Drives Insulin Resistance Research Articles

Human umbilical cord-derived mesenchymal stem cells alleviate insulin resistance in diet-induced obese mice via an interaction with splenocytes

BackgroundPrevious research has demonstrated that the spleen plays an important role in mesenchymal stem cell (MSC)-mediated alleviation of acute inflammation, as MSC infusion increases the spleen-derived anti-inflammatory cytokine interleukin 10 (IL-10) levels. However, studies on splenic involvement in MSC-induced protection against chronic inflammatory diseases are limited. Obesity is characterized by chronic low-grade inflammation, a key driver of insulin resistance. This study aims to evaluate the effects of MSCs on obesity-related insulin resistance and explore the underlying mechanism, particularly regarding splenic involvement.MethodsWe induced obesity in mice by feeding them high-fat diets for 20 weeks. Human umbilical cord-derived MSCs (UC-MSCs) were systemically infused into the obese mice once per week for 6 weeks. Systemic glucose metabolic homeostasis and insulin sensitivity in epididymal adipose tissue (EAT) were evaluated. Then, we conducted in vivo blockade of IL-10 during UC-MSC infusion by intraperitoneally administrating an IL-10-neutralizing antibody twice per week. We also investigated the therapeutic effects of UC-MSCs on obese mice after removal of the spleen by splenectomy.ResultsUC-MSC infusions improved systemic metabolic homeostasis and alleviated insulin resistance in EAT but elicited no change in weight. Despite rare engraftment of UC-MSCs in EAT, UC-MSC infusions attenuated insulin resistance in EAT by polarizing macrophages into the M2 phenotype, coupled with elevated serum IL-10 levels. In vivo blockade of IL-10 blunted the effects of UC-MSCs on obese mice. Furthermore, UC-MSCs overwhelmingly homed to the spleen, and the ability of UC-MSCs to elevate serum IL-10 levels and alleviate insulin resistance was impaired in the absence of the spleen. Further in vivo and in vitro studies revealed that UC-MSCs promoted the capacity of regulatory T cells (Treg cells) to produce IL-10 in the spleen.ConclusionsOur results demonstrated that UC-MSCs elevated serum IL-10 levels and subsequently promoted macrophage polarization, leading to alleviation of insulin resistance in EAT. The underlying mechanism was that UC-MSCs improved the capacity of Treg cells to produce IL-10 in the spleen. Our findings indicated that the spleen played a critical role in amplifying MSC-mediated immunomodulatory effects, which may contribute to maximizing MSC efficacy in clinical applications in the future.

Sirtuin deficiency and the adverse effects of fructose and uric acid synthesis.

Fructose metabolism and hyperuricemia have been shown to drive insulin resistance, metabolic syndrome, hepatic steatosis, hypertension, inflammation, and innate immune reactivity in experimental studies. We suggest that these adverse effects are at least in part the result of suppressed activity of sirtuins, particularly Sirtuin1. Deficiency of sirtuin deacetylations is a consequence of reduced bioavailability of its cofactor nicotinamide adenine dinucleotide (NAD+). Uric acid-induced inflammation and oxidative stress consume NAD+ and activation of the polyol pathway of fructose and uric acid synthesis also reduces the NAD+-to-NADH ratio. Variability in the compensatory regeneration of NAD+ could result in variable recovery of sirtuin activity that may explain the inconsistent benefits of treatments directed to reduce uric acid in clinical trials. Here, we review the pathogenesis of the metabolic dysregulation driven by hyperuricemia and their potential relationship with sirtuin deficiency. In addition, we discuss therapeutic options directed to increase NAD+ and sirtuins activity that may improve the adverse effects resulting from fructose and uric acid synthesis.

