In life, motivation can be the difference between success and failure, goal setting and purposelessness, and well-being and unhappiness. Still, staying motivated and motivated is often the hardest step, and it’s a problem that has spawned a lot of research. A very small part of this research has examined the problem of metabolism. “Do differences in metabolites in the brain affect our motivational capacity?” asks Professor Carmen Sandi of EPFL’s School of Life Sciences. “If this is the case, could nutritional interventions that can affect metabolite levels be an effective tool for improving motivated performance?”
Sandi’s group, along with colleagues at the Nestle Health Sciences Institute, published a study that sheds light on answering this question. The researchers focused on an area deep in the brain called the “core accumbens,” which is known to play an important role in regulating functions such as reward, reinforcement, aversion, and most importantly, motivation. The idea behind the study was that our brain itself – like all tissues in our body – is constantly exposed to oxidative stress as a result of its metabolism.
What is oxidative stress? When cells “eat” various molecules for fuel, they produce a number of toxic waste products in the form of highly reactive molecules, collectively known as “oxidative species.” Of course, cells have a number of mechanisms to scavenge oxidative species and restore the cell’s chemical balance. But this war continues, sometimes this balance is disturbed and we call this ailment “oxidative stress”. The brain is then subjected to extreme oxidative stress, often resulting from its neurometabolic processes – and the researchers’ question was whether antioxidant levels in the nucleus accumbens affect motivation. To answer the question, the scientists looked at a protein called glutathione (GSH), the brain’s most important antioxidant, and its relationship to motivation.
“We evaluated associations between metabolites in the nucleus accumbens, an important brain region, and motivated performance,” says Sandi. “We then turned to animals to understand the mechanism and explore causality between the metabolite found and performance, and we also demonstrated that nutritional interventions alter behavior along this pathway.” First, they used a technique called “proton magnetic resonance spectroscopy,” which can non-invasively evaluate and measure the biochemistry in a particular area of the brain. The researchers applied the technique to the nucleus accumbens of both humans and rats to measure GSH levels. They then compared these levels with how well or poorly human and animal subjects performed on standardized, effort-related tasks that measure motivation.
What they found was that higher GSH levels in the core accumbens were associated with better and stable performance on motivational tasks. But correlation doesn’t imply causation, so the team moved on to live experiments with mice given microinjections of a GSH blocker, downregulating antioxidant synthesis and levels. Rats now showed less motivation, as seen with lower performance on effort-based, reward-inducing tests.
In contrast, when the researchers gave the mice a nutritional intervention with the GSH precursor N-acetylcysteine—which increased GSH levels in the nucleus accumbens—the animals performed better. As the authors write, the effect was “potentially mediated by a cell-type-specific shift in glutamatergic inputs to accumbal medium spiny neurons”. “Our study provides new insights into how brain metabolism relates to behavior and highlights nutritional interventions that target the essential oxidative process as ideal interventions to facilitate laborious endurance,” the authors conclude. The study’s findings “suggest that improving scavenger antioxidant function may be a viable approach to increase motivation.”
“N-acetylcysteine, the dietary supplement we gave in our study, can also be synthesized in the body from precursor cysteine,” says Sandi. “Cysteine is found in ‘high protein foods’ such as meat, chicken, fish or seafood. Other sources of lower content are whole-grain foods such as eggs, bread and cereals, and certain vegetables such as broccoli and onions. Legumes: “Of course, There are other ways to increase GSH levels beyond N-acetylcysteine, but how these relate to levels in the brain – and especially in the nucleus accumbens – is largely unknown. Our study represents proof of the principle that dietary N-acetylcysteine can increase brain GSH levels and facilitate exertional behavior.” (ANI)
(This story was not edited by the Devdiscourse team and was generated automatically from the syndication feed.)