Tissue Protein Turnover Research Articles

Ingestion of a variety of non-animal-derived dietary protein sources results in diverse postprandial plasma amino acid responses which differ between young and older adults.

Whole-body tissue protein turnover is regulated, in part, by the postprandial rise in plasma amino acid concentrations, although minimal data exist on the amino acid response following non-animal-derived protein consumption. We hypothesised that the ingestion of novel plant- and algae-derived dietary protein sources would elicit divergent plasma amino acid responses when compared with vegan- and animal-derived control proteins. Twelve healthy young (male (m)/female (f): 6/6; age: 22 ± 1 years) and 10 healthy older (m/f: 5/5; age: 69 ± 2 years) adults participated in a randomised, double-blind, cross-over trial. During each visit, volunteers consumed 30 g of protein from milk, mycoprotein, pea, lupin, spirulina or chlorella. Repeated arterialised venous blood samples were collected at baseline and over a 5-h postprandial period to assess circulating amino acid, glucose and insulin concentrations. Protein ingestion increased plasma total and essential amino acid concentrations (P < 0·001), to differing degrees between sources (P < 0·001), and the increase was further modulated by age (P < 0·001). Postprandial maximal plasma total and essential amino acid concentrations were highest for pea (2828 ± 106 and 1480 ± 51 µmol·l-1) and spirulina (2809 ± 99 and 1455 ± 49 µmol·l-1) and lowest for chlorella (2053 ± 83 and 983 ± 35 µmol·l-1) (P < 0·001), but were not affected by age (P > 0·05). Postprandial total and essential amino acid availabilities were highest for pea, spirulina and mycoprotein and lowest for chlorella (all P < 0·05), but no effect of age was observed (P > 0·05). The ingestion of a variety of novel non-animal-derived dietary protein sources elicits divergent plasma amino acid responses, which are further modulated by age.

Caloric adequacy normalizes brain tissue protein turnover in a rat brain injury model

Traumatic brain injury (TBI) is a leading cause for hospitalization in America, often having long lasting effects including increased morbidity, mortality and cognitive deficits post recovery. Based on Standard of Care (SOC) treatment, TBI patients are grossly underfed, yet it is unclear how underfeeding effects protein turnover post-TBI. Thus, we designed a study to elucidate the effects of TBI and caloric restriction (CR) on protein dynamics post-TBI. Hypothesis: We hypothesize that TBI would elicit an increased fractional synthesis rate (FSR) in all brain tissue as compared to control, ad libitum (AL) fed animals, while CR would suppress FSR. Thus, we predicted that the CR+TBI animals would have an elevated FSR over CR control but suppressed compared to AL+TBI animals. Methods: Deuterium oxide was used to measure FSR 13-day post TBI in multiple tissues [skeletal muscle, heart, right and left cerebellum, right and left cortex and hippocampus] of Sprague Dawley rats, AL fed control (AL-Con: n=3), AL+TBI (n=6), or CR+TBI (n=5) and CR-Control (n=6). Tissue homogenates were fractionated to isolate the mitochondrial fraction, and cytoplasmic/sarcoplasmic fraction. Pentafluorobenzyl bromide derivatized alanine samples were measured by GC-MS to evaluate ions with m/z 448, 449, 450. FSR was determined using the m/z ion ratios and MIDA. We found that TBI significantly increased FSR over control animals in the left and right cortex (p≤0.05) and suppressed FSR in the cerebellum (p≤0.05). We found that CR in conjunction with TBI caused an increased FSR in the mitochondrial, cytosolic, and whole tissue of the cortical regions of the brain compared to CR control animals (p≤0.05). The increased FSR found with the CR-TBI group was mitigated with ad lib feeding, exhibiting caloric adequacy mitigates the effects of TBI in cortical and cerebral brain regions. This research shows evidence that caloric restriction has a negative impact on brain healing post-TBI. This project was funded by a grant to GAB from the PAC 12 athletic association (CAL-Brooks-17-02) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Tissue Protein Turnover is Altered during Catch-Up Growth Following Escherichia coli Infection in Weanling Rats

