To get at this problem, Liu and colleagues tested NMN’s effects on mouse hearts that had been exposed to a chemical called isoproterenol that creates scarring. To see how well the hearts were working, they measured the blood pumping capabilities and tissue thickness of mice exposed to these scarring chemicals. What they found was that this scarring causes heart cavity expansion during blood pumping, which indicates a lack of tissue elasticity. Liu and colleagues also saw that these hearts had larger hearts (hypertrophy), an indicator that heart muscle is thickening from a buildup of scar tissue. But when they treated these mice with NMN, the researchers saw an attenuation of heart size and a partial restoration of heart thickness.