Pathogenesis Of Insulin Resistance Research Articles

Exploring lipodystrophy gene expression in adipocytes: unveiling insights into the pathogenesis of insulin resistance, type 2 diabetes, and clustering diseases (metabolic syndrome) in Asian Indians

BackgroundStudying the molecular mechanisms of lipodystrophy can provide valuable insights into the pathophysiology of insulin resistance (IR), type 2 diabetes (T2D), and other clustering diseases [metabolic syndrome (MetS)] and its underlying adipocentric disease (MetS disease).MethodsA high-confidence lipodystrophy gene panel comprising 50 genes was created, and their expressions were measured in the visceral and subcutaneous (both peripheral and abdominal) adipose depots of MetS and non-MetS individuals at a tertiary care medical facility.ResultsMost lipodystrophy genes showed significant downregulation in MetS individuals compared to non-MetS individuals in both subcutaneous and visceral depots. In the abdominal compartment, all the genes showed relatively higher expression in visceral depot as compared to their subcutaneous counterpart, and this difference narrowed with increasing severity of MetS. Their expression level shows an inverse correlation with T2D, MetS, and HOMA-IR and with other T2D-related intermediate traits. Results also demonstrated that individualization of MetS patients could be done based on adipose tissue expression of just 12 genes.ConclusionAdipose tissue expression of lipodystrophy genes shows an association with MetS and its intermediate phenotypic traits. Mutations of these genes are known to cause congenital lipodystrophy syndromes, whereas their altered expression in adipose tissue contributes to the pathogenesis of IR, T2D, and MetS.

Associations of plasma phospholipid cis-vaccenic acid with insulin resistance markers in non-diabetic men with hyperlipidemia

BackgroundThe role of fatty acids (FA) in the pathogenesis of insulin resistance and hyperlipidemia is a subject of intensive research. Several recent works have suggested cis-vaccenic acid (cVA) in plasma lipid compartments, especially in plasma phospholipids (PL) or erythrocyte membranes, could be associated with markers of insulin sensitivity and cardiovascular health. Nevertheless, not all the results of research work testify to these beneficial effects of cVA. Therefore, we decided to investigate the relations of proportion of cVA in plasma PL to markers of insulin resistance in hyperlipidemic men.SubjectsIn 231 men (median age 50) with newly diagnosed hyperlipidemia, we analyzed basic clinical parameters together with FA composition of plasma PL and stratified them according to the content of cVA into upper quartile (Q4) and lower quartile (Q1) groups. We examined also small control group of 50 healthy men.ResultsThe individuals in Q4 differed from Q1 by lower plasma insulin (p < 0.05), HOMA-IR values (p < 0.01), and apolipoprotein B concentrations (p < 0.001), but by the higher total level of nonesterified FA (p < 0.01). Both groups had similar age, anthropometrical, and other lipid parameters. In plasma PL, the Q4 group had lower content of the sum of n-6 polyunsaturated FA, due to decrease of γ-linolenic and dihomo-γ-linolenic acids, whereas the content of monounsaturated FA (mainly oleic and palmitoleic) was in Q4 higher.ConclusionsOur results support hypothesis that plasma PL cVA could be associated with insulin sensitivity in men with hyperlipidemia.

Alterations in Choline Metabolism in Non-Obese Individuals with Insulin Resistance and Type 2 Diabetes Mellitus.

