Exerkine ß-aminoisobutyric acid protects against atrial structural remodeling and atrial fibrillation in obesity via activating AMPK signaling and improving insulin sensitivity.

Moderate exercise decreases the risk for atrial fibrillation (AF), an effect which is probably mediated via exercise-stimulated release of exerkines. ß-Aminoisobutyric acid (BAIBA), a novel exerkine, has been reported to provide protective benefits against many cardiovascular diseases, yet its role in AF remains elusive. Herein, using a mouse model of obesity-related AF through high-fat diet (HFD) feeding, we found that 12-week drinking administration of BAIBA (170 mg/kg/day) decreased AF susceptibility in obese mice. Atrial remodeling assessment showed that BAIBA attenuated obesity-induced atrial hypertrophy and interstitial fibrosis, thereby ablating the substrate for AF. Of note, to our knowledge, this is the first report of the direct association of BAIBA and hypertrophy. BAIBA has been reported to be a key regulator of glucose and lipid metabolism, and we found that BAIBA alleviated insulin resistance in obese mice. Transcriptional analysis of metabolism-related genes showed that BAIBA increased the transcription of fatty acids metabolism-related genes in the atria of lean mice but not in that of obese mice. Mechanistic investigation showed that BAIBA stimulated AMP-activated protein kinase (AMPK) signaling in the atria of obese mice and palmitic acid (PA)-treated neonatal rat cardiomyocytes (NRCM), whereas inhibition of AMPK via Compound C attenuated BAIBA-conferred cardioprotection against hypertrophy and insulin resistance in PA-treated NRCM. Collectively, BAIBA attenuates AF susceptibility in obese mice via activated AMPK signaling and resultant improvement of insulin sensitivity, thereby providing perspectives on the potential therapeutic role of BAIBA in AF treatment.

Circulating level of ß-aminoisobutyric acid (BAIBA), a novel myokine-like molecule, is inversely associated with fat mass in patients with heart failure.

Results of experimental studies have shown that ß-aminoisobutyric acid (BAIBA), an exercise-induced myokine-like molecule, is an endogenous negative regulator of fat mass in mice, but it remains unclear whether that is the case in humans, though an enhanced BAIBA concentration in patients receiving sodium-glucose cotransporter 2 inhibitors was found in our recent study. The objective of this study was to analyze the determinants of circulating BAIBA concentration in humans, with focus on the possible link between circulating BAIBA and body composition including fat mass. Data for 188 consecutive patients with heart failure (HF, 64 ± 13 years; 70% male) who received a dual energy X ray absorptiometry (DEXA) scan for assessment of body composition including fat mass index (FMI) and appendicular skeletal muscle mass index (ASMI) were used in this study. Plasma BAIBA concentration in a fasting state after stabilization of HF was determined using ultraperformance liquid chromatography. Plasma BAIBA was detected in 66% of the patients. In simple linear regression analyses of data from patients in whom plasma BAIBA was detected, plasma BAIBA concentration was positively correlated with uric acid and was negatively correlated with body mass index (BMI), estimated glomerular filtration rate (eGFR), FMI, and % body fat. There were no correlations between plasma BAIBA concentration and indexes of muscle mass and bone mass. The results of multiple linear regression analyses showed that FMI and % body fat in addition to BMI, but not ASMI, were independent explanatory factors for plasma BAIBA concentration. In conclusion, plasma BAIBA concentration is inversely correlated with indexes of fat mass, indicating that BAIBA may be a therapeutic target for excessive fat accumulation.

A Candidate Gliotransmitter, L-ß-Aminoisobutyrate, Contributes to Weight Gain and Metabolic Complication Induced by Atypical Antipsychotics.

