Lipoproteins and their genetic variation in subjects with and without angiographically verified coronary artery disease

To examine the concentration of serum lipoproteins and the association of their genetic variation with the occurrence of coronary artery disease (CAD), composite serum lipoprotein profiles including lipoprotein(a) (Lp[a]), apolipoprotein (apo) E phenotypes, and apo B Xba I genotypes were determined in patients with angiographically verified CAD (CAD+ group, n = 111) and in subjects with no angiographic evidence of CAD (CAD- group, n = 46). In addition, we determined the concentrations of serum lipids, lipoproteins, and apolipoproteins in 96 healthy controls. Both CAD- and CAD+ groups had lower concentrations of apos A-I and A-II but higher concentrations of serum total and very low density lipoprotein triglyceride and very low density lipoprotein cholesterol than did healthy controls. The mean concentrations of serum total and low density lipoprotein cholesterol and the median values of Lp(a) were similar in the CAD+ and CAD- groups, both having higher concentrations of low density lipoprotein cholesterol and apo B than the healthy controls. Irrespective of gender, patients with CAD had significantly lower serum high density lipoprotein cholesterol than did those without CAD (1.48 +/- 0.40 versus 1.16 +/- 0.29 mmol/l, p less than 0.001). In women, the mean serum total and very low density lipoprotein triglyceride concentration was also higher in the CAD+ than in the CAD- group. The frequency of the apo E4 allele (epsilon 4) was significantly higher in the CAD+ group (0.293) than in the CAD- group (0.174; p less than 0.001). The frequencies of the two apo B alleles, X1 (Xba I restriction site absent) and X2 (Xba I restriction site present), were similar in the two groups. Stepwise discriminant analysis revealed that in men, serum high density lipoprotein cholesterol had the highest power to discriminate for CAD. In addition, the concentration of plasma apo B levels and the occurrence of apo E phenotypes were independently associated with CAD in men. In women, the only independent factor associated with CAD after adjustment for beta-blocker and diuretics usage was the concentration of serum triglycerides.

A novel polymorphism of apolipoprotein A-IV is the result of an asparagine to serine substitution at residue 127

We have identified a hitherto unknown genetic polymorphism of apolipoprotein A-IV (apoA-IV). The molecular basis for this polymorphism is an A to G substitution at nucleotide 1687 resulting in an Asn to Ser change of amino acid 127. The frequencies of the two apoA-IV alleles (designated apoA-IV127Asn and apoA-IV127Ser), determined by Hin c II restriction analysis of PCR amplified exon three of the apoA-IV gene, were 0.788 and 0.212, respectively, in a Finnish population sample. Allele frequencies of another polymorphism due to a Thr to Ser substitution at amino acid 347 were determined using Hinf I restriction analysis. The allele frequencies were 0.823 for apoA-IV347Thr and 0.177 for apoA-IV347Ser. None of the apoA-IV polymorphisms (apoA-IV127:Asn----Ser, apoA-IV347:Thr----Ser and apoA-IV360:Gln----His) had any effect on plasma lipid and lipoprotein concentrations in cohorts of dyslipidemic men and in a population sample of normolipidemic controls. There was also no association between the history of previous myocardial infarction and any of the apoA-IV alleles.

The effect of moderate alcohol intake on serum apolipoprotein A-I-containing lipoproteins and lipoprotein (a)

Two main types of lipoprotein particles are identified within high-density lipoprotein (HDL): those containing both apolipoprotein (apo) A-I and apo A-II (Lp A-I:A-II) and those containing only apo A-I (Lp A-I). To study the effects of prolonged moderate alcohol intake on apo A-I-containing lipoproteins in serum, 60 g/d of ethanol was administered to 10 healthy male volunteers (age, 27 to 45 years) during 3 weeks. The drinking period was preceded and followed by an abstinence period of 3 weeks. The HDL3 cholesterol level increased by 17% (P less than .01) and decreased by 22% (P less than .001) on and off alcohol, respectively. The HDL2 cholesterol increased by 17% (P = NS) during ethanol intake and decreased by 14% during the following abstention (P less than .01). The serum concentration of apo A-I increased by 17% (P less than .001) during drinking and came back to the starting level after 2 weeks of abstention. Ethanol intake caused an increase in the serum levels of both Lp A-I and Lp A-I:A-II, the former explaining one third of the total increase of apo A-I. The Lp (a) concentration decreased by 33% (P less than .05) during the first week of ethanol intake, but increased back to the starting level until the end of drinking. These data suggest that the increment of the antiatherogenic Lp A-I may be one beneficial effect provided by ethanol with respect to coronary heart disease.

