β-aminoisobutyric acid attenuates hepatic endoplasmic reticulum stress and glucose/lipid metabolic disturbance in mice with type 2 diabetes

Xiasangju alleviates hepatic insulin resistance in db/db mice via AMPK pathway: Mechanisms and active components study

Type 2 diabetes mellitus (T2DM), one of the prevalent chronic diseases, significantly impacts individuals and society. Xiasangju (XSJ), a herbal tea formulation, has been commonly used in traditional Chinese medicine. Accumulating evidence suggests that XSJ can alleviate metabolic syndrome by regulating glucose and lipid metabolism, lowering liver index and improving glucose tolerance. In the present study, db/db mice were used to examine the effect of XSJ on treating T2DM, and Western blotting was performed to explore the underlying anti-T2DM pharmacological mechanisms. With AMP-activated protein kinase (AMPK) chosen as the target protein, surface plasmon resonance (SPR)-LC-MS technology was used to identify potential active ingredients of XSJ. To further explore the role of potential active ingredients of XSJ, their effects were investigated in insulin resistance (IR)-HepG2 cells. Our results demonstrate that in diabetic db/db mice, XSJ activated the AMPK pathway, which regulated hepatic glucose metabolism and inhibited oxidative stress caused by hepatic NADPH oxidase 4 (NOX4), thereby ameliorating hepatic IR. By means of SPR-LC-MS experiments, 4-Methylesculetin was identified as an important active ingredient in XSJ. Subsequently, to further elucidate the effects of this ingredient, in IR-HepG2 cells, 4-Methylesculetin was found to mitigate oxidative stress, enhance glucose consumption, and promote glycogen synthesis. This study demonstrated that XSJ improved T2DM and mitigated oxidative stress by activating the AMPK pathway. Specifically, 4-Methylesculetin emerged as a promising therapeutic agent for T2DM.

Fecal Microbiome and Urine Metabolome Profiling of Type 2 Diabetes

Type 2 diabetes is a prevalent metabolic disorder with serious health consequences, necessitating both enhanced diagnostic methodologies and comprehensive elucidation of its pathophysiological mechanisms. We compared fecal microbiome and urine metabolome profiles in type 2 diabetes patients versus healthy controls to evaluate their respective diagnostic potential. Using a cohort of 94 subjects (48 diabetics, 46 controls), this study employed 16S rRNA amplicon sequencing for fecal microbiome analysis and GC-MS for urinary metabolomics. While fecal microbiome alpha diversity showed no significant differences between groups, urinary metabolomics demonstrated distinct structural patterns and higher evenness in type 2 diabetes patients. The study identified several diabetes-associated urinary metabolites, including elevated levels of glucose and inositol, along with decreased levels of 6 urine metabolites including glycolic acid, hippurate, and 2-aminoethanol. In the fecal microbiome, genera such as Escherichia-Shigella showed positive correlation with type 2 diabetes, while Lacticaseibacillus demonstrated negative correlation. Receiver operating characteristic curve analyses revealed that urinary metabolites exhibited superior diagnostic potential compared to fecal microbiome features, with an area under the curve of 0.90 for the combined metabolite model versus 0.82 for the integrated bacterial taxa model. These findings suggest that urinary metabolomics may offer a more reliable approach for type 2 diabetes diagnosis compared to fecal 16S metabarcoding, while highlighting the potential of multi-marker panels for enhanced diagnostic accuracy.

In vivo and in silico insights into the antidiabetic efficacy of EVOO and hydroxytyrosol in a rat model

Extra virgin olive oil (EVOO) has a putative antidiabetic activity mostly attributed to its polyphenol Hydroxytyrosol. In this study, we explored the antidiabetic effects of EVOO and Hydroxytyrosol on an in vivo T2D-simulated rat model as well as in in silico study. Wistar rats were divided into four groups. The first group served as a normal control (NC), while type 2 diabetes (T2D) was induced in the remaining groups using a high-fat diet (HFD) for 12 weeks followed by a single dose of streptozotocin (STZ, 30 mg/kg). One diabetic group remained untreated (DC), while the other two groups received an 8-week treatment with either EVOO (90 g/kg of the diet) (DO) or Hydroxytyrosol (17.3 mg/kg of the diet) (DH). The DC group exhibited hallmark features of established T2D, including elevated fasting blood glucose levels, impaired glucose tolerance, increased HOMA-IR, widespread downregulation of insulin receptor expression, heightened oxidative stress, and impaired β-cell function. In contrast, treatments with EVOO and Hydroxytyrosol elicited an antidiabetic response, characterized by improved glucose tolerance, as indicated by accelerated blood glucose clearance. Systematic analysis revealed the underlying antidiabetic mechanisms: both treatments enhanced insulin receptor expression in the liver and skeletal muscles, increased adiponectin levels, and mitigated oxidative stress. Moreover, while EVOO reduced intramyocellular lipids, Hydroxytyrosol restored adipose tissue insulin sensitivity and enhanced β-cell survival. Molecular docking and dynamics confirm Hydroxytyrosol's high affinity binding to PGC-1α, IRE-1α, and PPAR-γ, particularly IRE-1α, highlighting its potential to modulate diabetic signaling pathways. Collectively, these mechanisms highlight the putative antidiabetic role of EVOO and Hydroxytyrosol. Moreover, the favorable docking scores of Hydroxytyrosol with PGC-1α, IRE-1α, and PPAR-γ support the antidiabetic potential and offer promising avenues for further research and the development of novel antidiabetic therapies.

β-aminoisobutyric acid ameliorated type 1 diabetes-induced germ cell toxicity in rat: Studies on the role of oxidative stress and IGF-1/AMPK/SIRT-1 signaling pathway

Diabetes mellitus is known as the "epidemic of the century" due to its global prevalence. Several pre-clinical and clinical studies have shown that male germ cell toxicity is one of the major consequences of diabetes mellitus. Although β-aminoisobutyric acid (BAIBA) has been shown to be advantageous in the diabetic nephropathy and cardiomyopathy, its specific role in the diabetes-induced testicular toxicity remains unknown. In this study, an attempt was made to elucidate the molecular mechanisms of BAIBA-mediated germ cell protection in diabetic rats. Adult male Sprague-dawley rats were subjected to either no treatment (control) or BAIBA (100 mg/kg; BAIBA control) or Streptozotocin (50 mg/kg; diabetic control) or low (25 mg/kg), medium (50 mg/kg) and high (100 mg/kg) doses of BAIBA in diabetic conditions. Significant alterations in sperm related parameters, oxidative stress and apoptotic biomarkers, pancreatic and testicular histology, DNA damage and changes in expression of proteins in testes were found in the diabetic rats. 100 mg/kg of BAIBA significantly reduced the elevated blood glucose levels (P ≤ 0.05), increased body weight (P ≤ 0.01 in the 4th week), lowered malondialdehyde (P ≤ 0.05) and nitrite levels (P ≤ 0.01), elevated testosterone (P ≤ 0.05) and FSH levels (P ≤ 0.05), increased sperm count and motility (P ≤ 0.01), decreased testicular DNA damage (P ≤ 0.001), improved histological features of pancreas and testes, decreased TUNEL positive cells (P ≤ 0.01), decreased RAGE (P ≤ 0.01) and Bax (P ≤ 0.05) expressions and increased SIRT1 (P ≤ 0.05) and Atg 12 (P ≤ 0.05) expressions in the testes. 50 mg/kg of BAIBA partially restored the above-mentioned parameters whereas 25 mg/kg of BAIBA was found to be insignificant in counteracting the toxicity. It is interesting to note that BAIBA protects male germ cell damage in diabetic rats by regulating the IGF-1/AMPK/SIRT-1 signaling pathway.

Bacterial reprogramming of tick metabolism impacts vector fitness and susceptibility to infection

Arthropod-borne pathogens are responsible for hundreds of millions of infections in humans each year. The blacklegged tick, Ixodes scapularis, is the predominant arthropod vector in the United States and is responsible for transmitting several human pathogens, including the Lyme disease spirochete Borrelia burgdorferi and the obligate intracellular rickettsial bacterium Anaplasma phagocytophilum, which causes human granulocytic anaplasmosis. However, tick metabolic response to microbes and whether metabolite allocation occurs upon infection remain unknown. Here we investigated metabolic reprogramming in the tick ectoparasite I. scapularis and determined that the rickettsial bacterium A. phagocytophilum and the spirochete B. burgdorferi induced glycolysis in tick cells. Surprisingly, the endosymbiont Rickettsia buchneri had a minimal effect on bioenergetics. An unbiased metabolomics approach following A. phagocytophilum infection of tick cells showed alterations in carbohydrate, lipid, nucleotide and protein metabolism, including elevated levels of the pleiotropic metabolite β-aminoisobutyric acid. We manipulated the expression of genes associated with β-aminoisobutyric acid metabolism in I. scapularis, resulting in feeding impairment, diminished survival and reduced bacterial acquisition post haematophagy. Collectively, we discovered that metabolic reprogramming affects interspecies relationships and fitness in the clinically relevant tick I. scapularis.

