Untargeted Metabolomic Screen Reveals Changes in Human Plasma Metabolite Profiles Following Consumption of Fresh Broccoli Sprouts

SCOPE

Several lines of evidence suggest that the consumption of cruciferous vegetables is beneficial to human health. Yet, underlying mechanisms and key molecular targets that are involved with achieving these benefits in humans are still not fully understood. To accelerate this research, we conduct a human study to identify potential molecular targets of crucifers for further study. This study aims to characterize plasma metabolite profiles in humans before and after consuming fresh broccoli sprouts (a rich dietary source of bioactive sulforaphane).

METHODS AND RESULTS

Ten healthy adults consume fresh broccoli sprouts (containing 200 μmol sulforaphane equivalents) at time 0 and provide blood samples at 0, 3, 6, 12, 24, and 48 h. An untargeted metabolomics screen reveals that levels of several plasma metabolites are significantly different before and after sprout intake, including fatty acids (14:0, 14:1, 16:0, 16:1, 18:0, and 18:1), glutathione, glutamine, cysteine, dehydroepiandrosterone, and deoxyuridine monophosphate. Evaluation of all time points is conducted using paired t-test (R software) and repeated measures analysis of variance for a within-subject design (Progenesis QI).

CONCLUSION

This investigation identifies several potential molecular targets of crucifers that may aid in studying established and emerging health benefits of consuming cruciferous vegetables and related bioactive compounds.

Centella asiatica - Phytochemistry and mechanisms of neuroprotection and cognitive enhancement

This review describes in detail the phytochemistry and neurological effects of the medicinal herb Centella asiatica (L.) Urban. C. asiatica is a small perennial plant that grows in moist, tropical and sub-tropical regions throughout the world. Phytochemicals identified from C. asiatica to date include isoprenoids (sesquiterpenes, plant sterols, pentacyclic triterpenoids and saponins) and phenylpropanoid derivatives (eugenol derivatives, caffeoylquinic acids, and flavonoids). Contemporary methods for fingerprinting and characterization of compounds in C. asiatica extracts include liquid chromatography and/or ion mobility spectrometry in conjunction with high-resolution mass spectrometry. Multiple studies in rodent models, and a limited number of human studies support C. asiatica's traditional reputation as a cognitive enhancer, as well as its anxiolytic and anticonvulsant effects. Neuroprotective effects of C.asiatica are seen in several in vitro models, for example against beta amyloid toxicity, and appear to be associated with increased mitochondrial activity, improved antioxidant status, and/or inhibition of the pro-inflammatory enzyme, phospholipase A2. Neurotropic effects of C. asiatica include increased dendritic arborization and synaptogenesis, and may be due to modulations of signal transduction pathways such as ERK1/2 and Akt. Many of these neurotropic and neuroprotective properties of C.asiatica have been associated with the triterpene compounds asiatic acid, asiaticoside and madecassoside. More recently, caffeoylquinic acids are emerging as a second important group of active compounds in C. asiatica, with the potential of enhancing the Nrf2-antioxidant response pathway. The absorption, distribution, metabolism and excretion of the triterpenes, caffeoylquinic acids and flavonoids found in C. asiatica have been studied in humans and animal models, and the compounds or their metabolites found in the brain. This review highlights the remarkable potential for C. asiatica extracts and derivatives to be used in the treatment of neurological conditions, and considers the further research needed to actualize this possibility.

Rice Protein Matrix Enhances Circulating Levels of Xanthohumol Following Acute Oral Intake of Spent Hops in Humans

SCOPE

Xanthohumol (XN), a prenylated flavonoid found in hops, exhibits anti-inflammatory and antioxidant properties. However, poor bioavailability may limit therapeutic applications. As food components are known to modulate polyphenol absorption, the objective is to determine whether a protein matrix could enhance the bioavailability of XN post oral consumption in humans.

