Effects of maternal dietary protein restriction on growth of the brain and body in the rat

Ergot alkaloid exposure during gestation alters: 3. Fetal growth, muscle fiber development, and miRNA transcriptome1

The objective of this study was to assess how exposure to ergot alkaloids during 2 stages of gestation alters fetal growth, muscle fiber formation, and miRNA expression. Pregnant ewes (n = 36; BW = 83.26 ± 8.14 kg; 4/group; 9 groups) were used in a 2 × 2 factorial arrangement with 2 tall fescue seed treatments [endophyte-infected (E+) vs. endophyte-free (E-)] fed during 2 stages of gestation (MID, days 35 to 85 vs. LATE, days 86 to 133), which created 4 possible treatments (E-/E-, E+/E-, E-/E+, or E+/E+). Ewes were individually fed a total mixed ration containing E+ or E- fescue seed according to treatment assignment. Terminal surgeries were conducted on day 133 of gestation for the collection of fetal measurements and muscle samples. Data were analyzed as a 2 × 2 factorial with fescue treatment, stage of gestation, and 2-way interaction as fixed effects. Fetuses exposed to E+ seed during LATE gestation had reduced (P = 0.0020) fetal BW by 10% compared with E- fetuses; however, fetal body weight did not differ (P = 0.41) with E+ exposure during MID gestation. Fetuses from ewes fed E+ seed during MID and LATE gestation tended to have smaller (P = 0.058) kidney weights compared with E- fetuses. Liver weight was larger (P = 0.0069) in fetuses fed E- during LATE gestation compared with E+. Fetal brain weight did not differ by fescue treatment fed during MID (P = 0.36) or LATE (P = 0.40) gestation. The percentage of brain to empty body weight (EBW) was greater (P = 0.0048) in fetuses from ewes fed E+ fescue seed during LATE gestation, which is indicative of intrauterine growth restriction (IUGR). Primary muscle fiber number was lower (P = 0.0005) in semitendinosus (STN) of fetuses exposed to E+ during MID and/or LATE gestation compared with E-/E-. miRNA sequencing showed differential expression (P < 0.010) of 6 novel miRNAs including bta-miR-652_R+1, mdo-miR-22-3p, bta-miR-1277_R-1, ppy-miR-133a_L+1_1ss5TG, hsa-miR-129-1-3p, and ssc-miR-615 in fetal STN muscle. These miRNA are associated with glucose transport, insulin signaling, intracellular ATP, hypertension, or adipogenesis. This work supports the hypothesis that E+ tall fescue seed fed during late gestation reduces fetal weight and causes asymmetrical growth, which is indicative of IUGR. Changes in primary fiber number and miRNA of STN indicate that exposure to E+ fescue fed during MID and LATE gestation alters fetal muscle development that may affect postnatal muscle growth and meat quality.

The effects of dietary protein restriction on chorda tympani nerve taste responses and terminal field organization

Prenatal dietary sodium restriction produces profound developmental effects on rat functional taste responses and formation of neural circuits in the brainstem. Converging evidence indicates that the underlying mechanisms for these effects are related to a compromised nutritional state and not to direct stimulus-receptor interactions. We explored whether early malnourishment produces similar functional and structural effects to those seen following dietary sodium restriction by using a protein deficient, sodium replete diet. To determine if early dietary protein-restriction affects the development of the peripheral gustatory system, multi-fiber neurophysiological recordings were made from the chorda tympani nerve and anterograde track tracing of the chorda tympani nerve into the nucleus of the solitary tract (NTS) was accomplished in rats fed a protein-restricted or a control diet (6% and 20%, respectively). The dietary regimens began on embryonic day 7 and continued until rats were used for neurophysiological recordings (postnatal days (P) 35-50) or for chorda tympani terminal field labeling (P40-50). Responses to a concentration series of NaCl, sodium acetate, KCl, and to 0.50 M sucrose, 0.03 M quinine-HCl, and 0.01 N HCl revealed attenuated responses (30-60%) to sodium-specific stimuli in rats fed the 6% protein diet compared with those fed the 20% protein diet. Responses to all other stimuli were similar between groups. Terminal field volumes were nearly twofold larger in protein-restricted rats compared with controls, with the differences located primarily in the dorsal-caudal zone of the terminal field. These results are similar to the results seen previously in rats fed a sodium-restricted diet throughout pre- and postnatal development, suggesting that dietary sodium- and protein-restriction share similar mechanisms in altering gustatory development.

