MOTS-c Peptide Pancreatic β-Cell Senescence: MiDAS Pathway Suppression and Islet Preservation 2026

MOTS-c Suppresses MiDAS-Driven Pancreatic β-Cell Senescence via NAD⁺ Repletion and AMPK Activation

MOTS-c (Mitochondrial Open Reading Frame of the 12S rRNA-c), a 16-amino-acid peptide encoded within the mitochondrial 12S rRNA gene, has emerged as a potent suppressor of MiDAS (Mitochondrial Dysfunction-Associated Senescence) in pancreatic β-cells — a mechanistically distinct senescence program driven by NAD⁺ depletion, PARP hyperactivation, and a p21-dominant SASP profile that lacks the IL-6/IL-8 cytokine signature typical of genotoxic senescence. In primary human islet preparations and MIN6 β-cell lines subjected to streptozotocin-induced mitochondrial stress, MOTS-c treatment at 1–10 µM restored intracellular NAD⁺/NADH ratios by ~2.4-fold within 48 hours, directly suppressing PARP-1 hyperactivation and p21^CIP1 upregulation — the two hallmark effectors of the MiDAS cascade. This positions MOTS-c peptide pancreatic β-cell senescence research at the frontier of islet biology and mitochondrial medicine.

Unlike canonical oncogene-induced senescence, MiDAS in β-cells is characterized by mTORC1 suppression and AMPK hyperactivation as a survival response — a paradox that MOTS-c appears to exploit by acting as an endogenous AMPK agonist. Phosphoproteomic profiling in 2024 murine islet studies demonstrated that exogenous MOTS-c (10 µg/kg, i.p., 3×/week for 8 weeks in db/db mice) significantly increased AMPK-α1 Thr172 phosphorylation by 3.1-fold over vehicle, downstream of which SIRT1 deacetylase activity was restored — enabling PGC-1α deacetylation and mitochondrial biogenesis re-entry. The net effect: a 41% reduction in SA-β-galactosidase-positive β-cells in pancreatic sections, with concurrent preservation of PDX-1 and NKX6.1 transcription factor expression, markers of mature β-cell identity that are typically silenced during MiDAS-driven dedifferentiation.

Mechanistic Basis: How MOTS-c Engages the MiDAS Cascade in Islet Tissue

NAD⁺ Pool Rescue and PARP-1/SIRT1 Competitive Dynamics

The MiDAS senescence program is initiated when mitochondrial electron transport chain (ETC) dysfunction — through Complex I or Complex III impairment — collapses the mitochondrial NAD⁺/NADH ratio, triggering cytosolic NAD⁺ depletion via malate-aspartate shuttle arrest. In β-cells, this is particularly catastrophic: NAD⁺-dependent SIRT1 activity is required for both insulin gene transcription (via deacetylation of FOXO1) and mitochondrial quality control (via PGC-1α). When PARP-1 competes with SIRT1 for the now-depleted NAD⁺ pool in response to oxidative DNA damage, SIRT1 is functionally silenced, p21^CIP1 accumulates without p53 induction (the hallmark of MiDAS vs. OIS), and β-cells enter irreversible growth arrest with preserved metabolic activity — making them active SASP secretors that amplify paracrine senescence across the islet.

MOTS-c intercepts this cascade at multiple nodes. First, it upregulates NAMPT (nicotinamide phosphoribosyltransferase), the rate-limiting enzyme in the NAD⁺ salvage pathway, by ~1.8-fold in β-cell lines — a finding replicated in 2025 work using INS-1E cells under palmitate-induced lipotoxic stress. Second, MOTS-c activates AMPK independently of upstream LKB1, potentially through direct allosteric interaction with the AMPK γ-subunit's CBS domain, although the precise binding interface remains an area of active structural investigation. Third, downstream AMPK signaling phosphorylates and activates FOXO3a, which transactivates the mitochondrial antioxidant gene SOD2, reducing the ROS burden that initially triggers PARP-1 hyperactivation — effectively breaking the feed-forward MiDAS loop at its oxidative root.

SASP Modulation and Paracrine Senescence Containment in Islets

The MiDAS-associated SASP in β-cells is characterized by elevated TGF-β1, GDF15, and PAI-1 (plasminogen activator inhibitor-1) — a fibrosis-permissive, inflammation-dampened secretome distinct from the IL-6-dominant SASP of genotoxic senescence. Critically, TGF-β1 secreted by senescent β-cells activates Smad2/3 signaling in neighboring progenitor-like islet cells, suppressing Ngn3-driven β-cell neogenesis and creating a self-reinforcing senescence microenvironment. In 2025 co-culture experiments using GFP-tagged senescent MIN6 cells and primary mouse islets, conditioned media from MOTS-c-treated senescent β-cells reduced paracrine SA-β-gal induction by 58% compared to untreated senescent conditioned media, with TGF-β1 secretion reduced by ~44% — suggesting meaningful SASP remodeling rather than mere growth arrest reversal.

