Systemic perturbations of key metabolites in diabetic rats during the evolution of diabetes studied by urine metabonomics

Metabolic perturbations associated with hIAPP-induced insulin resistance in skeletal muscles: Implications to the development of type 2 diabetes

The human islet amyloid polypeptide (hIAPP) tends to misfold and self-assemble to form amyloid fibrils, which has been associated with the loss of function and viability of pancreatic β-cells in type 2 diabetes mellitus (T2DM). The role of hIAPP in the development of insulin resistance (a hallmark of T2DM) in skeletal muscles - the major sites for glucose utilization - needs further investigation. Even though, insulin-resistant conditions have been known to stimulate hIAPP aggregation, the events that lead to the development of insulin resistance due to hIAPP aggregation in skeletal muscles remain unidentified. Here, we have attempted to identify metabolic perturbations in L6 myotubes that were exposed to increasing concentrations of recombinant hIAPP for different time durations. It was observed that hIAPP exposure was associated with increased mitochondrial and cellular ROS levels, loss in mitochondrial membrane potential and viability of the myotubes. Metabolomic investigations of hIAPP-treated myotubes revealed significant perturbations in o-phosphocholine, sn-glycero-3-phosphocholine and dimethylamine levels (p < 0.05). Therefore, we anticipate that defects in glycerophospholipid metabolism and the associated oxidative stress and membrane damage may play key roles in the development of insulin resistance due to protein misfolding in skeletal muscles. In summary, the perturbed metabolites and their pathways have not only the potential to be used as early biomarkers to predict the onset of insulin resistance and T2DM but also as therapeutic targets for the effective management of the same.

OXGR1-Dependent (Pro)Renin Receptor Upregulation in Collecting Ducts of the Clipped Kidney Contributes to Na+ Balance in Goldblatt Hypertensive Mice

The two-kidney, one-clip (2K1C) Goldblatt rodent model elicits a reduction in renal blood flow (RBF) in the clipped kidney (CK). The reduced RBF and oxygen bio-ability causes the accumulation of the tricarboxylic cycle intermediary, α-ketoglutarate, which activates the oxoglutarate receptor-1 (OXGR1). In the kidney, OXGR1 is abundantly expressed in intercalated cells (ICs) of the collecting duct (CD), thus contributing to sodium transport and electrolyte balance. The (pro)renin receptor (PRR), a member of the renin-angiotensin system (RAS), is a key regulator of sodium reabsorption and blood pressure (BP) that is expressed in ICs. The PRR is upregulated in 2K1C rats. Here, we tested the hypothesis that chronic reduction in RBF in the CK leads to OXGR1-dependent PRR upregulation in the CD and alters sodium balance and BP in 2K1C mice. To determine the role of OXGR1 in regulating the PRR in the CDs during renovascular hypertension, we performed 2K1C Goldblatt surgery (clip = 0.13 mm internal gap, 14 days) in two groups of male mice: (1) mice treated with Montelukast (OXGR1 antagonist; 5 mg/Kg/day); (2) OXGR1-/- knockout mice. Wild-type and sham-operated mice were used as controls. After 14 days, 2K1C mice showed increased systolic BP (SBP) (108 ± 11 vs. control 82 ± 5 mmHg, p < 0.01) and a lower natriuretic response after the saline challenge test. The CK group showed upregulation of erythropoietin, augmented α-ketoglutarate, and increased PRR expression in the renal medulla. The CK of OXGR1 knockout mice and mice subjected to the OXGR1 antagonist elicited impaired PRR upregulation, attenuated SBP, and better natriuretic responses. In 2K1C mice, the effect of reduced RBF on the OXGR1-dependent PRR upregulation in the CK may contribute to the anti-natriuretic and increased SBP responses.

Fibroblast growth factor 21 enhances learning and memory performance in mice by regulating hippocampal L-lactate homeostasis

Fibroblast growth factor 21 (FGF21) is one endogenous metabolic molecule that functions as a regulator in glucose and lipid homeostasis. However, the effect of FGF21 on L-lactate homeostasis and its mechanism remains unclear until now. Forty-five Six-week-old male C57BL/6 mice were divided into three groups: control, L-lactate, and FGF21 (1.5 mg/kg) groups. At the end of the treatment, nuclear magnetic resonance-based metabolomics, and key proteins related to L-lactate homeostasis were determined respectively to evaluate the efficacy of FGF21 and its mechanisms. The results showed that, compared to the vehicle group, the L-lactate-treated mice displayed learning and memory performance impairments, as well as reduced hippocampal ATP and NADH levels, but increased oxidative stress, mitochondrial dysfunction, and apoptosis, which suggesting inhibited L-lactate-pyruvate conversion in the brain. Conversely, FGF21 treatment ameliorated the L-lactate accumulation state, accompanied by restoration of the learning and memory defects, indicating enhanced L-lactate uptake and utilization in hippocampal neurons. We demonstrated that maintaining constant L-lactate-pyruvate flux is essential for preserving neuronal bioenergetic and redox levels. FGF21 contributed to preparing the brain for situations of high availability of L-lactate, thus preventing neuronal vulnerability in metabolic reprogramming.

Identification of potential serum biomarkers associated with HbA1c levels in Indian type 2 diabetic subjects using NMR-based metabolomics

BACKGROUND

The prevalence of type 2 diabetes mellitus (T2DM), a progressive metabolic disorder characterized by chronic hyperglycemia and the development of insulin resistance, has increased globally, with worrying statistics coming from children, adolescents, and young adults from developing countries like India. Here, we investigated unique circulating metabolic signatures associated with prediabetes and T2DM in an Indian cohort using NMR-based metabolomics.

MATERIALS AND METHODS

The study subjects included healthy volunteers (N = 101), prediabetic subjects (N = 75), and T2DM patients (N = 108). Serum metabolic profiling was performed using 1H NMR spectroscopy and major perturbed metabolites were identified by multivariate analysis and receiver operating characteristic (ROC) modules.

RESULTS

Of the 36 aqueous abundant metabolites, 24 showed a statistically significant difference between healthy volunteers, prediabetics, and established T2DM subjects. On performing multivariate ROC curve analysis with 5 commonly dysregulated metabolites (namely, glucose, pyroglutamate, o-phosphocholine, serine, and methionine) in prediabetes and T2DM, AUC values obtained were 0.96 (95 % confidence interval (CI) = 0.93, 0.98) for T2DM; and 0.88 (95 % CI = 0.81, 0.93) for prediabetic subjects, respectively.

CONCLUSION

We propose that the identified metabolite panel can be used in the future as a biomarker for clinical diagnosis, patient surveillance, and for predicting individuals at risk for developing diabetes.

Urinary phenotyping of SARS-CoV-2 infection connects clinical diagnostics with metabolomics and uncovers impaired NAD+ pathway and SIRT1 activation

OBJECTIVES

The stratification of individuals suffering from acute and post-acute SARS-CoV-2 infection remains a critical challenge. Notably, biomarkers able to specifically monitor viral progression, providing details about patient clinical status, are still not available. Herein, quantitative metabolomics is progressively recognized as a useful tool to describe the consequences of virus-host interactions considering also clinical metadata.

METHODS

The present study characterized the urinary metabolic profile of 243 infected individuals by quantitative nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography mass spectrometry (LC-MS). Results were compared with a historical cohort of noninfected subjects. Moreover, we assessed the concentration of recently identified antiviral nucleosides and their association with other metabolites and clinical data.

RESULTS

Urinary metabolomics can stratify patients into classes of disease severity, with a discrimination ability comparable to that of clinical biomarkers. Kynurenines showed the highest fold change in clinically-deteriorated patients and higher-risk subjects. Unique metabolite clusters were also generated based on age, sex, and body mass index (BMI). Changes in the concentration of antiviral nucleosides were associated with either other metabolites or clinical variables. Increased kynurenines and reduced trigonelline excretion indicated a disrupted nicotinamide adenine nucleotide (NAD+) and sirtuin 1 (SIRT1) pathway.

CONCLUSIONS

Our results confirm the potential of urinary metabolomics for noninvasive diagnostic/prognostic screening and show that the antiviral nucleosides could represent novel biomarkers linking viral load, immune response, and metabolism. Moreover, we established for the first time a casual link between kynurenine accumulation and deranged NAD+/SIRT1, offering a novel mechanism through which SARS-CoV-2 manipulates host physiology.

