Mediator Of Insulin Resistance Research Articles

JMJD8 regulates adipocyte hypertrophy through the interaction with Perilipin 2.

Adipocyte hypertrophy significantly contributes to insulin resistance and metabolic dysfunction. Our previous research established JMJD8 as a mediator of insulin resistance, noting its role in promoting adipocyte hypertrophy within an autonomous adipocyte context. Nevertheless, the precise mechanisms underlying this phenomenon remained elusive. In this study, we employed a proteomics approach to identify Perilipin 2 (PLIN2), a lipid-associated protein, as a binding partner of JMJD8. Our investigations unveiled a robust interaction between JMJD8 and PLIN2, demonstrating its pivotal role in driving adipocyte hypertrophy and promoting insulin resistance. Furthermore, we show that JMJD8 suppresses fasting-induced lipophagy and curtails energy production, which involves inhibition of PLIN2 phosphorylation. These findings underscore the critical roles played by JMJD8 and PLIN2 in governing lipid droplet homeostasis, while also shedding light on a potential regulatory mechanism governing fat store mobilization during energy deprivation.

A Population-Based Study of the Mediating Role of WBC, NEUT and PLT in the Relationship Between Triglyceride-Glucose Index and Urinary Albumin Excretion.

To assess the potential association between the TyG index and the risk of abnormal UACR. Additionally, we aimed to determine the role and degree of influence of inflammatory biomarkers between the TyG index and abnormal UACR. A cross-sectional study recruited 1021 participants from a health management center between 2021 and 2022. Logistic or linear regression models, as well as mediation analysis, were employed to investigate the associations between the TyG index, inflammatory biomarkers (total and differential white blood cell counts, platelet, mean platelet volume(MPV), C-reactive protein(CRP)), and the risk of abnormal UACR. The study included 1021 participants, of whom 55.0% were men. The median age (interquartile range [IQR]) was 61.0 (53, 70) years. In multivariable-adjusted logistic regression models, both with and without the inclusion of smoking, alcohol drinking, BMI, Lipid-lowering drugs using, TC, SUA, ALT, and AST as potential covariates, the TyG index was associated with the risk of UACR, both with the odds ratios (ORs) per 1-standard deviation (SD) increase were 1.32 (95% CI, 1.08-1.62) and 1.27 (95% CI, 1.05-1.52), respectively. This study also demonstrated a significant indirect effect of the TyG index on the risk of abnormal UACR through total white blood cell counts, neutrophil counts and platelet (P values < 0.05); The proportions mediated was 11.2%, 3.5% and 29.6% for each respective variable. Insulin resistance and inflammation are associated with an increased risk of kidney insufficiency. And indicators of inflammation weakly mediate insulin resistance and risk of kidney insufficiency.

Endothelial β1-integrins are necessary for microvascular function and glucose uptake.

Microvascular insulin delivery to myocytes is rate limiting for the onset of insulin-stimulated muscle glucose uptake. The structural integrity of capillaries of the microvasculature is regulated, in part, by a family of transmembrane adhesion receptors known as integrins, which are composed of an α and a β subunit. The integrin β1 (itgβ1) subunit is highly expressed in endothelial cells (ECs). EC itgβ1 is necessary for the formation of capillary networks during embryonic development, and its knockdown in adult mice blunts the reactive hyperemia that manifests during ischemia reperfusion. In this study, we investigated the contribution of EC itgβ1 in microcirculatory function and glucose uptake, with an emphasis on skeletal muscle. We hypothesized that loss of EC itgβ1 would impair microvascular hemodynamics and glucose uptake during insulin stimulation, creating "delivery"-mediated insulin resistance. An itgβ1 knockdown mouse model was developed to avoid the lethality of embryonic gene knockout and the deteriorating health resulting from early postnatal inducible gene deletion. We found that mice with (itgβ1fl/flSCLcre) and without (itgβ1fl/fl) inducible stem cell leukemia cre recombinase (SLCcre) expression at 10 days post cre induction have comparable exercise tolerance and pulmonary and cardiac functions. We quantified microcirculatory hemodynamics using intravital microscopy and the ability of mice to respond to the high metabolic demands of insulin-stimulated muscle using a hyperinsulinemic-euglycemia clamp. We show that itgβ1fl/flSCLcre mice compared with itgβ1fl/fl littermates have 1) deficits in capillary flow rate, flow heterogeneity, and capillary density; 2) impaired insulin-stimulated glucose uptake despite sufficient transcapillary insulin efflux; and 3) reduced insulin-stimulated glucose uptake due to perfusion-limited glucose delivery. Thus, EC itgβ1 is necessary for microcirculatory function and to meet the metabolic challenge of insulin stimulation.NEW & NOTEWORTHY The microvasculature is an important site of resistance to muscle glucose uptake. We show that microvasculature integrins determine the exchange of glucose between the circulation and muscle. Specifically, a 30% reduction in the expression of endothelial integrin β1 subunit is sufficient to cause microcirculatory dysfunction and lead to insulin resistance. This emphasizes the importance of endothelial integrins in microcirculatory function and the importance of microcirculatory function for the ability of muscle to consume glucose.

