Mark Philo

Relatedness of medically important strains of Saccharomyces cerevisiae as revealed by phylogenetics and metabolomics

Ten medically important Saccharomyces strains, comprising six clinical isolates of Saccharomyces cerevisiae and four probiotic strains of Saccharomyces boulardii, were characterized at the genetic and metabolic level and compared with non‐medical, commercial yeast strains used in baking and wine‐making. Strains were compared by genetic fingerprinting using amplified fragment length polymorphism (AFLP) analysis, by ribosomal DNA ITS1 sequencing and by metabolic footprinting using both direct injection mass spectrometry (DIMS) and gas chromatography–time of flight–mass spectrometry (GC–ToF–MS). Overall, the clinical isolates fell into different groupings when compared with the non‐medical strains, with good but not perfect correlation amongst strains at both the genetic and metabolic levels. Probiotic strains of S. boulardii that are used therapeutically to treat human gastro‐intestinal tract disorders showed tight clustering both genetically and metabolically. Metabolomics was found to be of value both as a taxonomic tool and as a means to investigate anomalous links between genotype and phenotype. Key discriminatory metabolites were identified when comparing the three main groups of clinical, probiotic and non‐medical strains and included molecules such as trehalose, myo‐inositol, lactic acid, fumaric acid and glycerol 3‐phosphate. This study confirmed the link between a subset of clinical isolates and baking or probiotic strains but also highlighted that in general the clinical strains were more diverse at both the genomic and metabolic levels. Copyright

Folic acid handling by the human gut: implications for food fortification and supplementation

Background: Current thinking, which is based mainly on rodent studies, is that physiologic doses of folic acid (pterylmonoglutamic acid), such as dietary vitamin folates, are biotransformed in the intestinal mucosa and transferred to the portal vein as the natural circulating plasma folate, 5-methyltetrahydrofolic acid (5-MTHF) before entering the liver and the wider systemic blood supply. Objective: We tested the assumption that, in humans, folic acid is biotransformed (reduced and methylated) to 5-MTHF in the intestinal mucosa. Design: We conducted a crossover study in which we sampled portal and peripheral veins for labeled folate concentrations after oral ingestion with physiologic doses of stable-isotope–labeled folic acid or the reduced folate 5-formyltetrahydrofolic acid (5-FormylTHF) in 6 subjects with a transjugular intrahepatic porto systemic shunt (TIPSS) in situ. The TIPSS allowed blood samples to be taken from the portal vein. Results: Fifteen minutes after a dose of folic acid, 80 ± 12% of labeled folate in the hepatic portal vein was unmodified folic acid. In contrast, after a dose of labeled 5-FormylTHF, only 4 ± 18% of labeled folate in the portal vein was unmodified 5-FormylTHF, and the rest had been converted to 5-MTHF after 15 min (postdose). Conclusions: The human gut appears to have a very efficient capacity to convert reduced dietary folates to 5-MTHF but limited ability to reduce folic acid. Therefore, large amounts of unmodified folic acid in the portal vein are probably attributable to an extremely limited mucosal cell dihydrofolate reductase (DHFR) capacity that is necessary to produce tetrahydrofolic acid before sequential methylation to 5-MTHF. This process would suggest that humans are reliant on the liver for folic acid reduction even though it has a low and highly variable DHFR activity. Therefore, chronic liver exposure to folic acid in humans may induce saturation, which would possibly explain reports of systemic circulation of unmetabolized folic acid. This trial was registered at clinicaltrials.gov as NCT02135393.

Meat Authentication via Multiple Reaction Monitoring Mass Spectrometry of Myoglobin Peptides

A rapid multiple reaction monitoring (MRM) mass spectrometric method for the detection and relative quantitation of the adulteration of meat with that of an undeclared species is presented. Our approach uses corresponding proteins from the different species under investigation and corresponding peptides from those proteins, or CPCP. Selected peptide markers can be used for species detection. The use of ratios of MRM transition peak areas for corresponding peptides is proposed for relative quantitation. The approach is introduced by use of myoglobin from four meats: beef, pork, horse and lamb. Focusing in the present work on species identification, by use of predictive tools, we determine peptide markers that allow the identification of all four meats and detection of one meat added to another at levels of 1% (w/w). Candidate corresponding peptide pairs to be used for the relative quantification of one meat added to another have been observed. Preliminary quantitation data presented here are encouraging.

