When human muscle cells are exposed to leucine before insulin stimulation, there is an increase in the phosphorylation of a specific protein site (4EBP1 at Thr37/46), but this increase is not...

Pro

Against

Mechanism

Synthesis from 1 study

How it works

Leucine makes muscle cells more sensitive to insulin, causing a brief but stronger signal that turns on protein-building machinery. This signal fades quickly, so if you check at the wrong time, you might not see it—and it can vary from cell to cell.

Most probable mechanism

In Simple Terms

When leucine is present before insulin, it makes the muscle cell more responsive to insulin, causing a stronger and longer-lasting signal that turns on a protein-building switch. This switch briefly activates a molecule that tags another protein with a phosphate group, which tells the cell to start making more proteins. Because this activation is short-lived and depends on timing, it doesn't always show up if you check at just one moment, and it can vary between cells.

Causal chain

Leucine pre-incubation enhances the sensitivity of the insulin signaling cascade, increasing the magnitude and duration of AKT phosphorylation at Ser473

Verified by multiple studies

which leads to

Phosphorylated AKT activates mTORC1 through inhibition of TSC2 and activation of Rheb

Supported by evidence

which leads to

Activated mTORC1 directly phosphorylates 4EBP1 at Thr37/46, releasing its inhibition on translation initiation factors

Supported by evidence

which leads to

The phosphorylation of 4EBP1 is transient due to feedback mechanisms that rapidly deactivate mTORC1 and phosphatases that remove phosphate groups

Verified by multiple studies

Evidence from Studies

Supporting (1)

Community contributions welcome

Leucine modulates dynamic phosphorylation events in insulin signaling pathway and enhances insulin-dependent glycogen synthesis in human skeletal muscle cells

Cross-Sectional Study

In Vitro

2014 Mar 20

Contradicting (0)

Community contributions welcome

No contradicting evidence found

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Source Study

Leucine modulates dynamic phosphorylation events in insulin signaling pathway and enhances insulin-dependent glycogen synthesis in human skeletal muscle cells

Score: 7

DOI: 10.1186/1471-2121-15-9

Similar Assertions

In human muscle cells deprived of nutrients, adding 100 micromolar leucine before insulin increases the activation of key signaling proteins and boosts glycogen production by 50% compared to insulin alone.

77%

In human muscle cells, leucine by itself does not change the activity of AKT, GSK3β, or glycogen synthesis, but when insulin is present, it temporarily increases ERK1/2 phosphorylation, with the highest effect at 10 minutes and no effect remaining after 60 minutes.

77%

At a concentration of 100 micromolar, leucine produces the maximum possible increase in insulin-driven GSK3β phosphorylation and glycogen synthesis in human muscle cells; higher concentrations up to 400 micromolar do not produce a greater effect.

73%

Leucine, an amino acid, triggers a cellular pathway called mTOR that starts the production of muscle proteins. When carbohydrates are consumed at the same time, the resulting increase in insulin levels boosts this process.

73%