Role of Polyamines and Hypusine in β Cells and Diabetes Pathogenesis

Serum proteomic and metabolomic profiling of hepatocellular carcinoma patients co-infected with Clonorchis sinensis

Background

Clonorchis sinensis (C. sinensis) infection is a significant risk factor for hepatocellular carcinoma (HCC), yet its underlying mechanisms remain poorly understood. This study aimed to investigate the impact of C. sinensis infection on the serum proteomic and metabolomic profiling of HCC patients, focusing on the potential mechanisms.

Method

A retrospective clinical analysis was conducted on 1121 HCC patients, comparing those with and without C. sinensis infection. The influence of C. sinensis on serum proteome and metabolome in HCC was further assessed.

Result

C. sinensis infection correlated with a younger age at cancer onset, male predominance, advanced cancer stage, liver cirrhosis, and microvascular invasion in HCC patients. It also associated with shorter overall survival (OS) and recurrence-free survival (RFS). The levels of blood lipids (e.g., APO-A, HDL-C, and TG) were significantly altered after C. sinensis infection. Proteomic and metabolomic analyses revealed metabolic reprogramming caused by C. sinensis, with excessive depletion of argininosuccinate synthase (ASS) and D-glucose as potential factors in C. sinensis-associated HCC malignancy. Key molecules ILF2, CNN2, OLFM4, NOTCH3, and LysoPA were implicated in HCC progression. Furthermore, C. sinensis triggered inflammation, insulin resistance, and pro-tumor immune escape, and exacerbated the complication of degenerative diseases.

Conclusion

This study not only provides compelling evidence for elucidating the mechanisms underlying C. sinensis-mediated HCC development but also identifies potential therapeutic targets for HCC patients co-infected with C. sinensis.

The Associations of Dietary Polyamines with Incident Type 2 Diabetes Mellitus: A Large Prospective Cohort Study

OBJECTIVES

This study aimed to analyze the associations between dietary polyamine intake and incident T2DM.

METHODS

This prospective analysis included 168,137 participants from the UK Biobank who did not have T2DM at baseline. Dietary polyamines were calculated based on portion sizes of food items and a nutrient database. Incident T2DM was defined by hospital admissions with ICD10 codes E11-E14. Cox proportional hazard regression models and restricted cubic splines were used to examine the associations between dietary polyamine intake and incident T2DM.

RESULTS

During a median follow-up of 11.2 years (IQR, 11.8-13.2), 4422 (2.6%) participants developed T2DM. The average (SD) daily dietary intake was 10.5 (11.8) mg/day for spermidine, 4.3 (2.1) mg/day for spermine, and 12.7 (6.9) mg/day for putrescine. Compared to quintile 1, the multivariable-adjusted hazard ratios (95% CI) for quintiles 2-5 of dietary spermidine were 0.87 (0.79 to 0.96), 0.87 (0.79 to 0.96), 0.91 (0.82 to 0.99), and 0.96 (0.88 to 1.06); for dietary spermine, they were 1.01 (0.91 to 1.11), 1.03 (0.93 to 1.13), 1.07 (0.97 to 1.18), and 1.11 (1.01 to 1.23); and for dietary putrescine, they were 0.84 (0.76 to 0.92), 0.83 (0.79 to 0.91), 0.82 (0.74 to 0.90), and 0.87 (0.80 to 0.96).

CONCLUSIONS

Higher dietary spermidine and putrescine were associated with a lower risk of T2DM, while higher dietary spermine appeared to be associated with a higher risk of T2DM. These findings suggest optimal levels of dietary polyamine intake and indicate that polyamines may be promising targets for nutritional interventions in the prevention and management of T2DM.

