Scientists show how interleukin 6 does affect obesity risk and also where this effect occurs in the brain.
Decreased levels of Lateral Parabrachial Nucleus (lPBN) interleukin 6 in obesity are found to be problematic and likely contribute to metabolic dysfunction and weight gain, said researchers at University of Gothenburg, Sweden. // Interleukin-6 (IL-6) is a well-known pro- inflammatory molecule, and an integral element of body's first line of defense during infection. Intriguingly, the brain may govern and utilize IL-6 differently from the rest of the body.
‘In the study the rats and mice that became obese, had reduced IL-6, but only in one brain region, called Lateral Parabrachial Nucleus (lPBN). ’
Researchers led by the laboratory of Karolina Skibicka at the Sahlgrenska Academy,Sweden (Mishra et al Cell Reports, 2019: https://www.ncbi.nlm.nih.gov/pubmed/30865890), asked: what happens to IL-6 levels in the brain following a diet that leads to obesity? Rats and mice were offered a high-calorie palatable food - a mix of fat and sugar, in addition to their regular low-calorie diet - like many humans, rodents choose to overeat when presented with calorie dense foods.
"To understand whether this reduction of IL-6 is a good or bad thing for the metabolic health of the rodents, we viro-genetically reduced IL-6 levels very selectively in the lPBN; this led to increased body weight and body fat, even in rodents fed a healthy diet".
Since body weight is a result of how much we eat i.e. energy intake and how much energy we use i.e. energy expenditure, weight gain can follow dysfunction of either one of these branches of energy balance.
What makes local parabrachial nucleus-produced IL-6 extra important, the study found, is that it affects both branches simultaneously: it decreases food intake and increases energy expenditure, the latter by increasing brown fat activity, so body's energy is utilized for heat generation or fat burning. Hence reduced levels of lPBN IL-6 disrupt the entire energy balance equation.
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There is one unsolved piece of the puzzle in these new findings - researchers found that the obesity-associated reduction in IL-6 was only present in males. Female rats and mice had normal IL-6 levels. The Sahlgrenska team is now investigating why females are protected from the obesity-associated IL-6-driven dysfunction.
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Source-Eurekalert