Systems-level analysis of insulin action in mouse strains provides insight into tissue- and pathway-specific interactions that drive insulin resistance

Skeletal muscle and adipose tissue insulin resistance are major drivers of metabolic disease. To uncover pathways involved in insulin resistance, specifically in these tissues, we leveraged the metabolic diversity of different dietary exposures and discrete inbred mouse strains. This revealed that muscle insulin resistance was driven by gene-by-environment interactions and was strongly correlated with hyperinsulinemia and decreased levels of ten key glycolytic enzymes. Remarkably, there was no relationship between muscle and adipose tissue insulin action. Adipocyte size profoundly varied across strains and diets, and this was strongly correlated with adipose tissue insulin resistance. The A/J strain, in particular, exhibited marked adipocyte insulin resistance and hypertrophy despite robust muscle insulin responsiveness, challenging the role of adipocyte hypertrophy per se in systemic insulin resistance. These data demonstrate that muscle and adipose tissue insulin resistance can occur independently and underscore the need for tissue-specific interrogation to understand metabolic disease.

Human and mouse muscle transcriptomic analyses identify insulin receptor mRNA downregulation in hyperinsulinemia-associated insulin resistance.

Hyperinsulinemia is commonly viewed as a compensatory response to insulin resistance, yet studies have demonstrated that chronically elevated insulin may also drive insulin resistance. The molecular mechanisms underpinning this potentially cyclic process remain poorly defined, especially on a transcriptome‐wide level. Transcriptomic meta‐analysis in >450 human samples demonstrated that fasting insulin reliably and negatively correlated with INSR mRNA in skeletal muscle. To establish causality and study the direct effects of prolonged exposure to excess insulin in muscle cells, we incubated C2C12 myotubes with elevated insulin for 16 h, followed by 6 h of serum starvation, and established that acute AKT and ERK signaling were attenuated in this model of in vitro hyperinsulinemia. Global RNA‐sequencing of cells both before and after nutrient withdrawal highlighted genes in the insulin receptor (INSR) signaling, FOXO signaling, and glucose metabolism pathways indicative of ‘hyperinsulinemia’ and ‘starvation’ programs. Consistently, we observed that hyperinsulinemia led to a substantial reduction in Insr gene expression, and subsequently a reduced surface INSR and total INSR protein, both in vitro and in vivo. Bioinformatic modeling combined with RNAi identified SIN3A as a negative regulator of Insr mRNA (and JUND, MAX, and MXI as positive regulators of Irs2 mRNA). Together, our analysis identifies mechanisms which may explain the cyclic processes underlying hyperinsulinemia‐induced insulin resistance in muscle, a process directly relevant to the etiology and disease progression of type 2 diabetes.

A Low-Glucose Eating Pattern Improves Biomarkers of Postmenopausal Breast Cancer Risk: An Exploratory Secondary Analysis of a Randomized Feasibility Trial.

Postmenopausal breast cancer is the most common obesity-related cancer death among women in the U.S. Insulin resistance, which worsens in the setting of obesity, is associated with higher breast cancer incidence and mortality. Maladaptive eating patterns driving insulin resistance represent a key modifiable risk factor for breast cancer. Emerging evidence suggests that time-restricted feeding paradigms (TRF) improve cancer-related metabolic risk factors; however, more flexible approaches could be more feasible and effective. In this exploratory, secondary analysis, we identified participants following a low-glucose eating pattern (LGEP), defined as consuming energy when glucose levels are at or below average fasting levels, as an alternative to TRF. Results show that following an LGEP regimen for at least 40% of reported eating events improves insulin resistance (HOMA-IR) and other cancer-related serum biomarkers. The magnitude of serum biomarkers changes observed here has previously been shown to favorably modulate benign breast tissue in women with overweight and obesity who are at risk for postmenopausal breast cancer. By comparison, the observed effects of LGEP were similar to results from previously published TRF studies in similar populations. These preliminary findings support further testing of LGEP as an alternative to TRF and a postmenopausal breast cancer prevention strategy. However, results should be interpreted with caution, given the exploratory nature of analyses.

JMJD8 is a Novel Molecular Nexus Between Adipocyte-Intrinsic Inflammation and Insulin Resistance.