Polymorphisms of the gene encoding cholesterol ester transfer protein and serum lipoprotein levels in subjects with and without coronary heart disease

We determined TaqI-A, TaqI-B and EcoNI genotypes at the cholesteryl ester transfer protein (CETP) locus in 111 healthy volunteers and in 187 hyperlipidemic men of whom 72 had suffered a myocardial infarction. There were no significant differences in the allele distributions at these polymorphic loci either between the population sample and the hyperlipidemic subjects, or between patients with and without previous myocardial infarction. To detect the associations between the CETP polymorphisms and serum lipid and apoprotein levels, we determined the serum concentrations of total cholesterol, triglycerides, high density lipoprotein (HDL)-cholesterol, apoA-I, apoA-II and apoB in the subjects studied and correlated them to the 3 RFLPs. No significant differences were observed in the serum levels of apoproteins and lipid parameters between subjects with different genotypes in any of these polymorphic CETP loci, either in the population sample or in hyperlipidemic men. Multivariate analyses did not reveal a significant independent role for any of the 3 polymorphisms in determining serum HDL-cholesterol or apoA-I levels after adjusting for triglyceride and low density lipoprotein cholesterol concentrations. This was evident for the group of healthy volunteers and for hyperlipidemic subjects, including those who had survived a myocardial infarction. We conclude that, in Finns, the CETP RFLPs are not useful markers for the risk of coronary heart disease.

Modulation of hepatic glucose production by non-esterified fatty acids in type 2 (non-insulin-dependent) diabetes mellitus

To study the effect of changes in plasma non-esterified fatty acid concentration on suppression of hepatic glucose production by insulin eight Type 2 (non-insulin-dependent) diabetic patients participated in three euglycaemic, hyperinsulinaemic (108pmol.m2-1.min-1) clamp studies combined with indirect calorimetry and infusion of [3-3H]-glucose and [1-14C]palmitate; (1) a control experiment with infusion of NaCl 154 mmol/l, (2) heparin was infused together with insulin, and (3) an antilipolytic agent, Acipimox, was administered at the beginning of the experiment. Six healthy volunteers participated in the control experiment. Plasma non-esterified fatty acid concentrations during the insulin clamp were in diabetic patients: (1) 151 +/- 36 mumol/l, (2) 949 +/- 178 mumol/l, and (3) 65 +/- 9 mumol/l; in healthy control subjects 93 +/- 13 mumol/l. Non-esterified fatty acid transport rate, oxidation and non-oxidative metabolism were significantly higher during the heparin than during the Acipimox experiment (p less than 0.001). Suppression of hepatic glucose production by insulin was impaired in the diabetic compared to control subjects (255 +/- 42 vs 51 +/- 29 mumol/min, p less than 0.01). Infusion of heparin did not affect the suppression of hepatic glucose production by insulin (231 +/- 49 mumol/min), whereas Acipimox significantly enhanced the suppression (21 +/- 53 mumol/min, p less than 0.001 vs 154 mmol/l NaCl experiment). We conclude that insulin-mediated suppression of hepatic glucose production is not affected by increased non-esterified fatty acid availability. In contrast, decreased non-esterified fatty acid availability enhances the suppression of hepatic glucose production by insulin.

Effects of continuous insulin infusion therapy on lipoprotein surface and core lipid composition in insulin-dependent diabetes mellitus