Antidiabetic effect of Ardisia elliptica extract and its mechanisms of action in STZ-NA-induced diabetic rat model via 1H-NMR-based metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

Ardisia elliptica Thunb. (AE) (Primulaceae) is a medicinal plant found in the Malay Peninsula and has been traditionally used to treat diabetes. However, limited studies to date in providing scientific evidence to support the antidiabetic efficacy of this plant by in-vitro and in-vivo models.

AIM OF THE STUDY

To investigate the anti-hyperglycemic potential of AE through in-vitro enzymatic activities and streptozotocin-nicotinamide (STZ-NA) induced diabetic rat models using proton-nuclear magnetic resonance (1H-NMR)-based metabolomics approach.

MATERIALS AND METHODS

Anti-α-amylase and anti-α-glucosidase activities of the hydroethanolic extracts of AE were evaluated. The absolute quantification of bioactive constituents, using ultra-high performance liquid chromatography (UHPLC) was performed for the most active extract. Three different dosage levels of the AE extract were orally administered for 4 weeks consecutively in STZ-NA induced diabetic rats. Physical assessments, biochemical analysis, and an untargeted 1H-NMR-based metabolomics analysis of the urine and serum were carried out on the animal model.

RESULTS

Type 2 diabetes mellitus (T2DM) rat model was successfully developed based on the clear separation observed between the STZ-NA induced diabetic and normal non-diabetic groups. Discriminating biomarkers included glucose, citrate, succinate, allantoin, hippurate, 2-oxoglutarate, and 3-hydroxybutyrate, as determined through an orthogonal partial least squares-discriminant analysis (OPLS-DA) model. A treatment dosage of 250 mg/kg body weight (BW) of standardized 70% ethanolic AE extract mitigated increase in serum glucose, creatinine, and urea levels, providing treatment levels comparable to that obtained using metformin, with flavonoids primarily contribute to the anti-hyperglycemic activities. Urinary metabolomics disclosed that the following disturbed metabolism pathways: the citrate cycle (TCA cycle), butanoate metabolism, glycolysis and gluconeogenesis, pyruvate metabolism, and synthesis and degradation of ketone bodies, were ameliorated after treatment with the standardized AE extract.

CONCLUSIONS

This study demonstrated the first attempt at revealing the therapeutic effect of oral treatment with 250 mg/kg BW of standardized AE extract on chemically induced T2DM rats. The present study provides scientific evidence supporting the ethnomedicinal use of Ardisia elliptica and further advances the understanding of the fundamental molecular mechanisms affected by this herbal antidote.

Food Polyphenols and Type II Diabetes Mellitus: Pharmacology and Mechanisms

Type II diabetes mellitus and its related complications are growing public health problems. Many natural products present in our diet, including polyphenols, can be used in treating and managing type II diabetes mellitus and different diseases, owing to their numerous biological properties. Anthocyanins, flavonols, stilbenes, curcuminoids, hesperidin, hesperetin, naringenin, and phenolic acids are common polyphenols found in blueberries, chokeberries, sea-buckthorn, mulberries, turmeric, citrus fruits, and cereals. These compounds exhibit antidiabetic effects through different pathways. Accordingly, this review presents an overview of the most recent developments in using food polyphenols for managing and treating type II diabetes mellitus, along with various mechanisms. In addition, the present work summarizes the literature about the anti-diabetic effect of food polyphenols and evaluates their potential as complementary or alternative medicines to treat type II diabetes mellitus. Results obtained from this survey show that anthocyanins, flavonols, stilbenes, curcuminoids, and phenolic acids can manage diabetes mellitus by protecting pancreatic β-cells against glucose toxicity, promoting β-cell proliferation, reducing β-cell apoptosis, and inhibiting α-glucosidases or α-amylase. In addition, these phenolic compounds exhibit antioxidant anti-inflammatory activities, modulate carbohydrate and lipid metabolism, optimize oxidative stress, reduce insulin resistance, and stimulate the pancreas to secrete insulin. They also activate insulin signaling and inhibit digestive enzymes, regulate intestinal microbiota, improve adipose tissue metabolism, inhibit glucose absorption, and inhibit the formation of advanced glycation end products. However, insufficient data are available on the effective mechanisms necessary to manage diabetes.

Oat β-glucan ameliorates diabetes in high fat diet and streptozotocin-induced mice by regulating metabolites

Oats are widely distributed worldwide and oat β-glucan has positive effects on human health. Particularly, oat β-glucan is reported to be beneficial in the management of type 2 diabetes. The aim of the present study is to investigate the effects of oat β-glucan and its possible underlying mechanisms on diabetes in type 2 diabetic mice that was induced by streptozotocin/high-fat diet (STZ/HFD). The data indicated that oat β-glucan significantly reduced the fasting blood glucose, improved glucose tolerance, and insulin sensitivity. The results further showed that oat β-glucan remarkably decreased the levels of total cholesterol (TCHO), total triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and free fatty acids. Moreover, oat β-glucan remarkably increased the hepatic glycogen content, but largely decreased the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in STZ/HFD-induced diabetic mice. Histological analysis showed that oat β-glucan alleviated visceral lesions. Finally, the metabolomic analysis indicated that the metabolic profile was remarkably changed after oat β-glucan intervention in diabetic mice. There were 88 and 106 differential metabolites screened as biomarkers in negative ion mode (NEG) and positive ion mode (POS) after oat β-glucan treatment, respectively. In addition, oat β-glucan significantly affected the serum metabolites of amino acids, organic acids and bile acids. Collectively, the current study elucidates oat β-glucan displays an effective nutritional intervention in diabetes.

Pathophysiology of type 2 diabetes and the impact of altered metabolic interorgan crosstalk

Diabetes is a complex and multifactorial disease that affects millions of people worldwide, reducing the quality of life significantly, and results in grave consequences for our health care system. In type 2 diabetes (T2D), the lack of β-cell compensatory mechanisms overcoming peripherally developed insulin resistance is a paramount factor leading to disturbed blood glucose levels and lipid metabolism. Impaired β-cell functions and insulin resistance have been studied extensively resulting in a good understanding of these pathways but much less is known about interorgan crosstalk, which we define as signaling between tissues by secreted factors. Besides hormones and organokines, dysregulated blood glucose and long-lasting hyperglycemia in T2D is associated with changes in metabolism with metabolites from different tissues contributing to the development of this disease. Recent data suggest that metabolites, such as lipids including free fatty acids and amino acids, play important roles in the interorgan crosstalk during the development of T2D. In general, metabolic remodeling affects physiological homeostasis and impacts the development of T2D. Hence, we highlight the importance of metabolic interorgan crosstalk in this review to gain enhanced knowledge of the pathophysiology of T2D, which may lead to new therapeutic approaches to treat this disease.

Effects of Fibroblast Growth Factor 21 on Lactate Uptake and Usage in Mice with Diabetes-Associated Cognitive Decline

Fibroblast growth factor 21 (FGF21) is an endocrine hormone that exerts beneficial effects on glucose and lipid metabolic homeostasis. However, the impact of FGF21 on type 1 diabetes-associated cognitive decline (DACD) and its mechanisms of action remain unclear. In this study, we aimed to evaluate the effects of FGF21 on lactate uptake and usage in a mouse model of streptozotocin-induced DACD. Six-week-old male C57BL/6 mice were divided into the control, diabetic, and FGF21 (which received 2 mg/kg recombinant human FGF21) groups. At the end of the treatment period, learning and memory performance, nuclear magnetic resonance-based metabonomics, and expressions of various hippocampal protein were analyzed to determine the efficacy of FGF21. The results showed that compared to the control mice, the diabetic mice had reduced long-term memory performance after the hyperglycemic insult; decreased hippocampal levels of lactate dehydrogenase-B (LDH-B) activity, bioenergy metabolites, and monocarboxylate transporter 2 (MCT2); and increased lactate levels. Impaired phosphoinositide 3-kinase (PI3K) signaling was also observed in the diabetic mice. However, FGF21 treatment improved LDH-B activity, β-nicotinamide adenine dinucleotide, and ATP levels, and increased MCT2 expression and PI3K signaling pathway, which in turn improved the learning and memory defects. These findings demonstrated that the effects of FGF21 on DACD were associated with its ability to improve LDH-B-mediated lactate usage and MCT2-dependent lactate uptake. Further, these beneficial effects of FGF21 in the hippocampus were mediated by the PI3K signaling pathways.

