Kinetics of lipids, apolipoproteins, and cholesteryl ester transfer protein in plasma after a bicycle marathon

Kinetics

of Lipids, Bernhard

Apolipoproteins, and Cholesteryl Ester Transfer in Plasma After a Bicycle Marathon F6ger, Thomas Wohlfarter, Carl H. Miller, Anton

Andreas

Ritsch, Monika

Protein

Lechleitner,

Dienstl, and Josef R. Patsch

The short-term effects of prolonged intense exercise on plasma lipid transport parameters including cholesterol, triglycerides (TGs), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and its subfractions HDLz cholesterol and HDLs cholesterol, on apolipoproteins (apes) A-l, A-II, and B, and on mass and activity of cholesteryl ester transfer protein (CETP) were studied in eight male endurance-trained athletes over the first week after a bicycle marathon. CETP mass concentration in plasma was quantified by a newly developed immunoradiometric assay (IRMA). Plasma concentrations of cholesterol, TGs, LDL cholesterol, apo B, CETP, and cholesteryl ester transfer activity (CETA) were significantly reduced in the recovery period compared with pre-exercise values (cholesterol by 20%. P c .05; TGs by 63%. P < .05; LDL cholesterol by 32%. P < .05; apo B by 16%, P c .05; CETP mass by 29%. P < .05; and CETA by 14%. P c .05). HDL cholesterol and HDLr cholesterol, in contrast, were significantly increased in the post-exercise period (HDL cholesterol by 12%, P < .05, and HDLr cholesterol by g6%, P < .05), whereas HDLs cholesterol showed a tendency to decrease in the late recovery period (by 6%, NS). Although changes in cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, apo B, and CETP mass and activity were already evident in the early recovery period, HDL, cholesterol showed a delayed response, reaching its maximum 72 hours after initiation of exercise. In addition, significant increases in plasma levels of apo A-l and A-II were found 8 days after the marathon (by 5%. P < .05, and by 12%, P c .05, respectively). Our data suggest that even in highly trained athletes, universally favorable lipoprotein changes of unexpected quantity result from a single episode of heavy exertion. The sustained and pronounced increase of HDLr cholesterol may be explained at least in part by the decrease in CETP after short-term exercise. Copyright 0 1994 by W.B. Saunders Company

A

EROBIC EXERCISE has been known to be associated with increased high-density lipoprotein (HDL) cholesterol.’ Most studies with cross-sectional design have shown considerably increased HDL cholesterol levels on the order of 10 to 24 mg/dL in physically trained subjects compared with sedentary controls.‘-” Most3-’ but not a118,ystudies with longitudinal design have demonstrated that aerobic endurance training in asymptomatic middle-aged men is followed by an increase in HDL cholesterol and decreases of total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides (TGs), respectively. The increase in HDL cholesterol has been attributed mostly to the less dense HDL- subfraction, whereas for HDLj cholesterol, rather marginal changes in both directions3-5 have been reported. The immediate effect of acute prolonged exercise, both continuedr@ix and intermittent,r9-” on lipoprotein metabolism in trained athletes has also been studied extensively. The more recent studies fairly unanimously conclude that HDL cholesterol is already elevated immediately after the exercise event,‘1-14 and persists up to 3 days.‘” Triglycerides clearly are decreased; following exertion, total cholesterol and LDL cholesterol show no immediate change,“~r3J4 but decrease after a delay of 24 to 48 hours.rZ.is,rx Numerous epidemiologic studies have established high HDL cholesterol levels as an indicator of decreased cardiovascular risk.?’ One of the mechanisms thought to account for this relationship is the transport of cholesterol, mediated by HDL, from peripheral tissues to the liver.z3 According to this concept, small HDL precursors are regarded as the primary acceptors of tissue cholesterol,‘J which is esterified consecutively by 1ecithin:cholesterol acyltransferase (LCAT)13 to form the hydrophobic core of HDL. HDL may consequently return their cholesteryl esters (CEs) to the liver for biliary excretion or to endocrine glands for synthesis of steroid hormones.

