Background: Osteoporosis is defined as “Disease of low bone mass and increase the risk of bone fracture”, and the number of estimated patients is 13 million in Japan. Bone strength is estimated by the bone density and quality. Bone quality is affected by bone architecture, turnover, accumulated damage, and mineralization. The bisphosphonates and selective estrogen receptor modulators (SEAM) are thrown for treatment in the current osteoporosis therapies, but effect of these drugs is only reduction of fracture risk and determinative in improvement of the bone density. On the other hand, it is reported that activated vitamin D3 and vitamin K2 improve the bone quality. But the effect of these vitamins is poor, effective therapeutic agents for improvement of the bone quality is required.
Objectives: The objective of this study is to determine the benefits of Salmon cartilage proteoglycan (SPG) diet in ovariectomized rats.
Materials and method: 1. Animal experiments Fifty 8-week-old female Sprague-Dawley rats were housed individual cages. The rats were randomized into sham or OVX experiments, and underwent either ovariectomy or sham-operation under anesthesia with sodium pentobarbital. The rats were divided into the following five groups. A) SHAM: sham-operated rats/receive MF B) OVX: ovariectomized rats/receive MF C) Ca-less: ovariectomized rats/receive Calcium-lessness Diet D) 5%SPG: ovariectomized rats/receive MF which includes SPG by the 5 wt% E) 10%SPG: ovariectomized rats/receive MF which includes SPG by the 10 wt% The respective groups received free access to water and Diet for 12 weeks, and the rats were sacrificed using intraperitoneal sodium pentobarbital at 12 weeks postoperatively. Whole blood was collected via abdominal aorta, and both side femurs were collected by surgery extraction. 2. Serum Biochemistry analysis Serum was separated from whole blood by centrifusion. Gla/Glu type Osteocalcin (Takara bio. INC., Japan) and TRAP-5b (DS Pharma Biomedical Co., Japan) were measured by EIA. 3. Peripheral quantitative computed tomography (pQCT) analysis To evaluate bone strength and density, pQCT sectional images were taken by XCT Research SA+ (Stratec Medizintechnik GmbH Pforzheim, Germany). Densitometric parameters and geometric parameters were analyzed. 4. Histopathological analysis To evaluate bone inner structure, left side femurs were fixed in the 10% formalin for 48 h and 70% ethanol for 72 h. After Calcium was removed by the 10% EDTA solution for 4 weeks, femurs were embedded in the paraffin (FFPE). HE stain, Azan stain and immunohistochemistry were performed on FFPE sections.
Results: Gla/Glu type Osteocalcin expression showed up-regulation in OVX rats. Gla/Glu type Osteocalcin expression showed down- regulation by SPG treatment, and it was equal to sham-operated rats. Although Bone strength and density showed weak improvement effect by SPG treatment, but it was not significantly. Trabecula showed decrease in OVX rats by histopathological evaluation. Meanwhile, SPG treatment suppressed decrease of trabecula.
Conclusions: It suggested that SPG suppress destroy of trabecula, and prevents deterioration of the bone quality. It is expected that SPG has the preventive effect to the osteoporosis.
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