The effect of diet on hypercholesterolemia in renal transplant recipients

The Effect of Diet on Hypercholesterolemia in Renal Transplant Recipients Susan S. Sullivan, DSc, RD,* Ellen J. Anderson, MS, RD,f Sharon Best, MA,# Lillian M. Sonnenberg,DSc, RD,§ and Winzed W. Williams, MD11

W Objective: To compare the effects of cholesterol-lowering diet intervention on lipid levels in hypercholesterolemit renal transplant recipients and hypercholesterolemic normal subjects. W Design: Controlled clinical trial. n Setting: Clinical research center. n Patients: Thirteen hypercholesterolemic subjects, 6 with renal transplants and 7 control subjects. W Intervention: Four weeks of the average American diet, followed by 4 weeks of the National Cholesterol Education Program’s Step-Two Diet. W Main Outcome Measures: Three lipid profiles measured on each diet. W Results: The control subjects experienced a significant average decrease in total cholesterol of 0.91 mmol/L (35 mg/dL) or 13.1% (p < .OOl). Although markedly lower, the transplantation subjects did experience a decrease in total cholesterol of 0.35 mmol/L (13.6 mg/dL) or 5.4%, which was significant (p < .05). Among the transplant subjects, response to the lipid-lowering diet was positively correlated with creatinine clearance and negatively correlated with blood cyclosporine levels. High-density lipoprotein cholesterol levels were higher in the transplant subjects than in the control subjects, suggesting a less atherogenic lipid profile in the transplant subjects. n Conclusions: Response to lipid-lowering diet intervention in renal transplant recipients may be less than in the general population, possibly relating to decreased creatinine clearance and/or cyclosporine therapy. More aggressive diet and medication interventions are needed to control hypercholesterolemia in the renal transplant population. o 1996 by the National Kidney Foundation, Inc.

E

LEVATED LIPID levels often occur after organ transplantation.‘” The posttransplant hyperlipidemia is usually characterized by elevated total and low-density lipoprotein (LDL) cholesterol levels and elevated very low-density lipoprotein (VLDL) triglyceride levels. Highdensity lipoprotein (HDL) cholesterol levels vary. is4Reports on the p revalence of hyperlipidemia after transplantation are variable because

*Cfmical Dietitian, Depafiment of Dietetics, Massachusetts General Hospital, Fruit St, Boston, ML4 fResearch Dietitian Manager, Mallrnckrodt General Clintcal Research Center, Mauachusetts General Hospital, Boston, MA. #Biostatistician, Mallinckrodt Massachusetts General Hospital,

General Chical Boston, MA.

Research

Center,

$Senror Manager, Ambulatory Nutrition Service, Department Dietetics, Massachusetts General Hospital, Boston, MA.

of

lllnstructor in Medicme, Harvard Medical School, and Renal Unit, Massachusetts General Hospital, Boston, MA. Address reprint requests to Susan S. Sullrvan, DSr, RD, Clinical Dtetitian, Department of Dietetics, Massachusetts General Hosprtal, Fruit St, Boston, MA Ml 14 0 1996 by the National Kidney IOSI-2276/96/0602-0004$03.00/O

/ournal

ofRenal

Nutrition,

Foundation,

Vol 6, No

3 (July),

Inc.

1996: pp 141-151

of differing standards used to define hyperlipidemia and differences in immunosuppression regimens between transplant centers. Approximately 50% of transplant recipients have hyperlipidemia.5 The cause of the hyperlipidemia after renal transplantation is believed to be multifactorial. Medications (including immunosuppressants and antihypertensives), glucose intolerance, obesity, elevated creatinine levels, and proteinuria may all contribute to the increased lipid levels after transplantation and may alter responsiveness to treatments for hyperlipidemia in this population. lo Studies ofposttransplant hyperlipidemia and its treatment often show conflicting results because of the heterogeneous nature of the group with respect to causes of hyperlipidemia. The relationship between elevated blood cholesterol levels and risk for coronary heart disease has been well established in the general population and supports the need for aggressive treatment of hypercholesterolemia.6-8 Because 141

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SULLIVAN

hypercholesterolemia and atherosclerotic vascular complications are common after organ transplantation, 4*9,10this relationship is presumed to be the same for organ transplant recipients with hypercholesterolemia. High blood cholesterol levels may also be a factor in the progression of allograft damage in renal transplant recipients.” Therefore, aggressive treatment strategies for hypercholesterolemia in transplant recipients should be established. Dietary treatment would be preferable to the use of cholesterol-lowering drugs in the transplant population because of an increased risk of complications from medication interactions with cyclosporine.5 In the general population, dietary modifications can successfully lower cholesterol levels for many individuals.6 Several studies of the efficacy of diet intervention for posttransplant hypercholesterolemia have found reductions in total cholesterol levels with diet therapy of 8% to 21%.12-15 The study samples were generally heterogeneous, including some diabetics and subjects on different medication regimens. A controlled diet trial was undertaken to provide more specific and conclusive information about the responsiveness of renal transplant recipients’ cholesterol levels to conventional cholesterol-lowering diet therapy. The purpose of this study was to compare the effects of diet intervention on lipid levels in hypercholesterolemic renal transplant recipients and in hypercholesterolemic normal subjects and to correlate changes in lipoprotein profiles with patient characteristics. In order to study the lipid abnormalities primarily related to cyclosporine and prednisone, and to limit the withingroup variability of responses to diet therapy, only patients with good renal and liver function, minimal proteinuria, and normal blood glucose were included.