Infection in young growing animals is manifested by poor tissue protein accretion; during subsequent catch-up growth this is reversed. To account for these changes, protein synthesis and degradation were measured in vivo in skeletal muscle, skin, liver and small intestine in weanling rats during catch-up growth after Escherichia coli infection. Observations were made at d 4, 6, 8, 11 and 14, when infected rats had elevated nitrogen balance. Liver protein mass and turnover were not affected by treatment. Although protein mass of small intestine fell during infection, catch-up was achieved before d 4, suggesting a high priority for protein repletion in this tissue. On d 4, protein mass was lower (P < 0.05) in muscle (-19%) and skin (-23%) in infected vs. control rats. Thereafter growth rates of skeletal muscle and skin were higher (P < 0.001) in infected rats compared with controls. Catch-up growth was most pronounced early, but continued throughout the study. During catch-up growth, protein synthesis (mg/d) in muscle and skin was not different between control and infected animals. Protein synthesis was maintained in muscle because RNA mass was maintained. During catch-up growth in muscle and skin of infected rats, there was lower protein degradation (mg/d) than in controls (P < 0.05). We conclude that alterations in protein turnover during catch-up growth are tissue and time dependent and are different from those described in other hyperanabolic states.

The protective pattern of chitosan-based active coating on texture stabilization of refrigerated carp fillets from the perspective of proteolysis

Herein, the protective pattern of chitosan coating enriched with green tea extract on texture stabilization of refrigerated grass carp fillets was explored. In general, higher shear force and lower endogenous enzyme activities were observed in coated fillets, with the max. level of cathepsins and calpain decreasing by 30.2 ∼ 39.6 % when compared to the control during storage. Meanwhile, the coating reduced protein composition changes and accumulation of protein degradation products. According to label-free proteomic analysis, the proteome closer to fresh sample was observed in coated fillets than that of the control, as supported by PCA and hierarchical cluster analysis. Meanwhile, 33 differential proteins involved in tissue structure, protein phosphorylation and protein turnover were further screened out, and most DAPs showed up-regulation in coated fillets compared to the control on day 12. Presumably, the coating modulated endogenous enzyme-induced myofibrillar protein degradation and protein phosphorylation level, thereby stabilizing the texture properties of refrigerated fillets.

A static model to analyze carbon and nitrogen partitioning in the mammary gland of lactating sows

Quantitative estimates of mammary nutrient inputs, outputs and metabolism in sows are scarce, despite being critical elements to identify parameters controlling milk synthesis central for the feeding of lactating sows. The objective of this study was to quantify the mammary gland input and output of nutrients as well as the intramammary partitioning of carbon and nitrogen with the purpose to identify mechanisms controlling mammary nutrient inputs, metabolism and milk production in lactating sows. A data set was assembled by integration of results from four studies. The data set included data on litter performance, mammary arterial-venous concentration differences (AV-difference) of energy metabolites and amino acids, and the contents of lactose, fat and amino acids in milk. Milk yield was estimated based on average litter size and litter gain, and mammary plasma flow (MPF) was estimated using the sum of phenylalanine and tyrosine as internal flow markers. The yield and composition of milk were used to estimate mammary nutrient output in milk, and MPF and AV-difference were used to estimate net mammary input of carbon and nitrogen and output of CO2. Carbon and nitrogen used for the synthesis of lactose, fat and protein in milk and CO2-yielding processes were represented in a static nutrient partitioning model. The origin of mammary CO2 output was calculated using theoretical estimates of carbon released in processes supporting mammary synthesis of de novo fat, protein and lactose in milk, mammary tissue protein turnover and transport of glucose and amino acids. Results indicated that total input of carbon from glucose and lactate was partitioned into lactose (36%), fat (31%) and CO2-yielding processes (34%). Theoretical CO2 estimates indicated that de novo fat synthesis, milk protein synthesis and mammary tissue protein turnover were the main processes related to mammary CO2 production. More than 90% of mammary gland amino acid input was used for milk protein. The quadratic relationship between AV-difference and mammary input of essential amino acids indicated that both changes in AV-difference and MPF contributed to the regulation of mammary input of essential amino acids. The impact of the arterial supply of amino acids on mammary input may be greater for the branched-chain amino acids, arginine and phenylalanine than for other essential amino acids. In conclusion, relationships between input and output parameters indicate that AV-difference and MPF regulate mammary nutrient input to match the supply and demand of nutrients for the mammary gland.

