Beyond glucose: metabolic shifts in responses to the effects of the oral glucose tolerance test and the high-fructose diet in rats

Vescalagin from Pink Wax Apple (Syzygium samarangense (Blume) Merrill and Perry) Protects Pancreatic β-Cells against Methylglyoxal-Induced Inflammation in Rats

Methylglyoxal (MG) is the primary precursor of advanced glycation end products involved in the pathogenesis of inflammation and diabetes. A previous study in our laboratory found anti-inflammatory and anti-hyperglycemic effects of the polyphenol vescalagin (VES) in rats with MG-induced carbohydrate metabolic disorder. The present study further investigated the occurrence of inflammation in pancreatic β-cells in MG-induced diabetic rats and the mechanism by which VES prevents it. The results showed that VES downregulates the protein expression levels of advanced glycation end product receptors and CCAAT/enhancer binding protein-β and upregulates the protein expression levels of pancreatic duodenal homeobox-1, nuclear factor erythroid 2-related factor 2 and glyoxalase I from the pancreatic cells. The results also revealed that VES elevates glutathione and antioxidant enzyme contents and then downregulates c-Jun N-terminal kinase and p38 mitogen-activated protein kinases pathways to protect pancreatic β-cells in MG-administered rats.

A review of the phytochemical, pharmacological, pharmacokinetic, and toxicological evaluation of Quercus Infectoria galls

ETHNOPHARMACOLOGICAL RELEVANCE

Quercus Infectoria galls (QIG) have a long history of use in traditional Chinese medicine and traditional Uyghur medicine for the treatment of diarrhea, hemorrhage, skin disease, and many other human ailments. Medicinal applications of QIG have become increasingly popular in Greece, Asia Minor, Syria, and Iran.

AIM OF THE REVIEW

The present paper reviewed the ethnopharmacology, phytochemistry, analytical methods, biological activities, metabolism, pharmacokinetics, toxicology, and drug interactions of QIG to assess the ethnopharmacological uses, explore its therapeutic potential, and identify future opportunities for research.

MATERIALS AND METHODS

Information on QIG was gathered via the Internet (using Google Scholar, Baidu Scholar, Elsevier, ACS, Pubmed, Web of Science, CNKI, and EMBASE) and libraries. Additionally, information was also obtained from local books and PhD and MS dissertations.

RESULTS

QIG has played an important role in traditional Chinese medicine. The main bioactive metabolites of QIG include tannins, phenolic acids, flavonoids, triterpenoids, and steroids. Scientific studies on the QIG extract and its components have shown its wide range of pharmacological activities, such as cholinesterase- and monoamine oxidase-inhibitory, antitumor, anti-hypertension, antidiabetic, antimicrobial, insecticidal, antiparasitic, antioxidant, and anti-inflammatory.

CONCLUSIONS

The ethnopharmacological, phytochemical, pharmacological, and analytical methods of QIG were highlighted in this review, which provides information for future studies and commercial exploration. QIG has a huge potential for pharmaceutical and nutraceutical applications. Moreover, comprehensive toxicity studies of this plant must be conducted to ensure its safety. Additional investigations are recommended to transmute the ethnopharmacological claims of this plant in folklore medicines into scientific rationale-based information. Research on pharmacokinetics studies and potential drug interactions with standard-of-care medications is still limited, which calls for additional studies particularly on humans. Further assessments and clinical trials should be performed before it can be integrated into medicinal practices.

Exposure to high fructose corn syrup during adolescence in the mouse alters hepatic metabolism and the microbiome in a sex-specific manner

KEY POINTS

The prevalence of obesity and non-alcoholic fatty liver disease in children is dramatically increasing at the same time as consumption of foods with a high sugar content. Intake of high fructose corn syrup (HFCS) is a possible aetiology as it is thought to be more lipogenic than glucose. In a mouse model, HFCS intake during adolescence increased fat mass and hepatic lipid levels in male and female mice. However, only males showed impaired glucose tolerance. Multiple metabolites including lipids, bile acids, carbohydrates and amino acids were altered in liver in a sex-specific manner at 6 weeks of age. Some of these changes were also present in adulthood even though HFCS exposure ended at 6 weeks. HFCS significantly altered the gut microbiome, which was associated with changes in key microbial metabolites. These results suggest that HFCS intake during adolescence has profound metabolic changes that are linked to changes in the microbiome and these changes are sex-specific.

ABSTRACT

The rapid increase in obesity, diabetes and fatty liver disease in children over the past 20 years has been linked to increased consumption of high fructose corn syrup (HFCS), making it essential to determine the short- and long-term effects of HFCS during this vulnerable developmental window. We hypothesized that HFCS exposure during adolescence significantly impairs hepatic metabolic signalling pathways and alters gut microbial composition, contributing to changes in energy metabolism with sex-specific effects. C57bl/6J mice with free access to HFCS during adolescence (3-6 weeks of age) underwent glucose tolerance and body composition testing and hepatic metabolomics, gene expression and triglyceride content analysis at 6 and 30 weeks of age (n = 6-8 per sex). At 6 weeks HFCS-exposed mice had significant increases in fat mass, glucose intolerance, hepatic triglycerides (females) and de novo lipogenesis gene expression (ACC, DGAT, FAS, ChREBP, SCD, SREBP, CPT and PPARα) with sex-specific effects. At 30 weeks, HFCS-exposed mice also had abnormalities in glucose tolerance (males) and fat mass (females). HFCS exposure enriched carbohydrate, amino acid, long chain fatty acid and secondary bile acid metabolism at 6 weeks with changes in secondary bile metabolism at 6 and 30 weeks. Microbiome studies performed immediately before and after HFCS exposure identified profound shifts of microbial species in male mice only. In summary, short-term HFCS exposure during adolescence induces fatty liver, alters important metabolic pathways, some of which continue to be altered in adulthood, and changes the microbiome in a sex-specific manner.

