Brain fatty acid profiles and spatial learning in malnourished rats: effects of nutritional intervention

The aim of the present study was to determine the effects of malnutrition and nutritional rehabilitation on learning and memory performance and brain fatty acid composition. Pregnant and lactating Wistar rats were either fed ad libitum on a commercial laboratory chow or a multideficient diet from north-eastern Brazil (regional basic diet; RBD). After weaning, RBD offspring either continued on the multideficient diet (malnourished group) or switched to a control diet (rehabilitated group), until day 70. There was no difference in the passive avoidance test among the experimental groups, but malnourished rats showed important deficits in performance of the Morris water maze which were improved in the rehabilitated group. The hippocampus and cerebellum of the malnourished rats showed important changes in fatty acid profile obtained by gas-liquid chromatography, but the rehabilitated group had decreased n-3 polyunsaturated fatty acids and an increase in the proportion of arachidonic acid. The data suggest that nutritional rehabilitation results in partial restoration of fatty acid profiles and cognitive performance.     

Effects of environmental enrichment on blood vessels in the optic tract of malnourished rats: A morphological and morphometric analysis

Objectives: This study aimed to compare the effects of environmental enrichment in nourished (on a diet containing 16% protein) and malnourished (on a diet containing 6% protein) rats during the critical period of brain development, specifically focusing on the optic nerve.

Methods: By means of morphologic and morphometric assessment of the optic nerve, we analyzed the changes caused by diet and stimulation (environmental enrichment) on postnatal day 35, a time point ideal for such morphological analysis since developmental processes are considered complete at this age.

Results: Malnourished animals presented low body and brain weights and high body-to-brain weight ratio compared to well-nourished rats. Furthermore, malnourished animals showed morphological changes in the optic nerve such as edema and vacuolization characterized by increased interstitial space. The malnourished-stimulated group presented lesions characteristic of early protein malnutrition but were milder than lesions exhibited by malnourished-non-stimulated group. The morphometric analysis revealed no difference in glial cell density between groups, but there was significantly higher blood vessel density in the stimulated rats, independent of their nutritional condition.

Discussion: Our data indicate that protein malnutrition imposed during the critical period of brain development alters the cytoarchitecture of the optic nerve. In addition, we affirm that a 1-hour exposure to an enriched environment everyday was sufficient for tissue preservation in rats maintained on a low-protein diet. This protective effect might be related to angiogenesis, as confirmed by the increased vascular density observed in morphometric analyses.     

Brain fatty acid profiles and spatial learning in malnourished rats: effects of nutritional intervention

Abstract

The aim of the present study was to determine the effects of malnutrition and nutritional rehabilitation on learning and memory performance and brain fatty acid composition. Pregnant and lactating Wistar rats were either fed ad libitum on a commercial laboratory chow or a multideficient diet from north-eastern Brazil (regional basic diet; RBD). After weaning, RBD offspring either continued on the multideficient diet (malnourished group) or switched to a control diet (rehabilitated group), until day 70. There was no difference in the passive avoidance test among the experimental groups, but malnourished rats showed important deficits in performance of the Morris water maze which were improved in the rehabilitated group. The hippocampus and cerebellum of the malnourished rats showed important changes in fatty acid profile obtained by gas-liquid chromatography, but the rehabilitated group had decreased n-3 polyunsaturated fatty acids and an increase in the proportion of arachidonic acid. The data suggest that nutritional rehabilitation results in partial restoration of fatty acid profiles and cognitive performance.     