Role of the Ubiquitin Proteasome System in the Regulation of Blood Pressure: A Review.

The kidney and the vasculature play crucial roles in regulating blood pressure. The ubiquitin proteasome system (UPS), a multienzyme process mediating covalent conjugation of the 76-amino acid polypeptide ubiquitin to a substrate protein followed by proteasomal degradation, is involved in multiple cellular processes by regulating protein turnover in various tissues. Increasing evidence demonstrates the roles of UPS in blood pressure regulation. In the kidney, filtered sodium is reabsorbed through diverse sodium transporters and channels along renal tubules, and studies conducted till date have provided insights into the complex molecular network through which ubiquitin ligases modulate sodium transport in different segments. Components of these pathways include ubiquitin ligase neuronal precursor cell-expressed developmentally downregulated 4-2, Cullin-3, and Kelch-like 3. Moreover, accumulating data indicate the roles of UPS in blood vessels, where it modulates nitric oxide bioavailability and vasoconstriction. Cullin-3 not only regulates renal salt reabsorption but also controls vascular tone using different adaptor proteins that target distinct substrates in vascular smooth muscle cells. In endothelial cells, UPS can also contribute to blood pressure regulation by modulating endothelial nitric oxide synthase. In this review, we summarize current knowledge regarding the role of UPS in blood pressure regulation, focusing on renal sodium reabsorption and vascular function.

Comparable Organ Protein Fractional Synthesis Rate of High and Low-Active Mice

Abstract Objectives With the rise in physical inactivity and its related diseases, it is necessary to understand the mechanisms involved in physical activity regulation. Scientists have explored physical activity regulation by investigating various physiological mechanisms involving hormones, neurotransmitters, and genetics; however, little is known about the role of metabolism on physical activity level. We hypothesize that protein turnover in specific organs like the muscle is higher in mice previously exhibiting high physical activity levels, as a mechanism to adapt to the increased demand. Therefore, we studied protein fractional synthesis rate (FSR) in tissues of inherently high and low active mice. Methods In order to study protein FSR of various organs, we assessed 12-week-old male inherently low-active (LA) mice (n = 23, lean body mass: 21.0 ± 1.1 g, C3H/HeJ strain) and high active (HA) mice (n = 20, lean body mass: 22.5 ± 1.3, C57L/J strain). One day before tissue collection, a D2O bolus was administered via intraperitoneal injection, and mice were provided D2O enriched drinking water to enrich the total body water to about 5% D2O. Eleven tissues (kidney, heart, lung, muscle, fat, jejunum, ileum, liver, brain, skin, and bone) were collected and analyzed for enrichment of alanine in the intracellular and protein-bound pool (LC-MS/MS). FSR was calculated as -ln(1-enrichment) as fraction per day. Data are mean ± SE (unpaired t-test: GraphPad Prism 8.2). Results We did not find significant differences between protein FSR of HA and LA mice in any measured organ. Example: Protein FSR (fraction/day): muscle (LA: 0.0326±-0.0026, HA: 0.0331 ± 0.0018, P = 0.8673), liver (0.3568 ± 0.0219, 0.3499 ± 0.0217, P = 0.8263), brain (0.0981 ± 0.0056, 0.1041 ± 0.0063, P = 0.4758). Conclusions The observed lack of significant differences in high and low-active mice suggests that differences in specific organ tissue protein turnover may not be a mechanism regulating inherent physical activity level. Since protein turnover is representative of the ability to adapt through upregulation and downregulation of metabolic processes, these results show that high-active mice are inherently no more equipped for metabolic regulation than the low active mice. Funding Sources Sydney and J.L. Huffines Institute for Sports Medicine, Human Performance Student Research Grant and CTRAL Grant.