Rice Bran Reduces Weight Gain and Modulates Lipid Metabolism in Rats with High-Energy-Diet-Induced Obesity

Obesity has become an epidemic worldwide. It is a complex metabolic disorder associated with many serious complications and high morbidity. Rice bran is a nutrient-dense by product of the rice milling process. Asia has the world’s highest rice production (90% of the world’s rice production); therefore, rice bran is inexpensive in Asian countries. Moreover, the high nutritional value of the rice bran suggests its potential as a food supplement promoting health improvements, such as enhancing brain function, lowering blood pressure, and regulating pancreatic secretion. The present study evaluated the anti-obesity effect of rice bran in rats with high-energy diet (HED)-induced obesity. Male Sprague–Dawley rats were randomly divided into one of five diet groups (n = 10 per group) and fed the following for eight weeks: Normal diet with vehicle treatment, HED with vehicle, rice bran-0.5X (RB-0.5X) (2% wt/wt rice bran), RB-1.0X (4% wt/wt rice bran), and RB-2.0X (8% wt/wt rice bran). Rice bran (RB-1.0X and RB-2.0X groups) markedly reduced obesity, including body weight and adipocyte size. In addition, treating rats with HED-induced obesity using rice bran significantly reduced the serum uric acid and glucose as well as the liver triglyceride (TG) and total cholesterol (TC). Furthermore, administration of an HED to obese rats significantly affected hepatic lipid homeostasis by increasing phosphotidylcholine (PC; 18:2/22:6), diacylglycerol (DG; 18:2/16:0), DG (18:2/18:1), DG (18:1/16:0), cholesteryl ester (CE; 20:5), CE (28:2), TG (18:0/16:0/18:3), and glycerol-1-2-hexadecanoate 3-octadecanoate. However, the rice bran treatment demonstrated an anti-adiposity effect by partially reducing the HED-induced DG (18:2/18:1) and TG (18:0/16:0/18:3) increases in obese rats. In conclusion, rice bran could act as an anti-obesity supplement in rats, as demonstrated by partially reducing the HED-induced DG and TG increases in obese rats, and thus limit the metabolic diseases associated with obesity and the accumulation of body fat and hepatic lipids in rats.

Mulberry leaf active components alleviate type 2 diabetes and its liver and kidney injury in db/db mice through insulin receptor and TGF-β/Smads signaling pathway

Mulberry leaf is one of the commonly used traditional Chinese medicines, has been shown to exert hypoglycemic effects against diabetes. The aim of this study is to investigate the effects and mechanism of mulberry leaf flavonoids (MF), polysaccharides (MP) and alkaloids (MA) on diabetic and its liver and kidney injury. The db/db mice was adopted and the results showed that the FBG (fasting blood glucose) of model group continued to increase and associated liver and kidney injury. After the intervention of MP and MA, the value of FBG exhibited the most obvious hypoglycemic effect. MF and MP have obvious improved effect on kidney injury, which reduced the content of mALB/Cre (microalbumin/creatinine) in urine and improved the tubular epithelial cells edematous and renal cystic epithelial thickening. While the MF and MA possessed a significant effect on liver damage, manifested in reducing the levels of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) and pathological changes of liver on db/db mice. Through metabolomics analysis, 13 endogenous potential biomarkers were identified in serum. The three effective components of mulberry can regulate the 13 potential biomarkers and the corresponding metabolic pathway. Collectively, the components of mulberry leaf have clear hypoglycemic effect and protective effect on liver and kidney injury and the effects are related to insulin receptor and TGF-β/Smads signaling pathway.

The complex human urinary sugar profile: determinants revealed in the cross-sectional KarMeN study

Background

Although sugars and sugar derivatives are an important class of metabolites involved in many physiologic processes, there is limited knowledge on their occurrence and pattern in biofluids.

Objective

Our aim was to obtain a comprehensive urinary sugar profile of healthy participants and to demonstrate the wide applicability and usefulness of this sugar profiling approach for nutritional as well as clinical studies.

Design

In the cross-sectional KarMeN study, the 24-h urine samples of 301 healthy participants on an unrestricted diet, assessed via a 24-h recall, were analyzed by a newly developed semitargeted gas chromatography-mass spectrometry (GC-MS) profiling method that enables the detection of known and unknown sugar compounds. Statistical analyses were performed with respect to associations of sex and diet with the urinary sugar profile.

Results

In total, 40 known and 15 unknown sugar compounds were detected in human urine, ranging from mono- and disaccharides, polyols, and sugar acids to currently unknown sugar-like compounds. A number of rarely analyzed sugars were found in urine samples. Maltose was found in statistically higher concentrations in the urine of women compared with men and was also associated with menopausal status. Further, a number of individual sugar compounds associated with the consumption of specific foods, such as avocado, or food groups, such as alcoholic beverages and dairy products, were identified.

