Restrição protéica na prenhez: efeitos relacionados ao metabolismo materno / Protein restriction in pregnancy: effects related to dam metabolism

Foram avaliadas as alterações no metabolismo materno durante a prenhez em ratas Wistar, prenhes e não-prenhes, submetidas à restrição protéica, que receberam dietas isocalóricas (15,74 kJ/g), controle ou hipoprotéica (17 por cento versus 6 por cento), distribuídas em quatro grupos (n = 7), quais sejam: controle não-prenhe (CNP) e prenhe (CP) e hipoprotéico não-prenhe (HNP) e prenhe (HP), do 1º ao 18º dia de prenhez. Parâmetros bioquímicos, hormonais e relacionados à síntese de lipídios foram considerados. Utilizou-se ANOVA a duas vias seguido de teste Tukey-HSD e teste t de Student, significância de p < 0,05. A restrição protéica elevou a síntese de lipídios e a atividade da enzima málica (EM) no fígado (FIG) e reduziu a massa ( por cento) e a razão lipí+dio/glicogênio nesse tecido, bem como reduziu a ingestão protéica (total e por cento), o conteúdo ( por cento) de lipídios na glândula mamária (GMA), as proteínas e a albumina séricas, com consequente redução nas massas da placenta e fetos. A prenhez reduziu a proteinemia, a albuminemia, a síntese de lipídios, a atividade da EM, os lipídios e o glicogênio no FIG. Mas elevou a massa corporal final, a massa ( por cento) do tecido adiposo gonadal (GON), do FIG e da GMA, e reduziu a massa ( por cento) da carcaça (CARC), a síntese e o conteúdo de lipídios no GON e, na GMA, o conteúdo de lipídios. A insulinemia elevou-se na prenhez, com glicemia reduzida, caracterizando resistência hormonal. A leptina e a prolactina também se elevaram na prenhez, sendo o aumento maior no HP. A restrição protéica na prenhez modificou o metabolismo materno, alterando a síntese de lipídios no FIG e o perfil hormonal, além de reduzir a massa da placenta e dos fetos.

Metabolism alterations were evaluated in female Wistar rats (dams) during pregnancy. Pregnant and non-pregnant dams submitted to protein restriction, were fed isocaloric (15.74 kJ/g), control or hypoproteic (17 percent vs. 6 percent) diets, and distributed in four Groups (n=7) as follows: non-pregnant control (NPC), pregnant control (PC), non-pregnant hypoproteic (NPH), and pregnant hypoproteic (PH); from Day 1 to Day 18 of pregnancy. Biochemical, hormonal and metabolic parameters related to lipid synthesis were assessed. The two-way ANOVA, followed by Tukey-HSD and Student-t tests were used, with a significance of p< 0.05. Protein restriction elevated lipid synthesis and malic enzyme (ME) activity in the liver, and reduced mass and the lipid/glycogen ratio in this tissue; it also lowered protein ingestion (total and percent), lipid content ( percent) in the mammary gland (MAG), serum proteins and albumin, with consequent reduction of placenta and fetal masses. Pregnancy reduced serum protein and albumin concentrations, lipid synthesis, ME activity, hepatic lipid and glycogen content. However, it increased final body mass; increased relative masses of gonad (GON), liver and MAG; but reduced lipid synthesis and content of GON, lipid content of MAG and the relative mass of carcass. Pregnancy Insulinemia increased during pregnancy with reduced glycemia, characterizing hormonal resistance. Leptin and prolactin were also increased during pregnancy, being the highest increase in observed in HP rats. Protein restriction in pregnancy modified maternal metabolism, altering lipid synthesis in the liver and hormonal profile and decreasing the placenta and fetus masses.

Non-coordinate expression of closely linked mouse casein genes.