Rapid fingerprinting of milk thermal processing history by intact protein mass spectrometry with nondenaturing chromatography.

Thermal processing of foods results in proteins undergoing conformational changes, aggregation, and chemical modification notably with sugars via the Maillard reaction. This can impact their functional, nutritional, and allergenic properties. Native size-exclusion chromatography with online electrospray mass spectrometry (SEC-ESI-MS) was used to characterize processing-induced changes in milk proteins in a range of milk products. Milk products could be readily grouped into either pasteurized liquid milks, heavily processed milks, or milk powders by SEC behavior, particularly by aggregation of whey proteins by thermal processing. Maillard modification of all major milk proteins by lactose was observed by MS and was primarily present in milk powders. The method developed is a rapid tool for fingerprinting the processing history of milk and has potential as a quality control method for food ingredient manufacture. The method described here can profile milk protein oligomeric state, aggregation, and Maillard modification in a single shot, rapid analysis.

An approach to the phytochemical profiling of rocket [Eruca sativa (Mill.) Thell].

BACKGROUND Eruca sativa (rocket) contains a wide range of compounds with nutraceutical and organoleptical properties. This research aimed to characterise the nutraceutical interest of four rocket accessions by analysis of glucosinolates, isothiocyanates, phenolics, carotenoids and carbohydrates. Different methods based on chromatographic separation with ultraviolet absorbance or mass spectrometry detection were used. RESULTS The total content of glucosinolates ranged from 14.02 to 28.24 µmol g(-1) of dry weight. Glucoraphanin represented up to 52% of the total glucosinolates in leaves of one accession. Accessions showed differences in the hydrolysis of glucoraphanin to the isothiocyanate sulforaphane. No correlation between these compounds was observed, which insisted differences in the myrosinase activity within accessions. Rocket leaves had variable phenolic profiles represented by quercetin-3-glucoside, rutin, myricetin, quercetin and ferulic and p-coumaric acids. A high variability was observed for the total carotenoids ranged from 16.2 to 275 µg g(-1) with lutein as the main carotenoid. Glucose was the predominant sugar, representing >70% of the total soluble carbohydrates. CONCLUSIONS Some accessions could be candidates for future breeding programmes because of their pattern of beneficial compounds for human health. However, further research is essential to evaluate the biological activity of these accessions before designing functional food.

Does epicatechin contribute to the acute vascular function effects of dark chocolate? A randomized, crossover study.

SCOPE Cocoa, rich in flavan-3-ols, improves vascular function, but the contribution of specific flavan-3-ols is unknown. We compared the effects of pure epicatechin, a major cocoa flavan-3-ol, and chocolate. METHODS AND RESULTS In a randomized crossover study, twenty healthy men (40-80 years) were supplemented with: (1) 70g dark chocolate (150 mg epicatechin) with placebo capsules; (2) pure epicatechin capsules (2 × 50 mg epicatechin) with 75g white chocolate; and (3) placebo capsules with 75 g white chocolate (0 mg epicatechin). Vascular function (flow-mediated dilation (FMD) and augmentation index (AIx)) were measured before and 2 hours after interventions. Epicatechin metabolites time-profiles were measured in blood to calculate the bioavailability. Pure epicatechin did not significantly improve FMD (+0.75%; p = 0.10) or AIx (-2.2%; p = 0.23) compared to placebo. Dark chocolate significantly improved FMD (+0.96%; p = 0.04) and AIx (-4.6%; p = 0.02). Differences in improvements in FMD (+ 0.21%; p = 0.65) or Aix (-2.4%; p = 0.20) between pure epicatechin and dark chocolate were not significant. The bioavailability of epicatechin did not differ between pure epicatechin and dark chocolate (p = 0.14). CONCLUSIONS Despite differences in epicatechin dose, improvements in vascular function after pure epicatechin and chocolate were similar and the bioavailability did not differ, suggesting a role for epicatechin.