Conclusions

We here provide data on the complex nature of the sugar profile in human urine, of which some compounds may have the potential to serve as dietary markers or early disease biomarkers. Thus, comprehensive urinary sugar profiling not only has the potential to increase our knowledge of host sugar metabolism, but can also reveal new dietary markers after consumption of individual food items, and may lead to the identification of early disease biomarkers in the future. The KarMeN study was registered at drks.de as DRKS00004890.

Gallic Acid Alleviates Hypertriglyceridemia and Fat Accumulation via Modulating Glycolysis and Lipolysis Pathways in Perirenal Adipose Tissues of Rats Fed a High-Fructose Diet

This study investigated the ameliorative effect of gallic acid (GA) on hypertriglyceridemia and fat accumulation in perirenal adipose tissues of high-fructose diet (HFD)-induced diabetic rats. The previous results showed that orally administered GA (30 mg/kg body weight) for four weeks significantly reduced the levels of plasma glucose and triglyceride (TG) in HFD rats. GA also markedly decreased the perirenal adipose tissues weight of HFD rats in present study (p < 0.05). Western blot assay indicated that GA restored expression of insulin signaling-related proteins, such as insulin receptor (IR), protein kinase C-zeta (PKC-ζ), and glucose transporter-4 (GLUT4) in the perirenal adipose tissues of HFD rats. Moreover, GA enhanced expression of glycolysis-related proteins, such as phosphofructokinase (PFK) and pyruvate kinase (PK), and increased the expression of lipolysis-related proteins, such as adipose triglyceride lipase (ATGL), which is involved in lipolysis in the perirenal adipose tissues of HFD rats. This study revealed that GA may alleviate hypertriglyceridemia and fat accumulation through enhancing glycolysis and lipolysis pathways in perirenal adipose tissues of HFD rats. These findings also suggest the potential of GA in preventing the progression of diabetes mellitus (DM) complications.

Targeted metabolome profiling by dual-probe microdialysis sampling and treatment using Gardenia jasminoides for rats with type 2 diabetes

Diabetes causes a variety of end-stage organ complications, including diabetic nephropathy. Metabolomics offers an approach for characterizing biofluid metabolic changes, but studies focusing on diabetic nephropathy are limited due to the loss of tissue-specific metabolic information. A microdialysis application for the sampling of intact endogenous metabolites has been developed, utilizing two probes simultaneously inserted into the kidney tissues and jugular vein of rats with type 2 diabetes. The comprehensive and quantitative analysis of 20 diagnostic biomarkers closely realated to type 2 diabetes and its complications were performed. Results indicated that amino acid and nucleotide levels were lower in diabetic rats, revealing that the metabolic pathways of amino acid, as well as purine and pyrimidine, were disturbed. Targeted metabolomics using mass spectrometry was performed to find potential therapeutic biomarkers and related metabolic pathways of Gardenia jasminoides (G. jasminoides) for treating diabetes. Results suggested that seven biomarkers in the kidney and five biomarkers in the blood were related to G. jasminoides. In addition, the marked perturbations of pathways were regulated after treatment with G. jasminoides, including amino acid metabolism and purine metabolism. These biomarkers and metabolic pathways provided new understanding for molecular mechanisms of G. jasminoides for treating diabetes and its complications.

Metabolomics reveals that vine tea (Ampelopsis grossedentata) prevents high-fat-diet-induced metabolism disorder by improving glucose homeostasis in rats

Background

Vine tea (VT), derived from Ampelopsis grossedentata (Hand.-Mazz.) W.T. Wang, is an alternative tea that has been consumed widely in south China for hundreds of years. It has been shown that drinking VT on a daily basis improves hyperlipidemia and hyperglycemia. However, little is known about the preventive functions of VT for metabolic dysregulation and the potential pathological mechanisms involved. This paper elucidates the preventive effects of VT on the dysregulation of lipid and glucose metabolism using rats maintained on a high-fat-diet (HFD) in an attempt to explain the potential mechanisms involved.

Methods

Sprague Dawley (SD) rats were divided into five groups: a group given normal rat chow and water (control group); a group given an HFD and water (HFD group); a group given an HFD and Pioglitazone (PIO group), 5 mg /kg; and groups given an HFD and one of two doses of VT: 500 mg/L or 2000 mg/L. After 8 weeks, changes in food intake, tea consumption, body weight, serum and hepatic biochemical parameters were determined. Moreover, liver samples were isolated for pathology histology and liquid chromatography-mass spectrometry (LC-MS)-based metabolomic research.

Results

VT reduced the serum levels of glucose and total cholesterol, decreased glucose area under the curve in the insulin tolerance test and visibly impaired hepatic lipid accumulation. Metabolomics showed that VT treatment modulated the contents of metabolic intermediates linked to glucose metabolism (including gluconeogenesis and glycolysis), the TCA cycle, purine metabolism and amino acid metabolism.

Conclusion

The current results demonstrate that VT may prevent metabolic impairments induced by the consumption of an HFD. These effects may be caused by improved energy-related metabolism (including gluconeogenesis, glycolysis and TCA cycle), purine metabolism and amino acid metabolism, and reduced lipid levels in the HFD-fed rats.

