Amino acids and amino acid sensing: implication for aging and diseases

A Review from a Clinical Perspective: Recent Advances in Biosensors for the Detection of L-Amino Acids

The field of biosensors is filled with reports and designs of various sensors, with the vast majority focusing on glucose sensing. However, in addition to glucose, there are many other important analytes that are worth investigating as well. In particular, L-amino acids appear as important diagnostic markers for a number of conditions. However, the progress in L-amino acid detection and the development of biosensors for L-amino acids are still somewhat insufficient. In recent years, the need to determine L-amino acids from clinical samples has risen. More clinical data appear to demonstrate that abnormal concentrations of L-amino acids are related to various clinical conditions such as inherited metabolic disorders, dyslipidemia, type 2 diabetes, muscle damage, etc. However, to this day, the diagnostic potential of L-amino acids is not yet fully established. Most likely, this is because of the difficulties in measuring L-amino acids, especially in human blood. In this review article, we extensively investigate the 'overlooked' L-amino acids. We review typical levels of amino acids present in human blood and broadly survey the importance of L-amino acids in most common conditions which can be monitored or diagnosed from changes in L-amino acids present in human blood. We also provide an overview of recent biosensors for L-amino acid monitoring and their advantages and disadvantages, with some other alternative methods for L-amino acid quantification, and finally we outline future perspectives related to the development of biosensing devices for L-amino acid monitoring.

Immune Remodeling during Aging and the Clinical Significance of Immunonutrition in Healthy Aging

Aging is associated with changes in the immune system and the gut microbiota. Immunosenescence may lead to a low-grade, sterile chronic inflammation in a multifactorial and dynamic way, which plays a critical role in most age-related diseases. Age-related changes in the gut microbiota also shape the immune and inflammatory responses. Nutrition is a determinant of immune function and of the gut microbiota. Immunonutrion has been regarded as a new strategy for disease prevention and management, including many age-related diseases. However, the understanding of the cause-effect relationship is required to be more certain about the role of immunonutrition in supporting the immune homeostasis and its clinical relevance in elderly individuals. Herein, we review the remarkable quantitative and qualitative changes during aging that contribute to immunosenescence, inflammaging and microbial dysbiosis, and the effects on late-life health conditions. Furthermore, we discuss the clinical significance of immunonutrition in the treatment of age-related diseases by systematically reviewing its modulation of the immune system and the gut microbiota to clarify the effect of immunonutrition-based interventions on the healthy aging.

Senescence Induced by UVB in Keratinocytes Impairs Amino Acids Balance

Skin is one of the most exposed organs to external stress. Namely, UV rays are the most harmful stress that could induce important damage leading to skin aging and cancers. At the cellular level, senescence is observed in several skin cell types and contributes to skin aging. However, the origin of skin senescent cells is still unclear but is probably related to exposure to stresses. In this work, we developed an in vitro model of UVB-induced premature senescence in normal human epidermal keratinocytes. UVB-induced senescent keratinocytes display a common senescent phenotype resulting in an irreversible cell cycle arrest, an increase in the proportion of senescence-associated β-galactosidase‒positive cells, unrepaired DNA damage, and a long-term DNA damage response activation. Moreover, UVB-induced senescent keratinocytes secrete senescence-associated secretory phenotype factors that influence cutaneous squamous cell carcinoma cell migration. Finally, a global transcriptomic study highlighted that senescent keratinocytes present a decrease in the expression of several amino acid transporters, which is associated with reduced intracellular levels of glycine, alanine, and leucine. Interestingly, the chemical inhibition of the glycine transporter SLC6A9/Glyt1 triggers senescence features.

The Genetic Variability of Members of the SLC38 Family of Amino Acid Transporters (SLC38A3, SLC38A7 and SLC38A9) Affects Susceptibility to Type 2 Diabetes and Vascular Complications

Type 2 Diabetes (T2D) is a metabolic disease associated with long-term complications, with a multifactorial pathogenesis related to the interplay between genetic and modifiable risk factors, of which nutrition is the most relevant. In particular, the importance of proteins and constitutive amino acids (AAs) in disease susceptibility is emerging. The ability to sense and respond to changes in AA supplies is mediated by complex networks, of which AA transporters (AATs) are crucial components acting also as sensors of AA availability. This study explored the associations between polymorphisms in selected AATs genes and T2D and vascular complications in 433 patients and 506 healthy controls. Analyses revealed significant association of SLC38A3-rs1858828 with disease risk. Stratification of patients based on presence/absence of vascular complications highlighted significant associations of SLC7A8-rs3783436 and SLC38A7-rs9806843 with diabetic retinopathy. Additionally, the SLC38A9-rs4865615 resulted associated with chronic kidney disease. Notably, these genes function as AAs sensors, specifically glutamine, leucine, and arginine, linked to the main nutrient signaling pathway mammalian target of rapamycin complex 1 (mTORC1). Thus, their genetic variability may contribute to T2D by influencing the ability to properly transduce a signal activating mTORC1 in response to AA availability. In this scenario, the contribution of dietary AAs supply to disease risk may be relevant.

