Bjørn O. Christophersen

Lipoprotein Changes and Reduction in the Incidence of Major Coronary Heart Disease Events in the Scandinavian Simvastatin Survival Study (4S)

BACKGROUND The Scandinavian Simvastatin Survival Study (4S) randomized 4444 patients with coronary heart disease (CHD) and serum cholesterol 5.5 to 8.0 mmol/L (213 to 310 mg/dL) with triglycerides < or =2.5 mmol/L (220 mg/dL) to simvastatin 20 to 40 mg or placebo once daily. Over the median follow-up period of 5.4 years, one or more major coronary events (MCEs) occurred in 622 (28%) of the 2223 patients in the placebo group and 431 (19%) of the 2221 patients in the simvastatin group (34% risk reduction, P<.00001). Simvastatin produced substantial changes in several lipoprotein components, which we have attempted to relate to the beneficial effects observed. METHODS AND RESULTS The Cox proportional hazards model was used to assess the relationship between lipid values (baseline, year 1, and percent change from baseline at year 1) and MCEs. The reduction in MCEs within the simvastatin group was highly correlated with on-treatment levels and changes from baseline in total and LDL cholesterol, apolipoprotein B, and less so with HDL cholesterol, but there was no clear relationship with triglycerides. We estimate that each additional 1% reduction in LDL cholesterol reduces MCE risk by 1.7% (95% CI, 1.0% to 2.4%; P<.00001). CONCLUSIONS These analyses suggest that the beneficial effect of simvastatin in individual patients in 4S was determined mainly by the magnitude of the change in LDL cholesterol, and they are consistent with current guidelines that emphasize aggressive reduction of this lipid in CHD patients.

Formation of monohydroxy-polyenic fatty acids from lipid peroxides by a glutathione peroxidase

Abstract 1. 1. It has been confirmed that the oxidation of GSH by linoleic acid hydroperoxide is enzymically catalyzed in rat liver. 2. 2. By thin-layer chromatography, gas-liquid chromatography and mass spectrometry, and by chemical modifications such as acetylation, methylation and hydrogenation, the products formed by the enzymic removal of linoleic acid hydroperoxide have been identified as 9-hydroxy-10,12-octadecadienoic acid and 13-hydroxy-9,11-octadecadienoic acid. The hydroperoxide can thus be detoxified to products that can be metabolized in the cell. 3. 3. It is suggested that the extremely rapid enzymic reaction of GSH with lipid hydroperoxides breaks the autocatalytic chain reactions of lipid peroxidation and thus protects the vital cellular compounds from the effect of lipid peroxides.

Reduction of linolenic acid hydroperoxide by a glutathione peroxidase

Abstract 1. 1. It has been shown that the reduction of linolenic acid hydroperoxide and of linoleic acid hydroperoxide by GSH is catalysed at approximately the same rate by a glutathione peroxidase in rat liver. 2. 2. The products formed by the enzymatic reduction of linolenic acid hydroperoxide have been identified as 9-hydroxy-10,12,15-octadecatrienoic acid, 12-hydroxy-9,13,15-octadecatrienoic acid, 13-hydroxy-9,11,15-octadecatrienoic acid, 16-hydroxy-9,12,14-octadecatrienoic acid and probably 8-hydroxy-9,12,15-octadecatrienoic acid. 3. 3. Since the glutathione peroxidase seems to accept both five isomeric linolenic acid hydroperoxides and two isomeric linoleic acid hydroperoxides as substrates, it is probable that it can catalyse the reduction of the hydroperoxides of all the polyunsaturated fatty acids that occur in subcellular membranes.

Lp(a) lipoprotein level predicts survival and major coronary events in the Scandinavian Simvastatin Survival Study

The Scandinavian Simvastatin Survival Study (4S) was a double‐blind. randomized placebo‐controlled multi‐centre clinical trial of long‐term Simvastatin therapy in patients with coronary heart disease who had total cholesterol levels between 5.5 and 8.0 mmol/1, comprising 4444 patients, equally distributed to a Simvastatin and a placebo group. Patients achieved a significant 30% relative reduction in overall mortality with Simvastatin therapy through a 42% relative reduction in coronary heart disease mortality. Lp(a) lipoprotein levels in Scandinavian coronary heart disease patients were strikingly higher than in healthy controls. Numbers of deaths in the Simvastatin group differed significantly between quartiles of Lp(a) lipoprotein levels, the reduction in deaths being most pronounced in the second (next to lowest) quartile. Subjects with major coronary events had significantly higher Lp(a) lipoprotein levels than subjects without such events, in all groups. The relationship between Lp(a) lipoprotein level and total mortality as well as between Lp(a) lipoprotein level and major coronary events was significantly different from zero, in logistic regression analyses. The findings show that Lp(a) lipoprotein predicts major coronary events as well as death in secondary prevention with Simvastatin. This prospective study provides independent confirmation that a high Lp(a) lipoprotein level is a significant coronary heart disease risk factor.