Short-Term Fructose Feeding Induces Inflammation and Oxidative Stress in the Hippocampus of Young and Adult Rats

The drastic increase in the consumption of fructose encouraged the research to focus on its effects on brain physio-pathology. Although young and adults differ largely by their metabolic and physiological profiles, most of the previous studies investigated brain disturbances induced by long-term fructose feeding in adults. Therefore, we investigated whether a short-term consumption of fructose (2 weeks) produces early increase in specific markers of inflammation and oxidative stress in the hippocampus of young and adult rats. After the high-fructose diet, plasma lipopolysaccharide and tumour necrosis factor (TNF)-alpha were found significantly increased in parallel with hippocampus inflammation, evidenced by a significant rise in TNF-alpha and glial fibrillar acidic protein concentrations in both the young and adult groups. The fructose-induced inflammatory condition was associated with brain oxidative stress, as increased levels of lipid peroxidation and nitro-tyrosine were detected in the hippocampus. The degree of activation of the protein kinase B, extracellular signal-regulated kinase 1/2, and insulin receptor substrate 1 pathways found in the hippocampus after fructose feeding indicates that the detrimental effects of the fructose-rich diet might largely depend on age. Mitochondrial function in the hippocampus, together with peroxisome proliferator-activated receptor gamma coactivator 1-alpha content, was found significantly decreased in fructose-treated adult rats. In vitro studies with BV-2 microglial cells confirmed that fructose treatment induces TNF-alpha production as well as oxidative stress. In conclusion, these results suggest that unbalanced diet, rich in fructose, may be highly deleterious in young people as in adults and must be strongly discouraged for the prevention of diet-associated neuroinflammation and neurological diseases.

FREE FATTY ACIDS PROFILING IN RESPONSE TO CARNITINE SYNERGIZE WITH LUTEIN IN DIABETIC RATS

BACKGROUND

The objective of this study was to investigate the fatty acids profiling in diabetic rats induced by sterptozocine (STZ) and their response to administration of lutein and carnitine.

MATERIALS AND METHODS

Ninety male albino rats were divided into 6 groups as follows: Normal control. The remaining rats were injected i.p a single dose of STZ (65 mg /kg bw) for induction of diabetes. Diabetic rats were grouped as: GP II: (Untreated): GP III: Rats were given orally with L-lutein (100 mg/kg bw).GP IV: Rats were given carnitine (30 μg/kg) i.p. GP V: Rats were given carnitine and lutein GP VI were given metformin (100mg/kg bw/d) for 6 weeks.

RESULTS

Treatment of diabetic rats with lutein, L-carnitine, combined decreased the levels of glucose, HA1C compared with untreated diabetic (p<0.001). Administration of L-lutein, carnitine, combined to normal rats significantly decreased the levels of myristic, palmitice, palmitoleic, stearic, linoleic, α-linolenic, arachidic and eicosadienoic when compared with control normal rats (p<0.001).

CONCLUSION

Abnormalities of fatty acids composition was observed in diabetic rats. Combination treatment with lutein and carnitine could ameliorate deleterious effect induced by STZ and attenuate the changed fatty acid composition.

Vescalagin from Pink Wax Apple [Syzygium samarangense (Blume) Merrill and Perry] Alleviates Hepatic Insulin Resistance and Ameliorates Glycemic Metabolism Abnormality in Rats Fed a High-Fructose Diet

This study investigates the ameliorative effect of vescalagin (VES) isolated from Pink wax apple fruit on hepatic insulin resistance and abnormal carbohydrate metabolism in high-fructose diet (HFD)-induced hyperglycemic rats. The results show that in HFD rats, VES significantly reduced the values of the area under the curve for glucose in an oral glucose tolerance test and the homeostasis model assessment of insulin resistance index. VES significantly enhanced the activity of hepatic antioxidant enzymes while reducing thiobarbituric acid-reactive substances in HFD rats. Western blot assay revealed that VES reduced hepatic protein expression involved in inflammation pathways while up-regulating expression of hepatic insulin signaling-related proteins. Moreover, VES up-regulated the expression of hepatic glycogen synthase and hepatic glycolysis-related proteins while down-regulating hepatic gluconeogenesis-related proteins in HFD rats. This study suggests some therapeutic potential of VES in preventing the progression of diabetes mellitus.

Halofuginone reduces the inflammatory responses of DSS-induced colitis through metabolic reprogramming

Halofuginone inhibits both HIF-1alpha and incomplete FAO to reduce the inflammatory response in DSS-induced colitis.

Metabolomic and Lipidomic Analysis of Serum Samples following Curcuma longa Extract Supplementation in High-Fructose and Saturated Fat Fed Rats