Axenic Culture of Caenorhabditis elegans Alters Lysosomal/Proteasomal Balance and Increases Neuropeptide Expression

Axenically cultured C. elegans show many characteristic traits of worms subjected to dietary restriction, such as slowed development, reduced fertility, and increased stress resistance. Hence, the term axenic dietary restriction (ADR) is often applied. ADR dramatically extends the worm lifespan compared to other DR regimens such as bacterial dilution. However, the underlying molecular mechanisms still remain unclear. The primary goal of this study is to comprehensively investigate transcriptional alterations that occur when worms are subjected to ADR and to estimate the molecular and physiological changes that may underlie ADR-induced longevity. One of the most enriched clusters of up-regulated genes under ADR conditions is linked to lysosomal activity, while proteasomal genes are significantly down-regulated. The up-regulation of genes specifically involved in amino acid metabolism is likely a response to the high peptide levels found in axenic culture medium. Genes related to the integrity and function of muscles and the extracellular matrix are also up-regulated. Consistent down-regulation of genes involved in DNA replication and repair may reflect the reduced fertility phenotype of ADR worms. Neuropeptide genes are found to be largely up-regulated, suggesting a possible involvement of neuroendocrinal signaling in ADR-induced longevity. In conclusion, axenically cultured worms seem to rely on increased amino acid catabolism, relocate protein breakdown from the cytosol to the lysosomes, and do not invest in DNA maintenance but rather retain muscle integrity and the extracellular matrix. All these changes may be coordinated by peptidergic signaling.

Quantitative analysis of nutrients for nucleosides, nucleobases and amino acids hidden behind five distinct regions-derived Poria cocos using ultra-performance liquid chromatography coupled with triple-quadrupole linear ion-trap tandem mass spectrometry

Poria cocos is an edible fungus used as a health product and traditional Chinese medicinal preparation. Nevertheless, little is known about its nutrients. In this study, ultra-high performance liquid chromatography coupled with triple-quadrupole linear ion-trap tandem mass spectrometry was conducted to quantify nucleosides, nucleobases, and amino acids in 32 batches of Poria cocos samples collected from Anhui, Sichuan, Hubei, Hunan and Guizhou. Subsequently, the linearity, precision, repeatability, stability, and recovery of our methods were validated. Samples from different regions were clearly separated by partial least squares discriminant analysis and cluster analysis. Our results suggested that Poria cocos samples from different geographical environments differed in nucleosides, nucleobases, and amino acids. The plot of variable importance for projection disclosed differential compositions of L-Leucine, Uridine, L-Asparagine, L-Glutamine, L-phenylalanine, L-Ornithine monohydrochloride, L-Hydroxyproline, Taurine and Inosine in Poria cocos from five regions. We found the highest content of total analytes, total amino acids and total non-essential amino acids in Poria cocos from Anhui, total essential amino acids in the Sichuan samples and total nucleosides in Hunan samples. Overall, we determined the content of Poria cocos-derived nucleosides, nucleobases, and amino acids, providing the foothold for further chemical mining and use of Poria cocos. This article is protected by copyright. All rights reserved.

SLC6A14 Depletion Contributes to Amino Acid Starvation to Suppress EMT-Induced Metastasis in Gastric Cancer by Perturbing the PI3K/AKT/mTORC1 Pathway

Metastasis is the main obstacle for the treatment of gastric cancer (GC), leading to low survival rate and adverse outcomes in CG patients. SLC6A14, a general amino acid transporter, can import all the essential amino acids in a manner dependent on the NaCl-generated osmotic gradients. Herein, we constructed GC cell sublines with high (SGC7901-M and MKN28-M) and low (MKN28-NM and SGC7901-NM) metastatic ability. Putative functional genes advancing GC metastasis were identified using mRNA microarray analysis and High-Content Screening. In particular, most significant change with a dampening trend in the migration potentiality of GC cells emerged after SLC6A14 gene was silenced. SLC6A14 expression was positively correlated with the migrated capability of different GC cell lines, and SLC6A14 was also constitutively expressed in GC patients with venous or lymphatic invasion, lymph node, or distant metastasis and poor prognosis, thus prompting SLC6A14 as a nonnegligible presence in supporting GC migration and invasion. Consistently, SLC6A14 depletion drastically depressed GC metastasis in vitro and in vivo. Most importantly, pharmacological blockade and gene silence of SLC6A14 both restricted epithelial-mesenchymal transition- (EMT-) driven GC metastasis, in which attenuated activation of the PI3K/AKT/mTORC1 pathway caused by amino acid starvation was involved. In summary, it is conceivable that targeting SLC6A14 has a tremendous promising for the treatment of metastatic GC.

