Cancellous bone formation response to simulated resistance training during disuse is blunted by concurrent alendronate treatment

Abstract

The purpose of this study was to assess the effectiveness of simulated resistance training (SRT) exercise combined with alendronate (ALEN) in mitigating or preventing disuse-associated losses in cancellous bone microarchitecture and formation. Sixty male SpragueDawley rats (6 months old) were randomly assigned to either cage control (CC), hind limb unloading (HU), HU plus either ALEN (HU þ ALEN), SRT (HU þ SRT), or a combination of ALEN and SRT (HU þ SRT/ALEN) for 28 days. HU þ SRT and HU þ SRT/ALEN rats were anesthetized and subjected to muscle contractions once every 3 days during HU (four sets of five repetitions, 1000 ms isometric þ 1000 ms eccentric). Additionally, HU þ ALEN and HU þ SRT/ALEN rats received 10 mg/kg of body weight of ALEN three times per week. HU reduced cancellous bone-formation rate (BFR) by 80%, with no effect of ALEN treatment (À85% versus CC). SRT during HU significantly increased cancellous BFR by 123% versus CC, whereas HU þ SRT/ALEN inhibited the anabolic effect of SRT (À70% versus HU þ SRT). SRT increased bone volume and trabecular thickness by 19% and 9%, respectively, compared with CC. Additionally, osteoid surface (OS/BS) was significantly greater in HU þ SRT rats versus CC (þ32%). Adding ALEN to SRT during HU reduced Oc.S/BS (À75%), Ob.S/BS (À72%), OS/BS (À61%), and serum TRACP5b (À36%) versus CC. SRT and ALEN each independently suppressed a nearly twofold increase in adipocyte number evidenced with HU and inhibited increases in osteocyte apoptosis. These results demonstrate the anabolic effect of a low volume of high-intensity muscle contractions during disuse and suggest that both bone resorption and bone formation are suppressed when SRT is combined with bisphosphonate treatment. ß

Impaired bone microarchitecture at the distal radius in older men with low muscle mass and grip strength: The STRAMBO study

“…(36) In rat models of unloading, stimulated resistance training increased trabecular bone formation and Tb.Th. (37) In this model, dynamic muscle stimulation increased Tb.N and trabecular connectivity at the femur. Lifelong acting and aging-related factors may also contribute to these associations.…”

Beta-1 Adrenergic Agonist Treatment Mitigates Negative Changes in Cancellous Bone Microarchitecture and Inhibits Osteocyte Apoptosis during Disuse

“…In situ osteocyte apoptosis was assessed from distal femur sections as previously described [23]. In brief, distal left femurs were decalcified and subsequently embedded in paraffin, and serial frontal sections were cut 8 µm thick and mounted on slides.…”

Jump exercise during hindlimb unloading protect against the deterioration of trabecular bone microarchitecture in growing young rats

“…Rubin et al (2001), employed low-magnitude high frequency mechanical signals, finding that 10 min/day of mechanical stimulation was effective in maintaining metaphyseal bone volume and did attenuate bone formation losses at the proximal tibia. Swift et al (2011) recently demonstrated that high-intensity simulated resistance training completed every other day during a period of disuse can prevent the loss of cancellous bone mass and material properties. However, their results could differ from that of the physiological (exercise) model in trabecular bone architecture because these studies used artificial mechanical loading models under anesthesia.…”