Metabolomic Analysis of Follicular Fluid in Normal-Weight Patients with Polycystic Ovary Syndrome

BACKGROUND

This study aimed to examine the differential variations in the metabolic composition of follicular fluid (FF) among normal-weight patients with polycystic ovary syndrome (PCOS) and controls and to identify potential biomarkers that may offer insights into the early identification and management of these patients.

METHODS

We collected FF samples from 45 normal-weight women with PCOS and 36 normal-weight controls without PCOS who were undergoing in vitro fertilization-embryo transfer. An untargeted metabolomic study of collected FF from infertile women was performed using high-performance liquid chromatography-tandem spectrometry (LC-MS). The tendency of the two groups to separate was demonstrated through multivariate analysis. Univariate analysis and variable importance in projection were used to screen out differential metabolites. Metabolic pathway analysis was conducted using the Kyoto Encyclopedia of Genes and Genomes (KEGG), and a diagnostic model was established using the random forest algorithm.

RESULTS

The metabolomics analysis revealed an increase in the expression of 23 metabolites and a decrease in that of 10 metabolites in the FF of normal-weight women with PCOS. According to the KEGG pathway analysis, these differential metabolites primarily participated in the metabolism of glycerophospholipids and the biosynthesis of steroid hormones. Based on the biomarker combination of the top 10 metabolites, the area under the curve value was 0.805. The concentrations of prostaglandin E2 in the FF of individuals with PCOS exhibited an inverse association with the proportion of high-quality embryos (p < 0.05).

CONCLUSIONS

Our research identified a distinct metabolic profile of the FF from normal-weight women with PCOS. The results offer a broader comprehension of the pathogenesis and advancement of PCOS, and the detected differential metabolites could be potential biomarkers and targets for the treatment of PCOS.

Targeting Crosstalk of Signaling Pathways among Muscles-Bone-Adipose Tissue: A Promising Therapeutic Approach for Sarcopenia

The aging process is associated with the development of a wide range of degenerative disorders in mammals. These diseases are characterized by a progressive decline in function at multiple levels, including the molecular, cellular, tissue, and organismal. Furthermore, it is responsible for various healthcare costs in developing and developed countries. Sarcopenia is the deterioration in the quality and functionality of muscles, which is extremely concerning as it manages many functions in the human body. This article reviews the molecular crosstalk involved in sarcopenia and the specific roles of many mediator molecules in establishing cross-talk between muscles, bone, and fatty tissues, eventually leading to sarcopenia. Besides, the involvement of various etiological factors, such as neurology, endocrinology, lifestyle, etc., makes it exceedingly difficult for clinicians to develop a coherent hypothesis that may lead to the well-organized management system required to battle this debilitating disease. The several hallmarks contributing to the progression of the disease is a vital question that needs to be addressed to ensure an efficient treatment for sarcopenia patients. Also, the intricate molecular mechanism involved in developing this disease requires more studies. The direct relationship of cellular senescence with aging is one of the pivotal issues contributing to disease pathophysiology. Some patented treatment strategies have been discussed, including drugs undergoing clinical trials and emerging options like miRNA and protein-enclosed extracellular vesicles. A clear understanding of the secretome, including the signaling pathways involved between muscles, bone, and fatty tissues, is extremely beneficial for developing novel therapeutics for curing sarcopenia.

Impact of Lipids on Insulin Resistance: Insights from Human and Animal Studies

Insulin resistance (IR) is a complex pathological condition central to metabolic diseases such as type 2 diabetes mellitus (T2DM), cardiovascular disease, non-alcoholic fatty liver disease, and polycystic ovary syndrome (PCOS). This review evaluates the impact of lipids on insulin resistance (IR) by analyzing findings from human and animal studies. The articles were searched on the PubMed database using two keywords: (1) "Role of Lipids AND Insulin Resistance AND Humans" and (2) "Role of Lipids AND Insulin Resistance AND Animal Models". Studies in humans revealed that elevated levels of free fatty acids (FFAs) and triglycerides (TGs) are closely associated with reduced insulin sensitivity, and interventions like metformin and omega-3 fatty acids show potential benefits. In animal models, high-fat diets disrupt insulin signaling and increase inflammation, with lipid mediators such as diacylglycerol (DAG) and ceramides playing significant roles. DAG activates protein kinase C, which eventually impairs insulin signaling, while ceramides inhibit Akt/PKB, further contributing to IR. Understanding these mechanisms is crucial for developing effective prevention and treatment strategies for IR-related diseases.

Myokines: metabolic regulation in obesity and type 2 diabetes

Skeletal muscle plays a vital role in the regulation of systemic metabolism, partly through its secretion of endocrine factors which are collectively known as myokines. Altered myokine levels are associated with metabolic diseases, such as type 2 diabetes (T2D). The significance of interorgan crosstalk, particularly through myokines, has emerged as a fundamental aspect of nutrient and energy homeostasis. However, a comprehensive understanding of myokine biology in the setting of obesity and T2D remains a major challenge. In this review, we discuss the regulation and biological functions of key myokines that have been extensively studied during the past two decades, namely interleukin 6 (IL-6), irisin, myostatin (MSTN), growth differentiation factor 11 (GDF11), fibroblast growth factor 21 (FGF21), apelin, brain-derived neurotrophic factor (BDNF), meteorin-like (Metrnl), secreted protein acidic and rich in cysteine (SPARC), β-aminoisobutyric acid (BAIBA), Musclin, and Dickkopf 3 (Dkk3). Related to these, we detail the role of exercise in myokine expression and secretion together with their contributions to metabolic physiology and disease. Despite significant advancements in myokine research, many myokines remain challenging to measure accurately and investigate thoroughly. Hence, new research techniques and detection methods should be developed and rigorously tested. Therefore, developing a comprehensive perspective on myokine biology is crucial, as this will likely offer new insights into the pathophysiological mechanisms underlying obesity and T2D and may reveal novel targets for therapeutic interventions.

Molecular insights of exercise therapy in disease prevention and treatment

Despite substantial evidence emphasizing the pleiotropic benefits of exercise for the prevention and treatment of various diseases, the underlying biological mechanisms have not been fully elucidated. Several exercise benefits have been attributed to signaling molecules that are released in response to exercise by different tissues such as skeletal muscle, cardiac muscle, adipose, and liver tissue. These signaling molecules, which are collectively termed exerkines, form a heterogenous group of bioactive substances, mediating inter-organ crosstalk as well as structural and functional tissue adaption. Numerous scientific endeavors have focused on identifying and characterizing new biological mediators with such properties. Additionally, some investigations have focused on the molecular targets of exerkines and the cellular signaling cascades that trigger adaption processes. A detailed understanding of the tissue-specific downstream effects of exerkines is crucial to harness the health-related benefits mediated by exercise and improve targeted exercise programs in health and disease. Herein, we review the current in vivo evidence on exerkine-induced signal transduction across multiple target tissues and highlight the preventive and therapeutic value of exerkine signaling in various diseases. By emphasizing different aspects of exerkine research, we provide a comprehensive overview of (i) the molecular underpinnings of exerkine secretion, (ii) the receptor-dependent and receptor-independent signaling cascades mediating tissue adaption, and (iii) the clinical implications of these mechanisms in disease prevention and treatment.

Relationships and Mendelian Randomization of Gut Microbe-Derived Metabolites with Metabolic Syndrome Traits in the METSIM Cohort

The role of gut microbe-derived metabolites in the development of metabolic syndrome (MetS) remains unclear. This study aimed to evaluate the associations of gut microbe-derived metabolites and MetS traits in the cross-sectional Metabolic Syndrome In Men (METSIM) study. The sample included 10,194 randomly related men (age 57.65 ± 7.12 years) from Eastern Finland. Levels of 35 metabolites were tested for associations with 13 MetS traits using lasso and stepwise regression. Significant associations were observed between multiple MetS traits and 32 metabolites, three of which exhibited particularly robust associations. N-acetyltryptophan was positively associated with Homeostatic Model Assessment for Insulin Resistant (HOMA-IR) (β = 0.02, p = 0.033), body mass index (BMI) (β = 0.025, p = 1.3 × 10-16), low-density lipoprotein cholesterol (LDL-C) (β = 0.034, p = 5.8 × 10-10), triglyceride (0.087, p = 1.3 × 10-16), systolic (β = 0.012, p = 2.5 × 10-6) and diastolic blood pressure (β = 0.011, p = 3.4 × 10-6). In addition, 3-(4-hydroxyphenyl) lactate yielded the strongest positive associations among all metabolites, for example, with HOMA-IR (β = 0.23, p = 4.4 × 10-33), and BMI (β = 0.097, p = 5.1 × 10-52). By comparison, 3-aminoisobutyrate was inversely associated with HOMA-IR (β = -0.19, p = 3.8 × 10-51) and triglycerides (β = -0.12, p = 5.9 × 10-36). Mendelian randomization analyses did not provide evidence that the observed associations with these three metabolites represented causal relationships. We identified significant associations between several gut microbiota-derived metabolites and MetS traits, consistent with the notion that gut microbes influence metabolic homeostasis, beyond traditional risk factors.

