Obesity and diabetes can be treated or prevented by deleting the FLCN gene in the white adipocyte and including TFE3 gene, which helps in browning of the white fat cells.
Scientists in the Perelman School of Medicine at the University of Pennsylvania have said that obesity can be treated sooner with signaling pathways in fat cells. About 36 percent of American adults are considered obese and nearly 10 percent have type 2 diabetes.
Fat cells also called as white adipocytes, stuff themselves with fat molecules to store up energy and their overloading leads to obesity and related conditions, including diabetes.
The signaling pathway discovered by the Penn scientists activates a "browning program" in white adipocytes, making them more like energy-burning brown adipocytes.
"It's conceivable that one would be able to target this pathway with a drug, to push white fat to become brown fat and thereby treat obesity," said the study's senior author Zoltan P. Arany, MD, PhD, an associate professor of Cardiovascular Medicine.
Arany and colleagues found that the browning program in white adipocytes is normally suppressed by a protein called FLCN. It performs this function in cooperation with a major cellular signaling hub, a protein complex known as mTOR.
The FLCN-mTOR interaction keeps the browning program switched off by preventing a protein called TFE3 from entering the cell nucleus.
The scientists showed that deleting the FLCN gene in the white adipocytes of mice allows TFE3 to migrate into the nucleus, where it binds to DNA and activates a key regulator of cellular metabolism called PGC-1β. It then turns on the set of genes for the browning program.
In the mice in which FLCN was deleted, white adipocytes became visibly browner as they produced more mitochondria which are tiny, oxygen reactors that supply chemical energy within cells and convert energy to heat in brown adipocytes.
In several other ways, including their altered cellular structures, mitochondria's higher capacity for consuming oxygen and their distinctive pattern of gene expression, the cells became more like brown adipocytes.
Arany and his team showed that they could reproduce this browning effect merely by forcing the overexpression of PGC-1β in the white adipocytes of mice.
"In principle, a drug that boosts the activity of PGC-1β or some of its target genes might serve as a therapeutic activator of the browning program to curb obesity and treat or prevent diabetes," Arany said.
Aside from its potential medical relevance, the discovery is an important advance in understanding cell biology.
"Cellular metabolism is regulated by major signaling pathways and with this study we're linking two of these major pathways, the mTOR and the PGC-1 pathways," Arany said. "The connection between them hasn't been well understood, but here we're clarifying it significantly."
Arany and his team plan further studies of the pathway and its relation to other mTOR signaling pathways.