Amount Of Dietary Protein Research Articles

Dietary Protein Quantity and Source Impact Weight and Body Composition of Older Adults: Analysis of NHANES 2001‐2006 Data

We assessed the effect of dietary protein on weight and body composition (BC) of older adults using dietary (food records) and BC (DXA) data from NHANES 2001‐2006. Data from 5,102 men and women, aged 50+ y, were analyzed using multiple linear regressions with age, sex, ethnicity, BMI, and carbohydrate and fat intakes as co‐variables and protein intake as a categorical variable separated into quartiles. Among all subjects, the 5th, 25th, 50th, 75th, and 95th percentiles of total protein intake (TPro, g•kg‐1•d‐1, mean±SE) were 0.51±0.01, 0.73±0.01, 0.92±0.01, 1.14±0.01, and 1.51±0.03, respectively. Higher TPro predicted lower weight, fat mass (FM, kg), FM%, FM index (kg/m2) and non‐bone lean mass (LM, kg), and higher LM% and LM index (kg/m2) for all subjects (all P‐values <0.007). Total bone mineral content (BMC, kg) and bone mineral density (BMD, g/cm2) were not influenced, and BMC index (kg/m2) was higher with higher TPro. Relationships between sources of protein (dairy, non‐dairy animal, and plant) and these BC parameters were varied. In general, the protein intake‐related patterns for weight and the indices of soft tissue BC related to TPro also were shown for non‐dairy animal and plant protein, but not dairy protein. For bone, higher intakes of dairy, non‐dairy animal, and plant protein intakes were not associated with BMC or BMD, while higher dairy protein intake predicted higher BMC index. These epidemiological results underscore the importance of dietary protein for weight control and improved adiposity and bone among older adults in the United States.Support: Dairy Res. Inst.

Effects of Dietary Protein Quantity and Source in Appetite Responses in Energy‐Restricted Overweight and Obese Adults

Weight loss is pivotal for improving obesity‐related comorbidities. Under ad libitum conditions, high‐protein diets reportedly aid weight loss partially by sustaining satiety. However, it is not clear during energy restriction (ER), how 1) protein quantity across the acceptable macronutrient distribution range (AMDR) and 2) predominant protein source affect appetitive responses in overweight/obese adults adapted to such diets. In this study, 23F/11M overweight/obese adults (age 蠅21y, BMI 30.8±0.4 kg/m2) were randomly assigned to two groups with either lean pork/beef or soy/legume as the predominant protein source (30% total protein). Each subject consumed ER diets (‐750 kcal/d) containing 10%, 20%, or 30% energy from protein for 3 consecutive 4‐wk trials (in random order). At the end of each trial, perceived appetite ratings (fullness, hunger, and desire to eat) were measured using visual analog scales (0‐100mm) under free‐living (days 25‐27, waking hours) and in‐lab (day 28, for 4 hours post‐breakfast consumption) conditions with all foods and breakfast provided, respectively. Neither protein quantity nor predominant protein source affected appetite ratings, with the exception that during the 30% protein trial daily fullness was higher than during the 10% trial (areas under the curve: 638±45 vs. 582±43 mm*13h, P<0.05). Our results suggest that protein quantity within the AMDR, regardless of predominant source, has a minimal impact on daily and meal‐specific appetite during weight loss.Support: National Cattleman's Beef Assoc.; National Pork Board; NIH UL1TR001108.

Induced lung inflammation and dietary protein supply affect nitrogen retention and amino acid metabolism in growing pigs.

It is hypothesised that during immune system activation, there is a competition for amino acids (AA) between body protein deposition and immune system functioning. The aim of the present study was to quantify the effect of immune system activation on N retention and AA metabolism in growing pigs, depending on dietary protein supply. A total of sixteen barrows received an adequate (Ad) or restricted (Res) amount of dietary protein, and were challenged at day 0 with intravenous complete Freund's adjuvant (CFA). At days -5, 3 and 8, an irreversible loss rate (ILR) of eight AA was determined. CFA successfully activated the immune system, as indicated by a 2- to 4-fold increase in serum concentrations of acute-phase proteins (APP). Pre-challenge C-reactive protein concentrations were lower (P<0·05) and pre- and post-challenge albumin tended to be lower in Res-pigs. These findings indicate that a restricted protein supply can limit the acute-phase response. CFA increased urinary N losses (P=0·04) and tended to reduce N retention in Ad-pigs, but not in Res-pigs (P=0·07). The ILR for Val was lower (P=0·05) at day 8 than at day 3 in the post-challenge period. The ILR of most AA, except for Trp, were strongly affected by dietary protein supply and positively correlated with N retention. The correlations between the ILR and APP indices were absent or negative, indicating that changes in AA utilisation for APP synthesis were either not substantial or more likely outweighed by a decrease in muscle protein synthesis during immune system activation in growing pigs.

