[Isolation of isoforms of apolipoprotein CIII from human serum by chromatofocusing].

This study aimed to isolate isoforms of apolipoprotein (apo) C III from human serum. 24-hour fasting serum from normal and hyperlipidemic subjects was pooled and subjected to ultracentrifugation at plasma density for 20 hours. Very low density lipoprotein (VLDL) was collected at density of d < 1.006 g/ml, and it was delipidated by ethanol and ether. The delipidated apo-VLDL was dissolved in a solution containing 7.2 mol/L urea and 20 mmol/L dithiothreitol. The insoluble apo B was removed by centrifugation. The soluble apo-VLDL was applied to PBE94 column, and eluted with elution buffer containing polybuffer 74 and 8 mol/L urea (1:8, pH4.0). After pooled, the eluted peaks of apolipoproteins were applied to column chromatography of hydroxylapatite to remove the polybuffer. The purified isoforms of apoC III and the purified apo C I, C II and E, were characterized by isoelectrofocusing and west blot. The results showed that the purified apoC III1, C III2, and C II were pure.

Apolipoprotein C subtype distribution in type 2 diabetes mellitus.

Plasma lipid levels and apolipoprotein C (apo C) composition of VLDL were investigated in a group of Type 2 diabetic patients at first attendance at the outpatient clinic and before any therapeutic intervention. Patients were distributed into two groups of 26 individuals, normo- and hyperlipidaemic, respectively, and compared with two matched control groups. Normolipidaemic diabetic patients had higher serum triglycerides, VLDL cholesterol, and lower HDL cholesterol than matched normolipidaemic control subjects. While hyperlipidaemic non-diabetic individuals showed increased apo C II and decreased apo C III-1 percentages when compared with normolipidaemic non-diabetic individuals (12.1 +/- 4.9 vs 8.5 +/- 3.2% and 44.0 +/- 6.7 vs 48.1 +/- 7.0%, respectively, mean +/- SD, both with p less than 0.05), the relative distribution of apo C III isoforms and apo C II was similar in both normo- and hyperlipidaemic diabetic patients.

Plasma kinetics of VLDL and HDL apoC-I in normolipidemic and hypertriglyceridemic subjects.

ApoC-I has several different lipid-regulating functions including, inhibition of receptor-mediated uptake of plasma triglyceride-rich lipoproteins, inhibition of cholesteryl ester transfer activity, and mediation of tissue fatty acid uptake. Since little is known about the rate of production and catabolism of plasma apoC-I in humans, the present study was undertaken to determine the plasma kinetics of VLDL and HDL apoC-I using a primed constant (12 h) intravenous infusion of deuterium-labeled leucine. Data were obtained for 14 subjects: normolipidemics (NL, n = 4), hypertriglyceridemics (HTG, n = 4) and combined hyperlipidemics (CHL, n = 6). Plasma VLDL triglyceride (TG) levels were 0.59 +/- 0.03, 4.32 +/- 0.77 (P < 0.01 vs. NL), and 2.20 +/- 0.39 mmol/l (P < 0.01 vs. NL), and plasma LDL cholesterol (LDL-C) levels were 2.34 +/- 0.22, 2.48 +/- 0.26, and 5.35 +/- 0.48 mmol/l (P < 0.01 vs. NL), respectively. HTG and CHL had significantly (P < 0.05) increased levels of total plasma apoC-I (12.5 +/- 1.2 and 12.4 +/- 1.3 mg/dl, respectively) versus NL (7.9 +/- 0.6 mg/dl), due to significantly (P < 0.01) elevated levels of VLDL apoC-I (5.8 +/- 0.8 and 4.5 +/- 0.8 vs. 0.3 +/- 0.1 mg/dl). HTG and CHL also had increased rates of VLDL apoC-I transport (i.e., production) versus NL: 2.29 +/- 0.34 and 3.04 +/- 0.53 versus 0.24 +/- 0.11 mg/kg.day (P < 0.01), with no significant change in VLDL apoC-I residence times (RT): 1.16 +/- 0.12 versus 0.69 +/- 0.06 versus 0.74 +/- 0.17. Although HDL apoC-I concentrations were not significantly lower in HTG and CHL versus NL, HDL apoC-I rates of transport were inversely related to plasma and VLDL-TG levels (r = -0.63 and -0.62, respectively, P < 0.05). Our results demonstrate that increased levels of plasma and VLDL apoC-I in hypertriglyceridemic subjects (with or without elevated LDL-C levels) are associated with increased levels of plasma VLDL apoC-I production.