Oral Glutamine Supplementation Reduces Obesity, Pro-Inflammatory Markers, and Improves Insulin Sensitivity in DIO Wistar Rats and Reduces Waist Circumference in Overweight and Obese Humans

Diagnostic indicators and lifestyle interventions of metabolic-associated fatty liver disease

MAFLD has become a major global health problem and is the leading cause of liver disease worldwide. The disease progresses from a simple fatty liver to gradual fibrosis, which progresses to cirrhosis and even hepatocellular liver cancer. However, the methods currently used for diagnosis are invasive and do not facilitate clinical assessment of the condition. As a result, research on markers for the diagnosis of MAFLD is increasing. In addition, there are no clinical medications for the treatment of MAFLD, and lifestyle interventions remain effective in the prevention and treatment of MAFLD. In this review, we attempt to make a summary of the emerging diagnostic indicators and effective lifestyle interventions for MAFLD and to provide new insights into the diagnosis and treatment of MAFLD.

Transcriptome analysis suggests broad jejunal alterations in Linghu's obesity-diarrhea syndrome: A pilot study

BACKGROUND

Obesity is associated with a significantly increased risk for chronic diarrhea, which has been proposed as Linghu's obesity-diarrhea syndrome (ODS); however, its molecular mechanisms are largely unknown.

AIM

To reveal the transcriptomic changes in the jejunum involved in ODS.

METHODS

In a cohort of 6 ODS patients (JOD group), 6 obese people without diarrhea (JO group), and 6 healthy controls (JC group), high-throughput sequencing and bioinformatics analyses were performed to identify jejunal mucosal mRNA expression alterations and dysfunctional biological processes. In another cohort of 16 ODS patients (SOD group), 16 obese people without diarrhea (SO group), and 16 healthy controls (SC group), serum diamine oxidase (DAO) and D-lactate (D-LA) concentrations were detected to assess changes in intestinal barrier function.

RESULTS

The gene expression profiles of jejunal mucosa in the JO and JC groups were similar, with only 1 differentially expressed gene (DEG). The gene expression profile of the JOD group was significantly changed, with 411 DEGs compared with the JO group and 211 DEGs compared with the JC group, 129 of which overlapped. The enrichment analysis of these DEGs showed that the biological processes such as digestion, absorption, and transport of nutrients (especially lipids) tended to be up-regulated in the JOD group, while the biological processes such as rRNA processing, mitochondrial translation, antimicrobial humoral response, DNA replication, and DNA repair tended to be down-regulated in the JOD group. Eight DEGs (CDT1, NHP2, EXOSC5, EPN3, NME1, REG3A, PLA2G2A, and PRSS2) may play a key regulatory role in the pathological process of ODS, and their expression levels were significantly decreased in ODS patients (P < 0.001). In the second cohort, compared with healthy controls, the levels of serum intestinal barrier function markers (DAO and D-LA) were significantly increased in all obese individuals (P < 0.01), but were higher in the SOD group than in the SO group (P < 0.001).

CONCLUSION

Compared with healthy controls and obese individuals without diarrhea, patients with Linghu's ODS had extensive transcriptomic changes in the jejunal mucosa, likely affecting intestinal barrier function and thus contributing to the obesity and chronic diarrhea phenotypes.

Impacts of glutamate, an exercise-responsive metabolite on insulin signaling

AIMS

Disruption of the insulin signaling pathway leads to insulin resistance (IR). IR is characterized by impaired glucose and lipid metabolism. Elevated levels of circulating glutamate are correlated with metabolic indicators and may potentially predict the onset of metabolic diseases. Glutamate receptor antagonists have significantly enhanced insulin sensitivity, and improved glucose and lipid metabolism. Exercise is a well-known strategy to combat IR. The aims of our narrative review are to summarize preclinical and clinical findings to show the correlations between circulating glutamate levels, IR and metabolic diseases, discuss the causal role of excessive glutamate in IR and metabolic disturbance, and present an overview of the exercise-induced alteration in circulating glutamate levels.

MATERIALS AND METHODS

A literature search was conducted to identify studies on glutamate, insulin signaling, and exercise in the PubMed database. The search covered articles published from December 1955 to January 2024, using the search terms of "glutamate", "glutamic acid", "insulin signaling", "insulin resistance", "insulin sensitivity", "exercise", and "physical activity".

KEY FINDINGS

Elevated levels of circulating glutamate are correlated with IR. Excessive glutamate can potentially hinder the insulin signaling pathway through various mechanisms, including the activation of ectopic lipid accumulation, inflammation, and endoplasmic reticulum stress. Glutamate can also modify mitochondrial function through Ca2+ and induce purine degradation mediated by AMP deaminase 2. Exercise has the potential to decrease circulating levels of glutamate, which can be attributed to accelerated glutamate catabolism and enhanced glutamate uptake.

SIGNIFICANCE

Glutamate may act as a mediator in the exercise-induced improvement of insulin sensitivity.

Glutamine prevents high-fat diet-induced hepatic lipid accumulation in mice by modulating lipolysis and oxidative stress

Metabolic-associated fatty liver disease (MAFLD) is related to metabolic dysfunction and is characterized by excess fat storage in the liver. Several studies have indicated that glutamine could be closely associated with lipid metabolism disturbances because of its important role in intermediary metabolism. However, the effect of glutamine supplementation on MAFLD progression remains unclear. Here, we used a high-fat diet (HFD)-induced MAFLD C57BL/6 mouse model, and glutamine was supplied in the drinking water at different time points for MAFLD prevention and reversal studies. A MAFLD prevention study was performed by feeding mice an HFD concomitant with 4% glutamine treatment for 24 weeks, whereas the MAFLD reversal study was performed based on 4% glutamine treatment for 13 weeks after feeding mice an HFD for 10 weeks. In the prevention study, glutamine treatment ameliorated serum lipid storage, hepatic lipid injury, and oxidative stress in HFD-induced obese mice, although glutamine supplementation did not affect body weight, glucose homeostasis, energy expenditure, and mitochondrial function. In the MAFLD reversal study, there were no noticeable changes in the basic physiological phenotype and hepatic lipid metabolism. In summary, glutamine might prevent, but not reverse, HFD-induced MAFLD in mice, suggesting that a cautious attitude is required regarding its use for MAFLD treatment.