Dietary protein considerations to support active aging.

Given our rapidly aging world-wide population, the loss of skeletal muscle mass with healthy aging (sarcopenia) represents an important societal and public health concern. Maintaining or adopting an active lifestyle alleviates age-related muscle loss to a certain extent. Over time, even small losses of muscle tissue can hinder the ability to maintain an active lifestyle and, as such, contribute to the development of frailty and metabolic disease. Considerable research focus has addressed the application of dietary protein supplementation to support exercise-induced gains in muscle mass in younger individuals. In contrast, the role of dietary protein in supporting the maintenance (or gain) of skeletal muscle mass in active older persons has received less attention. Older individuals display a blunted muscle protein synthetic response to dietary protein ingestion. However, this reduced anabolic response can largely be overcome when physical activity is performed in close temporal proximity to protein consumption. Moreover, recent evidence has helped elucidate the optimal type and amount of dietary protein that should be ingested by the older adult throughout the day in order to maximize the skeletal muscle adaptive response to physical activity. Evidence demonstrates that when these principles are adhered to, muscle maintenance or hypertrophy over prolonged periods can be further augmented in active older persons. The present review outlines the current understanding of the role that dietary protein occupies in the lifestyle of active older adults as a means to increase skeletal muscle mass, strength and function, and thus support healthier aging.

Higher versus lower protein intake in formula-fed low birth weight infants.

The ideal quantity of dietary protein for formula-fed low birth weight infants is still a matter of debate. Protein intake must be sufficient to achieve normal growth without negative effects such as acidosis, uremia, and elevated levels of circulating amino acids. To determine whether higher (≥ 3.0 g/kg/d) versus lower (< 3.0 g/kg/d) protein intake during the initial hospital stay of formula-fed preterm infants or low birth weight infants (< 2.5 kilograms) results in improved growth and neurodevelopmental outcomes without evidence of short- and long-term morbidity.To examine the following distinctions in protein intake. 1. Low protein intake if the amount was less than 3.0 g/kg/d. 2. High protein intake if the amount was equal to or greater than 3.0 g/kg/d but less than 4.0 g/kg/d. 3. Very high protein intake if the amount was equal to or greater than 4.0 g/kg/d.If the reviewed studies combined alterations of protein and energy, subgroup analyses were to be carried out for the planned categories of protein intake according to the following predefined energy intake categories. 1. Low energy intake: less than 105 kcal/kg/d. 2. Medium energy intake: greater than or equal to 105 kcal/kg/d and less than or equal to 135 kcal/kg/d. 3. High energy intake: greater than 135 kcal/kg/d.As the Ziegler-Fomon reference fetus estimates different protein requirements for infants based on birth weight, subgroup analyses were to be undertaken for the following birth weight categories. 1. < 800 grams. 2. 800 to 1199 grams. 3. 1200 to 1799 grams. 4. 1800 to 2499 grams. The standard search methods of the Cochrane Neonatal Review Group were used. MEDLINE, CINAHL, PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library) were searched. Randomized controlled trials contrasting levels of formula protein intake as low (< 3.0 g/kg/d), high (≥ 3.0 g/kg/d but < 4.0 g/kg/d), or very high (≥ 4.0 g/kg/d) in formula-fed hospitalized neonates weighing less than 2.5 kilograms were included. Studies were excluded if infants received partial parenteral nutrition during the study period or were fed formula as a supplement to human milk. Studies in which nutrients other than protein also varied were added in a post-facto analysis. The standard methods of the Cochrane Neonatal Review Group were used. Five studies compared low versus high protein intake. Improved weight gain and higher nitrogen accretion were demonstrated in infants receiving formula with higher protein content while other nutrients were kept constant. No significant differences were seen in rates of necrotizing enterocolitis, sepsis, or diarrhea.One study compared high versus very high protein intake during and after an initial hospital stay. Very high protein intake promoted improved gain in length at term, but differences did not remain significant at 12 weeks corrected age. Three of the 24 infants receiving very high protein intake developed uremia.A post-facto analysis revealed further improvement in all growth parameters in infants receiving formula with higher protein content. No significant difference in the concentration of plasma phenylalanine was noted between high and low protein intake groups. However, one study (Goldman 1969) documented a significantly increased incidence of low intelligence quotient (IQ) scores among infants of birth weight less than 1300 grams who received a very high protein intake (6 to 7.2 g/kg). Higher protein intake (≥ 3.0 g/kg/d but < 4.0 g/kg/d) from formula accelerates weight gain. However, limited information is available regarding the impact of higher formula protein intake on long-term outcomes such as neurodevelopmental abnormalities. Available evidence is not adequate to permit specific recommendations regarding the provision of very high protein intake (> 4.0 g/kg/d) from formula during the initial hospital stay or after discharge.

