Influence of the Dietary Protein Deficiency on the Protein Synthetic Activity of Microsome and Soluble Fraction from Muscle and Liver of Rats

Phytochromes are photoreceptors that regulate many aspects of plant growth and development in response to red/far-red light signals from the environment. In this study, we analyzed chromophore ligation and photochromism of missense phytochrome mutants in the Per-Arnt-Sim (PAS)-related domain (PRD). Among the 14 mutants analyzed, the Gly768Asp mutant of Avena phytochrome A showed aberrant photochromism and dark reversion, suggesting that amino acid residues in the C-terminal domain affect the photochemical properties of the photosensory N-terminal domain.     

氨基酸组成对蛋白质耐热性的影响

为了研究一级结构对蛋白质耐热性的影响,利用软件DNAMAN对16个家族32种蛋白质序列进行了氨基酸含量分析,并统计分析了氨基酸组成对蛋白质耐热性的影响。通过比较同一家族的高低温蛋白质序列及16个家族中所有高温和低温蛋白质序列中氨基酸含量的变化可以推断(从低温到高温)：Ser、Cys．含量降低显著,Arg、Ile、Pro含量升高显著。由此可知高温蛋白质倾向于含有疏水性氨基酸而避免亲水性氨基酸。     

Influence of the Dietary Protein Deficiency on the Activities of Ribosomes and Polysome Patterns in Muscle and Liver of Rats

A group of rats weighing about 120 g were killed at the beginning of the experiment and after 10 days on the 20% casein diet (C-0 and C-10 groups), and another group of rats were killed after 1, 2 and 10 days on the protein-free diet (PF-1, PF-2 and PF-10 groups). From muscle and the liver of each group ribosomes were prepared, and the protein synthesis activity and the polysome patterns were investigated. The activity of polysome fractionated into each size was also measured.

Muscle ribosome activity in PF-1, PF-2 and PF-10 groups decreased to about 60%, 40% and 40% of that in C groups, respectively, and this decrease was due to a fall in activity of polysome itself rather than disaggregation of polysome. Liver ribosome activity in PF-1, PF-2 and PF-10 groups were reduced to about 95%, 90% and 65% of that in C groups, respectively. These alterations in PF-1 and PF-2 groups seemed to be in part related to changes in polysome pattern, whereas ribosome activity in PF-10 group was reduced without changes in polysome pattern.     

Effect of Dietary Macronutrient Composition on AMPK and SIRT1 Expression and Activity in Human Skeletal Muscle

Adenosine monophosphate-activated protein kinase (AMPK), silent mating type information regulation 2 homologue 1 (SIRT 1), and peroxisome proliferator-activated receptor γ co-activator α (PGC1α) constitute an energy sensing cellular network that controls mitochondrial biogenesis. Caloric restriction activates both AMPK and SIRT-1 to increase ATP production from fat oxidation. We characterized AMPK and SIRT 1 expression and activity in human skeletal muscle in response to dietary fat or carbohydrate intake on the background of either overfeeding or caloric restriction. AMPK phosphorylation and acetylation of PGC1α (as a measure of SIRT activity) were determined. Euglycemic-hyperinsulinemic clamp and muscle biopsies were performed in human subjects participating in 2 separate studies. In study 1, 21 lean healthy individuals were overfed for 5 days, while in study 2, 18 obese otherwise healthy individuals consumed a calorie-restricted diet for 5 days. Under both conditions - overfeeding and caloric restriction - high fat/low carbohydrate (HF/LC) diet significantly increased phosphorylation of AMPK and deacetylation of PGC1α in skeletal muscle without affecting total amounts of AMPK, PGC1α, or SIRT 1. In contrast, low fat/high carbohydrate (LF/HC) hypocaloric diet reduced phosphorylation of AMPK and deacetylation of PGC1α. Our data indicate that a relative deficiency in carbohydrate intake or, albeit less likely, a relative excess of fat intake even in the absence of caloric deprivation is sufficient to activate the AMPK-SIRT 1-PGC1α energy-sensing cellular network in human skeletal muscle.     