Metabolomics analysis of urine from rats given long-term high-protein diet using ultra-high-performance liquid chromatography-mass spectrometry

Previous studies have indicated high-protein diet (HPD) promotes weight loss and improves metabolic parameters, but most of these studies have focused on the impact of short-term, long-term effects remain unclear. In this study, male Wistar rats were fed two diets for 88 weeks: normal control diet (NCD, 20.5% of energy as protein) or HPD (30.5% of energy as protein). At 88 weeks intervention, compared to NCD rats, HPD rats had lower fat tissue and higher skeletal muscle to body weight ratio, but there were no significantly differences in body weight and food intake. To explore the mechanism underlying metabolism and diet, we further collected rat urine samples at 16, 40, 64 and 88 weeks diet treatment and analyzed metabolomics profiles using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS). Partial least squares-discriminant analysis (PLS-DA) scores plots from ESI- or ESI+ model revealed a perfect separation between two diets at four time points. We identified 11 dramatically different metabolites (with VIP cut-off value > 1) in HPD, including 3 up-regulated and 8 down-regulated. And these 11 metabolites were identified as effective biomarkers, which were significantly related to HPD-induced metabolism related outcomes (fat tissue and skeletal muscle to body weight ratio). Our results provided vital information regarding metabolism in long-term HPD and more importantly, a few potentially promising metabolites were firstly identified which may related to metabolic responses.

Possible Gender Influence in the Mechanisms Underlying the Oxidative Stress, Inflammatory Response, and the Metabolic Alterations in Patients with Obesity and/or Type 2 Diabetes

The number of patients afflicted by type 2 diabetes and its morbidities has increased alarmingly, becoming the cause of many deaths. Normally, during nutrient intake, insulin secretion is increased and glucagon secretion is repressed, but when plasma glucose concentration increases, a state of prediabetes occurs. High concentration of plasma glucose breaks the redox balance, inducing an oxidative stress that promotes chronic inflammation, insulin resistance, and impaired insulin secretion. In the same context, obesity is one of the most crucial factors inducing insulin resistance, inflammation, and contributing to the onset of type 2 diabetes. Measurements of metabolites like glucose, fructose, amino acids, and lipids exhibit significant predictive associations with type 2 diabetes or a prediabetes state and lead to changes in plasma metabolites that could be selectively affected by gender and age. In terms of gender, women and men have biological dissimilarities that might have an important role for the development, diagnosis, therapy, and prevention of type 2 diabetes, obesity, and relevant hazards in both genders, for type 2 diabetes. Therefore, the present review attempts to analyze the influence of gender on the relationships among inflammatory events, oxidative stress, and metabolic alterations in patients undergoing obesity and/or type 2 diabetes.

Urinary metabolites of type 2 diabetes rats fed with palm oil-enriched high fat diet

High fat diet (HFD) is one of the risk factors of obesity and diabetes. Recommended diet regimen for diabetes is difficult to abide by especially for HFD as it adds flavour to the taste buds. In this study, palm oil-enriched HFD and normal diet were fed to nicotinamide-induced type 2 diabetes rats, respectively for six weeks. Additionally, metformin, a common drug used to treat diabetes was given to rats under treatment groups. We evaluated the change of urinary metabolites of diabetes rats fed with palm oil-enriched HFD, and also after metformin treatment. Rats were divided into six-groups with different feeding diets, disease condition and with or without metformin treatment. Rats’ urine were collected at the end of six weeks feeding program and subjected to 1H-NMR and multivariate data analysis to evaluate their metabolite profiles. At the early phase of diabetes, metabolites changes in diabetic rats were associated with the disease itself. Our data showed that continuous consumption of HFD altered various metabolic pathways of diabetic rats and caused detrimental effects to the rats. On the other hand, metformin treatment combined with normal diet lessened the physiological impacts caused by diabetes condition.

How Perturbated Metabolites in Diabetes Mellitus Affect the Pathogenesis of Hypertension?

The presence of hypertension (HTN) in type 2 diabetes mellitus (DM) is a common phenomenon in more than half of the diabetic patients. Since HTN constitutes a predictor of vascular complications and cardiovascular disease in type 2 DM patients, it is of significance to understand the molecular and cellular mechanisms of type 2 DM binding to HTN. This review attempts to understand the mechanism via the perspective of the metabolites. It reviewed the metabolic perturbations, the biological function of perturbated metabolites in two diseases, and the mechanism underlying metabolic perturbation that contributed to the connection of type 2 DM and HTN. DM-associated metabolic perturbations may be involved in the pathogenesis of HTN potentially in insulin, angiotensin II, sympathetic nervous system, and the energy reprogramming to address how perturbated metabolites in type 2 DM affect the pathogenesis of HTN. The recent integration of the metabolism field with microbiology and immunology may provide a wider perspective. Metabolism affects immune function and supports immune cell differentiation by the switch of energy. The diverse metabolites produced by bacteria modified the biological process in the inflammatory response of chronic metabolic diseases either. The rapidly evolving metabolomics has enabled to have a better understanding of the process of diseases, which is an important tool for providing some insight into the investigation of diseases mechanism. Metabolites served as direct modulators of biological processes were believed to assess the pathological mechanisms involved in diseases.

α-Ketoglutarate Upregulates Collecting Duct (Pro)renin Receptor Expression, Tubular Angiotensin II Formation, and Na+ Reabsorption During High Glucose Conditions

Diabetes mellitus (DM) causes high glucose (HG) levels in the plasma and urine. The (pro)renin receptor (PRR) is a key regulator of renal Na+ handling. PRR is expressed in intercalated (IC) cells of the collecting duct (CD) and binds renin to promote angiotensin (Ang) II formation, thereby contributing to Na+ reabsorption. In DM, the Kreb's cycle is in a state of suppression in most tissues. However, in the CD, expression of glucose transporters is augmented, boosting the Kreb's cycle and consequently causing α-ketoglutarate (αKG) accumulation. The αKG receptor 1 (OXGR1) is a Gq-coupled receptor expressed on the apical membrane of IC cells of the CD. We hypothesize that HG causes αKG secretion and activation of OXGR1, which increases PRR expression in CD cells. This effect then promotes intratubular AngII formation and Na+ reabsorption. To test this hypothesis, streptozotocin (STZ)-induced diabetic mice were treated with or without montelukast (ML), an OXGR1 antagonist, for 6 days. STZ mice had higher urinary αKG and PRR expression along with augmented urinary AngII levels and Na+ retention. Treatment with ML prevented all these effects. Similarly, primary cultured inner medullary CD cells treated with HG showed increased PRR expression, while OXGR1 antagonist prevented this effect. αKG increases PRR expression, while treatments with ML, PKC inhibition, or intracellular Ca2+ depletion impair this effect. In silico analysis suggested that αKG binds to mouse OXGR1. These results indicate that HG conditions promote increased levels of intratubular αKG and OXGR1-dependent PRR upregulation, which impact AngII formation and Na+ reabsorption.

Measuring the health effects of food by metabolomics

Metabolomics of human biological fluids or tissues is used to discover markers for diseases by comparing the metabolome of the patients against healthy individuals. Ultimately, these markers can be used in drug discovery to determine how medications normalize (at least in part) the human metabolome at specific disease stages to homeostatic. Likewise, the health effects of food can be studied. Even metabolomics of the food can be combined with metabolomics of the treated patients to correlate compounds from food with measurable health effects from clinical studies. Various chemometric analyses of these metabolomics data are used to identify markers for diseases and to obtain evidence for health effects. This review discusses recent researches (published from 2013 to 2021) on whether specific dietary intervention to humans suffering from metabolic disorders may improve their pathological status. The scope is limited to those associated with major lifestyle diseases such as diabetes, obesity, and cardiovascular diseases, for which food is thought may have detrimental as well as beneficial effects on human health. It includes metabolites characterization of different biological samples such as the human serum/plasma, urine, saliva, feces, or ileal fluid. Whether the study results supported the claimed health benefits and whether the research was conducted with appropriate study design, was criticized.

