexity into RNA structure and function. Here, we describe N4-acetylcytidine (ac4C) as an mRNA modification that is catalyzed by the acetyltransferase NAT10. Transcriptome-wide mapping of ac4C revealed discretely acetylated regions that were enriched within coding sequences. Ablation of NAT10 reduced ac4C detection at the mapped mRNA sites and was globally associated with target mRNA downregulation. Analysis of mRNA half-lives revealed a NAT10-dependent increase in stability in the cohort of acetylated mRNAs. mRNA acetylation was further demonstrated to enhance substrate translation in vitro and in vivo. Codon content analysis within ac4C peaks uncovered a biased representation of cytidine within wobble sites that was empirically determined to influence mRNA decoding efficiency. These findings expand the repertoire of mRNA modifications to include an acetylated residue and establish a role for ac4C in the regulation of mRNA translation.

Bioorthogonal pro-metabolites for profiling short chain fatty acylation.

Short chain fatty acids (SCFAs) play a central role in health and disease. One function of these signaling molecules is to serve as precursors for short chain fatty acylation, a class of metabolically-derived posttranslational modifications (PTMs) that are established by lysine acetyltransferases (KATs) and lysine deacetylases (KDACs). Via this mechanism, short chain fatty acylation serves as an integrated reporter of metabolism as well as KAT and KDAC activity, and has the potential to illuminate the role of these processes in disease. However, few methods to study short chain fatty acylation exist. Here we report a bioorthogonal pro-metabolite strategy for profiling short chain fatty acylation in living cells. Inspired by the dietary component tributyrin, we synthesized a panel of ester-caged bioorthogonal short chain fatty acids. Cellular evaluation of these agents led to the discovery of an azido-ester that is metabolized to its cognate acyl-coenzyme A (CoA) and affords robust protein labeling profiles. We comprehensively characterize the metabolic dependence, toxicity, and histone deacetylase (HDAC) inhibitor sensitivity of these bioorthogonal pro-metabolites, and apply an optimized probe to identify novel candidate protein targets of short chain fatty acids in cells. Our studies showcase the utility of bioorthogonal pro-metabolites for unbiased profiling of cellular protein acylation, and suggest new approaches for studying the signaling functions of SCFAs in differentiation and disease.

Profiling Cytidine Acetylation with Specific Affinity and Reactivity.

The human acetyltransferase NAT10 has recently been shown to catalyze formation of N4-acetylcytidine (ac4C), a minor nucleobase known to alter RNA structure and function. In order to better understand the role of RNA acetyltransferases in biology and disease, here we report the development and application of chemical methods to study ac4C. First, we demonstrate that ac4C can be conjugated to carrier proteins using optimized protocols. Next, we describe methods to access ac4C-containing RNAs, enabling the screening of anti-ac4C antibodies. Finally, we validate the specificity of an optimized ac4C affinity reagent in the context of cellular RNA by demonstrating its ability to accurately report on chemical deacetylation of ac4C. Overall, these studies provide a powerful new tool for studying ac4C in biological contexts, as well as new insights into the stability and half-life of this highly conserved RNA modification. More broadly, they demonstrate how chemical reactivity may be exploited to aid the development and validation of nucleobase-targeting affinity reagents designed to target the emerging epitranscriptome.

Rapid production of new oligodendrocytes is required in the earliest stages of motor-skill learning.

We identified mRNA encoding the ecto-enzyme Enpp6 as a marker of newly forming oligodendrocytes, and used Enpp6 in situ hybridization to track oligodendrocyte differentiation in adult mice as they learned a motor skill (running on a wheel with unevenly spaced rungs). Within just 2.5 h of exposure to the complex wheel, production of Enpp6-expressing immature oligodendrocytes was accelerated in subcortical white matter; within 4 h, it was accelerated in motor cortex. Conditional deletion of myelin regulatory factor (Myrf) in oligodendrocyte precursors blocked formation of new Enpp6(+) oligodendrocytes and impaired learning within the same ∼2-3 h time frame. This very early requirement for oligodendrocytes suggests a direct and active role in learning, closely linked to synaptic strengthening. Running performance of normal mice continued to improve over the following week accompanied by secondary waves of oligodendrocyte precursor proliferation and differentiation. We concluded that new oligodendrocytes contribute to both early and late stages of motor skill learning.