Nanoparticles as an invisible diet

Sep 28 2005

Utah State University researchers are in the early stages of scientifically tricking the body into eating less and finding a treatment for obesity without dangerous side effects.

“You could call it an invisible diet,” said Tim Gilbertson, Utah State biology professor “It’s really simple. This technology will help people to feel satisfied with a small serving of food instead of a large helping.”

The process involves nanoparticles, or microscopic medical devices, said Gilbertson.

A feeling of fullness is created by a smaller amount of food when the nanoparticles are inside the cells because the nanoparticles are made of the same fat molecules that are naturally in the body’s cells.

The lipid molecules are replicated in the laboratory and then directed toward specific fat cells in the body. In obesity treatment, the fat cells in the intestines are used.

“We’re trying to trick receptors into thinking they have fat when it’s actually not there,” said Gilbertson.

Although the research is in the early stages, Gilbertson’s team is encouraged by preliminary results and the technology’s success in other medical fields. Nanoparticle treatments are already used as treatments for some forms of cancer and cardiovascular disease.

“Our bodies, our taste buds, are trained to help us get the nutrients we need,” said Gilbertson. “For instance, our ability to taste sweet things helps us identify foods with carbohydrates. Our salty taste helps us find minerals. And our general aversion to bitter foods helps us avoid ingesting poisonous substances.

Gilbertson said, In recent years, scientists have made great strides in identifying molecules that explain how we identify those different things, but the general consensus was that fat had no taste.

“Early in my career, I asked the question, ‘If fat is the most nutritionally dense energy source we know of, shouldn’t we be able to taste it?’” he said.

Subsequent tests by Gilbertson showed that fat does in fact have a taste, but not just on specific subsets of cells as sweet and salty tastes do.

“We found that 90 percent of taste buds can detect fat, but instead of having a specific taste, we believe its main role is in enhancing existing flavors,” said Gilbertson. “Fat makes sweet foods taste more sweet and salty food more salty.

What’s more, Gilbertson found that fat receptors are not just located in the mouth but are found throughout the entire body. The job of the receptors, some of which are located in the small intestine, is to send chemicals to the brain that signal when we’ve ingested fat. In some people, these fat receptors are not as sensitive, causing these individuals to eat more fatty foods than someone who has more sensitive receptors, he said.

“Therefore, one approach is to fool our body’s fat sensors into thinking we’re eating fat by developing fat substitutes that target this particular receptor,” said Gilbertson. “The problem is that these receptors are in many places in the body, and we only want to target those that directly control food intake to avoid harmful side effects.”

One solution, said Gilbertson, is to develop nanoparticle technology that can find the fat receptors in specific sites only. The particles could deliver a drug to cause the cell to increase its release of feeding-related hormones, the chemical signals that are sent to the brain when food, in particular fat, is ingested. The goal, then, is for people to be satisfied with eating a lower fat diet. Gilbertson’s lab is working on identifying the drug that will speed up production of these satiety hormones.

Nanoparticle technology combines basic biology with advanced biomedical engineering tools. This is a completely novel approach to counteract dietary-induced obesity, Gilbertson said.

Unlike most conventional drugs that spread through the entire body and treat all cells indiscriminately, nanoparticles are tailored to only treat specific types of cells or tissues. This helps prevent the serious side effects often experienced with drugs, including nausea and hair loss from chemotherapy, heart attacks and strokes associated with osteoarthritis drugs like Vioxx, and heart valve damage occurring in patients who have taken Fen-Phen for obesity.

Measured in nanometers (one billionth of a meter), nanoparticles are small enough to slip through tiny openings in cell membranes. A special “target” chemical is attached to the nanoparticle, along with the treatment drug, and the chemical acts as a tiny escort, delivering the drug only to the specific cells that need it.