GFAP Expression in Astrocytes of Suprachiasmatic Nucleus and Medial Preoptic Area are Differentially Affected by Malnutrition during Rat Brain Development

Abstract

The aim of the present study was investigate, in young rats, the effects of malnutrition on astrocyte distribution of two hypothalamic regions, the circadian pacemaker suprachiasmatic nucleus (SCN) and the medial preoptic area (MPA). Control rats were born from mothers fed on commercial diet since gestation and malnourished rats from mothers fed on multideficient diet, from the beginning of gestation (GLA group) or from the onset of lactation (LA group). After weaning, pups received ad libitum the same diet as their mothers, and were maintained under a 12/12 h light/dark cycle. The animals were analyzed either at 30-33, or 60-63 days of life. Brain coronal sections (50 μm) were processed to visualize glial fibrillary acidic protein (GFAP) immunoreactivity. Compared to control rats, both malnourished groups of 30 and 60 days exhibited a reduced number of GFAP-immunoreactive astrocytes in the SCN. The total GFAP-immunoreactive area in the SCN of the GLA group differed from the control group at both age ranges analyzed. The GFAP expression as measured by the relative optical density (ROD) exhibited a 50-60% reduction in the MPA in both malnourished groups, compared to controls. The results suggest that malnutrition early in life leads to alterations in gliogenesis or glial cell proliferation in both nuclei, being these alterations greater in the MPA. Compensatory plasticity mechanisms in the GFAP-expression seem to be developed in the astrocyte differentiation process in the SCN, especially when the malnutrition is installed from the lactation.     

GFAP expression in astrocytes of suprachiasmatic nucleus and medial preoptic area are differentially affected by malnutrition during rat brain development

The aim of the present study was investigate, in young rats, the effects of malnutrition on astrocyte distribution of two hypothalamic regions, the circadian pacemaker suprachiasmatic nucleus (SCN) and the medial preoptic area (MPA). Control rats were born from mothers fed on commercial diet since gestation and malnourished rats from mothers fed on multideficient diet, from the beginning of gestation (GLA group) or from the onset of lactation (LA group). After weaning, pups received ad libitum the same diet as their mothers, and were maintained under a 12/12 h light/dark cycle. The animals were analyzed either at 30-33, or 60-63 days of life. Brain coronal sections (50 microm) were processed to visualize glial fibrillary acidic protein (GFAP) immunoreactivity. Compared to control rats, both malnourished groups of 30 and 60 days exhibited a reduced number of GFAP-immunoreactive astrocytes in the SCN. The total GFAP-immunoreactive area in the SCN of the GLA group differed from the control group at both age ranges analyzed. The GFAP expression as measured by the relative optical density (ROD) exhibited a 50-60% reduction in the MPA in both malnourished groups, compared to controls. The results suggest that malnutrition early in life leads to alterations in gliogenesis or glial cell proliferation in both nuclei, being these alterations greater in the MPA. Compensatory plasticity mechanisms in the GFAP-expression seem to be developed in the astrocyte differentiation process in the SCN, especially when the malnutrition is installed from the lactation.     

Gestational protein-energy malnutrition affects the composition of developing skins of rat fetuses and their dams

1. Various biochemical variables of the skins of rat dams and their fetuses in which protein-energy malnutrition was induced during pregnancy were analysed. 2. One group of dams was fed on a 200 g protein/kg diet as a control and the other was fed on a 60 g protein/kg diet as an experimental group. Each group of dams was fed from day 13 of gestation until day 22. 3. Water, protein and hexosamine concentrations of the fetal skins in the malnourished group were greater than those in the control group, whereas in the dams' skins, protein concentration was greater in the malnourished group than in the control group. 4. Extractability of collagen with neutral salt and pepsin showed no difference between the groups in the skins of fetuses and dams. The content of type III collagen in the fetal skin did not differ between the groups, but was increased in the malnourished dams' skins compared with that of the control group. 5. The present study showed that protein-energy malnutrition during pregnancy significantly affects the metabolism of the skin in both fetuses and their dams. Furthermore, the skins of fetuses and dams are structurally altered in different ways by this nutritional stress.     

Effects of vitamin B-6 deficiency on the developing central nervous system of the rat. Myelination

The effects of different levels of dietary pyridoxine (1.0, 1.2, 1.4, and 20.0 mg/kg diet) fed to dams during growth, gestation and lactation on myelination in progeny were investigated. Degree of myelination at 15 days, postnatally, was determined from closely matched micrographs of the four dietary treatment groups. Electron micrographs showed markedly less myelination in the 1.0 group as compared with the 1.4 and 20.0 groups with the 1.2 group appearing intermediate in the number of myelinated axons. Some myelinated axons of the 1.0 group exhibited an "unusual" appearance of whorls of lamina separated by cytoplasmic space occupied by widely separated lamina. The results indicate that brain development, particularly myelination, was affected by a deficiency of vitamin B-6 prior to and including the period of rapid myelination.     