The Influence of Dietary Protein Intake on Mammalian Tryptophan and Phenolic Metabolites

Although there has been increasing interest in the use of high protein diets, little is known about dietary protein related changes in the mammalian metabolome. We investigated the influence of protein intake on selected tryptophan and phenolic compounds, derived from both endogenous and colonic microbial metabolism. Furthermore, potential inter-species metabolic differences were studied. For this purpose, 29 healthy subjects were allocated to a high (n = 14) or low protein diet (n = 15) for 2 weeks. In addition, 20 wild-type FVB mice were randomized to a high protein or control diet for 21 days. Plasma and urine samples were analyzed with liquid chromatography–mass spectrometry for measurement of tryptophan and phenolic metabolites. In human subjects, we observed significant changes in plasma level and urinary excretion of indoxyl sulfate (P 0.004 and P 0.001), and in urinary excretion of indoxyl glucuronide (P 0.01), kynurenic acid (P 0.006) and quinolinic acid (P 0.02). In mice, significant differences were noted in plasma tryptophan (P 0.03), indole-3-acetic acid (P 0.02), p-cresyl glucuronide (P 0.03), phenyl sulfate (P 0.004) and phenylacetic acid (P 0.01). Thus, dietary protein intake affects plasma levels and generation of various mammalian metabolites, suggesting an influence on both endogenous and colonic microbial metabolism. Metabolite changes are dissimilar between human subjects and mice, pointing to inter-species metabolic differences with respect to protein intake.     

Effects of Dietary Crude Protein Levels and Cysteamine Supplementation on Protein Synthetic and Degradative Signaling in Skeletal Muscle of Finishing Pigs

Dietary protein levels and cysteamine (CS) supplementation can affect growth performance and protein metabolism of pigs. However, the influence of dietary protein intake on the growth response of CS-treated pigs is unclear, and the mechanisms involved in protein metabolism remain unknown. Hence, we investigated the interactions between dietary protein levels and CS supplementation and the effects of dietary crude protein levels and CS supplementation on protein synthetic and degradative signaling in skeletal muscle of finishing pigs. One hundred twenty barrows (65.84 ± 0.61 kg) were allocated to a 2 × 2 factorial arrangement with five replicates of six pigs each. The primary variations were dietary crude protein (CP) levels (14% or 10%) and CS supplemental levels (0 or 700 mg/kg). The low-protein (LP) diets (10% CP) were supplemented with enough essential amino acids (EAA) to meet the NRC AA requirements of pigs and maintain the balanced supply of eight EAA including lysine, methionine, threonine, tryptophan, valine, phenylalanine, isoleucine, and leucine. After 41 days, 10 pigs per treatment were slaughtered. We found that LP diets supplemented with EAA resulted in decreased concentrations of plasma somatostatin (SS) (P<0.01) and plasma urea nitrogen (PUN) (P<0.001), while dietary protein levels did not affect other traits. However, CS supplementation increased the average daily gain (P<0.001) and lean percentage (P<0.05), and decreased the feed conversion ratio (P<0.05) and back fat (P<0.05). CS supplementation also increased the concentrations of plasma insulin-like growth factor 1 (IGF-1) (P<0.001), and reduced the concentrations of leptin, SS, and PUN (P<0.001). Increased mRNA abundance of Akt1 and IGF-1 signaling (P<0.001) and decreased mRNA abundance of Forkhead Box O (FOXO) 4 (P<0.01) and muscle atrophy F-box (P<0.001) were observed in pigs receiving CS. Additionally, CS supplementation increased the protein levels for the phosphorylated mammalian target of rapamycin (mTOR), eIF-4E binding protein 1, and ribosomal protein S6 kinase 1 (P<0.001). There were no interactions between dietary protein levels and CS supplementation for all traits. In conclusion, dietary protein levels and CS supplementation influenced growth and protein metabolism through independent mechanisms in pigs. In addition, LP diets supplemented with EAA did not affect growth performance and other traits except the concentrations of SS and PUN probably through maintenance of protein synthesis and degradation signaling. Moreover, CS supplementation improved growth performance by increasing plasma IGF-1 concentrations possibly through alterations of mTOR and Akt/FOXO signaling pathways in skeletal muscle of finishing pigs.     

