Is there value in liver function test and creatine phosphokinase monitoring with statin use?

Statins have transformed the care of patients with vascular disease. Patients in almost every category that has been studied have benefited substantially. On the other hand, although the incidence of side effects is remarkably low, statins, like any other therapy, are not entirely free of serious risks. From the outset, based on the mechanism of action of statins, hepatotoxicity has been a concern. Moreover, although the mechanisms remain obscure, significant skeletal muscle injury, which can lead to renal failure and death, unquestionably does occur. To mitigate these risks, screening and monitoring programs for hepatic and skeletal muscle injury were put in place when statins were introduced into clinical practice. This article reviews the benefits and the costs of these efforts. Although the benefits have not been shown, the costs are real and substantial. These include the harm caused by inappropriate withdrawal of therapy, which has been shown to be life-saving, as well as the considerable financial expenditure. The conclusion that follows, based on the evidence in hand, is that although these programs were appropriate at the time statins were introduced, they are not appropriate now.

Comparison of the Associations of Apolipoprotein B and Non-High-Density Lipoprotein Cholesterol With Other Cardiovascular Risk Factors in Patients With the Metabolic Syndrome in the Insulin Resistance Atherosclerosis Study

Background— The metabolic syndrome (MetS) as defined by the National Cholesterol Education Panel definition has been proposed as an indicator of cardiovascular disease risk. Both apolipoprotein (apo)B and non-HDL cholesterol (NHDLC) have been proposed as an additional indicator to identify patients at higher risk in MetS patients.

Methods and Results— We studied 1522 individuals in the Insulin Resistance Atherosclerosis Study (IRAS) who were 40 to 69 years of age and from 3 ethnic groups. Their anthropometric measures, lipids, apoB, C-reactive protein, fibrinogen, plasminogen activator inhibitor-1, fasting and post-glucose load glucose, and insulin concentrations were measured, and insulin sensitivity was determined by intravenous glucose tolerance test. Differences in risk parameters in individuals with hyper-apoB/normo-NHDLC, and normo-apoB/hyper-NHDLC were compared in all IRAS subjects and again in those with MetS. In both cases, despite anticipated lower LDL cholesterol, the hyper-apoB/normo-NHDLC group had elevated risk indicated by greater waist circumference (both P <0.05) and fasting insulin ( P <0.01) and lower insulin sensitivity ( P <0.001). They also had higher C-reactive protein ( P <0.05). Moreover, the Spearman correlation of apoB was significantly stronger ( P <0.05) in the direction of greater associated risk than that of NHDLC with body mass index, waist circumference, systolic blood pressure, 2-hour glucose, fasting glucose, fasting insulin, 2-hour insulin, insulin sensitivity, C-reactive protein, fibrinogen, and plasminogen activator inhibitor-1.

Conclusions— In conclusion, apoB is more closely associated with central adiposity, insulin resistance, thrombosis, and inflammation than NHDLC. Our data suggest that apoB is a better candidate risk parameter than NHDLC for identifying a subgroup of individuals with or without MetS with elevated cardiovascular risk.

Applying apoB to the diagnosis and therapy of the atherogenic dyslipoproteinemias: a clinical diagnostic algorithm

PURPOSE OF REVIEW

The first objective is to present the most recent evidence relating to the efficacy of apolipoprotein B as a diagnostic index of the risk of vascular disease and a therapeutic target for statin therapy. The second is to present a diagnostic algorithm for the apolipoprotein B100 dyslipidemias based on triglyceride and apoB.

RECENT FINDINGS

The results from several recent prospective epidemiological studies demonstrate apoB to be superior to any of the cholesterol indices to estimate the risk of vascular disease. Similarly, the results of several of the major statin clinical trials demonstrate that apoB is a more adequate index of the adequacy of statin therapy than any of the cholesterol indices. Recent studies of lipoprotein subclass distribution in subjects with familial combined hyperlipidemia are reviewed. They demonstrate the limitations of the original lipid-based criteria and point to the necessity of using apoB as a fundamental diagnostic criterion for the disorder. A diagnostic algorithm for an apoB100 atherogenic dyslipoproteinemias is presented and the limitations of the lipid-based system described.

