A marked increase in pre-beta-lipoprotein was found in eleven of twenty-one untreated diabetic children and six of twenty treated diabetic children. In both diabetic and nondiabetic pregnant women there was a steady increase in the amount of this lipoprotein after the sixteenth week of pregnancy whereas earlier in pregnancy a marked increase was found only in a small group of diabetic women (five of fifty-two).
A detailed study of the nature of pre-beta-lipoprotein showed that the protein moiety is immunochemically the same as that of beta-lipoprotein, but that the lipid moiety contains more triglyceride and less cholesterol than that of beta-lipoprotein. Pre-beta-lipoprotein as defined by paper electrophoresis was found, on ultracentrifugal separation using the salt density gradient method, to have a flotation rate of Sf15–100. Paper electrophoresis provides a useful though rough means of recognizing excessive amounts of this lipoprotein. A marked pre-beta band suggests the presence of more than 125 mg. per 100 ml. of Sf15–100 lipoprotein-lipid.
Studies of the lipid composition of Sf15–100, 10–15, 3–9 and high-density lipoproteins showed that, for each fraction, the lipid composition remains constant irrespective of the amount of total lipid within the fraction and irrespective of whether the individual is diabetic or nondiabetic, pregnant or nonpregnant.
