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In vitro–in vivo Validation of Stimulatory Effect of Oat Ingredients on Lactobacilli

Can in vitro models be successfully utilized to ensure validity of a prebiotic Human Clinical Trial?

Findings of a recent study conducted by researchers of APC Microbiome Ireland showed significant benefit of utilizing a scientifically validated in vitro gut model (M-SHIME) prior to a human clinical trial. The in vitro analysis conducted by Duysburgh et al. (2020), reported a significant increase of Bifidobacterium and Lactobacillus levels in response to prebiotic oat treatment, confirming the validity of a human clinical trial. This resulted in a partnership with Atlantia Clinical Trials to further test the validity of prebiotics to stimulate Lactobacillaceae and Bifidobacteriaceae/ increasing propionate and butyrate production.

The involvement of prebiotic activity in oat products is not a new field in microbiome research, Connolly et al. (2016) conducted a particularly relevant human study which found that consumption of whole grain oat granola, and oat derived fractions (particularly B-glucan) is associated with a significant reduction in blood TC (total cholesterol) and LDL-C (low-density lipoprotein cholesterol) in hypercholesterolemic populations.

However, the focus of this study was healthy individuals with mild hypercholesterolemia. The benefit of performing in vitro prior to clinical trials include the ability to investigate the interactions between the gut microbiota and dietary fibers in a strictly controlled environment, removing environmental/external parameters.

Further expanding on the technology utilized in the in vitro analysis, a validated gut model M-SHIME ®, which is a complete model of the gastrointestinal tract consisting of five reactors which allow for stimulation of each section of the tract (stomach, small intestine, and the three regions of the large intestine). As mentioned, this allows for fully stable analysis of microbial activity, prior to treatment.

Although there are previous studies relating to the role of potential prebiotics in stimulating Lactobacillaceae and Bifidobacteriaceae/ increasing propionate and butyrate production, there continues to be an insufficient number of studies in humans to validate in vitro observations. This deficiency becomes even more apparent when one focuses on specific sub-categories of prebiotics, such as beta-glucan containing products explained, Dr. Paul Cotter of APC Microbiome Ireland, and lead author in the study, in an interview with Atlantia Clinical Trials.

The in vitro analysis revealed altered microbial metabolic activity in response to oat treatment, particularly in detection of short chain fatty acids (acetate, propionate, and butyrate) in the colon regions, compared to the control period. Similarly, a significant increase in lactate levels was observed in proximal in response to oat treatments. Quantitative Polymerase chain reaction Analysis (qPCR) was utilised on specific health-related groups (Bifidobacterium spp. and Lactobacillus spp.) when analysing the faecal samples during the in vivo trial.

This new study focuses on two β-glucan-containing products, pre-cooked oat flour (POF) and old-fashioned oats (OFO), and their impact on gut microbiota composition or function. Such analyses provide an insight as to how these products may impact health via gut microbiota modulation, “the study showed that, when tested in the laboratory, both products had a positive impact on components of the gut microbiota that are generally associated with health, Lactobacillaceae and Bifidobacteriaceae, as well as desirable changes in a group of metabolites referred to as the short chained fatty acids. Notably, when one of these products (OFO) was selected to be consumed as part of a human study, several of these desirable changes were again evident” stated Dr. Cotter.

In Vivo study

Conducted by Atlantia Clinical Trials, this was a single-blind, placebo-controlled cross over study assessing the effects of old-fashioned oats (OFO) on variables such a faecal bacterial composition and plasma SCFAs. The sample population consisted of healthy adults with elevated levels of cholesterol (within then same range as then in vitro study). Subjects of the study attended six visits over a six-week period (6-week intervention period), followed by a four-week washout phase.

The study consisted of 24 randomised subjects, aged between 18-65 years old, with a BMI of 18.5-30kg. More information on Atlantia’s recruitment strategy can be found here. Prior to the study, subjects were required to write informed consent, and complete the required screening procedures to assess eligibility to enrol in the trial. The screening process for this particular trial consisted of fasted blood sample collection (to examine subjects safety and blood lipid profile), followed by a food frequency questionnaire (as subjects were required to have low to moderate consumption of dietary fibre).

In conclusion, the next steps in exploring the role of prebiotics in improving health outcomes related to dietary modulation and well-being, was outlined by Dr, Paul Cotter “the logical next step will be to carry out further human studies, including in specific groups of individuals, to tease out how these findings can best be applied to enhanced health. This research reflects the ever-greater interest in applying prebiotics to modulate the gut microbiota composition and function and, in turn, health”.

Atlantia has experience in inflammatory disease such as IBD, and testing inflammatory biomarkers using a disease activity index. Lastly, Barry will speak on immunity/infection, such as URTI, H. Pylori and antibiotic associated diarrhoea, along with a discussion of the range of measurements which can be utilised, depending on the desired outcome of a study. Visit our clinical expertise areas and our research services to learn more.

References:

Connolly, M., Tzounis, X., Tuohy, K. and Lovegrove, J., 2016. Hypocholesterolemic and Prebiotic Effects of a Whole-Grain Oat-Based Granola Breakfast Cereal in a Cardio-Metabolic “At Risk” Population. Frontiers in Microbiology, 7.

Duysburgh C, Van den Abbeele P, Kamil A, Fleige L, De Chavez PJ, Chu Y, Barton W, O'Sullivan O, Cotter PD, Quilter K, Joyce SA, Murphy M, DunnGalvin G, Dinan TG, Marzorati M. In vitro-in vivo Validation of Stimulatory Effect of Oat Ingredients on Lactobacilli. Pathogens. 2021 Feb 19;10(2):235.

Molly, K., Vande Woestyne, M. and Verstraete, W., 1993. Development of a 5-step multi-chamber reactor as a simulation of the human intestinal microbial ecosystem. Applied Microbiology and Biotechnology, 39(2), pp.254-258.

 

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