Population-based plasma lipidomics reveals developmental changes in metabolism and signatures of obesity risk : a mother-offspring cohort study

Publisher Copyright: © 2022, The Author(s).Background: Lipids play a vital role in health and disease, but changes to their circulating levels and the link with obesity remain poorly characterized in expecting mothers and their offspring in early childhood. Methods: LC-MS/MS-based quantitation of 480 lipid species was performed on 2491 plasma samples collected at 4 time points in the mother-offspring Asian cohort GUSTO (Growing Up in Singapore Towards healthy Outcomes). These 4 time points constituted samples collected from mothers at 26–28 weeks of gestation (n=752) and 4–5 years postpartum (n=650), and their offspring at birth (n=751) and 6 years of age (n=338). Linear regression models were used to identify the pregnancy and developmental age-specific variations in the plasma lipidomic profiles, and their association with obesity risk. An independent birth cohort (n=1935), the Barwon Infant Study (BIS), comprising mother-offspring dyads of Caucasian origin was used for validation. Results: Levels of 36% of the profiled lipids were significantly higher (absolute fold change > 1.5 and Padj < 0.05) in antenatal maternal circulation as compared to the postnatal phase, with phosphatidylethanolamine levels changing the most. Compared to antenatal maternal lipids, cord blood showed lower concentrations of most lipid species (79%) except lysophospholipids and acylcarnitines. Changes in lipid concentrations from birth to 6 years of age were much higher in magnitude (log2FC=−2.10 to 6.25) than the changes observed between a 6-year-old child and an adult (postnatal mother) (log2FC=−0.68 to 1.18). Associations of cord blood lipidomic profiles with birth weight displayed distinct trends compared to the lipidomic profiles associated with child BMI at 6 years. Comparison of the results between the child and adult BMI identified similarities in association with consistent trends (R2=0.75). However, large number of lipids were associated with BMI in adults (67%) compared to the children (29%). Pre-pregnancy BMI was specifically associated with decrease in the levels of phospholipids, sphingomyelin, and several triacylglycerol species in pregnancy. Conclusions: In summary, our study provides a detailed landscape of the in utero lipid environment provided by the gestating mother to the growing fetus, and the magnitude of changes in plasma lipidomic profiles from birth to early childhood. We identified the effects of adiposity on the circulating lipid levels in pregnant and non-pregnant women as well as offspring at birth and at 6 years of age. Additionally, the pediatric vs maternal overlap of the circulating lipid phenotype of obesity risk provides intergenerational insights and early opportunities to track and intervene the onset of metabolic adversities. Clinical trial registration: This birth cohort is a prospective observational study, which was registered on 1 July 2010 under the identifier NCT01174875.Peer reviewe