Phenotyping obesity: A focus on metabolically healthy obesity and metabolically unhealthy normal weight

Over the past 4 decades, research has shown that having a normal body weight does not automatically imply preserved metabolic health and a considerable number of lean individuals harbour metabolic abnormalities typically associated with obesity. Conversely, excess adiposity does not always equate with an abnormal metabolic profile. In fact, evidence exists for the presence of a metabolically unhealthy normal weight (MUHNW) and a metabolically healthy obese (MHO) phenotype. It has become increasingly recognised that different fat depots exert different effects on the metabolic profile of each individual by virtue of their location, structure and function, giving rise to these different body composition phenotypes. Furthermore, other factors have been implicated in the aetiopathogenesis of the body composition phenotypes, including genetics, ethnicity, age and lifestyle/behavioural factors. Even though to date both MHO and MUHNW have been widely investigated and documented in the literature, studies report different outcomes on long-term cardiometabolic morbidity and mortality. Future large-scale, observational and population-based studies are required for better profiling of these phenotypes as well as to further elucidate the pathophysiological role of the adipocyte in the onset of metabolic disorders to allow for better risk stratification and a personalised treatment paradigm.

Butyrate Alleviates High-Fat-Induced Metabolic Disorders Partially through Increasing Systematic Glutamine

Obesity has emerged as a worldwide epidemic. Both butyrate and glutamine counteract obesity-related metabolic disorders; however, whether and how they synergistically cooperate with each other remains a mystery. In the study, a high-fat diet (HFD, 60% calories from fat) was used to develop a model of obesity-related metabolic disorder and compared with administrated saline and sodium butyrate (SB, 300 mg/kg body weight) daily by gavage. Compared with HFD counterparts, oral administration of SB in mice exhibited significantly reduced body weight and fat mass and decreased hepatic triglyceride content. The targeted mass spectrum revealed that SB restored serum contents of glutamine, which were significantly decreased by HFD. Furthermore, SB significantly elevated the expression of glutamine synthetase (GS, encoded by GLUL) in the liver, accompanied by more enrichment of H3K27ac modifications within its promoter. In summary, the study verified the contribution of elevated glutamine to the beneficial effects of butyrate on metabolic disorders induced by a high-fat diet, providing a novel pathway for understanding how butyrate benefits metabolic homeostasis.

The essential role of glutamine metabolism in diabetic cardiomyopathy: A review

Diabetic cardiomyopathy (DCM) is a pathophysiological condition caused by diabetes mellitus and is the leading cause of diabetes mellitus-related mortality. The pathophysiology of DCM involves various processes, such as oxidative stress, inflammation, ferroptosis, and abnormal protein modification. New evidence indicates that dysfunction of glutamine (Gln) metabolism contributes to the pathogenesis of DCM by regulating these pathophysiological mechanisms. Gln is a conditionally essential amino acid in the human body, playing a vital role in maintaining cell function. Although the precise molecular mechanisms of Gln in DCM have yet to be fully elucidated, recent studies have shown that supplementing with Gln improves cardiac function in diabetic hearts. However, excessive Gln may worsen myocardial injury in DCM by generating a large amount of glutamates or increasing O-GlcNacylation. To highlight the potential therapeutic method targeting Gln metabolism and its downstream pathophysiological mechanisms, this article aims to review the regulatory function of Gln in the pathophysiological mechanisms of DCM.

Untargeted metabolomic analysis investigating links between unprocessed red meat intake and markers of inflammation

BACKGROUND

Whether red meat consumption is associated with higher inflammation or confounded by increased adiposity remains unclear. Plasma metabolites capture the effects of diet after food is processed, digested, and absorbed, and correlate with markers of inflammation, so they can help clarify diet-health relationships.

OBJECTIVE

To identify whether any metabolites associated with red meat intake are also associated with inflammation.

METHODS

A cross-sectional analysis of observational data from older adults (52.84% women, mean age 63 ± 0.3 y) participating in the Multi-Ethnic Study of Atherosclerosis (MESA). Dietary intake was assessed by food-frequency questionnaire, alongside C-reactive protein (CRP), interleukin-2, interleukin-6, fibrinogen, homocysteine, and tumor necrosis factor alpha, and untargeted proton nuclear magnetic resonance (1H NMR) metabolomic features. Associations between these variables were examined using linear regression models, adjusted for demographic factors, lifestyle behaviors, and body mass index (BMI).

RESULTS

In analyses that adjust for BMI, neither processed nor unprocessed forms of red meat were associated with any markers of inflammation (all P > 0.01). However, when adjusting for BMI, unprocessed red meat was inversely associated with spectral features representing the metabolite glutamine (sentinel hit: β = -0.09 ± 0.02, P = 2.0 × 10-5), an amino acid which was also inversely associated with CRP level (β = -0.11 ± 0.01, P = 3.3 × 10-10).

CONCLUSIONS

Our analyses were unable to support a relationship between either processed or unprocessed red meat and inflammation, over and above any confounding by BMI. Glutamine, a plasma correlate of lower unprocessed red meat intake, was associated with lower CRP levels. The differences in diet-inflammation associations, compared with diet metabolite-inflammation associations, warrant further investigation to understand the extent that these arise from the following: 1) a reduction in measurement error with metabolite measures; 2) the extent that which factors other than unprocessed red meat intake contribute to glutamine levels; and 3) the ability of plasma metabolites to capture individual differences in how food intake is metabolized.

