| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Original Article |
Divisions of Clinical Chemistry (K.W., M.M.H., I.F., H.W., W.M.) and Sports Medicine (M.W.B.), Department of Medicine, Albert Ludwigs-University, D-79106 Freiburg, Germany; and Medical Department (C.A.), Novartis Pharma GmbH, D-90429 Nürnberg, Germany
Address all correspondence and requests for reprints to: Karl Winkler, M.D., Department of Medicine, Hugstetter Strasse 55, D-79106 Freiburg, Germany. E-mail: kwinkler{at}ukl.uni-freiburg.de.
Abstract
The objective of this study was to determine the effect of slow-release (XL) fluvastatin on low density lipoprotein (LDL) subfractions in type 2 diabetes. A multicenter, double-blind, randomized, parallel-group comparison of fluvastatin XL 80 mg (n = 42) and placebo (n = 47), each given once-daily for 8 wk, in 89 patients with type 2 diabetes (HbA1c: 7.2 ± 1.0%, LDL cholesterol (LDL-C): 3.4 ± 0.7 mmol/liter, high density lipoprotein cholesterol: 1.1 ± 0.3 mmol/liter, and triglycerides (TG): 2.4 ± 1.4 mmol/liter). At baseline and on treatment, plasma lipoproteins were isolated and quantified. Eight weeks of fluvastatin treatment decreased total cholesterol (–23.0%, P < 0.001), LDL-C (–29%, P < 0.001) and TG (–18%, P < 0.001), compared with placebo. At baseline, there was a preponderance of dense LDL (dLDL) (apolipoprotein B in LDL-5 plus LDL-6 > 25 mg/dl) in 79% of patients, among whom fluvastatin decreased all LDL subfractions, reductions in dLDL being greatest (–28%, P = 0.001; cholesterol in dLDL –29%). In patients with low baseline dLDL (apolipoprotein B in LDL-5 plus LDL-6 
25 mg/dl), but a preponderance of buoyant LDL (LDL-1 through LDL-3), fluvastatin significantly decreased only these subfractions. Fluvastatin 80 mg XL, once daily, decreased total cholesterol and total LDL-C. In patients with atherogenic dLDL, absolute changes of dLDL were most pronounced, emphasizing the value of fluvastatin treatment in type 2 diabetes. The antiatherogenic potential of fluvastatin in type 2 diabetes may thus be greater than that expected from its effects on LDL-C and TG alone.
PATIENTS WITH TYPE 2 diabetes are at high risk of developing coronary artery disease (CAD) (1, 2), their risk being approximately that of nondiabetic patients with a history of myocardial infarction (3). Furthermore, lipid metabolism in type 2 diabetes is disturbed, with increased plasma concentrations of triglycerides (TG), low plasma levels of high density lipoprotein (HDL) cholesterol (HDL-C), but only slightly elevated plasma levels of low density lipoprotein (LDL) cholesterol (LDL-C) (4). However, patients with type 2 diabetes also tend to have a preponderance of atherogenic dense LDL (dLDL) (5, 6).
Case-control and prospective studies have shown that a preponderance of dLDL increases CAD risk up to 7-fold (7, 8, 9, 10, 11, 12, 13), although in many of the studies the association was not independent from traditional risk factors. In two studies, however, the LDL subfraction profile remained at least in part predictive of CAD after adjustment for triglycerides (TG) or HDL (11, 13), and elevated dLDL may also cause endothelial dysfunction independently of abnormal lipid levels (14). dLDL exhibit reduced uptake by the LDL receptor (15), are particularly susceptible to oxidation, and show increased binding to proteoglycans of the vessel wall (16). There is, however, also evidence that large LDL particles may induce increased risk for CAD (17). In fact, in 837 survivors of myocardial infarction of the CARE trial large LDL was an independent predictor of CAD (18).
Only fibrates (19, 20, 21, 22, 23, 24) and niacin (25) are generally believed to change the relative proportions of LDL subfractions.
