Engineering the lipid emulsion interface to regulate lipolysis

Obesity is a major health problem in the western world, and one of the key priorities outlined in the Government's recent White Paper Choosing Health. One of the problems is that people eat too much fatty food, even though they know that they should eat more healthily. This is mainly because they prefer the taste of the fatty food to low fat alternatives. Many processed foods contain emulsified fats which are broken down in the gut by an enzyme called lipase. The enzyme attaches itself the fat droplets and breaks the fat down into a form which the body can absorb. We know that if we can slow the breakdown of fat, so that some of it passes through to the lower small intestine, it can stimulate a loss in appetite, causing people to eat less in subsequent meals. We also know that certain lipids or fat-like molecules called glycolipids can slow down the breakdown of fat by lipase, and could therefore be used to reduce appetite. It is thought that these glycolipids prevent the enzyme from attaching to the droplet surface, preventing it from breaking down the fat within the droplet. Therefore we plan to use some naturally occurring glycolipids from plants (galactolipids) to see if we can slow down the breakdown of fats. We will develop model systems containing mixtures of components found in the stomach and small intestine following the consumption of a fatty meal. We will measure how much glycolipid will stay on the surface and how much that affects the activity of the lipase. These models will be used in a model gut system which simulates the action of the stomach and small intestine to see if we can really cause a significant reduction in the breakdown of fat. This may lead to the development of a whole range of foods specifically designed to reduce appetite by controlling the composition of molecules on the surface of fat droplets.

The main aim of this project is to develop a novel method for modulating dietary fat uptake through the control of interfacial composition in emulsified foods. The approach is to reduce lipase activity through the presence of glycolipids at the oil-water interface. The approach has been developed from previous work, some of it involving the Institute of Food Research which has made the following observations:- 1) The activity of pancreatic lipase is an interfacial process and is very sensitive to interfacial composition. 2) The presence of glycolipids at interfaces is known to reduce lipase activity, possibly via steric hindrance, preventing adsorption of lipase or colipase. 3) Elevated levels of undigested lipid in the distal ileum can stimulate an entero-endocrine feedback response that can reduce appetite and induce feelings of satiety. This has allowed the formulation of the hypothesis that we can control the rate of lipolysis by manipulating the interfacial glycolipid composition. This can subsequently induce a loss of appetite due to the presence of undigested fat in the distal ileum. We aim to address the first part of the hypothesis by combining expertise in both colloid science and nutrition to determine the interfacial and molecular mechanisms responsible for hindering lipolysis by glycolipids. The interfacial composition of glycolipids will be determined using a range of tensiometric and interfacial methodologies together with imaging techniques such as atomic force and Brewster angle microscopies. This will be correlated with in-vitro lipolysis experiments to quantify the levels of adsorbed glycolipids necessary to restrict lipolysis. The findings will be used to optimise the effect of glycolipids on rigorous in-vitro digestion experiments using a model gut system that simulates the physiological conditions encountered during digestion. Interactions with other food components and products of digestion will also be studied. These results will be used to develop a strategy for controlling dietary intake, and develop further projects to test this strategy on in-vivo trials to quantify the efficacy of glycolipids on reducing dietary energy intake. This will ultimately lead to the development of a range of food products specifically designed to reduce fat intake through rational control of interfacial composition.