Background: Fracture risk is significantly increased in patients with myocardial infarction (MI) and heart failure but the causal relationship of this association is unknown. Using an experimental model of MI in mice and rats, we aimed to investigate whether MI per se induces osteoporosis.
Methods: MI was induced in adult 5-month-old C57BL/6 mice by permanent ligation of the left anterior descendent (LAD) coronary artery. Ischaemia/reperfusion injury was induced in 4- and 9-month-old Fischer-344 rats by LAD ligation for 30 minutes followed by reperfusion. Cardiac function was assessed by echocardiography. Bone mineral density (BMD) was analysed using quantitative peripheral computed tomography (pQCT) 4- and 9 weeks after MI in mice, and 4 weeks after MI in rats. Bone resorption was analysed by urinary deoxypyridinoline (DPD) excretion.
Results: In mice, MI reduced fractioning shortening (FS) from 31.32±0.56% to 22.11±1.8%. Four weeks after MI, total BMD of the femoral metaphysis (423.7±7.4mg/cm3) and the femoral shaft (591.6±9.7mg/cm3) did not significantly differ from sham (metaphysis: 427.5±8.7mg/cm3, shaft: 612.7±9.1 mg/cm3). Vertebral BMD was also unchanged. Similarly, femoral and vertebral BMD was unaffected 9 weeks after MI. In addition, bone resorption remained unchanged, 4 weeks after MI. To exclude a species specific skeletal response to cardiac ischemia, we additionally employed a rat I/R injury MI model. MI decreased FS by 9%, but BMD and bone resorption in young rats (4-month-old) remained largely unchanged as measured at the tibial metaphysis, tibial shaft and first lumbar vertebra, 4 weeks after ischaemia (BMD at tibial metaphysis 581.1±9.2mg/cm3 in sham vs. 602.9±8.9mg/cm3 in MI). Finally, BMD was also not affected by cardiac ischemia in aged 9-month-old rats.
Conclusion: Our data suggest that experimental myocardial infarction per se has no direct effect on bone resorption or bone mineral density. Further research is needed to explain the increased bone fragility in cardiovascular patients.
Disclosure: The authors declared no competing interests.