The prevalence of non-obese individuals with insulin resistance (IR) and type 2 diabetes (T2D) is increasing worldwide. This study investigates the metabolic signature of phospholipid-associated metabolites in non-obese individuals with IR and T2D, aiming to identify potential biomarkers for these metabolic disorders. The study cohort included non-obese individuals from the Qatar Biobank categorized into three groups: insulin sensitive, insulin resistant, and patients with T2D. Each group comprised 236 participants, totaling 708 individuals. Metabolomic profiling was conducted using high-resolution mass spectrometry, and statistical analyses were performed to identify metabolites associated with the progression from IS to IR and T2D. The study observed significant alterations in specific phospholipid metabolites across the IS, IR, and T2D groups. Choline phosphate, glycerophosphoethanolamine, choline, glycerophosphorylcholine (GPC), and trimethylamine N-oxide showed significant changes correlated with disease progression. A distinct metabolic signature in non-obese individuals with IR and T2D was characterized by shifts in choline metabolism, including decreased levels of choline and trimethylamine N-oxide and increased levels of phosphatidylcholines, phosphatidylethanolamines, and their degradation products. These findings suggest that alterations in choline metabolism may play a critical role in the development of glucose intolerance and insulin resistance. Targeting choline metabolism could offer potential therapeutic strategies for treating T2D. Further research is needed to validate these biomarkers and understand their functional significance in the pathogenesis of IR and T2D in non-obese populations.

Exploring the Effect of Exercise versus Metformin on Insulin Resistance amongst Nigerians with Pre-diabetes: A Randomised Controlled Trial.

Pre-diabetes is an important risk factor for the development of type 2 diabetes and is common in Nigeria. Effective intervention can reverse the underlying pathogenesis of insulin resistance in pre-diabetes. This study aimed to determine and compare the impact of moderate exercise and metformin interventions on insulin resistance among participants with pre-diabetes. Using a randomised placebo-controlled design, 54 Nigerians with pre-diabetes were selected using simple random sampling. They were offered metformin, moderate exercise or placebo treatment and followed up for 12 weeks. Insulin resistance was assessed before and after the interventions and the outcome was compared. Forty-nine participants with pre-diabetes completed the study. Participants in both the exercise and metformin groups had significantly decreased insulin resistance compared to placebo after 12 weeks of intervention. However, there was a decrease in insulin resistance by 77.3% (homeostasis model assessment-insulin resistance [HOMA-IR]) and an increase in insulin sensitivity by 81.2% (quantitative insulin sensitivity check index [QUICKI]) in the exercise group. In comparison, participants in the metformin group had a decrease in insulin resistance by 66.3% (HOMA-IR) and an increase in insulin sensitivity by 76.2% (QUICKI). Amongst Nigerians with pre-diabetes, both moderate exercise and metformin have significantly higher efficacy than placebo in improving insulin resistance. However, moderate exercise improved insulin resistance more than the metformin intervention. Participants in this study need to be followed up for a longer period to assess the long-term effects of these interventions.

Role of selenium in the pathogenesis of insulin resistance and diabetes mellitus

Role of selenium in the pathogenesis of insulin resistance and diabetes mellitus

The role of exosome derived miRNAs in inter-cell crosstalk among insulin-related organs in type 2 diabetes mellitus.

Exosomes are small extracellular vesicles secreted by almost all cell types, and carry diverse cargo including RNA, and other substances. Recent studies have focused exosomal microRNAs (miRNAs) on various human diseases, including type 2 diabetes mellitus (T2DM) and metabolic syndrome (METS) which accompany the occurrence of insulin resistance. The regulation of insulin signaling has connected with some miRNA expression which play a significant regulatory character in insulin targeted cells or organs, such as fat, muscle, and liver. The miRNAs carried by exosomes, through the circulation in the body fluids, mediate all kinds of physiological and pathological process involved in the human body. Studies have found that exosome derived miRNAs are abnormally expressed and cross-talked with insulin targeted cells or organs to affect insulin pathways. Further investigations of the mechanisms of exosomal miRNAs in T2DM will be valuable for the diagnostic biomarkers and therapeutic targets of T2DM. This review will summarize the molecular mechanism of action of the miRNAs carried by exosomes which are secreted from insulin signaling related cells, and elucidate the pathogenesis of insulin resistance to provide a new strategy for the potential diagnostic biomarkers and therapeutic targets for the type 2 diabetes.

Interleukin-38 and Insulin Resistance.