Glutamine Production by Glul Promotes Thermogenic Adipocyte Differentiation Through Prdm9-Mediated H3K4me3 and Transcriptional Reprogramming

Thermogenic adipocytes have been extensively investigated because of their energy-dissipating property and therapeutic potential for obesity and diabetes. Besides serving as fuel sources, accumulating evidence suggests that intermediate metabolites play critical roles in multiple biological processes. However, their role in adipocyte differentiation and thermogenesis remains unexplored. Here, we report that human and mouse obesity is associated with marked downregulation of glutamine synthetase (Glul) expression and activity in thermogenic adipose tissues. Glul is robustly upregulated during brown adipocyte (BAC) differentiation and in brown adipose tissue (BAT) upon cold exposure and Cl316,243 stimulation. Further genetic, pharmacologic, or metabolic manipulations of Glul and glutamine levels reveal that glutamine cells autonomously stimulate BAC differentiation and function and BAT remodeling and improve systemic energy homeostasis in mice. Mechanistically, glutamine promotes transcriptional induction of adipogenic and thermogenic gene programs through histone modification-mediated chromatin remodeling. Among all the glutamine-regulated writer and eraser genes responsible for histone methylation and acetylation, only Prdm9, a histone lysine methyltransferase, is robustly induced during BAC differentiation. Importantly, Prdm9 inactivation by shRNA knockdown or a selective inhibitor attenuates glutamine-triggered adipogenic and thermogenic induction. Furthermore, Prdm9 gene transcription is regulated by glutamine through the recruitment of C/EBPb to its enhancer region. This work reveals glutamine as a novel activator of thermogenic adipocyte differentiation and uncovers an unexpected role of C/EBPb-Prdm9-mediated H3K4me3 and transcriptional reprogramming in adipocyte differentiation and thermogenesis.

ARTICLE HIGHLIGHTS

Glutamine Ameliorates Liver Steatosis via Regulation of Glycolipid Metabolism and Gut Microbiota in High-Fat Diet-Induced Obese Mice

Obesity and its associated conditions, such as nonalcoholic fatty liver disease (NAFLD), are risk factors for health. The aim of this study was to explore the effects of glutamine (Gln) on liver steatosis induced by a high-fat diet (HFD) and HEPG2 cells induced by oleic acid. Gln demonstrated a positive influence on hepatic homeostasis by suppressing acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS) and promoting sirtuin 1 (SIRT1) expression while improving glucose metabolism by regulating serine/threonine protein kinase (AKT)/factor forkhead box O1 (FOXO1) signals in vivo and in vitro. Obese Gln-fed mice had higher colonic short-chain fatty acid (SCFA) contents and lower inflammation factor protein levels in the liver, HEPG2 cells, and jejunum. Gln-treated obese mice had an effective decrease in Firmicutes abundance. These findings indicate that Gln serves as a nutritional tool in managing obesity and related disorders.

Effects of Mealworm Fermentation Extract and Soy Protein Mix Ratio on Hepatic Glucose and Lipid Metabolism in Obese-Induced Mice

Previous studies found that mealworm fermentation extract (TMP) reduced alcoholic hepatic steatogenesis. This study examined how the ratio of TMP and soy protein (SP) mix affected glucose and lipid metabolism in obese mice given a high-fat diet (HFD). Mice were given HFD supplemented with 100% SP or the following three ratios of TMP and SP mix for 12 weeks: 20% (S4T1), 40% (S3T2), and 60% (S2T3) TMP. When compared to the SP group, the S2T3 group had considerably lower body weight gain and food consumption. When compared to the SP group, the S2T3 group had slightly lower blood insulin and leptin levels, as well as a lower homeostasis model assessment of insulin resistance score. The use of TMP instead of SP reduced the size of epididymal adipose tissue cells. An increase in the extent of substitution of SP with TMP inhibited the gene expression of hepatic fructolysis/gluconeogenesis (KHK, ALDOB, DLD, and FBP1), lipogenesis (FAS, SCD1, CD36, and DGAT2), and its transcriptional factors (PPARγ and ChREBP). Furthermore, the S2T3 group dramatically reduced the expression of hepatic genes implicated in endoplasmic reticulum stress (PDI) and antioxidant defense (SOD1). The 60% TMP mix, in particular, reduced the expression of hepatic glucose and lipid metabolismrelated genes in HFD-fed mice. The manufacturing of functional processed goods may be accomplished by combining SP and TMP in a 2:3 ratio.

Exogenous glutamine ameliorates diabetic nephropathy in a rat model of type 2 diabetes mellitus through its antioxidant and anti-inflammatory activities

This study aimed to evaluate the effects of glutamine (Gln) on diabetic nephropathy and other complications in a rat model of type 2 diabetes mellitus. Streptozotocin/nicotinamide induced diabetic rats were enrolled as an animal model of type 2 diabetes mellitus. Animals were divided into control, diabetic, and Gln (1000 mg/l in drinking water, eight weeks) treated diabetic groups. Gln alleviated renal inflammatory and oxidative stress biomarkers (tumour necrosis factor-alpha, interleukin 6, glutathione peroxidase, total superoxide dismutase, and glutathione), decreased serum uric acid and creatinine, and restored renal histopathological changes (glomerular volume, sclerosis, and leukocyte infiltration). Additionally, Gln ameliorated other complications, including systemic oxidative stress (serum malondialdehyde and nitric oxide, serum and liver glutathione, glutathione peroxidase, and total superoxide dismutase, and liver catalase), insulin resistance, hyperglycaemia, and hyperlipidaemia. Collectively, Gln attenuates diabetic nephropathy and other complications in type 2 diabetes mellitus in rats through its antioxidant and anti-inflammatory activities.

Repurposing Pitavastatin and L-Glutamine: Replenishing β-Cells in Hyperlipidemic Type 2 Diabetes Mouse Model

Type 2 diabetes (T2D) is associated with obesity and declining β-cells. L-glutamine has been implicated in the amelioration of T2D by virtue of its incretin secretagogue property while, there are mixed reports on pitavastatin’s adiponectin potentiating ability. We aimed to investigate the effect of pitavastatin (P), L-glutamine (LG), and combination (P + LG) on glycemic control and β-cell regeneration in a high-fat diet (HFD) + streptozotocin (STZ)-induced T2D mouse model. C57BL6/J mice treated with HFD + STZ were divided into four groups: diabetes control (HFD + STZ), P, LG, and P + LG, while the control group (NCD) was fed with the normal-chow diet. Significant amelioration was observed in the combination therapy as compared to monotherapies in respect of (i) insulin resistance, glucose intolerance, lipid profile, adiponectin levels, and mitochondrial complexes I, II, and III activities, (ii) reduced phosphoenolpyruvate carboxykinase, glucose 6-phophatase, glycogen phosphorylase, and GLUT2 transcript levels with increased glycogen content in the liver, (iii) restoration of insulin receptor 1β, pAkt/Akt, and AdipoR1 protein levels in skeletal muscle, and (iv) significant increase in islet number due to β-cell regeneration and reduced β-cell death. L-glutamine and pitavastatin in combination can ameliorate T2D by inducing β-cell regeneration and regulating glucose homeostasis.