Polysaccharides from fermented Momordica charantia L. with Lactobacillus plantarum NCU116 ameliorate metabolic disorders and gut microbiota change in obese rats

Obesity is a chronic disease characterized by overweight resulting from fat accumulation, along with disturbance of metabolism and gut microbiota. Fermentation, as a green processing method, is beneficial for improving the nutrition capacity of food components. Polysaccharides are considered as one of the important components in food and are also potential supplements for anti-obesity treatment. This study aimed to investigate the anti-obesity effects of polysaccharides from fermented and non-fermented Momordica charantia L. with Lactobacillus plantarum NCU116 (FP and NFP) on obese rats by serum metabolomics and gut microbiota analysis. Metabolomics results revealed that abnormal lipid metabolism was formed due to obesity. The supplement of FP and NFP improved the glycerophospholipids, glycosphingolipids, and amino acid metabolism of the obese rats, which alleviated the hypercholesterolemia and overweight in rats. Furthermore, the disorder of gut microbiota was ameliorated by FP and NFP. FP promoted the growth of beneficial bacteria, such as phylum Firmicutes, Actinobacteria, and genera Anaerostipes, Coprococcus, Lactobacillus, and Bifidobacterium. FP also reduced several harmful bacteria belonging to the phylum Proteobacteria and genera Helicobacter. The positive correlation of the weight loss and lowering of serum lipids with the increased beneficial bacteria further elucidated that the anti-obesity effect of FP in obese rats is associated with the regulation of gut microbiota and serum metabolites. The results of this study could provide information for developing probiotic products in the future that may have beneficial effects on the prevention or treatment of obesity.

Metformin Attenuates the Metabolic Disturbance and Depression-like Behaviors Induced by Corticosterone and Mediates the Glucose Metabolism Pathway

BACKGROUND

Metabolism disturbances are common in patients with depression. The drug metformin has been reported to exhibit antidepressant activity. The purpose of this study was to investigate metabolism disturbances induced by corticosterone (CORT) and determine if metformin can reverse these effects and their accompanying depression-like behaviors.

METHODS

Rats were exposed to corticosterone with or without metformin administration. Depression-like behaviors were tested. Gene expression was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analysis. In addition, the metabolites were quantified by LC-MS/MS analysis.

RESULTS

Metformin attenuated the depression-like behaviors induced by CORT. Furthermore, metformin reversed disturbances in body weight, serum glucose, and triglyceride levels, as well as hepatic TG levels induced by CORT. Metformin normalized the alterations in the expression of glucose metabolism-related genes (PGC-1α, G6pc, Pepck, Gck, PYGL, Gys2, PKLR, GLUT4) and insulin resistance-related genes (AdipoR1, AdipoR2) in the muscles and livers of rats induced by CORT. Metabolomic analysis showed that metformin reversed the effects of CORT on 11 metabolites involved in the pathways of the tricarboxylic acid cycle, glycolysis, and gluconeogenesis (3-phospho-D-glycerate, β-D-fructose 6-phosphate, D-glucose 6-phosphate, and pyruvate).

CONCLUSION

Our findings suggest that metformin can attenuate metabolism disturbances and depression-like behaviors induced by CORT mediating the glucose metabolism pathway.

Urinary Metabolomic Profiling in Streptozotocin-Induced Diabetic Mice after Treatment with Losartan

Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease and end-stage kidney disease. Renin-angiotensin system inhibitors such as losartan are the predominant therapeutic options in clinical practice to treat DKD. Therefore, it is necessary to identify DKD-related metabolic profiles that are affected by losartan. To investigate the change in metabolism associated with the development of DKD, we performed global and targeted metabolic profiling using 800 MHz nuclear magnetic resonance spectroscopy of urine samples from streptozotocin-induced diabetic mice (DM) with or without losartan administration. A principal component analysis plot showed that the metabolic pattern in the losartan-treated diabetic mice returned from that in the DM group toward that in the control mice (CM). We found that 33 urinary metabolites were significantly changed in DM compared with CM, and the levels of 16 metabolites among them, namely, glucose, mannose, myo-inositol, pyruvate, fumarate, 2-hydroxyglutarate, isobutyrate, glycine, threonine, dimethylglycine, methyldantoin, isoleucine, leucine, acetylcarnitine, 3-hydroxy-3-methylglutarate, and taurine, shifted closer to the control level in response to losartan treatment. Pathway analysis revealed that these metabolites were associated with branched-chain amino acid degradation; taurine and hypotaurine metabolism; glycine, serine, and threonine metabolism; the tricarboxylic acid cycle; and galactose metabolism. Our results demonstrate that metabolomic analysis is a useful tool for identifying the metabolic pathways related to the development of DKD affected by losartan administration and may contribute to the discovery of new therapeutic agents for DKD.

The total flavonoids from Selaginella tamariscina (beauv.) Spring improve glucose and lipid metabolism in db/db mice

Objectives

This study aimed to investigate the glucose and lipid metabolism improving effect of the total flavonoids from Selaginella tamariscina (Beauv.) Spring (TFST) on db/db mice, and to study its mechanism of action.

Materials and Methods

The db/db mice were divided into 5 groups: the normal group (NC), the diabetic group (DM), the gliclazide group (GZ), the DM+TFST (110 mg/kg), and the DM+TFST (220 mg/kg). The body weight, blood glucose, INS, GC, TC, TG, LDL, and HDL were detected. HE staining was used to observe the liver and pancreas. Urine was tested by UPLC-QTOF-MS to study the metabolic differences of each group, coupled with SIMCA-P13.0 for PCA and OPLS-DA analysis, to identify potential biomarkers, find the metabolic pathway. Western blot was used to examine liver tissue of mice for studying effect of TFST on the PPAR-γ/PI3K/GLU4 pathway.

Results

TFST can reduce the weight and levels of TC, TG, and LDL-C, increase the level of GC in blood, and reduce the fat accumulation and inflammation in the liver, and repair the islet cell. 13 biomarkers were identified, they are mainly involved in amino acid metabolism, and purine and pyrimidine metabolism. The results of Western blot show TFST can improve the utilization rate of GLU4 by regulating PPAR-γ and PI3K expression in the liver of db/db mice.

Conclusion

TFST can improve glucose and lipid metabolism of DM, which relates to regulation of the PPAR-γ/PI3K/GLU4 signaling pathway, and affect the amino acid metabolism, purine, and pyrimidine metabolism.

Hypoglycemic and Hypolipidemic Mechanism of Tea Polysaccharides on Type 2 Diabetic Rats via Gut Microbiota and Metabolism Alteration

Diabetes mellitus is a serious threat to human health. Tea is cultivated around the world, and its polysaccharide components are reported to be an effective approach for managing type 2 diabetes with fewer adverse effects than medication. To examine the therapeutic effect of tea polysaccharides on diabetes, a type 2 diabetic rat model was generated. We showed that tea polysaccharides remarkably decreased fasting blood glucose and the levels of total cholesterol, total triglyceride, low-density lipoprotein cholesterol, and free fatty acid of type 2 diabetic rats. 16S rRNA sequencing and metabolomics were used to investigate the variation of gut microbiota and the metabolites profiles of diabetic rats after intervention of tea polysaccharides. We found that tea polysaccharides maintained the diversity of gut microbiota and restored the relative abundance of some bacterial genera (Lachnospira, Victivallis, Roseburia, and Fluviicola) which was reduced by diabetes. According to metabolomics analysis, we found that amino acid and other related metabolites was influenced by tea polysaccharides intervention. Correlation analysis among metabolites, gut microbiota, and parameters of hypoglycemic indicated that tea polysaccharides had hypoglycemic and hypolipidemic effect on type 2 diabetes via the modulation of gut microbiota and the improvement of host metabolism.

The effects of high-fat diet and metformin on urinary metabolites in diabetes and prediabetes rat models

High-fat diet (HFD) interferes with the dietary plan of patients with type 2 diabetes mellitus (T2DM). However, many diabetes patients consume food with higher fat content for a better taste bud experience. In this study, we examined the effect of HFD on rats at the early onset of diabetes and prediabetes by supplementing their feed with palm olein oil to provide a fat content representing 39% of total calorie intake. Urinary profile generated from liquid chromatography-mass spectrometry analysis was used to construct the orthogonal partial least squares discriminant analysis (OPLS-DA) score plots. The data provide insights into the physiological state of an organism. Healthy rats fed with normal chow (NC) and HFD cannot be distinguished by their urinary metabolite profiles, whereas diabetic and prediabetic rats showed a clear separation in OPLS-DA profile between the two diets, indicating a change in their physiological state. Metformin treatment altered the metabolomics profiles of diabetic rats and lowered their blood sugar levels. For prediabetic rats, metformin treatment on both NC- and HFD-fed rats not only reduced their blood sugar levels to normal but also altered the urinary metabolite profile to be more like healthy rats. The use of metformin is therefore beneficial at the prediabetes stage.