Methods Subjects Hypercholesterolemic renal transplant subjects were recruited from the outpatient transplant clinic at Massachusetts General Hospital (MGH). Hypercholesterolemic control subjects were recruited from the MGH staff and visitor community. Those subjects who agreed to participate attended an initial screening visit

ET AL

at the MGH Mallinckrodt General Clinical Research Center (GCRC) to determine eligibility. Inclusion criteria for all subjects consisted of total cholesterol level 2 6.21 mmol/L (240 mg/dL), ratio of total cholesterol to HDLcholesterol 2 4.5 and/or LDL-cholesterol level 24.14 mmol/L (160 mg/dL), normal serum creatinine level, 24-hour urine protein excretion 10.3 g/d (300 mg/24 h), hemoglobin Ai, I 7%, and age 220 years. The transplant subjects had to be at least 1 year beyond renal transplantation, on both cyclosporine and prednisone, and on stable medication regimens (no dosage change during the past 3 months). Exclusion criteria were use of lipid-lowering medications, active angina symptoms, fasting triglyceride levels >3.95 mmol/L (350 mg/ dL), abnormal liver function test results, malabsorption syndromes, smoking, diabetes, and a history of noncompliance with medication regimens.

Diet Intervention All control and transplant subjects underwent the same diet intervention consisting of two consecutive 4-week diets. For the first 4 weeks, subjects consumed the average American diet as defined by food consumption surveys.6 The purpose of this diet was to standardize all subjects’ diets to the same baseline before diet intervention. Goals for the average American diet were as follows: 37% of calories from fat; 15% of calories from saturated fat; 7% of calories from polyunsaturated fat; and 400 mg cholesterol per day. For the next 4 weeks, subjects consumed meals in accordance with the National Cholesterol Education Program’s (NCEP) Step-Two Diet for cholesterol reduction6 Daily intake goals included: 30% of calories from fat; <7% of calories from saturated fat, up to 10% of calories from polyunsaturated fat, and monounsaturated fat providing the remaining fat calories; and < 200 mg cholesterol per day. Meal plans for both diets consisted of a 4-day rotating menu cycle. Menus were arranged so that the Recommended Dietary Allowances were met. Both diets contained no alcoholic beverages. The meal frequency was three or more meals per day. The fiber content of each diet was approximately the same.

DIET

AND

LIPIDS

IN RENAL

To promote compliance with the diet, most food for the 4-week standardization and intervention diet periods was provided to the subjects by the GCRC kitchen. Food was cooked in the hospital kitchen, and weighed to the nearest 0.1 g, packaged, and frozen in the GCRC metabolic kitchen. On the average American diet, egg yolk powder was added to the entrees to adjust the cholesterol content of the menus. Subjects were responsible for purchasing and weighing highly perishable items including milk, juice, fruits, and salad ingredients at home. Food scales were provided. Calorie intake goals for weight maintenance were estimated for each subject using the HarrisBenedict equations with actual body weight. Activity factors between 1.3 and 1.5 times the basal energy expenditures were chosen and adjusted throughout the study to promote weight maintenance. Subjects were encouraged to maintain their usual physical activity levels during the study. Also available to the subjects on a daily basis was the choice of including a modular diet component (cake) to satisfy hunger. The cakes were portioned to provide 200 calories per slice and contained the same fat percentages as the total diets. The cakes did not contain cholesterol. This modular component was useful in fine-tuning caloric intakes to meet requirements. Subjects received their food in 7-day allotments with written meal plans for each day. The subjects checked off each item on the meal plan sheet as it was eaten. They were instructed to return any food which was not consumed to the GCRC kitchen to be quantified. Close telephone contact was maintained with the subjects by the investigator. Complete compliance was encouraged, but subjects were also advised to record any foods eaten that were not part of the meal plan. The subjects reported to the GCRC once per week to review their eating during the previous week, and to discuss any events, symptoms, or difficulties they had. They were instructed to record physical activity and unusual physical events on the daily meal plan sheets. Weights, blood pressures, and temperatures were measured and blood samples were drawn at these weekly visits. The subjects then received food and daily meal plan sheets for the following week.

143

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Laboratory

Analyses

Fasting serum lipid profiles (total, HDL-, and LDL-cholesterol and triglyceride levels) were measured eight times during the study. Before starting the average American diet, a fasting lipid profile was drawn. Lipid profiles were then drawn after 2,3, and 4 weeks on both the average American and the Step-Two diets. A final lipid profile was measured after the subjects had returned to their own eating habits for 8 weeks. For all blood tests, the subjects were instructed to fast for 12 hours with nothing by mouth except water. Medications were held until the blood samples were drawn. Samples were drawn into EDTA tubes. Cholesterol levels were analyzed on fresh serum using the Boehringer Mannheim High Performance Cholesterol Method of enzymatic analysis. l6 Triglyceride levels were determined by enzymatic hydrolysis.” HDL levels were measured by precipitation of LDL and VLDL with subsequent cholesterol analysis as described above. LDL-cholesterol levels were calculated using the Friedwald formula.i8 Other measurements included whole blood cyclosporine levels with each lipid profile (transplant subjects only), and, on the fourth week of each of the two diets, blood urea nitrogen (BUN), creatinine, blood glucose, hemoglobin Ai,, and serum insulin. Blood samples for measurement of BUN, creatinine, blood glucose, and hemoglobin Ai, were analyzed in the hospital chemistry laboratory in the usual manner. Blood samples for serum insulin levels were frozen at -70°C and analyzed in two batches (the first eight subjects and the next five subjects). Fasting serum insulin levels were analyzed by a solid-phase iz51 radioimmunoassay19 (Coat-A Count, Diagnostic Procedures Corporation).

