Metformin hydrochloride

Male C57BL/6J mice (The Jackson Laboratory, Bar Harbor, ME), 10 to 12 weeks of age, were used for all experiments. Experimental AAAs were created via transient intra-aortic porcine pancreatic elastase (PPE) infusion as previously described^{16 (link)–18 (link)}. In brief, at laparotomy under inhaled isoflurane anesthesia, 30 μl of type 1 PPE (1.5 U/mL in saline, Catalog # E1250-100MG; Sigma-Aldrich, St. Louis, MO) was infused into a controlled segment of infrarenal aorta for 5 minutes under constant pressure.
Metformin hydrochloride (MP Biomedicals, LLC, Solon, OH) was freshly prepared in phosphate-buffered saline (PBS, pH 7.2) prior to each use. Mice were administered metformin, 250 mg/kg/day in PBS (n=10 mice), or PBS alone (n=7 mice) as vehicle control via oral gavage. The metformin dose was selected based on published rodent modeling system precedents^{19 (link)}, comparable to dosing required for insulin-resistant (type 2) diabetes management in humans (up to 35 mg/kg/day) as determined by allometric scaling^{20 (link)}. Metformin therapy was initiated 3 days prior to, and terminated 14 days following, PPE infusion.
All murine modeling experiments were conducted in compliance with the Laboratory Animal Care Guidelines of Stanford University, with prior approval of the Administrative Panel on Laboratory Animal Care (protocol #11131).