New York, November 16: Some types of belly fat accumulates around organs as animals age, contributing to increased inflammation and metabolic decline, according to a study which may offer new ways to tackle age related diseases. The researchers, including Indian origin scientist Vishwa Deep Dixit from Yale University in the US, said the human body's ability to generate energy by burning the belly fat reduces with age.

Dixit's lab had earlier found that the immune cells needed for the fat-burning process -- called macrophages -- were still active, but their overall numbers declined as belly fat increased with ageing. In the current study, the researchers found that Adipose B cells in belly fat proliferated as animals aged, contributing to increased inflammation and metabolic decline. Does Black Coffee Burn Belly Fat? How Caffeine Can Help You Shed Those Extra Kilos.

"These adipose B cells are a unique source of inflammation," Dixit said. "Normally the B cells produce antibodies, and defend against infection. But with ageing, the increased adipose B cells become dysfunctional, contributing to metabolic disease," he added.

Dixit added that some B cells expanded as needed to protect the body from infection, and contracted to their natural state. But with ageing, he said, they don't contract in the belly fat. "This predisposes an animal to diabetes and metabolic dysfunction like inability to burn fat," he said.

Dixit suspects that an increased human life expectancy may be behind this - pushing the body's cells beyond the limits imposed by evolution. "Several mechanisms in the body are not selected for longevity," he said. The researchers also discovered that adipose B cells expand by receiving signals from nearby macrophages.

They found that the expansion process could be reversed to protect against age-induced decline in metabolic health by reducing the macrophage signal and by removing adipose B cells. Dixit theorised that some drugs could be repurposed to target the dysfunctional adipose B cells for improved health outcomes.

Some immunotherapy drugs that neutralize B cells -- used in certain cancers -- could be tested for their effectiveness in reducing metabolic disease in elderly people, Dixit said.