Apolipoprotein E levels in vegetarians

Apolipoprotein E levels in vegetarians

Apolipoprotein Dennis R. Lock, Anne Varhol, E Levels in Vegetarians Susan Grimes, Wolfgang Patsch, and Gustav Schonfeld Vegetarians are known to...

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Apolipoprotein Dennis R. Lock, Anne Varhol,

E Levels in Vegetarians

Susan Grimes,

Wolfgang

Patsch,

and Gustav Schonfeld

Vegetarians are known to have low lipoprotein lipid and apolipoprotein Al and 6 levels. Since dietary cholesterol has recently been shown to have important effects on apolipoprotein E (ape E) metabolism, we measured plasma apo E levels in three groups of vegetarians. Group I (n = 36) consumed ~10 mg cholesterol daily and 42% of calories as fat (P:S ratio 2.6). Group II (n = 10) and Group Ill (n = 18) consumed 97 and 179 mg cholesterol daily, and 35% of calories as fat (P:S ratios 0.7 and 0.9) respectively. Compared to control values, vegetarian plasma cholesterol and triglyceride levels were decreased by lo%-30% and 30%-55%. Plasma apo E levels were decreased equally in all groups by 35% (2.4 -+ 0.1 mg/dl versus 3.6 + 0.1 mg/dl, p i 601). Plasma apo E levels were increased in parallel with lipid levels in pregnant vegetarians but were not different from non-lactating vegetarians in postpartum lactating women. Decreased apo E levels did not correlate with relative body weight, P:S ratio or intake of fat, carbohydrates or protein. Since all vegetarian diets studied were low cholesterol diets, decreased cholesterol intake may contribute to the low apo E levels. The apparent modification of apo E metabolism by vegetarian diets may be important in mediating effects of lipid lowering diets on atherogenesis.

A

POLIPOPROTEIN E (apo E, MW approximately 35,000) is a marker on lipoproteins which is recognized by cellular apolipoprotein B receptors, thereby facilitating the adsorptive endocytosis of some lipoproteins.‘-5 In plasma, apo E is found in very low density, intermediate density, and high density lipoproteins.6.7 Several studies have demonstrated that plasma levels measured by radial immunodiffusion,’ electro-immunodiffusion.8 or radioimmunoassay,6,9.‘0 are elevated severalfold in subjects with familial type III hyperlipidemia. Kushwaha et al.’ found normal plasma levels in subjects with Type Ila, IIb. and IV hyperlipidemia. Others’.‘” have reported elevated levels in all types of hyperlipidemia. The extent to which dietary intake affects plasma apo E levels in man is unclear. In animals, cholesterol feeding is followed by the appearance in plasma of apo E rich lipoproteins, HDL, and PVLDL.‘.” In some species, high fat, high cholesterol diets also elevate plasma apo E levels.“~” However, short-term cholesterol feeding in humans does not change plasma apo E levels.‘4.‘5 There is also no change in plasma apo E in subjects given a high carbohydrate diet.’ Vegetarians have lower IipidJ6-” and apolipoprotein AI and B levelsi than normal non-vegetarians. The addition of meat to their diet raises plasma lipid levels.” Since hyperlipidemia inducing diets fail to effect plasma apo E in humans, this study was conducted to determine if lipid lowering diets such as vegetarians eat affect plasma apo E levels. MATERIALS

AND

METHODS

Three groups of vegetarians were studied. Group 1 consisted of volunteers from the Farm.*O d complete vegetarian agrarian community in Tennessee. Group II and III arevolunteers from two Trappist Monk monasteries in Missouri and Georgia, respectively. Their diet includes eggs, dairy products and fish, but no meat except on five annual feasts. All vegetarians studied had followed their diet for at least one year. Plasmas obtained from normolipemic subjects (less than 90 percentile for age and sex**), during routine lipid screening and matched for age were used for control lipid and apo E levels.