Insulin resistance, i.e., decreased biological response to insulin, is a risk factor for many diseases, such as obesity, type 2 diabetes (T2DM), cardiovascular disease, polycystic ovary syndrome, some forms of cancer and neurodegenerative diseases. One of its main causes is chronic low-grade inflammation, mediated by the proinflammatory pathways, such as the c-Jun N-terminal kinase (JNK) pathway and the nuclear factor kappa B (NFκB) pathway. Interleukin (IL)-38 (IL-38) is a newly discovered cytokine that belongs to the IL-1 family. There are three hypothetical pathways through which IL-38 may bind to the specific receptors and inhibit their proinflammatory activity. Those pathways are associated with IL-36 receptor (IL-36R), IL-1 receptor accessory protein-like 1 (IL1RAPL1) and IL-1 receptor 1 (IL1R1). There are studies linking IL-38 to improve insulin sensitivity through the difference in serum IL-38 in patients with insulin resistance or the correlation of IL-38 concentrations with insulin resistance indexes. However, many questions still remain regarding the biological activity of IL-38 itself and its role in the pathogenesis of insulin resistance. The goal of this study is to showcase IL-38, its biological activity, hypothesized signaling pathways, connection with insulin resistance and future perspectives of research on IL-38. We present that IL-38 associated signaling can be a potential target for the treatment of insulin resistance and associated diseases.

Gestational diabetes-related gut microbiome dysbiosis is not influenced by different Asian ethnicities and dietary interventions: a pilot study.

Gut microbiome dysbiosis contributes to the pathophysiology of both gestational diabetes mellitus (GDM) and its associated adverse outcomes in the woman and offspring. Even though GDM prevalence, complications, and outcomes vary among different ethnic groups, limited information is available about the influence of ethnicity on gut microbiome dysbiosis in pregnancies complicated by GDM. This pilot prospective cohort study examined the impact of ethnicity on gut dysbiosis in GDM among three Asian ethnic groups (Chinese, Malay, Indian) living in Singapore, and investigated the potential modulatory roles of diet and lifestyle modifications on gut microbiome post-GDM diagnosis. Women with GDM (n = 53) and without GDM (n = 16) were recruited. Fecal samples were collected at 24-28- and 36-40-weeks' gestation and analyzed by targeted 16S rRNA gene-based amplicon sequencing. Permutational multivariate analysis of variance (PERMANOVA) analysis was performed to evaluate differences between groups. Differentially abundant taxa were identified by DeSeq2 based analysis. Functional prediction was performed using thephylogeneticinvestigation of communities by reconstruction of unobserved states (PICRUSt2). Among women with GDM, gut microbiome from different ethnicities harbored common microbial features. However, among those without GDM, there was contrasting microbiome composition between ethnic groups. Microbial members such as Collinsella, Blautia, Ruminococcus, Ruminococcus gnavus, Ruminococcus torques, and Eubacterium hallii groups were differentially enriched (p < 0.05) in women with GDM compared to those without. Among women with GDM, no differences in alpha- and beta- diversity were observed when comparing 24-28weeks' samples with 36-40weeks' samples, a period covering intense dietary and lifestyle modification, suggesting an inability to modulate gut microbiota through classic GDM management. Women with GDM have a distinct gut microbiome profile which harbours common features across different Asian ethnic groups, consistent with the notion that specific microbes are involved in the pathogenesis of insulin resistance, pro-inflammatory conditions, and other metabolic dysregulation known to be present in GDM.

NAMPT, IL-6, and vaspin gene expressions and serum protein levels in type 2 diabetes mellitus and related complication.

