Development of linagliptin-loaded liposomes using aspartic acid conjugate for bone-targeted delivery to combat osteoporosis

Abstract

Osteoporosis is a common metabolic bone disorder that requires new treatment strategies. Linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, is a proven osteogenic agent in diabetes-linked bone loss. However, poor solubility, low oral bioavailability and inadequate bone-targeting limit its use in osteoporosis. We have successfully developed the bone-targeted liposomes of linagliptin using an aspartic acid conjugate, that is poly (aspartic acid-co-lactide)-1,2-dipalmitoyl-sn-glycero-3-phospho ethanolamine (PAL-DPPE), which was prior synthesised and identified using FTIR and NMR. Liposomes were evaluated for particle size, encapsulation efficacy, drug loading and release study in addition to in vitro hydroxyapatite binding ability. To determine the anti-osteoporosis effect of liposomes, in vivo testing was performed in glucocorticoid-induced osteoporosis model in mice. Bone targeted liposomes of linagliptin having particle size of 281.7 nm and hydroxyapatite affinity of 89% significantly improved the bone architecture parameters and bone mineral density in micro-computed tomography analysis. Further, these liposomes positively modulated sclerostin, bone morphogenetic protein-2, receptor activator of nuclear factor kappa beta/osteoprotegerin ratio and other bone turnover biomarkers. The findings demonstrate that aspartic acid conjugate (PAL-DPPE)-based bone-targeted liposomes of linagliptin hold promise for the treatment of osteoporosis. Moreover, the possible mechanistic pathways involved here is Wnt and AMPK pathway.

Keywords: AMP-activated protein kinase (AMPK) pathway; Osteoporosis; Wnt signaling; aspartic acid; bone targeting; linagliptin; liposomes.