Branched-chain amino acids in metabolic signalling and insulin resistance

Decoding the nexus: branched-chain amino acids and their connection with sleep, circadian rhythms, and cardiometabolic health

The sleep-wake cycle stands as an integrative process essential for sustaining optimal brain function and, either directly or indirectly, overall body health, encompassing metabolic and cardiovascular well-being. Given the heightened metabolic activity of the brain, there exists a considerable demand for nutrients in comparison to other organs. Among these, the branched-chain amino acids, comprising leucine, isoleucine, and valine, display distinctive significance, from their contribution to protein structure to their involvement in overall metabolism, especially in cerebral processes. Among the first amino acids that are released into circulation post-food intake, branched-chain amino acids assume a pivotal role in the regulation of protein synthesis, modulating insulin secretion and the amino acid sensing pathway of target of rapamycin. Branched-chain amino acids are key players in influencing the brain's uptake of monoamine precursors, competing for a shared transporter. Beyond their involvement in protein synthesis, these amino acids contribute to the metabolic cycles of γ-aminobutyric acid and glutamate, as well as energy metabolism. Notably, they impact GABAergic neurons and the excitation/inhibition balance. The rhythmicity of branched-chain amino acids in plasma concentrations, observed over a 24-hour cycle and conserved in rodent models, is under circadian clock control. The mechanisms underlying those rhythms and the physiological consequences of their disruption are not fully understood. Disturbed sleep, obesity, diabetes, and cardiovascular diseases can elevate branched-chain amino acid concentrations or modify their oscillatory dynamics. The mechanisms driving these effects are currently the focal point of ongoing research efforts, since normalizing branched-chain amino acid levels has the ability to alleviate the severity of these pathologies. In this context, the Drosophila model, though underutilized, holds promise in shedding new light on these mechanisms. Initial findings indicate its potential to introduce novel concepts, particularly in elucidating the intricate connections between the circadian clock, sleep/wake, and metabolism. Consequently, the use and transport of branched-chain amino acids emerge as critical components and orchestrators in the web of interactions across multiple organs throughout the sleep/wake cycle. They could represent one of the so far elusive mechanisms connecting sleep patterns to metabolic and cardiovascular health, paving the way for potential therapeutic interventions.

Sex Hormone: A Potential Target at Treating Female Metabolic Dysfunction-Associated Steatotic Liver Disease?

The global prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is rising due to rapid lifestyle changes. Although females may be less prone to MASLD than males, specific studies on MASLD in females should still be conducted. Previous research has shown that sex hormone levels are strongly linked to MASLD in females. By reviewing a large number of experimental and clinical studies, we summarized the pathophysiological mechanisms of estrogen, androgen, sex hormone-binding globulin, follicle-stimulating hormone, and prolactin involved in the development of MASLD. We also analyzed the role of these hormones in female MASLD patients with polycystic ovarian syndrome or menopause, and explored the potential of targeting sex hormones for the treatment of MASLD. We hope this will provide a reference for further exploration of mechanisms and treatments for female MASLD from the perspective of sex hormones.

Branched-chain amino acids levels associated with risk of erectile dysfunction: A Mendelian randomization analysis

BACKGROUND

Erectile dysfunction (ED) is a prevalent male sexual dysfunction that remarkably impacts patients' quality of life and is also recognized as a precursor to cardiovascular disease (CVD) events. Branched-chain amino acids (BCAAs) are derived from dietary intake and mainly involved in energy metabolism. Previous studies have underscored the association between BCAAs and CVD, but the causal link between BCAAs and ED remains uncertain.

METHODS

The bidirectional Mendelian randomization (MR) study used the genetic data from genome-wide association studies (GWAS) to identify single nucleotide polymorphisms (SNPs) associated with total BCAAs, leucine, isoleucine, and valine. The genetic data for ED were acquired from the FinnGen study (n = 95,178). The primary method used to assess causal associations was the inverse variance-weighted (IVW) method, supplemented by MR-Egger, weighted median, and simple median analyses. Cochrane's Q test was utilized to evaluate heterogeneity within the results, while the MR-Egger intercept test was utilized to evaluate the Level pleiotropy. A sensitivity analysis was performed employing leave-one-out analysis.

RESULTS

The MR analysis results indicate a positive correlation between levels of total BCAA (OR = 1.984, 95 % CI = 1.018-3.868, P = 0.044), leucine (OR = 2.277, 95 % CI = 1.121-4.626, P = 0.023), isoleucine (OR = 2.584, 95 % CI = 1.167-5.722, P = 0.019), valine (OR = 1.894, 95 % CI = 1.119-3.206, P = 0.017), and the risk of ED. Sensitivity tests confirmed the accuracy and robustness of the study findings. Moreover, the reverse MR analysis found no association between ED and the BCAAs.

CONCLUSION

The results of this analysis indicate a positive association between the circulating BCAA concentrations and the risk of ED, but their underlying mechanisms require further investigation.

Branched-chain amino acid metabolism: Pathophysiological mechanism and therapeutic intervention in metabolic diseases

Branched-chain amino acids (BCAAs), including leucine, isoleucine, and valine, are essential for maintaining physiological functions and metabolic homeostasis. However, chronic elevation of BCAAs causes metabolic diseases such as obesity, type 2 diabetes (T2D), and metabolic-associated fatty liver disease (MAFLD). Adipose tissue, skeletal muscle, and the liver are the three major metabolic tissues not only responsible for controlling glucose, lipid, and energy balance but also for maintaining BCAA homeostasis. Under obese and diabetic conditions, different pathogenic factors like pro-inflammatory cytokines, lipotoxicity, and reduction of adiponectin and peroxisome proliferator-activated receptors γ (PPARγ) disrupt BCAA metabolism, leading to excessive accumulation of BCAAs and their downstream metabolites in metabolic tissues and circulation. Mechanistically, BCAAs and/or their downstream metabolites, such as branched-chain ketoacids (BCKAs) and 3-hydroxyisobutyrate (3-HIB), impair insulin signaling, inhibit adipogenesis, induce inflammatory responses, and cause lipotoxicity in the metabolic tissues, resulting in multiple metabolic disorders. In this review, we summarize the latest studies on the metabolic regulation of BCAA homeostasis by the three major metabolic tissues-adipose tissue, skeletal muscle, and liver-and how dysregulated BCAA metabolism affects glucose, lipid, and energy balance in these active metabolic tissues. We also summarize therapeutic approaches to restore normal BCAA metabolism as a treatment for metabolic diseases.

Ningxiang pig-derived lactobacillus reuteri modulates host intramuscular fat deposition via branched-chain amino acid metabolism

BACKGROUND

Gut microbiota has been extensively demonstrated to modulate host lipid metabolism. Higher intramuscular fat (IMF) accumulation in Chinese indigenous breed pigs is associated with their special gut microbiota structure. However, the specific microbes and metabolic pathways responsible for lipid deposition are still poorly understood.

RESULTS

In the present study, a comparative analysis of the gut microbiota and metabolome in obese Ningxiang (NX) pigs and lean Duroc × Landrace × Yorkshire (DLY) pigs was conducted. The results revealed a higher abundance of gut lactobacilli and a correlation of branched-chain amino acid (BCAA) metabolism pathway in NX pigs. We proceeded to verify the roles of various lactobacilli strains originating from NX pigs in BCAA metabolism and lipids deposition in SD rats. We demonstrated that L. reuteri is a fundamental species responsible for modulating lipid deposition in NX pigs and that increased circulating levels of BCAA are positively linked to greater lipid deposition. Additionally, it has been verified that L. reuteri originating from NX pigs has the ability to improve BCAA synthesis in the gut and enhance IMF content in lean DLY pigs. The expression of genes related to lipid synthesis was also significantly upregulated.

CONCLUSIONS

Taken together, our results imply that NX pig-derived L. reuteri regulates BCAA metabolism and plays a potential role in improving the meat quality of lean pig breeds through modulation of host intramuscular lipid deposition. The results provide a new strategy for improving the meat quality of commercial pigs by influencing host metabolism through supplementing dietary additives. Video Abstract.

Exploration of the Fasting Hypoglycemic Mechanism of Casein Hydrolysate Enriched with Glu/Gln and Glu/Gln-Containing Peptides in db/db Diabetic-like Mice Using Multiomics Analysis

The fasting hypoglycemic effect of casein hydrolysate (CH) was investigated in db/db diabetic-like mice using a multiomics integrated analysis of peptidome, transcriptome, and metabolome. Results showed that the oral administration of CH at a dose of 600 mg/kg/day for 4 weeks reduced the fasting blood glucose levels by 14.73 ± 9.77%, alleviated insulin resistance (HOMA-IR index) by 36.91 ± 22.62%, and mitigated hepatic damage in db/db diabetic-like mice. Hepatic differential metabolites after CH treatment were enriched in Glu-related metabolites, which acted as substrates for the TCA cycle, enhancing hepatic glucose consumption. The hepatic transcriptomic results revealed that CH treatment upregulated (p < 0.05) hub gene expressions of pparg and pik3cb, leading to an activation of the PPAR signaling pathway, further improving the insulin/PI3K/AKT signaling pathway. The hub gene expressions were highly correlated with Glu-related metabolites in multiomics integrated analysis. Glx/Glx-containing peptides (Glx represents Glu and Gln) in CH, as a dietary supplement to increase hepatic Glu-related metabolites, might be the key active component responsible for its hypoglycemic effect. Particularly, the supplement of Glx was confirmed to effectively (p < 0.05) enhance glucose consumption in hepatocytes. This provides a basis for the development of CHs as functional food.