Type 2 diabetes mellitus (T2DM) is the most common type of diabetes and occurs due to insufficient insulin secretion or inability to use existing insulin and the effects of environmental factors. Although there are many studies on the pathophysiology of T2DM, the mechanisms contributing to the pathogenesis of insulin resistance and pancreatic beta-cell dysfunction have not been completely elucidated. Some adipokines secreted from adipose tissue, which are the primary regulators of insulin resistance, affect immune and inflammatory functions. Altered adipokine profiles have been observed in obesity and T2DM, leading to severe metabolic risks and changes in insulin sensitivity. This study used quantitative PCR and ELISA techniques to analyze samples from individuals without diabetes (control group) and with T2DM (macrovascular and microvascular complications and without complications) for at least 10 years. The mRNA expression and protein levels of NAMPT, IL-6, and vaspin genes were determined. While there was no significant difference in NAMPT, IL-6, and vaspin mRNA expression levels between diabetic groups, there was a significant decrease between the patient and control groups (p < 0.001). For serum protein levels, NAMPT protein levels decreased significantly in the uncomplicated group, while IL-6 and vaspin protein levels increased significantly in both microvascular and macrovascular complication groups (p < 0.001). The correlations between gene expressions, clinical parameters, and protein levels are crucial to understanding the implications of the findings.

Assessing the impact of body composition, metabolic and oxidative stress parameters on insulin resistance as a prognostic marker for reactive hypoglycemia: a cross-sectional study in overweight, obese, and normal weight individuals.

Oxidative stress (OS) plays a pivotal role in the pathogenesis of insulin resistance (IR), particularly in its association with obesity. This study evaluate both the diagnostic and clinical significance of assessing oxidative status in patients affected by overweight and obesity displaying IR, especially with reactive hypoglycemic episodes (RH). A comprehensive examination of OS biomarkers was carried out, encompassing measurements of total oxidative capacity (TOC) and total antioxidant capacity (TAC). Our analysis results reveal noteworthy connections between OS levels and the severity of IR in overweight and obese patients. Moreover, in the study, we demonstrated the diagnostic utility of serum concentrations of TAC and TOC as indicators of the risk of RH, the occurrence of which, even at the stage of overweight, may be associated with increased OS and further development of obesity. Our findings imply that the evaluation of oxidative status could serve as a crucial diagnostic and prognostic tool for patients observed with IR and overweight and obesity. In conclusion, our study underscores the potential utility of assessing oxidative status in the context of IR and highlights the possibility of identifying novel therapeutic targets for the treatment of overweight and obese patients.

The Role of GABA and Insulin Regulated Aminopeptidase on Insulin Resistance and GLUT4 in Prediabetes and Type 2 Diabetes Mellitus

Background: Different proposed mechanisms for insulin resistance have been put forth to understand the relationship and changes in insulin resistance. Looking at the levels of insulin, the neurotransmitter gamma-aminobutyric acid, glucose transport type 4, and the newly discovered enzyme insulin regulated aminopeptidase may provide an integrated perspective on insulin resistance. Objectives: To study the role of serum gamma-aminobutyric acid and insulin regulated aminopeptidase enzyme levels in pathogenesis of insulin resistance and translocation of glucose transport type 4 in patients with type2 diabetes mellitus and pre-diabetes ones. Subjects and methods: Ninety individuals were divided into three age- and BMI matched groups (diabetics, prediabetics, healthy) were assessed for glycated hemoglobin (turbidometry method), fasting serum glucose (colorimetric method), serum insulin (electrochemiluminescence immunoassay method), homeostatic model assessment for insulin resistance, serum gamma-aminobutyric acid, glucose transporter type 4, and insulin regulated aminopeptidase measured by the sandwich ELISA method. The cut-off value was adopted according to the World Health Organization, individuals with their fasting serum glucose lower than 110 mg/ml, and glycated hemoglobin level not more than 5.7 % are considered healthy individuals. Result: The mean (±SD) values of serum insulin regulated aminopeptidase, gamma-aminobutyric acid and glucose transport type 4 showed significantly lower levels with greater increases in insulin resistance, represented by the significant decrease in diabetics group who have high insulin resistance compared with pre-diabetics and healthy individuals’ groups (p &lt; 0.05). They also significantly decrease in individuals with the pre-diabetic stage compared to healthy individuals without insulin resistance (p &lt; 0.05). Significant negative correlations were found between HOMA-IR values and each of GABA, IRAP, and GLUT4. Conclusion: Decreasing gamma-aminobutyric acid may promote insulin resistance and prediabetes/diabetes onset. Decreased insulin regulated aminopeptidase levels suggest a role alongside glucose transport type 4 in glucose uptake, allowing screening for prediabetes risk.