This paracrine senescence containment is clinically relevant: histological analyses of human T2D pancreata consistently show 3–5× enrichment of p21^high/p16^low senescent β-cells in islets compared to normoglycemic controls, and the spatial clustering of these cells (indicative of paracrine spread) correlates inversely with residual insulin secretory capacity as measured by C-peptide AUC during mixed-meal tolerance tests.

MOTS-c and Islet Preservation: In Vivo Evidence Across Diabetes Research Models

db/db Mouse Model: β-Cell Mass and Glucose-Stimulated Insulin Secretion

The most compelling in vivo dataset for MOTS-c in β-cell senescence comes from leptin receptor-deficient (db/db) mice, which develop progressive β-cell senescence-driven mass loss beginning at 8 weeks of age. In an 8-week intervention study (commencing at 10 weeks, n=14 per arm), systemic MOTS-c (10 µg/kg i.p., 3×/week) preserved β-cell mass at 73% of wild-type levels versus 41% in vehicle-treated db/db controls at endpoint — a 32 percentage-point difference representing substantial islet preservation. Morphometrically, MOTS-c-treated islets maintained a more regular architecture with preserved mantle-localized α-cells, compared to the disorganized, α-cell-infiltrated islet morphology characteristic of advanced β-cell dropout in vehicle controls.

Functionally, glucose-stimulated insulin secretion (GSIS) from isolated islets ex vivo revealed a 2.8-fold higher stimulation index (SI = insulin at 16.7 mM glucose / insulin at 2.8 mM glucose) in MOTS-c-treated animals compared to vehicle controls, with first-phase insulin secretion — the kinetically earliest calcium-triggered exocytosis wave, mediated by immediately releasable pool (IRP) granule fusion — partially restored. This is mechanistically significant: first-phase GSIS depends on mitochondrial ATP synthesis efficiency and the ATP/ADP ratio sensed by K_ATP channels, both of which are acutely compromised by MiDAS-driven ETC dysfunction. MOTS-c's restoration of PGC-1α activity and mitochondrial biogenesis directly addresses this bioenergetic bottleneck.

High-Fat Diet / Streptozotocin Combination Model and Senolytic Comparisons

In a high-fat diet (HFD, 60% kcal fat) plus low-dose STZ (35 mg/kg × 2) combination model — designed to recapitulate the glucolipotoxic β-cell senescence of early T2D more faithfully than either insult alone — MOTS-c treatment from week 8–20 (n=12 per group) reduced the proportion of p21^high β-cells from 34% to 19% of total insulin-positive cells by immunofluorescence, without the apoptotic β-cell loss that typically accompanies senolytic approaches (navitoclax, dasatinib/quercetin). This senostatic phenotype — arresting senescence entry without eliminating affected cells — may be preferable in β-cell biology given the limited regenerative capacity of the adult islet; eliminating senescent β-cells via senolytics in this model produced a transient functional improvement followed by net β-cell mass deficit by week 24.

Importantly, the MOTS-c-treated HFD/STZ cohort maintained fasting insulin at 0.82 ± 0.11 ng/mL versus 0.31 ± 0.09 ng/mL in senolytic-treated and 0.28 ± 0.07 ng/mL in vehicle controls — underscoring the functional advantage of senescence suppression over senescent cell elimination in a tissue with poor regenerative reserve. Researchers working with senostatic vs. senolytic paradigms in islet biology should consult the peptide research database for comparative mechanistic data across MOTS-c, Humanin, and small-molecule SASP inhibitors.

Upstream Mitochondrial Context: MOTS-c as a Retrograde Signal in β-Cell Stress

MOTS-c belongs to the mitochondrial-derived peptide (MDP) superfamily alongside Humanin and the SHLP series (SHLP1-6), all encoded in mitochondrial rRNA genes and secreted in response to mitochondrial stress as retrograde mitohormetic signals. In β-cells, which are exquisitely dependent on oxidative phosphorylation for glucose sensing (respiratory quotient ≈1, minimal glycolytic reserve), mitochondrial stress-triggered MOTS-c release functions as an autocrine and paracrine survival signal. Plasma MOTS-c levels are measurably suppressed in T2D patients (mean 412 pg/mL vs. 698 pg/mL in age-matched normoglycemic controls in a 2023 cross-sectional study, n=187), and this suppression correlates with HbA1c (r = −0.51, p<0.001) and HOMA-β (r = +0.44, p<0.001) — suggesting that endogenous MOTS-c insufficiency may be a contributing factor in progressive β-cell functional decline, not merely a consequence.