Specific Patterns of Spinal Metabolite Ratio Underlying α-Me-5-HT-evoked Pruritus Compared with Compound 48/80 Based on Proton Nuclear Magnetic Resonance Spectroscopy

Mechanisms of pruritus are implicated in the dysregulation of the metabolites in the spinal cord. We investigated pruritus behavioral testing in three groups of young adult male C57Bl/6 mice, including one group treated with normal saline, while the other groups intradermally injected with α-Me-5-HT (histamine-independent pruritogen), compound 48/80 (histamine-dependent pruritogen) at the nape skin of the neck, respectively. Proton nuclear magnetic resonance spectroscopy (MRS) was used to compare spinal metabolites from the vertebral cervical among three groups, and to study the association of spinal metabolite ratio and pruritus intensity. The MRS-measured N-acetylaspartate-to-myoinositol ratio (NAA/Ins) was significantly correlated with the number of scratches between normal saline group and 48/80 group or α-Me-5-HT group (both P<0.0001), indicating that NAA/Ins may be a robust surrogate marker of histamine-independent/dependent pruritogen. There was significant difference in Glu/Ins between normal saline group and 48/80 group (P=0.017), indicating that Glu/Ins may be a surrogate marker of histamine-dependent pruritogen, while GABA/Ins was highly significantly different between normal saline group and α-Me-5-HT group (P=0.008), suggesting that GABA/Ins may be a surrogate marker of histamine-independent pruritogen. MRS may reflect the extent of pruritus intensity elicited by α-Me-5-HT and compound 48/80 with sensitivity similar to the number of scratches, and above potential markers need to be further validated in pre-clinical and clinical treatment trials.

The Protective Effect of Basic Fibroblast Growth Factor on Diabetic Nephropathy Through Remodeling Metabolic Phenotype and Suppressing Oxidative Stress in Mice

Diabetic nephropathy is a common complication in diabetes, but still lack of effective therapeutic strategies. This study aimed to investigate the therapeutic effect of basic fibroblast growth factor (bFGF) in db/db mice with diabetic nephropathy and explore its possible metabolic mechanisms using a nuclear magnetic resonance-based metabolomic approach. We found that bFGF treatment significantly alleviate urinary albumin to creatinine ratio and renal fibrosis in db/db mice, suggesting a potential renal protective effect. Metabolomics results reveal that bFGF remodeled metabolic phenotypes of the kidney and urine in db/db mice, mainly involving energy metabolism, methylamine metabolism, osmoregulation, and oxidative stress. Furthermore, the results show that bFGF-induced reductions of oxidative stress and apoptosis in db/db mice might be mediated by NOX-ROS-Nrf2 signaling. Therefore, our study suggests that the protective effect of bFGF on diabetic nephropathy could be mediated by remodeling metabolic phenotype and suppressing oxidative stress.

Blueberry-Based Meals for Obese Patients with Metabolic Syndrome: A Multidisciplinary Metabolomic Pilot Study

A pilot study was carried out on five obese/overweight patients suffering from metabolic syndrome, with the aim to evaluate postprandial effects of high fat/high glycemic load meals enriched by blueberries. Postprandial urine samples were analyzed by ¹H-NMR spectroscopy after 2 and 4 h from ingestion to identify potential markers of blueberry intake. Significant decrease of methylamines, acetoacetate, acetone and succinate, known indicators of type 2 diabetes mellitus, were observed after the intake of meals enriched with blueberries. On the other hand, an accumulation of p-hydroxyphenyl-acetic acid and 3-(3’-hydroxyphenyl)-3-hydropropionic acid originating from gut microbial dehydrogenation of proanthocyanidins and procyanidins was detected. Real-time PCR-analysis of mRNAs obtained from mononuclear blood cells showed significant changes in cytokine gene expression levels after meals integrated with blueberries. In particular, the mRNAs expression of interleukin-6 (IL-6) and Transforming Growth Factor-β (TGF-β), pro and anti-inflammation cytokines, respectively, significantly decreased and increased after blueberry supplementation, indicating a positive impact of blueberry ingestion in the reduction of risk of inflammation. The combined analysis of the urine metabolome and clinical markers represents a promising approach in monitoring the metabolic impact of blueberries in persons with metabolic syndrome.

Metabolic signatures suggest o-phosphocholine to UDP-N-acetylglucosamine ratio as a potential biomarker for high-glucose and/or palmitate exposure in pancreatic β-cells

INTRODUCTION

Chronic exposure to high-glucose and free fatty acids (FFA) alone/or in combination; and the resulting gluco-, lipo- and glucolipo-toxic conditions, respectively, have been known to induce dysfunction and apoptosis of β-cells in Diabetes. The molecular mechanisms and the development of biomarkers that can be used to predict similarities and differences behind these conditions would help in easier and earlier diagnosis of Diabetes.

OBJECTIVES

This study aims to use metabolomics to gain insight into the mechanisms by which β-cells respond to excess-nutrient stress and identify associated biomarkers.

METHODS

INS-1E cells were cultured in high-glucose, palmitate alone/or in combination for 24 h to mimic gluco-, lipo- and glucolipo-toxic conditions, respectively. Biochemical and cellular experiments were performed to confirm the establishment of these conditions. To gain molecular insights, abundant metabolites were identified and quantified using ¹H-NMR.

RESULTS

No loss of cellular viability was observed in high-glucose while exposure to FFA alone/in combination with high-glucose was associated with increased ROS levels, membrane damage, lipid accumulation, and DNA double-strand breaks. Forty-nine abundant metabolites were identified and quantified using ¹H-NMR. Chemometric pair-wise analysis in glucotoxic and lipotoxic conditions, when compared with glucolipotoxic conditions, revealed partial overlap in the dysregulated metabolites; however, the dysregulation was more significant under glucolipotoxic conditions.

CONCLUSION

The current study compared gluco-, lipo- and glucolipotoxic conditions in parallel and elucidated differences in metabolic pathways that play major roles in Diabetes. o-phosphocholine and UDP-N-acetylglucosamine were identified as common dysregulated metabolites and their ratio was proposed as a potential biomarker for these conditions.

Metabolomic Study of Obesity and Its Treatment with Palmitoylated Prolactin-Releasing Peptide Analog in Spontaneously Hypertensive and Normotensive Rats

In this study, the combination of metabolomics and standard biochemical and biometric parameters was used to describe the metabolic effects of diet-induced obesity and its treatment with the novel antiobesity compound palm¹¹-PrRP31 (palmitoylated prolactin-releasing peptide) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). The results showed that SHR on a high-fat (HF) diet were normoglycemic with obesity and hypertension, while WKY on the HF diet were normotensive and obese with prediabetes. NMR-based metabolomics revealed mainly several microbial cometabolites altered by the HF diet, particularly in urine. The HF diet induced similar changes in both models. However, two groups of genotype-specific metabolites were defined: metabolites specific to the genotype at baseline (e.g., 1-methylnicotinamide, phenylacetylglycine, taurine, methylamine) and metabolites reacting specifically to the HF diet in individual genotypes (2-oxoglutarate, dimethylamine, N-butyrylglycine, p-cresyl sulfate). The palm¹¹-PrRP31 lowered body weight and improved biochemical and biometric parameters in both strains, and it improved glucose tolerance in WKY rats on the HF diet. In urine, the therapy induced significant decrease of formate and 1-methylnicotinamide in SHR and alanine, allantoin, dimethylamine, and N-butyrylglycine in WKY. Altogether, our study confirms the effectiveness of palm¹¹-PrRP31 for antiobesity treatment.