Novel "Turn-On" Luminescent Chemosensor for Arginine by Using a Lanthanide Metal-Organic Framework Photosensitizer

Arginine is considered as a biomarker of cystinuria and other diseases, and thus, it is of urgency to develop a simple and rapid method with high sensitivity and selectivity for arginine detection to meet the demand of on-site analysis and bedside diagnosis. In this work, a lanthanide metal-organic framework, La(TATB), was prepared using a triazine-based planar ligand, 4,4',4″-s-triazine-2,4,6-triyltribenzoate (H₃TATB), and lanthanide ion (La³⁺). La(TATB) can be used as a highly photosensitive agent to activate molecular oxygen to ¹O₂ to achieve efficient photosensitive oxidation of arginine accompanied by strong blue fluorescence emission under 302 nm UV irradiation. Due to the porous structure and high specific surface area of La(TATB), short-life ¹O₂ can effectively approach and react with amino acid substrate molecules, thus leading to higher sensitivity than other systems. Therefore, the "turn-on" fluorescence sensing of trace arginine can be realized, with a measured linear response range of 10-20,000 nM and a limit of detection as low as 7 nM. This method can be used for the detection of trace arginine in urine, which is conducive to the bedside diagnosis and rapid screening of cystinuria and other diseases. The proposed method not only expands the application scope of Ln-MOFs but also provides a new construction strategy for "turn-on" luminescence sensors.

Regulation of Aging and Longevity by Ion Channels and Transporters

Despite significant advances in our understanding of the mechanisms that underlie age-related physiological decline, our ability to translate these insights into actionable strategies to extend human healthspan has been limited. One of the major reasons for the existence of this barrier is that with a few important exceptions, many of the proteins that mediate aging have proven to be undruggable. The argument put forth here is that the amenability of ion channels and transporters to pharmacological manipulation could be leveraged to develop novel therapeutic strategies to combat aging. This review delves into the established roles for ion channels and transporters in the regulation of aging and longevity via their influence on membrane excitability, Ca2+ homeostasis, mitochondrial and endolysosomal function, and the transduction of sensory stimuli. The goal is to provide the reader with an understanding of emergent themes, and prompt further investigation into how the activities of ion channels and transporters sculpt the trajectories of cellular and organismal aging.

Effect of a 40-weeks multicomponent exercise program and branched chain amino acids supplementation on functional fitness and mental health in frail older persons

BACKGROUND

The ageing process implies several physiological and psychological changes that hence affect the general health, mood states, and quality of life of older persons. Exercise and adequate nutrition are renowned non-pharmacological strategies that significantly delay and alleviate the adverse consequences of the ageing process. This study aimed to evaluate the effects of branched-chain amino acid (BCAA) supplementation and a multicomponent exercise program (ME) on the physical frailty and mood states of older persons.

METHODS

35 participants (women and men; 83 ± 3 years old) from residential care homes were submitted to a 40-week exercise-washout-retraining intervention (16 weeks of the elastic band based exercise and/or supplementation, 8 weeks of washout, and 16 weeks of multicomponent exercise and/or resupplementing), with or without BCAA supplementation. The experimental groups were: (i) ME plus BCAA supplementation (ME+BCAA); (ii) ME; (iii) BCAA supplementation (BCAA), and (iv) control group (CG). Fried's phenotype was used to assess frailty prevalence. Geriatric Depression Scale (GDS), Profile of Mood State (POMS), Mini-Mental State Examination (MMSE), were used to access mental health and cognition. The Short Physical Performance Battery (SPPB) was used to access functional capacity. Salivary testosterone levels (ST) were also determined to access the anabolic effects of the intervention.

RESULTS

Exercise was effective in improving functional capacity and prevented the increase in frailty that occurred in the non-exercising CG, where the frailty scores increased over time (p < 0.01). BCAAs supplement alone had no impact on functional fitness, but in a short time (16 weeks) contributed to diminishing frailty and combined with exercise may have the potential to reduce the effect of a detraining period on functional capacity. Salivary testosterone levels correlated with handgrip strength and could be a useful indicator of susceptibility to frailty. No effects were found for mood states, cognition, and depression.