Postnatal protein malnutrition affects inhibitory avoidance and risk assessment behaviors in two models of anxiety in rats

Protein malnutrition induces structural, neurochemical and functional alterations in the central nervous system, leading to alterations in behavioral function. In order to study the effects of early protein malnutrition on inhibitory avoidance and escape behaviors we used the elevated T-maze (ETM), while the risk assessment behaviors were evaluated by the canopy stretched attend posture (SAP) test. Rat pups were fed by lactating females receiving 16% (control) or 6% (malnourished) protein diets during the lactation period. After weaning the animals received the same diets until 49 days of age, when all animals started receiving a lab chow diet. Behavioral tests were started at 70 days of age. ETM results showed lower inhibitory avoidance in malnourished animals, without differences in escape behavior. SAP test results showed higher exploration and lower risk assessment behaviors in malnourished animals compared to control. These results suggest that malnourished animals are less anxious and/or more impulsive as measured by these two animal models and that malnutrition seems to affect differently behavioral strategies underlying fear and anxiety responses.     

Early malnourished rats are not affected by anorexia induced by a selective serotonin reuptake inhibitor in adult life

The effect of early postnatal malnutrition upon food intake and its modulation by the selective serotonin reuptake inhibitor (SSRI) citalopram, was investigated in adult rats. Sixty four Wistar rats were allocated to two groups, according to their mother's diet during lactation. Mothers receiving a 23% protein diet fed the well-nourished group; mothers receiving 8% protein diet fed the malnourished. After weaning, all rats received the 23% protein diet ad libitum. On the 120th day after birth, each nutritional group was divided in two subgroups (each one, n = 16) which received a single daily injection of citalopram (10 mg/kg) or saline (0.9% NaCl) for 14 days. Chronic treatment with citalopram decreased both the food intake and weight gain in the well-nourished rats, but not in the malnourished ones. These data are consistent with findings concerning the nutritional manipulation of the nervous system during its higher vulnerable phase, suggesting that early malnutrition alters the effect of treatment of SSRI in adult rats, and that malnutrition during the critical period of brain development affects the serotoninergic system.     

Postnatal Protein Malnutrition Affects Inhibitory Avoidance and Risk Assessment Behaviors in Two Models of Anxiety in Rats

Abstract

Protein malnutrition induces structural, neurochemical and functional alterations in the central nervous system, leading to alterations in behavioral function. In order to study the effects of early protein malnutrition on inhibitory avoidance and escape behaviors we used the elevated T-maze (ETM), while the risk assessment behaviors were evaluated by the canopy stretched attend posture (SAP) test. Rat pups were fed by lactating females receiving 16% (control) or 6% (malnourished) protein diets during the lactation period. After weaning the animals received the same diets until 49 days of age, when all animals started receiving a lab chow diet. Behavioral tests were started at 70 days of age. ETM results showed lower inhibitory avoidance in malnourished animals, without differences in escape behavior. SAP test results showed higher exploration and lower risk assessment behaviors in malnourished animals compared to control. These results suggest that malnourished animals are less anxious and/or more impulsive as measured by these two animal models and that malnutrition seems to affect differently behavioral strategies underlying fear and anxiety responses.     

Dietary phospholipids rich in long-chain polyunsaturated fatty acids improve the repair of small intestine in previously malnourished piglets.