Potential of Natural Honey in Controlling Obesity and its Related Complications

Honey has a long history of therapeutic properties for multiple diseases, including inflammation and oxidative stress. This review aimed to provide a better understanding and renewed interest in the potential role of honey in obesity control, obesity-related diseases treatment and weight management, with specific reference to its components and the effect of honey overall. There is compelling evidence that honey possesses the desired properties for this purpose, as seen in the in vitro, in silico, in vivo and clinical analyses discussed in this review. This review also highlights the components potentially responsible for the health benefits of honey. Honey and its components reduce blood sugar levels, improve insulin sensitivity and lipid metabolism by reducing triglycerides, and reduce total cholesterol and LDL levels while increasing HDL levels that prevent excessive weight gain and reduce the risk of obesity and its complications. Further controlled studies are necessary to validate the role of honey in the management of obesity, both as a preventive and as a therapeutic agent.

Obesity influences composition of salivary and fecal microbiota and impacts the interactions between bacterial taxa

Obesity is an increasing global health concern and is associated with a broad range of morbidities. The gut microbiota are increasingly recognized as important contributors to obesity and cardiometabolic health. This study aimed to characterize oral and gut microbial communities, and evaluate host: microbiota interactions between clinical obesity classifications. We performed 16S rRNA sequencing on fecal and salivary samples, global metabolomics profiling on plasma and stool samples, and dietary profiling in 135 healthy individuals. We grouped individuals by obesity status, based on body mass index (BMI), including lean (BMI 18-124.9), overweight (BMI 25-29.9), or obese (BMI ≥30). We analyzed differences in microbiome composition, community inter-relationships, and predicted microbial function by obesity status. We found that salivary bacterial communities of lean and obese individuals were compositionally and phylogenetically distinct. An increase in obesity status was positively associated with strong correlations between bacterial taxa, particularly with bacterial groups implicated in metabolic disorders including Fretibacterium, and Tannerella. Consumption of sweeteners, especially xylitol, significantly influenced compositional and phylogenetic diversities of salivary and fecal bacterial communities. In addition, obesity groups exhibited differences in predicted bacterial metabolic activity, which was correlated with host's metabolite concentrations. Overall, obesity was associated with distinct changes in bacterial community dynamics, particularly in saliva. Consideration of microbiome community structure and inclusion of salivary samples may improve our ability to understand pathways linking microbiota to obesity and cardiometabolic disease.

Glutamine Regulates Skeletal Muscle Immunometabolism in Type 2 Diabetes

Dysregulation of skeletal muscle metabolism influences whole-body insulin sensitivity and glucose homeostasis. We hypothesized that type 2 diabetes-associated alterations in the plasma metabolome directly contribute to skeletal muscle immunometabolism and the subsequent development of insulin resistance. To this end, we analyzed the plasma and skeletal muscle metabolite profile and identified glutamine as a key amino acid that correlates inversely with BMI and insulin resistance index (HOMA-IR) in men with normal glucose tolerance or type 2 diabetes. Using an in vitro model of human myotubes and an in vivo model of diet-induced obesity and insulin resistance in male mice, we provide evidence that glutamine levels directly influence the inflammatory response of skeletal muscle and regulate the expression of the adaptor protein GRB10, an inhibitor of insulin signaling. Moreover, we demonstrate that a systemic increase in glutamine levels in a mouse model of obesity improves insulin sensitivity and restores glucose homeostasis. We conclude that glutamine supplementation may represent a potential therapeutic strategy to prevent or delay the onset of insulin resistance in obesity by reducing inflammatory markers and promoting skeletal muscle insulin sensitivity.

Cord blood metabolomics reveals gestational metabolic disorder associated with anti-thyroid peroxidase antibodies positivity

Background

Thyroid disease is one of the common endocrine disorders affecting the pregnant women, in which thyroid autoimmunity can alter the progress and the outcome of pregnancy. Women with euthyroid status but anti-thyroid peroxidase (anti-TPO) antibodies positivity before pregnancy are prone to subclinical gestational hypothyroidism. However, the connections between anti-TPO antibodies positivity and gestational hypothyroidism remain largely unknown. The aim of the present study is to investigate the differences of fetal metabolic profile at birth according to maternal anti-TPO status.

Methods

We performed 1H-NMR metabolomics on cord blood of a nested case control cohort of 22 pregnant women with matched thyroid hormone levels and demographic data, including 11 women with euthyroid status but anti-thyroid antibodies positivity (into the anti-TPO antibodies positivity group) and 11 matched women as controls with euthyroid status and negative anti-thyroid antibodies (into the control group).

Results

Distinct metabolic profiles were observed between the anti-TPO antibody positivity group and the nested control group, from which a total of 10 metabolites with between-group altered abundances were structurally identified. Five out of the 10 metabolites were up-regulated in the anti-TPO antibodies positivity group, including D-Glucose, L-Glutamine, 3-Hydroxybutyric acid, Myo-Inositol, Creatinine. The other 5 metabolites were down-regulated in the anti-TPO antibodies positivity group, including L-Leucine, L-Lysine, L-Glutamic acid, L-Tyrosine, and L-Phenylalanine. All the 10 metabolites have been previously reported to be correlated with hypothyroidism. Metabolite set enrichment analysis and pathway analysis suggested that amino acid metabolism pathways (especially the phenylalanine metabolism) were associated with anti-TPO antibodies positivity.

Conclusion

The results of this study suggested that fetal metabolic disorder is correlated with anti-TPO antibodies positivity, representing by abundance alteration of hypothyroidism associated metabolites and the related disturbance of amino acid metabolism pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04564-8.

Solid-State Fermented Okara with Aspergillus spp. Improves Lipid Metabolism and High-Fat Diet Induced Obesity

Okara is a major by-product of soymilk and tofu production. Despite retaining abundant nutrients after the process, okara is often under-utilized. In this study, solid-state fermentation (SSF) of okara was carried out using a koji starter (containing both Aspergillus oryzae and Aspergillus sojae) with the intention of releasing its untapped nutrients. Its effects on lipid metabolism in diet-induced obesity (DIO) were observed. The nutritional profile of fermented okara was elucidated using the following parameters: total phenolic content (TPC), pH, protein content, dietary fiber, amino acid content, and free sugar content. In vivo experiments were conducted using high-fat diets supplemented with unfermented okara and fermented okara over three weeks. Supplementation with fermented okara reduced body weight gain, adipose tissue weight, the serum triglyceride profile, and lipid accumulation in the liver, and altered the mRNA expression levels related to lipid metabolism; however, it did not affect pH and short-chain fatty acid (SCFA) production in this study. In conclusion, high-fat diets supplemented using okara fermented with Aspergillus spp. improved the lipid metabolism in mice, due to their high nutritional value, such as TPC, soy protein, and amino acids, and their synergistic effects without altering the gut microbiota.