Lurasidone and quetiapine are effective atypical mood-stabilizing antipsychotics, but lurasidone and quetiapine are listed as lower-risk and high-risk for weight gain/metabolic complications, respectively. The pathophysiology of the discrepancy of metabolic adverse reactions between these antipsychotics remains to be clarified. The GABA isomer, ß-aminoisobutyric acid (BAIBA) enantiomer, was recently re-discovered as myokine via an AMP-activated protein kinase activator (AMPK) enhancer and inhibitory gliotransmitter. Notably, activation of AMPK in peripheral organs improves, but in the hypothalamus, it aggravates metabolic disturbances. Therefore, we determined effects of chronic administration of lurasidone and quetiapine on intracellular and extracellular levels of the BAIBA enantiomer. L-BAIBA is a major BAIBA enantiomer in the hypothalamus and astrocytes, whereas L-BAIBA only accounted for about 5% of total plasma BAIBA enantiomers. Chronic lurasidone administration did not affect body weight but decreased the L-BAIBA level in hypothalamus and cultured astrocytes, whereas chronic quetiapine administration increased body weight and the L-BAIBA level in hypothalamus and astrocytes. Contrary, neither lurasidone nor quetiapine affected total plasma levels of the BAIBA enantiomer since D-BAIBA levels were not affected by these antipsychotics. These results suggest that activation of intracellular L-BAIBA signaling is, at least partially, involved in the pathophysiology of metabolic adverse reaction of quetiapine. Furthermore, this study also demonstrated that lurasidone and quetiapine suppressed and enhanced astroglial L-BAIBA release induced by ripple-burst stimulation (which physiologically contributes to cognitive memory integration during sleep), respectively. Therefore, L-BAIBA probably contributes to the pathophysiology of not only metabolic adverse reactions, but also a part of clinical action of lurasidone or quetiapine.

Elevated circulating level of ß-aminoisobutyric acid (BAIBA) in heart failure patients with type 2 diabetes receiving sodium-glucose cotransporter 2 inhibitors.

AIMS: The mechanism by which a sodium-glucose cotransporter inhibitor (SGLT2i) induces favorable effects on diabetes and cardiovascular diseases including heart failure (HF) remains poorly understood. Metabolomics including amino acid profiling enables detection of alterations in whole body metabolism. The aim of this study was to determine whether plasma amino acid profiles are modulated by SGLT2i use in HF patients with type 2 diabetes mellitus (T2DM). METHODS: We retrospectively examined 81 HF patients with T2DM (68 ± 11 years old; 78% male). Plasma amino acid concentrations in a fasting state after stabilization of HF were determined using ultraperformance liquid chromatography. To minimize potential selection bias in the retrospective analyses, the differences in baseline characteristics between patients receiving an SGLT2i and patients not receiving an SGLT2i were controlled by using an inverse probability of treatment weighting (IPTW)-adjusted analysis. RESULTS: Of amino acids measurable in the present assay, plasma ß-aminoisobutyric acid (BAIBA), an exercise-induced myokine-like molecule also known as 3-aminoisobutyric acid or 3-amino-2-methyproponic acid, was detected in 77% of all patients and the proportion of patients in whom plasma BAIBA was detected was significantly higher in patients receiving an SGLT2i than in patients not receiving an SGLT2i (93% vs. 67%, p = 0.01). Analyses in patients in whom plasma BAIBA was detected showed that plasma BAIBA concentration was significantly higher in patients receiving an SGLT2i than in patients not receiving an SGLT2i (6.76 ± 4.72 vs. 4.56 ± 2.93 nmol/ml, p = 0.03). In multivariate logistic regression analyses that were adjusted for age and sex, SGLT2i use was independently associated with BAIBA detection. The independent association between BAIBA and SGLT2i use remained after inclusion of body mass index, HF with reduced ejection fraction, ischemic etiology, renal function, NT-proBNP, albumin, hemoglobin, and HbA1c into the Cox proportional hazards model. When the differences in baseline characteristics between patients receiving an SGLT2i and patients not receiving an SGLT2i were controlled by using an IPTW-adjusted analysis, least squares mean of plasma BAIBA concentration was significantly higher in patients receiving an SGLT2i than in patients not receiving an SGLT2i. CONCLUSION: SGLT2i use is closely associated with increased circulating BAIBA concentration in HF patients with T2DM.

Regulation of Skeletal Muscle Function by Amino Acids, Especially Non-Proteinogenic Amino Acids.