Taurine modulates protein turnover in several tissues of meagre juveniles

This study aimed to evaluate the modulatory effect of dietary taurine supplementation on protein turnover of meagre juveniles fed semi-purified plant-based diets. For that purpose, fish (3.2 ± 0.2 g) were fed with five isoproteic (61.2%), isolipidic (16.6%) and isoenergetic (21.9 kJ g−1) experimental diets supplemented with 0.5% (Tau0.5), 1% (Tau1), 1.5% (Tau1.5) and 2% (Tau2) taurine or not (Tau0) for 38 days. The resulting growth parameters, protein expression levels and the activity of several proteolytic markers involved in the two major degradation pathways in vertebrates (autophagy-lysosomal and ubiquitin-proteasome) were assessed in the liver, intestine and white muscle of meagre. Increasing dietary taurine concentrations promoted fish growth, feed utilization and whole-body protein, lipid and energy contents. Dietary taurine seemed to modulate the activity of cathepsins D and B in white muscle and cathepsin L in the liver. Although, no significant effects were observed on proteasome activity, 1% dietary taurine supplementation decreased the expression of the Psmb4 proteasome subunit in the liver of fish when compared to lower taurine concentrations. No taurine effects were detected on the proteolytic markers analysed in the intestine of meagre. Hsp70 expression levels were also not affected by any of the experimental dietary taurine concentrations. Overall, experimental diet Tau2 promoted the highest growth rate which can be explained by a significant decrease in protein degradation in the liver and white muscle preferentially via the autophagy-lysosomal pathway (cathepsins) over the ubiquitin-proteasome route.

Survival strategies and molecular responses of two marine mussels to gradual burial by sediment

Increasing use of the marine environment and changes in weather extremes from climate change are altering patterns of sediment deposition on benthic habitats. There is a need to understand behavioural responses to such stressors, especially in sessile species that are of conservation, ecological or commercial interest. We investigated how two biogenic reef-forming, epifaunal mussels, Modiolus modiolus (horse mussel) and Mytilus edulis (blue mussel) responded to gradual burial by sediment. Here we used experiments to assess behavioural strategies for surviving modest, but regular sediment deposition regimes (0.5, 1.0 or 1.5 cm d−1 of coarse, medium-fine or fine sediment for 2, 4, 8 or 16 days), that result in gradual burial. M. modiolus was only capable of maintaining contact with the sediment-water interface during slow rates of deposition for short durations (tested in fine sediment only). M. edulis, however, were capable of vertical migration through sediment in all experimental sedimentation rates, sediment fractions and durations, but the frequency of burial increased with increasing sedimentation rate and duration. In this study, the sediment fraction was not influential on the levels of burial observed in M. edulis. Inter-individual variation in the ability of M. edulis to vertically migrate was investigated to understand sub-lethal effects of exposure to sedimentation. In M. edulis a molecular approach was used to assess variation in the condition and protein turnover in tissues with different functional roles (gill, adductor and foot tissue). Concentrations of RNA in the muscular foot were positively associated with the frequency of burial and the total depth of burial, indicating that burial stimulates protein production, most likely associated with byssus production used in the burial escape response. These findings contribute to a better understanding of how mussels respond to, and survive gradual burial by sediment and provide insight into how ongoing changes in sediment dynamics may influence these ecologically and commercially important reef-building species. These findings can be used to assist in managing activities which may result in sedimentation around these important species.

