Insulin resistance is associated with altered amino acid metabolism and adipose tissue dysfunction in normoglycemic women

Role of AMP deaminase in diabetic cardiomyopathy

Diabetes mellitus is one of the major causes of ischemic and nonischemic heart failure. While hypertension and coronary artery disease are frequent comorbidities in patients with diabetes, cardiac contractile dysfunction and remodeling occur in diabetic patients even without comorbidities, which is referred to as diabetic cardiomyopathy. Investigations in recent decades have demonstrated that the production of reactive oxygen species (ROS), impaired handling of intracellular Ca2+, and alterations in energy metabolism are involved in the development of diabetic cardiomyopathy. AMP deaminase (AMPD) directly regulates adenine nucleotide metabolism and energy transfer by adenylate kinase and indirectly modulates xanthine oxidoreductase-mediated pathways and AMP-activated protein kinase-mediated signaling. Upregulation of AMPD in diabetic hearts was first reported more than 30 years ago, and subsequent studies showed similar upregulation in the liver and skeletal muscle. Evidence for the roles of AMPD in diabetes-induced fatty liver, sarcopenia, and heart failure has been accumulating. A series of our recent studies showed that AMPD localizes in the mitochondria-associated endoplasmic reticulum membrane as well as the sarcoplasmic reticulum and cytosol and participates in the regulation of mitochondrial Ca2+ and suggested that upregulated AMPD contributes to contractile dysfunction in diabetic cardiomyopathy via increased generation of ROS, adenine nucleotide depletion, and impaired mitochondrial respiration. The detrimental effects of AMPD were manifested at times of increased cardiac workload by pressure loading. In this review, we briefly summarize the expression and functions of AMPD in the heart and discuss the roles of AMPD in diabetic cardiomyopathy, mainly focusing on contractile dysfunction caused by this disorder.

Branched-Chain Amino Acids, Alanine, and Thyroid Function: A Cross-Sectional, Nuclear Magnetic Resonance (NMR)-Based Approach from ELSA-Brasil

The association of thyroid function with essential and non-essential amino acids is understudied, despite their common metabolic roles. Thus, our aim was to evaluate the association of thyroid function with the levels of branched-chain amino acids (BCAAs-leucine, isoleucine, and valine) and of alanine in the general population. We utilized data from the São Paulo research center of ELSA-Brasil, a longitudinal population-based cohort study. Thyroid parameters included thyroid stimulating hormone (TSH), free T4 and free T3 levels, and the FT4:FT3 ratio. BCAAs and alanine were analyzed on a fully automated NMR platform. The current analysis included euthyroid participants and participants with subclinical hyperthyroidism and hypothyroidism. We used Pearson's coefficient to quantify the correlation between thyroid-related parameters and amino acids. Linear regression models were performed to analyze whether thyroid parameters were associated with BCAAs and alanine levels. We included 4098 participants (51.3 ± 9.0 years old, 51.5% women) in this study. In the most adjusted model, higher levels of TSH were associated with higher levels of alanine, FT4 levels were inversely associated with isoleucine levels, FT3 levels were statistically significant and positively associated with valine and leucine, and the T3:T4 ratio was positively associated with all amino acids. We observed that subclinical hypothyroidism was positively associated with isoleucine and alanine levels in all models, even after full adjustment. Our findings highlight the association of subclinical hypothyroidism and thyroid-related parameters (including TSH, free T4, free T3, and FT4:FT3 ratio) with BCAAs and alanine. Further studies are needed to explore the mechanisms underlying this association. These insights contribute to our understanding of the influence of thyroid-related parameters on BCAA and alanine metabolism.

Alteration of Branched-Chain and Aromatic Amino Acid Profile as a Novel Approach in Studying Polycystic Ovary Syndrome Pathogenesis

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that affects reproductive-age women and predisposes them to the development of metabolic disturbances. Recent research has shown that several metabolic factors may play a role in PCOS pathogenesis, and it has been suggested that an alteration in the amino acid profile might be a predictive sign of metabolic disorders. Metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) are concepts that have attracted scientific attention; however, a universal definition has not been established yet for these terms. Already existing definitions of MHO involve the coexistence of obesity with the absence or minimal presence of other metabolic syndrome parameters. A group of 326 women, 209 diagnosed with PCOS and 117 healthy individuals, participated in this study. Multiple parameters were assessed, including anthropometrical, biochemical, and hormonal ones, and gas-liquid chromatography, combined with tandem mass spectrometry, was used to investigate the amino acid profile. Statistical analysis revealed noticeably higher levels of all aromatic amino acids in PCOS women compared to the control group: phenylalanine 47.37 ± 7.0 vs. 45.4 ± 6.09 nmol/mL (p = 0.01), tyrosine 61.69 ± 9.56 vs. 58.08 ± 8.89 nmol/mL (p < 0.01), and tryptophan 53.66 ± 11.42 vs. 49.81 ± 11.18 nmol/mL (p < 0.01); however, there was no significant difference in the "tryptophan ratio" between the PCOS and control group (p = 0.88). A comparison of MHO and MUO PCOS women revealed that LAP, leucine, and isoleucine concentrations were significantly higher among the MUO subgroup: respectively, 101.98 ± 34.74 vs. 55.80 ± 24.33 (p < 0.001); 153.26 ± 22.26 vs. 137.25 ± 25.76 nmol/mL (p = 0.04); and 92.92 ± 16.09 vs. 82.60 ± 18.70 nmol/mL (p = 0.02). No significant differences in BMI, fasting glucose, and HOMA-IR between MHO and MUO were found: respectively, 35.0 ± 4.8 vs. 36.1 ± 4.6 kg/m2 (p = 0.59); 88.0 ± 6.0 vs. 87.73 ± 6.28 mg/dL (p = 0.67); and 3.36 ± 1.70 vs. 4.17 ± 1.77 (p = 0.1). The identification of altered amino acid profiles in PCOS holds potential clinical implications. Amino acids may serve as biomarkers for diagnosing and monitoring the metabolic status of individuals with PCOS. The alteration of BCAAs and AAAs may be involved in PCOS pathogenesis, but the underlying mechanism should be further investigated.

Metabolic impact of polyphenol-rich aronia fruit juice mediated by inflammation status of gut microbiome donors in humanized mouse model

Background

The Aronia melanocarpa fruit is emerging as a health food owing to its high polyphenolic content and associated antioxidant activity. Antioxidant-rich foods, such as Aronia fruit, may counter inflammatory stimuli and positively modulate the gut microbiome. However, a comprehensive study characterizing the impact of Aronia fruit supplementation has not been completed. Therefore, we completed analyses measuring the metabolic, microbial, and inflammatory effects of a diet supplemented with Aronia fruit juice.

Method

Humanized mice were generated by colonizing gnotobiotic mice with microbiomes from human donors presenting disparate inflammation levels. Blood and fecal samples were collected throughout the course of an 8-week dietary intervention with either Aronia juice or a carbohydrate-matched beverage alone (2 weeks) or in combination with a high-fat diet to induce inflammation (6 weeks). Samples were analyzed using 16S rRNA gene sequencing (stool) and liquid chromatography-mass spectrometry (serum).

Results

We demonstrated transfer of microbiome composition and diversity and metabolic characteristics from humans with low and high inflammation levels to second-generation humanized mice. Aronia supplementation provided robust protection against high-fat diet induced metabolic and microbiome changes that were dependent in part on microbiome donor. Aronia induced increases in bacteria of the Eggerthellaceae genus (7-fold) which aligns with its known ability to metabolize (poly)phenols and in phosphatidylcholine metabolites which are consistent with improved gut barrier function. The gut microbiome from a low inflammation phenotype donor provided protection against high-fat diet induced loss of microbiome β-diversity and global metabolomic shifts compared to that from the high inflammation donor.

Conclusion

These metabolic changes elucidate pathway-specific drivers of reduced inflammation stemming from both Aronia and the gut microbiota.

Impaired Adipocyte SLC7A10 Promotes Lipid Storage in Association With Insulin Resistance and Altered BCAA Metabolism

CONTEXT

The neutral amino acid transporter SLC7A10/ASC-1 is an adipocyte-expressed gene with reduced expression in insulin resistance and obesity. Inhibition of SLC7A10 in adipocytes was shown to increase lipid accumulation despite decreasing insulin-stimulated uptake of glucose, a key substrate for de novo lipogenesis. These data imply that alternative lipogenic substrates to glucose fuel continued lipid accumulation during insulin resistance in obesity.

OBJECTIVE

We examined whether increased lipid accumulation during insulin resistance in adipocytes may involve alter flux of lipogenic amino acids dependent on SLC7A10 expression and activity, and whether this is reflected by extracellular and circulating concentrations of marker metabolites.

METHODS

In adipocyte cultures with impaired SLC7A10, we performed RNA sequencing and relevant functional assays. By targeted metabolite analyses (GC-MS/MS), flux of all amino acids and selected metabolites were measured in human and mouse adipose cultures. Additionally, SLC7A10 mRNA levels in human subcutaneous adipose tissue (SAT) were correlated to candidate metabolites and adiposity phenotypes in 2 independent cohorts.

RESULTS

SLC7A10 impairment altered expression of genes related to metabolic processes, including branched-chain amino acid (BCAA) catabolism, lipogenesis, and glyceroneogenesis. In 3T3-L1 adipocytes, SLC7A10 inhibition increased fatty acid uptake and cellular content of glycerol and cholesterol. SLC7A10 impairment in SAT cultures altered uptake of aspartate and glutamate, and increased net uptake of BCAAs, while increasing the net release of the valine catabolite 3- hydroxyisobutyrate (3-HIB). In human cohorts, SLC7A10 mRNA correlated inversely with total fat mass, circulating triacylglycerols, BCAAs, and 3-HIB.

CONCLUSION

Reduced SLC7A10 activity strongly affects flux of BCAAs in adipocytes, which may fuel continued lipogenesis during insulin resistance, and be reflected in increased circulating levels of the valine-derived catabolite 3-HIB.

