Effects of a cardioselective beta-blocker on postprandial triglyceride-rich lipoproteins, low density lipoprotein particle size and glucose-insulin homeostasis in middle-aged men with modestly increased cardiovascular risk

Using genetics to assess the association of commonly used antihypertensive drugs with diabetes, glycaemic traits and lipids: a trans-ancestry Mendelian randomisation study

AIMS/HYPOTHESIS

Diabetes and hyperlipidaemia are common comorbidities in people with hypertension. Despite similar protective effects on CVD, different classes of antihypertensive drugs have different effects on CVD risk factors, including diabetes, glucose metabolism and lipids. However, these pleiotropic effects have not been assessed in long-term, large randomised controlled trials, especially for East Asians.

METHODS

We used Mendelian randomisation to obtain unconfounded associations of ACE inhibitors, β-blockers (BBs) and calcium channel blockers (CCBs). Specifically, we used genetic variants in drug target genes and related to systolic BP in Europeans and East Asians, and applied them to the largest available genome-wide association studies of diabetes (74,124 cases and 824,006 controls in Europeans, 77,418 cases and 356,122 controls in East Asians), blood glucose levels, HbA_1c, and lipids (LDL-cholesterol, HDL-cholesterol and triacylglycerols) (approximately 0.5 million Europeans and 0.1 million East Asians). We used coronary artery disease (CAD) as a control outcome and used different genetic instruments and analysis methods as sensitivity analyses.

RESULTS

As expected, genetically proxied ACE inhibition, BBs and CCBs were related to lower risk of CAD in both ancestries. Genetically proxied ACE inhibition was associated with a lower risk of diabetes (OR 0.85, 95% CI 0.78-0.93), and genetic proxies for BBs were associated with a higher risk of diabetes (OR 1.05, 95% CI 1.02-1.09). The estimates were similar in East Asians, and were corroborated by systematic review and meta-analyses of randomised controlled trials. In both ancestries, genetic proxies for BBs were associated with lower HDL-cholesterol and higher triacylglycerols, and genetic proxies for CCBs were associated with higher LDL-cholesterol. The estimates were robust to the use of different genetic instruments and analytical methods.

CONCLUSIONS/INTERPRETATION

Our findings suggest protective association of genetically proxied ACE inhibition with diabetes, while genetic proxies for BBs and CCBs possibly relate to an unfavourable metabolic profile. Developing a deeper understanding of the pathways underlying these diverse associations would be worthwhile, with implications for drug repositioning as well as optimal CVD prevention and treatment strategies in people with hypertension, diabetes and/or hyperlipidaemia.

Marked hypertriglyceridemia in a woman receiving metoprolol succinate

β-blockers are commonly used therapies after acute myocardial infarction and in the management of congestive heart failure and hypertension. We report a case of a middle-aged woman with a history of mild hypertension who was placed on metoprolol succinate. Before initiation of the β-blocker, her triglyceride level was in the borderline-high range (150-199 mg/dL). On treatment, her triglyceride levels exceeded 1000 mg/dL. She developed fatigue and mild abdominal discomfort but without biochemical evidence of pancreatitis. After discontinuation of metoprolol succinate, her triglyceride levels receded. This case illustrates an uncommon side effect with a very commonly used therapy in clinical practice. Clinicians should closely evaluate medications and/or other therapies in patients presenting with new-onset hypertriglyceridemia especially when levels are sufficiently elevated to pose increased risk of pancreatitis.

Does combination therapy with statins and fibrates prevent cardiovascular disease in diabetic patients with atherogenic mixed dyslipidemia?

