Generational effects of protein malnutrition in the rat

Developmental Brain Research, 15 (1984) 219-227 Elsevier

219

BRD 50088

Generational Effects of Protein Malnutrition in the Rat O. RESNICK and P. J. MORGANE

Worcester Foundation for Experimental Biology, Shrewsbury, MA 01545 (U.S.A.) (Accepted April 24th, 1984)

Key words: protein malnutrition - - generational effects of malnutrition - - brain serotonin - - brain 5-hydroxyindoleacetic acid - brain tryptophan --plasma non-esterified fatty acids - - brain weight in newborns - - body weight in newborns - brain growth and development - - malnutrition and developing brain

The most prevalent form of malnutrition in humans is characterized by its chronic and generational nature. We, therefore, have carried out preliminary studies in rats of the generational effects of protein malnutrition. Our studies to date indicate that a mild protein restriction (8% casein diet) in the first generation becomes a more severe protein restriction in the second generation. This is based on weight gains of the dams during pregnancy, the mean number of pups (F2) per litter, the mean pup (F2) body weight and brain weight at birth, growth curves, levels of brain tryptophan (TRP), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) from birth to weaning, and the levels of certain plasma constituents, especially non-esterified fatty acids (NEFA). We propose this paradigm as an animal model for some types of chronic undernutrition in socioeconomically underprivileged human populations. INTRODUCTION Z a m e n h o f et al. 16 have reported that brain underdevelopment caused by prenatal malnutrition in females of one generation (F1) can be transmitted to the next generation (F2), even in the absence of postnatal malnutrition of F 1. This has now been extended to well over 10 generations 17. They also reported learning deficits in the F 2 rats with malnourished grandmothers 2. Cowley and GrieseP found that one generation of nutritional rehabilitation was not sufficient to offset two generations of malnutrition. In addition, Stewart et al. 15, McLeod et al. 9 and Galler et al. 6 have also studied generational effects of malnutrition in animals using various dietary manipulations and experimental paradigms. The notion that the deleterious effects of undernutrition can be transferred to succeeding generations (even those that are well fed) through the mothers is worthy of attention. Also, animals who are continuously malnourished show progressively greater learning deficits across successive generations, that disappear after several generations of adequate feeding3. The implications of these findings are extremely

important, since the most prevalent form of malnutrition in humans is characterized by its chronic and generational nature. Since all of the above-mentioned studies manipulated the diets only of the females who were then mated with normal males, the dietary histories of females before mating may be very important. We, therefore, have undertaken preliminary investigations of the generational effects of protein malnutrition. The present studies indicate that a mild protein restriction (8% casein diet) in the first generation becomes a more severe protein restriction in the second generation. The implications of these findings are discussed. MATERIALS AND METHODS

Dietary and rearing conditions The diets and rearing procedures were the same as those previous.ly described 12. Briefly, virgin female albino S p r a g u e - D a w l e y rats, age 60-70 days (Charles River Laboratories) were fed isocaloric (4.3 kcal/g) diets containing either low (8% casein) or normal amounts (25% casein) of protein. This dietary paradigm was commenced 5 weeks prior to

Correspondence: 0. Resnick, Worcester Foundation for Experimental Biology, 222 Maple Avenue, Shrewsbury, MA 01545, U.S.A. 0165-3806/84/$03.00 © 1984 Elsevier Science Publishers B.V.

22O mating with a normally fed male and continued through gestation and lactation. A t parturition, each litter was culled to 8 pups and r a n d o m i z e d with other litters from dams fed the same diet and born on the same day. A f t e r weaning at age 21 days. the rats were housed 2 - 4 per cage and continued receiving their respective diets. Throughout the study all rats were given food and water ad libitum and maintained on a 12-h light:dark cycle (lights on from 07.00 to 19.00 h). Female rats, which were exposed either to the 8% (8El) or the 25% (25F1) casein diets in utero and postnatally, were m a t e d at 110 days of age with normal males. Studies were then carried out on the F, progeny. Brain dissection