Sex- and age-associated factors drive the pathophysiology of MASLD.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is strongly associated with obesity. Sex and age affect MASLD prevalence and pathophysiology. The use of animal models fed Western-style diets is vital for investigating the molecular mechanisms contributing to metabolic dysregulation and for facilitating novel drug target identification. However, the sex-associated and age-associated mechanisms underlying the pathophysiology remain poorly understood. This knowledge gap limits the development of personalized sex-specific and age-specific drug treatments. Young (7wk) and aged (52wk) male and female mice were fed a high-fat diet (HFD) or low-fat diet. Liver metabolome (>600 molecules) and transcriptome profiles were analyzed. Male and female mice fed an HFD developed obesity, glucose intolerance, and hepatic steatosis. However, fasting blood glucose, insulin, and serum alanine aminotransferase levels were higher in males fed an HFD, indicating a more severe metabolic disease. In addition, males showed significant increases in liver diacylglycerides and glycosylceramides (known mediators of insulin resistance and fibrosis), and more changes in the transcriptome: extracellular matrix organization and proinflammatory genes were elevated only in males. In contrast, no major increase in damaging lipid classes was observed in females fed an HFD. However, aging affected the liver to a greater extent in females. Acylcarnitine levels were significantly reduced, suggestive of changes in fatty acid oxidation, and broad changes in the transcriptome were observed, including reduced oxidative stress response gene expression and alterations in lipid partitioning genes. Here, we show distinct responses to an HFD between males and females. Our study underscores the need for using both sexes in drug target identification studies, and characterizing the molecular mechanisms contributing to the MASLD pathophysiology in aging animals.

Endothelial β1 Integrins are Necessary for Microvascular Function and Glucose Uptake.

Microvascular insulin delivery to myocytes is rate limiting for the onset of insulin-stimulated muscle glucose uptake. The structural integrity of capillaries of the microvasculature is regulated, in part, by a family of transmembrane adhesion receptors known as integrins, which are composed of an α and β subunit. The integrin β1 (itgβ1) subunit is highly expressed in endothelial cells (EC). EC itgβ1 is necessary for the formation of capillary networks during embryonic during development and its knockdown in adult mice blunts the reactive hyperemia that manifests during ischemia reperfusion. In this study we investigated the contribution of skeletal muscle EC itgβ1 in microcirculatory function and glucose uptake. We hypothesized that loss of EC itgβ1 would impair microvascular hemodynamics and glucose uptake during insulin stimulation, creating 'delivery'-mediated insulin resistance. An itgβ1 knockdown mouse model was developed to avoid lethality of embryonic gene knockout and the deteriorating health resulting from early post-natal inducible gene deletion. We found that mice with (itgβ1fl/flSCLcre) and without (itgβ1fl/fl) inducible stem cell leukemia cre recombinase (SLCcre) expression at 10 days post cre induction have comparable exercise tolerance and pulmonary and cardiac functions. We quantified microcirculatory hemodynamics using intravital microscopy and the ability of mice to respond to the high metabolic demands of insulin-stimulated muscle using a hyperinsulinemic-euglycemia clamp. We show that itgβ1fl/flSCLcre mice compared to itgβ1fl/fl littermates have, i) deficits in capillary flow rate, flow heterogeneity, and capillary density; ii) impaired insulin-stimulated glucose uptake despite sufficient transcapillary insulin efflux; and iii) reduced insulin-stimulated glucose uptake due to perfusion-limited glucose delivery. Thus, EC itgβ1 is necessary for microcirculatory function and to meet the metabolic challenge of insulin stimulation.

