Serine Supplementation Alleviates Doxorubicin-Induced Oxidative Damage in Skeletal Muscle of Mice

Muscle weakness affects physical activity and quality of life of patients. Serine, a nutritionally non-essential amino acid has been reported to enhance protein synthesis and implicate in biosynthesis of multiple bioactive molecules. It remains unknown whether it can protect mice against oxidative stress-induced muscles weakness. This study was conducted to test the hypothesis that serine administration alleviates doxorubicin-induced oxidative damage in skeletal muscle of mice. Mice pre-treated with or without serine were intraperitoneally injected with either doxorubicin or equal volume of saline. Reactive oxygen species (ROS) accumulation, activity of antioxidant enzymes, oxidation product of protein, DNA, and lipid, activity of mitochondrial complex, and protein level of nuclear-factor-erythroid-2-related factor 2 (NRF2)/constitutive-androstane-receptor (CAR) signaling in skeletal muscle of mice were determined. Compared with the control, doxorubicin exposure led to oxidative damage as shown by increased ROS accumulation, decreased activity of antioxidant enzymes, and enhanced oxidative product of protein, DNA, and lipid in the skeletal muscle of mice. These effects of doxorubicin were associated with increased activity of complex I and reduced glutathione. Interestingly, doxorubicin-induced oxidative damage was alleviated by serine administration. Further study showed that the beneficial effect of serine was associated with enhanced NRF2/CAR signaling. Our result showed that serine attenuated doxorubicin-induced muscle weakness in mice. Serine supplementation might be a nutritional strategy to improve the function of skeletal muscle in patients exposed to doxorubicin.

Novel S. cerevisiae Hybrid Synthetic Promoters Based on Foreign Core Promoter Sequences

Promoters are fundamental components of synthetic gene circuits. They are DNA segments where transcription initiation takes place. New constitutive and regulated promoters are constantly engineered in order to meet the requirements for protein and RNA expression into different genetic networks. In this work, we constructed and optimized new synthetic constitutive promoters for the yeast Saccharomyces cerevisiae. We started from foreign (e.g., viral) core promoters as templates. They are, usually, unfunctional in yeast but can be activated by extending them with a short sequence, from the CYC1 promoter, containing various transcription start sites (TSSs). Transcription was modulated by mutating the TATA box composition and varying its distance from the TSS. We found that gene expression is maximized when the TATA box has the form TATAAAA or TATATAA and lies between 30 and 70 nucleotides upstream of the TSS. Core promoters were turned into stronger promoters via the addition of a short UAS. In particular, the 40 nt bipartite UAS from the GPD promoter can enhance protein synthesis considerably when placed 150 nt upstream of the TATA box. Overall, we extended the pool of S. cerevisiae promoters with 59 new samples, the strongest overcoming the native TEF2 promoter.

Quick and effective improvement of leucine enriched dietary supplement on malnutrition in acute stroke patients receiving enteral tube feeding

Background Malnutrition often occurs in acute stroke patients receiving enteral tube feeding (ETF). Unless malnutrition is improved, their clinical outcome is poor. However, strategies to improve malnutrition in these patients have not been established. Branched-chain amino acids (BCAA) may enhance protein synthesis and attenuate inflammation. Our study aimed to investigate whether a leucine enriched BCAA dietary supplement (LEBDs) could quickly increase serum levels of albumin (Alb) or transthyretin (TTR) and decrease high-sensitivity C-reactive protein (CRP) in the development of severe malnutrition within a few days after stroke onset compared to standard BCAA dietary supplement (SBDs). Methods We retrospectively included acute stroke patients who: 1) were admitted between August 2016 and July 2017; 2) underwent ETF for 7 days or longer after admission, and 3) underwent blood examination of Alb, TTR, and CRP on admission, the fifth day and the seventh day. We defined severe malnutrition as severe hypoproteinemia: decrease of TTR to less than 15 mg/dl on the 5th day. In LEBDs and SBDs groups, patients started to receive a dietary supplement containing leucine of 1.44 and 0. 72 g twice a day on the fifth day, respectively. We evaluated Alb (g/dl), TTR (mg/dl), and CRP (mg/dl) on admission, the fifth day, and the seventh day. Results Twenty-nine patients met our inclusion criteria:15 in LEBDs and 14 in SBDs. In LEBDs and SBDs groups, the median Alb was 3.5 and 3.3 g/dl, TTR was 12.7 and 10.7 mg/dl, and CRP was 1.02 and 0.673 mg/dl on admission, respectively. In LEBDs, the median Alb and TTR decreased to 2.6 g/dl and 11.9 mg/dl, and CRP increased to 5.337 mg/dl on the fifth day. On the 7th day, TTR increased, and CRP decreased, although Alb did not improve. In SBDs, the median Alb and TTR decreased to 2.6 g/dl and 9.7 mg/dl, and CRP increased to 4.077 mg/dl on the fifth day. On the 7th day, Alb, TTR, and CRP did not improve. Conclusion In acute stroke patients receiving leucine enriched BCAA dietary supplement, quick improvements in transthyretin and CRP were observed.

