BackgroundThe presence of perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHS), and perfluorooctanoate (PFOA) has been reported in humans and wildlife. Pharmacokinetic differences have been observed in laboratory animals.ObjectiveThe purpose of this observational study was to estimate the elimination half-life of PFOS, PFHS, and PFOA from human serum.MethodsTwenty-six (24 male, 2 female) retired fluorochemical production workers, with no additional occupational exposure, had periodic blood samples collected over 5 years, with serum stored in plastic vials at −80°C. At the end of the study, we used HPLC-mass spectrometry to analyze the samples, with quantification based on the ion ratios for PFOS and PFHS and the internal standard 18O2-PFOS. For PFOA, quantitation was based on the internal standard 13C2-PFOA.ResultsThe arithmetic mean initial serum concentrations were as follows: PFOS, 799 ng/mL (range, 145–3,490); PFHS, 290 ng/mL (range, 16–1,295); and PFOA, 691 ng/mL (range, 72–5,100). For each of the 26 subjects, the elimination appeared linear on a semi-log plot of concentration versus time; therefore, we used a first-order model for estimation. The arithmetic and geometric mean half-lives of serum elimination, respectively, were 5.4 years [95% confidence interval (CI), 3.9–6.9] and 4.8 years (95% CI, 4.0–5.8) for PFOS; 8.5 years (95% CI, 6.4–10.6) and 7.3 years (95% CI, 5.8–9.2) for PFHS; and 3.8 years (95% CI, 3.1–4.4) and 3.5 years (95% CI, 3.0–4.1) for PFOA.ConclusionsBased on these data, humans appear to have a long half-life of serum elimination of PFOS, PFHS, and PFOA. Differences in species-specific pharmacokinetics may be due, in part, to a saturable renal resorption process.

Human milk contains large amounts of complex oligosaccharides that putatively modulate the intestinal microbiota of breast-fed infants by acting as decoy binding sites for pathogens and as prebiotics for enrichment of beneficial bacteria. Several bifidobacterial species have been shown to grow well on human milk oligosaccharides. However, little data exists on other bacterial species. In this work we examined 16 bacterial strains belonging to 10 different genera for growth on human milk oligosaccharides. For this propose, we used a chemically-defined medium, ZMB1, which allows vigorous growth of a number gut–related microorganisms in a fashion similar to complex media. Interestingly, Bifidobacterium longum subsp. infantis, Bacteroides fragilis and Bacteroides vulgatus strains were able to metabolize milk oligosaccharides with high efficiency, while Enterococcus, Streptococcus, Veillonella, Eubacterium, Clostridium, and Escherichia coli strains grew less well or not at all. Mass spectrometry-based glycoprofiling of the oligosaccharide consumption behavior revealed a specific preference for fucosylated oligosaccharides by Bifidobacterium longum subsp. infantis and Bacteroides vulgatus. This work expands the current knowledge of human milk oligosaccharides consumption by gut microbes, revealing bacteroides as avid consumer of this substrate. These results provide insight on how human milk oligosaccharides shape the infant intestinal microbiota.

Summary of Recent Advances-Glycosylation is one of the most common post-translational modifications (PTMs) of proteins. At least 50% of human proteins are glycosylated with some estimates being as high as 70%. Glycoprotein analysis requires determining both the sites of glycosylation as well as the glycan structures associated with each site. Recent advances have led to the development of new analytical methods that employ mass spectrometry extensively making it possible to obtain the glycosylation site and the site microheterogeneity. These tools will be important for the eventual development of glycoproteomics.

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Human milk lactoferrin (hmLF) is the most abundant glycoprotein present in human milk and displays a broad range of protective functions in the gut of newborn infants. hmLF is N-glycosylated, but little is known about the lactation stage-related development of the glycosylation phenotype. hmLF glycosylation from milk samples from five donors during the first 10 weeks of lactation was assessed and observed to be more diverse than previously reported. During this period dynamic changes in glycosylation were observed corresponding to a decrease in glycosylation in the second week followed by an increase in total glycosylation as well as higher order fucosylation thereafter. Gene expression analysis was performed in milk somatic cells from a sixth subject. It was found that fucosyltransferase expression increased during entire period, whereas expression of genes for the oligosaccharyl transferase complex decreased in the second week. The effect of hmLF glycosylation was examined for the protein's ability to affect bacterial binding to epithelial cells. hmLF significantly inhibited pathogen adhesion and purified hmLF glycans significantly reduced

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While milk proteins have been studied for decades, strikingly little effort has been applied to determining how the post-translational modifications (PTMs) of these proteins may change during the course of lactation. PTMs, particularly glycosylation, can greatly influence protein structure, function, and stability and can particularly influence the gut where their degradation products are potentially bioactive. In this work, previously undiscovered temporal variations in both expression and glycosylation of the glycoproteome of human milk are observed. Lactoferrin, one of the most abundant glycoproteins in human milk, is shown to be dynamically glycosylated during the first ten days of lactation. Variations in expression or glycosylation levels are also demonstrated for several other abundant whey proteins, including tenascin, bile salt-stimulated lipase, xanthine dehydrogenase, and mannose receptor.

Glycosylation is a topic of intense current interest in the development of biopharmaceuticals because it is related to drug safety and efficacy. This work describes results of an interlaboratory study on the glycosylation of the Primary Sample (PS) of NISTmAb, a monoclonal antibody reference material. Seventy-six laboratories from industry, university, research, government, and hospital sectors in Europe, North America, Asia, and Australia submitted a total of 103 reports on glycan distributions. The principal objective of this study was to report and compare results for the full range of analytical methods presently used in the glycosylation analysis of mAbs. Therefore, participation was unrestricted, with laboratories choosing their own measurement techniques. Protein glycosylation was determined in various ways, including at the level of intact mAb, protein fragments, glycopeptides, or released glycans, using a wide variety of methods for derivatization, separation, identification, and quantification. Consequently, the diversity of results was enormous, with the number of glycan compositions identified by each laboratory ranging from 4 to 48. In total, one hundred sixteen glycan compositions were reported, of which 57 compositions could be assigned consensus abundance values. These consensus medians provide community-derived values for NISTmAb PS. Agreement with the consensus medians did not depend on the specific method or laboratory type. The study provides a view of the current state-of-the-art for biologic glycosylation measurement and suggests a clear need for harmonization of glycosylation analysis methods.