Metabolism. Vol. 3 1, No. 9 (September),

1982

These control subjects were similar to people screened previously19 and were assumed to follow an average American diet. The three groups of vegetarians were visited by dietitians especially trained in the evaluation and dietary treatment of lipid disorders. Nutrition histories and 24 hr recalls were obtained from each participant. In addition, the dietitians interviewed those people involved in the purchasing and preparation of the food to aid in the nutrient calculations. Total protein. fat. carbohydrate. calories, PS ratio and cholesterol intake were calculated from standard tables2’,” and the Farm Cookbook” by computer. Fasting blood samples were drawn on site and the EDTA plasma was separated immediately. The plasma was kept on ice until processing was begun at the Core Laboratory of the Lipid Research Center at Washington University, within 24 hr. A questionnaire was also completed by each vegetarian subject including the following information: height, weight, use of medication. menstrual history, and presence of cardiovascular or metabolic disorders. An abbreviated form containing only this information was obtained from control subjects. Epidemiologic data are displayed in Table I. Members of the Farm were homemakers and mothers, paramedical personnel working in the Farm’s clinic, employees of local business, or directly involved in growing produce. Only 14% of the subjects fell into the last category. The Trappists from Missouri operated a concrete factory. The Georgian Monk? worked in the monastery greenhouse or bakery, or made stained glass for religious and commercial use, Groups were comprised of as many vegetarians from each location as were willing to volunteer. Two subjects from group I, one male and one female. and one subject from group II. were excluded from the study because of hyperlipidemia. Six subjects from group I were in the third trimester of pregnancy, and another six were postpartum and lactating. These twelve subjects are not included in group 1. but are reported separately. Two subjects from group II took diuretics _ Fronr rhe Lipid Research Center. Departments of Preventive Medicine and Medicine, Washingron. University School ofMedicine, St. Louis, Missouri. Supporwd in parr by NIH grams ROI HL 15308. HOI. HL 24743. and NHLBI contract NOI HV-2-2916L of the Lipid Research Clinics Program. D.R.L. is a recepienr (!f NIAMDD Training Grant in Nurrition 8%732-AM07226. Neceivedfor publicalion September 21. 1981. Address reprint requests fo Dennis Lock, M.D., Lipid Research Center. Department of Preventive Medicine, Washington University School of Medicine, St. Louis. Missouri. (~81982 bv Grune & Stratton. Inc. 0026-a495/82/3109-0011$01.00/0

917

918

LOCK

Table 1. Epidemiological Data GroupI Male

Female

Male

8

28

10



30 * 1

Age RBW

COtltrOl

0.94

29 + 1

+ 0.04.

1.03

33 t

+ 0.02t

1.24

Female 26 1

+ 0.09

31 + 1 1.14

f 0.05

Cigarettes

0

1

2

6

Hypertenswn

0

0

0

0

ASH0

0

0

0

0

Group II ”

Group III

10

RBW

1.06

B

18

56 2 3

Age

C0ntr0l

56 + 3

? 0.03

1.02

49

f 0.02

1.17

2 2 t 0.07

Cigarettes

0

0

2

Hypertension

2

0

0

ASH0

2

1

0

Results are means + 1 SEM. RBW = relative body weight ASHD

= atherosclerotic

lp

c 0.01.

tp

c 0.05.

for hypertension.

(reported/tdeal).

heart disease.

One took thyroid hormone replacement

These subjects were not hyperlipidemic

therapy.

and were not excluded from

this group. With these exceptions, none of the vegetarians or control subjects took any medications known to affect lipid levels. None of the group I subjects used alcoholic beverages. Among the monks, eight reported a sip of wine at daily communion,

and two

drank a glass of beer once weekly. Seven of the monks drank one glass of beer at their

annual

entirely. No information

about alcoholic intake was available for the

feasts.

Fourteen

monks abstained

control groups. Lipids were assayed by Auto-Analyzer

I! methods on isopropano!

extracts of whole plasma in the case of the control subjects and on extracts of lipoproteins and

heparin-MgC!,

Research Clinics (LRC) radioimmunoassay

prepared

precipitation

by the combined ultracentrifugal procedures

used by the Lipid

system.25 Ape E levels were measured by a

described previously.’

Data were entered into the SAS statistical analysis and management system.26 Group means and standard errors of the mean were calculated.

Two

tailed

nonpaired

t tests were used to determine

significant differences between means. RESULTS

The results of the nutritional histories revealed differences among the vegetarian groups (Table 2). Group I consumed virtually no cholesterol and ate fats

ET AL.