Type 2 diabetes mellitus (T2DM) is associated with the development and progression of cardiovascular disease (CVD). Statins have an established efficacy in the management of dyslipidemia primarily by decreasing the levels of low-density lipoprotein cholesterol and thus decreasing CVD risk. They also have a favorable safety profile. Despite the statin-mediated benefit of CVD risk reduction a residual CVD risk remains, especially in T2DM patients with high triglyceride (TG) and low high-density lipoprotein cholesterol (HDL-C) values. Fibrates decrease TG levels, increase HDL-C concentrations, and improve many other atherosclerosis-related variables. Fibrate/statin co-administration improves the overall lipoprotein profile in patients with mixed dyslipidemia and may reduce the residual CVD risk during statin therapy. However, limited data exists regarding the effects of statin/fibrate combination on CVD outcomes in patients with T2DM. In the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study the statin/fibrate combination did not significantly reduce the rate of CVD events compared with simvastatin/placebo in patients with T2DM. However, it did show a possible benefit in a pre-specified analysis in the subgroup of patients with high TG and low HDL-C levels. Furthermore, in the ACCORD study the simvastatin/fenofibrate combination significantly reduced the rate of progression of retinopathy compared with statin/placebo administration in patients with T2DM. The present review presents the available data regarding the effects of statin/fibrate combination in patients with T2DM and atherogenic mixed dyslipidemia.

A high-fat meal is accompanied by increased plasma interleukin-6 concentrations

BACKGROUND AND AIM

Enhanced and prolonged postprandial lipaemia is associated with coronary heart disease (CHD). However, the mechanisms linking postprandial lipaemia to the increased risk of atherosclerosis and CHD remain to be determined. The aim of the present study was to examine the effects of a high-fat meal on plasma levels of the pro-inflammatory cytokine interleukin-6 (IL-6) and cellular adhesion molecules in CHD patients and control subjects.

METHODS AND RESULTS

Forty-one middle-aged men with premature CHD and 26 healthy male controls were investigated. The plasma triglyceride response to the high-fat meal was significantly greater among cases than controls. The oral fat load induced a twofold increase in plasma concentrations of IL-6, an increase that was similar in CHD patients and control subjects. No changes could be detected in plasma concentrations of cellular adhesion molecules in response to postprandial lipaemia in either CHD patients or control subjects.

CONCLUSION

The results of the present study suggest that a high-fat meal affects mechanisms that induce increased inflammatory activity, which is recognised as a key modulator in the development of atherosclerosis and CHD. However, the increased levels of plasma IL-6 appear not to be determined by the magnitude of the postprandial triglyceridaemia.

Combining beta-adrenergic and peroxisome proliferator-activated receptor gamma stimulation improves lipoprotein composition in healthy moderately obese subjects

Current pharmacological regimens for hypertriglyceridemia and low high-density lipoprotein (HDL) are limited to the peroxisome proliferator-activated receptor (PPAR) alpha activating fibrates, niacin, and statins. This pilot study examined the impact of simultaneous stimulation of cyclic adenosine monophosphate with a beta-adrenergic agonist and PPARgamma with pioglitazone (PIO) on lipoprotein composition in moderately obese, healthy subjects. Subjects were treated with PIO (45 mg) to stimulate PPARgamma or a combination of ephedrine (25 mg TID), a beta-agonist, with caffeine (200 mg TID), a phosphodiesterase inhibitor (ephedrine plus caffeine), or both for 16 weeks. Lipoproteins were separated by gradient ultracentrifugation into very low-density lipoprotein (VLDL), intermediate-density lipoprotein, low-density lipoprotein (LDL), and 3 HDL (L, M, and D) subfractions. Apolipoproteins were measured by high-performance liquid chromatography. PIO alone reduced the core triglyceride (TG) content relative to cholesterol ester (CE) in VLDL (-40%), IDL (-25%), and HDL-M (-38%). Ephedrine plus caffeine alone reduced LDL CE (-13%), phospholipids (-9%), and apolipoprotein (apo) B (-13%); increased HDL-M LpA-I (HDL containing apoA-I without apoA-II, 28%), CE/TG (23%), and CE/apoA-I (8%) while reducing apoA-II (-10%); and increased HDL-L LpA-I (29%). Combination therapy reduced total plasma TG (-28%), LDL cholesterol (LDL-C, -10%), apoB (-16%), apoB/apoA-I ratio (-21%) while increasing HDL cholesterol (HDL-C, 21%), total plasma apoA-I (12%), LpA-I (43%), and apoC-I (26%). It also reduced VLDL total mass (-34%) and apoC-III (-39%), LDL CE (-13%), apoB (-13%), and total mass (-11%). Combination therapy increased HDL-L CE/TG (32%), apoC-I (30%), apoA-I (56%), and LpA-I (70%), as well as HDL-M CE (35%), phospholipids (24%), total mass (19%), apoC-I (25%), apoA-I (18%), and LpA-I (56%). In conclusion, simultaneous beta-adrenergic and PPARgamma activation produced beneficial effects on VLDL, LDL, HDL-L, and HDL-M. Perhaps the most important impact of combination therapy was dramatic increases in LpA-I and apoC-I in HDL-L and HDL-M, which were much greater than the sum of the monotherapies. Because LpA-I appears to be the most efficient mediator of reverse-cholesterol transport and a major negative risk factor for cardiovascular disease, this combination therapy may provide very effective treatment of atherosclerosis.