Rats of either sex were used in this study. They were taken from the nursery room to an adjoining laboratory for sacrifice by guillotine between 1300 and 1500 h at ages 0 (birth), 5, 11, 16, 21 (weaning) and 30 days. The brains were rapidly r e m o v e d , frozen in liquid nitrogen, and stored at - 2 0 °C for subsequent analyses. The regional brain dissection procedure for the various age points was the same as previously described TM, with the maximum n u m b e r of regions (at days 21 and 30) consisting of the telencephalon, diencephalon, midbrain, pons-medulla and cerebellum. Plasma collection Blood from the trunk of each rat was collected into

measured by G e n e r a l Diagnostics Albustrate and Hycell Biuret procedures, respectively. Plasma samples were unfrozen for a minimum of time during all manipulations to prevent increases in the concentrations of N E F A and free tryptophan as a consequence of in vitro action of plasma lipase. Statistics

Evaluation of brain region data was by two-way analyses of variance ( A N O V A ) of diet by age (with repeated measures) for serotonin, 5 - H I A A and tryptophan at each of the 6 age points. When the d i e t age interaction was significant, individual post hoc t-test comparisons between 8F 2 and control groups were performed. Evaluation of diet effects on plasma tryptophan, N E F A , albumin and total protein were assessed by t-test at each age point. RESULTS Summary o f breeding results The weight gains of the F1 females during gestation, the summary of the F 1 breeding data and the growth of the F 2 offspring are summarized in Tables I-III. Ninety-two female rats (F 0 whose mothers were

fed an 8% or a 25% isocaloric casein diet fortified with methionine 5 weeks prior to mating and during gestation and lactation and which were maintained on the m o t h e r ' s diet upon weaning, were m a t e d at 110 days of age with normal males. A t this time, the

individual chilled tubes with heparin, immediately centrifuged at 10 °C, and the plasma stored at - 2 0 °C.

TABLE I

Biochemical methods Serotonin, 5 - H I A A and tryptophan were deter-

Time interval

mined in each brain sample by previously described spectrofluorometric procedures 11. Plasma tryptophan was measured by the p r o c e d u r e of D e n k l a and Dewey5 in each rat on whole plasma (total tryptophan) and on a sample (50-100 #1) of plasma ultrafiltrate (free tryptophan) p r e p a r e d by centrifuging 0.15-0.3 ml plasma at p H 7.49 in A m i c o n ' s Micropartition system MPS-1 m e m b r a n e cells at 1500 g for 15 min. Plasma N E F A were assayed using the method of Laurell and Tibbling s. A l b u m i n and total protein concentrations in each plasma sample were

Weights of the 8F1 and 25F1females during gestation and lactationa

Initial weights b Pregnancy 1 week 2 weeks 3 weeks Lactation 1-2 h postpartum 1 week 2 weeks 3 weeks

Diet groups

8F~

25F~

153 + 5c (20)

274 _+7 (24)

172 + 5c (18) 196 _+7c (18) 240 + 8~ (18)

290 _+8 (17) 329 _+ 11 (17) 401 + 14 (17)

184 + 6c (18) 168 _+5c (18) 166 + 8c (18) 178 + 9~ (18)

327 + 12 (17) 324 _+ 12 (17) 319 + 14 (17) 315 + 20(17)

Breeding number 63. b Mean weight + S.E. c p < 0.001 for 8F 1females vs 25% females; two-tailed t-tests.

221 8F 1 female rats had b o d y weights that were 44% lower than the 25F 1 females (153 g vs 274 g) m a i n t a i n e d on the 25% casein diet during the same time interval. This degree of weight deficit ( a p p r o x i m a t e l y 40%) persisted in the 8F 1 dams t h r o u g h o u t their pregnancy. Consequently, just prior to parturition their b o d y weights averaged 240 g, whereas their normal counterparts averaged 401 g (Table I). The n u m b e r of 8F 1 females giving birth was the same as with the control 25F 1 dams. H o w e v e r , the mean n u m b e r of pups (F2) p e r litter was significantly lower in one breeding and showed a non-significant trend to be lower in a second breeding. The mean pup (F2) body weight and brain weight at birth were significantly lower than those seen in the control groups (Table II). This is in contrast to our observation 12 that young, female rats fed the 8% casein diet 5 weeks prior to mating with n o r m a l males and during gestation, show a normal weight gain during pregnancy. In addition, the n u m b e r of females giving birth, the mean n u m b e r of pups p e r litter, the m e a n pup b o d y weight and brain weight at birth are essentially the same in both the 8% casein derived pups (8F1) and the 25% casein derived pups (25F1). The 8F 2 rats had significantly lower b o d y and brain weights c o m p a r e d to their well-nourished counterparts during postnatal d e v e l o p m e n t (Table III). TABLE II Summary ofF 1 breeding data Variable

