Hypothesis

We propose that the amplitude and frequency of glycemic excursions, as captured by continuous glucose monitoring (CGM), actively shape the selective autophagy hierarchy by modulating the phosphorylation state of specific autophagy receptors (SARs). High‑frequency spikes activate AMPK in a pulsatile manner, favoring phosphorylation of p62/SQSTM1 at Ser403 and OPTN at Ser177, which preferentially tags mitochondria for mitophagy. Conversely, prolonged hyperglycemia drives sustained mTORC1 inhibition and activates TBK1‑dependent phosphorylation of NDP52 and TAX1BP1, shifting cargo preference toward ER‑phagy and lipophagy. Thus, the temporal pattern of glucose—not just mean concentration—determines which organelle is cannibalized first, encoding a metabolic triage that influences cellular homeostasis and aging.

Mechanistic Rationale

1. AMPK pulsatility and SAR phosphorylation – Intermittent AMPK activation, mimicking post‑prandial glucose dips, promotes transient phosphorylation of p62 and OPTN, enhancing their affinity for ubiquitinated mitochondrial proteins [1][2].

2. Chronic hyperglycemia and TBK1‑dependent signaling – Elevated glucose sustains ROS production, activating TBK1, which phosphorylates NDP52 and TAX1BP1 at residues that increase binding to ER‑associated and lipid‑droplet ubiquitinated cargos [3][4].

3. Hierarchy shift – Under low GV, basal autophagy favors non‑selective bulk cargo; under high spike frequency, mitophagy spikes; under sustained elevation, ER‑phagy and lipophagy dominate. This predicts a measurable organelle‑specific flux signature in circulating extracellular vesicles or PBMCs.

Testable Predictions

• Individuals with high glycemic variability (GV > 15 % coefficient of variation) will show increased mitochondrial DNA efflux and elevated phospho‑p62 (Ser403) in monocytes after a mixed‑meal challenge, indicating heightened mitophagy.
• Those with prolonged hyperglycemia (time‑in‑range < 70 %) will exhibit elevated ER‑stress markers (e.g., phospho‑eIF2α) and increased lipid‑droplet associated protein perilipin‑2 in autophagosome isolates, reflecting ER‑phagy/lipophagy preference.
• Pharmacological dampening of glucose spikes (using acarbose) will normalize SAR phosphorylation patterns and restore the basal autophagy hierarchy, rescuing organelle turnover rates measured via Lysotracker flux assays.

Experimental Design

A crossover trial in 30 healthy volunteers: each participant receives three 24‑hour dietary protocols in random order—(i) low‑GV diet (high fiber, low GI), (ii) high‑GV diet (rapid‑acting carbs), (iii) hyperglycemic clamp (constant elevated glucose). Continuous glucose monitoring records GV metrics. Peripheral blood mononuclear cells are isolated at 0, 2, 4, and 6 h post‑start; autophagic flux is assessed by LC3‑II turnover with bafilomycin A1, while organelle‑specific cargo is measured by immunoblotting for phospho‑p62 (mitochondria), phospho‑NDP52 (ER), and perilipin‑2 (lipid droplets) within immunoprecipitated autophagosomes. Mixed‑effects models will test the interaction between GV metrics and SAR phosphorylation on organelle‑specific flux.

Falsifiability

If GV metrics fail to predict differential phosphorylation of SARs or organelle‑specific autophagy markers across the dietary conditions, the hypothesis is refuted. Conversely, a consistent direction‑specific relationship would support the claim that glucose dynamics encode a hierarchical cannibalism ritual that dictates which cellular components are prioritized for demolition.