Body growth and substrate partitioning for fat and protein gain in weaned BALB/c mice treated with growth hormone.

Previously we have found that recombinant human growth hormone (rhGH) (GH; 74 ng g body wt.(-1)) administration to weaned BALB/c male mice (fed 12% or 20% protein diet) induced a growth lag and subsequent repletion similar to the catch-up growth process. We studied the partitioning of feed and protein intakes between adipose and protein body stores through the linear relationships among them. The non-linear relationship of protein intake with body fat gain/protein gain (FG/PG) ratio was especially adequate in determining the partitioning of substrates. rhGH induced an increase in feed and protein intake utilization for body weight gain (50%) and fat gain (75-140%) over saline; macronutrient utilization was the greatest in rhGH-treated mice fed 20% protein. However, growth recovery of rhGH mice was anomalous and protein intake was derived primarily for fat gain. Mice fed 12% protein (treated and control) also derived protein intake in preference to fat stores. Treatment and diet had a cumulative effect with the result that rhGH-treated animals fed 12% protein showed the greatest FG/PG ratio (1.6), and therefore, the lowest efficiency to gain protein. Weaning is a critical stage in mice when treating with rhGH, as this could provoke a growth lag. The study showed that a high protein level is required to surpass the rhGH-induced lag, but it is not enough to obtain an enhanced protein deposition. Feeding a 12% protein diet was even worse as mice did not improve on the growth lag and substrates were directed mainly to body fat.

Feed intake and protein skeletal muscle in growing mice treated with growth hormone: time course effects.

The exogenous recombinant human growth hormone (rhGH) administration on gastrocnemius muscle growth performance and its contribution to body growth of male and female BALB/c mice fed a 12 % protein diet from 25 to 50 days of age, as well as the mechanism of utilization of feed intake to the lean muscle deposition were studied. Male and female weaning mice (21 days of age) were injected subcutaneously for 29 days with rhGH (74 ng x g(-1)) or saline vehicle (control). Feed intake and body weight (BW) were measured daily. At 25, 30, 35, 40, 45 and 50 days of age twenty mice were killed by cervical dislocation and the gastrocnemius muscle was isolated, weighed and the protein content was measured. The rhGH administration caused a biphasic response of BW and muscle growth as a consequence of age-specific feed intake changes. The initial feed intake fall induced the allometric proportion decreases in both muscle growth versus body growth and protein muscle versus muscle growth. That effect was due to ineffient utilization of energy and protein intake on protein muscle store. Later on, the self-controlled increase of feed intake leads to the recovery of muscle weight to control values, through nutrient partitioning toward non protein tissue showing a compensatory muscle growth. This suggests that a higher dietary protein level should be necessary for promoting the protein anabolic effect of GH during weaning.

Recombinant human growth hormone modifies the inherent partition of nutrients in growing female and male BALB/c mice.

BALB/c mice weaned at 21 days were used to investigate the effects of exogenous recombinant human growth hormone (rhGH) administration on the growth performance and carcass composition in females and males allowed to consume feed ad libitum. Forty mice were assigned within each sex (female [F] and male [M] to treatment of either 20 microL g-1 saline (Fs and Ms groups) or 74 ng rhGH g-1 body weight (BW) in 20 microL saline (FGH and MGH groups). At 50 d of age the mice were weighed and then killed by cervical dislocation. Treatment with rhGh improved feed conversion only in growing female mice by enhancing weight gain relative to feed protein intake and weight growth rate without modification of feed consumption, according to a multiple comparison test (LSD). Ms mice showed less carcass fat gain (162%), less fat accretion rate (129%), higher carcass water gain (12%) and higher water accretion rate (28%) than Fs mice. The administration of rhGH modified this distribution inducing an increase in gain and accretion rates of protein (34%), water (41%) and ash (33%) and a reduction in gain and accretion rate of fat (50%) in FGH mice, and only an increase of gain (91%) and accretion rate of fat (67%) in MGH mice compared to saline mice. As result, a decrease in protein gain:fat gain ratio of MGH mice compared to FGH (34%) and Ms (63%) mice was elicited by rhGH, inverting the inherent sexual propensity for fat and protein deposition in growing male mice, due to GH, sex, and to GH x sex interaction influence.

Muscle cell growth in protein deficient rats following administration of sheep red blood cells.

