Postmenopausal osteoporosis fingerprinted by miRNAs

MicroRNAs (miRNAs) are short stretches of genetic material that circulate in the blood, and they are increasingly being investigated as biomarkers, from food allergy, to heart disease to cancer. Now, researchers at Creighton University in Nebraska have linked a circulating miRNA to postmenopausal osteoporosis.

After menopause, the fall in natural estrogen can lead to low bone mineral density (BMD), causing bone thinning and loss. This condition is known as postmenopausal osteoporosis, and it increases the risk of bone breaks, which are painful and distressing, and can end with a loss of independence. Osteoporosis is diagnosed through bone scans and blood and urine bone markers, including bone-specific alkaline phosphatase (bone ALP or BALP), osteocalcin, urinary N-telopeptide of type I collagen (uNTX) and vitamin D levels, but additional markers could help physicians to predict risk and track the disease.

The researchers screened circulating monocytes (white blood cells) in women with high and low BMD for miRNAs, and they found increased levels of MiR-133a in women with low bone density. This miRNA has known links with bone and muscle development. This was also linked with three possible target genes, CXCL11 and CXCR3 (genes for the small proteins known as chemokines) and SLC39A1, which is involved in the uptake of zinc (zinc deficiency is linked with osteoporosis), but this connection was not statistically significant, perhaps because of the small study size of 20 women. The researchers are planning a larger independent population to look at miRNA, genes and proteins.

Osteoporosis is linked to a great many genes. In other research, an international meta-analysis of genome-wide association studies of osteoporosis has found 56 genetic variants that influence BMD, and 14 of these were linked to fractures. Women who have an increased number of BMD genetic variants are at a higher risk of osteoporosis.

- see the abstract in PLoS ONE
- check out the press release on osteoporosis genes