Data Analysis The three lipid profiles drawn on each diet were averaged together. Data were analyzed for significant changes in mean total, HDL-, and LDL-cholesterol and triglyceride levels from the average American diet to the Step-Two diet within groups using the paired t-test. The mean changes in lipid levels were compared between groups using the unpaired t-test. Other t-tests

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SULLIVAN

were performed to look for significant changes in all areas of data collection from the first diet to the second diet. Unpaired t-tests were then performed to compare data points between the two groups of subjects. Correlation analyses were performed (for each group separately) between changes in lipoprotein fractions and all other data points to look for characteristics that correlated with the lipid changes.

Results Subjects Fourteen subjects started and finished the 16-week protocol. The data analysis includes 7 control subjects and 6 renal transplant recipients. Data from one transplant recipient were excluded because she experienced an increase in blood cyclosporine level above the normal range, necessitating a change in cyclosporine dosage during the diet intervention. Table 1 contains a summary of the subjects’ characteristics. Three of 7 control subjects and all 6 transplant subjects were taking blood pressure medications. All transplant subjects were taking prednisone, cyclosporine, and azathioprine. Laboratory values from the screening visit further characterize the groups and the differences between them (Table 2). The control group had significantly better creatinine clearance as defined by 24-hour urine collection. The transplant group had significantly higher

ET AL

levels of BUN, creatinine, serum glutamicoxaloacetic transaminase (SGOT), and total and direct bilirubin. Mean SGOT and total bilirubin levels were slightly above the normal range in the transplant subjects. At the screening visit, there were no significant differences between the groups in total cholesterol or triglyceride levels. However, the profile of hypercholesterolemia was different between groups. The control group had a significantly higher mean LDL-cholesterol level, whereas the ratio of total to HDL-cholesterol was significantly lower in the transplant group (Table 2).

Diet Intervention The actual composition of the standardization and intervention diets as consumed was calculated from the subjects’ records of their daily food intake (Table 3). Both groups experienced significant increases (P < .05) in intake of calories, protein, carbohydrate, and polyunsaturated fat from the average American diet to the Step-Two diet and significant decreases (P < .Ol) in intake of total fat, cholesterol, saturated fat, and monounsaturated fat. There was minima1 variation between subjects in the degree of change between the two diets. Using actual dietary intake data for each group, the Keys equation20 predicts an average decrease in total cholesterol of 0.93 mmol/L (35.8 mg/dL) for the control group and 0.98 mmol/L (37.9 mg/dL) for the transplant group.

Table 1. Comparison of Subject Characteristics Variable

Control

Transplant

Number of subjects (Female, male) 7 (4,3) 6 (3, 3) 49.3 (k10.2) 43.7 (+13.8)* Age (Y) 168.4 (k11.0) 162.6 (*9.8)* Height (cm) Weight at screening 81.0 (215.7) 77.2 (?14.1)* (kg) Body mass index 28.4 (24.1) 29.6 (?7.4)* (kg/m*) Predicted basal energy expenditure (calories/d) 1598 (+335) 1554 (+205)* Prednisone dose 11.3 (k2.1) @w/d) Cyclosporine dose 3.3 (21 .l) O-wW Azathioprine dose 95.8 (k10.2) @xt/d) Note: Data is expressed as mean (*SD). *No significant difference between groups.

Lipid Responses to Diet Intervention The control group experienced significant decreases in mean total, LDL-, and HDLcholesterol levels from the average American diet to the Step-Two diet (Table 4). Triglyceride levels did not change significantly. The average decrease in serum cholesterol between the two diets was 0.91 mmol/L (35.0 mg/dL) or 13.1%. The ratio of total- to HDL-cholesterol did not change significantly. The transplant subjects also experienced significant decreases in total, LDL-, and HDL-cholesterol between the two diets (Table 4). Mean total cholesterol levels decreased by 0.35 mmol/L (13.6 mg/dL) or 5.4%. Figure 1 compares the lipid responses with diet intervention between the two groups. The decreases in total and LDL-cholesterol in

DIET

AND

LIPIDS

IN RENAL

145

TJUNSPLANTATION

Table 2. Comparison of Screening Data Between Groups Control BUN

(mmol/L)

Creatinine Fasting

[mg/dL]

(pmol/L) blood

[mg/dL]

glucose

(mmol/L)

Hemoglobin A,, (“Y) Serum albumin (g/L) SGOT

(kkat/L)

5.0 114 71 [0.8 5.2 [93 5.38 39 [3.9 0.3

[mg/dL]

[g/dL]

[U/L]

(20.7)

(231 (29) (+O.l)] (20.8) (%lO)] (20.51) (23) (*0.3)] (20.1)

118W)l Alkaline Direct

phosphatase bilirubin

(pkat/L)

(kmol/L)

Total

bilirubin

(pmol/L)

Urine

protein

(g/d)

Creatinine Serum

cholesterol

1.4 [86 2 [O.l 10 (0.6 0.02 [18 1.98 [119 6.82 [263.6 4.89 [189.0 1.16 [45.0 8.1 1.68 [149.0

[mg/dL] [mg/dL]

[mg/24

clearance

[U/L]

h]

(mL/.s)

[mL/min]

(mmol/L)

[mg/dL]

LDL-cholesterol

(mmol/L)

[mg/dL]

HDL-cholesterol

(mmol/L)

[mg/dL]

Ratio of total- to HDL-cholesterol Serum triglycerides (mmol/L)

[mg/dL]

Note: Data is expressed as mean (*SD). Abbreviations: BUN, blood urea nitrogen;

SGOT,

serum

the control group were significantly greater than the decreases seen in the transplant group (P < .05). There were no significant differences in change in HDL-cholesterol or triglycerides between groups. The lipid profiles drawn immediately before starting the average American diet and those drawn 8 weeks after the conclusion of the Step-Two diet reflect the subjects’ self-selected eating habits. Both of these lipid profiles were not significantly different from the mean values on the average American diet for either group.