Acute Consumption of Flavan-3-ol-Enriched Dark Chocolate Affects Human Endogenous Metabolism

Flavan-3-ols and methylxanthines have potential beneficial effects on human health including reducing cardiovascular risk. We performed a randomized controlled crossover intervention trial to assess the acute effects of consumption of flavan-3-ol-enriched dark chocolate, compared with standard dark chocolate and white chocolate, on the human metabolome. We assessed the metabolome in urine and blood plasma samples collected before and at 2 and 6 h after consumption of chocolates in 42 healthy volunteers using a nontargeted metabolomics approach. Plasma samples were assessed and showed differentiation between time points with no further separation among the three chocolate treatments. Multivariate statistics applied to urine samples could readily separate the postprandial time points and distinguish between the treatments. Most of the markers responsible for the multivariate discrimination between the chocolates were of dietary origin. Interestingly, small but significant level changes were also observed for a subset of endogenous metabolites. 1H NMR revealed that flavan-3-ol-enriched dark chocolate and standard dark chocolate reduced urinary levels of creatinine, lactate, some amino acids, and related degradation products and increased the levels of pyruvate and 4-hydroxyphenylacetate, a phenolic compound of bacterial origin. This study demonstrates that an acute chocolate intervention can significantly affect human metabolism.

16-O-methylcafestol is present in ground roast Arabica coffees: Implications for authenticity testing

Highlights • Lipophilic extracts of ground roast Arabica coffees were authenticated by benchtop NMR.• Small amounts of esterified 16-O-methylcafestol were found in Arabica coffees.• The compound identity was confirmed by NMR and MS experiments.• 16-OMC remains a useful marker for non-Arabicas as these contain much higher amounts.• 6 out of 60 retail Arabicas contained significant amounts of non-Arabica species.

Comparative bio-accessibility, bioavailability and bioequivalence of quercetin, apigenin, glucoraphanin and carotenoids from freeze-dried vegetables incorporated into a baked snack versus minimally processed vegetables: Evidence from in vitro models and a human bioavailability study

Graphical abstract

Fine-tuning of SIRT1 expression is essential to protect the liver from cholestatic liver disease

Cholestasis comprises aetiologically heterogeneous conditions characterized by accumulation of bile acids in the liver that actively contribute to liver damage. Sirtuin 1 (SIRT1) regulates liver regeneration and bile acid metabolism by modulating farnesoid X receptor (FXR); we here investigate its role in cholestatic liver disease. We determined SIRT1 expression in livers from patients with cholestatic disease, in two experimental models of cholestasis, as well as in human and murine liver cells in response to bile acid loading. SIRT1‐overexpressing (SIRToe) and hepatocyte‐specific SIRT1‐KO (knockout) mice (SIRThep–/–) were subjected to bile duct ligation (BDL) and were fed with a 0.1% DDC (3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine) diet to determine the biological relevance of SIRT1 during cholestasis. The effect of NorUDCA (24‐norursodeoxycholic acid) was tested in BDL/SIRToe mice. We found that SIRT1 was highly expressed in livers from cholestatic patients, mice after BDL, and Mdr2 knockout mice (Mdr2–/–) animals. The detrimental effects of SIRT1 during cholestasis were validated in vivo and in vitro. SIRToe mice showed exacerbated parenchymal injury whereas SIRThep–/– mice evidenced a moderate improvement after BDL and 0.1% DDC feeding. Likewise, hepatocytes isolated from SIRToe mice showed increased apoptosis in response to bile acids, whereas a significant reduction was observed in SIRThep–/– hepatocytes. Importantly, the decrease, but not complete inhibition, of SIRT1 exerted by norUDCA treatment correlated with pronounced improvement in liver parenchyma in BDL/SIRToe mice. Interestingly, both SIRT1 overexpression and hepatocyte‐specific SIRT1 depletion correlated with inhibition of FXR, whereas modulation of SIRT1 by NorUDCA associated with restored FXR signaling. Conclusion: SIRT1 expression is increased during human and murine cholestasis. Fine‐tuning expression of SIRT1 is essential to protect the liver from cholestatic liver damage.