Amino acids are compounds that contain an amino group (-NH2) and a carboxyl group (-COOH) and are components of proteins and materials for various bioactive molecules. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage-processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids, especially non-proteinogenic amino acids, in the skeletal muscle. Leucine, a BCAA, and its metabolite, ß-hydroxy-ß-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), ß-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. ß-alanine levels are decreased in the skeletal muscles of aged mice. ß-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases.

ß-Aminoisobutyric acid, L-BAIBA, protects PC12 cells from hydrogen peroxide-induced oxidative stress and apoptosis via activation of the AMPK and PI3K/Akt pathway.

ß-Aminoisobutyric acid (BAIBA) is a myokine that is secreted from skeletal muscles by the exercise. Recently, increasing evidence has suggested the multifocal physiological activities of BAIBA. In this study, we investigated whether L-BAIBA has protective effects on rat pheochromocytoma (PC12) cells. Cultured PC12 cells were stimulated with L-BAIBA. Western blot analyses revealed that L-BAIBA stimulation significantly increased the phosphorylation of AMPK and Akt. In contrast, no effect was observed on neurite outgrowth by L-BAIBA. To investigate the effects of L-BAIBA on oxidative stress, PC 12 cells were exposed to hydrogen peroxide (H2O2) with and without L-BAIBA. Hydrogen peroxide significantly increased reactive oxygen species (ROS) production and apoptosis in PC12 cells. Pretreatment with L-BAIBA suppressed H2O2-induced ROS production and apoptosis, which was abolished by the inhibition of AMPK by compound C. On the other hand, the inhibitory effects of L-BAIBA on oxidative stress-induced apoptosis were abolished by the inhibition of both AMPK and PI3K/Akt. In conclusion, we demonstrated that L-BAIBA confers protection against oxidative stress in PC12 cells by activating the AMPK and PI3K/Akt pathways. These results suggest that L-BAIBA may play a crucial role on protection of neuron-like cells and become a pharmacological agent to treat neuronal diseases.

ß-Aminoisobutyric acid supplementation attenuated salt-sensitive hypertension in Dahl salt-sensitive rats through prevention of insufficient fumarase.

The human Dietary Approaches to Stop Hypertension-Sodium Trial has shown that ß-aminoisobutyric acid (BAIBA) may prevent the development of salt-sensitive hypertension (SSHT). However, the specific antihypertensive mechanism remains unclear in the renal tissues of salt-sensitive (SS) rats. In this study, BAIBA (100 mg/kg/day) significantly attenuated SSHT via increased nitric oxide (NO) content in the renal medulla, and it induced a significant increase in NO synthesis substrates (L-arginine and malic acid) in the renal medulla. BAIBA enhanced the activity levels of total NO synthase (NOS), inducible NOS, and constitutive NOS. BAIBA resulted in increased fumarase activity and decreased fumaric acid content in the renal medulla. The high-salt diet (HSD) decreased fumarase expression in the renal cortex, and BAIBA increased fumarase expression in the renal medulla and renal cortex. Furthermore, in the renal medulla, BAIBA increased the levels of ATP, ADP, AMP, and ADP/ATP ratio, thus further activating AMPK phosphorylation. BAIBA prevented the decrease in renal medullary antioxidative defenses induced by the HSD. In conclusion, BAIBA's antihypertensive effect was underlined by the phosphorylation of AMPK, the prevention of fumarase's activity reduction caused by the HSD, and the enhancement of NO content, which in concert attenuated SSHT in SS rats.

ß­aminoisobutyric acid ameliorates hypertensive vascular remodeling via activating the AMPK/SIRT1 pathway in VSMCs.