(kO.2) (*12)] (-CO) (*0.05)] (*6) (?0.3)] (20.03) (?33)] (kO.50) (‘30)] (20.76) (+29.4)] (kO.68) (?26.1)] (20.22) (?8.7)] (k1.3) (kO.65) (*57.6)]

glutamic-oxaioacetic

Transplant 8.2 123 115 [1.3 5.5 [99 5.46 37 [3.7 0.4 [27 1.3 [78 6 [0.4 22 [1.3 0.06 [65 1.02 [81 6.58 [254.3 4.12 [159.3 1.40 [54.0 4.7 2.31 [204.3 transaminase;

P Value

(k2.9) (*8)1 (218) (*0.2)] (21 .l) (*19)] (k0.9) (*2) (*0.2)] (20.2) (*lo)] (20.4) (?22)] (-c4) (+0.2)] (?8) (*0.5)] (kO.08) (?79)] (kO.37) (*22)] (20.72) (?27.7)] (eO.63) (?24.5)] (20.17) (?6.4)] (kO.2) (20.61) (?53.8)]

<.05 < ,001 NS NS NS .06 NS < .05 < .Ol NS < .Ol NS < .05 .06 < .05 NS

NS, not significant.

fasting blood glucose, hemoglobin Aic, and serum insulin levels did not change significantly between the two diets for either group. Insulin levels did not differ significantly between groups on either diet. As seen in the screening data, BUN and creatinine levels were higher in the transplant group. Mean fasting blood cyclosporine levels decreased significantly (P < .05) from the average American diet to the Step-Two diet (186.4 [ + 129.71 to 165.8 [ 2 128.51 ng/mL).

Factors Related to Lipid Responses Other Data Collected During the Controlled Diets The control group experienced a significant decrease (P < .05) in weight from the average American diet to the Step-Two diet of 0.6 kg. The transplant subjects did not experience a significant change in weight between the two diets. Mean blood pressure, BUN, creatinine,

Within the transplant group, two factors correlated with the serum cholesterol response. Creatinine clearance was positively correlated (I = 3) with the decrease in total and LDLcholesterol. Those transplant subjects with the highest creatinine clearance rates showed better cholesterol lowering in response to diet change. Blood cyclosporine levels correlated negatively

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Table 3. Reported

Diet Composition Control Average American Diet

Diet Component Calories

per day

Caloric

intake

Protein

(g/d)

(“? of predicted

BEE)

Fat (g/d) Fat (96 of calories) Carbohydrate Cholesterol

(g/d) intake

SFA

(g/d)

SFA

(% of calories)

PUFA

(g/d)

PUFA

(% of calories)

MUFA

(g/d)

MUFA

(% of calories)

ET AL

(mgld)

2277.6 (k406.0) 144% (*-8) 95.1 (*15.9) 96.8 (k16.9) 38.3% (20.4%) 254.6 (249.3) 452.1 (244.0) 37.1 (26.7) 14.7% (&0.2%) 16.7 (23.2) 6.6% (?0.2%) 34.9 (*5.8) 13.8% (?0.2%)

Note: Data is expressed as mean (*SD). All differences Abbreviations: BEE, basal energy expenditure; SFA, monounsaturated fatty acids.

Subjects

Transplant

Step-Two Diet

Difference

2381.1 (k418.8) 150%

103.5 (2118.3) 6%

(+6) 105.0 (k17.8) 78.3 (213.3) 29.6% (20.3%) 321.4 (k58.8) 171.8 (233.2) 15.8 (k2.4) 6.0% (?0.2%) 24.9 (k4.9) 9.4% (-cO.3%) 32.0 (?3.2) 12.1% (20.3%)

10.0 (27.0) -18.5 (25.8) -8.6% (?0.3%) 66.8 (k17.2) -280.3 (k19.4) -21.4 (k4.5) -8.7 (kO.2) 8.2 (22.1) 2.8 (kO.2) -3.0 (22.1) -1.7 (20.3)

Subjects

Average American Diet

Step-Two Diet

2097.2 (k300.7) 135% (9 88.1 (k6.5) 89.4 (212.8) 38.4% (20.2%) 233.5 (2233.6) 473.6 (a26.3) 34.3 (k4.9) 14.7% (20.1%) 14.9 (k2.5) 6.4% (?0.2%) 32.9 (24.7) 14.1% (20.2%)

2287.7 (2420.3) 147% (?16) 101.9 (+16.7) 74.9 (k13.8) 29.5% (?0.3%) 308.4 (259.8) 159.4 (225.9) 15.2 (22.8) 6.0% (20.2%) 24.2 (24.7) 9.5% (20.1%) 30.6 (k4.9) 12.1% (20.4%)

Difference 190.5 (2186.2) 12% 13.8 (510.9) -14.5 (25.2) -8.9 (20.4) 74.9 (k31.5) -314.2 (k31.6) -19.1 (k2.4) -8.7 (kO.3) 9.3 (a2.7) 3.1 (20.3) -2.3 (k2.3) -2.0 (kO.5)

from average American to Step-Two diet are significant (P < .05). saturated fatty acids; PUFA, polyunsaturated fatty acids; MUFA,

(I = -.S) with serum cholesterol response. Those with higher mean cyclosporine levels on either diet had lower cholesterol responses to diet change. Blood cyclosporine levels did not correlate with creatinine clearance or with cyclosporine dosage. In the control group no factors (other than dietary changes) correlated significantly with lipid responses. Weight changes throughout the study did not correlate with changes in any lipoprotein fraction for either group.

