Influence of dietary protein, energy and corticosteroids on protein turnover, proteoglycan sulphation and growth of long bone and skeletal muscle in the rat.

1. We report here the extent to which changes in protein turnover contribute to the previously described inhibition of growth of rat tibial length and skeletal muscle mass in response to protein deficiency [1], energy restriction and corticosterone treatment [2]. Measurements of 35S uptake in vivo also enabled the qualitative pattern of changes in proteoglycan synthesis in bone and muscle to be established. 2. Protein deficiency was examined by ad libitum feeding of 20%, 7%, 3.5% and 0.5% protein diets with measurements at 1, 3 and 7 days (all diets), and 14 and 21 days (0.5% protein). In bone this induced delayed inhibition of tibial growth with parallel inhibition of protein synthesis, as measured by the phenylalanine flooding dose method. This was mediated by reductions in both ribosomal capacity (RNA/protein ratio) and activity (protein synthesis/RNA) in the 0.5% protein group. The pattern of inhibition of proteoglycan sulphation, measured as 35S uptake 60 min after injection of a tracer dose of labelled sulphate, was similar to that of protein synthesis. 3. In muscle there was an intermediate graded inhibition of protein synthesis by protein deficiency, mediated by reductions in both ribosomal capacity and activity in the 0.5% protein group, which preceded growth inhibition in the 7% and 3.5% groups, and which was progressive with time. Transient increases in proteolysis contributed to the growth inhibition is some groups, but the rate fell eventually in the 0.5% group. The pattern of response of proteoglycan sulphation differed from protein synthesis with a delayed inhibition, but with subsequent marked reduction. 4. Energy restriction was induced by diets fed for 4 or 8 days at 75%, 50% and 25% ad libitum intakes with protein intakes held constant, and corticosterone treatment involved a dose of 10 mg day-1 100-1 g (subcutaneous) with ad libitum feeding. In bone this induced a pattern of length growth inhibition which was dissociated from inhibition of protein synthesis in the moderately restricted (75% and 50%) groups. Only in the 25% group and in the 8 day corticosterone group was protein synthesis inhibited, through reductions in ribosomal capacity and activity. 35S uptake was also dissociated from growth inhibition, with reduced 35S uptake observed only after corticosterone treatment or 8 days of the 50% or 25% diets. 5. In muscle the energy restriction and corticosterone treatment induced parallel inhibitions of growth and protein synthesis, mediated by similar graded reductions in the RNA/protein ratios and in the 25% group in the KRNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Dietary energy, glucocorticoids and the regulation of long bone and muscle growth in the rat.

1. The influence of dietary energy restriction and corticosterone on long bone and muscle growth, and their interrelationships, was studied in rats fed a range of restricted amounts of diets containing increasing concentrations of protein, thus maintaining constant protein intakes. Tibial length and epiphyseal cartilage width were measured radiographically. 2. In experiment 1, tibial length and gastrocnemius muscle growth were examined in ad libitum fed rats and during 4 days of severe energy restriction (25% ad libitum intake), starvation and ad libitum feeding with corticosterone treatment (10 mg/100 g), a mediator of the response to energy restriction. Weight loss occurred in all groups. Tibial growth continued in the 25% and starvation groups albeit at reduced rates with the inhibition of starvation > 25% group (P < 0.05), but was arrested after 2 days of corticosterone treatment. 3. Muscle growth inhibition was proportional to tibial growth inhibition of the 25% group, insofar as the muscle/bone ratio (W/L), was maintained. This inter-relationship between muscle and bone growth previously reported for ad libitum high-protein-fed rats, is likely to reflect the anabolic influence of bone on muscle via passive muscle stretching induced by length growth. For both starvation and corticosterone groups the muscle/bone ratio fell (P < 0.05 compared with the ad libitum group), suggesting that muscle growth inhibition included an additional direct catabolic influence of starvation and corticosterone treatment. 4. In experiment 2, measurements of bone, muscle and liver growth were made in rats fed 75%, or 50% and 25% ad libitum intakes with corticosterone treatment for 8 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum concentrations of insulin-like growth factor-I and proteoglycan synthesis rates in young rats: a comparative study between the regional diet of São Paulo state and casein diets.

