Branched-chain amino acids in disease

Cross-feeding-based rational design of a probiotic combination of Bacterides xylanisolvens and Clostridium butyricum therapy for metabolic diseases

The human gut microbiota has gained interest as an environmental factor that contributes to health or disease. The development of next-generation live biotherapeutic products (LBPs) is a promising strategy to modulate the gut microbiota and improve human health. In this study, we identified a novel cross-feeding interaction between Bacteroides xylanisolvens and Clostridium butyricum and developed their combination into a novel LBP for treating metabolic syndrome. Using in-silico analysis and in vitro experiments, we demonstrated that B. xylanisolvens supported the growth and butyrate production of C. butyricum by supplying folate, while C. butyricum reciprocated by providing pABA for folate biosynthesis. Animal gavage experiments showed that the two-strain combination LBP exhibited superior therapeutic efficacy against metabolic disorders in high-fat diet-induced obese (DIO) mice compared to either single-strain treatment. Further omics-based analyses revealed that the single-strain treatments exhibited distinct taxonomic preferences in modulating the gut microbiota, whereas the combination LBP achieved more balanced modulation to preserve taxonomic diversity to a greater extent, thereby enhancing the stability and resilience of the gut microbiome. Moreover, the two-strain combinations more effectively restored gut microbial functions by reducing disease-associated pathways and opportunistic pathogen abundance. This work demonstrates the development of new LBP therapy for metabolic diseases from cross-feeding microbial pairs which exerted better self-stability and robust efficacy in complex intestinal environments compared to conventional single-strain LBPs.

Research on the release and absorption regularities of free amino acids and peptides in vitro digestion of yeast protein

Based on INFOGEST digestion model and Dynamic Human Stomach-Intestine in vitro (DHSI-IV), the content of free amino acids (FAAs) and peptides in yeast protein (YP) digestion products were analyzed, as well as the molecular weight distribution of digestive products. The transport and absorption of FAAs and peptides from YP static digestive products were studied by Caco-2 cells monolayer model. The highest content of branched-chain amino acids (BCAAs) and essential amino acids (EAAs) were highlighted during YP digestion. The digestibility of YP (97.66 %) was close to that of whey protein isolate (WPI), slightly higher than pea protein (PP), but significantly higher than soy protein isolate (SPI) (p < 0.05). More FAAs of YP were released in static digestion (755.40 mg/g) than in dynamic digestion (28.34 mg/g). Accordingly, more peptides of YP were released in dynamic digestion (433.76 mg/g) than in static digestion (44.44 mg/g). The intestinal phase released more FAAs and peptides than the gastric phase both static and dynamic digestion for these four proteins. Molecular weight distribution proportion of digestion products with <150 Da of the four proteins exceeded 50 %. After the absorption and transport, the absorption rate of FAAs for YP (92.75 %) was slightly lower than that of WPI. Large molecular weight peptides (>1000 Da) were not easily absorbed, and the highest distribution ratio of molecular weight with <150 Da (mainly FAAs) was detected. These proved that YP is the protein with a good quality, such as high digestive and absorption properties, which could be used as a beneficial supplement and partial replacement of animal and plant protein sources.

Valine acts as an early biomarker and exacerbates pathological cardiac hypertrophy by impairing mitochondrial quality control

OBJECTIVE

Pathological cardiac hypertrophy is an independent risk factor for heart failure (HF). Early identification and timely treatment are crucial for significantly delaying the progression of HF.

METHODS

Targeted amino acid metabolomics and RNA sequencing (RNA-seq) were combined to explore the underlying mechanism. In vitro, H9c2 cells were stimulated with angiotensin II (Ang II) or were incubated with extra valine after Ang II stimulation. The branched chain alpha-ketoate dehydrogenase kinase (Bckdk) inhibitor 3,6-dichlorobenzo[b]thiophene-2-carboxylic acid (BT2) and rapamycin were utilized to confirm the role of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway in this process.

RESULTS

A significant accumulation of valine was detected within hypertrophic hearts from spontaneously hypertensive rats (SHR). When branched chain amino acid (BCAA) degradation was increased by BT2, the most pronounced decrease was observed in the valine level (Δ = 0.185 μmol/g, p < 0.001), and cardiac hypertrophy was ameliorated. The role of imbalanced mitochondrial quality control (MQC), including the suppression of mitophagy and excessive mitochondrial fission, was revealed in myocardial hypertrophy. In vitro, high concentrations of valine exacerbated cardiomyocyte hypertrophy stimulated by Any II, resulting in the accumulation of impaired mitochondria and respiratory chain dysfunction. BT2, rapamycin, and mitochondrial division inhibitor 1 (Mdivi-1) all ameliorated MQC imbalance, mitochondrial damage and oxidative stress in hypertensive models with high valine concentration.

CONCLUSION

Valine exacerbated pathological cardiac hypertrophy by causing a MQC imbalance, probably as an early biomarker for cardiac hypertrophy under chronic hypertension.

Genome-wide association study of plasma amino acids and Mendelian randomization for cardiometabolic traits

Plasma amino acids (AAs) have emerged as promising biomarkers for metabolic disorders, yet their causality remains unclear. We aimed to investigate the genetic determinants of AA levels in a cohort of 10,333 individuals and their causal effects on cardiometabolic traits using Mendelian randomization (MR). Plasma levels of 20 AAs were quantified using capillary electrophoresis mass spectrometry. Genome-wide association studies were conducted using BOLT-LMM and heritability estimation via LDSC analysis. Causal effects of AAs on 11 cardiometabolic traits were examined using two-sample MR analyses. We identified 85 locus-metabolite associations across 43 genes for 18 AAs, including 44 novel loci linked to metabolic genes. Heritability for AAs was estimated at 16%. MR analysis demonstrated cystine to positively associate with systolic blood pressure (SBP) (β = 0.056, SE = 0.010), while serine indicated protective effects on SBP (β = - 0.040, SE = 0.011), diastolic BP (β = - 0.044, SE = 0.010), and coronary artery disease (odds ratio 0.888, SE = 0.028). We identified potentially novel genetic loci associated with AA levels and demonstrated robust causal associations between several AAs and cardiometabolic traits. These findings reinforce the importance of AAs as potential biomarkers and therapeutic targets in cardiometabolic health.

Endogenous Metabolites in Metabolic Diseases: Pathophysiologic Roles and Therapeutic Implications

Breakthroughs in metabolomics technology have revealed the direct regulatory role of metabolites in physiology and disease. Recent data have highlighted the bioactive metabolites involved in the etiology and prevention and treatment of metabolic diseases such as obesity, nonalcoholic fatty liver disease, type 2 diabetes mellitus, and atherosclerosis. Numerous studies reveal that endogenous metabolites biosynthesized by host organisms or gut microflora regulate metabolic responses and disorders. Lipids, amino acids, and bile acids, as endogenous metabolic modulators, regulate energy metabolism, insulin sensitivity, and immune response through multiple pathways, such as insulin signaling cascade, chemical modifications, and metabolite-macromolecule interactions. Furthermore, the gut microbial metabolites short-chain fatty acids, as signaling regulators have a variety of beneficial impacts in regulating energy metabolic homeostasis. In this review, we will summarize information about the roles of bioactive metabolites in the pathogenesis of many metabolic diseases. Furthermore, we discuss the potential value of metabolites in the promising preventive and therapeutic perspectives of human metabolic diseases.

Microbiome-metabolome dynamics associated with impaired glucose control and responses to lifestyle changes

Type 2 diabetes (T2D) is a complex disease shaped by genetic and environmental factors, including the gut microbiome. Recent research revealed pathophysiological heterogeneity and distinct subgroups in both T2D and prediabetes, prompting exploration of personalized risk factors. Using metabolomics in two Swedish cohorts (n = 1,167), we identified over 500 blood metabolites associated with impaired glucose control, with approximately one-third linked to an altered gut microbiome. Our findings identified metabolic disruptions in microbiome-metabolome dynamics as potential mediators of compromised glucose homeostasis, as illustrated by the potential interactions between Hominifimenecus microfluidus and Blautia wexlerae via hippurate. Short-term lifestyle changes, for example, diet and exercise, modulated microbiome-associated metabolites in a lifestyle-specific manner. This study suggests that the microbiome-metabolome axis is a modifiable target for T2D management, with optimal health benefits achievable through a combination of lifestyle modifications.

Lymphatic Endothelial Branched-Chain Amino Acid Catabolic Defects Undermine Cardiac Lymphatic Integrity and Drive HFpEF

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) has become the most prevalent type of heart failure, but effective treatments are lacking. Cardiac lymphatics play a crucial role in maintaining heart health by draining fluids and immune cells. However, their involvement in HFpEF remains largely unexplored.

METHODS

We examined cardiac lymphatic alterations in mice with HFpEF with comorbid obesity and hypertension, and in heart tissues from patients with HFpEF. Using genetically engineered mouse models and various cellular and molecular techniques, we investigated the role of cardiac lymphatics in HFpEF and the underlying mechanisms.