To determine whether intensive insulin therapy has the same beneficial effects on lipoprotein composition that it has been shown to have in insulin-dependent diabetes mellitus (IDDM) on the routinely measured plasma lipids, we studied 10 patients after 6 months of conventional therapy (CIT) and again after 6 months of therapy with continuous subcutaneous insulin infusion (CSII). While the mean of home blood glucose levels (8.1 +/- 0.5 v 7.9 +/- 0.5 mmol/L) decreased no further, plasma triglycerides (TG) (CIT, 102.7 +/- 25.0; CSII, 89.6 +/- 27.1 mg/dL; P less than .001) decreased after CSII, and high-density lipoprotein cholesterol (HDL-C) increased significantly, primarily as a consequence of an increase in HDL2 (CIT, 12.2 +/- 6.0; CSII, 18.1 +/- 6.3 mg/dL; P less than .02). Low-density lipoprotein cholesterol (LDL-C) was unchanged (CIT, 82.2 +/- 32; CSII, 84.0 +/- 27.8 mg/dL). After CIT, two indices of lipoprotein surface composition were altered: (1) the free cholesterol (FC) to lecithin ratio, which is a new cardiovascular risk factor, was abnormally increased in plasma, very-low-density lipoprotein (VLDL) + LDL, and HDL, and (2) the sphingomyelin to lecithin ratio, an index of the surface rigidity of lipoproteins, was increased in the HDL subfractions. While CSII treatment resulted in favorable changes in whole plasma lipids, it failed to correct these disturbances in composition. Since the participation of lipoproteins in certain steps in reverse cholesterol transport appears to be impaired when their surface constituents are altered, persistence of these disturbances may sustain the increased cardiovascular risk of IDDM patients, even when their clinical control is very good and their plasma lipids are normal.

Demonstration of a novel feedback mechanism between FFA oxidation from intracellular and intravascular sources

We examined the regulation of intracellular and intravascular lipolysis in vivo. In the first series of studies, plasma free fatty acids (FFA) were elevated moderately by heparin (plus approximately 600 mumol/l) in patients with non-insulin-dependent diabetes mellitus (NIDDM) and in normal subjects. The increase in plasma FFA increased plasma FFA oxidation "submaximally" (plasma FFA oxidation less than 100% of total lipid oxidation) in a plasma FFA concentration-dependent manner. The increase in plasma FFA oxidation significantly suppressed direct intracellular oxidation of FFA. In another group of patients with NIDDM, plasma FFA was markedly increased (plus approximately 1,500 mumol/l). Plasma FFA oxidation now accounted for all lipid oxidation. Compared with substrate oxidation rates observed at submaximally elevated plasma FFAs in the same subjects at similar insulin concentrations, total lipid oxidation increased, carbohydrate oxidation decreased, and total energy production increased. These data demonstrate the existence of an FFA-dependent insulin-independent feedback mechanism between FFA oxidation from intracellular and intravascular sources. Thus the preferred response of body tissues to a change in plasma FFA oxidation is a reciprocal change in direct intracellular FFA oxidation. Substrate competition between carbohydrate and lipid, as proposed by P. J. Randle et al. (Lancet 1:785, 1963), becomes operative after the capacity for regulation within components of lipid oxidation has been utilized.

Hyperlipidaemia in diabetes

Currently our knowledge of the role of lipid abnormalities as risk factors for CHD in diabetes is insufficient. We need to define exact risk parameters to target correctly the therapy of lipid disorders and to outline optimum therapeutic strategies. Therefore it is necessary to identify quantitative and qualitative abnormalities of lipoproteins and apoproteins which signify the risk of CHD and to define their predictive power in prospective trials. Obviously we need to know more about the pathophysiology of lipid abnormalities and the action of insulin. Because diabetic patients carry a high inherent risk of CHD, target values recommended for non-diabetic populations may not be optimal for diabetic populations, but should be lower. To date no primary or secondary intervention trials in diabetic populations have been carried out to show that the lowering of lipid values (serum and LDL cholesterol) will reduce the risk of CHD morbidity or mortality or will prevent the progression of CHD in diabetes. Since hypertriglyceridaemia and low HDL levels are typical abnormalities in NIDDM it is a unique target group to test whether lowering of triglycerides and raising of HDL cholesterol levels will reduce the risk of CHD. Therefore there is a pressing need for clinical trials in both IDDM and NIDDM to provide adequate information on the benefits of lipid-lowering therapy and to confirm treatment strategies.

