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Lysophosphatidic acid (lysoPtdOH) levels have previously been reported to decrease in rodents with shortterm fasting. We investigated whether a 16 h fast would change expression of autotaxin, the predominant phospholipase D responsible for adipose-derived lysoPtdOH synthesis, or any of the lysophosphatidic acid receptors (1-6) in four white adipose tissue (WAT) depots and interscapular brown adipose tissue (BAT) in male C57Bl/6J mice fed ad libitum, or fasted for 16 h. Aside from small inductions of Lpar1 in epididymal WAT and Lpar2 in epididymal and inguinal WAT, no significant changes were observed in expression of the Lpar family members, or autotaxin in perirenal, retroperitoneal, epididymal, or inguinal WAT or BAT with fasting. Comparison of the relative expression of Lpar1-6 in various depots showed that Lpar6 was the predominant Lpar in both WAT and BAT, and suggests that further work on the adipose-specific role of Lpar6 is warranted.

Introduction: Denosumab, a fully human monoclonal antibody to RANK-ligand, has been shown to increase bone mineral density (BMD) and reduce the risk of hip, vertebral and non-vertebral fractures in postmenopausal women with osteoporosis (1-3). Varying doses of denosumab including 30mg/3months have demonstrated a decrease in bone remodelling in a dose-dependent manner (2,4-6). The primary objective of this study is to evaluate the efficacy of low dose denosumab (30mg/6 months) in postmenopausal women with osteoporosis who are reluctant to consider or continue the full dose of denosumab due to adverse events (AE) or concerns of potential AE. Methods: Following informed consent, postmenopausal women with a T-score of ≤ -2.5 at the lumbar spine (LS) or at the total hip (TH) received denosumab 30mg/6months. Patients with an additional skeletal disorder, prior fragility fracture, or on oral steroids (daily in the past 12 months) were excluded. The primary endpoint was the percent change in BMD at the lumbar spine (LS), total hip (HP), femoral neck (FN) and 1/3 radius (1/3R) at 12 months. Secondary outcomes were 1) percent change in BMD at the LS, TH, FN, and 1/3R at 24 months and 2) AE. Results: We enrolled 183 patients. The mean age was 69 years (SD= 7.07), 80% of patients had a moderate fracture risk (CAROC tool), 3% were current smokers and 9% consumed alcohol daily. 14.4% of patients were on SSRI/SNRI, 9.6% were on PPI, and no patient was on an aromatase inhibitor. At 12 months (n=125), the mean BMD significantly increased by +2.0% (95% CI 2.8%-1.3%) at the LS (p<0.001). There was no significant change in BMD at the FN, TH, AND 1/3R. At 24 months (n=65), the percent change in BMD was +3.4% (95% CI 4.8%-2.0%: p<0.001) at the LS, +1.5% (95% CI 2.9%-0.15%: p=0.031) at the FN, +1.9% (95% CI 3.5%-0.24%: p=0.025) at the 1/3R. There was no significant change in BMD at the TH. Conclusion: Low dose denosumab appears to be effective in maintaining BMD in postmenopausal women with a moderate fracture risk and may be of benefit in individuals who are experiencing side effects or concerns of side effects. This may also be of value following 10 years of therapy in order to maintain BMD. References 1.Bekker, PJ, Holloway DL, Rasmussen AS, Murphy R, Martin SW, Leese PT... Depaoli AM. A Single-Dose Placebo-Controlled Study of AMG 162, a Fully Human Monoclonal Antibody to RANKL, in Postmenopausal Women. JBMR, 2004;19(7), 1059-1066. 2.Kumagai Y, Hasunuma T, Padhi D. A randomized, double-blind, placebo-controlled, single-dose study to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of denosumab administered subcutaneously to postmenopausal Japanese women. Bone, 2011;49(5), 1101-1107. 3.Lewiecki EM, Miller PD, Mcclung MR, Cohen SB, Bolognese MA, Liu Y, . . . Fitzpatrick LA. Two-Year Treatment With Denosumab (AMG 162) in a Randomized Phase 2 Study of Postmenopausal Women With Low BMD. JBMR, 2007;22(12), 1832-1841.

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Introduction: Denosumab is an effective antiresorptive molecule and reduces the risk of fracture in postmenopausal osteoporosis. Cessation of denosumab therapy however is associated with rapid declines in bone mineral density (BMD), rises in bone remodelling and an increased risk of fracture. We evaluated the effect of low dose denosumab (30mg every 6 months) on the prevention of bone loss following a switch from standard dose (60mg of denosumab every 6 months) in a prospective observational study. Methods We recruited 114 women 50–90 years of age with postmenopausal osteoporosis at a moderate fracture risk without prior fragility fractures who had been on denosumab 60mg every 6 month. These women switched to low dose denosumab 30mg every 6 months. Mean % change in lumbar spine (LS), femoral neck (FN), total hip (TH) and 1/3 distal radius (1/3RAD) BMD at 12 and 24 months were evaluated. Predictors for change in BMD were explored. Subgroup analysis for patients on denosumab 60mg every 6 months for < 3 years and for ≥ 3 years before switching to low dose denosumab 30mg was explored. Results At 12 months, there was an increase in LS BMD mean % change (+ 2.03%, 95% CI 1.18–2.88, p < 0.001). BMD was stable at the hip and radial sites. Age was found to be a predictor of the mean % change of LS BMD for the overall sample. At 24 months, there was a further increase in LS BMD mean % change (+ 3.44%, 95% CI 1.74–5.12, p < 0.001), with stable BMD at other skeletal sites. The 12 month mean BMD % change at the LS (p = 0.015), FN (p < 0.001), TH (p < 0.001), and 1/3 RAD (p < 0.001) were found to be predictors of the 24 month mean BMD % change. No clinical fractures were reported during 24 months of follow up. Conclusion We observed stable BMD following a switch from denosumab 60mg every 6 months to 30mg every 6 monhts in this prospective observational study conducted in postmenopausal women at a moderate fracture risk