METHODS AND RESULTS

This is a randomized, double-blind, crossover study in healthy participants (n = 6) evaluating XN and its major metabolites (isoxanthohumol [IX], 6- and 8-prenylnaringenin [6-PN, 8-PN]) for 6 h following consumption of 12.4 mg of XN delivered via a spent hops-rice protein matrix preparation or a control spent hops preparation. Plasma XN and metabolites are measured by LC-MS/MS. C_max , T_max , and area-under-the-curve (AUC) values were determined. Circulating XN and metabolite response to each treatment was not bioequivalent. Plasma concentrations of XN and XN + metabolites (AUC) are greater with consumption of the spent hops-rice protein matrix preparation.

CONCLUSION

Compared to a standard spent hops powder, a protein-rich spent hops matrix demonstrates enhanced plasma levels of XN and metabolites following acute oral intake.

Total synthesis of [13 C]2 -, [13 C]3 -, and [13 C]5 -isotopomers of xanthohumol, the principal prenylflavonoid from hops

Xanthohumol [(E)-6'-methoxy-3'-(3-methylbuten-2-yl)-2',4',4″-trihydroxychalcone], he principal prenylated flavonoid from hops, has a complex bioactivity profile, and ¹³ C-labeled isotopomers of this compound are of potential use as molecular probes and as analytical standards to study metabolism and mode of action. 1,3-[¹³ C]₂ -Xanthohumol was prepared by an adaptation of the total synthesis of Khupse and Erhardt in 7 steps and 5.7% overall yield from phloroglucinol by a route incorporating a cascade Claisen-Cope rearrangement to install the 3'-prenyl moiety from a 5'-prenyl aryl ether and an aldol condensation between 1-[¹³ C]-2',4'-bis(benzyloxymethyloxy)-6'-methoxy-3'-(3-methylbuten-2-yl)acetophenone and 1'-[¹³ C]-4-(methoxymethyloxy)benzaldehyde. The ¹³ C-atom in the methyl ketone was derived from 1-[¹³ C]-acetyl chloride while that in the aryl aldehyde was derived from [¹³ C]-iodomethane. Tri- and penta-¹³ C-labeled xanthohumols were similarly prepared by applying minor modifications to the route.

Effects of Time and Storage Conditions on the Chemical and Microbiologic Stability of Diluted Buprenorphine for Injection

Buprenorphine is a partial μ-opioid agonist used for analgesia. Due to the small size of laboratory rodents, buprenorphine HCl is typically diluted 10- or 20-fold with a sterile diluent, such as saline, for accurate dosing. Protocols for preparing and storing diluted buprenorphine vary by institution, and little published information is available regarding stability and beyond-use dating of specific buprenorphine preparations. The purpose of this study was to determine the chemical and microbiologic stability of diluted buprenorphine stored for a maximum of 180 d. Buprenorphine HCl was diluted 1:10 into sterile bacteriostatic saline by using aseptic technique. Diluted samples were stored in glass vials or plastic syringes, protected from light, and maintained at refrigerated or room temperature for as long as 180 d. Aerobic and anaerobic cultures on all stored samples were negative for bacterial and fungal growth. According to HPLC analysis, diluted buprenorphine stored in glass vials experienced less than 10% loss when stored for 180 d at either refrigerated or room temperature. However, the concentration of buprenorphine stored in syringes declined rapidly to more than 80% loss at room temperature and 28% loss in the refrigerator after 180 d. According to the results of this study, diluted buprenorphine stored in glass vials retains more than 90% of the initial concentration and is microbiologically stable for 180 d. However, our data suggest that, regardless of the duration, storing diluted buprenorphine in plastic syringes is inadvisable.

18O-Tracer Metabolomics Reveals Protein Turnover and CDP-Choline Cycle Activity in Differentiating 3T3-L1 Pre-Adipocytes