So far, the effects of statins on LDL subfractions have been studied by gradient gel electrophoresis and ultracentrifugation (20, 21, 26, 27, 28, 29, 30, 31, 32, 33). Gradient gel electrophoresis gives only a rough estimate of the size distribution of LDL rather than absolute concentrations of dLDL and showed no effect of statin treatment on LDL particle size distribution (27, 29, 30, 32). Some of the ultracentrifugation-based studies showed a decrease of the concentration of dLDL (26, 33) during statin treatment but others did not (20, 21, 28, 29, 31). Therefore, it is still controversial whether statins are effective in lowering concentrations of dLDL.
A slow-release (XL) formulation of fluvastatin 80 mg is now available. In a pooled analysis of data from three randomized, placebo-controlled studies of primary hypercholesterolemia, fluvastatin XL decreased LDL-C by a median of 38% and lowered TG by a median of 19%, while increasing HDL-C by a mean of up to 21% (34).
Using equilibrium density gradient ultracentrifugation, we examined whether these favorable effects of fluvastatin XL may also translate in a reduction of the concentration of dLDL in patients with type 2 diabetes known to have a preponderance of dLDL.
Materials and Methods
This was a double-blind, randomized, placebo-controlled, 12-wk study comprising a 4-wk dietary run-in phase followed by a treatment period of 8 wk, which was conducted at 10 centers in Germany. The study protocol was approved by the Ethics Committee of the University of Freiburg, Germany, and the institutional review boards at each study center. All patients gave their informed, written consent.
Patients
Men and women (n = 89; age: 39–86 yr) with type 2 diabetes and hyperlipidemia (LDL-C, 3.37–5.96 mmol/liter; TG, 1.37–6.84 mmol/liter) after 4-wk of NCEP step I or II diet (35) were included. Type 2 diabetes [HbA1c, 6–10% (mean, 7.2 ± 1.0%)] had to be diagnosed at least 12 wk before the dietary run-in. Exclusion criteria included surgery, myocardial infarction, or angioplasty during the 6 months before randomization; poorly controlled hypertension; liver disease; chronic renal failure; myopathy; alcohol/drug abuse; known hypersensitivity to statins; pregnancy or lactation; lipid-lowering therapy during the 8 wk before the study; and use of insulin and oral contraceptives at the start of the study. After the dietary run-in, patients were randomized to receive fluvastatin XL 80 mg (n = 42) or placebo (n = 47), at bedtime, for 8 wk.
Laboratory assessments
Before randomization (wk –4) and after 8 wk of treatment, venous blood was sampled from fasted patients and subsequently assayed for total blood count and biochemistry. LDL subfractions were measured at baseline (wk 0) and after 8 wk of treatment. Enzymes were analyzed using standard procedures and reagents (Roche Diagnostics, Mannheim, Germany).
Lipoprotein separation
Lipoproteins were isolated by sequential preparative ultracentrifugation using the following densities: d < 1.006 kg/liter for very low density lipoprotein (VLDL), 1.006 < d < 1.019 kg/liter for intermediate density lipoprotein (IDL), 1.019 < d < 1.063 kg/liter for LDL, and 1.063 < d < 1.21 kg/liter for HDL. LDL subfractions were separated according to Baumstark (36). Total LDL (1.019 < d < 1.063 kg/liter) was fractionated into six density classes by equilibrium density gradient centrifugation. Density ranges of LDL subfractions were: LDL-1, less than 1.031 kg/liter; LDL-2, 1.031–1.034 kg/liter; LDL-3, 1.034–1.037 kg/liter; LDL-4, 1.037–1.040 kg/liter; LDL-5, 1.040–1.044 kg/liter; LDL-6, more than 1.044 kg/liter. The assay of apolipoprotein (apo) B in LDL-5 and LDL-6 was linear down to a concentration of 43 mg/liter and 39 mg/liter, respectively, and the intraassay coefficients of variation at these low concentrations were 2.1% and 2.5%, respectively (data not shown). The interassay coefficients of variation for apoB for the six LDL subfractions were 5% or less (37).
