Research project to investigate cysteine-obesity link

“There is a very high correlation between high levels of cysteine and obesity,”​ explained Helga Refsum, professor of nutrition at the University of Oslo. However, she noted that the important question now is whether this is a causal relationship.

Prof. Refsum and her team will now perform a comprehensive study, funded under the Research Council of Norway’s funding scheme for independent basic research (FRIPRO). The study, which will run until 2013, aims to shed light on the underlying biological mechanism linking cysteine to obesity.

Refsum’s previous research indicates that cysteine may play a key role in how the body metabolises energy, stores, and breaks down fat. However it is, as yet, unknown whether much of the body’s fat due to a high cysteine level, and if so, what the mechanisms behind the connection are.

“We particularly want to find out if cysteine is associated with obesity-related morbidity – the myriad of diseases such as diabetes, cardiovascular diseases and certain types of cancer that are associated with obesity. From a public health perspective, it is this aspect of obesity we need to worry about,”​ he explained.

Genetic link​

“We know there is a strong genetic component to the body’s weight and fat content,” ​said Professor Refsum, who pointed out that between 50 and 80 per cent of body weight is due to genetic factors.

“Look at the difference between males and females! Women always have more body fat than men. Nature intended it this way; this is how it should be.”​

He added that genetic factors are also ‘undoubtedly’ involved in controlling cysteine levels, citing two genetic conditions that are known to affect cysteine levels.

Refsum noted that people with a genetic condition known as homocystinuria lack one of the enzymes that convert homocysteine to cysteine, adding that people with the condition have low cysteine levels and are generally extremely slender.

In contrast, he said that people with Down’s syndrome, who tend to be overweight, have 50 per cent more of the enzyme than normal– leading to higher than average cysteine levels.

Diet- related?​

Refsum noted that previous research findings have indicated that cysteine level is not directly affected by diet, but said that the links need to be investigated in greater depth.

“Once we determine whether it is possible to alter cysteine levels through diet, we can propose new nutritional recommendations,”​ he said.

The researchers are now investigating complex chain of chemical reactions during metabolism, from ingesting food to cysteine functions.

“Cysteine is clearly related to weight, but what determines cysteine levels? Where does it all begin?”​ they said.

As part of the new project, the research team will also study how cysteine affects the brain – for instance, whether it has influence over feelings of satiety.