Treatment with a constitutive androstane receptor ligand ameliorates the signs of preeclampsia in high-fat diet-induced obese pregnant mice

Constitutive androstane receptor (CAR) has been reported to decrease insulin resistance, while obesity and insulin resistance may also be involved in the pathogenesis of preeclampsia. We examined whether a CAR ligand, 1,4-bis(2-(3,5-dichloropyridyloxy)) benzene (TCPOBOP), can ameliorate the signs of preeclampsia in high-fat diet (HFD)-induced obese pregnant mice to examine a possibility of CAR as a therapeutic target. We employed six groups including non-pregnant, HFD-fed or control diet-fed pregnant mice with or without TCPOBOP treatment (n = 6). In HFD pregnant mice, insulin resistance increased with increasing expression of gluconeogenic and lipogenic genes and abnormal adipocytokine levels. TCPOBOP treatment, which was once-weekly intraperitoneal injections (0.5 mg/kg) and started at day 0.5 of pregnancy, improved glucose tolerance with significant changes of gluconeogenic, lipogenic and adipocytokine genes. HFD pregnant mice had hypertension and proteinuria, while TCPOBOP treatment ameliorated these signs. Our data suggested CAR might be a potential therapeutic target for obese preeclampsia patients with insulin resistance.     

Microbial biosynthesis of medium-chain 1-alkenes by a nonheme iron oxidase

Aliphatic medium-chain 1-alkenes (MCAEs, ∼10 carbons) are “drop-in” compatible next-generation fuels and precursors to commodity chemicals. Mass production of MCAEs from renewable resources holds promise for mitigating dependence on fossil hydrocarbons. An MCAE, such as 1-undecene, is naturally produced by Pseudomonas as a semivolatile metabolite through an unknown biosynthetic pathway. We describe here the discovery of a single gene conserved in Pseudomonas responsible for 1-undecene biosynthesis. The encoded enzyme is able to convert medium-chain fatty acids (C10–C14) into their corresponding terminal olefins using an oxygen-activating, nonheme iron-dependent mechanism. Both biochemical and X-ray crystal structural analyses suggest an unusual mechanism of β-hydrogen abstraction during fatty acid substrate activation. Our discovery unveils previously unidentified chemistry in the nonheme Fe(II) enzyme family, provides an opportunity to explore the biology of 1-undecene in Pseudomonas, and paves the way for tailored bioconversion of renewable raw materials to MCAE-based biofuels and chemical commodities.Surging energy consumption and environmental concerns have stimulated interest in the production of chemicals and fuels through sustainable and renewable approaches. Medium-chain 1-alkenes (MCAEs) are of particular interest because they are “drop-in”–ready next-generation fuels with superior properties such as low freezing point compared with long-chain diesels, high energy content compared with short-chain fuels, easy product recovery due to insolubility in water, and compatibility with the existing engine systems and transportation infrastructure (1, 2). Because of a readily derivatized terminal functionality, MCAEs are also valuable precursors to commodity chemicals such as lubricants, pesticides, polymers, and detergents (3, 4). Biological production of MCAEs from renewable resources holds promise for mitigating dependence on fossil hydrocarbons. Although MCAEs are naturally produced by diverse species as semivolatile metabolites (5, 6), little is known about the genetic and molecular basis for MCAE biosynthesis. Elucidation of MCAE biosynthetic pathway will serve as the basis for engineering efforts to establish bioprocesses for producing MCAE-based biofuels and chemical commodities from renewable resources.1-Undecene, an MCAE with 11 carbons, was identified as a biomarker of Pseudomonas aeruginosa, one of the most significant human pathogens (7–10). However, the biology of this characteristic semivolatile metabolite in P. aeruginosa remains enigmatic, and the biosynthetic pathway of 1-undecene has not previously been explored. It was also reported that some species of Pseudomonas produce 1-undecene, whereas some species do not (8), inspiring us to use a comparative genomics approach to reveal the genetic basis for 1-undecene biosynthesis (11). It is notable that one of the major challenges for MCAE biosynthetic study is the detection and quantification of MCAE production. MCAEs, such as 1-undecene, are only produced in trace amounts by their native producers (5, 6). In addition, MCAEs are insoluble in water, less dense than water, and readily escape the cell culture as semivolatile metabolites (8). Therefore, a reliable and sensitive method for MCAE detection is a prerequsite for their biosynthetic study. In this work, we used a headspace solid phase microextraction (SPME)–gas chromatography mass spectrometry (GCMS) analysis to detect the semivolatile metabolite 1-undecene, and we revealed that the production of 1-undecene is ubiquitous in the genus of Pseudomonas. We further discovered that a novel enzyme conserved in Pseudomonas is responsible for 1-undecene biosynthesis through an unusual catalytic mechanism.     