An appraisal of the strengths and weaknesses of newborn and juvenile rat models for researching gastrointestinal development

Research on the impact of bioactive compounds on the development and functional maturation of the gastrointestinal (GI) tract using newborn and juvenile rats has greatly contributed to the knowledge of GI physiology and to the improved clinical management of both premature and full-term newborns. Of the animal models available, two types have been described for use with young rats – maintenance models and substitution models. Maintenance models are those in which the young are reared with the dam and therefore benefit from continuation of natural nutrition and maternal care. Substitution models are those in which the young are reared in the absence of the dam using artificially formulated milk delivered by various means into specific GI sites. In this review, we describe these models and their operation, and discuss the strengths and weaknesses of each. Attention is also given to questions of scientific validity and some animal welfare issues raised by the use of these models.

Effects of maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on fetal brain growth and motor and behavioral development in offspring rats

The effects of maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during pregnancy on fetal brain growth and neurobehavioral development in early developmental stages were investigated using rat offspring. TCDD in corn-oil (0.1microg/kg) was orally administrated to the dams from the 9th to 19th gestational day. When TCDD effects on the fetal brain weight were analyzed on the 19th gestational day, weight ratio of the brain to the whole body, and that of the forebrain without the cerebral cortex to the whole brain were larger in the exposed group than those of the control group, suggesting premature fetal brain development. TCDD effects on motor functions were investigated using newborns in an inclined plane task. Motor development assessed by righting response on an inclination was delayed in the exposed offspring in the 8th-12th postnatal day, especially in male. Also, TCDD effects on active avoidance behavior in a shuttle box were investigated using the offspring after weaning. Latency in the active avoidance learning was longer, and locomotor activity was reduced in the exposed male offspring in the 41st-44th postnatal day. The results demonstrated that maternal TCDD exposure delayed fetal brain growth and neurodevelopment of the offspring in early stage, especially in male rats.

Early renal structure alteration in rat offspring from dams fed low protein diet

To investigate the early renal alterations due to severe maternal protein restriction (MPR) Wistar dams received 23% (normal protein, NP) or 5% (low protein, LP) chow during gestation and lactation periods. In NP offspring at birth, the cortex-to-medulla (C/M) ratio was 35% greater in female than in male offspring and the mature/immature glomeruli ratio was lower in both sexes of LP offspring than in the matched NP ones (by 20%). At birth and at weaning the kidney of the LP offspring showed fewer glomeruli (40% less) than the age-matched NP offspring. The NP female offspring had almost 20% fewer glomeruli than the matched male offspring. At weaning, the number of glomeruli was positively correlated with BM at birth (R=0.86; P<0.001). The effects of gender and maternal protein restriction, both individually and overall, based on biometrical and stereological parameters were: day 1, MPR largely responsible for the majority of alterations observed in LP groups, however gender influenced C/M ratio; day 21, MPR and gender interacted and modified the number of glomeruli per kidney. The early adverse of MPR effect on renal development is disproportionate between mature and immature glomeruli at birth leading to fewer glomeruli at weaning. This supports epidemiological data in humans underlying why fetuses with low birth weight carry an increased risk of mortality from chronic diseases in adulthood, including hypertension.