with extremely high P:S ratios, however total fat intake was similar to the average American diet.17 Groups II and III consumed low fat, low cholesterol diets with P:S ratios of - 1.O. Lipoprotein lipids are shown in Tables 3 and 4. Since only total lipids were measured in control plasmas, data from the LRC Prevalence Study** also are included for comparison. The control levels were not significantly different from the LRC reference group. In contrast, vegetarian cholesterols and triglycerides were IO-30 and 30-55 percent below the control and the LRC values. VLDL and LDL cholesterols were decreased 45-70 and I O-30 percent. HDL cholesterol was significantly decreased only in group I females. In groups II and III. use of wine in communion had no apparent effect on HDL cholesterol levels. Total cholesterol and LDL cholesterols were lowest in groups 1 and higher in groups II and III. Triglycerides and VLDL cholesterol did not follow this pattern. Pregnant vegetarians’ lipoprotein levels (Table 5) demonstrated the hyperlipemia of pregnancyz9-” relative to non-pregnant Farm (group I) women. Triglyceride levels were elevated to a greater extent than levels of cholesterol, and LDL and HDL were triglyceride enriched. Lactating Farm vegetarians had lower total triglycerides, lower VLDL cholesterol, and higher HDL cholesterol than group I females. No differences were found in lipoprotein triglycerides. The mean plasma apo E in controls was 3.6 mg/dl, similar to levels in normolipemic subjects reported by our laboratory’ and others.6,‘0 The mean level in vegetarians was 2.4 mg/dl. There were no significant differences among groups I, II, and III (Table 6). Pearson correlation coefficients were statistically significant for cholesterol vs apo E (r = .36, p < .005) and triglycerides versus apo E (r = .34, p < .Ol) for all non-pregnant and non-lactating vegetarians. There were no statistically significant correlations for cholesterol or triglycerides versus apo E for all controls. However, when all non-pregnant and non-lactating subjects were pooled, these correlations (cholesterol vs

Table 2. Nutritional Data Vegetarian

Total caloric intake

Diets

I

I

II

III

Average American Det

Male

[email protected]&3

Mate

Male

kef 27)

2,910

? 387

2,421

+ 156

13+

* 151

16 _t 1

14+

Fat I%)

43 Y! 3

41 * 1

Carbohydrate (%)

42 + 2

46 & 1

54 f 3



97 + 13 0.9 + 0.1

Cholesterol (mg/day) P:S Ratio

1

2.170

Protein 1%)

1

33 + 3

2,148

+ 134

19-c

1,971

1

16

35 * 2

38

46 ? 3 179 + 23 0.7 + 0.06

46 366 l

Diets of vegetarians were calculated from dietary recalls and other information obtained on site. Results are means f SEM.

lP:S ratios were not provided by the reference.” P:S ratios obtained from free living patients at the Washington University Lipid Research Clinic range from 0.2 to 0.7”

(unpublished observations).

919

APO E LEVELS IN VEGETARIANS

Table 3. Plasma Lipoproteins

Lipids of Residents of the Farm (Group 1) A. Males

Chol 135 i- 7. 9! 1*

Trig 57 * 7’ 27 f 5

LDL

a5 f 7’

20 +_2

HDL

42 r 3t

Total

Chol 137 * 4’

Total VLDL

-__ Referencq

Control

Vegetarian Chol 185 f- 8’

Trig

Tng

Chol

154 -r 15’

192 % 1 21 : 1

-

126 +_2

7*1

128 + 3 .._

46 + 1 E. Females

VLDL

7t

LDL HDL

Trig 53 -t 3.

Chol

Tug

Chol

Tug

178 f 5’

82 +_ 5’

171 t 1

75 t 1.0

1.

24 + 3

-

77 -f 4’ 49 k 2*

17+ 1 9+1

-

122

1

106 + 2 56 + 1

--

Results are in mg/dl mean k SEM.

lp

0.001,

tNS.

compared to reference value.

compared to reference value.

$Data from the LRC Prevalence Study (ref. 28).

apo E. r = .39, p C. .OOl; triglycerides vs apo E. r = .36, p c .002) were of similar magnitude and remained highly significant. Apo E levels did not correlate in a linear fashion with relative body weight, P:S ratio, or dietary intakes of cholesterol, fat, carbohydrate, protein or total calories. Further, to exclude the possibility that the vegetarians’ lower relative body weights might account for their lower apo E levels, the bottom quintiles for relative body weight of vegetarians (n = 13) and controls (n = 9) were compared. Although there was no statistically significant difference between mean relative body weights of the lowest vegetarian and control quintiles (0.90 + 0.01 vs 0.95 c 0.01). mean apo E levels of the lowest vegetarian quintile were 30 percent lower than mean apo E levels of the lowest control quintile (2.4 -tr 0.2 vs 3.3 + 0.4, p < 0.001). In addition. apo E levels of the lowest quintiles were not significantly different from those of the highest quintiles, either for the vegetarian or control population. Thus differences in weight were not responsible for the reduction in vegetarian apo E levels. Plasma apo E in pregnant vegetarians was elevated Table 4.

Plasma Lipoproteins

GroupII Chol Total VLDL

179 i 12t 6 ? 2’

LDL HDL

‘. tp sp ..