RESULTS

In mice with HFpEF, cardiac lymphatics displayed substantial structural and functional anomalies, including decreased lymphatic endothelial cell (LEC) density, vessel fragmentation, reduced branch connections, and impaired capacity to drain fluids and immune cells. LEC numbers and marker expression levels were also decreased in heart tissues from patients with HFpEF. Stimulating lymphangiogenesis with an adeno-associated virus expressing an engineered variant of vascular endothelial growth factor C (VEGFCC156S) that selectively activates vascular endothelial growth factor receptor 3 (VEGFR3) in LECs restored cardiac lymphatic integrity and substantially alleviated HFpEF. Through discovery-driven approaches, defective branched-chain amino acid (BCAA) catabolism was identified as a predominant metabolic signature in HFpEF cardiac LECs. Overexpression of branched-chain ketoacid dehydrogenase kinase (encoded by the Bckdk gene), which inactivates branched-chain ketoacid dehydrogenase (the rate-limiting enzyme in BCAA catabolism), resulted in spontaneous lymphangiogenic defects in LECs. In mice, inducible Bckdk gene deletion in LECs to enhance their BCAA catabolism preserved cardiac lymphatic integrity and protected against HFpEF. BCAA catabolic defects caused ligand-independent phosphorylation of VEGFR3 in the cytoplasm by Src kinase, leading to lysosomal degradation of VEGFR3 instead of its trafficking to the cell membrane. Reduced VEGFR3 availability on the cell surface impeded downstream Akt (protein kinase B) activation, hindered glucose uptake and utilization, and inhibited lymphangiogenesis in LECs with BCAA catabolic defects.

CONCLUSIONS

Our study provides evidence that cardiac lymphatic disruption, driven by impaired BCAA catabolism in LECs, is a key factor contributing to HFpEF. These findings unravel the crucial role of BCAA catabolism in modulating lymphatic biology, and suggest that preserving cardiac lymphatic integrity may present a novel therapeutic strategy for HFpEF.

Dietary branched-chain amino acids intake and coronary artery calcium progression: insights from the coronary artery risk development in young adults (CARDIA) study

OBJECTIVE

Branched-chain amino acids (BCAA) have been implicated in the risk of cardiovascular disease. However, it is unclear whether dietary BCAA intake, specifically isoleucine, leucine, and valine are associated with coronary artery calcium (CAC) progression.

METHODS

We included the participants from the Coronary Artery Risk Development in Young Adults (CARDIA) study cohort for the analysis. Dietary intake of BCAA was assessed at year 7 of the study. CAC was measured using standardized computed tomography scans at years 15, 20, and 25. CAC progression was defined as follows: for participants with a baseline CAC of 0, progression was defined as CAC > 0 at follow-up; for those with 0 < baseline CAC < 100, progression was defined as an annualized change of ≥ 10; and for those with baseline CAC ≥ 100, progression was defined as an annualized percent change of ≥ 10%. Multivariate adjusted Cox regression models were utilized to examine the associations between BCAA intake and CAC progression.

RESULTS

Among 2381 included participants (average age 40.4 ± 3.5 years, 44.9% men), 629 participants (26.4%) exhibited CAC progression during a follow-up period of 8.90 ± 2.03 years. In the fully adjusted model, high intake of total BCAA, and its individual components, isoleucine, leucine, and valine were associated with an increased risk of CAC progression by 35.6% (HR, 1.356 [95% CI, 1.040-1.769]), 30.5% (HR, 1.305 [95% CI, 1.001-1.701]), 30.9% (HR, 1.309 [95% CI, 1.003-1.706]), and 33.9% (HR, 1.339 [95% CI, 1.026-1.747]), respectively, compared to their corresponding low intake groups. The associations were consistent across various subgroups, including age, sex, race, and body mass index, but were stronger in participants without baseline CAC (interaction P < 0.001). These results remained robust in a series of sensitivity analyses.

CONCLUSIONS

High dietary intake of BCAA, including isoleucine, leucine, and valine, were independently associated with an increased risk of CAC progression. The findings may implication for dietary modifications in primary prevention of subclinical atherosclerosis.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov ; Unique identifier: NCT00005130.

Multi-omic profiling of sarcopenia identifies disrupted branched-chain amino acid catabolism as a causal mechanism and therapeutic target

Sarcopenia is a geriatric disorder characterized by a gradual loss of muscle mass and function. Despite its prevalence, the underlying mechanisms remain unclear, and there are currently no approved treatments. In this study, we conducted a comprehensive analysis of the molecular and metabolic signatures of skeletal muscle in patients with impaired muscle strength and sarcopenia using multi-omics approaches. Across discovery and replication cohorts, we found that disrupted branched-chain amino acid (BCAA) catabolism is a prominent pathway in sarcopenia, which leads to BCAA accumulation and decreased muscle health. Machine learning analysis further supported the causal role of BCAA catabolic dysfunction in sarcopenia. Using mouse models, we validated that defective BCAA catabolism impairs muscle mass and strength through dysregulated mTOR signaling, and enhancing BCAA catabolism by BT2 protects against sarcopenia in aged mice and in mice lacking Ppm1k, a positive regulator of BCAA catabolism in skeletal muscle. This study highlights improving BCAA catabolism as a potential treatment of sarcopenia.

Branched-chain amino acids promote hepatic Cyp7a1 expression and bile acid synthesis via suppressing FGF21-ERK pathway

Branched-chain amino acids (BCAAs) including leucine, isoleucine and valine have been linked with metabolic and cardiovascular diseases. BCAAs homeostasis is tightly controlled by their catabolic pathway. BCKA dehydrogenase (BCKD) complex is the rate-limiting step for BCAA catabolism. Mitochondrial phosphatase 2C (PP2Cm) dephosphorylates the BCKD E1alpha subunit and activates BCKD complex. Deficiency of PP2Cm impairs BCAA catabolism, leading to higher plasma BCAA concentrations. Emerging evidence shows that bile acids are key regulators of glucose, lipid and energy metabolism. In this study, we investigated whether a direct link existed between BCAAs and bile acids metabolism. Wild-type mice were fed with normal-BCAA or high-BCAA diet, while PP2Cm deficiency mice were fed with normal chow for 14 weeks. The mice were fasted for 6 h before tissue harvest to exclude metabolic changes due to immediate food intake. We showed that the bile acids in tissues and feces were significantly elevated in wild-type mice fed with high-BCAA diet as well as in PP2Cm deficiency mice fed with normal chow. These mice displayed significantly increased expression of cholesterol 7 alpha-hydroxylase (CYP7A1), the rate-limiting enzyme of bile acid synthesis in liver, and 7α-hydroxy-4-cholesten-3-one (C4), a freely diffusible metabolite downstream of CYP7A1 in plasma. BCAAs induced Cyp7a1 expression in cultured hepatocytes. In mouse liver and cultured hepatocytes, we demonstrated that elevated BCAAs inhibited fibroblast growth factor 21 (FGF21) expression and ERK signaling pathway. Direct inhibition of ERK by U0126 (800 nM) markedly induced Cyp7a1 expression in cultured hepatocytes. Moreover, the induced Cyp7a1 expression and inhibitory effects of BCAAs on ERK signaling pathway were abolished by treatment with recombinant FGF21 protein in mouse liver and cultured hepatocytes. Collectively, this study demonstrates a direct link between BCAAs and bile acid synthesis. BCAAs promotes Cyp7a1 expression and bile acid synthesis in liver via inhibiting FGF21-ERK signaling pathway. BCAAs-regulated bile acid synthesis and homeostasis may contribute to developing novel therapeutic strategies for the treatment of metabolic disorders.

Circulating branched-chain amino acids and the risk of major adverse cardiovascular events in the UK biobank

Objective

To investigate the relationship between circulating branched-chain amino acids (BCAAs) and the risk of major adverse cardiovascular events (MACE) in a national population-based cohort study.

Methods

UK Biobank, a prospective study involving 22 recruitment centers across the United Kingdom. For this analysis, we included 266,840 participants from the UK Biobank who had available BCAA data and no history of MACE at baseline. Cox regression analysis was conducted to evaluate these associations, adjusting for potential confounders.

Results

During a 13.80 ± 0.83-year follow-up, 52,598 participants experienced MACE, with the incidence of MACE increasing progressively across quintiles of circulating BCAAs, isoleucine, leucine, and valine. Overall, the fifth quintile exhibited a 7-12% higher MACE risk compared to the second quintile. In males, BCAAs were not associated with MACE risk. However, increased risks were observed for isoleucine (8-12% in higher quintiles), leucine (9% in the first quintile and 6% in the fifth quintile), and valine (8% in the first quintile). In females, higher quintiles of BCAAs, isoleucine, leucine, and valine were associated with increased MACE risk, ranging from 9% to 12%. Among participants under 65y, higher quintiles of BCAAs, isoleucine, and leucine were associated with increased MACE risk, while valine showed no significant association. No association was found in participants aged 65 and older. These analyses were adjusted for multiple potential confounders.