In order to observe the effects of sheep red blood cells (SRBC) administration on the muscle cell growth in malnourished states, adult male Wistar rats (135 +/- 10 g 10 animals per group) subjected during 30 days to 1% and 10% protein diets, were injected (i.v.) either 15.5 x 10(8) sheep red blood cells or 0.5 ml saline/100 g b.w. after 20 days of experiment. On the 10th day after injection the animals were sacrificed and the gastrocnemius muscle was removed, weighed and homogenized. The supernatant fluids were used to evaluate muscle protein, DNA and RNA rates and acid DNase activity. All parameters were depleted in malnourished rats, indicating a muscle cellular atrophy as well as a decrease in muscle protein synthesis per DNA-unit. Muscle hyperplasia and hypertrophy were found in antigenically stimulated rats fed 10% protein against non-stimulated control. In contrast, muscle growth in protein-deficient rats SRBC-treated was unmodified when compared to non-stimulated malnourished muscle, although RNA functionality seems to be enhanced (RNA/DNA). These data suggest that a redistribution of essential nutrients occurred for muscle growth adaptation rather than for defensive mechanism.

[Blood glucose, insulin, GH, and amino acids in rats receiving 3 levels of dietary proteins]. / Glucosa, insulina, GH y aminoácidos plásmaticos en ratas sometidas a tres niveles de proteína dietarios.

The effect of dietary protein content on the variations in plasma insulin, GH, glucose and both gluconeogenic and branched-chain amino acids (BCAA) levels, was studied in Wistar rats. For 21 days animals consumed ad libitum diets containing 4% (LP group) 10% (MP group) or 20% (HP group) protein. Body weight gain and plasma concentrations of the glucose, insulin and both the insulin/glucose (I/G) and insulin/GH (I/GH) ratios varied directly with the protein content of the diet. In contrast the relationships between dietary protein content and GH levels, were inverse. These results indicate that an increase of energy yielding nutrients availability and an decrease of tissue sensitivity to insulin was produced as the protein content of the diet was increased. The increase of plasma aspartate, serine, histidine and alanine levels on LP group suggest a low gluconeogenic process, and the higher rate of BCAA on HP group against to MP and LP groups can be related to a lower tissue uptake. Both effects can be mediated by the tissular sensitivity to insulin.

[Cell growth of skeletal muscle as an indicator of protein requirements of the adult rat]. / Crecimiento celular del músculo esquelético como índice de los requerimientos de proteína en la rata adulta.

Skeletal muscle growth, muscle nucleic acids and muscle protein synthesis capacity, were measured to evaluate the protein requirement of adult rats. Wistar rats were fed on diets containing 4%, 10% or 20% casein + D,L-methionine. All diets were provided for 21 days beginning at 90 days of age. Body weight, food efficiency and net weight change increased as the casein content of the diet increased. Muscle DNA, RNA and RNA/protein were lost, but protein and protein/DNA increased on the 4% and 20% protein diet. This fact involves an aplasia phenomenon although the hypertrophic growth is maintained. Alterations of the insulin and GH plasma levels were observed. These findings indicate that for adult rats the 4% and 20% protein diets are not adequate for the period of adult maintenance.

[Influence of dietary protein levels on the electrophoretic pattern and plasma IgG and IgM levels in pregnant rats and their offspring]. / Influencia del nivel proteínico dietario sobre el patrón electroforético y los niveles de Ig G e Ig M plasmáticos en ratas gestantes y sus neonatos.

In view of the influence that nutritional and physiological status exert on the immunological capacity of the subject, a study was carried out for the purpose of studying the changes induced by three protein levels in the diet: (4%, 10% (control), and 20%) on total plasma proteins (TPP) and their fractions, as well as Ig G and Ig M levels in non-pregnant (NP) and pregnant (P) rats and their offspring. Effect of the diet on adult rats--In non-pregnant rats submitted to the high protein diet, Ig G levels increased while TPP decreased in P rats fed on 4% and 20% protein diets. The higher the protein level in the diet, the higher were the TPP values. Effect of pregnancy--Ig G and Ig M levels suffered an increase in rats fed the 4% and 10% protein diets, while a decrease was observed in rats submitted to the 20% protein level diet. The TPP rate diminished in rats fed on the low protein diets, and increased when the highest protein diet was administered. Effect of the diet on offspring--Ig M levels were only detected in neonates from rats fed with the low and high protein diets. Moreover, the TPP rate increased as a direct function of the dietary protein intake.

