In older adults with insulin resistance, levels of a specific protein called IP6K1 in the blood and muscles are lower after consuming whey protein, compared to younger adults. These lower levels are...
Mechanism
Synthesis from 1 study
After eating protein or exercising, older adults don't turn down a specific enzyme the way younger people do, and this keeps a key signal from activating. As a result, muscle cells can't pull in amino acids effectively or build new proteins, even when insulin is high. This explains why older adults...
Most probable mechanism
In older adults, the body doesn't reduce a specific enzyme called IP6K1 properly after eating protein or exercising, which keeps a key signaling protein (Akt) from turning on fully. This prevents the cell from taking in amino acids efficiently and building new muscle proteins, even when insulin levels are high. Younger people reduce this enzyme after eating, which lets amino acids enter muscle cells and triggers protein synthesis, but older adults lose this ability, leading to poor nutrient use.
In older adults, muscle and plasma levels of IP6K1 remain elevated or fail to decrease after protein ingestion and resistance exercise, unlike in younger individuals where IP6K1 declines.
Persistently high IP6K1 generates elevated levels of IP7, which binds to the PH domain of Akt and blocks its movement to the cell membrane.
Blocked Akt translocation prevents its phosphorylation at Thr308 by PDK1, reducing downstream activation of the mTORC1 pathway.
Impaired mTORC1 signaling reduces phosphorylation of 4E-BP1, limiting the release of eIF4E and suppressing the initiation of mRNA translation for muscle protein synthesis.
Reduced translation initiation and impaired amino acid transporter (LAT1) upregulation decrease the rate of phenylalanine disposal, indicating diminished amino acid uptake and utilization by skeletal muscle.
Evidence from Studies
Supporting (1)
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Inositol hexakisphosphate kinase 1 is implicated in the insulin response to protein ingestion in older adults
Contradicting (0)
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