Quantity of dietary protein, but not pattern of intake, affects net protein accretion in older adults (272.4)

We examined 16‐h whole body protein turnover [protein synthesis (PS), breakdown (PB), and net balance (NB), expressed as delta changes from the fasted state] in four permutations: a level of protein intake of 0.8g/kg/day (1RDA) or 1.5g/kg/day (2RDA) with an uneven [U: 15/20/65%)] or even distribution patterns of intake (E: 33/33/33%) for breakfast, lunch, &amp;amp; dinner of intake over the day. Twenty healthy older subjects were randomly assigned into one of 4 groups: 1RDA‐U, 1RDA‐E, 2RDA‐U, or 2RDA‐E, and were studied with primed continuous infusions of ring‐[2H5]phenylalanine &amp;amp; ring‐[2H2]tyrosine on day 4 following 3 days of diet habituation. Positive NB was achieved at both protein levels, but NB was significantly greater in 2RDA vs. 1RDA [NB: 94.75 ± 6.01 vs. 58.86 ± 4.91 g protein/kg/750min; p = 0.0001], without effects of distribution on NB. The greater NB was due to the higher PS with 2RDA vs. 1RDA [PS: 15.40 ± 4.84 vs. ‐17.98 ± 8.44 g protein/kg/750min; p = 0.0018]. PS was significantly correlated with delta changes of mean plasma concentrations of leucine from the fasted state (R2 = 0.51, p = 0.0004). We conclude that in the context of mixed meals whole body net protein accretion is greater with protein intake above recommended dietary allowance (0.8 g protein/kg/day), regardless of protein intake pattern, primarily through increased protein synthesis.Grant Funding Source: Supported by Dairy Research Institute and Award Number UL1TR000039 and KL2TR000063 (NCATS and NIH)

Effects of dietary protein source and quantity on glycemic control in energy‐restricted overweight and obese adults (381.8)

The acceptable macronutrient distribution range (AMDR) for protein ranges from 10‐35% of daily total energy intake. It is unknown how diets with predominate sources of protein from animal flesh vs. plant, with protein intakes spanning the AMDR affect glycemic control during weight loss in overweight/obese adults. 23F/11M overweight/obese adults (age蠅21 y; BMI 30.8±2.6 kg/m2) were randomly assigned to two groups (lean pork/beef or soy/legume products). Each subject consumed, in random order, energy restricted (ER) diets (‐750 kcal/d) which contained 10%, 20%, or 30% energy from protein (30% of total protein provided from lean pork/beef or soy/legume products) for 3 consecutive 4‐week trials. Chronic adaptations to the experimental diets did not affect fasting glucose, fasting insulin, insulin resistance (HOMA‐IR), or pancreatic beta function (HOMA‐β). Acute glucose responses (area under the curve, 4h) to breakfast meals corresponding to the assigned diets were not different, despite an elevation of insulin area under the curve (P=0.02) with 30% protein compared to 20%. These results suggest that neither protein source nor quantity spanning the ADMR range influence fasting and postprandial glucose responses in overweight/obese adults adapted to energy restricted diets.Grant Funding Source: Supported by National Cattleman’s Beef Association, National Pork Board, NIH UL1 TR000006.

