Biomarkers for type 2 diabetes and impaired fasting glucose using a nontargeted metabolomics approach

Effect of dapagliflozin on the serum metabolome in patients with type 2 diabetes mellitus

Objectives

SGLT-2 inhibitors have been shown to exert cardio- and renoprotective actions. We aimed to investigate the underlying mechanisms using 1H-NMR based metabolomics in patients with type-2 diabetes mellitus who received dapagliflozin.

Methods

50 patients with type 2 diabetes mellitus, inadequately controlled on metformin monotherapy (HbA1c > 7%) received dapagliflozin for 3 months and 30 matched patients received insulin degludec for 3 months. Clinical and laboratory values, as well as 1H-NMR based metabolomics were assessed before treatment and after completion of 3 months of treatment.

Results

Dapagliflozin reduced weight, body mass index, systolic and diastolic blood pressure significantly. Using 1H-NMR based metabolomics, the dapagliflozin group showed a good separation with a degree of overlap before and after treatment initiation. Regarding targeted metabolomics, dapagliflozin increased serum ketone, citrate and tryptophan levels compared with insulin. On the other hand, serum taurine, threonine and mannose levels were significantly decreased following dapagliflozin administration.

Conclusions

Dapagliflozin led to a small, but significant change in serum metabolome. The observed changes may indicate improvement in energy metabolism, reduction in inflammatory activity and decreased insulin resistance which may provide further evidence of the agent's observed cardiac and renal protection. The study was registered with ClinicalTrials.gov (identifier: NCT02798757).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01508-1.

Association of the gut microbiome with diabetic nephropathy and the mediated effect of metabolites: friend or enemy?

OBJECTIVE

The effects of gut microbiome and its metabolites on diabetic nephropathy (DN) have been inadequately elucidated. The aim of this study is to assess the causal effect of gut microbiome on DN and the mediated effect of metabolites by a two-step Mendelian randomization (MR).

METHODS

Datasets of gut microbiome, metabolites, and DN were acquired in genome-wide association studies and screened for single nucleotide polymorphisms according to the underlying assumptions of MR. Subsequently, inverse variance weighted was used as the primary method for MR analysis to assess the causal effect of gut microbiome on DN and the mediated effect of metabolites. Finally, MR-Egger intercept, Cochran's Q test, and leave-one-out sensitivity analysis were used to assess the horizontal pleiotropy, heterogeneity, and robustness of the results, respectively.

RESULTS

The MR analysis demonstrated that Parabacteroides merdae increased the genetic susceptibility to DN by reducing acetylcarnitine (C2) to propionylcarnitine (C3) ratio (mediated proportion 8.95%, mediated effect 0.024) and alpha-ketobutyrate to 3-methyl-2-oxovalerate ratio (mediated proportion 19.90%, mediated effect 0.053). MR Egger showed that these results lack horizontal pleiotropy (p ≥ 0.05). Cochran's Q and sensitivity analysis suggested these results had no heterogeneity (p ≥ 0.05) and were robust.

CONCLUSION

Our findings revealed the pathway by which Parabacteroides merdae increased the genetic susceptibility to DN by regulating acetylcarnitine (C2) to propionylcarnitine (C3) ratio and alpha-ketobutyrate to 3-methyl-2-oxovalerate ratio. It provides new genetic insights for understanding the pathogenesis of DN and related drug research.

Multi-omics approaches for biomarker discovery and precision diagnosis of prediabetes

Recent advancements in multi-omics technologies have provided unprecedented opportunities to identify biomarkers associated with prediabetes, offering novel insights into its diagnosis and management. This review synthesizes the latest findings on prediabetes from multiple omics domains, including genomics, epigenomics, transcriptomics, proteomics, metabolomics, microbiomics, and radiomics. We explore how these technologies elucidate the molecular and cellular mechanisms underlying prediabetes and analyze potential biomarkers with predictive value in disease progression. Integrating multi-omics data helps address the limitations of traditional diagnostic methods, enabling early detection, personalized interventions, and improved patient outcomes. However, challenges such as data integration, standardization, and clinical validation and translation remain to be resolved. Future research leveraging artificial intelligence and machine learning is expected to further enhance the predictive power of multi-omics technologies, contributing to the precision diagnosis and tailored management of prediabetes.

Metabolomic analyses of multiple biologic matrices reveal metabolic heterogeneity in diabetic complications

AIMS

Type 2 diabetes mellitus (T2DM) arises from a complex interplay of genetic and environmental factors. Patients with T2DM are susceptible to hyperglycemia-related complications that can impair organ function, underscoring the need to explore the metabolic profiles of affected organs.

METHODS

In this study, a comprehensive metabolomic analysis was conducted on the serum, kidney, and heart tissues from a rat model of diabetic complications (DC). Pattern recognition and multivariate statistical analyses were applied to identify the potential biomarkers of DC, and metabolic network analysis served to understand the specific metabolic pathways associated with DC.

RESULTS

Fourteen significantly altered metabolites were identified in serum, 20 in the kidney, and 14 in the heart. The corresponding metabolic pathways included mineral absorption, mTOR signaling pathway, taurine and hypotaurine metabolism, glycine, serine and threonine metabolism, ABC transporters, glucagon signaling pathway, protein degradation and uptake, galactose metabolism, purine metabolism, nicotinic acid and nicotinamide metabolism, and glycolysis and gluconeogenesis. Differential metabolite network analysis revealed instinct metabolic patterns among the serum, kidney, and heart. Notably, the serum's metabolic correlation patterns were found to be somewhat similar to those observed in the kidney, whereas the heart exhibited less pronounced metabolite correlations compared to the other two biological matrices.

CONCLUSIONS

These findings provide insights into the mechanism underlying the development of diabetic complications. The integration of metabolomics and biological network analyses into diabetes research can potentially revolutionize the field by revealing novel biomarkers for early detection and personalized treatment of diabetes and its associated complications.

Erythritol, Erythronate, and Cardiovascular Outcomes in Older Adults in the ARIC Study

BACKGROUND

Circulating erythritol, an endogenously produced metabolite and an artificial sweetener, is associated with cardiovascular outcomes.

OBJECTIVES

The authors assessed associations of erythritol and its downstream metabolite, erythronate, with cardiovascular risk factors and events in older adults in the ARIC (Atherosclerosis Risk In Communities) study (visit 5, 2011-2013).

METHODS

We included 4,006 participants without prevalent cardiovascular disease and with metabolomic profiling. Erythritol and erythronate were measured by mass spectrometry. We analyzed associations of log-transformed erythritol and erythronate with cardiovascular risk factors and events using Cox proportional hazard models.

RESULTS

Participants in the highest tertiles of erythritol or erythronate were older, more likely to have diabetes, hypertension, hyperlipidemia, or microalbuminuria, and had higher body mass index and cardiac biomarkers and lower estimated glomerular filtration rate (P < 0.001). Over median follow-up of 8.41 (7.62, 8.93) years, higher erythritol and erythronate concentrations were significantly associated with heart failure (HF) hospitalization, HF with preserved ejection fraction, cardiovascular death, and total mortality after adjustment for demographics and traditional cardiovascular risk factors. Erythronate was additionally significantly associated with coronary heart disease (HR: 1.30 [95% CI: 1.04-1.61], P = 0.02), stroke (1.40 [95% CI: 1.08-1.83], P = 0.012), and HF with reduced ejection fraction (1.38 [95% CI: 1.09-1.74], P = 0.007). Diabetes status did not modify any of these associations (P for interaction >0.20).

CONCLUSIONS

Circulating erythritol and erythronate levels are markers of cardiometabolic health and cardiovascular outcomes in an older adult population. In particular, erythronate is associated with all cardiovascular outcomes assessed. Future studies should assess the role of erythronate and its related pathways in cardiovascular disease.

The association of objective daytime sleepiness with impaired glucose metabolism in patients with obstructive sleep apnea: a multi-omics study

STUDY OBJECTIVES

To examine the joint effect of obstructive sleep apnea (OSA) and objective excessive daytime sleepiness (EDS) on glucose metabolism and the underlying mechanisms.

METHODS

We included 127 patients with OSA. The multiple sleep latency test (MSLT) and Epworth sleepiness scale (ESS) were used to assess objective and subjective EDS, respectively. Disordered glucose metabolism was defined as either a physician diagnosis or having fasting blood glucose levels ≥5.6 mmol/L. Values of fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) higher than the median values of our sample were defined as high fasting insulin and insulin resistance. Serum metabolomics and fecal microbiota were used to explore underlying mechanisms.

RESULTS

Lower MSLT values were associated with higher levels of fasting blood glucose, fasting insulin, and HOMA-IR. Furthermore, objective EDS was associated with increased odds of disordered glucose metabolism, elevated fasting insulin, and insulin resistance. Dysregulation of serum valine degradation and dysbiosis of fecal Bacteroides thetaiotaomicron were associated with impaired glucose metabolism in OSA with objective EDS. No association between subjective EDS and impaired glucose metabolism was observed.

CONCLUSIONS

OSA with objective, but not subjective, EDS is associated with an increased risk of disordered glucose metabolism and insulin resistance. Dysregulation of valine degradation and dysbiosis of B. thetaiotaomicron appear to link objective EDS and disordered glucose metabolism in OSA.

Elevated fasting serum xylitol levels are associated with a lower risk of incident type 2 diabetes among individuals with prediabetes in the Chinese population

BACKGROUND

It is important to detect the predictors of prediabetes progressing to diabetes. Although polyols affect glycometabolism, little is known about the association between fasting serum polyol levels of participants with habitual diet and the risk of prediabetes progressing to type 2 diabetes.

METHODS

In this nested case-control study, 180 participants who developed from prediabetes to type 2 diabetes (progressors), and 180 matched controls (non-progressors) with prediabetes during a 3.5-year follow-up were enrolled. The baseline levels of serum polyols in the fasting state were quantified using time-of-flight mass spectrometry. Multivariate conditional logistic regression was performed to assess the effects of the differential polyol levels on the risk of incident diabetes from prediabetes.

