Prevalence of a large panel of systemic autoantibodies in the Bavarian adult population.

Objective: Autoimmune diseases commonly feature the presence of specific humoral autoantibodies. However, the prevalence of a large panel of systemic autoantibodies has never been assessed in the general population. We, therefore, described the prevalence of about 50 humoral systemic autoantibodies in a sample of the general Bavarian adult population. Methods: Non-fasting venous serum samples from 331 participants were analyzed for 7 autoantibody screening tests (nuclear, cytoplasmic, and mitotic ANA, ANCA, cANCA and pANCA, anti-ENA autoantibodies) and 44 different monospecific humoral non-organ specific/systemic autoantibodies using indirect immunofluorescence tests, ELISAs, and line blots. In order to assess associations between sex, age, BMI, education level, smoking status and the presence of systemic autoantibodies, logistic regression analyses were conducted. Results: At least one screening test was positive in 29.9% of the participants, and 42.3% of the participants were seropositive for at least one monospecific autoantibody. The most frequently found monospecific autoantibodies were rheumatoid factor (35.6%), ß2-glycoprotein 1 IgM (4.8%), and cardiolipin IgG (1.8%). Only few associations between sex, age, BMI, education, smoking status and autoantibody frequencies were observed. Conclusion: Systemic autoantibodies are common in the general Bavarian population, and largely independent of sex, age, BMI, education, or smoking status. The study results may give orientation to clinicians about the occurrence of autoantibodies in the population, not (yet) associated with clinical symptoms.

Transport Versus Hydrolysis: Reassessing Intestinal Assimilation of Di- and Tripeptides by LC-MS/MS Analysis.

SCOPE: The role of PEPT1 in the uptake of intact peptides as compared to hydrolysis prior to uptake of their constituents is unknown. Here, dipeptides, tripeptides, and amino acids are quantified to study the fate of selected peptides in different intestinal models. METHODS AND RESULTS: An LC-MS/MS-based method is applied for the simultaneous assessment of rates of hydrolysis and transport of a peptide panel in Caco-2 transwell cell culture, in vitro and in vivo in mice expressing or lacking PEPT1, and in hydrolysis studies in vitro using human intestinal samples. It is shown that susceptibility to hydrolysis of peptides at the brush border membrane or within epithelial cells is practically identical in all tested models and strictly structure-dependent. Peptides with high luminal disappearance show substantial hydrolysis and low basolateral appearance, while peptides with low disappearance show strong PEPT1 dependency and high basolateral appearance in intact form in Caco-2 transwell culture. CONCLUSION: Hydrolysis and transport of intact peptides are highly variable and structure-dependent. For peptides possessing less polar N-terminal residues, hydrolysis usually dominates over transport via PEPT1. For other peptides with high intrinsic hydrolysis resistance, including anserine, carnosine, ɣ-glutamyl-dipeptides, and aminocephalosporins, PEPT1 is the main determinant for appearance in peripheral blood.

Appearance of Di- and Tripeptides in Human Plasma after a Protein Meal Does Not Correlate with PEPT1 Substrate Selectivity.

SCOPE: Peptide transporter 1 (PEPT1) function is well understood, yet little is known about its contribution toward the absorption of dietary amino acids in the form of di- and tripeptides. In the present human study, changes in plasma concentrations of a representative oligopeptide panel are investigated after meat intake. METHODS AND RESULTS: Based on a method for quantitative analysis of a panel of selected di- and tripeptides in biological samples, the kinetics of plasma changes of peptides derived from a widely accessible dietary protein source are described. The findings demonstrate postprandial changes of a whole spectrum of dipeptides of different size, charge, and polarity in peripheral blood in a dose-dependent manner after consumption of chicken breast in healthy human volunteers. Although the substrate specificity of PEPT1 is well known, the spectrum of peptides appearing in blood cannot be matched to the affinity to PEPT1. Stability against hydrolysis by exo- and endopeptidases appears to be another factor influencing their presence in blood. In addition, the study shows that dipeptides, including gamma-glutamyl-peptides, as well as tripeptides are common components present in human plasma. CONCLUSION: Besides amino acids, human peripheral blood contains numerous di- and tripeptides. The dietary source determines their abundance and composition.

Proton Coupled Oligopeptide Transporter 1 (PepT1) Function, Regulation, and Influence on the Intestinal Homeostasis.

As the organ with one of the largest surface areas facing the environment and responsible for nutrient uptake, the small intestine expresses numerous transport proteins in its brush-border membrane for efficient absorption and supply of dietary macro- and micronutrients. The understanding of regulation and functional interplay of these nutrient transporters is of emerging interest in nutrition and medical physiology research in respect to development of diabetes, obesity, and inflammatory bowel disease worldwide. The peptide transporter 1 (PepT1, SLC15A1) is abundantly expressed particularly in the intestinal tract and provides highly effective transport of amino acids in the form of di- and tripeptides and features a substantial acceptance for structurally related compounds and drugs. These characteristics bring PepT1 into focus for nutritional and medical/pharmaceutical approaches, as it is the essential hub responsible for oral bioavailability of dietary protein/peptide supplements and peptide-like drugs in eukaryotic organisms. Detailed analysis of molecular processes regulating PepT1 expression and function achieved in the last two decades has helped to define and use adjusting tools and to better integrate the transporter's role in cell and organ physiology. In this article, we provide an overview of the current knowledge on PepT1 function in health and disease, and on regulatory factors modulating its gene and protein expression as well as transport activity. © 2018 American Physiological Society. Compr Physiol 8:843-869, 2018.

Gut barrier impairment by high-fat diet in mice depends on housing conditions.

SCOPE: Diet-induced obesity (DIO) is proposed to cause impairments in intestinal barrier integrity, but contradictory results have been published and it appears that the outcomes depend on other environmental factors. We therefore assessed whether the hygienic status of animal facilities alters the gut barrier in DIO mice. METHODS AND RESULTS: Male C57BL/6N mice were housed in a conventional (CV) or a specific pathogen-free (SPF) animal facility and were fed identical diets represented by a high-fat (60kJ% fat) or control diet (11kJ% fat) for 12 wks. Intestinal barrier function in small and large intestine was evaluated in Ussing chambers by electrical resistance and permeability measurements. Jejunal (p < 0.01) and proximal colonic (p < 0.05) barrier function was altered in CV DIO mice, but not in SPF DIO mice. Moreover, only CV DIO mice were characterized by metabolic endotoxemia and low-grade inflammation. High-throughput 16S rRNA gene sequencing revealed significant differences in fecal bacterial diversity and composition between the two animal facilities, but only in mice fed the HFD. Moreover, cecal DCA concentrations correlated positively with two yet uncultivated Clostridiales species. CONCLUSIONS: We demonstrated that housing conditions and associated changes in gut bacterial colonization are pivotal for maintenance of gut barrier integrity in DIO mice.