We explored, using nuclear magnetic resonance (NMR) metabolomics and fatty acids profiling, the effects of a common nutritional complement, Curcuma longa, at a nutritionally relevant dose with human use, administered in conjunction with an unbalanced diet. Indeed, traditional food supplements have been long used to counter metabolic impairments induced by unbalanced diets. Here, rats were fed either a standard diet, a high level of fructose and saturated fatty acid (HFS) diet, a diet common to western countries and that certainly contributes to the epidemic of insulin resistance (IR) syndrome, or a HFS diet with a Curcuma longa extract (1% of curcuminoids in the extract) for ten weeks. Orthogonal projections to latent structures discriminant analysis (OPLS-DA) on the serum NMR profiles and fatty acid composition (determined by GC/MS) showed a clear discrimination between HFS groups and controls. This discrimination involved metabolites such as glucose, amino acids, pyruvate, creatine, phosphocholine/glycerophosphocholine, ketone bodies and glycoproteins as well as an increase of monounsaturated fatty acids (MUFAs) and a decrease of n-6 and n-3 polyunsaturated fatty acids (PUFAs). Although the administration of Curcuma longa did not prevent the observed increase of glucose, triglycerides, cholesterol and insulin levels, discriminating metabolites were observed between groups fed HFS alone or with addition of a Curcuma longa extract, namely some MUFA and n-3 PUFA, glycoproteins, glutamine, and methanol, suggesting that curcuminoids may act respectively on the fatty acid metabolism, the hexosamine biosynthesis pathway and alcohol oxidation. Curcuma longa extract supplementation appears to be beneficial in these metabolic pathways in rats. This metabolomic approach highlights important serum metabolites that could help in understanding further the metabolic mechanisms leading to IR.

Nutritional systems biology of type 2 diabetes

Type 2 diabetes (T2D) has become an increasingly challenging health burden due to its high morbidity, mortality, and heightened prevalence worldwide. Although dietary and nutritional imbalances have long been recognized as key risk factors for T2D, the underlying mechanisms remain unclear. The advent of nutritional systems biology, a field that aims to elucidate the interactions between dietary nutrients and endogenous molecular entities in disease-related tissues, offers unique opportunities to unravel the complex mechanisms underlying the health-modifying capacities of nutritional molecules. The recent revolutionary advances in omics technologies have particularly empowered this incipient field. In this review, we discuss the applications of multi-omics approaches toward a systems-level understanding of how dietary patterns and particular nutrients modulate the risk of T2D. We focus on nutritional studies utilizing transcriptomics, epigenomomics, proteomics, metabolomics, and microbiomics, and integration of diverse omics technologies. We also summarize the potential molecular mechanisms through which nutritional imbalances contribute to T2D pathogenesis based on these studies. Finally, we discuss the remaining challenges of nutritional systems biology and how the field can be optimized to further our understanding of T2D and guide disease management via nutritional interventions.

The Flower Tea Coreopsis tinctoria Increases Insulin Sensitivity and Regulates Hepatic Metabolism in Rats Fed a High-Fat Diet

An infusion of Coreopsis tinctoria (CT) flowering tops is traditionally used in Portugal to control hyperglycemia; however, the effects of CT protection against high-fat diet (HFD)-induced hepatic insulin resistance have not been systematically studied and the precise mechanism of action is not clear. The metabolomic profiles of insulin-resistant rats fed a HFD and a CT-supplemented diet (HFD supplemented with CT drinking) for 8 weeks were investigated. Serum samples for clinical biochemistry and liver samples for histopathology and liquid chromatography-mass spectrometry-based metabolomic research were collected. Western blot and quantitative real-time PCR analyses were further used to measure the expression of several relevant enzymes together with perturbed metabolic pathways. Using analysis software, the CT treatment was found to significantly ameliorate the disturbance in 10 metabolic pathways. Combined metabolomic, Western blot, and quantitative real-time PCR analyses revealed that CT treatment significantly improved the glucose homeostasis by, on the one hand, through inhibiting the expression of gluconeogenic pathway key proteins glucose-6-phosphatase and phosphoenolpyruvate carboxykinase and, on the other hand, via regulating the mRNA or protein levels of the Krebs cycle critical enzymes (citrate synthase, succinate dehydrogenase complex, subunit A, flavoprotein, and dihydrolipoamide S-succinyltransferase). These results provide metabolic evidence of the complex pathogenic mechanism involved in hepatic insulin resistance and that the supplementation with CT improves insulin resistance at a global scale. Liquid chromatography-mass spectrometry-based metabolomics approaches are helpful to further understand diabetes-related mechanisms.

Temporal metabolomic responses of cultured HepG2 liver cells to high fructose and high glucose exposures

High fructose consumption has been implicated with deleterious effects on human health, including hyperlipidemia elicited through de novo lipogenesis. However, more global effects of fructose on cellular metabolism have not been elucidated. In order to explore the metabolic impact of fructose-containing nutrients, we applied both GC-TOF and HILIC-QTOF mass spectrometry metabolomic strategies using extracts from cultured HepG2 cells exposed to fructose, glucose, or fructose + glucose. Cellular responses were analyzed in a time-dependent manner, incubated in media containing 5.5 mM glucose + 5.0 mM fructose in comparison to controls incubated in media containing either 5.5 mM glucose or 10.5 mM glucose. Mass spectrometry identified 156 unique known metabolites and a large number of unknown compounds, which revealed metabolite changes due to both utilization of fructose and high-carbohydrate loads independent of hexose structure. Fructose was shown to be partially converted to sorbitol, and generated higher levels of fructose-1-phosphate as a precursor for glycolytic intermediates. Differentially regulated ratios of 3-phosphoglycerate to serine pathway intermediates in high fructose media indicated a diversion of carbon backbones away from energy metabolism. Additionally, high fructose conditions changed levels of complex lipids toward phosphatidylethanolamines. Patterns of acylcarnitines in response to high hexose exposure (10.5 mM glucose or glucose/fructose combination) suggested a reduction in mitochondrial beta-oxidation.

