Obesity and overweight are among the biggest health challenges of the 21st century, according to the World Health Organization (WHO). Almost 60% of Germans are considered overweight, while 25% are obese. Moreover, being overweight often triggers severe secondary diseases such as diabetes, arteriosclerosis, or heart attacks.

Immunological processes determine the course of this disease. As part of a new study, a group of LMU researchers led by Dr. Susanne Stutte and Professor Barbara Walzog has shown that a high-caloric diet, even for a period of only three weeks, has drastic effects on the immune system.

"A particular kind of immune cells known as plasmacytoid dendritic cells (pDCs) begins to accumulate in the visceral adipose tissue," explains Stutte. This adipose tissue is located inside the abdomen and surrounds internal organs. With high caloric diet, small clusters of immune cells form tertiary lymphoid structures inside this fat, resulting in fatal immune responses.

"Now, these pDCs in visceral fat are in a constant state of alarm and release type-I interferon," explains Walzog. This interferon usually mediates the control of infections, but here it triggers the metabolic syndrome: the metabolism derails and inflammatory markers rise. When the migration of pDCs into the fat is blocked, weight gain is reduced and the metabolic condition improves considerably.

The results of this study, which was carried out in collaboration with Harvard Medical School in Boston, could now contribute to the development of new approaches toward a therapeutic intervention of the metabolic syndrome.