Influence of Dietary Carbohydrate,Fat, and Protein on Lipogenesis in Rats

The incorporation of ¹⁴C of acetate-1-¹⁴C into the lipids of the liver and carcass, and the changes in the concentrations of nucleotides and citric acid in the liver were studied in the rats fed individual nutrients; starch, casein or corn oil. And the metabolism of citric acid-1,5-¹⁴C was also investigated after the feeding of nutrients. Lipogenesis in the liver and carcass was more markedly stimulated with starch than with casein or corn oil. In the liver of rats fed starch, the concentration of ATP doubled and that of citric acid was one-half of those with casein or corn oil, respectively. And the conversion of citric acid to carbon dioxide and lipids was stimulated with starch.     

Ultrasound Pretreatment Increases the Bioavailability of Dietary Proteins by Dissociating Protein Structure and Composition

Food Biophysics - Bioavailability is an important indicator for evaluating the nutritional value of protein. In this study, we investigated the effect of ultrasound on improving the bioavailability...     

Defective Dietary Induction of Uncoupling Protein 3 in Skeletal Muscle of Obesity‐Prone Rats

Objective: The goal of this study was to determine whether differential induction of skeletal muscle uncoupling protein 3 (UCP3) contributes to the development of diet‐induced obesity (DIO) or resistance to the development of obesity (DR) when rats are placed on a moderate fat (31%) high energy (HE) diet. Research Methods and Procedures: Gastrocnemius muscle was obtained from Sprague‐Dawley rats that were identified as DIO‐prone (n = 5) or DR (n = 5) on the basis of urinary norepinephrine excretion while consuming a chow diet. Muscle was also obtained from animals in the top tertile of weight gain (DIO_HE, n = 5) and the bottom tertile of weight gain (DR_HE, n = 5) after 2 weeks on the HE diet. UCP3 and actin mRNA levels were measured in all muscle samples by Northern analysis. To distinguish the effect of dietary energy content from the effect of obesity itself, we studied additional DIO and DR animals that had been returned to a chow diet for 10 weeks after consuming a HE diet for 10 weeks. Results: The muscle UCP3/actin mRNA ratio in animals that resisted the development of obesity during 2 weeks on the HE diet was 3‐fold higher than in the other groups (DR_HE = 3.24 ± 0.83, DIO_HE = 0.91 ± 0.20, DIO‐prone = 0.72 ± 0.15, DR = 0.63 ± 0.15; p = 0.002). However, there was no difference in muscle UCP3/actin mRNA ratios between DIO animals and DR animals that had been fed the HE diet for 10 weeks and then returned to either an ad libitum chow diet for 10 weeks (DIO = 13.8 ± 3.53, DR = 11.1 ± 3.43, p = NS) or to a restricted chow diet for 10 weeks (DIO = 11.0 ± 2.85, DR = 10.6 ± 2.20, p = NS) despite significantly greater body weight of the DIO animals. Discussion: DR animals may initially resist weight gain when placed on a HE diet through a greater induction of muscle UCP3. This induction is transient and is related more closely to dietary fat content than to body fat stores. DIO animals show no initial induction of muscle UCP3, which may contribute to their increased metabolic efficiency soon after exposure to a HE diet.     

Cytoskeletal and Cytocontractile Protein Composition of Smooth Muscle Cells in Developing and Obstructed Rabbit Bladder

The differentiation patterns of smooth muscle cells (SMC) in rabbit bladder during development and in the hypertrophic response to partial outflow obstruction induced in adult animals were evaluated by biochemical and immunochemical techniques and by using a panel of monoclonal antibodies specific for desmin, vimentin, α-actin of smooth muscle (SM) type, SM myosin, and nonmuscle (NM) myosin isoforms. Desmin and SM α-actin were homogeneously distributed in SMC of developing, adult, and obstructed bladders. Conversely, marked changes in the ratio and antigenicity of SM myosin isoforms were observed by SDS electrophoresis and Western blotting, respectively. In particular, the 205 K (SM1) isoform was down-regulated with development whereas the 200 K (SM2) isoform was up-regulated around 7 days after birth and down-regulated in the obstructed bladder. Vimentin was expressed in SMC of the fetal bladder and declined markedly during postnatal, physiological hypertrophy of SMC, which occurs concomitantly with diminution of DNA synthesis. This polypeptide became detectable, however, in SMC of obstructed bladders. The 196 K (NM) myosin isoform recognized by NM-A9 antibody, present only in endothelium of blood vessels and in mucosa of normal fetal and adult bladders, became expressed in detrusor muscle, when SMC underwent a process of pathological hypertrophy. The reexpression of vimentin and the de novo appearance of NM myosin isoform in hypertrophic bladders can be reversed when the tissue mass is reduced, such as in bladders after 1-month recovery from partial obstruction. Thus, a specific NM myosin isoform can be used as a marker of SMC hypertrophy in obstructed bladder. In addition, the combined use of anti-vimentin and NM-A9 antibodies can distinguish between SMC which are in the physiological or in the pathological condition of adaptive bladder hypertrophy.     

