Interesting!
Gerald Shulman has done similar with fat flux in muscle cells, using fMRI. Human cells, in vivo. Also mice. He was looking to see how insulin resistance occurs - which he figured out. It's diglycerides (DAGs), which are, essentially triglycerides (TAGs) with a FA on the backbone replaced with a hydroxyl. One isomer blocks the cascade that starts with insulin hitting the cell membrane and ends with glucose transporters (GLUT4 in this case) poked through the cell wall.
In humans that initial insulin resistance in skeletal (striated) muscle drives a system-wide cascade of insulin resistance.
He's found he can induce IR in skeletal muscle cells by simultaneous high serum TAGs and glucose. Also, from Robert Lustig’s work, sucrose or HFCs do this naturally. Think about that the next time you drink a soda or fruit juice.
fMRI is perfect for this kind of work as MRI 'sees' hydrogen atoms - and can tell the difference between, say, water (contains H) and fat (also contains H), as they emit at different frequencies when the magnetic field is momentarily countered (the 'bang' you hear if you're in a MRI machine). I find this interesting on many levels, starting with just the physics of MRI - and ending with a critical human endocrine system.
For anyone else interested, check Peter Attia's interview with Shulman as a starting point.
Oh, and he’s discovered that, short term, exercise can trigger that same cascade that ends with GLUT4 receptors soaking up glucose through the cell walls, and posits that long term exercise can undo the DAG blockage.
Finally, I’d point out that, in the presence of insulin, fat cells take in glucose and turn it into fatty acids, convert that into TAGs for storage alongside the serum TAGs that are de-esterified, transported in, re-esterified, stored. So fat cells are hoovering up the glucose the muscle cells need — but can’t absorb because of DAG interference. The glucose has to go somewhere. The muscles are our primary storage organ for it.
I’ve no clue how that might be examined in fruit flies. But one thing is very clear: the route to decreasing fat in fat cells leads through fixing IR in muscle cells.