Discussion Hypercholesterolemia is a frequent longterm complication of organ transplantation.1-5 Because atherosclerotic vascular complications are also common after transplantation, high LDL-cholesterol levels are thought to be causatively related to vascular disease as in the general population.3,4,6 Posttransplant hypercholesterolemia has many potential contributing

factors, including prednisone and cyclosporine immunosuppressive medications.5 The factors that contribute to posttransplant hypercholesterolemia may also influence the transplant recipient’s ability to respond to dietary treatment of hypercholesterolemia. This study was undertaken to compare the efficacy of conventional cholesterol-lowering diet therapy in hypercholesterolemic renal transplant recipients and control subjects. The control group responded to the diet manipulations with a reduction in serum cholesterol consistent with the reduction predicted by the Keys equation. 2o Mean cholesterol levels decreased by 13.1%. The decrease in total cholesterol was accompanied by decreases in LDL-cholesterol of 14% and HDL-cholesterol of 12.5%. Fasting triglyceride levels and the ratio of total to HDL-cholesterol were not significantly affected by the change in diet. A similarly designed study by Lichtenstein et a121

DIET

Table 4. Lipid Response

AND

LIPIDS

IN

RENAL

147

TRANSPLANTATION

to Diet Intervention

Control subjects Total cholesterol (mmol/L) [mg/dL] LDL-cholesterol

(mmol/L) [mg/dL]

HDL-cholesterol

(mmol/L) [mg/dL]

Triglyceride (mmol/L) [mg/dL] Total:HDL ratio Transplant subjects Total-cholesterol (mmol/L) [mg/dL] LDL-cholesterol

(mmol/L) [mg/dL]

HDL-cholesterol

(mmol/L) [mg/dL]

Triglyceride (mmol/L) [mg/dL] Total:HDL ratio

Average American Diet

Step-Two Diet

Difference Between Diets

Percent Change

P Value

6.89 (20.54) [266.6 (?20.8)] 4.89 (20.59) [189.0 (*23.0)] 1.35 (kO.34) [52.1 (+13.2)] 1.43 (kO.60) [126.6 (?53.2)] 5.4 (k1.2)

5.99 (20.70) [231.6 (?27.1)] 4.20 (kO.68) [162.6 (?26.2)] 1 .18 (kO.27) [45.6 (?10.4)] 1.32 (kO.37) [116.6 (-c32.8)] 5.3 (kl .l)

0.91 (k0.32) [-35.0 (?12.5)] 0.68 (20.32) [-26.4 (+12.3)] 0.17 (kO.11) [-6.5 (r4.2)] 0.11 (20.27) [-lo.0 (?23.6)] -0.1 (kO.3)

13.1%

< ,001

14.0%

< ,001

12.5%

< .Ol

7.9%

NS

2.0%

NS

6.50 (20.84) [251.2 (?32.3)] 4.20 (k0.82) [162.6 (?31.6)] 1.43 (20.16) [55.2 (*6.2)] 1.89 (20.30) [167.6 (?26.6)] 4.6 (20.7)

6.14 (20.99) [237.6 (?38.1)] 3.95 (20.97) [152.7 (+37.5)] 1.32 (k0.19) (50.9 (*7.4)] 1.92 (20.14) [170.4 (?12.1)] 4.8 (k-1.0)

0.35 (20.18) [-13.6 (+6.9)] 0.26 (k0.24) [-9.9 (*9.2)] 0.11 (kO.05) [-4.3 (?2.0)] 0.03 (a0.22) [2.8 (?19.8)] 0.2 (k.32)

5.4%

< .Ol

6.1%

< .05

7.8%

< .Ol

1.7%

NS

4.3%

NS

Note: Data is expressed as mean (*SD). Abbreviations: total:HDL ratio, ratio of total cholesterol to HDL-cholesterol;

achieved comparable reductions in total, LDL-, and HDL-cholesterol of 7% to 13%, 13% to 16%, and 7% respectively with implementation of the NCEP Step-Two diet. They also did not see significant changes in triglyceride levels or in the ratio of total to HDL-cholesterol. In the transplant subjects, the cholesterol reduction caused by the diet intervention was also statistically significant. Mean total cholesterol levels decreased from the average Ameri-

NS, not significant.

can to the Step-Two diet by 5.4%, with significant decreases in both LDL- and HDLcholesterol. This cholesterol response, however, was markedly lower than that predicted by the Keys equation and was significantly lower than the change observed in the control group. Because the primary mechanism for the effects of diet changes on cholesterol levels is through the impact on LDL-metabolism,22 these data suggest that some characteristic(s) of the

