The Effect of Changes in Body Weight on Atherosclerosis in the Rabbit

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Abstract
The striking clinical association of atherosclerosis with obesity has led to an investigation of the effect of decreased caloric intake on the severity of experimentally induced atherosclerosis in the rabbit. 28 rabbits were sorted into pairs or groups of 3 on the basis of body wt.; one animal of each group was given a Purina Chow diet ad libitum throughout the expt., the other member of the pair was allowed only 50% of the previous day''s food intake of the freely fed member, and the other 2 members of the groups of 3 were allowed 40 and 60%, respectively. After 2 wks. on this regimen all rabbits were given 1 g. of cholesterol in suspension daily by stomach tube for periods ranging from 30 to 51 days. Blood cholesterol level was detd. before the initiation of cholesterol admn. and weekly during the period of admn. After 4-7 weeks on the cholesterol regimen animals were sacrificed; the intact aortas were removed, fixed in 10% formalin, stained with Sudan IV, and graded as to the severity of symptoms as detd. by the area of the aortic intima involved by lesions. Statistical analysis showed a highly significant correlation between the food intake and ratio of final to initial wt. The degree of atherosclerosis was not significantly correlated with initial wt., wt. change, or the duration of cholesterol treatment; correlation with avg. blood cholesterol level was significant at the 5% level (r = 0.43). The coeff. of multiple correlation of the degree of atherosclerosis (Y) to total cholesterol dosage (1), avg. blood cholesterol level (2), initial wt. (3), and ratio of final to initial wt. (4) was significant beyond the 1% point (rm= 0.7165). Standard partial regression coeffs. indicating the relative significance of these independent variables in determining the estimated value of the dependent variable were as follows: b''y1.234, 0.150; b''y2.134 0.553; b''y3.124, 0.484; and b''y4.123, 0.535; thus (2), (3), and (4) are of approx. equal importance. In evaluation of agents suspected of causing atherosclerosis there must be exptl. or statistical control of changes in body wt.