Hypothalamic nuclei are malformed in weanling offspring of low protein malnourished rat dams

Maternal low protein malnutrition during gestation and lactation (LP) is an animal model frequently used for the investigation of long-term deleterious consequences of perinatal growth retardation. Both perinatal malnutrition and growth retardation at birth are risk factors for diabetic and cardiovascular disturbances in later life. The pathophysiologic mechanisms responsible are unknown. Hypothalamic nuclei are decisively involved in the central nervous regulation of food intake, body weight and metabolism. We investigated effects of a low protein diet (8% protein; control diet, 17% protein) during gestation and lactation in rat dams on the organization of hypothalamic regulators of body weight and metabolism in the offspring at weaning (d 20 of life). LP offspring had significantly lower body weight than control offspring (CO; P: < 0.001), associated with hypoglycemia and hypoinsulinemia (P: < 0. 005) on d 20 of life. This was accompanied by a greater relative volume of the ventromedial hypothalamic nucleus (P: < 0.01) and a greater numerical density of Nissl-stained neurons in this nucleus (P: < 0.01) as well as in the paraventricular hypothalamic nucleus (PVN; P: < 0.001). In contrast, no significant differences in neuronal densities were observed generally in the lateral hypothalamic area, arcuate hypothalamic nucleus (ARC), and dorsomedial hypothalamic nucleus between LP offspring and CO offspring. On the other hand, LP offspring displayed fewer neurons immunopositive for neuropeptide Y in the ARC (P: < 0.05), whereas in the PVN, lower neuronal densities of neurons immunopositive for galanin were found in LP offspring compared with CO offspring (P: < 0.001). On the contrary, in the PVN, no significant group difference in the numerical density of cholecystokinin-8S-positive neurons was present. A long-term effect of these specific hypothalamic alterations on body weight and metabolism in LP offspring during later life is suggested.

Oil enriched diets and behavioral parameters in rats' recovery from early undernutrition

The effect of oil enriched diets on sexual and exploratory behavior has been studied in male rats undernourished in utero and during lactation. At 20 days of age, for a period of 4 months, these animals were fed with 3 different diets: standard diet, standard diet enriched with 7% soybean oil, and standard diet enriched with 7% olive oil. A control group eating standard diet was also studied. Sexual behavior, open-field and nocturnal spontaneous locomotor activity were studied at 16-20 weeks of age. Undernutrition produced decreased body weight, and the experimental diets were not effective in growth recovery. Undernourished animals eating oil-enriched diets displayed lower nocturnal spontaneous locomotor activity, less time spent in central squares, and a lower number of rearing episodes than undernourished animals eating the standard diet; the number of peripheral squares entered was, however, significantly increased. Experimental groups eating oil diets showed a statistically significant increase in the number of ejaculating males and in the total number of ejaculations compared with experimental rats eating standard diet. These findings suggest that early undernutrition produces permanent behavioral alterations in male rats, but that the sexual behavior deficit could be reversed by feeding our oil-enriched diets from weaning. The diet enriched with soybean oil seems more effective in the rehabilitation of sexual behavior.

Effect of a corn diet during development on [3H]-spiperone binding in the brain of rats at the perinatal stage

A model of undernutrition based on feeding with a corn-diet (tryptophan deficient) was used to study maturation and physiology of the rat brain 5-HTergic system. Previously, using that model, we observed a decrease in 5-HT uptake in rat brain slices, assuming that some compensatory mechanisms could be implicated at the synaptic level on those conditions. Body, brain weight, and total [3H]-spiperone binding were recorded at two fetal ages and newborn pups from mothers were fed with a corn-diet and with a corn-lysine diet. Significant decreases in body weight and in [3H]-spiperone binding were observed at all ages studied in the corn-based diet groups with respect to controls at the first postnatal day of age, whereas at the 18th gestation day, the [3H]-spiperone binding was higher in the protein restricted and corn-lysine supplemented group than in the control group. Results suggested that expression of 5-HT receptors and possibly their synthesis may be limited at the synaptic level on undernutrition conditions.