Enhanced Chronic Inflammation and Increased Branched-Chain Amino Acids in Adrenal Disorders: A Cross-Sectional Study

CONTEXT

Patients with adrenal hormone excess demonstrate increased cardiovascular (CV) risk and mortality.

OBJECTIVE

We aimed to determine the effect of adrenal disorders on the inflammation marker glycoprotein acetylation (GlycA), total branched-chain amino acids (BCAAs), ketone bodies, and the gut microbiome-derived metabolites trimethylamine N-oxide (TMAO) and betaine.

METHODS

We conducted a single-center cross-sectional study of patients with nonfunctioning adenomas (NFAs), mild autonomous cortisol secretion (MACS), primary aldosteronism (PA), Cushing syndrome (CS), pheochromocytoma/paragangliomas (PPGLs), other benign or malignant adrenal masses, and adrenocortical carcinoma (ACC) between January 2015 and July 2022 (n = 802). Referent individuals included participants in the PREVEND (Prevention of Renal and Vascular End-Stage Disease) study (n = 5241). GlycA, BCAAs, ketone bodies, TMAO, and betaine were measured using nuclear magnetic resonance spectroscopy. Multivariable logistic analyses were adjusted for age, sex, body mass index, smoking, hypertension, diabetes mellitus, and statin therapy.

RESULTS

In age- and sex-adjusted comparison to referent individuals, increased GlycA was noted in all patient categories, increased BCAAs in NFA, MACS, CS, PA, and ACC, increased TMAO in patients with other malignant adrenal masses, increased betaine in NFA and MACS, and increased ketone bodies in NFA, CS, and ACC. Essentially similar findings were observed in fully adjusted analysis and after exclusion of participants with diabetes and CV disease.

CONCLUSION

Patients with functioning and nonfunctioning adrenal masses demonstrated increased GlycA and BCAAs, biomarkers associated with adverse cardiometabolic disorders and mortality. Patients with NFA demonstrated an adverse metabolic profile similar to patients with MACS and CS.

Valine metabolite, 3-hydroxyisobutyrate, promotes lipid metabolism and cell proliferation in porcine mammary gland epithelial cells

Improving mammary gland epithelial cells proliferation through nutrition is an important approach for enhancing sow milk production and piglet growth. An intermediate metabolite of valine, 3-hydroxyisobutyrate (3-HIB), regulates cellular lipid metabolism. In the present study, we investigated the effects of 3-HIB on porcine mammary gland epithelial cells proliferation and lipid metabolism. The addition of an appropriate concentration of 3-HIB significantly increased mammary gland epithelial cell proliferation and the expression of proteins associated with cell proliferation. Compared to the control group, the addition of 0.4-0.8 mM 3-HIB increased the expression levels of mTOR signaling pathway-related proteins and the cell cycle protein, Cyclin D1, while inhibiting the expression of the cell cycle arrest protein, P27. The addition of 0.8 mM 3-HIB increased the triglyceride and lipid droplet content in the cells. The addition of 3-HIB increased the expression of proteins related to de novo fatty acid synthesis and transport, resulting in a marked increase in most polyunsaturated fatty acids in the 3-HIB-added group. Compared to the control group, the addition of 0.8 mM 3-HIB increased the expression levels of the fatty acid oxidation-related proteins, ACSL and CAD, ultimately increasing cellular ATP synthesis. In summary, the addition of 0.8 mM 3-HIB to porcine mammary gland epithelial cells promotes cell proliferation by enhancing lipid metabolism and the expression of cell proliferation-related proteins.

Alzheimer's disease and infectious agents: a comprehensive review of pathogenic mechanisms and microRNA roles

Alzheimer's Disease (AD) is the most prevalent type of dementia and is characterized by the presence of senile plaques and neurofibrillary tangles. There are various theories concerning the causes of AD, but the connection between viral and bacterial infections and their potential role in the pathogenesis of AD has become a fascinating area of research for the field. Various viruses such as Herpes simplex virus 1 (HSV-1), Epstein-Barr virus (EBV), Cytomegalovirus (CMV), influenza viruses, and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), as well as bacteria such as Chlamydia pneumoniae (CP), Helicobacter pylori (HP), Porphyromonas gingivalis (P. gingivalis), Spirochetes and eukaryotic unicellular parasites (e.g., Toxoplasma gondii), have been linked to AD due to their ability to activate the immune system, induce inflammation and increase oxidative stress, thereby leading to cognitive decline and AD. In addition, microRNAs (miRNAs) might play a crucial role in the pathogenesis mechanisms of these pathogens since they are utilized to target various protein-coding genes, allowing for immune evasion, maintaining latency, and suppressing cellular signaling molecules. Also, they can regulate gene expression in human cells. This article provides an overview of the association between AD and various infectious agents, with a focus on the mechanisms by which these pathogens may be related to the pathogenesis of AD. These findings suggest important areas for further research to be explored in future studies.

Exploring the causal impact of body mass index on metabolic biomarkers and cholelithiasis risk: a Mendelian randomization analysis

Obesity is a well-established risk factor for various diseases, but the mechanisms through which it influences disease development remain unclear. Using Mendelian randomization (MR) analysis, we examined the causal relationship between BMI, 249 metabolic traits, and cholelithiasis. BMI data were obtained from four sources, and cholelithiasis data were from two distinct datasets. We analyzed the direct effect of BMI on cholelithiasis and identified key metabolic mediators. BMI was found to be positively associated with the risk of cholelithiasis across all datasets analyzed. A total of 176 metabolites were identified to be significantly associated with BMI, including amino acids, cholesterol esters, free cholesterol, triglycerides, and phospholipids. Among these, 49 metabolites were identified as mediators in the BMI-cholelithiasis relationship. Specifically, fatty acid levels, cholesteryl esters, phospholipids, triglycerides, and free cholesterol were key mediators in this relationship, with mediation proportions ranging from - 2.38-7.14%. This study provides robust evidence that BMI significantly impacts metabolic biomarkers, which in turn affect the risk of cholelithiasis. These findings highlight the importance of managing BMI to mitigate metabolic dysfunction and reduce the risk of gallstone formation. Future research should explore the specific metabolic pathways involved to identify potential therapeutic targets.

Relationship Between Amino Acid Intake in Maternal Diet and Risk of Gestational Diabetes Mellitus: Results from the BORN 2020 Pregnant Cohort in Northern Greece

Background/Objectives: Maternal amino acid intake and its biological value may influence glucose regulation and insulin sensitivity, impacting the risk of developing gestational diabetes mellitus (GDM). This study aimed to evaluate the association between amino acid intake from maternal diet before and during pregnancy and the risk of GDM. Methods: This study is part of the ongoing BORN2020 epidemiological Greek cohort. A validated semi-quantitative Food Frequency Questionnaire (FFQ) was used. Amino acid intakes were quantified from the FFQ responses. A multinomial logistic regression model, with adjustments made for maternal characteristics, lifestyle habits, and pregnancy-specific factors, was used. Results: A total of 797 pregnant women were recruited, of which 14.7% developed GDM. Higher cysteine intake during pregnancy was associated with an increase in GDM risk (adjusted odds ratio [aOR]: 5.75; 95% confidence interval [CI]: 1.42-23.46), corresponding to a 476% increase in risk. Additionally, higher intakes of aspartic acid (aOR: 1.32; 95% CI: 1.05-1.66), isoleucine (aOR: 1.48; 95% CI: 1.03-2.14), phenylalanine (aOR: 1.6; 95% CI: 1.04-2.45), and threonine (aOR: 1.56; 95% CI: 1.0-2.43) during pregnancy were also associated with increased GDM risk. Furthermore, total essential amino acid (EAA) (aOR: 1.04; 95% CI: 1.0-1.09) and non-essential amino acid (NEAA) (aOR: 1.05; 95% CI: 1.0-1.1) intakes during pregnancy were also linked to an increased risk of GDM. A secondary dose-response analysis affected by timing of assessment revealed that higher intake levels of specific amino acids showed a more pronounced risk. Conclusions: Optimizing the balance of certain amino acids during pregnancy may guide personalized nutritional interventions to mitigate GDM risk.

Disruption of branched-chain amino acid homeostasis promotes the progression of DKD via enhancing inflammation and fibrosis-associated epithelial-mesenchymal transition

BACKGROUND AND AIMS

The disrupted homeostasis of branched-chain amino acids (BCAAs, including leucine, isoleucine, and valine) has been strongly correlated with diabetes with a potential causal role. However, the relationship between BCAAs and diabetic kidney disease (DKD) remains to be established. Here, we show that the elevated BCAAs from BCAAs homeostatic disruption promote DKD progression unexpectedly as an independent risk factor.

METHODS AND RESULTS

Similar to other tissues, the suppressed BCAAs catabolic gene expression and elevated BCAAs abundance were detected in the kidneys of type 2 diabetic mice and individuals with DKD. Genetic and nutritional studies demonstrated that the elevated BCAAs from systemic disruption of BCAAs homeostasis promoted the progression of DKD. Of note, the elevated BCAAs promoted DKD progression without exacerbating diabetes in the animal models of type 2 DKD. Mechanistic studies demonstrated that the elevated BCAAs promoted fibrosis-associated epithelial-mesenchymal transition (EMT) by enhancing the activation of proinflammatory macrophages through mTOR signaling. Furthermore, pharmacological enhancement of systemic BCAAs catabolism using small molecule inhibitor attenuated type 2 DKD. Finally, the elevated BCAAs also promoted DKD progression in type 1 diabetic mice without exacerbating diabetes.