β-aminoisobutyrics acid, a metabolite of BCAA, activates the AMPK/Nrf-2 pathway to prevent ferroptosis and ameliorates lung ischemia-reperfusion injury

BACKGROUND

Lung ischemia-reperfusion (I/R) injury is a serious clinical problem without effective treatment. Enhancing branched-chain amino acids (BCAA) metabolism can protect against cardiac I/R injury, which may be related to bioactive molecules generated by BCAA metabolites. L-β-aminoisobutyric acid (L-BAIBA), a metabolite of BCAA, has multi-organ protective effects, but whether it protects against lung I/R injury is unclear.

METHODS

To assess the protective effect of L-BAIBA against lung I/R injury, an animal model was generated by clamping the hilum of the left lung, followed by releasing the clamp in C57BL/6 mice. Mice with lung I/R injury were pre-treated or post-treated with L-BAIBA (150 mg/kg/day), given by gavage or intraperitoneal injection. Lung injury was assessed by measuring lung edema and analyzing blood gases. Inflammation was assessed by measuring proinflammatory cytokines in bronchoalveolar lavage fluid (BALF), and neutrophil infiltration of the lung was measured by myeloperoxidase activity. Molecular biological methods, including western blot and immunofluorescence, were used to detect potential signaling mechanisms in A549 and BEAS-2B cells.

RESULTS

We found that L-BAIBA can protect the lung from I/R injury by inhibiting ferroptosis, which depends on the up-regulation of the expressions of GPX4 and SLC7A11 in C57BL/6 mice. Additionally, we demonstrated that the Nrf-2 signaling pathway is key to the inhibitory effect of L-BAIBA on ferroptosis in A549 and BEAS-2B cells. L-BAIBA can induce the nuclear translocation of Nrf-2. Interfering with the expression of Nrf-2 eliminated the protective effect of L-BAIBA on ferroptosis. A screening of potential signaling pathways revealed that L-BAIBA can increase the phosphorylation of AMPK, and compound C can block the Nrf-2 nuclear translocation induced by L-BAIBA. The presence of compound C also blocked the protective effects of L-BAIBA on lung I/R injury in C57BL/6 mice.

CONCLUSIONS

Our study showed that L-BAIBA protects against lung I/R injury via the AMPK/Nrf-2 signaling pathway, which could be a therapeutic target.

Effect of perioperative branched chain amino acids supplementation in liver cancer patients undergoing surgical intervention: A systematic review

BACKGROUND

Branched chain amino acid (BCAA) supplementation has been associated with favourable outcomes in liver malignancies requiring definitive resection or liver transplantation. Currently, there are no updated systematic reviews evaluating the efficacy of perioperative BCAA supplementation in patients undergoing surgery for liver cancer.

AIM

To evaluate the efficacy of perioperative BCAA supplementation in patients undergoing surgery for liver cancer.

METHODS

A systematic review of randomized control trials and observational studies was conducted on PubMed, Embase, Cochrane Library, Scopus, and Web of Science to evaluate the effect of perioperative BCAA supplementation compared to standard in-hospital diet, in liver cancer patients undergoing surgery. Clinical outcomes were extracted, and a meta-analysis was performed on relevant outcomes.

RESULTS

16 studies including 1389 patients were included. Perioperative BCAA administration was associated with reduced postoperative infection [risk ratio (RR) = 0.58 95% confidence intervals (CI): 0.39 to 0.84, P = 0.005] and ascites [RR = 0.57 (95%CI: 0.38 to 0.85), P = 0.005]. There was also a reduction in length of hospital stay (LOS) [weighted mean difference (WMD) = -3.03 d (95%CI: -5.49 to -0.57), P = 0.02] and increase in body weight [WMD = 1.98 kg (95%CI: 0.35 to 3.61, P = 0.02]. No significant differences were found in mortality, cancer recurrence and overall survival. No significant safety concerns were identified.

CONCLUSION

Perioperative BCAA administration is efficacious in reducing postoperative infection, ascites, LOS, and increases body weight in liver cancer patients undergoing surgical resection.

L-β-aminoisobutyric acid, L-BAIBA, a marker of bone mineral density and body mass index, and D-BAIBA of physical performance and age

As both L- and D-BAIBA are increased with exercise, we sought to determine if circulating levels would be associated with physical performance. Serum levels of L- and D-BAIBA were quantified in 120 individuals (50% female) aged 20-85 years and categorized as either a "low" (LP), "average" (AP) or "high" performing (HP). Association analysis was performed using Spearman (S) and Pearson (P) correlation. Using Spearman correlation, L-BAIBA positively associated with (1) body mass index BMI (0.23) and total fat mass (0.19) in the 120 participants, (2) total fat mass in the 60 males (0.26), and (3) bone mineral density, BMD, (0.28) in addition to BMI (0.26) in the 60 females. In HP females, L-BAIBA positively associated with BMD (0.50) and lean mass (0.47). D-BAIBA was positively associated with (1) age (P 0.20) in the 120 participants, (2) age (P 0.49) in the LP females and (3) with gait speed (S 0.20) in the 120 participants. However, in HP males, this enantiomer had a negative association with appendicular lean/height (S - 0.52) and in the AP males a negative correlation with BMD (S - 0.47). No associations were observed in HP or AP females, whereas, in LP females, a positive association was observed with grip strength (S 0.45), but a negative with BMD (P - 0.52, S - 0.63) and chair stands (P - 0.47, S - 0.51). L-BAIBA may play a role in BMI and BMD in females, not males, whereas D-BAIBA may be a marker for aging and physical performance. The association of L-BAIBA with BMI and fat mass may reveal novel, not previously described functions for this enantiomer.

β-Aminoisobutyric Acid Relates to Favorable Glucose Metabolism through Adiponectin in Adults with Obesity Independent of Prediabetes

β-Aminoisobutyric acid (BAIBA) is secreted by skeletal muscle and promotes insulin sensitivity, fat oxidation, and anti-inflammation. While BAIBA is purportedly lower in individuals with obesity, no work has examined if prediabetes (PD) differentially impacts BAIBA concentrations in people with obesity. Methods. Adults were classified as normal glucose tolerant (NGT; n = 22 (20F); 48.0 ± 2.4 yrs; 36.9 ± 1.2 kg/m2) or PD (n = 23 (18F); 54.2 ± 1.6 yrs; 38.4 ± 1.2 kg/m2) based on ADA criteria. A 180-minute 75 g OGTT was used to estimate fasting (HOMA-IR (liver)) and postprandial (Matsuda index (muscle)) insulin sensitivity as well as β-cell function (disposition index (DI), glucose-stimulated insulin secretion adjusted for insulin sensitivity). Body composition and fasting measures of BAIBA, fat oxidation (indirect calorimetry), and adipokines were determined. Results. NGT and PD had similar BAIBA concentrations (1.4 ± 0.1 vs. 1.2 ± 0.1 μM, P = 0.23) and fat oxidation (P = 0.31), despite NGT having lower fasting (92.2 ± 1.2 vs. 104.1 ± 3.2 mg/dL, P = 0.002) and tAUC180min glucose (P < 0.001) compared to PD. Moreover, NGT had higher postprandial insulin sensitivity (P = 0.01) and higher total phase DIliver (P = 0.003) and DImuscle (P = 0.001). Increased BAIBA was associated with adiponectin (r = 0.37, P = 0.02), adiponectin/leptin ratio (r = 0.39, P = 0.01), and lower glucose and insulin at 180 minutes (r = -0.31, P = 0.03 and r = -0.39, P = 0.03, respectively). Adiponectin also correlated with lower glucose at 180 minutes (r = -0.45, P = 0.005), and mediation analysis showed that BAIBA was no longer a significant predictor of glucose at 180 minutes after controlling for adiponectin (P = 0.08). Conclusion. While BAIBA did not differ between NGT and PD, higher BAIBA is related to favorable glucose metabolism, possibly through an adiponectin-related mechanism. Additional work is required to understand how exercise and/or diet impact BAIBA in relation to type 2 diabetes risk.

