Effects Of Protein Restriction Research Articles

Characteristics, lipogenic enzyme activity, and fatty acid composition of muscles in the Iberian pig: Effects of protein restriction and free-range feeding

In Iberian pigs, protein restriction during the final fattening period does not affect productive parameters and carcase fatness but increases the intramuscular lipid content. The aim of this study was to investigate the effects of a low-crude protein diet on the muscle characteristics, metabolism, lipogenic enzyme activity, and fatty acid composition of Iberian pigs fed under confinement and free-range conditions. Twenty-four castrated male Iberian pigs with an average initial body weight (BW) of 116.0 kg were divided into three groups (n = 8); the first and second groups were fed isoenergetic (4100 kcal ME/kg dry matter) concentrated diets with standard protein (12.8%) (SP) and low protein (6.6%) (LP) contents, respectively, under outdoor confinement; the third group was fed on natural resources (acorn and grass) under free-range conditions (FR). The pigs were slaughtered at an average BW of 174.2 kg. Compared with pigs fed the SP diet, LP and FR pigs showed significantly high intramuscular fat (IMF) contents and low muscle and fiber areas. In the muscle, the activities of glucose-6-phosphate dehydrogenase (G6PDH) and malic enzyme (ME) were not affected by diet, but a slight increase in ME activity was observed in SP pigs compared to that in LP and FR pigs when the results were expressed as per g lipid. Plasma concentrations of glucose, creatinine and protein were not affected by the experimental diets, but plasma urea concentration was significantly lower in FR than in SP pigs, with intermediate values in LP. The effect of protein reduction in diets was more marked on neutral than on polar lipid contents, and higher saturated fatty acid and lower polyunsaturated fatty acid proportions were observed in LP pigs than in SP and FR pigs. So, a reduction in protein levels in the diets of Iberian pigs during the fattening period affected muscle lipid composition, despite the slight effect observed on lipogenic enzyme activity. Furthermore, the longissimus lumborum and serratus ventralis muscles showed similar responses to diets with different protein levels but differed in their chemical compositions and metabolic activities, which suggested that serratus ventralis, with a lower commercial value, could be adequate as the muscle of choice for analysis of meat composition and quality in the Iberian pig.

Maxillary and dental development in the offspring of protein-restricted female rats.

Nutritional restriction during developmental periods impairs organ physiology. Female rats were subjected to protein restriction during pregnancy and lactation to analyze dental and maxillary development. Four exposure groups were considered: normal-protein diet during pregnancy and lactation (NP, 17% casein), low-protein diet during lactation (LP-L, 6% casein), low-protein diet during pregnancy and lactation (LP), and low-protein diet during pregnancy (LP-G). Maxillae from 15-day-old male pups were collected. All protein-restricted groups presented increased dentin thickness and reduced alveolar bone area. When protein restriction was applied during both gestation and lactation (LP), harmful effects were observed in the form of loss of protective OPG (osteoprotegerin) in tooth epithelium-mesenchyme, due to higher RANKL expression, delay in odontoblast maturation, less dental pulp vascularity, reduction in amount of alveolar bone, and less matrix mineralization. In the LP-L group, effects of protein restriction seemed less harmful, and despite less alveolar bone, the enhancement in BMP-7, VEGF, and RANKL seems a compensatory signal to maintain maxillary osteogenesis. In LP-G animals, Dspp expression was higher, suggesting a delay in odontoblast maturation or expression recuperation. In conclusion, maternal protein restriction affects dental and maxillary development. A low-protein diet only in gestation allows for normal development. A low-protein diet during gestation-lactation results in impaired odontogenesis that may increase susceptibility of dental anomalies.

Effects of Protein Restriction and Succedent Realimentation on Jejunal Function and Bacterial Composition of Different Colonic Niches in Weaned Piglets.

Recent studies have proved that protein succedent realimentation could rescue the loss of growth performance in weaning piglets caused by a prior protein restriction. However, how the protein restriction and succedent realimentation influence the jejunal function and bacterial composition of different colonic niches microbiota in weaning piglets needs a further investigation. After protein succedent realimentation, we found that the treatment group (TRE) piglets had a higher IGF-1 content and IGF-1R gene expression level in jejunal mucosa than the control group (CON) piglets. The ZO-1 gene expression level was up-regulated in the jejunal mucosa of TRE piglets during protein restriction and succedent realimentation, while the jejunal permeability of TRE piglets was only decreased after protein succedent realimentation. In addition, we found that protein restriction and succedent realimentation increased the gene expression of Pept-1 and the fecal apparent digestibility of crude protein in TRE piglets, but decreased the fecal nitrogen content. After 16S rRNA MiSeq sequencing of bacteria in different colonic niches (mucosa and digesta), TRE piglets had a higher relative abundance of beneficial bacteria and a lower relative abundance of potential pathogens than CON piglets in different colonic niches after protein restriction and succedent realimentation. Our data showed that protein restriction and succedent realimentation decreased the concentrations of branch chain fatty acids and ammonia-N in the colon of TRE piglets. In addition, protein succedent realimentation increased the concentration of total short chain fatty acids in the colon of TRE piglets. All these findings demonstrated that the strategy of protein restriction and succedent realimentation is an effective way to improve intestinal health of weaning piglets, and provided new insights into the nutrition management of piglets during the weaning period.