Expression levels of five mouse casein genes were analysed in the mammary gland of virgin, pregnant and lactating mice. We have already shown that the five murine casein genes are arranged in the order, alpha-beta-gamma-epsilon-kappa in a tandem array, very close to each other in a 250 kb DNA fragment of mouse genome. Northern blot analysis showed that, of the calcium-sensitive casein genes, the epsilon casein gene is expressed only during lactation unlike the alpha, beta and gamma casein genes which are expressed during pregnancy and lactation. Even though the alpha, beta and gamma genes exhibited a co-ordinated expression pattern from mid to the later stages of pregnancy, the mRNA levels varied considerably (60, 90 and 100% respectively) by the onset of lactation. The mRNA level of the calcium-insensitive kappa casein gene increased from mid-pregnancy but at a lower rate and reached approximately 60% by the first day of lactation. Considering the locations and closeness of the casein genes, a non-coordinate expression profile is exhibited by the mouse casein genes, particularly the epsilon casein gene.

Desnutrição na gestação e lactação altera a atividade da `gamaï-glutamiltranspeptidase e os níveis de glutationa em glândula mamária de ratas / Malnutrition during gestation and lactation changes `gamma'-glutamyltranspeptidase activity and glutathione levels in mammary gland of rats

O papel desempenhado pela `gamaï-glutamiltranspeptidase (GGT - EC 2.3.2.2.) no transporte de aminoácidos e na mobilização de cisteína da glutationa (GSH) justifica o interesse em avaliar suas respostas à desnutrição protéico-calórica durante o processo gestacional e de lactação. Para estudar as alterações na atividade da enzima e nos níveis de GSH, fêmeas prenhes e virgens receberam dietas controle (caseína-13 por cento) e restrita em proteína (caseína-6 por cento). Após 22 e 32 dias de experiência, correspondendo ao 1º e 10º dias de lactação, procedeu-se ao sacrifício e determinou-se GGT e GSH na glândula mamária das mães e no fígado de mães e filhotes. Elevação significativa na atividade da enzima nas mamas das ratas desnutridas foi observada no 1º dia de lactação, acompanhada de redução também significativa no conteúdo de GSH, tendo-se verificado correlação negativa entre esses parâmetros e entre a GGT e o CEA...

leucine catabolism in mammary tissue, liver and skeletal muscle of dam rat during lactation and weaning

Background. This study designed to determine the effect of lactation and weaning on the catabolism of branched-chain amino acids (BCAA). Methods. Rates of transamination and oxidation of leucine and branched chain a-ketoacid dehydrogenase(BCKD) activity were mesured in homogenates of mammary gland, skeletal muscle and liver on day 12 of lactation and 24 h after separation of dams from the litter (weaning). Results. Lactating dams consumed 250 percent more protein than control rats, extra protein is required for protein synthesis by the mammary gland, the extent to which the excess of amino acids consumed during lactation is utilized or oxidized by different tissues is not known. The rate of transamination of [1-14C] leucine by mammary tissue of lactating dams was sixfold higher than in virgin rats. The rate of transamination remained elevated fourfold in post-weaning dams. Rates of transamination were three times higher in mammary tissue than in muscle of lactating dams. Rate of oxidation [1-14C] leucine by lactanting mammary tissue was tenfold higher than in control tissue. Conclusions. The capacity of mammary tissue for transamination and oxidation of leucine increased greatly during lactation, suggesting that the mammary gland may play an important role in the catabolism of BCAA during lactation

Discrimination of transport systems of L-tyrosine in mouse mammary gland: characterization of system T.

On the basis of inhibition analysis, tyrosine uptake in mouse mammary gland was found to be mediated by Na(+)-dependent and Na(+)-independent systems. Na(+)-dependent system was insensitive to 2-(methylamino) isobutyric acid (MeAIB), with an apparent Km of 1.67 mM and maximal velocity 74.5 nmol.g-1 cell. min-1. Competition experiments showed the presence of two distinct Na(+)-independent components of tyrosine uptake. One component was sensitive to 2-aminobicyclo (2,2,1) heptane-2-carboxylic acid (BCH) and was similar to the system L, with an apparent Km of 0.23 mM and maximum velocity of 31 nmol.g-1 cell.min-1. Second component was BCH-insensitive but tryptophan-sensitive, with an apparent Km of 15.75 mM and Vmax of 157.5 nmol.g-1cell.min-1. BCH-insensitive, tryptophan-sensitive system was a low affinity system. It approached steady state slowly and was more sensitive, relative to the system L, to n-ethylmaleimide inhibition. Tyrosine uptake through this system did not respond to trans-stimulation, whereas system L mediated uptake responded considerably. BCH-insensitive, tryptophan-sensitive component of Na(+)-independent tyrosine uptake is attributed to the system T, previously described only in human red blood cells and rat liver cells.

