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

Tissue accumulation and hepatotoxicity of 8:2 chlorinated polyfluoroalkyl ether sulfonate: A multi-omics analysis deciphering hepatic amino acid metabolic dysregulation in mice

8:2 Chlorinated polyfluoroalkyl ether sulfonate (8:2 Cl-PFESA) is a substitute for perfluorooctane sulfonate and an emerging environmental pollutant, yet its bioaccumulation and health risks are poorly understood. We established a subchronic exposure model in mice (0.04, 0.2, and 1 mg/kg/d) to evaluate its adverse effects. Our findings show extensive distribution of 8:2 Cl-PFESA in various tissues (plasma, liver, kidney, brain, heart, lung, testis, ovary, spleen, thymus, thyroid, uterus, large intestine, small intestine, muscle, and fat), with the highest accumulation in the liver, identified as the primary storage organ. Liver histopathology revealed elevated alanine aminotransferase levels, reduced triglycerides, and ballooning degeneration. Proteomics analysis indicated significant involvement of amino acid metabolism in 8:2 Cl-PFESA-induced hepatotoxicity. Metabolomics analysis further highlighted pronounced alterations in amino acid interconversion. Multi-omics integration revealed disruptions in amino acid metabolism, particularly with alanine, histidine, and tryptophan, identifying key proteins EHHADH, HAL, MAO-A, ALDH3A2, and TDO2 as crucial connectors in these metabolic processes, validated by Western blot experiments. This study provides a comprehensive analysis of 8:2 Cl-PFESA accumulation and distribution in biological systems, demonstrating that hepatotoxicity is primarily mediated through amino acid metabolism disruption, offering insights for pollution mitigation strategies and future toxicological research.

Insulin activates parasympathetic hepatic-related neurons of the paraventricular nucleus of the hypothalamus through mTOR signaling

Integration of autonomic and metabolic regulation, including hepatic function, is a critical role played by the brain's hypothalamic region. Specifically, the paraventricular nucleus of the hypothalamus (PVN) regulates autonomic functions related to metabolism, such as hepatic glucose production. Although insulin can act directly on hepatic tissue to inhibit hepatic glucose production, recent evidence implicates that central actions of insulin within PVN also regulate glucose metabolism. However, specific central circuits responsible for insulin signaling with relation to hepatic regulation are poorly understood. As a heterogeneous nucleus essential to controlling parasympathetic motor output with notable expression of insulin receptors, PVN is an appealing target for insulin-dependent modulation of parasympathetic activity. Here, we tested the hypothesis that insulin activates hepatic-related PVN (PVNhepatic) neurons through a parasympathetic pathway. Using transsynaptic retrograde tracing, labeling within PVN was first identified 24 h after its expression in the dorsal motor nucleus of the vagus (DMV) and 72 h after hepatic injection. Critically, nearly all labeling in medial PVN was abolished after a left vagotomy, indicating that PVNhepatic neurons in this region are part of a central circuit innervating parasympathetic motor neurons. Insulin also significantly increased the firing frequency of PVNhepatic neurons in this subregion. Mechanistically, rapamycin pretreatment inhibited insulin-dependent activation of PVNhepatic neurons. Therefore, central insulin signaling can activate a subset of PVNhepatic neurons that are part of a unique parasympathetic network in control of hepatic function. Taken together, PVNhepatic neurons related to parasympathetic output regulation could serve as a key central network in insulin's ability to control hepatic functions.NEW & NOTEWORTHY Increased peripheral insulin concentrations are known to decrease hepatic glucose production through both direct actions on hepatocytes and central autonomic networks. Despite this understanding, how (and in which brain regions) insulin exerts its action is still obscure. Here, we demonstrate that insulin activates parasympathetic hepatic-related PVN neurons (PVNhepatic) and that this effect relies on mammalian target of rapamycin (mTOR) signaling, suggesting that insulin modulates hepatic function through autonomic pathways involving insulin receptor intracellular signaling cascades.

