Dr John Ingram is a senior research scientist with Plant & Food Research, Auckland. John gives an outline of the satiety research he is involved with, which is focused on how plant components interact with the chemosensory role of the gut. Three main mechanisms are being targeted: the production of CCK in the duodenum, the ileal brake and colonic fermentation.
Dr John Ingram
The research that we’re doing in the area of satiety is looking at how food or particularly plant components interact with the chemosensory role of the gut. We’re targeting 3 main mechanisms.
The initial 1 is the production of CCK from cells called entroendocrine cells. They are chemosensory cells that are in the duodenum – the 1st part of the small intestine. They are actually tasting the food as it passes out from the stomach. We’re looking at bitter taste receptors, because bitter compounds are potent stimulants of the production of the satiety hormone called CCK.
The 2nd mechanism we’re interested in is termed the ileal brake, and this mechanism is involved in the sensing of nutrients in the ileum, the lower 3rd of the small intestine. Our approach is to enhance delivery of carbohydrates to the ileum and promote the production of hormones such as GLP-1 and PYY, which impact on satiety.
The final mechanism is colonic fermentation. If we can enhance fermentation of fibre via the bacteria in the gut to increase production of butyrate, then we can enhance the production of a hormone called ApoA4, which is also involved in satiety. Butyrate is a short-chain fatty acid produced by fermenting bacteria. We want to enhance the production of that butyrate by either selecting for bacteria that produce this or providing substrates and phytochemicals particularly that may influence the production of butyrate.
These different mechanisms occur at different times post food consumption. The CCK response is actually quite rapid, occurring within 20 minutes or so after consumption of a meal, and lasting for about an hour. The ileal brake mechanism takes a bit longer, maybe about 1–2 hours after consumption of a meal. The colonic system is very long-term – the next meal or even the day after where you might be having an enhanced satiety effect.
So combining these different mechanisms together in the 1 food, we can get both an elevated and sustained level of satiety. We’re looking at a range of compounds in plant material from fruit, vegetables and grains. A lot of these compounds, particularly secondary metabolites or what we term phytochemicals, have evolved as defence compounds in plants, and they actually have a role in altering digestion and absorption in herbivores. We think that they may play a role in feeding behaviour in humans as well. Polyphenolics such as anthocyanins and flavonoids seem to have a very interesting role in modulating digestion and absorption and therefore affecting satiety.