EFFECTS OF CHRONIC ALCOHOL EXPOSURE ON GROWTH AND NUTRITION IN RATS*

Jack Wang, Mark Marvin, Bruce Abel, and Richard N. Pierson, Jr. Body Composition Unit Department of Medicine

St. Luke’s Hospital Center Columbia University

New York, New York 10025

Effects of chronic alcohol exposure on growth and development and on organ pathology have been studied in experimental animals since 1868.1-2 It is also well known that malnutrition is a concomitant of alcoh0lism.~~5 Whether the lesions associated with alcohol are caused by alcohol alone or are associated with malnutri- tion has remained unclear. The effects of alcohol consumption per se on nutrient intake have not been studied. In this study, rats were given 20% ethanol as the only water source to compare growth and nutrient intake with control and isocaloric malnutrition animals for 22 weeks. Nine additional weeks of recovery period after the ethanol exposure were studied t o investigate the reversibility of the damage caused by either alcohol exposure or malnutrition.

MATERIALS AND METHODS

Ninety-seven male Sprague-Dawley rats, 120 f 10 g and 5-6 weeks old, were used. Rats were grouped into control (32), ethanolic (32), and isocaloric malnutrition (33) randomly. Rats in the isocaloric malnutrition group were separated, one per cage, to avoid uneven food consumption or cannibalism. The alcohol group was exposed to 20% ethanol as the sole water source and regular rat chowt ad lib. The isocaloric malnutrition rats (termed “starvation rats”) were fed tap water ad lib. and a diet of rat chow isocaloric to that actually consumed by the alcohol rats. The exact amount of rat chow administered to starvation rats, F, is calculated as follows:

F = & +fE’ where F is measured in g/rat/day, fA is the average chow intake (g/rat/day) from ethanol groups from the previous day, j E = 0.2 E (7.00/4.25) a calorie conversion factor, and E is the volume of 20% ethanol consumed. Rat chow contains 4.25 kcal/ g, and pure ethanol contains 7.00 = kcal/g.h Ethanol consumption and dietary control were terminated after 22 weeks, and all rats were fed tap water and rat chow ad lib. for 9 weeks. Control groups were fed with tap water ad lib. throughout the study period.

RESULTS

Body weight increase in the three groups is illustrated in FIGURE 1. Normal weight gain occurred in the control rats. Ethanolic rats showed less weight gain than either control or starvation rats after 8 weeks of alcohol consumption. By 22 weeks,

*Supported by the John A. Hartford Foundation. tPurina Lab Chow that contained 23.4% protein, 4.5% fat, and 4.25 kcal/g gross energy.

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206 Annals New York Academy of Sciences

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0 2 4 6 8 10 12 14 16 1E 20 22 24 26 28 30 WEEKS OF CONTROLLED DIET RECOVERY

FIGURE I . Effects of alcohol and starvation on body weight growth.

normals weighed 386 f 12 g, starvation rats weighed 338 i 16 g, and ethanolic rats weighed 264 f 19 g. Each difference was statistically significant (p < 0.01). In the recovery period, ethanolic rats showed rapid weight gain in the first 4 weeks but did not match the final weight of the controls a t 9 weeks. The starvation rats caught up to control weight levels by 6 weeks of recovery.

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FIGURE 2. Effects of alcohol and starvation on calorie intake.

W a n g et al.: G r o w t h & Nutri t ion 207

Calorie intake, expressed in kcal/ rat/ day, 7 days averaged, is shown in FIGURE 2. A close correlation with weight increase is seen between ethanolic and control rats, but ethanolic rats consumed about 70% of the calories taken by control rats during the alcohol consumption period. During recovery, ethanolic rats increased calorie intake to match control levels within 2 weeks. Starvation animals maintained on the average a 15% lower calorie intake throughout the recovery period.

Fluid intake is illustrated in FIGURE 3. Similar in pattern to calorie intake, an increase occurred continuously through the first 7 weeks in all three groups and was then maintained a t a steady level. However, ethanolic and isocaloric starvation animals consumed 47 and 70%, respectively, of control levels during the first 22 weeks of the study period. During recovery, water intake by ethanolic rats increased to the control level in the first week and subsequently surpassed the control level by 20-25%. There was no significant change within the control or starvation groups.

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 WEEKS OF CONTROLLED DIET RECOVERY

FIGURE 3. Effects of alcohol and starvation on fluid intake.

FIGURE 4 shows that the ratio of dry food to fluid intake was higher in ethanolic rats than in control and starvation groups during the 22 weeks of the study period. The ratio decreased rapidly to well below control levels during recovery.