Protein content in larval diet affects adult longevity and antioxidant gene expression in honey bee workers

AbstractIn honey bees, adult longevity is strongly dependent on the quantity of dietary protein ingested after emergence, but relatively little is known about the role played by the protein content of larval diet. In total, 15 colonies of Apis mellifera ligustica Spinola (Hymenoptera: Apidae) bees with sister queens were randomly allocated to one of three groups (five colonies per group), provided with pollen substitutes (PS) with protein concentrations of 15, 25, or 35%, designated as PS15, PS25, and PS35, respectively. In a field experiment, we measured the PS consumption and collected samples for analyzing body protein content and gene expression. On day 29, groups of 50 newly emerged workers from each colony were obtained and confined in cages for measuring survival and longevity. Results showed that bees consumed significantly more PS15 and PS25 than PS35. However, the total protein intake of PS15 was less than that of the others. Increasing the protein available to larvae (PS35) significantly increased total accumulated protein before emergence, adult survival, and longevity. Furthermore, bees fed PS25 or PS35 tended to have higher mRNA levels for genes encoding antioxidant enzymes, providing a potential physiological mechanism for observed survival differences among the three dietary treatments. We conclude that protein content in larval diet could positively influence worker longevity likely because of the increased related antioxidant gene expression.

A randomized trial to manipulate the quality instead of quantity of dietary proteins to influence the markers of satiety

AimsTo test whether a breakfast including eggs (EB) containing high-quality protein decreases subsequent food intake and increases satiety-related hormones in overweight or obese adults more than a breakfast including cereal (CB) of lower protein quality, but matched for energy density and macronutrient composition. MethodsTwenty healthy overweight or obese subjects were randomized to eat an EB or a CB daily under supervision for one week, followed by a crossover to the opposite breakfast week after a two-week washout period. On days 1 and 7 of each test week, a structured lunch was provided ad libitum. Food intake, hunger and satiety scores, and blood parameters were measured before and after breakfast. Outcomes were analyzed using mixed effects statistical models for repeated measures analysis of variance. ResultsCompared to the CB week, during the EB week, a) feeling of fullness was greater (P<0.05) on day 1 but not on day 7; b) energy intake was not significantly lower on either day; c) right before lunch, acylated ghrelin was lower and PYY3-36 was higher on day 1 (P<0.01 and <0.002, respectively) but not on day 7; d) PYY3-36, but not ghrelin, showed greater rise between breakfast and lunch on days 1(P<0.001) and 7(P<0.01). ConclusionDespite a highly similar energy density and macronutrient composition, the higher protein quality breakfast significantly influenced fullness, ghrelin and PYY3-36. Only the effect on PYY3-36 lasted throughout the week. A next step would be to test if the benefits are pronounced and lasting, if protein quality of all meals is increased.

Dietary protein and muscle in older persons

The purpose of this study is to highlight recent advances in nutrition and protein research that have the potential to improve health outcomes and status in ageing adults. The beneficial effects of dietary protein on muscle health in older adults continue to be refined. Recent research has bolstered support for moderately increasing protein consumption beyond the current Recommended Dietary Allowance by adopting a meal-based approach in lieu of a less specific daily recommendation. Results from muscle protein anabolism, appetite regulation and satiety research support the contention that meeting a protein threshold (approximately 30 g/meal) represents a promising strategy for middle-aged and older adults concerned with maintaining muscle mass while controlling body fat. Optimizing dietary protein intake to improve health requires a detailed consideration of topics including muscle protein anabolism, appetite control and satiety. Although each area of research continues to advance independently, recent collaborative and translational efforts have highlighted broad, translational consistencies related to the daily distribution and quantity of dietary protein.

Food-derived bioactive peptides – a new paradigm

Food-derived bioactive peptides are regarded as important modulators of several physiological processes occurring both systemically and locally within the gastrointestinal tract (GIT). However, the concentrations of food-derived bioactive peptides in the GIT, and therefore attendant physiological effects, are likely to be highly variable given the wide variation in the type and amount of dietary protein consumed either during the day or on a day-to-day basis. In contrast, gut endogenous proteins (e.g. cell proteins, mucin, serum albumin and digestive enzymes) are a consistent and significant potential source of peptides for the GIT. With up to 80% of gut endogenous proteins being digested in the GIT, it is possible that a wide range of peptides is generated, but until now the significance of the gut endogenous proteins as a source of bioactive peptides has not been considered. A hypothesis is promulgated that the gut endogenous proteins may have a hidden role as a consistent and quantitatively important source of bioactive peptides in the GIT.

