Some others in the field are taking a wait-and-see stance, as obesity is a complex disorder. Among them is Richard Locksley, a professor at the University of California, San Francisco, who studies the same kinds of immune cells.
“It’s early days, but it’s interesting and plausible,” he said.
Measurements revealed that the animals’ weight loss was not the result of burning calories any faster or eating less food. Photo: Getty Images
The Penn scientists stimulated the mouse immune cells by treating them with a type of cytokine – from the same family of proteins involved in a harmful inflammatory overreaction to Covid-19, called a “cytokine storm”.
The scientists coaxed the animals to produce the cytokine by injecting them with a viral vector, loaded with genetic instructions to make the protein – much like the Covid-19 vaccine made by Johnson & Johnson.
If the concept were to be explored in people, researchers would probably try to achieve the same goal – ramping up production of this cytokine, called TSLP – by administering a drug instead of genetic instructions, he said.
Researchers are already testing drugs that accomplish the opposite objective (interfering with TSLP) as a possible treatment for atopic dermatitis. Commonly called eczema, the skin condition is triggered by an overreaction by the immune system.
Ramping up TSLP, on the other hand, would have to be done carefully, lest it result in an inappropriate immune response. Kambayashi already is laying the groundwork for follow-up studies in people.
Among the remaining questions is just how the cytokine results in the excess secretion of sebum. The researchers found that TSLP causes certain kinds of immune T-cells to move to the sebaceous glands, which somehow results in more secretions.
Ruth Choa is a graduate student who worked with Kambayashi on the experiments.
No matter the outcome of these studies, Kambayashi said that in hindsight, it makes sense that obesity might be addressed via the immune system.
As physicians have reminded us during the Covid-19 pandemic, obesity is often accompanied by a chronic level of immune-related inflammation. Excess adipose (body fat) tissue acts as a type of “organ”, releasing hormones and other chemicals that place the body in a chronic state of low-level stress, placing the person at higher risk in the event of infection.
Still, the weight loss in the mice was a surprise, to the point Kambayashi thought something must have gone wrong. “I thought they were sick, that they just weren’t eating,” he said.
Richard Locksley, a professor at the University of California, San Francisco.
But in fact, they were eating more than mice in a control group, which had not been treated with the cytokine.
The key clue came with a curious phenomenon that Kambayashi and others had ignored in the past: mice treated with TSLP were known to develop a shiny coat of fur.
He and Choa noticed that the same was true with these mice. So they shaved the animals’ fur, analysed it and discovered it was rich in calorie-dense, fatty molecules.
Would humans sign up for that kind of treatment, knowing it would increase the secretion of oily fats through the skin? Among possible drawbacks: excess sebum is associated with the teenage scourge of acne.
Still, with obesity among the leading health problems globally, millions remain eager to try new solutions. Kambayashi says he’s determined to give them the chance.