Impact of glucagon response on postprandial hyperglycemia in men with impaired glucose tolerance and type 2 diabetes mellitus

Glucagon is the physiological antagonist of insulin. Postprandial (pp) hyperglycemia in impaired glucose tolerance (IGT) and in type 2 diabetes mellitus (T2DM) may also depend on irregularities in glucagon secretion. This study investigated the glucagon excursion after a lipid-glucose-protein tolerance test in subjects with different stages of glucose intolerance. We also analyzed the relationship between pp glucagon secretion and hyperglycemias. A total of 64 men (27 healthy subjects with normal glucose tolerance [NGT], 15 with IGT, and 22 with T2DM) were examined. Plasma glucose (PG), insulin, proinsulin, free fatty acids, and triglycerides were measured in the fasting state and at 30 minutes and 2, 3, 4, and 6 hours after the intake of the test meal, which contained 126 g carbohydrates, 92 g fat, and 17 g protein. Postprandial concentrations of metabolic parameters were calculated as area under the curve (AUC). Glucagon was measured in the fasting state and at 30 minutes and 2 and 4 hours pp. Early glucagon increment was defined as glucagon at 30 minutes minus fasting glucagon. The insulin response was quantified as insulin increment divided by PG increment in the corresponding time. Insulin resistance was calculated using lomeostasis model assessment (HOMA). Fasting glucagon was significantly increased in IGT vs NGT (P<.05), and early glucagon increment was significantly higher in T2DM vs NGT and IGT (P<.05). The 2-hour glucagon concentration after the load (AUC) was increased in IGT and T2DM vs NGT (P<.05). Early glucagon increment and the 2-hour AUC of glucagon were strongly correlated to pp glycemia (r=0.494 and P=.001, and r=0.439 and P=.003, respectively). An inverse correlation was observed between early glucagon increment and insulin response at 30 minutes and 2 hours after the meal load (r=-0.287 and P=.026, and r=-0.435 and P=.001, respectively). The 2-hour AUC of glucagon was significantly associated with insulin resistance (r=0.354, P=.020). Multivariate analysis revealed 2-hour insulin response and early glucagon increment as significant independent determinants of the AUC of PG in IGT (R=0.787). In T2DM, 2-hour insulin response, insulin resistance, and early glucagon increment were significant determinants of the AUC of PG (R=0.867). Our study suggests an important role for the irregularities in glucagon response in the pp glucose excursion after a standardized oral mixed meal in IGT and in T2DM. According to our data, a bihormonal imbalance starts before diabetes is diagnosed. Prospective studies are needed to evaluate the impact of glucagon on the progression of glucose intolerance and the possible effects of medicinal suppression of glucagon increment to prevent the progression of glucose tolerance.