Malnourished piglets were studied to establish how a diet containing long-chain polyunsaturated fatty acids (LC-PUFA) of the (n-6) and (n-3) series, esterified in the form of phospholipids, affects intestinal recovery after severe malnutrition. Piglets (7-d-old) were randomly assigned to two groups. One group was fed a piglet milk formula and the other was malnourished by protein-energy restriction for 30 d. Healthy and malnourished piglets were then divided into two subgroups fed for 10 d either an adapted milk formula (C and M) or the same diet supplemented with LC-PUFA phospholipids (C-P and M-P). The M-P group had greater protein, DNA, cholesterol and phospholipid levels and a lower triglyceride level in the jejunal segment than did the M group. The fatty acid composition of the jejunal mucosa and microsomes of the M-P piglets did not differ from that of healthy piglets (C). However, in jejunal mucosa, microsomes and phospholipids from malnourished piglets that did not receive LC-PUFA (group M) had significantly lower percentages of (n-6) LC-PUFA than those in healthy piglets (C). The (n-3) LC-PUFA percentages of jejunal mucosa were also lower in the M group than in the C group. The small intestine of piglets fed the LC-PUFA-supplemented formula recovered more completely from histologic lesions and biochemical alterations caused by the malnutrition process than the small intestine of piglets fed the control formula without LC-PUFA.     

Effects of a leucine-rich diet on body composition during nutritional recovery in rats

OBJECTIVE: Protein malnutrition is characterized by a number of morphologic and physiologic alterations, including intestinal mucosal atrophy and impaired nutrient absorption. Impaired absorption accentuates nutritional deficiency and accelerates body weight loss and changes in body chemistry. Because leucine is a ketogenic and oxidative amino acid and stimulates the protein synthesis, we examined the ability of young rats to recover from protein malnutrition by feeding them a control balanced or a leucine-rich diet for 60 d. METHODS: At the end of the 60-d period, body, liver, and muscle weights; glucose, methionine, and leucine intestinal absorption; and carcass chemical composition were evaluated. RESULTS: Body weight gain was higher in the control balanced and leucine-rich groups than in control rats, indicating that adequate refeeding allows body weight to recover in these groups. Methionine and glucose absorptions were impaired in malnourished rats but were restored after nutritional recovery. The leucine-rich diet resulted in an increase in carcass collagen nitrogen but maintained the carcass structural nitrogen. CONCLUSIONS: These results indicated that leucine supplementation during nutritional recovery from protein malnutrition improves protein carcass restoration. However, the precise mechanism of the leucine effects involved in this response remains to be elucidated.     

Malnourished mice display an impaired hematologic response to granulocyte colony-stimulating factor administration

The aim of this study was to determine if protein-energy malnutrition could affect the hematologic response to granulocyte colony-stimulating factor (G-CSF). Swiss mice were fed a low-protein diet containing 4% protein, whereas control mice were fed a 20% protein-containing diet. After the malnourished group lost 20% of their original body weight, the mice were subdivided in 2 treatment groups, and hematopoietic parameters were studied. Mice were injected with either 8 μg/kg per day of G-CSF or saline twice daily for 4 days. Malnourished mice developed anemia with reticulopenia and leukopenia with depletion of granulocytes and lymphocytes. Both malnourished and control mice treated with G-CSF showed a significant increase in neutrophils; however, in the control group, this increase was more pronounced compared to the malnourished group (4.5-fold and 3.4-fold, respectively). Granulocyte colony-stimulating factor administration increased bone marrow blastic (P < .001) and granulocytic (P < .01) compartments in the controls but had no significant effect on these hematopoietic compartments in the malnourished animals (P = .08 and P = .62, respectively). We report that malnourished mice display an impaired response to G-CSF, which contributes to the decreased production of leukocytes in protein-energy malnutrition.     

Malnutrition is not related to alterations in energy balance in patients with stable liver cirrhosis