A cell-autonomous mechanism regulates BCAA catabolism in white adipocytes and systemic metabolic balance

Elevated plasma branched-chain amino acids (BCAAs) are strongly associated with obesity, insulin resistance (IR), and diabetes in humans and rodent models. However, the mechanisms of BCAA dysregulation and its systemic, organ, and cell-specific implications in the development of obesity and IR are not well understood. To gain mechanistic insight into the causes and effects of plasma BCAA elevations, we leveraged mouse models with high circulating BCAA levels prior to the onset of obesity and IR. Young mice lacking ankyrin-B in white adipose tissue (WAT) or bearing an ankyrin-B variant that causes age-driven metabolic syndrome exhibit downregulation of BCAA catabolism selectively in WAT and excess plasma BCAAs. Using cellular assays, we demonstrated that ankyrin-B promotes the surface localization of the amino acid transporter Asct2 in white adipocytes, and its deficit impairs BCAA uptake. Excess BCAA supplementation worsened glucose tolerance and insulin sensitivity across genotypes. In contrast, BCAA overconsumption only increased adiposity in control mice, implicating WAT utilization of BCAAs in their obesogenic effects. These results shed light into the mechanistic underpinnings of metabolic syndrome caused by ankyrin-B deficits and provide new evidence of the relevance of WAT in the regulation of systemic BCAA levels, adiposity, and glucose homeostasis.

Age-related metabolite profiles and their relation to clinical outcomes in young adults, middle-aged individuals, and older people

Age is a significant risk factor for common noncommunicable diseases, yet the physiological alterations of aging are poorly understood. We were interested in metabolic patterns between cross-sectional cohorts of different age ranges with particular emphasis on waist circumference. We recruited three cohorts of healthy subjects with different age ranges (adolescents 18-25 years, adults 40-65 years, and older citizens 75-85 years) and stratified these based on waist circumference. Using targeted LC-MS/MS metabolite profiling, we analyzed 112 analytes in plasma (amino acids, acylcarnitines, and derivatives). We associated age-related alterations with various anthropometric and functional parameters such as insulin sensitivity and handgrip strength. Strongest age-dependent increases were found for fatty acid-derived acylcarnitines. Amino acid-derived acylcarnitines displayed increased associations with BMI and adiposity. Some essential amino acids changed in opposite directions, being lower at increased age and higher with increasing adiposity. τ-methylhistidine was elevated in older subjects, especially on an adiposity background, suggesting an increased protein turnover. Both aging and adiposity are associated with impaired insulin sensitivity. Skeletal muscle mass decreased with age and increased with adiposity. Profound differences in the metabolite signatures during healthy aging and elevated waist circumference/body weight were found. Opposite changes in skeletal muscle mass as well as possible differences in insulin signaling (relative insulin deficiency in older subjects versus hyperinsulinemia associated with adiposity), might be underlying origins for the observed metabolite signatures. We describe novel associations between metabolites and anthropometric factors during aging which underlines the complex interplay of aging, insulin resistance, and metabolic health.

Untargeted metabolomic profiling identifies serum metabolites associated with type 2 diabetes in a cross-sectional study of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study

Type 2 diabetes (T2D) is a complex chronic disease with substantial phenotypic heterogeneity affecting millions of individuals. Yet, its relevant metabolites and etiological pathways are not fully understood. The aim of this study is to assess a broad spectrum of metabolites related to T2D in a large population-based cohort. We conducted a metabolomic analysis of 4,281 male participants within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. The serum metabolomic analysis was performed using an LC-MS/GC-MS platform. Associations between 1,413 metabolites and T2D were examined using linear regression, controlling for important baseline risk factors. Standardized β-coefficients and standard errors (SEs) were computed to estimate the difference in metabolite concentrations. We identified 74 metabolites that were significantly associated with T2D based on the Bonferroni-corrected threshold (P < 3.5 × 10-5). The strongest signals associated with T2D were of carbohydrates origin, including glucose, 1,5-anhydroglucitol (1,5-AG), and mannose (β = 0.34, -0.91, and 0.41, respectively; all P < 10-75). We found several chemical class pathways that were significantly associated with T2D, including carbohydrates (P = 1.3 × 10-11), amino acids (P = 2.7 × 10-6), energy (P = 1.5 × 10-4), and xenobiotics (P = 1.2 × 10-3). The strongest subpathway associations were seen for fructose-mannose-galactose metabolism, glycolysis-gluconeogenesis-pyruvate metabolism, fatty acid metabolism (acyl choline), and leucine-isoleucine-valine metabolism (all P < 10-8). Our findings identified various metabolites and candidate chemical class pathways that can be characterized by glycolysis and gluconeogenesis metabolism, fructose-mannose-galactose metabolism, branched-chain amino acids, diacylglycerol, acyl cholines, fatty acid oxidation, and mitochondrial dysfunction.NEW & NOTEWORTHY These metabolomic patterns may provide new additional evidence and potential insights relevant to the molecular basis of insulin resistance and the etiology of T2D.

Specific Alteration of Branched-Chain Amino Acid Profile in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies in reproductive age women; it is a complex health issue with numerous comorbidities. Attention has recently been drawn to amino acids as they are molecules essential to maintain homeostasis. The aim of the study was to investigate the branch chain amino acid (BCAA) profile in women with PCOS. A total of 326 women, 208 diagnosed with PCOS and 118 healthy controls, participated in the study; all the patients were between 18 and 40 years old. Anthropometrical, biochemical and hormonal parameters were assessed. Gas-liquid chromatography combined with tandem mass spectrometry was used to investigate BCAA levels. Statistical analysis showed significantly higher plasma levels of BCAAs (540.59 ± 97.23 nmol/mL vs. 501.09 ± 85.33 nmol/mL; p < 0.001) in women with PCOS. Significant correlations (p < 0.05) were found between BCAA and BMI, HOMA-IR, waist circumference and total testosterone levels. In the analysis of individuals with abdominal obesity, there were significant differences between PCOS and controls in BCAA (558.13 ± 100.51 vs. 514.22 ± 79.76 nmol/mL) and the concentrations of all the analyzed amino acids were higher in the PCOS patients. Hyperandrogenemia in PCOS patients was associated with significantly higher leucine, isoleucine and total BCAA levels. The increase of BCAA levels among PCOS patients in comparison to healthy controls might be an early sign of metabolic alteration and a predictive factor for other disturbances.

The Role of Molecular and Hormonal Factors in Obesity and the Effects of Physical Activity in Children

Obesity and overweight are defined as abnormal fat accumulations. Adipose tissue consists of more than merely adipocytes; each adipocyte is closely coupled with the extracellular matrix. Adipose tissue stores excess energy through expansion. Obesity is caused by the abnormal expansion of adipose tissue as a result of adipocyte hypertrophy and hyperplasia. The process of obesity is controlled by several molecules, such as integrins, kindlins, or matrix metalloproteinases. In children with obesity, metabolomics studies have provided insight into the existence of unique metabolic profiles. As a result of low-grade inflammation in the system, abnormalities were observed in several metabolites associated with lipid, carbohydrate, and amino acid pathways. In addition, obesity and related hormones, such as leptin, play an instrumental role in regulating food intake and contributing to childhood obesity. The World Health Organization states that physical activity benefits the heart, the body, and the mind. Several noncommunicable diseases, such as cardiovascular disease, cancer, and diabetes, can be prevented and managed through physical activity. In this work, we reviewed pediatric studies that examined the molecular and hormonal control of obesity and the influence of physical activity on children with obesity or overweight. The purpose of this review was to examine some orchestrators involved in this disease and how they are related to pediatric populations. A larger number of randomized clinical trials with larger sample sizes and long-term studies could lead to the discovery of new key molecules as well as the detection of significant factors in the coming years. In order to improve the health of the pediatric population, omics analyses and machine learning techniques can be combined in order to improve treatment decisions.

Associations of serum amino acids with insulin resistance among people with and without overweight or obesity: A prospective study in Japan

BACKGROUND & AIMS

Limited evidence exists regarding the prospective associations between amino acids and insulin resistance. In addition, amino acids have been suggested to promote insulin resistance with the requirement of obesity in animal studies, but the interaction between amino acids and obesity on the development of insulin resistance has not been examined in epidemiological studies. We aimed to investigate the differences in the prospective associations of serum amino acids with insulin resistance among adults with and without overweight or obesity.

METHODS

Fasting serum concentrations of 25 amino acids were quantified in 1131 non-diabetic Japanese workers aged 22-71 years at baseline. The homeostasis model assessment of insulin resistance (HOMA-IR) was estimated at baseline and the 3-year follow-up. Generalized linear models were used to assess the associations between amino acids at baseline and HOMA-IR at follow-up with adjustment for potential confounding factors. A Bonferroni-corrected threshold of p = 0.001 was considered significant for multiple tests.

RESULTS

The associations for the following amino acids with HOMA-IR at the 3-year follow-up significantly varied by obesity status: isoleucine, valine, tyrosine, alanine, and methionine (all p for interaction <0.05). Higher concentrations of serum isoleucine, valine, tyrosine, and alanine (per 1SD) were significantly associated with higher HOMA-IR levels in overweight/obese participants (multivariable-adjusted β coefficients ranging from 0.09 to 0.12; all p < 0.001), but no association was observed in the underweight/normal-weight participants. The associations for serum methionine were direct among overweight/obese participants, but inverse among underweight/normal-weight participants (all p < 0.001).

CONCLUSIONS

This study demonstrated the prospective associations of different individual serum amino acids with insulin resistance, with most pronounced associations being for overweight/obese adults. Our findings support the possibility of heterogeneous effects of individual amino acids, as well as their interplay with obesity in the progression of insulin resistance.

Branched-Chain and Aromatic Amino Acids Related to Visceral Adipose Tissue Impact Metabolic Health Risk Markers

CONTEXT

Visceral (VAT) and subcutaneous adipose tissue (SAT) function as endocrine organs capable of influencing metabolic health across adiposity levels.

OBJECTIVE

We aimed to investigate whether metabolites associated with VAT and SAT impact metabolic health through metabolite concentrations.

METHODS

Analyses are based on 1790 participants from the population-based Rhineland Study. We assessed plasma levels of methionine (Met), branched-chain amino acids (BCAA), aromatic amino acids (AAA), and their metabolic downstream metabolites with liquid chromatography-mass spectrometry. VAT and SAT volumes were assessed by magnetic resonance imaging (MRI). Metabolically healthy and unhealthy phenotypes were defined using Wildman criteria.