Comparing Methods for Induction of Insulin Resistance in Mouse 3T3-L1 Cells

Cell culture plays a crucial role in addressing fundamental research questions, particularly in studying insulin resistance (IR) mechanisms. Multiple in vitro models are utilized for this purpose, but their technical distinctions and relevance to in vivo conditions remain unclear. This study aims to assess the effectiveness of existing in vitro models in inducing IR and their ability to replicate in vivo IR conditions.

BACKGROUND

Insulin resistance (IR) is a cellular condition linked to metabolic disorders. Despite the utility of cell culture in IR research, questions persist regarding the suitability of various models. This study seeks to evaluate these models' efficiency in inducing IR and their ability to mimic in vivo conditions. Insights gained from this research could enhance our understanding of model strengths and limitations, potentially advancing strategies to combat IR and related disorders.

OBJECTIVE

1- Investigate the technical differences between existing cell culture models used to study molecular mediators of insulin resistance (IR). 2- Compare the effectiveness of present in vitro models in inducing insulin resistance (IR). 3- Assess the relevance of the existing cell culture models in simulating the in vivo conditions and environment that provoke the induction of insulin resistance (IR).

METHODS AND MATERIAL

In vitro, eight sets of 3T3-L1 cells were cultured until they reached 90% confluence. Subsequently, adipogenic differentiation was induced using a differentiation cocktail (media). These cells were then divided into four groups, with four subjected to normal conditions and the other four to hypoxic conditions. Throughout the differentiation process, each cell group was exposed to specific factors known to induce insulin resistance (IR). These factors included 2.5 nM tumor necrosis factor-alpha (TNFα), 20 ng/ml interleukin-6 (IL-6), 10 micromole 4-hydroxynonenal (4HNE), and high insulin (HI) at a concentration of 100 nM. To assess cell proliferation, DAPI staining was employed, and the expression of genes associated with various metabolic pathways affected by insulin resistance was investigated using Real-Time PCR. Additionally, insulin signaling was examined using the Bio-plex Pro cell signaling Akt panel.

RESULTS

We induced insulin resistance in 3T3-L1 cells using IL-6, TNFα, 4HNE, and high insulin in both hypoxic and normoxic conditions. Hypoxia increased HIF1a gene expression by approximately 30% (P<0.01). TNFα reduced cell proliferation by 10-20%, and chronic TNFα treatment significantly decreased mature adipocytes due to its cytotoxicity. We assessed the impact of insulin resistance (IR) on metabolic pathways, focusing on genes linked to branched-chain amino acid metabolism, detoxification, and chemotaxis. Notably, ALDH6A1 and MCCC1 genes, related to amino acid metabolism, were significantly affected under hypoxic conditions. TNFα treatment notably influenced MCP-1 and MCP-2 genes linked to chemotaxis, with remarkable increases in MCP-1 levels and MCP-2 expression primarily under hypoxia. Detoxification-related genes showed minimal impact, except for a significant increase in MAOA expression under acute hypoxic conditions with TNFα treatment. Additional genes displayed varying effects, warranting further investigation. To investigate insulin signaling's influence in vitro by IRinducing factors, we assessed phospho-protein levels. Our results reveal a significant p-Akt induction with chronic high insulin (10%) and acute TNFα (12%) treatment under hypoxia (both P<0.05). Other insulin resistance-related phospho-proteins (GSK3B, mTOR, PTEN) increased with IL-6, 4HNE, TNFα, and high insulin under hypoxia, while p-IRS1 levels remained unaffected.

CONCLUSION

In summary, different in vitro models using inflammatory, oxidative stress, and high insulin conditions under hypoxic conditions can capture various aspects of in vivo adipose tissue insulin resistance (IR). Among these models, acute TNFα treatment may offer the most robust approach for inducing IR in 3T3-L1 cells.

