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Fish-bone peptides (FBP) with a high affinity to Ca were isolated using hydroxyapatite affinity chromatography, and FBP II with a high ratio of phosphopeptide was fractionated in the range of molecular weight 5·0 -1·0 kDa by ultramembrane filtration. In vitro study elucidated that FBP II could inhibit the formation of insoluble Ca salts in neutral pH. In vivo effects of FBP II on Ca bioavailability were further examined in the ovariectomised rat. During the experimental period, Ca retention was increased and loss of bone mineral was decreased by FBP II supplementation in ovariectomised rats. After the low-Ca diet, the FBP II diet, including both normal level of Ca and vitamin D, significantly decreased Ca loss in faeces and increased Ca retention compared with the control diet. The levels of femoral total Ca, bone mineral density, and strength were also significantly increased by the FBP II diet to levels similar to those of the casein phosphopeptide diet group (no difference; P.0·05). In the present study, the results proved the beneficial effects of fish-meal in preventing Ca deficiency due to increased Ca bioavailability by FBP intake.Fish-bone peptides: Calcium solubility: Ovariectomised rats: Calcium bioavailabilityThe major source of Ca is the diet, and the most common and trusted source of Ca is milk or other dairy products (Anderson & Garner, 1996). Dairy products contain a high content of casein. Casein phosphopeptides (CPP) derived from the intestinal digestion of casein have been shown to enhance bone calcification in rats (Lee et al. 1980;Tsuchita et al. 1993). Such CPP have the capacity to chelate Ca and to prevent the precipitation of Ca phosphate salts (Berrocal et al. 1989), thereby increasing the amount of soluble Ca availability for absorption across the mucosa (Yuan & Kitts, 1991.However, some oriental people do not drink milk due to lactose indigestion and intolerance, which make them allergic to milk. Thus, there have been many studies on various Ca supplements as alternatives (for examples, soya protein isolate, fructo-oligosaccharide, fish-meal, etc), which may affect Ca bioavailability (Brouns & Vermeer, 2000;Larsen et al. 2000 Larsen et al. , 2003Kumagai et al. 2004). As reported by Larsen et al. (2000), the intake of small fish with bones could increase Ca bioavailability in rats, and small fish might be an important Ca dietary supplement, especially in population groups with low intakes of milk and dairy products.Annually, more than 50 % of total fishery products (over 120 million tons) are discarded as inedible by-products, such as bone, skin, fins, internal organs and head. Thus, many studies have been performed to utilise the large amounts of protein, oil, minerals, carbohydrate and nucleic acid originating from fishery by-products, and to improve their functional properties (Nair & Gopakumar, 1982;Rodriguez-Estrada et al. 1994;Nagai & Suzuki, 2000;Kim et al. 2001 Kim et al. , 2003Shahidi & Janak Kamil, 2001). However, studies on the utilisation of organic components or minerals ...

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Excessive bone resorption by osteoclasts causes bone loss-related diseases and reactive oxygen species (ROS) act as second messengers in intercellular signaling pathways during osteoclast differentiation. In this study, we explored the protective effects of fermented oyster extract (FO) against receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation in murine monocyte/macrophage RAW 264.7 cells. Our results showed that FO markedly inhibited RANKL-induced activation of tartrate-resistant acid phosphatase and formation of F-actin ring structure. Mechanistically, FO has been shown to down-regulate RANKL-induced expression of osteoclast-specific markers by blocking the nuclear translocation of NF-κB and the transcriptional activation of nuclear factor of activated T cells c1 (NFATc1) and c-Fos. Furthermore, FO markedly diminished ROS production by RANKL stimulation, which was associated with blocking the expression of nicotinamide adenine dinucleotide phosphate oxidase 1 (NOX1) and its regulatory subunit Rac-1. However, a small interfering RNA (siRNA) targeting NOX1 suppressed RANKL-induced expression of osteoclast-specific markers and production of ROS and attenuated osteoclast differentiation as in the FO treatment group. Collectively, our findings suggest that FO has anti-osteoclastogenic potential by inactivating the NF-κB-mediated NFATc1 and c-Fos signaling pathways and inhibiting ROS generation, followed by suppression of osteoclast-specific genes. Although further studies are needed to demonstrate efficacy in in vivo animal models, FO may be used as an effective alternative agent for the prevention and treatment of osteoclastogenic bone diseases.