Effect of insulin therapy on metabolic fate of apolipoprotein B-containing lipoproteins in NIDDM

Non-insulin-dependent diabetic (NIDDM) subjects exhibit abnormalities in their plasma lipid and lipoprotein profiles that increase the risk of ischemic heart disease. This study was designed to examine the metabolic behavior of very-low-density (VLDL), intermediate-density (IDL), and low-density (LDL) lipoproteins in NIDDM patients before treatment and after 4 wk of insulin therapy. Basal turnover studies of 131I-labeled VLDL1 (svedberg units [Sf] 60-400) and 131I-labeled VLDL2 (Sf 20-60) apolipoprotein B (apoB) were conducted in a group of seven NIDDM patients who had been off oral therapy for 1 wk. The subjects exhibited higher than normal transport rates for VLDL1 and a diminished input of apoB into the VLDL2 density range. These observations are concordant with the hypothesis that NIDDM patients overproduce VLDL triglyceride but not apoB. VLDL1 and VLDL2 were converted to IDL and ultimately to LDL at approximately normal rates, although the delipidation pathway by which apoB-containing particles were processed exhibited different properties from that seen in control subjects. Insulin therapy reduced plasma triglyceride by 38%, and this was associated with a 41% fall in VLDL1 mass (P less than 0.01). VLDL2 was less affected (19% reduction, P less than 0.05), IDL was unchanged, and LDL fell 17% (P less than 0.05). Repeat metabolic studies revealed that the major effects of insulin were to reduce VLDL1-apoB transport (from 811 to 488 mg/day) and increase the direct input of VLDL2 into the plasma (from 182 to 533 mg/day, P less than 0.05). These alterations in VLDL production led to normalization of apoB kinetics in IDL and LDL. The fractional catabolic rate of LDL increased 19% (P less than 0.05), whereas direct input into this fraction, which had been high before treatment, was reduced. Postheparin plasma lipoprotein lipase (LPL) and hepatic lipase levels were unaffected by insulin, although the hormone did increase LPL in adipose tissue. This lack of effect on lipase activities correlated well with the observation that the rates of catabolism of apoB in VLDL1, VLDL2, and IDL were not significantly affected by insulin therapy.

Persistent abnormalities in lipoprotein composition in noninsulin-dependent diabetes after intensive insulin therapy

To determine whether rigorous insulin therapy, which normalized the routinely measured plasma lipids, also reversed qualitative abnormalities in the composition of lipoproteins in noninsulin-dependent diabetes mellitus (NIDDM), we studied 18 NIDDM patients (eight men and 10 women) before and 2 months after intensive insulin therapy. Glycosylated hemoglobin levels (11.7% vs. 8.7%), plasma triglyceride (TG) (250 +/- 91 vs. 164 +/- 56 mg/dl, p less than 0.001), and cholesterol (214 +/- 43 vs. 198 +/- 31 mg/dl, p less than 0.025) all fell, and both HDL2 cholesterol and HDL3 cholesterol increased (59.1% and 10.9%, respectively, p less than 0.001). However, abnormalities in two indices of lipoprotein surface constituents, which were present before insulin therapy, remained so thereafter. The first of these, the new cardiovascular risk factor, the plasma free cholesterol/lecithin ratio, which was increased before treatment, fell only slightly after therapy (pre-therapy 1.02 +/- 0.29 vs. post-therapy 0.90 +/- 0.17, p less than 0.4; reference group, 0.83 +/- 0.14), and remained elevated in very low density lipoprotein (VLDL) and low density lipoprotein (LDL). Secondly, the sphingomyelin/lecithin ratio, an index of the surface rigidity of lipoproteins, was abnormal before treatment in VLDL, HDL2, and HDL3, and this alteration persisted after insulin therapy in HDL3 (p less than 0.001). Lipoprotein core lipid abnormalities were also present before treatment: the TG/cholesteryl ester ratio was reduced in VLDL and increased in LDL, HDL2, and HDL3. Rigorous insulin therapy improved, but failed to fully correct, this disturbance.(ABSTRACT TRUNCATED AT 250 WORDS)

Postheparin plasma lipoprotein and hepatic lipase are determinants of hypo- and hyperalphalipoproteinemia