The differentiation of precursor cells into mature adipocytes (adipogenesis) has been an area of increased focus, spurred by a rise in obesity rates. Though our understanding of adipogenesis and its regulation at the cellular level is growing, many questions remain, especially regarding the regulation of the metabolome. The 3T3-L1 cell line is the most well characterized cellular model of adipogenesis. Using a time course metabolomics approach, we show that the 3T3-L1 preadipocyte metabolome is greatly altered during the first 48 hours of differentiation, where cells go through about two rounds of cell division, a process known as mitotic clonal expansion. Short-chain peptides were among several small molecules that were increased during mitotic clonal expansion. Additional indicators of protein turnover were also increased, including bilirubin, a degradation product of heme-containing proteins, and 3-methylhistidine, a post-translationally modified amino acid that is not reutilized for protein synthesis. To study the origin of the peptides, we treated differentiating preadipocytes with ¹⁸O labeled water and found that ¹⁸O was incorporated into the short chain peptides, confirming them, at least in part, as products of hydrolysis. Inhibitors of the proteasome or matrix metalloproteinases affected the peptide levels during differentiation, but inhibitors of autophagy or peptidases did not. ¹⁸O was also incorporated into several choline metabolites including cytidine 5'-diphosphocholine (CDP-choline), glycerophosphocholine, and several phosphatidylcholine species, indicative of phosphatidylcholine synthesis/degradation and of flux through the CDP-choline cycle, a hallmark of proliferating cells. ¹⁸O-Tracer metabolomics further showed metabolic labeling of glutamate, suggestive of glutaminolysis, also characteristic of proliferating cells. Together, these results highlight the utility of ¹⁸O isotope labeling in combination with metabolomics to uncover changes in cellular metabolism that are not detectable by time-resolved metabolomics.

The Chemistry of Gut Microbial Metabolism of Polyphenols

Gut microbiota contribute to the metabolism of dietary polyphenols and affect the bioavailability of both the parent polyphenols and their metabolites. Although there is a large number of reports of specific polyphenol metabolites, relatively little is known regarding the chemistry and enzymology of the metabolic pathways utilized by specific microbial species and taxa, which is the focus of this review. Major classes of dietary polyphenols include monomeric and oligomeric catechins (proanthocyanidins), flavonols, flavanones, ellagitannins, and isoflavones. Gut microbial metabolism of representatives of these polyphenol classes can be classified as A- and C-ring cleavage (retro Claisen reactions), C-ring cleavage mediated by dioxygenases, dehydroxylations (decarboxylation or reduction reactions followed by release of H₂O molecules), and hydrogenations of alkene moieties in polyphenols, such as resveratrol, curcumin, and isoflavones (mediated by NADPH-dependent reductases). The qualitative and quantitative metabolic output of the gut microbiota depends to a large extent on the metabolic capacity of individual taxa, which emphasizes the need for assessment of functional analysis in conjunction with determinations of gut microbiota compositions.

Xanthohumol improves dysfunctional glucose and lipid metabolism in diet-induced obese C57BL/6J mice

Xanthohumol (XN) is a prenylated flavonoid found in hops (Humulus lupulus) and beer. The dose-dependent effects of XN on glucose and lipid metabolism in a preclinical model of metabolic syndrome were the focus of our study. Forty-eight male C57BL/6J mice, 9 weeks of age, were randomly divided into three XN dose groups of 16 animals. The mice were fed a high-fat diet (60% kcal as fat) supplemented with XN at dose levels of 0, 30, or 60 mg/kg body weight/day, for 12 weeks. Dietary XN caused a dose-dependent decrease in body weight gain. Plasma levels of glucose, total triglycerides, total cholesterol, and MCP-1 were significantly decreased in mice on the 60 mg/kg/day treatment regimen. Treatment with XN at 60 mg/kg/day resulted in reduced plasma LDL-cholesterol (LDL-C), IL-6, insulin and leptin levels by 80%, 78%, 42%, and 41%, respectively, compared to the vehicle control group. Proprotein Convertase Subtilisin Kexin 9 (PCSK-9) levels were 44% lower in the 60 mg/kg dose group compared to the vehicle control group (p ≤ 0.05) which may account for the LDL-C lowering activity of XN. Our results show that oral administration of XN improves markers of systemic inflammation and metabolic syndrome in diet-induced obese C57BL/6J mice.