Chronic low-grade inflammation, often referred to as metainflammation, develops in response to overnutrition and is a major player in the regulation of insulin sensitivity. While many studies have investigated adipose tissue inflammation from the perspective of the immune cell compartment, little is known about how adipocytes intrinsically contribute to metainflammation and insulin resistance at the molecular level. Here, we demonstrate a novel role for Jumonji C Domain Containing Protein 8 (JMJD8) as an adipocyte-intrinsic molecular nexus between inflammation and insulin resistance. We determined that JMJD8 was highly enriched in white adipose tissue, especially in the adipocyte fraction. Adipose JMJD8 levels were dramatically increased in obesity-associated insulin resistance models. Its levels were increased by feeding and insulin, and inhibited by fasting. A JMJD8 gain of function was sufficient to drive insulin resistance, whereas loss of function improved insulin sensitivity in mouse and human adipocytes. Consistent with this, Jmjd8-ablated mice had increased whole-body and adipose insulin sensitivity and glucose tolerance on both chow and a high-fat diet, while adipocyte-specific Jmjd8-overexpressing mice displayed worsened whole-body metabolism on a high-fat diet. We found that JMJD8 affected the transcriptional regulation of inflammatory genes. In particular, it was required for LPS-mediated inflammation and insulin resistance in adipocytes. For this, JMJD8 required Interferon Regulatory Factor (IRF3) to mediate its actions in adipocytes. Together, our results demonstrate that JMJD8 acts as a novel molecular factor that drives adipocyte inflammation in conjunction with insulin sensitivity.

Serum- and glucocorticoid-induced kinase drives hepatic insulin resistance by directly inhibiting AMP-activated protein kinase.

SUMMARYA hallmark of type 2 diabetes (T2D) is hepatic resistance to insulin’s glucose-lowering effects. The serum- and glucocorticoid-regulated family of protein kinases (SGK) is activated downstream of mechanistic target of rapamycin complex 2 (mTORC2) in response to insulin in parallel to AKT. Surprisingly, despite an identical substrate recognition motif to AKT, which drives insulin sensitivity, pathological accumulation of SGK1 drives insulin resistance. Liver-specific Sgk1-knockout (Sgk1Lko) mice display improved glucose tolerance and insulin sensitivity and are protected from hepatic steatosis when fed a high-fat diet. Sgk1 promotes insulin resistance by inactivating AMP-activated protein kinase (AMPK) via phosphorylation on inhibitory site AMPKαSer485/491. We demonstrate that SGK1 is dominant among SGK family kinases in regulation of insulin sensitivity, as Sgk1, Sgk2, and Sgk3 triple-knockout mice have similar increases in hepatic insulin sensitivity. In aggregate, these data suggest that targeting hepatic SGK1 may have therapeutic potential in T2D.

Hyperglycemia in acute COVID-19 is characterized by insulin resistance and adipose tissue infectivity by SARS-CoV-2

Individuals infected with SARS-CoV-2 who also display hyperglycemia suffer from longer hospital stays, higher risk of developing acute respiratory distress syndrome (ARDS), and increased mortality. Nevertheless, the pathophysiological mechanism of hyperglycemia in COVID-19 remains poorly characterized. Here, we show that hyperglycemia is similarly prevalent among patients with ARDS independent of COVID-19 status. Yet among patients with ARDS and COVID-19, insulin resistance is the prevalent cause of hyperglycemia, independent of glucocorticoid treatment, which is unlike patients with ARDS but without COVID-19, where pancreatic beta cell failure predominates. A screen of glucoregulatory hormones revealed lower levels of adiponectin in patients with COVID-19. Hamsters infected with SARS-CoV-2 demonstrated a strong antiviral gene expression program in the adipose tissue and diminished expression of adiponectin. Moreover, we show that SARS-CoV-2 can infect adipocytes. Together these data suggest that SARS-CoV-2 may trigger adipose tissue dysfunction to drive insulin resistance and adverse outcomes in acute COVID-19.

