Plasma Amino Acids May Improve Prediction Accuracy of Cerebral Vasospasm after Aneurysmal Subarachnoid Haemorrhage

Aneurysmal subarachnoid haemorrhages (aSAH) account for 5% of strokes and continues to place a great burden on patients and their families. Cerebral vasospasm (CVS) is one of the main causes of death after aSAH, and is usually diagnosed between day 3 and 14 after bleeding. Its pathogenesis remains poorly understood. To verify whether plasma concentration of amino acids have prognostic value in predicting CVS, we analysed data from 35 patients after aSAH (median age 55 years, IQR 39–62; 20 females, 57.1%), and 37 healthy volunteers (median age 50 years, IQR 38–56; 19 females, 51.4%). Fasting peripheral blood samples were collected on postoperative day one and seven. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis was performed. The results showed that plasma from patients after aSAH featured a distinctive amino acids concentration which was presented in both principal component analysis and direct comparison. No significant differences were noted between postoperative day one and seven. A total of 18 patients from the study group (51.4%) developed CVS. Hydroxyproline (AUC = 0.7042, 95%CI 0.5259–0.8826, p = 0.0248) and phenylalanine (AUC = 0.6944, 95%CI 0.5119–0.877, p = 0.0368) presented significant CVS prediction potential. Combining the Hunt-Hess Scale and plasma levels of hydroxyproline and phenylalanine provided the model with the best predictive performance and the lowest leave-one-out cross-validation of performance error. Our results suggest that plasma amino acids may improve sensitivity and specificity of Hunt-Hess scale in predicting CVS.

Plasma Amino Acids and Risk of Impaired Lower-Extremity Function and Role of Dietary Intake: A Nested Case-Control Study in Older Adults

<b><i>Introduction:</i></b> Amino acids are key elements in the regulation of the aging process which entails a progressive loss of muscle mass. The health effects of plasma amino acids can be influenced by dietary intake. This study assessed the prospective association between amino acid species and impaired lower-extremity function (ILEF) in older adults, exploring the role of diet on this association. <b><i>Methods:</i></b> This is a case-control design comprising 43 incident cases of ILEF and 85 age- and sex-matched controls. Plasma concentrations of 20 amino acid species were measured at baseline using liquid chromatography-tandem mass spectrometry, and incident cases of ILEF were measured after 2 years by means of the Short Physical Performance Battery. Conditional logistic regression models were used to assess longitudinal relationships. <b><i>Results:</i></b> After adjusting for potential confounders, higher levels of tryptophan were associated with a decreased 2-year risk of ILEF (OR per 1-SD increase = 0.64, 95% CI = [0.42, 0.97]), while glutamine and total essential amino acids were linked to higher ILEF risk (OR = 1.57, 95% CI = [1.01, 2.45]; OR = 1.89, 95% CI = [1.18, 3.03], respectively). Those with a lower adherence to a Mediterranean diet, a higher BMI, a higher consumption of red meat, and a lower consumption of nuts and legumes had an increased risk of ILEF associated with higher levels of essential amino acids. <b><i>Discussion/Conclusion:</i></b> Some amino acid species could serve as risk markers for physical function decline in older adults, and healthy diet might attenuate the excess risk of ILEF linked to essential amino acids.

Dampened Muscle mTORC1 Response Following Ingestion of High-Quality Plant-Based Protein and Insect Protein Compared to Whey

Increased amino acid availability acutely stimulates protein synthesis partially via activation of mechanistic target of rapamycin complex 1 (mTORC1). Plant-and insect-based protein sources matched for total protein and/or leucine to animal proteins induce a lower postprandial rise in amino acids, but their effects on mTOR activation in muscle are unknown. C57BL/6J mice were gavaged with different protein solutions: whey, a pea–rice protein mix matched for total protein or leucine content to whey, worm protein matched for total protein, or saline. Blood was drawn 30, 60, 105 and 150 min after gavage and muscle samples were harvested 60 min and 150 min after gavage to measure key components of the mTORC1 pathway. Ingestion of plant-based proteins induced a lower rise in blood leucine compared to whey, which coincided with a dampened mTORC1 activation, both acutely and 150 min after administration. Matching total leucine content to whey did not rescue the reduced rise in plasma amino acids, nor the lower increase in mTORC1 compared to whey. Insect protein elicits a similar activation of downstream mTORC1 kinases as plant-based proteins, despite lower postprandial aminoacidemia. The mTORC1 response following ingestion of high-quality plant-based and insect proteins is dampened compared to whey in mouse skeletal muscle.

The effect of time of feeding on plasma amino acids during exercise and recovery in horses

Feeding management in horses suggests feeding horses in advance of exercise, particularly the grain portion of the diet. Plasma amino acids (AA) peak at 3-6 hours post feeding depending on the amino acid. The timeframe between feeding and exercise may affect the availability of amino acids during and after exercise. The purpose of this study was to observe the differences in plasma amino acids in horses fed prior to exercise or after exercise. Eight light type horses were fed a diet with adequate protein and amino acids for horses in light to moderate exercise. After an adjustment period, horses completed a standardized exercise test (SET). Relative to the SET, horses were fed either 2hr prior (PRE horses) to the SET, 1hr after completing the SET (POST horses) or horses remained fasted throughout the sampling period (FASTED horses). Plasma was drawn prior to exercise, at the peak of exercise as well as at 1, 2, 4 and 7 hours post exercise. Plasma was analyzed for amino acids, glucose, lactate, creatinine, creatine kinase, ammonia, urea-N and 3-methylhistdine. After completion of the SET and sampling period, horses entered a one-week recovery period which was followed by another SET. The protocol repeated until horses rotated through all feeding protocols in the study (3 SETs). The majority of the plasma amino acids were elevated in PRE horses compared to POST horses prior to the SET until 2hr post exercise where POST horses’ plasma amino acid concentrations became elevated and remained elevated until the end of the sampling period. In that same time frame, plasma amino acids for the PRE group decreased out to the end of the sampling period. The elevation of plasma amino acids in POST horses would be expected as they were fed at 1hr post exercise while PRE horses were reaching a 4hr post feeding time frame at this point. This elevation was not observed for plasma concentrations of isoleucine, leucine, methionine and histidine. Concentrations of these amino acids initially were greater for POST horses in the post exercise period however they declined more rapidly than the other amino acids. The rapid decrease of some of the plasma amino acid concentrations may suggest uptake by muscle for recovery. This in conjunction with a decrease in plasma creatine kinase concentrations for POST horses suggests that feeding post exercise may facilitate better muscle protein balance (synthesis vs. breakdown) in the recovery period following exercise.