Normalization of triglycerides in type IV hyperlipoproteinemia fails to correct low levels of high-density-lipoprotein cholesterol

One third of the variability in HDL-cholesterol level in a large dyslipidaemic population is predicted by age, sex and triglyceridaemia: The Paris La Pitié Study

OBJECTIVE

The objective of this study was to identify key determinants of high-density lipoprotein-cholesterol (HDL-C) level, including subclinical inflammation and insulin resistance, and to determine the prevalence of a low HDL-C phenotype in dyslipidaemic patients at high cardiovascular risk.

METHODS

In a cross-sectional study, we assessed the prevalence of low HDL-C phenotypes in 14 667 dyslipidaemic patients attending our specialised lipid clinic and evaluated the potential relationships between HDL-C level and 16 clinical and biological parameters.

RESULTS

In univariate analysis, women exhibited higher plasma concentrations of HDL-C as compared with men. Levels of triglycerides, fasting blood glucose, uric acid, waist circumference, body mass index, high sensitivity C-reactive protein (hs-CRP), insulin resistance (as HOMA-IR index) and smoking were all negatively correlated with HDL-C, whereas age was positively correlated with HDL-C levels. Moderate drinkers (10-30 g/day) displayed higher HDL-C concentrations as compared with abstinent subjects; in contrast, consumption of more than 30 g alcohol/day was associated with a further non-significant elevation of HDL-C levels as compared to moderate drinkers. Multivariate analysis identified eight independent correlates of HDL-C. Age, sex and TG accounted for 37% of variability in HDL-C; modifiable factors including waist circumference, alcohol consumption and smoking, in addition to HOMA-IR and hs-CRP, accounted for an additional 5% of the variability in HDL-C. Using a cut-off of 40 mg/dL (1.03 mmol/L) for men and 50 mg/dL (1.29 mmol/L) for women, 33% and 28% of men and women displayed low levels of HDL-C.

CONCLUSION

Eight independent determinants of HDL-C account for 41% of variability in HDL-C in our dyslipidaemic population. Three of them, i.e. age, sex and degree of triglyceridaemia accounted for more than one third of such variability. The high prevalence of low HDL-C phenotypes in dyslipidaemic patients at elevated cardiovascular risk emphasises the need for both lifestyle and pharmacological strategies of intervention to raise HDL-C.

Oxidized LDL receptor gene (OLR1) is associated with the risk of myocardial infarction

Lectin-like oxidized low-density lipoprotein receptor (LOX-1/OLR1) has been suggested to play a role in the progression of atherogenesis. We analyzed the OLR1 gene and found a single nucleotide polymorphism (SNP), G501C, in patients with ischemic heart disease from a single family, which resulted in the missense mutation of K167N in LOX-1 protein. We compared the group of patients with myocardial infarction (MI) (n=102) with a group of clinically healthy subjects (n=102), and found that the MI group had a significantly high frequency of 501G/C+501C/C (38.2%) compared with the healthy group (17.6%; p<0.002). The odds ratio for the risk of MI associated with the 501G/C+501C/C genotype was 2.89 (95% CI, 1.51-5.53). These findings suggest that OLR1 or a neighboring gene linked with G501C SNP is important for the incidence of MI. Manipulating LOX-1 activity might be a useful therapeutic and preventative approach for coronary artery disease, especially for individuals with the G501C genotype of OLR1.

Triglycerides and HDL-cholesterol as risk factors for ischemic heart disease. Results from the Québec cardiovascular study

The relative importance of reduced plasma high density lipoprotein-cholesterol (HDL-C) levels and elevated plasma triglyceride (TG) concentrations as risk factors for ischemic heart disease (IHD) was examined in a sample of 2177 men from the Québec City suburbs. The sample included 202 men with known IHD. The relationship between HDL-C and TG levels, although significant (r = -0.49, P < 0.0001), was not linear, as most of the variation in HDL-C levels was observed within TG levels below 2.5 mmol/l. Reduced HDL-C (< 0.9 mmol/l) was a prevalent condition in men with IHD (50%) compared to those without IHD (30%). On the other hand 26% and 20% of men with and without IHD, respectively, had elevated TG levels (TG > 2.3 mmol/l). A 2-fold increase in prevalence odds ratio (OR) was observed in men with TG levels > 2.3 mmol/l (95% confidence intervals (CI) [1.2;3.3]). No residual association between elevated TG levels and IHD was found, however, after adjustment for HDL-C concentrations (OR 1.2, 95% CI 0.7;2.1). On the other hand, HDL-C remained a significant predictor of IHD after adjustment for other risk factors (OR 0.3, 95%, CI 0.2;0.6). Men with reduced HDL-C levels were also characterized by a cluster of risk factors such as obesity, diabetes mellitus and hypertension, which may contribute to increase the risk of IHD. Finally, the independent interpretation of cholesterol, TG or LDL-C levels may lead to an inadequate prediction of risk, as a large number of IHD patients showed a cluster of risk factors which included low HDL-C concentrations.

Persistence of low HDL-C levels after weight reduction in older men with small LDL particles

LDL subclass pattern B is characterized by a predominance of small LDL particles (LDL peak particle size < or = 255 A) and is associated with increased plasma triglyceride (TG) and reduced HDL cholesterol (HDL-C) concentrations. This study compared the effect of weight loss on lipoprotein and glucose metabolism in 15 healthy, obese (body mass index [BMI], 30.9 +/- 2.4 kg/m2), older (60 +/- 9 years) men with LDL pattern B and in 25 men of comparable age and BMI with LDL pattern A (LDL peak particle size > or = 260 A). At baseline, men with LDL pattern B had higher TG and lower apolipoprotein (apo) A-I, HDL-C, and HDL2-C levels (P < .001) than men with LDL pattern A, while the total cholesterol and LDL cholesterol levels and fasting and 2-hour postprandial glucose and insulin levels did not differ between groups. With weight loss (10.1 +/- 3.6 kg) there were significant decreases in 2-hour postprandial glucose and insulin levels in men with LDL patterns B and A (P < .05). However, the change in plasma TG, HDL-C, HDL2-C, and apoA-I levels with weight loss differed between groups. In men with LDL pattern A, plasma TG levels decreased by 15% (P < .001) compared with a 34% (P < .001) decrease in LDL pattern B (two-factor ANOVA, P < .01). Plasma HDL-C concentrations increased by 0.16 mmol/L (P < .001) in the men with LDL pattern A but by only 0.07 mmol/L in the men with LDL pattern B (two-factor ANOVA, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulatory function of glucose and insulin on high-density lipoprotein cholesterol in normolipidemic subjects