Plasma metabolic signatures reveal the regulatory effect of exercise training in db/db mice

Regulatory effect of moderate exercise training on fatty acid oxidation.

Decreased basal chloride secretion and altered cystic fibrosis transmembrane conductance regulatory protein, Villin, GLUT5 protein expression in jejunum from leptin-deficient mice

Patients with diabetes and obesity are at increased risk of developing disturbances in intestinal function. In this study, we characterized jejunal function in the clinically relevant leptin-deficient ob/ob mouse, a model of diabetes and obesity. We measured transepithelial short circuit current (Isc), across freshly isolated segments of jejunum from 12-week-old ob/ob and lean C57BL/6J (female and male) mice. The basal Isc was significantly decreased (~30%) in the ob/ob mice (66.5±5.7 μA/cm(2) [n=20]) (P< 0.05) compared with their lean counterparts (95.1±9.1 μA/cm(2) [n=19]). Inhibition with clotrimazole (100 μM, applied bilaterally) was significantly reduced in the ob/ob mice (-7.92%±3.67% [n=15]) (P<0.05) compared with the lean mice (10.44%±7.92% [n=15]), indicating a decreased contribution of Ca(2+)-activated K(+) (KCa) channels in the ob/ob mice. Inhibition with ouabain (100 μM, applied serosally) was significantly reduced in the ob/ob mice (1.40%±3.61%, n=13) (P< 0.05) versus the lean mice (18.93%±3.76% [n=18]), suggesting a potential defect in the Na(+)/K(+)-adenosine triphosphate (ATP)ase pump with leptin-deficiency. Expression of cystic fibrosis transmembrane conductance regulatory protein (CFTR) (normalized to glyceraldehyde-3-phosphate dehydrogenase [GAPDH]) was significantly decreased ~twofold (P<0.05) in the ob/ob mice compared with the leans, whilst crypt depth was unchanged. Villi length was significantly increased by ~25% (P<0.05) in the ob/ob mice compared with the leans and was associated with an increase in Villin and GLUT5 expression. GLUT2 and SGLT-1 expression were both unchanged. Our data suggests that reduced basal jejunal Isc in ob/ob mice is likely a consequence of reduced CFTR expression and decreased activity of the basolateral KCa channel and Na(+)/K(+)-ATPase. Understanding intestinal dysfunctions in ob/ob jejunum may allow for the development of novel drug targets to treat obesity and diabetes.

Identification of differential responses to an oral glucose tolerance test in healthy adults

Background

In recent years an individual’s ability to respond to an acute dietary challenge has emerged as a measure of their biological flexibility. Analysis of such responses has been proposed to be an indicator of health status. However, for this to be fully realised further work on differential responses to nutritional challenge is needed. This study examined whether metabolic phenotyping could identify differential responders to an oral glucose tolerance test (OGTT) and examined the phenotypic basis of the response.

Methods and Results

A total of 214 individuals were recruited and underwent challenge tests in the form of an OGTT and an oral lipid tolerance test (OLTT). Detailed biochemical parameters, body composition and fitness tests were recorded. Mixed model clustering was employed to define 4 metabotypes consisting of 4 different responses to an OGTT. Cluster 1 was of particular interest, with this metabotype having the highest BMI, triacylglycerol, hsCRP, c-peptide, insulin and HOMA- IR score and lowest VO_2max. Cluster 1 had a reduced beta cell function and a differential response to insulin and c-peptide during an OGTT. Additionally, cluster 1 displayed a differential response to the OLTT.

Conclusions

This work demonstrated that there were four distinct metabolic responses to the OGTT. Classification of subjects based on their response curves revealed an “at risk” metabolic phenotype.

Metabolite profiles during oral glucose challenge

To identify distinct biological pathways of glucose metabolism, we conducted a systematic evaluation of biochemical changes after an oral glucose tolerance test (OGTT) in a community-based population. Metabolic profiling was performed on 377 nondiabetic Framingham Offspring cohort participants (mean age 57 years, 42% women, BMI 30 kg/m(2)) before and after OGTT. Changes in metabolite levels were evaluated with paired Student t tests, cluster-based analyses, and multivariable linear regression to examine differences associated with insulin resistance. Of 110 metabolites tested, 91 significantly changed with OGTT (P ≤ 0.0005 for all). Amino acids, β-hydroxybutyrate, and tricarboxylic acid cycle intermediates decreased after OGTT, and glycolysis products increased, consistent with physiological insulin actions. Other pathways affected by OGTT included decreases in serotonin derivatives, urea cycle metabolites, and B vitamins. We also observed an increase in conjugated, and a decrease in unconjugated, bile acids. Changes in β-hydroxybutyrate, isoleucine, lactate, and pyridoxate were blunted in those with insulin resistance. Our findings demonstrate changes in 91 metabolites representing distinct biological pathways that are perturbed in response to an OGTT. We also identify metabolite responses that distinguish individuals with and without insulin resistance. These findings suggest that unique metabolic phenotypes can be unmasked by OGTT in the prediabetic state.