MO436: The Effect of Protein-Restriction on the Tubular Handling of the Uraemic Retention Solute Indoxyl Sulfate

Abstract BACKGROUND AND AIMS Chronic kidney disease (CKD) patients present an increased plasma level of protein-bound solutes known as uraemic toxins. Their accumulation is associated with, amongst others, cardiovascular events. The gut microbiome plays an important role in the generation of part of the uraemic toxins. It has been postulated that proximal tubule cells in kidneys are able to sense augmented levels of gut microbial metabolites via receptors and signalling pathways [1]. According to the so-called remote sensing hypothesis, kidney tubular cells respond to uraemic toxins plasma variations modulating the activity of membrane transporters involved in their excretion. Indoxyl sulfate (IS) originates from the microbial fermentation of tryptophan, a diet-derived amino acid. Nonetheless, few studies have investigated whether gut generation, absorption and plasma retention of indolic uraemic toxins and kidney cells’ secretory mechanisms are affected by the protein content in the diet. METHOD A total of 18 Sprague–Dawley male rats (Janvier, Le Genest- St Isle, France) 7–8 weeks old (weighing 270–388 g) were induced with CKD utilizing 5/6 nephrectomy and were randomly assigned to a low protein (LP) (n = 10) or a high protein (HP) (n = 8) diet. A sham-operated control group for each diet was used (n = 7 and n = 8 respectively). 24 h-urine was collected after 7 weeks, and euthanasia was carried out after 8 weeks from the induction of the disease (Figure 1). Blood and colon samples were collected. Diffusion chambers were used to assess colon permeability to indole over time (t = 0, 60, 90, 120 min). Indole concentration was quantified by Kovacs assay. Blood creatinine and urea were determined with standard laboratory techniques. Total plasmatic and urinary IS concentrations were measured using LC-MS/MS. The fractional excretion (FE) i.e. the percentage of IS excreted relatively to the kidney filtered load, was calculated to assess IS remote sensing. RESULTS Plasmatic levels of IS were significantly higher (P <0.001) in CKD rats compared to sham rats. However, CKD rats on an HP diet showed no difference in plasma IS (P = 0.63) compared to rats on an LP diet. Conversely, 24-h urinary IS was significantly increased in CKD rats on a HP diet (P <0.001). The FE of IS was significantly higher (P = 0.005) in CKD rats on an HP diet (Figure 2) and correlated with 24 h-urinary IS (Spearman r = 0.51, P -value = 0.03) and with protein intake (Spearman r = 0.52, P-value = 0.03) in CKD rats. Therefore, CKD rodent models’ results suggest higher absorption and/or production of indole at the intestinal level when an HP is administered to CKD rats. Plus, they provide additional proof of the remote sensing theory of indole metabolites. The permeability of colon to indole evaluated ex vivo with the diffusion chamber technique, showed an increased apparent apical-to-basolateral transport of indole (P = 0.049) in CKD rats on an HP diet compared to that of sham rats on the same diet, again suggesting modulatory mechanisms affecting indole metabolites transporters uptake. CONCLUSION An HP diet in 5/6 nephrectomized CKD rats leads to increased production of indole in the colon and increased fractional excretion of IS. These results provide an additional proof of mechanisms of remote sensing and signalling of indole-derived uraemic toxins. To conclude, the adoption of a low protein diet remains recommended in chronic kidney disease.