BACKGROUND AND AIMS: Little information are available on the relationship between energy balance and the alterations in nutritional status occurring in cirrhotic patients. The aim of the present study was to evaluate the daily energy balance in clinically stable cirrhotic patients with or without malnutrition.PATIENTS: Seventy-four consecutive cirrhotic patients and nine healthy controls were studied.METHODS: Basal energy expenditure was measured by indirect calorimetry and adjusted according to the patients' physical activity to estimate the daily energy expenditure. Food intake was evaluated based on a 3-day dietary diary. Nutritional status and body composition were assessed using skinfold anthropometry and dual energy X-ray absorptiometry, respectively.RESULTS: Thirty-two patients in the cirrhotic group were classified as severely malnourished according to anthropometric parameters. Two different patterns of soft-tissue loss were observed in the malnourished cirrhotic group: a significant reduction in fat mass and in fat-free mass was observed in males, whereas, females showed a significant reduction in fat mass only. Basal energy expenditure was similar in all groups, while the non-protein respiratory quotient was lower in cirrhotics notwithstanding their nutritional status. This suggests that lipids were the preferred oxidized fuel in the post-absorptive state in these patients. No difference in the estimated daily energy expenditure and energy intake was observed among groups. Lipid content of the diet was significantly lower in malnourished cirrhotics than in controls (33.1+/-1% vs 37.8+/-1%, P=0.02).CONCLUSIONS: Cirrhotic patients in stable clinical condition with malnutrition show a normal energy balance.     

Early Malnourished Rats are not Affected by Anorexia Induced by a Selective Serotonin Reuptake Inhibitor in Adult Life

Abstract

The effect of early postnatal malnutrition upon food intake and its modulation by the selective serotonin reuptake inhibitor (SSRI) citalopram, was investigated in adult rats. Sixty four Wistar rats were allocated to two groups, according to their mother's diet during lactation. Mothers receiving a 23% protein diet fed the well-nourished group; mothers receiving 8% protein diet fed the malnourished. After weaning, all rats received the 23% protein diet ad libitum. On the 120th day after birth, each nutritional group was divided in two subgroups (each one, n=16) which received a single daily injection of citalopram (10 mg/kg) or saline (0.9% NaCl) for 14 days. Chronic treatment with citalopram decreased both the food intake and weight gain in the well-nourished rats, but not in the malnourished ones. These data are consistent with findings concerning the nutritional manipulation of the nervous system during its higher vulnerable phase, suggesting that early malnutrition alters the effect of treatment of SSRI in adult rats, and that malnutrition during the critical period of brain development affects the serotoninergic system.     

NADPH-Diaphorase Containing Neurons and Biocytin-labelled Axon Terminals in the Visual Cortex of Adult Rats Malnourished During Development

This is the first report of the effects of malnutrition during brain development on biocytin-labelled axon terminals and histochemical pattern of NADPH-diaphorase (NADPH-d)-containing neurons in area 17 of the adult rat. Wistar rats (n = 6) were submitted early in life (from gestation up to 42 days of age) to a multideficient diet (the ‘regional basic diet’ (RBD) of low-income human populations of north-east Brazil, containing only 8% protein). From day 43 up to adulthood (135–212 days), they were switched to a commercial laboratory chow diet (Purina do Brasil Ltda), with 22% protein. These animals were compared to control rats (n = 11), fed the laboratory chow diet until adulthood. The brains of four adult malnourished and five controls were processed according to the indirect method of the malic enzyme to reveal NADPH-d-containing neurons. Five other adult subjects (three controls and two malnourished) received iontophoretic injections of the tracer biocytin in area 17and were processed according to the glucose oxidase-DAB-nickel protocol in order to visualize axon terminals filled with biocytin. Three other control rats were processed for both techniques. In these last brains, no double-labelled cells could be found, suggesting that the NADPH-d-containing-neurons and the biocytin-labelled ones belong to different groups of cells, in area 17. The appendages of the NADPH-d-positive cells showed minor qualitative and quantitative differences between undernourished and control rats. The soma area of these cells was reduced in the white matter of malnourished rats, as compared to the controls (468.6 ± 54.3 μm²; n = 4 and 515.4 ± 30.5 μm²;n = 8, respectively; p < 0.05). The cell density (cells/mm²) was greater in the malnourished group than in the control, both at the grey matter (16.6 ± 4.4; n = 4 and 11.3 ± 4.3; n = 8, respectively; p < 0.05) and at the white matter (55.9 ± 15.7; n = 4 and 24.4 ± 8.5; n = 8; p < 0.005). The number of potential synaptic sites in the biocytin-labelled axon terminals was reduced as compared to the control (126 ± 33 boutons/mm, n = 32 and 160 ± 37; n = 30, respectively; p < 0.01). The results indicate that the rat area 17 is affected differently by early malnutrition, regarding biocytin-labelled axon terminals, on the one hand, and NADPH-d-containing neurons, on the other. Concerning these last cells, the data also suggest that they are less sensitive to the injury represented by early malnutrition.     