Gut microbiota metabolite tyramine ameliorates high-fat diet-induced insulin resistance via increased Ca2+ signaling

The gut microbiota and their metabolites are closely linked to obesity-related diseases, such as type 2 diabetes, but their causal relationship and underlying mechanisms remain largely elusive. Here, we found that dysbiosis-induced tyramine (TA) suppresses high-fat diet (HFD)-mediated insulin resistance in both Drosophila and mice. In Drosophila, HFD increases cytosolic Ca2+ signaling in enterocytes, which, in turn, suppresses intestinal lipid levels. 16 S rRNA sequencing and metabolomics revealed that HFD leads to increased prevalence of tyrosine decarboxylase (Tdc)-expressing bacteria and resulting tyramine production. Tyramine acts on the tyramine receptor, TyrR1, to promote cytosolic Ca2+ signaling and activation of the CRTC-CREB complex to transcriptionally suppress dietary lipid digestion and lipogenesis in enterocytes, while promoting mitochondrial biogenesis. Furthermore, the tyramine-induced cytosolic Ca2+ signaling is sufficient to suppress HFD-induced obesity and insulin resistance in Drosophila. In mice, tyramine intake also improves glucose tolerance and insulin sensitivity under HFD. These results indicate that dysbiosis-induced tyramine suppresses insulin resistance in both flies and mice under HFD, suggesting a potential therapeutic strategy for related metabolic disorders, such as diabetes.

AMPK Regulates M1 Macrophage Polarization through the JAK2/STAT3 Signaling Pathway to Attenuate Airway Inflammation in Obesity-Related Asthma.

Abstract-Obesity-related asthma is primarily characterized by nonallergic inflammation, with pathogenesis involving oxidative stress, metabolic imbalance, and immunoinflammatory mechanisms. M1 macrophages, which predominantly secrete pro-inflammatory factors, mediate insulin resistance and systemic metabolic inflammation in obese individuals. Concurrently, adenosine monophosphate-activated protein kinase (AMPK) serves as a critical regulator of intracellular energy metabolism and is closely associated with macrophage activation. However, their specific roles and associated mechanisms in obesity-related asthma remain to be explored. In this study, we investigated the macrophage polarization status and potential interventional mechanisms through obesity-related asthmatic models and lipopolysaccharide (LPS) -treated RAW264.7 cell with a comprehensive series of evaluations, including HE, PAS and Masson staining of lung histopathology, immunohistochemical staining, immunofluorescence technology, qRT-PCR, Western Blot, and ELISA inflammatory factor analysis. The results revealed M1 macrophage polarization in obesity-related asthmatic lung tissue alongside downregulation of AMPK expression. Under LPS stimulation, exogenous AMPK activation attenuated M1 macrophage polarization via the Janus kinase 2/ signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway. Additionally, in obesity-related asthmatic mice, AMPK activation was found to alleviate airway inflammation by regulating M1 macrophage polarization, the mechanism closely associated with the JAK2/STAT3 pathway. These findings not only advance our understanding of macrophage polarization in obesity-related asthma, but also provide new therapeutic targets for its treatment.

JAK/STAT mediated insulin resistance in muscles is essential for effective immune response

