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Short chain fatty acids (SCFAs) are primarily produced in the caecum and proximal colon via the bacterial fermentation of undigested carbohydrates that have avoided digestion in the small intestine. Increasing evidence supports the critical role that SCFAs play in health and homeostasis. Microbial SCFAs, namely butyric acid, serve as a principal energy source for colonocytes, and their production is essential for gut integrity. A direct link between SCFAs and some human pathological conditions, such as inflammatory bowel disease, irritable bowel syndrome, diarrhea, and cancer, has been proposed. The direct measurement of SCFAs in feces provides a non-invasive approach to demonstrating connections between SCFAs, microbiota, and metabolic diseases to estimate their potential applicability as meaningful biomarkers of intestinal health. This study aimed to adapt a robust analytical method (liquid–liquid extraction, followed by isobutyl chloroformate derivatization and GC–MS analysis), with comparable performances to methods from the literature, and to use this tool to tackle the question of pre-analytical conditions, namely stool processing. We focused on the methodology of managing stool samples before the analysis (fresh stool or dilution in either ethanol/methanol, lyophilized stool, or RNAlater®), as this is a significant issue to consider for standardizing results between clinical laboratories. The objective was to standardize methods for future applications as diagnostic tools. In this paper, we propose a validated GC–MS method for SCFA quantification in stool samples, including pre- and post-analytical comparison studies that could be easily used for clinical laboratory purposes. Our results show that using lyophilization as a stool-processing method would be the best method to achieve this goal. [ABSTRACT FROM AUTHOR]

Introduction: Haemoglobin A1c (HbA1c) is a key analyte for the monitoring of glycemic balance in diabetic patients and is used for diabetes diagnosis in many countries. The potential interference of carbamylated haemoglobin (cHb) and labile glycated haemoglobin (LA1c) on HbA1c assays must remain a matter of vigilance. Such a situation has occurred in our laboratory with a kit replacement on the Bio-Rad Variant? II testing system, a cation-exchange high performance liquid chromatography (HPLC) system. With this method, LA1c and cHb coeluted in a same peak which may have different consequences on HbA1c values. Materials and methods: The influence of increasing LA1c and cHb values on HbA1c results was studied with in vitro glycation and carbamylation of samples. Samples from patients with high and normal blood urea concentrations were assayed by HPLC and immunological assay. Results: We observed that the degree of interference greatly varied depending on the nature of the interfering Hb fractions found under the socalled "LA1c peak". Thus, we have decided to apply a decision tree using "LA1c" thresholds depending on: (i) the retention time, (ii) the shape of the peak, (iii) other analytes, like urea. If the peak recognized as "LA1c" is mainly formed by LA1c, we consider that there is no interference until 4%. If the peak is mainly formed by cHb, we consider an interference threshold equal to 2%. Conclusions: This situation reminds that cHb and LA1c remain critical issues in chromatography-based HbA1c assays and that adapted criteria must be set up for result interpretation. [ABSTRACT FROM AUTHOR]

Introduction: Haemoglobin A1c (HbA1c) is considered to be the gold standard for the follow-up of glycaemic control in patients with diabetes mellitus and is also a diagnostic tool. Accordingly, reliable and efficient methods must be used for its quantification. Roche Diagnostics have recently adapted the Tina-quant® HbA1c Third Generation immunoassay on a fully dedicated analyser, the Cobas c513, which allows a high throughput of up to 400 samples per hour. The present article deals with the evaluation of the analytical performances of this system which has been recently introduced to the market. Materials and methods: Precision, comparison with two ion-exchange high-performance liquid chromatography (HPLC) methods (Variant II and D-100 systems, BioRad Laboratories) using Passing Bablok and Bland-Altman analyses, accuracy and interference of the most frequent haemoglobin (Hb) variants on HbA1c measurement were evaluated. Results: Precision was high, with coefficients of variation lower than 1.1% (HbA1c values expressed in National Glycohemoglobin Standardization Program units, 1.7% for values expressed in International Federation of Clinical Chemistry and Laboratory Medicine [IFCC] units). The comparison study showed similar results with the two HPLC systems. The analysis of samples with IFCC-assigned values showed high methodological accuracy. Finally, no interference of bilirubin, triglycerides and common Hb variants (Hb AC, AD, AE, AS) was observed. Conclusions: This evaluation showed that the analytical performance of the Cobas c513 analyser for HbA1c assay makes it suitable for a routine use in clinical chemistry laboratories. [ABSTRACT FROM AUTHOR]

The current pandemic of coronavirus disease (COVID) 2019 constitutes a global public health issue. Regarding the emerging importance of the gut-lung axis in viral respiratory infections, analysis of the gut microbiota's composition and functional activity during a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection might be instrumental in understanding and controling COVID 19. We used a nonhuman primate model (the macaque), that recapitulates mild COVID-19 symptoms, to analyze the effects of a SARS-CoV-2 infection on dynamic changes of the gut microbiota. 16S rRNA gene profiling and analysis of β diversity indicated significant changes in the composition of the gut microbiota with a peak at 10-13 days post-infection (dpi). Analysis of bacterial abundance correlation networks confirmed disruption of the bacterial community at 10-13 dpi. Some alterations in microbiota persisted after the resolution of the infection until day 26. Some changes in the relative bacterial taxon abundance associated with infectious parameters. Interestingly, the relative abundance of Acinetobacter (Proteobacteria) and some genera of the Ruminococcaceae family (Firmicutes) was positively correlated with the presence of SARS-CoV-2 in the upper respiratory tract. Targeted quantitative metabolomics indicated a drop in short-chain fatty acids (SCFAs) and changes in several bile acids and tryptophan metabolites in infected animals. The relative abundance of several taxa known to be SCFA producers (mostly from the Ruminococcaceae family) was negatively correlated with systemic inflammatory markers while the opposite correlation was seen with several members of the genus Streptococcus . Collectively, SARS-CoV-2 infection in a nonhuman primate is associated with changes in the gut microbiota's composition and functional activity.

Carbamylation, which corresponds to the binding of isocyanic acid to the amino groups of proteins, is a nonenzymatic post-translational modification responsible for alterations of protein structural and functional properties. Tissue accumulation of carbamylation-derived products and their role in pathological processes such as atherosclerosis or chronic renal failure have been previously documented. However, few studies have focused on the carbamylation of intracellular proteins and their subsequent role in cellular aging. This study aimed to determine the extent of intracellular protein carbamylation, its impact on cell functions and the ability of cells to degrade these modified proteins. Fibroblasts were incubated with cyanate or urea and the carbamylation level was evaluated by immunostaining and homocitrulline quantification. The results showed that carbamylated proteins accumulated intracellularly and that all proteins were susceptible. The presence of intracellular carbamylated proteins did not modify cell proliferation or type I collagen synthesis nor did it induce cell senescence, but it significantly decreased cell motility. Fibroblasts were able to degrade carbamylated proteins through the ubiquitin-proteasome system. In conclusion, intracellular proteins are susceptible to carbamylation but their accumulation does not seem to deeply affect cell function, owing largely to their elimination by the ubiquitin-proteasome system.

Protein molecular aging corresponds to all modifications affecting proteins during their biological life, which lead to the alteration of their structural and functional properties. This phenomenon participates in cell and tissue aging and is therefore involved in the aging of human organism. It is also amplified in various chronic diseases such as diabetes mellitus or chronic kidney disease, where it participates in the development of long-term complications. This review aims at describing the main reactions responsible for molecular aging, their impact on protein properties and the parameters which could influence this phenomenon. A general scheme explaining its role in physiopathology is also proposed., (© 2017 médecine/sciences – Inserm.)