Metabolism, Vol43, No 5 (May), 1994: pp 633-639

Alternatively, HDL CE may be diverted to TG-rich lipoproteins in exchange for their major core lipid, ie, TGs. a process catalyzed by cholesteryl ester transfer protein (CETP).25 If remnants of TG-rich lipoproteins are not cleared efficiently, deposition of excess CE shunted from HDL to TG-rich lipoproteins may contribute to the formation of atheroma.Zh CETP plasma levels have been known to be increased in hyperlipoproteinemic states,:’ after treatment with the lipid-lowering drug probucol,2s and in complicated insulin-dependent diabetes mellitus.z4 Little information is available regarding regulation of CETP levels by perturbations such as exercise. In this study, we set out to investigate the effects of intense aerobic exercise on lipid metabolism for up to 8 days after the event, with particular attention to changes in CETP mass and activity. We report here that CETP shows a drastic decrease after exertion, followed by a pronounced increase of HDL: cholesterol. SUBJECTS AND METHODS

Subjects Eight endurance-trained athletes participating thon were studied. All were amateur sportsmen

in a bicycle maraaccustomed to a

From the Division of Clinical Atherosclerosis Research, Department of Medicine, Universityof Innsbruck, Innsbruck. Austria Submitted March 22, 1993; accepted July 30, 1993. Supported by Grant No. S-46106 from the Austrian “Fonds zur Fcrderung der wissenschafrlichen Forschung” and by Grant No. HL-27341 from the National Institutes of Health. Address reprint requests to Josef R. Patsch, ML). Department of Medicine, Universityof Innsbruck, Anichstrape 35. A-6020 Innsbruck. Austria. Copvright 0 1994 by W.B. Saunders Company 0026-049519414305-0018$03.0010 633

634

FGGER ET AL

Table 1. Characteristics of Eight Male Athletes Studied After a Bicycle Marathon

Age Wr)

34.6 (7.4)

Height (cm)

181.0 (5.2)

Pre-bicycle marathon weight (kg)

76.8 (8.1)

Post-bicycle marathon weight (kg)

75.0 (7.6)

Body mass index (kgimz)

23.7 (2.0)

Exercise time (min)

711.0 (65)

NOTE. Values are the mean (SD).

200 to 400 kmiwk. Age, height, body mass index (BMI), weight before and after the bicycle marathon, and exercise time are shown in Table 1. The marathon event covered a distance of 230 km and a difference in altitude of 5,500 m (htztal-Marathon, September 1991). In the recovery period after the race subjects did not engage in any physical exercise. and food and fluid consumption were unrestricted. bicycling distance of

Methods Blood was withdrawn from an antecubital vein after an overnight fast 2 days before the race (day -2) and on days 1, 2, 3, 5. and 8 after the race (day 1 represents 24 hours after the initiation of the race). Blood was collected in EDTA, the plasma was stored at 4°C. and lipid determinations were performed within 48 hours after collecting the blood samples. The cholesterol level was measured by an enzymatic calorimetric test using cholesterase, cholesterol oxidase, and aminophenazone (Cholesterol PAP, MA-kit 100, Roche, Basle, Switzerland). TG levelswere determined by a calorimetric reaction with iodonitrotetrazolium chloride after enzymatic hydrolysis (Triglyceride PAP. Uni-Kit III, Roche). The LDL cholesterol level was calculated according to the method of Friedewald et al.-‘” HDL, HDL2, and HDL3 cholesterol levels were determined using a stepwise precipitation procedure with dextrane sulfate and magnesium ch1oride.s’ Levels of plasma apolipoproteins (apos) A-I and B were determined by immunoturbidimetric tests (Tina-quant, Boehringer. Table 2. Plasma Lipids, Apolipoproteins,