In Vivo Differentiation of Endogenous Bone Marrow-Derived Cells into Insulin-Producing Cells Using Four Soluble Factors

Four soluble factors-putrescine, glucosamine, nicotinamide, and signal transducer and activator of transcription 3 (STAT3) inhibitor BP-1-102-were shown to differentiate bone marrow mononucleated cells (BMNCs) into functional insulin-producing cells (IPCs) in vitro. Transplantation of these IPCs improved hyperglycemia in diabetic mice. However, the role of endogenous BMNC regeneration in this effect was unclear. This study aimed to evaluate the effect of these factors on in vivo BMNC differentiation into IPCs in diabetic mice. Mice were orally administered the factors for 5 days, twice at 2-week intervals, and monitored for 45-55 days. Glucose tolerance, glucose-stimulated insulin secretion, and pancreatic insulin content were measured. Chimeric mice harboring BMNCs from insulin promoter luciferase/green fluorescent protein (GFP) transgenic mice were used to track endogenous BMNC fate. These factors lowered blood glucose levels, improved glucose tolerance, and enhanced insulin secretion. Immunostaining confirmed IPCs in the pancreas, showing the potential of these factors to induce β-cell regeneration and improve diabetes treatment.

Protective effects of spermidine levels against cardiovascular risk factors: An exploration of causality based on a bi-directional Mendelian randomization analysis

The study investigated the causal relationships between spermidine levels and CVD risk factors using a bi-directional MR approach. Employing genetic variants from extensive GWAS datasets as IVs, the study aimed to determine whether spermidine levels can influence CVD risk factors such as blood pressure, blood glucose, and lipid profiles, and vice versa. The findings suggest a protective role of elevated spermidine levels against hypertension, elevated blood glucose, and lipid profiles (LDL-C and HDL-C). Specifically, increased spermidine levels were significantly associated with lower risk of hypertension (IVW beta = -0.0013453913, p = 0.01597648) and suppression risk of elevated blood glucose (IVW beta = -0.08061330, p = 0.02450205). Additionally, there was a notable association with lipid modulation, showing a decrease in LDL-C (IVW beta = -0.01849161, p = 0.01086728) and an increase in HDL-C (IVW beta = 0.0044608332, P = 0.01760051). Conversely, the influence of CVD risk factors on spermidine levels was minimal, with the exception that elevated blood glucose levels resulted in reduced spermidine levels. (IVW beta = -0.06714391, P = 0.01096123). These results underline the potential of spermidine as a modifiable dietary target for the prevention and management of cardiovascular diseases. Further investigations are warranted to explore the underlying biological mechanisms and the applicability of these findings in broader and diverse populations.

Crystal structure of archaeal IF5A-DHS complex reveals insights into the hypusination mechanism

The translation factor IF5A is highly conserved in Eukarya and Archaea and undergoes a unique post-translational hypusine modification by the deoxyhypusine synthase (DHS) enzyme. DHS transfers the butylamine moiety from spermidine to IF5A using NAD as a cofactor, forming a deoxyhypusine intermediate. IF5A is a key player in protein synthesis, preventing ribosome stalling in proline-rich sequences during translation elongation and facilitating translation elongation and termination. Additionally, human eIF5A participates in various essential cellular processes and contributes to cancer metastasis, with inhibiting hypusination showing anti-proliferative effects. The hypusination pathway of IF5A is therefore an attractive new therapeutic target. We elucidated the 2.0 Å X-ray crystal structure of the archaeal DHS-IF5A complex, revealing hetero-octameric architecture and providing a detailed view of the complex active site including the hypusination loop. This structure, along with biophysical data and molecular dynamics simulations, provides new insights into the catalytic mechanism of the hypusination reaction.

Unveiling the hidden players: noncoding RNAs orchestrating polyamine metabolism in disease

Polyamines (PA) are polycations with pleiotropic functions in cellular physiology and pathology. In particular, PA have been involved in the regulation of cell homeostasis and proliferation participating in the control of fundamental processes like DNA transcription, RNA translation, protein hypusination, autophagy and modulation of ion channels. Indeed, their dysregulation has been associated to inflammation, oxidative stress, neurodegeneration and cancer progression. Accordingly, PA intracellular levels, derived from the balance between uptake, biosynthesis, and catabolism, need to be tightly regulated. Among the mechanisms that fine-tune PA metabolic enzymes, emerging findings highlight the importance of noncoding RNAs (ncRNAs). Among the ncRNAs, microRNA, long noncoding RNA and circRNA are the most studied as regulators of gene expression and mRNA metabolism and their alteration have been frequently reported in pathological conditions, such as cancer progression and brain diseases. In this review, we will discuss the role of ncRNAs in the regulation of PA genes, with a particular emphasis on the changes of this modulation observed in health disorders.