Morphofunctional and immunological cardiac evaluation of protein restriction on rat offspring

Cardiovascular diseases affect a large part of the population during adulthood. Several epidemiological and experimental studies have demonstrated an association between maternal protein restriction and a marked risk of developing heart disease during early intrauterine and postnatal life. Maternal nutritional conditions act by modulating the microenvironment, thus favoring adaptive processes of the fetal organism for development to occur. However, the physiological profile is established in this period and its effects can be observed in the long term. In the present study, the cardiac muscles of 15-day-old offspring of Wistar rats subjected to maternal protein restriction during pregnancy and/or lactation were evaluated to identify possible cardiac changes relevant for heart disease in adulthood. The offspring of restricted female rats during pregnancy had a lower birth weight. Male offspring subjected to restriction during pregnancy and lactation showed an increase in the concentration of H2O2, a reduction in the expression of the Mn-SOD enzyme, and a greater expression of β-MHC and Connexin 43. There was also an increase in the MPO enzyme activity in the tissue. It was observed that the effects of protein restriction are sex-specific, since the cardiac muscle of male animals showed alterations suggestive of oxidative stress, hypertrophy, signs of tissue inflammation, and increased expression of important proteins in intercellular communication. These changes characterize the ongoing cardiac remodeling process. Finally, the data revealed that the lactation phase accentuated harmful effects on the cardiac tissue of the offspring.

Gestational and Breastfeeding Low-Protein Intake on Blood Pressure, Kidney Structure, and Renal Function in Male Rat Offspring in Adulthood.

Background: Our previous studies demonstrated that maternal protein-restricted (low-protein, LP) 16-week-old offspring had pronounced nephron number reduction and arterial hypertension associated with an unchanged glomerular filtration rate (GFR). An enhanced gomerular area may be related to increased glomerular filtration and overflow, which accounts for glomerular filtration barrier breakdown and early glomerulosclerosis. The effect of protein restriction during gestational and breastfeeding periods is unknown. Method: The functional e-structural kidney evaluation was obtained using lithium and creatinine clearance, kidney morphometry, immunoblotting, and immunostaining analysis in 16 and 24-week-old LP offspring compared to age-matched NP progeny. Results: Low protein rats’ progeny had significantly reduced birth weight, without previous catch-up growth phenomena, in parallel with a decreased adiposity index. Transforming growth factor-beta 1 (TGF-β1) glomerular expression was significantly enhanced in the LP group. Also, the LP offspring had a 38% lower nephron number and an increased glomerular volume. They also presented with a higher cardiac index and arterial blood pressure compared with age-matched NP offspring. The LP rats exhibited augmented Na+/K+-ATPase in the proximal segments, and NOS1 immunoreactivity in whole renal tissue was associated with sodium retention in the proximal nephron segments. We also found significantly enhanced collagen content associated with increased TGFβ1 and ZEB1/2 renal immunoreactivity in LP offspring compared with NP offspring. Increased hypertrophy markers in LP podocytes were associated with an amplified IL-6/STAT3 pathway activity. Conclusion: To our knowledge, these are the first data demonstrating renal functional and structural changes in protein restriction during gestation and lactation model of fetal programming. The fetal-programmed adult offspring showed pronounced structural glomerular disorders with an accentuated and advanced fibrosis stage, without a change in the GFR. These findings suggest that the glomerular enhanced TGF-β1 action may induce ZEB1/2 expression that may cause glomeruli epithelial-to-mesenchymal transition. Besides, decreased nephron number in the LP offspring with preserved glomerular function may be related to protective or even attenuate the activated IL-6/STAT3 pathway.

Perspective: Low Risk of Parkinson's Disease in Quasi-Vegan Cultures May Reflect GCN2-Mediated Upregulation of Parkin

Mitochondrial dysfunction in dopaminergic neurons of the substantia nigra (SN) appears to be a key mediating feature of Parkinson's disease (PD), a complex neurodegenerative disorder of still unknown etiology. Parkin is an E3 ubiquitin ligase that promotes mitophagy of damaged depolarized mitochondria while also boosting mitochondrial biogenesis-thereby helping to maintain efficient mitochondrial function. Boosting Parkin expression in the SN with viral vectors is protective in multiple rodent models of PD. Conversely, homozygosity for inactivating mutations of Parkin results in early-onset PD. Moderate protein plant-based diets relatively low in certain essential amino acids have the potential to boost Parkin expression by activating the kinase GCN2, which in turn boosts the expression of ATF4, a factor that drives transcription of the Parkin gene. Protein-restricted diets also upregulate the expression of PINK1, a protein that binds to the outer membrane of depolarized mitochondria and then recruits and activates Parkin. This effect of protein restriction is mediated by the downregulation of the kinase activity of mammalian target of rapamycin complex 1; the latter suppresses PINK1 expression at the transcriptional level. During the 20th century, cultures in East Asia and sub-Sahara Africa consuming quasi-vegan diets were found to be at notably decreased risk of PD compared with the USA or Europe. It is proposed that such diets may provide protection from PD by boosting Parkin and PINK1 expression in the SN. Other measures that might be expected to upregulate protective mitophagy include supplemental N-acetylcysteine (precursor for hydrogen sulfide) and a diet rich in spermidine-a polyamine notably high in corn.

