Effects of Different Sources of n-3 Fatty Acids on Bone Loss, Body Fat and Inflammatory Markers in Osteoporotic Condition with Diabetes

The most important risk factors for osteoporosis are advanced age and female sex. Estrogen deficiency contributes bone loss and adiposity in postmenopausal women. Bone remodeling is crucial for maintenance of bone mass density (BMD), size, shape and integrity. The remodeling is dependent on the balance of deposition by osteoblasts and resorption by osteocytes. Bone specific alkaline phosphate (BAP) and osteocalcin(OCN) are markers of bone formation. Deoxypyridinoline, and tartrate-resistant acid phosphate (TRAP) are related with bone resorption and bone matrix breakdown. Studies showed that the receptor activator of nuclear factor kappa B ligand (RANKL) promotes the osteoclast differentiation and inhibit its apoptosis. The expression of nuclear factor kappa B (NF-κB) can regulate its downstream cytokines expression such as tumor necrosis factor receptor (TNF)-α, interleukin (IL)-1 and IL-6 and directly regulate osteoclastogenesis. Attenuation of cytokines secretion and NF-κB expression and reduced RANKL activation could be the possible mechanisms to improve the balance of bone remodeling. Moreover, recent studies showed that higher fat mass and diabetes also provoke the risk of osteoporosis and bone fracture. Inflammatory cytokines, reactive oxygen species (ROS) and advanced glycation end products (AGEs) are thought to play important roles in the pathogenesis of diabetic-related bone metabolic imbalance. High-fat-diet induces adipose tissue inflammation and bone resorption. Adipose tissue inflammation plays a key role in the development of insulin resistance. Fish oil and perilla oil, rich in n-3 polyunsaturated fatty acids, both are able to reducing the level of prostaglandin E2 as well as proinflammatory cytokines. The source of a lower n-3/n-6 fatty acids ratio in dietary oil is implicated in causing osteoporosis and adipose tissue inflammation. Several studies have shown that increasing diet content of n-3 fatty acids will inhibit osteoclast production, reduce bone loss and RANKL expression. However, no studies were performed with co-morbidities as osteoporosis and diabetes. Ovariectomized(OVX) and high fat diet-induced diabetic animal model were widely used in osteoporotic and diabetic studies, respectively. Therefore, this 3-year-study will be carried out to investigate the effect of n-3 fatty acids on bone loss, body fat and inflammatory response in osteoporotic condition with diabetes. In the first year, we will treat OVX C57BL/6 with different dietary sources of n-3 fatty acids and adjustment for different ratio of n-3/n-6 fatty acids to investigate the effect of these n-3 fatty acids on bone metabolic-related biomarker, cytokines, the BMD, degree of bone bending as well as body fat percentage and adipose tissue inflammation in OVX mice. In the second year, according the results of dietary n-3/n-6 fatty acids ratio in the previous year, we will create an OVX with high-fat diet induced diabetic co-morbidities animal model to assess whether the appropriate dietary n-3/n-6 ratio administration may alleviate bone loss and inflammatory response. Because our animal studies cannot explore the mechanism of bone cell metabolism. Thus, in the third year we will cultivate MC3T3-E1 (osteoblast-like cell) and RAW 264.7(murine macrophage, a pre-osteoclast cell line) with n-3 fatty acids under high concentration of glucose. MC3T3-E1 will be used to observe the proliferation of osteoblast. RAW 264.7, after stimulation with soluble RANKL, will differentiate into osteoclast we will further characterize the mechanisms of n-3 fatty acids on bone matrix hydrolytic protein, osteoblast proliferation, RANKL expression as well as NF-κB activity. The results of this proposal will lead to a better knowledge to understand the effect of n-3 fatty acids on bone loss, body fat mass and inflammatory response in osteoporotic condition with diabetes for clinical applications.