CONCLUSION

BCAA homeostatic disruption serves as an independent risk factor for DKD and restoring BCAA homeostasis pharmacologically or dietarily represents a promising therapeutic strategy to ameliorate the progression of DKD.

Comparing Methods for Induction of Insulin Resistance in Mouse 3T3-L1 Cells

Cell culture plays a crucial role in addressing fundamental research questions, particularly in studying insulin resistance (IR) mechanisms. Multiple in vitro models are utilized for this purpose, but their technical distinctions and relevance to in vivo conditions remain unclear. This study aims to assess the effectiveness of existing in vitro models in inducing IR and their ability to replicate in vivo IR conditions.

BACKGROUND

Insulin resistance (IR) is a cellular condition linked to metabolic disorders. Despite the utility of cell culture in IR research, questions persist regarding the suitability of various models. This study seeks to evaluate these models' efficiency in inducing IR and their ability to mimic in vivo conditions. Insights gained from this research could enhance our understanding of model strengths and limitations, potentially advancing strategies to combat IR and related disorders.

OBJECTIVE

1- Investigate the technical differences between existing cell culture models used to study molecular mediators of insulin resistance (IR). 2- Compare the effectiveness of present in vitro models in inducing insulin resistance (IR). 3- Assess the relevance of the existing cell culture models in simulating the in vivo conditions and environment that provoke the induction of insulin resistance (IR).

METHODS AND MATERIAL

In vitro, eight sets of 3T3-L1 cells were cultured until they reached 90% confluence. Subsequently, adipogenic differentiation was induced using a differentiation cocktail (media). These cells were then divided into four groups, with four subjected to normal conditions and the other four to hypoxic conditions. Throughout the differentiation process, each cell group was exposed to specific factors known to induce insulin resistance (IR). These factors included 2.5 nM tumor necrosis factor-alpha (TNFα), 20 ng/ml interleukin-6 (IL-6), 10 micromole 4-hydroxynonenal (4HNE), and high insulin (HI) at a concentration of 100 nM. To assess cell proliferation, DAPI staining was employed, and the expression of genes associated with various metabolic pathways affected by insulin resistance was investigated using Real-Time PCR. Additionally, insulin signaling was examined using the Bio-plex Pro cell signaling Akt panel.

RESULTS

We induced insulin resistance in 3T3-L1 cells using IL-6, TNFα, 4HNE, and high insulin in both hypoxic and normoxic conditions. Hypoxia increased HIF1a gene expression by approximately 30% (P<0.01). TNFα reduced cell proliferation by 10-20%, and chronic TNFα treatment significantly decreased mature adipocytes due to its cytotoxicity. We assessed the impact of insulin resistance (IR) on metabolic pathways, focusing on genes linked to branched-chain amino acid metabolism, detoxification, and chemotaxis. Notably, ALDH6A1 and MCCC1 genes, related to amino acid metabolism, were significantly affected under hypoxic conditions. TNFα treatment notably influenced MCP-1 and MCP-2 genes linked to chemotaxis, with remarkable increases in MCP-1 levels and MCP-2 expression primarily under hypoxia. Detoxification-related genes showed minimal impact, except for a significant increase in MAOA expression under acute hypoxic conditions with TNFα treatment. Additional genes displayed varying effects, warranting further investigation. To investigate insulin signaling's influence in vitro by IRinducing factors, we assessed phospho-protein levels. Our results reveal a significant p-Akt induction with chronic high insulin (10%) and acute TNFα (12%) treatment under hypoxia (both P<0.05). Other insulin resistance-related phospho-proteins (GSK3B, mTOR, PTEN) increased with IL-6, 4HNE, TNFα, and high insulin under hypoxia, while p-IRS1 levels remained unaffected.

CONCLUSION

In summary, different in vitro models using inflammatory, oxidative stress, and high insulin conditions under hypoxic conditions can capture various aspects of in vivo adipose tissue insulin resistance (IR). Among these models, acute TNFα treatment may offer the most robust approach for inducing IR in 3T3-L1 cells.

Intrahepatic levels of microbiome-derived hippurate associates with improved metabolic dysfunction-associated steatotic liver disease

OBJECTIVE

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterised by lipid accumulation in the liver and is often associated with obesity and type 2 diabetes. The gut microbiome recently emerged as a significant player in liver metabolism and health. Hippurate, a host-microbial co-metabolite has been associated with human gut microbial gene richness and with metabolic health. However, its role on liver metabolism and homeostasis is poorly understood.

METHODS

We characterised liver biospies from 318 patients with obesity using RNAseq and metabolomics in liver and plasma to derive associations among hepatic hippurate, hepatic gene expression and MASLD and phenotypes. To test a potential beneficial role for hippurate in hepatic insulin resistance, we profile the metabolome of (IHH) using ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-MS/MS), and characterised intracellular triglyceride accumulation and glucose internalisation after a 24 h insulin exposure.

RESULTS

We first report significant associations among MASLD traits, plasma and hepatic hippurate. Further analysis of the hepatic transcriptome shows that liver and plasma hippurate are inversely associated with MASLD, implicating lipid metabolism and regulation of inflammatory responses pathways. Hippurate treatment inhibits lipid accumulation and rescues insulin resistance induced by 24-hour chronic insulin in IHH. Hippurate also improves hepatocyte metabolic profiles by increasing the abundance of metabolites involved in energy homeostasis that are depleted by chronic insulin treatment while decreasing those involved in inflammation.

CONCLUSIONS

Altogether, our results further highlight hippurate as a mechanistic marker of metabolic health, by its ability to improve metabolic homeostasis as a postbiotic candidate.

Early life stress shifts critical periods and causes precocious visual cortex development

The developing nervous system displays remarkable plasticity in response to sensory stimulation during critical periods of development. Critical periods may also increase the brain's vulnerability to adverse experiences. Here we show that early-life stress (ELS) in mice shifts the timing of critical periods in the visual cortex. ELS induced by animal transportation on postnatal day 12 accelerated the opening and closing of the visual cortex critical period along with earlier maturation of visual acuity. Staining of a molecular correlate that marks the end of critical period plasticity revealed premature emergence of inhibitory perineuronal nets (PNNs) following ELS. ELS also drove lasting changes in visual cortex mRNA expression affecting genes linked to psychiatric disease risk, with hemispheric asymmetries favoring the right side. NMR spectroscopy and a metabolomics approach revealed that ELS was accompanied by activated energy metabolism and protein biosynthesis. Thus, ELS may accelerate visual system development, resulting in premature opening and closing of critical period plasticity. Overall, the data suggest that ELS desynchronizes the orchestrated temporal sequence of regional brain development potentially leading to long-term functional deficiencies. These observations provide new insights into a neurodevelopmental expense to adaptative brain plasticity. These findings also suggest that shipment of laboratory animals during vulnerable developmental ages may result in long lasting phenotypes, introducing critical confounds to the experimental design.

Primary Roles of Branched Chain Amino Acids (BCAAs) and Their Metabolism in Physiology and Metabolic Disorders

Leucine, isoleucine, and valine are collectively known as branched chain amino acids (BCAAs) and are often discussed in the same physiological and pathological situations. The two consecutive initial reactions of BCAA catabolism are catalyzed by the common enzymes referred to as branched chain aminotransferase (BCAT) and branched chain α-keto acid dehydrogenase (BCKDH). BCAT transfers the amino group of BCAAs to 2-ketoglutarate, which results in corresponding branched chain 2-keto acids (BCKAs) and glutamate. BCKDH performs an oxidative decarboxylation of BCKAs, which produces their coenzyme A-conjugates and NADH. BCAT2 in skeletal muscle dominantly catalyzes the transamination of BCAAs. Low BCAT activity in the liver reduces the metabolization of BCAAs, but the abundant presence of BCKDH promotes the metabolism of muscle-derived BCKAs, which leads to the production of glucose and ketone bodies. While mutations in the genes responsible for BCAA catabolism are involved in rare inherited disorders, an aberrant regulation of their enzymatic activities is associated with major metabolic disorders such as diabetes, cardiovascular disease, and cancer. Therefore, an understanding of the regulatory process of metabolic enzymes, as well as the functions of the BCAAs and their metabolites, make a significant contribution to our health.