Effects of protein restriction on performance, ruminal fermentation and microbial community in Holstein bulls fed high-concentrate diets

The aim of this work was to study the impact of a crude protein (CP) restriction on performance, ruminal fermentation and microbial community composition in fattening Holstein bulls (from 118 to 331 d of age and from 165 to 522 kg body weight [BW]) fed high-concentrate diets. Twenty animals were assigned to two dietary treatments: concentrate CP was formulated either based on the levels used commercially (CTR: 140 g CP/kg dry matter [DM]) or reducing them (LP: 120 g CP/kg DM). Concentrate was supplemented with barley straw and both were supplied ad libitum. Animal BW and concentrate intake were automatically recorded on a daily basis. Feces, urine and ruminal fluid were sampled twice, during the growing period (160 d of age and 225 kg BW) and during the finishing period (280 d of age and 444 kg BW), for digestibility, ruminal fermentation and microbial population characterization. No differences in BW or cumulated concentrate intake were found between treatments, despite the fact that average daily gain was lower in LP group at the beginning of the growing period (P < 0.001). Crude protein limitation did not penalize dry matter (P = 0.654) or organic matter (P = 0.526) apparent digestibility, but it did affect CP apparent digestibility during the finishing period (P = 0.042). Nitrogen (N) excretion was greater in CTR animals (P = 0.017). Regardless of treatment (P = 0.511), ruminal ammonia-N concentration was low (4.36 ± 1.01 mg/L). Even though 135 OTUs (out of 489) were shared between treatments and periods (gathering 98.7 % of analyzed sequences), ruminal microbial community composition was different between periods (P = 0.003) and also between diets in either growing (P < 0.001) or finishing (P = 0.046) bulls. Bacteroidetes, Firmicutes and Actinobacteria were the three dominant phyla and Prevotella ruminicola was the most abundant species. Ruminal microbial biodiversity was low but increased with age (P = 0.002 for Shannon index and P = 0.035 for Simpson index), as well as, ruminal microbial heterogeneity. Crude protein limitation increased functional interdependency among microbial genera, so LP-fed bulls were found to have a more complex microbiota community structure than CTR-fed bulls. No relevant correlations between microbial genera and ruminal fermentation parameters were detected.

Significant changes in caecal microbial composition and metabolites of weaned piglets after protein restriction and succedent realimentation.

The present study aimed to investigate the effects of protein restriction and subsequent realimentation on caecal barrier function, caecal microbial composition and metabolites in weaned piglets. Thirty-six 28-day-old weaned piglets were randomly assigned to a control group and a treatment group. The piglets were fed diets containing 18.83% (normal) or 13.05% (low) of crude protein from the 1st to 14th day, after which all piglets were fed diets containing 18.83% of crude protein from the 15th to 28th day. The results showed that protein restriction increased caecal bacterial diversity and richness as well as the abundance of Ruminococcus 2, Faecalibacterium and Lachnospiraceae_uncultured, but reduced the abundance and the gene copies of Lactobacillus in the treatment group compared with the control group on day 14. Protein restriction also decreased the concentrations of isovaleric acid and total branched-chain fatty acids. During the succedent protein realimentation stage, the abundance of Ruminococcaceae UCG-014 and the concentrations of lactic acid, acetic acid, butyric acid and total short-chain fatty acids were increased in the treatment group on day 28. Furthermore, the ammonia concentration was reduced, while the gene mRNA levels of caecal barrier function were increased in the treatment group both on days 14 and 28. In conclusion, dietary protein restriction and realimentation could change caecal microbial composition and metabolites, and eventually influence caecal barrier function. The present study may provide a new insight into protein restriction and realimentation in weaned piglets.

MON-PO626: A Randomized Controlled Trial of the Effect of Protein Restriction to Delay Renal Replacement Therapy in Septic Patients with Acute Renal Failure in Thammasat University Hospital, Preliminary Analysis

MON-PO626: A Randomized Controlled Trial of the Effect of Protein Restriction to Delay Renal Replacement Therapy in Septic Patients with Acute Renal Failure in Thammasat University Hospital, Preliminary Analysis

Dietary protein restriction increases hepatic leptin receptor mRNA and plasma soluble leptin receptor in male rodents.