Effects of hydrochlorothiazide and propranolol treatment on chylomicron metabolism in hypertensive subjects

Modifications in chylomicron metabolism caused by antihypertensive drugs were investigated in hypertensive subjects because previous studies had indicated that diuretics and beta-blockers modify the plasma lipid concentrations through mechanisms that were not fully understood. A triglyceride-rich emulsion resembling lymph chylomicrons, labeled with (3H) triolein and (14C) cholesteryl oleate, was infused intravenously into mildly hypertensive patients after 8 weeks on placebo and subsequently on hydrochlorothiazide (n = 10) or propranolol (n = 8). The residence time of both radioactivities in plasma was utilized for the simultaneous calculation of the particle remnant removal rate and of the lipoprotein lipase activity expressed as a delipidation index = 1 – [(3H) triolein residence time/(14C) cholesteryl oleate residence time]. Treatment with hydrochlorothiazide diminished the delipidation rate value whereas propranolol mildly increased the removal rate of the remnant particle. These alterations of the chylomicron kinetics were not accompanied by changes in plasma triglycerides, glucose, and insulin concentration as measured in the fasting state. The impairment of the lipoprotein lipase activity by thiazides and the faster removal rate of the whole particle by propranolol could explain the reason why in previous clinical studies the simultaneous use of these drugs does not aggravate the hyperlipidemia known to be induced by thiazides alone. Key words: hydrochlorothiazide, propranolol, hypertension, plasma lipoproteins, chylomicron metabolism.

Differential postprandial lipoprotein responses in type 2 diabetic men with and without clinical evidence of a former myocardial infarction

Postprandial lipemia plays an important role in the development of coronary heart disease through an elevation of triglyceride-rich lipoproteins. In type 2 diabetic male subjects, our aim was to compare postprandial lipemia in a high-risk population with former myocardial infarction (MI) with that of a lower risk population free of clinically detectable heart disease. 32 male type 2 diabetic subjects were included in the study. We matched 17 cases with a verified history of MI with 15 controls according to age, BMI, HbA1c, diabetes duration, smoking, and treatment of diabetes. Ongoing metformin, insulin, or lipid lowering pharmacological treatment were exclusion criteria. After a maximal exercise tolerance test and echocardiography, the subjects underwent a hyperinsulinemic, euglycemic clamp and a vitamin A fat loading test. Plasma triglyceride levels in the case group were significantly higher after 360 minutes (4.6 +/- 3.1 vs. 2.8 +/- 1.8 mmol/l, p = 0.04) and 480 minutes (3.6 +/- 2.2 vs. 2.4 +/- 2.4 mmol/l, p = 0.03), as was the incremental Area Under the Curve (iAUC) for the whole period (560 +/- 452 vs. 297 +/- 214 mmol x 480 min./l; p = 0.048). In addition, the retinyl palmitate responses in the chylomicron-fraction from the case group were significantly higher (iAUC 311,502 +/- 194,933 vs. 187,004 +/- 102,928 ng x 480 min./ml; p = 0.035). Type 2 diabetic males with prior MI had higher postprandial triglyceride-rich lipoprotein responses than those without MI, indicating that high responses may be a marker for a high-risk population.

Abnormal glucose tolerance--a common risk factor in patients with acute myocardial infarction in comparison with population-based controls

BACKGROUND

A high prevalence of newly detected diabetes and impaired glucose tolerance (abnormal glucose tolerance) was recently reported in patients with acute myocardial infarction. It is important to verify whether this finding is specific for the patients or attributable to the population, from which they were recruited.

OBJECTIVE

To verify whether abnormal glucose tolerance is more prevalent in patients than in controls chosen from the same population and to compare metabolic characteristics between the two groups.

DESIGN AND SUBJECTS

The metabolic state was assessed in patients (n = 181) admitted with acute myocardial infarction and no history of diabetes before discharge and after 3 months. Sex- and age-matched controls (n = 185) without previously known diabetes or cardiovascular disease except hypertension were recruited from the general population.

MAIN OUTCOME MEASURES

Oral glucose tolerance test, glucosylated haemoglobin A1c (HbA1c), insulin, proinsulin, lipid profile, fibrinolytic function and inflammatory markers.