402 Awardee Talk - Efficiency of nutrient use in ruminants: Current understanding and emerging questions

Abstract Because feed costs represent a large proportion of total costs for ruminant production systems, improving the efficiency of nutrient utilization is an important goal for improving profitability and sustainability. Research on nutrient utilization in ruminants dates back to the 1800s when the first nutrient balance experiments were conducted. The concept of efficiency is complex and can be expressed in many ways. Different approaches should be used when examining economic efficiency vs. biological efficiency, growing vs. mature animals, or answering research questions vs. use in a production setting. Additionally, animal efficiency can be examined at different scales of complexity including animal, tissue, cell, or molecular levels, and at the level of total feed, feedstuff, or specific nutrient. Some of the facets that have been shown to be associated with animal efficiency include body composition, feed intake and digestion, heat production, blood metabolites and hormones, tissue mass, cell proliferation, protein turnover, ion transport, mitochondrial function, mRNA or protein expression profiles, and genomic polymorphisms within the animal, and composition and diversity of the gastrointestinal microbiome. Large amounts of information are being generated at the genomic, transcriptomic, and proteomic levels which will add to our knowledge about what factors are associated with animal efficiency. Nutrients, such as amino acids, play an important role to meet requirements for maintenance and production and have many other physiological functions regulating metabolism in the animal. There is potential to develop nutrient supplementation, or feeding, strategies to alter metabolism and improve nutrient utilization. Future research is needed to better define the mechanisms influencing efficiency of utilization of individual nutrients, rather than feed dry matter, and to develop management, nutritional, or animal breeding approaches to improve animal efficiency through altering whole animal, tissue, cellular, and molecular facets known to be associated with differences in animal efficiency.

Analgesic and anti-inflammatory drugs in sports: Implications for exercise performance and training adaptations.

Over-the-counter analgesics, such as anti-inflammatory drugs (NSAIDs) and paracetamol, are widely consumed by athletes worldwide to increase pain tolerance, or dampen pain and reduce inflammation from injuries. Given that these drugs also can modulate tissue protein turnover, it is important to scrutinize the implications of acute and chronic use of these drugs in relation to exercise performance and the development of long-term training adaptations. In this review, we aim to provide an overview of the studies investigating the effects of analgesic drugs on exercise performance and training adaptations relevant for athletic development. There is emerging evidence that paracetamol might acutely improve important endurance parameters as well as aspects of neuromuscular performance, possibly through increased pain tolerance. Both NSAIDs and paracetamol have been demonstrated to inhibit cyclooxygenase (COX) activity, which might explain the reduced anabolic response to acute exercise bouts. Consistent with this, NSAIDs have been reported to interfere with muscle hypertrophy and strength gains in response to chronic resistance training in young individuals. Although it remains to be established whether any of these observations also translate into detriments in sport-specific performance or reduced training adaptations in elite athletes, the extensive use of these drugs certainly raises practical, ethical, and important safety concerns that need to be addressed. Overall, we encourage greater awareness among athletes, coaches, and support staff on the potential adverse effects of these drugs. A risk-benefit analysis and professional guidance are strongly advised before the athlete considers analgesic medicine for training or competition.

Existence of life-time stable proteins in mature rats—Dating of proteins’ age by repeated short-term exposure to labeled amino acids throughout age

In vivo turnover rates of proteins covering the processes of protein synthesis and breakdown rates have been measured in many tissues and protein pools using various techniques. Connective tissue and collagen protein turnover is of specific interest since existing results are rather diverging. The aim of this study is to investigate whether we can verify the presence of protein pools within the same tissue with very distinct turnover rates over the life-span of rats with special focus on connective tissue. Male and female Lewis rats (n = 35) were injected with five different isotopically labeled amino acids tracers. The tracers were injected during fetal development (Day -10 to -2), after birth (Day 5–9), at weaning (Day 25–32) at puberty (Day 54–58) and at adulthood (Day 447–445). Subgroups of rats were euthanized three days after every injection period, at different time point between injection periods and lastly at day 472. Tissue (liver, muscle, eye lens and patellar tendon) and blood samples were collected after euthanization. The enrichment of the labeled amino acids in the tissue or blood samples was measured using GC-MS-MS. In muscle and liver we demonstrated a rapid decrease of tracer enrichments throughout the rat’s life, indicating that myofibrillar and cytoskeleton proteins have a high turnover. In contrast, the connective tissue protein in the eye lens and patellar tendon of the mature rat showed detainment of tracer enrichment injected during fetal development and first living days, indicating very slow turnover. The data support the hypothesis that some proteins synthesized during the early development and growth still exist much later in life of animals and hence has a very slow turnover rate.