Leptin is an adipokine that regulates adipose tissue mass through membrane-anchored leptin receptor (Ob-R). Extracellular domain of Ob-R in plasma is called soluble leptin receptor (sOb-R), and is the main leptin-binding protein. Based on a previous DNA microarray analysis that showed induction of hepatic Ob-R mRNA in low-protein diet-fed mice, this study aimed to clarify the effect of dietary protein restriction on hepatic Ob-R mRNA and plasma sOb-R levels. First, the effect of protein restriction on hepatic Ob-R mRNA level was examined together with fasting and food restriction using male rats as common experimental model for nutritional research. Hepatic Ob-R mRNA level was increased by feeding low-protein diet for 7 d, although not significantly influenced by 12-h fasting and sixty percent restriction in food consumption. Then, effect of protein restriction on liver Ob-R and plasma sOb-R was investigated using male mice because specific sOb-R ELISA was more available for mice. Hepatic Ob-R mRNA level was also increased in protein restricted-mice although it did not increase in hypothalamus. Hepatic Ob-R protein was decreased, whereas plasma sOb-R was increased by protein restriction. Because the concentration of sOb-R increased without changing plasma leptin concentration, free leptin in plasma was significantly reduced. The direct effect of amino acid deprivation on Ob-R mRNA level was not observed in rat hepatoma cells H4IIE cultured in amino acid deprived medium. In conclusion, dietary protein restriction increased hepatic Ob-R mRNA, resulting in increased plasma sOb-R concentration, which in turn, reduces plasma free leptin level and may modulate leptin activity.

Effects of Protein Restriction on Performances and Meat Quality of Cinta Senese Pig Reared in an Organic System.

Simple SummaryFat contained in meat is an important contributor to sensory traits: it increases meat tenderness and flavor. In commercial pigs, increasing meat’s fat was obtained by feeding, until the fattening period, a diet slightly lower in protein respect to their requirements. Local pig breeds, such as Cinta Senese, are known as obese pigs because their great potential to deposit fat, which is mainly stored in backfat deposits. This study was aimed to assess if protein restriction in growing can further increase meat’s fat without alter overall body fatness of obese pigs. The normal feeding management and the restricted one were compared in two groups of Cinta Senese pigs. Results showed that protein restriction during the growing phase affected only few traits. The restricted animal was more able to use the protein in feeding, but few modifications were found in the chemical composition of meat, including the meat’s fat, that remained unchanged. So, obese genotype might be less responsive to this kind of feeding management.In lean genotypes, protein restriction during growing increases intramuscular fat content without affecting the overall carcass fatness. The present study aims to assess the feasibility of applying this feeding management on an obese pig, the Cinta Senese, since obese genotypes are characterized by great lipogenic potential often leading to excessively high backfat deposits. Twenty pigs of average weight 38 kg, were divided in two groups, the first group was fed a protein restricted diet (9% of crude protein), while the second one a normal diet (13.5% of crude protein). During finishing, both groups were fed the same diet (10% of crude protein). Average daily gain, protein conversion index, backfat thickness, carcass weight, and prime cuts were determined. A loin sample joint was dissected in intermuscular fat, bone, subcutaneous fat, longissimus lumborum, and psoas major. On longissimus lumborum, physical and chemical analysis was carried out. The fatty acid profile of longissimus lumborum and loin subcutaneous fat were determined. Data were analyzed by analysis of variance. Protein conversion index resulted lower in the restricted group, while backfat was slightly greater. Meat quality traits were not affected by feeding management. Slightly modifications in subcutaneous outer layer fatty acids profile were observed. The protein restriction during growing did not seem a suitable mode of feeding management for Cinta Senese pigs.

Low-protein diet decreased the adrenal function and spontaneous activity of mice during chronic heat stress

Protein restriction is a well-known risk factor that induces the deterioration of various biological functions. However, little is known about the effects of protein restriction on behavioral markers and the adrenal function of mice exposed to chronic stress. Here we evaluated the effects of a low-protein diet on the spontaneous activity and adrenal function of chronic heat-stressed mice. ICR mice were fed a control diet (20% protein) or a low-protein diet (10% protein) for 14 consecutive days. From the 10th day of the diet period, the mice were repeatedly exposed to a temperature condition of 35 ± 1 °C for 2 hr/day for four consecutive days. The spontaneous activities of the mice were estimated for the behavioral analysis. On the last day, we performed a blood collection test and an ACTH stimulation test for adrenal function analysis. For the blood collection test, mice were exposed to heat stress again for 2 hr, and blood was collected immediately after this heat stress. We measured the plasma levels of corticotropin releasing hormone, adrenocorticotropin (ACTH), and corticosterone. For the ACTH stimulation test, cosyntropin was intraperitoneally administered, and the plasma corticosterone levels were measured. The spontaneous activity of the low-protein mice was significantly lower than that of the control mice during the dark period of heat stress. The plasma corticosterone levels were greatly increased by heat stress, with no significant difference between the control and low-protein groups. The ACTH stimulation test revealed that the plasma corticosterone concentration of the heat-stressed low-protein mice was significantly lower than that of the heat-stressed controls. In conclusion, the low-protein diet decreased the spontaneous activity and the adrenal function of mice during heat stress, which implies that protein restriction during chronic heat stress induces fatigue by reducing the adrenal function.