CONCLUSION

This study showed that a long-term exercise program, independent of being multicomponent or strength elastic band-based, was effective in improving functional capacity and prevented an increase in frailty in frail and pre-frail older persons living in residential care homes.

Dietary intake of creatine and risk of medical conditions in U.S. older men and women: Data from the 2017-2018 National Health and Nutrition Examination Survey

We examined dietary intake of creatine in U.S. men and women aged 65 years and over, and evaluated the association between creatine intake and risk of self-reported medical conditions, and physical functioning/disability variables using data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES). The NHANES 2017-2018 target population included the noninstitutionalized civilian resident population of the United States aged 65 years and over. Detailed dietary intake data from NHANES elderly were obtained by dietary interview component through a 24-h dietary recall interview, with estimated individual values for total grams of creatine consumed per day for each respondent. A threshold for dietary intake of creatine used to calculate risk between creatine intake and medical conditions was set at 1.00 g/day. The sample population included 1500 participants aged 65 years and older, of which 1221 individuals (627 men and 594 women) provided detailed dietary data via a dietary interview. Creatine intake across all participants was 0.76 ± 0.79 g/day (95% CI from 0.72 to 0.81). As much as 70% of U.S. elderly consume <1.00 g of creatine per day, with about 1 in 5 individuals (19.8%) consume no creatine at all. Elderly with the suboptimal intake of creatine were found to have 2.62 times higher risk of angina pectoris (adjusted OR = 2.62, 95% CI from 1.14 to 6.01, p = .023) and 2.59 times higher risk of liver conditions (adjusted OR = 2.59, 95% CI from 1.23 to 5.48, p = .013), compared with older counterparts who consume ≥1.00 g of creatine per day after controlling for demographic and nutritional variables. The considerable shortage of dietary creatine is associated with an increased risk of heart and liver conditions, which calls for public measures that foster diets rich in creatine-containing foods, and additional research to investigate the role of creatine in age-related diseases.

Serum Amino Acids Patterns and 4-Year Sarcopenia Risk in Community-Dwelling Chinese Older Adults

INTRODUCTION

Dietary protein intake and serum amino acids (AAs) are factors controlling the rate of muscle protein synthesis and catabolism. This study examined the association between serum AAs patterns and incident sarcopenia in community-dwelling older adults.

METHODS

Chinese older adults in Hong Kong aged ≥65 years attended a health check at baseline and 4-year follow-up. At baseline, fasting blood was collected to measure 17 serum AAs. Serum AAs patterns were identified using principal component analysis. Dietary protein intake was assessed using a validated food frequency questionnaire. A composite score was computed by summing the principal component score and sex-standardized protein intake. Six composite scores representing each AAs pattern were available for each participant. Sarcopenia was defined using the updated version of the Asian Working Group for Sarcopenia. Crude and adjusted multiple logistic regressions were performed to examine the associations between each of the 6 composite scores and sarcopenia over 4 years. Results are presented as odds ratio (OR) and 95% confidence interval (CI). To address multiple testing, a Bonferroni correction was applied using a corrected significance level of p < 0.008 (α 0.05/6 patterns).

RESULTS

Data of 2,610 participants (mean age 71.6 years, 45.4% men) were available. In men, serum AAs patterns characterized by high branched-chain AAs (BCAAs) (OR 0.77, 95% CI 0.69-0.87, p < 0.001) and tyrosine, tryptophan, and phenylalanine (OR 0.79, 95% CI 0.71-0.89, p < 0.001) were significantly associated with a lower risk of sarcopenia over 4-year follow-up. After adjusting for confounders, the associations were no longer significant. In women, serum AAs patterns characterized by glutamine, glutamic acid, and methionine (OR 1.28, 95% CI 1.11-1.47, p = 0.001) and arginine, taurine, and serine (OR 1.20, 95% CI 1.06-1.35, p = 0.003) were associated with a higher risk of sarcopenia. After adjusting for confounders, serum AAs pattern characterized by high BCAAs (adjusted OR 1.52, 95% CI 1.25-1.86, p < 0.001) and arginine, taurine, and serine (adjusted OR 1.30, 95% CI 1.09-1.56, p = 0.004) were significantly associated with a higher risk of sarcopenia. No association between other AAs patterns with incident sarcopenia was found.

CONCLUSIONS

In community-dwelling Chinese older adults, serum AAs patterns characterized by high BCAAs and nonessential AAs (arginine, taurine, and serine) were associated with a higher risk of sarcopenia in women. Findings may allow identifying new targets for interventions.