RESULTS

Abnormal glucose tolerance was more common (number/all classified) in patients at discharge 113/168 (67%) and after 3 months 95/145 (66%) than in controls 65/185 (35%) (P < 0.001). Dyslipidaemia (70% vs. 29%; P < 0.001) and previously treated hypertension (32% vs. 18%; P = 0.028) were more frequent amongst patients whilst obesity (18% vs. 24%) did not differ significantly. Blood glucose, HbA1c, proinsulin, proinsulin/insulin ratio, triglycerides, insulin resistance (by HOMA) and fibrinogen were consistently higher in patients than controls (P < 0.01).

CONCLUSIONS

Abnormal glucose tolerance was almost twice as common amongst patients with acute myocardial infarction as in matched controls. Impaired glycaemic control accompanied by insulin resistance, dyslipidaemia, hypertension, together with increased plasma fibrinogen and proinsulin levels were main features characterizing patients.

Clearance of a 3H-labeled chylomicron-like emulsion following the acute phase of myocardial infarction

BACKGROUND

Plasma lipids may be altered during acute myocardial infarction and may not reflect patient baseline lipid profile. The metabolism of chylomicrons, the lipoproteins that carry the dietary lipids in the bloodstream has not yet been studied in acute myocardial infarction patients.

METHODS

In this study, a lipidic emulsion that mimics the intravascular behavior of chylomicrons labeled with cholesteryl oleate ((3)H-CO) was injected intravenously in 17 normolipidemic patients on the seventh and on the 45th day post-non complicated acute myocardial infarction after a 12-h fast. The plasma decay curve of the emulsion label was determined from blood samples collected during 60 min. Data were also compared with a group of 10 patients with chronic coronary artery disease.

RESULTS

In the acute myocardial infarction group, the plasma fractional catabolic rates of the emulsion (3)H-CO, expressed as median and confidence intervals, did not change from the seventh to the 45th day after the acute event [0.0773 (0.061, 0.1025) min(-1) vs. 0.0672 (0.00507, 0.1009) min(-1) P=0.61] and was similar to that determined in chronic coronary artery disease patients. High-density lipoprotein cholesterol and apolipoprotein AI were lower on the seventh day when compared to the 45th day post acute myocardial infarction (P=0.01 and P=0.004, respectively). No changes were found in LDL and total cholesterol as well as in plasma triglycerides in myocardial infarction group.

CONCLUSIONS

No changes were found in chylomicron metabolism is in the acute phase of myocardial infarction.

Postprandial regulation of blood lipids and adipose tissue lipoprotein lipase in type 2 diabetes patients and healthy control subjects

BACKGROUND/AIM

In type 2 diabetes and other insulin-resistant conditions, postprandial hypertriglyceridaemia is an important metabolic perturbation. To further elucidate alterations in the clearance of triglyceride-rich lipoproteins in type 2 diabetes we focused on the nutritional regulation of adipose tissue lipoprotein lipase (LPL).

SUBJECTS AND METHODS

Eight subjects with type 2 diabetes and eight age-, sex- and body mass index (BMI)-matched control subjects underwent subcutaneous abdominal adipose tissue biopsies in the fasting state and 3.5 h following a standardized lipid-enriched meal. LPL activity and mass were measured in adipose tissue and also in plasma after an intravenous injection of heparin.

RESULTS

Postprandial, but not fasting, triglycerides were significantly higher in the diabetic subjects than in the control subjects (3.0+/-0.4 vs 2.0+/-0.2 mmol/l, P=0.028). Adipose tissue LPL activity was increased following the meal test by approximately 35-55% (P=0.021 and 0.004, respectively). There was no significant difference between the groups in this respect. The specific enzyme activity of LPL was not altered in the postprandial state. Fasting and postprandial adipose tissue LPL activity as well as post-heparin plasma LPL activity tended to be lower among the diabetes patients (NS). There was a significant and independent inverse association between insulin resistance (homeostasis model assessment insulin resistance (HOMA-IR) index) vs post-heparin plasma LPL activity and postprandial triglyceride levels, respectively. Adipose tissue LPL activity was related to insulin action in vitro on adipocyte glucose transport, but not to HOMA-IR.