A Novel Gliotransmitter, L-β-Aminoisobutyric Acid, Contributes to Pathophysiology of Clinical Efficacies and Adverse Reactions of Clozapine

Clozapine is listed as one of the most effective antipsychotics and has been approved for treating treatment-resistant schizophrenia (TRS); however, several type A and B adverse reactions, including weight gain, metabolic complications, cardiotoxicity, convulsions, and discontinuation syndromes, exist. The critical mechanisms of clinical efficacy for schizophrenia, TRS, and adverse reactions of clozapine have not been elucidated. Recently, the GABA isomer L-β-aminoisobutyric acid (L-BAIBA), a protective myokine in the peripheral organs, was identified as a candidate novel transmission modulator in the central nervous system (CNS). L-BAIBA activates adenosine monophosphate-activated protein kinase (AMPK) signalling in both the peripheral organs and CNS. Activated AMPK signalling in peripheral organs is an established major target for treating insulin-resistant diabetes, whereas activated AMPK signalling in the hypothalamus contributes to the pathophysiology of weight gain and metabolic disturbances. Clozapine increases L-BAIBA synthesis in the hypothalamus. In addition, the various functions of L-BAIBA in the CNS have recently been elucidated, including as an activator of GABA-B and group-III metabotropic glutamate (III-mGlu) receptors. Considering the expressions of GABA-B and III-mGlu receptors (localised in the presynaptic regions), the activation of GABA-B and III-mGlu receptors can explain the distinct therapeutic advantages of clozapine in schizophrenia or TRS associated with N-methyl-D-aspartate (NMDA) receptor disturbance compared with other atypical antipsychotics via the inhibition of the persistent tonic hyperactivation of thalamocortical glutamatergic transmission in the prefrontal cortex. L-BAIBA has also been identified as a gliotransmitter, and a detailed exploration of the function of L-BAIBA in tripartite synaptic transmission can further elucidate the pathophysiology of effectiveness for treating TRS and/or specific adverse reactions of clozapine.

Melphalan induced germ cell toxicity and dose-dependent effects of β-aminoisobutyric acid in experimental rat model: Role of oxidative stress, inflammation and apoptosis

The success of chemotherapy regimens has led to an increase in cancer survival rate over the last decades. Melphalan has been widely used for the treatment of several types of cancers despite its gonadotoxic effects. Due to its ability to cause mutations in the spermatogonial stem cells and spermatids, melphalan can exert a negative impact on male reproductive health in young cancer survivors. β-aminoisobutyric acid (BAIBA), a myokine released by skeletal muscles, has been reported to have beneficial effects in diabetic nephropathy, cardiomyopathy and hepatic toxicity. However, the exact role of BAIBA in chemotherapy-induced germ cell toxicity is still unexplored. The present study aims to determine the dose-dependent (25, 50, and 100 mg/kg) effects of BAIBA on melphalan-induced (1.5 mg/kg) germ cell toxicity in sprague-dawley (SD) rats. The evaluation parameters included quantification of oxidative stress biomarkers, sperm count, sperm motility and head morphology, sperm and testicular DNA damage, sperm mitochondrial membrane potential, ultrastructural changes in sperms, histological and protein expression studies in testes. Melphalan treatment significantly altered all the above-mentioned parameters and the high dose (100 mg/kg) of BAIBA restored melphalan-induced toxicity in a significant manner by exerting antioxidant, anti-inflammatory and antiapoptotic effects. However, the medium dose (50 mg/kg) of BAIBA decreased the toxicity of melphalan and the low dose (25 mg/kg) of BAIBA failed to counteract the melphalan-induced male germ cell toxicity as well as the peripheral blood micronucleus induction. The antioxidant, anti-inflammatory and antiapoptotic role of BAIBA in melphalan-induced gonadal damage is a novel finding in an experimental rat model.

A low-calorie diet raises β-aminoisobutyric acid in relation to glucose regulation and leptin independent of exercise in women with obesity

Introduction: β-aminoisobutyric acid (BAIBA) is a suggested cytokine secreted from skeletal muscles that regulates insulin sensitivity, pancreatic function, and fat oxidation. However, no studies to date have examined if a low-calorie diet (LCD) or LCD + with interval exercise (LCD + INT) differentially raises BAIBA. The purpose was to examine if LCD or LCD + INT raises circulating BAIBA in relation to cardiometabolic health. Methods: For this, twenty-three women with obesity were randomized to either 2-weeks of LCD (n = 12, 48.4 ± 2.5 y, 37.84 ± 1.5 kg/m2; ∼1200 kcal/day) or LCD + INT (n = 11, 47.6 ± 4.3 y, 37.9 ± 2.3 kg/m2; ∼60 min/d of INT alternating 3 min of 90% and 50% HRpeak), with matched energy availability. Fasting BAIBA and adipokines along with glucose, insulin, C-peptide, and FFA after every 30 min up to 120 min were obtained during a 75 g OGTT to estimate total area under the curve (tAUC), insulin sensitivity (SIIS), pancreatic function [disposition index (DI)], and hepatic insulin clearance (HIC). Fuel use (indirect calorimetry) was tested at 0, 60, and 120 min of the OGTT along with fitness (VO2peak) and body composition (BodPod). Results: Both treatments lowered body weight (p < 0.001) and leptin (p < 0.001) but raised BAIBA (p = 0.007) and insulin sensitivity (p = 0.02). LCD + INT increased VO2peak (p = 0.02) and REE tAUC120min (p = 0.02) while LCD and LCD + INT decreased carbohydrate oxidation (CHOox) tAUC120min (p < 0.001). Increased BAIBA associated with reduced weight (r = -0.67, p < 0.001), leptin (r = -0.66, p = 0.001), CHOox tAUC120min (r = -0.44, p = 0.03) and DImuscle120min (r = -0.45, p = 0.03), but elevated HIC120min (r = 0.47, p = 0.02). Discussion: Concluding, LCD and LCD + INT increased BAIBA in relation to reduced body weight and pancreatic function in women with obesity. This suggests energy deficit is a key factor regulating circulating BAIBA.

L-BAIBA Synergizes with Sub-Optimal Mechanical Loading to Promote New Bone Formation

The L-enantiomer of β-aminoisobutyric acid (BAIBA) is secreted by contracted muscle in mice, and exercise increases serum levels in humans. In mice, L-BAIBA reduces bone loss with unloading, but whether it can have a positive effect with loading is unknown. Since synergism can be more easily observed with sub-optimal amounts of factors/stimulation, we sought to determine whether L-BAIBA could potentiate the effects of sub-optimal loading to enhance bone formation. L-BAIBA was provided in drinking water to C57Bl/6 male mice subjected to either 7 N or 8.25 N of sub-optimal unilateral tibial loading for 2 weeks. The combination of 8.25 N and L-BAIBA significantly increased the periosteal mineral apposition rate and bone formation rate compared to loading alone or BAIBA alone. Though L-BAIBA alone had no effect on bone formation, grip strength was increased, suggesting a positive effect on muscle function. Gene expression analysis of the osteocyte-enriched bone showed that the combination of L-BAIBA and 8.25 N induced the expression of loading-responsive genes such as Wnt1, Wnt10b, and the TGFb and BMP signaling pathways. One dramatic change was the downregulation of histone genes in response to sub-optimal loading and/or L-BAIBA. To determine early gene expression, the osteocyte fraction was harvested within 24 hours of loading. A dramatic effect was observed with L-BAIBA and 8.25 N loading as genes were enriched for pathways regulating the extracellular matrix (Chad, Acan, Col9a2), ion channel activity (Scn4b, Scn7a, Cacna1i), and lipid metabolism (Plin1, Plin4, Cidec). Few changes in gene expression were observed with sub-optimal loading or L-BAIBA alone after 24 hours. These results suggest that these signaling pathways are responsible for the synergistic effects between L-BAIBA and sub-optimal loading. Showing that a small muscle factor can enhance the effects of sub-optimal loading of bone may be of relevance for individuals unable to benefit from optimal exercise. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Signaling metabolite β-aminoisobutyric acid as a metabolic regulator, biomarker, and potential exercise pill

Signaling metabolites can effectively regulate the biological functions of many tissues and organs. β-Aminoisobutyric acid (BAIBA), a product of valine and thymine catabolism in skeletal muscle, has been reported to participate in the regulation of lipid, glucose, and bone metabolism, as well as in inflammation and oxidative stress. BAIBA is produced during exercise and is involved in the exercise response. No side effect has been observed in human and rat studies, suggesting that BAIBA can be developed as a pill that confers the benefits of exercise to subjects who, for some reason, are unable to do so. Further, BAIBA has been confirmed to participate in the diagnosis and prevention of diseases as an important biological marker of disease. The current review aimed to discuss the roles of BAIBA in multiple physiological processes and the possible pathways of its action, and assess the progress toward the development of BAIBA as an exercise mimic and biomarker with relevance to multiple disease states, in order to provide new ideas and strategies for basic research and disease prevention in related fields.