BackgroundThe metabolically demanding nature of immune response requires nutrients to be preferentially directed towards the immune system at the expense of peripheral tissues. We study the mechanisms by which this metabolic reprograming occurs using the parasitoid infection of Drosophila larvae. To overcome such an immune challenge hemocytes differentiate into lamellocytes, which encapsulate and melanize the parasitoid egg. Hemocytes acquire the energy for this process by expressing JAK/STAT ligands upd2 and upd3, which activates JAK/STAT signaling in muscles and redirects carbohydrates away from muscles in favor of immune cells.MethodsImmune response of Drosophila larvae was induced by parasitoid wasp infestation. Carbohydrate levels, larval locomotion and gene expression of key proteins were compared between control and infected animals. Efficacy of lamellocyte production and resistance to wasp infection was observed for RNAi and mutant animals.ResultsAbsence of upd/JAK/STAT signaling leads to an impaired immune response and increased mortality. We demonstrate how JAK/STAT signaling in muscles leads to suppression of insulin signaling through activation of ImpL2, the inhibitor of Drosophila insulin like peptides.ConclusionsOur findings reveal cross-talk between immune cells and muscles mediates a metabolic shift, redirecting carbohydrates towards immune cells. We emphasize the crucial function of muscles during immune response and show the benefits of insulin resistance as an adaptive mechanism that is necessary for survival.

Chronic intermittent hypoxia-induced oxidative stress activates TRB3 and phosphorylated JNK to mediate insulin resistance and cell apoptosis in the pancreas.

This study explores the potential mechanisms of obstructive sleep apnoea (OSA) complicates type 2 diabetes mellitus (T2DM) by which chronic intermittent hypoxia (CIH) induces insulin resistance and cell apoptosis in the pancreas through oxidative stress. Four- and eight-week CIH rat models were established, and Tempol (100 mg/kg/d), was used as an oxidative stress inhibitor. This study included five groups: 4-week CIH, 4-week CIH-Tempol, 8-week CIH, 8-week CIH-Tempol and normal control (NC) groups. Fasting blood glucose and insulin levels were measured in the serum. The expression levels of 8-hidroxy-2-deoxyguanosine (8-OHdG), tribbles homologue 3 (TRB3), c-Jun N-terminal kinase (JNK), phosphorylated JNK (p-JNK), insulin receptor substrate-1 (IRS-1), phosphorylated IRS-1 (Ser307) (p-IRS-1ser307 ), protein kinase B (AKT), phosphorylated AKT (Ser473) (p-AKTser473 ), B cell lymphoma protein-2 (Bcl-2), cleaved-caspase-3 (Cl-caspase-3), and the islet cell apoptosis were detected in the pancreas. CIH induced oxidative stress in the pancreas. Compared with that in the NC group and CIH-Tempol groups individually, the homeostasis model assessment of insulin resistance (HOMA-IR) and apoptosis of islet cells was increased in the CIH groups. CIH-induced oxidative stress increased the expression of p-IRS-1Ser307 and decreased the expression of p-AKTSer473 . The expression levels of TRB3 and p-JNK were higher in the CIH groups than in both the CIH-Tempol and NC groups. Meanwhile, the expressions of Cl-caspase-3 and Bcl-2 were upregulated and downregulated, respectively, in the CIH groups. Hence, the present study demonstrated that CIH-induced oxidative stress might not only induce insulin resistance but also islet cell apoptosis in the pancreas through TRB3 and p-JNK.

The role of branched-chain amino acids and their downstream metabolites in mediating insulin resistance.

Elevated levels of circulating branched-chain amino acids (BCAAs) and their associated metabolites have been strongly linked to insulin resistance and type 2 diabetes. Despite extensive research, the precise mechanisms linking increased BCAA levels with these conditions remain elusive. In this review, we highlight the key organs involved in maintaining BCAA homeostasis and discuss how obesity and insulin resistance disrupt the intricate interplay among these organs, thus affecting BCAA balance. Additionally, we outline recent research shedding light on the impact of tissue-specific or systemic modulation of BCAA metabolism on circulating BCAA levels, their metabolites, and insulin sensitivity, while also identifying specific knowledge gaps and areas requiring further investigation. Finally, we summarize the effects of BCAA supplementation or restriction on obesity and insulin sensitivity.