Lack of functional correlation between gamma-glutamyl transpeptidase and amino acid transport in the lactating mouse mammary gland.

Gamma-glutamyl transpeptidase (EC 2.3.2.2) in lactating mouse mammary gland was inhibited by affinity labelling of the tissue with 6-diazo-5-oxo-L-norleucine. Amino acid (L-alanine, L-methionine) uptake by the affinity labelled mammary gland tissue and the control tissue was measured in vitro. Uptake of amino acids by the affinity-labelled tissue was comparable to that of control tissue. These findings suggest that gamma-glutamyl cycle is not involved in amino acid uptake by the mammary gland.

Expression of active human erythropoietin in the mammary gland of lactating transgenic mice and rabbits

Transgenic mice and rabbits were generated using a chimeric gene comprising the human erythropoietin (hEPO) cDNA under the 5' and 3' regulatory sequences of the rabbit whey acidic protein gene. Transgenic mice expressed hEPO at levels of 0.01 mg/l in the milk of lactating females showing that the genetic construct was functional. Reverse transcriptase polymerase chain reaction with RNA from various tissues showed that this transgene was expressed mainly in the ovary and mammary gland. In rabbits, we demonstrated the germ line transmission of the transgene. The hEPO was obtained in the milk of lactating females at levels of up to 0.0003 mg/l. Although the expression levels were low, biologically active hEPO was obtained in the milk of transgenic rabbits without any apparent detrimental effect for the animals. In vitro, the specific activity of the rabbit-derived hEPO was higher than that reported for the natural hEPO, thus suggesting differences in the glycosylation pattern in at least part of the molecules secreted by the mammary gland of transgenic rabbits

Characterisation of the routes of methionine transport in mouse mammary glands.

The sites of methionine uptake by mammary glands from late pregnant and lactating mice were studied in vitro. Using the specific A system inhibitor, N-(methylamino) isobutyric acid (MeAIB) and the specific L system inhibitor, 2-amino-bicyclo (2.2.1) heptane 2-carboxylic acid (BCH), we have defined four modes of methionine entry into these tissues. (i) A sodium-dependent A system with a Vmax of 13.4 and 18.8 n mol/g cells/min in pregnant and lactating mice, respectively. This mode of entry was completely inhibited by MeAIB and its Km value was similar (0.45 mM) in both groups. (ii) A sodium-dependent mode with a Vmax of 6.7 and 12.4 n mol/g cells/min and a Km of 0.24 and 0.46 mM in pregnant and lactating mice, respectively. This mode of entry was insensitive to inhibition by MeAIB, and was similar to the ASC (alanine, serine, cysteine) system in other tissues. (iii) A sodium-independent L system with a Vmax of 13.8 and 30.0 n mol/g cells/min and a Km of 0.27 and 0.46 mM in pregnant and lactating mice, respectively. This mode of entry was completely inhibited by BCH. (iv) A sodium-independent non-specific entry amounting to 25 per cent of the total entry at 0.1 mM external methionine which was not inhibited by high concentration of BCH. The results of our studies show an increase in the number of active carriers of the A, ASC and L systems of methionine uptake in mammary glands of mouse during lactation.

Effect of neonatal pineal ablation on estradiol receptors in mammary glands of rats housed under varying photoperiods.