Metabolic profiling reveals altered amino acid and fatty acid metabolism in children with Williams Syndrome

Williams Syndrome (WS) is a rare neurodevelopmental disorder with a prevalence of 1 in 7500 to 1 in 20,000 individuals, caused by a microdeletion in chromosome 7q11.23. Despite its distinctive clinical features, the underlying metabolic alterations remain largely unexplored. This study employs targeted metabolomics to investigate the metabolic characteristics of children with WS. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we identified significant dysregulation of 15 metabolites, with 11 upregulated and 4 downregulated. Notably, amino acids such as alanine, proline, and arginine were significantly elevated. Fatty acid metabolism showed pronounced upregulation of long-chain saturated fatty acids (C18:0, C20:0, C22:0, C24:0, C26:0, and C28:0) and downregulation of long-chain unsaturated fatty acids (C18:2 LA, C22:6 DHA, C16:1 PLA, and t-C18:1 EA), except for upregulated nervonic acid (C24:1) and arachidonic acid (C20:4). Metabolic pathway analysis highlighted disruptions in arginine synthesis, arginine/proline metabolism, alanine, aspartate and glutamate metabolism, biosynthesis of unsaturated fatty acids, linoleic acid metabolism, and arachidonic acid metabolism. This study provides the first comprehensive analysis of amino acid and fatty acid metabolism in children with WS, offering insights into the disorder's complex metabolic landscape. Further validation in larger cohorts is essential to confirm these findings and their potential as biomarkers and therapeutic targets.

Energy metabolism and redox balance: How phytochemicals influence heart failure treatment

Heart Failure (HF) epitomizes a formidable global health quandary characterized by marked morbidity and mortality. It has been established that severe derangements in energy metabolism are central to the pathogenesis of HF, culminating in an inadequate cardiac energy milieu, which, in turn, precipitates cardiac pump dysfunction and systemic energy metabolic failure, thereby steering the trajectory and potential recuperation of HF. The conventional therapeutic paradigms for HF predominantly target amelioration of heart rate, and cardiac preload and afterload, proffering symptomatic palliation or decelerating the disease progression. However, the realm of therapeutics targeting the cardiac energy metabolism remains largely uncharted. This review delineates the quintessential characteristics of cardiac energy metabolism in healthy hearts, and the metabolic aberrations observed during HF, alongside the associated metabolic pathways and targets. Furthermore, we delve into the potential of phytochemicals in rectifying the redox disequilibrium and the perturbations in energy metabolism observed in HF. Through an exhaustive analysis of recent advancements, we underscore the promise of phytochemicals in modulating these pathways, thereby unfurling a novel vista on HF therapeutics. Given their potential in orchestrating cardiac energy metabolism, phytochemicals are emerging as a burgeoning frontier for HF treatment. The review accentuates the imperative for deeper exploration into how these phytochemicals specifically intervene in cardiac energy metabolism, and the subsequent translation of these findings into clinical applications, thereby broadening the horizon for HF treatment modalities.

Serum metabolomics profiling by proton nuclear magnetic resonance spectrometry of the response to single oral macronutrient challenges in women with polycystic ovary syndrome (PCOS) compared with male and female controls

BACKGROUND

The polycystic ovary syndrome (PCOS) is associated with insulin resistance, obesity and cardiometabolic comorbidities. We here challenged the hypothesis, using state-of-the-art proton nuclear magnetic resonance spectrometry (1H-NMRS) metabolomics profiling, that androgen excess in women induces a certain masculinization of postprandial metabolism that is modulated by obesity.

MATERIALS AND METHODS

Participants were 53 Caucasian young adults, including 17 women with classic PCOS consisting of hyperandrogenism and ovulatory dysfunction, 17 non-hyperandrogenic women presenting with regular menses, and 19 healthy men, selected to be similar in terms of age and body mass index (BMI). Half of the subjects had obesity. Patients were submitted to isocaloric separate glucose, lipid and protein oral challenges in alternate days and fasting and postprandial serum samples were submitted to 1H-NMRS metabolomics profiling for quantification of 36 low-molecular-weight polar metabolites.