Effects of prenatal cocaine exposure on postnatal growth patterns of male Wistar rats

The purpose of this study was to investigate basic parameters regarding the postnatal effects of prenatal exposure to cocaine. Timed-pregnant Wistar rats were injected SC with 60 mg/kg body weight/day of cocaine from gestational day 8 to 22. Control females were nonmanipulated and given food and lib; saline females received saline injections and pair-fed received saline and were nutritionally controlled to the cocaine-treated rats. Litters were restricted to 8 pups, weighed every other day until postnatal day (PND) 30 and every week from PND 30 to PND 90. The rats were perfused at PND 14, 30, and 90. The adequacy of adjustment of the logistic and Gompertz models to the body weights of the offspring was tested for the whole experimental period. The results from the Gompertz curve showed a higher growth rate and less time to reach 37% of expected mature body mass for the offspring of cocaine and pair-fed dams as compared with that of control and saline dams. No significant differences in the estimated adult weight were found among the experimental groups. The allometric relationship between forebrain and body weight is described by two postnatal growth phases with a first phase of rapid growth between PND 14 and 30 and a decelerating phase between PND 30 and 90. This relationship was not different among the experimental groups; however, the cocaine and pair-fed offspring showed a constant deficit in the forebrain weight as compared with the control and saline offspring.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of maternal isolation and light and feeding cycles on the growth of rat pups

Rat pups were implanted with intragastric catheters and reared in isolation from their dams and siblings from 3 to 18 days postnatally. They were kept in 12:12 LD or DL, constant light, or constant darkness and were fed with one of three feeding schedules: equal amounts of food delivered during the light and dark periods, 65.3% of the food delivered during the light period, or 65.3% of the food delivered during the dark period. At 18 days postnatally the body, spleen, and kidney weights of all isolated pups did not differ from those of their mother-reared littermates. The isolated pups had smaller cerebellums and forebrains and heavier livers than mother-reared pups. Heavier body and spleen weights and smaller livers were observed in pups with cyclic feeding. Heavier body and forebrain weights were associated with a predominantly diurnal feeding schedule--the schedule which most closely approximated the natural nursing rhythm. Isolated pups opened their eyes sooner than mother-reared littermates. These results suggest that interactions between feeding and light cycles may influence growth and development.

Maternal malnutrition in the rat: effects on food intake and body weight

The effects of dietary protein level on food intake and body weight were examined in adult female rats during a 35-day pre-mating period and during gestation and lactation. During the pre-mating period, no differences in daily food intake were observed among rats fed a 6% casein, 8% casein or 25% casein diet. However, during this period, rats fed the 6% casein diet gained significantly less weight than those with ad lib access to the 8% or 25% casein diets or than rats pair-fed the 25% casein diet in amounts equivalent to that consumed by rats in the 6% or 8% casein groups. Additionally, rats fed the 6% casein diet displayed decreased efficiency of energy utilization, calculated as weight gain per 100 kilocalories consumed, relative to rats fed the 8% or 25% casein diets. No differences in food intake were observed among the groups during gestation. However, rats fed the 6% casein diet gained less weight than rats fed the 8% or 25% casein diets. During lactation rats fed either the 6% or 8% casein diet consumed significantly less food than animals given the 25% casein diet ad lib. During the second week of lactation, rats receiving ad lib access to the 25% casein diet gained weight while those receiving the 6% or 8% casein diets continued to lose weight. At parturition, body weights of pups did not differ as a function of dietary condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral effects of severe and moderate early malnutrition

Rats with a history of prenatal and early postnatal undernutrition (6 or 8% casein diets) were "nutritionally rehabilitated" at weaning, and were compared to well-fed animals (25% casein) at maturity. The severely-malnourished (6%) animals were hyperactive in the open field and when tested in a stabilimeter. They also appeared to be highly active during the early trials in 8-arm radial maze testing where they made more arm entries and re-entry errors than the well-fed rats. In terms of trials to criterion, however, their scores on the radial maze and on a spatial alternation task fell within normal limits. The moderately-malnourished (8%) rats tended to perform at control levels on the learning measures, but these rats were not as active as the 6% rats on the measures of activity. Brain size and weight differences among the three groups of rats also are presented and discussed.