RESULTS

The baseline fasting xylitol levels, but not sorbitol or erythritol levels, were higher in non-progressors than in progressors (P < 0.001). Non-progressors, in comparison with progressors, had significantly higher proportions within the third tertile of xylitol levels (71/180 non-progressors [39.4%] vs. 49/180 progressors [27.2%]). After adjusting for potential confounders, the odds ratio of risk for incident diabetes in the highest tertile of xylitol levels was 0.338 (95% confidence interval 0.182-0.628), when compared with those in the lowest tertile. In addition, the association between xylitol levels and incident diabetes was persistent in those with fasting hyperglycemia and both fasting and 2h-post-glucose-load hyperglycemia, but not in the isolated 2h-post-glucose-load hyperglycemia.

CONCLUSIONS

Elevated baseline fasting serum xylitol levels are associated with a lower risk of prediabetes progressing to diabetes. This association was particularly evident in those with fasting hyperglycemia. These findings suggest that fasting serum xylitol levels may serve as an important predictor and protective factor against the development of diabetes.

Branched chain amino acid metabolism and microbiome in adolescents with obesity during weight loss therapy

BACKGROUND

Towards improving outcomes for adolescents with obesity, we aimed to define metabolic and microbiome phenotypes at baseline and post-weight loss intervention.

METHODS

The Pediatric Obesity Microbiome and Metabolism Study enrolled 220 adolescents aged 10-18 with severe obesity (OB) and 67 healthy weight controls (HWC). Blood, stool, and clinical measures were collected at baseline and after a 6-month intervention for the OB group. Serum metabolomic and fecal microbiome data were analyzed for associations with BMI, insulin resistance, and inflammation. Fecal microbiome transplants were performed on germ-free mice using samples from both groups to assess weight gain and metabolomic changes.

RESULTS

Adolescents with OB exhibited elevated serum branched-chain amino acids (BCAA) but reduced ketoacid metabolites (BCKA) compared to HWC. This pattern was sex- and age-dependent, unlike adults with OB, who showed elevated levels of both. The fecal microbiomes of adolescents with OB and HWC had similar diversity but differed in membership and functional potential. FMT from OB and HWC donors had similar effects on mouse body weight, with specific taxa linked to weight gain in FMT recipients. Longitudinal analysis identified metabolic and microbial features correlated with changes in health measures during the intervention.

CONCLUSION

Adolescents with OB have unique metabolomic adaptations and microbiome signatures compared to their HWC counterparts and adults with OB.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03139877 (Observational Study) and NCT02959034 (Repository).

FUNDING SOURCES

American Heart Association Grants: 17SFRN33670990, 20PRE35180195National Institute of Diabetes and Digestive and Kidney Diseases Grant: R24-DK110492.

Subcutaneous adipose tissue compensates for the perturbations in circulating one-carbon metabolism in women with gestational diabetes

The prevalence of gestational diabetes mellitus (GDM) is rising and poses important health risks for the mother, developing fetus and offspring, even when maternal glycemic control is well managed. This study aimed to identify the differently expressed metabolites (DEMs) in maternal plasma between GDM pregnancies with good glycemic control and healthy pregnancies, along with the DEMs-related metabolism in adipose tissue. Pregnant women with scheduled caesarean sections were recruited. Venous blood samples were collected on the day prior to delivery for targeted metabolomics analysis focusing on the 200 polar metabolites in central carbon metabolism. Subcutaneous and omental white adipose tissue (sWAT and oWAT) were harvested at delivery. A total of 162 metabolites were quantified, revealing 2 up-regulated (D-glucose 6-phosphate (G6P), succinate) and 8 down-regulated DEMs, which exhibited a fold change of ≥ 1.5 or ≤ 0.67, respectively. Among the down-regulated DEMs, 5 metabolites-pyridoxine, glycine, S-methyl-L-cysteine, methionine, and S-carboxymethyl-L-cysteine-are related to one-carbon metabolism (OCM). In response to perturbation in circulating OCM, boosted methionine cycle, NAD + metabolism, and adipogenesis were observed in sWAT of GDM subjects, with no changes detected in oWAT. None of the 10 DEMs correlates with either blood glucose or insulin, but showed significant correlations with TG, TC, LDL-C and HDL-C. The present study indicates that sWAT compensates for the perturbations in circulating OCM associated with GDM and targeting to the OCM may be an effective strategy to control the long-term metabolic risk of GDM offsprings.

Proline exacerbates hepatic gluconeogenesis via paraspeckle-dependent mRNA retention

Type 2 diabetes (T2D) is a global health issue characterized by abnormal blood glucose levels and is often associated with excessive hepatic gluconeogenesis. Increased circulating non-essential amino acids (NEAAs) are consistently observed in individuals with T2D; however, the specific contribution of each amino acid to T2D pathogenesis remains less understood. Here, we report an unexpected role of the NEAA proline in coordinating hepatic glucose metabolism by modulating paraspeckle, a nuclear structure scaffolded by the long non-coding RNA Neat1. Mechanistically, proline diminished paraspeckles in hepatocytes, liberating the retained mRNA species into cytoplasm for translation, including the mRNAs of Ppargc1a and Foxo1, contributing to enhanced gluconeogenesis and hyperglycaemia. We further demonstrated that the proline-paraspeckle-mRNA retention axis existed in diabetic liver samples, and intervening in this axis via paraspeckle restoration substantially alleviated hyperglycaemia in both female and male diabetic mouse models. Collectively, our results not only delineated a previously unappreciated proline-instigated, paraspeckle-dependent mRNA-retention mechanism regulating gluconeogenesis, but also spotlighted proline and paraspeckle as potential targets for managing hyperglycaemia.

Opportunities, challenges, and difficulties in NMR-based metabolomics applied to neovascular age-related macular degeneration (nAMD) patient follow-up

Introduction

This study applies NMR-based metabolomics to investigate neovascular age-related macular degeneration (nAMD), addressing challenges in patient management, disease progression evaluation, and treatment response assessment. A two-year follow-up of 29 nAMD patients undergoing treatment provided 231 time points for analysis.

Methods

Over the two-year period, 11 males and 18 females (aged 61-92 years) were monitored, yielding 231 time points. At each time point, blood samples for NMR metabolomics analysis, clinical measurements (e.g., lactate, glucose levels, HDL/LDL cholesterol, and blood pH), and optical coherence tomography (OCT) images were collected to evaluate the progression of choroidal neovascularization. 1H-NMR metabolomic analysis led to the quantification of over 60 metabolites and of the major lipoprotein fractions. Both multivariate and univariate statistical approaches tailored for longitudinal data were employed to identify biomarkers correlating metabolomic changes with ocular alterations during disease progression.

Results and Discussion

Despite a rigorous analytical workflow enabling precise quantification of over 60 metabolites and the application of advanced statistical tools for longitudinal data, achieving consistent results across the cohort proved challenging. The dataset's heterogeneity, reflecting real-world clinical practice, complicated the derivation of global conclusions. Personalized analyses on a patient-by-patient basis successfully identified individual correlation models, but a universal model remained elusive. This study highlights the inherent challenges of translating findings from controlled settings into clinical practice, where factors such as visit frequency, treatment variability, and disease heterogeneity limit data uniformity. We emphasize the importance of experimental design in longitudinal studies, particularly when dealing with incomplete and variable datasets. We are therefore confident that, considering both the challenges and difficulties identified in this work and the preliminary results presented here, it is possible to develop predictive and individualized models for monitoring patients with nAMD. Such models could greatly assist clinicians in providing better care for these patients.

Reduced circulating sphingolipids and CERS2 activity are linked to T2D risk and impaired insulin secretion

Gestational diabetes mellitus (GDM), a transient form of diabetes that resolves postpartum, is a major risk factor for type 2 diabetes (T2D) in women. While the progression from GDM to T2D is not fully understood, it involves both genetic and environmental components. By integrating clinical, metabolomic, and genome-wide association study (GWAS) data, we identified associations between decreased sphingolipid biosynthesis and future T2D, in part through the rs267738 allele of the CERS2 gene in Hispanic women shortly after a GDM pregnancy. To understand the impact of the CERS2 gene and risk allele on glucose regulation, we examined whole-body Cers2 knockout and rs267738 knock-in mice. Both models exhibited glucose intolerance and impaired insulin secretion in vivo. Islets isolated from these models also demonstrated reduced β cell function, as shown by decreased insulin secretion ex vivo. Overall, reduced circulating sphingolipids may indicate a high risk of GDM-to-T2D progression and reflect deficits in CERS2 activity that negatively affect glucose homeostasis and β cell function.

Untargeted metabolome atlas for sleep-related phenotypes in the Hispanic community health study/study of Latinos

BACKGROUND

Sleep is essential to maintaining health and wellbeing of individuals, influencing a variety of outcomes from mental health to cardiometabolic disease. This study aims to assess the relationships between various sleep-related phenotypes and blood metabolites.

METHODS

Utilising data from the Hispanic Community Health Study/Study of Latinos, we performed association analyses between 40 sleep-related phenotypes, grouped in several domains (sleep disordered breathing (SDB), sleep duration, sleep timing, self-reported insomnia symptoms, excessive daytime sleepiness (EDS), and heart rate during sleep), and 768 metabolites measured via untargeted metabolomics profiling. Network analysis was employed to visualise and interpret the associations between sleep phenotypes and metabolites.

FINDINGS

The patterns of statistically significant associations between sleep phenotypes and metabolites differed by superpathways, and highlighted subpathways of interest for future studies. For example, primary bile acid metabolism showed the highest cumulative percentage of statistically significant associations across all sleep phenotype domains except for SDB and EDS phenotypes. Several metabolites were associated with multiple sleep phenotypes, from a few domains. Glycochenodeoxycholate, vanillyl mandelate (VMA) and 1-stearoyl-2-oleoyl-GPE (18:0/18:1) were associated with the highest number of sleep phenotypes, while pregnenolone sulfate was associated with all sleep phenotype domains except for sleep duration. N-lactoyl amino acids such as N-lactoyl phenylalanine (lac-Phe), were associated with sleep duration, SDB, sleep timing and heart rate during sleep.

INTERPRETATION

This atlas of sleep-metabolite associations will facilitate hypothesis generation and further study of the metabolic underpinnings of sleep health.