SUMMARY

The evidence supporting the clinical use of apoB is solid, its measurement is standardized, and automated, inexpensive laboratory testing could easily be widely available. However, clinical benefit will only follow clinical application.

Addition of glucose to an oral fat load reduces postprandial free fatty acids and prevents the postprandial increase in complement component 3

BACKGROUND

Elevated fasting plasma concentrations of complement component 3 (C3) are associated with elevated fasting and postprandial triacylglycerol concentrations, insulin resistance, obesity, and coronary artery disease. C3 is the central component of the complement system and the precursor of acylation-stimulating protein (ASP). Insulin and ASP are principal determinants of free fatty acid (FFA) trapping by adipose tissue.

OBJECTIVE

Because controversy exists concerning postprandial changes in C3 and because meal composition may influence complement activation, we studied postprandial lipemia in relation to changes in plasma C3.

DESIGN

After an overnight fast, 6 healthy men ( +/- SD age: 23 +/- 2 y) underwent 4 oral liquid challenges: fat (50 g/m(2) body surface), glucose (37.5 g/m(2)), fat and glucose (mixed test), and water (as a control test) in a random, crossover design.

RESULTS

Plasma ASP concentrations did not change postprandially in any test. Changes in C3 concentration were observed only after the fat challenge: elevated concentrations occurred between 1 and 3 h, and a maximum increase of 11% occurred at 2 h (P = 0.05). Postprandial triacylglycerolemia did not differ significantly between the fat and mixed tests. The FFA response after the fat challenge was the highest of all the tests (P < 0.05 for all comparisons) and was accompanied by an increase in ketone bodies (maximum at 6 h); this increase did not occur after the mixed test, which suggests less hepatic FFA delivery.

CONCLUSIONS

When glucose is added to an oral fat load, the postprandial FFA response is reduced, and the fat-specific increase in C3 is prevented. After ingestion of fat without glucose, the lack of insulin response may lead to C3-mediated peripheral FFA trapping, which probably serves as a backup system in case of insufficient or inefficient insulin-dependent FFA trapping.

The apoB/apoA-I ratio is better than the cholesterol ratios to estimate the balance between plasma proatherogenic and antiatherogenic lipoproteins and to predict coronary risk

Background: The apolipoprotein B (apoB)/apoA-I ratio represents the balance of proatherogenic and antiatherogenic lipoproteins. The purpose of this study was to determine whether the apoB/apoA-I ratio was superior to any of the cholesterol ratios – total cholesterol/high-density lipoprotein cholesterol (TC/HDL-C), low-density lipoprotein cholesterol (LDL-C)/HDL-C and non-HDL-C/HDL-C – in predicting the risk of coronary disease. Moreover, we examined whether any lipids, lipoproteins or cholesterol ratios add significant predictive information beyond that provided by the apoB/apoA-I ratio.

Methods: Plasma lipids, lipoproteins, apoB, and apoA-I were measured in 69,030 men and 57,168 women above 40years of age. After a mean follow-up of 98months, 1183 men and 560 women had died from a myocardial infarction in this prospective apolipoprotein-related mortality risk (AMORIS) study.

Results: High apoB and a high apoB/apoA-I ratio were strongly related to increased coronary risk, while high apoA-I was inversely related to risk. The apoB/apoA-I ratio was superior to any of the cholesterol ratios in predicting risk. This advantage was most pronounced in subjects with LDL-C levels <3.6mmol/l. Addition of lipids, lipoproteins or any cholesterol ratio to apoB/apoA-I in risk models did not further improve the strong predictive value of apoB/apoA-I.

Conclusions: These results indicate that the apoB/apoA-I ratio is at present the best single lipoprotein-related variable to quantitate coronary risk. Given the additional advantages apolipoproteins possess – fasting samples are not required, apoB/apoA-I is a better index of the adequacy of statin therapy than LDL-C, and the measurement of apoB and apoA-I are standardized, whereas LDL-C and HDL-C are not – there would appear to be considerable advantage to integrating apolipoproteins into clinical practice.