BCKDK loss impairs mitochondrial Complex I activity and drives alpha-synuclein aggregation in models of Parkinson's disease

Mitochondrial dysfunction and α-synuclein (αSyn) aggregation are key contributors to Parkinson's Disease (PD). While genetic and environmental risk factors, including mutations in mitochondrial-associated genes, are implicated in PD, the precise mechanisms linking mitochondrial defects to αSyn pathology remain incompletely understood, hindering the development of effective therapeutic interventions. Here, we identify the loss of branched chain ketoacid dehydrogenase kinase (BCKDK) as a mitochondrial risk factor that exacerbates αSyn pathology by disrupting Complex I function. Our findings reveal a consistent downregulation of BCKDK in dopaminergic (DA) neurons from A53T-αSyn mouse models, PD patient-derived induced pluripotent stem (iPS) cells, and postmortem brain tissues. BCKDK deficiency leads to mitochondrial dysfunction, including reduced membrane potential and increased reactive oxygen species (ROS) production upon administration of a stressor, which in turn promotes αSyn oligomerization. Mechanistically, BCKDK interacts with the NDUFS1 subunit of Complex I to stabilize its function. Loss of BCKDK disrupts this interaction, leading to Complex I destabilization and enhanced αSyn aggregation. Notably, restoring BCKDK expression in neuron-like cells rescues mitochondrial integrity and restores Complex I activity. Similarly, in patient-derived iPS cells differentiated to form dopaminergic neurons, NDUFS1 and phosphorylated aSyn levels are partially restored upon BCKDK expression. These findings establish a mechanistic link between BCKDK deficiency, mitochondrial dysfunction, and αSyn pathology in PD, positioning BCKDK as a potential therapeutic target to mitigate mitochondrial impairment and neurodegeneration in PD.

Phosphatase activity-based PPM1K: a key player in the regulation of mitochondrial function and its multifaceted impact in diseases

PPM1K is a significant metal-dependent phosphatase predominantly located in the mitochondrial matrix, where it plays a crucial role in the metabolism of branched-chain amino acids (BCAAs). It is implicated in cellular function and development across various tissues and is associated with diseases like Alzheimer's, cardiomyopathy, and maple syrup urine disease (MSUD). This article reviews PPM1K's impact on mitochondrial function and cellular metabolism, as well as its role in disease progression. The regulation of PPM1K expression and activity by various factors is complex and highlights its therapeutic potential. PPM1K's dysfunction can lead to the accumulation of BCAAs and the excessive opening of the mitochondrial permeability transition pore (MPTP), disrupting physiological metabolism and function. It also regulates the degradation of BCAAs by acting as a specific phosphatase for the E1α subunit of the BCKD complex. Outside the mitochondria, PPM1K suppresses de novo fatty acid synthesis and promotes fatty acid oxidation by dephosphorylating ACL. Furthermore, PPM1K has anti-inflammatory effects and modulates immune cell infiltration in tumor tissues. The expression and activity of PPM1K are influenced by factors such as BCAA concentration, fructose intake, and drug treatments, making it a promising target for therapeutic applications and further basic research.

Mapping Thrombosis Serum Markers by 1H-NMR Allied with Machine Learning Tools

Machine learning and artificial intelligence tools were used to investigate the discriminatory potential of blood serum metabolites for thromboembolism and antiphospholipid syndrome (APS). 1H-NMR-based metabonomics data of the serum samples of patients with arterial or venous thromboembolism (VTE) without APS (n = 32), thrombotic primary APS patients (APS, n = 32), and healthy controls (HCs) (n = 32) were investigated. Unique metabolic profiles between VTE and HCs, APS and HCs, and between VTE and triple-positive APS groups were indicative of the significant alterations in the metabolic pathways of glycolysis, the TCA cycle, lipid metabolism, and branched-chain amino acid (BCAA) metabolism, and pointed to the complex pathogenesis mechanisms of APS and VTE. Histidine, 3-hydroxybutyrate, and threonine were shown to be the top three metabolites with the most substantial impact on model predictions, suggesting that these metabolites play a pivotal role in distinguishing among APS, VTE, and HCs. These metabolites might be potential biomarkers to differentiate APS and VTE patients.

Sphingoid Base Diversity

Sphingolipids (SL) are crucial components of cellular membranes and play pivotal roles in various biological processes, including cell growth, differentiation, apoptosis, and stress responses. All SL contain a sphingoid base (SPB) backbone which is the shared and class-defining element. SPBs are heterogeneous in length and structure. This review summarizes our current understanding on minor SPBs and the role of the serine palmitoyltransferase (SPT) in particular of its subunits SPTLC3 and SPTSSA/B in forming a spectrum of structurally and metabolically distinct SPBs. Some minor SPBs, such as 1-deoxysphingolipids (1-deoxySL) are neurotoxic and associated with neurological disorders such as hereditary sensory neuropathy type 1 (HSAN1) and diabetic neuropathy. Furthermore, the review discusses the pathological implications of atypical SPBs in cardiometabolic conditions such as obesity, type 2 diabetes or cardiomyopathy, where the induction of the SPTLC3 subunit alters the SPB profile and contributes to disease progression. Understanding these, often neglected aspects of the sphingolipid metabolism provides potential therapeutic targets for metabolic and neurodegenerative diseases, emphasizing the need for continued research in this area.

Achieving High Protein Quality Is a Challenge in Vegan Diets: A Narrative Review

The transition toward plant-based (PB) diets has gained attention as a plausible step toward achieving sustainable and healthy dietary goals. However, the complete elimination of all animal-sourced foods from the diet (ie, a vegan diet) may have nutritional ramifications that warrant close examination. Two such concerns are the adequacy and bioavailability of amino acids (AAs) from plant-sourced foods and the consequences for older vegan populations who have elevated AA requirements. This narrative review describes the challenges of achieving high protein quality from vegan diets. Data were synthesized from peer-reviewed research articles and reviews. Plant-sourced proteins provide poorer distribution of indispensable AAs (IAAs) and have poorer digestibility, partly due to their inherent structural components within the food matrix. The review addresses complexities of combinations of varied plant protein sources and why the inclusion of novel PB alternatives adds uncertainty to the achievement of adequate protein adequacy. Meal distribution patterns of protein and the ensuing physiological impacts deserve further research and are outlined in this review. Particular attention is given to describing the challenges of achieving sufficient protein and IAA intakes by aging populations who choose to follow a vegan diet. This review contributes to the emerging discussions of nutritional risks associated with vegan diets and adds perspective to the current dietary shifts toward PB diets.

Emerging Biomarkers in Metabolomics: Advancements in Precision Health and Disease Diagnosis

Metabolomics has come to the fore as an efficient tool in the search for biomarkers that are critical for precision health approaches and improved diagnostics. This review will outline recent advances in biomarker discovery based on metabolomics, focusing on metabolomics biomarkers reported in cancer, neurodegenerative disorders, cardiovascular diseases, and metabolic health. In cancer, metabolomics provides evidence for unique oncometabolites that are important for early disease detection and monitoring of treatment responses. Metabolite profiling for conditions such as neurodegenerative and mental health disorders can offer early diagnosis and mechanisms into the disease especially in Alzheimer's and Parkinson's diseases. In addition to these, lipid biomarkers and other metabolites relating to cardiovascular and metabolic disorders are promising for patient stratification and personalized treatment. The gut microbiome and environmental exposure also feature among the influential factors in biomarker discovery because they sculpt individual metabolic profiles, impacting overall health. Further, we discuss technological advances in metabolomics, current clinical applications, and the challenges faced by metabolomics biomarker validation toward precision medicine. Finally, this review discusses future opportunities regarding the integration of metabolomics into routine healthcare to enable preventive and personalized approaches.

Skeletal muscle cystathionine γ-lyase deficiency promotes obesity and insulin resistance and results in hyperglycemia and skeletal muscle injury upon HFD in mice

OBJECTIVES

The objective of this study was to investigate whether skeletal muscle cystathionine γ-lyase (CTH) contributes to high-fat diet (HFD)-induced metabolic disorders using skeletal muscle Cth knockout (CthΔskm) mice.

METHODS

The CthΔskm mice and littermate Cth-floxed (Cthf/f) mice were fed with either HFD or chow diet for 13 weeks. Metabolomics and transcriptome analysis were used to assess the impact of CTH deficiency in skeletal muscle.

RESULTS

Metabolomics coupled with transcriptome showed that CthΔskm mice displayed impaired energy metabolism and some signaling pathways linked to insulin resistance (IR) in skeletal muscle although the mice had normal insulin sensitivity. HFD led to reduced CTH expression and impaired energy metabolism in skeletal muscle in Cthf/f mice. CTH deficiency and HFD had some common pathways enriched in the aspects of amino acid metabolism, carbon metabolism, and fatty acid metabolism. CthΔskm+HFD mice exhibited increased body weight gain, fasting blood glucose, plasma insulin, and IR, and reduced glucose transporter 4 and CD36 expression in skeletal muscle compared to Cthf/f+HFD mice. Impaired mitochondria and irregular arrangement in myofilament occurred in CthΔskm+HFD mice. Omics analysis showed differential pathways enriched between CthΔskm mice and Cthf/f mice upon HFD. More severity in impaired energy metabolism, reduced AMPK signaling, and increased oxidative stress and ferroptosis occurred in CthΔskm+HFD mice compared to Cthf/f+HFD mice.

DISCUSSION

Our results indicate that skeletal muscle CTH expression dysregulation contributes to metabolism disorders upon HFD.

Dysregulation of amino acids balance as potential serum-metabolite biomarkers for diagnosis and prognosis of diabetic retinopathy: a metabolomics study

Objectives

Diabetic retinopathy (DR), an earnest complication of diabetes, is one of the most common causes of blindness worldwide. This study aimed to investigate the altered metabolites in the serum of non-DR (NDR) and DR including non-proliferative diabetic retinopathy (NPDR), and proliferative diabetic retinopathy (PDR) subjects.