Protective effects of vescalagin from pink wax apple [Syzygium samarangense (Blume) Merrill and Perry] fruit against methylglyoxal-induced inflammation and carbohydrate metabolic disorder in rats

The unbalance of glucose metabolism in humans may cause the excessive formation of methylglyoxal (MG), which can react with various biomolecules to form the precursor of advanced glycation end products (AGEs). Vescalagin (VES) is an ellagitannin that alleviates insulin resistance in cell study. Results showed that VES reduced the value of oral glucose tolerance test, cardiovascular risk index, AGEs, and tumor necrosis factor-α contents while increasing C-peptide and d-lactate contents significantly in rats orally administered MG and VES together. The preventive effect of VES on MG-induced inflammation and carbohydrate metabolic disorder in rats was thus proved. On the basis of the experiment data, a mechanism, which involves the increase in d-lactate to retard AGE formation and the decrease in cytokine release to prevent β-cell damage, is proposed to explain the bioactivities of VES in antiglycation and in the alleviation of MG-induced carbohydrate metabolic disorder in rats.

Hippocampal metabolomics using ultrahigh-resolution mass spectrometry reveals neuroinflammation from Alzheimer's disease in CRND8 mice

In the wake of genomics, metabolomics characterizes the small molecular metabolites revealing the phenotypes induced by gene mutants. To address the metabolic signatures in the hippocampus of the amyloid-beta (Aβ) peptides produced in transgenic (Tg) CRND8 mice, high-field ion cyclotron resonance-Fourier transform mass spectrometry supported by LC-LTQ-Orbitrap was introduced to profile the extracted metabolites. More than 10,000 ions were detected in the mass profile for each sample. Subsequently, peak alignment and the 80% rule followed by feature selection based on T score computation were performed. The putative identification was also conducted using the highly accurate masses with isotopic distribution by interfacing the MassTRIX database as well as MS/MS fragmentation generated in the LTQ-Orbitrap after chromatographic separation. Consequently, 58 differentiating masses were tentatively identified while up to 44 differentiating elemental compositions could not be biologically annotated in the databases. Nonetheless, of the putatively annotated masses, eicosanoids in arachidonic acid metabolism, fatty acid beta-oxidation disorders as well as disturbed glucose metabolism were highlighted as metabolic traits of Aβ toxicity in Tg CRND8 mice. Furthermore, a web-based bioinformatic tool was used for simulation of the metabolic pathways. As a result of the obtained metabolic signatures, the arachidonic acid metabolism dominates the metabolic perturbation in hippocampal tissues of Tg CRND8 mice compared to non-Tg littermates, indicating that Aβ toxicity functions neuroinflammation in hippocampal tissue and new theranostic opportunities might be offered by characterization of altered arachidonic acid metabolism for Alzheimer's disease.

Computational tools for the secondary analysis of metabolomics experiments

Metabolomics experiments have become commonplace in a wide variety of disciplines. By identifying and quantifying metabolites researchers can achieve a systems level understanding of metabolism. These studies produce vast swaths of data which are often only lightly interpreted due to the overwhelmingly large amount of variables that are measured. Recently, a number of computational tools have been developed which enable much deeper analysis of metabolomics data. These data have been difficult to interpret as understanding the connections between dozens of altered metabolites has often relied on the biochemical knowledge of researchers and their speculations. Modern biochemical databases provide information about the interconnectivity of metabolism which can be automatically polled using metabolomics secondary analysis tools. Starting with lists of altered metabolites, there are two main types of analysis: enrichment analysis computes which metabolic pathways have been significantly altered whereas metabolite mapping contextualizes the abundances and significances of measured metabolites into network visualizations. Many different tools have been developed for one or both of these applications. In this review the functionality and use of these software is discussed. Together these novel secondary analysis tools will enable metabolomics researchers to plumb the depths of their data and produce farther reaching biological conclusions than ever before.

Plasma lipid levels and body weight altered by intrauterine growth restriction and postnatal fructose diet in adult rats

BACKGROUND

Intrauterine growth restriction (IUGR) is known to affect the risk of adult diseases. Consumption of lipogenic fructose is increasing, and it is used as an enhancer of metabolic syndrome in rat experiments. The effects of IUGR, postnatal fructose diet, and their interaction on the lipid profile and adiposity were studied in adult rats.

METHODS

IUGR was induced by providing pregnant rats with 50% of daily food intake. From 1 mo onward, half of the offspring received a fructose-rich diet and were then followed to the age of 1 and 6 mo, when plasma lipid, glucose, and insulin levels were measured. The adipose tissue was visualized by magnetic resonance imaging at the age of 6 mo.

RESULTS

IUGR and fructose diet decreased body weight in adult rats. IUGR increased low-density lipoprotein cholesterol in 6-mo-old rats. The fructose diet evoked hypertriglyceridemia and hyperinsulinemia in both the sexes and decreased fasting glucose levels in female rats. Postnatal fructose diet increased lipid content percentage in the retroperitoneal and intra-abdominal adipose tissues in male rats. Interactions between IUGR and postnatal fructose diet were observed in adult weight in males.

CONCLUSION

These results demonstrate the importance of IUGR and fructose diet in adverse changes in lipid and glucose metabolism.