Stearoyl-acyl carrier protein desaturases are associated with floral isolation in sexually deceptive orchids

The orchids Ophrys sphegodes and O. exaltata are reproductively isolated from each other by the attraction of two different, highly specific pollinator species. For pollinator attraction, flowers chemically mimic the pollinators' sex pheromones, the key components of which are alkenes with different double-bond positions. This study identifies genes likely involved in alkene biosynthesis, encoding stearoyl-acyl carrier protein (ACP) desaturase (SAD) homologs. The expression of two isoforms, SAD1 and SAD2, is flower-specific and broadly parallels alkene production during flower development. SAD2 shows a significant association with alkene production, and in vitro assays show that O. sphegodes SAD2 has activity both as an 18:0-ACP Δ(9) and a 16:0-ACP Δ(4) desaturase. Downstream metabolism of the SAD2 reaction products would give rise to alkenes with double-bonds at position 9 or position 12, matching double-bond positions observed in alkenes in the odor bouquet of O. sphegodes. SAD1 and SAD2 show evidence of purifying selection before, and positive or relaxed purifying selection after gene duplication. By contributing to the production of species-specific alkene bouquets, SAD2 is suggested to contribute to differential pollinator attraction and reproductive isolation among these species. Taken together, these data are consistent with the hypothesis that SAD2 is a florally expressed barrier gene of large phenotypic effect and, possibly, a genic target of pollinator-mediated selection.     

Saturated fatty acid metabolism is key link between cell division,cancer, and senescence in cellular and whole organism aging

Cellular senescence is an in vivo and in vitro phenomenon, accompanied by physiological changes including cessation of division and disturbances of organelle structure and function. Review of the literature was undertaken to determine whether there is evidence that whole organism aging and cell senescence share a common initiation pathway. In vivo aged cells of different lineages, including aged T lymphocytes, show high expression of the INK4A-p16 gene. In cell culture when telomeres are shortened past a key length or state, the Arf/Ink gene system (p16/p14 humans, p16/p19 mice) switches on and activates p53, which suppresses further cell division. The p53 gene is a key tumor suppressor and its deletion or mutation allows cancerous growth. The switching on of p53 also causes changes in fatty acid metabolism, especially down-regulation of both fatty acid synthase and stearoyl-CoA (delta-9) desaturase. The co-suppression of these genes together with enhanced uptake of extracellular fatty acids, leads to raised levels of cellular palmitate and induction of either apoptosis or senescence. In senescent cells, the fatty acid composition of the cellular membranes alters and leads to changes in both structure and function of organelles, especially mitochondria. Animal models of accelerated aging exhibit repression of stearoyl-CoA desaturase activity while anti-aging calorie restriction stimulates the same enzyme system. It is concluded that aging in cells and whole organisms share a common initiation pathway and that cellular senescence is protective against cancer. Healthy longevity is likely to be most enhanced by factors that actively suppress excessive cell division.     

Genetic variants in desaturase gene,erythrocyte fatty acids,and risk for type 2 diabetes in Chinese Hans

ObjectiveThe aim of this study was to examine the association of the genetic variants in the fatty acid desaturase (FADS) gene cluster with erythrocyte phospholipid fatty acids (PLFA), and their relation to risk for type 2 diabetes mellitus (T2DM) in Han Chinese.MethodsSeven hundred and fifty-eight patients with T2DM and 400 healthy individuals were recruited. The erythrocyte PLFA and single-nucleotide polymorphism were determined by standard method.ResultsMinor allele homozygotes and heterozygotes of rs174575 and rs174537 had lower PL 20:4 ω-6 levels in healthy individuals. Minor allele homozygotes and heterozygotes of rs174455 in FADS3 gene had lower levels of 22:5 ω-3, 20:4 ω-6, and Δ5desaturase activity in patients with T2DM. Erythrocyte membrane PL 18:3 ω-3 (P for trend = 0.002), 22:5 ω-3 (P for trend < 0.001), ω-3 polyunsaturated fatty acid (P for trend < 0.001), and ω-3:ω-6 (P for trend < 0.001) were significantly inversely associated with risk for T2DM.ConclusionGenetic variants in the FADS gene cluster are associated with altered erythrocyte PLFAs. High levels of PL 18:3 ω-3, 22:5 ω-3, and total ω-3 polyunsaturated fatty acid were associated with low risk for T2DM.     

Soraphen A, an inhibitor of acetyl CoA carboxylase activity, interferes with fatty acid elongation

Acetyl CoA carboxylase (ACC1 and ACC2) generates malonyl CoA, a substrate for de novo lipogenesis (DNL) and an inhibitor of mitochondrial fatty acid β-oxidation (FAO). Malonyl CoA is also a substrate for microsomal fatty acid elongation, an important pathway for saturated (SFA), mono- (MUFA) and polyunsaturated fatty acid (PUFA) synthesis. Despite the interest in ACC as a target for obesity and cancer therapy, little attention has been given to the role ACC plays in long chain fatty acid synthesis. This report examines the effect of pharmacological inhibition of ACC on DNL and palmitate (16:0) and linoleate (18:2, n − 6) metabolism in HepG2 and LnCap cells. The ACC inhibitor, soraphen A, lowers cellular malonyl CoA, attenuates DNL and the formation of fatty acid elongation products derived from exogenous fatty acids, i.e., 16:0 and 18:2, n − 6; IC₅₀ ∼ 5 nM. Elevated expression of fatty acid elongases (Elovl5, Elovl6) or desaturases (FADS1, FADS2) failed to override the soraphen A effect on SFA, MUFA or PUFA synthesis. Inhibition of fatty acid elongation leads to the accumulation of 16- and 18-carbon unsaturated fatty acids derived from 16:0 and 18:2, n − 6, respectively. Pharmacological inhibition of ACC activity will not only attenuate DNL and induce FAO, but will also attenuate the synthesis of very long chain saturated, mono- and polyunsaturated fatty acids.