Hepatic Amino Acid-Degrading Enzyme Expression Is Downregulated by Natural and Synthetic Ligands of PPARα in Rats1–3

Body nitrogen retention is dependent on the amount of dietary protein consumed, as well as the fat and carbohydrate content in the diet, due to the modulation of amino acid oxidation. PPARα is a transcription factor involved in the upregulation of the expression of enzymes of fatty acid oxidation. However, the role of putative PPARα response elements (PPREs) in the promoter of several amino acid-degrading enzymes (AADEs) is not known. The aim of this work was to study the effect of the synthetic ligand Wy 14643 and the natural ligands palmitate, oleate, and linoleate in rats fed graded concentrations of dietary protein (6, 20, or 50 g/100 g of total diet) on the expression of the AADEs histidase, serine dehydratase, and tyrosine aminotransferase. Thus, we fed male Wistar rats diets containing 6, 20, or 50% casein for 10 d. The results showed that addition of Wy 14643 to the diet significantly reduced the expression of the AADEs. Furthermore, the incubation of hepatocytes with natural ligands of PPARα or feeding rats with diets containing soybean oil, safflower oil, lard, or coconut oil as sources of dietary fat significantly repressed the expression of the AADEs. Gene reporter assays and mobility shift assays demonstrated that the PPRE located at −482 bp of the histidase gene actively bound PPARα in rat hepatocytes. These data indicate that PPARα ligands may reduce amino acid catabolism in rats.

Refining dietary protein recommendations for the athlete

Refining dietary protein recommendations for the athlete

Effects of dietary protein quantity on sleep quality in energy‐restricted overweight and obese adults

Research suggests ingesting protein before sleep may improve sleep quality, but the effect of habitual protein intake on sleep quality is not well known. For this pilot study, nine overweight/obese people (6F:3M, age 59 ± 11 y, BMI 30.0 ± 1.6 kg/m2, mean ± SD) consumed lacto‐ovo vegetarian diets with an energy restriction (ER) of 750 kcal/d below need for 3 months. During this time, each person randomly completed three consecutive 4‐wk periods with the diets containing 10, 20 or 30% of total energy from protein. At baseline and the end of each ER period, global sleep quality (GSQ) was assessed using the Pittsburgh Sleep Quality Index questionnaire. GSQ scores range between 0–21 arbitrary units (au) with a higher value representing worse GSQ during the preceding month. At baseline, 78% of the participants were classified with poor GSQ (&gt;;5 au), and 44%, 56%, and 11% had poor GSQ while consuming 10%, 20%, and 30% protein during ER, respectively. During ER, GSQ was lower when 30 vs. 10% protein was consumed (4.38 ± 1.51 vs. 5.78 ± 2.59, P = 0.05), with 20% protein intermediate (5.67 ± 2.69). When expressed as change from the previous month, delta GSQ was larger for 30% (−1.75 ± 1.49) vs. 20% (−0.11 ± 0.78) and 10% (0.13 ± 1.13) protein (P = 0.0179). These results suggest that consuming a greater proportion of energy from protein may improve global sleep quality during weight loss.Grant Funding Source: The Beef Checkoff, National Pork Board, and NIH RR025761

The muscle protein synthetic response to the combined ingestion of protein and carbohydrate is not impaired in healthy older men

Aging is associated with a progressive decline in skeletal muscle mass. It has been hypothesized that an attenuated muscle protein synthetic response to the main anabolic stimuli may contribute to the age-related loss of muscle tissue. The aim of the present study was to compare the muscle protein synthetic response following ingestion of a meal-like amount of dietary protein plus carbohydrate between healthy young and older men. Twelve young (21 ± 1 years) and 12 older (75 ± 1 years) men consumed 20 g of intrinsically L-[1-(13)C]phenylalanine-labeled protein with 40 g of carbohydrate. Ingestion of specifically produced intrinsically L-[1-(13)C]phenylalanine-labeled protein allowed us to assess the subsequent incorporation of casein-derived amino acids into muscle protein. Blood samples were collected at regular intervals, with muscle biopsies obtained prior to and 2 and 6 h after protein plus carbohydrate ingestion. The acute post-prandial rise in plasma glucose and insulin concentrations was significantly greater in the older compared with the younger males. Plasma amino acid concentrations increased rapidly following drink ingestion in both groups. However, plasma leucine concentrations were significantly lower at t = 90 min in the older when compared with the young group (P < 0.05). Muscle protein-bound L-[1-(13)C]phenylalanine enrichments increased to 0.0071 ± 0.0016 and 0.0072 ± 0.0013 mole percent excess (MPE) at 2 h and 0.0229 ± 0.0016 and 0.0213 ± 0.0024 MPE at 6 h following ingestion of the intrinsically labeled protein in the young and older males, respectively, with no differences between groups (P > 0.05). We conclude that the use of dietary protein-derived amino acids for muscle protein synthesis is not impaired in healthy older men following intake of protein plus carbohydrate.

