Amber Jannasch

An alternative pathway contributes to phenylalanine biosynthesis in plants via a cytosolic tyrosine:phenylpyruvate aminotransferase

Phenylalanine is a vital component of proteins in all living organisms, and in plants is a precursor for thousands of additional metabolites. Animals are incapable of synthesizing phenylalanine and must primarily obtain it directly or indirectly from plants. Although plants can synthesize phenylalanine in plastids through arogenate, the contribution of an alternative pathway via phenylpyruvate, as occurs in most microbes, has not been demonstrated. Here we show that plants also utilize a microbial-like phenylpyruvate pathway to produce phenylalanine, and flux through this route is increased when the entry point to the arogenate pathway is limiting. Unexpectedly, we find the plant phenylpyruvate pathway utilizes a cytosolic aminotransferase that links the coordinated catabolism of tyrosine to serve as the amino donor, thus interconnecting the extra-plastidial metabolism of these amino acids. This discovery uncovers another level of complexity in the plant aromatic amino acid regulatory network, unveiling new targets for metabolic engineering.

Determination of urine 3-HPMA, a stable acrolein metabolite in a rat model of spinal cord injury.

Acrolein has been suggested to be involved in a variety of pathological conditions. The monitoring of acrolein is of significant importance in delineating the pathogenesis of various diseases. Aimed at overcoming the reactivity and volatility of acrolein, we describe a specific and stable metabolite of acrolein in urine, N-acetyl-S-3-hydroxypropylcysteine (3-HPMA), as a potential surrogate marker for acrolein quantification. Using the LC/MS/MS method, we demonstrated that 3-HPMA was significantly elevated in a dose-dependent manner when acrolein was injected into rats IP or directly into the spinal cord, but not when acrolein scavengers were co-incubated with acrolein solution. A nonlinear mathematic relationship is established between acrolein injected directly into the spinal cord and a correlated dose-dependent increase of 3-HPMA, suggesting the increase of 3-HPMA becomes less apparent as the level of injected acrolein increases. The elevation of 3-HPMA was further detected in the rat spinal cord injury, a pathological condition known to be associated with elevated endogenous acrolein. This finding was further validated by concomitant confirmation of increased acrolein-lysine adducts using established dot immunoblotting techniques. The noninvasive nature of measuring 3-HPMA concentrations in urine allows for long-term monitoring of acrolein in the same animal and ultimately in human clinical studies. Due to wide spread involvement of acrolein in human health, the benefits of this study have the potential to enhance human health significantly.

An embryonic atrazine exposure results in reproductive dysfunction in adult zebrafish and morphological alterations in their offspring

The herbicide atrazine, a suspected endocrine disrupting chemical (EDC), frequently contaminates potable water supplies. Studies suggest alterations in the neuroendocrine system along the hypothalamus-pituitary-gonadal axis; however, most studies address either developmental, pubertal, or adulthood exposures, with few investigations regarding a developmental origins hypothesis. In this study, zebrafish were exposed to 0, 0.3, 3, or 30 parts per billion (ppb) atrazine through embryogenesis and then allowed to mature with no additional chemical exposure. Reproductive function, histopathology, hormone levels, offspring morphology, and the ovarian transcriptome were assessed. Embryonic atrazine exposure resulted in a significant increase in progesterone levels in the 3 and 30 ppb groups. A significant decrease in spawning and a significant increase in follicular atresia in the 30 ppb group were observed. In offspring, a decrease in the head length to body ratio in the 30 ppb group, along with a significant increase in head width to body ratio in the 0.3 and 3 ppb groups occurred. Transcriptomic alterations involved genes associated with endocrine system development and function, tissue development, and behavior. This study provides evidence to support atrazine as an EDC causing reproductive dysfunction and molecular alterations in adults exposed only during embryogenesis and morphological alterations in their offspring.

Development of a new method for improved identification and relative quantification of unknown metabolites in complex samples: determination of a triterpenoid metabolic fingerprint for the in situ characterization of Ganoderma bioactive compounds.

