The purpose of this study was to investigate possible relationships between lipoprotein (a) [Lp(a)] levels and NIDDM in African-Americans. The objectives were to identify associations between Lp(a) levels of subjects with and without NIDDM and to determine the influence of glycemic control, determined by GHb, and of mode of therapy on Lp(a) levels.
We studied 141 African-American subjects, 103 with NIDDM and 38 without NIDDM. Their Lp(a) levels, GHb levels, and apolipoprotein (a) [apo(a)] isoforms were determined. Clinical information, including mode of therapy (sulfonylurea, insulin, or no pharmacological therapy), date of diagnosis, and medical history, was obtained by chart review and patient interview.
There was no significant difference in median Lp(a) levels between the non-NIDDM (25.5 mg/dl) and NIDDM (24.0 mg/dl) study subjects. No statistically significant difference was found in Lp(a) levels when NIDDM patients with GHb < 12.3% were compared to those with GHb ≥ 12.3% (P = 0.096). An inverse relationship was found between apo(a) root-mean-square isoform size and Lp(a) level (r2 = 0.091, P = 0.0035). Analysis of the cases by mode of therapy indicates that there is evidence of an increased median level of Lp(a) in African-Americans with NIDDM on insulin therapy relative to those on sulfonylurea (34.0 vs. 16.0 mg/dl; P = 0.013) and to nondiabetic subjects (34.0 vs. 25.5 mg/dl; P = 0.043).
We conclude that the level of plasma Lp(a) is higher in African-Americans with NIDDM who are being treated with insulin when compared to those on sulfonylurea therapy and to those who are non-NIDDM subjects, and this does not seem to be due to genetic variance or method bias.