Overview of genomics and post-genomics research on type 2 diabetes mellitus: Future perspectives and a framework for further studies

In this review, we briefly outlined salient features of pathophysiology and results of the genetic association studies hitherto conducted on type 2 diabetes. Primarily focusing on the current status of genomic research, we briefly discussed the limited progress made during the post-genomic era and tried to identify the limitations of the post-genomic research strategies. We suggested reanalysis of the existing genomic data through advanced statistical and computational methods and recommended integrated genomics-metabolomics approaches for future studies to facilitate understanding of the gene-environment interactions in the manifestation of the disease. We also propose a framework for research that may be apt for determining the effects of urbanization and changing lifestyles in the manifestation of complex genetic disorders like type 2 diabetes in the Indian populations and offset the confounding effects of both genetic and environmental factors in the natural way.

1H NMR-based metabolomics approach to investigating the renal protective effects of Genipin in diabetic rats

Diabetic nephropathy is one of the various complications of diabetes mellitus, affecting patients for lifetime. Earlier studies have revealed that genipin can not only improve diabetes, but also induce cytotoxicity. Therefore, it is not clear which effect of genipin on kidneys occurs, when it is used in the treatment of diabetes. In the present study, we performed nuclear magnetic resonance (NMR)-based metabolomics analysis of urine and kidney tissue samples obtained from diabetic rats to explore the change of endogenous metabolites associated with diabetes and concomitant kidney disease. Nine significant differential metabolites that were closely related to renal function were screened. They were mainly related to three metabolic pathways: synthesis and degradation of ketone bodies, glycine, serine and threonine metabolism, and butanoate metabolism, which are involved in methylamine metabolism, energy metabolism and amino acid metabolism. In addition, after the intervention of genipin, the metabolic levels of all the metabolites tended to be normal, indicating a protective effect of genipin on kidneys. Our results may be helpful for understanding the antidiabetic effect of genipin.

Metabolic changes in urine and serum during progression of diabetic kidney disease in a mouse model

Diabetic kidney disease (DKD) involves various pathogenic processes during progression to end stage renal disease, and activated metabolic pathways might be changing based on major pathophysiologic mechanisms as DKD progresses. In this study, nuclear magnetic resonance spectroscopy (NMR)-based metabolic profiling was performed in db/db mice to suggest potential biomarkers for early detection and its progression. We compared concentrations of serum and urinary metabolites between db/m and db/db mice at 8 or 20 weeks of age and investigated whether changes between 8 and 20 weeks in each group were significant. The metabolic profiles demonstrated significantly increased urine levels of glucose and tricarboxylic acid cycle intermediates at both 8 and 20 weeks of age in db/db mice. These intermediates also exhibited strong positive associations with urinary albumin excretion, suggesting that they may be potential biomarkers for early diagnosis. On the contrary, branched chain amino acid and homocysteine-methionine metabolism were activated early in the disease, whereas ketone and fatty acid metabolism were significantly changed in the late phase of the disease. We demonstrated phase-specific alterations in metabolites during progression of DKD. This study provides insights into perturbed mechanisms during evolution of the disease and identifies potential novel biomarkers for DKD.

Non-targeted metabolomic biomarkers and metabotypes of type 2 diabetes: A cross-sectional study of PREDIMED trial participants

AIM

To characterize the urinary metabolomic fingerprint and multi-metabolite signature associated with type 2 diabetes (T2D), and to classify the population into metabotypes related to T2D.

METHODS

A metabolomics analysis using the ¹H-NMR-based, non-targeted metabolomic approach was conducted to determine the urinary metabolomic fingerprint of T2D compared with non-T2D participants in the PREDIMED trial. The discriminant metabolite fingerprint was subjected to logistic regression analysis and ROC analyses to establish and to assess the multi-metabolite signature of T2D prevalence, respectively. Metabotypes associated with T2D were identified using the k-means algorithm.

RESULTS

A total of 33 metabolites were significantly different (P<0.05) between T2D and non-T2D participants. The multi-metabolite signature of T2D comprised high levels of methylsuccinate, alanine, dimethylglycine and guanidoacetate, and reduced levels of glutamine, methylguanidine, 3-hydroxymandelate and hippurate, and had a 96.4% AUC, which was higher than the metabolites on their own and glucose. Amino-acid and carbohydrate metabolism were the main metabolic alterations in T2D, and various metabotypes were identified in the studied population. Among T2D participants, those with a metabotype of higher levels of phenylalanine, phenylacetylglutamine, p-cresol and acetoacetate had significantly higher levels of plasma glucose.

CONCLUSION

The multi-metabolite signature of T2D highlights the altered metabolic fingerprint associated mainly with amino-acid, carbohydrate and microbiota metabolism. Metabotypes identified in this patient population could be related to higher risk of long-term cardiovascular events and therefore require further studies. Metabolomics is a useful tool for elucidating the metabolic complexity and interindividual variation in T2D towards the development of stratified precision nutrition and medicine. Trial registration at www.controlled-trials.com: ISRCTN35739639.

Traumatic Brain Injury Alters the Metabolism and Facilitates Alzheimer's Disease in a Murine Model

A majority of Alzheimer's disease (AD) cases are sporadic without known cause. People who suffered from traumatic brain injury (TBI) are more likely to develop neurodegeneration and cognitive impairments. However, the role of TBI in pathophysiology of AD remains elusive. The present study intended to explore the effect of TBI on metabolism and its role in AD pathogenesis. We subjected double transgenic AD model mice APP23/PS45 to TBI. We found that TBI promoted β-secretase cleavage of amyloid β precursor protein and amyloid β protein deposition, and exuberated the cognitive impairments in AD mouse models. ¹H nuclear magnetic resonance (¹H-NMR)-based metabolomics with multivariate analysis was performed to investigate the characteristic metabolites and the related metabolic pathways in the serum and urine samples of the mice. TBI affected the metabolic patterns, methylamine metabolism, and amino acid metabolism in serum samples. Urinary metabolites showed that glycolysis and the tricarboxylic acid (TCA) cycle were perturbed. The results indicate that TBI might facilitate Alzheimer's pathogenesis by altering metabolism and inducing mitochondrial dysfunction. The study suggests that metabolite changes could also serve as biomarkers for TBI-induced neurodegeneration.

Nuclear magnetic resonance- and mass spectrometry-based metabolomics to study maleic acid toxicity from repeated dose exposure in rats

Maleic acid (MA), a chemical intermediate used in many consumer and industrial products, was intentionally adulterated in a variety of starch-based foods and instigated food safety incidents in Asia. We aim to elucidate possible mechanisms of MA toxicity after repeated exposure by (1) determining the changes of metabolic profile using ¹ H nuclear magnetic resonance spectroscopy and multivariate analysis, and (2) investigating the occurrence of oxidative stress using liquid chromatography tandem mass spectrometry by using Sprague-Dawley rat urine samples. Adult male rats were subjected to a 28 day subchronic study (0, 6, 20 and 60 mg kg^-1 ) via oral gavage. Urine was collected twice a day on days 0, 7, 14, 21 and 28; organs underwent histopathological examination. Changes in body weight and relative kidney weights in medium- and high-dose groups were significantly different compared to controls. Morphological alterations were evident in the kidneys and liver. Metabolomic results demonstrated that MA exposure increases the urinary concentrations of 8-hydroxy-2'-deoxyguanosine, 8-nitroguanine and 8-iso-prostaglandin F_2α ; levels of acetoacetate, hippurate, alanine and acetate demonstrated time- and dose-dependent variations in the treatment groups. Findings suggest that MA consumption escalates oxidative damage, membrane lipid destruction and disrupt energy metabolism. These aforementioned changes in biomarkers and endogenous metabolites elucidate and assist in characterizing the possible mechanisms by which MA induces nephro- and hepatotoxicity.

