Category Archives: Drugs

AMPK Activators: Lipoic Acid, Metformin, EGCG, Berberine, Resveratrol Can Inhibit Bone Resorption in Mice

Abstract

AMP kinase acts as a negative regulator of RANKL in the differentiation of osteoclasts.

AMP-activated protein kinase (AMPK) has been reported to stimulate differentiation and proliferation of osteoblasts, but the role of AMPK in the physiology of osteoclasts has not been investigated.
Osteoclasts were differentiated from mouse BMMϕs. TRAP-positive multinucleated cells were considered to be osteoclasts using TRAP staining, and resorption area was determined by incubation of cells on dentine discs. Signaling pathways were investigated using Western blotting and RT-PCR.
RANKL induced phosphorylation/activation of AMPK-α in BMMϕs and stimulated formation of TRAP-positive multinucleated cells. Pharmacological inhibition of AMPK with compound C and siRNA-mediated knockdown of AMPK-α1, the predominant α-subunit isoform in BMMϕs, increased RANKL-induced formation of TRAP-positive multinucleated cells and bone resorption via activation of the downstream signaling elements p38, JNK, NF-κB, Akt, CREB, c-Fos, and NFATc1. STO-609, an inhibitor of CaMKK, completely blocked the RANKL-induced activation of AMPK-α, but KN-93, an inhibitor of CaMK, did not. siRNA-mediated TAK1 knockdown also blocked RANKL-induced activation of AMPK-α. The AMPK activators metformin, (-)-epigallocatechin-3-gallate, berberine, resveratrol, and α-lipoic acid dose-dependently suppressed formation of TRAP-positive multinucleated cells and bone resorption.
AMPK negatively regulates RANKL, possibly by acting through CaMKK and TAK1. Thus, the development of AMPK activators may be a useful strategy for inhibiting the resorption of bone that is stimulated under RANKL-activated conditions.

Lee YS, Kim YS, Lee SY, Kim GH…
Bone Nov 2010
PMID: 20696287

Lipoic Acid Inhibits Resorption from Adrenaline

Abstract

β-Adrenergic signaling stimulates osteoclastogenesis via reactive oxygen species.

Sympathetic signaling regulates bone resorption through receptor activator of nuclear factor-κB ligand (RANKL) expression via the β-adrenergic receptor (β-AR) on osteoblasts. Reactive oxygen species (ROS) are known as one type of osteoclast regulatory molecule. Here we show that an antioxidant, α-lipoic acid (α-LA), treatment prevent the β-adrenergic signaling-induced bone loss by suppressing osteoclastogenesis, and sympathetic signaling directly regulates osteoclastogenesis through β2-AR expressed on osteoclasts via intracellular ROS generation. In an in vitro study, the β-AR agonist isoprenaline increased intracellular ROS generation in osteoclasts prepared from bone marrow macrophages (BBMs) and RAW 264.7 cells. Isoprenaline enhanced osteoclastogenesis through β2-AR expressed on BMMs and RAW 264.7 cells. The antioxidant α-LA inhibited isoprenaline-enhanced osteoclastogenesis. Isoprenaline increased the expression of osteoclast-related genes such as nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1, tartrate-resistant acid phosphatase, and cathepsin K on osteoclasts. α-LA also inhibited isoprenaline-induced increases of these gene expressions. These in vitro results led to the hypothesis that β-adrenergic signaling directly stimulates osteoclastogenesis via ROS generation. In an in vivo study, isoprenaline treatment alone caused oxidative damage in local bone and reduced bone mass because of an increase in bone resorption, and, in α-LA-treated mice, isoprenaline did not increase tibial osteoclast number even though the RANKL-to-osteoprotegerin ratio increased. These in vitro and in vivo results indicate that β-adrenergic signaling, at least in part, directly stimulates osteoclastogenesis through β2-AR on osteoclasts via ROS generation.

Kondo H, Takeuchi S, Togari A
Am. J. Physiol. Endocrinol. Metab. Mar 2013
PMID: 23169789

Ellagic Acid May Be a Natural SERM

Abstract

Evaluation of estrogenic/antiestrogenic activity of ellagic acid via the estrogen receptor subtypes ERalpha and ERbeta.

Ellagic acid is a plant-derived polyphenol, possessing antioxidant, antiproliferative, and antiatherogenic properties. Whether this compound has estrogenic/antiestrogenic activity, however, remains largely unknown. To answer this question, we first investigated the ability of ellagic acid to influence the activity of the estrogen receptor subtypes ERalpha and ERbeta in HeLa cells. Cells co-transfected with an estrogen response element (ERE)-driven luciferase (Luc) reporter gene and an ERalpha- or ERbeta-expression vector were exposed to graded concentrations of ellagic acid. At low concentrations (10(-7) to 10(-9) M), this compound displayed a small but significant estrogenic activity via ERalpha, whereas it was a complete estrogen antagonist via ERbeta. Further evaluation revealed that ellagic acid was a potent antiestrogen in MCF-7 breast cancer-derived cells, increasing, like the pure estrogen antagonist ICI182780, IGFBP-3 levels. Moreover, ellagic acid induced nodule mineralization in an osteoblastic cell line (KS483), an effect that was abolished by the estrogen antagonist. Endometrium-derived epithelial cells (Ishikawa) showed no response to the natural compound by using a cell viability assay (MTT). These findings suggest that ellagic acid may be a natural selective estrogen receptor modulator (SERM).