RESULTS

Metabolically unhealthy participants had higher concentrations of BCAA than metabolically healthy participants (P < 0.001). In metabolically unhealthy participants, VAT volumes were significantly associated with levels of L-isoleucine, L-leucine, indole-3-lactic acid, and indole-3-propionic acid (in log SD units: β = 0.16, P = 0.003; β = 0.12, P = 0.038; β = 0.11, P = 0.035 and β = -0.16, P = 0.010, respectively). Higher concentrations of certain BCAA and AAA-downstream metabolites significantly increased the odds of cardiometabolic risk markers. The relation between VAT volume and cardiometabolic risk markers was mediated by BCAA (indirect effects 3.7%-11%, P = 0.02 to < 0.0001), while the effect of VAT on systemic inflammation was mediated through higher kynurenine concentrations (indirect effect 6.4%, P < 0.0001).

CONCLUSION

Larger volumes of VAT in metabolically unhealthy individuals are associated with altered concentrations of circulating BCAA and AAA-downstream metabolites, increasing the odds of cardiometabolic risk markers. This suggests that these metabolites are involved in the mechanisms that underlie the relationship of abdominal VAT with metabolic health.

Potential Mechanisms for How Long-Term Physical Activity May Reduce Insulin Resistance

Insulin became available for the treatment of patients with diabetes 100 years ago, and soon thereafter it became evident that the biological response to its actions differed markedly between individuals. This prompted extensive research into insulin action and resistance (IR), resulting in the universally agreed fact that IR is a core finding in patients with type 2 diabetes mellitus (T2DM). T2DM is the most prevalent form of diabetes, reaching epidemic proportions worldwide. Physical activity (PA) has the potential of improving IR and is, therefore, a cornerstone in the prevention and treatment of T2DM. Whereas most research has focused on the acute effects of PA, less is known about the effects of long-term PA on IR. Here, we describe a model of potential mechanisms behind reduced IR after long-term PA to guide further mechanistic investigations and to tailor PA interventions in the therapy of T2DM. The development of such interventions requires knowledge of normal glucose metabolism, and we briefly summarize an integrated physiological perspective on IR. We then describe the effects of long-term PA on signaling molecules involved in cellular responses to insulin, tissue-specific functions, and whole-body IR.

Flavonoid-enriched extract from Millettia speciosa Champ prevents obesity by regulating thermogenesis and lipid metabolism in high-fat diet-induced obese C57BL/6 mice

Millettia speciosa (M. speciosa) Champ is a medicinal and edible plant. The roots are rich in flavonoids, which possess multiple biological activities, including lipid-lowering effects. This study aimed to explore the effect of flavonoid-enriched extract from M. speciosa (FMS) on obesity. The UPLC-Q-TOF-MS analysis and chromatographic analysis were adopted to identify flavonoid compounds in FMS. Male C57BL/6J mice were fed with a high-fat diet for 3 months and were then treated with FMS (50 or 100 mg/kg/d) or Orlistat (10 mg kg-1 d-1) for another 8 weeks. A total of 35 flavonoids were identified in the extract of M. speciosa root. FMS reduced body weight gain, liver weight gain, white adipose tissue, lipid accumulation, and blood glucose. The levels of TG, ALT, AST, and inflammatory-related adipokines (TNF-α and IL-6) in serum were also reduced by FMS. In addition, FMS promoted thermogenesis in brown adipose tissue and induced the activation of lipolysis, fatty acid oxidation, and oxidative phosphorylation in white adipose tissues. In summary, long-term administration of FMS could ameliorate high-fat diet-induced obesity by stimulating adipose thermogenesis and lipid metabolism.

Alleviation of Dyslipidemia via a Traditional Balanced Korean Diet Represented by a Low Glycemic and Low Cholesterol Diet in Obese Women in a Randomized Controlled Trial

A traditional balanced Korean diet (K-diet) may improve energy, glucose, and lipid metabolism. To evaluate this, we conducted a randomized crossover clinical trial, involving participants aged 30–40 years, who were randomly assigned to two groups—a K-diet or westernized Korean control diet daily, with an estimated energy requirement (EER) of 1900 kcal. After a 4-week washout period, they switched the diet and followed it for 4 weeks. The carbohydrate, protein, and fat ratios based on energy intake were close to the target values for the K-diet (65:15:20) and control diet (60:15:25). The glycemic index of the control diet and the K-diet was 50.3 ± 3.6 and 68.1 ± 2.9, respectively, and daily cholesterol contents in the control diet and K-diet were 280 and 150 mg, respectively. Anthropometric and biochemical parameters involved in energy, glucose, and lipid metabolism were measured while plasma metabolites were determined using UPLC-QTOF-MS before and after the 4-week intervention. After the four-week intervention, both diets improved anthropometric and biochemical variables, but the K-diet significantly reduced them compared to the control diet. Serum total cholesterol, non-high-density lipoprotein cholesterol, and triglyceride concentrations were significantly lower in the K-diet group than in the control diet group. The waist circumference (p = 0.108) and insulin resistance index (QUICKI, p = 0.089) tended to be lower in the K-diet group than in the control diet group. Plasma metabolites indicated that participants in the K-diet group tended to reduce insulin resistance compared to those in the control diet group. Amino acids, especially branched-chain amino acids, tyrosine, tryptophan, and glutamate, and L-homocysteine concentrations were considerably lower in the K-diet group than in the control diet group (p < 0.05). Plasma glutathione concentrations, an index of antioxidant status, and 3-hydroxybutyric acid concentrations, were higher in the K-diet group than in the control diet group. In conclusion, a K-diet with adequate calories to meet EER alleviated dyslipidemia by decreasing insulin resistance-related amino acids and increasing ketones in the circulation of obese women.

Mechanismbased role of the intestinal microbiota in gestational diabetes mellitus: A systematic review and meta-analysis

Background

Metabolic disorders caused by intestinal microbial dysregulation are considered to be important causes of gestational diabetes mellitus (GDM). Increasing evidence suggests that the diversity and composition of gut microbes are altered in disease states, yet the critical microbes and mechanisms of disease regulation remain unidentified.

Methods

PubMed^® (National Library of Medicine, Bethesda, MD, USA), Embase^® (Elsevier, Amsterdam, the Netherlands), the Web of Science™ (Clarivate™, Philadelphia, PA, USA), and the Cochrane Library databases were searched to identify articles published between 7 July 2012 and 7 July 2022 reporting on case-control and controlled studies that analyzed differences in enterobacteria between patients with GDM and healthy individuals. Information on the relative abundance of enterobacteria was collected for comparative diversity comparison, and enterobacterial differences were analyzed using random effects to calculate standardized mean differences at a p-value of 5%.

Results

A total of 22 studies were included in this review, involving a total of 965 GDM patients and 1,508 healthy control participants. Alpha diversity did not differ between the participant groups, but beta diversity was significantly different. Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria were the dominant bacteria, but there was no significant difference between the two groups. Qualitative analysis showed differences between the groups in the Firmicutes/Bacteroidetes ratio, Blautia, and Collinsella, but these differences were not statistically different.

Conclusion

Enterobacterial profiles were significantly different between the GDM and non-GDM populations. Alpha diversity in patients with GDM is similar to that in healthy people, but beta diversity is significantly different. Firmicutes/Bacteroidetes ratios were significantly increased in GDM, and this, as well as changes in the abundance of species of Blautia and Collinsella, may be responsible for changes in microbiota diversity. Although the results of our meta-analysis are encouraging, more well-conducted studies are needed to clarify the role of the gut microbiome in GDM. The systematic review was registered with PROSPERO (https://www.crd.york.ac.uk/prospero/) as CRD42022357391.

The Association between Branched-Chain Amino Acids (BCAAs) and Cardiometabolic Risk Factors in Middle-Aged Caucasian Women Stratified According to Glycemic Status

We examined the glycemic status-stratified relationships between total serum branched-chain amino acid (BCAA) concentrations and cardiometabolic risk factors in middle-aged Caucasian women. The study included 349 women divided into 2 subgroups: a normoglycemic group (NG, n = 184) and a dysglycemic group (DG, n = 165). Blood samples, anthropometric parameters, and blood pressure were measured. HOMA-IR, albumin-corrected calcium (CCa), and fatty liver index (FLI) were calculated. BCAA concentrations were higher in the women with dysglycemia. BCAAs moderately correlated with BMI and FLI in the NG group and with BMI, FLI, total calcium (TCa), CCa, HbA1c, TG/HDL-C, and HDL-C in the DG group. After adjusting for age and BMI, correlations for TCa, CCa, HbA1c, HDL-C, and TG/HDL-C remained significant. The coexistence of increased BCAAs with dysglycemic status was associated with markedly higher concentrations of TCa, CCa, HbA1c, and TG, which were not observed in the DG women with low level of BCAAs. Multiple regression showed that TCa or CCa, age and BCAAs were significantly associated with HbA1c independently of BMI only in the DG group. We conclude that dysglycemia in particular predisposes women to a significant relationship between total BCAAs and circulating calcium and HbA1c, and that these relationships are independent of BMI and may reflect the pathophysiological calcium-dependent mechanisms connecting BCAAs with metabolic disturbances.

