Sterol Metabolism in Ovariectomized Rats: Potential Roles of Campesterol and 4β‐Hydroxycholesterol in Osteoporosis

Osteoporosis is characterized by low bone mass and microarchitectural deterioration of bone tissue. Lipid metabolism disorders may contribute to osteoporosis in postmenopausal women. Phytosterols and oxysterols (OC) are involved in lipid metabolism. However, their roles in bone metabolism and in the development of osteoporosis remain unclear. This study used ovariectomized (OVX) rats, commonly used to study osteoporosis, to analyze the levels of sterols, including phytosterols, cholesterol, and oxysterols in the humerus, femur, femoral bone marrow, blood, and liver. Sterol levels were measured through gas chromatography. We observed that campesterol and cholesterol exhibited similar patterns of change in the blood, liver, and bone marrow. Conversely, cholesterol and campesterol levels in the femur did not change significantly, while bone marrow cholesterol levels decreased. The similar changes in campesterol and cholesterol levels suggest that these sterols are derived from the blood and taken up by the bone marrow. Significant increases in 4β-hydroxycholesterol were found in the humerus, plasma, and liver of OVX rats. The ratio of 4β-hydroxycholesterol to cholesterol in the bone marrow was significantly increased in OVX rats. These findings suggest that 4β-hydroxycholesterol is associated with OVX-induced osteoporosis and contributes to the decline in bone density.