Mannheim, Germany). For all procedures described above, a Cobas Mira Autoanalyzer (Roche) was used. The apo A-II level was determined by radial immunodiffusion (COMB1 R.I.D. Immuno, Vienna, Austria). Cholesteryl ester transfer activity (CETA) was determined as described by Groener et al?’ using a substrate-independent isotope assay measuring radiolabeled cholesteryl ester transfer from exogenous LDL to exogenous HDL. mediated by a fraction of the respective proband’s fasting plasma from which very-low-density lipoprotein (VLDL) and LDL had been removed before the assay procedure. Radiolabeling of exogenous LDL was performed according to the method of Morton and Zilversmit.33 CETP mass measurements were performed with an immunoradiometric assay (IRMA) using a polyclonal antibody,“j which gives results in close agreement with previously published radioimmunoassay (RIA) procedures.s5,30

Statistical Analysis Mean values and standard deviations of the parameters tested were calculated. Differences between pre- and post-exercise samples were tested for significance using a repeated-measures Friedman ANOVA and the Wilcoxon matched-pairs signed-ranks test with the help of a Complete Statistical System (CSS; Stat Soft, Release 3.O.C. Tulsa, OK) software package. Spearman rank correlation coefficients between percent changes of CETP mass on day 2 after the bicycle marathon relative to baseline (day -2) values (ACETP mass = [CETP mass {baseline] - CETP mass [day 2JJICETP mass [baseline)) and the corresponding percent changes of HDL lipids and HDL apolipoproteins were calculated. P less than .05 was used as the level of significance.

RESULTS Although they were amateur athletes, all study subjects were highly endurance-trained as evidenced by their ability to complete the bicycle marathon in time. Their HDL cholesterol values (Table 2) exceeded the 95th percentile of

and CETP Before and After the Bicycle Marathon

Before After Exerme

Exercise’ Day -2

Day 1

Day 2

Day 3

Day 5

Day 8

Pt

Cholesterol

224 (32)

182 (31)t

180 (18)$

188 (26)$

204 (26)

212 (27)

,013

TGs

132 (67)

49 (ll)*

88 (33)s

102 (34)

134 (62)

149 (53)

i ,001

HDL cholesterol

67 (15)

75 (13)$

73 (15)

75 (18)

69 (21)

67 (9)

,005

HDLz cholesterol

12 (6)

16 (6)

19 (Jo)*

25 (lo)*

19 (12)

16 (6)

,013

HDLJ cholesterol HDLP cholesterol/HDL,

55 (9) cholesterol

0.22 (0.08)

58 (7) 0.28 (0.1 I)$

54 (8) 0.35 (0.16)$

LDL cholesterol

130 (27)

96 (27)Z

Apo A-l

144 (14)

133 (20)t

Apo A-II

53 (5)

48 (5)*

Apo B

77 (13)

63 (15)*

1.23 (0.27)

1.03 (0.19)$

0.87 (0.21)$

CETA

109 (14)

99 (12)*

Plasma volume

100 (0)

82 (15)*

CEPT mass

89 (18)Z

51 (9) 0.49 (0.17)$ 93 (15)*

51 (71 0.36 (0.18)

51 (6) 0.31 (0.1 l)$

,011 ,007

108 (17)

116 (26)

,011

146 (19)

151 (24)

150 (16)$

.020

54 (6)

52 (3)

56 (4)*

60 (7)*

64 (9)s

65 (8)*

71 19)

78 (14)

,002

0.95 (0.23)t

1.02 (0.20)

1.14 (0.36)

,028

98 (13)

104 (13)

112 (22)

121 (14)$

114 (9)*

106 (9)

142 (19)

94 (14)$ 122 (7)*

< ,001

.018 < ,001

NOTE. Results are the mean (SD). Lipids and apolipoproteins are mg/dL; the ratio of HDL, cholesterol to HDL3 cholesterol is in arbitrary units; CETPmass is in pg/mL; CETA is in nmol

mL-’

h-l; and relative plasma volume is % plasma volume on day -2.

