Concordant lipoprotein and weight responses to dietary fat change in identical twins with divergent exercise levels 1.
BACKGROUND
Individuals vary greatly in their lipoprotein responses to low-fat diets, with some of this variation being attributable to genes.


OBJECTIVE
The purpose was to test the extent to which individual lipoprotein responses to diet can be attributed to genes in the presence of divergent exercise levels.


METHODS
Twenty-eight pairs of male monozygotic twins (one twin mostly sedentary, the other running an average of 50 km/wk more than the sedentary twin) went from a 6-wk 40%-fat diet to a 6-wk 20%-fat diet in a crossover design. The diets reduced fat primarily by reducing saturated and polyunsaturated fat (both from 14% to 4%) while increasing carbohydrate intake from 45% to 65%.


RESULTS
Despite the twins' differences in physical activity, the dietary manipulation produced significantly correlated changes (P < 0.05) in the twins' total cholesterol (r = 0.56); LDL cholesterol (r = 0.70); large, buoyant LDL [Svedberg flotation rate (S(f)) 7-12; r = 0.52]; apolipoprotein A-I (r = 0.49); lipoprotein(a) (r = 0.49); electrophoresis measurements of LDL-I (LDLs between 26 and 28.5 nm in diameter; r = 0.48), LDL-IIB (25.2-24.6 nm; r = 0.54), and LDL-IV (22-24.1 nm; r = 0.50); and body weight (r = 0.41). Replacing fats with carbohydrates significantly decreased the size and ultracentrifuge flotation rate of the major LDL and the LDL mass concentrations of large, buoyant LDL; LDL-I; HDL cholesterol; and apolipoprotein A-I and significantly increased concentrations of LDL-IIIA (24.7-25.5 nm) and lipoprotein(a).


CONCLUSIONS
Even in the presence of extreme differences in exercise, genes significantly affect changes in LDL, apolipoprotein A-I, lipoprotein(a), and body weight when dietary fats are replaced with carbohydrates.
Williams
Paul T
PT
Lawrence Berkeley National Laboratory, Donner Laboratory, Berkeley, CA 94720, USA. ptwilliams@lbl.gov
Blanche
Patricia J
PJ
Rawlings
Robin
R
Krauss
Ronald M
RM
D001835:Body Weight / Q000187:drug effects; D002784:Cholesterol / Q000097:blood*; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000494:pharmacology*; D004041:Dietary Fats / Q000008:administration & dosage / Q000494:pharmacology*; D015444:Exercise; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D014430:Twins, Monozygotic / Q000378:metabolism*
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D008074:Lipoproteins; D002784:Cholesterol