Enhanced L-β-Aminoisobutyric Acid Is Involved in the Pathophysiology of Effectiveness for Treatment-Resistant Schizophrenia and Adverse Reactions of Clozapine

Clozapine is an effective antipsychotic for the treatment of antipsychotic-resistant schizophrenia; however, specific types of A/B adverse effects and clozapine-discontinuation syndromes are also well known. To date, both the critical mechanisms of clinical actions (effective for antipsychotic-resistant schizophrenia) and the adverse effects of clozapine remain to be elucidated. Recently, we demonstrated that clozapine increased the synthesis of L-β-aminoisobutyric acid (L-BAIBA) in the hypothalamus. L-BAIBA is an activator of the adenosine monophosphate-activated protein kinase (AMPK), glycine receptor, GABA_A receptor, and GABA_B receptor (GABA_B-R). These targets of L-BAIBA overlap as potential targets other than the monoamine receptors of clozapine. However, the direct binding of clozapine to these aminoacidic transmitter/modulator receptors remains to be clarified. Therefore, to explore the contribution of increased L-BAIBA on the clinical action of clozapine, this study determined the effects of clozapine and L-BAIBA on tripartite synaptic transmission, including GABA_B-R and the group-III metabotropic glutamate receptor (III-mGluR) using cultured astrocytes, as well as on the thalamocortical hyper-glutamatergic transmission induced by impaired glutamate/NMDA receptors using microdialysis. Clozapine increased astroglial L-BAIBA synthesis in time/concentration-dependent manners. Increased L-BAIBA synthesis was observed until 3 days after clozapine discontinuation. Clozapine did not directly bind III-mGluR or GABA_B-R, whereas L-BAIBA activated these receptors in the astrocytes. Local administration of MK801 into the reticular thalamic nucleus (RTN) increased L-glutamate release in the medial frontal cortex (mPFC) (MK801-evoked L-glutamate release). Local administration of L-BAIBA into the mPFC suppressed MK801-evoked L-glutamate release. These actions of L-BAIBA were inhibited by antagonists of III-mGluR and GABA_B-R, similar to clozapine. These in vitro and in vivo analyses suggest that increased frontal L-BAIBA signaling likely plays an important role in the pharmacological actions of clozapine, such as improving the effectiveness of treating treatment-resistant schizophrenia and several clozapine discontinuation syndromes via the activation of III-mGluR and GABA_B-R in the mPFC.

In Vitro Fermentation of Hyaluronan with Different Molecular Weights by Human Gut Microbiota: Differential Effects on Gut Microbiota Structure and Metabolic Function

Hyaluronan (HA) has various biological functions and is used extensively as a dietary supplement. Previous studies have shown that the probiotic effects of polysaccharides are closely associated with their molecular properties. The intestinal microbiota has been demonstrated to degrade HA; however, the regulatory effects of different molecular weights (MW) of HA on gut microbiota and metabolites are unknown. In the present study, we performed in vitro fermentation of human-derived feces for three MWs of HA (HA1, 32.3 kDa; HA2, 411 kDa; and HA3, 1510 kDa) to investigate the differences in the fermentation properties of HA with different MWs. We found that gut microbiota can utilize all HAs and, consequently, produce large amounts of short-chain fatty acids (SCFAs). In addition, we showed that all three HA MWs promoted the growth of Bacteroides, Parabacteroides, and Faecalibacterium, with HA1 being more effective at promoting the growth of Bacteroides. HAs have various regulatory effects on the structure and metabolites of the gut microbiota. Spearman's correlation analysis revealed that alterations in gut microbiota and their metabolites were significantly correlated with changes in metabolic markers. For instance, HA1 enriched α-eleostearic acid and DL-3-aminoisobutyric acid by regulating the abundance of Bacteroides, and HA3 enriched Thymidin by regulating Faecalibacterium. Collectively, the fermentation properties of HA vary across MW, and our results provide insights into the potential association between the MW of HA and its fermentation characteristics by the gut microbiota. These findings provide insights into the influence of the gut microbiota and HAs on the health of the host.

A Candidate Gliotransmitter, L-β-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, β-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.

Opposing effects of clozapine and brexpiprazole on β-aminoisobutyric acid: Pathophysiology of antipsychotics-induced weight gain

Clozapine is one of the most effective antipsychotics and has the highest risk of weight gain and metabolic complications; however, the detailed pathophysiology of its clinical action and adverse reactions remains to be clarified. Therefore, the present study determined the chronic effects of clozapine (high risk of weight gain) and brexpiprazole (relatively low risk of weight gain) on intracellular and extracellular levels of β-aminoisobutyric acid (BAIBA) enantiomers, which are endogenous activators of AMP-activated protein kinase (AMPK). L-BAIBA is the dominant BAIBA enantiomer in the rat hypothalamus and cultured astrocytes, whereas L-BAIBA accounts for only approximately 5% of the total plasma BAIBA enantiomers. L-BAIBA displayed GABAB receptor agonistic action in the extracellular space and was released through activated astroglial hemichannels, whereas in the intracellular space, L-BAIBA activated AMPK signalling. Chronic administration of the effective doses of clozapine increased intracellular and extracellular levels of L-BAIBA in the hypothalamus and cultured astrocytes, whereas that of brexpiprazole decreased them. These results suggest that enhancing hypothalamic AMPK signalling by increasing intracellular L-BAIBA levels is, at least partially, involved in the pathophysiology of clozapine-induced weight gain and metabolic complications.

β-Aminoisobutyric acid (L-BAIBA) is a novel regulator of mitochondrial biogenesis and respiratory function in human podocytes

Podocytes constitute an external layer of the glomerular filtration barrier, injury to which is a hallmark of renal disease. Mitochondrial dysfunction often accompanies podocyte damage and is associated with an increase in oxidative stress and apoptosis. β-Aminoisobutyric acid (BAIBA) belongs to natural β-amino acids and is known to exert anti-inflammatory and antioxidant effects. BAIBA has been reported to be involved in regulating mitochondrial dynamics, but unknown is whether BAIBA influences podocyte bioenergetics. The present study showed that human podocytes express the BAIBA receptor, Mas-related G protein-coupled receptor type D (MRGPRD), which is sensitive to BAIBA stimulation. The treatment of podocytes with L-BAIBA significantly increased their respiratory parameters, such as basal and maximal respiration, adenosine triphosphate (ATP) production, and spare respiratory capacity. We also found that L-BAIBA altered mitochondrial quantity, size, and shape, promoting organelle elongation and branching. L-BAIBA significantly upregulated peroxisome proliferator activated receptor γ coactivator-1α (PGC-1α) and transcription factor A mitochondrial (TFAM), indicating an increase in mitochondrial biogenesis. Our results demonstrate a novel regulatory mechanism of mitochondrial dynamics in podocytes, which may be important for maintaining their functions in the renal filtration barrier and prompting further investigations of preventing or ameliorating mitochondrial damage in podocytes in pathological states.

Metabokines in the regulation of systemic energy metabolism

Metabolism consists of life-sustaining chemical reactions involving metabolites. Historically, metabolites were defined as the intermediates or end products of metabolism and considered to be passive participants changed by metabolic processes. However, recent research has redefined how we view metabolism. There is emerging evidence of metabolites which function to mediate cellular signalling and interorgan crosstalk, regulating local metabolism and systemic physiology. These bioactive metabolite signals have been termed metabokines. Metabokines regulate diverse energy metabolism pathways across multiple tissues, including fatty acid β-oxidation, mitochondrial oxidative phosphorylation, lipolysis, glycolysis and gluconeogenesis. There is increasing impetus to uncover novel metabokine signalling axes to better understand how these may be perturbed in metabolic diseases and determine their utility as therapeutic targets.

Dose-Response Absorption Kinetics of Oral L-Beta-Aminoisobutyric Acid (L-BAIBA) Supplementation in Healthy Men and Women

L-Beta-amino isobutyric acid (L-BAIBA) is a myokine produced in skeletal muscle during exercise and has been shown to impact carbohydrate and fat metabolism in both animals and humans. This study was designed to determine the rate and extent to which L-BAIBA appeared in human plasma after oral ingestion. In a randomized, double-blind, placebo-controlled, crossover fashion, six males and 6 females (N = 12; 24 ± 5 yrs; 173.6 ± 12.0 cm; 72.3 ± 11.3 kg; 21.0 ± 7.0 body fat %) completed a single-dose supplementation protocol of placebo (PLA), L-BAIBA at 250 mg (B250), 500 mg (B500), 1,500mg (B1500), and 1,500mg of valine (V1500). Participants fasted overnight (8-10 h) and consumed their dose with 8-12 fluid ounces of cold water. Venous blood samples were collected 0, 30, 60, 90, 120, 180, 240 and 300 min after ingestion and analyzed for L-BAIBA. Complete blood counts and comprehensive metabolic panels were analyzed 0 and 300 min after ingestion. Peak concentration (CMax) and area under the curve (AUC) were calculated for all variables. Baseline L-BAIBA levels were not different between conditions (p = 0.46). The observed AUC for B1500 (30,513 ± 9190 µM•300 min) was significantly higher than B500 (11,087 ± 3378 µM•300 min, p < 0.001), B250 (7081 ± 2535 µM•300 min, p < 0.001), V1500 (2837 ± 2107 µM•300 min, p < 0.001), and PLA (2836 ± 2061 µM•300 min, p < 0.001). Similarly, L-BAIBA CMax for B1500 (278.1 ± 52.1 µM) was significantly higher than all other supplement conditions: B500 (95.4 ± 33.5 µM, p < 0.001), B250 (63.3 ± 61.1 µM, p < 0.001), V1500 (10.1 ± 7.2 µM, p < 0.001), PLA (11.0 ± 7.1 µM, p = 0.001). AUC and CMax for B500 was significantly higher than B250 (p < 0.001), V1500 (p < 0.001), and PLA (p < 0.001). BAIBA AUC for B250 was significantly higher than V1500 (p < 0.001) and PLA (p < 0.001). No clinically significant changes in blood-based markers of health or adverse events were observed across the study protocol. L-BAIBA doses of 250 mg, 500 mg, and 1500 mg produced significantly greater concentrations of plasma L-BAIBA across a five-hour measurement window when compared to a 1500 mg dose of valine or a placebo. Follow-up efficacy studies on resting and exercise metabolism should be completed to assess the impact of L-BAIBA supplementation in normal weight and overweight individuals. Retrospectively registered on April 22, 2022 at ClinicalTrials.gov as NCT05328271.

