Warm milk makes you sleepy -- peptides could explain why

Date:
October 13, 2021
Source:
American Chemical Society
Summary:
According to time-honored advice, drinking a glass of warm milk at
bedtime will encourage a good night's rest. Milk's sleep-enhancing
properties are commonly ascribed to tryptophan, but scientists have
also discovered a mixture of milk peptides, called casein tryptic
hydrolysate (CTH), that relieves stress and enhances sleep. Now,
researchers have identified specific peptides in CTH that might
someday be used in new, natural sleep remedies.



FULL STORY ========================================================================== According to time-honored advice, drinking a glass of warm milk at bedtime
will encourage a good night's rest. Milk's sleep-enhancing properties are commonly ascribed to tryptophan, but scientists have also discovered a
mixture of milk peptides, called casein tryptic hydrolysate (CTH), that relieves stress and enhances sleep. Now, researchers reporting in ACS'
Journal of Agricultural and Food Chemistry have identified specific
peptides in CTH that might someday be used in new, natural sleep remedies.


========================================================================== According to the U.S. Centers for Disease Control and Prevention,
one-third of U.S. adults don't get enough sleep. Sedatives, such as benzodiazepines and zolpidem, are commonly prescribed for insomnia,
but they can cause side effects, and people can become addicted to
them. Many sedatives work by activating the GABA receptor, a protein in
the brain that suppresses nerve signaling. Scientists have also discovered several natural peptides, or small pieces of proteins, that bind the GABA receptor and have anti-anxiety and sleep-enhancing effects. For example, treating a protein in cow's milk, called casein, with the digestive
enzyme trypsin produces the mixture of sleep- enhancing peptides known
as CTH. Within this mixture, a specific peptide known as a-casozepine
(a-CZP) has been identified that could be responsible for some of these effects. Lin Zheng, Mouming Zhao and colleagues wondered if they could
find other, perhaps more powerful, sleep-enhancing peptides in CTH.

The researchers first compared the effects of CTH and a-CZP in mouse sleep tests, finding that CTH showed better sleep-enhancing properties than
a-CZP alone. This result suggested that other sleep-promoting peptides
besides a-CZP exist in CTH. The team then used mass spectrometry to
identify bioactive peptides released from CTH during simulated gastric digestion, and they virtually screened these peptides for binding to the
GABA receptor and for the ability to cross the blood-brain barrier. When
the strongest candidates were tested in mice, the best one (called YPVEPF) increased the number of mice that fell asleep quickly by about 25% and
the sleep duration by more than 400% compared to a control group. In
addition to this promising peptide, others in CTH should be explored
that might enhance sleep through other pathways, the researchers say.

The authors acknowledge funding from the National Natural Science
Foundation of China, the Guangdong Provincial Key R&D Program, the
Shandong Provincial Key R&D Program, and the Specific Fund Program for
Basic and Applied Basic Research of Guangdong Province.

========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jingjing Qian, Lin Zheng, Guowan Su, Mingtao Huang, Donghui Luo,
Mouming
Zhao. Identification and Screening of Potential Bioactive
Peptides with Sleep-Enhancing Effects in Bovine Milk Casein
Hydrolysate. Journal of Agricultural and Food Chemistry, 2021; 69
(38): 11246 DOI: 10.1021/ acs.jafc.1c03937 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211013104610.htm

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