7.16 *o

7.50

-I

6.98

-

6.12

ii “o8

6.46

6

5.95

$

5.69

ix

5.43

7.24

T

6.21 -

5.17 4.91

Figure 1. Comparison serum sponse groups. error)

of cholesterol reto diet between (mean + standard

I. 0

1

. . . I”‘. 2

I’...I”.‘I. 3

.“,‘..‘I. 4

5

.. 6

7

Week Number 8tudy Groupa Weeks

l-4 = Average

American

Control Diet,

------ Tmnsplant Weeks 4-3 = Step-Two

Diet

.I.,

. I

8

9

148

SULLIVXN

transplant subjects rendered the regulation of their LDL-cholesterol levels less responsive to dietary fat and cholesterol modifications than the control group. Changes in dietary intake of fatty acids and cholesterol mainly affect the production of LDL-cholesterol and the number of LDL receptors. 22 From this study, it is not possible to identify the factor resulting in the decreased diet responsiveness of LDL-cholesterol levels in the transplant subjects. The transplant subjects could have shown alterations in LDL production rates, affinity of LDL for the receptor, and/or control of LDL receptor synthesis. The study was designed so that the predominant difference between groups would be the immunosuppressive medication regimen of the transplant subjects. All transplant subjects were taking azathioprine, prednisone, and cyclosporine. Prednisone and cyclosporine are etiologic factors in posttransplant hyperlipidemia.!j Prednisone has been shown to cause increased hepatic triglyceride synthesis and increased circulating VLDL-triglyceride levels.23,24Because VLDL is a precursor for LDL particles, LDL-cholesterol levels may increase with prednisone therapy.5 In this study, it was not possible to stratify the transplant subjects’ lipid responses based on prednisone dosage because there was little variation in prednisone dosage among the subjects (four subjects were taking 10 mg per day). Prednisone dosage did not correlate with cholesterol response or with lipid levels. Because prednisone may also influence HMG-CoA reductase activity,25 some influence of prednisone on intracellular cholesterol levels and regulation of the LDL receptor cannot be ruled out by this study. The effects of prednisone might be responsible for the difference in lipid profiles between groups at screening (Table 2). The transplant subjects had higher mean HDL-cholesterol with a significantly lower ratio of total to HDL-cholesterol. The high HDL-cholesterol levels may be related to increased VLDL synthesis and hydrolysis stimulated by prednisone.24 The control subjects had significantly higher LDL-cholesterol levels, suggesting that, with the same degree of hypercholesterolemia, the control subjects had more atherogenic lipid profiles than the transplant subjects. The Framingham Study data found low HDL-

ET AL

cholesterol levels to be a strong, independent predictor of heart disease risk.26 Triglyceride levels have also been suggested to be an independent risk factor for heart disease. Multivariate analysis is complicated because high triglyceride levels commonly occur with low HDLcholesterol levels2’ The transplant subjects showed a lipoprotein profile with slightly elevated triglyceride levels and high LDL- and HDL-cholesterol levels. The relative atherogenicity of each component of the lipid profile is difficult to determine. Prospective studies of the incidence of cardiovascular events in relation to LDL- and HDL-cholesterol levels and triglyceride levels are needed in the transplant population. Several studies have suggested that greater doses of cyclosporine are associated with higher serum cholesterol levels.28-30 In this study, cyclosporine therapy was related to serum cholesterol responses to diet change. The fasting blood cyclosporine level on either diet correlated negatively with serum cholesterol response. Lower cyclosporine levels were associated with greater cholesterol responses to diet change, suggesting that cyclosporine has an impact on regulation of LDL-cholesterol levels. The transport and metabolism of cyclosporine are closely related to sites of lipid metabolism. Cyclosporine is transported in the bloodstream in erythrocytes and leukocytes (60%) and plasma (40%). In the plasma, cyclosporine is primarily carried in lipoproteins.31 In body tissues, the distribution of cyclosporine mimics the distribution of LDL receptors, with the greatest drug concentration found in the liver.32 The proximity of cyclosporine to sites of LDL metabolism may allow for some role of cyclosporine in LDL receptor regulation. Princen et aP3 found that LDL receptor activity was not altered by incubation of cyclosporine with rat hepatocytes in vitro. However, they suggested that the 26-hydroxylase enzyme involved in bile acid synthesis was inhibited by cyclosporine. Decreased synthesis of bile acids from intracellular cholesterol was thought to explain the increase in LDL-cholesterol caused by cyclosporine therapy. Because the majority (about 70%) of LDL receptors are found in the liver,22 one might speculate that decreased responsiveness of LDL receptors to diet change might relate to some

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effect of transplantation on the liver. Hepatotoxicity is a well-known side effect of cyclosporine therapy with elevations commonly seen in bilirubin and transaminase 1evels.34 In this study, total and direct bilirubin and SGOT levels were significantly higher in the transplant group than in the control group (Table 2). However, responsiveness of serum cholesterol levels to diet therapy for cholesterol lowering did not correlate with any liver function tests. Cyclosporine blood levels and dose did not correlate with liver function tests. Another notable difference between the transplant and control groups was in renal function. Although mean BUN and creatinine levels for the transplant group were in the normal ranges, the transplant subjects had significantly higher levels of BUN and creatinine and lower levels of creatinine clearance than the control subjects. The decreased renal function in the renal transplant recipients may be caused by cyclosporine nephrotoxicity, immunological injury, or by having a single functioning kidney that is denervated. In this group of patients, cyclosporine dosage or blood levels did not correlate with creatinine clearance. In other studies, cyclosporine blood levels have not been reliably predictive of nephrotoxicity.36 In the transplant subjects, creatinine clearance correlated negatively with serum cholesterol response to diet change in the transplant subjects. Those with worse renal function had less response to the diet change. Studies of the effects of renal dysfunction on lipid levels show the primary effects of uremia to be on enzymes involved in triglyceride clearance.37 In this study, mean fasting triglyceride levels were above the normal range in the transplant subjects on all diets. The elevation in fasting triglyceride levels in the transplant subjects may have been caused by abnormal creatinine clearance and/or by increased triglyceride production on prednisone. The correlation between decreased renal function and decreased serum cholesterol response to diet was more likely related to the effects of cyclosporine on the kidney and on lipid metabolism. The reduction in serum cholesterol observed in the control group validates the diet protocol used in this study and suggests that subject diet compliance was adequate. The subjects in this study were free-living and returned to the