Lipidomics and H2(18)O labeling techniques reveal increased remodeling of DHA-containing membrane phospholipids associated with abnormal locomotor responses in α-tocopherol deficient zebrafish (danio rerio) embryos

We hypothesized that vitamin E (α-tocopherol) is required by the developing embryonic brain to prevent depletion of highly polyunsaturated fatty acids, especially docosahexaenoic acid (DHA, 22:6), the loss of which we predicted would underlie abnormal morphological and behavioral outcomes. Therefore, we fed adult 5D zebrafish (Danio rerio) defined diets without (E−) or with added α-tocopherol (E+, 500 mg RRR-α-tocopheryl acetate/kg diet) for a minimum of 80 days, and then spawned them to obtain E− and E+ embryos. The E− compared with E+ embryos were 82% less responsive (p<0.01) to a light/dark stimulus at 96 h post-fertilization (hpf), demonstrating impaired locomotor behavior, even in the absence of gross morphological defects. Evaluation of phospholipid (PL) and lysophospholipid (lyso-PL) composition using untargeted lipidomics in E− compared with E+ embryos at 24, 48, 72, and 120 hpf showed that four PLs and three lyso-PLs containing docosahexaenoic acid (DHA), including lysophosphatidylcholine (LPC 22:6, required for transport of DHA into the brain, p<0.001), were at lower concentrations in E− at all time-points. Additionally, H₂¹⁸O labeling experiments revealed enhanced turnover of LPC 22:6 (p<0.001) and three other DHA-containing PLs in the E− compared with the E+ embryos, suggesting that increased membrane remodeling is a result of PL depletion. Together, these data indicate that α-tocopherol deficiency in the zebrafish embryo causes the specific depletion and increased turnover of DHA-containing PL and lyso-PLs, which may compromise DHA delivery to the brain and thereby contribute to the functional impairments observed in E− embryos.

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α-Tocopherol deficient (E-) embryos are abnormal and have impaired locomotor responses.

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DHA-containing phospholipids and lysophospholipids are depleted in E− embryos.

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E- embryos have increased turnover of DHA-containing phospholipids and lysophospholipids.

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DHA delivery to tissues is compromised, contributing to the functional impairments in E- embryos.

Metabolomic analysis to define and compare the effects of PAHs and oxygenated PAHs in developing zebrafish

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives are ubiquitously present in diesel exhaust, atmospheric particulate matter and soils sampled in urban areas. Therefore, inhalation or non-dietary ingestion of both PAHs and oxy-PAHs are major routes of exposure for people; especially young children living in these localities. While there has been extensive research on the parent PAHs, limited studies exist on the biological effects of oxy-PAHs which have been shown to be more soluble and more mobile in the environment. Additionally, investigations comparing the metabolic responses resulting from parent PAHs and oxy-PAHs exposures have not been reported. To address these current gaps, an untargeted metabolomics approach was conducted to examine the in vivo metabolomic profiles of developing zebrafish (Danio rerio) exposed to 4 µM of benz[a]anthracene (BAA) or benz[a]anthracene-7,12-dione (BAQ). By integrating multivariate, univariate and pathway analyses, a total of 63 metabolites were significantly altered after 5 days of exposure. The marked perturbations revealed that both BAA and BAQ affect protein biosynthesis, mitochondrial function, neural development, vascular development and cardiac function. Our previous transcriptomic and genomic data were incorporated in this metabolomics study to provide a more comprehensive view of the relationship between PAH and oxy-PAH exposures on vertebrate development.

Isolation and identification of antioxidant peptides from enzymatically hydrolyzed rice bran protein

Khao Dawk Mali 105 rice bran protein (RBP) was fractionated into albumin (12.5%), globulin (13.9%), glutelin (70.8%) and prolamine (2.9%). The native and denatured RBP fractions were hydrolyzed with papain and trypsin for 3h at optimum conditions. The RBP fractions and their hydrolysates were evaluated for their antioxidant activity by the Oxygen Radical Absorbance Capacity (ORAC) assay. The trypsin-hydrolyzed denatured albumin exhibited the highest antioxidant activity with an ORAC value of 4.07 μmol of Trolox equivalent (TE)/mg protein. This hydrolysate was separated by using RP-HPLC and three fractions with high antioxidant activity were examined by LTQ-FTICR ESI mass spectrometry. The MW of the peptides from these fractions were 800-2100 Da. and consisted of 6-21 amino acid residues. Most of the peptides from the fractions demonstrated typical characteristics of well-known antioxidant peptides. The results suggest that trypsin-hydrolyzed denatured rice bran albumin might be useful as a natural food antioxidant.