Identification of markers that distinguish adipose tissue and glucose and insulin metabolism using a multi-modal machine learning approach

The study of metabolomics has improved our knowledge of the biology behind type 2 diabetes and its related metabolic physiology. We aimed to investigate markers of adipose tissue morphology, as well as insulin and glucose metabolism in 53 non-obese male individuals. The participants underwent extensive clinical, biochemical and magnetic resonance imaging phenotyping, and we also investigated non-targeted serum metabolites. We used a multi-modal machine learning approach to evaluate which serum metabolomic compounds predicted markers of glucose and insulin metabolism, adipose tissue morphology and distribution. Fasting glucose was associated with metabolites of intracellular insulin action and beta-cell dysfunction, namely cysteine-s-sulphate and n-acetylgarginine, whereas fasting insulin was predicted by myristoleoylcarnitine, propionylcarnitine and other metabolites of beta-oxidation of fatty acids. OGTT-glucose levels at 30 min were predicted by 7-Hoca, a microbiota derived metabolite, as well as eugenol, a fatty acid. Both insulin clamp and HOMA-IR were predicted by metabolites involved in beta-oxidation of fatty acids and biodegradation of triacylglycerol, namely tartrate and 3-phosphoglycerate, as well as pyruvate, xanthine and liver fat. OGTT glucose area under curve (AUC) and OGTT insulin AUC, was associated with bile acid metabolites, subcutaneous adipocyte cell size, liver fat and fatty chain acids and derivates, such as isovalerylcarnitine. Finally, subcutaneous adipocyte size was associated with long chain fatty acids, markers of sphingolipid metabolism, increasing liver fat and dopamine-sulfate 1. Ectopic liver fat was predicted by methylmalonate, adipocyte cell size, glutathione derived metabolites and fatty chain acids. Ectopic heart fat was predicted visceral fat, gamma-glutamyl tyrosine and 2-acetamidophenol sulfate. Adipocyte cell size, age, alpha-tocopherol and blood pressure were associated with visceral fat. We identified several biomarkers associated with adipose tissue pathophysiology and insulin and glucose metabolism using a multi-modal machine learning approach. Our approach demonstrated the relative importance of serum metabolites and they outperformed traditional clinical and biochemical variables for most endpoints.

Lack of Increase in Muscle Mitochondrial Protein Synthesis During the Course of Aerobic Exercise and Its Recovery in the Fasting State Irrespective of Obesity

Acute aerobic exercise induces skeletal muscle mitochondrial gene expression, which in turn can increase muscle mitochondrial protein synthesis. In this regard, the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), is a master regulator of mitochondrial biogenesis, and thus mitochondrial protein synthesis. However, PGC-1α expression is impaired in muscle of humans with obesity in response to acute aerobic exercise. Therefore, we sought to determine whether muscle mitochondrial protein synthesis is also impaired under the same conditions in humans with obesity. To this end, we measured mitochondrial and mixed-muscle protein synthesis in skeletal muscle of untrained subjects with (body fat: 34.7 ± 2.3%) and without (body fat: 25.3 ± 3.3%) obesity in a basal period and during a continuous period that included a 45 min cycling exercise (performed at an intensity corresponding to 65% of heart rate reserve) and a 3-h post-exercise recovery. Exercise increased PGC-1α mRNA expression in muscle of subjects without obesity, but not in subjects with obesity. However, muscle mitochondrial protein synthesis did not increase in either subject group. Similarly, mixed-muscle protein synthesis did not increase in either group. Concentrations of plasma amino acids decreased post-exercise in the subjects without obesity, but not in the subjects with obesity. We conclude that neither mitochondrial nor mixed-muscle protein synthesis increase in muscle of humans during the course of a session of aerobic exercise and its recovery period in the fasting state irrespective of obesity. Trial Registration: The study has been registered within ClinicalTrials.gov (NCT01824173).

Amino Acid-Induced Impairment of Insulin Signaling and Involvement of G-Protein Coupling Receptor

Amino acids are needed for general bodily function and well-being. Despite their importance, augmentation in their serum concentration is closely related to metabolic disorder, insulin resistance (IR), or worse, diabetes mellitus. Essential amino acids such as the branched-chain amino acids (BCAAs) have been heavily studied as a plausible biomarker or even a cause of IR. Although there is a long list of benefits, in subjects with abnormal amino acids profiles, some amino acids are correlated with a higher risk of IR. Metabolic dysfunction, upregulation of the mammalian target of the rapamycin (mTOR) pathway, the gut microbiome, 3-hydroxyisobutyrate, inflammation, and the collusion of G-protein coupled receptors (GPCRs) are among the indicators and causes of metabolic disorders generating from amino acids that contribute to IR and the onset of type 2 diabetes mellitus (T2DM). This review summarizes the current understanding of the true involvement of amino acids with IR. Additionally, the involvement of GPCRs in IR will be further discussed in this review.

Assessing the Contribution of Relative Macrophage Frequencies to Subcutaneous Adipose Tissue

Background: Macrophages play an important role in regulating adipose tissue function, while their frequencies in adipose tissue vary between individuals. Adipose tissue infiltration by high frequencies of macrophages has been linked to changes in adipokine levels and low-grade inflammation, frequently associated with the progression of obesity. The objective of this project was to assess the contribution of relative macrophage frequencies to the overall subcutaneous adipose tissue gene expression using publicly available datasets.

Methods: Seven publicly available microarray gene expression datasets from human subcutaneous adipose tissue biopsies (n = 519) were used together with TissueDecoder to determine the adipose tissue cell-type composition of each sample. We divided the subjects in four groups based on their relative macrophage frequencies. Differential gene expression analysis between the high and low relative macrophage frequencies groups was performed, adjusting for sex and study. Finally, biological processes were identified using pathway enrichment and network analysis.

Results: We observed lower frequencies of adipocytes and higher frequencies of adipose stem cells in individuals characterized by high macrophage frequencies. We additionally studied whether, within subcutaneous adipose tissue, interindividual differences in the relative frequencies of macrophages were reflected in transcriptional differences in metabolic and inflammatory pathways. Adipose tissue of individuals with high macrophage frequencies had a higher expression of genes involved in complement activation, chemotaxis, focal adhesion, and oxidative stress. Similarly, we observed a lower expression of genes involved in lipid metabolism, fatty acid synthesis, and oxidation and mitochondrial respiration.

Conclusion: We present an approach that combines publicly available subcutaneous adipose tissue gene expression datasets with a deconvolution algorithm to calculate subcutaneous adipose tissue cell-type composition. The results showed the expected increased inflammation gene expression profile accompanied by decreased gene expression in pathways related to lipid metabolism and mitochondrial respiration in subcutaneous adipose tissue in individuals characterized by high macrophage frequencies. This approach demonstrates the hidden strength of reusing publicly available data to gain cell-type-specific insights into adipose tissue function.

Metagenomic insights into the effects of Urtica dioica vegetable on the gut microbiota of C57BL/6J obese mice, particularly the composition of Clostridia

Urtica dioica (UT) vegetable attenuates diet induced weight gain and insulin resistance. We hypothesized that UT imparts metabolic health by impacting the gut microbiota composition. We examined effects of UT on the cecal bacterial taxonomic signature of C57BL/6J mice fed isocaloric diets: a low-fat diet (LFD) with 10% fat, a high fat diet (HFD) with 45% fat or the HFD supplemented with 9% UT (HFUT). Among Firmicutes, the HFD had no significant impact on Clostridia, but increased Bacilli particularly genus Lactococcus and Lactobacillus. HFUT lowered Lactococcus but not Lactobacillus to levels of the LFD (P<.01; n=9). Further examination of Clostridia showed that HFUT increased genus Clostridium by over 2-fold particularly the species C. vincentii and C. disporicum and increased genus Turicibacter by three-fold (P<.05; n=9). Abundance of Clostridium and Turicibacter negatively correlated with body weight (P<.05; R2=0.42) and HOMA-IR (P<.05; R2=0.45). Turicibacter and Clostridium have been shown to be more abundant in lean phenotypes compared to obese. Clostridium impacts host phenotype by inducing intestinal T cell responses. The HFUT diet had no effect on members of Actinobacteria. Among Bacteroidetes, HFUT mainly increased proliferation of Bacteroides thetaiotaomicron (P<.05; n=9) with no significant impact on other groups. Functional analysis showed that HFUT enhanced bacterial beta-alanine and D-arginine metabolism both of which are associated with a lean phenotype and enhanced insulin sensitivity. We conclude that increasing the proliferation of Clostridium and Turicibacter and altering amino acid metabolism may be contributing mechanism(s) by which Urtica dioica impacts metabolic health.

Molecular pathways behind acquired obesity: Adipose tissue and skeletal muscle multiomics in monozygotic twin pairs discordant for BMI

Tissue-specific mechanisms prompting obesity-related development complications in humans remain unclear. We apply multiomics analyses of subcutaneous adipose tissue and skeletal muscle to examine the effects of acquired obesity among 49 BMI-discordant monozygotic twin pairs. Overall, adipose tissue appears to be more affected by excess body weight than skeletal muscle. In heavier co-twins, we observe a transcriptional pattern of downregulated mitochondrial pathways in both tissues and upregulated inflammatory pathways in adipose tissue. In adipose tissue, heavier co-twins exhibit lower creatine levels; in skeletal muscle, glycolysis- and redox stress-related protein and metabolite levels remain higher. Furthermore, metabolomics analyses in both tissues reveal that several proinflammatory lipids are higher and six of the same lipid derivatives are lower in acquired obesity. Finally, in adipose tissue, but not in skeletal muscle, mitochondrial downregulation and upregulated inflammation are associated with a fatty liver, insulin resistance, and dyslipidemia, suggesting that adipose tissue dominates in acquired obesity.

Multiomics analyses of adipose tissue and skeletal muscle in BMI-discordant twins

Excess body weight downregulates mitochondrial pathways in both tissues

Excess body weight upregulates proinflammatory pathways in both tissues

Adipose tissue alterations are associated with metabolic health in acquired obesity

Whole-body metabolic fate of branched-chain amino acids

Oxidation of branched-chain amino acids (BCAAs) is tightly regulated in mammals. We review here the distribution and regulation of whole-body BCAA oxidation. Phosphorylation and dephosphorylation of the rate-limiting enzyme, branched-chain α-ketoacid dehydrogenase complex directly regulates BCAA oxidation, and various other indirect mechanisms of regulation also exist. Most tissues throughout the body are capable of BCAA oxidation, and the flux of oxidative BCAA disposal in each tissue is influenced by three key factors: 1. tissue-specific preference for BCAA oxidation relative to other fuels, 2. the overall oxidative activity of mitochondria within a tissue, and 3. total tissue mass. Perturbations in BCAA oxidation have been implicated in many disease contexts, underscoring the importance of BCAA homeostasis in overall health.