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Clinical Research Center once per week. The advantage of this protocol was that subjects could maintain their usual daily activities. The disadvantage was that diet compliance could not be easily monitored. Compliance was encouraged during telephone calls from the investigator several times per week. Subjects were advised to accurately document their food intake and to report any deviations from the meal plans. Use of an optional diet component (cake) that could be added to the meal plan to satisfy hunger also increased compliance. Presumably compliance did not differ markedly between the two groups because they were wellmatched in age and gender. Because weight loss may have cholesterollowering effects,38 a difference in weight loss between groups might result in a difference in serum cholesterol responses. Although the study was designed for weight maintenance, some weight loss occurred. The control group experienced a greater weight change from the average American to the Step-Two diet. However, weight or weight change at any point in the study did not correlate with change in serum cholesterol. Despite the similarity of weights between the two groups, there may have been some difference in body composition caused by prednisone therapy in the transplant subjects. Corticosteroids may cause alterations in body composition including increased fluid retention, decreased lean body mass, and increased fat mass. The corticosteroids may also affect body fat distribution by causing deposition of fat in the central abdominal area, which is associated with increased cardiovascular disease risk.39 The potential role of body composition in lipid metabolism was not explored in this study. In the normal population, total cholesterol levels decrease more in response to diet therapy in those individuals with higher initial cholesterol leve1s.h Although total cholesterol levels were higher in the control group than in the transplant group on the average American diet, this difference was not statistically significant. The subjects in both groups had received some counseling for cholesterol reduction at the end of the experimental diets before they returned home for 8 weeks on self-selected diets. However, total cholesterol levels, which had been significantly lowered on the Step-

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Two diet, returned to prestudy levels. This supports the need for intensive diet counseling over longer periods of time for people to significantly modify their usual eating habits to achieve cholesterol reduction.

Conclusion The control subjects’ serum cholesterol levels responded as expected to the cholesterollowering diet. The transplant subjects had a significantly reduced response. The blunted responsiveness of total and LDL-cholesterol levels to dietary fat and cholesterol modifications in transplant recipients may relate to decreased creatinine clearance and/or to the effects of cyclosporine among other factors. Findings from studies of lipid metabolism and treatment in transplant recipients should be generalized with caution because posttransplant hyperlipidemia has a diverse etiology. Results from this study are applicable to patients with similar characteristics (nondiabetics, patients with normal creatinine levels, patients on both prednisone and cyclosporine). Because some patients may have a reasonable response to diet therapy, a trial of cholesterol-lowering diet modification should be the first step in treatment of posttransplant hypercholesterolemia. Additional cholesterol-lowering dietary measures such as increasing water-soluble fiber, decreasing trans fatty acid intake, weight loss, and diet modification for improved blood glucose control should be included. For some patients with decreased renal function, response to diet changes may be inadequate and drug therapy may be necessary. Blood cyclosporine levels should be maintained as low as possible. Further research on treatment of posttransplant hypercholesterolemia should look more directly at factors affecting LDL-receptor numbers and function.

Acknowledgment The authors thank the National Kidney Foundation Council on Renal Nutrition and the MGH Mallinckrodt General Clinical Research Center (GCRC) for funding; the GCRC Dietetics Staff-Jane Hubbard, Debbie Lentz, Fungai Maswoswe, Mae Nelson, and Tanya Walsh-for their tireless efforts toward this labor-intensive study; the staffs of the MGH GCRC, Department of Dietetics, Transplant Unit, and Clinical Laboratories; and 14 wonder-

ET AL ful subjects whose study a success.

dedication

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References 1. Bittar AE, Ratcliffe PJ, Richardson AJ, et al: The prevalence of hyperlipidemia in renal transplant recipients. Associations with immunosuppressive and antihypertensive therapy. Transplantation 50:987-992,199O 2. Costanzo-Nordin MR, Grady KL, Johnson MR, et al: Long-term effects of cyclosporine-based immunosuppression in cardiac transplantation: The Loyola experience. Transplant Proc 22:6-l 1, 1990 (suppl) 3. Vathsala A, Weinburg RB, Schoenberg L, et al: Lipid abnormalities in cyclosporine-predmsone-treated renal transplant recipients. Transplantation 48:37-43, 1989 4. Drueke TB, Abdulmassih Z, Lacour B, et al: Atherosclerosis and lipid disorders after renal transplantation. Kidney Int 39:S24-S28,1991 5. Markell MS, Friedman EA: Hyperlipidemia after organ transplantanon. Am J Med 87:5-61N-S-67N, 1989 6. Report of the National Cholesterol Education Program Expert Pane1 on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Arch Intern Med 148:36-69, 1988 7. Martin MJ, Hulley SB, Browner WS, et al: Serum cholesterol, blood pressure, and mortality: Implications from a cohort of 361,662 men. Lancet 2:933-936,1986 8. The Lipid Research Clinics Coronary Primary Prevention Trial Results: II. The relationship of reduction in incidence of coronary heart disease to cholesterol lowering. JAMA 251:365-374,1984 9. Brunner FP, Broyer M, Brynger H, et al: Survival on renal replacement therapy: Data from the EDTA registry. Nephrol Dial Transplant 2:109-122,1988 10. Kasiske BL: Risk factors for accelerated atherosclerosis in renal transplant recipients. Am J Med 84:985-992,1988 11. Keane WF, Mulcahy WS, Kasiske BL, et al: Hyperlipidemia and progressive renal disease. Kidney Int 39:S41-S48, 1991 12. Moore RA, Callahan MF, Cody M, et al: The effect of the American Heart Association step one diet on hyperlipidemia following renal transplantation. Transplantation 49:6062,1990 13. Nelson J, Beauregard H, Gelinas M, et al: Rapid improvement of hyperlipidemia in kidney transplant patients with a multifactorial hypolipidemic diet. Transplant Proc 20:1264-1270,1988 14. Shen SY, Lukens CW, Alongi SV, et al: Patient profile and effect of dietary therapy on post-transplant hyperhpidemia. Kidney Int 24:S147-S152.1983 (suppl) 15. Disler PB, Goldberg RB, Kuhn L, et al: The role of diet in the pathogenesis and control of hyperlipidemia after renal transplantation. Clin Nephrol 16:29-34,198l 16. Trinder P: Oxidase determmanon of plasma cholesterol as cholest-4-en-3-one using iso-octane extraction. Ann Chn Biochem 1864-70.1981 17. Bergmeyer HU (ed): Methods of Enzymatic Analysis (ed 2). NewYork, NY, Academic Press, 1974, pp 1831 18. Friedewald WI, Levy RI, Fredrickson DS: Estimation of the concentration of low-density lipoprotein cholesterol in