Conclusion

Generally, higher levels of BCAAs, isoleucine, leucine, and valine were associated with an increased risk of MACE, except in participants older than 65. Additionally, in males, the lowest quintiles of leucine and valine were also associated with an increased risk of MACE.

Dietary Branched-Chain Amino Acids Modify Postinfarct Cardiac Remodeling and Function in the Murine Heart

BACKGROUND

Branched-chain amino acids (BCAAs), which are derived from the diet, are markedly elevated in cardiac tissue following myocardial infarction (MI). Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling.

METHODS

To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, we fed mice a low or a high BCAA diet for 2 weeks before MI and for 4 weeks after MI. Cardiac structural and functional changes were evaluated by echocardiography, gravimetry, and histopathological analyses. Immunoblotting was used to evaluate the effects of BCAAs on isolated cardiac myofibroblast differentiation.

RESULTS

The low BCAA diet decreased circulating BCAA concentrations by >2-fold when compared with the high BCAA diet. Although neither body weights nor heart masses were different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. The low BCAA diet preserved stroke volume and cardiac output after MI, whereas the high BCAA diet promoted progressive decreases in cardiac function. Although BCAAs were required for myofibroblast differentiation in vitro, cardiac fibrosis, scar collagen topography, and cardiomyocyte cross-sectional area were not different between the dietary groups; however, male mice fed the high BCAA diet had longer cardiomyocytes and higher capillary density compared with the low BCAA group.

CONCLUSIONS

A low BCAA diet mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI in mice, with dietary effects more prominent in males.

Obesity and Cardiometabolic Disease: Insights From Genetic Studies

Obesity is a highly prevalent chronic disease and major driver of both atherosclerotic heart disease and heart failure. Obesity is also a heritable neuronal disease with heritability estimates of up to 70%. In this work I review how common genetic variants, usually with small effect sizes, contribute to the risk for developing obesity and cardiometabolic disease in the majority of people and how this can be further modulated by environmental factors. In some individuals, rare genetic variants with large effect sizes can influence the risk of developing obesity, in some cases in a Mendelian manner. I also address how identification of these rare variants has led to fundamental biologic insights into how satiety and reward are biologic processes, has led to more personalized treatments, and has identified potential novel drug treatments. Biologic insights derived from genetic studies of obesity have also improved our understanding of the causal mediators between obesity and cardiovascular disease. A major limitation of studies to date is that they involved mostly people of European ancestry. Studying more diverse populations will improve our understanding of obesity and cardiometabolic disease. Lessons derived from genetic studies make a compelling case for increasing accessibility to therapies that have sustained efficacy in managing obesity and improving health. This increased knowledge must also inform public health initiatives that will reduce the prevalence of obesity in the coming decades.

Serum homocysteine is a biomarker for hearing loss associated with or without cardiovascular risk: a cross-sectional study in men

PURPOSE

Hearing loss (HL) represents a major health problem worldwide, and increasingly so due to population ageing and new leisure activities, such as video gaming or virtual reality experiences. HL has a multifactorial origin including both genetic and environmental issues with nutrition status emerging as a new contributing factor. In fact, certain micronutrient deficiencies, along with excessive consumption of specific macronutrients, have been related to HL This study aimed to examine the association of HL with dietary fat intake, nutritional status biomarkers, and serum metabolic signature in aviation pilots and controls.

METHODS

A cohort of aviation pilots, chronically exposed to noise pollution at work, was compared to a cohort of non-exposed university workers (controls). Hearing function was determined by tonal audiometry and dietary fat intake was assessed by three 24-h recalls. In addition, lipoprotein profiles as well as serum homocysteine (Hcy), folate, vitamins B12 and D were analysed. Two multiple linear regression models adjusted for age were constructed to explain HL variability.

RESULTS

HL prevalence was similar and elevated in both cohorts (controls: 64% vs. noise-exposed: 65%), when compared to the American Speech-Language-Hearing Association (ASHA) classification. When comparing both cohorts, although no significant differences were found in Hcy and folate levels, controls had significantly lower vitamins B12 and D concentrations and, conversely, higher serum lipids and lipoprotein values (triglycerides, total cholesterol, HDL-cholesterol and LDL-cholesterol subfractions), suggesting the possible involvement of CV risk in HL in the control cohort. In the noise-exposed cohort, HL was associated with flight hours, Hcy, and folate (r2 = 0.439), while in controls, HL was associated with Hcy and vitamin D (r2 = 0.474). After adjusting for CV profile, the positive association between HL and Hcy was maintained (β = 0.444; p < 0.001), evidencing the strong involvement of this metabolite not only in CV risk, but also in HL.

CONCLUSION

Folate insufficiency together with hyperhomocysteinemia increased susceptibility to noise-induced HL. However, the role of Hcy in HL without noise exposure at work seems to be partially masked by an altered CV profile.

Reducing Dietary Branched-Chain Amino Acids Intake Alleviates High-Fat Diet-Induced Pain Sensitization and Postoperative Pain in Male Mice

BACKGROUND

Poor dietary intake is associated with peripheral pain sensitization and postoperative pain. Given the limited research on diet and pain, it is essential to examine the possible analgesic effects of dietary interventions in preclinical studies.

OBJECTIVES

This study aimed to elucidate the role of high-fat diet (HFD) on pain sensitivity and postoperative pain, and determine the potential effects of modulating branched-chain amino acids (BCAA) intake on pain phenotypes.

METHODS

Four-week-old male mice were fed a purified control diet (CD) or HFD for 10 wk, followed by a hind paw incision. Four-week-old male mice were initially fed a CD or HFD for 8 wk, then switched to the high or low BCAA diet, and underwent a hind paw incision at 10 wk of these diets. Pain behaviors were assessed. Several proinflammatory genes in the lumbar dorsal root ganglion (DRG) were detected by quantitative polymerase chain reaction. Immunohistochemistry was used to estimate nerve fiber density at the incision site. Two-tailed unpaired Student's t-test, 2-way repeated-measures analysis of variance (ANOVA) with Bonferroni posttests, and 1-way ANOVA with Tukey's multiple comparisons test were used for data analysis.

RESULTS

HFD consumption induced pain sensitization and worsened postoperative pain in male mice (P < 0.0001). In CD group, mice switching to high or low BCAA diet displayed minor impacts on pain phenotypes. In HFD mice, switching to high BCAA diet exacerbated hyperalgesia and postsurgical pain (P < 0.05), leading to proinflammatory responses in the DRG and the reduction of nerve fiber density near the incision site on day 3 postsurgery (P < 0.05); whereas low BCAA diet intake alleviated these effects (P < 0.05).

CONCLUSIONS

High BCAA intake has negative impacts on pain sensitivity and postoperative pain in HFD-fed mice. Reducing dietary BCAA may be a novel nonpharmacological therapeutic to relieve pain in individuals on a conventional HFD.

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.

Comparative study of the anti-obesity effects of white tea and dark tea: Insights from microbiome and metabolomics

The anti-obesity effects of tea and its functional components have been extensively studied. However, the protective effects of different types of tea against obesity induced by a high-fat diet (HFD) and the underlying mechanisms remain unclear. This study systematically compared the effects of white tea and dark tea on obese rats and explored their mechanisms. The results indicated that dark tea extracts (DT) higher concentrations of theabrownins and gallic acid, while white tea extracts (WT) contained abundant levels of polyphenols and amino acids. Moreover, both WT and DT effectively improved obesity-related symptoms, including weight loss, reduced fat accumulation, improved dyslipidemia, and alleviated liver and colon damage. Specifically, WT primarily functioned by inhibiting white fat accumulation and enhancing UCP1 expression in brown fat, leading to more significant weight loss. Conversely, DT increased both the quantity and uniform distribution of colonic goblet cells and elevated the expression levels of tight junction proteins in obese rats, thereby providing better protection for the intestinal barrier. Furthermore, 16S rRNA sequencing revealed that WT and DT regulated gut microbiota imbalances, restored microbiota diversity, inhibited the growth of potentially harmful bacteria, and promoted the proliferation of beneficial bacteria. Metabolomics analyses demonstrated that WT and DT increased the concentration of short-chain fatty acids in the feces of obese rats, regulated the biosynthesis of phenylalanine, tyrosine, and tryptophan, as well as the biosynthesis pathways of valine, leucine, and isoleucine, while decreasing the levels of these amino acids in feces. In conclusion, this study provides new evidence supporting the idea that tea can mitigate HFD-induced obesity through the regulation of gut microbiota and alteration of fecal metabolite profiles.

