Supporting Publication: Activation of Central Orexin/Hypocretin Neurons by Dietary Amino Acids
The Atkins diet involves limiting your consumption of carbohydrates. This forces the body to metabolize stored fat for energy instead of metabolizing the abundance of glucose that is made available from high carb diets. I recently stumbled upon some research that indicates that the Atkins diet might not only be good for your figure, but also for your orexin cells! Before I go into details about why exactly that may be, I should probably first explain what orexin cells are and why you should be concerned about them…
Orexin cells, located within the hypothalamus (see diagram), are responsible for regulating vitally important states of the human body such as hunger and energy levels. Orexin cells operate by secreting excitatory neuropeptide hormones called orexins (or hypocretins). Orexin was discovered in 1998 by two different research teams. One team called the hormone orexin, and the other called it hypocretin. While both names are used in scientific literature, I will only use the term orexin here on my blog because I have some major beef with a member of the “hypocretin” research team. [Disclaimer: Only joking about that. In all honesty, orexin just sounds cooler.]
Orexins stimulate important nuclei in the brain such as the locus coeruleus (norepinephrine production) and the ventral tegmental area (dopamine production). Dopamine and norepinephrine are of course two hormones that play a key role in keeping a person consciously aroused and physically mobile.
Orexin cells belong to a very rare category of cells in the body that are sensitive to external glucose levels. When a person consumes food, blood sugar levels rise and cause orexin cells to lower their activity. Conversely, if blood sugar levels become depleted, orexin cells will again become active. Every time that you eat something, orexin cells in the hypothalamus must work in order to compensate for the change in blood sugar levles.
Scientists at the University of Cambridge studied the actions of a variety of different nutrients on orexin cells and found that of all nutrients, amino acids stimulated orexin production the greatest amount. The most common natural sources of amino acids include meat, eggs and dairy products. It was known that the electrical impulses emitted by orexin cells direct the body to burn calories for energy but the Cambridge scientists wanted to know if dietary nutrients were capable of altering the excitability of orexin cells.
The researchers approached this problem by using a genetic fluorescence targeting technique in order to identify orexin cells in mouse brains. They then recorded the electrical impulses from the cells when they were exposed to a variety of nutrients. In a previous study, Cambridge researchers revealed that glucose blocks orexin cell impulses and they used this finidng in order to explain the “after-meal sleepiness” that some of you may have experienced recently after eating your Thanksgiving dinner.
Ok so we now know the importance of the orexin system and how it can be regulated by main dietary nutrients such as sugars and proteins. Sugars turn off the orexin cells and make you sleepy and protein stimulates the cells, making your body and mind more alert. Well our Cambridge friends took their research one step further and studied interactions between comparable amounts of sugar and protein when exposed simultaneously to orexin cells.
This is the interesting part—get ready for it—turns out that amino acids actually prevent glucose from inhibiting orexin cell function. So… theoretically this means that if we consume a meal that has a proper protein/carbohydrate ratio, we can keep the orexin system firing and avoid passing out on Uncle Dave’s couch after finishing off the Thanksgiving meal with two pieces of pumpkin pie.
This research is interesting because it identifies a rational way to “tune” specific brain cells to be more or less active by simply choosing certain foods to eat over others. A meal that is rich in protein will not only keep you more alert, but it will also cause your body to burn more calories. The next time you are on the fence about what to eat for lunch, go with the meal that has more protein and less carbs and you may avoid that afternoon slump!