Branched-chain amino acid metabolism, insulin sensitivity and liver fat response to exercise training in sedentary dysglycaemic and normoglycaemic men

AIMS/HYPOTHESIS

Obesity and insulin resistance may be associated with elevated plasma concentration of branched-chain amino acids (BCAAs) and impaired BCAA metabolism. However, it is unknown whether the insulin-sensitising effect of long-term exercise can be explained by concomitant change in BCAAs and their metabolism.

METHODS

We included 26 sedentary overweight and normal-weight middle-aged men from the MyoGlu clinical trial, with or without dysglycaemia, for 12 weeks of supervised intensive exercise intervention, including two endurance and two resistance sessions weekly. Insulin sensitivity was measured as the glucose infusion rate (GIR) from a hyperinsulinaemic-euglycaemic clamp. In addition, maximum oxygen uptake, upper and lower body strength and adipose tissue depots (using MRI and spectroscopy) were measured, and subcutaneous white adipose tissue (ScWAT) and skeletal muscle (SkM) biopsies were harvested both before and after the 12 week intervention. In the present study we have measured plasma BCAAs and related metabolites using CG-MS/MS and HPLC-MS/MS, and performed global mRNA-sequencing pathway analysis on ScWAT and SkM.

RESULTS

In MyoGlu, men with dysglycaemia displayed lower GIR, more fat mass and higher liver fat content than normoglycaemic men at baseline, and 12 weeks of exercise increased GIR, improved body composition and reduced liver fat content similarly for both groups. In our current study we observed higher plasma concentrations of BCAAs (14.4%, p = 0.01) and related metabolites, such as 3-hydroxyisobutyrate (19.4%, p = 0.034) in dysglycaemic vs normoglycaemic men at baseline. Baseline plasma BCAA levels correlated negatively to the change in GIR (ρ = -0.41, p = 0.037) and [Formula: see text] (ρ = -0.47, p = 0.015) after 12 weeks of exercise and positively to amounts of intraperitoneal fat (ρ = 0.40, p = 0.044) and liver fat (ρ = 0.58, p = 0.01). However, circulating BCAAs and related metabolites did not respond to 12 weeks of exercise, with the exception of isoleucine, which increased in normoglycaemic men (10 μmol/l, p = 0.01). Pathway analyses of mRNA-sequencing data implied reduced BCAA catabolism in both SkM and ScWAT in men with dysglycaemia compared with men with normoglycaemia at baseline. Gene expression levels related to BCAA metabolism correlated positively with GIR and markers of mitochondrial content in both SkM and ScWAT, and negatively with fat mass generally, and particularly with intraperitoneal fat mass. mRNA-sequencing pathway analysis also implied increased BCAA metabolism after 12 weeks of exercise in both groups and in both tissues, including enhanced expression of the gene encoding branched-chain α-ketoacid dehydrogenase (BCKDH) and reduced expression of the BCKDH phosphatase in both groups and tissues. Gene expression of SLC25A44, which encodes a mitochondrial BCAA transporter, was increased in SkM in both groups, and gene expression of BCKDK, which encodes BCKDH kinase, was reduced in ScWAT in dysglycaemic men. Mediation analyses indicated a pronounced effect of enhanced SkM (~53%, p = 0.022), and a moderate effect of enhanced ScWAT (~18%, p = 0.018) BCAA metabolism on improved insulin sensitivity after 12 weeks of exercise, based on mRNA sequencing. In comparison, plasma concentration of BCAAs did not mediate any effect in this regard.

CONCLUSION/INTERPRETATION

Plasma BCAA concentration was largely unresponsive to long-term exercise and unrelated to exercise-induced insulin sensitivity. On the other hand, the insulin-sensitising effect of long-term exercise in men may be explained by enhanced SkM and, to a lesser degree, also by enhanced ScWAT BCAA catabolism. Graphical abstract.

Metabolic Syndrome and Its Components Are Associated With Altered Amino Acid Profile in Chinese Han Population

OBJECTIVE

Recent studies have found that the levels of plasma amino acids, such as branched-chain amino acids and aromatic amino acids, were associated with visceral obesity, insulin resistance, future development of diabetes and cardiovascular diseases. However, few studies have involved a Chinese Han population. This study aimed to examine the association between amino acid profile and metabolic syndrome (MetS) and its components in the Chinese Han population.

METHODS

This is a cross-sectional study, which enrolled a cohort of 473 participants from a community. We employed the isotope internal standard method to determine the plasma concentrations of 28 amino acids using high-performance liquid chromatography-tandem mass spectrometry (LC/MS). Participants were divided into MetS (n = 72) and non-MetS groups (n = 401) to analyze the association between amino acids and MetS and its components.

RESULTS

The prevalence of MetS was 15.2% according to the criteria. Plasma concentrations of isoleucine (Ile), leucine (Leu), valine (Val), tyrosine (Tyr), tryptophan (Trp), phenylalanine (Phe), glutamic acid (Glu), aspartic acid (Asp), alanine (Ala), histidine (His), methionine (Met), asparagine (Asn), and proline (Pro) were significantly higher in the MetS group than those in the non-MetS group (P < 0.05), but taurine (Tau) was significantly lower (P < 0.05). When MetS components were increased, the concentrations of these 13 amino acids significantly increased (P < 0.05), but Tau concentration was significantly decreased (P < 0.05). We extracted the amino acid profile by principal component analysis (PCA), PC1 and PC2, which extracted from the 14 amino acids, were significantly associated with MetS (odds ratio, 95% confidence interval: 1.723, 1.325-2.085 and 1.325, 1.043-1.684, respectively). A total of 260 non-MetS participants were followed up effectively, and 42 participants developed new-onset MetS within 5 years. We found that the amino acid profile of PC1 was linked to the occurrence of future MetS. Decreased Tau was correlated with the future development of MetS.

CONCLUSION

Participants with MetS exhibit an abnormal amino acid profile, and its components gradually increase when these amino acids are altered. Amino acid PCA profile can be employed for assessing and monitoring MetS risk. Finally, decreased Tau may be linked to the future development of MetS.

Metabolism and Metabolic Disorders and the Microbiome: The Intestinal Microbiota Associated With Obesity, Lipid Metabolism, and Metabolic Health-Pathophysiology and Therapeutic Strategies

Changes in the intestinal microbiome have been associated with obesity and type 2 diabetes, in epidemiological studies and studies of the effects of fecal transfer in germ-free mice. We review the mechanisms by which alterations in the intestinal microbiome contribute to development of metabolic diseases, and recent advances, such as the effects of the microbiome on lipid metabolism. Strategies have been developed to modify the intestinal microbiome and reverse metabolic alterations, which might be used as therapies. We discuss approaches that have shown effects in mouse models of obesity and metabolic disorders, and how these might be translated to humans to improve metabolic health.

DNA methylation during human adipogenesis and the impact of fructose

BACKGROUND

Increased adipogenesis and altered adipocyte function contribute to the development of obesity and associated comorbidities. Fructose modified adipocyte metabolism compared to glucose, but the regulatory mechanisms and consequences for obesity are unknown. Genome-wide methylation and global transcriptomics in SGBS pre-adipocytes exposed to 0, 2.5, 5, and 10 mM fructose, added to a 5-mM glucose-containing medium, were analyzed at 0, 24, 48, 96, 192, and 384 h following the induction of adipogenesis.

RESULTS

Time-dependent changes in DNA methylation compared to baseline (0 h) occurred during the final maturation of adipocytes, between 192 and 384 h. Larger percentages (0.1% at 192 h, 3.2% at 384 h) of differentially methylated regions (DMRs) were found in adipocytes differentiated in the glucose-containing control media compared to adipocytes differentiated in fructose-supplemented media (0.0006% for 10 mM, 0.001% for 5 mM, and 0.005% for 2.5 mM at 384 h). A total of 1437 DMRs were identified in 5237 differentially expressed genes at 384 h post-induction in glucose-containing (5 mM) control media. The majority of them inversely correlated with the gene expression, but 666 regions were positively correlated to the gene expression.

CONCLUSIONS

Our studies demonstrate that DNA methylation regulates or marks the transformation of morphologically differentiating adipocytes (seen at 192 h), to the more mature and metabolically robust adipocytes (as seen at 384 h) in a genome-wide manner. Lower (2.5 mM) concentrations of fructose have the most robust effects on methylation compared to higher concentrations (5 and 10 mM), suggesting that fructose may be playing a signaling/regulatory role at lower concentrations of fructose and as a substrate at higher concentrations.

Elevated serum levels of galectin-3 binding protein are associated with insulin resistance in non-diabetic women after menopause

OBJECTIVE

Galectin-3 binding protein (Gal-3BP) is one of the major fucosylated glycoprotein family members and has recently been implicated in non-alcoholic fatty liver disease, hyperlipaemia and coronary artery disease. Here, we analysed the serum concentrations of Gal-3BP in menopausal women to evaluate the association of circulating Gal-3BP and insulin resistance in females after menopause.

MATERIALS AND METHODS

We evaluated serum levels of Gal-3BP in sixty-two non-diabetic women with menopausal status for at least one year. The clinical features, biochemical profiles and homeostasis model assessment of insulin resistance (HOMA-IR) indices were obtained routinely.

RESULTS

Gal-3BP levels increased in women with higher HOMA-IR indices and were positively correlated with HOMA-IR indices. The Gal-3BP level was also an independent risk factor for a high HOMA-IR index and showed the most influence on the HOMA-IR index compared to fasting plasma glucose, triglyceride, age and body mass index. The cut-off value of the serum Gal-3BP level was 2234.32 ng/ml, with areas under the ROC curve (AUCs) of 0.68 (HOMA-IR index 1.5), 0.81 (HOMA-IR index 2.0) and 0.93 (HOMA-IR index 2.5).

CONCLUSION

Serum levels of Gal-3BP are associated with impaired insulin sensitivity in non-diabetic menopausal women.

Why Are Branched-Chain Amino Acids Increased in Starvation and Diabetes?

Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are increased in starvation and diabetes mellitus. However, the pathogenesis has not been explained. It has been shown that BCAA catabolism occurs mostly in muscles due to high activity of BCAA aminotransferase, which converts BCAA and α-ketoglutarate (α-KG) to branched-chain keto acids (BCKAs) and glutamate. The loss of α-KG from the citric cycle (cataplerosis) is attenuated by glutamate conversion to α-KG in alanine aminotransferase and aspartate aminotransferase reactions, in which glycolysis is the main source of amino group acceptors, pyruvate and oxaloacetate. Irreversible oxidation of BCKA by BCKA dehydrogenase is sensitive to BCKA supply, and ratios of NADH to NAD⁺ and acyl-CoA to CoA-SH. It is hypothesized that decreased glycolysis and increased fatty acid oxidation, characteristic features of starvation and diabetes, cause in muscles alterations resulting in increased BCAA levels. The main alterations include (i) impaired BCAA transamination due to decreased supply of amino groups acceptors (α-KG, pyruvate, and oxaloacetate) and (ii) inhibitory influence of NADH and acyl-CoAs produced in fatty acid oxidation on citric cycle and BCKA dehydrogenase. The studies supporting the hypothesis and pros and cons of elevated BCAA concentrations are discussed in the article.

Genetic and nongenetic profiling of milk β-hydroxybutyrate and acetone and their associations with ketosis in Holstein cows

Ketosis is a metabolic disorder of increasing importance in high-yielding dairy cows, but accurate population-wide binary health trait recording is difficult to implement. Against this background, proper Gaussian indicator traits, which can be routinely measured in milk, are needed. Consequently, we focused on the ketone bodies acetone and β-hydroxybutyrate (BHB), measured via Fourier-transform infrared spectroscopy (FTIR) in milk. In the present study, 62,568 Holstein cows from large-scale German co-operator herds were phenotyped for clinical ketosis (KET) according to a veterinarian diagnosis key. A sub-sample of 16,861 cows additionally had first test-day observations for FTIR acetone and BHB. Associations between FTIR acetone and BHB with KET and with test-day traits were studied phenotypically and quantitative genetically. Furthermore, we estimated SNP marker effects for acetone and BHB (application of genome-wide association studies) based on 40,828 SNP markers from 4,384 genotyped cows, and studied potential candidate genes influencing body fat mobilization. Generalized linear mixed models were applied to infer the influence of binary KET on Gaussian-distributed acetone and BHB (definition of an identity link function), and vice versa, such as the influence of acetone and BHB on KET (definition of a logit link function). Additionally, linear models were applied to study associations between BHB, acetone and test-day traits (milk yield, fat percentage, protein percentage, fat-to-protein ratio and somatic cell score) from the first test-day after calving. An increasing KET incidence was statistically significant associated with increasing FTIR acetone and BHB milk concentrations. Acetone and BHB concentrations were positively associated with fat percentage, fat-to-protein ratio and somatic cell score. Bivariate linear animal models were applied to estimate genetic (co)variance components for KET, acetone, BHB and test-day traits within parities 1 to 3, and considering all parities simultaneously in repeatability models. Pedigree-based heritabilities were quite small (i.e., in the range from 0.01 in parity 3 to 0.07 in parity 1 for acetone, and from 0.03-0.04 for BHB). Heritabilites from repeatability models were 0.05 for acetone, and 0.03 for BHB. Genetic correlations between acetone and BHB were moderate to large within parities and considering all parities simultaneously (0.69-0.98). Genetic correlations between acetone and BHB with KET from different parities ranged from 0.71 to 0.99. Genetic correlations between acetone across parities, and between BHB across parities, ranged from 0.55 to 0.66. Genetic correlations between KET, acetone, and BHB with fat-to-protein ratio and with fat percentage were large and positive, but negative with milk yield. In genome-wide association studies, we identified SNP on BTA 4, 10, 11, and 29 significantly influencing acetone, and on BTA 1 and 16 significantly influencing BHB. The identified potential candidate genes NRXN3, ACOXL, BCL2L11, HIBADH, KCNJ1, and PRG4 are involved in lipid and glucose metabolism pathways.

Branched-chain ketoacid overload inhibits insulin action in the muscle

Branched-chain α-keto acids (BCKAs) are catabolites of branched-chain amino acids (BCAAs). Intracellular BCKAs are cleared by branched-chain ketoacid dehydrogenase (BCKDH), which is sensitive to inhibitory phosphorylation by BCKD kinase (BCKDK). Accumulation of BCKAs is an indicator of defective BCAA catabolism and has been correlated with glucose intolerance and cardiac dysfunction. However, it is unclear whether BCKAs directly alter insulin signaling and function in the skeletal and cardiac muscle cell. Furthermore, the role of excess fatty acids (FAs) in perturbing BCAA catabolism and BCKA availability merits investigation. By using immunoblotting and ultra-performance liquid chromatography MS/MS to analyze the hearts of fasted mice, we observed decreased BCAA-catabolizing enzyme expression and increased circulating BCKAs, but not BCAAs. In mice subjected to diet-induced obesity (DIO), we observed similar increases in circulating BCKAs with concomitant changes in BCAA-catabolizing enzyme expression only in the skeletal muscle. Effects of DIO were recapitulated by simulating lipotoxicity in skeletal muscle cells treated with saturated FA, palmitate. Exposure of muscle cells to high concentrations of BCKAs resulted in inhibition of insulin-induced AKT phosphorylation, decreased glucose uptake, and mitochondrial oxygen consumption. Altering intracellular clearance of BCKAs by genetic modulation of BCKDK and BCKDHA expression showed similar effects on AKT phosphorylation. BCKAs increased protein translation and mTORC1 activation. Pretreating cells with mTORC1 inhibitor rapamycin restored BCKA's effect on insulin-induced AKT phosphorylation. This study provides evidence for FA-mediated regulation of BCAA-catabolizing enzymes and BCKA content and highlights the biological role of BCKAs in regulating muscle insulin signaling and function.

Changed Amino Acids in NAFLD and Liver Fibrosis: A Large Cross-Sectional Study without Influence of Insulin Resistance

Altered amino acid levels have been found in nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). However, it is not clear whether this alteration is due to altered hepatic metabolism or insulin resistance. The aim of this study was to clarify the association among amino acid levels, fatty liver, and liver fibrosis while eliminating the influence of insulin resistance. NAFLD and liver fibrosis were diagnosed using transient elastography and subjects were divided into three groups: normal, NAFLD, and liver fibrosis. To exclude the influence of insulin resistance, the subjects were matched using the homeostasis model assessment of insulin resistance (HOMA-IR). The amino acid serum levels were compared among the groups. Of 731 enrolled subjects, 251 and 33 were diagnosed with NAFLD and liver fibrosis. Although significant differences were observed among the groups in the serum levels of most amino acids, all but those of glutamate and glycine disappeared after matching for HOMA-IR. The multivariate logistic regression revealed that glutamate, glycine, and HOMA-IR were independent risk factors for liver fibrosis. The altered serum levels of most amino acids were associated with insulin resistance, while the increase in glutamate and the decrease in glycine levels were strongly associated not only with insulin resistance, but also with altered liver metabolism in patients with liver fibrosis.

Insights into the gut microbiota of Nigerian elderly with type 2 diabetes and non-diabetic elderly persons

Type 2 diabetes (T2D) is a prevalent non-communicable disease among the world's growing elderly population. The contribution of the gut microbiota to T2D in several Westernized countries has been established. However, there is little information on the role of the gut microbiota in T2D from the African continent where lifestyle and life expectancy are different.

AIMS

This study sought to investigate gut microbiota variation in relation to elderly people living with T2D. in Nigeria.

METHODS

Whole microbial community DNA were derived from the stool samples of healthy urban-dwelling elderly individuals and urban-dwelling elderly individuals with T2D. The V4 region of the 16S rRNA gene was Illumina-sequenced and analyzed using QIIME2.

RESULTS

Beta taxonomic diversity was significantly different between healthy elderly individuals and elderly individuals with T2D. However, no difference in the alpha taxonomic diversity and predicted functional alpha diversity of the gut microbiota was observed. The genus Ruminococcus (T2D versus Healthy: 2.89% vs 2.21%), families Coriobacteriaceae (Collinsella, T2D versus Healthy: 2.62 % vs 1.25%) and Bifidobacteriaceae were enriched in elderly individuals with T2D, while members of Clostridiaceae (Clostridium, Healthy versus T2D: 5.6% vs 3.2%) and Peptostreptococcaceae (Healthy versus T2D: 3.45% vs 1.99%) were enriched in healthy volunteers. Pathways involved in amino acid biosynthesis were enriched in elderly individuals with T2D, while pathways involved in respiration and the biosynthesis of vital building blocks were enriched in healthy volunteers.

CONCLUSIONS

The study demonstrated for the first time in an African elderly population that the abundance of Bifidobacteriaceae, Collinsella, and Ruminococcus within the gut varies in relation to T2D. Findings from this study suggest that the restoration of features associated with healthiness via the way of gut microbiota modification could be one step needed to improve elderly patient care.

Transcriptome analysis reveals the difference between "healthy" and "common" aging and their connection with age-related diseases

A key goal of aging research was to understand mechanisms underlying healthy aging and develop methods to promote the human healthspan. One approach is to identify gene regulations unique to healthy aging compared with aging in the general population (i.e., "common" aging). Here, we leveraged Genotype-Tissue Expression (GTEx) project data to investigate "healthy" and "common" aging gene expression regulations at a tissue level in humans and their interconnection with diseases. Using GTEx donors' disease annotations, we defined a "healthy" aging cohort for each tissue. We then compared the age-associated genes derived from this cohort with age-associated genes from the "common" aging cohort which included all GTEx donors; we also compared the "healthy" and "common" aging gene expressions with various disease-associated gene expressions to elucidate the relationships among "healthy," "common" aging and disease. Our analyses showed that 1. GTEx "healthy" and "common" aging shared a large number of gene regulations; 2. Despite the substantial commonality, "healthy" and "common" aging genes also showed distinct function enrichment, and "common" aging genes had a higher enrichment for disease genes; 3. Disease-associated gene regulations were overall different from aging gene regulations. However, for genes regulated by both, their regulation directions were largely consistent, implying some aging processes could increase the susceptibility to disease development; and 4. Possible protective mechanisms were associated with some "healthy" aging gene regulations. In summary, our work highlights several unique features of GTEx "healthy" aging program. This new knowledge could potentially be used to develop interventions to promote the human healthspan.