A decreased plasma concentration of high-density lipoprotein (HDL) cholesterol is associated with a higher incidence of coronary artery disease in populations. Therefore, there is intense investigation into the mechanisms responsible for the regulation of HDL cholesterol concentration in plasma. Insulin has a potent effect on HDL cholesterol, but it is unclear whether this is mediated by the primary effect insulin has on plasma triglycerides (TG). In this study, the question of the relationship between glucose, insulin, and HDL cholesterol has been addressed by investigating a cohort of nondiabetic normolipidemic men living in the Venice, Italy, area. One hundred twenty-eight men aged 30 to 69 years were initially recruited. The following parameters were measured: fasting plasma cholesterol, TG, HDL cholesterol, glucose, and insulin. One hundred seventeen of these subjects underwent an oral glucose tolerance test (OGTT), and the glucose and insulin responses were assessed. The final statistical analysis was performed on 98 nondiabetic individuals with plasma lipid levels within the 75th percentile for cholesterol and TG concentrations of the general population of the same age. The insulin response was a positive independent variable for plasma TG (P < .005) and HDL cholesterol (P < .005). On the other hand, HDL cholesterol was negatively associated with plasma TG. This relationship remained significant (P < .0001) also after controlling for age, body mass index (BMI), and glucose- and insulin-related measurements. Consistent with these results, both a stepwise variable selection analysis and a stratification analysis of the data indicated that the plasma TG concentration is the major determinant of HDL cholesterol level.(ABSTRACT TRUNCATED AT 250 WORDS)

Conjoint high triglycerides and low HDL cholesterol across generations. Analysis of proband hypertriglyceridemia and lipid/lipoprotein disorders in first-degree family members

BACKGROUND

To discern whether hypertriglyceridemia (hyper-TG, TG > 95th percentile) and hypoalphalipoporteinemia (hypoalpha, high-density lipoprotein [HDL-C] < or = 10th percentile) are jointly transmitted in families, we studied 385 probands with marked elevations in TG or cholesterol levels (TG or cholesterol > 99th percentile in a previous visit) and their 2072-first-degree relatives in the Lipid Research Clinics' Family Study. Repeat TG measurement, with exclusion criterion of TG < or = 95th percentile, resulted in 162 probands with hyper-TG.

METHODS AND RESULTS

When the proband demonstrated the conjoint trait (CT; ie, TG > 95th percentile, HDL-C < or = 10th percentile, n = 82), an average of 10.6% of first-degree relatives conjointly expressed hyper-TG and hypoalpha in contrast to only 4.1% of first-degree relatives of a proband who expressed high TG levels with normal HDL-C levels (TG > 95th percentile, HDL-C > 10th percentile, n = 80). Hyper-TG was expressed in 24.2% of first-degree relatives of probands with CT. However, hyper-TG was expressed in only 14.4% of first-degree degree relatives of probands with hyper-TG alone. CT probands and their family members tended to have more reported cardiac events and symptoms (P = .02 and .09, respectively) than those subjects associated with hyper-TG alone.

CONCLUSIONS

The differences in HDL-C-TG abnormalities between families related to hyper-TG probands with or without hypoalpha indicate that bottom decile HDL-C is not simply secondary to hyper-TG. A familial interaction is suggested between HDL-C and TG levels consistent with the transmission of hyper-TG and hypoalpha among first-degree relatives. Among subjects and their families with hyper-TG, those who in addition have low HDL-C demonstrate a tendency for more coronary artery disease than do those with normal HDL-C levels.

Long-term effects of Aroclor 1254 (PCBs) on plasma lipid and carnitine concentrations in rhesus monkey

Sixty-seven female rhesus monkeys (Macaca mulatta) were orally dosed daily for 152 weeks with 0, 5, 20, 40, and 80 micrograms Aroclor 1254 (PCB)/kg body wt. Blood polychlorinated biphenyl (PCB) concentrations were highly positively correlated (r = 0.92, P < 0.001) with doses of PCB administered. A comprehensive analysis of plasma lipids/lipoproteins revealed a PCB-associated increase in plasma triglycerides and decreases in plasma total cholesterol, high-density lipoprotein cholesterol (HDL-chol), very-low plus low-density lipoprotein cholesterol (VLDL+LDL-chol), and total carnitine (which is involved in fatty acid metabolism). All of the lipid/lipoprotein changes were significantly (P < or = 0.05) correlated with blood PCB concentration. These data, obtained after 152 weeks of continuous daily exposure of a primate model to PCB support a causal relationship between plasma lipid changes and PCB intake. Previously, causality has been refuted on the premise that the commonly observed elevation of triglycerides with increasing concentration of blood PCB is a reflection, not of PCB dose, but of the partitioning of PCB between tissues (adipose) and blood in proportion to the blood lipid present. The mechanism of the plasma lipid changes was not investigated in this study but the altered lipid/lipoprotein pattern is discussed with respect to known cardiovascular risk profiles.

Diet and lifestyle modification and its relationship to atherosclerosis

Much of the CHD protective effects of diet are mediated through the effects of diet on risk factor levels. The best studied are the effects of diet on lipoprotein levels and blood pressure. With these effects in mind, specific dietary recommendations have been made to reduce CHD rates among healthy Americans. Dietary modification will reduce risk factor levels in the majority of people and will have measurable impact on CHD rates in the nation (Table 9). In the treatment of patients, it is important to distinguish which lipoprotein and blood pressure abnormalities are amenable to diet and which ones require drug therapy. This distinction can be made by understanding the quantitative relationship between dietary intake and risk factor levels that has been presented here and by assessing the current dietary intake of the individual. There must be a significant change in dietary composition to produce a significant change in risk factor level. This point, although it appears obvious when stated, is a common source of confusion concerning the efficacy of diet. For individuals, most nonresponse to dietary change reflects the lack of a dietary change. Poor adherence, in turn, may be the direct result of inadequate diet counseling. Counseling with a registered dietitian may be useful not only in educating the high-risk patient concerning the nutrient content of food, but also in establishing the current dietary intake of the patient. Compliance is not the only cause of nonresponse. For some patients who are already following a CHD prevention diet, additional risk factor reductions may not be evident when minor dietary constituents are altered. Because the majority of the diet effect has already been achieved, this "nonresponse" should not be surprising. The benefit of a change in a minor dietary constituent may not be detectable above the random day-to-day variation in risk factor levels. Lastly, although true nonresponders to diet have been observed, at least for blood cholesterol levels, the prevalence of nonresponse or minimal response is less than 10% of the population. Although the small changes in risk factor levels achieved by diet cannot compare with the greater changes achieved by drug therapy, dietary therapy will always have an important place in altering the health of the United States and its people. For some individuals, dietary and lifestyle modification may be all that is needed for CHD prevention; for others, dietary and lifestyle modifications provide a foundation on which drug therapy can be added for maximum CHD risk reduction.