Observations of the ethanolic rats revealed some noteworthy phenomena in contrast to the control rats. Fur became dry and rough in all alcoholic rats. Seven spontaneous deaths occurred in 32 animals, or 22%, compared with no deaths in the other groups. A staggering gait and marked slowing of physical activity were observed in 6-10 rats by 12 weeks of alcohol consumption, and these phenomena were progressive. Red conjunctivae and tearing of the eyes were common in the ethanolic group.

Starvation animals were irritable and hyperactive. Fur changes also occurred in these rats, characterized by reddening of the hair on top of the head and by patchy baldness distributed throughout the body. These changes occurred at 4-7 weeks and cleared spontaneously a t about 14 weeks.

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The average nutrient intake per 100 g of rat weight is summarized in TABLE 1. There was no significant difference in calorie intake among the three groups during the study period. During recovery, ethanolic rats consumed more calories (25.3 i 0.4 kcal/ 100 g body weight) than controls (p < 0.05) and starvation rats (p < 0,001). However, fluid intake, 6.7 * 1.2 ml/ 100 g, was only about 50% of control and starvation group levels (p < 0.001) during the study period. Fluid consumption in this group doubled during recovery, reaching levels higher than control and starva- tion groups (p < 0.05). The ratio of solid foodifluid intake was higher in ethanolic rats (0.64 f 0.06, p < 0.05) during the study period but decreased during recovery to 0.48 f 0.07. There was no significant change in this ratio in control and starvation groups, which remained a t 0.5 1 f 0.04. All rats were immature at 5-6 weeks of age, when the study began. Total food consumption was therefore highest in the first 8 weeks of the study, when calculated in rat chow per body weight. Thus, all food intake figures, including those for the control group, show greater food intake during the rapid growth phase than at maturity, which coincided with the recovery period.

DISCUSSION

Patients who receive more than 20% of their daily calorie requirements from alcohol are described as alcoholic.6 Our data show that ethanolic rats were indeed “alcoholic,” by this definition consuming 33 f 4% of daily calories as ethanol. In this study, unlike those of previous workers,4J alcohol consumption was separated from food intake. By contrast, others have combined ethanol with a formula diet, thereby linking ethanol ingestion to food intake. In the current study, rats were allowed to set their own level of food intake independently, at whatever level the ethanolic state permitted, without increasing total alcohol intake. This experimental design there-

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210 Annals New York Academy of Sciences

fore separates the effects of starvation from those of alcohol alone: the caloric malnutrition of the ethanol exposed rats was indeed caused by the ethanol.

The age-weight plots of normal and ethanolic rats (FIGURE I) in this study are similar to those in previous reports from our laboratory8 and others.ss6 Artificial diets have been used to match the caloric reduction associated with ethanol consump- tions-’ in paired control experiments. The isocaloric balanced diet was designed to separate the effects of alcohol consumption from those of caloric semistarvation. Our data clearly show that rats who receive one third of their calories as ethanol gain weight more slowly than either ad lib. controls or isocaloric controls. Further, alcohol-exposed rats failed to recover in 9 weeks of normal diet, although starvation controls did so completely. This “deficit” in growth is of special interest, because total calorie intake normalized to body weight in ethanolic rats was higher than that in the control group. Calorie wasting is thus indicated, although the nature of the energy wasting is not known. This suggests that the growth retardation of alcoholism is not solely due to caloric malnutrition, the effects of which are less severe and are subject to more rapid and more complete recovery. The toxic effects of ethanol on growth were followed by some recovery but a t a slower rate, which fell short of catch up in 9 weeks.

The present results confirm the findings in earlier studies that alcohol preference of rats is relatively ~OW,~.’O with tap water chosen over 20% ethanol.11 Our data, particularly the ratio of solid food/ fluid, show that ethanolic rats consumed 50% less fluid than did the controls. Dehydration caused by ethanol exposure has been suggested as a factor in weight loss in anirnals.II Our data are consistent with Porta and Gomez-Dunn’s hypotheses5 that the rat regulates caloric intake by relating solid food to fluid consumption.

In the recovery period, increased fluid intake is associated with increased food intake and weight gain, in both ethanolic and starvation cohorts. Recovery is more rapid after starvation than after ethanol, which suggests that a toxic effect of ethanol persists, limiting both rate and extent of recovery. Essig’s’2 suggestion that ad lib. water consumption after a period of ethanol intake results in overhydration was not confirmed in the present study; the postethanolic polydipsia of the ethanolic rats was also measured in this study, but the total weight gain was less than that in the starvation control group.

Reduced total fluid intake and parallel reduction in food intake in the ethanolic cohort suggest that rats have a distaste for alcohol, consume it only to avoid severe dehydration, and never gain habituation in 22 weeks. These conclusions confirm the findings of Wize.I3 Failure of rats to achieve addiction to ethanol has been recognized previously and mitigates against use of the rat model for study of the psychologic dimensions of alcoholism.

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