ASP enhances in situ lipoprotein lipase activity by increasing fatty acid trapping in adipocytes

Acylation-stimulating protein (ASP) increases triglyceride (TG) storage (fatty acid trapping) in adipose tissue and plays an important role in postprandial TG clearance. We examined the capacity of ASP and insulin to stimulate the activity of lipoprotein lipase (LPL) and the trapping of LPL-derived nonesterified fatty acid (NEFA) in 3T3-L1 adipocytes. Although insulin increased total LPL activity (secreted and cell-associated; P < 0.001) in 3T3-L1 adipocytes, ASP moderately stimulated secreted LPL activity (P = 0.04; 5% of total LPL activity). Neither hormone increased LPL translocation from adipocytes to endothelial cells in a coculture system. However, ASP and insulin increased the V(max) of in situ LPL activity ([(3)H]TG synthetic lipoprotein hydrolysis and [(3)H]NEFA incorporation into adipocytes) by 60% and 41%, respectively (P </= 0.01) without affecting K(m). Tetrahydrolipstatin (LPL inhibitor) diminished baseline, ASP-, and insulin-stimulated in situ LPL activity, resulting in [(3)H]TG accumulation (P < 0.0001). Unbound oleate inhibited in situ LPL activity (P < 0.0001) but did not eliminate the ASP stimulatory effect. Therefore, 1) the clearance of TG-rich lipoproteins is enhanced by ASP through increasing TG storage and relieving NEFA inhibition of LPL; and 2) the effectiveness of adipose tissue trapping of LPL-derived NEFAs determines overall LPL activity, which in turn determines the efficiency of postprandial TG clearance.

Comparison of the Associations of Apolipoprotein B and Low-Density Lipoprotein Cholesterol With Other Cardiovascular Risk Factors in the Insulin Resistance Atherosclerosis Study (IRAS)

Background— Risk factors for vascular disease include obesity, dyslipidemia, hypertension, dysglycemia, insulin resistance, inflammation, thrombosis, and subclinical atherosclerosis. This study compares the associations of apolipoprotein B (apoB) and LDL cholesterol (LDLC) with a wide array of measures of these risk factors.

Methods and Results— In 1522 individuals in the Insulin Resistance Atherosclerosis Study, anthropometric measures and measures of lipids, apoB, C-reactive protein, fibrinogen, plasminogen activator inhibitor-1 (PAI-1), fasting and postglucose load glucose and insulin concentrations, and carotid artery intima-media thickness (IMT) were taken and insulin sensitivity was determined by frequently sampled intravenous glucose tolerance test. There were significant differences in measures of abdominal obesity, dyslipidemia, hyperinsulinemia, and thrombosis between subjects with elevated apoB but normal LDLC versus those with elevated LDLC but normal apoB. In each statistically significant comparison, the elevated-apoB group had higher associated risk than the elevated-LDLC group. Moreover, apoB is highly significantly ( P <0.0001) correlated with each measure in the direction of higher risk, whereas LDLC was significantly correlated ( P <0.05) only with blood pressure, triglyceride, fibrinogen, and C-reactive protein. After further adjustment for LDLC, apoB correlations remained significant, whereas several LDLC correlations adjusted for apoB became significant in the direction of lower risk.

Conclusions— Elevated apoB is more strongly associated than LDLC with other risk factors, including measures in the National Cholesterol Education Program guidelines for lipid treatment and other more recently established risk factors. This may provide new insight into why apoB is a better predictor of vascular risk than LDLC.

Concordance/discordance between plasma apolipoprotein B levels and the cholesterol indexes of atherosclerotic risk