Recent advances for measurement of protein synthesis rates, use of the ‘Virtual Biopsy’ approach, and measurement of muscle mass

Flux-rate measurements of protein synthesis and breakdown (turnover) in muscle represent an ideal class of mechanism-based biomarkers for conditions of altered muscle mass and function. We describe here new metabolic labeling techniques for flux-rate measurements in humans, focusing on skeletal muscle. Dynamics of the muscle proteome are accurately measured in humans by combining long-term heavy water labeling with tandem mass spectrometry. Broad proteomic flux signatures or kinetics of targeted proteins are measurable. After interventions, early fractional synthesis rates of skeletal muscle proteins predict later changes in muscle mass. The 'virtual biopsy' method for measuring tissue protein turnover rates from body fluids has been validated for skeletal muscle, from labeling of plasma creatine kinase-type M or carbonic anhydrase-3. Label in these proteins in plasma reflects label of cognate proteins in the tissue, and response in plasma predicts longer term outcomes. Skeletal muscle mass can also be measured noninvasively from a spot urine, based on dilution of labeled creatine. This method correlates well with whole body MRI assessment of muscle mass and predicts clinical outcomes in older men. Flux measurements are available and more interpretable functionally than static measurements for several reasons, which are discussed.

Brain Plasticity: Measuring Protein Synthesis Rates in the Human Brain

IntroductionBrain plasticity is a term typically used to refer to the ability of the brain to reorganize itself throughout life. Though the term is often applied in neuroscience to express synaptic or non‐synaptic plasticity, information on whether neuroplasticity is also accompanied by a high brain tissue protein turnover rate is scarce. Because of obvious limitations with regard to brain tissue sampling no study has ever directly measured brain protein synthesis rates in vivo in humans. In this study, we applied contemporary stable isotope methodology to assess protein synthesis rates in vivo in human brain tissue of patients operated for drug‐resistant epilepsy.MethodsSix otherwise healthy patients (47±6 y), scheduled to undergo resective surgery for treatment of drug‐resistant temporomesial epilepsy, were included in this study. Primed continuous intravenous infusions with L‐[ring‐13C6]‐Phenylalanine and L‐[3,5‐2H2]‐Tyrosine were initiated 2.5 h prior to surgery and continued during surgery. Throughout the surgical procedure the following tissue samples were obtained: temporal neocortex, hippocampus, temporalis muscle, and vastus lateralis muscle. Tissue‐specific fractional protein synthesis rates (%/h) were assessed by measuring the incorporation of labelled L‐[ring‐13C6]‐Phenylalanine in tissue protein and were compared between the different tissues using a paired t test.ResultsSerum L‐[ring‐13C6]‐Phenylalanine enrichments averaged 8.1±0.7 MPE throughout the surgical procedure. Protein synthesis rates of temporal neocortex and hippocampus tissue averaged 0.17±0.01 and 0.13±0.01 %/h, respectively, with a significant difference between both tissues (P&lt;0.05). Brain tissue protein synthesis rates were 3–4 fold higher compared to skeletal muscle protein synthesis rates (0.05±0.01 %/h; P&lt;0.001).ConclusionThis is the first study to present protein synthesis rates in vivo in the human brain. With brain protein synthesis rates being several‐fold higher compared to skeletal muscle protein synthesis rates, the human brain displays a degree of tissue plasticity much higher than generally assumed.

Adjustments of Protein Metabolism in Fasting Arctic Charr, Salvelinus alpinus

Protein metabolism, including the interrelated processes of synthesis and degradation, mediates the growth of an animal. In ectothermic animals, protein metabolism is responsive to changes in both biotic and abiotic conditions. This study aimed to characterise responses of protein metabolism to food deprivation that occur in the coldwater salmonid, Arctic charr, Salvelinus alpinus. We compared two groups of Arctic charr: one fed continuously and the other deprived of food for 36 days. We measured the fractional rate of protein synthesis (KS) in individuals from the fed and fasted groups using a flooding dose technique modified for the use of deuterium-labelled phenylalanine. The enzyme activities of the three major protein degradation pathways (ubiquitin proteasome, lysosomal cathepsins and the calpain systems) were measured in the same fish. This study is the first to measure both KS and the enzymatic activity of protein degradation in the same fish, allowing us to examine the apparent contribution of different protein degradation pathways to protein turnover in various tissues (red and white muscle, liver, heart and gills). KS was lower in the white muscle and in liver of the fasted fish compared to the fed fish. There were no observable effects of food deprivation on the protease activities in any of the tissues with the exception of liver, where the ubiquitin proteasome pathway seemed to be activated during fasting conditions. Lysosomal proteolysis appears to be the primary degradation pathway for muscle protein, while the ubiquitin proteasome pathway seems to predominate in the liver. We speculate that Arctic charr regulate protein metabolism during food deprivation to conserve proteins.