[Changes in the metabolism of muscle RNA in rats given a high protein diet]. / Modificaciones del metabolismo del RNA muscular en ratas sometidas a una dieta hiperproteica.

The effect of a high protein diet (20% casein + D,L-methionine) administered to adult Wistar rats on some aspects of muscle RNA metabolism has been studied. Body weight increased in spite of lower intake. However, gastrocnemius muscle remained unmodified, although protein content increased. Total RNA decreased in the whole muscle although RNA/DNA ratio did not change. Protein synthesis capacity diminished 81% relative to controls in spite the fact that an excessive amount of available amino acids exists. RNA loss might depend on a high catabolism, since acid RNase activity increased over control values. Therefore, it may be concluded that a high protein diet leads to a lower protein synthesis capacity through an elevated RNA breakdown.

[Additive effects of protein malnutrition and cortisol on plasma proteins and immunoglobulins of pregnant rats, and their offsprings]. / Efectos aditivos de la malnutrición proteínica y del cortisol en las proteínas plasmáticas e inmunoglobulinas de ratas gestantes, y sus neonatos.

This research work was carried out to study the effects of two immunosuppressive mechanisms: protein malnutrition and cortisol treatment on the feto-maternal unit. Therefore, plasma Ig G and Ig M levels were tested in pregnant rats submitted to a low protein diet (4%) and cortisol treatment (0.5 mg/100 g b.w.) during pregnancy and in their offspring. Nutritional status was evaluated by measuring ponderal parameters and plasma protein levels in rat dams and their neonates. Thus, a fall in ponderal parameters and in plasma protein levels was observed, both in rat dams suffering protein malnutrition as well as in their newborns. Cortisol treatment produced a decrease in the ponderal parameters of the control group, and an increase in plasma protein levels of the malnourished one, both in rat dams and in their neonates. Apparently, protein malnutrition might lead to a low functionality of B lymphocytes, caused by a decrease in Ig G and Ig M rates of malnourished rat dams. Ig M levels, however, increased in neonates as a consequence of possible concomitant infections. Cortisol treatment promoted humoral immune deficiency, since Ig G and Ig M levels decreased both in the control and in the malnourished pregnant rat groups. Nevertheless, cortisol administration seemed to increase susceptibility to infection in the newborns, especially in those born from malnourished rat dams.

[Dietary protein level during pregnancy. Its influence on maternal-fetal exchange of substrates]. / Nivel proteínico dietario durante la gestación. Su influencia sobre el reparto materno-fetal de sustratos.

It is well known that the dietary protein level influences both the pregnancy process and development of the offspring. Therefore, a study was carried out to determine the effect that different protein percentages: 10%, 4% and 20% in diets administered to rats during pregnancy, had on food efficiency and on the substrates partition between rat dams and their neonates. Experimentation was thus carried out over a period of 21 days (pregnancy) and comparisons were made with well-nourished rats receiving 10% protein (controls) and between one and other group. Moreover, the effect on pregnancy was observed by comparing pregnant rats with non pregnant rats within each dietary situation. Food intake, weight parameters and food efficiency ratio were recorded in adult rats. Weight parameters were also evaluated in newborns. As results revealed, the highest the protein level in the diet, the highest the food efficiency ratio, both in the pregnant group and in the non pregnant group. Weight changes were determined in rat dams and their neonates, as a consequence of the different protein intakes. These also involved alterations in the substrates partition between the mothers and their offspring. Such findings might lead to the retention of substrates by the maternal tissues and, hence, to impairment of neonatal development.

[High protein diet in pregnancy. Effects on neonatal metabolism]. / Dieta hiperproteica en la gestación. Efectos sobre el metabolismo neonatal.

The effect of a high protein diet (20% casein + D,L-methionine) administered to Wistar rats during pregnancy on some aspects of cellular growth and RNA metabolism of progeny has been studied. Comparisons were made with well-nourished (10% casein + D,L-methionine) controls. Newborns individual weight, litter weight and number of newborns per litter were unmodified. However, neonate protein content dropped significantly when compared with controls. Both rate of DNA and number of nuclei were unchanged. Protein/DNA ratio (cellular size relative to protein) decreased, which might have led to an atrophy phenomenon, even if the newborn weight/number of nuclei ratio was not modified. Acid DNase activity rose, bringing about DNA breakdown. Total RNA content together with RNase activity fell in newborn from rats suffering high protein diet. Moreover, protein synthesis capacity (RNA/protein ratio) did not change. These results suggest that the administration of a high protein diet to pregnant rats lead to changes in newborn protein rate and nucleic acid turnover by modulating specific nuclease activity.