Excessive proliferation and migration of vascular smooth muscle cells (VSMCs) play a fundamental role in the pathogenesis of hypertension-related vascular remodeling. ß-aminoisobutyric acid (BAIBA) is a nonprotein ß-amino acid with multiple pharmacological actions. Recently, BAIBA has been shown to attenuate salt­sensitive hypertension, but the role of BAIBA in hypertension-related vascular remodeling has yet to be fully clarified. This study examined the potential roles and underlying mechanisms of BAIBA in VSMC proliferation and migration induced by hypertension. Primary VSMCs were cultured from the aortas of Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Our results showed that BAIBA pretreatment obviously alleviated the phenotypic transformation, proliferation, and migration of SHR-derived VSMCs. Exogenous BAIBA significantly inhibited the release of inflammatory cytokines by diminishing phosphorylation and nuclear translocation of p65 NFκB, retarding IκBα phosphorylation and degradation, as well as erasing STAT3 phosphorylation in VSMCs. Supplementation of BAIBA triggered Nrf2 dissociation from Keap1 and inhibited oxidative stress in VSMCs from SHR. Mechanistically, activation of the AMPK/sirtuin 1 (SIRT1) axis was required for BAIBA to cube hypertension-induced VSMC proliferation, migration, oxidative damage and inflammatory response. Most importantly, exogenous BAIBA alleviated hypertension, ameliorated vascular remodeling and fibrosis, abated vascular oxidative burst and inflammation in SHR, an effect that was abolished by deficiency of AMPKα1 and SIRT1. BAIBA might serve as a novel therapeutic agent to prevent vascular remodeling in the context of hypertension.

Investigation of the protective and therapeutic effects of ß-aminoisobutyric acid (BAIBA) and Thymoquinone in the diabetic nephropathy / Investigación de los efectos protectores y terapéuticos del ácido ß-aminoisobutírico (BAIBA) y la timoquinona en la nefropatía diabética

In this study, against streptozotocin (STZ) induced diapetic nephropathy (DN); it is aimed to investigate the use of thymoquinone (TQ) and ß-aminoisobutyric acid (BAIBA) and to compare the effects of these agents. With random selection of 35 male rats, five groups (seven rats in each group) were constituted as follows: Control, STZ, STZ + TQ, STZ + BAIBA, STZ + TQ + BAIBA. In the STZ group; body weight, glutathione (GSH) and insulin levels decreased, relative kidney weight, malondialdehyde (MDA), glucose, blood urea nitrogen (BUN) and creatinine (Cr) levels were increased. Also, in kidney tissue; histopathological changes (such as thickening of the capsular, glomerular and tubular basement membranes, increased mesangial matrix amount, increased cytoplasmic vacuolization in some of the tubular epithelial cells, increased tumor necrosis factor-alpha (TNF-α) expression, and inflammatory cell infiltrations in interstitial tissue) were detected. It was observed that these changes occurring after diabetes mellitus (DM) reversed significantly in TQ, BAIBA and TQ + BAIBA groups.

En este estudio, contra la nefropatía diapética (ND) inducida por estreptozotocina (STZ); tiene como objetivo investigar el uso de timoquinona (TQ) y ácido ß-aminoisobutírico (BAIBA) y comparar los efectos de estos agentes. Con la selección aleatoria de 35 ratas macho, se constituyeron cinco grupos (siete ratas en cada grupo) como sigue: Control, STZ, STZ + TQ, STZ + BAIBA, STZ + TQ + BAIBA. En el grupo STZ; el peso corporal, los niveles de glutatión (GSH) y de insulina disminuyeron, el peso relativo de los riñones, el malondialdehído (MDA), la glucosa, el nitrógeno ureico en sangre (BUN) y los niveles de creatinina (Cr) aumentaron. Además, en tejido renal; se detectaron cambios histopatológicos (como engrosamiento de las membranas basales capsular, glomerular y tubular, aumento de la cantidad de matriz mesangial, aumento de la vacuolización citoplasmática en algunas de las células epiteliales tubulares, aumento de la expresión del factor de necrosis tumoral alfa (TNF-α) e infiltraciones de células inflamatorias en tejido intersticial). Se observó que estos cambios que ocurren después de la diabetes mellitus (DM) se revirtieron significativamente en los grupos TQ, BAIBA y TQ + BAIBA.

ß-Aminoisobutyric Acid Suppresses Atherosclerosis in Apolipoprotein E-Knockout Mice.