Hypertriglyceridemia and cholesteryl ester transfer protein interact to dramatically alter high density lipoprotein levels, particle sizes, and metabolism. Studies in transgenic mice

Several types of transgenic mice were used to study the influence of hypertriglyceridemia and cholesteryl ester transfer protein (CETP) expression on high density lipoprotein (HDL) levels, particle sizes, and metabolism. The presence of the CETP transgene in hypertriglyceridemic human apo CIII transgenic mice lowered HDL-cholesterol (HDL-C) 48% and apolipoprotein (apo) A-I 40%, decreased HDL size (particle diameter from 9.8 to 8.8 nm), increased HDL cholesterol ester (CE) fractional catabolic rate (FCR) 65% with a small decrease in HDL CE transport rate (TR) and increased apo A-I FCR 15% and decreased apo A-I TR 29%. The presence of the CETP transgene in hypertriglyceridemic mice with human-like HDL, human apo A-I apo CIII transgenic mice, lowered HDL-C 61% and apo A-I 45%, caused a dramatic diminution of HDL particle size (particle diameters from 10.3 and 9.1 to 7.6 nm), increased HDL CE FCR by 107% without affecting HDL CE TR, and increased apo A-I FCR 35% and decreased apo A-I TR 48%. Moreover, unexpectedly, hypertriglyceridemia alone in the absence of CETP was also found to cause lower HDL-C and apo A-I levels primarily by decreasing TRs. Decreased apo A-I TR was confirmed by an in vivo labeling study and found to be associated with a decrease in intestinal but not hepatic apo A-I mRNA levels. In summary, the introduction of the human apo A-I, apo CIII, and CETP genes into transgenic mice produced a high-triglyceride, low-HDL-C lipoprotein phenotype. Human apo A-I gene overexpression caused a diminution of mouse apo A-I and a change from monodisperse to polydisperse HDL. Human apo CIII gene overexpression caused hypertriglyceridemia with a significant decrease in HDL-C and apo A-I levels primarily due to decreased HDL CE and apo A-I TR but without a profound change in HDL size. In the hypertriglyceridemic mice, human CETP gene expression further reduced HDL-C and apo A-I levels, primarily by increasing HDL CE and apo A-I FCR, while dramatically reducing HDL size. This study provides insights into the genes that may cause the high-triglyceride, low-HDL-C phenotype in humans and the metabolic mechanisms involved.

Disparate effects of a triglyceride lowering diet and of bezafibrate on the HDL system: a study in patients with hypertriglyceridaemia and low HDL-cholesterol levels

The response of plasma triglyceride and of the high density lipoprotein (HDL) system to a triglyceride lowering diet and to a bezafibrate was compared in a group of 24 human subjects with mild to moderate hypertriglyceridaemia and low HDL-cholesterol levels. Post-heparin plasma lipoprotein (LPL) and hepatic (HL) lipase activities were determined before the initiation of the study and at the end of the diet (12 weeks) and bezafibrate (12 weeks) periods. HDL structure and composition were determined on a zonal centrifugation system at the end of the diet and bezafibrate periods. Diet caused a 9-20% reduction of plasma triglycerides but there was no change in LPL, HL or HDL levels. The individual responses between plasma triglycerides and HDL cholesterol levels however were highly correlated (r = 0.60 to 0.78). Combined diet plus bezafibrate therapy caused a further 38% decrease of plasma triglycerides with a 28% increase of HDL-cholesterol and a 47% increase of LPL activity. HDL3 density decreased and the contribution of cholesteryl ester to the HDL mass was increased while the contribution of proteins and triglycerides decreased. In the majority of the subjects (61%) HDL cholesterol levels increased by 20% or more and in these subjects the change of HDL was highly correlated with the change of the LPL/HL ratio (r = 0.74) but not with the change of the plasma triglyceride levels. In the remaining subjects (39%), HDL cholesterol levels remained unchanged or increased by less than 20%. The change of HDL cholesterol levels in these subjects was unrelated to the decrease of plasma triglycerides or the change of post-heparin lipase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of lipoprotein lipase and hepatic triglyceride lipase in postheparin plasma of patients with low concentrations of HDL cholesterol

Previous investigations have shown that abnormalities in the postheparin plasma levels of the lipolytic enzymes, lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL), are correlated with variations in plasma high-density lipoprotein cholesterol (HDL-C) levels. The present study was performed to determine correlations between the postheparin plasma activities of these two enzymes and HDL levels in a sizable number of subjects with low HDL-C levels. Two types of low-HDL subjects were investigated: 159 male subjects with low HDL-C (< 40 mg/dL) and normal triglyceride (< 250 mg/dL) levels (the low-HDL group) and 80 male subjects with low HDL-C (< 40 mg/dL) and elevated triglyceride (> or = 250 mg/dL) levels (the low-HDL/high-TG group). Postheparin plasma activities of LPL and HTGL were determined in these two groups, and these levels were compared with those obtained from 51 normolipidemic (normal-HDL) male subjects. Postheparin LPL activities were significantly lower in the low-HDL and low-HDL/high-TG groups (mean +/- SD, 9.9 +/- 2.9 and 10.4 +/- 3.0 mmol/h per liter, respectively; P < .001 for both) compared with the normal-HDL group (12.5 +/- 3.7 mmol/h per liter). Conversely, postheparin HTGL activities were significantly higher in the low-HDL and low-HDL/high-TG groups (39.3 +/- 16.2 and 44.4 +/- 16.7 mmol/h per liter, respectively; P < .001 for both) compared with the normal-HDL group (29.7 +/- 11.3 mmol/h per liter). Consequently, mean LPL/HTGL ratios were markedly lower in the two low-HDL groups compared with the normal-HDL group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intralipid-induced hypertriglyceridemia on plasma high-density lipoprotein metabolism in the cynomolgus monkey

Low plasma levels of high-density lipoprotein (HDL) and apolipoprotein (apo) A-I often accompany human hypertriglyceridemia. In an animal model of hypertriglyceridemia, the lipoprotein lipase (LPL)-inhibited cynomolgus monkey, we reported that plasma levels of apo A-I were decreased and the fractional catabolic rate (FCR) of HDL apo was increased. To explore whether hypertriglyceridemia alone would alter plasma apo A-I levels and catabolism, hypertriglyceridemia was produced by intravenous (IV) infusion of 20% Intralipid into female cynomolgus monkeys. Baseline plasma triglyceride (TG) levels averaged 106 mg/dL. With infusion of 200 mg/kg/h Intralipid TG, plasma TG levels peaked at 967 mg/dL (range, 413 to 1,069; n = 6). More prolonged or more severe hypertriglyceridemia caused serious complications in several monkeys. Despite the severe hypertriglyceridemia, HDL TG content, HDL apoproteins, and plasma apo A-I levels did not markedly change, suggesting that very little HDL remodeling had occurred. Kinetic studies of HDL protein and apo A-I were performed in four pairs of monkeys. The two tracers were removed from the plasma at identical rates. In five pairs of animals, apo A-I turnover during control and Intralipid-induced hypertriglyceridemia was not significantly different. We hypothesize that apo A-I FCR is a function of HDL composition. Because Intralipid infusion did not alter HDL composition to the same degree as did LPL inhibition, its effects on HDL apo catabolism were not apparent.