8% Casein diet

Number of females mated (F1) Br. 63 20 Br. 66-67 18 Number of litters born (F2) Br. 63 18 Br. 66-67 13 % Females giving birth (F 1 Br. 63 90% Br. 66-67 72% Number of pups/littera (F2) Br. 63 9.2 + 0.3 b Br. 66-67 11.0 + 0 Pup weight at birtha (F2) Br. 63 5.40 + 0.10¢ (166) Br. 66-67 5.29 + 0.13c (143) Brain weight at birth (F2) Br. 63d 235 + 9b (8)

25% Casein diet 24 30 17 20 71% 67% 11.7 + 0.9 12.0 + 1.0 6.14 + 0.14 (199) 6.44 + 0.85 (234) 265 + 8 (8)

a Mean + S.E. b p < 0.01. c p < 0.001; for 8% vs 25%, two-tailed t-tests. d One litter from Br. 63 sacrificed for brain weights.

80 I hl

ca

701

+1

60

~

FI Generation

Z <

50

~:]

F2 G e n e r a t i o n

Body Growth ,

I~

-1-

.-~

35

I

25

LU

20

VA

10

VA , ~

Q O

~

~

vr AA

0

v.~

uJ

~

FI Generation

44 2 o o 0

~

F2 G e n e r a t i o n

Brain Growth

Z 1800 ; 1600 A

1400

I-- IOO0

~

__Z 4 0 0

/~

/

*

800

;<

~

//

FI

F2 0

FI

F2

FI V2

5

•~ p < o . 0 5 for 8% FI RATS

I I vs.

FI

F"2

FI

I6

21

F2

VI

F2

30

A G E IN DAYS 8% F2 RATS, TWO-TAILED t - T E S T

•~ "~ p
Fig. 1. Body and brain growth in 8F2 and 8Fv

These rats continued to exhibit e x t r e m e emaciation even after weaning at day 21. The brain growth of the 8F 2 pups was not as severely affected as their b o d y weights, demonstrating the brain sparing effects. A t weaning (day 21) there was a 73% reduction in body weight and only a 26% reduction in brain weight of the 8F 2 offspring as c o m p a r e d to the controls. A t 30 days of age, there was a 71% reduction in b o d y weight and a 23% reduction in brain weight of the 8F 2 offspring as c o m p a r e d to the controls. It can be seen in Fig. 1 that at all age points studied, the b o d y and brain weights of the 8F 2 rats were significantly less than those of the 8F 1 rats, except on day 16. Ontogeny o f brain tryptophan, serotonin and 5 - H I A A The d e v e l o p m e n t a l alterations in regional brain serotonin, 5 - H I A A and t r y p t o p h a n concentrations are summarized in Table IV. The o u t c o m e of individual brain region comparisons are d e n o t e d by asterisk superscripts. F o r all diet factor comparisons,

222 T A B L E III

Growth of the 8Fe and the control offspring~ Age (days): Diet (n)

0 (Birth)

5

." 8% (8)

Body weight (g) Brain weight (mg)

25% (8)

4.96 + 0.18 c 235 ± 9 b

6.4 ± 0.2 286 ± 11

1]

8% (8)

25% (8)

8% (8)

25% (8)

8.50 ± 0.20 ~ 533 ± 19c

14.8 + 0.3 683 + 17

11.40 ± 0.20 ~" 972 ± 23 c

31.8 ± ].9 1361 ± 17

a Mean weight ± S.E. b P < 0.01 c p < 0.001, for 8F 2 pups vs 25F 2 pups, two-tailed t-tests. the 8F 2 rats had significantly (P < 0.001) higher se-

areas

rotonin,

and the cerebellum

5-HIAA

and

tryptophan

concentrations

the 8F 2 rats compared

than the control animals. The regional brain analyses for the amine, metabolite tions show

that

the

and precursor

telencephalon,

midbrain

and

pons-medulla)

all h a d s i g n i f i c a n t e l e v a t i o n s

in

to the controls.