The Amino Acid-mTORC1 Pathway Mediates APEC TW-XM-Induced Inflammation in bEnd.3 Cells

The blood-brain barrier (BBB) is key to establishing and maintaining homeostasis in the central nervous system (CNS); meningitis bacterial infection can disrupt the integrity of BBB by inducing an inflammatory response. The changes in the cerebral uptake of amino acids may contribute to inflammatory response during infection and were accompanied by high expression of amino acid transporters leading to increased amino acid uptake. However, it is unclear whether amino acid uptake is changed and how to affect inflammatory responses in mouse brain microvascular endothelial (bEnd.3) cells in response to Avian Pathogenic Escherichia coli TW-XM (APEC XM) infection. Here, we firstly found that APEC XM infection could induce serine (Ser) and glutamate (Glu) transport from extracellular into intracellular in bEnd.3 cells. Meanwhile, we also shown that the expression sodium-dependent neutral amino acid transporter 2 (SNAT2) for Ser and excitatory amino acid transporter 4 (EAAT4) for Glu was also significantly elevated during infection. Then, in amino acid deficiency or supplementation medium, we found that Ser or Glu transport were involving in increasing SNAT2 or EAAT4 expression, mTORC1 (mechanistic target of rapamycin complex 1) activation and inflammation, respectively. Of note, Ser or Glu transport were inhibited after SNAT2 silencing or EAAT4 silencing, resulting in inhibition of mTORC1 pathway activation, and inflammation compared with the APEC XM infection group. Moreover, pEGFP-SNAT2 overexpression and pEGFP-EAAT4 overexpression in bEnd.3 cells all could promote amino acid uptake, activation of the mTORC1 pathway and inflammation during infection. We further found mTORC1 silencing could inhibit inflammation, the expression of SNAT2 and EAAT4, and amino acid uptake. Taken together, our results demonstrated that APEC TW-XM infection can induce Ser or Glu uptake depending on amino acid transporters transportation, and then activate amino acid-mTORC1 pathway to induce inflammation in bEnd.3 cells.

Redox Signaling and Sarcopenia: Searching for the Primary Suspect

Sarcopenia, the age-related decline in muscle mass and function, derives from multiple etiological mechanisms. Accumulative research suggests that reactive oxygen species (ROS) generation plays a critical role in the development of this pathophysiological disorder. In this communication, we review the various signaling pathways that control muscle metabolic and functional integrity such as protein turnover, cell death and regeneration, inflammation, organismic damage, and metabolic functions. Although no single pathway can be identified as the most crucial factor that causes sarcopenia, age-associated dysregulation of redox signaling appears to underlie many deteriorations at physiological, subcellular, and molecular levels. Furthermore, discord of mitochondrial homeostasis with aging affects most observed problems and requires our attention. The search for the primary suspect of the fundamental mechanism for sarcopenia will likely take more intense research for the secret of this health hazard to the elderly to be unlocked.

Interactive effects of dietary amino acid density and environmental temperature on growth performance and expression of selected amino acid transporters, water channels, and stress-related transcripts

Exposure to heat stress (HS) is one of the challenges facing the broiler industry worldwide. Various nutritional strategies have been suggested, such as altering dietary concentrations of some nutrients. Thus, we evaluated feeding different amino acid (AA) densities on live performance, Pectoralis (P.) muscles, and expression of selected AA transporters, water channels, and stress-related transcripts in a fast-growing broiler strain. Ross 308 chicks (n = 576) were randomly assigned to 4 dietary treatments (24 reps, 6 chicks per rep), differing in AA density (110, 100, 90, and 80% of a breeder's AA specifications). During 24 to 36 days of age, half of the birds were kept at a thermoneutral (TN) temperature of 20°C, whereas the other half were subjected to HS at 32° C for 8 h daily, making the treatment design a 4 × 2. The results revealed no interaction between housing temperature and AA density on growth performance or P. muscles weights. Feeding 80% AAs depressed BWG, FCR, and P. muscles at 36 d (P < 0.001). There was an interaction (P < 0.001) between AA density and temperature on the expression of all examined genes. Reducing the AA density beyond 100% upregulated the expression of AA transporter (CAT1, B⁰AT, b^0,+AT, SNAT1, LAT1), HSP70, HSP90, glucocorticoid receptor (GR), and AQP3 in the TN birds’ jejunum. Whereas in the HS birds, inconsistent expressions were observed in the jejunum, of which CAT1, B⁰AT, and LAT1 were markedly downregulated as AA density was reduced. In P. major of TN birds, reducing AA density resulted in upregulating the expression of all AA transporters, HSP70, GR, and AQP1, while downregulating HSP90 and AQP9. In contrast, AA reduction markedly downregulated CAT1, B⁰AT, and LAT1 in the P. major of HS birds. These findings indicate that the dietary AA level alters the expression of various genes involved in AA uptake, protein folding, and water transport. The magnitude of alteration is also dependent on the housing temperature. Furthermore, the results highlight the importance of adequate AA nutrition for fast-growing chickens under HS.