Persistence of abnormalities in metabolism of apolipoproteins B-100 and A-I after weight reduction in patients with primary hypertriglyceridemia

Obesity commonly accompanies hypertriglyceridemia, and weight reduction is widely recommended for treatment of elevated triglyceride levels. To determine whether weight reduction will normalize lipoprotein metabolism in overweight, hypertriglyceridemic patients, 10 such male patients underwent weight loss until their body weights were within the desirable range. After reestablishment of a steady state in body weight at the lower level, measurements were made of plasma lipid, lipoprotein, and apolipoprotein levels and the kinetics of low density lipoprotein (LDL) apolipoprotein B-100 (apo B) and apolipoprotein A-I (apo A-I). The patients lost an average of 10.6 +/- 2.1 kg (mean +/- SEM). Plasma triglyceride concentrations fell from 431 +/- 42 mg/dl to 248 +/- 27 mg/dl (p less than 0.001), whereas concentrations of total cholesterol, LDL cholesterol, total apo B, and high density lipoprotein (HDL) cholesterol were unchanged after weight loss. On average, the fractional catabolic rates (FCRs) for LDL were much higher in the patients after weight loss than in 16 normal control subjects (0.55 +/- 0.06 versus 0.31 +/- 0.06 pool/day), and input rates for LDL also were higher for hypertriglyceridemic patients after weight loss (22.2 +/- 2.4 versus 12.8 +/- 2.3 mg/kg.day). Compared with 20 normal control subjects, hypertriglyceridemic patients after weight reduction had persistent low HDL cholesterol levels (32 +/- 2 versus 54 +/- 3 mg/dl) as well as low apo A-I levels (99 +/- 5 versus 122 +/- 4 mg/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of reduction of plasma triglycerides with gemfibrozil on high-density-lipoprotein-cholesterol concentrations

The aim of this study was to test the hypothesis that the plasma triglyceride (TG) concentration must be reduced below approximately 0.85-1.13 mmol l-1 (75-100 mg/dl-1) in order to achieve a substantial increase in plasma high-density-lipoprotein-cholesterol (HDL-C) levels. The study design consisted of a non-randomized clinical trial, which was conducted at an out-patient clinic at a university-affiliated VA Medical Center. The participants consisted of 55 ambulatory middle-aged men with a baseline fasting HDL-C concentration of less than or equal to 1.17 mmol l-1 (45 mg dl-1) and baseline TG in the range 1.13-5.6 mmol l-1 (100-500 mg dl-1). Subjects were treated with gemfibrozil, 600 mg twice a day for 3 months. Fasting plasma HDL-C, TG, low density lipoprotein-cholesterol, and total cholesterol were measured at 1-month intervals for 3 months. Subjects were divided into three groups on the basis of TG level achieved on therapy: Group I (n = 14), TG less than 0.85 mmol l-1 (75 mg dl-1); Group II (n = 20), TG 0.86-1.41 mmol l-1 (76-125 mg dl-1); Group III (n = 21), TG greater than 1.41 mmol l-1 (125 mg dl-1). The mean increase in HDL-C in Group I was 0.20 mmol l-1 (7.8 mg dl-1), a significantly (P = 0.0067) greater increase than was observed in the other two groups. There was no correlation between the magnitude of change in TG and the magnitude of change in HDL-C concentration in the group as a whole (Pearson's correlation coefficient, r = -0.06, P = 0.6). In conclusion, the increase in HDL-C levels observed with gemfibrozil therapy is associated with the absolute level of TG achieved by therapy. Substantial increases in HDL-C concentration might not be expected to occur consistently unless TG levels are reduced to values that are considered below the usually cited 'normal' range.

Relationship of triglycerides and HDL cholesterol in hypertriglyceridemia

Hypoalphalipoproteinemia (plasma HDL-cholesterol concentration at or below 35 mg/dl as reported in the National Cholesterol Education Program Guidelines) is a well known risk factor for premature coronary artery disease (CAD). In hypertriglyceridemic patients, hypoalphalipoproteinemia is commonly believed to be linked to the derangement of triglyceride metabolism. In this study the occurrence of primary hypoalphalipoproteinemia has been investigated in a cohort of hypertriglyceridemic patients whose plasma triglyceride concentration had been normalized either through diet or diet plus drug treatment. Following the initial visit, 115 hypertriglyceridemic patients received dietary advice and returned for the second visit four months later. Diet reduced plasma triglycerides in all the patients. HDL-cholesterol increased in 76 patients whereas in the others, it remained unchanged or even decreased. Plasma triglyceride concentration was normalized (less than 200 mg/dl) in 54 patients by diet alone, but among these 11 remained hypoalphalipoproteinemics. Patients in whom, despite dietary restrictions, triglycerides exceeded 200 mg/dl, were considered for pharmacological treatment with Bezafibrate (300 mg t.i.d.) for 4 months. Thirty-nine concluded the study. Treatment significantly decreased plasma triglyceride concentration in all the subjects. Normalization was achieved in 32 patients. Four of them, however, remained hypoalphalipoproteinemic. These results indicate that a subgroup of hypertriglyceridemic patients remained hypoalphalipoproteinemic even after normalization of triglyceride levels. In these patients hypertriglyceridemia and hypoalphalipoproteinemia may occur as expression of two distinct primary metabolic defects.

Fat and cholesterol intake of attendees at two national USA cardiovascular annual meetings

Using a 1-page bar-coded food frequency questionnaire, the food habits of 996 adults who participated in diet screening at the annual meetings of the American Heart Association (1989) and the American College of Cardiology (1990) were analyzed for sex, age and regional differences. Estimated nutrient intakes were also compared with those from the Department of Agriculture's 1985 and 1986 Continuing Survey of Food Intake of Individuals. The average diet reported in this study satisfied National Cholesterol Education Program guidelines for cholesterol intake, but was higher than that recommended for total and saturated fats. In addition, dietary fat intake was influenced by sex, age and geographic region. Reduction in total and saturated fat intake was confined to men greater than 35 years of age; intake of these nutrients was highest among young, Mid-western women. These results suggest the need for diet intervention programs, targeted specifically to young adults with additional consideration given to regional variation. Repeated surveys of cardiac care givers might be used as an early indicator of the nationwide effectiveness of dietary intervention programs.

Lipid metabolism in renal failure

Many patients with renal failure show abnormalities of lipid metabolism. Hypertriglyceridemia and low levels of high density lipoprotein (HDL) cholesterol are frequent abnormalities in uremic patients. The hypertriglyceridemia and low HDL cholesterol are thought to result from decreased lipoprotein lipase activity. The decreased levels of hepatic lipase observed in renal failure may account for the presence of intermediate density lipoproteins (IDL) and the high HDL2 subfraction. The risk factor for coronary artery disease expressed as the ratio of total cholesterol to HDL cholesterol is elevated in renal failure patients, especially in those with hypertriglyceridemia. Treatment of renal patients with gemfibrozil partially reverses many of the lipid abnormalities including the low HDL cholesterol. However, only the HDL3 subfraction increased while HDL2 remained unchanged.