Insulin-like growth factor-I (IGF-I), also known as somatomedin-C, is an important mediator of growth regulation. Serum concentrations of IGF-I and proteoglycan synthesis rates in the tibial epiphysis, an estimate of the biological response to IGF-I in a target tissue, were compared in weanling Wistar rats fed ad libitum (group 1) and with 50% restriction (group 2) with the regional diet of São Paulo State (RDSPS--a mean diet consumed by low-income families with rice, beans, sugar, meat, milk, fruits and other vegetables) and in pair-fed animals fed with casein diets (groups 3 and 4). Data are reported as mean +/- SD for 8 rats in each group. Proteoglycan synthesis rates (cpm/mg) were significantly higher in rats fed with the RDSPS-based diet (groups 1 and 2: 210.8 +/- 58.8, 136.6 +/- 17.6) than in pair-fed animals fed with an 11% casein diet (groups 3 and 4: 62.9 +/- 11.6, 37.7 +/- 13.7) and in control animals fed ad libitum with a 20% casein diet (group 5: 58.1 +/- 22.7). Furthermore, these rates were higher in animals fed ad libitum than in those fed with the same diets but with 50% restriction. However, similar differences between groups 1 to 4 were not observed in serum concentrations (ng/100 microliters) of IGF-I (group 1: 44.1 +/- 7.1; group 2: 40.8 +/- 3.8; group 3: 46.0 +/- 3.6; group 4: 41.6 +/- 3.4, and group 5: 63.2 +/- 7.8). These results suggest that serum IGF-I levels are not reliable indicators of IGF-I status in this experimental model.

Serum concentrations of insulin-like growth factor-I and proteoglycan synthesis rates in young rats: a comparative study between the regional diet of Säo Paulo state and casein diets

Insulin-like growth factor-I (IGF-I), also known as somatomedin-C, is an important mediator of growth regulation. Serum concentrations of IGF-I and proteoglycan synthesis rates in the tibial epiphysis, an estimate of the biological response to IGF-I in a target tissue, were compared in weanling Wistar rats fed ad libitum (group 1) and with 50% restriction (group 2) with the regional diet of Säo Paulo State (RDSPS--a mean diet consumed by low-income families with rice, beans, sugar, meat, milk, fruits and other vegetables) and in pair-fed animals fed with casein diets (groups 3 and 4). Data are reported as mean +/- SD for 8 rats in each group. Proteoglycan synthesis rates (cpm/mg) were significantly higher in rats fed with the RDSPS-based diet (groups 1 and 2: 210.8 +/- 58.8, 136.6 +/- 17.6) than in pair-fed animals fed with an 11% casein diet (groups 3 and 4: 62.9 +/- 11.6, 37.7 +/- 13.7) and in control animals fed ad libitum with a 20% casein diet (group 5: 58.1 +/- 22.7). Furthermore, these rates were higher in animals fed ad libitum than in those fed with the same diets but with 50% restriction. However, similar differences between groups 1 to 4 were not observed in serum concentrations (ng/100 microliters) of IGF-I (group 1: 44.1 +/- 7.1; group 2: 40.8 +/- 3.8; group 3: 46.0 +/- 3.6; group 4: 41.6 +/- 3.4, and group 5: 63.2 +/- 7.8). These results suggest that serum IGF-I levels are not reliable indicators of IGF-I status in this experimental model

[Somatomedin, growth and nutritional status]. / Somatomedina, crescimento e estado nutricional.

Serum somatomedins, or insulin-like growth factor(s) (IGF), originally characterized as primarily GH-dependent peptides, were found to also be dependent on insulin levels and nutritional status. Four properties characterize somatomedin peptides: their concentrations in serum are growth hormone dependent; they possess insulin actions in extraskeletal tissues; they promote the incorporation of sulfate into proteoglycans of cartilage; and they stimulate DNA synthesis and cell multiplication in certain types of cultured cells. Reduced somatomedin C levels are found in children with severe protein-energy malnutrition. Plasma concentration of growth hormone and cortisol are both elevated and there are low levels of insulin and somatomedin C. There is evidence that the ability of somatomedin C to stimulate cartilage is modulated by somatomedin inhibitor, factor that may act to limit growth in conditions of hormonal and/or nutritional deficiency. Dietary energy and protein appears to be particularly important for both generation of somatomedins and their action on growing cartilage. Measurement of somatomedins C concentration shows promise as a means for monitoring the response of malnourished patients and rats to nutrition repletion.

[Effect of the average diet of the State of São Paulo, from time of pregnancy on body weight and composition of the offspring. Study in rats]. / Efeito da dieta média do Estado de São Paulo, desde a gestação, no peso corporal e composição dos filhotes. Estudo em ratos.

The effect of diet of São Paulo State on some biochemical parameters in the liver, brain and plasma of rats at weaning and 90 days was studied. The tissue parameters studied were the amounts of DNA, RNA and protein in the liver and brain. For the plasma were the total protein and albumin. Wistar rat were fed a 13% casein (control) and 13% protein of experimental diet since the gestation. In experimental diet weight at birth, weaning and 90 days were considerably reduced. A comparison of the data of the experimental rats in relation to the control group indicated that: a) organ weight, total organ DNA, RNA and protein were all reduced; b) no differences in total protein and albumin in plasma were observed between the control and the experimental group. These results suggest that the diet experimental is deficient in some nutrients (minerals, vitamins?) and affected the cellular development of brain and liver.

Effects of protein deficiency and rehabilitation on growth and tissue composition in growing rats.