Maternal propionate supplementation ameliorates glucose and lipid metabolic disturbance in hypoxia-induced fetal growth restriction

Intrauterine growth restriction (IUGR), one of the major complications of pregnancy, is characterized by low birth weight and results in higher risks for long-term problems including developing metabolic and cardiovascular diseases. Short-chain fatty acids (SCFAs), especially propionate, have been reported to correct glucose and lipid disorders in metabolic diseases. We hypothesized that maternal propionate supplementation could prevent glucose and lipid metabolic disturbance in hypoxia-induced IUGR. Here, in our study, maternal hypoxia was induced from gestational day (GD) 11 to GD 17.5 to establish an IUGR mouse model. Maternal propionate treatment reversed reduced birth weight in male IUGR offspring. Hepatic transcriptomics demonstrated that SP treatment significantly lowered glucose and lipid metabolism-related genes (Scd1, G6pc, Pck1 and Fasl) in IUGR offspring. KOG enrichment analysis showed that propionate-induced down-regulated differential expressed genes (DEGs) mainly belonged to lipid transport and metabolism. KEGG enrichment results showed that the down-regulated DEGs were mostly enriched in PPAR and FoxO signaling pathways. We also found that maternal oral administration of SP decreased serum lipid content, attenuated hepatic insulin resistance and liver lipid accumulation, reduced hepatic key gene expressions of gluconeogenesis and lipogenesis, increased energy expenditure and improved liver function in 11-week-old male IUGR offspring. These results indicate that maternal propionate supplementation increases birth weight and corrects hepatic glucose and lipid metabolic disturbance and energy expenditure in male mice born with IUGR, which may provide a basis for using propionate to treat IUGR disease.

Oxidative and endoplasmic reticulum stress develop adverse metabolic effects due to the high-fat high-fructose diet consumption from birth to young adulthood

AIMS

The early postnatal dietary intake has been considered a crucial factor affecting the offspring later life metabolic status. Consistently, this study investigated the oxidative and endoplasmic reticulum (ER) stress intervention in the induction of adverse metabolic effects due to the high-fat high-fructose diet (HFHFD) consumption from birth to young adulthood in rat offspring.

MATERIALS AND METHODS

After delivery, the dams with their pups were randomly allocated into the normal diet (ND) and HFHFD groups. At weaning, the male offspring were divided into ND-None, ND-DMSO, ND-4-phenyl butyric acid (4-PBA), HFHFD-None, HFHFD-DMSO, and HFHFD-4-PBA groups and fed on their respected diets for five weeks. Then, the drug was injected for ten days. Subsequently, glucose and lipid metabolism parameters, oxidative and ER stress markers, and Wolfram syndrome1 (Wfs1) expression were assessed.

KEY FINDINGS

In the HFHFD group, anthropometrical parameters, plasma high-density lipoprotein (HDL), and glucose-stimulated insulin secretion and content were decreased. Whereas, the levels of plasma leptin, low-density lipoprotein (LDL) and glucose, hypothalamic leptin, pancreatic catalase activity and glutathione (GSH), pancreatic and hypothalamic malondialdehyde (MDA), binding immunoglobulin protein (BIP) and C/EBP homologous protein (CHOP), and pancreatic WFS1 protein were increased. 4-PBA administration in the HFHFD group, decreased the hypothalamic and pancreatic MDA, BIP and CHOP levels. While, increased the Insulin mRNA and glucose-stimulated insulin secretion and content.

SIGNIFICANCE

HFHFD intake from birth to young adulthood through the development of pancreatic and hypothalamic oxidative and ER stress, increased the pancreatic WFS1 protein and impaired glucose and lipid homeostasis in male rat offspring.

Safety Assessment of L-β-Aminoisobutyric Acid (L-BAIBA): Subchronic Toxicity Study in Sprague Dawley Rats

L-3-Aminoisobutyric acid (L-BAIBA) is an endogenous compound in human metabolism when thymine and valine undergo catabolism. L-BAIBA represents one of the two isomers of BAIBA in biological systems. BAIBA has been shown to reduce body fat percentage via an increase in fatty acid oxidation and a decrease in hepatic lipogenesis. However, no toxicological effects of L-BAIBA in animals or humans have been established. The present study was designed to evaluate the safety and toxic potentials of this compound, where L-BAIBA was administered orally to Sprague Dawley rats at 100, 300, and 900 mg/kg/day for 90 days. No treatment-related adverse effects were observed in any of the treatment groups. Based on the results, the No-Observed-Adverse-Effect Level (NOAEL) of L-BAIBA was 900 mg/kg/day.

Mechanisms by Which Skeletal Muscle Myokines Ameliorate Insulin Resistance

The skeletal muscle is the largest organ in the body and secretes circulating factors, including myokines, which are involved in various cellular signaling processes. Skeletal muscle is vital for metabolism and physiology and plays a crucial role in insulin-mediated glucose disposal. Myokines have autocrine, paracrine, and endocrine functions, serving as critical regulators of myogenic differentiation, fiber-type switching, and maintaining muscle mass. Myokines have profound effects on energy metabolism and inflammation, contributing to the pathophysiology of type 2 diabetes (T2D) and other metabolic diseases. Myokines have been shown to increase insulin sensitivity, thereby improving glucose disposal and regulating glucose and lipid metabolism. Many myokines have now been identified, and research on myokine signaling mechanisms and functions is rapidly emerging. This review summarizes the current state of the field regarding the role of myokines in tissue cross-talk, including their molecular mechanisms, and their potential as therapeutic targets for T2D.

Exercise-Generated β-Aminoisobutyric Acid (BAIBA) Reduces Cardiomyocyte Metabolic Stress and Apoptosis Caused by Mitochondrial Dysfunction Through the miR-208b/AMPK Pathway

Objective

To explore the cardioprotective effects of exercise-derived β-aminoisobutyric (BAIBA) on cardiomyocyte apoptosis and energy metabolism in a rat model of heart failure (HF).

Methods

In male Sprague-Dawley rats (8-week-old), myocardial infarction (MI) was used to induce HF by ligating the left anterior descending branch of the coronary artery. In the Sham group, the coronary artery was threaded but not ligated. After HF development, Sham and HF rats were exercised 60 min daily, 5 days/week on a treadmill for 8 weeks (50–60% maximal intensity) and exercise-induced cardiac remodeling after MI were assessed using echocardiography, hematoxylin and eosin (H&E), Masson's Trichrome, and TUNEL staining for the detection of apoptosis-associated factors in cardiac tissue. High-throughput sequencing and mass spectrometry were used to measure BAIBA production and to explore its cardioprotective effects and molecular actions. To further characterize the cardioprotective effects of BAIBA, an in vitro model of apoptosis was generated by applying H₂O₂ to H9C2 cells to induce mitochondrial dysfunction. In addition, cells were transfected with either a miR-208b analog or a miR-208b inhibitor. Apoptosis-related proteins were detected by Western Blotting (WB). ATP production was also assessed by luminometry. After administration of BAIBA and Compound C, the expression of proteins related to apoptosis, mitochondrial function, lipid uptake, and β-oxidative were determined. Changes in the levels of reactive oxygen species (ROS) were assessed by fluorescence microscopy. In addition, alterations in membrane potential (δψm) were obtained by confocal microscopy.