Nutritional management of plasma lipid disorders

Prevention of vascular disease and acute pancreatitis is the goal of hyperlipidemia treatment. The risk of coronary heart disease (CHD) increases with increasing plasma cholesterol levels because low-density lipoprotein (LDL), the major carrier of cholesterol in the plasma, is atherogenic. High-density lipoprotein (HDL), especially the HDL2 subfraction, protects against CHD. Hypertriglyceridemia, although not an independent risk factor for CHD, is generally accompanied by low HDL cholesterol (HDLch), which may predispose to CHD. Reducing plasma LDL and raising HDL levels are thus goals in preventing CHD. Serum LDL levels may be lowered by reducing saturated fat and cholesterol intake; weight loss may decrease LDL but is more effective in lowering plasma triglycerides and raising HDLch. The percent of total calories from polyunsaturated, monounsaturated, and saturated fats should be less than 10%, up to 10-15%, and less than 10%, respectively. High cholesterol intake increases the flux of cholesterol, which may be harmful to arterial walls, but beyond a certain point does not increase plasma cholesterol levels. Some diets change the composition rather than the level of LDL and apoproteins. Weight reduction and maintenance are the most effective dietary measures to lower plasma triglycerides; omega-3 fatty acids (fish oils) have shown promise in reducing triglyceride but not cholesterol levels. Substitution of starch for sugar lowered triglyceride levels toward normal in hypertriglyceridemia patients. Fasting triglyceride levels rise in all individuals fed high-carbohydrate diets, but the high levels persist in hypertriglyceridemia patients. Weight loss, cessation of cigarette smoking, increased physical activity, good control of diabetes, and moderate alcohol use all raise HDLch levels. Vitamin E deficiency causes neurological sequelae in children with severe malabsorption problems due to abetalipoproteinemia or cholestatic liver disease.

Lipoprotein lipase. A multifunctional enzyme relevant to common metabolic diseases

Lipoprotein lipase is an important regulator of lipid and lipoprotein metabolism. It also contributes to the lipid and energy metabolism of different tissues in varying ways. Although the synthesis, manner of secretion, and mechanism of endothelial binding of lipoprotein lipase appear similar in all tissues, the factors that control gene expression and posttranslational events related to processing vary from tissue to tissue. The actual molecular events that determine this tissue specificity are not yet understood. In the future, however, it may be possible to stimulate or inhibit the activity of lipoprotein lipase in specific tissues and to alter metabolic processes so as to improve the quality and length of life in patients with metabolic diseases such as hypertriglyceridemia, HDL2 deficiency, and obesity.

Heterogeneity of apolipoprotein A-I turnover in subjects with reduced concentrations of plasma high density lipoprotein cholesterol

Reduced plasma levels of high density lipoprotein cholesterol (HDLC) and apolipoprotein A-I (apoA-I) are both indicators of increased risk of developing coronary artery disease. We have used autologous 125-I-HDL to determine the rates of production (PR) and fractional catabolism (FCR) of apoA-I, the major, structural apolipoprotein in HDL, in three groups of men that included the following: four normal subjects (triglyceride [TG] = 61.0 +/- 5.0 mg/dL, HDLC = 51.5 +/- 7.0 mg/dL), four subjects with both hypertriglyceridemia and reduced HDLC (TG = 360.3 +/- 111.1 mg/dL, HDLC = 23.8 +/- 6.1 mg/dL), and seven subjects with only reduced HDLC (TG = 103.7 +/- 49.5 mg/dL, HDLC = 25.6 +/- 6.1 mg/dL). In the group with both the high TG and low HDL, apoA-I PR was significantly greater than the apoA-I PR in the normal group (14.2 +/- 2.3 v 10.6 +/- 1.9 mg/kg.d, P less than .05). ApoA-I FCR was also significantly greater in the former group v normals (0.38 +/- 0.08 v 0.21 +/- 0.04 d-1, P less than .02). In contrast, the group of subjects with only low HDLC had a significantly lower apoA-I PR v the normal subjects (7.1 +/- 2.0 v 10.6 +/- 1.9 mg/kg.d; P less than .05). ApoA-I FCR was variable in the group with isolated low HDLC, but the mean FCR was not different from normal (0.26 +/- 0.09 v 0.21 +/- 0.04 d-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Change in composition of high density lipoprotein during gemfibrozil therapy

We investigated the high density lipoprotein cholesterol (HDL-C) response in 20 middle-aged males during a 12-week course of gemfibrozil. Three aspects of the increase in HDL-C (25%) were studied and our observations are as follows: (1) subfraction analysis showed that HDL3-C rose earlier and to a larger extent (28%) than HDL2-C (15%), (2) analysis of variance group--time interaction effect and correlation studies of HDL-C and total triglycerides suggest the increase in HDL-C was due to a direct effect of gemfibrozil on HDL metabolism, and (3) HDL-C was the only one of 4 HDL components to increase. Apoprotein A-I (apo A-I) and HDL-phospholipid (HDL-PL) did not change, and HDL-triglyceride (HDL-TG) decreased. This pattern is consistent with a change in composition of HDL, i.e. cholesterol enrichment and triglyceride depletion.

Borderline fasting hypertriglyceridemia: absence of excess risk of all-cause and cardiovascular disease mortality in healthy men without hypercholesterolemia

The majority of prospective studies have shown no independent effect of triglyceride on the prediction of cardiovascular disease after the effects of cholesterol and other heart disease risk factors have been accounted for statistically. Because the association of borderline elevation of triglyceride levels (250-499 mg/dl) with cardiovascular risk might be obscured by its strong correlation with hypercholesterolemia, we examined the relationship in healthy men without hypercholesterolemia. In a population sample of 1,589 healthy fasting men ages 30-79 without known cardiovascular disease or categorical hypercholesterolemia, the prevalence of borderline hypertriglyceridemia was 4.2%, and was unrelated to age. There was no significant excess of borderline hypertriglyceridemia in men with systolic hypertension, or in men who reported use of antihypertensive drugs, current cigarette smoking, or a family history of heart attack before or after age 50. Only obesity, a personal history of diabetes, and fasting hyperglycemia were significantly more common in men with borderline hypertriglyceridemia. Moreover, hypertriglyceridemia was a relatively weak marker for those with diabetes or obesity, being present in only 9% of the former and 6% of the latter. A 12-year follow-up of these men showed no significant association of hypertriglyceridemia with all-cause or cardiovascular death either by univariate analysis or after adjusting for risk factors. These data support the conclusion that borderline hypertriglyceridemia is a poor marker for cardiovascular risk in healthy older men without hypercholesterolemia.