FUNDING

R01HL161012, R35HL135818, R01AG80598.

Pro-inflammatory and hyperinsulinaemic dietary patterns are associated with specific gut microbiome profiles: a TwinsUK cohort study

Metabolic dietary patterns, including the Empirical Dietary Index for Hyperinsulinaemia (EDIH) and Empirical Dietary Inflammatory Pattern (EDIP), are known to impact multiple chronic diseases, but the role of the colonic microbiome in mediating such relationships is poorly understood. Among 1,610 adults with faecal 16S rRNA data in the TwinsUK cohort, we identified the microbiome profiles for EDIH and EDIP (from food frequency questionnaires) cross-sectionally using elastic net regression. We assessed the association of the dietary pattern-related microbiome profile scores with circulating biomarkers in multivariable-adjusted linear regression. In addition, we used PICRUSt2 to predict biological pathways associated with the enriched microbiome profiles, and further screened pathways for associations with the dietary scores in linear regression analyses. Microbiome profile scores developed with 32 (EDIH) and 15 (EDIP) genera were associated with higher insulin and homeostatic model assessment of insulin resistance. Six genera were associated with both dietary scores: Ruminococcaceae_UCG-008, Lachnospiraceae_UCG-008, Defluviitaleaceae_UCG-011 Anaeroplasma, inversely and Negativibacillus, Streptococcus, positively. Further, pathways in fatty acid biosynthesis, sugar acid degradation, and mevalonate metabolism were associated with insulinaemic and inflammatory diets. Dietary patterns that exert metabolic effects on insulin and inflammation may influence chronic disease risk by modulating gut microbial composition and function.

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

Metabolomic Applications in Gut Microbiota-Host Interactions in Human Diseases

The human gut microbiota, consisting of trillions of microorganisms, encodes diverse metabolic pathways that impact numerous aspects of host physiology. One key way in which gut bacteria interact with the host is through the production of small metabolites. Several of these microbiota-dependent metabolites, such as short-chain fatty acids, have been shown to modulate host diseases. In this review, we examine how disease-associated metabolic signatures are identified using metabolomic platforms, and where metabolomics is applied in gut microbiota-disease interactions. We further explore how integration of metagenomic and metabolomic data in human studies can facilitate biomarkers discoveries in precision medicine.

Metabolomics Characterization of Disease Markers in Diabetes and Its Associated Pathologies

With the change in lifestyle of people, there has been a considerable increase in diabetes, which brings with it certain follow-up pathological conditions, which lead to a substantial medical burden. Identifying biomarkers that aid in screening, diagnosis, and prognosis of diabetes and its associated pathologies would help better patient management and facilitate a personalized treatment approach for prevention and treatment. With the advancement in techniques and technologies, metabolomics has emerged as an omics approach capable of large-scale high throughput data analysis and identifying and quantifying metabolites that provide an insight into the underlying mechanism of the disease and its progression. Diabetes and metabolomics keywords were searched in correspondence with the assigned keywords, including kidney, cardiovascular diseases and critical illness from PubMed and Scopus, from its inception to Dec 2023. The relevant studies from this search were extracted and included in the study. This review is focused on the biomarkers identified in diabetes, diabetic kidney disease, diabetes-related development of CVD, and its role in critical illness.

Metabolomics and Lipidomics for Studying Metabolic Syndrome: Insights into Cardiovascular Diseases, Type 1 & 2 Diabetes, and Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolomics and lipidomics have emerged as tools in understanding the connections of metabolic syndrome (MetS) with cardiovascular diseases (CVD), type 1 and type 2 diabetes (T1D, T2D), and metabolic dysfunction-associated steatotic liver disease (MASLD). This review highlights the applications of these omics approaches in large-scale cohort studies, emphasizing their role in biomarker discovery and disease prediction. Integrating metabolomics and lipidomics has significantly advanced our understanding of MetS pathology by identifying unique metabolic signatures associated with disease progression. However, challenges such as standardizing analytical workflows, data interpretation, and biomarker validation remain critical for translating research findings into clinical practice. Future research should focus on optimizing these methodologies to enhance their clinical utility and address the global burden of MetS-related diseases.

Genome-scale community modelling elucidates the metabolic interaction in Indian type-2 diabetic gut microbiota

Type-2 diabetes (T2D) is a rapidly growing multifactorial metabolic disorder that induces the onset of various diseases in the human body. The compositional and metabolic shift of the gut microbiota is a crucial factor behind T2D. Hence, gaining insight into the metabolic profile of the gut microbiota is essential for revealing their role in regulating the metabolism of T2D patients. Here, we have focused on the genome-scale community metabolic model reconstruction of crucial T2D-associated gut microbes. The model-based analysis of biochemical flux in T2D and healthy gut conditions showed distinct biochemical signatures and diverse metabolic interactions in the microbial community. The metabolic interactions encompass cross-feeding of short-chain fatty acids, amino acids, and vitamins among individual microbes within the community. In T2D conditions, a reduction in the metabolic flux of acetate, butyrate, vitamin B5, and bicarbonate was observed in the microbial community model, which can impact carbohydrate metabolism. The decline in butyrate levels is correlated with both insulin resistance and diminished glucose metabolism in T2D patients. Compared to the healthy gut, an overall reduction in glucose consumption and SCFA production flux was estimated in the T2D gut environment. Moreover, the decreased consumption profiles of branch chain amino acids (BCAAs) and aromatic amino acids (AAAs) in the T2D gut microbiota can be a distinct biomarker for T2D. Hence, the flux-level analysis of the microbial community model can provide insights into the metabolic reprogramming in diabetic gut microbiomes, which may be helpful in personalized therapeutics and diet design against T2D.

Genetically predicted 1091 blood metabolites and 309 metabolite ratios in relation to risk of type 2 diabetes: a Mendelian randomization study

Background

Metabolic dysregulation represents a defining characteristic of Type 2 diabetes (T2DM). Nevertheless, there remains an absence of substantial evidence establishing a direct causal link between circulating blood metabolites and the promotion or prevention of T2DM. In addressing this gap, we employed Mendelian randomization (MR) analysis to investigate the potential causal association between 1,091 blood metabolites, 309 metabolite ratios, and the occurrence of T2DM.

Methods

Data encompassing single-nucleotide polymorphisms (SNPs) for 1,091 blood metabolites and 309 metabolite ratios were extracted from a Canadian Genome-wide association study (GWAS) involving 8,299 participants. To evaluate the causal link between these metabolites and Type 2 diabetes (T2DM), multiple methods including Inverse Variance Weighted (IVW), Weighted Median, MR Egger, Weighted Mode, and Simple Mode were employed. p-values underwent correction utilizing False Discovery Rates (FDR). Sensitivity analyses incorporated Cochran's Q test, MR-Egger intercept test, MR-PRESSO, Steiger test, leave-one-out analysis, and single SNP analysis. The causal effects were visualized via Circos plot, forest plot, and scatter plot. Furthermore, for noteworthy, an independent T2DM GWAS dataset (GCST006867) was utilized for replication analysis. Metabolic pathway analysis of closely correlated metabolites was conducted using MetaboAnalyst 5.0.

Results

The IVW analysis method utilized in this study revealed 88 blood metabolites and 37 metabolite ratios demonstrating a significant causal relationship with T2DM (p < 0.05). Notably, strong causal associations with T2DM were observed for specific metabolites: 1-linoleoyl-GPE (18:2) (IVW: OR:0.930, 95% CI: 0.899-0.962, p = 2.16 × 10-5), 1,2-dilinoleoyl-GPE (18:2/18:2) (IVW: OR:0.942, 95% CI: 0.917-0.968, p = 1.64 × 10-5), Mannose (IVW: OR:1.133, 95% CI: 1.072-1.197, p = 1.02 × 10-5), X-21829 (IVW: OR:1.036, 95% CI: 1.036-1.122, p = 9.44 × 10-5), and Phosphate to mannose ratio (IVW: OR:0.870, 95% CI: 0.818-0.926, p = 1.29 × 10-5, FDR = 0.008). Additionally, metabolic pathway analysis highlighted six significant pathways associated with T2DM development: Valine, leucine and isoleucine biosynthesis, Phenylalanine metabolism, Glycerophospholipid metabolism, Alpha-Linolenic acid metabolism, Sphingolipid metabolism, and Alanine, aspartate, and glutamate metabolism.

Conclusion

This study identifies both protective and risk-associated metabolites that play a causal role in the development of T2DM. By integrating genomics and metabolomics, it presents novel insights into the pathogenesis of T2DM. These findings hold potential implications for early screening, preventive measures, and treatment strategies for T2DM.

Bidirectional modulation of TCA cycle metabolites and anaplerosis by metformin and its combination with SGLT2i

BACKGROUND

Metformin and sodium-glucose-cotransporter-2 inhibitors (SGLT2i) are cornerstone therapies for managing hyperglycemia in diabetes. However, their detailed impacts on metabolic processes, particularly within the citric acid (TCA) cycle and its anaplerotic pathways, remain unclear. This study investigates the tissue-specific metabolic effects of metformin, both as a monotherapy and in combination with SGLT2i, on the TCA cycle and associated anaplerotic reactions in both mice and humans.

METHODS

Metformin-specific metabolic changes were initially identified by comparing metformin-treated diabetic mice (MET) with vehicle-treated db/db mice (VG). These findings were then assessed in two human cohorts (KORA and QBB) and a longitudinal KORA study of metformin-naïve patients with Type 2 Diabetes (T2D). We also compared MET with db/db mice on combination therapy (SGLT2i + MET). Metabolic profiling analyzed 716 metabolites from plasma, liver, and kidney tissues post-treatment, using linear regression and Bonferroni correction for statistical analysis, complemented by pathway analyses to explore the pathophysiological implications.

