Effects of niacin and omega-3 fatty acids on the apolipoproteins in overweight patients with elevated triglycerides and reduced HDL cholesterol.

OBJECTIVE: Prescription omega-3 acid ethyl esters (P-OM3) and extended release niacin (ERN) both have beneficial effects on plasma lipids and lipoproteins. The purpose of this study was to describe the effects of mono- and combination (Combo) therapy of these agents in patients with the metabolic syndrome. METHODS: Very low density (VLDL), intermediate/low density (IDL/LDL, hereafter LDL), and high density lipoproteins (HDL) were isolated from 56 overweight patients with elevated triglyceride/HDL-C ratios at baseline and after 16 weeks of treatment with placebo, ERN (2g/day), P-OM3 (4g/day), or Combo and then analyzed by quantitative electrophoresis for apolipoproteins (apo) A1, A2, B, C2, C3 and E. Total plasma concentrations and the ratios of each apo with apoB (in VLDL and LDL) and with apoA1 (in HDL) were calculated. An apoC3 glycosylation index (a ratio between di- and mono-sialylated isoforms) was also determined in plasma and in each lipoprotein fraction. RESULTS: ERN reduced plasma apoB (-11%, p < 0.05). Combo increased LDL apoE/apoB ratio (64%, p < 0.01) and LDL apoA1/apoB (91%, p < 0.05). ERN increased the apoC3 glycosylation index only in HDL (37%, p < 0.05), whereas P-OM3 and Combo increased the index in whole plasma (48% and 49%, respectively, p < 0.05 for both) and in every lipoprotein class (VLDL: 26%, p < 0.01 and 26%, p < 0.05; LDL: 55%, p < 0.01 and 61%, p < 0.01; HDL: 43%, p < 0.001 and 44%, p < 0.001, respectively). All findings were significant after adjustment for age, sex, body mass index (BMI), smoking, medications, and baseline apo value. CONCLUSIONS: ERN produced a beneficial reduction in plasma apoB. The enrichment of LDL with apoE and apoA1 was unique to the Combo group and might be beneficial owing to the atheroprotective properties of apoE and HDL2 (a likely source of apoA1 in LDL fraction). The effect of therapies on the apoC3 glycosylation index is a novel finding, the implications of which will require further study.

Reduced apolipoprotein glycosylation in patients with the metabolic syndrome.

OBJECTIVE: The purpose of this study was to compare the apolipoprotein composition of the three major lipoprotein classes in patients with metabolic syndrome to healthy controls. METHODS: Very low density (VLDL), intermediate/low density (IDL/LDL, hereafter LDL), and high density lipoproteins (HDL) fractions were isolated from plasma of 56 metabolic syndrome subjects and from 14 age-sex matched healthy volunteers. The apolipoprotein content of fractions was analyzed by one-dimensional (1D) gel electrophoresis with confirmation by a combination of mass spectrometry and biochemical assays. RESULTS: Metabolic syndrome patients differed from healthy controls in the following ways: (1) total plasma--apoA1 was lower, whereas apoB, apoC2, apoC3, and apoE were higher; (2) VLDL--apoB, apoC3, and apoE were increased; (3) LDL--apoC3 was increased, (4) HDL--associated constitutive serum amyloid A protein (SAA4) was reduced (p<0.05 vs. controls for all). In patients with metabolic syndrome, the most extensively glycosylated (di-sialylated) isoform of apoC3 was reduced in VLDL, LDL, and HDL fractions by 17%, 30%, and 25%, respectively (p<0.01 vs. controls for all). Similarly, the glycosylated isoform of apoE was reduced in VLDL, LDL, and HDL fractions by 15%, 26%, and 37% (p<0.01 vs. controls for all). Finally, glycosylated isoform of SAA4 in HDL fraction was 42% lower in patients with metabolic syndrome compared with controls (p<0.001). CONCLUSIONS: Patients with metabolic syndrome displayed several changes in plasma apolipoprotein composition consistent with hypertriglyceridemia and low HDL cholesterol levels. Reduced glycosylation of apoC3, apoE and SAA4 are novel findings, the pathophysiological consequences of which remain to be determined.

Basal omega-3 fatty acid status affects fatty acid and oxylipin responses to high-dose n3-HUFA in healthy volunteers.

A subject's baseline FA composition may influence the ability of dietary highly unsaturated omega-3 FAs (n3-HUFA) to change circulating profiles of esterified FAs and their oxygenated metabolites. This study evaluates the influence of basal n3-HUFA and n3-oxylipin status on the magnitude of response to n3-HUFA consumption. Blood was collected from fasting subjects (n = 30) before and after treatment (4 weeks; 11 ± 2 mg/kg/day n3-HUFA ethyl esters). Esterified FAs were quantified in erythrocytes, platelets, and plasma by GC-MS. Esterified oxylipins were quantified in plasma by LC-MS/MS. Treatment with n3-HUFAs increased n3-HUFAs and decreased n6-HUFAs in all reservoirs and increased plasma n3-oxylipins without significantly changing n6-oxylipin concentrations. As subject basal n3-HUFAs increased, treatment-associated changes decreased, and this behavior was reflected in the percentage of 20:5n3 + 22:6n3 in red blood cell membrane FAs (i.e., the omega-3 index). To maintain an omega-3 index of 8% and thus reduce cardiovascular disease risk, our analyses suggest a maintenance dose of 7 mg/kg/day n3-HUFA ethyl esters for a 70-kg individual. These results suggest that the basal n3 index may have clinical utility to establish efficacious therapeutic experimental feeding regimens and to evaluate the USDA Dietary Guidelines recommendations for n3-HUFA consumption.