RESULTS

The largest postprandial changes were observed after glucose and protein intake, with lipid ingestion inducing smaller differences. Changes after glucose intake consisted of a marked increase in carbohydrates and byproducts of glycolysis, and an overall decrease in byproducts of proteolysis, lipolysis and ketogenesis. After the protein load, most amino acids and derivatives increased markedly, in parallel to an increase in pyruvate and a decrease in 3-hydroxybutyric acid and glycerol. Obesity increased β- and D-glucose and pyruvate levels, with this effect being observed mostly after glucose ingestion in women with PCOS. Regardless of the type of macronutrient, men presented increased lysine and decreased 3-hydroxybutyric acid. In addition, non-obese men showed increased postprandial β-glucose and decreased pyroglutamic acid, compared with non-obese control women. We observed a common pattern of postprandial changes in branched-chain and aromatic amino acids, where men showed greater amino acids increases after protein intake than control women and patients with PCOS but only within the non-obese participants. Conversely, this increase was blunted in obese men but not in obese women, who even presented a larger increase in some amino acids compared with their non-obese counterparts. Interestingly, regardless of the type of macronutrient, only obese women with PCOS showed increased leucine, lysine, phenylalanine and tryptophan levels compared with non-obese patients.

CONCLUSIONS

Serum 1H-NMRS metabolomics profiling indicated sexual dimorphism in the responses to oral macronutrient challenges, which were apparently driven by the central role of postprandial insulin effects with obesity, and to a lesser extent PCOS, exerting modifying roles derived from insulin resistance. Hence, obesity impaired metabolic flexibility in young adults, yet sex and sex hormones also influenced the regulation of postprandial metabolism.

Microbial taxonomic and functional shifts in adolescents with type 1 diabetes are associated with clinical and dietary factors

BACKGROUND

Evidence indicates a link between the pathogenesis of type 1 diabetes (T1D) and the gut microbiome. However, the regulation of microbial metabolic pathways and the associations of bacterial species with dietary factors in T1D are largely unknown. We investigated whether microbial metagenomic signatures in adolescents with T1D are associated with clinical/dietary factors.

METHODS

Adolescents with T1D (case) and healthy adolescents (control) were recruited, and microbiome profiling in participants' stool samples was performed using shotgun metagenomic sequencing. The bioBakery3 pipeline (Kneaddata, Metaphlan 4 and HUMAnN) was used to assign taxonomy and functional annotations. Clinical (HbA1c) and dietary information (3-day food record) were collected for conducting association analysis using Spearman's correlation.

FINDINGS

Adolescents with T1D exhibited modest changes in taxonomic composition of gut microbiome. Nineteen microbial metabolic pathways were altered in T1D, including downregulation of biosynthesis of vitamins (B2/flavin, B7/biotin and B9/folate), enzyme cofactors (NAD+ and s-adenosyl methionine) and amino acids (aspartate, asparagine and lysine) with an upregulation in the fermentation pathways. Furthermore, bacterial species associated with dietary and clinical factors differed between healthy adolescents and adolescents with T1D. Supervised models modeling identified taxa predictive of T1D status, and the top features included Coprococcus and Streptococcus.

INTERPRETATION

Our study provides new insight into the alteration of microbial and metabolic signatures in adolescents with T1D, suggesting that microbial biosynthesis of vitamins, enzyme cofactors and amino acids may be potentially altered in T1D.

FUNDING

Research grants from NIH/NCCIH: R01AT010247 and USDA/NIFA: 2019-67017-29253; and Larry & Gail Miller Family Foundation Assistantship.

How dietary amino acids and high protein diets influence insulin secretion

Glucose homeostasis is the maintenance and regulation of blood glucose concentration within a tight physiological range, essential for the functioning of most tissues and organs. This is primarily achieved by pancreatic secretion of insulin and glucagon. Deficient pancreatic endocrine function, coupled with or without peripheral insulin resistance leads to prolonged hyperglycemia with chronic impairment of glucose homeostasis, most commonly seen in diabetes mellitus. High protein diets (HPDs) are thought to modulate glucose homeostasis through various metabolic pathways. Insulin secretion can be directly modulated by the amino acid products of protein digestion, which activate nutrient receptors and nutrient transporters expressed by the endocrine pancreas. Insulin secretion can also be modulated indirectly, through incretin release from enteroendocrine cells, and via vagal neuronal pathways. Additionally, glucose homeostasis can be promoted by the satiating effects of anorectic hormones released following HPD consumption. This review summarizes the insulinotropic mechanisms by which amino acids and HPDs may influence glucose homeostasis, with a particular focus on their applicability in the management of Type 2 diabetes mellitus.