Plant protein reduces serum cholesterol levels in hypercholesterolemia hamsters by modulating the compositions of gut microbiota and metabolites

Plant proteins exert effects of reducing cardio-cerebrovascular disease-related mortality partly via cholesterol-lowering, which was associated with gut microbiota. Here, we verify that there are significant differences in cholesterol levels among hamsters consuming different proteins. The decisive roles of gut microbiota in regulating host cholesterol are illustrated by the fact that the difference in serum cholesterol levels between hamsters feeding with pea protein and pork protein disappeared when treated with antibiotics. The results of cross-over intervention of pea and pork protein show that serum cholesterol levels are reversed with dietary exchange. The corresponding changes in microbiota suggest that Muribaculaceae are responsible for the inhibitory effect of pea protein on serum cholesterol level, whereas the opposite effect of pork protein is due to Erysipelotrichaceae. Moreover, pea protein supplement alters cecal metabolites including arginine/histidine pathway, primary bile acid biosynthesis, short-chain fatty acids, and other lipid-like molecules involved in cholesterol metabolism.

Sexual dimorphism in glucose metabolism is shaped by androgen-driven gut microbiome

Males are generally more susceptible to impaired glucose metabolism and type 2 diabetes (T2D) than females. However, the underlying mechanisms remain to be determined. Here, we revealed that gut microbiome depletion abolished sexual dimorphism in glucose metabolism. The transfer of male donor microbiota into antibiotics-treated female mice led the recipients to be more insulin resistant. Depleting androgen via castration changed the gut microbiome of male mice to be more similar to that of females and improved glucose metabolism, while reintroducing dihydrotestosterone (DHT) reversed these alterations. More importantly, the effects of androgen on glucose metabolism were largely abolished when the gut microbiome was depleted. Next, we demonstrated that androgen modulated circulating glutamine and glutamine/glutamate (Gln/Glu) ratio partially depending on the gut microbiome, and glutamine supplementation increases insulin sensitivity in vitro. Our study identifies the effects of androgen in deteriorating glucose homeostasis partially by modulating the gut microbiome and circulating glutamine and Gln/Glu ratio, thereby contributing to the difference in glucose metabolism between the two sexes.

Comorbidity-associated glutamine deficiency is a predisposition to severe COVID-19

SARS-CoV-2 vaccinations have greatly reduced COVID-19 cases, but we must continue to develop our understanding of the nature of the disease and its effects on human immunity. Previously, we suggested that a dysregulated STAT3 pathway following SARS-Co-2 infection ultimately leads to PAI-1 activation and cascades of pathologies. The major COVID-19-associated metabolic risks (old age, hypertension, cardiovascular diseases, diabetes, and obesity) share high PAI-1 levels and could predispose certain groups to severe COVID-19 complications. In this review article, we describe the common metabolic profile that is shared between all of these high-risk groups and COVID-19. This profile not only involves high levels of PAI-1 and STAT3 as previously described, but also includes low levels of glutamine and NAD+, coupled with overproduction of hyaluronan (HA). SARS-CoV-2 infection exacerbates this metabolic imbalance and predisposes these patients to the severe pathophysiologies of COVID-19, including the involvement of NETs (neutrophil extracellular traps) and HA overproduction in the lung. While hyperinflammation due to proinflammatory cytokine overproduction has been frequently documented, it is recently recognized that the immune response is markedly suppressed in some cases by the expansion and activity of MDSCs (myeloid-derived suppressor cells) and FoxP3+ Tregs (regulatory T cells). The metabolomics profiles of severe COVID-19 patients and patients with advanced cancer are similar, and in high-risk patients, SARS-CoV-2 infection leads to aberrant STAT3 activation, which promotes a cancer-like metabolism. We propose that glutamine deficiency and overproduced HA is the central metabolic characteristic of COVID-19 and its high-risk groups. We suggest the usage of glutamine supplementation and the repurposing of cancer drugs to prevent the development of severe COVID-19 pneumonia.

Managing mood-related symptoms utilizing diet, targeted nutrient supplementation, and lifestyle changes: A case series

BACKGROUND

The Office of Disease Prevention and Health Promotion reports that mental health disorders are one of the most "common causes of disability," affecting 18.1% of adults in the United States. This case series examines the use of diet, targeted nutrient supplementation with a focus on amino acids, and lifestyle interventions for the management of mood-related symptoms as a treatment option.

CASE PRESENTATIONS

The three cases included a personalized amino acid therapy protocol, nutrient cofactor supplementation, and diet and lifestyle recommendations. Clinical assessment questionnaires completed by the clients at intervals during care were used to determine proper amino acid dosing. The first client is a 65-year-old Caucasian male presenting with increased stress, anxiety, depression, and sleep disturbances. A marked decrease in symptoms was experienced three months. The second client is a 24-year-old Caucasian male presenting with concentration and memory impairment, anxiety and depression, food cravings leading to binge eating of carbohydrates, low sleep quality, and unsustainable energy. A substantial decrease in symptoms was achieved in under four months. The third client is a 23-year-old Caucasian male presenting with depression, easy agitation while ruminating on negative thoughts, difficulty focusing and making decisions, poor memory, concentration, and sleep quality, gaming addiction, and low energy and motivation. The client experienced considerable relief from all symptoms in under six months.

CONCLUSION

The case series demonstrated marked improvement in mood-related symptoms in as little as 3-6 months for three individuals utilizing amino acid therapy along with dietary, targeted nutrient supplementation, and lifestyle choices.

Metabolic profiling links cardiovascular risk and vascular end organ damage

BACKGROUND AND AIMS

An untargeted metabolomics approach allows for a better understanding and identification of new candidate metabolites involved in the etiology of vascular disease. We aimed to investigate the associations of cardiovascular (CV) risk factors with the metabolic fingerprint and macro- and microvascular health in an untargeted metabolomic approach in predefined CV risk groups of aged individuals.