RESULTS

Metformin monotherapy significantly upregulated TCA cycle intermediates such as malate, fumarate, and α-ketoglutarate (α-KG) in plasma, and anaplerotic substrates including hepatic glutamate and renal 2-hydroxyglutarate (2-HG) in diabetic mice. Downregulated hepatic taurine was also observed. The addition of SGLT2i, however, reversed these effects, such as downregulating circulating malate and α-KG, and hepatic glutamate and renal 2-HG, but upregulated hepatic taurine. In human T2D patients on metformin therapy, significant systemic alterations in metabolites were observed, including increased malate but decreased citrulline. The bidirectional modulation of TCA cycle intermediates in mice influenced key anaplerotic pathways linked to glutaminolysis, tumorigenesis, immune regulation, and antioxidative responses.

CONCLUSION

This study elucidates the specific metabolic consequences of metformin and SGLT2i on the TCA cycle, reflecting potential impacts on the immune system. Metformin shows promise for its anti-inflammatory properties, while the addition of SGLT2i may provide liver protection in conditions like metabolic dysfunction-associated steatotic liver disease (MASLD). These observations underscore the importance of personalized treatment strategies.

1H-NMR-based metabolomics reveals the preventive effect of Enteromorpha prolifera polysaccharides on diabetes in Zucker diabetic fatty rats

The primary objective of this investigation was to explore the beneficial impacts of Enteromorpha prolifera polysaccharide (EP) on dysglycemia in Zucker diabetic fatty (ZDF) rats, while also shedding light on its potential mechanism using 1H-NMR-based metabolomics. The results demonstrated a noteworthy reduction in fasting blood glucose (FBG, 46.3%), fasting insulin (50.17%), glycosylated hemoglobin A1c (HbA1c, 44.1%), and homeostatic model assessment of insulin resistance (HOMA-IR, 59.75%) following EP administration, while the insulin sensitivity index (ISI, 19.6%) and homeostatic model assessment of β-cell function (HOMA-β, 2.5-fold) were significantly increased. These findings indicate that EP enhances β-cell function, increases insulin sensitivity, and improves insulin resistance caused by diabetes. Moreover, EP significantly reduced serum lipid levels, suggesting improvement of dyslipidemia. Through the analysis of serum metabolomics, 17 metabolites were found to be altered in diabetic rats, 14 of which were upregulated and 3 of which were downregulated. Notably, the administration of EP successfully reversed the abnormal levels of 9 out of the 17 metabolites. Pathway analysis further revealed that EP treatment partially restored metabolic dysfunction, with notable effects observed in valine, leucine, and isoleucine metabolism; aminoacyl-transfer RNA (tRNA) biosynthesis; and ketone body metabolism. These findings collectively indicate the potential therapeutic efficacy of EP in preventing glycemic abnormalities and improving insulin resistance. Thus, EP holds promise as a valuable treatment option for individuals with diabetes.

Differences in metabolomic profiles between Black and White women in the U.S.: Analyses from two prospective cohorts

There is growing interest in incorporating metabolomics into public health practice. However, Black women are under-represented in many metabolomics studies. If metabolomic profiles differ between Black and White women, this under-representation may exacerbate existing Black-White health disparities. We therefore aimed to estimate metabolomic differences between Black and White women in the U.S. We leveraged data from two prospective cohorts: the Nurses' Health Study (NHS; n = 2077) and Women's Health Initiative (WHI; n = 2128). The WHI served as the replication cohort. Plasma metabolites (n = 334) were measured via liquid chromatography-tandem mass spectrometry. Observed metabolomic differences were estimated using linear regression and metabolite set enrichment analyses. Residual metabolomic differences in a hypothetical population in which the distributions of 14 risk factors were equalized across racial groups were estimated using inverse odds ratio weighting. In the NHS, Black-White differences were observed for most metabolites (75 metabolites with observed differences ≥ |0.50| standard deviations). Black women had lower average levels than White women for most metabolites (e.g., for N6, N6-dimethlylysine, mean Black-White difference = - 0.98 standard deviations; 95% CI: - 1.11, - 0.84). In metabolite set enrichment analyses, Black women had lower levels of triglycerides, phosphatidylcholines, lysophosphatidylethanolamines, phosphatidylethanolamines, and organoheterocyclic compounds, but higher levels of phosphatidylethanolamine plasmalogens, phosphatidylcholine plasmalogens, cholesteryl esters, and carnitines. In a hypothetical population in which distributions of 14 risk factors were equalized, Black-White metabolomic differences persisted. Most results replicated in the WHI (88% of 272 metabolites available for replication). Substantial differences in metabolomic profiles exist between Black and White women. Future studies should prioritize racial representation.

Advanced Mass Spectrometry-Based Biomarker Identification for Metabolomics of Diabetes Mellitus and Its Complications

Over the years, there has been notable progress in understanding the pathogenesis and treatment modalities of diabetes and its complications, including the application of metabolomics in the study of diabetes, capturing attention from researchers worldwide. Advanced mass spectrometry, including gas chromatography-tandem mass spectrometry (GC-MS/MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS), and ultra-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-Q-TOF-MS), etc., has significantly broadened the spectrum of detectable metabolites, even at lower concentrations. Advanced mass spectrometry has emerged as a powerful tool in diabetes research, particularly in the context of metabolomics. By leveraging the precision and sensitivity of advanced mass spectrometry techniques, researchers have unlocked a wealth of information within the metabolome. This technology has enabled the identification and quantification of potential biomarkers associated with diabetes and its complications, providing new ideas and methods for clinical diagnostics and metabolic studies. Moreover, it offers a less invasive, or even non-invasive, means of tracking disease progression, evaluating treatment efficacy, and understanding the underlying metabolic alterations in diabetes. This paper summarizes advanced mass spectrometry for the application of metabolomics in diabetes mellitus, gestational diabetes mellitus, diabetic peripheral neuropathy, diabetic retinopathy, diabetic nephropathy, diabetic encephalopathy, diabetic cardiomyopathy, and diabetic foot ulcers and organizes some of the potential biomarkers of the different complications with the aim of providing ideas and methods for subsequent in-depth metabolic research and searching for new ways of treating the disease.

Global status and trends of metabolomics in diabetes: A literature visualization knowledge graph study

BACKGROUND

Diabetes is a metabolic disease characterized by hyperglycemia, which has increased the global medical burden and is also the main cause of death in most countries.

AIM

To understand the knowledge structure of global development status, research focus, and future trend of the relationship between diabetes and metabolomics in the past 20 years.

METHODS

The articles about the relationship between diabetes and metabolomics in the Web of Science Core Collection were retrieved from 2002 to October 23, 2023, and the relevant information was analyzed using CiteSpace6.2.2R (CiteSpace), VOSviewer6.1.18 (VOSviewer), and Bibliometrix software under R language.

RESULTS

A total of 3123 publications were included from 2002 to 2022. In the past two decades, the number of publications and citations in this field has continued to increase. The United States, China, Germany, the United Kingdom, and other relevant funds, institutions, and authors have significantly contributed to this field. Scientific Reports and PLoS One are the journals with the most publications and the most citations. Through keyword co-occurrence and cluster analysis, the closely related keywords are "insulin resistance", "risk", "obesity", "oxidative stress", "metabolomics", "metabolites" and "biomarkers". Keyword clustering included cardiovascular disease, gut microbiota, metabonomics, diabetic nephropathy, molecular docking, gestational diabetes mellitus, oxidative stress, and insulin resistance. Burst detection analysis of keyword depicted that "Gene", "microbiota", "validation", "kidney disease", "antioxidant activity", "untargeted metabolomics", "management", and "accumulation" are knowledge frontiers in recent years.

CONCLUSION

The relationship between metabolomics and diabetes is receiving extensive attention. Diabetic nephropathy, diabetic cardiovascular disease, and kidney disease are key diseases for future research in this field. Gut microbiota, molecular docking, and untargeted metabolomics are key research directions in the future. Antioxidant activity, gene, validation, mass spectrometry, management, and accumulation are at the forefront of knowledge frontiers in this field.

Causal relationships between blood metabolites and diabetic retinopathy: a two-sample Mendelian randomization study

Background

Diabetic retinopathy (DR) is a microvascular complication of diabetes, severely affecting patients' vision and even leading to blindness. The development of DR is influenced by metabolic disturbance and genetic factors, including gene polymorphisms. The research aimed to uncover the causal relationships between blood metabolites and DR.

Methods

The two-sample mendelian randomization (MR) analysis was employed to estimate the causality of blood metabolites on DR. The genetic variables for exposure were obtained from the genome-wide association study (GWAS) dataset of 486 blood metabolites, while the genetic predictors for outcomes including all-stage DR (All DR), non-proliferative DR (NPDR) and proliferative DR (PDR) were derived from the FinnGen database. The primary analysis employed inverse variance weighted (IVW) method, and supplementary analyses were performed using MR-Egger, weighted median (WM), simple mode and weighted mode methods. Additionally, MR-Egger intercept test, Cochran's Q test, and leave-one-out analysis were also conducted to guarantee the accuracy and robustness of the results. Subsequently, we replicated the MR analysis using three additional datasets from the FinnGen database and conducted a meta-analysis to determine blood metabolites associated with DR. Finally, reverse MR analysis and metabolic pathway analysis were performed.

Results

The study identified 13 blood metabolites associated with All DR, 9 blood metabolites associated with NPDR and 12 blood metabolites associated with PDR. In summary, a total of 21 blood metabolites were identified as having potential causal relationships with DR. Additionally, we identified 4 metabolic pathways that are related to DR.

Conclusion

The research revealed a number of blood metabolites and metabolic pathways that are causally associated with DR, which holds significant importance for screening and prevention of DR. However, it is noteworthy that these causal relationships should be validated in larger cohorts and experiments.

Canagliflozin regulates metabolic reprogramming in diabetic kidney disease by inducing fasting-like and aestivation-like metabolic patterns

AIMS/HYPOTHESIS

Sodium-glucose co-transporter 2 (SGLT2) inhibitors (SGLT2i) are antihyperglycaemic drugs that protect the kidneys of individuals with type 2 diabetes mellitus. However, the underlying mechanisms mediating the renal benefits of SGLT2i are not fully understood. Considering the fuel switches that occur during therapeutic SGLT2 inhibition, we hypothesised that SGLT2i induce fasting-like and aestivation-like metabolic patterns, both of which contribute to the regulation of metabolic reprogramming in diabetic kidney disease (DKD).