A quick and improvement effect of leucine enriched dietary supplement on malnutrition in acute stroke patients receiving enteral tube feeding

Background:Malnutrition often occurs in acute stroke patients receiving enteral tube feeding (ETF). Unless malnutrition is improved, their clinical outcome is poor. However, strategies to improve malnutrition in these patients have not been established. Branched-chain amino acids (BCAA) may enhance protein synthesis and attenuate inflammation. Our study aimed to investigate whether a leucine enriched BCAA dietary supplement (LEBDs) could quickly improve a patient's nutritional status during the early stage of malnutrition. Methods:We retrospectively analyzed acute stroke patients who 1) were admitted between December 2016 and July 2017; 2) underwent ETF for seven days or longer after admission; 3) who underwent blood examination on admission, the 5th day, and seventh day; 4) in whom transthyretin (TTR) was less than 15 mg/dl on the 5th day, and 5) received LEBDs containing 1.44 g leucine per 200 kcal twice a day on the 5th day. We evaluated patients' features, serum albumin (Alb) (g/dl), transthyretin (TTR) (mg/dl), and high sensitive C-reactive protein (CRP) (mg/dl) on admission, the fifth day, and the seventh day. Results:Fifteen patients met our inclusion criteria. Their median age, body mass index (BMI), body weight (BW), serum blood glucose (BG), Alb, TTR, and CRP were 82 years, 21.8 kg/m2, 50 kg, 150 mg/dl, 3.5 g/dl, 12.7 mg/dl, and 1.02 mg/dl, respectively. Their median calorie intake was 1,200 kcal/day. On the 5th day, their median Alb and TTR decreased to 2.6 g/dl (p<0.0001) and 11.8 mg/dl (p<0.01), respectively, and their median CRP increased to 5.24 mg/dl (p<0.01). On the 7th day, TTR increased to 15.7 mg/dl (p<0.001), and CRP decreased to 4.77 mg/dl (p<0.05), whereas their median Alb was 2.6 g/dl (ns) and did not significantly change. ConclusionThe leucine enriched BCAA dietary supplement had a quick and improvement effect on the transthyretin and CRP level.

E. colitranslation strategies differ across nutrient conditions

For cells to grow faster they must increase their protein production rate. Microorganisms have traditionally been thought to accomplish this increase by producing more ribosomes to enhance protein synthesis capacity, leading to the linear relationship between ribosome level and growth rate observed under most growth conditions previously examined. Past studies have suggested that this linear relationship represents an optimal resource allocation strategy for each growth rate, independent of any specific nutrient state. Here we investigate protein production strategies in continuous cultures limited for carbon, nitrogen, and phosphate, which differentially impact substrate supply for protein versus nucleic acid metabolism. Unexpectedly, we find that at slow growth rates,E. coliachieves the same protein production rate using three different strategies under the three different nutrient limitations. Upon phosphate (P) limitation, translation is slow due to a particularly low abundance of ribosomes, which are RNA-rich and thus particularly costly for phosphorous-limited cells. In nitrogen (N) limitation, translation is slowed by limited glutamine and stalling at glutamine codons, resulting is slow elongation. In carbon (C) limitation, translation is slowed by accumulation of inactive ribosomes not bound to mRNA. These extra ribosomes enable rapid growth acceleration upon nutrient upshift. Thus, bacteria tune ribosome usage across different limiting nutrients to enable balanced nutrient-limited growth while also preparing for future nutrient upshifts.