*See Methods for details. tFriedman

ANOVA was performed on each variable to provide a single test of the hypothesis that there is no difference between pre- and

post-exercise time points. Only after the null hypothesis was rejected at the P < .05 level were individual pre- and post-exercise time points compared by the Wilcoxon matched-pairs signed-ranks test. SP < .05, Wilcoxon matched-pairs signed-ranks test “values obtained before exercise.

635

KINETICS OF LIPIDS

before exercise

1

2

3

5

8

days after exercise

Fig 1. Relative changes in plasma concentrations of cholesterol (A), triglycerides (0). and LDL cholesterol (*) after a bicycle marathon compared with pm-exercise values. For absolute values, SD, and levels of significance, see Table 2 and the Results.

age- and sex-matched controls,37 and TGs and LDL cholesterol were near the 50th percentile.37 Table 2 shows the kinetics of lipids and apolipoproteins in response to the bicycle marathon. Plasma cholesterol and LDL cholesterol, when compared with pre-exercise values, were significantly decreased on days 1, 2, and 3, reaching their respective minima on day 2 with reductions of 20% and 32%, respectively (Fig 1, Table 2). TGs showed a sharp decrease of 63% on day 1 and a subsequent steady increase to baseline values by day 5 (Fig 1, Table 2). HDL. cholesterol levels displayed a precipitous increase already on the first morning after the race (+12%) and returned to baseline by day 8 (Fig 2, Table 2). The HDL subfraction HDLz cholesterol showed an increase of almost 100% on day 3, thus constituting the lipoprotein species with the most drastic change in plasma concentration (Fig 2, Table 2). HDL3 cholesterol showed a tendency to decrease in the late recovery period (Fig 2, Table 2). After a temporary 24-hour decrease, levels of apo A-I (day 8) and apo A-II (days 5 and 8) were significantly * increased in the late recovery period (+5% and + 12%; Fig 3, Table 2). Levels of apo B displayed a maximum decrease of 18% on day 1, returning to baseline levels as late as day 8 of the recovery period (Fig 3, Table 2). Mean plasma CETP mass of the athletes before the race was not significantly different from that of eight male healthy controls (1.23 2 0.27 and 1.05 -C 0.17 pg/mL, respectively; P = .32 by Mann-Whitney U test). However, after exertion, CETP mass showed a drastic decrease of up to 29% on day 2 after the race (Fig 4. Table 2). This decrease in CETP mass

concentration was also rather sustained in that it only slowly approached baseline levels, such that even on day 8 it was not entirely restored (94% of baseline). The decrease in CETP mass was paralleled by CETP activity (r = .77, P < .OOl; Fig 4, Table 2). Associations between relative changes in CETP and relative changes in lipids and apolipoproteins from baseline to day 2, where the maximum decrease of CETP mass was noted, are shown in Table 3. The decrease in CETP mass was strongly and directly related to both the increase in HDLz cholesterol (P < .05) and the increase in the ratio of HDb cholesterol to HDL3 cholesterol (P < .05). Thus, athletes with the largest decrease in CETP mass showed the most pronounced increase in both HDLZ cholesterol and the HDLz cholesterol to HDL3 cholesterol ratio. In contrast, no significant correlations were found between changes in CETP mass and changes in HDL3 cholesterol and HDL apolipoproteins. Relative changes in plasma volume were estimated on the basis of hematocrit (%) and hemoglobin (g . dL_‘) values3* obtained before and after the bicycle marathon. Plasma volume was decreased on day 1 and increased on days 2 through 5 (Table 2). When adjusting accordingly for changes in plasma volume, the maximum increase of HDL cholesterol, HDLr cholesterol, apo A-I, and apo A-II would be accentuated to +32%, +138%, +23%, and +24%, respectively. The maximum decrease in TGs, cholesterol, LDL cholesterol, apo B, CETP mass, and CETA would also be accentuated to -69%, -33%, -38%, -31%, -30%. and -25%, respectively. Although after this correction changes in lipoproteins and CETP mass remained statisti-

1 Q -50

efore exercise

i

2

3

days after

5

8

exercise

Fig 2. Relative changes in plasma concentrations of HDL cholesterol (A), HDL? cholesterol (0). and HDLt cholesterol (*) after a bicycle marathon compared with pre-exercise values. For absolute values, SD, and levels of significance, see Table 2 and the Results.