Structural Insights into the Mechanisms Underlying Polyaminopathies

Polyamines are ubiquitous in almost all biological entities and involved in various crucial physiological processes. They are also closely associated with the onset and progression of many diseases. Polyaminopathies are a group of rare genetic disorders caused by alterations in the function of proteins within the polyamine metabolism network. Although the identified polyaminopathies are all rare diseases at present, they are genetically heritable, rendering high risks not only to the carriers but also to their descendants. Meanwhile, more polyaminopathic patients might be discovered with the increasing accessibility of gene sequencing. This review aims to provide a comprehensive overview of the structural variations of mutated proteins in current polyaminopathies, in addition to their causative genes, types of mutations, clinical symptoms, and therapeutic approaches. We focus on analyzing how alterations in protein structure lead to protein dysfunction, thereby facilitating the onset of diseases. We hope this review will offer valuable insights and references for the future clinical diagnosis and precision treatment of polyaminopathies.

Non-linear associations of serum spermidine with type 2 diabetes mellitus and fasting plasma glucose: a cross-sectional study

Background

Previous animal experiments have demonstrated the potential of spermidine to mitigate glucose intolerance, insulin resistance, and hyperinsulinemia. However, there remains a scarcity of epidemiological evidence supporting these findings. Therefore, we aimed to elucidate the associations of serum spermidine with T2DM and FPG.

Materials and methods

The cross-sectional study was conducted from June to August 2019 in the rural areas of Fuxin County, Liaoning Province, China. A total of 4,437 participants were included in the study. The serum spermidine was detected using high-performance liquid chromatography with a fluorescence detector. FPG was measured using the hexokinase method. T2DM was defined as participants with a FPG level of 7.0 mmol/L or greater, or self-reported diagnosis of diabetes by a doctor. Restricted cubic spline model and piecewise linear regression model were used to explore the associations of serum spermidine with T2DM and FPG, respectively.

Results

The mean (SD) age of the participants was 59.3 (10.0) years, with 622 out of 4,437 participants being defined as T2DM. The serum spermidine in participants stratified by age and BMI categories was significantly different, with p values of 0.006 and 0.001, respectively. Among all the participants, the association of serum spermidine with T2DM was J-shaped. The log (spermidine) was negatively associated with T2DM (OR = 0.68, 95% CI: 0.52 to 0.92, p = 0.01) below the inflection point, while log (spermidine) was not significantly associated with T2DM (OR = 1.97, 95% CI: 0.93 to 4.15, p = 0.07) above the inflection point. Among the participants without T2DM, the association of serum spermidine with FPG was inverted J-shaped. The log (spermidine) was positively associated with FPG (β = 0.13, 95% CI: 0.05 to 0.21, p = 0.001) below the inflection point, while log (spermidine) was negatively associated with FPG (β = -0.29, 95% CI: -0.42 to -0.16, p < 0.001) above the inflection point.

Conclusion

In conclusion, non-linear associations of serum spermidine with T2DM and FPG were found in the cross-sectional study in Chinese rural adults. This provided insights into the use of spermidine for the prevention of T2DM, highlighting the potential role in public health prevention strategies of spermidine.

Age-specific Metabolomic profiles in children with food allergy

BACKGROUND

Food allergy (FA) in young children is often associated with eczema, frequently directed to egg/cow milk allergens and has a higher chance of resolution, while FA that persists in older children has less chance of resolution and is less clearly associated with atopy.

