Association Between Midpregnancy Polyunsaturated Fatty Acid Levels and Offspring Autism Spectrum Disorder in a California Population-Based Case-Control Study

Polyunsaturated fatty acids (PUFAs) are critical for brain development and have been linked with neurodevelopmental outcomes. We conducted a population-based case-control study in California to examine the association between PUFAs measured in midpregnancy serum samples and autism spectrum disorder (ASD) in offspring. ASD cases (n = 499) were identified through the California Department of Developmental Services and matched to live-birth population controls (n = 502) on birth month, year (2010 or 2011), and sex. Logistic regression models were used to examine crude and adjusted associations. In secondary analyses, we examined ASD with and without co-occurring intellectual disability (ID; n = 67 and n = 432, respectively) and effect modification by sex and ethnicity. No clear patterns emerged, though there was a modest inverse association with the top quartile of linoleic acid level (highest quartile vs. lowest: adjusted odds ratio = 0.74, 95% confidence interval: 0.49, 1.11; P for trend = 0.10). Lower levels of total and ω-3 PUFAs were associated with ASD with ID (lowest decile of total PUFAs vs. deciles 4-7: adjusted odds ratio = 2.78, 95% confidence interval: 1.13, 6.82) but not ASD without ID. We did not observe evidence of effect modification by the factors examined. These findings do not suggest a strong association between midpregnancy PUFA levels and ASD. In further work, researchers should consider associations with ASD with ID and in other time windows.

Suppression of p16 Induces mTORC1-Mediated Nucleotide Metabolic Reprogramming

Reprogrammed metabolism and cell cycle dysregulation are two cancer hallmarks. p16 is a cell cycle inhibitor and tumor suppressor that is upregulated during oncogene-induced senescence (OIS). Loss of p16 allows for uninhibited cell cycle progression, bypass of OIS, and tumorigenesis. Whether p16 loss affects pro-tumorigenic metabolism is unclear. We report that suppression of p16 plays a central role in reprogramming metabolism by increasing nucleotide synthesis. This occurs by activation of mTORC1 signaling, which directly mediates increased translation of the mRNA encoding ribose-5-phosphate isomerase A (RPIA), a pentose phosphate pathway enzyme. p16 loss correlates with activation of the mTORC1-RPIA axis in multiple cancer types. Suppression of RPIA inhibits proliferation only in p16-low cells by inducing senescence both in vitro and in vivo. These data reveal the molecular basis whereby p16 loss modulates pro-tumorigenic metabolism through mTORC1-mediated upregulation of nucleotide synthesis and reveals a metabolic vulnerability of p16-null cancer cells.

Senescence bypass through p16 loss predisposes to transformation and tumorigenesis. Buj et al. found that the loss of p16 upregulates nucleotide metabolism through increased mTORC1-mediated translation of RPIA to bypass senescence in an RB-independent manner. Thus, the mTORC1-RPIA axis is a metabolic vulnerability for p16-null cancers.

C4-Phenylthio β-lactams: Effect of the chirality of the β-lactam ring on antimicrobial activity

C4-phenylthio β-lactams are a new family of antibacterial agents that have activity against two phylogenetically distant bacteria - Mycobacterium tuberculosis (Mtb) and Moraxella catarrhalis (M. cat). These compounds are effective against β-lactamase producing Mtb and M. cat unlike the clinically relevant β-lactam antibiotics. The structure-activity relationship for the C4 phenylthio β-lactams has not yet been completely defined. Earlier efforts in our laboratories established that the C4-phenylthio substituent is essential for antimicrobial activity, while the N1 carbamyl substituent plays a more subtle role. In this present study, we investigated the role that the stereochemistry at C4 plays in these compounds' antibacterial activity. This was achieved by synthesizing and testing the antimicrobial activity of diastereomers with a chiral carbamyl group at N1. Our findings indicate that a strict stereochemistry for the C4-phenylthio β-lactams is not required to obtain optimal anti-Mtb and anti-M. cat activity. Furthermore, the structure-bioactivity profiles more closely relate to the electronic requirement of the phenylthiogroup. In addition, the MICs of Mtb are sensitive to growth medium composition. Select compounds showed activity against non-replicating and multi-drug resistant Mtb.