METHODS

The metabolic fingerprint and the macro- and microvascular health from 155 well-characterized aged (50-80 years) individuals, based on the EXAMIN AGE study, were analysed. Nuclear magnetic resonance spectroscopy was used to analyse the metabolic fingerprint. Carotid-femoral pulse wave velocity and retinal vessel diameters were assessed to quantify macro- and microvascular health.

RESULTS

The metabolic fingerprint became more heterogeneous with an increasing number of risk factors. There was strong evidence for higher levels of glutamine [estimate (95% CI): -14.54 (-17.81 to -11.27), p < 0.001], glycine [-5.84 (-7.88 to -3.79), p < 0.001], histidine [-0.73 (-0.96 to -0.50), p < 0.001], and acetate [-1.68 (-2.91 to -0.46), p = 0.007] to be associated with a lower CV risk profile. Tryptophan, however, was positively associated with higher CV risk [0.31 (0.06-0.56), p = 0.015]. The combination of a priori defined CV risk factors explained up to 45.4% of the metabolic variation. The metabolic fingerprint explained 20% of macro- and 23% of microvascular variation.

CONCLUSIONS

Metabolic profiling has the potential to improve CV risk stratification by identifying new underlying metabolic pathways associated with atherosclerotic disease development, from cardiovascular risk to metabolites, to vascular end organ damage.

Do oral amino acid supplements facilitate the healing of rat lung injuries?

OBJECTIVES

Prolonged air leaks following lung injury cause extended hospital stays. This study investigated the effect of nutritional supplements containing arginine, glutamine and β-hydroxy β-methyl butyrate, which were theoretically proven to accelerate wound healing, on air leak and wound healing parameters in a rat lung injury model.

METHODS

Twenty-eight female rats were randomly divided into 4 groups. Experimental groups were given glutamine (Resource Glutamine®) or a mixture of arginine, glutamine and β-hydroxy β-methyl butyrate (Abound®) as a dietary supplement at isonitrogenous and isocaloric doses. On day 3, standard sized lung injuries were created in all rats except the sham group. The rats were sacrificed on day 6, and the lungs were removed for air-leak threshold pressure measurement and histopathological and biochemical analyses.

RESULTS

Loss of body mass was greater in the glutamine group than in the other groups (P = 0.004). Rats that received the amino acid mixture had better results for mature collagen fibre density (P = 0.002) and inflammation suppression (P = 0.003). The sham group had higher values for air-leak threshold pressure and all other histochemical parameters compared to the other groups. Hydroxyproline level did not differ significantly in any of the groups.

CONCLUSIONS

Our results indicated that an oral amino acid mixture was effective in the healing of lung injuries. Isolated glutamine supplementation had an adverse impact on body mass. Randomized clinical studies including larger series are needed. Hydroxyproline does not seem to be a suitable marker for this purpose.

Effect of glutamine supplementation on cardiometabolic risk factors and inflammatory markers: a systematic review and meta-analysis

Background

Evidence exists that glutamine plays multiple roles in glucose metabolism, insulin sensitivity, and anti-inflammatory effects. This systematic review and meta-analysis of controlled trials aimed to assess the effect of glutamine supplementation on cardio-metabolic risk factors and inflammatory markers.

Methods

The processes of systematic reviews and meta-analyses were performed according to the PRISMA checklist. PubMed, Web of Sciences, Cochrane library, and Scopus databases were search for relevant studies without time or language restrictions up to December 30, 2020. All randomized clinical trials which assessed the effect of glutamine supplementation on “glycemic indices”, “level of triglyceride, “and “inflammatory markers” were included in the study. The effect of glutamine supplementation on cardio-metabolic risk factors and inflammatory markers was assessed using a standardized mean difference (SMD) and 95% confidence interval (CI). Heterogeneity between among studies was assessed using Cochran Q-statistic and I-square. Random/fixed-effects meta-analysis method was used to estimate the pooled SMD. The risk of bias for the included trials was evaluated using the Cochrane quality assessment tool.

Results

In total, 12 studies that assessed the effect of glutamine supplementation on cardio-metabolic risk factors were included in the study. Meta-analysis showed that glutamine supplementation significantly decreased significantly serum levels of FPG [SMD: − 0.73, 95% CI − 1.35, − 0.11, I²: 84.1%] and CRP [SMD: − 0.58, 95% CI − 0.1, − 0.17, I²: 0%]. The effect of glutamine supplementation on other cardiometabolic risk factors was not statistically significant (P > 0.05).

Conclusion

Our findings showed that glutamine supplementation might have a positive effect on FPG and CRP; both of which are crucial as cardio-metabolic risk factors. However, supplementation had no significant effect on other cardio-metabolic risk factors.

Effect of riluzole on weight in short-term and long-term survivors of amyotrophic lateral sclerosis

INTRODUCTION

Riluzole is the first disease-modifying therapy for amyotrophic lateral sclerosis (ALS) approved in 1995 by the Food and Drug Administration in the USA, and is now available worldwide. It delays time to tracheostomy or death and prolongs survival. The precise mechanism of the survival prolonging effect is unknown. Malnutrition and ensuing weight loss are associated with shorter survival in ALS. Given the life-prolonging effects of riluzole and nutritional maintenance, we examined the relationship between riluzole and weight in ALS patients. Materials and Methods: Using data from the National ALS Center of Excellence clinic database at the University of Vermont Medical Center, we stratified 244 patients into cohorts based on riluzole use, and duration of survival from the baseline visit into short-term (≤3 years) and long-term (>3 years) survivors. We examined average monthly weight change in patients during the first year after the baseline visit, and the last year before death. Results and Discussion: In 156 short-term survivors taking riluzole compared to those not taking riluzole, there was a 37% attenuation of weight loss in the first year after baseline, and 46% attenuation of weight loss in the last year before death. Seventy-four n long-term survivors on riluzole showed reduced weight decline in the first year after the baseline visit. We speculate that one mechanism by which riluzole may affect survival is by attenuating weight loss and possibly maintaining nutritional status and body composition, although this warrants prospective study.