To study the role of the two postheparin plasma lipolytic enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL) in high density lipoprotein (HDL) metabolism at a population level, we determined serum lipoproteins, apoproteins A-I, A-II, B, and E, and postheparin plasma LPL and HL activities in 65 subjects with a mean HDL-cholesterol of 34 mg/dl and in 62 subjects with a mean HDL-cholesterol of 87 mg/dl. These two groups represented the highest and lowest 1.4 percentile of a random sample consisting 4,970 subjects. The variation in HDL level was due to a 4.1-fold difference in the HDL2 cholesterol (P less than 0.001) whereas the HDL3 cholesterol level was increased only by 32% (P less than 0.001) in the group with high HDL-cholesterol. Serum apoA-levels were 128 +/- 2.2 mg/dl and 210 +/- 2.8 mg/dl (mean +/- SEM) in hypo- and hyper-HDL cholesterolemia, respectively. Serum apoA-II concentration was elevated by 28% (P less than 0.001) in hyperalphalipoproteinemia. The apoA-I/A-II ratio was elevated only in women with high HDL-cholesterol but not in men, suggesting that elevation of apoA-I is involved in hyperalphalipoproteinemia in females, whereas both apoA proteins are elevated in men with high HDL cholesterol. Serum concentration of apoE and its phenotype distribution were similar in the two groups. The HL activity was reduced in the high HDL-cholesterol group (21.2 +/- 1.5 vs. 38.5 +/- 1.8 mumol/h/ml, P less than 0.001), whereas the LPL activity was elevated in the group with high HDL-cholesterol compared to subjects with low HDL-cholesterol (27.8 +/- 1.3 vs. 19.9 +/- 0.8 mumol/h/ml, P less than 0.001). The HL and LPL activities correlated in opposing ways with the HDL2 cholesterol (r = 0.57, P less than 0.001 and r = 0.51, P less than 0.001, respectively), and this appeared to be independent of the relative ponderosity by multiple correlation analysis. The results demonstrate major influence of both HL and LPL on serum HDL cholesterol concentration at a population level.

Insulin inhibition of overnight glucose production and gluconeogenesis from lactate in NIDDM

Increased gluconeogenesis contributes to fasting hyperglycemia in non-insulin-dependent diabetes mellitus (NIDDM). We examined whether insulin inhibits gluconeogenesis from lactate by altering the fate of lactate and/or by reducing lactate flux. Seven patients with NIDDM (age 51 +/- 4 yr, body mass index 28 +/- 2 kg/m2) were studied before and 3 wk after achieving normoglycemia with evening insulin therapy. Basal glucose production (Ra) and utilization were measured overnight [( 3-3H]glucose infusion from 9 P.M. to 8 A.M.) and lactate turnover and conversion to glucose between 4 and 8 A.M. [( U-14C]lactate infusion) before and after insulin therapy. During insulin therapy, fasting plasma glucose decreased from 188 +/- 13 to 99 +/- 7 mg/dl (P less than 0.001) due to inhibition of glucose Ra from 3.0 +/- 0.1 to 2.2 +/- 0.1 mumol.kg-1.min-1 (P less than 0.005). Plasma free insulin increased from 6 +/- 1 to 11 +/- 1 microU/ml (P less than 0.005). Plasma lactate concentrations (1.1 +/- 0.2 vs. 1.0 +/- 0.1 mmol/l before vs. after insulin therapy) and the lactate turnover rate (15.6 +/- 0.9 vs. 14.2 +/- 0.8 mumol.kg.min) remained unchanged, whereas the amount of glucose formed from lactate decreased from 2.0 +/- 0.1 to 1.4 +/- 0.2 mumol.kg-1.min-1 (P less than 0.02) and the percent of lactate turnover converted to glucose decreased from 26 +/- 1 to 20 +/- 2% (P less than 0.05). We conclude that insulin inhibits overnight glucose Ra from lactate by decreasing the proportion of lactate diverted towards gluconeogenesis rather than by altering lactate availability or total flux.

Bedtime insulin for suppression of overnight free-fatty acid, blood glucose, and glucose production in NIDDM

