Researchers find potential key to protect against obesity
ADDING the nutrient selenium to diets protects against obesity and provides metabolic benefits to mice, according to a study published today in eLife.
The results could lead to interventions that reproduce many of the anti-ageing effects associated with dietary restriction while also allowing people to eat as normal.
Several types of diet have been shown to increase healthspan – that is, the period of healthy lifespan. One of the proven methods in many organisms, including non-human mammals, is to restrict dietary intake of an amino acid called methionine.
Recent studies have suggested that the effects of methionine restriction on healthspan are likely to be conserved in humans. Although it might be feasible for some people to practice methionine restriction, for example, by adhering to a vegan diet, such a diet might not be practical or desirable for everyone. In the current study, a research team from the Orentreich Foundation for the Advancement of Science, (Ofas), New York state, aimed to develop an intervention that produces the same effects as methionine restriction, while allowing an individual to eat a normal, unrestricted diet.
An important clue for developing such a treatment is that methionine restriction causes a decrease in the amounts of an energy-regulating hormone called IGF-1. If a treatment could be found that causes a similar decrease in IGF-1, this might also have beneficial effects on healthspan. Previous research has shown selenium supplementation reduces the levels of circulating IGF-1 in rats, suggesting this could be an ideal candidate.
The team first studied whether selenium supplementation offered the same protection against obesity as methionine restriction. They fed young male and older female mice one of three high-fat diets: a control diet containing typical amounts of methionine, a methionine-restricted diet, and a diet containing typical amounts of methionine as well as a source of selenium. For both male and female mice of any age, the authors found selenium supplementation completely protected against the dramatic weight gain and fat accumulation seen in mice fed the control diet, and to the same extent as restricting methionine.
Next, they explored the effects of the three diets on physiological changes normally associated with methionine restriction. To do this, they measured the amounts of four metabolic markers in blood samples from the previously treated mice. As hoped, they found dramatically reduced levels of IGF-1 in both male and female mice.
They also saw reductions in the levels of the hormone leptin, which controls food intake and energy expenditure. Their results indicate that selenium supplementation produces most, if not all, of the hallmarks of methionine restriction, which suggests that this intervention may have a similar positive effect on healthspan.
“One of the major goals of ageing research is to identify simple interventions that promote human healthspan,” notes senior author Jay Johnson, senior scientist at Ofas.
“Here we present evidence that short-term administration of either organic or inorganic sources of selenium provides multiple health benefits to mice, the most notable of which being the prevention of diet-induced obesity. In the long term, we expect that supplementation with these compounds will also prevent age-related disease and extend the overall survival of mice. It is our hope that many of the benefits observed for mice will also hold true for humans.”