Long term Objectives: To define the types of high fiber diet most suitable for the dietary management of specific types of hyperlipidemia.
Specific Aims : To compare the effects of soluble and insoluble fiber diets on the blood lipids and clotting-factors in-groups of patients with specific dyslipoproteinemias and the possible mechanisms of action of - fiber - as they relate to: 1) increased bile acid loss 2) altered fat absorption; 3) absorbed products of colonic fiber fermentation; 4) reduced postprandial insulin levels. Health Relatedness of project: Different fibers have different effects which will determine their appropriateness in the treatment of specific dyslipoproteinemias. Recognition of many of these properties is new. The successful use of fiber depends on a detailed knowledge of mechanism and the logical application of this to specific lipid disorders. Information on-the effect of fiber-on hemostatic-variables-in addition-to blood lipids, is_highly desirable if the ultimate-dietary objective is-to reduce-risk factors associated with CHD. Methodology to Achieve Goals: Three groups of 20 hyperlipidemic patients (Types IIa, IIb, and IV) will be studied for two 4-month test periods on diets rich in soluble and insoluble fiber in a randomized crossover design separated by 2 months on their regular diet. A fourth group of patients will also be studied where the insoluble fiber diet will be recruited for this final part of the project. Complete diets metabolically defined will be provided for each dietary fiber period. Detailed measurements of blood lipids and lipoproteins will be made over the course of the study with ultracentrifugal flotation, gel electrophoresis, rocket electroimmunoassay, GLC, and enzyme activation analysis. Clotting factors will be measured by radioimmunoassay. An assessment of mechanisms will include measurement of: l) fecal bile acid lost type and amount by GLC) ; 2) fat tolerance test meal studies at the beginning and end of each period; 3) in vitro colonic fermentation by measurement of day long breath H2, urine and plasma short chain fatty acids and their generation in an in vitro colonic model; 4) chronic reduction in insulin secretion by 24 h urinary C-peptide output and glucose tolerance tests performed across the periods.