Abelmoschus esculentus Improves Hippocampal Function Associated with Dipeptidyl Peptidase‐4 in High Fat Diet‐Fed db/db Mice

Hippocampal function can be impaired by diabetes mellitus (DM) and obesity. Abelmoschus esculentus (AE) fractions reportedly mitigate the symptoms of Alzheimer’s disease (AD) by downregulating dipeptidyl peptidase‐4 (DPP‐4)‐mediated insulin resistance. AE extracted by alcohol (fraction 1, F1) and water (fraction 2, F2) contained quercetin glycosides and polysaccharides, respectively. In this study, we investigated whether AE affects hippocampal function in in vitro and in vivo systems. Our results indicate that F1 or F2 enhanced neurogenesis and synapse formation in palmitate‐treated hippocampal neural cells, presumably by downregulating DPP‐4. In db/db mice fed with high fat diet, the hippocampal insulin resistance correlated spatial recognition, with fraction F2 improving hippocampal function. Of note, the alteration of neurogenesis seems interconnecting with changes in gut microbiota. In summary, AE can improve hippocampal function, attenuate insulin resistance, and promote neurogenesis by regulating DPP‐4. AE, particularly F2, has the potential to serve as an adjuvant in preventing DM‐associated AD.

Olive Oil's Attenuating Effects on Lipotoxicity.

Dietary fatty acids play a role in the pathogenesis of obesity-associated nonalcoholic fatty liver disease. Lipotoxicity in obesity mediates insulin resistance, endothelial dysfunction, atherosclerosis, and gut microbiota dysbiosis. Cardiovascular complications are the main cause of morbidity and mortality in obese, insulin-resistant, and type 2 diabetes mellitus patients.Interventions targeting lipotoxicity are the main issue in preventing its multiple insults. Lifestyle modifications including healthy eating and regular exercise are the primary recommendations. Treatments also include drugs targeting energy intake, energy disposal, lipotoxic liver injury, and the resulting inflammation, fibrogenesis, and cirrhosis.Diet and nutrition have been linked to insulin resistance, an increased risk of developing type 2 diabetes, and impaired postprandial lipid metabolism. Low-fat diets are associated with higher survival. The Mediterranean diet includes an abundance of olive oil. Extra-virgin olive oil is the main source of monounsaturated fatty acids in Mediterranean diets. An olive oil-rich diet decreases triglyceride accumulation in the liver, improves postprandial triglyceride levels, improves glucose and insulin secretions, and upregulates GLUT-2 expression in the liver. The exact molecular mechanisms of olive oil's effects are unknown, but decreasing NF-kB activation, decreasing LDL oxidation, and improving insulin resistance by reducing the production of inflammatory cytokines (TNF-α and IL-6) and upregulating kinases and JNK-mediated phosphorylation of IRS-1 are possible principal mechanisms. Olive oil phenolic compounds also modulate gut microbiota diversity, which also affects lipotoxicity.In this review, we document lipotoxicity in obesity manifestations and the beneficial health effects of the Mediterranean diet derived from monounsaturated fatty acids, mainly from olive oil.

MODERN VIEWS ON THE PATHOGENESIS OF IMMUNE DYSFUNCTION AGAINST THE BACKGROUND OF THE METABOLIC SYNDROME IN ISCHEMIC HEART DISEASE