Methods

In this study, the 1HNMR platform was applied to reveal the discriminating serum metabolites in three diabetic groups based on the status of their complications: T2D or NDR (n = 15), NPDR, (n = 15), and PDR (n = 15) groups. Multivariate analyses include principal component analysis (PCA) and Partial Least Structures-Discriminant Analysis (PLS-DA) analysis that were performed using R software. The main metabolic pathways were also revealed by KEGG pathway enrichment analysis.

Results

The results revealed the significantly different metabolites include 10 metabolites of the NPDR versus PDR group, 24 metabolites of the PDR versus NDR group, and 25 metabolites of the NPDR versus NDR group. The results showed that the significantly altered metabolites in DR compared with NDR serum samples mainly belonged to amino acids. The most important pathways between NPDR/PDR, and NDR/DR groups include ascorbate and aldarate metabolism, galactose metabolism, glutathione metabolism, and tryptophan metabolism, respectively. In addition, some metabolites were detected for the first time.

Conclusions

We created a metabolomics profile for NDR, PDR and NPDR groups. The impairment in the ascorbate/aldarate, galactose, and especially amino acids metabolism was identified as metabolic dysregulation associated with DR, which may provide new insights into potential pathogenesis pathways for DR.

Graphical Abstract

Identification of putative allosteric inhibitors of BCKDK via virtual screening and biological evaluation

Abnormal accumulation of branched-chain amino acids (BCAAs) can lead to metabolic diseases and cancers. Branched-chain α-keto acid dehydrogenase kinase (BCKDK) is a key negative regulator of BCAA catabolism, and targeting BCKDK provides a promising therapeutic approach for diseases caused by BCAA accumulation. Here, we screened PPHN and POAB as novel putative allosteric inhibitors by integrating allosteric binding site prediction, large-scale ligand database virtual screening, and bioactivity evaluation assays. Both of them showed a high binding affinity to BCKDK, with Kd values of 3.9 μM and 1.86 μM, respectively. In vivo experiments, the inhibitors demonstrated superior kinase inhibitory activity and notable antiproliferative and proapoptotic effects on diverse cancer cells. Finally, bulk RNA-seq analysis revealed that PPHN and POAB suppressed cell growth through a range of signalling pathways. Taken together, our findings highlight two novel BCKDK inhibitors as potent therapeutic candidates for metabolic diseases and cancers associated with BCAA dysfunctional metabolism.

Fueling the fight against cancer: Exploring the impact of branched-chain amino acid catalyzation on cancer and cancer immune microenvironment

Metabolism of Branched-chain amino acids (BCAAs) is essential for the nutrient necessities in mammals. Catalytic enzymes serve to direct the whole-body BCAAs oxidation which involve in the development of various metabolic disorders. The reprogrammed metabolic elements are also responsible for malignant oncogenic processes, and favor the formation of distinctive immunosuppressive microenvironment surrounding different cancers. The impotent immune surveillance related to BCAAs dysfunction is a novel topic to investigate. Here we focus on the BCAA catalysts that contribute to metabolic changes and dysregulated immune reactions in cancer progression. We summarize the current knowledge of BCAA catalyzation, highlighting the interesting roles of BCAA metabolism in the treatment of cancers.

Comparable glucagon-stimulated amino acid suppression in individuals with and without hepatic steatosis or steatohepatitis

Hepatic amino acid (AA) metabolism and glucagon secretion are linked in a feedback cycle in which circulating AAs stimulate glucagon secretion and alpha-cell proliferation, whereas glucagon stimulates hepatic AA catabolism. It has been proposed that metabolic dysfunction-associated steatotic liver disease (MASLD) leads to hepatic glucagon resistance, which may result in hyperaminoacidemia and hyperglucagonemia. We tested the glucagon effect on AA metabolism in subjects with obesity; 11 with steatohepatitis (MASH), 10 with steatosis (MAS), and 7 subjects [control (CON)] without steatosis. We performed a somatostatin clamp with infusions of insulin and low dose followed by high-dose glucagon. We measured plasma levels of 17 AAs and assessed hepatic fat content (FF%) and body fat distribution (visceral and subcutaneous adipose tissue mass) by MRI. HighGlucagon suppressed plasma total AA equally in all groups; MASH 13% (SD 9%), MAS 14% (7%), and CON 11% (5%), respectively. In univariate regression analyses, visceral adipose tissue mass (β = 0.471, P = 0.011) and AA concentration at LowGlucagon (β = -0.524, P = 0.004), but not FF% (β = -0.243, P = 0.213), were significant predictors of AA reduction. Using a stepwise backward multiple regression approach revealed similar results. Total and specific AA levels (glutamic acid and tyrosine) were higher in both MASLD groups during the study, and FF% was positively correlated to a number of individual AAs. Although finding elevated AA concentrations in subjects with MASLD, we conclude that in patients with MASLD that do not have elevated glucagon at baseline, glucagon suppresses circulating AA levels equally in subjects with and without MASLD. ClinicalTrials.gov: NCT04042142.NEW & NOTEWORTHY The purpose of the study was to investigate the concept of "glucagon resistance" in metabolic dysfunction-associated steatotic liver disease (MASLD) pathogenesis. We asked if a disruption of the glucagon-mediated suppression of hepatic amino acid (AA) catabolism is present in individuals with MASLD compared with individuals with obesity but no MASLD. Contrary to expectations, we found no disruption of the glucagon-stimulated suppression of plasma AA concentration, which disputes the hypothesis that MASLD causes resistance to glucagon.

Gut microbiota, physical activity and/or metabolic markers in healthy individuals - towards new biomarkers of health

Background

The global prevalence of the metabolic disease Type 2 Diabetes (T2D) is increasing. Risk factors contributing to the development of T2D include overweight and obesity, lack of physical activity (PA), and an unhealthy diet. In addition, the gut microbiota has been shown to affect metabolic regulation. Since T2D is preventable, efforts should be put into the discovery of new biomarkers for early detection of individuals at risk of developing the disease.

Objective

The objective of the cross-sectional study was to explore the relationship between gut microbiota and physical activity (PA) and/or metabolic markers such as selected amino acids (AA), markers of glycaemic regulation and lipid metabolism and anthropometric measures.

Design

Healthy adults (18 and 65 years) with BMI between 18.5 and 27.5 kg/m2 originally recruited to a randomised controlled trial (RCT) (n = 17: six males, eleven females), were included in this exploratory cross-sectional study. Physical activity data was calculated based on a 3-days registration, and blood metabolome, gut microbiota analyses and anthropometric measures from one visit of the intervention were used in this cross-sectional study.

Results

Of the 47 gut bacteria analysed, there were a total of 87 significant correlations with AA, PA, body composition and/or metabolic markers. Several of the gut bacteria correlated with both PA, metabolic or anthropometric markers.

Conclusion

In this study, we demonstrate associations between gut bacteria and PA and/or metabolic markers including AA in healthy individuals. The results may guide future studies aiming at identifying new and early biomarkers of metabolic health and diseases.

Association of maternal blood metabolomics and gestational diabetes mellitus risk: a systematic review and meta-analysis

Gestational diabetes mellitus (GDM) is a common complication of pregnancy that has short- and long-term adverse effects. Therefore, further exploration of the pathophysiology of GDM and related biomarkers is important. In this study, we performed a systematic review and meta-analysis to investigate the associations between metabolites in blood detected via metabolomics techniques and the risk of GDM and to identify possible biomarkers for predicting the occurrence of GDM. We retrieved case‒control and cohort studies of metabolomics and GDM published in PubMed, Embase, and Web of Science through March 29, 2024; extracted metabolite concentrations, odds ratios (ORs), or relative risks (RRs); and evaluated the integrated results with metabolites per-SD risk estimates and 95% CIs for GDM. We estimated the results via the random effects model and the inverse variance method. Our study is registered in PROSPERO (CRD42024539435). We included a total of 28 case‒control and cohort studies, including 17,370 subjects (4,372 GDM patients and 12,998 non-GDM subjects), and meta-analyzed 67 metabolites. Twenty-five of these metabolites were associated with GDM risk. Some amino acids (isoleucine, leucine, valine, alanine, aspartate, etc.), lipids (C16:0, C18:1n-9, C18:1n-7, lysophosphatidylcholine (LPC) (16:0), LPC (18:0), and palmitoylcarnitine), and carbohydrates and energy metabolites (glucose, pyruvate, lactate, 2-hydroxybutyrate, 3-hydroxybutyrate) were discovered to be associated with increased GDM risk (hazard ratio 1.06-2.77). Glutamine, histidine, C14:0, and sphingomyelin (SM) (34:1) were associated with lower GDM risk (hazard ratio 0.75-0.84). These findings suggest that these metabolites may play essential roles in GDM progression, and serve as biomarkers, contributing to the early diagnosis and prediction of GDM.

Increased rumen Prevotella enhances BCAA synthesis, leading to synergistically increased skeletal muscle in myostatin-knockout cattle

Myostatin (MSTN) is a negative regulator of muscle growth, and its relationship with the gut microbiota is not well understood. In this study, we observed increase muscle area and branched-chain amino acids (BCAAs), an energy source of muscle, in myostatin knockout (MSTN-KO) cattle. To explore the link between increased BCAAs and rumen microbiota, we performed metagenomic sequencing, metabolome analysis of rumen fluid, and muscle transcriptomics. MSTN-KO cattle showed a significant increase in the phylum Bacteroidota (formerly Bacteroidetes), particularly the genus Prevotella (P = 3.12e-04). Within this genus, Prevotella_sp._CAG:732, Prevotella_sp._MSX73, and Prevotella_sp._MA2016 showed significant upregulation of genes related to BCAA synthesis. Functional enrichment analysis indicated enrichment of BCAA synthesis-related pathways in both rumen metagenomes and metabolomes. Additionally, muscle transcriptomics indicated enrichment in muscle fiber and amino acid metabolism, with upregulation of solute carrier family genes, enhancing BCAA transport. These findings suggest that elevated rumen Prevotella in MSTN-KO cattle, combined with MSTN deletion, synergistically improves muscle growth through enhanced BCAA synthesis and transport.

