Autophagy & Lysosomal Degradation Kinetics: Extended Fasting Biomarkers, LC3-II Lipidation, and Cellular Rejuvenation

The Cellular Recycling Machinery of Fasting

Awarded the Nobel Prize in Physiology or Medicine in 2016 (Dr. Yoshinori Ohsumi), Autophagy ("Self-Eating") is the evolutionary conserved process by which cells deconstruct damaged organelles, misfolded protein aggregates, and intracellular pathogens inside specialized lysosomes to recycle amino acids and fuel cellular rejuvenation.

In this guide, we examine the molecular switches of mTORC1 and AMPK, outline the biological timeline of autophagy during fasting intervals, and track fasting windows using our Intermittent Fasting Tracker.

1. Molecular Signaling: The mTORC1 vs. AMPK Switch

1. Inhibition of mTORC1 (Mechanistic Target of Rapamycin):

1. AMPK Activation:

1. LC3-I to LC3-II Lipidation:

2. Fasting Timelines & Physiological Milestones

• 12 Hours (Glycogen Depletion): Liver glycogen drops by 50%; basal insulin falls.
• 14–16 Hours (Autophagy Induction): AMPK elevates; initial hepatic and muscular autophagic recycling begins.
• 18–24 Hours (Deep Cellular Cleansing): Ketone production rises; systemic autophagosome formation peaks.

3. References & Academic Citations

• Mizushima, N., & Komatsu, M. (2011). Autophagy: renovation of cells and tissues. Cell, 147(4), 728-741. [PubMed: 22078875]
• Madeo, F., et al. (2015). Essential role for autophagy in life extension by caloric restriction or dietary restriction. Cell Metabolism, 21(2), 224-238.