METHODS

Children with FA (n = 62) and healthy controls (n = 28) were categorized into "younger" (≤5 years) and "older" (>5 years). Mass spectrometry-based untargeted metabolomic profiling as wells as cytokine profiling were performed on plasma samples in FA children in each age group.

RESULTS

Younger FA children manifested unique alterations in bile acids, polyamine metabolites and chemokines associated with Th2 responses, while older FA children displayed pronounced changes in long chain fatty acids, acylcarnitines and proinflammatory cytokines.

CONCLUSIONS

FA children of different ages manifest unique metabolic changes which may reflect at least in part pathogenic mechanisms and environmental influences operative at different time points in the disease course.

Age-Related Gut Microbiota Transplantation Disrupts Myocardial Energy Homeostasis and Induces Oxidative Damage

BACKGROUND

Aging-related energy homeostasis significantly affects normal heart function and disease development. The relationship between the gut microbiota and host energy metabolism has been well established. However, the influence of an aged microbiota on energy metabolism in the heart remains unclear.

OBJECTIVE

The objective of this was to explore the effects of age-related microbiota composition on energy metabolism in the heart.

METHODS

In this study, we used the fecal microbiota transplantation (FMT) method. The fecal microbiota from young (2-3 mo) and aged (18-22 mo) donor mice were transplanted into separate groups of young (2-3 mo) recipient mice. The analysis utilized whole 16S rRNA sequencing and plasma metabolomics to assess changes in the gut microbiota composition and metabolic potential. Energy changes were monitored by performing an oral glucose tolerance test, biochemical testing, body composition analysis, and metabolic cage measurements. Metabolic markers and markers of DNA damage were assessed in heart samples.

RESULTS

FMT of an aged microbiota changed the composition of the recipient's gut microbiota, leading to an elevated Firmicutes-to-Bacteroidetes ratio. It also affected overall energy metabolism, resulting in elevated plasma glucose concentrations, impaired glucose tolerance, and epididymal fat accumulation. Notably, FMT of an aged microbiota increased the heart weight and promoted cardiac hypertrophy. Furthermore, there were significant associations between heart weight and cardiac hypertrophy indicators, epididymal fat weight, and fasting glucose concentrations. Mechanistically, FMT of an aged microbiota modulated the glucose metabolic pathway and induced myocardial oxidative damage.

CONCLUSIONS

Our findings suggested that an aged microbiota can modulate metabolism and induce cardiac injury. This highlights the possible role of the gut microbiota in age-related metabolic disorders and cardiac dysfunction.

Insights into the action of the pharmaceutical metformin: Targeted inhibition of the gut microbial enzyme agmatinase

Metformin is the first-line treatment for type 2 diabetes, yet its mechanism of action is not fully understood. Recent studies suggest metformin's interactions with gut microbiota are responsible for exerting therapeutic effects. In this study, we report that metformin targets the gut microbial enzyme agmatinase, as a competitive inhibitor, which may impair gut agmatine catabolism. The metformin inhibition constant (Ki) of E. coli agmatinase is 1 mM and relevant in the gut where the drug concentration is 1-10 mM. Metformin analogs phenformin, buformin, and galegine are even more potent inhibitors of E. coli agmatinase (Ki = 0.6, 0.1, and 0.007 mM, respectively) suggesting a shared mechanism. Agmatine is a known effector of human host metabolism and has been reported to augment metformin's therapeutic effects for type 2 diabetes. This gut-derived inhibition mechanism gives new insights on metformin's action in the gut and may lead to significant discoveries in improving metformin therapy.