Estradiol receptors (ER) in mammary glands of female Holtzman rats, either intact or neonatally pinealectomised and housed in 10:14 or 24:0 L:D (light:dark) schedule were studied at 30, 40, 50 +/- 5 and 65 +/- 5 days of age. Whereas ER were detectable only at the age of 60-65 days in intact rats housed in 10:14 L:D, they were present as early as 30 days onwards in the pineal ablated group. In the 24:0 L:D pinealectomised group, though mammary gland ER were maximum around 40 days of age and temporarily undetectable around day 50, they had stabilized around the age of 60-65 days. The data demonstrates for the first time, the modulation of ER in rat mammary glands in response to varying photoperiods as well as pineal ablation. Earlier reports on incidence of chemically induced mammary tumours have been compared to the receptor modulation.

Aspectos morfologicos e morfometricos de glandulas mamarias de ratas albinas tratadas com sulpiride / Morphological and morphometric aspects of mammary glands of albinic female rats treated with sulpiride

Procurou-se observar aspectos morfologicos e morfometricos das glandulas mamarias de ratas albinas tratadas com sulpiride, submetidas ou nao a ooforectomia. Tivemos como resultados da morfologia, no grupo de ratas na fase de estro e nas ooforectomizadas, tratadas ou nao pelo sulpiride, glandulas mamarias atrofiadas. Nas ratas apenas tratadas com sulpiride as glandulas mamarias apresentaram-se bem desenvolvidas, com alveolos contendo secrecao no seu interior. A proporcao de ductos e de alveolos mamarios se mostrou significantemente maior no grupo de ratas tratadas apenas com sulpiride.

Effects of feeding low protein diet with and without leucine supplementation on protein status of lactating females and their pups.

Female rats were fed low protein diet (10% casein) either as such or supplemented with 3% leucine during pregnancy and lactation. Changes in litter size and the survival rate, growth and protein status of the pups were noted. The milk yield and hepatic and mammary gland protein status of the mothers were also studied. Feeding low protein diet reduced litter size, increased their mortality and resulted in poor growth of the pups. It also resulted in poor hepatic and mammary gland protein status of the mothers, as well as reduced their milk yield. On adding 3% leucine to 10% casein in the diet, the changes observed in the low protein group, did not alter in any manner.

Steroid receptors in mammary glands and tumors of hysterectomised rats.

Epidemiological survey suggests that longer exposure of the breast to sex steroids may be one of the factors involved in increased risk for cancer. Using an experimental model of bilaterally hysterectomised rats, the sex steroid receptors in the mammary glands during growth as well as incidence and hormonal characteristics of chemically induced mammary tumors have been studied. Though steroid receptors were detectable in the mammary glands of the model earlier than in intact rats, the incidence or hormone dependency of the mammary tumors in the two groups were not considerably altered.

Effect of ethanol intake during lactation on the metabolism of dams and pup development

Ethanol intake during lactation causes growth deficiency and decreased plasma and liver protein content in pups. The lipid content of pup liver and brain was similar to that of the control group. Mammary gland protein content decreased, but the rate of lipogenesis in this gland was increased. This fact may be relevant to an adequate supply of lipid substrate to the pups

Actividad de gama glutamil transpeptidasa y contenido de glutation en la gladula mamaria durante el proceso de la preñez y la lactancia en ratas cronicamente desnutridas / Gamma-glutamyltranspeptidase activity and glutathione content in the mammary gland during the processes of pregnancy and lactation in rats

Se estudio, en la rata, el efecto de la restricción de la ingesta de una dieta balanceada durante la preñez y lactancia, sobre la actividad de gama glutamil transpeptidasa (GGTPO) (E.C.2.3.2.2.) en la glándula mamaria. Los resultados informan que la desnutrición calRorico-proteínica impuesta permanentemente a la rata hembra, disminuye significativamente el crecimiento, contenido de DNA, contenido de proteína y actividad de GGTP en la glándula mamaria, desde el día 16 post-gestación hasta el 5§ día de lactancia, lo que equivale a la duración del experimento. El peso de las crías al nacer y la ganancia de peso al 5§ día de vida postnatal se encontró significativamente disminuida en el grupo desnutrido. Se postula que la disminución de la actividad de GGTP afectó el transporte de algunos aminoácidos y péptidos, en la glándula mamaria, originando una menor disponibilidad intracelular de aminoácidos necesarios para la síntesis de la proteína de la leche y, por lo tanto, una disminución en la secreción láctea