Novel function of vitamin E in regulation of zebrafish (Danio rerio) brain lysophospholipids discovered using lipidomics

We hypothesized that brains from vitamin E-deficient (E-) zebrafish (Danio rerio) would undergo increased lipid peroxidation because they contain highly polyunsaturated fatty acids, thus susceptible lipids could be identified. Brains from zebrafish fed for 9 months defined diets without (E-) or with (E+) added vitamin E (500 mg RRR-α-tocopheryl acetate per kilogram diet) were studied. Using an untargeted approach, 1-hexadecanoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine [DHA-PC 38:6, PC 16:0/22:6]was the lipid that showed the most significant and greatest fold-differences between groups. DHA-PC concentrations were approximately 1/3 lower in E- (4.3 ± 0.6 mg/g) compared with E+ brains (6.5 ± 0.9 mg/g, mean ± SEM, n = 10 per group, P = 0.04). Using lipidomics, 155 lipids in brain extracts were identified. Only four phospholipids (PLs) were different (P < 0.05) between groups; they were lower in E- brains and contained DHA with DHA-PC 38:6 at the highest abundances. Moreover, hydroxy-DHA-PC 38:6 was increased in E- brains (P = 0.0341) supporting the hypothesis of DHA peroxidation. More striking was the depletion in E- brains of nearly 60% of 19 different lysophospholipids (lysoPLs) (combined P = 0.0003), which are critical for membrane PL remodeling. Thus, E- brains contained fewer DHA-PLs, more hydroxy-DHA-PCs, and fewer lysoPLs, suggesting that lipid peroxidation depletes membrane DHA-PC and homeostatic mechanisms to repair the damage resulting in lysoPL depletion.

Absorption and chemopreventive targets of sulforaphane in humans following consumption of broccoli sprouts or a myrosinase-treated broccoli sprout extract

SCOPE

Sulforaphane (SFN), an isothiocyanate derived from crucifers, has numerous health benefits. SFN bioavailability from dietary sources is a critical determinant of its efficacy in humans. A key factor in SFN absorption is the release of SFN from its glucosinolate precursor, glucoraphanin, by myrosinase. Dietary supplements are used in clinical trials to deliver consistent SFN doses, but myrosinase is often inactivated in available supplements. We evaluated SFN absorption from a myrosinase-treated broccoli sprout extract (BSE) and are the first to report effects of twice daily, oral dosing on SFN exposure in healthy adults.

METHODS AND RESULTS

Subjects consumed fresh broccoli sprouts or the BSE, each providing 200 μmol SFN daily, as a single dose and as two 100-μmol doses taken 12 h apart. Using HPLC-MS/MS, we detected ∼3 x higher SFN metabolite levels in plasma and urine of sprout consumers, indicating enhanced SFN absorption from sprouts. Twelve-hour dosing retained higher plasma SFN metabolite levels at later time points than 24-hour dosing. No dose responses were observed for molecular targets of SFN (i.e. heme oxygenase-1, histone deacetylase activity, p21).

CONCLUSION

We conclude that the dietary form and dosing schedule of SFN may impact SFN absorption and efficacy in human trials.

Caffeoylquinic acids in Centella asiatica protect against amyloid-β toxicity

The accumulation of amyloid-β (Aβ) is a hallmark of Alzheimer's disease and is known to result in neurotoxicity both in vivo and in vitro. We previously demonstrated that treatment with the water extract of Centella asiatica (CAW) improves learning and memory deficits in Tg2576 mice, an animal model of Aβ accumulation. However the active compounds in CAW remain unknown. Here we used two in vitro models of Aβ toxicity to confirm this neuroprotective effect and identify several active constituents of the CAW extract. CAW reduced Aβ-induced cell death and attenuated Aβ-induced changes in tau expression and phosphorylation in both the MC65 and SH-SY5Y neuroblastoma cell lines. We confirmed and quantified the presence of several mono- and dicaffeoylquinic acids (CQAs) in CAW using chromatographic separation coupled to mass spectrometry and ultraviolet spectroscopy. Multiple dicaffeoylquinic acids showed efficacy in protecting MC65 cells against Aβ-induced cytotoxicity. Isochlorogenic acid A and 1,5-dicaffeoylquinic acid were found to be the most abundant CQAs in CAW, and the most active in protecting MC65 cells from Aβ-induced cell death. Both compounds showed neuroprotective activity in MC65 and SH-SY5Y cells at concentrations comparable to their levels in CAW. Each compound not only mitigated Aβ-induced cell death, but was able to attenuate Aβ-induced alterations in tau expression and phosphorylation in both cell lines, as seen with CAW. These data suggest that CQAs are active neuroprotective components in CAW, and therefore are important markers for future studies on CAW standardization, bioavailability, and dosing.