Dysregulated cysteine metabolism leads to worsened liver pathology in diabetes-tuberculosis comorbid condition

Diabetes mellitus (DM) is a risk factor for developing active tuberculosis (TB) with a 3-fold increase in susceptibility and a 4-fold higher relapse rate. With increasing DM prevalence in TB endemic regions, understanding pathophysiological changes associated with DM-TB comorbidity is imperative. In this study, streptozotocin (STZ)-induced DM C57BL/6 mice were aerosol infected with low dose (100-120 CFU) Mycobacterium tuberculosis H37Rv. At 3 weeks post infection (w.p.i.), multiple tissue mycobacterial load and metabolites were profiled. The liver proteome of DM-TB and controls were analyzed using quantitative proteomics, and multi-omics data were integrated. DM-TB mice showed dysregulated multi-tissue (lungs, liver, brain, kidney and thigh muscle) metabolism. In contrast, the mycobacterial burden in the lung, spleen and liver was similar at 3 w.p.i. in DM-TB and TB groups. Enrichment analysis of deregulated liver metabolites (n = 20; log2DM-TB/TB>±1.0) showed significant perturbation in cysteine-methionine, glycine-serine, BCAA and fatty acid metabolism. 60 out of 1660 identified liver proteins showed deregulation (log2DM-TB/TB>±1.0) and contributed from perturbed cysteine-methionine metabolism corroborating metabolomics data. In addition, amino acid biosynthesis, retinol metabolism and polyol biosynthetic process were also differentially enriched in the livers of DM-TB groups. Global correlation analysis of liver metabolome and proteome data showed a strong association between aspartic acid, pyruvic acid, leucine and isoleucine with CYP450 enzymes involved in retinol metabolism, while iminodiacetic acid, isoleucine and γ-aminobutyric acid (GABA) strong positive correlation involved in cysteine metabolism. Targeting perturbed cysteine metabolism using micro molecules, like DL-Propargylglycine, might help prevent liver damage in DM-TB comorbid conditions.

Discordant Effects of Polyamine Depletion by DENSpm and DFMO on β-cell Cytokine Stress and Diabetes Outcomes in Mice

Type 1 diabetes (T1D) is an autoimmune disease leading to dysfunction and loss of insulin-secreting β cells. In β cells, polyamines have been implicated in causing cellular stress and dysfunction. An inhibitor of polyamine biosynthesis, difluoromethylornithine (DFMO), has been shown to delay T1D in mouse models and preserve β-cell function in humans with recent-onset T1D. Another small molecule, N1,N11-diethylnorspermine (DENSpm), both inhibits polyamine biosynthesis and accelerates polyamine metabolism and is being tested for efficacy in cancer clinical trials. In this study, we show that DENSpm depletes intracellular polyamines as effectively as DFMO in mouse β cells. RNA-sequencing analysis, however, suggests that the cellular responses to DENSpm and DFMO differ, with both showing effects on cellular proliferation but the latter showing additional effects on mRNA translation and protein-folding pathways. In the low-dose streptozotocin-induced mouse model of T1D, DENSpm, unlike DFMO, did not prevent or delay diabetes outcomes but did result in improvements in glucose tolerance and reductions in islet oxidative stress. In nonobese diabetic (NOD) mice, short-term DENSpm administration resulted in a slight reduction in insulitis and proinflammatory Th1 cells in the pancreatic lymph nodes. Longer term treatment resulted in a dose-dependent increase in mortality. Notwithstanding the efficacy of both DFMO and DENSpm in reducing potentially toxic polyamine levels in β cells, our results highlight the discordant T1D outcomes that result from differing mechanisms of polyamine depletion and, more importantly, that toxic effects of DENSpm may limit its utility in T1D treatment.

Inhibition of polyamine biosynthesis preserves β cell function in type 1 diabetes

In preclinical models, α-difluoromethylornithine (DFMO), an ornithine decarboxylase (ODC) inhibitor, delays the onset of type 1 diabetes (T1D) by reducing β cell stress. However, the mechanism of DFMO action and its human tolerability remain unclear. In this study, we show that mice with β cell ODC deletion are protected against toxin-induced diabetes, suggesting a cell-autonomous role of ODC during β cell stress. In a randomized controlled trial (ClinicalTrials.gov: NCT02384889) involving 41 recent-onset T1D subjects (3:1 drug:placebo) over a 3-month treatment period with a 3-month follow-up, DFMO (125-1,000 mg/m2) is shown to meet its primary outcome of safety and tolerability. DFMO dose-dependently reduces urinary putrescine levels and, at higher doses, preserves C-peptide area under the curve without apparent immunomodulation. Transcriptomics and proteomics of DFMO-treated human islets exposed to cytokine stress reveal alterations in mRNA translation, nascent protein transport, and protein secretion. These findings suggest that DFMO may preserve β cell function in T1D through islet cell-autonomous effects.

