Dr. Bray Links

Friday, February 13, 2015

Activation of central orexin/hypocretin neurons by dietary amino acids


"Hypothalamic orexin/hypocretin (orx/hcrt) neurons regulate energy balance, wakefulness, and reward; their loss produces narcolepsy and weight gain. Glucose can lower the activity of orx/hcrt cells, but whether other dietary macronutrients have similar effects is unclear. We show that orx/hcrt cells are stimulated by nutritionally relevant mixtures of amino acids (AAs), both in brain slice patch-clamp experiments, and in c-Fos expression assays following central or peripheral administration of AAs to mice in vivo. Physiological mixtures of AAs electrically excited orx/hcrt cells through a dual mechanism involving inhibition of K(ATP) channels and activation of system-A amino acid transporters. Nonessential AAs were more potent in activating orx/hcrt cells than essential AAs. Moreover, the presence of physiological concentrations of AAs suppressed the glucose responses of orx/hcrt cells. These results suggest a new mechanism of hypothalamic integration of macronutrient signals and imply that orx/hcrt cells sense macronutrient balance, rather than net energy value, in extracellular fluid."

http://www.ncbi.nlm.nih.gov/pubmed?Db=pubmed&Cmd=Retrieve&list_uids=22099463&dopt=abstractplus

"nonessential AAs elicited large responses, with a relative potency order glycine > aspartate > cysteine > alanine > serine > asparagine > proline > glutamine, while essential AAs were much less effective"

http://www.sciencedirect.com/science/article/pii/S0896627311007823

"FDA approves new type of sleep drug, Belsomra

The U.S. Food and Drug Administration today approved Belsomra (suvorexant) tablets for use as needed to treat difficulty in falling and staying asleep (insomnia).

Belsomra is an orexin receptor antagonist and is the first approved drug of this type. Orexins are chemicals that are involved in regulating the sleep-wake cycle and play a role in keeping people awake. Belsomra alters the signaling (action) of orexin in the brain.

Insomnia is a common condition in which a person has trouble falling or staying asleep. It can range from mild to severe, depending on how often it occurs and for how long. Insomnia can cause daytime sleepiness and lack of energy. It also can make a person feel anxious, depressed, or irritable. People with insomnia may have trouble with attentiveness, learning, and memory."

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