Glucosamine Mediated Hexosamine Biosynthesis Pathway Activation Utilizes ATF4 to Promote “Exercise-Like” Angiogenesis and Perfusion Recovery in Peripheral Arterial Disease

Background: Endothelial cells (ECs) use glycolysis to produce energy. In pre-clinical models of peripheral arterial disease (PAD), the further activation of EC glycolysis was ineffective and/or deleterious in promoting hypoxia-dependent angiogenesis while pentose phosphate pathway (PPP) activation was effective. Hexosamine biosynthesis pathway (HBP), PPP, and glycolysis are closely linked. Glucosamine directly activates HBP.Methods:Hind-limb ischemia (HLI)ineNOS-/-and Balb/c mice was used. Glucosamine (600 ug/g/day) was injected intraperitoneally. Blood flow recovery was assessed using laser Doppler perfusion imaging (LDPI), angiogenesis was studied by CD31immunostaining.In-vitro: human umbilical vein ECs (HUVECs) and mouse microvascular EC with glucosamine, L-glucose or vascular endothelial growth factor (VEGF165a), were tested underhypoxiaand serum starvation (HSS). Cell counting kit-8 (CCK-8), tube formation, intracellular reactive oxygen species (ROS), Electric Cell-substrate Impedance Sensing (ECIS) and FITC dextran permeability were assessed. Glycolysis and oxidative phosphorylation were assessed by seahorse assay. Gene expression was assessed using RNA sequencing, real-time qPCR, and western blot. Human muscle biopsies from patients with PAD were assessed for EC O-GlcNAcylation before and after supervised exercise vs. standard medical care. Results: Day-3 post-HLI,glucosamine vs. control-treated eNOS-/-had less necrosis.Beginning Day-7 post-HLI, glucosamine vs. control-treated Balb/chad higherblood flowthat persisted to Day-21whereischemic musclesshowed greaterCD31 staining/muscle fiber. In-vitro,glucosamine vs. L-glucoseshowedimproved EC survival and tube formation. RNA-sequencing of glucosamine vs. L-glucose showed increased amino acid metabolism. That resulted in increased oxidative phosphorylation and serine biosynthesis pathway (SBP) without an increase in glycolysis or PPP genes. This was associated with better barrier function and less ROS compared to activating glycolysis by VEGF165a. These effects were mediated by activating transcription factor 4 (ATF4); a driver of exercise-induced angiogenesis. Finally, in muscle biopsies from humans with PAD,EC/O-GlcNAcylation was increased by 12 weeks of supervised exercise vs. standard medical care. Conclusion: In-cells, mice, and humans activation of HBP by glucosamine in PAD inducesan “exercise-like” angiogenesis and offers a promising novel therapeutic pathway to treat this challenging disorder.