The association of increased levels of intermediate-density lipoproteins with smoking and with coronary artery disease

Studies were undertaken to determine whether there is an association between elevated levels of intermediate-density lipoproteins (IDL) (Sf 12-60 lipoproteins) and coronary artery disease. Forty-five to sixty-five-year-old men with objectively documented coronary artery disease (n = 58) who were free of known risk factors (diabetes, hypertension, obesity, hyperuricemia, and hypercholesterolemia) were compared with similar men who were free of coronary artery disease (n = 52). Smokers could not be excluded. The coronary artery disease group had a higher rate of cigarette smoking (NS, due to large variations); higher concentrations of triglycerides in their plasma (p = .003) and higher levels of very low-density lipoproteins (VLDL) (p = .007), IDL (p = .016), and low-density lipoproteins (LDL) (p = .04); as well as somewhat lower levels of high-density lipoprotein (HDL) cholesterol (p = .04). Chi-squared analysis demonstrated a strong association between coronary artery disease and IDL apolipoprotein (apo) B (p = .006), coronary artery disease and IDL triglyceride (p = .032), and coronary artery disease and IDL apo B times IDL triglyceride (p = .006) when the top quintile of the population was compared with the bottom quintile for each of these variables. Stepwise logistic regression analysis resulted in rejection of an association between coronary artery disease and HDL cholesterol, plasma triglyceride, VLDL triglyceride, or LDL triglyceride. However, it did show that coronary artery disease was most strongly associated with smoking and that the second strongest association was with IDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertriglyceridemia and carbohydrate intolerance: interrelations and therapeutic implications

Atherosclerosis, the most frequent complication of diabetes, could be the result of hyperlipidemia, among other factors. Mounting evidence suggests that reducing the concentration of triglyceride-rich lipoprotein, which influences the production of the possibly atherogenic intermediate density lipoprotein (IDL), might diminish the circulating level of potentially atherogenic lipoproteins. Hypertriglyceridemia, even in the absence of obesity, is associated with insulin resistance. To compensate, pancreatic B cells respond to glucose challenge by producing hyperinsulinemia. If the B cells cannot respond adequately, carbohydrate intolerance ensues. Insulin-treated diabetics may also become hyperinsulinemic because routine insulin injection may not reflect physiologic need and because the insulin is administered peripherally rather than portally. Hyperinsulinemia increases the production of circulating triglyceride. It appears to do this in rats by causing the production of more triglyceride-rich lipoprotein particles rather than by increasing the triglyceride content of each particle. Further, at least in rats, the insulin-induced increase in triglyceride production requires the presence of supplementary dietary fructose. Hyperinsulinemia also increases the activity of adipose tissue lipoprotein lipase and the degradation of very low density lipoprotein (VLDL). The concentration of VLDL depends on balance of production and degradation. Accelerated VLDL degradation leads to an increase in IDL production. Because there is mounting evidence that IDL may be atherogenic, this cycle could accelerate atherogenesis. As such, it is reasonable to postulate that reducing the concentration of triglyceride-rich lipoproteins would break this cycle and would diminish the circulating level of potentially atherogenic lipoproteins.

Effect of gemfibrozil on lipids, apoproteins, and postheparin lipolytic activities in normolipidemic subjects

The lipid lowering agent Gemfibrozil was tested in 8 normolipidemic subjects during a three-month intake. Plasma triglycerides decreased by 41% and Very Low Density Lipoprotein (VLDL) triglycerides decreased by 54%. The reduction of plasma cholesterol, less marked (by 10%), was due to a decrease of Low Density Lipoprotein by 20% while High Density Lipoprotein (HDL) increased up to 30%. The separation of HDL demonstrated that only HDL3 were increased. The determination of the apoproteins in plasma and lipoprotein fractions showed similar results with a decrease of apo B (by 20%) and an increase of apo A-I and apo A-II, mainly in the HDL3 fraction. Plasma postheparin lipolytic activities (PHLA) were not influenced by the therapy and no correlation was found between these activities and any of the plasma or lipoprotein lipids. The apo C-III/apo C-II ratio in VLDL decreased by 30%; however, no correlation was found between this ratio in plasma as well as VLDL and triglycerides. In addition, the Intra Venous Fat Tolerance Test did not demonstrate any improvement of the clearance of exogenous fat. The lipid lowering efficacy of Gemfibrozil, its collateral effects, and the possible mechanisms of action are discussed.

Nonpharmacologic and pharmacologic alteration of high-density lipoprotein cholesterol: therapeutic approaches to prevention of atherosclerosis

High-density lipoprotein (HDL) cholesterol, an independent coronary heart disease (CHD) risk factor, is inversely associated with CHD. Whether interventions to increase concentrations of HDL--particularly the HDL2, HDL3, and apolipoprotein A1 subfractions--will reduce the incidence of CHD in high-risk patients is thus an area of intense speculation. Both nonpharmacologic and pharmacologic regimens will raise HDL concentrations. Nonpharmacologic approaches include habitual high-level aerobic exercise and weight loss--both of these somewhat more effective in men than in women--cessation of cigarette smoking, and changing of dietary habits. A number of drugs have been found to elevate HDL cholesterol. These include the bile acid-binding resin cholestyramine, nicotinic acid, gemfibrozil, phenytoin, exogenous estrogens, and alcohol. Terbutaline has also been reported to raise HDL cholesterol. It is not yet known whether, and to what degree, pharmacologic and nonpharmacologic elevation of HDL cholesterol will retard or reverse the progression of atherosclerosis. Conversely, HDL cholesterol is lowered by a broad variety of drugs, including anabolic--androgenic steroids, exogenous progestins, and probucol, which are used therapeutically to reduce low-density lipoprotein (LDL) cholesterol. Some agents used to treat hypertension also reduce HDL cholesterol, especially thiazide diuretics and the beta blockers, with the possible exception of pindolol. In the antiadrenergic class of antihypertensive agents, reserpine and methyldopa lower HDL cholesterol, but the alpha blocker prazosin does not appear to affect HDL cholesterol. The alpha agonist guanabenz has no effect on HDL cholesterol, and the vasodilator carprazidil has been reported to raise HDL cholesterol. In light of these facts, investigations should be undertaken to determine whether the metabolic effects of antihypertensive agents blunt their beneficial effects on CHD.(ABSTRACT TRUNCATED AT 250 WORDS)

Demographic, behavioral, biochemical, and dietary correlates of plasma triglycerides. Lipid Research Clinics Program Prevalence Study

Few studies have simultaneously examined the relationship of triglyceride levels with a wide variety of potential covariates. Thus, the present study was designed to assess in a large, free-living population the association of fasting plasma triglyceride values with selected demographic, behavioral, biochemical, and dietary measures. These analyses were done using data obtained from 5189 white men and women aged 20 to 69 years who participated in the Lipid Research Clinics Program Prevalence Study. Of the eight nondietary factors examined, age, Quetelet Index, fasting plasma glucose, and cigarette smoking were strongly, positively associated (p less than 0.0001) with triglycerides in men and in women not using gonadal hormones. Among women using oral contraceptives or estrogens, only Quetelet Index (p less than 0.01) and cigarette smoking (p = 0.01) were significantly related to triglyceride values. Physical activity was inversely associated (p less than 0.0001) and use of diuretic medications was positively related (p less than 0.01) to triglycerides only in men. Results of analyses of triglycerides and six selected dietary measures varied by age, sex, and hormone-use subgroups. Although none of the dietary variables showed consistent associations with triglycerides across all of the subgroups, triglycerides tended to be inversely associated with total calories per kilogram of body weight and the percentage of calories as dietary fat.