Stress and human health in diabetes: A report from the 19th Chicago Biomedical Consortium symposium

Stress and diabetes coexist in a vicious cycle. Different types of stress lead to diabetes, while diabetes itself is a major life stressor. This was the focus of the Chicago Biomedical Consortium's 19th annual symposium, "Stress and Human Health: Diabetes," in November 2022. There, researchers primarily from the Chicago area met to explore how different sources of stress - from the cells to the community - impact diabetes outcomes. Presenters discussed the consequences of stress arising from mutant proteins, obesity, sleep disturbances, environmental pollutants, COVID-19, and racial and socioeconomic disparities. This symposium showcased the latest diabetes research and highlighted promising new treatment approaches for mitigating stress in diabetes.

Impact of dietary interventions on pre-diabetic oral and gut microbiome, metabolites and cytokines

Diabetes and associated comorbidities are a global health threat on the rise. We conducted a six-month dietary intervention in pre-diabetic individuals (NCT03222791), to mitigate the hyperglycemia and enhance metabolic health. The current work explores early diabetes markers in the 200 individuals who completed the trial. We find 166 of 2,803 measured features, including oral and gut microbial species and pathways, serum metabolites and cytokines, show significant change in response to a personalized postprandial glucose-targeting diet or the standard of care Mediterranean diet. These changes include established markers of hyperglycemia as well as novel features that can now be investigated as potential therapeutic targets. Our results indicate the microbiome mediates the effect of diet on glycemic, metabolic and immune measurements, with gut microbiome compositional change explaining 12.25% of serum metabolites variance. Although the gut microbiome displays greater compositional changes compared to the oral microbiome, the oral microbiome demonstrates more changes at the genetic level, with trends dependent on environmental richness and species prevalence in the population. In conclusion, our study shows dietary interventions can affect the microbiome, cardiometabolic profile and immune response of the host, and that these factors are well associated with each other, and can be harnessed for new therapeutic modalities.

The first evidence of biological activity for free Hypusine, an enigmatic amino acid discovered in the '70s

Hypusine amino acid [N^ε-(4-amino-2-hydroxybutyl)-lysine] was first isolated in 1971 from bovine brain extracts. Hypusine originates from a post-translational modification at the eukaryotic translation initiation factor 5A (eIF5A), a protein produced by archaebacteria and eukaryotes. The eIF5A protein is the only one described containing the hypusine residue, which is essential for its activity. Hypusine as a free amino acid is a consequence of proteolytic degradation of eIF5A. Herein, we showed, for the first time, evidence of biological activity for the free hypusine. C6 rat glioma cells were treated with hypusine, and different cellular parameters were evaluated. Hypusine treatment significantly reduced C6 cell proliferation and potently suppressed their clonogenic capacity without leading to apoptosis. Hypusine also decreased the Eif5A transcript content and the global protein synthesis profile that may occur due to negative feedback in response to high hypusine concentration, controlling the content of newly synthesized eIF5A, which can affect the translation process. Besides, hypusine treatment also altered cellular metabolism by changing the pathways for energy production, reducing cellular respiration coupled with oxidative phosphorylation, and increasing the anaerobic metabolism. These observed results and the relationship between eIF5A and tumor processes led us to test the combination of hypusine with the chemotherapeutic drug temozolomide. Combining temozolomide with hypusine reduced the MTT conversion to the same levels as those observed using double temozolomide dosage alone, demonstrating a synergetic action between the compounds. Thus, since 1971, this is the first study showing evidence of biological activity for hypusine not associated with being an essential component of the eiF5A protein. Finding out the molecular targets of hypusine are the following efforts to completely characterize its biological activity.