Effect of dietary fats on arachidonic acid and eicosapentaenoic acid biosynthesis and conversion to C22 fatty acids in isolated rat liver cells.

The desaturation, chain elongation and esterification of [1-14C]eicosapentaenoic acid, [1-14C]arachidonic acid, [1-14C]eicosatrienoic acid, [1-14C]linolenic acid and [1-14C]linoleic acid were studied in isolated liver cells. Rats fed diets with either 15% hydrogenated coconut oil or 15% partially hydrogenated marine oil, both deficient in essential fatty acids, 15% soybean oil or standard pellet diet with 6% fat, were used. The delta 4-desaturation of 22:5(n - 3) and 22:4(n - 6) as well as the delta 6-desaturase activity was distinctly higher in cells from animals fed coconut or marine oil than with soybean oil or standard pellet. The rate of delta 5-desaturation of 20:3(n - 6) and 20:4(n - 3) was nearly the same in cells from rats fed coconut, marine and soybean oils and higher than with standard pellet. The chain elongation of 20:5(n - 3) to 22:5(n - 3) was distinctly more pronounced than the elongation of 20:4(n - 6) with all four diets. 20:5(n - 3) was mainly esterified in the phospholipids with marine and coconut oils, and mainly in triacylglycerol with standard pellet and soybean oils. The proportion of [1-14C]20:4(n - 6) in the phospholipids to that in triacylglycerol decreased in the order marine oil greater than coconut oil greater than standard pellet greater than soybean oil. The different endogenous arachidonic acid content in the phospholipids induced by the different diets increased in the same order. 20:5(n - 3) was rapidly esterified in triacylglycerol and phospholipids, then liberated especially from the triacylglycerol fraction, chain elongated to 22:5(n - 3) and reesterified.

Relation of Total Homocysteine and Lipid Levels in Children to Premature Cardiovascular Death in Male Relatives

We assessed the relative importance of lipid, apo B, lipoprotein(a)[Lp(a)], and total homocysteine (tHcy) levels in children in relation to premature cardiovascular disease in family members. Parents of 381 girls and 375 boys age 8-12 y completed family history questionnaires. Nonfasting serum lipids and lipoproteins and plasma tHcy and cysteine levels were measured in the children. Serum folate and vitamin B12 levels were determined in a random subsample of 23% of the children, who participated in a food frequency interview. Children whose parents reported hypercholesterolemia had higher total and non-HDL cholesterol and apo B levels than the rest, but these levels were not associated with cardiovascular disease. tHcy levels were similar in girls and boys. tHcy was higher in children whose father, grandfather, or uncle died at age ≤55 y of myocardial infarction or sudden cardiac arrest(n = 42) than in control children [5.92 μmol/L (95% confidence interval [CI] of 5.47-6.36) versus 5.25 μmol/L (95% CI, 5.16-5.34)], also after adjustment for socioeconomic group. Intake and serum levels of vitamin B12 and folate were within recommended or reference ranges. In a stepwise multiple regression analysis, serum folate (negative correlation), plasma creatinine, and sugar intake as percent of dietary energy(positive correlations) were significantly associated with tHcy (multipler = 0.44, adjusted r2 = 18%; 95% CI, 5-30%). Our data show that a modest elevation in tHcy in children was related to premature cardiovascular death in their male relatives and may partly account for the contribution of family history to risk of cardiovascular disease. tHcy may be modifiable through the diet, even in children with apparently adequate vitamin nutriture.

Peroxisomal retroconversion of docosahexaenoic acid (22:6(n-3)) to eicosapentaenoic acid (20:5(n-3)) studied in isolated rat liver cells

Retroconversion of docosahexaenoic acid (DHA, 22:6(n-3)) to eicosapentaenoic acid (EPA, 20:5(n-3)) was studied in isolated rat liver cells. 20% of the substrate was retroconverted to EPA in control cells by one cycle of beta-oxidation probably with delta 4 enoyl CoA reductase and delta 3, delta 2 enoyl CoA isomerase as auxiliary enzymes. This conversion was not stimulated by (-)-carnitine and was not inhibited by the addition of (+)-decanoylcarnitine. In hepatocytes from fasted rats little EPA was formed from DHA. These results strongly suggest that the retroconversion of DHA to EPA is a peroxisomal function. Retroconverted EPA, produced from DHA was rapidly incorporated in triacylglycerol, the phosphatidylcholine and phosphatidyletanolamine fractions. During longer incubation time EPA was partly removed from the phospholipid fractions, chain-elongated to 22:5(n-3) and incorporated in the triacylglycerol fraction.