The objective of the present study was to examine concordance/discordance among 4 atherogenic indexes of cardiovascular risk: plasma total cholesterol, low-density lipoprotein (LDL) cholesterol, non-high-density lipoprotein (non-HDL) cholesterol, and apolipoprotein B-100 (apoB). Analyses were conducted in a cohort of 2,103 men without coronary artery disease (CAD) at the onset of the Quebec Cardiovascular Study. Although there were strong and highly significant correlations among the 4 risk indexes (0.78 < r < 0.97), only 50% of all subjects had concordant apoB and LDL cholesterol levels (i.e., values that fell into the same quintile of the population distribution). Moreover, concordance/discordance was not the same throughout the range of both variables; it was greater at the extremes of their respective distributions (65%), but significantly less in the midpoints (<40%). ApoB appeared to be more concordant with non-HDL cholesterol than with LDL cholesterol, although >1/3 of all subjects had discordant levels. Kappa analysis confirmed that there was only fair agreement between apoB and total or LDL cholesterol (0.38 and 0.36, respectively) and only moderate agreement between non-HDL cholesterol and apoB (0.47). Finally, a significant proportion of subjects (528 of 2,103) who had disproportionately higher apoB levels than would have been predicted based on their LDL cholesterol concentrations was more obese and manifested several features of the metabolic syndrome. They also had a significantly increased cardiovascular risk. In summary, plasma apoB and the various cholesterol indexes are complementary rather than competitive indexes of atherosclerotic risk and provide further evidence as to why measurement of apoB should be part of a standard lipoprotein assessment of CAD risk.

Plasma acylation-stimulating protein, adiponectin, leptin, and ghrelin before and after weight loss induced by gastric bypass surgery in morbidly obese subjects

We examined fasting plasma insulin, acylation-stimulating protein (ASP), leptin, adiponectin, ghrelin, and metabolic/cardiovascular risk profile before and 15 +/- 6 months after isolated Roux-en-Y gastric bypass surgery in 50 morbidly obese subjects. Average preoperative plasma lipids were mostly normal, whereas ASP, insulin, and leptin were elevated, and adiponectin and ghrelin were decreased. Postoperatively, body weight decreased significantly (-36.4 +/- 9.6%) and was best predicted by preoperative adiponectin concentration in weight-stable subjects (r = -0.59; P = 0.02). Plasma lipids and insulin resistance improved, leptin and ASP decreased (-76.3 +/- 14.6% and -35.9 +/- 52.2%; P < 0.001), and adiponectin increased (50.1 +/- 47.0%; P < 0.001). The decrease in apolipoprotein B was best predicted by the decrease in ASP (r = 0.55; P = 0.009), whereas the improved postoperative insulin sensitivity was best predicted by the increase in adiponectin (r = 0.70; P = 0.01). Despite bypassing 95% of the stomach and isolating the fundus from contact with ingested nutrients, circulating ghrelin did not decrease after surgery. In fact, plasma ghrelin increased postoperatively in the subset of subjects undergoing active weight loss (+60.5 +/- 23.2%; P < 0.001); ghrelin, however, remained unchanged in weight-stable subjects. In summary, 1) preoperative adiponectin concentrations may be predictive of the extent of weight loss; 2) changes in ASP and adiponectin are predictive of decreased apolipoprotein B and improved insulin action, respectively; and 3) plasma ghrelin increases after gastric bypass surgery in patients experiencing active weight loss.

The chemoattractant receptor-like protein C5L2 binds the C3a des-Arg77/acylation-stimulating protein

The orphan receptor C5L2 has recently been described as a high affinity binding protein for complement fragments C5a and C3a that, unlike the previously described C5a receptor (CD88), couples only weakly to G(i)-like G proteins (Cain, S. A., and Monk, P. N. (2002) J. Biol. Chem. 277, 7165-7169). Here we demonstrate that C5L2 binds the metabolites of C4a and C3a, C4a des-Arg(77), and C3a des-Arg(77) (also known as the acylation-stimulating protein or ASP) at a site distinct from the C5a binding site. The binding of these metabolites to C5L2 does not stimulate the degranulation of transfected rat basophilic leukemia cells either through endogenous rat G proteins or when co-transfected with human G(alpha 16). C3a des-Arg(77)/ASP and C3a can potently stimulate triglyceride synthesis in human skin fibroblasts and 3T3-L1 preadipocytes. Here we show that both cell types and human adipose tissue express C5L2 mRNA and that the human fibroblasts express C5L2 protein at the cell surface. This is the first demonstration of the expression of C5L2 in cells that bind and respond to C3a des-Arg(77)/ASP and C3a. Thus C5L2, a promiscuous complement fragment-binding protein with a high affinity site that binds C3a des-Arg(77)/ASP, may mediate the acylation-stimulating properties of this peptide.