Effect of perinatal food deficiencies on the compound action potential evoked in sensory nerves of developing rats

The aim of this study was to analyze the possible alterations produced by inadequate perinatal food intake, in quantity (undernutrition) or quality (malnutrition), on the generation and propagation of the compound action potential (CAP) evoked in sensory sural nerves, during the postnatal development of the rat. Low intensity stimulation (2-3 times the threshold of the most excitable nerve fibers; xT) of the sural nerve evoked an early potential (CAP-A component) which is due to activation of low-threshold, fast-conducting myelinated group A afferent fibers. Meanwhile, at higher stimulus intensity (20-30T) it produced a second, long-lasting potential (CAP-C component) probably due to activation of high-threshold, slow-conducting group Adelta or C afferent fibers. Compared to control nerves, the CAP-A component, but not the CAP-C component of undernourished and malnourished nerves showed significant changes in amplitude, area, electrical threshold and conduction velocity (except absolute refractory period) at several postnatal ages. Our results may suggest that a relative large number of myelinated group A afferent fibers in the sural nerve of undernourished and malnourished animals suffer severe alterations on their electrophysiological properties of generation and propagation of the action potential during the postnatal development of the rat.     

Early postnatal protein malnutrition causes resistance to the anxiolytic effects of diazepam as assessed by the fear-potentiated startle test

Given that protein malnutrition induces structural, neurochemical and functional changes in the CNS, the present study aimed to investigate the effects of different early periods of protein malnutrition on the behavior and reactivity to diazepam (DZ) in a model of anxiety: the fear-potentiated startle (FPS). Male Wistar rats (n = 110) from well-nourished (16 %-protein) or malnourished (6%-protein) litters were distributed in five different groups: W (well-nourished), M7 (malnourished for 7-days, since day 0), M14 (14-days), M21 (21-days) and M28 (28-days). The results obtained in FPS revealed that malnourished-animals acquired the startle response, irrespective of the time they were exposed to the diet. Besides, DZ reduced the startle amplitude in the noise-alone and light-noise trials. The data concerning the total freezing time showed that the expression of this response was affected by malnutrition and varied in accordance with the findings of previous studies in which malnutrition procedures was imposed for long periods (more than 50 days). Therefore, we suggest that early protein malnutrition: (a) did not produce deficits in the associative learning process of these animals in the FPS, and (b) decreased freezing time in the FPS and produce hyporeactivity to the effects of DZ in rats malnourished for 21 days or more, indicating alterations in the GABAergic neurotransmitter system.     

Effect of Perinatal Food Deficiencies on the Compound Action Potential Evoked in Sensory Nerves of Developing Rats

The aim of this study was to analyze the possible alterations produced by inadequate perinatal food intake, in quantity (undernutrition) or quality (malnutrition), on the generation and propagation of the compound action potential (CAP) evoked in sensory sural nerves, during the postnatal development of the rat. Low intensity stimulation (2–3 times the threshold of the most excitable nerve fibers; X T) of the sural nerve evoked an early potential (CAP-A component) which is due to activation of low-threshold, fast-conducting myelinated group A afferent fibers. Meanwhile, at higher stimulus intensity (20–30T) it produced a second, long-lasting potential (CAP-C component) probably due to activation of high-threshold, slow-conducting group Aδ or C afferent fibers. Compared to control nerves, the CAP-A component, but not the CAP-C component of undernourished and malnourished nerves showed significant changes in amplitude, area, electrical threshold and conduction velocity (except absolute refractory period) at several postnatal ages. Our results may suggest that a relative large number of myelinated group A afferent fibers in the sural nerve of undernourished and malnourished animals suffer severe alterations on their electrophysiological properties of generation and propagation of the action potential during the postnatal development of the rat.