Evaluation and comparison of short chain fatty acids composition in gut diseases

BACKGROUND An altered (dysbiosis) and unhealthy status of the gut microbiota is usually responsible for a reduction of short chain fatty acids (SCFAs) concentration. SCFAs obtained from the carbohydrate fermentation processes are crucial in maintaining gut homeostasis and their determination in stool samples could provide a faster, reliable and cheaper method to highlight the presence of an intestinal dysbiosis and a biomarker for various gut diseases. We hypothesize that different intestinal diseases, such as celiac disease (CD), adenomatous polyposis (AP) and colorectal cancer (CRC) could display a particular fecal SCFAs’ signature. AIM To compare the fecal SCFAs’ profiles of CD, AP, CRC patients and healthy controls, using the same analytical method. METHODS In this cross-sectional study, we defined and compared the SCFAs’ concentration in fecal samples of 9 AP, 16 CD, 19 CRC patients and 16 healthy controls (HC). The SCFAs’ analysis were performed using a gas-chromatography coupled with mass spectrometry method. Data analysis was carried out using Wilcoxon ranksum test to assess pairwise differences of SCFAs’ profiles, partial least squaresdiscriminate analysis (PLS-DA) to determine the status membership based on distinct SCFAs’ profiles, and Dirichlet regression to determine factors influencing concentration levels of SCFAs. RESULTS We have not observed any difference in the SCFAs’ amount and composition between CD and healthy control. On the contrary, the total amount of SCFAs was significantly lower in CRC patients compared to HC (P = 0.044) and CD (P = 0.005). Moreover, the SCFAs’ percentage composition was different in CRC and AP compared to HC. In detail, HC displayed higher percentage of acetic acid (P value = 1.3 × 10-6) and a lower amount of butyric (P value = 0.02192), isobutyric (P value = 7.4 × 10-5), isovaleric (P value = 0.00012) and valeric (P value = 0.00014) acids compared to CRC patients. AP showed a lower abundance of acetic acid (P value = 0.00062) and higher percentages of propionic (P value = 0.00433) and isovaleric (P value = 0.00433) acids compared to HC. Moreover, AP showed higher levels of propionic acid (P value = 0.03251) and a lower level of isobutyric acid (P value = 0.00427) in comparison to CRC. The PLS-DA model demonstrated a significant separation of CRC and AP groups from HC, although some degree of overlap was observed between CRC and AP. CONCLUSION Analysis of fecal SCFAs shows the potential to provide a non-invasive means of diagnosis to detect patients with CRC and AP, while CD patients cannot be discriminated from healthy subjects.

Effects of viremia and CD4 recovery on gut“microbiome-immunity”axis in treatment-na?ve HIV-1-infected patients undergoing antiretroviral therapy

BACKGROUND Human immunodeficiency virus type 1(HIV-1)infection is characterized by persistent systemic inflammation and immune activation,even in patients receiving effective antiretroviral therapy(ART).Converging data from many cross-sectional studies suggest that gut microbiota(GM)changes can occur throughout including human immunodeficiency virus(HIV)infection,treated by ART;however,the results are contrasting.For the first time,we compared the fecal microbial composition,serum and fecal microbial metabolites,and serum cytokine profile of treatment-na?ve patients before starting ART and after reaching virological suppression,after 24 wk of ART therapy.In addition,we compared the microbiota composition,microbial metabolites,and cytokine profile of patients with CD4/CD8 ratio<1(immunological non-responders[INRs])and CD4/CD8>1(immunological responders[IRs]),after 24 wk of ART therapy.AIM To compare for the first time the fecal microbial composition,serum and fecal microbial metabolites,and serum cytokine profile of treatment-na?ve patients before starting ART and after reaching virological suppression(HIV RNA<50 copies/m L)after 24 wk of ART.METHODS We enrolled 12 treatment-na?ve HIV-infected patients receiving ART(mainly based on integrase inhibitors).Fecal microbiota composition was assessed through next generation sequencing.In addition,a comprehensive analysis of a blood broad-spectrum cytokine panel was performed through a multiplex approach.At the same time,serum free fatty acid(FFA)and fecal short chain fatty acid levels were obtained through gas chromatography-mass spectrometry.RESULTS We first compared microbiota signatures,FFA levels,and cytokine profile before starting ART and after reaching virological suppression.Modest alterations were observed in microbiota composition,in particular in the viral suppression condition,we detected an increase of Ruminococcus and Succinivibrio and a decrease of Intestinibacter.Moreover,in the same condition,we also observed augmented levels of serum propionic and butyric acids.Contemporarily,a reduction of serum IP-10 and an increase of IL-8 levels were detected in the viral suppression condition.In addition,the same components were compared between IRs and INRs.Concerning the microflora population,we detected a reduction of Faecalibacterium and an increase of Alistipes in INRs.Simultaneously,fecal isobutyric,isovaleric,and 2-methylbutyric acids were also increased in INRs.CONCLUSION Our results provided an additional perspective about the impact of HIV infection,ART,and immune recovery on the"microbiome-immunity axis"at the metabolism level.These factors can act as indicators of the active processes occurring in the gastrointestinal tract.Individuals with HIV-1 infection,before ART and after reaching virological suppression with 24 wk of ART,displayed a microbiota with unchanged overall bacterial diversity;moreover,their systemic inflammatory status seems not to be completely restored.In addition,we confirmed the role of the GM metabolites in immune reconstitution.