Nutritional status and incidence of hepatocellular carcinoma in patients with compensated liver cirrhosis

BACKGROUND

Malnutrition in patients with liver cirrhosis (LC) and/or hepatocellular carcinoma (HCC) has been associated with adverse outcomes. However, there is little information on the incidence of HCC during the compensated phase of LC in relation to the nutritional status.

AIM

To evaluate the association between the incidence of HCC in compensated LC and their nutritional status.

METHODS

Patients with compensated liver cirrhosis with no previous history of ascites, hepatic encephalopathy, or variceal bleeding attending the Gastroenterology outpatient service at Centro Medico Nacional Siglo XXI were included in a prospective cohort. Clinical and nutritional parameters were collected, including the Royal Free Hospital Subjective Global Assessment (RFH-SGA) as an indicator of protein-calorie malnutrition and the triceps skinfold thickness, which classified patients as having normal subcutaneous adipose tissue (SAT), above average SAT, and below average SAT. Follow-up was censored at the time of HCC diagnosis or LC decompensation.

RESULTS

About 31/187 (16.0 %) and 22/187 (11.8 %) patients were categorized as having above- or below-average SAT at baseline, respectively. 10/187 patients (5.3 %) developed HCC during the compensated phase of LC at a median of 22 months (IQR: 10.0-36.75). A higher risk of HCC was observed in subjects below average SAT (HR: 4.064, CI 95 %: 1.012-16.317, p = 0.048). After adjusting the Cox models for age and α-fetoprotein at baseline, the statistical significance of the association between SAT and HCC was not modified.

CONCLUSION

These results suggest that decreased SAT may precede the diagnosis of HCC in compensated LC.

Discovery of First Branched-Chain Ketoacid Dehydrogenase Kinase (BDK) Inhibitor Clinical Candidate PF-07328948

Inhibition of branched-chain ketoacid dehydrogenase kinase (BDK or BCKDK), a negative regulator of branched-chain amino acid (BCAA) metabolism, is hypothesized to treat cardio-metabolic diseases. From a starting point with potential idiosyncratic toxicity risk, modification to a benzothiophene core and discovery of a cryptic pocket allowed for improved potency with 3-aryl substitution to arrive at PF-07328948, which was largely devoid of protein covalent binding liability. This BDK inhibitor was shown also to be a BDK degrader in cells and in vivo rodent studies. Plasma biomarkers, including BCAAs and branched-chain ketoacids (BCKAs), were lowered in vivo with enhanced pharmacodynamic effect upon chronic dosing due to BDK degradation. This molecule improves metabolic and heart failure end points in rodent models. PF-07328948 is the first known selective BDK inhibitor candidate to be examined in clinical studies, with Phase 1 single ascending dose data showing good tolerability and a pharmacokinetic profile commensurate with once-daily dosing.

Bicyclic Inhibitors of Branched-Chain α-Keto Acid Dehydrogenase Kinase (BDK) with In Vivo Activity

Elevated levels of the branched chain α-amino acids valine, leucine, and isoleucine are associated with heart disease and metabolic disorders. The kinase BDK, also known as branched-chain ketoacid dehydrogenase kinase (BCKDK), is a negative regulator of branched-chain α-amino acid metabolism through deactivation of BCKDC, the branched-chain α-ketoacid dehydrogenase complex. Inhibitors of BDK increase the activity of BCKDC and could be useful therapeutic leads for cardiometabolic diseases. We describe a novel bicyclic carboxy amide as an inhibitor of BDK with in vivo activity.

Double-Edge Effects of Leucine on Cancer Cells

Leucine is an essential amino acid that cannot be produced endogenously in the human body and therefore needs to be obtained from dietary sources. Leucine plays a pivotal role in stimulating muscle protein synthesis, along with isoleucine and valine, as the group of branched-chain amino acids, making them one of the most popular dietary supplements for athletes and gym-goers. The individual effects of leucine, however, have not been fully clarified, as most of the studies so far have focused on the grouped effects of branched-chain amino acids. In recent years, leucine and its metabolites have been shown to stimulate muscle protein synthesis mainly via the mammalian target of the rapamycin complex 1 signaling pathway, thereby improving muscle atrophy in cancer cachexia. Interestingly, cancer research suggests that leucine may have either anti-cancer or pro-tumorigenic effects. In the current manuscript, we aim to review leucine's roles in muscle protein synthesis, tumor suppression, and tumor progression, specifically summarizing the molecular mechanisms of leucine's action. The role of leucine is controversial in hepatocellular carcinoma, whereas its pro-tumorigenic effects have been demonstrated in breast and pancreatic cancers. In summary, leucine being used as nutritional supplement for athletes needs more attention, as its pro-oncogenic effects may have been identified by recent studies. Anti-cancer or pro-tumorigenic effects of leucine in various cancers should be further investigated to achieve clear conclusions.

Evidence-based sports supplements: A redox analysis

Despite the overwhelming number of sports supplements on the market, only seven are currently recognized as effective. Biological functions are largely regulated through redox reactions, yet no comprehensive analysis of the redox properties of these supplements has been compiled. Here, we analyze the redox characteristics of these seven supplements: bicarbonates, beta-alanine, caffeine, creatine, nitrates, carbohydrates, and proteins. Our findings suggest that all sports supplements exhibit some degree of redox activity. However, the precise physiological implications of these redox properties remain unclear. Future research, employing unconventional perspectives and methodologies, will reveal new redox pixels of the exercise physiology and sports nutrition picture.

Selenium polysaccharide form sweet corn cob mediated hypoglycemic effects in vitro and untargeted metabolomics study on type 2 diabetes

Type 2 diabetes mellitus (T2D) causes complications due to metabolic disorders besides increasing blood glucose. Sweet corn cob selenium polysaccharide (SeSCP) is a complex of Se with Sweet corn cob polysaccharide that has good hypoglycemic efficacy, but its effect on T2D metabolism has not been determined. In this study, the hypoglycemic effect of SeSCP was investigated by in vitro and in vivo experiments, and the levels of metabolites in feces were analyzed in a high-fat diet and STZ-induced T2D mouse model by Liquid chromatography-mass spectrometry (LC-MS). The results indicated that SeSCP regulates α-amylase and α-glucosidase through competitive reversible inhibition, and the reaction is spontaneous, driven by van der Waals forces and hydrogen bonding. In vivo, SeSCP modulates glucose transport decreasing glucose entry into the bloodstream. The metabolites mainly affected by SeSCP-MC were adenine, LysoPA (0:0/18:2(9Z, 12Z)), cysteine-S-sulfate, and demeclocycline (hydrochloride) metabolites. SeSCP interfered with β-alanine metabolism, starch and sucrose metabolism, ether lipid metabolism, glycerophospholipid metabolism, glyoxylate and dicarboxylate metabolism, pantothenate and CoA biosynthesis, etc. Additionally, SeSCP exhibited more effective metabolic interventions than metformin and SCP. Therefore, SeSCP can reduce complications while improving T2D blood glucose.

The Novel Insight of Gut Microbiota from Mouse Model to Clinical Patients and the Role of NF-κB Pathway in Polycystic Ovary Syndrome

Polycystic Ovary Syndrome (PCOS) is a metabolic disorder characterized by hyperandrogenism and related symptoms in women of reproductive age. Emerging evidence suggests that chronic low-grade inflammation plays a significant role in the development of PCOS. The gut microbiota, a complex bacterial ecosystem, has been extensively studied for various diseases, including PCOS, while the underlying mechanisms are not fully understood. This review comprehensively summarizes the changes in gut microbiota and metabolites observed in PCOS and their potential association with the condition. Additionally, we discuss the role of abnormal nuclear factor κB signaling in the pathogenesis of PCOS. These findings offer valuable insights into the mechanisms of PCOS and may pave the way for the development of control and therapeutic strategies for this condition in clinical practice. By bridging the gap between mouse models and clinical patients, this review contributes to a better understanding of the interplay between gut microbiota and inflammation in PCOS, thus paving new ways for future investigations and interventions.