As part of the adaptive metabolic responses to pro-

concentra-

the

(diencephalon,

tein deprivation,

brainstem

t h e 8F2 r a t s d i s p l a y e d s i g n i f i c a n t i n -

T A B L E IV

Ontogenetic development of 5-HT, 5-HIAA and TRP in 8F2 and control rats Age (days) : 0 (Birth) Diet (n)

11

5

: 8% : (8)

25% (8)

8% (8)

25% (8)

8% (8)

25% (8)

Brain region Mean serotonin concentration ± S.E. (ng/g) WB a Tel Dien Mid Cereb P-Mb. c (ANOVA)

833 ± 17d 757 ± 43 d

384 + 29 329 ± 32

623 ± 17d 448 ± 14d

311 ± 10 232 ± 12

767 ± 14d 546 ± 18d 1101 ± 56 d

356 ± 17 246 ± 22 572 ± 23

913 ± 31 d

462 ± 38

896 ± 33 d

425 ± 31

1139 ± 40d

502 ± 38

8 > 25

8 > 25

8 > 25

Mean 5-hydroxyindoleacetic acid concentration ± S.E. (ng/g) WB a Tel Dien Mid Cereb P-M b,c (ANOVA)

1154 ± 41 d 1121 ± 75 d

546 ± 43 524 ± 54

934 ± 61 d 665 ± 25 d

399 ± 15 315 ± 30

918 ± 24 ~ 647 ± 31 d 1221 ± 37 d

1196 ± 57 d

574 ± 46

1356 + 144 d

519 + 26

1479 + 71 d

8 > 25

8 > 25

Mean tryptophan concentration ± S.E. (ng/g) WB a Tel Dien Mid Cereb p-M b.c (ANOVA) a b c d

425 ± 21 287 ± 17 673 ± 29

662 + 42 8 > 25

18680 ± 521 d 19645 ± 1091 d

8785 + 337 8508 ± 598

9892 + 221 d 9193 + 301 d

1476 + 105 1418 + 83

6304 + 235 d 5910 + 236 d 7077 + 386 d

2747 + 142 2405 + 136 2711 + 190

17764 ± 591 d

9163 ± 425

11005 + 453 d

1565 + 153

6763 + 295 d

3572 + 328

8 > 25

8 > 25

8 > 25

Abbreviations: W B , whole brain; Tel, teleneephalon; Dien, diencephalon; Mid, midbrain; Cereb, cerebellum; P-M, pons-medulla; A NO~ Consists of hypothalamus, midbrain, ports-medulla and cerebellum at age 0 and 5 days. Consists of midbrain, pons-medulla and cerebellum at age 11 and 16 days. p < 0.001; two-tailed t-tests.

223

16

21

30

8%

25%

8%

25%

8%

25%

(8)

(8)

(8)

(8)

(8)

(8)

31.50 ± 1.10 ~ 1403 ± 27 c

108.6 ± 3.4 1828 ± 47

15.80 ± 0.30 ~ 1276 ± 35 c

45.6 ± 0.7 1520 __+26

18.60 ± 0.61Y 1344 ± 29¢

69.9 + 1.0 1815 ± 21

observed during the remainder of the study. The increases in amine levels in the 8F 2 pups were seen in all brain regions examined, indicating that both the perikarya and the terminals of the serotonin-containing neurons were equally affected by protein in-

creases in brain indoleamine levels at all ages examined. For example, at birth the brain 5-HT levels of the 8F 2 pups were markedly higher than those seen for the control rats. Marked elevations in regional brain 5-HT of these rats vs the normal animals were

16

21

30

8%

25%

8%

25%

8%

25%

(8)

(8)

(8)

(8)

(8)

(8)