Immuno-detection of PPAR overexpression with no change protein turnover endocardial tissues suggests major alterations in energy metabolism during ischemic and dilated cardiomyopathy conditions of heart

Immuno-Detection of PPAR Overexpression in Protein Turnover in Endocardial Tissues Suggesting Alterations in Energy Metabolism during Ischemic and Dilated Cardiomyopathy Conditions The peroxisome proliferator-activated receptor (PPAR) family regulates genes encoding enzymes involved in fatty acid and glucose metabolism. This role in the high-energy consuming heart organ has been a major target in cardiomyopathy studies. PPARs and nuclear protein levels were investigated in endocardial tissues samples obtained from ischemic and dilated cardiomyopathy male patients. Control samples were obtained from male accident victims of same age group. The expression of PPAR isoforms in each sample was analyzed by, protein assay, SDS-PAGE, western blotting and densitometry. The mean milligram nuclear protein of endocardial tissues for each of the three groups was measured as follows: ischemic 17.6 ± 8.1; dilated 13.7 ± 3.4; control 21.0 ± 6.0; (n=3 per group). The range of protein variability by Pearson correlation coefficient r was -0.91 ≤ r ≤ +0.77, (n=9). However, the sample means of the ischemic and dilated groups were not significantly different from the control mean, P>0.5 in each case by student’s test. The isoforms of PPAR are strongly expressed in cardiomyopathy conditions without change in nuclear protein turnover. The results also show that PPAR-α and PPAR-γ may be more predominant in the heart than PPAR-s. Furthermore, the expression of the spliced variants of PPAR-α and PPAR-γ were not affected by the cardiomyopathy conditions and PPAR-s have no spliced variant in the heart. The study provides an evidence of alteration in the heart’s energy metabolic processes during cardiomyopathies.

Tendon protein synthesis rate in classic Ehlers-Danlos patients can be stimulated with insulin-like growth factor-I.

The classic form of Ehlers-Danlos syndrome (cEDS) is an inherited connective tissue disorder, where mutations in type V collagen-encoding genes result in abnormal collagen fibrils. Thus the cEDS patients have pathological connective tissue morphology and low stiffness, but the rate of connective tissue protein turnover is unknown. We investigated whether cEDS affected the protein synthesis rate in skin and tendon, and whether this could be stimulated in tendon tissue with insulin-like growth factor-I (IGF-I). Five patients with cEDS and 10 healthy, matched controls (CTRL) were included. One patellar tendon of each participant was injected with 0.1 ml IGF-I (Increlex, Ipsen, 10 mg/ml) and the contralateral tendon with 0.1 ml isotonic saline as control. The injections were performed at both 24 and 6 h prior to tissue sampling. The fractional synthesis rate (FSR) of proteins in skin and tendon was measured with the stable isotope technique using a flood-primed continuous infusion over 6 h. After the infusion one skin biopsy and two tendon biopsies (one from each patellar tendon) were obtained. We found similar baseline FSR values in skin and tendon in the cEDS patients and controls [skin: 0.005 ± 0.002 (cEDS) and 0.007 ± 0.002 (CTRL); tendon: 0.008 ± 0.001 (cEDS) and 0.009 ± 0.002 (CTRL) %/h, mean ± SE]. IGF-I injections significantly increased FSR values in cEDS patients but not in controls (delta values: cEDS 0.007 ± 0.002, CTRL 0.001 ± 0.001%/h). In conclusion, baseline protein synthesis rates in connective tissue appeared normal in cEDS patients, and the patients responded with an increased tendon protein synthesis rate to IGF-I injections.

Stress in the kidney is the road to pERdition: is endoplasmic reticulum stress a pathogenic mediator of diabetic nephropathy?