Transcriptome Analysis of Redox Systems and Polyamine Metabolic Pathway in Hepatoma and Non-Tumor Hepatocyte-like Cells

Reactive oxygen species (ROS) play a major role in the regulation of various processes in the cell. The increase in their production is a factor contributing to the development of numerous pathologies, including inflammation, fibrosis, and cancer. Accordingly, the study of ROS production and neutralization, as well as redox-dependent processes and the post-translational modifications of proteins, is warranted. Here, we present a transcriptomic analysis of the gene expression of various redox systems and related metabolic processes, such as polyamine and proline metabolism and the urea cycle in Huh7.5 hepatoma cells and the HepaRG liver progenitor cell line, that are widely used in hepatitis research. In addition, changes in response to the activation of polyamine catabolism that contribute to oxidative stress were studied. In particular, differences in the gene expression of various ROS-producing and ROS-neutralizing proteins, the enzymes of polyamine metabolisms and proline and urea cycles, as well as calcium ion transporters between cell lines, are shown. The data obtained are important for understanding the redox biology of viral hepatitis and elucidating the influence of the laboratory models used.

Serum Metabolomics Reveals a Potential Benefit of Methionine in Type 1 Diabetes Patients with Poor Glycemic Control and High Glycemic Variability

Glycemic variability (GV) in some patients with type 1 diabetes (T1D) remains heterogeneous despite comparable clinical indicators, and whether other factors are involved is yet unknown. Metabolites in the serum indicate a broad effect of GV on cellular metabolism and therefore are more likely to indicate metabolic dysregulation associated with T1D. To compare the metabolomic profiles between high GV (GV-H, coefficient of variation (CV) of glucose ≥ 36%) and low GV (GV-L, CV < 36%) groups and to identify potential GV biomarkers, metabolomics profiling was carried out on serum samples from 17 patients with high GV, 16 matched (for age, sex, body mass index (BMI), diabetes duration, insulin dose, glycated hemoglobin (HbA1c), fasting, and 2 h postprandial C-peptide) patients with low GV (exploratory set), and another 21 (GV-H/GV-L: 11/10) matched patients (validation set). Subsequently, 25 metabolites were significantly enriched in seven Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways between the GV-H and GV-L groups in the exploratory set. Only the differences in spermidine, L-methionine, and trehalose remained significant after validation. The area under the curve of these three metabolites combined in distinguishing GV-H from GV-L was 0.952 and 0.918 in the exploratory and validation sets, respectively. L-methionine was significantly inversely related to HbA1c and glucose CV, while spermidine was significantly positively associated with glucose CV. Differences in trehalose were not as reliable as those in spermidine and L-methionine because of the relatively low amounts of trehalose and the inconsistent fold change sizes in the exploratory and validation sets. Our findings suggest that metabolomic disturbances may impact the GV of T1D. Additional in vitro and in vivo mechanistic studies are required to elucidate the relationship between spermidine and L-methionine levels and GV in T1D patients with different geographical and nutritional backgrounds.

Inside the β Cell: Molecular Stress Response Pathways in Diabetes Pathogenesis

The pathogeneses of the 2 major forms of diabetes, type 1 and type 2, differ with respect to their major molecular insults (loss of immune tolerance and onset of tissue insulin resistance, respectively). However, evidence suggests that dysfunction and/or death of insulin-producing β-cells is common to virtually all forms of diabetes. Although the mechanisms underlying β-cell dysfunction remain incompletely characterized, recent years have witnessed major advances in our understanding of the molecular pathways that contribute to the demise of the β-cell. Cellular and environmental factors contribute to β-cell dysfunction/loss through the activation of molecular pathways that exacerbate endoplasmic reticulum stress, the integrated stress response, oxidative stress, and impaired autophagy. Whereas many of these stress responsive pathways are interconnected, their individual contributions to glucose homeostasis and β-cell health have been elucidated through the development and interrogation of animal models. In these studies, genetic models and pharmacological compounds have enabled the identification of genes and proteins specifically involved in β-cell dysfunction during diabetes pathogenesis. Here, we review the critical stress response pathways that are activated in β cells in the context of the animal models.

