1823-P: The Beta-Cell Secretagogue Glyceraldehyde Induces Mitochondrial Leak Respiration, Not OXPHOS

by sugaradmin



Introduction and Objective: Current beta cell glucose sensing models require that substrate limited mitochondria can respond to glucose by increasing OxPhos ATP synthesis to close KATP channels (Rutter & Sweet, Diabetes 2024). A primary argument supporting their model is that glyceraldehyde (GA) can increase both respiration and insulin release. Here we test the axiom that GA is an electron donor controlling OxPhos.Methods: Oxygen consumption was measured on a XFPro 96 in intact INS-1 cells pre-incubated in glucose free HEPES buffered KRB without (KRBH) or with (KRBHQ) 2 mM glutamine (n=6). Substrate and complex specific mitochondrial respiration (0.5mM ADP) was measured in situ after plasma membrane permeabilization (PMP Agilent, n=8) and metabolites were measured by LC-MS/MS.Results: 3 and 11mM glucose increased respiration from intact INS cells in KRBH, but 2mM DLGA did not. Rather, in KRBHQ, DLGA further stimulated respiration by 25±1% (P=4.8E-05). Succinate robustly increased Complex 2 respiration (1,063±50%) from mitochondria in situ, but 10 mM DLGA did not. Surprisingly, DLGA plus succinate robustly increased respiration (887±44%) with NADH oxidation ruled out with rotenone. Likewise, the mitochondrial sn-glycerol-3-phosphate (G3P) dehydrogenase (mG3PDH) substrate, G3P (a Q-cycle electron donor), increased respiration (234±23%), but enantiomers DGA, LGA, and DLGA did not. Both exogenous LGA and racemic DLGA further increased respiration (82±3 & 82±9%, P<0.1E-06) when added to G3P, while endogenous DGA (6%+3) did not. Antimycin A suppressed respiration from all substrates, while oligomycin sensitive respiration (i.e., OxPhos) was unaffected. GA generated glycerate produces NADH and was higher with DGA than with LGA (2,901±91 & 573±23%, P<0.1E-12) but respiration was insensitive to C1 inhibition by rotenone.Conclusion: GA induces respiration via increasing mitochondrial leak rather than OxPhos and does not support the substrate limited OxPhos models of GSIS as proposed by Rutter and Sweet.

Disclosure

R.L. Cardone: None. R. Kibbey: Consultant; Structure Therapeutics, Inc. X. Zhao: None.

Funding

R01DK127637



Source link