We studied the clinical effectiveness and mechanism underlying the glucose-lowering effect of evening insulin therapy. Nocturnal profiles of blood glucose, plasma free fatty acid (FFA), glycerol, and lactate and overnight glucose kinetics [( 3-3H] glucose infusion) were measured in 15 non-insulin-dependent diabetic (NIDDM) patients with a relative body weight of 128 +/-4% who were poorly controlled with oral therapy alone. The patients were studied before and 2 wk and 3 mo after bedtime insulin (23 +/- 3 IU) was given in addition to oral therapy. An early-morning rise in blood glucose (greater than 31 mg/dl = 1.5 mM) was present in two-thirds of the patients and was associated with an overnight rise in plasma FFA and an increase in glucose production (Ra) during the early-morning hours (change 0.42 +/- 0.10 mg.kg-1.min-1, P less than .05, between 0300 and 0800). The overnight mean levels of blood glucose, plasma FFA, and serum insulin averaged 212 +/- 9 vs. 137 +/- 11 vs. 133 +/- 11 mg/dl (P less than .001), 674 +/- 61 vs. 491 +/- 57 vs. 484 +/- 36 microM (P less than 0.01) and 12.7 +/- 1.6 vs. 18.1 +/- 2.2 vs. 20.7 +/- 2.4 microU/L (P less than .01) before and 2 wk and 3 mo after the combination therapy. The decrements in overnight glucose and FFA levels after 2 wk of bedtime insulin therapy were closely correlated (r = .86, (P less than .001). The nocturnal profile of plasma lactate was similar before and during bedtime insulin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Apoprotein E polymorphism and coronary artery disease. Increased prevalence of apolipoprotein E-4 in angiographically verified coronary patients

Several studies have indicated that genetic polymorphism of apolipoprotein (apo) E is related to coronary artery disease (CAD). We therefore determined the apo E phenotype in 91 consecutive Finnish men with angiographically confirmed CAD. The apo E phenotype distribution differed significantly from that observed in the Finnish population (p less than 0.05). In the patient group, the frequency of the epsilon 4 allele was 0.324, which is 1.4-fold higher than in the normal Finnish population and twice as high as in other Caucasian populations. Serum lipoproteins and postheparin plasma lipase activities did not display any significant variation according to apo E phenotype. These studies confirm and extend, in a population with high epsilon 4 allele frequency, the previous data on the impact of the epsilon 4 allele on the risk of CAD and suggest that the high epsilon 4 allele frequency in the Finnish population may be one factor contributing to Finns' increased susceptibility to CAD.

Short-term effects of moderate alcohol consumption on lipid metabolism and energy balance in normal men

The short-term effects of moderate alcohol consumption on energy balance, serum lipids, and lipoproteins were studied in eight healthy middle-aged men (age 30 to 47 years and body mass index 23.1 to 27.7 w/h2). A crossover dietary trial included two isocaloric periods without (20% protein, 50% carbohydrate, 30% fat) or with alcohol (12% protein, 29% carbohydrate, 25% fat, 75 g of alcohol as red wine). Each period lasted 2 weeks. The body weight of the subjects remained stable over the study. Fasting blood glucose, serum insulin, total cholesterol, and LDL cholesterol were similar at the end of both dietary periods. Mean values of serum total triglyceride (108 +/- 18 v 85 +/- 24 mg/dL, P less than 0.05), VLDL-Tg (88 +/- 24 v 73 +/- 16 mg/dL, NS), and total HDL cholesterol (49.4 +/- 6.0 v 43.4 +/- 5.5 mg/dL, P less than 0.05) were higher after the diet with alcohol than without alcohol. The increase of HDL cholesterol was primarily due to that of HDL2 cholesterol (10.4 +/- 5.1 v 5.7 +/- 3.9 mg/dL, P less than 0.05). The concentration of apoprotein A-I, A-II, and B averaged 104 +/- 17 v 89 +/- 16 mg/dL, 33 +/- 4 v 28 +/- 8 mg/dL, P less than 0.02, and 111 +/- 24 v 105 +/- 33 mg/dL after the diets with and without alcohol, respectively. Adipose tissue LPL activity increased in six of the eight volunteers during the diet with alcohol. Resting metabolic rate, postprandial energy expenditure, and postprandial responses of blood glucose, serum insulin, triglyceride, and plasma FFA were similar after the both diets.(ABSTRACT TRUNCATED AT 250 WORDS)

XbaI and c/g polymorphisms of the apolipoprotein B gene locus are associated with serum cholesterol and LDL-cholesterol levels in Finland

