Excess body fat increases the risk of depression

August 27, 2019

Science Daily/Aarhus University

Carrying ten kilograms of excess body fat increases the risk of depression by seventeen per cent. The more fat, the greater the probability of developing depression. This is the main conclusion of a new study carried out by researchers from Aarhus University and Aarhus University Hospital, Denmark.

"Our study also indicated that the location of the fat on the body makes no difference to the risk of depression. This suggests that it is the psychological consequences of being overweight or obese which lead to the increased risk of depression, and not the direct biological effect of the fat. If the opposite was true we would have seen that fat located centrally on the body increased the risk the most, as it has the most damaging effect in biological terms," says the study's last author Dr. Søren Dinesen Østergaard.

He is professor at the Department of Clinical Medicine at Aarhus University and affiliated with the Department of Affective Disorders at Aarhus University Hospital.

Prior studies in the field have predominantly used Body Mass Index (BMI) to measure obesity. BMI is calculated solely on the basis of body weight and height and is therefore a fairly crude measure, that does not, for example, take build and muscle mass into account.

"BMI is an inaccurate way of measuring overweight and obesity. Many elite athletes with a large muscle mass and a low body fat mass will have a BMI above 25, which is classified as overweight according to the common definition. This obviously doesn't make much sense. Therefore, one of the strengths of our study is that we've been able to zoom in and look at the specific relationship between the amount of body fat and the risk of depression," explains Dr. Østergaard.

In the study, which has been published in the journal Translational Psychiatry, the researchers have analysed data from two large genetic data sets: the UK Biobank, which contains data on the correlation between genetic variants and physical measurements (including body fat mass distributed around parts of the body); and the Psychiatric Genomics Consortium, which contains information on the correlation between genetic variants and depression.

Dr. Østergaard also highlights his research group's choice of the 'Mendelian randomization' method as the main reason why the study was successful. He also emphasises that the findings are particularly significant in light of the fact that almost 40 per cent of the world's adult population is overweight.

"In addition to the known physical consequences of obesity such as diabetes and cardiovascular disease, there is also a significant and now well-documented psychological component, which needs to be dealt with as well. This is yet another argument for resolving the obesity epidemic," he says, before emphasising that it is important to have a balanced approach to the issue:

"As it appears to be the psychological consequences of obesity, such as a negative body image and low self-esteem that is the main driving force behind the increased risk of depression, society's efforts to combat obesity must not stigmatise, as this will probably increase the risk of depression even further. It is important to bear this in mind so we can avoid doing more harm than good in the effort to curb the obesity epidemic," says Dr. Østergaard.

FACTS ABOUT MENDELIAN RANDOMIZATION:

Mendelian randomization (named after the Austrian monk Gregor Mendel, who was the father of modern genetics) is a method which in recent years has helped researchers to overcome a major challenge associated with observational studies -- namely that of making causal inference. In observational studies researchers often find correlations between two conditions -- e.g. between obesity and depression -- where it is difficult, or rather impossible, to determine whether there is indeed a causal effect going from obesity to depression -- or vice versa. Mendelian randomization may solve this challenge.

Mendelian randomization can be described as nature's version of the randomised controlled trials that are carried out when testing whether a new drug has the desired (causal) effect in the treatment of a disease. In the clinical trials of drugs, lots are drawn to determine whether individual participants will receive the active drug or a placebo, without them knowing which treatment they have been assigned to. Instead, Mendelian randomization takes advantage of the fact that a completely natural randomization takes place during the formation of the sex cells (egg cells and sperm cells), which represent the origin of all human beings. When sex cells are formed, the parents' genetic variants -- including those that give rise to increased body fat- are randomly distributed. Therefore, some individuals will have received many of these variants and others less. In the study in question, the researchers have utilised this natural and random source of variation to determine whether people who have received many genetic variants for increased body fat have an increased risk of suffering depression.

THE RESEARCH RESULT -- MORE INFORMATION

Genetic epidemiological study utilising data from the UK Biobank (with information on the association between genetic variants and fat mass based on a study of 330,000 people) and the Psychiatric Genomics Consortium (with information on the association between genetic variants and depression based on a study of 135,000 people with depression and 345,000 control subjects).

https://www.sciencedaily.com/releases/2019/08/190827095100.htm

Depression, obesity, chronic pain could be treated by targeting the same key protein

April 1, 2019

Science Daily/American Chemical Society

Major depression, obesity and chronic pain are all linked to the effects of one protein, called "FK506-binding protein 51," or FKBP51. Until now, efforts to inhibit this target have been hampered by the difficulty of finding something specific enough to do the job and not affect similar proteins. Now a research group has developed a highly selective compound that can effectively block FKBP51 in mice, relieving chronic pain and having positive effects on diet-induced obesity and mood. The new compound also could have applications in alcoholism and brain cancer.

The researchers will present their results today at the American Chemical Society (ACS) Spring 2019 National Meeting & Exposition.

"The FKBP51 protein plays an important role in depression, obesity, diabetes and chronic pain states," says Felix Hausch, Ph.D., the project's principal investigator. "We developed the first highly potent, highly selective FKBP51 inhibitor, called SAFit2, which is now being tested in mice. Inhibition of FKBP51 could thus be a new therapeutic option to treat all of these conditions."

Hausch, who is at the Technical University of Darmstadt, started the project when studies were published linking the protein to depression. "I was intrigued by the peculiar regulatory role it seemed to play in cells," he says. "And there was a known natural product that could serve as a starting point. Collectively, this looked like an interesting protein to work on."

FKBP51 is expressed in multiple places throughout the body, such as the brain, skeletal muscle tissue and fat. It also has multiple effects. For example, the protein can restrict the uptake of glucose and the browning of fat, so that the body stores fat instead of burning it. It also affects stress responses. So, Hausch and his colleagues figured that blocking this protein could be the key to developing drugs to treat a variety of conditions.

But FKBP51 looks a lot like its closest protein cousin, FKBP52. "These two proteins are very similar in structure, but they are doing opposing things in cells," Hausch says. "We have this yin-yang situation. Selectivity between these two proteins is thought to be crucial, but this is hard to achieve since the two proteins are so similar. We discovered that FKBP51 can change its shape in a way that FKBP52 can't, and this allowed the development of highly selective inhibitors."

The researchers have now used nuclear magnetic resonance techniques to detect a previously hidden binding site in FKBP51. The approach could help other researchers identify similar "cryptic" binding sites in challenging drug targets in the future, Hausch says.

His team is now testing SAFit2, the lead FKBP51 inhibitor they developed from these studies, in animals. "It indeed helps mice cope better in stressful situations," Hausch says. In mice, SAFit2 reduced stress hormone levels, promoted more active stress coping, was synergistic with antidepressants, protected against weight gain, helped normalize glucose levels and reduced pain in three animal models.

According to Hausch, much more needs to be done to get FKBP1 inhibitors to the point where they could be used as a drug molecule in human testing. In the meantime, the team is also exploring FKBP51 inhibitors in other applications. So far, the group has conducted a number of mouse studies on the involvement of FKBP51 in alcoholism, but results are still preliminary. In addition, Hausch points out that certain types of glioblastoma tumors overexpress FKBP51. He hopes that this result indicates FKBP51 inhibitors could be used in cancer treatment, when patients' tumors mutate beyond current drugs' capacity to treat them. "We may be able to resensitize them to different types of chemotherapy using these specific inhibitors," he says.

https://www.sciencedaily.com/releases/2019/04/190401075208.htm