Lipoprotein chemistry
Cholesterol and TG concentrations were determined enzymatically with the cholesterol oxidase-peroxidase aminophenazone phenol and the glycerol-3-phosphate oxidase-peroxidase aminophenazone phenol methods, respectively (Roche Diagnostics). Apo concentrations were determined by turbidimetry, using specific polyclonal antisera (Rolf Greiner Biochemica, Flacht, Germany).
Stratification by baseline dLDL
The effect of fluvastatin XL, 80 mg, on lipid concentrations was analyzed according to predefined baseline dLDL level: patients were classified as having notable dLDL at baseline (apoB in LDL-5 plus LDL-6 > 250 mg/liter) or as having little dLDL at baseline (apoB in LDL-5 plus LDL-6 250 mg/liter) (33).
Statistical analysis
The primary endpoint of the study was the change from baseline in apoB in dLDL (LDL-5 plus LDL-6). Changes in lipid and lipoprotein levels between baseline (wk 0) and wk 8 were compared between treatment groups using Student’s t test, or the Mann-Whitney U test if appropriate. Bivariate correlations were analyzed by Pearson’s correlation coefficients. Changes were considered statistically significant if P < 0.05.
Results
Patient characteristics at baseline
In this study, 79% of the patients with type 2 diabetes had notable levels of dLDL. All patients had similar clinical characteristics and lipid and lipoprotein concentrations at baseline (Table 1
). There was a high proportion of diagnosed hypertension (
70% of patients) in all groups which is in line with previous findings (38), stressing the high prevalence of hypertension in type 2 diabetes.
|
After 8 wk of treatment, fluvastatin XL decreased plasma total cholesterol, TG, and LDL-C concentrations from baseline values compared with the changes from baseline in patients receiving placebo (Table 2); all treatment group differences for changes in lipid values between baseline and the end of the study were significant. ApoCIII and apoE showed significant reductions in the fluvastatin group vs. placebo (Table 2) which may mirror the reduction of apoCIII and apoE containing TG-rich lipoproteins. Among patients with baseline TG more than 3.4 mmol/liter (>300 mg/dl) fluvastatin XL decreased TG by 24.2% (P = 0.03 compared with placebo) (Fig. 1). HDL-C levels did not change significantly.
|
|
Each VLDL, IDL, and LDL particle contains one apoB molecule. The concentration of apoB in each lipoprotein fraction therefore indicates the number of VLDL, IDL, and LDL particles present. The LDL subfraction profile of patients with notable dLDL at baseline was, by definition, dominated by the most dense subfractions, LDL-5 and LDL-6 (Fig. 2A); in patients with little dLDL at baseline, however, the levels of the medium-dense subfractions, LDL-3 and LDL-4, were higher than those of LDL-5 and LDL-6 (Fig. 2B). In patients with notable levels of dLDL at baseline, fluvastatin XL lowered each of the apoB containing lipoproteins (Fig. 2A). The mean percent changes of apoB of the fluvastatin-treated group in IDL (-18%, P = 0.023), LDL-2 (-18%, P = 0.002), LDL-3 (-21%, P < 0.001), LDL-4 (-25%, P = 0.001) and small, dense LDL (LDL-5 plus LDL-6) (-28%, P = 0.001; cholesterol in small, dense LDL -29%, P = 0.001) were significant vs. placebo, the relative changes being highest for dLDL.
|
). The mean percent changes of apoB of the fluvastatin-treated group in VLDL (-30%, P = 0.045), IDL (-30%, P = 0.031), LDL-2 (-35%, P = 0.007), and LDL-3 (-33%, P = 0.023) were significant compared with placebo.
Excluding the outlier shown in brackets in Fig. 3A from statistical analysis, in fluvastatin-treated patients with dLDL, the percent change in TGs was positively correlated to the percent change in apoB in dLDL (r = 0.377; P = 0.04). Remarkably, in patients without dLDL, there was a tendency toward a negative correlation between the percent change in TGs and the percent change in apoB in dLDL (r = -0.541; P = 0.086) (Fig. 3).
|
None of the patients in the study experienced any serious drug-related adverse event. Aspartate aminotransferase, alanine aminotransferase, and plasma creatine phosphokinase activities remained less than three times the upper limit of normal range in all patients at all occasions during the study.