Endurance exercise training has been shown to induce peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression in skeletal muscle. We recently reported that skeletal muscle-specific PGC-1α overexpression suppressed atherosclerosis in apolipoprotein E-knockout (ApoE-/-) mice. ß-Aminoisobutyric acid (BAIBA) is a PGC-1α-dependent myokine secreted from myocytes that affects multiple organs. We have also reported that BAIBA suppresses tumor necrosis factor-alpha-induced vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) gene expression in endothelial cells. In the present study, we hypothesized that BAIBA suppresses atherosclerosis progression, and tested that hypothesis with ApoE-/- mice. The mice were administered water containing BAIBA for 14 weeks, and were then sacrificed at 20 weeks of age. Atherosclerotic plaque area, plasma BAIBA concentration, and plasma lipoprotein profiles were assessed. Immunohistochemical analyses of the plaque were performed to assess VCAM-1 and MCP-1 protein expression levels and macrophage infiltration. The results showed that BAIBA administration decreased atherosclerosis plaque area by 30%, concomitant with the elevation of plasma BAIBA levels. On the other hand, plasma lipoprotein profiles were not changed by the administration. Immunohistochemical analyses indicated reductions in VCAM-1, MCP-1, and Mac-2 protein expression levels in the plaque. These results suggest that BAIBA administration suppresses atherosclerosis progression without changing plasma lipoprotein profiles. We propose that the mechanisms of this suppression are reductions in both VCAM-1 and MCP-1 expression as well as macrophage infiltration into the plaque.

Regulation of Skeletal Muscle Function by Amino Acids.

Amino acids are components of proteins that also exist free-form in the body; their functions can be divided into (1) nutritional, (2) sensory, and (3) biological regulatory roles. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage-processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids in the skeletal muscle. The expression of PGC1α, a transcriptional coactivator, is increased in the skeletal muscle during exercise. PGC1α activates branched-chain amino acid (BCAA) metabolism and is used for energy in the tricarboxylic acid (TCA) cycle. Leucine, a BCAA, and its metabolite, ß-hydroxy-ß-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), ß-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. ß-alanine levels are decreased in the skeletal muscles of aged mice. ß-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases.

Myokines in skeletal muscle physiology and metabolism: Recent advances and future perspectives.

Myokines are molecules produced and secreted by skeletal muscle to act in an auto-, para- and endocrine manner to alter physiological function of target tissues. The growing number of effects of myokines on metabolism of distant tissues provides a compelling case for crosstalk between skeletal muscle and other tissues and organs to regulate metabolic homoeostasis. In this review, we summarize and discuss the current knowledge regarding the impact on metabolism of several canonical and recently identified myokines. We focus specifically on myostatin, ß-aminoisobutyric acid, interleukin-15, meteorin-like and myonectin, and discuss how these myokines are induced and regulated as well as their overall function. We also review how these myokines may serve as potential prognostic biomarkers that reflect whole-body metabolism and how they may be attractive therapeutic targets for treating muscle and metabolic diseases.

Myotube Protein Content Associates with Intracellular L-Glutamine Levels.

BACKGROUND/AIMS: Skeletal mass loss is reported in several catabolic conditions and it has been associated with a reduced intracellular L-glutamine content. We investigated the association of intracellular L-glutamine concentration with the protein content in skeletal muscle cells. METHODS: We cultivated C2C12 myotubes in the absence or presence of 2 (reference condition), 8 or 16 mM L-glutamine for 48 hours, and the variations in the contents of amino acids and proteins measured. We used an inhibitor of L-glutamine synthesis (L-methionine sulfoximine - MSO) to promote a further reduction in intracellular L-glutamine levels. Amino acids contents in cells and media were measured using LC-MS/MS. We measured changes in phosphorylated Akt, RP-S6, and 4E-BP1contents in the absence or presence of insulin by western blotting. RESULTS: Reduced intracellular L-glutamine concentration was associated with decreased protein content and increased protein breakdown. Low intracellular glutamine levels were also associated with decreased p-Akt contents in the presence of insulin. A further decrease in intracellular L-glutamine caused by glutamine synthetase inhibitor reduced protein content and levels of amino acids generated from glutamine metabolism and increased bAib still further. Cells exposed to high medium glutamine levels did not have any change in protein content but exhibited increased contents of the amino acids derived from L-glutamine metabolism. CONCLUSION: Intracellular L-glutamine levels per se play a role in the control of protein content in skeletal muscle myotubes.