Identification and phytotoxicity of a new glucosinolate breakdown product from Meadowfoam (Limnanthes alba) seed meal

Meadowfoam (Limnanthes alba Hartw. ex Benth.) is an oilseed crop grown in the Willamette Valley of Oregon. Meadowfoam seed meal (MSM), a byproduct after oil extraction, contains 2-4% glucosinolate (glucolimnanthin). Activated MSM, produced by adding freshly ground myrosinase-active meadowfoam seeds to MSM, facilitates myrosinase-mediated formation of glucosinolate-derived degradation products with herbicidal activity. In the activated MSM, glucolimnanthin was converted into 3-methoxybenzyl isothiocyanate ("isothiocyanate") within 24 h and was degraded by day three. 3-Methoxyphenylacetonitrile ("nitrile") persisted for at least 6 days. Methoxyphenylacetic acid (MPAA), a previously unknown metabolite of glucolimnanthin, appeared at day three. Its identity was confirmed by LC-UV and high resolution LC-MS/MS comparisons with a standard of MPAA. Isothiocyanate inhibited lettuce germination 8.5- and 14.4-fold more effectively than MPAA and nitrile, respectively. Activated MSM inhibited lettuce germination by 58% and growth by 72% compared with the control. Results of the study suggest that MSM has potential uses as a pre-emergence bioherbicide.

Deuterium-labeled phylloquinone fed to α-tocopherol-injected rats demonstrates sensitivity of low phylloquinone-containing tissues to menaquinone-4 depletion

SCOPE

The influence of excess α-tocopherol (α-T) on tissue depletion of phylloquinone (PK) and menaquinone-4 (MK-4) was evaluated.

METHODS AND RESULTS

Rats (n = 5 per group) were fed deuterium-labeled PK (2 μmol/kg diet) for 17 days, thereby labeling the conversion from deuterium-labeled PK to d₄-MK-4. Then they were injected subcutaneously daily for the last 7 days with saline, vehicle, or α-T (100 mg/kg body weight). α-T injections (i) increased α-T concentrations by tenfold in liver, doubled them in plasma and most tissues, but they were unchanged in brain; (ii) increased the α-T metabolite, carboxyethyl hydroxychromanol (α-CEHC) concentrations: >25-fold in liver and kidney, tenfold in plasma and lung, and 50-fold in heart; brain contained detectable α-CEHC (0.26 ± 0.03 nmol/g) only in α-T-injected animals; and (iii) depleted most tissues' vitamin K. Compared with vehicle-injected rats, brains from α-T rats contained half the total vitamin K (10.3 ± 0.5 versus 21 ± 2 pmol/g, p = 0.0002) and one-third the d₄-MK-4 (5.8 ± 0.5 versus 14.6 ± 1.7 pmol/g, p = 0.0002). Tissues with high PK concentrations (liver, 21-30 pmol/g and heart, 28-50 pmol/g) were resistant to K depletion.

CONCLUSION

We propose that α-T-dependent vitamin K depletion is likely mediated at an intermediate step in MK-4 production; thus, tissues with high PK are unaffected.

Simultaneous, untargeted metabolic profiling of polar and nonpolar metabolites by LC-Q-TOF mass spectrometry

At its most ambitious, untargeted metabolomics aims to characterize and quantify all of the metabolites in a given system. Metabolites are often present at a broad range of concentrations and possess diverse physical properties complicating this task. Performing multiple sample extractions, concentrating sample extracts, and using several separation and detection methods are common strategies to overcome these challenges but require a great amount of resources. This protocol describes the untargeted, metabolic profiling of polar and nonpolar metabolites with a single extraction and using a single analytical platform.