Exploring the action mechanism and effective components of Yupingfeng powder on influenza based on computational system pharmacology and metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

Yupingfeng powder (YPF) is a classic traditional Chinese medicine prescription with a long history of clinical application. However, there is a consensus on the clinical efficacy of YPF in the prevention and treatment of influenza, the underlying pharmacological mechanisms and functional substances have not been thoroughly investigated.

AIM OF THE STUDY

This study aimed to elucidate the functional substances and potential mechanisms of YPF against influenza infections by integrating network analysis, metabolomics, computational system pharmacology, and in vitro experiments.

MATERIALS AND METHODS

In this study, the active ingredients, related targets, and potential mechanisms of YPF against influenza were identified through network pharmacology and GEO database mining. Combined with metabolomics to corroborate the results of network pharmacology analysis and construct C-T-P-D-M network. Based on this, the key network motifs (KNM) with significance were predicted by system pharmacology algorithm. Finally, the key components as functional substances in the KNM were validated by the coverage of influenza-causing genes and functional pathways, and in vitro experiments.

RESULTS

A total of 238 active components and 158 potential target genes intersecting with influenza infection differential genes were screened from YPF. KEGG enrichment analysis indicated that metabolism participated in YPF-provided prevention and treatment on influenza, and metabolomic results further corroborated the significance of the metabolic pathways intervened by YPF included pyruvate metabolism, Valine, leucine and isoleucine degradation, etc. The KNM prediction strategy was computed to include wogonin and isoimperaporin, a group of 48 potential functional components. This functional component group maintained a high degree of consistency with the corresponding C-T network in terms of the coverage of influenza pathogenic genes, and the coverage of functional pathways. Meanwhile, the in vitro results showed that wogonin and isoimperaporin had significant inhibitory effects on inflammation induced by influenza infection, confirming the reliability and accuracy of the KNM prediction strategy.

CONCLUSION

YPF against influenza has multi-target and multi-pathway effects, and the underlying mechanisms may be related to metabolism. The pharmacodynamic effects of core components such as wogonin and isoimperaporin on influenza prevention and treatment were confirmed, which represent promising functional candidates for subsequent influenza prevention and treatment, and provide references for the pharmacological and mechanistic analyses of subsequent formulas.

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.

Gut-brain axis and brain health: modulating neuroinflammation, cognitive decline, and neurodegeneration

The microbiota-gut-brain axis is a pivotal medium of crosstalk between the central nervous system (CNS) and the gastrointestinal tract. It is an intricate network of synergistic molecular pathways that exert their effects far beyond their local vicinity and even affect the systemic functioning of the body. The current review explores the involvement of the gut-brain axis (GBA) in the functioning of the nervous system, with a special emphasis on the neurodegeneration, cognitive decline, and neuroinflammation that occur in Alzheimer's disease (AD) and Parkinson's disease (PD). Gut-derived microbial metabolites play an important role in facilitating this interaction. We also highlighted the complex interaction between gut-derived metabolites and CNS processes, demonstrating how microbial dysbiosis might result in clinical disorders. Short-chain fatty acids have neuroprotective properties, whereas branched-chain amino acids, trimethylamine-N-oxide (TMAO), and tryptophan derivatives such as indole have negative effects at high concentrations. Furthermore, we cover pharmaceutical and nonpharmacological approaches for restoring the gut microbial balance and promoting neurological health. We further expanded on nutritional therapies and lifestyle changes, such as the Mediterranean diet and exercise. Next, we focused on food-controlling habits such as caloric restriction and intermittent fasting. Moreover, interventional techniques such as prebiotics, probiotics, and pharmacological medications have also been utilized to modify the GBA. Historical microbiome research from early discoveries to recent studies linking gut health to cognitive and emotional well-being has increased our understanding of the GBA.

The role of metabolites in the progression of osteoarthritis: Mechanisms and advances in therapy

Osteoarthritis (OA) is a progressive degenerative disease affected by many factors, and there is currently no effective treatment. In recent years, the latest progress in metabolomics in OA research has revealed several metabolic pathways and new specific metabolites involved in OA. Metabolites play significant roles in the identification and management of OA. This review looks back on the development history of metabolomics and the progress of this technology in OA as well as its potential clinical applications. It summarizes the applications of metabolites in the field of OA and future research directions. This understanding will advance the identification of metabolic treatment goals for OA.

The translational potential of this article

The development of metabolomics offers possibilities for the treatment of OA. This article reviews the relationship between metabolites associated with chondrocytes and OA. Selectively altering these three metabolic pathways and their associated metabolites may hold great potential as new focal points for OA treatment.

The Potential of Metabolomics as a Tool for Identifying Biomarkers Associated with Obesity and Its Complications: A Scoping Review

Obesity and its related diseases, such as type 2 diabetes (T2DM), cardiovascular disease (CVD), and metabolic fatty liver disease (MAFLD), require new diagnostic markers for earlier detection and intervention. The aim of this study is to demonstrate the potential of metabolomics as a tool for identifying biomarkers associated with obesity and its comorbidities in every age group. The presented systematic review makes an important contribution to the understanding of the potential of metabolomics in identifying biomarkers of obesity and its complications, especially considering the influence of branched-chain amino acids (BCAAs), amino acids (AAs) and adipokines on the development of T2DM, MAFLD, and CVD. The unique element of this study is the combination of research results from the last decade in different age groups and a wide demographic range. The review was based on the PubMed and Science Direct databases, and the inclusion criterion was English-language original studies conducted in humans between 2014 and 2024 and focusing on the influence of BCAAs, AAs or adipokines on the above-mentioned obesity complications. Based on the PRISMA protocol, a total of 21 papers were qualified for the review and then assigned to a specific disease entity. The collected data reveal that elevated levels of BCAAs and some AAs strongly correlate with insulin resistance, leading to T2DM, MAFLD, and CVD and often preceding conventional clinical markers. Valine and tyrosine emerge as potential markers of MAFLD progression, while BCAAs are primarily associated with insulin resistance in various demographic groups. Adipokines, although less studied, offer hope for elucidating the metabolic consequences of obesity. The review showed that in the case of CVDs, there is still a lack of studies in children and adolescents, who are increasingly affected by these diseases. Moreover, despite the knowledge that adipokines play an important role in the pathogenesis of obesity, there are no precise findings regarding the correlation between individual adipokines and T2DM, MAFLD, or CVD. In order to be able to introduce metabolites into the basic diagnostics of obesity-related diseases, it is necessary to develop panels of biochemical tests that will combine them with classical markers of selected diseases.

In Situ Regenerable Molecularly Imprinted Polymer Biosensor for Electrochemical Detection of Nonelectroactive Branched-Chain Amino Acids in Human Sweat

The significant challenge in achieving in situ regeneration for conventional molecularly imprinted polymers (MIPs) restricts their promising application in continuous monitoring of biochemical molecules closely related to human health, especially nonelectroactive molecules. This is because they are either limited to a single use or require removal of imprinted templates through chemical washing steps, which is clearly impractical for sustainable monitoring. Here, a class of in situ regenerable MIP biosensors, taking nonelectroactive branched-chain amino acids (BCAAs) as templates and methyldopa as a functional monomer, was engineered to achieve repeatable in situ regeneration and in situ target recognition. The in situ regeneration was realized through an amperometric i-t technique with a negative voltage (-0.9 V) according to intrinsic isoelectric points of analytes instead of conventional wash steps. This electrochemical extraction process not only maximally repelled the imprinted templates, creating a large number of cavities (recognition sites) and significantly enhancing sensitivity, but also ensured the successful in situ regeneration of developed biosensing interfaces. The template extraction was evaluated by examining changes in the surface morphology, elemental composition, distribution, content, and interfacial properties. The developed BCAA MIP biosensors achieved sensitive target detection with the linear range from 0.001 to 10.0 μg/mL and limits of detection down to 0.45 (Leu), 0.47 (Ile), and 0.31 (Val) ng/mL. Beyond that, the biosensors demonstrated an excellent ability in decreasing biofouling, realizing repeatable in situ target detection in human sweat, and the obtained results were highly consistent with those of the enzyme-linked immunosorbent assay, indicating high feasibility, reliability, and accuracy in practical application. Meanwhile, the biosensors showed excellent specificity, selectivity, and stability.

Current study of pathogenetic mechanisms and therapeutics of chronic atrophic gastritis: a comprehensive review

Chronic atrophic gastritis (CAG) is a prevalent digestive system disease characterized by atrophy of the gastric mucosa and the disappearance of inherent gastric glands. According to the theory of Correa's cascade, CAG is an important pathological stage in the transformation from normal condition to gastric carcinoma. In recent years, the global incidence of CAG has been increasing due to pathogenic factors, including Helicobacter pylori infection, bile reflux, and the consumption of processed meats. In this review, we comprehensively described the etiology and clinical diagnosis of CAG. We focused on elucidating the regulatory mechanisms and promising therapeutic targets in CAG, with the expectation of providing insights and theoretical support for future research on CAG.