Genetic Causal Relationship Between Alanine Aminotransferase Levels and Risk of Gestational Diabetes Mellitus: Mendelian Randomization Analysis Based on Two Samples.

Gestational diabetes mellitus (GDM) is a frequent complication of pregnancy. The specific mechanisms underlying GDM have not yet been fully elucidated. Contemporary research indicates a potential association between liver enzyme irregularities and an increased risk of metabolic disorders, including diabetes. The alanine aminotransferase (ALT) level is recognized as a sensitive marker of liver injury. An increase in ALT levels is hypothesized to be linked to the pathogenesis of insulin resistance and diabetes. Nonetheless, the definitive causal link between ALT levels and GDM still needs to be determined. This investigation utilized two-sample Mendelian randomization (MR) to examine the genetic causation between alanine aminotransferase (ALT) and GDM. We acquired alanine aminotransferase (ALT)-related GWAS summary data from the UK Biobank, Million Veteran Program, Rotterdam Study, and Lifeline Study. Gestational diabetes data were obtained from the FinnGen Consortium. We employed various MR analysis techniques, including inverse-variance weighted (IVW), MR Egger, weighted median, simple, and weighted weighting. In addition to MR-Egger intercepts, Cochrane's Q test was also used to assess heterogeneity in the MR data, and the MR-PRESSO test was used to assess horizontal pleiotropy. To assess the association's sensitivity, a leave-one-out approach was employed. The IVW results confirmed the independent risk factor for GDM development, as indicated by the ALT level (p = .011). As shown by leave-one-out analysis, horizontal pleiotrophy did not significantly skew the causative link (p > .05). Our dual-sample MR analysis provides substantiated evidence of a genetic causal relationship between alanine aminotransferase (ALT) levels and gestational diabetes.

Kaempferol alleviates adipose tissue inflammation and insulin resistance in db/db mice by inhibiting the STING/NLRP3 signaling pathway.

Chronic inflammation induced by obesity plays a crucial role in the pathogenesis of insulin resistance. The infiltration of macrophages into adipose tissues contributes to adipose tissue inflammation and insulin resistance. Kaempferol, a flavonoid present in various vegetables and fruits, has been shown to possess remarkable anti-inflammatory properties. In this study, we used leptin receptor-deficient obese mice (db/db) as an insulin-resistant model and investigated the effects of kaempferol treatment on obesity-induced insulin resistance. Our findings revealed that the administration of kaempferol (50 mg/kg/day, for 6 weeks) significantly reduced body weight, fat mass, and adipocyte size. Moreover, it effectively ameliorated abnormal glucose tolerance and insulin resistance in db/db mice. In the adipose tissue of obese mice treated with kaempferol, we observed a reduction in macrophage infiltration and a downregulation of mRNA expression of M1 marker genes TNF-α and IL-1β, accompanied by an upregulation of Arg1 and IL-10 mRNA expression. Additionally, kaempferol treatment significantly inhibited the STING/NLRP3 signaling pathway in adipose tissue. In vitro experiments, we further discovered that kaempferol treatment suppressed LPS-induced inflammation through the activation of NLRP3/caspase 1 signaling in RAW 264.7 macrophages. Our results suggest that kaempferol may effectively alleviate inflammation and insulin resistance in the adipose tissue of db/db mice by modulating the STING/NLRP3 signaling pathway.