Application of Paper Strip Extraction in Combination with LC-MS-MS in Pharmacokinetics

Recent advances in sampling techniques in the pharmaceutical industry sparked significant interest in applying improvements to extraction methods for greater analyte detection and quantitation. In particular, the dried blood spot (DBS) sampling technique has numerous advantages compared to traditional methods such as liquid-liquid extraction, including the use of small sample volumes, less sample processing, and less exposure to toxic solvents (ether, methyl tert-butyl ether [MTBE], and dichloromethane). In this article, we discuss the adaptation of DBS technology to develop and validate a novel paper strip extraction method for the analysis of natural product metabolites in biological samples obtained from a human pharmacokinetic study of xanthohumol, a hop prenylflavonoid.

Human pharmacokinetics of xanthohumol, an antihyperglycemic flavonoid from hops

SCOPE

Xanthohumol (XN) is a bioactive prenylflavonoid from hops. A single-dose pharmacokinetic (PK) study was conducted in men (n = 24) and women (n = 24) to determine dose-concentration relationships.

METHODS AND RESULTS

Subjects received a single oral dose of 20, 60, or 180 mg XN. Blood was collected at 0, 0.25, 0.5, 1, 2, 4, 8, 12, 24, 48, 72, 96, and 120 h. Plasma levels of XN and its metabolites, isoxanthohumol (IX), 8-prenylnaringenin (8PN), and 6-prenylnaringenin (6PN) were measured by LC-MS/MS. Xanthohumol (XN) and IX conjugates were dominant circulating flavonoids among all subjects. Levels of 8PN and 6PN were undetectable in most subjects. The XN PK profile showed peak concentrations around 1 h and between 4-5 h after ingestion. The maximum XN concentrations (C(max)) were 33 ± 7 mg/L, 48 ± 11 mg/L, and 120 ± 24 mg/L for the 20, 60, and 180 mg dose, respectively. Using noncompartmental modeling, the area under the curves (AUC(0→∞)) for XN were 92 ± 68 h × μg/L, 323 ± 160 h × μg/L, and 863 ± 388 h × μg/L for the 20, 60, and 180 mg dose, respectively. The mean half-life of XN was 20 h for the 60 and 18 h for the 180 mg dose.

CONCLUSION

XN has a distinct biphasic absorption pattern with XN and IX conjugates being the major circulating metabolites.

Electrospray Quadrupole Travelling Wave Ion Mobility Time-of-Flight Mass Spectrometry for the Detection of Plasma Metabolome Changes Caused by Xanthohumol in Obese Zucker (fa/fa) Rats

This study reports on the use of traveling wave ion mobility quadrupole time-of-flight (ToF) mass spectrometry for plasma metabolomics. Plasma metabolite profiles of obese Zucker fa/fa rats were obtained after the administration of different oral doses of Xanthohumol; a hop-derived dietary supplement. Liquid chromatography coupled data independent tandem mass spectrometry (LC-MSE) and LC-ion mobility spectrometry (IMS)-MSE acquisitions were conducted in both positive and negative modes using a Synapt G2 High Definition Mass Spectrometry (HDMS) instrument. This method provides identification of metabolite classes in rat plasma using parallel alternating low energy and high energy collision spectral acquisition modes. Data sets were analyzed using pattern recognition methods. Statistically significant (p < 0.05 and fold change (FC) threshold > 1.5) features were selected to identify the up-/down-regulated metabolite classes. Ion mobility data visualized using drift scope software provided a graphical read-out of differences in metabolite classes.

