Prevalence of vertebral fractures in adults with cystic fibrosis and their relationship to bone mineral density

Fenretinide prevents the development of osteoporosis in Cftr-KO mice

BACKGROUND

The most recently described phenotype associated with Cystic Fibrosis (CF) is reduced bone mineral density which results in osteopenia and osteoporosis. The etiology of the early onset of osteoporosis in CF patients has remained to be established. It has been suggested that inadequate nutritional absorption of essential fatty acids may play a role in the altered bone metabolism. In this study, we characterized the protective effect of fenretinide [N-(4-hydroxyphenyl) retinamide], a vitamin A derivative, on the early onset of osteoporosis in cystic fibrosis transmembrane conductance regulator knockout (Cftr-KO) mice.

METHODS

Using micro-computed-tomography we examined the effect of fenretinide on the bone composition and architecture in a Cftr-KO mouse model which was then confirmed with histological analyses. Plasma fatty acids were quantified using thin layer chromatography-ELISA method.

RESULTS

Twice-weekly treatments with fenretinide, over four weeks dramatically increased trabecular bone volume compared to controls. This increase in bone volume was also related to an increased concentration of ceramide in the plasma resulting in the down regulation of phospholipid-bound AA in Cftr-KO mice.

CONCLUSIONS

To our knowledge, this is the first time that fenretinide's protective effect against osteoporosis has been demonstrated. The results of this study strongly suggest that fenretinide has potential to be used as a prophylaxis by preventing the early onset of osteoporosis.

Nutritional management of cystic fibrosis patients

PURPOSE OF REVIEW

We critique recent advances in nutritional care of patients with cystic fibrosis focusing on our understanding of the role of fecal elastase as a pancreatic function test, enzyme replacement therapy and bone health.

RECENT FINDINGS

Fecal elastase measured by the monoclonal antibody method is a useful screening test for delineating cystic fibrosis patients with pancreatic insufficiency (needing enzyme replacement therapy) from those with pancreatic sufficiency. Cutoff levels, however, have not been clearly defined, particularly in infancy. Newer enzyme products that attempt to improve the intralumenal intestinal pH with bicarbonate or using a combination of unprotected and enteric coated products fail to completely correct nutrient maldigestion. Compromised bone health in cystic fibrosis patients may be due to multiple factors including calcium, vitamin D, and vitamin K deficiencies and lung inflammation. Current recommendations for treatment of bone health in cystic fibrosis are not evidence-based.

SUMMARY

Fecal elastase is a useful marker of pancreatic function but limitations for this test exist. The presence of an acidic intestinal milieu and hitherto poorly defined intestinal factors may contribute to the failure of current enzyme preparations to correct nutrient assimilation in cystic fibrosis. The many factors that contribute to bone health must be evaluated when developing treatment strategies.