The role of ceramide accumulation in human induced pluripotent stem cell-derived cardiomyocytes on mitochondrial oxidative stress and mitophagy

Oversupply of fatty acids (FAs) to cardiomyocytes (CMs) is associated with increased ceramide content and elevated the risk of lipotoxic cardiomyopathy. Here we investigate the role of ceramide accumulation on mitochondrial function and mitophagy in cardiac lipotoxicity using CMs derived from human induced pluripotent stem cell (hiPSC). Mature CMs derived from hiPSC exposed to the diabetic-like environment or transfected with plasmids overexpressing serine-palmitoyltransferase long chain base subunit 1 (SPTLC1), a subunit of the serine-palmitoyltransferase (SPT) complex, resulted in increased intracellular ceramide levels. Accumulation of ceramides impaired insulin-dependent phosphorylation of Akt through activating protein phosphatase 2A (PP2A) and disturbed gene and protein levels of key metabolic enzymes including GLUT4, AMPK, PGC-1α, PPARα, CD36, PDK4, and PPARγ compared to controls. Analysis of CMs oxidative metabolism using a Seahorse analyzer showed a significant reduction in ATP synthesis-related O2 consumption, mitochondrial β-oxidation and respiratory capacity, indicating an impaired mitochondrial function under diabetic-like conditions or SPTLC1-overexpression. Further, ceramide accumulation increased mitochondrial fission regulators such as dynamin-related protein 1 (DRP1) and mitochondrial fission factor (MFF) as well as auto/mitophagic proteins LC3B and PINK-1 compared to control. Incubation of CMs with the specific SPT inhibitor (myriocin) showed a significant increase in mitochondrial fusion regulators the mitofusin 2 (MFN2) and optic atrophy 1 (OPA1) as well as p-Akt, PGC-1 α, GLUT-4, and ATP production. In addition, a significant decrease in auto/mitophagy and apoptosis was found in CMs treated with myriocin. Our results suggest that ceramide accumulation has important implications in driving insulin resistance, oxidative stress, increased auto/mitophagy, and mitochondrial dysfunction in the setting of lipotoxic cardiomyopathy. Therefore, modulation of the de novo ceramide synthesis pathway may serve as a novel therapeutic target to treat metabolic cardiomyopathy.

Tregs facilitate obesity and insulin resistance via a Blimp-1/IL-10 axis.

Interleukin-10 (IL-10) is a critical cytokine used by immune cells to suppress inflammation. Paradoxically, immune cell–derived IL-10 can drive insulin resistance in obesity by suppressing adipocyte energy expenditure and thermogenesis. However, the source of IL-10 necessary for the suppression of adipocyte thermogenesis is unknown. We show here that CD4+Foxp3+ regulatory T cells (Tregs) are a substantial source of IL-10 and that Treg-derived IL-10 can suppress adipocyte beiging. Unexpectedly, Treg-specific loss of IL-10 resulted in increased insulin sensitivity and reduced obesity in high-fat diet–fed male mice. Mechanistically, we determined that Treg-specific loss of the transcription factor Blimp-1, a driver of IL-10 expression by Tregs, phenocopied the Treg-specific IL-10–deficient mice. Loss of Blimp-1 expression in Tregs resulted in reduced ST2+KLRG1+, IL-10-secreting Tregs, particularly in the white adipose tissue. Blimp-1–deficient mice were protected from glucose intolerance, insulin resistance, and diet-induced obesity, through increased white adipose tissue browning. Taken together, our data show that Blimp-1–regulated IL-10 secretion by Tregs represses white adipose tissue beiging to maintain adipose tissue homeostasis.

Heme Oxygenase-1 Regulates Ferrous Iron and Foxo1 in Control of Hepatic Gluconeogenesis.