Evidence for peroxisomal retroconversion of adrenic acid (22:4(n-6)) and docosahexaenoic acids (22:6(n-3)) in isolated liver cells

The intracellular localization of the oxidation of [2-14C]adrenic acid (22:4(n-6)) and [1-14C]docosahexaenoic acid (22:6(n-3)) was studied in isolated liver cells. The oxidation of 22:4(n-6) was 2-3-times more rapid than the oxidation of 22:6(n-3), [1-14C]arachidonic acid (20:4(n-6)) or [1-14C]oleic acid (18:1). (+)-Decanoylcarnitine and lactate, both known to inhibit mitochondrial beta-oxidation, reduced the oxidation of 18:1 distinctly more efficiently than with 22:4(n-6) and 22:6(n-3). In liver cells from rats fed a diet containing partially hydrogenated fish oil, the oxidation of 22:6(n-6) and 22:6(n-3) was increased by 30-40% compared with cells from rats fed a standard pellet diet. With 18:1 as substrate, the amount of fatty acid oxidized was very similar in cells from animals fed standard pellets or partially hydrogenated fish oil. Shortened fatty acids were not produced from [5,6,8,9,11,12,14,15-3H]arachidonic acid. In hepatocytes from rats starved and refed 20% fructose, a large fraction of 14C from 22:4 was recovered in 14C-labelled C14-C18 fatty acids. Oxidation of 22:4 thus caused a high specific activity of the extramitochondrial pool of acetyl-CoA. The results suggest that 22:4(n-6) and to some extent 22:6(n-3) are oxidized by peroxisomal beta-oxidation and by this are retroconverted to arachidonic acid and eicosapentaenoic acid.

Effects of dietary purified eicosapentaenoic acid (20:5(n − 3)) and docosahexaenoic acid (22:6(n − 3)) on fatty acid desaturation and oxidation in isolated rat liver cells

The effects of dietary supplementation of eicosapentaenoic acid (20:5(n-3), EPA) and docosahexaenoic acid (22:6(n-3), DHA) on the metabolism of polyunsaturated fatty acids were studied in isolated rat liver cells. Both pure EPA and pure DHA and a mixture of the two n-3 fatty acids in different doses were used. The supplementation of moderate amounts of n-3 fatty acids suppressed the activity of delta 6-desaturase (50%) and to a smaller extent of the delta 5-desaturase (60-70%) compared to controls. When higher doses of dietary purified EPA and DHA were used, this inhibitory effect on the delta 6- and delta 5-desaturase activities disappeared. The delta 4-desaturase activity seemed to be unaffected by the feeding conditions used. The supplementation of the n-3 fatty acids in the diet at all dose levels used increased the beta-oxidation of all the polyunsaturated fatty acids, especially of linoleic acid, linolenic acid and eicosapentaenoic acid. The results suggest an increase both in peroxisomal and mitochondrial beta-oxidation. The peroxisomal beta-oxidation of n-3 fatty acids seemed to be particularly increased.

Erucic acid—an inhibitor of fatty acid oxidation in the heart

Abstract In the present work the carnitine ester of erucic acid has been studied. The oxygen uptake of heart and liver mitochondria from young rats was much lower with erucylcarnitine as the substrate than with palmitylcarnitine. The presence of erucylcarnitine caused a significant inhibition of the mitochondrial oxidation of palmitylcarnitine. The inhibition was more pronounced with heart mitochondria than with liver mitochondria. With liver mitochondria the inhibitory effect of erucylcarnitine on the oxygen uptake was stronger in the presence of malonate than with malate. Erucylcarnitine did not inhibit the formation of intramitochondrial long-chain acyl-CoA from added palmitylcarnitine. Erucylcarnitine did not inhibit the activity of long-chain carnitine acyltransferase with palmitylcarnitine as the substrate. The presence of erucylcarnitine did not inhibit the acylation of glycerophosphate by palmityl groups in heart and liver homogenate. The findings suggest that a mitochondrial metabolite of erucic acid inhibits the mitochondrial oxidation of other fatty acids, especially in the heart, and that this causes the accumulation of triglycerides in the hearts of rats fed rapeseed oil.