Obesity remains on the cellular level

Professor Kirsi Pietiläinen has located the impact of obesity in the mitochondria of fat tissue. Mitochondrial dysfunction likely results in excess weight that is difficult to lose.

Kirsi Pietiläinen, a recently appointed professor at the Faculty of Medicine, has studied obesity since the early 90s. Professor Jaakko Kaprio’s extensive twin study data is central to her research.

After studying the genetics and epidemiology of obesity as well as conducting extensive surveys, she is now studying the metabolism of fat tissue through identical twins in which one of the twins is obese. As identical twins share a genome, the discrepancy in their weight must be caused by living environment or lifestyle.

"This has become something of a Pandora’s box, or a treasure trove that has led our research group into many unexpected areas we had no idea of when we started our research."

The study revealed that the some of the obese twins had disorders in the mitochondria of their fat tissue cells, which are responsible for the metabolism of the cells. Pietiläinen’s group is currently investigating whether weight loss can rectify the dysfunction.

"I’m almost willing to bet my doctoral hat on the disorder being a consequence of obesity, which triggers a vicious circle. The body begins to slow down metabolic activity at a very early stage, and it is very difficult to get rid of the accumulated fat. In addition, such people are quick to regain the weight they have lost.”

The twins in Pietiläinen’s study were young, between 25 and 30 years of age, their obesity was not severe, and they had no prominent mutations in their mitochondria or hereditary diseases.

Variation in the severity of mitochondrial dysfunction

In her follow-up studies, Pietiläinen has found that obesity can nearly always be traced back to the mitochondria, but the severity of the dysfunction varies. Among healthy obese people, with no preliminary stages of diabetes or vascular diabetes, the dysfunctions are milder or non-existent.

However, the reason for the variation in the severity of the mitochondrial dysfunction is unknown.

"At the moment we’re trying to find out how we could prevent mitochondrial disorder and treat existing disorders."

In this, Pietiläinen’s research group is working together with docent Eija Pirinen and Academy Professor Anu Wartiovaara who study mitochondrial diseases.

Earlier studies have revealed that certain B vitamins are effective against some mitochondrial diseases, and the same vitamins are now being administered to the twins in the current research. Preliminary results can be expected later this year, when the research subjects are studied after a five-month course of the vitamin.

Pietiläinen wants to next examine the muscle metabolism of the twins in the study, with the goal of finding out whether the metabolic changes associated with obesity are different in the muscles than they are in fat tissue.

A study on the metabolism of patients before and after bariatric surgery is also underway. The intention is to discover whether the changes effected by the surgery influence the behaviour of the mitochondria in morbidly obese patients.  

"In my research career, one thing has led to the next, and one answer has always opened the door to new questions," she says.

The first tenured professor

Kirsi Pietiläinen (in the photo) is the first person to complete the tenure track and receive a permanent tenured professorship at the University of Helsinki.

In the three-level tenure track, launched in 2010, a fixed-term assistant professorship of three to five years leads to an associate professorship of three to five years, and culminates in a permanent professorship, if the criteria for granting tenure are met.

The intention of the system is to increase the predictability, competitiveness and attractiveness of academic careers. The University strives to find the most talented and motivated people for the tenure track.

Currently there are 54 tenure track assistant and associate professors working in the University of Helsinki. 18 of them have been recruited outside Finland, and 19 are women.

Professor Pietiläinen heads a 15-person Obesity Research Unit at the Faculty of Medicine, teaches future doctors and nutritional scientists, and serves as the senior physician at the Obesity Centre of Jorvi Hospital.

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