Got an Appetite That Won’t Subside? You’ve Got Hungry Peptides

Source: University of Southern California

Summary: A new study shows the brain’s plumbing system serves double duty, flushing waste and channeling a hunger molecule that tells you when you should eat.

In cell-to-cell communication, the neurons are discretely passing notes to individual neurons or other cells. However, cerebrospinal fluid distributes a newsletter to many subscribers. Cerebrospinal fluid has three chief assignments. First, its grueling eternal task is buoyancy, like the Greek Titan Atlas, supporting the brain. Second, it acts as a cushion after a blow to the head. Third, it is the brain’s sewer system, clearing away metabolic waste. As neuroscience technologies have advanced, scientists have seen indications that what is sometimes dismissed as sewage actually has a role in the brain’s regulation of behaviors such as stress, energy balance and reproduction. Researchers from the USC found that the brain regulates some processes by releasing and dispersing molecules, and in this case, a neuropeptide, through cerebrospinal fluid. The study findings were published in the journal Cell Metabolism.

Melanin concentrating hormone

Cells that communicate with the cerebrospinal fluid are marked with a red fluorescent tracer, whereas cells that make the appetite-promoting neuropeptide melanin-concentrating hormone (MCH) are shown with a green fluorescent marker. This shows that many MCH cells communicate with cerebrospinal fluid (yellow cells), the first clue that MCH may increase feeding through cerebrospinal fluid signaling. Credit: Kanoski lab at the USC Dornsife College

For their study, the researchers focused on the molecule “melanin-concentrating hormone” (MCH). This neuropeptide is generated by neurons in the brain’s hunger center, the lateral hypothalamus, at the base of the brain just above the pituitary gland. A protein molecule, MCH stimulates appetite. It also can slow energy expenditure. Through a series of experiments with rats, the researchers stimulated a release of the hunger peptide and then tracked it in the cerebrospinal fluid. Based on their findings, the researchers determined the peptide’s release is likely influenced by the circadian clock and a daily mealtime routine. Drug developers are interested in creating pharmaceuticals that would target the MCH system to control appetite, and thereby address obesity and other weight-related health problems.

Asst. Prof. Scott Kanoski said, “When we released MCH into the cerebrospinal fluid, the animals would start eating and when we reduced the levels of the molecule, then we saw the opposite effect and the animals would eat less.”

More Information: Emily E.Noble et al, “Control of Feeding Behavior by Cerebral Ventricular Volume Transmission of Melanin-Concentrating Hormone”, Cell Metabolism (2018). … 1550-4131(18)30308-5 

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