OBJECTIVES: I. Examine the concentration of docosahexanoic acid (DHA) and other n-3 fatty
acids in plasma, erythrocyte, and adipose tissue in patients with various forms of retinitis
pigmentosa and Usher syndrome.
II. Determine the synthesis and catabolism of DHA from linolenic acid in these patients.
III. Determine the synthesis, absorption, and catabolism of DHA under different dietary
conditions in these patients.
PROTOCOL OUTLINE: Patients may participate in one or more of the arms of this study.
Arm I (adipose tissue study): Adipose tissue is collected from the buttocks of patients
with Usher II retinitis pigmentosa (RP), patients with non-Usher RP, and control subjects.
Dietary histories are obtained from all patients and subjects.
Arm II (isotope study): Patients meeting the same criteria as in arm I receive oral
D5-labeled linolenic acid and oral D4-labeled linolenic acid that is dissolved in oil and
incorporated into foods. Subjects must avoid eating fish and shellfish during the 35 days
of the isotope study. Blood samples are collected at 0, 8, 24, and 48 hours, daily on days
3-7, and then on days 10, 18, and 35.
Arm III (flaxseed oil feeding): Patients with all types of RP and control subjects receive
flaxseed oil, a form of linolenic acid, for 12 weeks. Subjects may also receive high oleic
safflower oil or olive oil as a control fat for 12 weeks. Subjects complete a diet history
at the end of each fatty acid supplementation period. All subjects must follow a diet free
of seafood and fish oil supplements.
PROTOCOL ENTRY CRITERIA:
- Retinitis pigmentosa, including: Usher syndrome (types I and II) Simplex
- The following inheritance patterns eligible: X-linked recessive; Autosomal
dominant; Autosomal recessive