METHODS

Untargeted and targeted metabolomics assays were performed on plasma samples from participants with type 2 diabetes and kidney disease (n=35, 11 women) receiving canagliflozin (CANA) 100 mg/day at baseline and 12 week follow-up. Next, a systematic snapshot of the effect of CANA on key metabolites and pathways in the kidney was obtained using db/db mice. Moreover, the effects of glycine supplementation in db/db mice and human proximal tubular epithelial cells (human kidney-2 [HK-2]) cells were studied.

RESULTS

Treatment of DKD patients with CANA for 12 weeks significantly reduced HbA1c from a median (interquartile range 25-75%) of 49.0 (44.0-57.0) mmol/mol (7.9%, [7.10-9.20%]) to 42.2 (39.7-47.7) mmol/mol (6.8%, [6.40-7.70%]), and reduced urinary albumin/creatinine ratio from 67.8 (45.9-159.0) mg/mmol to 47.0 (26.0-93.6) mg/mmol. The untargeted metabolomics assay showed downregulated glycolysis and upregulated fatty acid oxidation. The targeted metabolomics assay revealed significant upregulation of glycine. The kidneys of db/db mice undergo significant metabolic reprogramming, with changes in sugar, lipid and amino acid metabolism; CANA regulated the metabolic reprogramming in the kidneys of db/db mice. In particular, the pathways for glycine, serine and threonine metabolism, as well as the metabolite of glycine, were significantly upregulated in CANA-treated kidneys. Glycine supplementation ameliorated renal lesions in db/db mice by inhibiting food intake, improving insulin sensitivity and reducing blood glucose levels. Glycine supplementation improved apoptosis of human proximal tubule cells via the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway.

CONCLUSIONS/INTERPRETATION

In conclusion, our study shows that CANA ameliorates DKD by inducing fasting-like and aestivation-like metabolic patterns. Furthermore, DKD was ameliorated by glycine supplementation, and the beneficial effects of glycine were probably due to the activation of the AMPK/mTOR pathway.

L-arginine supplementation abrogates hypoxia-induced virulence of Staphylococcus aureus in a murine diabetic pressure wound model

Diabetic foot ulcers (DFUs) are the most common complications of diabetes resulting from hyperglycemia leading to ischemic hypoxic tissue and nerve damage. Staphylococcus aureus is the most frequently isolated bacteria from DFUs and causes severe necrotic infections leading to amputations with a poor 5-year survival rate. However, very little is known about the mechanisms by which S. aureus dominantly colonizes and causes severe disease in DFUs. Herein, we utilized a pressure wound model in diabetic TALLYHO/JngJ mice to reproduce ischemic hypoxic tissue damage seen in DFUs and demonstrated that anaerobic fermentative growth of S. aureus significantly increased the virulence and the severity of disease by activating two-component regulatory systems leading to expression of virulence factors. Our in vitro studies showed that supplementation of nitrate as a terminal electron acceptor promotes anaerobic respiration and suppresses the expression of S. aureus virulence factors through inactivation of two-component regulatory systems, suggesting potential therapeutic benefits by promoting anaerobic nitrate respiration. Our in vivo studies revealed that dietary supplementation of L-arginine (L-Arg) significantly attenuated the severity of disease caused by S. aureus in the pressure wound model by providing nitrate. Collectively, these findings highlight the importance of anaerobic fermentative growth in S. aureus pathogenesis and the potential of dietary L-Arg supplementation as a therapeutic to prevent severe S. aureus infection in DFUs.IMPORTANCES. aureus is the most common cause of infection in DFUs, often resulting in lower-extremity amputation with a distressingly poor 5-year survival rate. Treatment for S. aureus infections has largely remained unchanged for decades and involves tissue debridement with antibiotic therapy. With high levels of conservative treatment failure, recurrence of ulcers, and antibiotic resistance, a new approach is necessary to prevent lower-extremity amputations. Nutritional aspects of DFU treatment have largely been overlooked as there has been contradictory clinical trial evidence, but very few in vitro and in vivo modelings of nutritional treatment studies have been performed. Here we demonstrate that dietary supplementation of L-Arg in a diabetic mouse model significantly reduced duration and severity of disease caused by S. aureus. These findings suggest that L-Arg supplementation could be useful as a potential preventive measure against severe S. aureus infections in DFUs.

Integrated 16S rRNA sequencing and metabolomic analysis reveals the potential protective mechanism of Germacrone on diabetic nephropathy in mice

Diabetic nephropathy (DN) is a severe complication of diabetes and the leading cause of end-stage renal disease and death. Germacrone (Ger) possesses anti-inflammatory, antioxidant and anti-DN properties. However, it is unclear whether the improvement in kidney damage caused by Ger in DN mice is related to abnormal compositions and metabolites of the gut microbiota. This study generates a mouse model of DN to explore the potent therapeutic ability and mechanism of Ger in renal function by 16S rRNA sequencing and untargeted fecal metabolomics. Although there is no significant change in microbiota diversity, the structure of the gut microbiota in the DN group is quite different. Serratia_marcescens and Lactobacillus_iners are elevated in the model group but significantly decreased after Ger intervention ( P<0.05). Under the treatment of Ger, no significant differences in the diversity and richness of the gut microbiota are observed. An imbalance in the intestinal flora leads to the dysregulation of metabolites, and non-targeted metabolomics data indicate high expression of stearic acid in the DN group, and oleic acid could serve as a potential marker of the therapeutic role of Ger in the DN model. Overall, Ger improves kidney injury in diabetic mice, in part potentially by reducing the abundance of Serratia_marcescens and Lactobacillus_iners, as well as regulating the associated increase in metabolites such as oleic acid, lithocholic acid and the decrease in stearic acid. Our research expands the understanding of the relationship between the gut microbiota and metabolites in Ger-treated DN. This contributes to the usage of natural products as a therapeutic approach for the treatment of DN via microbiota regulation.

Branched-chain amino acid catabolic defect promotes α-cell proliferation via activating mTOR signaling

Elevated circulating level of branched-chain amino acids (BCAAs) is closely related to the development of type 2 diabetes. However, the role of BCAA catabolism in various tissues in maintaining glucose homeostasis remains largely unknown. Pancreatic α-cells have been regarded as amino acid sensors in recent years. Therefore, we generated α-cell specific branched-chain alpha-ketoacid dehydrogenase E1α subunit (BCKDHA) knockout (BCKDHA-αKO) mice to decipher the effects of BCAA catabolism in α-cells on whole-body energy metabolism. BCKDHA-αKO mice showed normal body weight, body fat, and energy expenditure. Plasma glucagon level and glucose metabolism also remained unchanged in BCKDHA-αKO mice. Whereas, the deletion of BCKDHA led to increased α-cell number due to elevated cell proliferation in neonatal mice. In vitro, only leucine among BCAAs promoted aTC1-6 cell proliferation, which was blocked by the agonist of BCAA catabolism BT2 and the inhibitor of mTOR Rapamycin. Like Rapamycin, BT2 attenuated leucine-stimulated phosphorylation of S6 in αTC1-6 cells. Elevated phosphorylation level of S6 protein in pancreatic α-cells was also observed in BCKDHA-αKO mice. These results suggest that local accumulated leucine due to defective BCAA catabolism promotes α-cell proliferation through mTOR signaling, which is insufficient to affect glucagon secretion and whole-body glucose homeostasis.

Heterogeneously elevated branched-chain/aromatic amino acids among new-onset type-2 diabetes mellitus patients are potentially skewed diabetes predictors

BACKGROUND

The lack of specific predictors for type-2 diabetes mellitus (T2DM) severely impacts early intervention/prevention efforts. Elevated branched-chain amino acids (BCAAs: Isoleucine, leucine, valine) and aromatic amino acids (AAAs: Tyrosine, tryptophan, phenylalanine)) show high sensitivity and specificity in predicting diabetes in animals and predict T2DM 10-19 years before T2DM onset in clinical studies. However, improvement is needed to support its clinical utility.

AIM

To evaluate the effects of body mass index (BMI) and sex on BCAAs/AAAs in new-onset T2DM individuals with varying body weight.

METHODS

Ninety-seven new-onset T2DM patients (< 12 mo) differing in BMI [normal weight (NW), n = 33, BMI = 22.23 ± 1.60; overweight, n = 42, BMI = 25.9 ± 1.07; obesity (OB), n = 22, BMI = 31.23 ± 2.31] from the First People's Hospital of Yunnan Province, Kunming, China, were studied. One-way and 2-way ANOVAs were conducted to determine the effects of BMI and sex on BCAAs/AAAs.

RESULTS

Fasting serum AAAs, BCAAs, glutamate, and alanine were greater and high-density lipoprotein (HDL) was lower (P < 0.05, each) in OB-T2DM patients than in NW-T2DM patients, especially in male OB-T2DM patients. Arginine, histidine, leucine, methionine, and lysine were greater in male patients than in female patients. Moreover, histidine, alanine, glutamate, lysine, valine, methionine, leucine, isoleucine, tyrosine, phenylalanine, and tryptophan were significantly correlated with abdominal adiposity, body weight and BMI, whereas isoleucine, leucine and phenylalanine were negatively correlated with HDL.

CONCLUSION

Heterogeneously elevated amino acids, especially BCAAs/AAAs, across new-onset T2DM patients in differing BMI categories revealed a potentially skewed prediction of T2DM development. The higher BCAA/AAA levels in obese T2DM patients would support T2DM prediction in obese individuals, whereas the lower levels of BCAAs/AAAs in NW-T2DM individuals may underestimate T2DM risk in NW individuals. This potentially skewed T2DM prediction should be considered when BCAAs/AAAs are to be used as the T2DM predictor.

Predictive metabolites for incident myocardial infarction: a two-step meta-analysis of individual patient data from six cohorts comprising 7897 individuals from the COnsortium of METabolomics Studies

AIMS

Myocardial infarction (MI) is a major cause of death and disability worldwide. Most metabolomics studies investigating metabolites predicting MI are limited by the participant number and/or the demographic diversity. We sought to identify biomarkers of incident MI in the COnsortium of METabolomics Studies.