Enhanced small neutral but not branched chain amino acid transport after epigenetic sodium coupled neutral amino acid transporter-2 (SNAT2) cDNA expression in myoblasts

BACKGROUND

Skeletal muscle mass and function are partly maintained by the supply of amino acids, altered amino acid transport is an important cause of frailty that can lead to decreased independence with increasing age and slow trauma recovery. The system-A sodium coupled neutral amino acid transporter (SNAT)-2 coded by gene family SLC38A2 generates a 506 amino acid 56 kDa protein that is an important transporter of amino acids in skeletal muscle. Ageing is associated with a decrease in expression of SNAT2 transporters.

METHODS

In this study, we used the C2C12 cell line, using myoblast cells and cells differentiated into myotubes. We investigated if the expression of SNAT2 DNA would enhance intracellular amino acid levels and increase their availability for protein synthesis.

RESULTS

In control myoblasts and myotubes, we found significantly decreased expression of SNAT2 (6.5× decrease, n = 4 per group, P < 0.05) in myotubes than found in myoblasts. After transfection with a SNAT2-eGFP cDNA plasmid, C2C12 myoblasts significantly increased perinuclear punctate SNAT2-eGFP expression that persisted and was more cytoplasmic after differentiation into myotubes. Interestingly, transfected cells were significantly more responsive to the hormone 5α-dihydrotestosterone (DHT, 4.5 nM, by 1.6×, n = 3 per group, P < 0.04). Starvation significantly enhanced the amino acid C¹⁴ -MeAIB transport (1.7×, n = 3 per group, P < 0.05) indicating increased function of SNAT2. Inhibiting SNAT2 with high concentrations of MeAIB (3.3 or 5 mM) significantly reduced C¹⁴ -Isoleucine transport by L-type amino acid transporter (LAT2, 52.8% and 77%, respectively, n = 3 per group, P < 0.05). However, there was no increase in the LAT2 transport of C¹⁴ -isoleucine detectable in SNAT2-eGFP transfected cells after DHT (4.5 nM) exposure. This indicated that small amino acid availability was not rate limiting to LAT2 function in myoblasts.

CONCLUSIONS

Overall, these data show that transfection of SNAT2-eGFP expression enhanced its function following starvation and treatment with physiological levels of DHT. Enhanced SNAT2 expression in muscle cells offers a viable epigenetic target in pathological conditions associated with altered amino acid transport.

Self-powered liquid chemical sensors based on solid-liquid contact electrification

Triboelectric nanogenerators (TENGs) have attracted many research endeavors as self-powered sensors for force, velocity, and gas detection based on solid-solid or solid-air interactions. Recently, triboelectrification at liquid-solid interfaces also showed intriguing capability in converting physical contacts into electricity. Here, we report a self-powered triboelectric sensor for liquid chemical sensing based on liquid-solid electrification. As a liquid droplet passed across the tribo-negative sensor surface, the induced surface charge balanced with the electrical double layer charge in the liquid droplet. The competition between the double layer charge and surface charge generated characteristic positive and negative voltage spikes, which may serve as a "binary feature" to identify the chemical compound. The sensor showed distinct sensitivity to three amino acids including glycine, lysine and phenylalanine as a function of their concentration. The versatile sensing ability was further demonstrated on several other inorganic and organic chemical compounds dissolved in DI water. This work demonstrated a promising sensing application based on the triboelectrification principle for biofluid sensor development.

