Pilose antler peptide promotes osteoblast

Osteoporosis is a severe bone disease characterized by a decrease in the density and structure of bones, with high risks of fractures. Pilose antler peptide (PAP), extracted and purified from deer antlers, can promote regeneration and fracture healing, and strengthen sinews and bone. To determine whether PAP can promote osteoblast development and to elucidate the molecular mechanisms underlying its functions, the present study investigated the effects of PAP on osteoblast proliferation, differentiation and mineralization, and the role of the insulin signaling pathway using MTT assay, alkaline phosphatase activity assay, western blot analysis and reverse transcription-quantitative PCR. The present results suggested that PAP promoted osteoblast proliferation, differentiation and mineralization in vitro via the insulin signaling pathway. The effect of PAP on insulin signaling in osteoblasts may be mediated via the ERK pathway and partially by the PI3K/Akt pathway. The present results indicated that PAP could potentially be developed as an alternative treatment strategy for bone diseases related to diabetes characterized by insulin signaling impairment. Introduction Osteoporosis is a major health concern characterized by a decrease in the density and quality of bones, with high risks of bone fractures (1). Worldwide, osteoporosis causes >8.9 million fractures annually, resulting in an osteoporotic fracture every 3 sec (1). In China, osteoporosis affects ~70 million individuals aged ≥50, and causes ~687,000 hip fractures annually (2). The overall prevalence of osteoporosis in mainland China is 7% among adults; 22.5% among males and 50.1% among females aged ≥50 years (3). The imbalance between the function of osteoblasts and osteoclasts contributes to bone disease (4). Osteoblast maturation is a multistep series of events, including proliferation, differentiation and mineralization, which are modulated by the interactions of a variety of cytokines and signaling pathways (4). Since the discovery of insulin receptor in osteoblasts (5), the role of insulin signaling in bone has attracted increasing attention. Previous studies have confirmed that insulin signaling is essential for osteoblast function (5). Mice lacking insulin receptors in osteoblasts have been shown to develop postnatal osteopenia, and IR-deficient osteoblasts in vitro have been shown to have a lower proliferative and differentiation capacity (6). Moreover, direct treatment with insulin promotes osteoblast proliferation, differentiation and collagen synthesis (7,8). After insulin binds to its receptor, the insulin receptor substrate (IRS) family acts as docking proteins between insulin receptors and intracellular signaling molecules (7). There are four subtype members of the IRS family, IRS‐1, IRS‐2, IRS‐3 and IRS‐4, but only IRS‐1 and IRS‐2 play important roles in bone development via insulin signal transduction (9,10). Specifically, genetically modified mice lacking the IRS‐1 or IRS‐2 gene exhibit severe osteopenia with a low bone turnover, and cultured IRS-1‐/‐ and IRS-2‐/‐ osteoblasts exhibit reduced proliferation, differentiation and matrix synthesis (10). Furthermore, a previous in vitro study that suppressed the expression of IRS-1 and IRS-2 in L6 myotubes using small interfering RNA, revealed IRS‐1 more closely regulated glucose uptake and IRS‐2 seemed to Pilose antler peptide promotes osteoblast proliferation, differentiation and mineralization via the insulin signaling pathway CHANGJUN YUN1,2, WENJIE QIAN1,2, JUNYI WU1,2, CHENXI YUAN1,2, SONGZHOU JIANG3 and JINPENG LV1-3 1Department of Orthopedics, Wujin Hospital Affiliated with Jiangsu University; 2The Wujin Clinical College of Xuzhou Medical University; 3College of Pharmaceutical Engineering and Life Sciences, Changzhou University, Changzhou, Jiangsu 213000, P.R. China Received April 27, 2019; Accepted November 15, 2019 DOI: 10.3892/etm.2019.8286 Correspondence to: Dr Changjun Yun, Department of Orthopedics, Wujin Hospital Affiliated with Jiangsu University, 2 Yongning North Road, Changzhou, Jiangsu 213000, P.R. China E‐mail: yunchangjun@sina.com Dr Jinpeng Lv, College of Pharmaceutical Engineering and Life Sciences, Changzhou University, 1 Gehu Road, Changzhou, Jiangsu 213000, P.R. China E‐mail: lvjinpeng1988@126.com