METHODS AND RESULTS

We included 7897 individuals aged on average 66 years from six intercontinental cohorts with blood metabolomic profiling (n = 1428 metabolites, of which 168 were present in at least three cohorts with over 80% prevalence) and MI information (1373 cases). We performed a two-stage individual patient data meta-analysis. We first assessed the associations between circulating metabolites and incident MI for each cohort adjusting for traditional risk factors and then performed a fixed effect inverse variance meta-analysis to pull the results together. Finally, we conducted a pathway enrichment analysis to identify potential pathways linked to MI. On meta-analysis, 56 metabolites including 21 lipids and 17 amino acids were associated with incident MI after adjusting for multiple testing (false discovery rate < 0.05), and 10 were novel. The largest increased risk was observed for the carbohydrate mannitol/sorbitol {hazard ratio [HR] [95% confidence interval (CI)] = 1.40 [1.26-1.56], P < 0.001}, whereas the largest decrease in risk was found for glutamine [HR (95% CI) = 0.74 (0.67-0.82), P < 0.001]. Moreover, the identified metabolites were significantly enriched (corrected P < 0.05) in pathways previously linked with cardiovascular diseases, including aminoacyl-tRNA biosynthesis.

CONCLUSIONS

In the most comprehensive metabolomic study of incident MI to date, 10 novel metabolites were associated with MI. Metabolite profiles might help to identify high-risk individuals before disease onset. Further research is needed to fully understand the mechanisms of action and elaborate pathway findings.

EFSA Panel on Food Additives and Flavourings (FAF), Younes M, Aquilina G, Castle L, Degen G, Engel K, Fowler PJ, Frutos Fernandez MJ, Fürst P, Gundert‐Remy U, Gürtler R, Husøy T, Manco M, Mennes W, Moldeus P, Passamonti S, Shah R, Waalkens‐Berendsen I, Wright M, Batke M, Boon P, Bruzell E, Chipman J, Crebelli R, FitzGerald R, Fortes C, Halldorsson T, LeBlanc J, Lindtner O, Mortensen A, Ntzani E, Wallace H, Barmaz S, Civitella C, D'Angelo L, Lodi F, Laganaro M, Rincon AM, Smeraldi C, Tard A. Re-evaluation of erythritol (E 968) as a food additive

This opinion addresses the re-evaluation of erythritol (E 968) as food additive and an application for its exemption from the laxative warning label requirement as established under Regulation (EU) No 1169/2011. Erythritol is a polyol obtained by fermentation with Moniliella pollinis BC or Moniliella megachiliensis KW3-6, followed by purifications and drying. Erythritol is readily and dose-dependently absorbed in humans and can be metabolised to erythronate to a small extent. Erythritol is then excreted unchanged in the urine. It does not raise concerns regarding genotoxicity. The dataset evaluated consisted of human interventional studies. The Panel considered that erythritol has the potential to cause diarrhoea in humans, which was considered adverse because its potential association with electrolyte and water imbalance. The lower bound of the range of no observed adverse effect levels (NOAELs) for diarrhoea of 0.5 g/kg body weight (bw) was identified as reference point. The Panel considered appropriate to set a numerical acceptable daily intake (ADI) at the level of the reference point. An ADI of 0.5 g/kg bw per day was considered by the Panel to be protective for the immediate laxative effect as well as potential chronic effects, secondary to diarrhoea. The highest mean and 95th percentile chronic exposure was in children (742 mg/kg bw per day) and adolescents (1532 mg/kg bw per day). Acute exposure was maximally 3531 mg/kg bw per meal for children at the 99th percentile. Overall, the Panel considered both dietary exposure assessments an overestimation. The Panel concluded that the exposure estimates for both acute and chronic dietary exposure to erythritol (E 968) were above the ADI, indicating that individuals with high intake may be at risk of experiencing adverse effects after single and repeated exposure. Concerning the new application, the Panel concluded that the available data do not support the proposal for exemption.

Causal effects of genetically determined blood metabolites on multiple myeloma: a Mendelian randomization study

Previous studies have shown that metabolites play an important role in phenotypic regulation. However, the causal relationship between metabolites and multiple myeloma has not been adequately investigated. Here, we attempt to explore the causal effects of genetically determined blood metabolites on multiple myeloma. The large-scale public blood metabolites and multiple myeloma datasets from independently published genome-wide association studies (GWAS) were used to explore the causal relationship between each genetically determined blood metabolite and multiple myeloma through inverse variance weighted (IVW), weighted median, MR-Egger and mode-based estimation methods. Sensitivity tests were performed to evaluate the stability and reliability of the results by MR-Egger regression and leave-one-out methods. Metabolic pathway analysis was further explored using filtered data. Statistical analyses were all performed in R. Among 452 metabolites, ten known metabolites and three unknown metabolites had significant causal relationship with multiple myeloma (P < 0.05). Four known metabolites, 3-methyl-2-oxovalenate, oxidized bilirubin, isovalerylcarnitine and glutamine carnitine, reached statistical significance in IVW models. Metabolic pathways analysis identified four significant pathways. The occurrence of multiple myeloma may have a causal relationship with these four metabolites, and there are four metabolic pathways that are also related to the occurrence of multiple myeloma. This can provide new ideas for exploring early screening and treatment of multiple myeloma.

Metabolite profiles of diabetes mellitus and response to intervention in anti-hyperglycemic drugs

Type 2 diabetes mellitus (T2DM) has become a major health problem, threatening the quality of life of nearly 500 million patients worldwide. As a typical multifactorial metabolic disease, T2DM involves the changes and interactions of various metabolic pathways such as carbohydrates, amino acid, and lipids. It has been suggested that metabolites are not only the endpoints of upstream biochemical processes, but also play a critical role as regulators of disease progression. For example, excess free fatty acids can lead to reduced glucose utilization in skeletal muscle and induce insulin resistance; metabolism disorder of branched-chain amino acids contributes to the accumulation of toxic metabolic intermediates, and promotes the dysfunction of β-cell mitochondria, stress signal transduction, and apoptosis. In this paper, we discuss the role of metabolites in the pathogenesis of T2DM and their potential as biomarkers. Finally, we list the effects of anti-hyperglycemic drugs on serum/plasma metabolic profiles.

Mitochondrial Reactive Oxygen Species, Insulin Resistance, and Nrf2-Mediated Oxidative Stress Response-Toward an Actionable Strategy for Anti-Aging

Reactive oxygen species (ROS) are produced mainly by mitochondrial respiration and function as signaling molecules in the physiological range. However, ROS production is also associated with the pathogenesis of various diseases, including insulin resistance (IR) and type 2 diabetes (T2D). This review focuses on the etiology of IR and early events, especially mitochondrial ROS (mtROS) production in insulin-sensitive tissues. Importantly, IR and/or defective adipogenesis in the white adipose tissues (WAT) is thought to increase free fatty acid and ectopic lipid deposition to develop into systemic IR. Fatty acid and ceramide accumulation mediate coenzyme Q reduction and mtROS production in IR in the skeletal muscle, while coenzyme Q synthesis downregulation is also involved in mtROS production in the WAT. Obesity-related IR is associated with the downregulation of mitochondrial catabolism of branched-chain amino acids (BCAAs) in the WAT, and the accumulation of BCAA and its metabolites as biomarkers in the blood could reliably indicate future T2D. Transcription factor NF-E2-related factor 2 (Nrf2), which regulates antioxidant enzyme expression in response to oxidative stress, is downregulated in insulin-resistant tissues. However, Nrf2 inducers, such as sulforaphane, could restore Nrf2 and target gene expression and attenuate IR in multiple tissues, including the WAT.

Elevated Erythritol: A Marker of Metabolic Dysregulation or Contributor to the Pathogenesis of Cardiometabolic Disease?

Erythritol is a non-nutritive sugar replacement that can be endogenously produced by humans. Witkowski et al. reported that elevated circulating erythritol is associated with adverse cardiovascular events in three independent cohorts, demonstrated in vitro and ex vivo that erythritol promotes platelet activation, and showed faster clotting time in mice injected with erythritol. It was concluded that erythritol fosters enhanced thrombosis. This narrative review presents additional evidence that needs to be considered when evaluating these data and conclusions. We conducted a search of all studies related to erythritol exposure with focus on those that reported vascular health outcomes. Patients with chronically elevated erythritol levels due to inborn errors of metabolism do not exhibit higher platelet activation or thrombosis risk. Most long-term studies in which animals consumed high levels of erythritol do not support its role in platelet activation and thrombosis formation. Clinical data on the effects of chronic intake of erythritol are limited. Erythritol may be merely a marker of dysregulation in the Pentose Phosphate Pathway caused by impaired glycemia. However, this suggestion and the findings of Witkowski et al. need to be further examined. Clinical trials examining the long-term effects of erythritol consumption on cardiometabolic outcomes are required to test the causality between dietary erythritol and cardiometabolic risk. Until supportive data from these trials are available, it cannot be concluded that dietary erythritol promotes platelet activation, thrombosis, and cardiometabolic risk.

Unlocking the Potential: Amino Acids' Role in Predicting and Exploring Therapeutic Avenues for Type 2 Diabetes Mellitus

Diabetes mellitus, particularly type 2 diabetes mellitus (T2DM), imposes a significant global burden with adverse clinical outcomes and escalating healthcare expenditures. Early identification of biomarkers can facilitate better screening, earlier diagnosis, and the prevention of diabetes. However, current clinical predictors often fail to detect abnormalities during the prediabetic state. Emerging studies have identified specific amino acids as potential biomarkers for predicting the onset and progression of diabetes. Understanding the underlying pathophysiological mechanisms can offer valuable insights into disease prevention and therapeutic interventions. This review provides a comprehensive summary of evidence supporting the use of amino acids and metabolites as clinical biomarkers for insulin resistance and diabetes. We discuss promising combinations of amino acids, including branched-chain amino acids, aromatic amino acids, glycine, asparagine and aspartate, in the prediction of T2DM. Furthermore, we delve into the mechanisms involving various signaling pathways and the metabolism underlying the role of amino acids in disease development. Finally, we highlight the potential of targeting predictive amino acids for preventive and therapeutic interventions, aiming to inspire further clinical investigations and mitigate the progression of T2DM, particularly in the prediabetic stage.