A comparison of intestinal integrity, digestive function, and egg quality in laying hens with different ages

Intestinal integrity, digestive enzyme activity, nutrient utilization, and egg quality of laying hens at different ages were evaluated and compared in this study. A total of 192 Hy-line Brown laying hens at 195-d-old (D195 group), 340-d-old (D340 group), and 525-d-old (D525 group) were allocated into one of 3 groups in accordance with their ages. Each group had 8 replicates of 8 birds each, and all birds were fed a maize-soybean meal basal diet for a 2-wk experiment. Compared with the D195 group, intestinal villus height and ratio of villus height to crypt depth, as well as serum D-lactate content increased in the D525 group (P < 0.05). The sucrase and maltase activities in the jejunal mucosa, amylase activity in the pancreas, and trypsin activity in the jejunal chyme of 525-d-old hens were lower than their 195-d-old counterparts (P < 0.05). In addition, there was a decline of trypsin and lipase activities in the ileal chyme of hens from D525 group in comparison with D195 or D340 group (P < 0.05). Apparent retention of dry matter and crude protein of birds in D340 and D525 group decreased when compared with the D195 group (P < 0.05). Moreover, birds in the D525 group exhibited a lower level of ether extract retention, and higher contents of several excreted amino acids than those in the D195 group (P < 0.05). Compared with the D195 group, eggs harvested from D525 group exhibited lower albumen height, eggshell strength and thickness, and a higher egg weight (P < 0.05). In conclusion, increased intestinal permeability (higher serum D-lactate content), compromised digestive function (lower digestive enzyme activities and apparent nutrient retention, and higher concentrations of excreted amino acids), and poor egg quality (lower albumen height, eggshell strength, and thickness) were observed with increasing age in the laying hens.

Serum amino acid concentrations are modified by age, insulin resistance, and BCAT2 rs11548193 and BCKDH rs45500792 polymorphisms in subjects with obesity

BACKGROUND & AIMS

The amino acid profile of young adults is modified by sex, body mass index (BMI) and insulin resistance (IR). However, we do not know if age or the presence of specific polymorphisms in the genes of BCAT2 and BCKDH contribute to changes in the amino acid profile, especially in subjects with obesity. Therefore, we have evaluated the effect of age, the presence of IR and the polymorphisms of BCAT2 rs11548193 and BCKDH rs45500792 on the concentration of amino acids in subjects with obesity.

METHODS

This was a cross-sectional study conducted with 487 subjects with obesity. Participants underwent a physical examination in which their clinical history was obtained and a blood sample was taken for biochemical, hormonal, and DNA analysis.

RESULTS

Adults <30 years old with obesity had higher levels of alanine, arginine, aspartate, histidine, leucine, lysine, methionine, phenylalanine, proline, serine and valine than adults ≥30 years old. Interestingly, regardless of age, we found that arginine, aspartate, serine decreased, while proline and tyrosine increased in the presence of IR; tyrosine and sum of branched-chain amino acids (∑BCAA) were the amino acids that increased in the presence of BCAT2 rs11548193 and BCKDH rs45500792 polymorphisms.

CONCLUSIONS

We found that the amino acid profiles of subjects with obesity are differentially modified by age, the presence of IR, and the presence of the BCAT2 rs11548193 and BCKDH rs45500792 polymorphisms.

Essential amino acid formulations to prevent mitochondrial dysfunction and oxidative stress

PURPOSE OF REVIEW

Both restriction and supplementation of specific amino acids or branched-chain amino acids (BCAAs) are described to improve metabolic homeostasis, energy balance, and health span. This review will discuss the recent findings of the role of amino acid supplements in the regulation of mitochondrial health.

RECENT FINDINGS

A mixture of essential amino acids (EAAs), BCAA enriched mixture, was found to extend healthy life span in elderly mice and prevent multiple diseases associated with an energy deficit, similarly to caloric restriction or fasting-mimicking diets. A growing body of evidence highlights mitochondria as the central target of this supplement: it promotes mitochondrial biogenesis and the activation of antioxidant defence systems in different physiological (e.g., exercise or ageing) or pathological conditions (e.g., sarcopenia, muscular dystrophy, liver steatosis, or impaired cognition). Based on these results, new formulas have been created enriched with Krebs cycle substrates, behaving more efficiently than BCAA enriched mixture.

SUMMARY

EAA-BCAA balanced supplements might be valuable not only for healthy individuals undergoing to energy deficit (e.g., athletes) during strenuous exercise or training but also against diseases characterized by a dysregulated catabolic state or mitochondrial dysfunction, such as age-related disorders. The associated mechanistic processes should be identified as potential pharmacological targets.