Quantitative metabolomic and lipidomic profiling reveals aberrant amino acid metabolism in type 2 diabetes

Type 2 diabetes (T2DM) is a multi-factorial disease with a complex pathogenic mechanism; however a complete understanding of precise biochemical alterations accompanying the onset and progression of T2DM is lacking. Using a combination of untargeted and targeted metabolomic profiling approach we were able to delineate significantly altered metabolites in the diabetic (T2DM) group. Our results indicate significant perturbations in amino acid metabolism, TCA cycle and glycerol-phospholipid metabolism possibly impacting the overall glucose homeostasis in T2DM. A systems approach offers promise towards identification of clinically relevant markers of T2DM and novel molecular targets to foster drug discovery for effective therapeutic development for diabetes.

Metabolomics in diabetes research

Diabetes represents one of the most important global health problems because it is associated with a large economic burden on the health systems of many countries. Whereas the diagnosis and treatment of manifest diabetes have been well investigated, the identification of novel pathways or early biomarkers indicative of metabolic alterations or insulin resistance related to the development of diabetes is still in progress. Over half of the type 2 diabetes patients show manifestations of diabetes-related diseases, which highlight the need for early screening markers of diabetes. During the last decade, the rapidly growing research field of metabolomics has introduced new insights into the pathology of diabetes as well as methods to predict disease onset and has revealed new biomarkers. Recent epidemiological studies first used metabolism to predict incident diabetes and revealed branched-chain and aromatic amino acids including isoleucine, leucine, valine, tyrosine and phenylalanine as highly significant predictors of future diabetes. This review summarises the current findings of metabolic research regarding diabetes in animal models and human investigations.

Alterations of LXRα and LXRβ expression in the hypothalamus of glucose-intolerant rats

Liver X receptor (LXR) α and β are nuclear receptors that are crucial for the regulation of carbohydrate and lipid metabolism. Activation of LXRs in the brain facilitates cholesterol clearance and improves cognitive deficits, thus they are considered as promising drug targets to treat diseases such as atherosclerosis and Alzheimer's disease. Nevertheless, little is known about the function and localization of LXRs in the brain. Here, we studied the expression of LXR in the brains of rats that received free access to 10% (w/v) fructose group (FG) in their beverages or water control drinks (control group (CG)). After 6 weeks rats in the FG presented with hypertriglyceridemia, hyperinsulinemia, and became glucose intolerant, suggesting a progression toward type 2 diabetes. We found that hypothalamic LXR expression was altered in fructose-fed rats. Rats in the FG presented with a decrease in LXRβ levels while showing an increase in LXRα expression in the hypothalamus but not in the hippocampus, cerebellum, or neocortex. Moreover, both LXRα and β expression correlated negatively with insulin and triglyceride levels. Interestingly, LXRβ showed a negative correlation with the area under the curve during the glucose tolerance test in the CG and a positive correlation in the FG. Immunocytochemistry revealed that the paraventricular and ventromedial nuclei express mainly LXRα whereas the arcuate nucleus expresses LXRβ. Both LXR immunosignals were found in the median preoptic area. This is the first study showing a relationship between glucose and lipid homeostasis and the expression of LXRs in the hypothalamus, suggesting that LXRs may trigger neurochemical and neurophysiological responses for the control of food intake and energy expenditure through these receptors.

Hypotriglyceridemic and hypoglycemic effects of vescalagin from Pink wax apple [Syzygium samarangense (Blume) Merrill and Perry cv. Pink] in high-fructose diet-induced diabetic rats

Vescalagin, an active component from Pink wax apple [Syzygium samarangense (Blume) Merrill and Perry cv. Pink] fruit, with glucose uptake enhancing ability in insulin-resistant FL83B mouse hepatocytes, as shown in our previous study, was further evaluated for its hypotriglyceridemic and hypoglycemic effects in high-fructose diet (HFD)-induced diabetic rats. Wistar rats were fed HFD for 16 weeks and orally administered with vescalagin from Pink wax apple daily during the last 4 weeks. The results of biochemical parameters showed that fasting blood glucose, C-peptide, fructosamine, triglyceride and free fatty acid contents decreased by 44.7%, 46.2%, 4.0%, 42.5%, and 10.8%, respectively, in the HFD-induced diabetic rats administered with vescalagin at 30 mg/kg body weight in comparison with those of control HFD-induced diabetic rats. However, high-density-lipoprotein-cholesterol content increased by 14.4% in the HFD rats treated with vescalagin. The present study reveals that vescalagin could have therapeutic value against diabetic progression via its anti-hypertriglyceridemic and anti-hyperglycemic effects.

Hippocampal metabolomics reveals 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity associated with ageing in Sprague-Dawley rats

Metabolomics, the exponentially developing technique, could provide a systemic mapping in toxicology by directly measuring small molecular metabolites. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was found to be neurotoxic in mammalian animals. In this study, we employed liquid chromatography/quadrupole time-of-flight mass spectrometry for non-targeted analysis of metabolic profiling in hippocampal sample sets of the rats exposed to TCDD. Hippocampal metabolome from different ages of the healthy rats (4-week, 12-week and 20-week) was also deciphered. The relationship between the two tested cases was unlocked to delineate TCDD toxicity associated with ageing. Tandem mass spectrometry fragmentation in conjunction with metabolic database searching and compared to authentic standards was utilized for metabolite identification. As a consequence, the reduced levels of phenylalanine and leucine/isoleucine as well as the up-regulation of inosine and hypoxanthine were highlighted for understanding of TCDD toxicity related to age in rats and the trajectory was depicted by principal components analysis.