[Changes at the liver cell level in rats subjected to protein-calorie malnutrition]. / Modificaciones a nivel celular hepático en ratas sometidas a malnutrición proteico-calórica.

The effect of a low protein-calorie diet (restricted diet) on cellular growth and on RNA metabolism in Wistar rat liver has been studied. Experimentation was carried out over 30 days and the comparisons were made against well-nourished group (10% protein, controls). Liver weight and hepatic proteins dropped significantly in malnourished rats. Both rate of DNA and number of nuclei were unchanged. However, protein/DNA and liver weight/number of nuclei ratios decreased, which led to an atrophy phenomenon. DNase specific activity however, was not modified. Liver RNA content together with RNase activity dropped in deficient rats. Protein synthesis capacity (RNA/protein) did not change. These results suggest that restricted diet leads to a lower hepatocyte size with a decreased rat of RNA turnover.

[Changes in hydrolytic lysosomal enzymes of liver associated with protein and protein-calorie malnutrition]. / Cambios en enzimas lisosómicos hidrolíticos del hígado asociados a malnutrición proteica y calórico-proteica.

The effect of a low protein (1%) diet (protein-deficient diet) and a low protein-calorie diet (restricted diet) on the activity of the hydrolytic enzymes acid ribonuclease, acid deoxiribonuclease, acid and alkaline phosphatases and beta-glucuronidase has been studied in the liver of Wistar rts. Experimentation was carried out over 30 days and then comparisons were made against well-nourished (10% protein, controls), and one another. Body weight of deficient animals decreased in deficient animals, especially in protein-deficient rats. Liver weight also dropped significantly in malnourished rats. In terms of organ weight relative to body weight, there was a clear increase of protein-deficient rats, compared with controls. Enzyme activities expressed per total organ fell significantly in deficient rats compared with controls, but alkaline phosphatase activity increased. A large increase in hydrolytic activity expressed per mg of protein in beta-glucuronidase and alkaline phosphatase values was registered in protein-deficient and restricted rats. Also, acid ribonuclease activity increased in deficient-protein animals, but it fell in protein-calorie deficient animals compared with controls. However, acid deoxiribunuclease and acid phosphatase activities were not modified. We therefore concluded that protein-deficient and restricted diets increase catabolism in liver through a modulation of lysosomal hydrolase activities.

Effect of protein deficiency on the lysosomal enzyme activities of the spleen and thymus of weanling rats.

The effect of a low protein (4%) diet on the activity of the hydrolytic enzymes ribonuclease, deoxyribonuclease, acid and alkaline phosphatases, beta-glucuronidase and lysozyme has been studied in the spleen and thymus of weanling Wistar rats. Experimentation was carried out over 20 and 30 days, and comparisons were made with well-nourished (12% protein) controls. Body weight decreased during the terminal period in protein-deficient animals (P less than 0.001). Spleen and thymus absolute net weights also dropped significantly (P less than 0.001). In terms of organ weight relative to body weight, there was a clear decrease in thymus compared with controls (P less than 0.001). Enzyme activities expressed per total organ fell significantly. Thus, in spleen at 20 days the decrease was maximum in ribonuclease activity (91.15%) and minimum in acid phosphatase activity (44.09%). Thymus decreases ranged from 83.60% activity in beta-glucuronidase and 93.56% in ribonuclease. At 30 days decreases were accentuated; the maximum value in spleen was 92.34% lysozyme and, in thymus, 97.09% acid phosphatase. A large increase in hydrolytic activity expressed per milligram of protein was registered, especially at 30 days. This increase reached a maximum of 78.08% beta-glucuronidase in thymus and a minimum of 56.1% alkaline phosphatase; acid phosphatase and ribonuclease activities were not modified. In spleen, however, acid phosphatase (34.00%), alkaline phosphatase (62.50%), deoxyribonuclease (39.25%), and beta-glucuronidase (36.01%) increased, but lysozyme and ribonuclease enzymes decreased. We concluded that a low protein diet increases catabolism in spleen and thymus through an enhancement of lysosomal hydrolase activities.