CONCLUSION

Following food intake adipose tissue LPL activity is enhanced to a similar degree in patients with type 2 diabetes and in healthy control subjects matched for BMI, age and gender. If LPL dysregulation is involved in the postprandial hypertriglyceridaemia found in type 2 diabetes, it should occur in tissues other than subcutaneous fat.

Effects of atorvastatin on postprandial plasma lipoproteins in postinfarction patients with combined hyperlipidaemia

Enhanced and prolonged postprandial lipaemia is implicated in coronary and carotid artery disease. This study assessed the effects of atorvastatin, a 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, on postprandial plasma concentrations of triglyceride-rich lipoproteins (TRLs). Sixteen middle-aged men with combined hyperlipidaemia (baseline low density lipoprotein (LDL) cholesterol and plasma triglyceride concentrations (median (interquartile range) of 4.54 (4.17-5.26)) and 2.66 (2.04-3.20) mmol/l, respectively) and previous myocardial infarction were randomised to atorvastatin 40 mg or placebo once daily for 8 weeks in a double-blind, cross-over design. The apolipoprotein (apo) B-48 and B-100 contents were determined in subfractions of TRLs as a measure of chylomicron remnant and very low density lipoprotein (VLDL) particle concentrations (expressed as mg apo B-48 or apo B-100 per litre of plasma), in the fasting state and after intake of a mixed meal. Atorvastatin treatment reduced significantly the fasting plasma concentrations of VLDL cholesterol, LDL cholesterol and VLDL triglycerides (median% change) by 29, 44 and 27%, respectively, and increased high density lipoprotein (HDL) cholesterol by 19%, compared with baseline. The postprandial plasma concentrations of large (Svedberg flotation rate (Sf) 60-400) and small (Sf 20-60) VLDLs and chylomicron remnants were almost halved compared with baseline (mean 0-6 h plasma concentrations were reduced by 48% for Sf 60-400 apo B-100, by 46% for Sf 60-400 apo B-48, by 46% for Sf 20-60 apo B-100 and by 27% for Sf 20-60 apo B-48), and the postprandial triglyceridaemia was reduced by 23% during active treatment. In conclusion, atorvastatin 40 mg once daily causes profound reductions of postprandial plasma concentrations of all TRLs in combined hyperlipidaemic patients with premature coronary artery disease.

Mechanism of differential effects of antihypertensive agents on serum lipids

Essential hypertension is frequently associated with the metabolic abnormalities of insulin resistance and dyslipidemia. This prevalent clustering of multiple cardiovascular risk factors may help explain the less-than-expected improvement in coronary heart disease mortality provided by simple blood pressure reduction alone. Many antihypertensive medications effectively reduce blood pressure while providing no benefit or even causing a detrimental effect on the associated metabolic abnormalities. beta-Blockers and diuretics tend to negatively affect both glucose tolerance and plasma lipids. Calcium channel blockers, angiotensin converting enzyme inhibitors, and angiotensin II receptor blockers are most often found to be metabolically neutral. alpha-Blockers provide the most favorable metabolic effects of antihypertensive agents by improving both insulin sensitivity and dyslipidemia. The multiple physiologic mechanisms by which blood pressure medications alter plasma lipids are discussed in detail. The effects of antihypertensive medications on postprandial lipid metabolism and the associated postprandial lipemia-induced endothelial dysfunction deserve special attention.