Salbutamol Attenuates Diabetic Skeletal Muscle Atrophy by Reducing Oxidative Stress, Myostatin/GDF-8, and Pro-Inflammatory Cytokines in Rats

Type 2 diabetes is a metabolic disorder that leads to accelerated skeletal muscle atrophy. In this study, we aimed to evaluate the effect of salbutamol (SLB) on skeletal muscle atrophy in high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic rats. Male Sprague Dawley rats were divided into four groups (n = 6): control, SLB, HFD/STZ, and HFD/STZ + SLB (6 mg/kg orally for four weeks). After the last dose of SLB, rats were assessed for muscle grip strength and muscle coordination (wire-hanging, rotarod, footprint, and actophotometer tests). Body composition was analyzed in live rats. After that, animals were sacrificed, and serum and gastrocnemius (GN) muscles were collected. Endpoints include myofibrillar protein content, muscle oxidative stress and antioxidants, serum pro-inflammatory cytokines (interleukin-1β, interleukin-2, and interleukin-6), serum muscle markers (myostatin, creatine kinase, and testosterone), histopathology, and muscle 1H NMR metabolomics. Findings showed that SLB treatment significantly improved muscle strength and muscle coordination, as well as increased lean muscle mass in diabetic rats. Increased pro-inflammatory cytokines and muscle markers (myostatin, creatine kinase) indicate muscle deterioration in diabetic rats, while SLB intervention restored the same. Also, Feret's diameter and cross-sectional area of GN muscle were increased by SLB treatment, indicating the amelioration in diabetic rat muscle. Results of muscle metabolomics exhibit that SLB treatment resulted in the restoration of perturbed metabolites, including histidine-to-tyrosine, phenylalanine-to-tyrosine, and glutamate-to-glutamine ratios and succinate, sarcosine, and 3-hydroxybutyrate (3HB) in diabetic rats. These metabolites showed a pertinent role in muscle inflammation and oxidative stress in diabetic rats. In conclusion, findings showed that salbutamol could be explored as an intervention in diabetic-associated skeletal muscle atrophy.

New insight into the virulence and inflammatory response of Staphylococcus aureus strains isolated from diabetic foot ulcers

Staphylococcus aureus strains isolated from diabetic foot ulcers (DFUs) have less virulence, but still cause severe infections. Furthermore, hypovirulent S. aureus strains appear to be localized in the deep tissues of diabetic foot osteomyelitis, indicating that the unique environment within DFUs affects the pathogenicity of S. aureus. In this study, the cell-free culture medium (CFCM) of S. aureus strains isolated from DFUs exhibited higher cytotoxicity to human erythrocytes than those isolated from non-diabetic patients with sepsis or wounds. Among these S. aureus strains isolated from DFUs, β-toxin negative strains have less virulence than β-toxin positive strains, but induced a higher expression of inflammatory cytokines. Our study and previous studies have shown that the synergistic effect of phenol-soluble modulin α and β-toxin contributes to the higher hemolytic activity of β-toxin positive strains. However, lysis of human erythrocytes by the CFCM of β-toxin negative strains was greatly inhibited by an autolysin inhibitor, sodium polyanethole sulfonate (SPS). A high level of glucose greatly reduced the hemolytic activity of S. aureus, but promoted the expression of interleukin-6 (IL-6) in human neutrophils. However, 5 mM glucose or glucose-6-phosphate (G6P) increased the hemolytic activity of SA118 (a β-toxin negative strain) isolated from DFUs. Additionally, patients with DFUs with growth of S. aureus had lower level of serum IL-6 than those with other bacteria, and the CFCM of S. aureus strains significantly reduced lipopolysaccharide-induced IL-6 expression in human neutrophils. Therefore, the virulence and inflammatory response of S. aureus strains isolated from DFUs are determined by the levels of glucose and its metabolites, which may explain why it is the predominant bacteria isolated from DFUs.

Increased cardiac PFK-2 protects against high-fat diet-induced cardiomyopathy and mediates beneficial systemic metabolic effects

A healthy heart adapts to changes in nutrient availability and energy demands. In metabolic diseases like type 2 diabetes (T2D), increased reliance on fatty acids for energy production contributes to mitochondrial dysfunction and cardiomyopathy. A principal regulator of cardiac metabolism is 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2), which is a central driver of glycolysis. We hypothesized that increasing PFK-2 activity could mitigate cardiac dysfunction induced by high-fat diet (HFD). Wild type (WT) and cardiac-specific transgenic mice expressing PFK-2 (GlycoHi) were fed a low fat or HFD for 16 weeks to induce metabolic dysfunction. Metabolic phenotypes were determined by measuring mitochondrial bioenergetics and performing targeted quantitative proteomic and metabolomic analysis. Increasing cardiac PFK-2 had beneficial effects on cardiac and mitochondrial function. Unexpectedly, GlycoHi mice also exhibited sex-dependent systemic protection from HFD, including increased glucose homeostasis. These findings support improving glycolysis via PFK-2 activity can mitigate mitochondrial and functional changes that occur with metabolic syndrome.

Exploring Metabolomic Patterns in Type 2 Diabetes Mellitus and Response to Glucose-Lowering Medications-Review

The spectrum of information related to precision medicine in diabetes generally includes clinical data, genetics, and omics-based biomarkers that can guide personalized decisions on diabetes care. Given the remarkable progress in patient risk characterization, there is particular interest in using molecular biomarkers to guide diabetes management. Metabolomics is an emerging molecular approach that helps better understand the etiology and promises the identification of novel biomarkers for complex diseases. Both targeted or untargeted metabolites extracted from cells, biofluids, or tissues can be investigated by established high-throughput platforms, like nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques. Metabolomics is proposed as a valuable tool in precision diabetes medicine to discover biomarkers for diagnosis, prognosis, and management of the progress of diabetes through personalized phenotyping and individualized drug-response monitoring. This review offers an overview of metabolomics knowledge as potential biomarkers in type 2 diabetes mellitus (T2D) diagnosis and the response to glucose-lowering medications.

Integration of metabolomics and network pharmacology for enhancing mechanism understanding and medication combination recommendation for diabetes mellitus and diabetic nephropathy

With the increasing prevalence of diabetes mellitus (DM) and diabetic nephropathy (DN), effective treatment is particularly important for the recovery of patients. However, the currently approved drugs are usually tailored to clinical symptoms and no mechanism-targeted drugs are available. In this study, the combination of metabolomics and network pharmacology was applied to provide reasonable medication combination regimens to meet the different clinical needs for the targeted treatment of DM and DN. An NMR-based metabolomic strategy was applied to identify the potential urinary biomarkers of DM or/and DN, while network pharmacology was used to identify the therapy targets of DM and DN by intersecting the targets of diseases and currently approved drugs. According to the enriched signaling pathways using the potential biomarkers and the therapy targets, the specific medication combinations were recommended for the specific clinical demands in terms of hypoglycemic, hypertensive, and/or lipid-lowering. For DM, 17 potential urinary biomarkers and 12 disease-related signaling pathways were identified, and 34 combined medication regimens related to hypoglycemia, hypoglycemia, and hypertension, and hypoglycemia, hypertension, and lipid-lowering were administered. For DN, 22 potential urinary biomarkers and 12 disease-related signaling pathways were identified, and 21 combined medication regimens related to hypoglycemia, hypoglycemia, and hypertension were proposed. Molecular docking was used to verify the binding ability, docking sites, and structure of the drug molecules to target proteins. Moreover, an integrated biological information network of the drug-target-metabolite-signaling pathways was constructed to provide insights into the underlined mechanism of DM and DN as well as clinical combination therapy.

Sucrose Intake Elevates Erythritol in Plasma and Urine in Male Mice

BACKGROUND

Elevated serum erythritol concentration is a predictive biomarker of diabetes and cardiovascular incidence and complications. Erythritol is synthesized endogenously from glucose, but little is known regarding the origin of elevated circulating erythritol in vivo.

OBJECTIVES

In vitro evidence indicates that intracellular erythritol is elevated by high-glucose cell culture conditions and that final step of erythritol synthesis is catalyzed by the enzymes sorbitol dehydrogenase (SORD) and alcohol dehydrogenase (ADH) 1. The purpose of this study was to determine whether dietary intake and/or diet-induced obesity affect erythritol synthesis in mice and whether this relationship is modified by the loss of the enzymes SORD or ADH1.

METHODS

First, 8-wk-old male Sord+/+, Sord-/-, Adh1+/+, and Adh1-/- mice were fed either low-fat diet (LFD) with 10% fat-derived calories or diet-induced obesity high-fat diet (HFD) with 60% fat-derived calories for 8 wk. Plasma and tissue erythritol concentrations were measured using gas chromatography-mass spectrometry. Second, male wild-type 8-wk-old C57BL/6J mice were fed LFD or HFD with plain drinking water or 30% sucrose water for 8 wk. Blood glucose and plasma and urinary erythritol concentrations were measured in nonfasted and fasted samples. Tissue erythritol was measured after killing. Finally, male Sord+/+ and Sord-/- mice were fed LFD with 30% sucrose water for 2 wk; then, nonfasted plasma, urine, and tissue erythritol concentrations were quantified.

RESULTS

Plasma and tissue erythritol concentrations were not affected by loss of Sord or Adh1 in mice fed LFD or HFD. In wild-type mice, consumption of 30% sucrose water significantly elevated plasma and urinary erythritol concentrations on both LFD-fed and HFD-fed mice compared with that of plain water. Sord genotype did not affect plasma or urinary erythritol concentration in response to sucrose feeding, but Sord-/- mice had reduced kidney erythritol content compared with wild-type littermates in response to sucrose.

CONCLUSIONS

Sucrose intake, not HFD, elevates erythritol synthesis and excretion in mice. Loss of ADH1 or SORD does not significantly affect erythritol concentration in mice.