BAIBA Attenuates the Expression of Inflammatory Cytokines and Attachment Molecules and ER Stress in HUVECs and THP-1 Cells.

OBJECTIVE: ß-Aminoisobutyric acid (BAIBA), a myokine, is a thymine catabolite that is induced during exercise, leading to browning of white fat, hepatic fatty acid oxidation, and suppression of hepatic lipogenesis. However, the effects of BAIBA on the progression of atherosclerosis remain unclear. METHODS: We performed a Western blot analyses to determine various protein expression. ELISAs (enzyme-linked immunosorbent assays), cell adhesion assays, and cell viability assays were also performed on human umbilical vascular endothelial cells (HUVECs) and human monocytes (THP-1 cells). RESULTS: In the current study, we demonstrate that BAIBA suppresses atherosclerotic reactions caused by lipopolysaccharide (LPS) treatment via an AMPK-dependent pathway. Treatment of HUVECs and THP-1 cells with BAIBA inhibited the LPS-induced phosphorylation of nuclear factor-κB (NFκB) and the secretion of proinflammatory cytokines. In HUVECs, expression of adhesion molecules and LPS-stimulated adhesion of THP-1 cells to the endothelium were significantly decreased after BAIBA treatment. Furthermore, LPS-induced endoplasmic reticulum (ER) stress and cell toxicity were significantly decreased after BAIBA treatment of HUVECs. Notably, all of these proatherosclerotic effects were fully abrogated by treatment with small interfering RNA targeting AMPK. CONCLUSION: BAIBA ameliorates LPS-induced atherosclerotic reactions via AMPK-mediated suppression of inflammation and ER stress.

ß-aminoisobutyric acid accelerates the proliferation and differentiation of MC3T3-E1 cells via moderate activation of ROS signaling.

BACKGROUD: Osteoporosis is one of the bone-metabolic diseases associated with decreased bone renewal and bone mineral density. ß-aminoisobutyric acid (BAIBA), a natural thymine catabolite, can reduce inflammation in skeletal muscle and alleviate hepatic endoplasmic reticulum stress. However, the roles of BAIBA in osteoblast proliferation and differentiation remain largely unknown. METHODS: The cultured MC3T3-E1 cells received various treatments in this study, including BAIBA alone, H2O2 alone, BAIBA plus N-acetyl-l-cysteine and BAIBA plus apocynin. Cell proliferation was determined by CCK-8 assay and 3H-Thymidine incorporation. Cell differentiation was evaluated by determining mRNA level of differentiation makers and ALP, and ALP activity. Reactive oxygen species (ROS) were determined by DHE staining while superoxide anion level and NAD(P)H oxidase activity were determined by the lucigenin-derived chemiluminescence method. The content of hydrogen peroxide (H2O2) was detected using a commercial kit. The level of NOX1, NOX2 and NOX4 was determined by Western-blot or qRT-PCR. RESULTS: We show that treatment of BAIBA stimulated the proliferation of MC3T3-E1 osteoprogenitor cells and enhanced the gene expression of osteoblast differentiation markers. Incubation of MC3T3-E1 cells with BAIBA evoked increases in NAD(P)H oxidase-derived reactive oxygen species (ROS). Scavenging of reactive oxygen species (N-acetyl-l-cysteine) or inhibition of NAD(P)H oxidase (apocynin) abolished the BAIBA-elicited proliferation and differentiation of MC3T3-E1 cells. CONCLUSION: Our results provide the first evidence that BAIBA stimulates proliferation and differentiation of osteoprogenitor cells via activation of NAD(P)H oxidase/ROS signaling.

ß-aminoisobutyric Acid, l-BAIBA, Is a Muscle-Derived Osteocyte Survival Factor.

