Surprising new clue to the roots of hunger, neurons that drive appetite

Surprising new clue to the roots of hunger, neurons that drive appetite

A scientific team has made a surprising discovery about the brain’s hunger-inducing neurons, a finding with important implications for the treatment of obesity.

via All Top News — ScienceDaily:

While the function of eating is to nourish the body, this is not what actually compels us to seek out food. Instead, it is hunger, with its stomach-growling sensations and gnawing pangs that propels us to the refrigerator – or the deli or the vending machine. Although hunger is essential for survival, abnormal hunger can lead to obesity and eating disorders, widespread problems now reaching near-epidemic proportions around the world.Over the past 20 years, Beth Israel Deaconess Medical Center (BIDMC) neuroendocrinologist Bradford Lowell, MD, PhD, has been untangling the complicated jumble of neurocircuits in the brain that underlie hunger, working to create a wiring diagram to explain the origins of this intense motivational state. Key among his findings has been the discovery that Agouti-peptide (AgRP) expressing neurons – a group of nerve cells in the brain’s hypothalamus – are activated by caloric deficiency, and when either naturally or artificially stimulated in animal models, will cause mice to eat voraciously after conducting a relentless search for food.Now, in a new study published on-line this week in the journal Nature, Lowell’s lab has made the surprising discovery that the hunger-inducing neurons that activate these AgRP neurons are located in the paraventricular nucleus — a brain region long thought to cause satiety, or feelings of fullness. This unexpected finding not only provides a critical addition to the overall wiring diagram, but adds an important extension to our understanding of what drives appetite.“Our goal is to understand how the brain controls hunger,” explains Lowell, an investigator in BIDMC’s Division of Endocrinology, Diabetes and Metabolism and Professor of Medicine at Harvard Medical School. “Abnormal hunger can lead to obesity and eating disorders, but in order to understand what might be wrong – and how to treat it – you first need to know how it works. Otherwise, it’s like trying to fix a car without knowing how the engine operates.”Hunger is notoriously complicated and questions abound: Why do the fed and fasted states of your body increase or decrease hunger? And how do the brain’s reward pathways come into play – why, as we seek out food, especially after an otherwise complete meal, do we prefer ice cream to lettuce?“Psychologists have explained how cues from the environment and from the body interact, demonstrating that food and stimuli linked with food [such as a McDonald’s sign] are rewarding and therefore promote hunger,” explains Lowell. “It’s clear that fasting increases the gain on how rewarding we find food to be, while a full stomach decreases this reward. But while this model has been extremely important in understanding the general features of the ‘hunger system,’ it’s told us nothing about what’s inside the ‘black box’ – the brain’s neural circuits that actually control hunger.”To deal with this particularly complex brain region – a dense and daunting tangle of circuits resembling a wildly colorful Jackson Pollack painting – the Lowell team is taking a step-by-step approach to find out how the messages indicating whether the body is in a state of feeding or fasting enter this system. …

For more info: Surprising new clue to the roots of hunger, neurons that drive appetite

All Top News — ScienceDaily

Surprising new clue to the roots of hunger, neurons that drive appetite

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