Results

Rats with HF after MI are accompanied by mitochondrial dysfunction, metabolic stress and apoptosis. Reduced expression of apoptosis-related proteins was observed, together with increased ATP production and reduced mitochondrial dysfunction in the exercised compared with the Sham (non-exercised) HF group. Importantly, exercise increased the production of BAIBA, irrespective of the presence of HF. To assess whether BAIBA had similar effects to exercise in ameliorating HF-induced adverse cardiac remodeling, rats were treated with 75 mg/kg/ day of BAIBA and we found BAIBA had a similar cardioprotective effect. Transcriptomic analyses found that the expression of miR-208b was increased after BAIBA administration, and subsequent transfection with an miR-208b analog ameliorated both the expression of apoptosis-related proteins and energy metabolism in H₂O₂-treated H9C2 cells. In combining transcriptomic with metabolomic analyses, we identified AMPK as a downstream target for BAIBA in attenuating metabolic stress in HF. Further cell experiments confirmed that BAIBA increased AMPK phosphorylation and had a cardioprotective effect on downstream fatty acid uptake, oxidative efficiency, and mitochondrial function, which was prevented by the AMPK inhibitor Compound C.

Conclusion

Exercise-generated BAIBA can reduce cardiomyocyte metabolic stress and apoptosis induced by mitochondrial dysfunction through the miR-208b/AMPK pathway.

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

β-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.

Multifactorial Mechanism of Sarcopenia and Sarcopenic Obesity. Role of Physical Exercise, Microbiota and Myokines

Obesity and ageing place a tremendous strain on the global healthcare system. Age-related sarcopenia is characterized by decreased muscular strength, decreased muscle quantity, quality, and decreased functional performance. Sarcopenic obesity (SO) is a condition that combines sarcopenia and obesity and has a substantial influence on the older adults’ health. Because of the complicated pathophysiology, there are disagreements and challenges in identifying and diagnosing SO. Recently, it has become clear that dysbiosis may play a role in the onset and progression of sarcopenia and SO. Skeletal muscle secretes myokines during contraction, which play an important role in controlling muscle growth, function, and metabolic balance. Myokine dysfunction can cause and aggravate obesity, sarcopenia, and SO. The only ways to prevent and slow the progression of sarcopenia, particularly sarcopenic obesity, are physical activity and correct nutritional support. While exercise cannot completely prevent sarcopenia and age-related loss in muscular function, it can certainly delay development and slow down the rate of sarcopenia. The purpose of this review was to discuss potential pathways to muscle deterioration in obese individuals. We also want to present the current understanding of the role of various factors, including microbiota and myokines, in the process of sarcopenia and SO.

Glucose metabolism enhancement by 10-hydroxy-2-decenoic acid via the PI3K/AKT signaling pathway in high-fat-diet/streptozotocin induced type 2 diabetic mice

Here, we used high fat diet (HFD) combined with streptozotocin (STZ) injection to establish a diabetes model, with the aim of exploring the hypoglycemic effects of 10-hydroxy-2-decenoic acid (10-HDA), and...

Bacillus toyonensis SAU-19 Ameliorates Hepatic Insulin Resistance in High-Fat Diet/Streptozocin-Induced Diabetic Mice

Insulin resistance (IR) is a hallmark of type 2 diabetes mellitus (T2DM). This study was performed to investigate the antidiabetic effect of Bacillus toyonensis SAU-19 and its possible mechanisms of action in mice with type 2 diabetes mellitus (T2DM). Thirty SPFKM mice were randomly assigned to three groups: control, diabetic model, and diabetes + Bacillus toyonensis SAU-19 group. After 35 days, blood was collected for biochemical analysis and liver tissue samples for histopathological analysis using H&E staining, qPCR, and ELISA. The results showed that the administration of B. toyonensis SAU-19 significantly improved the blood glucose, hepatic insulin resistance, and morphological changes of the liver characterized by significant improvement of dyslipidemia, glycogen synthesis, and antioxidant status (p < 0.05), indicating the strains’ ameliorating effects on hepatic insulin resistance in T2DM. In conclusion, the probiotic strain (B. toyonensis SAU-19) inhibits T2DM by reducing insulin resistance, improving antioxidant status, and downregulating genes related to glucose synthesis; hence, it may be used in treating diabetes and other metabolic disorders. This study provides the basis for further studies into the molecular mechanisms of B. toyonensis SAU-19 in treating T2DM.

β-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 β-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.

Branched chain amino acids-friend or foe in the control of energy substrate turnover and insulin sensitivity?

Branched chain amino acids (BCAA) and their derivatives are bioactive molecules with pleiotropic functions in the human body. Elevated fasting blood BCAA concentrations are considered as a metabolic hallmark of obesity, insulin resistance, dyslipidaemia, nonalcoholic fatty liver disease, type 2 diabetes and cardiovascular disease. However, since increased BCAA amount is observed both in metabolically healthy and obese subjects, a question whether BCAA are mechanistic drivers of insulin resistance and its morbidities or only markers of metabolic dysregulation, still remains open. The beneficial effects of BCAA on body weight and composition, aerobic capacity, insulin secretion and sensitivity demand high catabolic potential toward amino acids and/or adequate BCAA intake. On the opposite, BCAA-related inhibition of lipogenesis and lipolysis enhancement may preclude impairment in insulin sensitivity. Thereby, the following review addresses various strategies pertaining to the modulation of BCAA catabolism and the possible roles of BCAA in energy homeostasis. We also aim to elucidate mechanisms behind the heterogeneity of ramifications associated with BCAA modulation.

Role of Physical Activity in Bone-Muscle Crosstalk: Biological Aspects and Clinical Implications

Bone and muscle tissues influence each other through the integration of mechanical and biochemical signals, giving rise to bone-muscle crosstalk. They are also known to secrete osteokines, myokines, and cytokines into the circulation, influencing the biological and pathological activities in local and distant organs and cells. In this regard, even osteoporosis and sarcopenia, which were initially thought to be two independent diseases, have recently been defined under the term "osteosarcopenia", to indicate a synergistic condition of low bone mass with muscle atrophy and hypofunction. Undoubtedly, osteosarcopenia is a major public health concern, being associated with high rates of morbidity and mortality. The best current defence against osteosarcopenia is prevention based on a healthy lifestyle and regular exercise. The most appropriate type, intensity, duration, and frequency of exercise to positively influence osteosarcopenia are not yet known. However, combined programmes of progressive resistance exercises, weight-bearing impact exercises, and challenging balance/mobility activities currently appear to be the most effective in optimising musculoskeletal health and function. Based on this evidence, the aim of our review was to summarize the current knowledge about the role of exercise in bone-muscle crosstalk, highlighting how it may represent an effective alternative strategy to prevent and/or counteract the onset of osteosarcopenia.

The ameliorative effects of thymoquinone and beta-aminoisobutyric acid on streptozotocin-induced diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a cardiac dysfunction observed in a patient with diabetes that may lead to heart failure. No specific treatment has yet been tested in DCM. Therefore, in this study, it was investigated that the potential of thymoquinone (TYM) and beta-aminoisobutyric acid (BAIBA) to treat DCM. Five groups (n = 7) were formed, namely control, diabetes, TYM, BAIBA and TYM + BAIBA, with a random selection from 35 adult male rats. Diabetes mellitus was induced by intraperitoneal administration of 50 mg/kg streptozotocin to all groups except the control. After establishing experimental diabetes, TYM (20 mg/kg/day) and BAIBA (100 mg/kg/day) were administered alone or in combination with other groups other than the control and diabetes groups for five weeks by gavage. Serum aspartate aminotransferase, lactate dehydrogenase, creatine kinase-MB, and tissue malondialdehyde levels increased significantly, and tissue glutathione levels decreased in the diabetes group compared to the control group. An increase in the expression of tumor necrosis factor-α in the myocardium and the rate of fibrosis and apoptosis were found in the histopathological analysis. In the TYM and BAIBA groups, all pathological changes observed in the diabetes group improved significantly. The therapeutic effects of these agents on DCM are probably due to their antihyperglycemic, antidiabetic, antioxidant, and anti-inflammatory effects. The present results suggested that TYM and BAIBA have the potential therapeutic effects on DCM that were used alone or combined.

Roles of amino acid derivatives in the regulation of obesity

Obesity is an issue of great concern to people all over the world. It is accompanied by serious complications, leading to reduced quality of life and higher morbidity and mortality. Over the past few years, there has been an explosion in knowledge about the roles of potential therapeutic agents in obesity management. Among them, amino acid (AA) derivatives, such as taurine, glutathione (GSH), betaine, α-ketoglutarate (AKG), β-aminoisobutyric acid (BAIBA), and β-hydroxy-β-methylbutyrate (HMB), have recently gained popularity due to their beneficial effects on the promotion of weight loss and improvement in the lipid profile. The mechanisms of action of these derivatives mainly include inhibiting adipogenesis, increasing lipolysis, promoting brown/beige adipose tissue (BAT) development, and improving glucose metabolism. Therefore, this review summarizes these AA derivatives and the possible mechanisms responsible for their anti-obesity effects. Based on the current findings, these AA derivatives could be potential therapeutic agents for obesity and its related metabolic diseases.

