NPGL, a protein involved in brain signaling, has been found to increase fat storage by the body — even when on a low-calorie diet. In addition, NPGL was shown to increase appetite in response to high caloric food intake, suggesting that perhaps we shouldn't feel so guilty about gorging on junk food from time to time. This discovery by Hiroshima University's Professor Kazuyoshi Ukena, along with collaborators from Japan and UC Berkeley has recently published in eLife.
Professor Ukena has documented the protein in mice and humans. Ukena has found that when NPGL was present in high concentrations in a specific part of the rat's hypothalamus, the brain's control center for appetite and metabolism, suggesting involvement in bodily energy regulation.
With this in mind, the researchers then carried out experiments on rats fed on two distinct diets for six weeks. One diet was highly caloric and the other contained only sufficient calories required for healthy survival. A virus was then prepared that would cause NPGL secreting cells to increase production in the hypothalamus of both sets of rats.
In rats fed the high-calorie diet, body mass, and the proportion of the body composed of fatty tissue, both markedly increased. Food intake greatly increased despite animals having an overabundance of calories. In regular-calorie fed rats in which NPGL production was induced, animals did not increase overall body mass and only moderately increased food consumption. However, body fat composition, as with the high calorie diet, did increase.
Conversely, when the rats on the high-calorie diet were exposed to an antibody that inhibited NPGL synthesis, the proportion of fatty tissues in the body decreased, further demonstrating the role of NPGL in regulating body fat composition. In these rats, food intake and overall body mass remained unchanged.
NPGL levels were also seen to increase and decrease proportionally with blood insulin levels, suggesting that this blood sugar/energy storing hormone harmonizes with the NPGL system to store fat during times of plenty and limit fat production when times are lean.