Several restriction fragment length polymorphisms (RFLPs) have been identified within or adjacent to the gene locus for apolipoprotein B (apo B), the major protein component of serum low density lipoprotein (LDL). One of these, detected with the restriction enzyme XbaI, has been suggested to be involved in the determination of serum lipid levels in some but not all populations. We determined the XbaI genotypes and serum lipoprotein levels of 176 apparently healthy unrelated Finns. Subjects homozygous (genotype X2X2) or heterozygous (genotype X1X2) for the presence of the XbaI restriction site within the apolipoprotein B gene (n = 113) had, on the average, an 11% higher serum total cholesterol (P = 0.01) level than those homozygous for the absence of this site (genotype X1X1, n = 63). In addition, the X2 allele was significantly associated with apo B(c), another allele reportedly associated with elevated serum cholesterol levels. The combined genotype (both X2 and apo B(c) alleles present) resulted in a greater elevation of total cholesterol (P = 0.004, when compared to subjects with neither allele) and LDL-cholesterol (P = 0.02) than the presence of either allele alone. The results suggest that both the XbaI and apo B(c/g) sites are in linkage disequilibrium with a functionally important DNA alteration within or adjacent to the apo B gene but the XbaI locus may be in stronger linkage disequilibrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of two different doses of alcohol on serum lipoproteins, HDL-subfractions and apolipoproteins A-I and A-II: a controlled study

Our earlier studies have shown that heavy alcohol intake increases the serum concentration of HDL2. The present study aimed to test which HDL subfraction is affected by moderate alcohol intake, and to examine the time- and dose-dependency of alcohol-induced changes in serum lipoproteins. Therefore, 30 or 60 g day-1 of alcohol were given to 10 healthy male volunteers during two 3-week periods separated by an abstinence period of 3 weeks. Lipoproteins were fractioned by sequential flotation. On both doses the total HDL3 concentrations rose progressively, the maximum increases being 10 and 25% at the end of respective drinking periods. In contrast, the HDL2 increased slightly only on the dose of 60 g day-1. The serum concentrations of apoprotein A-I and A-II increased on both doses but significantly only on the dose of 60 g day-1; the increments being 22 and 35%, respectively. On the basis of these and our earlier findings we conclude that (i) the effects of heavy and moderate alcohol intake on serum HDL-subfractions are different: the former preferentially increases the HDL2 whereas the latter augments the HDL3; (ii) alcohol-induced changes in serum lipoproteins are both time- and dose-dependent.

Changes in serum lipoprotein pattern induced by acute infections

To study the effects of acute infections on serum lipids and lipoproteins we measured the concentration and composition of different lipoproteins, apoproteins A-I, A-II, and B, and the activities of plasma postheparin lipolytic enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL) during acute and convalescence phase and after complete recovery in 72 infectious patients (33 with viral infection and 39 with bacterial infection). The mass concentrations of both low density lipoprotein (LDL) (P less than .001) and high density lipoprotein (HDL)2 (P less than .002) were reduced during acute infections due to the lowering of their cholesterol, phospholipid, and protein contents. The reduction of LDL cholesterol was maximal at the acute stage of infection (change -15%, P less than .001) while the reduction of HDL2 cholesterol was maximal during the convalescence (change -35%, P less than .001). During acute infections LDL became triglyceride-enriched (11.8 v 8.6%, P less than .0001) but cholesterol-poor (36.6 v 39.3%, P less than .0001). The ratio of HDL cholesterol/LDL cholesterol was significantly reduced during the convalescence (0.42 +/- 0.15 v 0.53 +/- 0.19, P less than .0001). The concentrations of apo A-I and apo A-II were decreased during acute infections (changes -22%, P less than .001, and -16%, P less than .001, respectively). The very low density lipoprotein (VLDL) was 18% higher during the convalescence period than after the recovery due to the elevations of VLDL triglycerides, cholesterol, and phospholipids. The activity of LPL was reduced both in the acute and convalescence phase, whereas that of HL was reduced only in the acute phase of infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationships among insulin's antilipolytic and glucoregulatory effects and plasma triglycerides in nondiabetic and diabetic patients with endogenous hypertriglyceridemia

