Hormones produced by the adipose tissue can cause diseases.
The risk of arthritis is much higher among the obese than people of normal weight, and one reason for this is the added burden on the joints.
However, new research shows that the burden on the joints is not the only cause of arthritis; it is also the result of hormones produced by the adipose tissue – the fatty tissue beneath our skin and around our internal organs.
“Being overweight causes a mild inflammatory reaction in the body. Many inflammatory diseases have been shown to be associated with overweight,” says Eeva Moilanen, professor of pharmacology at the University of Tampere.
“Being overweight also increases the risk of arthritis in the finger joints, so weight does not appear to play a major role, unless the patients walk a lot on their hands!”
Moilanen’s research group investigates inflammatory diseases and develops new drugs to treat them. Over the past few years, the research group has focused on adipokines – hormones secreted by the adipose tissue.
Adipokines regulate metabolism, appetite and feelings of satisfaction from food. These hormones have been proven to regulate many inflammatory diseases, such as asthma, chronic obstructive pulmonary disease, arthritis and rheumatoid arthritis. The hormone seems to explain why some types of inflammatory diseases occur more frequently among the obese.
Moilanen’s research group has been observing adipokines in order to discover the types of inflammatory diseases they cause, and to determine which medicines are effective in the treatment of these diseases. The research is currently focusing on whether adipokines could be targets for drugs, and whether they could be used clinically in the prevention, treatment and cure of inflammatory diseases.
Resistin levels reveal inflammation
The hormone leptin seems to link obesity and arthritis. In overweight people’s bodies, leptin is harmful to joint cartilage, and its effects are stronger than in people of normal weight.
In addition, high levels of leptin are also associated with more severe asthma symptoms in people of normal weight. This was shown in respiratory physician Sirpa Leivo-Korpela’s recent doctoral dissertation, which investigated adipokines in pulmonary diseases.
One of the most recent discoveries is an adipokine called resistin. According to research conducted by Eeva Moilanen and Katriina Vuolteenaho, resistin is associated with many severe inflammatory conditions.
This new and interesting association was first noted by medical student Antti Laurikka, who investigated blood samples taken from patients after heart surgery. He found that the post-treatment plasma levels of resistin were very high, indicating damage to the heart tissue.
“The resistin level has the potential of becoming the new sedimentation rate, which can be used to measure inflammation in the body,” Moilanen says.
The obesity epidemic must be controlled
There are over two million overweight people in Finland. To be classed as overweight you must have a body-mass index (BMI) of 25 or over. The BMI threshold for obesity is 30, and there are over 650,000 such people in Finland. The health risks are quite significant in this latter group.
“Even in the short term, the obesity epidemic changes the spectrum of diseases and the treatments that patients need. Health care costs will also increase. If we cannot control the epidemic, it can lower average life expectancy, which has been rising so far,” Moilanen says.
The United States and the United Kingdom have already reacted to the epidemic. Obesity numbers have not declined, but the growth curve shows signs of flattening out in both countries.
The obesity problem cannot be solved by one simple pill because many physical, psychological and social aspects are involved, and hormonal regulation is also associated with obesity.
Moilanen thinks that the research results on obesity hormones are very inspiring new medical discoveries.
“Time will tell us how significant these findings are and whether some of them will lead to drug development. I am confident that we will eventually find answers to these questions.”
Obesity hormones control metabolism
- Adipokines are obesity hormones produced by the fatty tissue. Among other things, they regulate metabolism, appetite and insulin resistance.
- A hormone is a chemical transmitter that is produced by some tissue or organ of the body. Hormones spread throughout the body, so they also have an effect in places other than where they are produced.
- According to recent research findings, adipokines have properties that increase or regulate inflammation.
Searching for new innovations
- Eeva Moilanen’s research group in immuno-pharmacology studies inflammatory diseases and their mechanisms. The group’s aim is to find new drug targets and to develop drug prototypes.
- The group also tests disease models and is involved in projects that have discovered completely new drug molecules.
- The research group is based at the University of Tampere in Finland.
Text: Tiina Lankinen
Photographs: Jonne Renvall
Translation: Laura Tohka