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.

Intracellular metabolome elucidates the time-of-day-dependent response to hydrogen peroxide in salmonid gill epithelial cells

The internal timekeeping system regulates the daily cycle of physiological and behavioural changes in living organisms. This rhythmic phenomenon also influences cellular responses to reactive oxygen species, such as hydrogen peroxide (H2O2). However, the temporal interaction between H2O2 and fish mucosal cells is not well understood. This study examined the temporal variations of immunological and physiological responses to H2O2 in salmonid gill cells using the RTgill-W1 cell line. The results showed that gene expression levels varied during a 24-h cycle but did not exhibit rhythmicity. The presence of a 12-h light-dark cycle (12L:12D) signal increased gene expression levels compared to a 24-h dark cycle (0L:24D). To investigate whether the time of day affects the defences in gills, cells were exposed to H2O2 at two different times (Zeitgebertime 2, ZT2, or ZT14). Although significant expression changes were observed in genes related to stress and NF-κB signalling, only a limited time-dependent pattern of response to H2O2 was observed. The intracellular metabolome of gill cells was primarily composed of organic acid and derivatives, organoheterocyclic compounds, benzoids, organic oxygen and nitrogen compounds. Exposure to H2O2 at ZT2 led to significant changes in the metabolome compared to the control group, while no such changes were observed at ZT14. Within the control groups, the concentrations of 11 metabolites significantly varied between ZT2 and ZT14, with higher levels at ZT14. These metabolites were involved in arginine biosynthesis, amino acid metabolism, and nitrogen metabolism. In contrast, the level of 26 metabolites significantly varied between ZT2 and ZT14 in H2O2-exposed groups, with lower levels at ZT14. Comparing control and H2O2-exposed groups at ZT2, 38 metabolites were affected, primarily organic acid and derivatives and organic oxygen compounds. Functional annotation revealed that these altered metabolites were involved in 15 different pathways, with valine, leucine, and isoleucine biosynthesis being the most affected. This study reveals the presence of a time-dependent response to H2O2 in salmonid gill cells, which is reflected in the intracellular metabolome. The findings provide new insights into the temporal regulation of mucosal defences in fish.

Ameliorating effects of Orostachys japonica against high-fat diet-induced obesity and gut dysbiosis

ETHNOPHARMACOLOGICAL RELEVANCE

Orostachys japonica (rock pine) has been used as a folk remedy to treat inflammation, hepatitis, and cancer in East Asia.

AIM OF THE STUDY

The aim of this study was to investigate the effect of rock pine extract (RPE) on high-fat diet-induced obesity in mice and to examine its effects on gut dysbiosis.

MATERIALS AND METHODS

The characteristic compound of RPE, kaempferol-3-O-rutinoside, was quantified using high-performance liquid chromatography. The prebiotic potential of RPE was evaluated by assessing the prebiotic activity score obtained using four prebiotic strains and high-fat (HF)-induced obesity C57BL/6 mice model. Analysis included examining the lipid metabolism and inflammatory proteins and evaluating the changes in gut permeability and metabolites to elucidate the potential signaling pathways involved.

RESULTS

In vitro, RPE enhanced the proliferation of beneficial probiotic strains, including Lactiplantibacillus and Bifidobacterium. HF-induced model showed that the administration of 100 mg/kg/day of RPE for 8 weeks significantly (p < 0.05) reduced the body weight, serum lipid levels, and insulin resistance, which were associated with notable changes in lipid metabolism and inflammation-related markers.

CONCLUSIONS

Our results demonstrate that rock pine consumption could mitigate obesity and metabolic endotoxemia in HF-fed mice through enhancing intestinal environment.

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.

The impact of small intestinal bacterial overgrowth on the efficacy of fecal microbiota transplantation in patients with chronic constipation

To investigate the impact of Small Intestinal Bacterial Overgrowth (SIBO) on the efficacy of Fecal Microbiota Transplantation (FMT) in patients with chronic constipation, our research team included 218 patients with chronic constipation treated with FMT. Based on the results of the SIBO breath test, the patients were divided into two groups: the constipation with SIBO group (SIBO) and the constipation without SIBO group (non-SIBO). The efficacy of the two groups was evaluated using constipation-related scoring scales. At the same time, feces and small intestinal fluid samples were collected from both groups before and after FMT to compare the changes in the intestinal microbiota through 16S rRNA sequencing. In this study, it was found that the clinical efficacy of FMT in the SIBO group was superior to that in the non-SIBO group. After FMT treatment, both groups showed a significant increase in bowel frequency and improvement in stool characteristics. Abdominal symptoms, rectal symptoms, and defecation symptoms were significantly alleviated (P < 0.05), and patients' quality of life was significantly enhanced (P < 0.05). After FMT, except for the Constipation Assessment Scale scores, other scale scores showed significant differences between the two groups, the SIBO group scoring significantly better than the non-SIBO group (P < 0.05). After FMT, there were minor changes in the colonic microbiota but more substantial changes in the small intestinal microbiota. At baseline, the SIBO group had a higher abundance of Veillonella, and lower abundances of Escherichia-Shigella and Acinetobacter compared to the non-SIBO group. Chronic constipation patients with SIBO have a better response to FMT than those without SIBO.

IMPORTANCE

Existing studies have rarely considered the impact of the small intestine's microbial state on the efficacy of fecal microbiota transplantation (FMT), nor have they extensively explored the effect of the small intestine's microbial state on the recovery of colonic motility. Therefore, this study investigates the influence of small intestinal bacterial overgrowth (SIBO) on the efficacy of FMT in treating constipation, specifically the impact of the microbial state of the small intestine on the restoration of colonic homeostasis, and consequently on the recovery of colonic motility.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

Branched-Chain Amino Acids Deficiency Promotes Diabetic Neuropathic Pain Through Upregulating LAT1 and Inhibiting Kv1.2 Channel

Diabetic neuropathic pain (DNP), one of the most common complications of diabetes, is characterized by bilateral symmetrical distal limb pain and substantial morbidity. To compare the differences  is aimed at serum metabolite levels between 81 DNP and 73 T2DM patients without neuropathy and found that the levels of branched-chain amino acids (BCAA) are significantly lower in DNP patients than in T2DM patients. In high-fat diet/low-dose streptozotocin (HFD/STZ)-induced T2DM and leptin receptor-deficient diabetic (db/db) mouse models, it is verified that BCAA deficiency aggravated, whereas BCAA supplementation alleviated DNP symptoms. Mechanistically, using a combination of RNA sequencing of mouse dorsal root ganglion (DRG) tissues and label-free quantitative proteomic analysis of cultured cells, it is found that BCAA deficiency activated the expression of L-type amino acid transporter 1 (LAT1) through ATF4, which is reversed by BCAA supplementation. Abnormally upregulated LAT1 reduced Kv1.2 localization to the cell membrane, and inhibited Kv1.2 channels, thereby increasing neuronal excitability and causing neuropathy. Furthermore, intraperitoneal injection of the LAT1 inhibitor, BCH, alleviated DNP symptoms in mice, confirming that BCAA-deficiency-induced LAT1 activation contributes to the onset of DNP. These findings provide fresh insights into the metabolic differences between DNP and T2DM, and the development of approaches for the management of DNP.

Interactions between Gut Microbiota and Natural Bioactive Polysaccharides in Metabolic Diseases: Review

The gut microbiota constitutes a complex ecosystem, comprising trillions of microbes that have co-evolved with their host over hundreds of millions of years. Over the past decade, a growing body of knowledge has underscored the intricate connections among diet, gut microbiota, and human health. Bioactive polysaccharides (BPs) from natural sources like medicinal plants, seaweeds, and fungi have diverse biological functions including antioxidant, immunoregulatory, and metabolic activities. Their effects are closely tied to the gut microbiota, which metabolizes BPs into health-influencing compounds. Understanding how BPs and gut microbiota interact is critical for harnessing their potential health benefits. This review provides an overview of the human gut microbiota, focusing on its role in metabolic diseases like obesity, type II diabetes mellitus, non-alcoholic fatty liver disease, and cardiovascular diseases. It explores the basic characteristics of several BPs and their impact on gut microbiota. Given their significance for human health, we summarize the biological functions of these BPs, particularly in terms of immunoregulatory activities, blood sugar, and hypolipidemic effect, thus providing a valuable reference for understanding the potential benefits of natural BPs in treating metabolic diseases. These properties make BPs promising agents for preventing and treating metabolic diseases. The comprehensive understanding of the mechanisms by which BPs exert their effects through gut microbiota opens new avenues for developing targeted therapies to improve metabolic health.