Plasma lipoproteins enhance tissue factor-independent factor VII activation

The effect of plasma lipoprotein fractions (large very-low-density lipoprotein, small very-low-density lipoprotein, intermediate-density lipoprotein, and low-density lipoprotein) on initiation of blood coagulation by supporting factor VII activation or by stimulating monocytes to express tissue factor was investigated in vitro. Endotoxin-free preparations of lipoprotein fractions did not induce functional tissue factor in monocytes, whereas all lipoprotein fractions enhanced tissue factor-independent activation of factor VII by factor Xa and by factors Xa/Va. In contrast, no or only slight enhancement of factor IXa-, factor IXa/VIIIa-, factor XIa-, or thrombin-mediated factor VII activation was observed. The effect of small very-low-density lipoprotein was less than that of large very-low-density lipoprotein, and intermediate-density and low-density lipoproteins caused an even lower but still significant increase of factor Xa- and factor Xa/Va-mediated factor VII activation. When the data were normalized for apolipoprotein B-100 content, differences remained between lipoprotein fractions. In contrast, when phospholipid content was used for normalization, differences between lipoprotein fractions in factor Xa- and factor Xa/Va-mediated factor VII activation disappeared, indicating that phospholipids were involved in factor VII activation. This was supported by enhancement of factor Xa-mediated factor VII activation by synthetic phospholipid vesicles containing negatively charged phospholipids.

Postprandial metabolism of apolipoprotein B-48- and B-100-containing particles in type 2 diabetes mellitus: relations to angiographically verified severity of coronary artery disease

The aim of the present cross-sectional angiographic study was to examine if there is a relationship between the severity of CAD and postprandial lipemia in patients with type 2 diabetes mellitus. Special emphasis was directed to determining the contribution of apolipoprotein B-48 (apoB-48)-containing and B-100 (apoB-100)-containing triglyceride-rich particles to the magnitude of postprandial lipemia and degree of CAD. The role of apolipoprotein E (apoE) phenotype as a modulator of postprandial lipemia was also evaluated. The severity of CAD was determined by a quantitative coronary angiography and the subjects were classified into two groups based on the presence (severe CAD) or absence (mild CAD) of at least 50% stenosis in a major coronary vessel. The study population consisted of 43 subjects (31 men and 12 women) with fair glycemic control and comparable fasting lipids and body mass index. Postprandial responses of TG, apoB-48 and apoB-100 in lipoprotein subfractions (chylomicrons, VLDL1, VLDL2 and IDL) were determined after a fat load. Type 2 diabetic patients exhibited the classical dyslipidemia of the insulin resistance syndrome and delayed clearance of both hepatic and intestinal particles. Fasting or postprandial lipid or lipoprotein measurements, including apoB-48 and apoB-100 concentrations, did not differ between the groups. The presence or absence of apoE-4 allele did not significantly influence postprandial lipemia. The severity of the most significant coronary stenosis in angiography correlated with plasma and with chylomicron area under curve (AUC) for TG (n=27) and chylomicron AUC for apoB-48 (n=20). The strongest correlate of maximal stenosis was area under incremental curve (AUIC) for apoB-100 in IDL fraction (r=0.548, P=0. 012, n=20). In conclusion, postprandial apoB-48 and apoB-100 metabolism in triglyceride rich lipoproteins is distorted in type 2 diabetic patients, even in those with only mild CAD. The data suggest that postprandial change in small remnant particle numbers may contribute to the severity of CAD in type 2 diabetes.

Differences in postprandial concentrations of very-low-density lipoprotein and chylomicron remnants between normotriglyceridemic and hypertriglyceridemic men with and without coronary heart disease

