Hypothesis

Chronic sleep fragmentation eliminates a sleep‑dependent autophagy flux that normally triages misfolded proteins and nascent IAPP oligomers in beta cells, converting a protective clearance window into a permissive period for amyloid‑seeded ER stress.

Mechanistic Rationale

• Circadian autophagy gating: In neurons, autophagosome formation peaks during wakefulness and lysosomal degradation aligns with sleep‑linked glymphatic efflux (1). Parallel circadian regulation of ATG transcription factors (e.g., TFEB, FOXO1) has been documented in liver and muscle (2). We propose that pancreatic beta cells inherit this rhythm, with LC3‑II conversion rising during the active phase and lysosomal acidification peaking during the rest phase.
• Sleep fragmentation disrupts lysosomal signaling: Fragmented sleep blunts melatonin and glucocorticoid rhythms, attenuating TFEB nuclear translocation (3). Consequently, autophagosomes generated during wakefulness fail to fuse with lysosomes, leading to cytosolic accumulation of p62‑positive inclusions.
• IAPP oligomer handling: Newly synthesized IAPP is prone to form transient oligomers that are normally captured by autophagosomes and degraded (4). When autophagic flux is stalled, these oligomers seed extracellular amyloid deposits, triggering NLRP3 inflammasome activation and chronic ER stress (BiP/CHOP up).
• Feedback amplification: ER stress further suppresses autophagy via PERK‑eIF2α‑ATF4 signaling, creating a vicious cycle that accelerates beta‑cell dedifferentiation and senescence (p16^INK4a rise).

Testable Predictions

1. In vivo: Mice subjected to chronic sleep fragmentation (e.g., gentle handling every 2 min during the rest phase) will show reduced LC3‑II/LC3‑I ratio and increased p62 in isolated islets at ZT6 (mid‑rest) compared with ad‑liquid‑sleep controls, while total autophagosome number (GFP‑LC3 puncta) will be elevated.
2. Pharmacologic rescue: Nightly administration of a TFEB activator (e.g., trehalose or small‑molecule CPT‑1) during the rest phase will restore lysosomal flux, decrease intracellular IAPP oligomer levels (measured by FRET‑based sensor), and attenuate glucose‑stimulated insulin secretion decline over 12 weeks.
3. Human relevance: Shift workers with documented sleep fragmentation will exhibit higher plasma exosomal p62 and lower LC3‑II in isolated peripheral blood mononuclear cells‑derived autophagy flux assays, correlating with elevated serum IAPP autoantibodies and worsened HOMA‑β.

Falsifiability

If sleep fragmentation does not alter the circadian pattern of autophagic flux in beta cells (i.e., LC3‑II turnover remains unchanged) or if enhancing lysosomal activity fails to mitigate IAPP aggregation and beta‑cell dysfunction, the hypothesis would be refuted.

Broader Implication

Positioning sleep‑dependent autophagy as a nightly "audit" that decides which protein conformations persist reframes sleep loss not as a passive risk factor but as an active editor of proteostatic identity, linking metabolic aging to the same triage logic that governs neuronal survival.

References

[1] https://elifesciences.org/articles/64140 [2] https://www.oaepublish.com/articles/and.2021.10 [3] https://gethealthspan.com/science/article/glymphatic-system-autophagy-neurodegenerative-disease-prevention [4] https://pmc.ncbi.nlm.nih.gov/articles/PMC2734275/