FoGER ET AL

Table 3. Correlations Between Relative Changes in CETP and Relative Changes in HDL Lipids and HDL Apolipoproteins After the

20

Bicycle Marathon

Parameter

10 GHDL

Correlation

Statistical

Coefficient

Probability

cholesterol

0

GHDL, cholesterol/HDL,

.02

.40

.16

GApo A-II

.26

.26

NOTE. Percent changes of all parameters

(Table 2) on day 2 after the

relative to baseline (day -2) values were calculated

(eg, GCETP mass = [CETP mass /baseline\

- CETP mass /day ZJIICETP

mass jbaseline)). Variables were not normally the Lilliefors

-30

.31

-.?I

cholesterol

GApo A-l

bicycle marathon

-20

.04

.20

GHDL, cholesterol

- 10

.3?

.14 -.64

GHDL* cholesterol

correlation

statistic, coefficients

and therefore between

CETP mass) and percent changes cholesterol)

were

calculated.

distributed

nonparametric

percent

changes

as judged by

Spearman

in the other parameters

R values

rank

in CETP mass (8

and two-sided

(eg, GHDL

P values

are

shown.

-40

before exercise

i

2

3

5

8

days after exercise

Fig 3. Relative changes in plasma concentrations of apo A-l (A), apo A-II (0). and apo B (*) after a bicycle marathon compared with pm-exercise values. For absolute values, SD, and levels of significance, see Table 2 and the Results.

tally significant, CETA showed only a tendency to decrease after the bicycle marathon (P < .l). In addition, a significant increase in HDLa cholesterol was noted on day 2 of the recovery period. The data presented in Table 2 corrected for estimated changes in plasma volume arc shown in Table 4. DISCUSSION

During prolonged heavy exercise, insulin levels decrease and counterregulatory hormones, ie, glucagon, catechol-

80

before I exercise

2

3

days after

5

a

exercise

Fig 4. Changes in mass and activity of CETP after a bicycle marathon. CETP mass is given in pg . mL-’ plasma, and CETA is given in nmol . mL-’ . h-1. Data are the mean @EM). lP < .05 by Wilcoxon matched-pairs signed-ranks test between pre- and post-exercise values.

amines. and glucocorticosteroids. help control fuel metabolism.‘” The resulting activation of hormone-sensitive lipase in adipose tissue leads to increased hpolysis of endogenous TG stores.4u The free fatty acids liberated either serve directly as energy substrate for exercising muscle and heart or are taken up by the liver, reassembled to TGs, and resecreted as VLDL.4’ Utilization of VLDL, in turn, depends on the activity of lipoprotein lipase (LPL), the rate-limiting enzyme of plasma TG catabolism, in the target tissues. A number of studies have documented exercise-induced increases in postheparin plasma LPL.1”~‘z~42resulting from increased activity of LPL in both muscle21,43 and adipose tissue.5,4’,4? Thus, hepatic oversynthesis of VLDL, induced by increased free fatty acid flux to the liver,‘” and enhanced peripheral LPL activity lead to augmented shedding of VLDL surface components, which are thought to be integrated into HDL particles effecting the conversion of HDL3 to HDL2.44 Most recent studies of lipoprotein metabolism in acute exercise focused on changes immediately after exercise.*L.13J4 In our study, the decrease in serum TGs as a response to the bicycle marathon was more pronounced, both in magnitude (-63%) and in duration (up to 5 days), than that described in most previous reports. This quantitative difference can be explained by the higher level and the longer period of exertion of about 12 hours. Hand in hand with the decrease in TGs, HDL cholesterol increased on the first day after exercise due to a roughly equal increase of HDL? cholesterol and HDL3 cholesterol. Subsequently, HDL subfractions diverged, with HDb cholesterol levels nearly doubling on the third day and HDL3 cholesterol decreasing below baseline levels. Our data therefore confirm and extend previous observations,iriJ2.‘s where HDLz cholesterol increased between 48 and 72 hours. In our observation period of 8 days, a delayed HDLz peak at 3 days and a divergent pattern of changes in HDLz and HDL? subfractions are consistent with the view outlined above of a rather sustained, enhanced LPL activity giving rise to HDL, formation from VLDL surface components and HDL3.44