The objective of the present work was to study the influence of protein quantity and quality on some biochemical parameters in the liver, brain and plasma of rats at 51 days of age. This profile was sketched through the weight of the liver and brain and their content of DNA, RNA and protein and through the total amount of protein, the ratio NE/E and the activity of transaminase GOT and GPT in the plasma. During gestation and lactation, diets of 20% casein, 8% casein and 8% corn were used. At weaning, five experimental groups, with and without nutritional recuperation, were established. As a result, it was observed that the groups fed on a hypoprotein diet (8% casein or 8% corn) were the most seriously compromised in body weight and biochemical parameters with the group fed on corn being the most seriously affected. The animal which were recuperated nutritionally presented a net improvement in all of the parameters. However, the values describing the development of the body and organs in these groups remained inferior to those obtained in the control group. The success of reversibility will depend on the phase of development during which malnutrition occurred and the duration and intensity of the original deficit and the subsequent rehabilitation treatment. Organs in a phase of accelerated development will be especially sensitive to the irreversible effects of malnutrition.

Marginal protein deficiency in pregnant rats. Changes in offspring body composition.

The influence of protein on some biochemical parameters in the liver, brain and plasma of rats at weaning was studied. The tissue parameters studied were the amounts of DNA, RNA and protein in the liver and brain. For the plasma, the parameters studied were the total amount of protein and the ratio of non-essential to essential amino acids (ratio NE/E). During the gestation and lactation period, the rats were divided into three groups according to the diet received: group 1, 20% casein; group 2, 8% casein; and group 3, 8% corn. As a result we can assert that groups 2 and 3, fed on hypoprotein diets, were seriously compromised in body weight and in the biochemical parameters and these alteration were enhanced by the corn diet. These results suggest that the alterations depend on the duration and intensity of the malnourishment and that the quality of the protein is an important factor to be considered.

[Quality of maternal diet and biochemical changes in the brain of the offspring. Study in rats]. / Qualidade da dieta materna e alteracões bioquímicas no cérebro dos filhotes. Estudo em ratos.

The present study was undertaken to assess the effect of different levels of nutritional restriction during fetal life, suckling, and after weaning of the brain biochemical composition. At 41 days of age, the rats were killed and the brain was processed for analyses of DNA, RNA and protein. The results showed that the brain weights as well as DNA, RNA and protein brain contents were impaired by hypoprotein diet, and these alterations were enhanced by the corn diet.

[Effect of the intake of imbalanced protein on the liver of growing rats]. / Efeito da ingestão de proteína desbalanceada em fígado de ratos em crescimento.

The goal of the present work was to reproduce in laboratory animals situations frequently observed in low-income population, such as the insufficient energetic ingestion associated with protein sources of inferior quality. Corn was chosen as the protein source of low biological value and casein as the reference protein. The latter was administered in adequate quantity (20%) or equal to that of the corn (10%). Several biochemical parameters and the amounts of DNA, RNA and protein in the liver of rats in a phase of rapid growth were studied. In result, we can attest that the group fed on corn were the most seriously compromised in body weight, liver weight and biochemical parameters with the group fed a restricted diet of corn being the most seriously affected. The results suggest that the alterations caused by ingestion of a balanced diet restricted in quantity were less accentuated that those observed when the diet was of corn "ad libitum".

Qualidade da dieta materna e alteracoes bioquimicas no cerebro dos filhotes. Estudo em ratos. / Quality of maternal diet and biochemical changes in the brain of offsprings. Study in rats

Verificaram-se os efeitos da restricao alimentar durante a gestacao, lactacao e apos desmame na composicao quimica do cerebro de ratos em crescimento. Aos 41 dias de idade os ratos foram sacrificados e o cerebro foi analisado nos conteudos de DNA, RNA e proteina. Os grupos alimentados com dieta hiproproteica foram os mais gravemente comprometidos na avaliacao do peso cerebral e nos conteudos de DNA, RNA e proteina. Estas alteracoes foram mais acentuadas nos animais alimentados com dieta de milho em restricao alimentar

Efeito da ingestao de proteina desbalanceada em figado de ratos de crescimento. / Effect of the intake of imbalanced protein on liver of growing rats

Procura-se reproduzir em animais de laboratorio situacoes observadas frequentemente em populacoes de baixa renda, tais como insuficiente ingestao energetica associada a fontes proteicas de qualidade inferior. Escolheu-se o milho como fonte protetica de baixo valor biologico e a caseina como proteina de referencia, sendo esta administrada em quantidade adequada (20%) ou igual a do milho (10%) . Estudaram-se alguns parametros bioquimicos e conteudos de DNA, RNA e proteina no figado de ratos em fase aguda de crescimento.Como resultados, podemos assinalar que os grupos alimentados com milho foram os mais comprometidos na avaliacao do peso corporeo, peso do figado e parametros bioquimicos, sendo que o grupo alimentado com milho em restricao foi o mais seriamente afetado. Os resultados sugerem que as alteracoes decorrentes da ingestao de dietas balanceadas em quantidade restrita, foram menos acentuadas do que aquelas observadas quando a dieta utilizada foi o milho "ad libitum"