Effect of pistachio consumption on the modulation of urinary gut microbiota-related metabolites in prediabetic subjects

The specific nutritional composition of nuts could affect different metabolic pathways involved in a broad range of metabolic diseases. We therefore investigated whether chronic consumption of pistachio nuts modifies the urine metabolome in prediabetic subjects. We designed a randomized crossover clinical trial in 39 prediabetic subjects. They consumed a pistachio-supplemented diet (PD, 50% carbohydrates, 33% fat, including 57 g/d of pistachios daily) and a control diet (CD, 55% carbohydrates, 30% fat) for 4 months each, separated by a 2-week wash-out. Nuclear magnetic resonance (NRM) was performed to determine changes in 24-h urine metabolites. Significant changes in urine metabolites according to the different intervention periods were found in uni- and multivariate analysis. Score plot of the first two components of the multilevel partial least squares discriminant analysis (ML-PLS-DA) showed a clear separation of the intervention periods. Three metabolites related with gut microbiota metabolism (i.e., hippurate, p-cresol sulfate and dimethylamine) were found decreased in PD compared with CD (P<.05). Moreover, cis-aconitate [intermediate of the tricarboxylic acid (TCA)] was also found decreased following PD compared with CD. Intragroup analysis showed that creatinine levels were significantly increased in PD (P=.023), whereas trimethylamine N-oxide (TMAO) was found significantly reduced following PD (P=.034). Our results suggest that chronic pistachio consumption may modulate some urinary metabolites related to gut microbiota metabolism and the TCA cycle; all associated with metabolic derangements associated with insulin resistance and Type 2 diabetes.

Metabolite changes in the ipsilateral and contralateral cerebral hemispheres in rats with middle cerebral artery occlusion

Cerebral ischemia not only causes pathological changes in the ischemic areas but also induces a series of secondary changes in more distal brain regions (such as the contralateral cerebral hemisphere). The impact of supratentorial lesions, which are the most common type of lesion, on the contralateral cerebellum has been studied in patients by positron emission tomography, single photon emission computed tomography, magnetic resonance imaging and diffusion tensor imaging. In the present study, we investigated metabolite changes in the contralateral cerebral hemisphere after supratentorial unilateral ischemia using nuclear magnetic resonance spectroscopy-based metabonomics. The permanent middle cerebral artery occlusion model of ischemic stroke was established in rats. Rats were randomly divided into the middle cerebral artery occlusion 1-, 3-, 9- and 24-hour groups and the sham group. 1H nuclear magnetic resonance spectroscopy was used to detect metabolites in the left and right cerebral hemispheres. Compared with the sham group, the concentrations of lactate, alanine, γ-aminobutyric acid, choline and glycine in the ischemic cerebral hemisphere were increased in the acute stage, while the concentrations of N-acetyl aspartate, creatinine, glutamate and aspartate were decreased. This demonstrates that there is an upregulation of anaerobic glycolysis (shown by the increase in lactate), a perturbation of choline metabolism (suggested by the increase in choline), neuronal cell damage (shown by the decrease in N-acetyl aspartate) and neurotransmitter imbalance (evidenced by the increase in γ-aminobutyric acid and glycine and by the decrease in glutamate and aspartate) in the acute stage of cerebral ischemia. In the contralateral hemisphere, the concentrations of lactate, alanine, glycine, choline and aspartate were increased, while the concentrations of γ-aminobutyric acid, glutamate and creatinine were decreased. This suggests that there is a difference in the metabolite changes induced by ischemic injury in the contralateral and ipsilateral cerebral hemispheres. Our findings demonstrate the presence of characteristic changes in metabolites in the contralateral hemisphere and suggest that they are most likely caused by metabolic changes in the ischemic hemisphere.

Identification of key metabolic changes in renal interstitial fibrosis rats using metabonomics and pharmacology

Renal fibrosis is one of the important pathways involved in end-stage renal failure. Investigating the metabolic changes in the progression of disease may enhance the understanding of its pathogenesis and therapeutic information. In this study, (1)H-nuclear magnetic resonance (NMR)-based metabonomics was firstly used to screen the metabolic changes in urine and kidney tissues of renal interstitial fibrotic rats induced by unilateral ureteral obstruction (UUO), at 7, 14, 21, and 28 days after operation, respectively. The results revealed that reduced levels of bioenergy synthesis and branched chain amino acids (BCAAs), as well as elevated levels of indoxyl sulfate (IS) are involved in metabolic alterations of renal fibrosis rats. Next, by pharmacological treatment we found that reduction of IS levels could prevent the renal fibrotic symptoms. Therefore, we suggested that urinary IS may be used as a potential biomarker for the diagnosis of renal fibrosis, and a therapeutic target for drugs. Novel attempt combining metabonomics and pharmacology was established that have ability to provide more systematic diagnostic and therapeutic information of diseases.

An Evaluation of 1-Deoxynojirimycin Oral Administration in Eri Silkworm through Fat Body Metabolomics Based on (1) H Nuclear Magnetic Resonance

1-Deoxynojirimycin (DNJ), the main hypoglycemic constituent in mulberry (Morus alba) latex, has been extensively researched. Although there is considerable interest in the biological effects of DNJ, the roles of 1-deoxynojirimycin (DNJ) in glycometabolism and energy metabolism in insects have received little attention. In this paper, (1)H nuclear magnetic resonance ((1)H NMR) based metabonomic was performed to study the effects of the oral supplementation of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) on the fat body glycometabolism and energy metabolism of the fourth-instar larvae of Eri silkworms, Samia cynthia ricini. Metabolic pattern recognition analysis (partial least square-discriminant analysis, PLS-DA) of fat body extracts indicated that the groups of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) were significantly different from the control group. Further, compared to the control group, the metabolites levels of lactate, trehalose, succinate, malate, and fumarate were remarkably changed in experimental groups, which were involved in glycolysis, hydrolysis of trehalose, and tricarboxylic acid (TCA) cycle. Our results indicate that DNJ has a positive impact on the reverse energy metabolism of Eri silkworms and metabonomic analysis based on NMR can be used as a tool to identify potential biomarkers.

Metabolomic insights into the intricate gut microbial-host interaction in the development of obesity and type 2 diabetes

Gut microbiota has recently been proposed as a crucial environmental factor in the development of metabolic diseases such as obesity and type 2 diabetes, mainly due to its contribution in the modulation of several processes including host energy metabolism, gut epithelial permeability, gut peptide hormone secretion, and host inflammatory state. Since the symbiotic interaction between the gut microbiota and the host is essentially reflected in specific metabolic signatures, much expectation is placed on the application of metabolomic approaches to unveil the key mechanisms linking the gut microbiota composition and activity with disease development. The present review aims to summarize the gut microbial-host co-metabolites identified so far by targeted and untargeted metabolomic studies in humans, in association with impaired glucose homeostasis and/or obesity. An alteration of the co-metabolism of bile acids, branched fatty acids, choline, vitamins (i.e., niacin), purines, and phenolic compounds has been associated so far with the obese or diabese phenotype, in respect to healthy controls. Furthermore, anti-diabetic treatments such as metformin and sulfonylurea have been observed to modulate the gut microbiota or at least their metabolic profiles, thereby potentially affecting insulin resistance through indirect mechanisms still unknown. Despite the scarcity of the metabolomic studies currently available on the microbial-host crosstalk, the data-driven results largely confirmed findings independently obtained from in vitro and animal model studies, putting forward the mechanisms underlying the implication of a dysfunctional gut microbiota in the development of metabolic disorders.

Metabonomic analysis of potential biomarkers and drug targets involved in diabetic nephropathy mice

Diabetic nephropathy (DN) is one of the lethal manifestations of diabetic systemic microvascular disease. Elucidation of characteristic metabolic alterations during diabetic progression is critical to understand its pathogenesis and identify potential biomarkers and drug targets involved in the disease. In this study, (1)H nuclear magnetic resonance ((1)H NMR)-based metabonomics with correlative analysis was performed to study the characteristic metabolites, as well as the related pathways in urine and kidney samples of db/db diabetic mice, compared with age-matched wildtype mice. The time trajectory plot of db/db mice revealed alterations, in an age-dependent manner, in urinary metabolic profiles along with progression of renal damage and dysfunction. Age-dependent and correlated metabolite analysis identified that cis-aconitate and allantoin could serve as biomarkers for the diagnosis of DN. Further correlative analysis revealed that the enzymes dimethylarginine dimethylaminohydrolase (DDAH), guanosine triphosphate cyclohydrolase I (GTPCH I), and 3-hydroxy-3-methylglutaryl-CoA lyase (HMG-CoA lyase) were involved in dimethylamine metabolism, ketogenesis and GTP metabolism pathways, respectively, and could be potential therapeutic targets for DN. Our results highlight that metabonomic analysis can be used as a tool to identify potential biomarkers and novel therapeutic targets to gain a better understanding of the mechanisms underlying the initiation and progression of diseases.