Post-traumatic stress disorder, dyssomnias, and metabolic syndrome

Post-traumatic stress disorder (PTSD) and metabolic syndrome (MetS) frequently coexist and share neurobiological and clinical features. In particular, the results of meta-analyses indicate a higher prevalence of MetS in patients with PTSD compared to the general population. PTSD is also a recognized risk factor for MetS. This synchronicity can be partially explained by pathogenetic pathways present in both conditions. These include genetic factors, dysfunction of the hypothalamic-pituitary-adrenal axis, chronic low-grade inflammation, oxidative stress, insulin resistance, and immune dysregulation. Thus, similar mechanisms are involved in the clinical worsening of PTSD and the development of adverse cardiovascular events associated with MetS. Dyssomnias are one of the characteristic clinical features of PTSD. Today, it is believed that posttraumatic circadian rhythm disorders are the core and not a secondary feature of PTSD, which mediate the neurobiological correlates of disorders due to homeostasis imbalance. At the same time, dyssomnias, chronodestruction, and depressive disorders are part of the pathogenesis of insulin resistance, obesity, and MetS. Thus, treatment of dyssomnias is one of the key tasks in the prevention and treatment of comorbid PTSD and MetS. Regulation of sleep processes and circadian rhythms through exogenous intervention, especially with melatonergic drugs, is likely to be a key part of preventing and treating dyssomnias in people who have both PTSD and MetS. The purpose of this review is to analyze the specifics of the relationships between PTSD and MetS, PTSD and dyssomnias, MetS and sleep disorders. We conducted the search in Scopus, Science Direct (from Elsevier), and PubMed, including Medline databases. The key words used were “post-traumatic stress disorder,” “dyssomnias,” “chronodestruction,” and “metabolic syndrome”. The identification of research findings that were not found during online searches involved manual searching of the bibliography of publications.

Assessment of the triglyceride glucose index in adult patients with chronic diarrhea and constipation.

Accumulating evidence suggests that the gut microbiome is involved in the pathogenesis of insulin resistance (IR). However, the link between two of the most prevalent bowel disorders, chronic diarrhea and constipation, and the triglyceride glucose (TyG) index, a marker of IR, has not yet been investigated. To investigate the potential association between TyG and the incidence of chronic diarrhea and constipation. This cross-sectional study enrolled 2400 participants from the National Health and Nutrition Examination Survey database from 2009-2010. TyG was used as an exposure variable, with chronic diarrhea and constipation as determined by the Bristol Stool Form Scale used as the outcome variables. A demographic investigation based on TyG quartile subgroups was performed. The application of multivariate logistic regression models and weighted generalized additive models revealed potential correlations between TyG, chronic diarrhea, and constipation. Subgroup analyses were performed to examine the stability of any potential associations. In the chosen sample, chronic diarrhea had a prevalence of 8.00%, while chronic constipation had a prevalence of 8.04%. In multiple logistic regression, a more prominent positive association was found between TyG and chronic diarrhea, particularly in model 1 (OR = 1.45; 95%CI: 1.17-1.79, P = 0.0007) and model 2 (OR = 1.40; 95%CI: 1.12-1.76, P = 0.0033). No definite association was observed between the TyG levels and chronic constipation. The weighted generalized additive model findings suggested a more substantial positive association with chronic diarrhea when TyG was less than 9.63 (OR = 1.89; 95%CI: 1.05-3.41, P = 0.0344), and another positive association with chronic constipation when it was greater than 8.2 (OR = 1.74; 95%CI: 1.02-2.95, P = 0.0415). The results of the subgroup analyses further strengthen the extrapolation of these results to a wide range of populations. Higher TyG levels were positively associated with abnormal bowel health.

