Concentration and chemical composition of plasma lipoprotein subfractions in patients with peripheral vascular disease. Evidence for normal apolipoprotein B but low cholesteryl ester content in small VLDL

Niemann-Pick C1-deficient mice lacking sterol O-acyltransferase 2 have less hepatic cholesterol entrapment and improved liver function

Cholesteryl esters are generated at multiple sites in the body by sterol O-acyltransferase (SOAT) 1 or SOAT2 in various cell types and lecithin cholesterol acyltransferase in plasma. Esterified cholesterol and triacylglycerol contained in lipoproteins cleared from the circulation via receptor-mediated or bulk-phase endocytosis are hydrolyzed by lysosomal acid lipase within the late endosomal/lysosomal (E/L) compartment. Then, through the successive actions of Niemann-Pick C (NPC) 2 and NPC 1, unesterified cholesterol (UC) is exported from the E/L compartment to the cytosol. Mutations in either NPC1 or NPC2 lead to continuing entrapment of UC in all organs, resulting in multisystem disease, which includes hepatic dysfunction and in some cases liver failure. These studies investigated primarily whether elimination of SOAT2 in NPC1-deficient mice impacted hepatic UC sequestration, inflammation, and transaminase activities. Measurements were made in 7-wk-old mice fed a low-cholesterol chow diet or one enriched with cholesterol starting 2 wk before study. In the chow-fed mice, NPC1:SOAT2 double knockouts, compared with their littermates lacking only NPC1, had 20% less liver mass, 28% lower hepatic UC concentrations, and plasma alanine aminotransferase and aspartate aminotransferase activities that were decreased by 48% and 36%, respectively. mRNA expression levels for several markers of inflammation were all significantly lower in the NPC1 mutants lacking SOAT2. The existence of a new class of potent and selective SOAT2 inhibitors provides an opportunity for exploring if suppression of this enzyme could potentially become an adjunctive therapy for liver disease in NPC1 deficiency. NEW & NOTEWORTHY In Niemann-Pick type C1 (NPC1) disease, the entrapment of unesterified cholesterol (UC) in the endosomal/lysosomal compartment of all cells causes multiorgan disease, including neurodegeneration, pulmonary dysfunction, and liver failure. Some of this sequestered UC entered cells initially in the esterified form. When sterol O-acyltransferase 2, a cholesterol esterifying enzyme present in enterocytes and hepatocytes, is eliminated in NPC1-deficient mice, there is a reduction in their hepatomegaly, hepatic UC content, and cellular injury.

Apolipoproteins C-II and C-III in peripheral arterial disease

Apolipoprotein (apo) C-II and apo C-III serum concentrations were investigated in 119 normotriglyceridemic male subjects with peripheral arterial disease (PAD) or coronary heart disease (CHD) or without clinical manifestations of atherosclerotic disease. All subjects included in the study had similar blood levels of total cholesterol (< 400 mg/dL). High-density lipoproteins cholesterol (HDL-C) subfractions and apo A-I serum levels were significantly lower in CHD patients, as were apo A-I/apo B and HDL-cholesterol/total cholesterol ratios. Apo C-II and apo C-III showed similar serum concentrations in all three groups of subjects, but apo C-II/apo C-III ratio was significantly lower in PAD patients as compared with that in CHD patients and control subjects. This study confirms that PAD may be associated with a particular lipoprotein derangement that primarily involves very low-density lipoprotein catabolism.

Lipoprotein profile in men with peripheral vascular disease. Role of intermediate density lipoproteins and apoprotein E phenotypes

BACKGROUND

The role of lipoprotein disturbances in the development of peripheral vascular disease (PVD) has not been sufficiently clarified.

METHODS AND RESULTS

The relations among concentrations of intermediate density lipoproteins (IDL), apoprotein (apo) B, apo E, and other lipoproteins were studied in 102 men with PVD and 100 healthy men who formed the control group. Patients with PVD had significantly higher levels of serum triglycerides, very low density lipoprotein (VLDL) cholesterol, VLDL triglycerides, VLDL proteins, IDL cholesterol, and IDL triglycerides and lower levels of high density lipoproteins (HDL) than controls. Serum cholesterol and triglycerides were normal in 30 patients (cholesterol, less than 5.2 mmol/l; triglycerides, less than 2.3 mmol/l), who had significant increases in IDL triglycerides and significant decreases in HDL cholesterol compared with the 47 controls, who had normal cholesterol and triglyceride levels. Patients with more severe distal involvement showed higher cholesterol and triglycerides carried by IDL and a greater reduction in HDL cholesterol. Smoking patients with PVD showed increased VLDL cholesterol and VLDL triglycerides and lower HDL concentrations. Apo E polymorphism in our study population does not differ from that reported for other European populations. Alleles epsilon 2 and epsilon 4 had a major impact on serum triglycerides and VLDL lipids in our patients with PVD.

CONCLUSIONS

Lipoprotein disturbances are a major risk factor for PVD. IDL abnormalities play an important role in the development and severity of PVD and should also be considered a vascular risk factor in normocholesterolemic and normotriglyceridemic patients.

Serum lipoprotein (a) levels in men with peripheral vascular disease

The authors quantified serum lipoprotein (a) (Lp) (a) by enzymo-immuno-analysis in 86 outpatient men suffering peripheral vascular disease (PVD) and in 53 age-matched healthy men. They further measured serum cholesterol, serum triglycerides, low density lipoproteins-cholesterol, high density lipoproteins (HDL)-cholesterol and serum apolipoprotein B. Serum triglycerides were significantly increased in patients with PVD versus controls (148 +/- 8 and 114 +/- 7 mg/dL, mean +/- SEM). HDL-cholesterol levels were significantly lower in patients versus controls (36 +/- 1 and 43 +/- 2 mg/dL, respectively). Serum Lp(a) levels in patients with PVD were 20 +/- 2 mg/dL, whereas in controls they were 16 +/- 3 (p: NS). Serum Lp(a) concentrations were identical in smoker and nonsmoker patients. There was no correlation between Lp(a) concentration and the other lipid parameters. Conversely, as occurs in coronary heart disease and in cerebrovascular disease, Lp(a) does not seem to be a marker for PVD, although a trend toward a higher mean levels was found.

Abnormalities in serum lipoprotein composition in patients with premature coronary heart disease compared to serum lipid matched controls

Serum lipoprotein composition was examined in 18 male patients (mean age 44 +/- 0.9 years) who had undergone coronary artery by-pass surgery because of premature coronary heart disease (PCHD) and in 18 control subjects, matched with patients for sex, age, body mass index and serum cholesterol and triglyceride. Cholesterol, triglyceride and apolipoprotein B (apo B) concentrations in very low density lipoprotein (VLDL) and in low density lipoprotein (LDL) did not differ in the two groups, but high density lipoprotein (HDL)-cholesterol was significantly lower in PCHD patients (P less than 0.02). Cholesterol/apo B, triglyceride/apo B and phospholipid/apo B ratios in VLDL were significantly higher in patients than in controls (P less than 0.05, P less than 0.01 and P less than 0.001, respectively). The relative VLDL enrichment in cholesterol was mainly due to the non-esterified moiety (P less than 0.01). These VLDL abnormalities as well as the low HDL-cholesterol suggest an impairment of VLDL catabolism in PCHD patients.