Stable isotope evidence of meat eating and hunting specialization in adult male chimpanzees

Observations of hunting and meat eating in our closest living relatives, chimpanzees (Pan troglodytes), suggest that among primates, regular inclusion of meat in the diet is not a characteristic unique to Homo. Wild chimpanzees are known to consume vertebrate meat, but its actual dietary contribution is, depending on the study population, often either unknown or minimal. Constraints on continual direct observation throughout the entire hunting season mean that behavioral observations are limited in their ability to accurately quantify meat consumption. Here we present direct stable isotope evidence supporting behavioral observations of frequent meat eating among wild adult male chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d'Ivoire. Meat eating among some of the male chimpanzees is significant enough to result in a marked isotope signal detectable on a short-term basis in their hair keratin and long-term in their bone collagen. Although both adult males and females and juveniles derive their dietary protein largely from daily fruit and seasonal nut consumption, our data indicate that some adult males also derive a large amount of dietary protein from hunted meat. Our results reinforce behavioral observations of male-dominated hunting and meat eating in adult Taï chimpanzees, suggesting that sex differences in food acquisition and consumption may have persisted throughout hominin evolution, rather than being a recent development in the human lineage.

Soluble fibre, starch and protein level in diets for growing rabbits: Effects on digestive efficiency and productive traits

From 29d of age until slaughter (78d), 246 hybrid rabbits were divided into six experimental groups and fed six diets ad libitum according to a bi-factorial arrangement with two soluble fibre-to-starch ratios (0.5 and 1.1), obtained by replacing starch (from 178 to 130g/kg) with soluble fibre (from 84 to 141g/kg), and three levels of crude protein (139, 154, and 172g/kg diet). Growth traits were recorded on all rabbits; total tract apparent digestibility coefficients (CCTAD) were measured on 72 rabbits. Gut traits were obtained from further 36 rabbits slaughtered at 38d of age. The increase in the soluble fibre-to-starch ratio increased (P<0.001) the CTTAD of the dry matter (0.605–0.670) and almost all nutrients and decreased (P<0.001) feed intake (7.0%) and feed conversion (8.4%) over the whole trial. The increase in the soluble fibre-to-starch ratio decreased the pH (5.87–5.71, P<0.05) and the ammonia-N level (4.72–2.33mmol/L; P=0.001), and increased the total volatile fatty acid (VFA) content (64.0–78.4mmol/L; P<0.01) of the caecal contents. When the crude protein concentration was increased, the CTTAD of almost all nutrients increased linearly (P<0.01), the daily growth rate (5.3%; P<0.001) increased, and the feed conversion decreased (4.7%; P<0.001). At slaughter, a higher dietary protein level was associated with a greater live weight of animals (2729–2840g; P<0.01) and carcasses. The proportion of the gastro-intestinal tract decreased (190–184g/kg slaughter weight; P<0.05) and the dressing percentage increased (60.1–60.7% slaughter weight; P<0.05). In the caecum, the total VFA level linearly increased from rabbits fed low-protein diets to rabbits fed high-protein diets (61.2–78.4mmol/L; P<0.01). Neither the dietary soluble fibre-to-starch ratio nor the protein level affected the health status of the rabbits or the morphology of the gut mucosa. In conclusion, the use of diets with high soluble fibre concentrations (141g/kg) and low starch concentrations (130g/kg) enhanced the digestive efficiency, growth performance, and caecal fermentation of growing rabbits, despite the moderate level of acid detergent fibre (ADF: 164g/kg). In contrast, reducing the amount of dietary protein from 172 to 139g/kg decreased the growth performance and caecal fermentation activity of rabbits. In the tested range, the soluble fibre-to-starch ratio and the protein level did not show relevant interactions, and the health status was not affected by these dietary treatments.

Effects of the dietary amount and source of protein, resistance training and anabolic-androgenic steroids on body weight and lipid profile of rats.

