Bioengineers visualize fat storage in fruit flies

For the first time, researchers have visually monitored, in high resolution, the timing and location of fat storage in intact fruit fly cells. The new optical imaging tool from the lab of bioengineering professor Lingyan Shi at the University of California, San Diego is already being used to unravel the oft-discussed, but mysterious, links between diet and things like obesity. , diabetes and aging. UC San Diego Jacobs School of Engineering is published in the journal aging cell.

The optical microscopy platform developed by bioengineers at UC San Diego is unique. It allows researchers to visually track, in high resolution in fat cells, how specific dietary changes affect the way flies convert their food’s energy into fat. The tool also allows researchers to monitor the reverse process of turning fat into energy. Additionally, researchers can now visually monitor changes in size in individual “containers” of fat storage in the class of fruit fly cells that are analogous to mammalian adipose (adipose) cells.

In the new journal of aging cell, researchers demonstrated the ability to visually track changes in fat (lipid) metabolism in flies after they were subjected to a wide range of different diets. The diets included low-calorie diets, high-protein diets, and diets containing two, four times, and ten times more sugar than a standard diet.

“With our new optical microscopy system, we can see both where and when fat is stored and taken out of storage,” said Shi, professor of bioengineering at UC San Diego, who is the lead author. corresponding to the new article. “This is the first imaging technology capable of visualizing high-resolution fat metabolism in space and time within individual fat cells. changes.”

“Interest in optimizing human diets is intense,” Shi continued. “People want answers to questions like, ‘What are the best diets to slow aging? What are the best diets to lose weight? What are the best diets to extend lifespan?’ I don’t have answers to these questions yet, but in my lab we are developing new technologies that bring us closer to answering some of the big food questions.”

In the new work of aging cellfor example, researchers report a new way to answer questions such as:

To what extent does a specific diet, such as a high-protein diet, a high-sugar diet, or a low-calorie diet, alter the process by which a fruit fly converts energy from food to fat? And how do these same diets affect the process of turning fat into energy by a fruit fly?

“We developed this tool to help us unravel the relationships between diet and phenomena like obesity, diabetes, aging and longevity,” Shi said.

Tracking the size of fat droplets in intact fruit fly cells is an example of what is possible with the new visualization platform.

“Droplet size is a way to track how much stored fat is being ‘turned over’ or converted back into energy. It’s an important aspect of lipid metabolism, and we now have a tool that allows us to track changes size of specific lipid droplets in individual fruit fly cells,” said Yajuan Li, MD. PhD, who is a postdoctoral researcher at UC San Diego’s Shi lab and first author of the paper in aging cell.

heavy water

The new visualization platform builds on some of Shi’s earlier work using a variation of ordinary water, called heavy water or (D2O). Heavy water is literally heavier than regular water. Heavy water molecules contain an oxygen atom like ordinary water. But instead of the pair of hydrogen atoms – the “H2” in “H20” – heavy water contains a pair of heavier deuterium atoms.

Like “normal” water, heavy water incorporates freely into the cells of living organisms. So when researchers feed heavy water to a fruit fly, and that fruit fly begins to convert energy from its food into fat molecules to store, some of those fat molecules contain deuterium. In this way, the prevalence of deuterium atoms in lipids stored in the fat cells of fruit flies provides a means of measuring the amount of fat stored by the fly.

By changing a fly’s diet at the same time you introduce heavy water, you have a way to monitor how the diet changes lipid turnover. More details on how the system works can be found in this 2021 profile, in which Shi said, “When we develop a new technology, a new tool, it will definitely inspire us to ask new biological questions.”

When it comes to understanding the links between diet composition and lipid metabolism, new biological questions are leading researchers back to some of the oldest and most intriguing questions about the links between diet and fat. obesity, diabetes, aging and longevity.

NIH, Grant/Award Number: U54 pilot grant 2U54CA132378; Jacobs School of Engineering, University of California San Diego; UC San Diego Hellman Fellow Award

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