Gut microbiota: The key to the treatment of metabolic syndrome in traditional Chinese medicine - a case study of diabetes and nonalcoholic fatty liver disease

Metabolic syndrome mainly includes obesity, type 2 diabetes (T2DM), alcoholic fatty liver (NAFLD) and cardiovascular diseases. According to the ancient experience philosophy of Yin-Yang, monarch-minister compatibility of traditional Chinese medicine, prescription is given to treat diseases, which has the advantages of small toxic and side effects and quick effect. However, due to the diversity of traditional Chinese medicine ingredients and doubts about the treatment theory of traditional Chinese medicine, the mechanism of traditional Chinese medicine is still in doubt. Gastrointestinal tract is an important part of human environment, and participates in the occurrence and development of diseases. In recent years, more and more TCM researches have made intestinal microbiome a new frontier for understanding and treating diseases. Clinically, nonalcoholic fatty liver disease (NAFLD) and diabetes mellitus (DM) often co-occur. Our aim is to explain the mechanism of interaction between gastrointestinal microbiome and traditional Chinese medicine (TCM) or traditional Chinese medicine formula to treat DM and NAFLD. Traditional Chinese medicine may treat these two diseases by influencing the composition of intestinal microorganisms, regulating the metabolism of intestinal microorganisms and transforming Chinese medicinal compounds.

The Genetic Variability of Members of the SLC38 Family of Amino Acid Transporters (SLC38A3, SLC38A7 and SLC38A9) Affects Susceptibility to Type 2 Diabetes and Vascular Complications

Type 2 Diabetes (T2D) is a metabolic disease associated with long-term complications, with a multifactorial pathogenesis related to the interplay between genetic and modifiable risk factors, of which nutrition is the most relevant. In particular, the importance of proteins and constitutive amino acids (AAs) in disease susceptibility is emerging. The ability to sense and respond to changes in AA supplies is mediated by complex networks, of which AA transporters (AATs) are crucial components acting also as sensors of AA availability. This study explored the associations between polymorphisms in selected AATs genes and T2D and vascular complications in 433 patients and 506 healthy controls. Analyses revealed significant association of SLC38A3-rs1858828 with disease risk. Stratification of patients based on presence/absence of vascular complications highlighted significant associations of SLC7A8-rs3783436 and SLC38A7-rs9806843 with diabetic retinopathy. Additionally, the SLC38A9-rs4865615 resulted associated with chronic kidney disease. Notably, these genes function as AAs sensors, specifically glutamine, leucine, and arginine, linked to the main nutrient signaling pathway mammalian target of rapamycin complex 1 (mTORC1). Thus, their genetic variability may contribute to T2D by influencing the ability to properly transduce a signal activating mTORC1 in response to AA availability. In this scenario, the contribution of dietary AAs supply to disease risk may be relevant.

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.

Metabolite G-Protein Coupled Receptors in Cardio-Metabolic Diseases

G protein-coupled receptors (GPCRs) have originally been described as a family of receptors activated by hormones, neurotransmitters, and other mediators. However, in recent years GPCRs have shown to bind endogenous metabolites, which serve functions other than as signaling mediators. These receptors respond to fatty acids, mono- and disaccharides, amino acids, or various intermediates and products of metabolism, including ketone bodies, lactate, succinate, or bile acids. Given that many of these metabolic processes are dysregulated under pathological conditions, including diabetes, dyslipidemia, and obesity, receptors of endogenous metabolites have also been recognized as potential drug targets to prevent and/or treat metabolic and cardiovascular diseases. This review describes G protein-coupled receptors activated by endogenous metabolites and summarizes their physiological, pathophysiological, and potential pharmacological roles.

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.