We tested the hypothesis that the previously observed association among hypertriglyceridemia, hyperinsulinemia, and insulin resistance could be explained by a defect in insulin's antilipolytic effect. Insulin action was measured in 10 nondiabetic and 8 diabetic patients with hypertriglyceridemia (fasting plasma triglyceride 800 +/- 154 and 1105 +/- 445 mg/dl, respectively, P NS; fasting plasma glucose 99 +/- 3 and 161 +/- 12 mg/dl, respectively, P less than .001) and in 8 weight-matched normolipemic nondiabetic individuals (fasting plasma triglyceride and glucose 110 +/- 21 and 91 +/- 3 mg/dl). The slope of the decay in plasma free fatty acid (FFA) during insulin infusion was used as an index of insulin's antilipolytic effect. Insulin stimulation of glucose uptake in vivo during intravenous hyperinsulinemic clamp and in vitro in adipocytes were measures of insulin's glucoregulatory action. Both glucoregulatory and antilipolytic effects were similarly reduced in both hypertriglyceridemic groups compared with normal subjects. The plasma triglyceride concentration correlated positively with the slope of FFA suppression by insulin (r = .81, P less than .0001) and the fasting FFA concentration (r = .65, P less than .0001). In multiple linear regression analysis, insulin's antilipolytic effect and the fasting FFA concentration explained 83% of the variation in the plasma triglyceride concentration. These associations were independent of insulin's glucoregulatory effect and the fasting plasma insulin concentration. The data indicate that patients with endogenous hypertriglyceridemia are resistant to both the antilipolytic and glucoregulatory actions of insulin and that increased flux of FFA as a result of the latter, rather than hyperinsulinemia, is responsible for elevation of very-low-density lipoprotein production.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term effects of prednisone on serum lipids and high density lipoprotein subfractions in normolipidemic healthy men

To study the effects of short term low dose prednisone administration on serum lipids and lipoproteins we measured the concentration and composition of serum lipoproteins; serum apoproteins (apo) A-I, A-II, and B; and plasma lipolytic enzymes before and during prednisone administration (30 mg/day for 7 days) in eight normal men. We also measured insulin binding to adipocytes. Serum high density lipoprotein (HDL) cholesterol increased significantly after 2 days of prednisone administration; the maximal increase was 27% (P less than 0.01 after 5 days). The rise of HDL cholesterol was accounted for by that of HDL2 cholesterol. There were marked changes in the distribution of HDL particles; HDL2 increased, whereas HDL3 decreased. These changes were also apparent after 2 days of prednisone administration and were maximal at 5 days [mean, 1.58 +/- 0.12 (+/- SE) vs. 2.00 +/- 0.14 g/L (P less than 0.001) for HDL2; 1.82 +/- 0.11 vs. 1.61 +/- 0.06 g/L (P less than 0.05) for HDL3], and they were due to opposing changes in cholesterol, phospholipids, and proteins in the HDL subfractions. The change in HDL2 protein correlated inversely with that in HDL3 protein (r = -0.73; P less than 0.05). Notably, prednisone did not change the apo A-I concentration, but that of apo A-II decreased (0.32 +/- 0.02 vs. 0.27 +/- 0.01 g/L; P less than 0.05). Consequently, the lipid to protein ratio of HDL increased. Prednisone induced no significant changes in very low density or low density (LDL) lipoproteins. Adipose tissue LPL activity did not increase until after 7 days of prednisone intake (1.10 +/- 0.28 vs. 3.43 +/- 1.02 mumol FFA/g.h; P less than 0.05), and the same was true for muscle LPL (0.49 +/- 0.14 vs. 0.82 +/- 0.11 mumol FFA/g.h; n = 4; P = 0.06). Specific insulin binding was normal, but both basal and maximal insulin-stimulated glucose transport decreased significantly. In summary, prednisone induces changes in serum HDL which are characterized by redistribution of particles within HDL density toward less dense particles and a quantitative rise of lipids in the HDL2 fraction.

Elevated adipose tissue lipoprotein lipase activity in craniopharyngioma patients

The activity of lipoprotein lipase (LPL) was measured in adipose tissue (AT-LPL) and postheparin plasma (PH-LPL) of 13 obese patients (aged 11 to 31 years) who had surgery for craniopharyngioma 1 to 13 years earlier. AT-LPL activity (mean +/- SEM) was higher in them than in subjects matched with respect to age, sex, and relative body weight (4.6 +/- 1.1 v 2.1 +/- 0.4 mumol free fatty acids (FFA).h-1.g-1, P less than .05). The activity was also higher when expressed per fat cell.