Effects on apoB-100 secretion and bile acid synthesis by redirecting cholesterol efflux from HepG2 cells

This study determined the effects of apoA-I, HDL3, or hydroxy-beta-cyclodextrin on apoB-100 secretion and bile acid synthesis by HepG2 cells. The principal observations were that: 1) ApoB-100 secretion into the medium was significantly less after the addition of any of the three agents. 2) Triglyceride mass was not significantly changed from control in the medium but was significantly, although modestly, reduced in the cells. 3) Neither free cholesterol (FC) nor cholesteryl ester (CE) mass in the medium was changed; by contrast, CE mass was reduced within the cells although FC was not. 4) Although the total mass of cholesterol in the medium was unaffected, the proportion associated with apoB-100 was reduced, whereas the proportion associated with the non-apoB-100 fraction was increased. 5) There was also an unanticipated, but substantial, increase in bile acid synthesis induced by apoA-I, HDL3, or hydroxy-beta-cyclodextrin, which was time and concentration dependent, and which was associated with marked increases in cholesterol 7 alpha-hydroxylase activity. There were no significant changes in ACAT activity and only modest increases in HMG-CoA reductase activity. These findings support previous clinical observations that an elevated apoB-100 can accompany a low HDL cholesterol in normotriglyceridemic subjects. They also point to physiologically important, although still only partially understood, metabolic relationships amongst hepatic apoB-100 secretion, cholesterol efflux, and bile acid synthesis.

How, when, and why to use apolipoprotein B in clinical practice

The evidence is now clear that plasma apolipoprotein (apo) B is a better index of the risk of coronary artery disease (CAD) than total or low-density lipoprotein (LDL) cholesterol. Moreover, the evidence is also clear that clinical risk of apo B is determined not only by LDL particle number but also by whether small, dense LDL particles are present. The objective of this article, therefore, is to demonstrate how, when, and why apo B should be used in clinical practice. First, the evidence that apo B is superior to LDL cholesterol as an index of the risk of CAD and as a guide to the adequacy of statin therapy is briefly reviewed. Next, the biological bases for this superiority in identifying risk are outlined. Clinical scenarios are then outlined demonstrating the value of measuring apo B in hypertriglyceridemic, hypercholesterolemic, and normolipidemic subjects. The methodological soundness of the laboratory determinations of lipids and apo B is also an important issue. Concern has been raised regarding the measurement of apo B, but it is standardized, precise, and not expensive. Paradoxically, it is becoming ever more obvious that the methodological problems lie with calculated LDL cholesterol. To the known deficiencies must be added the fact that calculated LDL cholesterol systematically underestimates true LDL cholesterol at values close to target levels.Thus, from every perspective-pathophysiology, diagnosis, assessment of therapy, and methodologic soundness-there are powerful clinical arguments why apo B should be used in the routine diagnosis of dyslipidemias and assessment of the adequacy of statin therapy.

Acylation-stimulating protein (ASP) deficiency induces obesity resistance and increased energy expenditure in ob/ob mice

Acylation-stimulating protein (ASP) acts as a paracrine signal to increase triglyceride synthesis in adipocytes. ASP administration results in more rapid postprandial lipid clearance. In mice, C3 (the precursor to ASP) knockout results in ASP deficiency and leads to reduced body fat and leptin levels. The protective potential of ASP deficiency against obesity and involvement of the leptin pathway were examined in ob/ob C3(-/-) double knockout mice (2KO). Compared with age-matched ob/ob mice, 2KO mice had delayed postprandial triglyceride and fatty acid clearance; associated with decreased body weight (4-17 weeks age: male: -13.7%, female: -20.6%, p < 0.0001) and HOMA (homeostasis model assessment) index (-37.7%), suggesting increased insulin sensitivity. By contrast, food intake in 2KO mice was +9.1% higher over ob/ob mice (p < 0.001, 2KO 5.1 +/- 0.2 g/day, ob/ob 4.5 +/- 0.2 g/day, wild type 2.6 +/- 0.1 g/day). The hyperphagia/leanness was balanced by a 28.5% increase in energy expenditure (oxygen consumption: 2KO, 131 +/- 8.9 ml/h; ob/ob, 102 +/- 4.5 ml/h; p < 0.01; wild type, 144 +/- 8.9 ml/h). These results suggest that the ASP regulation of energy storage may influence energy expenditure and dynamic metabolic balance.