Introduction. Today, the pathology of the cardiovascular system is one of the most common and fatal diseases. Cardiovascular diseases are the cause of disability among the younger and younger population. Taking into account the frequency of cardiovascular diseases, the severity of the course and their lethality, the study of this topic remains one of the most urgent problems of medicine, in particular cardiology.&#x0D; The aim of the study. Consider modern views on the pathogenesis of coronary heart disease against the background of metabolic syndrome and the role of the immune system.&#x0D; Conclusions. Ischemic heart disease is the leading cause of mortality in Ukraine and the world. In recent years, there has been convincing evidence of a significant prevalence of cardiovascular disease in patients with metabolic syndrome. The presence of concomitant metabolic syndrome in patients with coronary heart disease worsens the course of the underlying disease and has an unfavorable prognosis, and even fatal cases.&#x0D; Therefore, the detection of an increase in the level of body mass index, dyslipidemia, hyperglycemia, arterial hypertension in a patient strengthens the effects of each other, that is, they have a synergistic effect, and in general, the risk of developing CHD becomes quite high.&#x0D; IL-6 is one of the cytokines released by both macrophages and adipocytes and its levels have been shown to be increased in insulin resistance and obesity. In fact, IL-6 is known to regulate fat and glucose metabolism, mediating insulin resistance through various complex mechanisms. This cytokine acts on various tissues, leading to the metabolic effects of obesity. In the liver, IL-6 increases the production of acute phase reactants, including CRP. Several studies have demonstrated that high CRP levels have the strongest correlation with cardiac events, T2DM, and MS. IL-6 also contributes to a prothrombotic state by increasing the level of fibrinogen, another acute phase reactant. In addition, IL-6 targets other tissues, such as endothelial cells, to promote the expression of vascular cell adhesion molecules, leading to vascular wall atherosclerosis, inflammation, and dysfunction.&#x0D; These data support the role of IL-6 in the development of insulin resistance, but do not support the hypothesis that IL-6 is involved in β-cell failure.&#x0D; IL-18 is a pro-inflammatory cytokine associated with insulin resistance and T2DM risk. IL-18 stimulates the production of gamma interferon (IFN-γ), which, in turn, is probably involved in the pathogenesis of atherosclerosis. IL-18 is a cytokine that is a predictor of metabolic syndrome.&#x0D; TNFα is another cytokine produced in adipose tissue, mainly from local macrophages, and its production also varies with adipose tissue mass and correlates with insulin resistance, both hallmarks of MS. TNFα exerts its pathogenic effects by disrupting insulin signaling in adipocytes and hepatocytes through serine phosphorylation and inactivation of insulin receptors and downstream signaling molecules, leading to decreased metabolic effects of insulin. TNFα also contributes to insulin resistance by inducing hepatic lipolysis.

The P2Y2 receptor mediates terminal adipocyte differentiation and insulin resistance: Evidence for a dual G-protein coupling mode

Several P2Y nucleotide receptors have been shown to be involved in the early stage of adipocyte differentiation in vitro and insulin resistance in obese mice; however, the exact receptor subtype(s) and its underlying molecular mechanism in relevant human cells are unclear. Here, using human primary visceral preadipocytes as a model, we found that during preadipocyte-to-mature adipocyte differentiation, the P2Y2 nucleotide receptor (P2Y2R) was the most upregulated subtype among the eight known P2Y receptors and the only one further dramatically upregulated after inflammatory TNFα treatment. Functional studies indicated that the P2Y2R induced intracellular Ca2+, ERK1/2, and JNK signaling but not the p38 pathway. In addition, stimulation of the P2Y2R suppressed basal and insulin-induced phosphorylation of AKT, accompanied by decreased GLUT4 membrane translocation and glucose uptake in mature adipocytes, suggesting a role of P2Y2R in insulin resistance. Mechanistically, we found that activation of P2Y2R did not increase lipolysis but suppressed PIP3 generation. Interestingly, activation of P2Y2R triggered Gi-protein coupling, and pertussis toxin pretreatment largely inhibited P2Y2R-mediated ERK1/2 signaling and cAMP suppression. Further, treatment of the cells with AR-C 118925XX, a selective P2Y2R antagonist, significantly inhibited adipogenesis, and P2Y2R knockout decreased mouse body weight gain with smaller eWAT mass infiltrated with fewer macrophages as compared to wild-type mice in response to a Western diet. Thus, we revealed that terminal adipocyte differentiation and inflammation selectively upregulate P2Y2R expression and that P2Y2R mediates insulin resistance by suppressing the AKT signaling pathway, highlighting P2Y2R as a potential new drug target to combat obesity and type-2 diabetes.

ZFYVE28 mediates insulin resistance by promoting phosphorylated insulin receptor degradation via increasing late endosomes production

Insulin resistance is associated with many pathological conditions, and an in-depth understanding of the mechanisms involved is necessary to improve insulin sensitivity. Here, we show that ZFYVE28 expression is decreased in insulin-sensitive obese individuals but increased in insulin-resistant individuals. Insulin signaling inhibits ZFYVE28 expression by inhibiting NOTCH1 via the RAS/ERK pathway, whereas ZFYVE28 expression is elevated due to impaired insulin signaling in insulin resistance. While Zfyve28 overexpression impairs insulin sensitivity and causes lipid accumulation, Zfyve28 knockout in mice can significantly improve insulin sensitivity and other indicators associated with insulin resistance. Mechanistically, ZFYVE28 colocalizes with early endosomes via the FYVE domain, which inhibits the generation of recycling endosomes but promotes the conversion of early to late endosomes, ultimately promoting phosphorylated insulin receptor degradation. This effect disappears with deletion of the FYVE domain. Overall, in this study, we reveal that ZFYVE28 is involved in insulin resistance by promoting phosphorylated insulin receptor degradation, and ZFYVE28 may be a potential therapeutic target to improve insulin sensitivity.