Altered HDL subclasses in endogenous hypertriglyceridemia are not affected by weight reduction

Reduction of body weight is commonly used to decrease the plasma lipids of patients with primary endogenous hypertriglyceridemia, but the effects of stabilized weight reduction on lipoprotein compositions and distribution are not well known. Since lipoprotein structures are perhaps as important in normal and abnormal metabolism and atherogenesis as are the levels of lipoproteins, we examined the effects of weight loss on the plasma concentrations, compositions, and ultracentrifugal flotation properties of plasma lipoproteins. Nine patients (eight males, one female) with endogenous hypertriglyceridemia and low high-density lipoprotein (HDL)-cholesterol levels who were approximately 130% of ideal body weight were studied during two dietary periods (basal and low weight). Subjects consumed an isocaloric diet for 5 weeks consisting of approximately 15% protein, approximately 45% carbohydrate, approximately 40% fat, approximately 500 mg/d cholesterol, P/S ratio 0.43 (basal), followed by a hypocaloric diet of the same composition, which was eaten for 16 to 52 weeks, until the desired weight was lost (9.6 +/- 3.6 kg). Then patients continued to eat a diet of the same composition lower in calories but sufficient in quantity to maintain their new lower body weights for the final 5 weeks (low-weight period). The last weeks of the basal and the low-weight periods were spent in a metabolic ward. Thus, high and low body weights were known to be stable for at least 5 weeks. Fasting (12 to 14 hours) plasma total triglycerides decreased in all patients (from 328 +/- 204 mg/dL at basal to 185 +/- 77 mg/dL at low weight, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Primary and familial hypoalphalipoproteinemia

Our specific aim was to assess within-family clustering of high-density lipoprotein cholesterol (HDLC) levels in kindreds identified through probands with primary hypoalphalipoproteinemia, and to determine whether, and to what degree, familial aggregation of HDLC less than or equal to the tenth percentile represents a heritable trait, familial hypoalphalipoproteinemia. Our probands were selected arbitrarily by virtue of HDLC less than or equal to the age-sex-race-specific tenth percentile as the sole dyslipoproteinemia, with an additional requirement that they be normotriglyceridemic (triglyceride levels less than the 90th percentile). The probands were also required to have primary hypoalphalipoproteinemia, not secondary to diseases and/or drugs. Fifteen of the 16 probands were men; 12 were referred because of premature myocardial infarction, angina, or stroke, 2 because of family history of premature myocardial infarction or stroke, and 2 because of low HDLC observed on routine health examinations. Two of the 16 kindreds exhibited three-generation vertical transmission of bottom decile HDLC. In three kindreds, there was also three-generation vertical transmission of bottom decile HDLC, but top decile triglycerides accompanied bottom decile HDLC in one or more generations. Eight kindreds displayed two-generation vertical transmission of bottom decile HDLC. After excluding probands, there were 11 critical matings (bottom decile HDLC by normal), with 30 living offspring, all of whom were sampled. Of these 30 offspring, 13 had bottom decile HDLC, 17 had HDLC greater than tenth percentile. The ratio of offspring with bottom decile HDLC to those of HDLC greater than tenth percentile was 13:17 (0.76/1), not significantly different from the ratio of 1/1, the ratio predictive of a dominant trait, X2(1) = 0.53, P greater than 0.4. The nearly 1:1 segregation ratio for the group of offspring was not due to the aggregation of sibships with, in general, most of the sibs, or none of the sibs affected; within-family expression of low HDLC was also not sex-linked. The 13 hypoalphalipoproteinemic offspring of 11 critical matings included only two subjects whose bottom decile HDLC was accompanied by top decile triglyceride. Our data suggests that not only (by selection) was low HDLC in the probands the sole dyslipoproteinemia, but that the segregation of low HDLC in offspring of critical matings was primarily accounted for by isolated low HDLC, not by hypoalphalipoproteinemia secondary to hypertriglyceridemia. Familial hypoalphalipoproteinemia is a heritable disorder with a pattern of transmission not significantly different from that expected by a hypothesis of mendel

Clofibrate and tiadenol treatment in hyperlipoproteinemias. A comparative trial of drugs affecting lipoprotein catabolism and biosynthesis

Changes in plasma lipoprotein levels and platelet reactivity were evaluated during sequential treatments with clofibrate and tiadenol, two hypolipidemic agents with apparently different mechanisms, in 27 hyperlipoproteinemic patients. The objective of the study was to determine the pattern of plasma lipoprotein variations, induced by a drug mainly affecting lipoprotein catabolism (clofibrate) and by a drug affecting biosynthesis (tiadenol), and to single out-patients specifically responding to either treatment. Both drugs proved significantly active in type IIA and IV hyperlipoproteinemias, not in type IIB. Clofibrate significantly lowered very low density lipoprotein (VLDL) associated cholesterol in all three hyperlipoproteinemia phenotypes, and it also lowered VLDL triglycerides in type IV, while increasing high density lipoprotein (HDL) cholesterol in type IIA patients. Low density lipoprotein (LDL) cholesterol levels were minimally reduced by clofibrate in type IIA (-4%), and increased in types IIB (+ 14.2%) and IV (+ 6.1%) patients. Conversely, tiadenol lowered VLDL cholesterol and triglycerides to a lesser extent, but it did significantly reduce LDL cholesterolemia in type IIA (-17.6%), while increasing HDL cholesterol in type IIB. Statistical evaluation of the results did not permit identification of parameters associated with the response to either drug, although individuals specifically responding to one or the other agent, or to both, were detected in all three phenotypes. The sensitivity to the major platelet aggregating factors, ADP, adrenaline and collagen, was not significantly altered after drug treatments. Evaluation of the hypolipidemic response to agents with different mechanisms may be of help in selecting the best treatment for individual patients.

Habitual physical activity and high-density lipoprotein cholesterol in men with primary hypercholesterolemia. The Lipid Research Clinics Coronary Primary Prevention Trial

The association of habitual physical activity with plasma high-density lipoprotein (HDL) cholesterol and total triglyceride (TG) was examined in 7106 asymptomatic 35-59-year-old white men with primary type II hyperlipoproteinemia who attended the second screening visit of the Lipid Research Clinics Coronary Primary Prevention Trial. Subjects were rated by usual level of physical activity at work and outside of work and the frequency of strenuous physical labor or exercise. By each of these three criteria, physical activity was monotonically related to HDL cholesterol and TG: the most physically active men had the highest HDL cholesterol and lowest TG levels. With respect to physical activity outside of work, for example, mean HDL cholesterol and TG were 46.4 and 152.1 mg/dl, respectively, in the most active group, and 41.4 and 186.7 mg/dl in the most sedentary group. Physical activity remained significantly predictive of HDL cholesterol and TG when other known correlates of these plasma constituents--age, Quetelet index, plasma total cholesterol, cigarette smoking, alcohol intake, and clinic--were controlled individually by two-way analyses of variance or jointly by analysis of covariance. The association of physical activity with very low density lipoprotein cholesterol was parallel to but weaker than its association with TG. Low-density lipoprotein and total cholesterol were not significantly related to physical activity.