DNA methylation mediates the effects of PM2.5 and O3 on ceramide metabolism: A novel mechanistic link between air pollution and insulin resistance

Insulin resistance (IR), linked to air pollution, is an initial stage of early-onset Type 2 diabetes mellitus (T2DM). While ceramide metabolism plays an important role in IR pathogenesis, the effects of air pollution on this process and its mechanisms remain unclear. We recruited young adults aged 18–30 years to a panel study in Wuhan, China. Using personal portable devices and stationary monitoring stations, we tracked particulate matter with aerodynamic diameters≤ 2.5 µm (PM2.5) and Ozone (O3) levels. Liquid chromatography/mass spectrometry (LC-MS) based metabolomics quantified ceramide metabolism, and Illumina Infinium Human Methylation 850 kBeadChip assay measured deoxyribonucleic acid (DNA) methylation. Linear mixed-effects models assessed relationships of air pollution with i) IR indexes, ii) ceramide metabolism, and iii) DNA methylation. Mediation analysis was subsequently performed to evaluate the potential mediating effect of DNA methylation in the association between air pollution and ceramide metabolism. PM2.5 and O3 were associated with elevated IR. Specifically, each 10 μg/m3 increase in PM2.5 and O3 at lag0–12 h significantly increased triglyceride‑glucose index (TyG index) and TyG-BMI (TyG - Body mass index) by 0.88%, 0.89% and 0.26%, 0.26%, respectively. Furthermore, levels of eight ceramides were altered by air pollution exposure, and nine methylated CpG sites in inflammation genes mediated the effects of air pollution on ceramide metabolism. Our findings imply the existence of a novel mechanism connecting air pollution to IR.

Association of insulin resistance with the accumulation of saturated intramyocellular lipid: A comparison with other fat stores.

It has been shown using proton magnetic resonance spectroscopy (1H MRS) that, in a group of females, whole-body insulin resistance was more closely related to accumulation of saturated intramyocellular lipid (IMCL) than to IMCL concentration alone. This has not been investigated in males. We investigated whether age- and body mass index-matched healthy males differ from the previously reported females in IMCL composition (measured as CH2:CH3) and IMCL concentration (measured as CH3), and in their associations with insulin resistance. We ask whether saturated IMCL accumulation is more strongly associated with insulin resistance than other ectopic and adipose tissue lipid pools and remains a significant predictor when these other pools are taken into account. In this group of males, who had similar overall insulin sensitivity to the females, IMCL was similar between sexes. The males demonstrated similar and even stronger associations of IMCL with insulin resistance, supporting the idea that a marker reflecting the accumulation of saturated IMCL is more strongly associated with whole-body insulin resistance than IMCL concentration alone. However, this marker ceased to be a significant predictor of whole-body insulin resistance after consideration of other lipid pools, which implies that this measure carries no more information in practice than the other predictors we found, such as intrahepatic lipid and visceral adipose tissue. As the marker of saturated IMCL accumulation appears to be related to these two predictors and has a much smaller dynamic range, this finding does not rule out a role for it in the pathogenesis of insulin resistance.

Macrophage CREBZF Orchestrates Inflammatory Response to Potentiate Insulin Resistance and Type 2 Diabetes.

Chronic adipose tissue inflammation accompanied by macrophage accumulation and activation is implicated in the pathogenesis of insulin resistance and type 2 diabetes in humans. The transcriptional coregulator CREBZF is a key factor in hepatic metabolism, yet its role in modulating adipose tissue inflammation and type 2 diabetes remains elusive. The present study demonstrates that overnutrition-induced CREBZF links adipose tissue macrophage (ATM) proinflammatory activation to insulin resistance. CREBZF deficiency in macrophages, not in neutrophils, attenuates macrophage infiltration in adipose, proinflammatory activation, and hyperglycemia in diet-induced insulin-resistant mice. The coculture assays show that macrophage CREBZF deficiency improves insulin sensitivity in primary adipocytes and adipose tissue. Mechanistically, CREBZF competitively inhibits the binding of IκBα to p65, resulting in enhanced NF-κB activity. In addition, bromocriptine is identified as a small molecule inhibitor of CREBZF in macrophages, which suppresses the proinflammatory phenotype and improves metabolic dysfunction. Furthermore, CREBZF is highly expressed in ATM of obese humans and mice, which is positively correlated with proinflammatory genes and insulin resistance in humans. This study identifies a previously unknown role of CREBZF coupling ATM activation to systemic insulin resistance and type 2 diabetes.