654 ± 21 d 518 ± 32 d 1022 ± 44 d

413 ± 22 305 ± 31 756 ± 33

781 ± 37 d

535 ± 26

810 ± 491 ± 1579 ± 1800± 516 ± 1751 ±

330 26 d 76 d 690 220 154a

8 > 25

379 ± 266± 736 ± 770 ± 229 ± 696 ±

7 8 51 4 18 23

930 540 1625 1953 584 1877

± ± ± ± ± ±

130 110 31 d 51 d 20 d 330

8>25

1124 ± 54 d 657 ± 26 d 2061 ± 1160

415 ± 24 297 ± 32 734 ± 30

1801 ± 1540

577 ± 25

1001 616 1888 2360 712 1996

± ± ± ± ± ±

25 d 39 a 1330 2500 470 1480

8>25

2865 ± 164 2677 ± 196 3188 ± 237

10162 ± 1241 d

3244 ± 126

7693 6721 9208 9142 8884 8988

8 > 25

~e of diet factor in analysis of variance at each age.

± ± ± ± ± ±

462 289 845 1024 367 912

392 d 554 d 688 d 777 a 469 d 499 d

± ± ± ± ± ±

6 8 52 29 15 17

7 12 34 38 23 24

1139 665 2031 2481 776 2153

± ± ± ± ± ±

200 12d 79 d 87 d 20 d 44 a

430 250 747 919 398 912

± ± ± ± ± ±

8 14 43 41 10 25

8 > 25

3040 ± 2790± 3677 ± 3153 ± 3546 ± 3224 ± 8 > 25

± ± ± ± ± ±

8 > 25

8 > 25

8787 ± 787 d 8475 ± 8520 8369 ± 478 d

373 259 606 643 321 728

38 63 232 172 134 118

8437 7577 9432 9892 8836 9852

± ± ± ± ± ±

81 d 125 d 144a 138a 120d 222 a

3090± 2870 ± 3138 ± 3794 ± 3205 ± 3796 ± 8 > 25

70 109 118 202 211 142

224 adequacies during the fetal and postnatal periods of

er, since it is the a m o u n t of T R P not b o u n d to plasma

development. Interestingly, the 8F 2 rats had signifi-

albumin (the free fraction) that determines the avail-

cantly higher values for brain 5-HT, 5 - H I A A and tryptophan at all ages examined compared to the 8F 1

ability and utilization of this amino acid by the brain rather than its total circulating levels 7, the significant

rats ~.

elevations for the free plasma T R P levels of the 8F2 pups at all ages explains the corresponding increases

The significant increases in brain 5-HT levels in the 8F 2 rats were accompanied by equally high values for

in their brain T R P levels.

its metabolite ( 5 - H I A A ) at all ages examined. The brain amine and metabolite displayed the same de-

DISCUSSION

velopmental pattern in response to the nutritional brain 5 - H I A A of the 8F 2 rats were greater than the

These data explain why the free plasma T R P levels were increased in the 8F 2 rats. Since free T R P avail-

normal rats through 30 days of age. Moreover, the

ability depends on the molar ratio of b o u n d T R P to

brain 5 - H I A A levels of the 8F 2 rats were significantly higher than those seen in the 8F1 rats from birth

ALB 10, the severe h y p o a l b u m i n e m i a of the 8F 2 rats

status of the 8F 2 rats. Consequently, the regional

through 30 days of age u. The brain T R P levels of the 8F 2 rats were significantly higher than those seen in the 8F1 ratsl~. Ontogeny o f p l a s m a constituents

The ontogenetic changes in plasma tryptophan, non-esterified fatty acids, albumin and total protein concentrations are illustrated in Table V. As these data indicate, the developmental alterations seen for the total plasma T R P levels of the 8F 2 rats do not follow the pattern observed for their brain values of this amino acid. Although the total a m o u n t of T R P in the plasma of these rats was significantly higher than in the control rats on days 0 - 8 of lactation, their total plasma T R P values became markedly lower vs the controls during the remainder of the study. Howev-

vs the controls (except on days 0 and 16) caused marked decreases in this ratio for the former group. More importantly, the decreases in the T R P : A L B ratios of the 8F 2 rats were due to the significant increases in the plasma N E F A levels of these animals at all ages. Because T R P and N E F A compete for the same binding sites on ALB, with the latter being a stronger binder than the former 4, increased N E F A levels prevent T R P from successful competition for binding sites on the ALB molecule. This resulted in more T R P in the free form in the plasma of these rats and thus available for transport into the tissues 11. Interestingly, these conditions of extreme hyperlipolysis and h y p o a l b u m i n e m i a seen for the 8F 2 rats have been noted in both the h u m a n smali-for-gestational age (SGA) n e o n a t e and marasmic infant as part of their peripheral metabolic adaptations to severe in