The liver is a key player for maintaining glucose homeostasis. Excessive hepatic glucose production is considered to be a key for the onset of type 2 diabetes. The primary function of heme oxygenase-1 (HO1) is to catalyze the degradation of heme into biliverdin, ferrous iron, and carbon monoxide. Previous studies have demonstrated that the degradation of heme by HO1 in the liver results in mitochondrial dysfunction and drives insulin resistance. In this study, by overexpressing HO1 in hepatocytes and mice, we showed that HO1 promotes gluconeogenesis in a Foxo1-dependent manner. Importantly, HO1 overexpression increased the generation of ferrous iron in the liver, which further activates nuclear factor-κB and phosphorylates Foxo1 at Ser273 to enhance gluconeogenesis. We further assessed the role of HO1 in insulin-resistant liver-specific knockout of IRS1 and IRS2 genes (L-DKO) mice, which exhibit upregulation of HO1 in the liver and hepatic ferrous iron overload. HO1 knockdown by shRNA or treatment of iron chelator rescued the aberrant gluconeogenesis in L-DKO mice. In addition, we found that systemic iron overload promotes gluconeogenesis by activating the hepatic protein kinase A→Foxo1 axis. Thus, our results demonstrate the role of HO1 in regulating hepatic iron status and Foxo1 to control gluconeogenesis and blood glucose.

Hyperglycemia in Acute COVID-19 is Characterized by Adipose Tissue Dysfunction and Insulin Resistance

COVID-19 has proven to be a metabolic disease resulting in adverse outcomes in individuals with diabetes or obesity. Patients infected with SARS-CoV-2 and hyperglycemia suffer from longer hospital stays, higher risk of developing acute respiratory distress syndrome (ARDS), and increased mortality compared to those who do not develop hyperglycemia. We find the prevalence of hyperglycemia in patients with COVID-19 ARDS to be equal to those with non-COVID-19 ARDS. Nevertheless, the pathophysiological mechanism(s) of hyperglycemia in COVID-19 remains poorly characterized. Here we show that insulin resistance rather than pancreatic beta cell failure is the prevalent cause of hyperglycemia in COVID-19 patients with ARDS, independent of glucocorticoid treatment. A screen of protein hormones that regulate glucose homeostasis reveals that the insulin sensitizing adipokine adiponectin is reduced in hyperglycemic COVID-19 patients. Hamsters infected with SARS-CoV-2 also have diminished expression of adiponectin. Together these data suggest that adipose tissue dysfunction may be a driver of insulin resistance and adverse outcomes in acute COVID-19.Funding Information: This work was supported by the following grants: NIH R01 DK121140 (J.C.L.) and R01 DK121844 (J.C.L.), NCI R01 CA234614 (R.E.S), NIAID 2R01 AI107301 (R.E.S), and NIDDK R01 DK121072 (R.E.S). R.E.S. and J.C.L are supported as Irma Hirschl Trust Research Award Scholars. In addition, this study received support from NewYork-Presbyterian Hospital (NYPH) and Weill Cornell Medical College (WCMC), including the Clinical and Translational Science Center (CTSC) (UL1 TR 0002384).Declaration of Interests: R.E.S. is on the scientific advisory board of Miromatrix Inc. R.E.S. is a speaker and consultant for Alnylam Inc. The other authors have no conflict of interest.Ethics Approval Statement: The registry was approved by the institutional review board of WCMC (1405015116, 20-05022072, 20-03021681).All animal experiment procedures, breeding, and ethical use were performed in accordance with the guidelines set by the Institutional Animal Care and Use Committee at Mount Sinai School of Medicine.

Neurogenic Obesity-Induced Insulin Resistance and Type 2 Diabetes Mellitus in Chronic Spinal Cord Injury.