Lacking P2X7-receptors protects substantia nigra dopaminergic neurons and hippocampal-related cognitive performance from the deleterious effects of high-fat diet exposure in adult male mice.

Dietary fat consumption, involved in the pathogenesis of insulin resistance and impaired glucose metabolism, is linked with decline in cognitive functions, dementia, and development of Parkinson's disease and Alzheimer's disease. Mature IL-1β, requiring the activation of the P2X7 receptor (P2X7R)-inflammasome complex, is an important mediator of neuroinflammation. The aim of the study was to test whether P2X7R activation might interfere with systemic and cerebral metabolic homeostasis. We treated WT and P2X7R KO mice with a high-fat diet (HFD) for 16 weeks, evaluating the effects on the Substantia Nigra and Hippocampus, target areas of damage in several forms of cognitive impairment. HFD-treated WT and P2X7R KO mice showed a different brain mRNA profile of Insulin and Igf-1, with these genes and relative receptors, more expressed in KO mice. Unlike P2X7R KO mice, WT mice treated with HFD displayed a diameter reduction in dopaminergic neurons in the Substantia Nigra, accompanied by an increased IBA1 expression in this area; they also showed poor performances during Y-Maze and Morris Water Maze, tasks involving Hippocampus activity. Conversely, Parkin, whose reduction might promote neuronal cell death, was increased in the brain of P2X7R KO animals. We report for the first time that HFD induces damage in dopaminergic neurons of the Substantia Nigra and a Hippocampus-related worse cognitive performance, both attenuated in the absence of P2X7R. The involved mechanisms might differ in the two brain areas, with a predominant role of inflammation in the Substantia Nigra and a metabolic derangement in the Hippocampus.

Hexokinase-linked glycolytic overload and unscheduled glycolysis in hyperglycemia-induced pathogenesis of insulin resistance, beta-cell glucotoxicity, and diabetic vascular complications.

Hyperglycemia is a risk factor for the development of insulin resistance, beta-cell glucotoxicity, and vascular complications of diabetes. We propose the hypothesis, hexokinase-linked glycolytic overload and unscheduled glycolysis, in explanation. Hexokinases (HKs) catalyze the first step of glucose metabolism. Increased flux of glucose metabolism through glycolysis gated by HKs, when occurring without concomitant increased activity of glycolytic enzymes-unscheduled glycolysis-produces increased levels of glycolytic intermediates with overspill into effector pathways of cell dysfunction and pathogenesis. HK1 is saturated with glucose in euglycemia and, where it is the major HK, provides for basal glycolytic flux without glycolytic overload. HK2 has similar saturation characteristics, except that, in persistent hyperglycemia, it is stabilized to proteolysis by high intracellular glucose concentration, increasing HK activity and initiating glycolytic overload and unscheduled glycolysis. This drives the development of vascular complications of diabetes. Similar HK2-linked unscheduled glycolysis in skeletal muscle and adipose tissue in impaired fasting glucose drives the development of peripheral insulin resistance. Glucokinase (GCK or HK4)-linked glycolytic overload and unscheduled glycolysis occurs in persistent hyperglycemia in hepatocytes and beta-cells, contributing to hepatic insulin resistance and beta-cell glucotoxicity, leading to the development of type 2 diabetes. Downstream effector pathways of HK-linked unscheduled glycolysis are mitochondrial dysfunction and increased reactive oxygen species (ROS) formation; activation of hexosamine, protein kinase c, and dicarbonyl stress pathways; and increased Mlx/Mondo A signaling. Mitochondrial dysfunction and increased ROS was proposed as the initiator of metabolic dysfunction in hyperglycemia, but it is rather one of the multiple downstream effector pathways. Correction of HK2 dysregulation is proposed as a novel therapeutic target. Pharmacotherapy addressing it corrected insulin resistance in overweight and obese subjects in clinical trial. Overall, the damaging effects of hyperglycemia are a consequence of HK-gated increased flux of glucose metabolism without increased glycolytic enzyme activities to accommodate it.