Subcutaneous Adipose Tissue and Systemic Inflammation Are Associated With Peripheral but Not Hepatic Insulin Resistance in Humans

Obesity-related insulin resistance (IR) may develop in multiple organs, representing various etiologies for cardiometabolic diseases. We identified abdominal subcutaneous adipose tissue (ScAT) transcriptome profiles in liver or muscle IR by means of RNA sequencing in overweight or obese participants of the Diet, Obesity, and Genes (DiOGenes) (NCT00390637, ClinicalTrials.gov) cohort (n = 368). Tissue-specific IR phenotypes were derived from a 5-point oral glucose tolerance test. Hepatic and muscle IR were characterized by distinct abdominal ScAT transcriptome profiles. Genes related to extracellular remodeling were upregulated in individuals with primarily hepatic IR, while genes related to inflammation were upregulated in individuals with primarily muscle IR. In line with this, in two independent cohorts, the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) (n = 325) and the Maastricht Study (n = 685), an increased systemic low-grade inflammation profile was specifically related to muscle IR but not to liver IR. We propose that increased ScAT inflammatory gene expression may translate into an increased systemic inflammatory profile, linking ScAT inflammation to the muscle IR phenotype. These distinct IR phenotypes may provide leads for more personalized prevention of cardiometabolic diseases.

Mitochondrial Dysfunctions: A Thread Sewing Together Alzheimer's Disease, Diabetes, and Obesity

Metabolic disorders are severe and chronic impairments of the health of many people and represent a challenge for the society as a whole that has to deal with an ever-increasing number of affected individuals. Among common metabolic disorders are Alzheimer's disease, obesity, and type 2 diabetes. These disorders do not have a univocal genetic cause but rather can result from the interaction of multiple genes, lifestyle, and environmental factors. Mitochondrial alterations have emerged as a feature common to all these disorders, underlining perhaps an impaired coordination between cellular needs and mitochondrial responses that could contribute to their development and/or progression.

Obesity Reduces mTORC1 Activity in Mucosal-Associated Invariant T Cells, Driving Defective Metabolic and Functional Responses

Obesity underpins the development of numerous chronic diseases, such as type II diabetes mellitus. It is well established that obesity negatively alters immune cell frequencies and functions. Mucosal-associated invariant T (MAIT) cells are a population of innate T cells, which we have previously reported are dysregulated in obesity, with altered circulating and adipose tissue frequencies and a reduction in their IFN-γ production, which is a critical effector function of MAIT cells in host defense. Hence, there is increased urgency to characterize the key molecular mechanisms that drive MAIT cell effector functions and to identify those which are impaired in the obesity setting. In this study, we found that MAIT cells significantly upregulate their rates of glycolysis upon activation in an mTORC1-dependent manner, and this is essential for MAIT cell IFN-γ production. Furthermore, we show that mTORC1 activation is dependent on amino acid transport via SLC7A5. In obese patients, using RNA sequencing, Seahorse analysis, and a series of in vitro experiments, we demonstrate that MAIT cells isolated from obese adults display defective glycolytic metabolism, mTORC1 signaling, and SLC7A5 aa transport. Collectively, our data detail the intrinsic metabolic pathways controlling MAIT cell cytokine production and highlight mTORC1 as an important metabolic regulator that is impaired in obesity, leading to altered MAIT cell responses.

Branched Chain Amino Acids

Branched chain amino acids (BCAAs) are building blocks for all life-forms. We review here the fundamentals of BCAA metabolism in mammalian physiology. Decades of studies have elicited a deep understanding of biochemical reactions involved in BCAA catabolism. In addition, BCAAs and various catabolic products act as signaling molecules, activating programs ranging from protein synthesis to insulin secretion. How these processes are integrated at an organismal level is less clear. Inborn errors of metabolism highlight the importance of organismal regulation of BCAA physiology. More recently, subtle alterations of BCAA metabolism have been suggested to contribute to numerous prevalent diseases, including diabetes, cancer, and heart failure. Understanding the mechanisms underlying altered BCAA metabolism and how they contribute to disease pathophysiology will keep researchers busy for the foreseeable future.

Associations of Mitochondrial and Nuclear Mitochondrial Variants and Genes with Seven Metabolic Traits

Mitochondria (MT), the major site of cellular energy production, are under dual genetic control by 37 mitochondrial DNA (mtDNA) genes and numerous nuclear genes (MT-nDNA). In the CHARGEmtDNA+ Consortium, we studied genetic associations of mtDNA and MT-nDNA associations with body mass index (BMI), waist-hip-ratio (WHR), glucose, insulin, HOMA-B, HOMA-IR, and HbA1c. This 45-cohort collaboration comprised 70,775 (insulin) to 170,202 (BMI) pan-ancestry individuals. Validation and imputation of mtDNA variants was followed by single-variant and gene-based association testing. We report two significant common variants, one in MT-ATP6 associated (p ≤ 5E-04) with WHR and one in the D-loop with glucose. Five rare variants in MT-ATP6, MT-ND5, and MT-ND6 associated with BMI, WHR, or insulin. Gene-based meta-analysis identified MT-ND3 associated with BMI (p ≤ 1E-03). We considered 2,282 MT-nDNA candidate gene associations compiled from online summary results for our traits (20 unique studies with 31 dataset consortia's genome-wide associations [GWASs]). Of these, 109 genes associated (p ≤ 1E-06) with at least 1 of our 7 traits. We assessed regulatory features of variants in the 109 genes, cis- and trans-gene expression regulation, and performed enrichment and protein-protein interactions analyses. Of the identified mtDNA and MT-nDNA genes, 79 associated with adipose measures, 49 with glucose/insulin, 13 with risk for type 2 diabetes, and 18 with cardiovascular disease, indicating for pleiotropic effects with health implications. Additionally, 21 genes related to cholesterol, suggesting additional important roles for the genes identified. Our results suggest that mtDNA and MT-nDNA genes and variants reported make important contributions to glucose and insulin metabolism, adipocyte regulation, diabetes, and cardiovascular disease.

Branched Chain Amino Acids in Metabolic Disease

PURPOSE OF REVIEW

Elevations in circulating branched chain amino acids (BCAAs) have gained attention as potential contributors to the development of insulin resistance and diabetes.

RECENT FINDINGS

Epidemiological evidence strongly supports this conclusion. Suppression of BCAA catabolism in adipose and hepatic tissues appears to be the primary drivers of plasma BCAA elevations. BCAA catabolism may be shunted to skeletal muscle, where it indirectly leads to FA accumulation and insulin resistance, via a number of proposed mechanisms. BCAAs have an important role in the development of IR, but our understanding of how plasma BCAA elevations occur, and how these elevations lead to insulin resistance, is still limited.

Pioglitazone improves hepatic mitochondrial function in a mouse model of nonalcoholic steatohepatitis

Pioglitazone is effective in improving insulin resistance and liver histology in patients with nonalcoholic steatohepatitis (NASH). Because dysfunctional mitochondrial metabolism is a central feature of NASH, we hypothesized that an important target of pioglitazone would be alleviating mitochondrial oxidative dysfunction. To this end, we studied hepatic mitochondrial metabolism in mice fed high-fructose high-transfat diet (TFD) supplemented with pioglitazone for 20 wk, using nuclear magnetic resonance-based ¹³C isotopomer analysis. Pioglitazone improved whole body and adipose insulin sensitivity in TFD-fed mice. Furthermore, pioglitazone reduced intrahepatic triglyceride content and fed plasma ketones and hepatic TCA cycle flux, anaplerosis, and pyruvate cycling in mice with NASH. This was associated with a marked reduction in most intrahepatic diacylglycerol classes and, to a lesser extent, some ceramide species (C22:1, C23:0). Considering the cross-talk between mitochondrial function and branched-chain amino acid (BCAA) metabolism, pioglitazone's impact on plasma BCAA profile was determined in a cohort of human subjects. Pioglitazone improved the plasma BCAA concentration profile in patients with NASH. This appeared to be related to an improvement in BCAA degradation in multiple tissues. These results provide evidence that pioglitazone-induced changes in NASH are related to improvements in hepatic mitochondrial oxidative dysfunction and changes in whole body BCAA metabolism.

Branched-chain amino acids promote endothelial dysfunction through increased reactive oxygen species generation and inflammation

Branched‐chain amino acids (BCAA: leucine, isoleucine and valine) are essential amino acids implicated in glucose metabolism and maintenance of correct brain function. Elevated BCAA levels can promote an inflammatory response in peripheral blood mononuclear cells. However, there are no studies analysing the direct effects of BCAA on endothelial cells (ECs) and its possible modulation of vascular function. In vitro and ex vivo studies were performed in human ECs and aorta from male C57BL/6J mice, respectively. In ECs, BCAA (6 mmol/L) increased eNOS expression, reactive oxygen species production by mitochondria and NADPH oxidases, peroxynitrite formation and nitrotyrosine expression. Moreover, BCAA induced pro‐inflammatory responses through the transcription factor NF‐κB that resulted in the release of intracellular adhesion molecule‐1 and E‐selectin conferring endothelial activation and adhesion capacity to inflammatory cells. Pharmacological inhibition of mTORC1 intracellular signalling pathway decreased BCAA‐induced pro‐oxidant and pro‐inflammatory effects in ECs. In isolated murine aorta, BCAA elicited vasoconstrictor responses, particularly in pre‐contracted vessels and after NO synthase blockade, and triggered endothelial dysfunction, effects that were inhibited by different antioxidants, further demonstrating the potential of BCAA to induce oxidative stress with functional impact. In summary, we demonstrate that elevated BCAA levels generate inflammation and oxidative stress in ECs, thereby facilitating inflammatory cells adhesion and endothelial dysfunction. This might contribute to the increased cardiovascular risk observed in patients with elevated BCAA blood levels.

Plasma branched chain/aromatic amino acids, enriched Mediterranean diet and risk of type 2 diabetes: case-cohort study within the PREDIMED Trial

AIMS/HYPOTHESIS

Branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs) are associated with type 2 diabetes. However, repeated measurements of BCAA/AAA and their interactions with dietary interventions have not been evaluated. We investigated the associations between baseline and changes at 1 year in BCAA/AAA with type 2 diabetes in the context of a Mediterranean diet (MedDiet) trial.