637

KINETICS OF LIPIDS

Table 4. Plasma Lipids, Apolipoproteins,

and CETP Before and After the Bicycle Marathon (corrected for changes in plasma volume)

Before Exercise*

After Exercise Day 1

Day -2

Day 2

Day 3

221 (37)

228 (41)

234 (42)

Day 5

226 (45)

125 (47)

154 (79)

157 (52)

,004

71 (12)

i ,001 ,002

Cholesterol

224 (32)

151 (45)$

TGs

132 (67)

41 (14)$

108 (43)$

67 (15)

61 (11)

89 (19)$

90 (24)*

77 (23)

HDL cholesterol

Day B

HDL2 cholesterol

12 (6)

13 (5)

23 (12)*

30 (13)*

22 (14)

17 (6)*

HDLB cholesterol

55 (9)

48 (10)

66 (lo)*

61 (12)

55 (11)

54 (8)

0.22 (0.08)

0.28 (0.1 I)*

0.35 (0.16)*

0.49 (0.17)$

0.36 (0.18)

HDL2 cholesterol/HDL,

cholesterol

Pt ,010

,011

0.31 (0.1 l)*

,007

LDL cholesterol

130 (27)

81 (35)s

110 (27)$

114 (28)$

126 (29)

124 (37)

Apo A.-l

144 (14)

110 (25)*

173 (26)Z

177 (28)Z

171 (31)$

159 (21)$

i .OOl

Apo A--II

53 (5)

40 (ll)*

66 (9)t

63 (8)*

63 (9)$

63 (ll)*

i ,001

Apo B

77 (13)

53 (20)$

79 (15)

79 (17)

81 (18)

83 (21)

,003

1.23 (0.27)

0.85 (0.26)*

1.05 (0.27)*

1.l 1 (0.24)

1.17 (0.25)

1.24 (0.441

.003

109 (14)

82 (21)

CETP mass CETA

NOTE. Results are the mean (SD). Lipids and apolipoproteins mass is in kg/mL;

CETA is in nmol

mL-’

115 (15)

are mg/dL;

118 (11)

the ratio of HDLl cholesterol

120 (9) to HDL, cholesterol

,006

120 (24)

,069

is in arbitrary units: CETP

hi’.

*See Methods for details. tFriedman post-exercise compared

ANOVA

was performed

time points.

by the Wilcoxon

SP < .05, Wilcoxon

on each variable

to provide

Only after the null hypothesis matched-pairs

matched-pairs

signed-ranks

signed-ranks

a single test of the hypothesis

was rejected

that there is no difference

at the P < .05 level were individual

between

pre- and post-exercise

pre- and

time points

test.