The problem of nitrogen disposal in the obese

Amino-N is preserved because of the scarcity and nutritional importance of protein. Excretion requires its conversion to ammonia, later incorporated into urea. Under conditions of excess dietary energy, the body cannot easily dispose of the excess amino-N against the evolutively adapted schemes that prevent its wastage; thus ammonia and glutamine formation (and urea excretion) are decreased. High lipid (and energy) availability limits the utilisation of glucose, and high glucose spares the production of ammonium from amino acids, limiting the synthesis of glutamine and its utilisation by the intestine and kidney. The amino acid composition of the diet affects the production of ammonium depending on its composition and the individual amino acid catabolic pathways. Surplus amino acids enhance protein synthesis and growth, and the synthesis of non-protein-N-containing compounds. But these outlets are not enough; consequently, less-conventional mechanisms are activated, such as increased synthesis of NO∙ followed by higher nitrite (and nitrate) excretion and changes in the microbiota. There is also a significant production of N2 gas, through unknown mechanisms. Health consequences of amino-N surplus are difficult to fathom because of the sparse data available, but it can be speculated that the effects may be negative, largely because the fundamental N homeostasis is stretched out of normalcy, forcing the N removal through pathways unprepared for that task. The unreliable results of hyperproteic diets, and part of the dysregulation found in the metabolic syndrome may be an unwanted consequence of this N disposal conflict.

Failure of Commercial Oral Amino Acid Supplements to Increase Serum Growth Hormone Concentrations in Male Body-Builders

Amino acids are commonly ingested as ergogenic aids in the belief that they enhance protein synthesis and stimulate growth hormone release. The aim of this study was to determine the acute effect that amino acid supplements have on serum growth hormone (GH) concentration. Seven male bodybuilders reported to the laboratory on four occasions after an 8-hr fast and ingested, in random order, either a placebo, a 2.4-g arginine/lysine supplement, a 1.85-g ornithine/tyrosine supplement, or a 20-g BovrilR drink. Blood was collected before each treatment and again every 30 minutes for 3 hours for the measurement of serum GH concentration. On a separate occasion, subjects had an intravenous infusion of 0.5 fig GH-releasing hormone-kg ' body weight to confirm that GH secretory response was normal. The main finding was that serum GH concentrations were not altered consistently in healthy young males following the ingestion of the amino acid supplements in the quantities recommended by the manufacturers.

Effect of lanthanum on pancreatic protein synthesis in streptozotocin-diabetic rats

The role of extracellular Ca2+ in mediating the stimulatory effect of cholecystokinin octapeptide (CCK8) on [3H]phenylalanine incorporation into protein was studied in isolated pancreatic acini from streptozotocin-diabetic rats. The stimulatory effect of CCK8 (10(-10) M) on [3H]phenylalanine incorporation was completely abolished by preincubating acini with either 10(-4) M lanthanum or 10(-3) M manganese. At these concentrations neither compound altered the basal rate of amino acid incorporation, and both compounds inhibited CCK-mediated Ca2+ influx without affecting either basal or CCK-mediated 45Ca2+ efflux. Lanthanum (10(-4) M) also blocked the stimulatory effect of the cholinergic analogue carbachol (10(-5) M) on amino acid incorporation but did not alter the stimulatory effect of insulin (1.67 x 10(-8) M). Vasoactive intestinal polypeptide and 12-O-tetradecanoyl-phorbol-13-acetate failed to increase the incorporation of [3H]phenylalanine into acinar protein. These findings suggest that CCK and other pancreatic secretagogues that act via Ca2+ enhance protein synthesis by increasing cell membrane permeability to Ca2+ and provide additional evidence that this may be an important mechanism by which CCK regulates pancreatic exocrine function.