Exercise has beneficial effects on metabolism and on tissues. The exercise-induced muscle factor ß-aminoisobutyric acid (BAIBA) plays a critical role in the browning of white fat and in insulin resistance. Here we show another function for BAIBA, that of a bone-protective factor that prevents osteocyte cell death induced by reactive oxygen species (ROS). l-BAIBA was as or more protective than estrogen or N-acetyl cysteine, signaling through the Mas-Related G Protein-Coupled Receptor Type D (MRGPRD) to prevent the breakdown of mitochondria due to ROS. BAIBA supplied in drinking water prevented bone loss and loss of muscle function in the murine hindlimb unloading model, a model of osteocyte apoptosis. The protective effect of BAIBA was lost with age, not due to loss of the muscle capacity to produce BAIBA but likely to reduced Mrgprd expression with aging. This has implications for understanding the attenuated effect of exercise on bone with aging.

ß-Aminoisobutyric acid ameliorates the renal fibrosis in mouse obstructed kidneys via inhibition of renal fibroblast activation and fibrosis.

Renal fibrosis is a hallmark feature of chronic kidney disease, which is reflected by proliferation and migration of interstitial fibroblasts and extracellular matrix (ECM) accumulation. ß-Aminoisobutyric acid (BAIBA) is recently demonstrated to exert a protective role from metabolic diseases. However, whether and how BAIBA on fibroblast activation and renal fibrosis response to angiotensin II (Ang II) remains largely obscure. Herein, we showed that BAIBA significantly depressed the proliferation and migration of NRK-49F cells in vitro. Treatment with Ang II remarkably up-regulated the expressions of fibronectin (FN), collagen 1 (COL 1), α-smooth muscle actin (α-SMA), interleukin-17 (IL-17) and nicotinamide adenine dinucleotide phosphate oxidase (NOX2)-derived reactive oxygen species (ROS) production in cultured NRK-49F cells. Pretreatment with BAIBA almost blocked Ang II-induced ECM production and IL-17-mediated oxidative stress in NRK-49F cells. BAIBA treatment ameliorates fibroblasts activation and renal fibrosis in rat obstructed kidneys involving inhibition of Ang II/IL-17/ROS signaling transduction, which may be considered as a therapeutic candidate for fibrosis-related diseases.

Associations between plasma branched-chain amino acids, ß-aminoisobutyric acid and body composition.

Plasma branched-chain amino acids (BCAA) are elevated in obesity and associated with increased cardiometabolic risk. ß-Aminoisobutyric acid (B-AIBA), a recently identified small molecule metabolite, is associated with decreased cardiometabolic risk. Therefore, we investigated the association of BCAA and B-AIBA with each other and with detailed body composition parameters, including abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT). A cross-sectional study was carried out with lean (n 15) and obese (n 33) men and women. Detailed metabolic evaluations, including measures of body composition, insulin sensitivity and plasma metabolomics were completed. Plasma BCAA were higher (1·6 (se 0·08) (×10(7)) v. 1·3 (se 0·06) (×10(7)) arbitrary units; P = 0·005) in obese v. lean subjects. BCAA were positively associated with VAT (R 0·49; P = 0·0006) and trended to an association with SAT (R 0·29; P = 0·052). The association between BCAA and VAT, but not SAT, remained significant after controlling for age, sex and race on multivariate modelling (P < 0·05). BCAA were also associated with parameters of insulin sensitivity (Matsuda index: R -0·50, P = 0·0004; glucose AUC: R 0·53, P < 0·001). BCAA were not associated with B-AIBA (R -0·04; P = 0·79). B-AIBA was negatively associated with SAT (R -0·37; P = 0·01) but only trended to an association with VAT (R 0·27; P = 0·07). However, neither relationship remained significant after multivariate modelling (P > 0·05). Plasma B-AIBA was associated with parameters of insulin sensitivity (Matsuda index R 0·36, P = 0·01; glucose AUC: R -0·30, P = 0·04). Plasma BCAA levels were positively correlated with VAT and markers of insulin resistance. The results suggest a possible complex role of adipose tissue in BCAA homeostasis and insulin resistance.