Discussion
Our primary objective was to investigate the effect of fluvastatin XL on atherogenic dLDL in patients with type 2 diabetes. In patients with notable levels of dLDL at baseline, 8 wk of treatment with fluvastatin XL decreased serum concentrations of dLDL by 28%, which translates into a decrease of cholesterol in dLDL of 29%.
The prevalence of dLDL in our study was 79%; fluvastatin significantly decreased all LDL subfractions in those patients with notable dLDL, absolute and relative reductions in dLDL being greatest (Fig. 2A).
Our results are different from most, but not all previous investigations that deny an influence of statins on dLDL. Those studies, however, differ from the current one in several aspects. In most of the previous studies, LDL subfractions were measured by determining the LDL peak particle diameter by gradient gel electrophoresis (27, 29, 30, 32). Most studies employing ultracentrifugation did not specifically address individuals with or without elevated dLDL at baseline (20, 21, 26, 28, 31) and some lacked appropriate placebo groups (20, 21, 26, 28, 29, 31). None of these limitations applies to the current study. Further, it is a strength of our study that we directly determine the concentration of each single LDL subfraction, thus providing absolute changes rather than relative LDL distribution.
Across the whole study population, fluvastatin decreased plasma LDL-C and TG by 29% and 18%, respectively, these changes also being significant when compared with those associated with placebo.
Taking into account the lower baseline LDL-C and the elevated TG concentrations in patients with type 2 diabetes, compared with levels in primary hypercholesterolemia, our results reflect the influence of fluvastatin on lipid levels shown in an earlier pooled analysis of data from patients with primary hypercholesterolemia, in which plasma LDL-C and TG were decreased by 33.7% and 14%, respectively (34).
The effect of fluvastatin XL on the minority (21%) of patients who did not have notable dLDL (Fig. 2B) differed markedly, however, from its effect in those with notable dLDL. In patients without notable dLDL, fluvastatin XL was associated with a more pronounced decrease in buoyant and medium-dense LDL particles, whereas the level of dLDL remained unchanged. This may be explained by statins increasing the activity of the LDL receptor (39). Because intermediate-dense LDL have a higher affinity than dLDL for the LDL receptor (15), up-regulation of the receptor by fluvastatin XL would produce a preferential decrease in buoyant and medium-dense LDL (28, 40). Although this concept contrasts with the observation that, in most patients with notable levels of dLDL, all LDL subfractions were lowered by fluvastatin (Fig. 2A), it corresponds with findings in nondiabetic patients with combined hyperlipoproteinemia and dLDL (20, 21, 40).
It is tempting to speculate whether variations in the amounts of lipoproteins such as glycated LDL and oxidized LDL in patients with type 2 diabetes (41) may account for these differences. There were, however, no differences in HbA1c levels in any groups in our study, making this hypothesis unlikely.
It was suggested that the effect of statins on LDL subfraction distribution may depend on the type of underlying hyperlipoproteinemia (42). The metabolism of TG-rich lipoproteins is linked directly to the metabolism of LDL subfractions (43). Because fluvastatin XL decreased plasma TG significantly only among patients with notable levels of dLDL at the start of our study, one might speculate whether the effect of fluvastatin XL on dLDL may be related to its action in decreasing TG. We did indeed identify a significantly positive correlation between the percentage change in TG levels and the percentage change in apoB found in dLDL among recipients of fluvastatin XL who had notable dLDL levels at baseline (Fig. 3). This is in line with previous data by Tilly-Kiesi (26), who reported reductions in dLDL during lovastatin treatment in those patients also responding with decreases of TG. In contrast, in patients without notable dLDL, there was a tendency to a negative, nonsignificant correlation between changes in TG and apoB in dLDL (Fig. 3).