Dietary protein amount and source, hypertrophy resistance training (RT) and anabolicandrogenic steroids (AAS) may affect body weight and plasma and hepatic lipid profile. 157 adult male Wistar rats were randomly distributed in 16 experimental groups resulting in: normal-protein (NP) or high-protein (HP) diets, whey or soy-protein diets, with or without RT and with or without AAS, for 3 months. Final body weight was lower in the RT and AAS groups compared to sedentary and non- AAS groups, respectively (all, p<0.001). Plasma total cholesterol (TC) was lower for the HP compared to the NP diets, for the whey compared to the soy-protein diets and for the AAS compared to the non-AAS groups (all, p<0.001). Plasma HDL-cholesterol was higher in the RT groups (p<0.05) but lower for the AAS groups (p<0.001), the HP and the soy-protein diets (p<0.05). Plasma triglycerides (TAG) were lower for the HP diet (p<0.001), for the RT (p=0.002) and the non-AAS groups (p=0.001). Liver TC was lower for the NP (p<0.01), for the soyprotein (p<0.05) and for the AAS groups (p<0.001). Liver TAG were lower for the whey-protein diet (p<0.001), RT and non-AAS groups (both, p<0.05). Some interactions were found, such as the greater effect of AAS on reducing body weight of rats that performed RT or ingested a HP diet (all, p<0.05). HDL-cholesterol was higher when RT was combined with HP diets (p=0.010) or non-AAS and when HP diets were combined with non-AAS (both,p<0.001). Groups that combined RT with non-AAS administration obtained the lowest hepatic TAG (p<0.05). Among all the interventions tested, AAS was the factor that most negatively affected plasma and hepatic lipid profile, whereas HP diets and RT could benefit lipid profile, especially when combined.

Role of specific dietary amino acids in clinical conditions

In a variety of chronic and acute disease states, alterations in protein synthesis, breakdown and protein turnover rates occur that are related to the loss of body protein and skeletal muscle wasting. A key observation is the stimulation of protein breakdown in muscle and the stimulation of protein synthesis in the splanchnic area; mainly liver. An altered splanchnic extraction of amino acids as well as an anabolic resistance to dietary protein, related to stress, disuse and aging play a key role in the pathogenesis of muscle wasting in these conditions. To overcome these factors, specific dietary protein and amino acid diets have been introduced. The main focus of these diets is the quantity and quality of dietary proteins and whether a balanced mixture or solely dietary essential amino acids are required with or without higher intake levels of specific amino acids. Specifically in cancer patients, stimulated muscle protein synthesis has been obtained by increasing the amount of protein in a meal and by providing additional leucine. Also in other chronic diseases such as chronic obstructive pulmonary disease and cystic fibrosis, meals with specific dietary proteins and specific combinations of dietary essential amino acids are able to stimulate anabolism. In acute diseases, a special role for the amino acid arginine and its precursor citrulline as anabolic drivers has been observed. Thus, there is growing evidence that modifying the dietary amino acid composition of a meal will positively influence the net balance between muscle protein synthesis and breakdown, leading to muscle protein anabolism in a variety of chronic and acute disease states. Specific amino acids with anabolic potential are leucine, arginine and citrulline.

Effect of the amount of dietary protein in the dam metabolism in rat liver and mammary gland during pregnancy and lactation

During pregnancy and lactation periods there are many metabolic adaptations in the liver, and mammary gland (MG) of the dam to use different metabolic fuels. The aim of the study was to analyze these adaptations on the expression of genes of glucose, lipid and amino acid metabolism in the liver and MG of pregnant and lactating rats fed graded concentrations of dietary protein (10, 20 or 30%). During pregnancy and lactation the expression of lipogenic (SREBP‐1, ACC and FAS), and glycolytic (PK) genes increased as the amount of dietary protein decreased, but hepatic lipogenesis was higher during lactation than pregnancy. The expression of amino acid degrading enzymes (SDH) and gluconeogenic (PEPCK) genes increased as the concentration of dietary increased during pregnancy. In the lactation period the expression of SDH did not increase with the amount of dietary protein. In contrast in the MG the expression of lipogenic, amino acid transport (SNAT2) and mTOR genes increased overtime independently of the amount of dietary protein whereas there was a reduced expression of lipolytic (HSL) and lipid oxidation (CPT‐1) genes. These results indicate that the excess of amino acids provide energy for the hepatic energy needs during gestation and lactation. The MG showed an increase fatty acids and protein synthesis to sustain the needs of the pups regardless of the amount of dietary protein during lactation.