Integrating (Nutri-)Metabolomics into the One Health Tendency-The Key for Personalized Medicine Advancement

Metabolomics is an advanced technology, still under development, with multiple research applications, especially in the field of health. Individual metabolic profiles, the functionality of the body, as well as its interaction with the environment, can be established using this technology. The body's response to various external factors, including the food consumed and the nutrients it contains, has increased researchers' interest in nutrimetabolomics. Establishing correlations between diet and the occurrence of various diseases, or even the development of personalized nutrition plans, could contribute to advances in precision medicine. The interdependence between humans, animals, and the environment is of particular importance today, with the dramatic emergence and spread of zoonotic diseases, food, water and soil contamination, and the degradation of resources and habitats. All these events have led to an increase in risk factors for functional diseases, burdening global health. Thus, this study aimed to highlight the importance of metabolomics, and, in particular, nutrimetabolomics, as a technical solution for a holistic, collaborative, and precise approach for the advancement of the One Health strategy.

Role of sodium pyruvate in maintaining the survival and cytotoxicity of Staphylococcus aureus under high glucose conditions

Glucose is a crucial carbon source for the growth of Staphylococcus aureus, but an excess of glucose is detrimental and even leads to cell death. Pyruvate, the central metabolite of glycolysis, has been shown to have anti-inflammatory and antioxidant properties. This study aimed to investigate the protective effect of pyruvate on S. aureus under high glucose conditions. Sodium pyruvate greatly increased the cytotoxicity of S. aureus strain BAA-1717 to human erythrocytes and neutrophils in vitro. However, the cytotoxicity and survival of S. aureus were significantly reduced by high glucose, which was restored to normal levels by the addition of sodium pyruvate. The expression of hlg and lukS in S. aureus was higher in the LB-GP cultures than that in LB-G cultures, but there was no significant difference in cytotoxicity between LB-GP and LB-G cultures. Furthermore, the hemolytic activity of S. aureus supernatants could be inhibited by the cell-free culture medium (CFCM) of LB-G cultures, suggesting that high levels of extracellular proteases were presence in the CFCM of LB-G cultures, resulting in degradation of the hemolytic factors. The expression of sarA, which negatively regulates extracellular protease secretion, was higher in LB-GP cultures than that in LB-G cultures. Additionally, sodium pyruvate increased acetate production in S. aureus, which helps maintain cell viability under acidic environment. In conclusion, pyruvate plays an important role in the survival and cytotoxicity of S. aureus under high glucose conditions. This finding may aid in the development of effective treatments for diabetic foot infections.

Characterisation of Fasting and Postprandial NMR Metabolites: Insights from the ZOE PREDICT 1 Study

BACKGROUND

Postprandial metabolomic profiles and their inter-individual variability are not well characterised. Here, we describe postprandial metabolite changes, their correlations with fasting values and their inter- and intra-individual variability, following a standardised meal in the ZOE PREDICT 1 cohort.

METHODS

In the ZOE PREDICT 1 study (n = 1002 (NCT03479866)), 250 metabolites, mainly lipids, were measured by a Nightingale NMR panel in fasting and postprandial (4 and 6 h after a 3.7 MJ mixed nutrient meal, with a second 2.2 MJ mixed nutrient meal at 4 h) serum samples. For each metabolite, inter- and intra-individual variability over time was evaluated using linear mixed modelling and intraclass correlation coefficients (ICC) were calculated.

RESULTS

Postprandially, 85% (of 250 metabolites) significantly changed from fasting at 6 h (47% increased, 53% decreased; Kruskal-Wallis), with 37 measures increasing by >25% and 14 increasing by >50%. The largest changes were observed in very large lipoprotein particles and ketone bodies. Seventy-one percent of circulating metabolites were strongly correlated (Spearman's rho >0.80) between fasting and postprandial timepoints, and 5% were weakly correlated (rho <0.50). The median ICC of the 250 metabolites was 0.91 (range 0.08-0.99). The lowest ICCs (ICC <0.40, 4% of measures) were found for glucose, pyruvate, ketone bodies (β-hydroxybutyrate, acetoacetate, acetate) and lactate.

CONCLUSIONS

In this large-scale postprandial metabolomic study, circulating metabolites were highly variable between individuals following sequential mixed meals. Findings suggest that a meal challenge may yield postprandial responses divergent from fasting measures, specifically for glycolysis, essential amino acid, ketone body and lipoprotein size metabolites.

Empagliflozin ameliorates diabetic cardiomyopathy via regulated branched-chain amino acid metabolism and mTOR/p-ULK1 signaling pathway-mediated autophagy

BACKGROUND

Empagliflozin, a sodium-glucose co-transporter 2 inhibitor (SGLT2i), has been reported to significantly reduce the risk of heart failure in multiple clinical studies. However, the underlying mechanisms remain elusive. This study aimed to investigate the effect of empagliflozin on branched-chain amino acid (BCAA) metabolism in diabetic cardiomyopathy.

METHODS

Thirty male 8-week KK Cg-Ay/J mice were used to study diabetic cardiomyopathy; here, 15 were used as the model group, and the remaining 15 were administered empagliflozin (3.75 mg/kg/day) by gavage daily for 16 weeks. The control group consisted of fifteen male 8-week C57BL/6J mice, whose blood glucose and body weight were measured simultaneously with the diabetic mice until 16 weeks without additional intervention. Echocardiography and histopathology were performed to evaluate cardiac structure and function. Proteomic sequencing and biogenic analysis were performed on mouse hearts. Parallel Reaction Monitoring and western blotting were performed to validate the expression levels of differentially expressed proteins.

RESULTS

The results showed that empagliflozin improved ventricular dilatation and ejection fraction reduction in diabetic hearts, as well as the elevation of myocardial injury biomarkers hs-cTnT and NT-proBNP. At the same time, empagliflozin alleviates myocardial inflammatory infiltration, calcification foci deposition, and fibrosis caused by diabetes. The results of the proteomics assay showed that empagliflozin could improve the metabolism of various substances, especially promoting the BCAA metabolism of diabetic hearts by up-regulating PP2Cm. Furthermore, empagliflozin could affect the mTOR/p-ULK1 signaling pathway by reducing the concentration of BCAA in diabetic hearts. When mTOR/p-ULK1 protein was inhibited, ULK1, the autophagy initiation molecule, increased. Moreover, autophagy substrate p62 and autophagy marker LC3B were significantly reduced, indicating that the autophagy activity of diabetes inhibition was reactivated.

CONCLUSIONS

Empagliflozin may attenuate diabetic cardiomyopathy-related myocardial injury by promoting the catabolism of BCAA and inhibiting mTOR/p-ULK1 to enhance autophagy. These findings suggest that empagliflozin could be a potential candidate drug against BCAA increase and could be used for other cardiovascular diseases with a metabolic disorder of BCAA.

Systematic metabolomic studies identified adult adiposity biomarkers with acetylglycine associated with fat loss in vivo

Obesity is associated with various adverse health outcomes. Body fat (BF) distribution is recognized as an important factor of negative health consequences of obesity. Although metabolomics studies, mainly focused on body mass index (BMI) and waist circumference, have explored the biological mechanisms involved in the development of obesity, these proxy composite measures are not accurate and cannot reflect BF distribution, and thus may hinder accurate assessment of metabolic alterations and differential risk of metabolic disorders among individuals presenting adiposity differently throughout the body. Thus, the exact relations between metabolites and BF remain to be elucidated. Here, we aim to examine the associations of metabolites and metabolic pathways with BF traits which reflect BF distribution. We performed systematic untargeted serum metabolite profiling and dual-energy X-ray absorptiometry (DXA) whole body fat scan for 517 Chinese women. We jointly analyzed DXA-derived four BF phenotypes to detect cross-phenotype metabolite associations and to prioritize important metabolomic factors. Topology-based pathway analysis was used to identify important BF-related biological processes. Finally, we explored the relationships of the identified BF-related candidate metabolites with BF traits in different sex and ethnicity through two independent cohorts. Acetylglycine, the top distinguished finding, was validated for its obesity resistance effect through in vivo studies of various diet-induced obese (DIO) mice. Eighteen metabolites and fourteen pathways were discovered to be associated with BF phenotypes. Six of the metabolites were validated in varying sex and ethnicity. The obesity-resistant effects of acetylglycine were observed to be highly robust and generalizable in both human and DIO mice. These findings demonstrate the importance of metabolites associated with BF distribution patterns and several biological pathways that may contribute to obesity and obesity-related disease etiology, prevention, and intervention. Acetylglycine is highlighted as a potential therapeutic candidate for preventing excessive adiposity in future studies.

Metabolomic profiling of glucose homeostasis in African Americans: the Insulin Resistance Atherosclerosis Family Study (IRAS-FS)

INTRODUCTION

African Americans are at increased risk for type 2 diabetes.

OBJECTIVES

This work aimed to examine metabolomic signature of glucose homeostasis in African Americans.

METHODS

We used an untargeted liquid chromatography-mass spectrometry metabolomic approach to comprehensively profile 727 plasma metabolites among 571 African Americans from the Insulin Resistance Atherosclerosis Family Study (IRAS-FS) and investigate the associations between these metabolites and both the dynamic (S_I, insulin sensitivity; AIR, acute insulin response; DI, disposition index; and S_G, glucose effectiveness) and basal (HOMA-IR and HOMA-B) measures of glucose homeostasis using univariate and regularized regression models. We also compared the results with our previous findings in the IRAS-FS Mexican Americans.

RESULTS

We confirmed increased plasma metabolite levels of branched-chain amino acids and their metabolic derivatives, 2-aminoadipate, 2-hydroxybutyrate, glutamate, arginine and its metabolic derivatives, carbohydrate metabolites, and medium- and long-chain fatty acids were associated with insulin resistance, while increased plasma metabolite levels in the glycine, serine and threonine metabolic pathway were associated with insulin sensitivity. We also observed a differential ancestral effect of glutamate on glucose homeostasis with significantly stronger effects observed in African Americans than those previously observed in Mexican Americans.

CONCLUSION

We extended the observations that metabolites are useful biomarkers in the identification of prediabetes in individuals at risk of type 2 diabetes in African Americans. We revealed, for the first time, differential ancestral effect of certain metabolites (i.e., glutamate) on glucose homeostasis traits. Our study highlights the need for additional comprehensive metabolomic studies in well-characterized multiethnic cohorts.