The endoplasmic reticulum (ER) is an organelle that primarily functions to synthesise new proteins and degrade old proteins. Owing to the continual and variable nature of protein turnover, protein synthesis is inherently an error-prone process and is therefore tightly regulated. Fortunately, if this balance between synthesis and degradation is perturbed, an intrinsic response, the unfolded protein response (UPR) is activated to restore ER homoeostasis through the action of inositol-requiring protein 1, activating transcription factor 6 and PKR-like ER kinase transmembrane sensors. However, if the UPR is oversaturated and misfolded proteins accumulate, the ER can shift into a cytotoxic response, a physiological phenomenon known as ER stress. The mechanistic pathways of the UPR have been extensively explored; however, the role of this process in such a synthetic organ as the kidney requires further clarification. This review will focus on these aspects and will discuss the role of ER stress in specific resident kidney cells and how this may be integral in the pathogenesis and progression of diabetic nephropathy (DN). Given that diabetes is a perturbed state of protein turnover in most tissues, it is important to understand if ER stress is a secondary or tertiary response to other changes within the diabetic milieu or if it is an independent accelerator of kidney disease. Modulators of ER stress could provide a valuable tool for the treatment of DN and are under active investigation in other contexts.

A systems approach to determine the effect of changes in gene expression in adipose tissue on productive and reproductive efficiency in dairy cattle

In order to assess the patterns of metabolism that affect efficiency, an existing mechanistic metabolic model of dairy cows (Molly) was expanded to include transcriptional control of metabolism in adipose tissue and reproductive processes. Our objective was to test the effects of changes in gene transcription in adipose tissue on patterns of metabolism, reproductive processes and efficiency. The model describes the substrate sensitivity and maximum velocity for lipogenesis, esterification and lipolysis. Data were collected from first and second parity cows from various studies, and included nutrient intake, milk component output, changes in adipose tissue lipid, visceral and body protein and lipid, and metabolism rates in adipose tissue and gene transcription. The lipogenic pathways were primarily controlled by transcriptional changes, whereas lipolysis varied primarily by post-translational control. We used the difference in transcriptional and post-translational metabolic control to alter Vmax and Ks for lipogenesis and lipolysis; in addition, we modelled a range of energy costs for ion transport and protein turnover in liver, muscle and adipose tissues. Changing rates of lipogenesis and lipolysis (~four-fold) did not affect milk production or feed intake, but altered maintenance costs, fat accretion, energetic efficiency and reproduction. Increases in lipogenesis decreased postpartum interval to first ovulation; increases in rates of lipolysis increased the interval. Changes in metabolic rate from changing either adipose tissue metabolism or rate of ion transport and protein turnover affected rates of oestrogen and progesterone degradation, which affected follicular growth and corpus luteum function. This model may be used to help interpret genomic and transcriptomic data to pinpoint the most effective ways to select and manage for changes in productive and reproductive efficiency.

Studies on the Effect of Antidiabetic Drugs on Collagen in Rats

To assess the effects of antidiabetic drugs on collagen, the study has been carried out. However, at present, no conclusive data available on the In vivo effect of antidiabetic drugs in collagen. It was therefore thought worthwhile to undertake a systemic study on the metabolic turnover of connective tissue proteins, particularly collagen which will help to understand the various changes taking place in conventional antidiabetic drug treated rats. The hydroxyproline content was determined by the method of Neumann and Logan. There was no significant difference in mean body weight of animals in treated groups when compared to control animals on 50th day. In drug treated group G5, urinary excretion of hydroxyproline was slightly increased in contrast to that of the rats in other groups and showed a significant difference (p < 0.001) between control and G5 group. The proportion of soluble collagen in treated group was somewhat higher than in the control but while taking the significance value there are no statistically significant changes. Liver showed the highest concentration of 0.98 g collagen/100 g tissue, whereas kidney and heart showed 0.57 and 0.72 g collagen/100 g tissue. Observations of the present study collectively indicate that the anabolic rate of collagen metabolism is not altered significantly by the administration of antidiabetic drugs in normal rats.