Xanthohumol lowers body weight and fasting plasma glucose in obese male Zucker fa/fa rats

Obesity contributes to increased risk for several chronic diseases including cardiovascular disease and type 2 diabetes. Xanthohumol, a prenylated flavonoid from hops (Humulus lupulus), was tested for efficacy on biomarkers of metabolic syndrome in 4 week old Zucker fa/fa rats, a rodent model of obesity. Rats received daily oral doses of xanthohumol at 0, 1.86, 5.64, and 16.9 mg/kg BW for 6 weeks. All rats were maintained on a high fat (60% kcal) AIN-93G diet for 3 weeks to induce severe obesity followed by a normal AIN-93G (15% kcal fat) diet for the last 3 weeks of the study. Weekly food intake and body weight were recorded. Plasma cholesterol, glucose, insulin, triglyceride, and monocyte chemoattractant protein-1 (MCP-1) levels were assessed using commercial assay kits. Plasma and liver tissue levels of XN and its metabolites were determined by liquid-chromatography tandem mass spectrometry. Plasma and liver tissue levels of xanthohumol were similar between low and medium dose groups and significantly (p<0.05) elevated in the highest dose group. There was a dose-dependent effect on body weight and plasma glucose levels. The highest dose group (n=6) had significantly lower plasma glucose levels compared to the control group (n=6) in male but not female rats. There was also a significant decrease in body weight for male rats in the highest dose group (16.9 mg/kg BW) compared to rats that received no xanthohumol, which was also not seen for female rats. Plasma cholesterol, insulin, triglycerides, and MCP-1 as well as food intake were not affected by treatment. The findings suggest that xanthohumol has beneficial effects on markers of metabolic syndrome.

A metabolomics-driven elucidation of the anti-obesity mechanisms of xanthohumol

Mild, mitochondrial uncoupling increases energy expenditure and can reduce the generation of reactive oxygen species (ROS). Activation of cellular, adaptive stress response pathways can result in an enhanced capacity to reduce oxidative damage. Together, these strategies target energy imbalance and oxidative stress, both underlying factors of obesity and related conditions such as type 2 diabetes. Here we describe a metabolomics-driven effort to uncover the anti-obesity mechanism(s) of xanthohumol (XN), a prenylated flavonoid from hops. Metabolomics analysis of fasting plasma from obese, Zucker rats treated with XN revealed decreases in products of dysfunctional fatty acid oxidation and ROS, prompting us to explore the effects of XN on muscle cell bioenergetics. At low micromolar concentrations, XN acutely increased uncoupled respiration in several different cell types, including myocytes. Tetrahydroxanthohumol also increased respiration, suggesting electrophilicity did not play a role. At higher concentrations, XN inhibited respiration in a ROS-dependent manner. In myocytes, time course metabolomics revealed acute activation of glutathione recycling and long term induction of glutathione synthesis as well as several other changes indicative of short term elevated cellular stress and a concerted adaptive response. Based on these findings, we hypothesize that XN may ameliorate metabolic syndrome, at least in part, through mitochondrial uncoupling and stress response induction. In addition, time course metabolomics appears to be an effective strategy for uncovering metabolic events that occur during a stress response.

Transcription factor Ctip2 controls epidermal lipid metabolism and regulates expression of genes involved in sphingolipid biosynthesis during skin development

The stratum corneum is composed of protein-enriched corneocytes embedded in an intercellular matrix of nonpolar lipids organized as lamellar layers and give rise to epidermal permeability barrier (EPB). EPB defects play an important role in the pathophysiology of skin diseases such as eczema. The transcriptional control of skin lipid metabolism is poorly understood. We have discovered that mouse lacking a transcription factor COUP-TF interacting protein 2 (Ctip2) exhibit EPB defects including altered keratinocyte terminal differentiation, delayed skin barrier development and interrupted neutral lipid distribution in the epidermis. We adapted herein a targeted lipidomic approach using mass spectrometry, and have determined that Ctip2^−/− mice (germline deletion of Ctip2 gene) display altered composition of major epidermal lipids such as ceramides and sphingomyelins compared to wildtype at different stages of skin development. Interestingly, expressions of several genes involved in skin sphingolipid biosynthesis and metabolism were altered in mutant skin. Ctip2 was found to be recruited to the promoter region of a subset of those genes, suggesting their possible direct regulation by Ctip2. Our results confirm an important role of Ctip2 in regulating skin lipid metabolism and indicate that profiling of epidermal sphingolipid could be useful for designing effective strategies to improve barrier dysfunctions.