Lipid class and molecular species interrelationships among plasma lipoproteins of type III and type IV hyperlipemic subjects

As a further appraisal of lipoprotein interconversion and equilibration of lipid components a detailed examination was made of the chemical class and molecular species interrelationships among the major fasting plasma lipoprotein fractions within each of six male Type IIi and Type IV hyperlipemic subjects subsisting on free choice diets. The lipoprotein fractions were prepared by conventional ultracentrifugation and the lipid class and molecular species composition of the corresponding lipoprotein fractions were determined by gas chromatography of the intact glycerol esters and ceramides. In general, each lipoprotein fraction possessed a well defined lipid class composition, which was characterized by a dramatically decreasing triacylglycerol and increasing phospholipid and cholesteryl ester content, when progressing from the very low (VLDL) to the low (LDL) and high (HDL) density lipoproteins, as already established for normolipemic subjects. Likewise, the LDL1, and LDL2 of the hyperlipemic subjects contained about two times higher proportion of total phospholipid as sphingomyelin than VLDL and HDL. Furthermore, the sphingomyelins of the HDL fraction contained about 30% more of the higher and 30% of the lower molecular weight species than the sphingomyelins of the VLDL. Smaller differences were seen in the molecular species composition of the phosphatidylcholines, cholesteryl esters and triacylglycerols among the corresponding lipoproteins. In comparison to normolipemic subjects analyzed previously, the hyperlipemic subjects showed greater individual variability. Despite this variability the lipid class and molecular species composition in the hyperlipemic subjects was again incompatible with the hypothesis which postulates direct VLDL conversion into LDL nd HDL under the influence of lipoprotein lipase and lecithin: cholesterol acyltransferase. The main differences between normolipemic and hyperlipemic plasma were found to reside in the number of the VLDL and LDL, lipoprotein particles and not in their chemical composition or physical structure, or in the apparent mechanism of their metabolic interconversion.

Body mass index and physical fitness as determinants of serum lipoprotein levels in middle-aged men

The aim of the present study was to analyse to what extent serum lipoproteins are determined by overweight and physical fitness. Fifty-eight middle-aged males were divided into lean, overweight and obese subgroups according to their body mass indices, which characterization was also well in accordance with two skinfold thicknesses. Maximal oxygen consumption per body weight was lowest in the obese. HDL cholesterol was decreased in the obese compared to the lean. HDL cholesterol correlated separately significantly with maximal oxygen consumption and body mass index when all the three groups were combined. Physical fitness was a less dominant determinant of HDL cholesterol than body mass index. The importance of physical fitness as a determinant of HDL cholesterol was less marked in the obese than in the lean and overweight suggesting a need for certain level of physical activity before it can influence serum lipoprotein levels.

Regulation of high density lipoprotein levels

Current concepts of the structure and metabolism of high density lipoproteins are presented and factors that influence their levels in human beings are surveyed.

The influence of thyroid function on serum lipid profile

Serum triglycerides, cholesterol, HDL-C and LDL-C levels as well as the LDL/HDL cholesterol ratio were determined in 11 patients suffering from hyperthyroidism and 7 patients suffering from hypothyroidism, and compared with those of 19 sex-and age-matched controls. In hypothyroidism a net increase of all lipid values was observed. In hyperthyroidism cholesterol and LDL-C values were reduced while those of the triglycerides and HDL-C were unchanged as compared with controls. The LDL/HDL cholesterol ratio in either group of patients was lower than in controls, the lowest being observed in thyrotoxicosis.

[Bezafibrate in primary hyperlipidemias (author's transl)]

The effect of long-term treatment over 40 weeks with Bezafibrate on lipids and lipoproteins was investigated in 27 patients with primary hyperlipoproteinemias (hlp) (12 patients with hlp type IV, 7 patients with type IIb, 3 patients with type IIa, 4 patients with type V and 1 patient with type III). Bezafibrate reduced total cholesterol by 16%, whereas HDL-cholesterol increased by 28% and 36% (p less than 0.05). Serumtriglycerides decreased by 59% (450 mg Bezafibrate daily) and by 66% (600 mg Bezafibrate daily) statistically significant (p less than 0.05). In hyperlipidemias type IV, IIb, IIa and V increases of HDL-cholesterol could be observed. The course of LDL-cholesterol was different in the various types of hlp. The postheparin-lipoprotein-lipase (PHLA) was activated by treatment with Bezafibrate from 10.5 +/- 0.7 to 14.7 +/- 0.7 and 15.5 +/- 0.8 mumol FFA/ml/h or by 30% (p less than 0.05). Only few side-effects during treatment with Bezafibrate could be ascertained.

Lipoproteins in familial hyperalphalipoproteinemia

Familial hyperalphalipoproteinemia is determined by a major gene and is characterized by high levels of high density lipoprotein cholesterol and longevity. To describe the plasma lipoproteins in this condition more completely, a kindred consisting of the proband, her affected father, add her two affected brothers was studied. Fasting plasmas were analyzed for lipoprotein lipids by combined preparative ultracentrifugal and precipitation methods. Levels of apolipoprotein A-1 and apolipoprotein A-11, the major apoproteins of high density lipoproteins, were assayed by radioimmunoassay. The flotation properties of very low density, low density and high density lipoprotein were determined by zonal ultracentrifugation, and the isolated high density lipoprotein subfractions were characterized according to their lipid and apoprotein compositions. Total cholesterol of all subjects was normal, but triglycerides were elevated (above the 90th percentile) in the two brothers. High density lipoprotein cholesterol ranged from 150 to 165 mg/dl in the proband and from 72 to 89 mg/dl in her relatives. Apolipoprotein A-1 was 318 mg/dl in the proband and 156 to 169 mg/dl in the siblings; respective apolipoprotein A-11 values were 67 and 82 to 83 mg/dl. The high density lipoprotein cholesterol and apolipoprotein A-1 and A-11 values for the relatives are above the 95th percentile for sex and age, while the levels of the proband are the highest recorded in our laboratories. On zonal ultracentrifugation, very low density lipoprotein and low density lipoprotein had normal flotation properties. High density lipoprotein was divisible into three populations, HDL2, HDL3L, and HDL3D (Sf(1,21,26 degrees C), 59, 2.9, and 1.7 respectively), each of which floated in its usual position. But HDL2 was grossly elevated, accounting for most of the rise in the high density lipoprotein fraction. The compositions of the high density lipoprotein fractions with respect to the major lipid and apoprotein classes did not differ from normal. Thus, in this kindred, high density lipoprotein was quantitatively rather than qualitatively unusual. It is of interest that hypertriglyceridemia and hyperalphalipoproteinemia coexisted in the siblings. These concurrent elevations differ from the expected reciprocal relationship between high density lipoprotein and very low density lipoprotein levels in plasma, and suggests that in some subject the two abnormalities may be independently transmitted.