Preovulatory exposure to a protein-restricted diet disrupts amino acid kinetics and alters mitochondrial structure and function in the rat oocyte and is partially rescued by folic acid

BackgroundDetrimental exposures during pregnancy have been implicated in programming offspring to develop permanent changes in physiology and metabolism, increasing the risk for developing diseases in adulthood such as hypertension, diabetes, heart disease and obesity. This study investigated the effects of protein restriction on the metabolism of amino acids within the oocyte, liver, and whole organism in a rat model as well as effects on mitochondrial ultrastructure and function in the cumulus oocyte complex.MethodsWistar outbred female rats 8–11 weeks of age (n = 24) were assigned to three isocaloric dietary groups, including control (C), low protein (LP) and low protein supplemented with folate (LPF). Animals were superovulated and 48 h later underwent central catheterization. Isotopic tracers of 1-13C-5C2H3-methionine, 2H2-cysteine, U-13C3-cysteine and U-13C3-serine were administered by a 4 h prime-constant rate infusion. After sacrifice, oocytes were denuded of cumulus cells and liver specimens were obtained.ResultsOocytes demonstrated reduced serine flux in LP vs. LPF (p < 0.05), reduced cysteine flux in LP and LPF vs. C (p < 0.05), and a trend toward reduced transsulfuration in LP vs. C and LPF. Folic acid supplementation reversed observed effects on serine flux and transsulfuration. Preovulatory protein restriction increased whole-body methionine transmethylation, methionine transsulfuration and the flux of serine in LP and LPF vs. C (p = 0.003, p = 0.002, p = 0.005). The concentration of glutathione was increased in erythrocytes and liver in LP and LPF vs. C (p = 0.003 and p = 0.0003). Oocyte mitochondrial ultrastructure in LP and LPF had increased proportions of abnormal mitochondria vs. C (p < 0.01 and p < 0.05). Cumulus cell mitochondrial ultrastructure in LP and LPF groups had increased proportions of abnormal mitochondria vs. C (p < 0.001 and p < 0.05). Preovulatory protein restriction altered oocyte expression of Drp1, Opa-1, Mfn1/2, Parl and Ndufb6 (p < 0.05) and Hk2 (p < 0.01), which are genes involved in mitochondrial fission (division) and fusion, mitochondrial apoptotic mechanisms, respiratory electron transport and glucose metabolism.ConclusionsPreovulatory protein restriction resulted in altered amino acid metabolism, abnormal cumulus oocyte complex mitochondrial ultrastructure and differential oocyte expression of genes related to mitochondrial biogenesis.

Protein restriction and succedent realimentation affecting ileal morphology, ileal microbial composition and metabolites in weaned piglets

Dietary protein restriction is one of the effective ways to reduce post-weaning diarrhoea and intestinal fermentation in piglets, but it may also reduce growth performance. The compensatory growth induced by subsequent protein realimentation may solve the issue. However, little research has been done on the impact of protein realimentation on the gut. In this study, the effects of protein restriction and realimentation on ileal morphology, ileal microbial composition and metabolites in weaned piglets were investigated. Thirty-six 28-day-old weaned piglets with an average body weight of 6.47 ± 0.04 kg were randomly divided into a control group and a treatment group. The CP level in the diet of the control group was 18.83% for the entire experimental period. The piglets in the treatment group were fed 13.05% CP between days 0 and 14 and restored to a diet of 18.83% CP for days 14 to 28. On day 14 and 28, six pigs from each group were sacrificed and sampled. It was found that the abundance of Lactobacillus and Salmonella in the ileal digesta was significantly lower in the treatment group than the control group on day 14, whereas the abundance of Clostridium sensu stricto 1, Streptococcus, Halomonas and Pseudomonas significantly increased in the ileal digesta of the treatment group on day 14 compared with the control group. In addition, reduced concentrations of lactic acid, total short-chain fatty acids (total SCFAs), total branched chain fatty acids, ammonia and impaired ileal morphology and mucosal barrier were observed in the treatment group on day 14. However, diarrhoea levels decreased in the treatment group throughout the experiment. During the succedent protein realimentation stage, the treatment group demonstrated compensatory growth. Compared with the control group, the treatment group showed increased abundance of Lactobacillus and reduced abundance of Salmonella, Halomonas and Pseudomonas in the ileum on day 28. The concentrations of lactic acid and total SCFAs increased significantly, whereas the concentration of ammonia remained at a lower level in the treatment group on day 28 compared with the control group. Overall, protein realimentation could improve ileal morphology and barrier functions and promote ileal digestive and absorptive functions. In conclusion, ileal microbial composition and metabolites could change according to dietary protein restriction and realimentation and eventually influence ileal morphology and barrier functions.

