Serum lipid profile in postmenopausal women with osteoporosis or osteopenia.

To the Editor: Clinical studies have suggested that atherosclerosis is also associated with reduced bone density. Data propose that lipid oxidation, which plays such a central role in the pathogenesis of atherosclerosis, may also promote osteoporosis, thereby linking lipid metabolism and inflammation to regulation of bone density. (1) We performed a study to determine the relationship between serum lipid profile values, bone mineral density (BMD) scores and serum osteocalcin levels of postmenopausal women with osteopenia or osteoporosis.

Five hundred and fifty postmenopausal women with osteopenia or osteoporosis were voluntarily enrolled in this study from September 2000 to March 2005. BMD of the left proximal femur (the femoral neck, the greater trochanter, and Ward triangle) and lumbar spine (L1-L4) was measured by duel energy x-ray absorptiometry (DXA) using a QDR-4000 scanner (Hologic Inc., Waltham, MA). Serum total cholesterol, triglyceride levels, low-density lipoprotein cholesterol (LDL-c), low serum high-density lipoprotein cholesterol (HDL-c), very low-density lipoprotein cholesterol, and osteocalcin analysis were performed at the University Hospital Biochemistry Laboratory.

According to the data analysis, HDL-c showed a significant positive correlation with a DXA score of the lumbar spine (r = 0.12, P < 0.05) and hip (r = 0.17, P < 0.01). Furthermore, a negative correlation was determined between LDL-c and DXA score at the hip (r = -0.11, P < 0.05). On the other hand, a significant negative correlation was found between osteocalcin values with total cholesterol (r = -0.13, P < 0.05) and triglycerides (r = -0.12, P < 0.05) and age (r = -0.10, P < 0.05). Negative correlation was detected between age with DXA score of the spine (r = -0.16, P < 0.01) and femur (r = -0.32, P < 0.01). The positive correlation was found between body mass index with a DXA score of the lumbar spine (r = 0.23, P < 0.01) and femur (r = 0.29, P < 0.01). However, no association of other variables was found (P > 0.05). There was negative correlation between duration of menopause with a DXA score of the lumbar spine (r = -0.19, P < 0.01), femur (r = -0.31, P < 0.01) and serum osteocalcin (r = -0.11, P < 0.05).

The original observation suggesting that oxidized lipids might play a role in bone cell function was the inhibition of osteoblastic differentiation upon treatment with certain oxidized lipids and lipoproteins. A study demonstrated decreased bone mineralization in the vertebrae of mice fed with an atherogenic high-fat diet. (1) Furthermore, a prospective study by Chan et al demonstrated that lipid-lowering therapy resulted in slight increases in osteocalcin without changes in C-terminal telopeptides of type I collagen, also suggesting a direct influence of serum cholesterol on osteoblast function. (2)

Yamaguchi et al performed a study in 214 postmenopausal women and reported a positive correlation between serum HDL-c levels and DXA scores and a negative correlation between serum LDL-c levels and DXA scores. They also found that serum triglyceride levels were lower in women with vertebral fractures than in those without fracture. (3) Tanko performed a study in 340 postmenopausal women and suggested that the weak associations between spine BMD and serum cholesterol can be explained by the fact that both variables are simultaneously affected by estrogen deficiency rather than by a direct influence of serum cholesterol on osteoblast function. (4) Andrea et al studied 1,303 postmenopausal women and reported that postmenopausal women with increased plasma LDL cholesterol levels had a greater probability of being classified as osteopenic than women with normal plasma LDL cholesterol levels. (5) We also found a positive correlation between DXA scores and HDL-c values, and a negative correlation between cholesterol and triglyceride levels with serum osteocalcin.

Thus, our results suggest that there are weak associations between BMD and serum lipid levels. However, vertebral or other skeletal fractures and biochemical markers for bone formation and resorption were not evaluated in this study. It appears that further studies are needed to investigate the relationship between osteoporosis and the lipid profile.

Gulcan Gurer, MD

Omer Faruk Sendur, MD

Ali Aydeniz, MD

Department of Physical Therapy and Rehabilitation

Adnan Menderes University 

Medical School

Aydin, Turkey

References

1. Parhami F, Tintut Y, Beamer WG, et al. Atherogenic high fat diet reduces bone mineralization in mice. J Bone MineralRes 2001; 16:182-188.

2. Chan MH, Mak TW, Chiu RW, et al. Simvastatin increases serum osteocalcin concentration in patients treated for hypercholesterolaemia. J Clin Endocrinol Metab 2001;86:4556-4559.

3. Yamaguchi T, Sugimoto T, Yano S, et al. Plasma lipids and osteoporosis in postmenopausal women. Endocr J 2002;49:211-217.

4. Tanko LB, Nielsen SB, Christiansen C. Does serum cholesterol contribute to vertebral bone loss in postmenopausal women? Bone 2003;32:8-14.

5. Poli A, Bruschi F, Cesana B, et al. Plasma low-density lipoprotein cholesterol and bone mass densitometry in postmenopausal women. Obstet Gynecol 2003;102:922-926.