FRI114 PUFAs Implicated In Platelet Activation Differ In Receptor Mediated Vs Post-receptor Insulin Resistance

Abstract Disclosure: R. Klein: None. S.T. Chung: None. R.J. Brown: None. Background: Severe insulin resistance (IR) can be classified as receptor mediated, in which all downstream signaling is blocked, or post receptor IR where some downstream signaling pathways are decreased and others are increased. Receptor-mediated IR occurs in rare mutations of the insulin receptor (INSR), whereas in most forms of IR, including type 2 diabetes (T2DM) and lipodystrophy (LD), IR is post-receptor. LD is a group of syndromes characterized by deficiency of fat depots leading to metabolic dysfunction similar to obesity. Patients with post-receptor IR have increased atherosclerotic cardiovascular disease (ASCVD) risk. Thrombosis underlies pathology of ASCVD and is a result of platelet (PLT) activation. Polyunsaturated fatty acids (PUFAs) are embedded in the PLT membrane and play a key role in thrombosis. During PLT activation, cytosolic phospholipase A2 (cPLA2) hydrolyzes membrane lipids, generating free PUFAs, leading to synthesis of mediators of blood vessel constriction, inflammation, and thrombosis. Methods: This was a cross-sectional study of subjects with INSR (N=30) and LD (N=30) matched for age, sex, HbA1c and pubertal stage. Untargeted metabolomic (848 compounds) and lipidomic (984 compounds) analysis was completed on serum after an 8-12 hour fast. Analyses were conducted by t-test and Mann-Whitney with adjustment for multiplicity. Bonferroni corrected P&amp;lt;0.05 was considered significant. Results: Of 19 long chain PUFAs (ω=3, ω=6) measured, 14 were significantly elevated in LD vs INSR, including arachidonate, docosahexaenoate, docosapentaenoate, stearidonate, and adrenate. There was no difference in linoleate, dihomo-linoleate, tetradecadienoate, linolenate, or docosadienoate levels between LD vs INSR. Among 8 long chain saturated FAs, only 3 were significantly higher in LD, 4 were comparable, and 1 was higher in INSR. All long and medium chain monounsaturated FAs were similar in LD vs INSR. cPLA2 was not different between LD and INSR. Conclusions: Our study shows that liberated PUFAs were higher in the patients with LD compared to INSR. A similar trend was not seen for other FFA such as saturated and monounsaturated FFA, suggesting that higher PUFAs in LD are unlikely to be caused by global differences in FFA metabolism, such as different peripheral uptake of FFA via lipoprotein lipase activity or diet. Instead, our data suggest an increase in PLT membrane ability to store and release PUFAs. These data suggest increased ASCVD risk in post-receptor insulin resistance may be partially mediated through differences in platelet activation. Presentation: Friday, June 16, 2023

TGS1/PIMT regulates pro-inflammatory macrophage mediated paracrine insulin resistance: Crosstalk between macrophages and skeletal muscle cells

Macrophage-driven chronic low-grade inflammatory response is intimately associated with pathogenesis of insulin resistance and type 2 diabetes (T2D). However, the molecular basis for skewing of pro-inflammatory macrophage is still elusive. Here, we describe the mechanism and significance of TGS1/PIMT (PRIP-Interacting protein with Methyl Transferase domain) in regulating macrophage activation and polarization and its impact on the development of insulin resistance in skeletal muscle cells. We show altered expression of TGS1 in M1 polarized cultured macrophages, bone marrow-derived (BMDM) and adipose tissue macrophages. Moreover, in High Fat Diet (HFD)-fed mice enhanced TGS1 expression is predominantly localized to the nucleus of adipose tissue macrophages suggesting its potential functional role. Gain and loss of TGS1 expression in macrophage further established its role in the secretion of pro-inflammatory mediators. Mechanistically, TGS1 controls the transcription of numerous genes linked to inflammation by forming a complex with Histone Acetyl Transferase (HAT)-containing transcriptional co-activators CBP and p300. Functionally, TGS1 mediated macrophage inflammatory response induces the development of insulin resistance in skeletal muscle cells and adipocytes. Our findings thus demonstrate an unexpected contribution of TGS1 in the regulation of macrophage mediated inflammation and insulin resistance highlighting that TGS1 antagonism could be a promising therapeutic target for the management of inflammation and insulin resistance in T2D.