Branched-chain amino acids alleviate NAFLD via inhibiting de novo lipogenesis and activating fatty acid β-oxidation in laying hens

The adverse metabolic impacts of branched-chain amino acids (BCAA) have been elucidated are mediated by isoleucine and valine. Dietary restriction of isoleucine promotes metabolic health and increases lifespan. However, a high protein diet enriched in BCAA is presently the most useful therapeutic strategy for nonalcoholic fatty liver disease (NAFLD), yet, its underlying mechanism remains largely unknown. Fatty liver hemorrhagic syndrome (FLHS), a specialized laying hen NAFLD model, can spontaneously develop fatty liver and hepatic steatosis under a high-energy and high-protein dietary background that the pathogenesis of FLHS is similar to human NAFLD. The mechanism underlying dietary BCAA control of NAFLD development in laying hens remains unclear. Herein, we demonstrate that dietary supplementation with 67 % High BCAA has unique mitigative impacts on NAFLD in laying hens. A High BCAA diet alleviates NAFLD, by inhibiting the tryptophan-ILA-AHR axis and MAPK9-mediated de novo lipogenesis (DNL), promoting ketogenesis and energy metabolism, and activating PPAR-RXR and pexophagy to promote fatty acid β-oxidation. Furthermore, we uncover that High BCAA strongly activates ubiquitin-proteasome autophagy via downregulating UFMylation to trigger MAPK9-mediated DNL, fatty acid elongation and lipid droplet formation-related proteins ubiquitination degradation, activating PPAR-RXR and pexophagy mediated fatty acid β-oxidation and lipolysis. Together, our data highlight moderating intake of high BCAA by inhibiting the AHR/MAPK9 are promising new strategies in NAFLD and FLHS treatment.

Therapeutic strategies to modulate gut microbial health: Approaches for sarcopenia management

Sarcopenia is a progressive and generalized loss of skeletal muscle and functions associated with ageing with currently no definitive treatment. Alterations in gut microbial composition have emerged as a significant contributor to the pathophysiology of multiple diseases. Recently, its association with muscle health has pointed to its potential role in mediating sarcopenia. The current review focuses on the association of gut microbiota and mediators of muscle health, connecting the dots between the influence of gut microbiota and their metabolites on biomarkers of sarcopenia. It further delineates the mechanism by which the gut microbiota affects muscle health with progressing age, aiding the formulation of a multi-modal treatment plan involving nutritional supplements and pharmacological interventions along with lifestyle changes compiled in the review. Nutritional supplements containing proteins, vitamin D, omega-3 fatty acids, creatine, curcumin, kefir, and ursolic acid positively impact the gut microbiome. Dietary fibres foster a conducive environment for the growth of beneficial microbes such as Bifidobacterium, Faecalibacterium, Ruminococcus, and Lactobacillus. Probiotics and prebiotics act by protecting against reactive oxygen species (ROS) and inflammatory cytokines. They also increase the production of gut microbiota metabolites like short-chain fatty acids (SCFAs), which aid in improving muscle health. Foods rich in polyphenols are anti-inflammatory and have an antioxidant effect, contributing to a healthier gut. Pharmacological interventions like faecal microbiota transplantation (FMT), non-steroidal anti-inflammatory drugs (NSAIDs), ghrelin mimetics, angiotensin-converting enzyme inhibitors (ACEIs), and butyrate precursors lead to the production of anti-inflammatory fatty acids and regulate appetite, gut motility, and microbial impact on gut health. Further research is warranted to deepen our understanding of the interaction between gut microbiota and muscle health for developing therapeutic strategies for ameliorating sarcopenic muscle loss.

Hypoglycemic effects of white hyacinth bean polysaccharide on type 2 diabetes mellitus rats involvement with entero-insular axis and GLP-1 via metabolomics study

The present study aimed to investigate the potential effects of white hyacinth bean polysaccharide (WHBP) against type 2 diabetic mellitus (T2DM) which was established by high-glucose/high-fat for 8 weeks, combined with a low-dose streptozotocin (STZ) injection. Our results showed that WHBP behaved the hypoglycemic effect by attenuating fasting blood glucose in vivo. WHBP-mediated anti-diabetic effects associated with the attenuation of insulin resistance and pancreatic impairment, as evidenced by the mitigation of pathological changes, inflammatory response and oxidative stress in the pancreas of T2DM rats. Meanwhile, gut protection was also shown during WHBP-mediated anti-diabetic effects, and glucagon-like peptide-1 (GLP-1), a mediator of the entero-insular axis, was observed to be elevated in both gut and pancreas of WHBP groups when compared to DM group, suggesting that hypoglycemic effects of WHBP were implicated in gut-pancreas interaction. Subsequently, untargeted metabolomics analysis performed by UPLC-QTOF/MS and showed that WHBP administration significantly adjusted the levels of 40 metabolites when compared to DM group. Further data concerning pathway analysis showed that WHBP administration significantly regulated the phenylalanine metabolism, tryptophan metabolism, arginine and proline, isoleucine metabolism, and glycerophospholipid metabolism in T2DM rats. Together, our results suggested that WHBP performed hypoglycemic effects and pancreatic protection linked to entero-insular axis involvement with GLP-1 and reversed metabolic disturbances in T2DM rats.

Neuregulin 4 Downregulation Alters Mitochondrial Morphology and Induces Oxidative Stress in 3T3-L1 Adipocytes

Neuregulin 4 (Nrg4) is an adipokine that belongs to the epidermal growth factor family and binds to ErbB4 tyrosine kinase receptors. In 3T3-L1 adipocytes, the downregulation of Nrg4 expression enhances inflammation and autophagy, resulting in insulin resistance. Here, we searched for the causes of this phenotype. Nrg4 knockdown (Nrg4 KD) adipocytes showed a significant reduction in mitochondrial content and elongation, along with a lower content of the mitochondria fusion protein mitofusin 2 (MFN2), and increased H2O2 production compared to the control scrambled cells (Scr). The antioxidant N-acetylcysteine reversed the oxidative stress and reduced the gene expression of the pro-inflammatory cytokine tumor necrosis factor α (TNFα). Nrg4 KD adipocytes showed enhanced lipolysis and reduced lipogenesis, in addition to a significant reduction in several intermediates of the Krebs cycle. In summary, Nrg4 downregulation in adipocytes affects mitochondrial content and functioning, causing impaired cellular metabolism, which in turn results in oxidative stress, inflammation, and insulin resistance.

A Mendelian Randomization Study about Causal Associations between Tofu Consumption and Stroke as well as Related Subtypes

OBJECTIVE

Consuming soy in the diet is beneficial for health, and tofu possess the richest source of dietary soy. However, the specific association with stroke and related subtypes remains controversial. In this study, the genetic causal relationship among tofu and stroke as well as the subtypes was investigated by utilizing the data in a number of genome-wide association study (GWAS) based on population.

METHODS

The tofu intake GWAS analysis is derived from the Medical Research Council (MRC) Integrative Epidemiology Unit at the University of Bristol (MRC-IEU) Consortium. The two-sample Mendelian randomization (MR) study was carried out, utilizing multiple analysis methods to analyze the associations with stroke and related subtypes. The sensitivity, heterogeneity, and potential pleiotropy could be investigated by multiple analysis method.

RESULTS

We found that tofu intake had no causal relationship with stroke. However, in stroke subtype, there is a causal relationship among tofu intake with the risk of intracerebral hemorrhage (ICH) (odds ratio, OR = 1.24 × 10-5, 95% CI: 1.54 × 10-8-9.95 × 10-3, p = 9.300 × 10-4), while tofu intake does not affect the risk of ischemic stroke (OR = 1.07 × 10-1, 95% CI: 3.84 × 10-4-2.97 × 101, p = 4.362 × 10-1) and subarachnoid hemorrhage (SAH) (OR = 3.33 × 10-3, 95% CI: 1.79 × 10-6-6.18, p = 1.373 × 10-1). Both the Mendelian randomization PRESSO (MR-PRESSO) global test and Cochran's Q test did not detect any sensitivity and heterogeneity.

CONCLUSIONS

While tofu consumption is associated with a higher risk of ICH, it does not show a significant relationship with ischemic stroke or SAH. The varying effects of tofu on different stroke subtypes underscore the need for considering potential confounding dietary and lifestyle factors in future studies.

Branched-chain amino acids deficiency promotes diabetic cardiomyopathy by activating autophagy of cardiac fibroblasts

Rationale: More than half of the patients with type II diabetes mellitus (T2D) develop diabetic cardiomyopathy (DCM). Glycemic control alone cannot effectively prevent or alleviate DCM. Methods: Herein, we concentrated on the variations in levels of metabolites between DCM and T2D patients without cardiomyopathy phenotype. In high-fat diet/low-dose streptozotocin-induced T2D and leptin receptor-deficient diabetic mouse models, we investigated the effect of altering branched-chain amino acids (BCAAs) levels on DCM. Results: We discovered that the levels of plasma BCAAs are notably lower in 15 DCM patients compared to 19 T2D patients who do not exhibit cardiomyopathy phenotype, using nuclear magnetic resonance analysis. This finding was further validated in two additional batches of samples, 123 DCM patients and 129 T2D patients based on the BCAA assay kit, and 30 DCM patients and 30 T2D patients based on the LC-MS/MS method, respectively. Moreover, it is verified that BCAA deficiency aggravated, whereas BCAA supplementation alleviated cardiomyopathy phenotypes in diabetic mice. Furthermore, BCAA deficiency promoted cardiac fibroblast activation by stimulating autophagy in DCM mice. Mechanistically, BCAA deficiency activated autophagy via the AMPK-ULK1 signaling pathway in cardiac fibroblasts. Using pharmacological approaches, we validated our findings that autophagy inhibition relieved, whereas autophagy activation aggravated, DCM phenotypes. Conclusions: Taken together, we describe a novel perspective wherein BCAA supplementation may serve as a potential therapeutic agent to mitigate DCM and fibrosis. Our findings provide insights for the development of preventive measures for DCM.