Short‐Term Effects of Dietary Fatty Acids on Muscle Lipid Composition and Serum Acylcarnitine Profile in Human Subjects

In cultured cells, palmitic acid (PA) and oleic acid (OA) confer distinct metabolic effects, yet, unclear, is whether changes in dietary fat intake impact cellular fatty acid (FA) composition. We hypothesized that short‐term increases in dietary PA or OA would result in corresponding changes in the FA composition of skeletal muscle diacylglycerol (DAG) and triacylglycerol (TAG) and/or the specific FA selected for β‐oxidation. Healthy males (N = 12) and females (N = 12) ingested a low‐PA diet for 7 days. After fasting measurements of the serum acylcarnitine (AC) profile, subjects were randomized to either high‐PA (HI PA) or low‐PA/high‐OA (HI OA) diets. After 7 days, the fasting AC measurement was repeated and a muscle/fat biopsy obtained. FA composition of intramyocellular DAG and TAG and serum AC was measured. HI PA increased, whereas HI OA decreased, serum concentration of 16:0 AC (P < 0.001). HI OA increased 18:1 AC (P = 0.005). HI PA was associated with a higher PA/OA ratio in muscle DAG and TAG (DAG: 1.03 ± 0.24 vs. 0.46 ± 0.08, P = 0.04; TAG: 0.63 ± 0.07 vs. 0.41 ± 0.03, P = 0.01). The PA concentration in the adipose tissue DAG (µg/mg adipose tissue) was 0.17 ± 0.02 in those receiving the HI PA diet (n = 6), compared to 0.11 ± 0.02 in the HI oa group (n = 4) (P = 0.067). The relative PA concentration in muscle DAG and TAG and the serum palmitoylcarnitine concentration was higher in those fed the high‐PA diet.     

The Influence of Low Protein Diet on the Composition of Rat Liver Cell Fractions

Rats were divided into high protein diet and low protein diet fed groups. Their livers were removed, homogenized, and fractionated into nuclei, mitochondria, microsome and supernatant fraction.

Amount of total- and phospho-lipids in each fraction was measured, and simultaneously, total nitrogen was measured. Then, the ratio of total- and phospho-lipids to nitrogen was calculated. The influence of low protein diet on this calculated value was seen in the mitochondrial and supernatant fraction but was not recognized in other fractions.

The relationship between this phenomenon and energy efficiency of diets was discussed.     

Effect of Dietary Protein and Energy Levels on the Growth Rate,Feed Efficiency and Carcass Composition of Chicks

Feeding day-old White Leghorn male chicks 9 different diets for 4 weeks with the orthogonal composite design, we studied the relationship among dietary protein, energy levels and chick’s responses.

The ellipsoid relationship has been found fitted to describe the relationship between dietary composition and weight gain or feed efficiency of chicks, whereas declined planes are fitted to show the relationship between dietary composition and carcass protein or fat levels of chicks. Dietary protein level has great influence on nitrogen retention, but dietary energy level has little effect.

The linear relationship between total digestible nutrients and metabolizable energy in diets is presented.     

Influence of Early and Prolonged Protein Depletion in the Diet on in vitro Protein Synthesis in Muscle and Liver of Rats

Male rats weighing about 200 g were killed after 1, 2, 4, 10, and 20 days on a protein-free diet, and in vitro synthesis of protein was measured by the incorporation of ¹⁴C-glycine into protein of liver slices and isolated soleus muscle. The incorporation value was corrected for the differences in specific radioactivity of intracellular free glycine, and protein and RNA contents of tissue were determined.