METHODS

We included 251 participants with incident type 2 diabetes and a random sample of 694 participants (641 participants without type 2 diabetes and 53 overlapping cases) in a case-cohort study nested within the PREvención con DIeta MEDiterránea (PREDIMED) trial. Participants were randomised to a MedDiet+extra-virgin olive oil (n = 273), a MedDiet+nuts (n = 324) or a control diet (n = 295). We used LC-MS/MS to measure plasma levels of amino acids. Type 2 diabetes was a pre-specified secondary outcome of the PREDIMED trial.

RESULTS

Elevated plasma levels of individual BCAAs/AAAs were associated with higher type 2 diabetes risk after a median follow-up of 3.8 years: multivariable HR for the highest vs lowest quartile ranged from 1.32 for phenylalanine ([95% CI 0.90, 1.92], p for trend = 0.015) to 3.29 for leucine ([95% CI 2.03, 5.34], p for trend<0.001). Increases in BCAA score at 1 year were associated with higher type 2 diabetes risk in the control group with HR per SD = 1.61 (95% CI 1.02, 2.54), but not in the MedDiet groups (p for interaction <0.001). The MedDiet+extra-virgin olive oil significantly reduced BCAA levels after 1 year of intervention (p = 0.005 vs the control group).

CONCLUSIONS/INTERPRETATION

Our results support that higher baseline BCAAs and their increases at 1 year were associated with higher type 2 diabetes risk. A Mediterranean diet rich in extra-virgin olive oil significantly reduced the levels of BCAA and attenuated the positive association between plasma BCAA levels and type 2 diabetes incidence. Clinical trial number: SRCTN35739639 ( www.controlled-trials.com ).

Obesity-induced metabolic disturbance drives oxidative stress and complement activation in the retinal environment

Purpose

Systemic increases in reactive oxygen species, and their association with inflammation, have been proposed as an underlying mechanism linking obesity and age-related macular degeneration (AMD). Studies have found increased levels of oxidative stress biomarkers and inflammatory cytokines in obese individuals; however, the correlation between obesity and retinal inflammation has yet to be assessed. We used the leptin-deficient (ob/ob) mouse to further our understanding of the contribution of obesity to retinal oxidative stress and inflammation.

Methods

Retinas from ob/ob mice were compared to age-matched wild-type controls for retinal function (electroretinography) and gene expression analysis of retinal stress (Gfap), oxidative stress (Gpx3 and Hmox1), and complement activation (C3, C2, Cfb, and Cfh). Oxidative stress was further quantified using a reactive oxygen species and reactive nitrogen species (ROS and RNS) assay. Retinal microglia and macrophage migration to the outer retina and complement activation were determined using immunohistochemistry for IBA1 and C3, respectively. Retinas and sera were used for metabolomic analysis using QTRAP mass spectrometry.

Results

Retinal function was reduced in ob/ob mice, which correlated to changes in markers of retinal stress, oxidative stress, and inflammation. An increase in C3-expressing microglia and macrophages was detected in the outer retinas of the ob/ob mice, while gene expression studies showed increases in the complement activators (C2 and Cfb) and a decrease in a complement regulator (Cfh). The expression of several metabolites were altered in the ob/ob mice compared to the controls, with changes in polyunsaturated fatty acids (PUFAs) and branched-chain amino acids (BCAAs) detected.

Conclusions

The results of this study indicate that oxidative stress, inflammation, complement activation, and lipid metabolites in the retinal environment are linked with obesity in ob/ob animals. Understanding the interplay between these components in the retina in obesity will help inform risk factor analysis for acquired retinal degenerations, including AMD.

Effects of Qijian mixture on type 2 diabetes assessed by metabonomics, gut microbiota and network pharmacology

Qijian mixture, a new traditional Chinese medicine (TCM) formula comprising of Astragalus membranaceus, Ramulus euonymi, Coptis chinensis and Pueraria lobata, was designed to ameliorate the type 2 diabetes (T2D), and its safety and efficacy were evaluated in the research by metabonomics, gut microbiota and system pharmacology. To study the hypoglycemic effect of Qijian mixture, male KKay mice (28-30 g, 8-9 week) and C57/BL6 mice (18-19 g, 8-9 week) were used. Thirty KKay diabetic mice were randomly distributed into 5 groups, abbreviated as Model group (Model), Low Qijian Mixture group (QJM(L)), High Qijian Mixture group (QJM(H)), Chinese Medicine (Gegen Qinlian Decoction) Positive group (GGQL), and Western Medicine (Metformin hydrochloride) Positive group (Metformin). C57/BL6 was considered as the healthy control group (Control). Moreover, a system pharmacology approach was utilized to assess the physiological targets involved in the action of Qijian mixture. There was no adverse drug reaction of Qijian mixture in the acute toxicity study and HE result, and, compared with Model group, Qijian mixture could modulate blood glycemic level safely and effectively. Qijian Mixture was lesser effective than metformin hydrochloride; however, both showed similar hypoglycemic trend. Based on ¹H NMR based metabonomics study, the profoundly altered metabolites in Qijian mixture treatment group were identified. Qijian mixture-related 55 proteins and 4 signaling pathways, including galactose metabolism, valine, leucine and isoleucine degradation metabolism, aminoacyl-tRNA biosynthesis metabolism and alanine, aspartate and glutamate metabolism pathways, were explored. The PCoA analysis of gut microbiota revealed that Qijian mixture treatment profoundly enriched bacteroidetes. In addition, the system pharmacology paradigm revealed that Qijian mixture acted through TP53, AKT1 and PPARA proteins. It was concluded that Qijian mixture effectively alleviated T2D, and this effect was linked with the altered features of the metabolite profiles and the gut microbiota.

Emerging perspectives on branched-chain amino acid metabolism during adipocyte differentiation

PURPOSE OF REVIEW

Adipogenesis has been extensively studied in the context of carbohydrate and lipid metabolism. However, little information exists on the role of amino acid metabolism during adipocyte differentiation. Here, we review how branched-chain amino acid (BCAA) metabolism is modified during adipogenesis and, due to the limited information in the area, address questions that remain to be answered with further research.

RECENT FINDINGS

BCAAs are rapidly consumed during adipocyte differentiation and are indispensable for this process. Furthermore, we describe how BCAA catabolic enzymes and the metabolic fate of BCAAs are modified during adipogenesis.

SUMMARY

Obesity is a chronic disease characterized by increased adipose tissue due to either an increase in the size (hypertrophy) and/or number of adipocytes (hyperplasia). Hyperplasia is determined by the rate of adipogenesis. Therefore, understanding the mechanism that modulates adipogenesis in the context of amino acid metabolism will help to establish pharmacological and dietary interventions involving the type and amount of dietary protein for the treatment of obesity and its associated comorbidities.Video abstract http://links.lww.com/COCN/A11.

Amino Acid Sensing via General Control Nonderepressible-2 Kinase and Immunological Programming

Metabolic adaptation to the changing nutrient levels in the cellular microenvironment plays a decisive role in the maintenance of homeostasis. Eukaryotic cells are equipped with nutrient sensors, which sense the fluctuating nutrients levels and accordingly program the cellular machinery to mount an appropriate response. Nutrients including amino acids play a vital role in maintaining cellular homeostasis. Therefore, over the evolution, different species have developed diverse mechanisms to detect amino acids abundance or scarcity. Immune responses have been known to be closely associated with the cellular metabolism especially amino acid sensing pathway, which influences innate as well as adaptive immune-effector functions. Thus, exploring the cross-talk between amino acid sensing mechanisms and immune responses in disease as well as in normal physiological conditions might open up avenues to explore how this association can be exploited to tailor immunological functions toward the design of better therapeutics for controlling metabolic diseases. In this review, we discuss the advances in the knowledge of various amino acid sensing pathways including general control nonderepressible-2 kinase in the control of inflammation and metabolic diseases.

Current level of evidence on causal association between hepatitis C virus and type 2 diabetes: A review

The association between hepatitis C virus (HCV) infection and type 2 diabetes (T2D) has been known for over 20 years. Cross-sectional and longitudinal studies have shown a higher prevalence and incidence, respectively, of T2D in patients with chronic HCV infection. HCV induces glucose metabolism alterations mostly interfering with the insulin signaling chain in hepatocytes, although extrahepatic mechanisms seem to contribute. Both IR and T2D accelerate the histological and clinical progression of chronic hepatitis C as well as the risk of extra-hepatic complications such as nephropathy, acute coronary events and ischemic stroke. Before the availability of direct-acting antivirals (DAAs), the therapeutic choice was limited to interferon (IFN)-based therapy, which reduced the incidence of the extra-hepatic manifestations but was burdened with several contraindications and poor tolerability. A better understanding of HCV-associated glucose metabolism derangements and their reversibility is expected with the use of DAAs.

Proteomics-Based Identification of the Molecular Signatures of Liver Tissues from Aged Rats following Eight Weeks of Medium-Intensity Exercise

Physical activity has emerged as a powerful intervention that promotes healthy aging by maintaining the functional capacity of critical organ systems. Here, by combining functional and proteomics analyses, we examined how hepatic phenotypes might respond to exercise treatment in aged rats. 16 male aged (20 months old) SD rats were divided into exercise and parallel control groups at random; the exercise group had 8 weeks of treadmill training with medium intensity. Whole protein samples of the liver were extracted from both groups and separated by two-dimensional gel electrophoresis. Alternatively objective protein spots with >2-fold difference in expression were selected for enzymological extraction and MS/MS identification. Results show increased activity of the manganese superoxide dismutase and elevated glutathione levels in the livers of exercise-treated animals, but malondialdehyde contents obviously decreased in the liver of the exercise group. Proteomics-based identification of differentially expressed proteins provided an integrated view of the metabolic adaptations occurring in the liver proteome during exercise, which significantly altered the expression of several proteins involved in key liver metabolic pathways including mitochondrial sulfur, glycolysis, methionine, and protein metabolism. These findings indicate that exercise may be beneficial to aged rats through modulation of hepatic protein expression profiles.