One might thereby speculate whether, in patients with type 2 diabetes, fluvastatin XL influences LDL subfraction distribution in patients with or without notable dLDL via different mechanisms. In the minority of patients with a preponderance of medium-dense LDL, fluvastatin-induced decreases in these particles may be explained entirely by induction of the LDL receptor. Among patients with a predominance of dLDL, however, additional mechanisms may be involved because, in such patients, decreases in TG correlated with a decrease in dLDL. Fluvastatin XL may thereby decrease large and medium-dense LDL by catabolism via LDL receptor induction and, at the same time, reduce dLDL via decreased synthesis from TG-rich precursors as a result of reduced TG levels. This hypothesis may be supported by further investigation using turnover studies.
In conclusion, among patients with or without notable levels of dLDL, fluvastatin decreased plasma LDL-C, despite the relatively low LDL-C in patients with type 2 diabetes. In patients with a similar decrease in LDL-C, fluvastatin XL exerts different effects on LDL subfractions depending on the prevailing LDL subfraction profile. Our findings may help to clarify which class of lipid lowering drugs is most appropriate in the treatment of diabetic dyslipidemia. Fluvastatin XL substantially lowered the concentration of dense and buoyant LDL. In patients with dLDL at baseline, the reduction in dLDL was greater than in buoyant and intermediate-dense LDL, although the differences between individual subfractions did not reach statistical significance. In that respect, statins may differ from fibrates, which appear to change the relative distribution of LDL subfractions more profoundly. However, merely considering size distribution disregards absolute changes and hence provides a misleading view of the actual efficacy of fluvastatin XL. The antiatherogenic potential of fluvastatin XL in patients with type 2 diabetes may thus be greater than that expected from its effects on LDL-C and TG levels alone.
Acknowledgments
We thank Elke Baumann, Novartis Pharma Dubai, for discussion; and Rita Gläser, Nülüfer Ödünc, Jutta Heinecke, and Günther Schäfer for excellent technical assistance.
Footnotes
This study was supported by Novartis Pharma GmbH (Nürnberg, Germany).
Abbreviations: apo, Apolipoprotein; CAD, coronary atery disease; dLDL, dense LDL; HDL, high density lipoprotein; HDL-C, HDL cholesterol; IDL, intermediate density lipoprotein; LDL, low density lipoprotein; LDL-C, LDL cholesterol; TG, triglyceride; VLDL, very LDL; XL, slow-release.
Received March 11, 2002.
Accepted August 15, 2002.
References
This article has been cited by other articles:
 |
|
 |
|
  J. Costa, M. Borges, C. David, and A. Vaz Carneiro Efficacy of lipid lowering drug treatment for diabetic and non-diabetic patients: meta-analysis of randomised controlled trials BMJ, May 13, 2006; 332(7550): 1115 - 1124. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Rizzo and K. Berneis Low-density lipoprotein size and cardiovascular risk assessment QJM, January 1, 2006; 99(1): 1 - 14. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M Backes and C. A Gibson Effect of Lipid-Lowering Drug Therapy on Small-Dense Low-Density Lipoprotein Ann. Pharmacother., March 1, 2005; 39(3): 523 - 526. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Winkler, C. Abletshauser, I. Friedrich, M. M. Hoffmann, H. Wieland, and W. Marz Fluvastatin Slow-Release Lowers Platelet-Activating Factor Acetyl Hydrolase Activity: A Placebo-Controlled Trial in Patients with Type 2 Diabetes J. Clin. Endocrinol. Metab., March 1, 2004; 89(3): 1153 - 1159. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. M. Sacks and H. Campos Low-Density Lipoprotein Size and Cardiovascular Disease: A Reappraisal J. Clin. Endocrinol. Metab., October 1, 2003; 88(10): 4525 - 4532. [Full Text] [PDF]
|
|
|
|
 |
|
 K. Winkler, T. Konrad, S. Fullert, I. Friedrich, R. Destani, M. W. Baumstark, K. Krebs, H. Wieland, and W. Marz Pioglitazone Reduces Atherogenic Dense LDL Particles in Nondiabetic Patients With Arterial Hypertension: A double-blind, placebo-controlled study Diabetes Care, September 1, 2003; 26(9): 2588 - 2594. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