Neuronal FGF-21 Signaling–A Sensor of Dietary Protein Restriction

The central nervous system is acknowledged as a major regulator of both energy and glucose homeostasis. Our data demonstrate that dietary protein restriction increases energy expenditure and improves glucose homeostasis, and that the metabolic hormone FGF-21 coordinates these adaptive responses. However, the tissue site mediating these FGF-21-dependent effects is unclear. In this study, mice with dysfunctional FGF-21 signaling in either the central nervous system (CNS) or adipose tissue were fed a control or low protein (LP) diet to assess changes in body weight and associated metabolic endpoints. We first deleted the required FGF co-receptor beta-Klotho (Klb) from neurons to test whether CNS FGF-21 signaling is required for increased energy expenditure or improved glucose homeostasis in mice consuming a low protein diet. Our data show that LP diet increased energy expenditure (p≤0.01) and reduced body weight (p≤0.001) in control littermates, but these effects were lost in mice bearing CNS-specific deletion of Klb (p=0.65). Protein restriction in the context of a high fat diet also improved glucose tolerance (P≤0.001) and insulin sensitivity (p≤0.001) in control littermates, but these effects were also lost in mice lacking Klb in the CNS. We next tested whether FGF-21 signaling within adipose tissue contributed to the metabolic effects of protein restriction. However, in this case LP diet reduced body weight (p=0.90) and increased food intake (p= 0.98) similarly in control littermates and mice bearing adipose-specific deletion of Klb. Collectively, these data highlight CNS FGF-21 signaling as the first known neuroendocrine mechanism to explain the coordinated metabolic changes induced by dietary protein restriction. Disclosure C.M. Hill: None. M.V. Dehner: None. D. McDougal: None. H. Berthoud: None. H. Muenzberg: None. C. Morrison: None.

Efficacy of low-protein diet for diabetic nephropathy: a systematic review of randomized controlled trials

BackgroundA low-protein diet (LPD) is believed to be beneficial in slowing the progression of kidney disease. It is reported that low protein diet can improve protein, sugar and lipid metabolism, and reduce the symptoms and complications of renal insufficiency. However, there has been controversial regarding the effects of protein restriction on diabetic nephropathy (DN).ObjectiveTo investigate the efficacy of LPD on renal function in patients with type 1 or 2 DN by meta-analysis of randomized controlled trials (RCTs).DesignPubMed, MEDLINE, EMBASE and China National Knowledge Infrastructure databases were searched. Eleven randomized controlled trials met the inclusion criteria, of which 10 were English and 1 was Chinese. The primary outcome was a change in glomerular filtration rate (GFR). The secondary outcome was a change in proteinuria. Random-effects models were used to calculate the standardized mean difference (SMD) and the corresponding 95% confidence intervals (CI). Subgroup analyses were also performed.ResultsOur research indicated that LPD was not associated with a significant improvement in GFR (1.59 ml · min−1 · 1.73 m−2, 95% CI -0.57, 3.75, I2 = 76%; p = 0.15). This effect was consistent across the subgroups regardless of type of diabetes, course of diabetes and intervention period. Our results also showed that there was no significant difference on improvement of proteinuria in patients of LPD and those in normal-protein diet groups (− 0.48, 95%CI-1.70, 0.74, I2 = 94%, p = 0.44). Subgroup analysis revealed that LPD resulted in increased excretion of proteinuria in patients with type 2 diabetes (1.32, 95% CI 0.17, 2.47, I2 = 86%, p = 0.02).ConclusionThe present research showed that LPD was not significantly associated with improvement of renal function in patients with either type 1 or 2 diabetic nephropathy. Although these results do not completely eliminate the possibility that LPD is beneficial for patients with diabetic nephropathy, it does not seem to be significant benefit to renal function.