It has been suggested that the postprandial elevation of plasma triglycerides is more closely linked to coronary heart disease (CHD) than the fasting triglyceride level. However, the postprandial situation is complex, as hepatogenous triglyceride-rich lipoprotein (TRL) particles (apolipoprotein [apo]B-100 and very-low-density lipoprotein [VLDL]) are mixed in the blood with apoB-48-containing lipoproteins secreted from the intestine. To analyze the relative proportion of liver-derived and intestinal apoB-containing TRL in subjects with and without CHD, we performed standardized oral fat-loading tests in young survivors of myocardial infarction, a large proportion of whom are hypertriglyceridemic (HTG), as well as sex- and population-matched healthy control subjects. A special effort was made to recruit healthy HTG subjects as controls for the HTG patients. Fasting plasma triglycerides (3.74+/-1.35 v3.01+/-0.83, NS), low-density lipoprotein (LDL) cholesterol, and VLDL lipids, and apoB-100 and apoB-48 content at Svedberg flotation rate (Sf) 60-400, Sf 20-60, and Sf 12-20 did not differ between HTG patients (n = 10) and HTG controls (n = 14). Normotriglyceridemic (NTG) patients (n = 15) had higher fasting plasma triglycerides (1.44+/-0.39 v 0.98+/-0.33 mmol/L, P < .05) and LDL cholesterol (4.07+/-0.71 v 3.43+/-0.64, P < .05) than NTG controls (n = 34). The triglyceride elevation was accounted for by a higher level of small VLDL (apoB-100 in the Sf 20-60 fraction, 52+/-17 v29+/-20 mg/L, P < .05). HTG patients responded with clearly elevated plasma triglycerides in the late postprandial phase, ie, 7, 8, and 9 hours after fat intake. Essentially, this was explained by a retention of large VLDL particles, since HTG patients exhibited no major differences in apoB-48 concentrations in the Sf > 400, Sf 60-400, and Sf 20-60 fractions but showed marked differences in the level of apoB-100 at Sf 60-400 (large VLDL) 9 hours after fat intake when compared with HTG controls (101+/-13 v 57+/-5 mg/L, P < .01). NTG patients were characterized by a more rapid increase of large VLDL in the early postprandial state, ie, 3 hours after fat intake, with a mean increase from baseline to 3 hours of 24.1+/-6.7 mg/L for NTG patients and 11.8+/-2.0 mg/L for controls (P < .05). ApoB-48 levels were also slightly higher, but all TRL parameters returned to baseline within 9 hours after fat intake. In conclusion, elevated triglyceride levels in the postprandial state in CHD patients are explained to a large extent by the accumulation of endogenous TRL. This suggests that the postprandial dyslipidemia encountered in CHD is more dependent on a failure of regulation of endogenous TRL versus the exogenous TRL species.

Treatment effects on serum lipoprotein lipids, apolipoproteins and low density lipoprotein particle size and relationships of lipoprotein variables to progression of coronary artery disease in the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT)

OBJECTIVES

To investigate the mechanisms by which bezafibrate retarded the progression of coronary lesions in the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT), we examined the relationships of on-trial lipoproteins and lipoprotein subfractions to the angiographic outcome measurements.

BACKGROUND

BECAIT, the first double-blind, placebo-controlled, randomized serial angiographic trial of a fibrate compound, showed that progression of focal coronary atherosclerosis in young survivors of myocardial infarction could be retarded by bezafibrate treatment.

METHODS

A total of 92 dyslipoproteinemic men who had survived a first myocardial infarction before the age of 45 years were randomly assigned to treatment for 5 years with bezafibrate (200 mg three times daily) or placebo; 81 patients underwent baseline and at least one post-treatment coronary angiography.

RESULTS

In addition to the decrease in very low density lipoprotein (VLDL) cholesterol (-53%) and triglyceride (-46%) and plasma apolipoprotein (apo) B (-9%) levels, bezafibrate treatment resulted in a significant increase in high density lipoprotein-3 (HDL3) cholesterol (+9%) level and a shift in the low density lipoprotein (LDL) subclass distribution toward larger particle species (peak particle diameter +032 nm). The on-trial HDL3 cholesterol and plasma apo B concentrations were found to be independent predictors of the changes in mean minimum lumen diameter (r=-0.23, p < 0.05), and percent (%) stenosis (r = 0.30, p < 0.01), respectively. Decreases in small dense LDL and/or VLDL lipid concentrations were unrelated to disease progression.

CONCLUSIONS

Our results suggest that the effect of bezafibrate on progression of focal coronary atherosclerosis could be at least partly attributed to a rise in HDL3 cholesterol and a decrease in the total number of apo B-containing lipoproteins.