A 1H-NMR Based Study on Hemolymph Metabolomics in Eri Silkworm after Oral Administration of 1-Deoxynojirimycin

We aimed to investigate whether 1-deoxynojirimycin (DNJ) modulates glycometabolism and has toxicity in Eri silkworm (Samia cynthia ricini, Saturniidae). In this paper, hemolymph metabolites were used to explore metabolic changes after oral administration of DNJ or mulberry latex and to characterize the biological function of DNJ at the metabolic and systemic levels. Hemolymph samples were collected from fourth-instar larvae of Eri silkworm and ex-vivo high-resolution 1H nuclear magnetic resonance (NMR) spectra were acquired from the collected hemolymph samples. Then the obtained spectra were analyzed by principal component analysis (PCA) and independent-samples t-test. Metabolic pattern recognition analysis of hemolymph samples indicated that the groups of 0.25% DNJ, latex, and the mixture of 0.5% DNJ and latex (1:1) were significantly different from the control group. Moreover, compared to the control group, the groups of 0.25% DNJ, latex, and the mixture of 0.5% DNJ and latex (1:1) showed the decreased levels of citrate, succinate, fumarate, malate, and glutamine in hemolymph, the groups of 0.25% DNJ and the mixture of 0.5% DNJ and latex (1:1) showed the increased levels of trehalose and lactate. In addition, mulberry leaves exude latex was highly toxic to Eri silkworm because rich unidentified high-molecular-weight factor (s) acted as toxic substances. In our results, latex caused 20 deaths among 50 fourth-instar larvae of Eri silkmoth, but DNJ or the mixture did not caused death. All these results suggest that DNJ has a positive impact on the reverse glycometabolism by modulating glycometabolism and inhibiting glucogenesis and energy metabolism. DNJ is a secure substance as a single-ingredient antidiabetic medicine due to its nontoxicity and bioactivity.

A Metabolomic Approach to Understanding the Metabolic Link between Obesity and Diabetes

Obesity and diabetes arise from an intricate interplay between both genetic and environmental factors. It is well recognized that obesity plays an important role in the development of insulin resistance and diabetes. Yet, the exact mechanism of the connection between obesity and diabetes is still not completely understood. Metabolomics is an analytical approach that aims to detect and quantify small metabolites. Recently, there has been an increased interest in the application of metabolomics to the identification of disease biomarkers, with a number of well-known biomarkers identified. Metabolomics is a potent approach to unravel the intricate relationships between metabolism, obesity and progression to diabetes and, at the same time, has potential as a clinical tool for risk evaluation and monitoring of disease. Moreover, metabolomics applications have revealed alterations in the levels of metabolites related to obesity-associated diabetes. This review focuses on the part that metabolomics has played in elucidating the roles of metabolites in the regulation of systemic metabolism relevant to obesity and diabetes. It also explains the possible metabolic relation and association between the two diseases. The metabolites with altered profiles in individual disorders and those that are specifically and similarly altered in both disorders are classified, categorized and summarized.

¹H-NMR and MS based metabolomics study of the intervention effect of curcumin on hyperlipidemia mice induced by high-fat diet

Curcumin, a principle bioactive component of Curcuma longa L, is well known for its anti-hyperlipidemia effect. However, no holistic metabolic information of curcumin on hyperlipidemia models has been revealed, which may provide us an insight into the underlying mechanism. In the present work, NMR and MS based metabolomics was conducted to investigate the intervention effect of curcumin on hyperlipidemia mice induced by high-fat diet (HFD) feeding for 12 weeks. The HFD induced animals were orally administered with curcumin (40, 80 mg/kg) or lovastatin (30 mg/kg, positive control) once a day during the inducing period. Serum biochemistry assay of TC, TG, LDL-c, and HDL-c was conducted and proved that treatment of curcumin or lovastatin can significantly improve the lipid profiles. Subsequently, metabolomics analysis was carried out for urine samples. Orthogonal Partial Least Squares-Discriminant analysis (OPLS-DA) was employed to investigate the anti-hyperlipidemia effect of curcumin and to detect related potential biomarkers. Totally, 35 biomarkers were identified, including 31 by NMR and nine by MS (five by both). It turned out that curcumin treatment can partially recover the metabolism disorders induced by HFD, with the following metabolic pathways involved: TCA cycle, glycolysis and gluconeogenesis, synthesis of ketone bodies and cholesterol, ketogenesis of branched chain amino acid, choline metabolism, and fatty acid metabolism. Besides, NMR and MS based metabolomics proved to be powerful tools in investigating pharmacodynamics effect of natural products and underlying mechanisms.

A gas chromatography-mass spectrometry based study on serum metabolomics in rats chronically poisoned with hydrogen sulfide

Hydrogen sulfide poisoning is a common occupational hazard, whose mortality and incidence rates are first and second, respectively, among occupational poisoning incidents in China. The main target organs of its toxicity are in the central nervous system and respiratory system. However, there are currently no specific direct tests that can be used to diagnose poisoned patients. In this study, we developed a serum metabonomic method using orthogonal partial least squares-discriminate analysis (OPLS-DA), based on gas chromatography-mass spectrometry (GC/MS) to evaluate the effect of chronic poisoning by hydrogen sulfide in rats. The OPLS-DA data demonstrated that the model group (n = 60) differed significantly from the control group (n = 30), suggesting that the metabolic profiles of the two groups are markedly different. Alterations in the levels of some metabolites such as citrate, galactose, lactate, mannose, inositol, urea, phosphate, alanine and valine were detected by OPLS-DA analysis. We observed changes in metabolic pathways including lipid metabolism, energy metabolism and amino metabolism in the model group. Our results indicate that GC/MS-based metabonomic methods may provide novel detection means for chronic hydrogen sulfide poisoning.

Metabolomics and diabetes: analytical and computational approaches

Diabetes is characterized by altered metabolism of key molecules and regulatory pathways. The phenotypic expression of diabetes and associated complications encompasses complex interactions between genetic, environmental, and tissue-specific factors that require an integrated understanding of perturbations in the network of genes, proteins, and metabolites. Metabolomics attempts to systematically identify and quantitate small molecule metabolites from biological systems. The recent rapid development of a variety of analytical platforms based on mass spectrometry and nuclear magnetic resonance have enabled identification of complex metabolic phenotypes. Continued development of bioinformatics and analytical strategies has facilitated the discovery of causal links in understanding the pathophysiology of diabetes and its complications. Here, we summarize the metabolomics workflow, including analytical, statistical, and computational tools, highlight recent applications of metabolomics in diabetes research, and discuss the challenges in the field.

A matrix-induced ion suppression method to normalize concentration in urinary metabolomics studies using flow injection analysis electrospray ionization mass spectrometry

Normalizing the total urine concentration is important for minimizing bias in urinary metabolomics analysis comparisons. In this study, we report a matrix-induced ion suppression (MIIS)-based method to normalize concentration using flow injection analysis coupled with electrospray ionization mass spectrometry (FIA-ESI-MS). An ion suppression indicator (ISI) was spiked into urine samples, and the intensity of the extracted ion chromatogram (EIC) for ISI in a urine matrix was subtracted by the EIC for a blank solution and used to calculate the extent to which the signal was reduced by the urine matrix. A series dilution of pooled urine samples was used to correlate the urine concentration and level of ion suppression for ISI. A regression equation was used to estimate the relative concentration of unknown urine samples. The MIIS method was validated for linearity, precision and accuracy. We obtained a good correlation using a quadratic regression model for 1- to 32-fold urine dilutions (R(2)=0.998). The reproducibility (n=4) and intermediate precision (n=3) were below 5% RSD, and the accuracy ranged from 97.15% to 102.10%. The established method was used to estimate the relative concentrations of 16 urine samples, and the results were compared with commonly used normalization methods. Pearson's correlation test was used to demonstrate that the MIIS method correlated highly with the creatinine and osmolarity methods; the correlation coefficients were 0.93 and 0.99, respectively. We successfully applied this method to a urinary metabolomics study on breast cancer. This study demonstrated the MIIS method is simple, accurate and can contribute to data integrity in urinary metabolomics studies.

Metabolomics – the complementary field in systems biology: a review on obesity and type 2 diabetes

This paper highlights the metabolomic roles in systems biology towards the elucidation of metabolic mechanisms in obesity and type 2 diabetes.