Lifestyle modifications result in alterations in the gut microbiota in obese children

Background

The association between the gut microbiota and pediatric obesity was analyzed in a cross-sectional study. A prospective study of obese children was conducted to assess the gut microbial alterations after a weight change. We collected fecal samples from obese children before and after a 2-month weight reduction program that consisted of individual counseling for nutritional education and physical activity, and we performed 16S rRNA gene amplicon sequencing using an Illumina MiSeq platform.

Results

Thirty-six participants, aged 7 to 18 years, were classified into the fat loss (n = 17) and the fat gain (n = 19) groups according to the change in total body fat (%) after the intervention. The baseline analysis of the gut microbiota in the preintervention stages showed dysbiotic features of both groups compared with those of normal-weight children. In the fat loss group, significantly decreased proportions of Bacteroidetes phylum, Bacteroidia class, Bacteroidales order, Bacteroidaceae family, and Bacteroides genus, along with increased proportions of Firmicutes phylum, Clostridia class, and Clostridiales order, were observed after intervention. The microbial richness was significantly reduced, without a change in beta diversity in the fat loss group. The fat gain group showed significantly deceased proportions of Firmicutes phylum, Clostridia class, Clostridiales order, Lachnospiraceae family, and Eubacterium hallii group genus, without a change in diversity after the intervention. According to the functional metabolic analysis by the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2, the “Nitrate Reduction VI” and “Aspartate Superpathway” pathways were predicted to increase significantly in the fat loss group. The cooccurring networks of genera were constructed and showed the different microbes that drove the changes between the pre- and postintervention stages in the fat loss and fat gain groups.

Conclusions

This study demonstrated that lifestyle modifications can impact the composition, richness, and predicted functional profiles of the gut microbiota in obese children after weight changes.

Trial registration

ClinicalTrials.govNCT03812497, registration date January 23, 2019, retrospectively registered.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12866-020-02002-3.

Distinctive Metabolomics Patterns Associated With Insulin Resistance and Type 2 Diabetes Mellitus

Obesity is associated with an increased risk of insulin resistance (IR) and type 2 diabetes mellitus (T2DM) which is a multi-factorial disease associated with a dysregulated metabolism and can be prevented in pre-diabetic individuals with impaired glucose tolerance. A metabolomic approach emphasizing metabolic pathways is critical to our understanding of this heterogeneous disease. This study aimed to characterize the serum metabolomic fingerprint and multi-metabolite signatures associated with IR and T2DM. Here, we have used untargeted high-performance chemical isotope labeling (CIL) liquid chromatography-mass spectrometry (LC-MS) to identify candidate biomarkers of IR and T2DM in sera from 30 adults of normal weight, 26 obese adults, and 16 adults newly diagnosed with T2DM. Among the 3633 peak pairs detected, 62% were either identified or matched. A group of 78 metabolites were up-regulated and 111 metabolites were down-regulated comparing obese to lean group while 459 metabolites were up-regulated and 166 metabolites were down-regulated comparing T2DM to obese groups. Several metabolites were identified as IR potential biomarkers, including amino acids (Asn, Gln, and His), methionine (Met) sulfoxide, 2-methyl-3-hydroxy-5-formylpyridine-4-carboxylate, serotonin, L-2-amino-3-oxobutanoic acid, and 4,6-dihydroxyquinoline. T2DM was associated with dysregulation of 42 metabolites, including amino acids, amino acids metabolites, and dipeptides. In conclusion, these pilot data have identified IR and T2DM metabolomics panels as potential novel biomarkers of IR and identified metabolites associated with T2DM, with possible diagnostic and therapeutic applications. Further studies to confirm these associations in prospective cohorts are warranted.

Intravenous Glutamine Administration Improves Glucose Tolerance and Attenuates the Inflammatory Response in Diet-Induced Obese Mice after Sleeve Gastrectomy

Obesity is a health problem associated with many metabolic disorders. Weight reduction can effectively alleviate obesity-associated complications. Sleeve gastrectomy is a commonly used bariatric surgery and is considered safe and effective for improving outcomes. Glutamine (GLN) is an amino acid with anti-oxidative and anti-inflammatory properties. This study used a mouse model of sleeve gastrectomy to investigate the impacts of intravenous GLN administration on glucose tolerance and adipocyte inflammation short-term after surgery. C57BL6 male mice were divided into normal control (NC) and high-fat diet groups. The high-fat diet provided 60% of energy from fat for 10 weeks to induce obesity. Mice fed the high-fat diet were then assigned to a sham (SH) or sleeve gastrectomy with saline (S) or GLN (G) groups. The S group was intravenously injected with saline, while the G group was administered GLN (0.75 g/kg body weight) via a tail vein postoperatively. Mice in the experimental groups were sacrificed on day 1 or 3 after the surgery. Results showed that obesity resulted in fat accumulation, elevated glucose levels, and adipokines production. Sleeve gastrectomy aggravated expressions of inflammatory cytokine and macrophage infiltration markers, cluster of differentiation 68 (CD68), epidermal growth factor-like module-containing mucin-like hormone receptor-like 1 (EMR-1), and macrophage chemoattractant protein-1, in adipose tissues. Treatment of obese mice with GLN downregulated hepatic proteomic profiles associated with the gluconeogenesis pathway and improved glucose tolerance. Moreover, macrophage infiltration and adipose tissue inflammation were attenuated after the sleeve gastrectomy. These findings imply that postoperative intravenous GLN administration may improve glucose tolerance and attenuate inflammation shortly after the bariatric surgery in subjects with obesity.

Gastrointestinal digestion and cecal fermentation of a mixed gel of lean pork meat and resistant starch in mice

The sensitivity of meat gel to digestive enzymes and the overall digestion pattern of the meat product is vital, and exerts an important influence on the growth and metabolism of mice. In order to provide a comprehensive understanding for better usage of resistant starch (RS) in functional meat products, the effects of a mixed gel (MS, a cooked mixture) of lean pork meat and RS on the gastrointestinal digestion and cecal fermentation of mice were investigated via comparing with those of RS-free meat gel (M) and the addition of RS to meat gel (M + S). The results showed that both M + S and MS promoted gastrointestinal digestion and cecal fermentation in mice. Specifically, the MS diet contributed to the hydrolysis of proteins, the formation of beneficial amino acids, and cecal health in spite of the larger particle size for digestion than that of the M + S group. Collectively, mixed gels of meat and RS are prospective for developing healthier meat products.