test v values obtained

The increase in HDL? after the marathon can be explained, in addition to augmented formation of HDLz by high LPL activity, by the reduced catabolic conversion of HDLz into HDL3. Both TG-rich lipoproteins and CETP play major roles in the catabolism of HDLl via its conversion to HDL+ TG-rich lipoproteins provide the TGs, and CETP catalyzes the transfer of these TGs from TG-rich particles to particles like HDL2, and the reciprocal transfer of CEs. The resulting TG-enriched HDLz are converted into the smaller HDL3 by hepatic lipase.45 Both the reduction of TG-rich lipoproteins (due to increased LPL activity) and the decrease in CETP mass and activity as a result of the marathon would help to decrease the catabolism of HDLz 1.0 HDL3, thus contributing to the observed increased post-exercise HDLz levels. The importance of CETP has been generally accepted since the discovery of humans with extremely high levels of HDL (cholesterol, especially HDL2 cholesterol, due to homozygous CETP deficiency caused by a splicing defect of the CE:TP gene. 46Obligate heterozygotes for the mutation display about half-normal CETP activity and increased HDL2 cholesterol consistent with a codominant inheritance of the trait.“’ Alterations in CETP activity have also been reportedly due to environmental factors including endocrine disturbances,29,48 ethanol consumption,4y and lipidlowering drugs.2x In various forms of primary hyperlipoproteinemia?’ and after prolonged intake of an atherogenic diet.50 increases in both cholesterol and CETP have been observed.17 Our findings add evidence of yet another perturbation that affects CETP mass levels and activity. Apo A-I and apo A-II, the two major HDL apoproteins. showed a significant increase, with a maximum on days 5 and 8 after exertion when all other lipid and lipoprotein parameters were already returning to baseline. This increase appears to be due to a decrease in the fractional catabolic rate of apo A-I as a consequence of the decreased

before exercise.

plasma TG concentrations. 51For long-distance runners, an association of plasma TG concentration with the fractional catabolic rate but not with the synthetic rate of apo A-I has been demonstrated.52 LDL cholesterol was decreased by up to 32%, an effect still significant 3 days after the race. Previous studies reported no decrease13J4J8 or variable decreases11’.12J7of LDL cholesterol. Again, differences in the level and duration of exertion most probably account for the reported discrepancies. The decrease in apo B reported in our study and also by others” and the 63% decrease in TGs with the rather small change in LDL cholesterol suggest that mainly apo B associated with VLDL decreased as a result of the marathon. However, increased LDL uptake via LDL receptors, as demonstrated for prolonged exercise,53 may also account for part of this effect. The profound post-exercise decrease in CETP in our bicycle marathon participants paralleled the decreases in their cholesterol levels. This supports the concept that CETP levels are determined by peripheral cholesterol transport via apo B-containing lipoproteinsZ7 In conclusion, we observed after strenuous exercise in our subjects major changes in plasma lipids, which returned only slowly to baseline levels after about 5 days. Most of these effects can be explained by the well-documented increase in LPL activity. However, the drastic decrease in CETP level and activity, not known before, also helps to explain some of these changes. The quantitative contribution to these changes by altered LPL and CETP activities remains to be elaborated further. The magnitude of the changes is considerable, equaling or exceeding the effects attainable by the most potent lipid-lowering drugs available. According to current concepts regarding risk factors and arteriosclerosis, all of the observed changes are beneficial in terms of offering protection against cardiovascular disease.

FbGER ET AL

638

NOTE ADDED IN PROOF

After submission of the manuscript, two study groups reported decreased plasma CETP also after long-term exercise training, in cross-sectional (Serrat-Serrat J, Ordonez-Llanos J, Serra-Grima R, et al: Marathon runners presented lower serum cholesteryl ester transfer activity than sedentary subjects. Atherosclerosis 101:43-49, 1993) and prospective (Seip RL, Moulin P, Cocke T, et al: Exercise training decreases plasma cholesteryl ester trans-

fer protein. Arterioscler Thromb 13:1359-1367, 1993) studies, respectively. ACKNOWLEDGMENT

The expert technical assistance of Gabriele Trobinger and Elisabeth Gasser, the secretarial help of Manuela Wittmann and Silvia Bitschnau, and the enthusiastic cooperation of the study subjects are gratefully acknowledged. The authors thank Dr G. Kemmler, Department of Medical Statistics, University of Innsbruck, for statistical advice.

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