Transcriptomics and UHPLC-QQQ-MS analyses reveal the dysregulation of branched chain amino acids metabolism in renal fibrotic rats

The dysregulated levels of branched chain amino acids (BCAA) contribute to renal fibrosis in chronic kidney disease (CKD), yet specific analysis of BCAA contents and how they are regulated still remain unclear. It is therefore of great scientific interest to understand BCAA catabolism in CKD and develop a sensitive method for simultaneous determination of individual BCAA and their metabolites branched chain α-ketoacids (BCKA). In this work, the important role of BCAA metabolism that drives renal fibrosis in the process of CKD was first revealed by using transcriptomics. The key target genes controlling BCAA metabolism were then validated, that is, mRNA levels of BCKDHA and BCKDHB, the regulating rate-limiting enzymes during BCAA metabolism were abnormally reduced by quantitative PCR (qPCR), and a similar drop-off trend of protein expression of BCKDH, HIBCH and MCCC2 that are closely related to BCAA metabolism was also confirmed by western blotting. Furthermore, we established a novel strategy that simultaneously determines 6 individual BCAA and BCKA in serum and tissue. The method based on dansylhydrazine derivatization and ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometry (UHPLC-QQQ-MS) achieved to simultaneously determine the contents of BCAA and BCKA, which is efficient and stable. Compared with normal rats, levels of BCAA including leucine, isoleucine and valine in serum and kidney of CKD rats was decreased, while BCKA including α-ketoisocaproic acid, α-ketomethylvaleric acid and α-ketoisovaleric acid was increased. Together, these findings revealed the abnormality of BCAA metabolism in driving the course of kidney fibrosis and CKD. Our current study sheds new light on changes in BCAA metabolism during CKD, and may facilitate development of drugs to treat CKD and renal fibrosis.

Dietary Branched Chain Amino Acids Modify Post-Infarct Cardiac Remodeling and Function in the Murine Heart

Introduction

Branch-chain amino acids (BCAA) are markedly elevated in the heart following myocardial infarction (MI) in both humans and animal models. Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling. We hypothesize that lowering dietary BCAA levels prevents adverse cardiac remodeling after MI.

Methods and Results

To assess whether altering dietary BCAA levels would impact circulating BCAA concentrations, mice were fed a low (1/3×), normal (1×), or high (2×) BCAA diet over a 7-day period. We found that mice fed the low BCAA diet had >2-fold lower circulating BCAA concentrations when compared with normal and high BCAA diet feeding strategies; notably, the high BCAA diet did not further increase BCAA levels over the normal chow diet. To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, male and female mice were fed either the low or high BCAA diet for 2 wk prior to MI and for 4 wk after MI. Although body weights or heart masses were not different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. Echocardiographic assessments revealed that the low BCAA diet preserved stroke volume and cardiac output for the duration of the study, while the high BCAA diet led to progressive decreases in cardiac function. Although no discernible differences in cardiac fibrosis, scar collagen topography, or cardiomyocyte cross-sectional area were found between the dietary groups, male mice fed the high BCAA diet showed longer cardiomyocytes and higher capillary density compared with the low BCAA group.

Conclusions

Provision of a diet low in BCAAs to mice mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI, with dietary effects more prominent in males.

Mechanism of cytochrome P450s mediated interference with glutathione and amino acid metabolisms from halogenated PAHs exposure

Epidemiological evidence indicates that exposure to halogenated polycyclic aromatic hydrocarbons (HPAHs) is associated with many adverse effects. However, the mechanisms of metabolic disorder of HPAHs remains limited. Herein, effects of pyrene (Pyr), and its halogenated derivatives (1-chloropyrene (1-Cl-Pyr), 1-bromopyrene (1-Br-Pyr)) on endogenous metabolic pathways were investigated, in human hepatoma (HepG2) and HepG2-derived cell lines expressing various human cytochrome P450s (CYPs). Non-targeted metabolomics results suggested that 1-Br-Pyr and Pyr exposure (625 nM) induced disruption in glutathione and riboflavin metabolism which associated with redox imbalance, through abnormal accumulation of oxidized glutathione, mediated by bioactivation of CYP2E1. Conversely, CYP2C9-mediated 1-Cl-Pyr significantly interfered with glutathione metabolism intermediates, including glycine, L-glutamic acid and pyroglutamic acid. Notably, CYP1A1-mediated Pyr-induced perturbation of amino acid metabolism which associated with nutrition and glycolipid metabolism, resulting in significant upregulation of most amino acids, whereas halogenated derivatives mediated by CYP1A2 substantially downregulated amino acids. In conclusion, this study suggested that Pyr and its halogenated derivatives exert potent effects on endogenous metabolism disruption under the action of various exogenous metabolic enzymes (CYPs). Thus, new evidence was provided to toxicological mechanisms of HPAHs, and reveals potential health risks of HPAHs in inducing diseases caused by redox and amino acid imbalances.

Metabolic Profiling Changes Induced by Fermented Blackberries in High-Fat-Diet-Fed Mice Utilizing Gas Chromatography-Mass Spectrometry Analysis

The aim of this study was to investigate the metabolic changes associated with the anti-obesity effects of fermented blackberry extracts in the liver tissues of high-fat-diet-fed mice using mass spectrometry-based metabolomics analysis. C57BL/6J mice were divided into eight groups: normal-diet-fed mice, high-fat-diet-fed mice, high-fat diet treated with blackberry extract, high-fat-diet mice treated with blackberry fermented by L. plantarum, and high-fat diet with blackberry fermented by L. brevis. After 12 weeks, the high-fat-diet group exhibited a greater increase in liver weight compared to the control group, and among the groups, the group administered with blackberry fermented with L. plantarum showed the most pronounced reduction in liver weight. As the primary organ responsible for amino acid metabolism, the liver is crucial for maintaining amino acid homeostasis. In our study, we observed that the levels of several essential amino acids, including isoleucine and valine, were decreased by the high-fat diet, and were recovered by administration of blackberry extract fermented with L. plantarum. Our results demonstrated the potential of blackberry extract fermented with L. plantarum as a functional material for metabolic disorders by restoring some of the amino acid metabolism disturbances induced by a high-fat diet.

The Gut and Skin Microbiome and Its Association with Aging Clocks

Aging clocks are predictive models of biological age derived from age-related changes, such as epigenetic changes, blood biomarkers, and, more recently, the microbiome. Gut and skin microbiota regulate more than barrier and immune function. Recent studies have shown that human microbiomes may predict aging. In this narrative review, we aim to discuss how the gut and skin microbiomes influence aging clocks as well as clarify the distinction between chronological and biological age. A literature search was performed on PubMed/MEDLINE databases with the following keywords: "skin microbiome" OR "gut microbiome" AND "aging clock" OR "epigenetic". Gut and skin microbiomes may be utilized to create aging clocks based on taxonomy, biodiversity, and functionality. The top contributing microbiota or metabolic pathways in these aging clocks may influence aging clock predictions and biological age. Furthermore, gut and skin microbiota may directly and indirectly influence aging clocks through the regulation of clock genes and the production of metabolites that serve as substrates or enzymatic regulators. Microbiome-based aging clock models may have therapeutic potential. However, more research is needed to advance our understanding of the role of microbiota in aging clocks.

Distinct Plasma Metabolomic and Gut Microbiome Profiles after Gestational Diabetes Mellitus Diet Treatment: Implications for Personalized Dietary Interventions

Gestational diabetes mellitus (GDM) triggers alterations in the maternal microbiome. Alongside metabolic shifts, microbial products may impact clinical factors and influence pregnancy outcomes. We investigated maternal microbiome-metabolomic changes, including over 600 metabolites from a subset of the "Choosing Healthy Options in Carbohydrate Energy" (CHOICE) study. Women diagnosed with GDM were randomized to a diet higher in complex carbohydrates (CHOICE, n = 18, 60% complex carbohydrate/25% fat/15% protein) or a conventional GDM diet (CONV, n = 16, 40% carbohydrate/45% fat/15% protein). All meals were provided. Diets were eucaloric, and fiber content was similar. CHOICE was associated with increases in trimethylamine N-oxide, indoxyl sulfate, and several triglycerides, while CONV was associated with hippuric acid, betaine, and indole propionic acid, suggestive of a healthier metabolome. Conversely, the microbiome of CHOICE participants was enriched with carbohydrate metabolizing genes and beneficial taxa such as Bifidobacterium adolescentis, while CONV was associated with inflammatory pathways including antimicrobial resistance and lipopolysaccharide biosynthesis. We also identified latent metabolic groups not associated with diet: a metabolome associated with less of a decrease in fasting glucose, and another associated with relatively higher fasting triglycerides. Our results suggest that GDM diets produce specific microbial and metabolic responses during pregnancy, while host factors also play a role in triglycerides and glucose metabolism.

Causality of metabolites and metabolic pathways on cholestatic liver diseases: a Mendelian randomization study

Background and Aims

Blood metabolite abnormalities have revealed an association with cholestatic liver diseases (CLDs), while the underlying metabolic mechanisms have remained sluggish yet. Accordingly, the present evaluation aims to investigate the causal relationship between blood metabolites and the risk of two major CLDs, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC).