SUN-P282: Sensitivity of a 13C-Protein Oxidation Breath Test Investigated with a Protein Restricted Diet in Healthy Subjects

RATIONALE: Disturbed protein metabolism may result in malnutrition. A non-invasive low cost clinical tool to measure protein metabolism is lacking. Explorative research (n=1) with a newly developed non-invasive 13C-protein breath test suggested a decrease in protein oxidation after a protein restricted diet. Now, we aimed to test the effect of protein restriction in more subjects, to assess sensitivity of the test. METHODS: In this exploratory study, 14 healthy male subjects (23±3 y) participated. Habitual intake was assessed by a 4-day food diary. Next, subjects were instructed to use a 4-day isocaloric protein restricted diet (0.25 g protein/kg bw/day). After an overnight fast, a 30 g naturally enriched 13C-milk protein test drink was consumed, followed by collection of breath samples up to 330 min. Protein oxidation was analyzed by Isotope Ratio Mass Spectrometry. 24-h urine was collected on day 4 of the habitual diet, and on every day of the 4-day protein restricted diet, to assess actual change in protein intake. RESULTS: After the protein restricted diet, 30.2%±7.7 of the 30 g 13C-milk protein was oxidized over 330 min, compared to 30.6%±6.2 (NS) after the subject’s habitual diet (1.4±0.3 g protein/kg bw/day). Within subjects, both increase and decrease in oxidation was found. During the 4-day protein restricted diet, urinary urea:creatinine ratio decreased by 56%±10, consistent with a reduction in protein intake of 44%±15 (g/day) and 53%±12 (g/kg bw/day), based on urea and food diary, respectively. CONCLUSIONS: The breath test shows variation within subjects and between diets, which could be related to the sensitivity of the test. We cannot explain the variation by the measured variables. Alternatively, our results may implicate that in some of our subjects, protein intake did not sufficiently decrease to levels that could alter protein metabolism.

Adult dietary protein has age- and context-dependent effects on male post-copulatory performance.

The highly conserved effect of dietary protein restriction on lifespan and ageing is observed in both sexes and across a vast range of taxa. This extension of lifespan is frequently accompanied by a reduction in female fecundity, and it has been hypothesized that individuals may reallocate resources away from reproduction and into somatic maintenance. However, effects of dietary protein restriction on male reproduction are less consistent, suggesting that these effects may depend on other environmental parameters. Using the neriid fly, Telostylinus angusticollis, we examined age-specific effects of adult dietary protein restriction on male post-copulatory reproductive performance (fecundity and offspring viability). To explore the context dependence of these effects, we simultaneously manipulated male larval diet and adult mating history. We found that protein-restricted males sired less viable offspring at young ages, but offspring viability increased with paternal age and eventually exceeded that of fully fed males. The number of eggs laid by females was not affected by male dietary protein, whereas egg hatching success was subject to a complex interaction of male adult diet, age, larval diet and mating history. These findings suggest that effects of protein restriction on male reproduction are highly context dependent and cannot be explained by a simple reallocation of resources from reproduction to somatic maintenance. Rather, these effects appear to involve changes in the scheduling of male reproductive investment with age.

Multicompartment analysis of protein-restricted phenylketonuric mice reveals amino acid imbalances in brain.

The mainstay of therapy for phenylketonuria (PKU) remains dietary protein restriction. Developmental and neurocognitive outcomes for patients, however, remain suboptimal. We tested the hypothesis that mice with PKU receiving protein-restricted diets would reveal disruptions of brain amino acids that shed light on these neurocognitive deficits. Phenylalanine hydroxylase-deficient (PKU) mice and parallel controls (both wild-type and heterozygous) were fed custom diets containing 18, 6, and 4% protein for 3weeks, after which tissues (brain, liver, sera) were collected for amino acid analysis profiling. Phenylalanine (phe) was increased in all tissues (p < 0.0001) of PKU mice and improved with protein restriction. In sera, decreased tyrosine (p < 0.01) was corrected (defined as not significantly different from the level in control mice receiving 18% chow) with protein restriction, whereas protein restriction significantly increased many other amino acids. A similar trend for increased amino acid levels with protein restriction was also observed in liver. In brain, the effects of protein restriction on large neutral amino acids (LNAAs) were variable, with some deficit correction (threonine, methionine, glutamine) and no correction of tyrosine under any dietary paradigm. Protein restriction (4% diet) in PKU mice significantly decreased lysine, arginine, taurine, glutamate, asparagine, and serine which had been comparable to control mice under 18% protein intake. Depletion of taurine, glutamate, and serine in the brain of PKU mice with dietary protein restriction may provide new insight into neurocognitive deficits of PKU.