Teriparatide (Human Parathyroid Hormone (1–34)) Inhibits Osteogenic Vascular Calcification in Diabetic Low Density Lipoprotein Receptor-deficient Mice

Abstract

Cardiovascular calcification is a common consequence of diabetes. High fat diets induce diabetes and arterial calcification in male low density lipoprotein receptor (LDLR) -/- mice; calcification occurs via Msx2 signaling that promotes the osteogenic differentiation of arterial myofibroblasts. We studied regulation of arterial osteogenesis by human parathyroid hormone (PTH) (1-34) (also called teriparatide) in LDLR -/- mice fed diabetogenic diets for 4 weeks. LDLR -/- mice were treated with vehicle or 0.4 mg/kg of PTH(1-34) subcutaneously five times/week. Gene expression was determined from single aortas and hind limb RNA by fluorescence reverse transcription-PCR. Valve calcification was determined by histological staining of cardiac sections using image analysis to quantify valve leaflet mineralization. PTH(1-34) increased bone mineral content (by dual energy x-ray absorptiometry) in LDLR -/- mice, with induction of osseous osteopontin (OPN) expression and serum OPN levels (>150 nM); PTH(1-34) did not significantly change serum glucose, lipids, body weight, or fat mass. PTH(1-34) suppressed aortic OPN and Msx2 expression >50% and decreased cardiac valve calcification 80% (8.3 +/- 1.5% versus 1.4 +/- 0.5%; p < 0.001). Of the known circulating regulators of vascular calcification (OPN, osteoprotegerin, and leptin), PTH(1-34) regulated only serum OPN. We therefore studied actions of PTH(1-34) and OPN in vitro on cells induced to mineralize with Msx2. OPN (5-50 nM) reversed Msx2-induced mineralization. PTH(1-34) inhibited mineralization by 40% and down-regulated Msx2 in aortic myofibroblasts. PTH(1-34) inhibits vascular calcification and aortic osteogenic differentiation via direct actions and potentially via circulating OPN. PTH(1-34) exerts beneficial actions at early stages of macrovascular disease responses to diabetes and dyslipidemia.