TABLE V Ontogenetic development of plasma constituents in 8F2 and control rats Age (days):

0 (Birth)

5

11

25% (8)

8% (8)

25% (8)

8% (8)

25o/(. (8)

Mean concentration ++_S.E. (pg/ml) Total tryptophan 17.50 + 0.04a Free tryptophan 17.00 _+0.03a Percentage free 97.13 4- 0.09a

10.32 + 0.40 9.63 + 0.36 93.25 _+ 1.08

8.96 + 0.06~ 7.27 + 0.06a 81.18 4- 0.38a

3.29 + 0.26 1.73 + 0.15 53.37 + 4.11

7.39 + 0.99a 5.00 _+0.03a 66.83 +_0.94a

10.32 _+0.22 3.72 + 0.16 36.03 _+1.43

Mean concentration +_S.E. (¢teq/ml) NEFA 0.67 _+0.01a

0.15 _+0.02

0.55 _+0.03"

0.14 + 0.03

0.89 + 0.02a

0.27 + 0.04

Mean concentration +_S.E. (mg/ml) Total protein 51.63 + 0.57 Albumin 6.22 + 0.08 Percentage albumin 12.04_+0.12

56.63 + 3.63 5.83 + 0.79 10.53 _+ 1.18

25.90 + 0.79 8.68 + 0.06a 33.69 + 0.92~

31.44 + 2.02 13.56 + 1.01 43.73 _+3.31

50.15 _+0.21 13.50 _+0.13a 26.93 + 0.29a

53.55 _+ 1.99 33.19 + 1.53 62.65 _+3.90

Diet (n)

: 8% : (8)

P < 0.001 for 8F2vs 25F2 rats; two-tailed t-tests.

225 utero or postnatal undernutrition. In particular, the hyperlipolysis of adipose tissue in malnourished humans or rats indicates inadequate energy, which is compensated for by the conversion of NEFA to ketone bodies. Also, while both species react to nutritional deficiency by withdrawing their essential amino acids from tissues to the liver to maintain homeostasis, the amount of albumin synthesized by the liver remains significantly lower than normal until they receive a sufficient amount of protein in their diets. Finally, it can be seen that the 8F 2 rats showed no differences in plasma total protein until day 21, from which time the levels were markedly decreased. We have previously reported 13 that young, virgin female rats fed an 8% casein diet 5 weeks prior to mating and during gestation showed a normal weight gain during pregnancy. The number of females giving birth, the mean number of pups per litter and the mean pup body weight and brain weight at birth were essentially the same in the 8% casein and the 25% casein (controls) diet groups. We now report that the 8 F 1 female rats showed a decreased weight gain during gestation. In addition, the mean pup (8F2) body weight and brain weight at birth were significantly lower than those seen in the 8F 1 pups. At all age points studied (except day 16), the body and brain weights of the 8F 2 rats nursed by the 8F 1 dams were significantly less than those of the 8 F 1 r a t s . Also, these 8F 2 rats had significantly higher values for brain 5-HT, 5-HIAA and TRP and plasma NEFAs at all ages examined compared to the 8 F 1

16

rats. The nutritional inadequacies incurred after one generation of protein deprivation (8F 1 dams) had a more noticeable effect on their offspring. Consequently, by day 11 of lactation the 8F 2 pups displayed the failure-to-thrive syndrome associated with the onset of infantile marasmus (>60% reductions in weight-for-age). These rats continued to exhibit a condition of emaciation after weaning (day 21). Thus, their body weights at 30 days of age were equal to those seen in the normal pups at 11 days of age. Several interesting points emerge from the results of these studies. First, the 8F 2 rat progeny displayed the same responses as humans to severe intergenerational malnutrition at all ages examined. Not only could they be categorized as low birth weight, but with the additional insults of unsatisfactory postnatal nutrition added to their poor gestational development, the 8F 2 pups also developed many of the typical signs of infantile marasmus. Moreover, the marasmic condition that developed in these pups during infancy persisted in the rats beyond the lactational period. Even as juveniles (30 days of age) or adults (data not shown) when they had ad libitum access to the 8% casein diet, they showed the severe growth retardation and emaciation which delineates chronic malnutrition. Such findings of short stature, low body weights, and sparse subcutaneous fat deposits in the mature 8F 2 rats allows them to be considered as comparable models to humans from low socioeconomic communities where undernutrition is intergenerational.