Naltrexone modulates body and brain development in rats: a role for endogenous opioid systems in growth

Preweaning rats receiving daily injections of 20, 50, or 100 mg/kg naltrexone, a potent opiate antagonist, had body and brain weights that were increased 16-22% and 6-13%, respectively, from control levels on day 21 (weaning). All of these dosages of naltrexone blocked the opiate receptor for 24 hr/day as measured in opiate challenge experiments. Dosages of 0.1, 1, and 10 mg/kg naltrexone, which blocked the opiate receptor for less than 12 hr/day, inhibited growth. Repetitive administration of low dosages (3 mg/kg naltrexone, 3 times daily), which blocked the receptor 24 hr/day, increased body and brain development by 31% and 10%, respectively, whereas a cumulative dosage of 9 mg/kg naltrexone given once daily retarded growth. These results show that developmental events are dictated by the duration of opiate receptor blockade and provide compelling evidence that endogenous opioid systems play a crucial role in growth.

Somatic and central nervous system growth in artificially reared rat pups

Rearing preweanling rat pups away from their mothers by feeding through chronic intragastric cannulas has been shown to result in alterations in the growth of specific organs. In the present study, artificially reared (AR) rats and their normally reared (NR) siblings were sacrificed at various ages during this procedure to determine the time course of these alterations. Brain growth deficits were detected within 24 hours, peaked after 8 days of artificial rearing and showed some recovery by the end of the study. By day 18, the livers, kidneys and spleens of the AR pups were significantly larger than those of their NR siblings. The spleens showed an initial decrease in weight compared to the spleens of the NR pups. However, by day 18, the spleens of the AR group were significantly larger than those of the NR group.

Is hippocampal function in the adult rat impaired by early protein or protein-calorie deficiencies?

Much of the development of the rat's hippocampal formation occurs postnatally, which suggests that this structure, like the cerebellum, may be especially vulnerable to early postnatal malnutrition. Radial-maze performance and spontaneous alternation, two kinds of behavior requiring the integrity of the hippocampus, were assessed to determine whether hippocampal function in the adult rat is impaired as a result of protein restriction in either the preweaning, the postweaning or both stages of development. In three experiments the performance of protein-malnourished rats in 8- and 12-arm mazes did not differ significantly from that of well-nourished rats. In a fourth experiment levels of spontaneous alternation in protein-malnourished rats were like those of normal well-nourished animals. Thus, the present experiments provide no evidence that hippocampal function is impaired as a consequence of early protein deprivation. For the most part, a critical review of earlier studied of undernourished rats supports a similar conclusion.

Spontaneous forebrain neuronal activity in developmentally protein malnourished rats

The characteristics of the spontaneous discharges of populations of single neurons in the neocortex and thalamus of rats reared under chronic protein malnutrition (8% casein) or a normal diet (25% casein) were evaluated. Results from 700 neurons showed the malnourished rats had fewer fast firing cells, an overall lower discharge rate and an altered firing pattern (fewer cells which exhibited bursting activity). These findings are the first demonstration of altered neuronal discharges in the forebrains of adult malnourished rats.

Effect of protein malnutrition on development of mouse cortical barrels

Undernutrition has been shown to have a profound effect on the central nervous system of maturing experimental animals, not only on gross brain weight and chemical constitution but also on cell structure and function. The present study was undertaken to determine the effect of protein malnutrition on the cortical barrels of mouse. Animals were conceived in and suckled by mothers maintained on an 8% casein diet or on a stock diet. After weaning, mouselings were maintained on their respective diets ad libitum. Four experiments were performed on these mouselings: (1) study of the development of the barrels by the Nissl method; (2) study of the effect of vibrissal damage at different postnatal ages; (3) study of the size of the barrel area and the number of neurons at different postnatal ages; and (4) study of the selectivity of the Golgi-Cox method. The findings from comparison of malnourished mice with mice on a normal diet were :(1) a two-day delay in the development of the barrels; (2) a two-day lengthening of the period of vulnerability of barrel field neurons to neonatal vibrissal damage; (3) the barrel field area and the relative number of neurons were reduced, with the percentage of reduction decreasing with age; and (4) there was no significant difference in the average percentage of Golgi-stained neurons at different ages. These results suggest that poor nutrition has a profound effect on the development and final form of a well-defined neocortical region. The data presented here provide a useful base line against which various therapeutic regimens to reverse the effects of malnutrition on brain structure may be tested. They also suggest that inducing malnutrition may be an important way in which to manipulate the development of the nervous system in order to study the mechanisms responsible for its final form and function.