Arginase: Biological and Therapeutic Implications in Diabetes Mellitus and Its Complications

Arginase is a ubiquitous enzyme in the urea cycle (UC) that hydrolyzes L-arginine to urea and L-ornithine. Two mammalian arginase isoforms, arginase1 (ARG1) and arginase2 (ARG2), play a vital role in the regulation of β-cell functions, insulin resistance (IR), and vascular complications via modulating L-arginine metabolism, nitric oxide (NO) production, and inflammatory responses as well as oxidative stress. Basic and clinical studies reveal that abnormal alterations of arginase expression and activity are strongly associated with the onset and development of diabetes mellitus (DM) and its complications. As a result, targeting arginase may be a novel and promising approach for DM treatment. An increasing number of arginase inhibitors, including chemical and natural inhibitors, have been developed and shown to protect against the development of DM and its complications. In this review, we discuss the fundamental features of arginase. Next, the regulatory roles and underlying mechanisms of arginase in the pathogenesis and progression of DM and its complications are explored. Furthermore, we review the development and discuss the challenges of arginase inhibitors in treating DM and its related pathologies.

Identification and Characterization of Novel Small-Molecule SMOX Inhibitors

The major intracellular polyamines spermine and spermidine are abundant and ubiquitous compounds that are essential for cellular growth and development. Spermine catabolism is mediated by spermine oxidase (SMOX), a highly inducible flavin-dependent amine oxidase that is upregulated during excitotoxic, ischemic, and inflammatory states. In addition to the loss of radical scavenging capabilities associated with spermine depletion, the catabolism of spermine by SMOX results in the production of toxic byproducts, including H₂O₂ and acrolein, a highly toxic aldehyde with the ability to form adducts with DNA and inactivate vital cellular proteins. Despite extensive evidence implicating SMOX as a key enzyme contributing to secondary injury associated with multiple pathologic states, the lack of potent and selective inhibitors has significantly impeded the investigation of SMOX as a therapeutic target. In this study, we used a virtual and physical screening approach to identify and characterize a series of hit compounds with inhibitory activity against SMOX. We now report the discovery of potent and highly selective SMOX inhibitors 6 (IC₅₀ 0.54 μM, Ki 1.60 μM) and 7 (IC₅₀ 0.23 μM, K_i 0.46 μM), which are the most potent SMOX inhibitors reported to date. We hypothesize that these selective SMOX inhibitors will be useful as chemical probes to further elucidate the impact of polyamine catabolism on mechanisms of cellular injury.

Topical Reappraisal of Molecular Pharmacological Approaches to Endothelial Dysfunction in Diabetes Mellitus Angiopathy

Diabetes mellitus (DM) is a frequent medical problem, affecting more than 4% of the population in most countries. In the context of diabetes, the vascular endothelium can play a crucial pathophysiological role. If a healthy endothelium—which is a dynamic endocrine organ with autocrine and paracrine activity—regulates vascular tone and permeability and assures a proper balance between coagulation and fibrinolysis, and vasodilation and vasoconstriction, then, in contrast, a dysfunctional endothelium has received increasing attention as a potential contributor to the pathogenesis of vascular disease in diabetes. Hyperglycemia is indicated to be the major causative factor in the development of endothelial dysfunction. Furthermore, many shreds of evidence suggest that the progression of insulin resistance in type 2 diabetes is parallel to the advancement of endothelial dysfunction in atherosclerosis. To present the state-of-the-art data regarding endothelial dysfunction in diabetic micro- and macroangiopathy, we constructed this literature review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We interrogated five medical databases: Elsevier, PubMed, PMC, PEDro, and ISI Web of Science.