Self-control study of multi-omics in identification of microenvironment characteristics in urine of uric acid stone

The aim of this study is to perform proteomic and metabolomic analyses in bilateral renal pelvis urine of patients with unilateral uric acid kidney stones to identify the specific urinary environment associated with uric acid stone formation. Using cystoscopy-guided insertion of ureteral catheters, bilateral renal pelvis urine samples are collected. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is employed to identify differentially expressed proteins and metabolites in the urine environment. Differentially expressed proteins and metabolites are further analyzed for their biological functions and potential metabolic pathways through Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In the urine from the stone-affected side, eight differential proteins were significantly upregulated, and six metabolites were dysregulated. The uric acid stone urinary environment showed an excess of α-ketoisovaleric acid and 3-methyl-2-oxovaleric acid, which may contribute to the acidification of the urine. Functional and pathway analyses indicate that the dysregulated metabolites are mainly associated with insulin resistance and branched chain amino acid metabolism.

Associations of Amino Acids with the Risk of Prediabetes: A Case-Control Study from Kazakhstan

BACKGROUND

The high global prevalence of prediabetes requires its early identification. Amino acids (AAs) have emerged as potential predictors of prediabetes. This study investigates the association between amino acids and prediabetes in the Kazakh population.

MATERIALS AND METHODS

In this case-control study, serum AAs levels were measured using the Trace GC 1310 gas chromatography system coupled with the TSQ 8000 triple quadrupole mass spectrometer (Thermo Scientific, Austin, TX, USA) followed by silylation with the BSTFA + 1% TMCS derivatization method. Biochemical parameters, including total cholesterol, HDL-C, LDL-C, triglycerides, fasting glucose, HbA1c, and Creatinine, were assessed for each participant. Trained professionals conducted anthropometric and physical examinations (which included taking blood pressure and heart rate measurements) and family history collection.

RESULTS

A total of 112 Kazakh individuals with prediabetes and 55 without prediabetes, aged 36-65 years, were included in the study. Only Alanine and valine showed a significant association with prediabetes risk among the 13 AAs analyzed. Our findings revealed an inverse relationship between Alanine and Valine and prediabetes in individuals of Kazakh ethnicity.

CONCLUSION

A lower serum level of Alanine and Valine may serve as a predictive biomarker for prediabetes in the Kazakh population.

Elevated BCAA catabolism reverses the effect of branched-chain ketoacids on glucose transport in mTORC1-dependent manner in L6 myotubes

Plasma levels of branched-chain amino acids (BCAA) and their metabolites, branched-chain ketoacids (BCKA), are increased in insulin resistance. We previously showed that ketoisocaproic acid (KIC) suppressed insulin-stimulated glucose transport in L6 myotubes, especially in myotubes depleted of branched-chain ketoacid dehydrogenase (BCKD), the enzyme that decarboxylates BCKA. This suggests that upregulating BCKD activity might improve insulin sensitivity. We hypothesised that increasing BCAA catabolism would upregulate insulin-stimulated glucose transport and attenuate insulin resistance induced by BCKA. L6 myotubes were either depleted of BCKD kinase (BDK), the enzyme that inhibits BCKD activity, or treated with BT2, a BDK inhibitor. Myotubes were then treated with KIC (200 μM), leucine (150 μM), BCKA (200 μM), or BCAA (400 μM) and then treated with or without insulin (100 nM). BDK depletion/inhibition rescued the suppression of insulin-stimulated glucose transport by KIC/BCKA. This was consistent with the attenuation of IRS-1 (Ser612) and S6K1 (Thr389) phosphorylation but there was no effect on Akt (Ser473) phosphorylation. The effect of leucine or BCAA on these measures was not as pronounced and BT2 did not influence the effect. Induction of the mTORC1/IRS-1 (Ser612) axis abolished the attenuating effect of BT2 treatment on glucose transport in cells treated with KIC. Surprisingly, rapamycin co-treatment with BT2 and KIC further reduced glucose transport. Our data suggests that the suppression of insulin-stimulated glucose transport by KIC/BCKA in muscle is mediated by mTORC1/S6K1 signalling. This was attenuated by upregulating BCAA catabolic flux. Thus, interventions targeting BCAA metabolism may provide benefits against insulin resistance and its sequelae.

Loss of atrial natriuretic peptide signaling causes insulin resistance, mitochondrial dysfunction, and low endurance capacity

Type 2 diabetes (T2D) and obesity are strongly associated with low natriuretic peptide (NP) plasma levels and a down-regulation of NP guanylyl cyclase receptor-A (GCA) in skeletal muscle and adipose tissue. However, no study has so far provided evidence for a causal link between atrial NP (ANP)/GCA deficiency and T2D pathogenesis. Here, we show that both systemic and skeletal muscle ANP/GCA deficiencies in mice promote metabolic disturbances and prediabetes. Skeletal muscle insulin resistance is further associated with altered mitochondrial function and impaired endurance running capacity. ANP/GCA-deficient mice exhibit increased proton leak and reduced content of mitochondrial oxidative phosphorylation proteins. We further show that GCA is related to several metabolic traits in T2D and positively correlates with markers of oxidative capacity in human skeletal muscle. Together, these results indicate that ANP/GCA signaling controls muscle mitochondrial integrity and oxidative capacity in vivo and plays a causal role in the development of prediabetes.

Causal relationship and mediation effects of immune cells and plasma metabolites in atopic dermatitis: A Mendelian randomization study

Atopic dermatitis (AD) is a chronic inflammatory skin condition with complex etiology involving genetic, environmental, and immunological factors. This study employs Mendelian randomization to explore the causal relationships between immune cell phenotypes and AD, and the mediating effects of plasma metabolites. Using data from European cohorts, we identified 7 immune cell phenotypes significantly associated with AD. Mediation analysis revealed that the alpha-ketobutyrate to 4-methyl-2-oxopentanoate ratio negatively regulates CCR2 on monocytes, while the glycerol to carnitine ratio positively regulates HLA-DR on CD14- CD16- cells. These findings underscore the critical role of metabolic pathways in modulating immune responses and suggest potential dietary and therapeutic interventions for AD management. Further research should consider more diverse populations to validate these findings.

BCKDH kinase promotes hepatic gluconeogenesis independent of BCKDHA

Elevated circulating branched-chain amino acids (BCAAs) are tightly linked to an increased risk in the development of type 2 diabetes mellitus. The rate limiting enzyme of BCAA catabolism branched-chain α-ketoacid dehydrogenase (BCKDH) is phosphorylated at E1α subunit (BCKDHA) by its kinase (BCKDK) and inactivated. Here, the liver-specific BCKDK or BCKDHA knockout mice displayed normal glucose tolerance and insulin sensitivity. However, knockout of BCKDK in the liver inhibited hepatic glucose production as well as the expression of key gluconeogenic enzymes. No abnormal gluconeogenesis was found in mice lacking hepatic BCKDHA. Consistent with the vivo results, BT2-mediated inhibition or genetic knockdown of BCKDK decreased hepatic glucose production and gluconeogenic gene expressions in primary mouse hepatocytes while BCKDK overexpression exhibited an opposite effect. Whereas, gluconeogenic gene expressions were not altered in BCKDHA-silenced hepatocytes. Mechanistically, BT2 treatment attenuated the interaction of cAMP response element binding protein (CREB) with CREB-binding protein and promoted FOXO1 protein degradation by increasing its ubiquitination. Our findings suggest that BCKDK regulates hepatic gluconeogenesis through CREB and FOXO1 signalings, independent of BCKDHA-mediated BCAA catabolism.

Association of childhood food consumption and dietary pattern with cardiometabolic risk factors and metabolomics in late adolescence: prospective evidence from 'Children of 1997' birth cohort

BACKGROUND

Healthy diet might protect against cardiometabolic diseases, but uncertainty exists about its definition and role in adolescence.

METHOD

In a subset of Hong Kong's 'Children of 1997' birth cohort (n=2844 out of 8327), we prospectively examined sex-specific associations of food consumption and dietary pattern, proxied by the Global Diet Quality Score (GDQS) at~12.0 years, with cardiometabolic risk factors and metabolomics at~17.6 years.

RESULT

Higher vegetable (-0.04 SD, 95% CIs: -0.09 to 0.00) and soy consumption (-0.05 SD, 95% CI: -0.09 to -0.01) were associated with lower waist-to-hip ratio. Higher fruit and vegetable consumption were associated with lower fasting glucose (p<0.05). Higher fish consumption was associated with 0.06 SD (95% CI: 0.01 to 0.10) high-density lipoprotein cholesterol and -0.07 SD (95% CI: -0.11 to -0.02) triglycerides. After correcting for multiple comparisons (p<0.001), higher fish, fruit and vegetable consumption were associated with higher fatty acid unsaturation, higher concentration and percentage of omega-3 and a lower ratio of omega-6/omega-3. At nominal significance (p<0.05), higher fish consumption was associated with lower very-low-density lipoprotein and triglycerides relevant metabolomics. Higher vegetable and fruit consumption were associated with lower glycolysis-related metabolomics. Lower sugar-sweetened beverages (SSBs) consumption was associated with lower branched-chain amino acids. Similar associations with adiposity and metabolomics biomarkers were observed for GDQS.

CONCLUSIONS

Higher consumption of fruit, vegetables and fish and lower ice cream and SSBs consumption were associated with lower cardiometabolic risk in adolescents.