Gut Microbiota Mediates Distinct Metabolic Effects through Different Types of Dietary Fibre

Aim:

Increasing evidence suggests that the gut microbiota plays an important role in the beneficial effects of nutrition. Dietary fibre is often considered an essential component of a healthy diet. In part these health benefits may be mediated by its ability to modulate gut microbial composition.

Nevertheless, dietary fibre is not a single molecular entity; instead it represents a vast array of complex carbohydrate molecules, which have markedly different physico-chemical properties. Given this complexity, the aim of this project is to understand how different types of fibre alter the gut microbiota to deliver distinct metabolic benefits to the host.

Hypothesis:

The soluble dietary fibre, pectin, promotes the growth and activity of specific gut microbiota, which direct the metabolic response of the host, in favour of lean mass accretion and reduced adiposity.

Background:

Global trends in adult BMI between 1974 and 2014 show steady increases in obesity and it remains a priority public health concern. In 2014, about 266 million men and 375 million women were obese in the world, compared with 34 million men and 71 million women in 1975 (1). The major health consequences associated with obesity include grossly elevated risks of developing co-morbidities such as type 2 diabetes, cardiovascular disease, hypertension, stroke, cancers and Alzheimer’s disease (AD).

Despite considerable advances in our understanding of the genetics of obesity through modern approaches such as genome wide association studies, this has not led to new therapies for the treatment of obesity. This is still likely to come from an understanding of mechanisms involved in the homeostatic regulation of energy balance, obesity and growth. Recent work on gut microbiota has ignited renewed interest in the role of the gut (and its microbiota) in these mechanisms.

The way that food and diet trigger mechanisms in the gut is particularly important in this regard. For healthy weight management, many different diets have been shown to help control food intake and reduce obesity. Recent evidence shows that increased levels of soluble fibre added to the diet of obese rats can reduce intake and adiposity substantially (2). A remarkable finding has been that one fibre type, pectin, appears to preserve lean body mass, while more weight is lost as fat.

This finding suggests that certain fibres have beneficial metabolic effects over others, which could be exploited for improved foods with better knowledge and understanding. This is important as one of the biggest problems following weight loss is weight regain, thought in part to be due to the drive to replenish lean mass that usually occurs along with fat loss.

Approach:

The project will explore the effects of supplementing three different types of fibre in the diets of both rats and mice. The approach will be to examine the effects of the different types of fibres on gut microbiota composition (using Next Generation Sequencing) to identify how different types of fibre influence the gut microbial community, down to the species level. This may reveal certain bacteria with specific metabolic effects. The study will examine the metabolic effects of consuming different dietary fibres on gene expression in adipose tissue, liver and muscle, using targeted as well as microarray analysis. At the gut level, the effects of dietary fibre on mucin production and gut integrity and function will be examined, using histological methods.

The project will also compare long and short term effects of consuming different fibre types to identify whether effects are transient or sustained. Although the main studies will be conducted on rats, some experiments will be conducted on mice to confirm the generic biological relevance of the findings.

http://www.abdn.ac.uk/ims/research/profiles/a.ross