The Role of Exercise, Diet, and Cytokines in Preventing Obesity and Improving Adipose Tissue

The prevalence of obesity continues to rise worldwide despite evidence-based public health recommendations. The promise to adopt a healthy lifestyle is increasingly important for tackling this global epidemic. Calorie restriction or regular exercise or a combination of the two is accepted as an effective strategy in preventing or treating obesity. Furthermore, the benefits conferred by regular exercise to overcome obesity are attributed not only to reduced adiposity or reduced levels of circulating lipids but also to the proteins, peptides, enzymes, and metabolites that are released from contracting skeletal muscle or other organs. The secretion of these molecules called cytokines in response to exercise induces browning of white adipose tissue by increasing the expression of brown adipocyte-specific genes within the white adipose tissue, suggesting that exercise-induced cytokines may play a significant role in preventing obesity. In this review, we present research-based evidence supporting the effects of exercise and various diet interventions on preventing obesity and adipose tissue health. We also discuss the interplay between adipose tissue and the cytokines secreted from skeletal muscle and other organs that are known to affect adipose tissue and metabolism.

Potential Roles of Exercise-Induced Plasma Metabolites Linking Exercise to Health Benefits

Regular exercise has a myriad of health benefits. An increase in circulating exercise factors following exercise is a critical physiological response. Numerous studies have shown that exercise factors released from tissues during physical activity may contribute to health benefits via autocrine, paracrine, and endocrine mechanisms. Myokines, classified as proteins secreted from skeletal muscle, are representative exercise factors. The roles of myokines have been demonstrated in a variety of exercise-related functions linked to health benefits. In addition to myokines, metabolites are also exercise factors. Exercise changes the levels of various metabolites via metabolic reactions. Several studies have identified exercise-induced metabolites that positively influence organ functions. Here, we provide an overview of selected metabolites secreted into the circulation upon exercise.

Exercise-Induced Myokines can Explain the Importance of Physical Activity in the Elderly: An Overview

Physical activity has been found to aid the maintenance of health in the elderly. Exercise-induced skeletal muscle contractions lead to the production and secretion of many small proteins and proteoglycan peptides called myokines. Thus, studies on myokines are necessary for ensuring the maintenance of skeletal muscle health in the elderly. This review summarizes 13 myokines regulated by physical activity that are affected by aging and aims to understand their potential roles in metabolic diseases. We categorized myokines into two groups based on regulation by aerobic and anaerobic exercise. With aging, the secretion of apelin, β-aminoisobutyric acid (BAIBA), bone morphogenetic protein 7 (BMP-7), decorin, insulin-like growth factor 1 (IGF-1), interleukin-15 (IL-15), irisin, stromal cell-derived factor 1 (SDF-1), sestrin, secreted protein acidic rich in cysteine (SPARC), and vascular endothelial growth factor A (VEGF-A) decreased, while that of IL-6 and myostatin increased. Aerobic exercise upregulates apelin, BAIBA, IL-15, IL-6, irisin, SDF-1, sestrin, SPARC, and VEGF-A expression, while anaerobic exercise upregulates BMP-7, decorin, IGF-1, IL-15, IL-6, irisin, and VEGF-A expression. Myostatin is downregulated by both aerobic and anaerobic exercise. This review provides a rationale for developing exercise programs or interventions that maintain a balance between aerobic and anaerobic exercise in the elderly.

KCNH6 protects pancreatic β-cells from endoplasmic reticulum stress and apoptosis

Adult patients with dysfunction in human ether-a-go-go 2 (hERG2) protein, encoded by KCNH6, present with hypoinsulinemia and hyperglycemia. However, the mechanism of KCNH6 action in glucose disorders has not been clearly defined. Previous studies identified that sustained endoplasmic reticulum (ER) stress-mediated apoptosis of pancreatic β-cells and directly contributed to diabetes. In the present study, we showed that Kcnh6 knockout (KO) mice had impaired glucose tolerance mediated by high ER stress levels, and showed increased apoptosis and elevated intracellular calcium levels in pancreatic β-cells. In contrast, KCNH6 overexpression in islets isolated from C57BL/6J mice attenuated ER stress induced by thapsigargin or palmitic acid. This effect contributed to better preservation of β-cells, as reflected in increased β cell survival and enhanced glucose-stimulated insulin secretion. These results were further corroborated by studies evaluating KCNH6 overexpression in KO islets. Similarly, induction of Kcnh6 in KO mice by lentivirus injection improved glucose tolerance by reducing pancreatic ER stress and apoptosis. Our data provide new insights into how Kcnh6 deficiency causes ER calcium depletion and β cell dysfunction.

Myokines mediate the cross talk between skeletal muscle and other organs

Myokines are muscle-derived cytokines and chemokines that act extensively on organs and exert beneficial metabolic functions in the whole-body through specific signal networks. Myokines as mediators provide the conceptual basis for a whole new paradigm useful for understanding how skeletal muscle communicates with other organs. In this review, we summarize and discuss classes of myokines and their physiological functions in mediating the regulatory roles of skeletal muscle on other organs and the regulation of the whole-body energy metabolism. We review the mechanisms involved in the interaction between skeletal muscle and nonmuscle organs through myokines. Moreover, we clarify the connection between exercise, myokines and disease development, which may contribute to the understanding of a potential mechanism by which physical inactivity affects the process of metabolic diseases via myokines. Based on the current findings, myokines are important factors that mediate the effect of skeletal muscle on other organ functions and whole-body metabolism.

Beta-aminoisobutyric acid is released by contracting human skeletal muscle and lowers insulin release from INS-1 832/3 cells by mediating mitochondrial energy metabolism

Aims/hypothesis

This study aimed to examine if beta-aminoisobutyric acid (BAIBA) is (i) secreted by skeletal muscle in humans during exercise, (ii) associated with insulin secretory function in vivo, and (iii) directly linked with acute glucose-mediated insulin release by pancreatic beta cells in vitro.

Methods

Following 2-weeks of single-leg immobilization, plasma BAIBA concentrations were measured in the brachial artery and the femoral veins of each leg in healthy male subjects, at rest and during two-legged dynamic knee-extensor exercise. During a 2-h hyperglycamic clamp, insulin secretory function and levels of plasma BAIBA were assessed in non-diabetic individuals, non-diabetic individuals following 24-h hyperglycemia and patients with type 2 diabetes. Direct effects of BAIBA on acute glucose-mediated insulin release were probed in INS-1832/3 cells under normal and ‘diabetes-like’ conditions. Finally, the effect of BAIBA on mitochondrial function was assessed in INS-1832/3 cells using extracellular flux analysis.

Results

(i) BAIBA is released from skeletal muscle at rest and during exercise under healthy conditions but is suppressed during exercise following leg immobilization, (ii) plasma BAIBA concentrations inversely associate with insulin secretory function in humans, (iii) BAIBA lowers mitochondrial energy metabolism in INS-1 832/3 cells in parallel with decreased insulin secretion

Conclusion/interpretation: BAIBA is a myokine released by skeletal muscle during exercise and indepedantly alters the triggering pathway of insulin secretion in cultured INS-1832/3 cells.

Bone-Muscle Mutual Interactions

PURPOSE OF REVIEW

The purpose of this review is to describe the current state of our thinking regarding bone-muscle interactions beyond the mechanical perspective.

RECENT FINDINGS

Recent and prior evidence has begun to dissect many of the molecular mechanisms that bone and muscle use to communicate with each other and to modify each other's function. Several signaling factors produced by muscle and bone have emerged as potential mediators of these biochemical/molecular interactions. These include muscle factors such as myostatin, Irisin, BAIBA, IL-6, and the IGF family and the bone factors FGF-23, Wnt1 and Wnt3a, PGE2, FGF9, RANKL, osteocalcin, and sclerostin. The identification of these signaling molecules and their underlying mechanisms offers the very real and exciting possibility that new pharmaceutical approaches can be developed that will permit the simultaneous treatments of diseases that often occur in combination, such as osteoporosis and sarcopenia.

Myokines and Osteokines in the Pathogenesis of Muscle and Bone Diseases

PURPOSE OF REVIEW

In this review we aim to summarize the latest findings on the network of molecules produced by muscle and bone under physiological and pathological conditions.

RECENT FINDINGS

The concomitant onset of osteoporosis and sarcopenia is currently one of the main threats that can increase the risk of falling fractures during aging, generating high health care costs due to hospitalization for bone fracture surgery. With the growing emergence of developing innovative therapies to treat these two age-related conditions that often have common onset, a broader understanding of molecular messengers regulating the communication between muscle and bone tissue became imperative. Recently it has been highlighted that two muscle-derived signals, such as the myokines Irisin and L-BAIBA, positively affect bone tissue. In parallel, there are signals derived from bone that affect either positively the skeletal muscle, such as osteocalcin, or negatively, such as RANKL.