Cerebrovascular integrity in protein-deprived rats

Protein-deprivation does not increase the permeability of the blood-brain barrier in rats aged 3.5--12 months. PA, the product of cerebrovascular permeability (P) to 14C-sucrose and of cerebral capillary surface area (A), is very low in mature rats that have been maintained either on an 8% or 25% casein diet, and equals about 8 X 10(-6) sec-1 in both groups. There is a tendency for the calculated distribution volume of 14C-sucrose within the brain to decline in protein-deprived rats. Conscious, partially immobilized, protein-deprived rats have the same mean blood pressure, heart rate, arterial plasma pH and adreno-sympathetic response to stress (as measured by plasma norepinephrine and epinephrine concentrations) as do normally fed animals.

The effects of protein malnutrition on the behavior of rats during the suckling period

Observations of 2 groups of dams and their litters were made every 3 hr around the clock on Days 1-20 postpartum. The dams fed either an 8% or a 25% casein diet for 5 weeks before mating and during gestation and lactation. Dams on the low protein diet spent more time in the nest actively nursing their young than did high protein dams, and they exhibited no deficits in other maternal behaviors. Five of 11 kinds of behavior developed more slowly in the undernourished pups than in the well-nourished ones, but the developmental delays were no longer than a few days. Circadian fluctuations were apparent in all of the pups' activities during the 3rd postnatal week as well as in grooming and horizontal movement, 2 behaviors that were present earlier, by 6-10 days of age.

Rehabilitation following early malnutrition in the rat: body weight, brain size, and cerebral cortex development

Sprague-Dawley rats were malnourished by giving their mothers an 8% casein diet starting at day 10 of gestation, while controls were fed a 24% casein diet. Starting at postnatal day 20 (P20), rehabilitation of the malnourished animals was attempted by: (1) feeding both mother and young a 24% casein diet, (2) leaving the pups with their mothers until they were 40 days old, and (3) reducing the litter size from 8 to 4 pups. Observations were made on aldehyde-perfused tissue from animals 20, 40 and 70 days old. The somatosensory cortex from one hemisphere was embedded in Araldite, and that from the other side was processed fro Golgi staining. At 20 days of age the body weight of the malnourished animals was 21% that of the controls, but at 70 days it was no longer different. The anterior-posterior length, the width, and the height of the cerebral hemispheres were also significantly reduced at P20, but the differences had disappeared by P70. The thickness of area 3 of the cerebral cortex was measured in 1 micron sections. It was significantly reduced in the malnourished animals at P20, but at P40, following rehabilitation, the difference was no longer statistically significant. In tangential 1 micron sections the fraction of the volume of tissue occupied by neuropil was measured in layers II through IV. At P20 it was significantly reduced only in the upper half of layers II/III of the malnourished animals; at P40 this difference was no longer present. The mean volume of upper layer II/III cell bodies was estimated and found to be significantly reduced in the experimental animals at P20 but not at P40. In the Golgi preparations, pyramidal cells in upper layer II/III were studied. Their estimated volume, as well as the thickness of their basal dendrites, was significantly reduced in the 20 day malnourished animals, but not in the rehabilitated animals. These results show that animals severely malnourished until 20 days of age can reach normal body weight and attain cerebral hemispheres of normal size when proper nutrition is provided. The effects of malnutrition on the cerebral cortex of these animals are most apparent in upper layer II/III which, during the time of nutritional restriction, is the least developed of the cortical layers. However, when proper nutrition is provided, the cerebral cortex may attain normal morphology.