Multivariate Analysis of Amino Acids and Health Beneficial Properties of Cantaloupe Varieties Grown in Six Locations in the United States

Cantaloupe is a good dietary source of amino acids, including γ-aminobutyric acid (GABA), glutamine, and citrulline. However, the levels of these amino acids vary among different cantaloupe varieties grown in different locations. Understanding the variation in amino acid contents provides fundamentally important information for quality control and improving melon varieties. To examine this variation, we measured the amino acid contents in cantaloupes grown in six locations in the United States (Texas, Georgia, North Carolina, California, Indiana, and Arizona). Principal component analyses were applied to analyze the effect of growing location on the amino acid profiles in different varieties. The GABA content ranged from 1006.14 ± 64.77 to 3187.12 ± 64.96 µg/g and citrulline ranged from 92.65 ± 9.52 to 464.75 ± 34.97 µg/g depending on the variety and location. Total phenolic contents, α-amylase inhibition, and antioxidant activities were also measured. Tuscan type Da Vinci had significantly higher phenolic contents in Arizona (381.99 ± 16.21 µg/g) but had the lowest level when grown in California (224.56 ± 14.62 µg/g). Our analyses showed significant differences in amino acid levels, phenolics contents, and antioxidant activity in the cantaloupe varieties based on the growing location. These findings underline the importance of considering growing location in the selection and improvement of cantaloupe varieties.

WNT5B exerts oncogenic effects and is negatively regulated by miR-5587-3p in lung adenocarcinoma progression

WNT5B glycoprotein belongs to the Wnt protein family. Limited investigations revealed a possible role of WNT5B in malignancies, such as triple-negative breast cancer and oral squamous cell carcinoma. However, whether WNT5B contributes to the progression of lung adenocarcinoma (LAD) remains unclear. Here, we initially determine that WNT5B is highly expressed in LAD and is positively correlated with lymph node metastasis and TNM stage. Consistently, clinical analysis reveals WNT5B as an independent prognostic biomarker in LAD. Silencing WNT5B suppresses the proliferation of LAD both in vitro and in vivo by interfering G1/S cell-cycle progression and modulating amino acid metabolism, revealing its remarkable oncogenic role in LAD. Of note, we also identified miR-5587-3p as a negative upstream regulator of WNT5B in LAD, which may help develop therapies targeting LAD patients with high WNT5B expression. Taken together, our results revealed an oncogenic role of WNT5B in LAD, which could be a prognostic biomarker and promising therapeutic target for LAD patients.

Exercise training in ad libitum and food-restricted old rats: effects on metabolic and physiological parameters

Aging is accompanied by a decline in the healthy function of multiple organs, leading to increased incidence and mortality from diseases such as cancer and inflammatory, cardiovascular and neurodegenerative diseases. Dietary restriction is the most effective experimental intervention known to consistently slow the aging process and with positive effects on health span in different organisms, from invertebrates to mammals. Age is also associated with progressive decline in physical activity levels in a wide range of animal species: therefore, regular physical exercise could represent a safe intervention to antagonize aging. In this research we explore the effects of exercise training initiated in late middle aged rats fed with different lifelong dietary regimens: one group was fed ad libitum and the second group was subjected to every-other-day fasting. These two groups might represent examples of "normal" aging and "successful" aging. The study shows the effects of exercise and food restriction and their interaction on plasma levels of total antioxidant capacity, lactate, amino acids, and on products of protein oxidation in soleus and tibialis anterior muscles. In addition, we evaluated body composition measurement by bioelectrical impedance analysis and muscle strength by grasping test. Results show that late-onset exercise training has the potential to improve some metabolic and physiological parameters in rats with the same "chronological age" but different "biological age", without negative effects, and highlight the relevance of a personalised and selected exercise protocol, since the responsiveness to exercise may depend on the individual's "biological age".

Inositol Polyphosphate Multikinase (IPMK), a Gene Coding for a Potential Moonlighting Protein, Contributes to Human Female Longevity

Biogerontological research highlighted a complex and dynamic connection between aging, health and longevity, partially determined by genetic factors. Multifunctional proteins with moonlighting features, by integrating different cellular activities in the space and time, may explain part of this complexity. Inositol Polyphosphate Multikinase (IPMK) is a potential moonlighting protein performing multiple unrelated functions. Initially identified as a key enzyme for inositol phosphates synthesis, small messengers regulating many aspects of cell physiology, IPMK is now implicated in a number of metabolic pathways affecting the aging process. IPMK regulates basic transcription, telomere homeostasis, nutrient-sensing, metabolism and oxidative stress. Here, we tested the hypothesis that the genetic variability of IPMK may affect human longevity. Single-SNP (single nuclear polymorphism), haplotype-based association tests as well as survival analysis pointed to the relevance of six out of fourteen genotyped SNPs for female longevity. In particular, haplotype analysis refined the association highlighting two SNPs, rs2790234 and rs6481383, as major contributing variants for longevity in women. Our work, the first to investigate the association between variants of IPMK and longevity, supports IPMK as a novel gender-specific genetic determinant of human longevity, playing a role in the complex network of genetic factors involved in human survival.