Simultaneous isotope dilution quantification and metabolic tracing of deoxyribonucleotides by liquid chromatography high resolution mass spectrometry

Quantification of cellular deoxyribonucleoside mono- (dNMP), di- (dNDP), triphosphates (dNTPs) and related nucleoside metabolites are difficult due to their physiochemical properties and widely varying abundance. Involvement of dNTP metabolism in cellular processes including senescence and pathophysiological processes including cancer and viral infection make dNTP metabolism an important bioanalytical target. We modified a previously developed ion pairing reversed phase chromatography-mass spectrometry method for the simultaneous quantification and ¹³C isotope tracing of dNTP metabolites. dNMPs, dNDPs, and dNTPs were chromatographically resolved to avoid mis-annotation of in-source fragmentation. We used commercially available ¹³C¹⁵N-stable isotope labeled analogs as internal standards and show that this isotope dilution approach improves analytical figures of merit. At sufficiently high mass resolution achievable on an Orbitrap mass analyzer, stable isotope resolved metabolomics allows simultaneous isotope dilution quantification and ¹³C isotope tracing from major substrates including ¹³C-glucose. As a proof of principle, we quantified dNMP, dNDP and dNTP pools from multiple cell lines. We also identified isotopologue enrichment from glucose corresponding to ribose from the pentose-phosphate pathway in dNTP metabolites.

Lecithin:Cholesterol Acyltransferase Activation by Sulfhydryl-Reactive Small Molecules: Role of Cysteine-31

Lecithin:cholesterol acyltransferase (LCAT) catalyzes plasma cholesteryl ester formation and is defective in familial lecithin:cholesterol acyltransferase deficiency (FLD), an autosomal recessive disorder characterized by low high-density lipoprotein, anemia, and renal disease. This study aimed to investigate the mechanism by which compound A [3-(5-(ethylthio)-1,3,4-thiadiazol-2-ylthio)pyrazine-2-carbonitrile], a small heterocyclic amine, activates LCAT. The effect of compound A on LCAT was tested in human plasma and with recombinant LCAT. Mass spectrometry and nuclear magnetic resonance were used to determine compound A adduct formation with LCAT. Molecular modeling was performed to gain insight into the effects of compound A on LCAT structure and activity. Compound A increased LCAT activity in a subset (three of nine) of LCAT mutations to levels comparable to FLD heterozygotes. The site-directed mutation LCAT-Cys31Gly prevented activation by compound A. Substitution of Cys31 with charged residues (Glu, Arg, and Lys) decreased LCAT activity, whereas bulky hydrophobic groups (Trp, Leu, Phe, and Met) increased activity up to 3-fold (P < 0.005). Mass spectrometry of a tryptic digestion of LCAT incubated with compound A revealed a +103.017 m/z adduct on Cys31, consistent with the addition of a single hydrophobic cyanopyrazine ring. Molecular modeling identified potential interactions of compound A near Cys31 and structural changes correlating with enhanced activity. Functional groups important for LCAT activation by compound A were identified by testing compound A derivatives. Finally, sulfhydryl-reactive β-lactams were developed as a new class of LCAT activators. In conclusion, compound A activates LCAT, including some FLD mutations, by forming a hydrophobic adduct with Cys31, thus providing a mechanistic rationale for the design of future LCAT activators.

Abstract 226: Mechanism of LCAT Activation by Compound A

Background: Lecithin:cholesterol acyltransferase (LCAT) catalyzes cholesteryl ester (CE) production from free cholesterol (FC) and phosphatidylcholine (lecithin), promoting HDL formation.

Objective: To investigate activation of LCAT by Compound A (Amgen), a previously described small-molecule activator of LCAT, with the ultimate goal of developing novel LCAT activators for therapeutic use.

Methods: LCAT activity in plasma from Familial LCAT Deficiency (FLD) patients with different mutations was quantitated by TLC before and after addition of Compound A. HEK293 cells were transiently transfected with plasmids containing wild-type (WT) or mutant LCAT cDNA. Media was then incubated with either vehicle or Compound A and LCAT activity was quantitated using a novel plate assay utilizing Methylumbelliferyl Palmitate as a substrate.

Results: Compound A increased LCAT activity for a subset of FLD mutations to a level above which renal disease may occur. Mutations of Cys31 in vitro strongly affected basal LCAT activity as well as activation by Compound A. Charged residues at position 31 profoundly decreased activity whereas bulky hydrophobic groups increased LCAT activity up to 3-fold (p < 0.005, all). Mass spectrometry of WT LCAT incubated with Compound A revealed a +103.017 m/z adduct to the tryptic peptide containing Cys31, indicative of a cyanopyrazine adduct to LCAT Cys31. Molecular modeling identified potential binding sites of Compound A to LCAT.

Conclusions: Our findings yield important mechanistic insight into LCAT activation that can be used to design novel LCAT activators for therapeutic use.

Non-transpeptidase binding arylthioether β-lactams active against Mycobacterium tuberculosis and Moraxella catarrhalis

The prevalence of drug resistance in both clinical and community settings as a consequence of alterations of biosynthetic pathways, enzymes or cell wall architecture is a persistent threat to human health. We have designed, synthesized, and tested a novel class of non-transpeptidase, β-lactamase resistant monocyclic β-lactams that carry an arylthio group at C4. These thioethers exhibit inhibitory and cidal activity against serine β-lactamase producing Mycobacterium tuberculosis wild type strain (Mtb) and multiple (n=8) β-lactamase producing Moraxella catarrhalis clinical isolates.