Methods

Univariable and multivariable Mendelian randomization (MR) approaches were employed to uncover potential causal associations between blood metabolites and 2 CLDs, including PBS and PSC, through extracting instrumental variables (IVs) for metabolites from genome-wide association studies (GWAS) conducted on European individuals. The GWAS summary data of PBC or PSC were sourced from two distinct datasets. The initial analysis employed inverse variance weighted (IVW) and an array of sensitivity analyses, followed by replication and meta-analysis utilizing FinnGen consortium data. Finally, a multivariable MR analysis was carried out to ascertain the independent effects of each metabolite. Furthermore, the web-based tool MetaboAnalyst 5.0 was used to perform metabolic pathway examination.

Results

A genetic causality between 15 metabolites and CLDs was recognized after preliminary analysis and false discovery rate (FDR) correction. Subsequently, 9 metabolites consistently represented an association through replication and meta-analysis. Additionally, the independent causal effects of 7 metabolites were corroborated by multivariable MR analysis. Specifically, the metabolites isovalerylcarnitine (odds ratio [OR] = 3.146, 95% confidence intervals [CI]: 1.471-6.726, p = 0.003), valine (OR = 192.44, 95%CI: 4.949-7483.27, p = 0.005), and mannose (OR = 0.184, 95%CI: 0.068-0.499, p < 0.001) were found to have a causal relationship with the occurrence of PBC. Furthermore, erythrose (OR = 5.504, 95%CI: 1.801-16.821, p = 0.003), 1-stearoylglycerophosphocholine (OR = 6.753, 95%CI: 2.621-17.399, p = 7.64 × 10-5), X-11847 (OR = 0.478, 95%CI: 0.352-0.650, p = 2.28 × 10-6), and X-12405 (OR = 3.765, 95%CI: 1.771-8.005, p = 5.71 × 10-4) were independently associated with the occurrence of PSC. Furthermore, the analysis of metabolic pathways identified seven significant pathways in two CLDs.

Conclusion

The findings of the present study have unveiled robust causal relationships between 7 metabolites and 2 CLDs, thereby providing novel insights into the metabolic mechanisms and therapeutic strategies for these disorders.

Branched-chain amino acid supplementation drives dynamic changes in gut microbiota without impairing glucose and lipid homeostasis at the different stages of insulin resistance in mice on a high-fat diet

OBJECTIVE

The potential role of dietary branched-chain amino acids on circulating branched-chain amino acid levels and their relationship with metabolic health are complex, and the literature is inconsistent. We aimed to explore the dynamic effects of branched-chain amino acid supplementation on glucose and lipid homeostasis at different stages of insulin resistance in high-fat diet-fed mice.

METHODS

Male C57BL/6J mice were fed with a normal chow diet, high-fat diet, or high-fat diet supplemented with 100% branched-chain amino acids for 12 or 24 wk. Metabolic parameters and gut microbiota profiling were performed at these two time points.

RESULTS

High-fat diet feeding caused varying degrees of branched-chain amino acid metabolic disorders in two different stages of insulin resistance. Supplementing with branched-chain amino acids further exacerbated branched-chain amino acid accumulation in the early stage of insulin resistance (12 wk), while adding branched-chain amino acids did not further elevate branched-chain amino acid levels in the hyperglycemia and hyperinsulinemia stage (24 wk). Compared with the high-fat diet group, branched-chain amino acid supplementation did not affect body weight; liver total cholesterol and triacylglycerol levels; and serum glucose, insulin, total cholesterol, triacylglycerol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels as well as glucose tolerance at these two time points but triggered dynamic changes in the gut bacterial diversity and gut microbiota composition and abundance, especially in the genus associated with obesity and related metabolic disorders.

CONCLUSION

Dietary branched-chain amino acid supplementation drives dynamic changes in circulating branched-chain amino acid levels and gut microbiome without subsequent effects on glucose and lipid homeostasis in high-fat diet-induced obese mice within the parameters of our study.

Multiomics Analysis Reveals Leucine Deprivation Promotes Bile Acid Synthesis by Upregulating Hepatic CYP7A1 and Intestinal Turicibacter sanguinis in Mice

BACKGROUND

Leucine, a branched-chain amino acid, participates in the regulation of lipid metabolism and the composition of the intestinal microbiota. However, the related mechanism remains unclear.

OBJECTIVES

Here, we aimed to reveal the potential mechanisms by which hepatic CYP7A1 (a rate-limiting enzyme for bile acid [BA] synthesis) and gut microbiota coregulate BA synthesis under leucine deprivation.

METHODS

To this end, 8-wk-old C57BL/6J mice were fed with either regular diets or leucine-free diets for 1 wk. Then, we investigated whether secondary BAs were synthesized by Turicibacter sanguinis in 7-wk-old C57BL/6J germ-free mice gavaged with T. sanguinis for 2 wk by determining BA concentrations in the plasma, liver, and cecum contents using liquid chromatography-tandem mass spectrometry.

RESULTS

The results showed that leucine deprivation resulted in a significant increase in total BA concentration in the plasma and an increase in the liver, but no difference in total BA was observed in the cecum contents before and after leucine deprivation. Furthermore, leucine deprivation significantly altered BA profiles such as taurocholic acid and ω-muricholic acid in the plasma, liver, and cecum contents. CYP7A1 expression was significantly upregulated in the liver under leucine deprivation. Leucine deprivation also regulated the composition of the gut microbiota; specifically, it significantly upregulated the relative abundance of T. sanguinis, thus enhancing the conversion of primary BAs into secondary BAs by intestinal T. sanguinis in mice.

CONCLUSIONS

Overall, leucine deprivation regulated BA profiles in enterohepatic circulation by upregulating hepatic CYP7A1 expression and increasing intestinal T. sanguinis abundance. Our findings reveal the contribution of gut microbiota to BA metabolism under dietary leucine deprivation.

A Comprehensive Pilot Study to Elucidate the Distinct Gut Microbial Composition and Its Functional Significance in Cardio-Metabolic Disease

Cardio-metabolic disease is a significant global health challenge with increasing prevalence. Recent research underscores the disruption of gut microbial balance as a key factor in disease susceptibility. We aimed to characterize the gut microbiota composition and function in cardio-metabolic disease and healthy controls. For this purpose, we collected stool samples of 18 subjects (12 diseased, 6 healthy) and we performed metagenomics analysis and functional prediction using QIIME2 and PICRUSt. Furthermore, we carried out assessments of microbe-gene interactions, gene ontology, and microbe-disease associations. Our findings revealed distinct microbial patterns in the diseased group, particularly evident in lower taxonomic levels with significant variations in 14 microbial features. The diseased cohort exhibited an enrichment of Lachnospiraceae family, correlating with obesity, insulin resistance, and metabolic disturbances. Conversely, reduced levels of Clostridium, Gemmiger, and Ruminococcus genera indicated a potential inflammatory state, linked to compromised butyrate production and gut permeability. Functional analyses highlighted dysregulated pathways in amino acid metabolism and energy equilibrium, with perturbations correlating with elevated branch-chain amino acid levels-a known contributor to insulin resistance and type 2 diabetes. These findings were consistent across biomarker assessments, microbe-gene associations, and gene ontology analyses, emphasizing the intricate interplay between gut microbial dysbiosis and cardio-metabolic disease progression. In conclusion, our study unveils significant shifts in gut microbial composition and function in cardio-metabolic disease, emphasizing the broader implications of microbial dysregulation. Addressing gut microbial balance emerges as a crucial therapeutic target in managing cardio-metabolic disease burden.

Nutritional Strategies for Muscle Atrophy: Current Evidence and Underlying Mechanisms

Skeletal muscle can undergo detrimental changes in various diseases, leading to muscle dysfunction and atrophy, thus severely affecting people's lives. Along with exercise, there is a growing interest in the potential of nutritional support against muscle atrophy. This review provides a brief overview of the molecular mechanisms driving skeletal muscle atrophy and summarizes recent advances in nutritional interventions for preventing and treating muscle atrophy. The nutritional supplements include amino acids and their derivatives (such as leucine, β-hydroxy, β-methylbutyrate, and creatine), various antioxidant supplements (like Coenzyme Q10 and mitoquinone, resveratrol, curcumin, quercetin, Omega 3 fatty acids), minerals (such as magnesium and selenium), and vitamins (such as vitamin B, vitamin C, vitamin D, and vitamin E), as well as probiotics and prebiotics (like Lactobacillus, Bifidobacterium, and 1-kestose). Furthermore, the study discusses the impact of a combined approach involving nutritional support and physical therapy to prevent muscle atrophy, suggests appropriate multi-nutritional and multi-modal interventions based on individual conditions to optimize treatment outcomes, and enhances the recovery of muscle function for patients. By understanding the molecular mechanisms behind skeletal muscle atrophy and implementing appropriate interventions, it is possible to enhance the recovery of muscle function and improve patients' quality of life.

