Views:15 Author:Site Editor Publish Time: 2016-08-22 Origin:Site
A bitter plant extract discovered by New Zealand researchers may offer hope to people wanting to lose weight. In a recent clinical trial of Amarasate, the substance found by Plant & Food Research scientists, the healthy adult participants had the edge taken off their appetites.
Amarasate exploits human sensitivity to bitter-tasting compounds, which has developed for good reason. Bitterness can indicate dietary danger, whether in the form of rancid fats, degraded proteins or plant-derived poisons and other toxins. The bitter-taste receptors in our mouth act as a first line of defence for our body by encouraging us to spit out potentially harmful foods.
However, our bitterness defences don’t end there. We also have taste receptors in the gut that sense bitterness, sweetness, umami and the flavour of fat in much the same way as those in our mouth do. But whereas the taste receptors in our mouth deliver a neuronal signal to our brain so we directly perceive the bitter or sweet taste, our gut taste receptors are attached to enteroendocrine cells, says Plant & Food senior research scientist John Ingram.
Those cells taste the composition of food in our gut as it’s digested and absorbed. And depending on what compounds they detect-bitter or sweet, for example- they transmit signals that control the secretion of different gut hormones, such as cholecystokinin (CCK), peptide YY (PYY), and glucagon-like peptide-1 (GLP-1), that are involved in appetite regulation.
The effect of bitter compounds on appetite regulation has been the focus of research since the discovery that chemicals such as denatonium benzoate-one of the most bitter compounds known to man - suppressed food intake in animals and healthy adults.
Bitter taste receptors in the gut seemingly act as a second line of defence, says Ingram, by suppressing appetite and thus encouraging us to stop eating the potentially poisonous food we’re chowing down on.
Ingram and colleagues have named this bitter suppression of appetite the ‘bitter brake’. They screened more than 900 plant extracts to identify those that stimulate gut enteroendocrine cells to release certain appetite-related hormones. “Of those, we found one in particular that is a very strong activator, which is the Amarasate extract that we took forward into clinical studies.”
Plant & Food’s double-blind trial of Amarasate among 19 lean, healthy male volunteers showed it significantly affected the amount of food they ate. After an overnight fast, a standardised breakfast and the administration of 500mg of extract designed to release its contents in either the stomach or small intestine, the participants ate from 911-944kJ less energy over the course of a subsequent lunch and snack than when given a placebo tablet.
“We were very excited about that result,” says Ingram. As well they should be: given that a typical adult consumes about 8700kJ of energy a day, that could equate to a cut in daily energy intake of 11%.
The key questions now are the long-term effect Amarasate has on food intake “do people simply eat a big dinner to make up for their smaller lunch and snack?”and whether this bitter pill is equally effective in overweight and obese adults?
We know, for instance, there are variations in the types and quantities of taste receptors in peoples mouths, with so-called super-tasters having more bitter receptors.“We’ve looked at biopsy samples from individuals and quantified the expression of these receptors in the gut and where they are expressed in the gut and we do see some variability between individuals,”says Ingram.
“The advantage we have is we have a range of plant compounds. There are multiple bitter compounds that you could potentially use to stimulate this response, so you could design products to cater for those individuals.”
Ingram’s team has funding to conduct dose-response trials of their bitter pill and these will include overweight adult participants. They then hope to get more funding to test Amarasate’s weight-management effectiveness in long-term studies.