Papoutsi Z, Kassi E, Tsiapara A, Fokialakis N…
J. Agric. Food Chem. Oct 2005
PMID: 16190622

Cissus Comparable to Raloxifine in Rats

Abstract

Effect of Cissus quadrangularis Linn on the development of osteopenia induced by ovariectomy in rats.

The aim of our study was to see the efficacy of petroleum ether extract of Cissus quadrangularis (CQ) on development of osteopenia in ovariectomy induced Wistar rats.
The female Wistar rats were ovariectomized or Sham operated. The rats were anesthetized with pentobarbital sodium (40 mg/ kg b.w, i.p.), the ovaries were removed bilaterally. Sham-operation was performed in the same manner but only exposing the ovaries (sham operated (SHAM) group). A day later, the ovariectomized rats were randomly divided into four groups of eight animals each. The groups are 1. Sham operated (SHAM), 2. Ovariectomized (OVX), 3. Ovariectomized and treated with 25 mg/kg b.w of raloxifene (OVX+RAL), 4. Ovariectomized and treated with 500 mg/kg b.w of petroleum ether extract of CQ (OVX+CQ). The treatment continued for 30 days. At the end of the treatment, rats in all groups were sacrificed by cervical dislocation. Before sacrifice, blood was collected for the estimation of serum ALP, TRAP, Calcium and hydroxyproline; where as the left femur was used for histomorphometrical analysis.
The findings assessed on the basis of animal weight, morphology of femur, histomorphometry and biochemical analysis. As compared to SHAM group, OVX group animals showed a significant rise in serum ALP, TRAP and hydroxyproline levels at the end of 1 month following ovariectomy while no significant change was seen in the serum calcium levels. ALP and TRAP levels of OVX + RAL and OVX + CQ groups showed a further increase following administration of raloxifene and Cissus quadrangularis. The serum hydroxyproline content was found to be increased in the OVX + CQ compared to SHAM group. CQ significantly increased the thickness of both cortical (p <0.001) and trabecular bone (p <0.001).This action of CQ is comparable to action of Raloxifene. These data suggest a strong anti-osteoporotic activity of CQ.
The results confirm, at least in part, for the use of Cissus quadrangularis in folk medicine to treat osteoporosis.

Potu BK, Nampurath GK, Rao MS, Bhat KM
Clin Ter 2011
PMID: 21912817

Alendronate + Exercise Prevents All Bone Loss During Spaceflight

Abstract

Bisphosphonates as a supplement to exercise to protect bone during long-duration spaceflight.

We report the results of alendronate ingestion plus exercise in preventing the declines in bone mass and strength and elevated levels of urinary calcium and bone resorption in astronauts during 5.5 months of spaceflight.
This investigation was an international collaboration between NASA and the JAXA space agencies to investigate the potential value of antiresorptive agents to mitigate the well-established bone changes associated with long-duration spaceflight.
We report the results from seven International Space Station (ISS) astronauts who spent a mean of 5.5 months on the ISS and who took an oral dose of 70 mg of alendronate weekly starting 3 weeks before flight and continuing throughout the mission. All crewmembers had available for exercise a treadmill, cycle ergometer, and a resistance exercise device. Our assessment included densitometry of multiple bone regions using X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) and assays of biomarkers of bone metabolism.
In addition to pre- and post-flight measurements, we compared our results to 18 astronauts who flew ISS missions and who exercised using an early model resistance exercise device, called the interim resistance exercise device, and to 11 ISS astronauts who exercised using the newer advanced resistance exercise device (ARED). Our findings indicate that the ARED provided significant attenuation of bone loss compared with the older device although post-flight decreases in the femur neck and hip remained. The combination of the ARED and bisphosphonate attenuated the expected decline in essentially all indices of altered bone physiology during spaceflight including: DXA-determined losses in bone mineral density of the spine, hip, and pelvis, QCT-determined compartmental losses in trabecular and cortical bone mass in the hip, calculated measures of fall and stance computed bone strength of the hip, elevated levels of bone resorption markers, and urinary excretion of calcium.
The combination of exercise plus an antiresoptive drug may be useful for protecting bone health during long-duration spaceflight.

Leblanc A, Matsumoto T, Jones J, Shapiro J…
Osteoporos Int Jul 2013
PMID: 23334732

Alendronate Suppresses Bone Formation From Exercise in Rats

Abstract

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

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 Sprague-Dawley rats (6 months old) were randomly assigned to either cage control (CC), hind limb unloading (HU), HU plus either ALEN (HU + ALEN), SRT (HU + SRT), or a combination of ALEN and SRT (HU + SRT/ALEN) for 28 days. HU + SRT and HU + SRT/ALEN rats were anesthetized and subjected to muscle contractions once every 3 days during HU (four sets of five repetitions, 1000 ms isometric + 1000 ms eccentric). Additionally, HU + ALEN and HU + SRT/ALEN rats received 10 µg/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 (-85% versus CC). SRT during HU significantly increased cancellous BFR by 123% versus CC, whereas HU + SRT/ALEN inhibited the anabolic effect of SRT (-70% versus HU + 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 + SRT rats versus CC (+32%). Adding ALEN to SRT during HU reduced Oc.S/BS (-75%), Ob.S/BS (-72%), OS/BS (-61%), and serum TRACP5b (-36%) 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.

Swift JM, Swift SN, Nilsson MI, Hogan HA…
J. Bone Miner. Res. Sep 2011
PMID: 21509821