Tng

In this study the consumption of vegetarian diets was associated with 25%35% decreases in plasma apo E levels. Three independent groups of vegetarian subjects, each consuming 200 mg cholesterol or less daily, had equally reduced levels of plasma apo E. Nondietary causes for low apo E levels of these vegetarians are not likely, due to the large geographical, age and lifestyle differences among the three groups. Putative dietary factors responsible for the low apo E levels were not identified. It should be noted, however, that although the various vegetarian diets varied widely from each other with respect to P:S ratio and calories consumed as fat, carbohydrate, and protein, low cholesterol content was common to all three. In addition to the vegetarian diets. pregnancy also

Lipid Levels of Two Groups of Vegetarians

194 + lO$ 12 r If

122 t lO$

19 f 3

131 k 8

52 k 25

13 + 1

51+4§

0.001. all comparisons to reference group.

0.05.

§NS. TData from the LRC Prevalence Study (ref 28).

Monks

COntrOl Trig

Chol

68 r 6’ 39 r 6

0.005.

DISCUSSION

GroupIII

Results in mg/dl are means c SEM.

lp

to non-vegetarian levels (Table 6). This represents an increase of approximately 45 percent in the face of a three-to-fourfold rise in VLDL cholesterol and triglycerides and HDL triglycerides. There were no differences between group I females and lactating vegetarian apo E levels.

79 f 7’ 40 2 6 18 + 2 l5*

1

Chol 203 + 10%

Referencell Tug

120 + 15.89

Chol

Tng

213.9 21.6

f 1.0 i_ 1.1

141.4

* 2.2 __

145.8

f 2.1

_-

47.6

t 0.9

_-

920

LOCK

Table 5. Plasma Lipoprotein Lipids of Pregnant and Lactating

Table 6. Plasma APO E Levels of Vegetarians and Controls

Vegetarians

vegetarm

Pregnant

Lactating

In = 6)

Total

Group

In = 6)

Chol

Trig

Chol

Trig

186 i 9’

217 z37*

148 t 67

45 * 37

VLDL

26 2 6t

122 + 389

LDL

107 f 9$

59 t 7’

88 k 7n

HDL

57 + 3,

32 k 3’

56 + 23

4+

1n

ill

15 r 2’

Results in mg/dl are means + SEM. ‘P < 0.001. tp < 0.005, $p

<

0.01.

§p

<

0.02.

all compared to group

I females.

CCJntKl

I

Male

2.2 k o.2e8

Female

2.3 + 0.1 *28

3.7 + o.226

Total

2.2 +- 0.1 lJS

3.6 r 0.2

It

Group

18 + 47 9+

ET AL.

3.4 5 0.2’O

2.4 it 0.2*”

Group III

2.5 t lt’*

Total

2.4 + 0.1’64

Pregnant

3.6 _t 0.3&

Lactating

2.5 + 0.206

3.5 f o.38 3.6 + 0.1q6

Results are in mg/dl mean + SEM. Number of subjects indicated in parentheses.

flNS.

appeared to affect apo E levels. The increased apo E concentrations in pregnancy paralleled the rises in lipid levels.” The total-, HDL-, LDL-cholesterol levels of the present group of vegetarians were low confirming previous resu1ts,‘6m’9 but total triglycerides, VLDL lipids and HDL triglycerides were lower in the present group I subjects than in the Farm subjects in an earlier report.” The reason for these differences is unclear. Identical techniques were used to collect dietary information and to measure lipoprotein lipids in both studies. Yet the present diet appeared to contain 40 percent of calories as fat, contrasted with the 32 percent reported previously. This is due to large increases in intake of polyunsaturated fats, a factor known to lower trig1ycerides.32~35 The diet followed by Farm members may have changed between studies. Alternatively, since different Farm members participated in the two studies, two different vegetarian subpopulations may have been sampled. Nutritional information about the controls is limited. It could be argued that the average diet of this group may have differed from the average American

lp

<

0.001.

tp

<

0.01.

diet. However, this possibility is very remote. The controls were free living people who did not differ in general life style from other groups screened by the Washington University Lipid Research Clinic,” (unpublished observations). In addition, since lipoproteinls and apo E levels6.‘0 of the present control group are similar to those reported by other investigators in free living normolipemic adults. it is very likely that differences between vegetarians and this control group reflect differences between vegetarian diets and the average American diet. In summary, the apo E levels of vegetarians are lower than those of free living Americans. Given the physiologic role of apo E as a recognition marker for lipoproteins, the apparent modification of apo E metabolism by vegetarian diets may be important in mediating the possible effects of lipid lowering diets on atherogenesis. ACKNOWLEDGMENT We are

grateful for the able assistance of John Grundhauser,

coordinator,

data

Phyllis Anderson, secretary and the technicians of the

Lipid Research Center’s Core Laboratory

and RIA

Laboratory.

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921

APO E LEVELS IN VEGETARIANS

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