Hypertriglyceridemic hyperapoB in type 2 diabetes

OBJECTIVES

Much less attention has been paid to LDL in type 2 diabetes than to VLDL or HDL. In particular, there are few data on apoB levels in these patients. Moreover, most reports have focused on mean lipoprotein levels and consequently there is little information on the frequencies of the various dyslipidemic phenotypes.

RESEARCH DESIGN AND METHODS

Plasma and lipoprotein lipids, apoB and apoA1 were measured by standardized methods. LDL particle size was determined by PAGE. The total cohort was divided into phenotypes by two different methods. The first was based on triglycerides (> or = or <1.5 mmol/l) and LDL cholesterol (> or = or <4 mmol/l), whereas the second was based on triglycerides (> or = or <1.5 mmol/l) and apoB (> or = or <120 mg/dl).

RESULTS

For the overall cohort, plasma triglycerides were elevated (2.13 +/- 1.6 mmol/l), total and LDL cholesterol were normal (5.34 +/- 1.1 and 3.28 +/- 0.88 mmol/l, respectively), and peak LDL size was reduced (252.9 +/- 5.8 A). HDL cholesterol was between the 25th and 50th percentiles of the general population (1.12 +/- 0.36 mmol/l). The average level of apoB was 114 +/- 29 mg/dl, a value that is between the 50th and 75th percentiles of the general population and is higher than that for LDL cholesterol, which was between the 25th and the 50th percentiles of the population. The results of the phenotyping analysis were as follows. Using the conventional approach, only 23% has abnormal LDL, i.e., an elevated LDL cholesterol level. Using the new approach, almost 40% has an elevated apoB and therefore an elevated LDL particle number. Only 12.8% has combined hyperlipidemia based on the conventional approach, whereas almost one-third had the equivalent, hypertriglyceridemic hyperapoB-based on the new algorithm. The severity of the dyslipoproteinemia in this group was noteworthy. Although the average LDL cholesterol was 3.91 mmol/l, a value just below the 75th percentile of the general population, the average apoB was 145 mg/dl, a value that approximates the 95th percentile of the population.

CONCLUSIONS

The dyslipidemic profile of patients with type 2 diabetes is not uniform. A substantial group have normal lipids and normal LDL particle number and size whereas others have markedly abnormal profiles. Diagnosis based on triglycerides and apoB rather than triglycerides and LDL cholesterol revealed that more than one in five had hypertriglyceridemic hyperapoB, which is characterized by hypertriglyceridemia, marked elevation of LDL particle number, small dense LDL, and low HDL, a constellation of abnormalities that is associated with markedly accelerated atherogenesis and therefore justifies intensive medical therapy.

Hypertriglyceridemic hyperapob: the unappreciated atherogenic dyslipoproteinemia in type 2 diabetes mellitus

Abnormalities in insulin and glucose metabolism do not seem to entirely account for the high frequency of cardiovascular disease in patients with type 2 diabetes mellitus. An important additional factor may be hypertriglyceridemic hyperapoB, an atherogenic dyslipoproteinemia that is common in these patients. The major features of hypertriglyceridemic hyperapoB are hypertriglyceridemia; low levels of high-density lipoprotein cholesterol; and increased numbers of small, dense low-density lipoprotein (LDL) particles. This article reviews the pathophysiology of this disorder, focusing on the changes in lipoprotein particle number and composition rather than lipoprotein lipid levels. The in vitro and in vivo evidence that small, dense LDL are more atherogenic than normal larger, buoyant LDL is summarized, and the particularly high-risk state conferred by increased numbers of small, dense LDL is delineated. This review demonstrates how abnormalities in the plasma lipoproteins may relate to the effectiveness with which adipose tissue traps and retains fatty acid. The effects of increased fatty acid flux on the hepatic metabolism of lipids and apoB secretion are detailed, and the mechanisms by which fibrates and statins may improve these are described. An understanding of these principles should provide the physician with a more physiologic basis on which to choose appropriate therapy.