21

30

8%

25%

8%

25%

8%

25%

(8)

(8)

(8)

(8)

(8)

(8)

7.55 + 0.11 6.24 + 0.09 a 83.94 + 1.98 a

7.82 + 0.80 1.92 + 0.21 26.21 + 4.14

8.57 + 0.11 a 5.92 + 0.16 a 69.08 + 1.76 a

16.96 + 0.37 2.48 + 0.20 14.72 + 1.38

7.58 + 0.15 a 6.02 + 0.06 a 72.11 + 1.25 a

16.93 + 1.04 2.06 --- 0.09 12.45 _-+ 0.86

0.91 _+ O.02a

0.31 + 0.02

0.94 + 0.01 a

0.44 + 0.03

1.48 + 0.07 a

0.53 --- 0.04

49.36 + 3.41 15.94 + 2.03 32.07 + 2.54

32.79 + 0.57 a 25.83 + 0.39 a 78.94 + 2.00

63.99 + 3.19 47.33 + 1.04 74.90 + 3,33

35.93 + 0.72 a 24.39 ___0.85 a 68.21 + 3.34

59.33 --- 1.26 42.30 +_- 2.29 71.38 + 3.78

46.37 + 0.32 16.76 + 0.09 36.14 + 0.25

226 It becomes a p p a r e n t from Table IV that the significant elevations in brain amine and metabolite levels of the 8F 2 rats were the result of metabolic adaptations, which increased the availability of the precursor amino acid to their brain. This greater precursor availability resulted in the 8F2 rats having significant increases for their regional brain T R P levels at all ages examined. Also, the d e v e l o p m e n t a l pattern shown for the brain 5-HT and 5 - H I A A levels of these animals could be related to the corresponding fluctuations in their brain T R P levels at these time points. Interestingly, although turnover studies have not yet been p e r f o r m e d on the conversion of T R P to 5-HT in the brains of either group, calculations using the steady state levels given in Table IV indicated that the ratios of brain 5 - H T / T R P in the 8F 2 and the control rats were a p p r o x i m a t e l y the same throughout development. Consequently, the greater availability of T R P in the brains of the 8F 2 rats does not seem to be utilized only for the manufacture of indoleamines. Rather, since the availability of T R P to tissues m a y be a limiting factor in protein synthesis during early d e v e l o p m e n t 1, the higher amounts of T R P in the brains of the 8F 2 rats may represent a c o m p e n s a t o r y mechanism favoring brain protein synthesis and thus may contribute to the brain sparing seen in these nutritionally deprived animals. In terms of the metabolic adaptations shown by these rats to chronic nutritional insults, their re-

sponses were equally typical of the S G A or marasmic human. Their conditions of hyperlipolysis, hypoalbuminemia, and alterations in peripheral T R P availability have been noted in both the S G A neonate and marasmic infant as part of their metabolic adaptations to severe in utero or postnatal undernutrition 12 In particular, the hyperlipolysis of adipose tissue in chronically malnourished humans or rats indicates the lack of a d e q u a t e energy which is c o m p e n s a t e d for by the conversion of N E F A to ketone bodies to fulfill their energy needs. Also, while both species react to severe postnatal nutritional insults by withdrawing their essential amino acids from circulation to the liver to maintain homeostasis, the amount of albumin synthesized by the liver in either species remains significantly lower than normal until they receive a sufficient amount of protein in their diets. H o w e v e r , it is not known whether these peripheral metabolic responses to undernutrition in humans cause the same impairments in their central nervous system neurochemistry as those found in the 8F 2 rats, since no measurements of brain indoleamine levels have been r e p o r t e d on children who died from either in utero or postnatal malnutrition.

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ACKNOWLEDGEMENT S u p p o r t e d by G r a n t HD-06364 ( N I C H H D ) .

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