Ganoderma lucidum is a mushroom with a long history of medical applications. Research has demonstrated chemotherapeutic effects of G. lucidum in tissue culture, and bioactive fractions of the mushroom have been shown to contain high levels of triterpenoids and polysaccharides. In this study, we developed a new method for the detection of ganoderic acids and other triterpenes in Ganoderma mushroom extracts based on a post-biosynthetic stable isotope encoding technique. Overall, 57 doublets were identified as potential ganoderic acids and 11 of those matched with the database. Ganoderic acid A, F and H were confirmed by standards and their absolute concentrations were measured in GLT (GA A: 3.88 mg/g; GA F: 0.95 mg/g and GA H: 1.74 mg/g) and ReishiMax (GA A: 2.32 mg/g; GA F: 0.43 mg/g and GA H: 0.85 mg/g) extracts. The method was also used for the evaluation of bioavailability of triterpenes after an oral application and demonstrated the presence of G. lucidum triterpenes in plasma.

Systems-Scale Analysis Reveals Pathways Involved in Cellular Response to Methamphetamine.

Background Methamphetamine (METH), an abused illicit drug, disrupts many cellular processes, including energy metabolism, spermatogenesis, and maintenance of oxidative status. However, many components of the molecular underpinnings of METH toxicity have yet to be established. Network analyses of integrated proteomic, transcriptomic and metabolomic data are particularly well suited for identifying cellular responses to toxins, such as METH, which might otherwise be obscured by the numerous and dynamic changes that are induced. Methodology/Results We used network analyses of proteomic and transcriptomic data to evaluate pathways in Drosophila melanogaster that are affected by acute METH toxicity. METH exposure caused changes in the expression of genes involved with energy metabolism, suggesting a Warburg-like effect (aerobic glycolysis), which is normally associated with cancerous cells. Therefore, we tested the hypothesis that carbohydrate metabolism plays an important role in METH toxicity. In agreement with our hypothesis, we observed that increased dietary sugars partially alleviated the toxic effects of METH. Our systems analysis also showed that METH impacted genes and proteins known to be associated with muscular homeostasis/contraction, maintenance of oxidative status, oxidative phosphorylation, spermatogenesis, iron and calcium homeostasis. Our results also provide numerous candidate genes for the METH-induced dysfunction of spermatogenesis, which have not been previously characterized at the molecular level. Conclusion Our results support our overall hypothesis that METH causes a toxic syndrome that is characterized by the altered carbohydrate metabolism, dysregulation of calcium and iron homeostasis, increased oxidative stress, and disruption of mitochondrial functions.

Analysis of vitamin E metabolites including carboxychromanols and sulfated derivatives using LC/MS/MS

Tocopherols and tocotrienols are metabolized via hydroxylation and oxidation of their hydrophobic side chain to generate 13′-hydroxychromanols (13′-OHs) and various carboxychromanols, which can be further metabolized by conjugation including sulfation. Recent studies indicate that long-chain carboxychromanols, especially 13′-carboxychromanol (13′-COOH), appear to be more bioactive than tocopherols in anti-inflammatory and anticancer actions. To understand the potential contribution of metabolites to vitamin E-mediated effects, an accurate assay is needed to evaluate bioavailability of these metabolites. Here we describe an LC/MS/MS assay for quantifying vitamin E metabolites using negative polarity ESI. This assay includes a reliable sample extraction procedure with efficacy of ≥ 89% and interday/intraday variation of 3–11% for major metabolites. To ensure accurate quantification, short-chain, long-chain, and sulfated carboxychromanols are included as external/internal standards. Using this assay, we observed that sulfated carboxychromanols are the primary metabolites in the plasma of rodents fed with γ-tocopherol or δ-tocopherol. Although plasma levels of 13′-COOHs and 13′-OHs are low, high concentrations of these compounds are found in feces. Our study demonstrates an LC/MS/MS assay for quantitation of sulfated and unconjugated vitamin E metabolites, and this assay will be useful for evaluating the role of these metabolites in vivo.