Muscle protein synthesis began to decrease from the 1st day of depletion, fell rapidly until the 4th day, and then was reduced gradually to about 30 % of the initial control by the 20th day. This reduction was due in a major part to a fall in the rate of protein synthesis per unit of RNA and in a minor part to a decline in RNA content. In the liver, protein synthesis increased in the early period of protein depletion, but declined with prolonged depletion, and was reduced greatly by severe depletion. These alterations were caused mainly by the changes in incorporative activity per unit of RNA.

From these results, it was suggested that different patterns of adaptive response to protein depletion occurred in both cases of early and prolonged depletion in connection with protein metabolism in rats.     

Role and Metabolism of Free Leucine in Skeletal Muscle in Protein Sparing Action of Dietary Carbohydrate and Fat

Feeding rats with either a carbohydrate meal or a fat meal to the previously fasted rats caused significant decrease in urinary output of urea and total nitrogen. The content of free leucine in skeletal muscle decreased in the rats fed either a carbohydrate meal or a fat meal. Feeding of either a carbohydrate meal or a fat meal stimulated incoiporation of l-leucine-1–¹⁴C into protein fraction of skeletal muscle and reduced its oxidation to ¹⁴CO₂.

These results suggest that the metabolism of leucine is under nutritional regulation and that the decrease in content of free leucine in skeletal muscle might be caused by enhanced reutilization of leucine into protein by the feeding of a carbohydrate meal or a fat meal. The role of free leucine in skeletal muscle as a regulator of protein turnover in the tissue are discussed in relation to the metabolism of this branched chain amino acid.     

Body Composition,and Utilization of Protein and Energy in Growing Rats at Different Dietary Protein to Energy Ratios by Use of Purified Whole Egg Protein

A study has been made on growing rats to investigate the effect of variation in percentage of dietary protein calories from 0 to 50% by the use of purified whole egg protein on the growth, food efficiency, protein efficiency ratio (PER), body composition, and efficiencies of protein and energy utilization.

Body weight gain and PER attained a maximum, and food efficiency reached a plateau at 10 PC% (protein calories percent) in the diet, having a constant metabolizable energy content (410 kcal). Body and liver compositions changed in systematic patterns, where liver lipid content showed a specific increase at 5 PC%.

Body protein retention reached a plateau at 15 PC% but with little difference from the value at 10 PC%, while body lipid retention give a maximum at 10 PC% showing a gradual decrease thereafter.

Throughout the given dietary protein to energy ratios, energy utilization was constant when expressed as the increment of body energy retention divided by the increment of metabolizable energy intake. At and above 12 or 13 PC%, the efficiency of net body protein energy retention against metabolizable energy intake was constant at about 12.5% on the average.     

Dietary Effects on the Composition of Fecal Flora of Rats

A long-term animal feeding experiment was conducted to compare the effect of meat and Wayne laboratory chow diets on the composition of rat fecal flora. Fecal bacteria were enumerated on selective media under both aerobic and anaerobic conditions. Intrarectal administration of N-methyl-N′ -nitro-N-nitro-soguanidine (MNNG) affected the count only on the phenylethylalcohol and veillonella-neomycin agars, whereas a slightly higher number of anaerobes appeared in the feces of rats that were treated with MNNG as compared with those obtained in the feces of untreated rats on the meat diet. In the absence of MNNG, feces of meat-fed rats yielded higher bacterial counts on aerobically incubated MacConkey agar, deoxycholate agar, and Pfizer selective enterococcus agar as well as higher numbers of clostridia on anaerobic egg yolk agar than did feces of rats on the Wayne diet. Feces of the group fed the Wayne diet produced more colonies on aerobic mitis-salivarius agar and lactobacillus agar as well as on anaerobically incubated phenylethylalcohol agar, veillonellaneomycin agar, bifidobacteria agar, fusobacterium (Nissui) agar, and kanamycin-vancomycin blood agar. These differences were consistent throughout the 1-year feeding period.