Circulating Branched Chain Amino Acids and Cardiometabolic Disease

Branched chain amino acids (BCAAs) are essential for protein homeostasis, energy balance, and signaling pathways. Changes in BCAA homeostasis have emerged as pivotal contributors in the pathophysiology of several cardiometabolic diseases, including type 2 diabetes, obesity, hypertension, atherosclerotic cardiovascular disease, and heart failure. In this review, we provide a detailed overview of BCAA metabolism, focus on molecular mechanisms linking disrupted BCAA homeostasis with cardiometabolic disease, summarize the evidence from observational and interventional studies investigating associations between circulating BCAAs and cardiometabolic disease, and offer valuable insights into the potential for BCAA manipulation as a novel therapeutic strategy for cardiometabolic disease.

Taohe Chengqi decoction alleviated metabolic-associated fatty liver disease by boosting branched chain amino acids catabolism in the skeletal muscles of type 2 diabetes mellitus

OBJECTIVE

Metabolic-associated fatty liver disease (MAFLD) is the most prevalent liver disease, whereas type 2 diabetes mellitus (T2DM) is considered an independent risk factor for MAFLD incidence. Taohe Chengqi decoction (THCQ) is clinically prescribed for T2DM treatment; however, the hepatoprotective effect of THCQ against MAFLD is still unknown. This study intended to elucidate the therapeutic effect of THCQ on T2DM-associated MAFLD and to investigate the underlying mechanisms.

METHODS

THCQ lyophilized powder was prepared and analyzed by UHPLC-MS/MS. A stable T2DM mouse model was established by high-fat diet (HFD) feeding combined with streptozotocin (STZ) injection. The T2DM mice were administered THCQ (2.5 g/kg or 5 g/kg) to explore the pharmacological effects of THCQ on T2DM-associated MAFLD. Liver tissue transcriptome was analyzed and the participatory roles of PPARα/γ pathways were verified both in vivo and in vitro. Serum metabolome analysis was used to explore the metabolome changes and skeletal muscle branched chain amino acid (BCAA) catabolic enzymes were further detected. Moreover, an AAV carrying BCKDHA shRNA was intramuscularly injected to verify the impact of THCQ on skeletal muscle BCAA catabolism and the potential therapeutic outcome on hepatic steatosis.

RESULTS

THCQ improved hepatic steatosis in MAFLD. RNA-sequencing analysis showed dysregulation in the hepatic PPARγ-related fatty acid synthesis, while PPARα-dependent fatty acid oxidation was elevated following THCQ treatment. Interestingly, in vitro analyses of these findings showed that THCQ had minor effects on fatty acid oxidation and/or synthesis. The metabolomic study revealed that THCQ accelerated BCAA catabolism in the skeletal muscles, in which knockdown of the BCAA catabolic enzyme BCKDHA diminished the THCQ therapeutic effect on hepatic steatosis.

CONCLUSION

This study highlighted the potential therapeutic effect of THCQ on hepatic steatosis in MALFD. THCQ upregulated fatty acid oxidation and reduced its synthesis via restoration of PPARα/γ pathways in HFD/STZ-induced T2DM mice, which is mediated through augmenting BCKDH activity and accelerating BCAA catabolism in the skeletal muscles. Overall, this study provided in-depth clues for "skeletal muscles-liver communication" in the therapeutic effect of THCQ against hepatic steatosis. These findings suggested THCQ might be a potential candidate against T2DM-associated MAFLD.

Phosphorylation of TG-interacting factor 1 at carboxyl-terminal sites in response to insulin regulates adipocyte differentiation

TG-interacting factor 1 (TGIF1) contributes to the differentiation of murine white preadipocyte and human adipose tissue-derived stem cells; however, its regulation is not well elucidated. Insulin is a component of the adipogenic cocktail that induces ERK signaling. TGIF1 phosphorylation and sustained stability in response to insulin were reduced through the use of specific MEK inhibitor U0126. Mutagenesis at T235 or T239 residue of TGIF1 in preadipocytes led to dephosphorylation of TGIF1. The reduced TGIF1 stability resulted in an increase in p27kip1 expression, a decrease in phosphorylated Rb expression and cellular proliferation, and a reduced accumulation of lipids compared to the TGIF1-overexpressed cells. These findings highlight that insulin/ERK-driven phosphorylation of the T235 or T239 residue at TGIF1 is crucial for adipocyte differentiation.

Sex Differences in Branched-chain Amino Acid and Tryptophan Metabolism and Pathogenesis of Youth-onset Type 2 Diabetes

OBJECTIVES

Insulin resistance is associated with elevations in plasma branched-chain amino acids (BCAAs). BCAAs compete with aromatic amino acids including tryptophan for uptake into β cells. To explore relationships between BCAAs and tryptophan metabolism, adiposity, and glucose tolerance, we compared urine metabolites in overweight/obese youth with type 2 diabetes (T2D) with those in nondiabetic overweight/obese and lean youth.

METHODS

Metabolites were measured in 24-hour and first-morning urine samples of 56 nondiabetic adolescents with overweight/obesity, 42 adolescents with T2D, and 43 lean controls, aged 12 to 21 years. Group differences were assessed by Kruskal Wallis or ANOVA.

RESULTS

Groups were comparable for age, pubertal status, and ethnicity. Youth with T2D were predominantly female and had highest percent body fat. BCAAs, branched-chain ketoacids (BCKAs), tryptophan, and kynurenine were higher in urine of subjects with T2D. There were no differences between lean controls and nondiabetic youth with overweight/obesity. T2D was associated with diversion of tryptophan from the serotonin to the kynurenine pathway, with higher urinary kynurenine/serotonin ratio and lower serotonin/tryptophan and 5-HIAA/kynurenine ratios. Urinary BCAAs, BCKAs, tryptophan, and ratios reflecting diversion to the kynurenine pathway correlated positively with metrics of body fat and hemoglobin A1c. Increases in these metabolites in the obese T2D group were more pronounced and statistically significant only in adolescent girls.

CONCLUSION

Increases in urinary BCAAs and BCKAs in adolescent females with T2D are accompanied by diversion of tryptophan metabolism from the serotonin to the kynurenine pathway. These adaptations associate with higher risks of T2D in obese adolescent females than adolescent males.

The BCKDK inhibitor BT2 is a chemical uncoupler that lowers mitochondrial ROS production and de novo lipogenesis

Elevated levels of branched chain amino acids (BCAAs) and branched-chain α-ketoacids are associated with cardiovascular and metabolic disease, but the molecular mechanisms underlying a putative causal relationship remain unclear. The branched-chain ketoacid dehydrogenase kinase (BCKDK) inhibitor BT2 (3,6-dichlorobenzo[b]thiophene-2-carboxylic acid) is often used in preclinical models to increase BCAA oxidation and restore steady-state BCAA and branched-chain α-ketoacid levels. BT2 administration is protective in various rodent models of heart failure and metabolic disease, but confoundingly, targeted ablation of Bckdk in specific tissues does not reproduce the beneficial effects conferred by pharmacologic inhibition. Here, we demonstrate that BT2, a lipophilic weak acid, can act as a mitochondrial uncoupler. Measurements of oxygen consumption, mitochondrial membrane potential, and patch-clamp electrophysiology show that BT2 increases proton conductance across the mitochondrial inner membrane independently of its inhibitory effect on BCKDK. BT2 is roughly sixfold less potent than the prototypical uncoupler 2,4-dinitrophenol and phenocopies 2,4-dinitrophenol in lowering de novo lipogenesis and mitochondrial superoxide production. The data suggest that the therapeutic efficacy of BT2 may be attributable to the well-documented effects of mitochondrial uncoupling in alleviating cardiovascular and metabolic disease.

Glucomannan promotes Bacteroides ovatus to improve intestinal barrier function and ameliorate insulin resistance

Bioactive dietary fiber has been proven to confer numerous health benefits against metabolic diseases based on the modification of gut microbiota. The metabolic protective effects of glucomannan have been previously reported in animal experiments and clinical trials. However, critical microbial signaling metabolites and the host targets associated with the metabolic benefits of glucomannan remain elusive. The results of this study revealed that glucomannan supplementation alleviated high-fat diet (HFD)-induced insulin resistance in mice and that its beneficial effects were dependent on the gut microbiota. Administration of glucomannan to mice promoted the growth of Bacteroides ovatus. Moreover, colonization with B. ovatus in HFD-fed mice resulted in a decrease in insulin resistance, accompanied by improved intestinal barrier integrity and reduced systemic inflammation. Furthermore, B. ovatus-derived indoleacetic acid (IAA) was established as a key bioactive metabolite that fortifies intestinal barrier function via activation of intestinal aryl hydrocarbon receptor (AhR), leading to an amelioration in insulin resistance. Thus, we conclude that glucomannan acts through the B. ovatus-IAA-intestinal AhR axis to relieve insulin resistance.