Beyond Thr172 phosphorylation: subunit-selective, spatial, and post-translational AMPK signaling in diabetic cardiomyopathy

AMP-activated protein kinase (AMPK) is widely examined in diabetic cardiomyopathy (DCM) through total protein abundance and activation-loop phosphorylation, typically reported as p -AMPK Thr172 . Yet these measurements cannot identify the active αβγ heterotrimer, cellular source, intracellular location, or regulatory modification underlying a response. This mechanistically focused narrative review integrates experimental evidence on subunit-selective, spatial, and post-translational modification (PTM)-dependent regulation of AMPK, distinguishing DCM-specific mechanisms from findings extrapolated from other models. In diabetic cardiomyocytes, α 2-associated signaling contributes to mitochondrial homeostasis and remodeling, whereas mitochondria-associated α 1 signaling in cardiac microvascular endothelium is linked to mitochondrial quality control and microvascular protection. AMPK γ 1 emerges as a regulator of inter-subunit interactions. Mechanistic studies further show that OTUD1 and VCPIP1 regulate non-degradative K63-linked ubiquitination of AMPK α 2 and γ 1, respectively, affecting interactions with upstream kinases without substantial loss of subunit abundance. Regulatory phosphorylation and the O-GlcNAc network provide additional layers of control, although direct endogenous O-GlcNAc modification of AMPK in diabetic myocardium remains unverified. These mechanisms may shape substrate metabolism, organelle quality control, redox injury, fibrosis, and microvascular dysfunction, but increased bulk AMPK phosphorylation does not necessarily establish restored metabolic flexibility or uniformly beneficial signaling. Direct evidence for native cardiac heterotrimers, compartment-specific AMPK activity, and disease-associated modified proteoforms remains limited in human diabetic myocardium. Consequently, subunit-, PTM-, and compartment-directed interventions remain experimental therapeutic hypotheses. Defining which molecular AMPK state drives a given cardiac phenotype is a prerequisite for testing whether selective intervention improves human diabetic myocardial disease.