Synergistic effect of Lactobacillus gasseri and Cudrania tricuspidata on the modulation of body weight and gut microbiota structure in diet-induced obese mice

High-fat diet (HFD)-induced obesity has been associated with alteration of gut microbiota alongside body weight gain. In this study, the synbiotic effect of Lactobacillus gasseri 505 (LG) and Cudrania tricuspidata (CT) in HFD-induced mice was revealed. After feeding mice with high-fat diet for 10 weeks, combination of LG and CT (LG_CT) exhibited the greatest reduction in the final body weight (11.9%). Moreover, microbial diversity significantly increased, and Principal Coordinate Analysis (PCoA) revealed that the LG_CT group showed closer cluster to NORM. At phylum level, the Firmicutes/Bacteroidetes (F/B) ratio increased in HFD, and the abundance of Bacteroidetes was restored by LG and CT. At genus level, notable changes in Alistipes, Desulfovibrio, Bilophila, and Acetatifactor were observed. Helicobacter elevated to 16.2% in HFD and diminished dramatically to less than 0.01% in LG and/or CT. At species level, L. gasseri increased after the administration of LG (0.54%) and LG_CT (1.14%), suggesting that LG may grow and colonize in the gut and CT can function as a prebiotic. Finally, functional analysis revealed certain metabolic factors correlated with body weight and gut microbiota. This study serves as a potential basis for the application of L. gasseri 505 and C. tricuspidata in the prevention and treatment of diet-induced obesity.Key Points • Combination of L. gasseri (LG) and C. tricuspidata (CT) reduced body weight gain.• Microbial diversity significantly increased in LG_CT treatment.• Abundance of microorganisms involved with leanness increased in LG, CT, and LG_CT.• Body weight is associated with some metabolic functions of gut microbiota.

Glutamine Links Obesity to Inflammation in Human White Adipose Tissue

While obesity and associated metabolic complications are linked to inflammation of white adipose tissue (WAT), the causal factors remain unclear. We hypothesized that the local metabolic environment could be an important determinant. To this end, we compared metabolites released from WAT of 81 obese and non-obese women. This identified glutamine to be downregulated in obesity and inversely associated with a pernicious WAT phenotype. Glutamine administration in vitro and in vivo attenuated both pro-inflammatory gene and protein levels in adipocytes and WAT and macrophage infiltration in WAT. Metabolomic and bioenergetic analyses in human adipocytes suggested that glutamine attenuated glycolysis and reduced uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) levels. UDP-GlcNAc is the substrate for the post-translational modification O-linked β-N-acetylglucosamine (O-GlcNAc) mediated by the enzyme O-GlcNAc transferase. Functional studies in human adipocytes established a mechanistic link between reduced glutamine, O-GlcNAcylation of nuclear proteins, and a pro-inflammatory transcriptional response. Altogether, glutamine metabolism is linked to WAT inflammation in obesity.

Mutual Interactions among Exercise, Sport Supplements and Microbiota

The adult gut microbiota contains trillions of microorganisms of thousands of different species. Only one third of gut microbiota are common to most people; the rest are specific and contribute to enhancing genetic variation. Gut microorganisms significantly affect host nutrition, metabolic function, immune system, and redox levels, and may be modulated by several environmental conditions, including physical activity and exercise. Microbiota also act like an endocrine organ and is sensitive to the homeostatic and physiological changes associated with training; in turn, exercise has been demonstrated to increase microbiota diversity, consequently improving the metabolic profile and immunological responses. On the other side, adaptation to exercise might be influenced by the individual gut microbiota that regulates the energetic balance and participates to the control of inflammatory, redox, and hydration status. Intense endurance exercise causes physiological and biochemical demands, and requires adequate measures to counteract oxidative stress, intestinal permeability, electrolyte imbalance, glycogen depletion, frequent upper respiratory tract infections, systemic inflammation and immune responses. Microbiota could be an important tool to improve overall general health, performance, and energy availability while controlling inflammation and redox levels in endurance athletes. The relationship among gut microbiota, general health, training adaptation and performance, along with a focus on sport supplements which are known to exert some influence on the microbiota, will be discussed.

The Role of Glutamine in the Complex Interaction between Gut Microbiota and Health: A Narrative Review

The scientific literature has demonstrated that glutamine is one of the main beneficial amino acids. It plays an important role in gut microbiota and immunity. This paper provides a critical overview of experimental studies (in vitro, in vivo, and clinical) investigating the efficacy of glutamine and its effect on gut microbiota. As a result of this review, we have summarized that glutamine could affect gut microbiota via different mechanisms including the reduction in the ratio of Firmicutes to Bacteroidetes, with the activation of NF-κB and PI3K-Akt pathways, reducing the intestinal colonization (Eimeria lesions) and bacterial overgrowth or bacterial translocation, increasing the production of secretory immunoglobulin A (SIgA) and immunoglobulin A+ (IgA+) cells in the intestinal lumen, and decreasing asparagine levels. The potential applications of glutamine on gut microbiota include, but are not limited to, the management of obesity, bacterial translocation and community, cytokines profiles, and the management of side effects during post-chemotherapy and constipation periods. Further studies and reviews are needed regarding the effects of glutamine supplementation on other conditions in humans.

Regulation of Gut Microbiota and Metabolic Endotoxemia with Dietary Factors

Metabolic endotoxemia is a condition in which blood lipopolysaccharide (LPS) levels are elevated, regardless of the presence of obvious infection. It has been suggested to lead to chronic inflammation-related diseases such as obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease (NAFLD), pancreatitis, amyotrophic lateral sclerosis, and Alzheimer’s disease. In addition, it has attracted attention as a target for the prevention and treatment of these chronic diseases. As metabolic endotoxemia was first reported in mice that were fed a high-fat diet, research regarding its relationship with diets has been actively conducted in humans and animals. In this review, we summarize the relationship between fat intake and induction of metabolic endotoxemia, focusing on gut dysbiosis and the influx, kinetics, and metabolism of LPS. We also summarize the recent findings about dietary factors that attenuate metabolic endotoxemia, focusing on the regulation of gut microbiota. We hope that in the future, control of metabolic endotoxemia using dietary factors will help maintain human health.