Modeling and therapeutic targeting of inflammation-induced hepatic insulin resistance using human iPSC-derived hepatocytes and macrophages

Hepatic insulin resistance is recognized as a driver of type 2 diabetes and fatty liver disease but specific therapies are lacking. Here we explore the potential of human induced pluripotent stem cells (iPSCs) for modeling hepatic insulin resistance in vitro, with a focus on resolving the controversy about the impact of inflammation in the absence of steatosis. For this, we establish the complex insulin signaling cascade and the multiple inter-dependent functions constituting hepatic glucose metabolism in iPSC-derived hepatocytes (iPSC-Heps). Co-culture of these insulin-sensitive iPSC-Heps with isogenic iPSC-derived pro-inflammatory macrophages induces glucose output by preventing insulin from inhibiting gluconeogenesis and glycogenolysis and activating glycolysis. Screening identifies TNFα and IL1β as the mediators of insulin resistance in iPSC-Heps. Neutralizing these cytokines together restores insulin sensitivity in iPSC-Heps more effectively than individual inhibition, reflecting specific effects on insulin signaling and glucose metabolism mediated by NF-κB or JNK. These results show that inflammation is sufficient to induce hepatic insulin resistance and establish a human iPSC-based in vitro model to mechanistically dissect and therapeutically target this metabolic disease driver.

Retraction Note: MiRNA-27a mediates insulin resistance in 3T3-L1 cells through the PPARγ.

Retraction Note: MiRNA-27a mediates insulin resistance in 3T3-L1 cells through the PPARγ.

Abelmoschus esculentus (Okra) Prevents Insulin Resistance and Restores Neuron Autophagy by Regulating Dipeptidyl Peptidase-4 and Thus Improving Hippocampal Function.

Diabetes is highly linked to the occurrence of Alzheimer disease (AD), which is characterized by beta amyloid peptide (Aβ) and hyperphosphorylation of tau (p-tau), and neuron damage particularly in hippocampus. Type 2 diabetes (T2D) is featured by insulin resistance, and phosphorylation of Ser307-IRS-1 is regarded as a resistance marker. Inhibitors of dipeptidyl peptidase-4 (DPP-4) are effective tools for treating T2D. Previously, we reported subfractions of Abelmoschus esculentus (AE, okra) (F1 rich in quercetin glycosides; F2 composed of polysaccharide) attenuated DPP-4 and its downstream signals of insulin resistance, thus preventing Aβ-induced neuron damage. Since autophagy could be protective, we now explore if AE works to modulate neuron autophagy by regulating DPP-4 and insulin resistance and, thus, improves the hippocampal function and behavior. We demonstrated that AE subfractions attenuate Aβ-induced insulin resistance and the expression of p-tau and normalize the autophagy and survival of hippocampal neurons. The action of AE may be attributed to the downregulation of DPP-4, which plays a critical role in mediating insulin resistance and hinders neuron autophagy. The in vivo findings reveal that the hippocampal insulin resistance appears to link with loss of memory, reduction of curiosity, and depression, whereas treatment with AE significantly improves the insulin sensitivity and hippocampal function. Noteworthy, even at only 5 μg/mL, F2 seems to exhibit a meaningful effect. In conclusion, we suggest that AE attenuates insulin resistance and recovers neuron autophagy which are regulated by DPP-4, thus preventing the damage to the hippocampus, improving recognition and emotion. AE may be an effective adjuvant or supplement to prevent insulin resistance-associated pathogenesis of AD if these results can be confirmed in human clinical trials.