Synthesis of immunogenic mycobacterial cell wall lipids

© 2017 Dr. Satvika BurugupalliThis thesis is comprised of two parts: Part I describes the synthesis and immunology of mycobacterial cell wall lipids and Part II describes the development of oxime-based activated esters as safer alternatives to hydroxylbenzotriazoles for chemo- and regioselective benzoylation. Part I: Synthesis of immunogenic mycobacterial cell wall lipids Tuberculosis is the most devastating infectious disease in the world. It is caused by infection with Mycobacterium tuberculosis (M.tb), a bacterium with a complex lipid rich cell wall that contributes to virulence and antibiotic resistance. The outer cell wall lipids are known to mingle with receptors of the host immune system. In Chapters 1-3, we report the synthesis of immunogenic glycolipids and phospholipid antigens present in the outer cell surface of the mycobacterial cell wall that can be presented by CD1 proteins. These antigens are characterized by the presence of a branched methyl fatty acid, 10-methyl stearic acid, called tuberculostearic acid (TBSA). Chapter 1 describes the synthesis of (R) and (S) enantiomers of TBSA. We developed efficient two-step and three-step approaches for the synthesis of TBSA. We used citronellyl bromide, a commercially available chiral pool starting material available as both enantiomers, and built the fatty acid chain by copper mediated cross-coupling and subsequent tandem cross metathesis/hydrogenation using Hoveyda-Grubbs second generation catalyst. In an attempt to ascertain the stereochemistry of natural TBSA we developed a chiral discrimination method using an anthracene based chiral derivatizing reagent; while some discrimination was possible, baseline separation of the key peaks could not be achieved. Chapter 2 describes the synthesis of an M.tb phosphatidyl glycerol (PG). Recently, a PG fraction containing a range of lipoforms was isolated from M.tb and shown to activate type II NKT cells by binding to CD1d. Towards this end, we undertook the synthesis of a homogenous representative PG bearing R-TBSA and two other analogues lacking the methyl branch. A one pot synthesis of a diacylglycerol was achieved by epoxide ring opening with R-TBSA using Jacobsen’s catalyst, and phosphoramidite chemistry was used to assemble the PG fragments. The availability of pure synthetic M.tb PG and analogues facilitated the immunological studies of their ability to activate CD1b-restricted T cells. Chapter 3 describes the development of a second-generation synthesis of mycobacterial glycolipid, Gl-A, an α-glucuronosyl diacylglyceride, in a short 8 step sequence using just a single protecting group. A highlight of this approach include a high fidelity regioselective acylation of a bromohydrin intermediate, synthesized by Jacobsen hydrolytic kinetic resolution of allyl α-D-glucoside derived epoxide and subsequent epoxide ring opening with Li2NiBr4. Using this method, Gl-A, and α-glucosyl and α-glucuronosyl analogues bearing (R)-TBSA and (S)-TBSA, were synthesized. Immunological studies of all the analogues on an assortment of NKT cells revealed that while type Ia NKT cells were tolerant to glucose and glucuronosyl head groups, type II NKT cells preferred glucuronosyl head group only. Part II: Development of oxime-based activated esters as safer alternatives to hydroxylbenzotriazoles for chemo- and regioselective benzoylation Benzoyloxybenzotriazole (BBTZ), is a useful selective benzoylating reagent, but has safety limitations owing to the explosive nature of its precursor HOBt. In Chapter 4, we have explored a range of benzoylated oxime-based reagents as alternatives to BBTZ, for the selective benzoylation of carbohydrate polyols. Of the reagents synthesized, the most effective reagent was identified as benzoyl-Oxyma, a highly crystalline, readily prepared alternative to BBTZ, which was shown to be useful in the selective benzoylation of carbohydrate polyols

Microwave-Assisted One-Pot Synthesis of Isoquinolines, Furopyridines, and Thienopyridines by Palladium-Catalyzed Sequential Coupling–Imination–Annulation of 2-Bromoarylaldehydes with Terminal Acetylenes and Ammonium Acetate

A palladium-catalyzed microwave-assisted one-pot reaction for the synthesis of isoquinolines is developed. The reaction is carried out by sequential coupling–imination–annulation reactions of <i>ortho</i>-bromoarylaldehydes and terminal alkynes with ammonium acetate, and a variety of substituted isoquinolines, furopyridines, and thienopyridines is prepared in moderate to excellent yields (up to 86%)

α-Glucuronosyl and α-Glucosyl Diacylglycerides, Natural Killer T Cell-Activating Lipids from Bacteria and Fungi

Natural killer T cells express T cell receptors (TCRs) that recognize glycolipid antigens in association with the antigen-presenting molecule CD1d. Here, we report the concise chemical synthesis of a range of saturated and unsaturated α-glucosyl and α-glucuronosyl diacylglycerides of bacterial and fungal origins from allyl α-glucoside with Jacobsen kinetic resolution as a key step. We show that these glycolipids could be recognized by a classical type I NKT TCR that uses an invariant Vα14-Jα18 TCR α-chain, but also by an atypical NKT TCR that uses a different TCR α-chain (Vα10-Jα50). In both cases, recognition was sensitive to the lipid fine structure, and included recognition of glycosyl diacylglycerides bearing branched (R- and S-tuberculostearic acid) and unsaturated (oleic and vaccenic) acids. The TCR footprints on CD1d-loaded with a mycobacterial α-glucuronosyl diacylglyceride was assessed using mutant CD1d molecules and, while similar to that for α-GalCer recognition by a type I NKT TCR, were more sensitive to mutations when α-glucuronosyl diacylglyceride was the antigen. In summary, we provide an efficient approach for synthesis of a broad class of bacterial and fungal α-glycosyl diacylglyceride antigens and demonstrate that they can be recognised by TCRs derived from type I and atypical NKT cells