DIET

AND

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IN RENAL

plasma, without use of the preparative centrifuge. Chn Chem l&499-502,1972 19. Marschner I, Botterman P, Erhardt F, et al: Group experiments on the radioimmunological insulin determination. Horm Metab Res 6:293-296, 1974 20. Keys A, Anderson JT, Grande F: Serum cholesterol response to changes in the diet. II. The effect of cholesterol m the diet. Metabolism 14:759-765, 1965 21. Lichtenstein AH, Ausman LM, Carrasco W, et al: Effects of canola, corn, and olive oils on fasting and postprandial plasma lipoproteins in humans as part of a National Cholesterol Education Program Step 2 Diet. Arterioscler Thromb 13:1533-1542,1993 22. Dietschy JM, Woollett LA, Spady DK: The Interaction of dietary cholesterol and specific fatty acids m the regulation of LDL receptor activity and plasma LDL-cholesterol concentrations. Ann NYAcad SCI 676:l l-26, 1993 23. Hays AP, Hill RB: Enzymes of lipid synthesis in the liver of the cortisone-treated rat. Biochim Biophys Acta 98:646-648.1965 24. Ettinger WI-I, Hazard WR: Prednisone mcreases very low density lipoprotein and high density lipoprotein in healthy men. Metabolism 37:1055-10581988 25. Higgins RM, Ratcliffe PJ: Hypercholesterolaemia and vascular disease after transplantation. Transplant Rev 5:131149,1991 26. Kannel WB, Castelli WP, Gordon T: Cholesterol in the prediction of athersclerotic disease: New perspectives based on the Framingham study. Ann Intern Med 90:85-91, 1979 27. Have1 R, McCollum Award Lecture, 1993: Triglyceriderich hpoproteins and atherosclerosis-new perspectives. Am J Chn Nutr 59:795-799,1994 28. Versulius DJ, Wenting GJ, Derkx FHM, et al: Who should be converted from cyclosporme to conventional immunosuppression in kidney transplantation, and why. Transplantation 44:387-389.1987

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29. Kasiske BL, Tortorice KL, Heim-Duthoy KL, et al: The adverse impact of cyclosporine on serum lipids in renal transplant recipients. Am J Kidney Dis 17:700-707,199l 30. Hricik DE, Mayes JT, Schulak JA: Independent effects of cyclosporine and prednisone on posttransplant hypercholesterolemia. Am J Kidney Dis 16:353-358.1991 31. Lemaire M, Fahr A, Maurer G: Pharmacokinetics of cyclosporine: Inter- and intra-individual variations and metabolic pathways. Transplant Proc 22:1110-l 112,199O 32. Niederberger W, Lemaire tion and bmding of cyclosporine plant Proc 15:2419-2421,1983

M, Maurer G, et al: Distribum blood and tissues. Trans-

33. Prmcen HMG, MeiJer P, Hofstee B, et al: Effects of cyclosporin A (CsA) on LDL-receptor activity and bile acid synthesis m hepatocyte monolayer cultures and in vivo in rat. Hepatology 7: 1109, 1987 (abstr) 34. Krupp P, Monka C: Side-effect profile of cyclosporin A m patients treated for psoriasis. Br J Dermatol 122:47-56, 1990 (suppl36) 35. Lloveras JJ, Durand D, Ader JL, et al: Comparison between glomerular filtration rate and renal plasma flow between kidney and heart transplant recipients mamtamed on a similar cyclosporine dosage. Transplant Proc 26:248, 1994 36. Bach JF, Feutren G, Noel LH, et al: Factors predictive of cyclosporine-induced nephrotoxicity: The role of cyclosporme blood levels. Transplant Proc 22:1296-1298,199O 37. Attman PO, Alaupovic P: Lipid abnormalities in chronic renal insufficiency. Kidney Int 39:S16-S23,1991 (suppl31) 38. Tran ZV, Weltman A: Differential effects of exercise on serum lipid and lipoprotem levels seen with changes in body weight. A meta-analysis. JAMA 254:919-924,1985 39. Johnson CP, Gallagher-Lepak S, Zhu YR, et al: Factors mfluencing weight gam after renal transplantation. Transplantation 56:822-827, 1993