METABOLITE PROFILES IN STARVED DIPOREIA SPP. USING LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY (LC-MS) BASED METABOLOMICS

ABSTRACT The holarctic amphipod Diporeia spp. was historically the most abundant benthic macroinvertebrate in the offshore region of the Laurentian Great Lakes basin. However, since the 1990s, the numbers of Diporeia have declined precipitously throughout the region. Competition for food with introduced dreissenid mussels may be partly to blame for this decline. Thus, a better understanding of how Diporeia responds and adjust to starvation is needed. For this purpose, we used liquid chromatography (LC) coupled with time-of-flight mass spectrometry (TOFMS) to study the metabolite profiles of Diporeia during starvation. Diporeia were collected from Lake Michigan, brought to the laboratory and starved for up to 60 days. During the starvation period, metabolite levels were determined at 12-day intervals and compared to those of day 0. Principal component and cluster analyses revealed differential abundance of metabolite profiles across groups. Significantly down-regulated metabolites included polyunsaturated fatty acids, phospholipids, and amino acids and their derivatives. Overall, starved organisms relied predominantly on glycerophospolipid metabolism and protein based catabolism for energy production. This research demonstrates that LC-MS based metabolomics can be used to assess physiological status and has shown that unique metabolite profiles are distinguishable over several weeks of starvation in this freshwater amphipod. More importantly these unique metabolites could be used to gain insights into the underlying cause(s) of Diporeias decline in the Laurentian Great Lakes.

Quantification of pentose phosphate pathway (PPP) metabolites by liquid chromatography-mass spectrometry (LC-MS).

The pentose phosphate pathway plays an important role in several cellular processes including biosynthesis and catabolism of five-carbon sugars and generation of reducing power through NADPH synthesis. Although the pentose phosphate metabolic reaction network has been mapped in substantial detail, the comprehensive quantitative analysis of the rates and regulation of individual reactions remains a major interest for various biofields. Here we describe a simple method for comprehensive quantitative analysis of pentose phosphate pathway intermediates. The method is based on Group Specific Internal Standard Technology (GSIST) labeling in which an experimental sample and corresponding internal standards are derivatized in vitro with isotope-coded reagents in separate reactions, then mixed and analyzed in a single LC-MS run. The use of co-eluting isotope-coded internal standards and experimental molecules eliminates potential issues with ion suppression and allows for precise quantification of individual metabolites. Derivatization also increases hydrophobicity of the metabolites enabling their effective separation using reversed-phase chromatography.

Starvation causes disturbance in amino acid and fatty acid metabolism in Diporeia.

The benthic amphipod Diporeia spp. was once the predominant macroinvertebrate in deep, offshore regions of the Laurentian Great Lakes. However, since the early 1990s, Diporeia populations have steadily declined across the area. It has been hypothesized that this decline is due to starvation from increasing competition for food with invasive dreissenid mussels. In order to gain a better understanding of the changes in Diporeia physiology during starvation, we applied two-dimensional gas chromatography coupled with time of flight mass spectrometry (GCXGC/TOF-MS) for investigating the responses in Diporeia metabolome during starvation. We starved Diporeia for 60 days and collected five organisms every 12 days for metabolome analyses. Upon arrival to the laboratory, organisms were flash frozen and served as control (day 0). We observed an increase in lipid oxidation and protein catabolism with subsequent declines of essential amino acids (proline, glutamine, and phenylalanine), down-regulation of glycerophospholipid and sphingolipid metabolism, and decreased polyunsaturated fatty acid abundance in nutritionally stressed Diporeia. Abundance of 1-Iodo-2-methylundecane, a metabolite closely related to insect pheromones, also declined with starvation. This research has further substantiated the applicability of GCXGC/TOF-MS as a research tool in the field of environmental metabolomics. The next step is to apply this new knowledge for evaluating nutritional status of feral Diporeia to elucidate the underlying cause(s) responsible for their decline in the Great Lakes.

Bowman-Birk inhibitor affects pathways associated with energy metabolism in Drosophila melanogaster

Bowman‐Birk inhibitor (BBI) is toxic when fed to certain insects, including the fruit fly, Drosophila melanogaster. Dietary BBI has been demonstrated to slow growth and increase insect mortality by inhibiting the digestive enzymes trypsin and chymotrypsin, resulting in a reduced supply of amino acids. In mammals, BBI influences cellular energy metabolism. Therefore, we tested the hypothesis that dietary BBI affects energy‐associated pathways in the D. melanogaster midgut. Through microarray and metabolomic analyses, we show that dietary BBI affects energy utilization pathways in the midgut cells of D. melanogaster. In addition, ultrastructure studies indicate that microvilli are significantly shortened in BBI‐fed larvae. These data provide further insights into the complex cellular response of insects to dietary protease inhibitors.