Genetics Influence Bone Loss after Liver Transplant

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The summary below is from the full report titled "Influence of the Vitamin D Receptor Gene Polymorphism on Bone Loss in Men after Liver Transplantation." It is in the 16 November 1999 issue of Annals of Internal Medicine (volume 131, pages 752-755). The authors are J. Guardiola, X. Xiol, R. Sallie, J.M. Nolla, D. Roig-Escofet, E. Jaurrieta, and L. Casais.

What is the problem and what is known about it so far?

Weakening of the bones, also known as osteoporosis, is a common problem for patients who get liver transplants. Many factors play a role in this bone weakening, including the medications people receive after transplant and the long period of decreased activity during recovery from the transplant surgery. However, some people, despite similar medicines and periods of inactivity, have very different degrees of bone loss. It is possible that genes influence how a person's body responds to conditions that cause bone loss.

Why did the researchers do this particular study?

The researchers wanted to see if there was any relationship between the amount of bone loss people suffer after a liver transplant and their genes. In particular, they were interested in a vitamin D-receptor gene. Vitamin D and the way the body handles it is very important to maintain healthy bones.

Who was studied?

The researchers studied 55 men who had liver transplants at a teaching hospital in Spain.

How was the study done?

The researchers measured bone mineral density in the spines of the study patients before and 3, 6, 12, and 24 months after liver transplant. Bone mineral density was measured with a test called bone densitometry that uses low-dose x-rays. The researchers also determined the Vitamin D-receptor gene type for each patient. Finally, they looked for relationships between gene types and bone loss measurements.

What did the researchers find?

The three different gene types they found were called BB, Bb, or bb. Patients that had types BB or Bb lost much more bone than people who had gene type bb. However, in all groups, bone loss was worst in the first 3 months after transplant and bone density increased between 3 and 24 months.

What were the limitations of the study?

This study included only men who had liver transplants. It is unclear if these findings would also apply to women with liver transplants or to people who have bone loss caused by other conditions.

What are the implications of the study?

Vitamin D-receptor genes influence the amount of bone loss after a liver transplant. Further study is needed to determine how these genes influence bone loss in other situations.