The population with SCI is at a significant risk for both insulin resistance and type 2 diabetes mellitus (T2DM) secondary to neurogenic obesity. The prevalence of insulin resistance and T2DM in persons with SCI suggests that disorders of carbohydrate metabolism are at epidemic proportions within the population. However, the true frequency of such disorders may be underestimated because biomarkers of insulin resistance and T2DM used from the population without SCI remain nonspecific and may in fact fail to identify true cases that would benefit from intervention. Furthermore, diet and exercise have been used to help mitigate neurogenic obesity, but results on disorders of carbohydrate metabolism remain inconsistent, likely because of the various ways carbohydrate metabolism is assessed. The objective of this article is to review current literature on the prevalence and likely mechanisms driving insulin resistance and T2DM in persons with SCI. This article also explores the various assessments and diagnostic criteria used for insulin resistance and T2DM and briefly discusses the effects of exercise and/or diet to mitigate disorders of carbohydrate metabolism brought on by neurogenic obesity.

Apolipoprotein A5 controls fructose-induced metabolic dysregulation in mice

Background and aimsWestern dietary habits are partially characterized by increased uptake of fructose, which contributes to metabolic dysregulation and associated liver diseases. For example, a diet enriched with fructose drives insulin resistance and non-alcoholic fatty liver disease (NAFLD). The molecular hubs that control fructose-induced metabolic dysregulation are poorly understood. Apolipoprotein A5 (apoA5) controls triglyceride metabolism with a putative role in hepatic lipid deposition. We explored apoA5 as a rheostat for fructose-induced hepatic and metabolic disease in mammals. Methods and resultsApoA5 knock out (−/−) and wildtype (wt) mice were fed with high fructose diet or standard diet for 10 weeks. Afterwards, we conducted a metabolic characterization by insulin tolerance test as well as oral glucose tolerance test. Additionally, hepatic lipid content as well as transcription patterns of key enzymes and transcription factors in glucose and lipid metabolism were evaluated. Despite comparable body weight, insulin sensitivity was significantly improved in high fructose diet fed apoA5 (−/−) when compared to wildtype mice on the same diet. In parallel, hepatic triglyceride content was significantly lower in apoA5 (−/−) mice than in wt mice. No difference was seen between apoA5 (−/−) and wt mice on a standard diet. ConclusionApoA5 is involved in fructose-induced metabolic dysregulation and associated hepatic steatosis suggesting that apoA5 may be a novel target to treat metabolic diseases.

The Relationship between Abdominal Fat Phenotypes and Insulin Resistance in Non-Obese Individuals after Acute Pancreatitis.

Both type 2 prediabetes/diabetes (T2DM) and new-onset prediabetes/diabetes after acute pancreatitis (NODAP) are characterized by impaired tissue sensitivity to insulin action. Although the outcomes of NODAP and T2DM are different, it is unknown whether drivers of insulin resistance are different in the two types of diabetes. This study aimed to investigate the associations between abdominal fat phenotypes and indices of insulin sensitivity in non-obese individuals with NODAP, T2DM, and healthy controls. Indices of insulin sensitivity (homeostasis model assessment of insulin sensitivity (HOMA-IS), Raynaud index, triglyceride and glucose (TyG) index, Matsuda index) were calculated in fasting and postprandial states. Fat phenotypes (intra-pancreatic fat, intra-hepatic fat, skeletal muscle fat, visceral fat, and subcutaneous fat) were determined using magnetic resonance imaging and spectroscopy. Linear regression and relative importance analyses were conducted. Age, sex, and glycated hemoglobin A1c were adjusted for. A total of 78 non-obese individuals (26 NODAP, 20 T2DM, and 32 healthy controls) were included. Intra-pancreatic fat was significantly associated with all the indices of insulin sensitivity in the NODAP group, consistently in both the unadjusted and adjusted models. Intra-pancreatic fat was not significantly associated with any index of insulin sensitivity in the T2DM and healthy controls groups. The variance in HOMA-IS was explained the most by intra-pancreatic fat (R2 = 29%) in the NODAP group and by visceral fat (R2 = 21%) in the T2DM group. The variance in the Raynaud index was explained the most by intra-pancreatic fat (R2 = 18%) in the NODAP group and by visceral fat (R2 = 15%) in the T2DM group. The variance in the TyG index was explained the most by visceral fat in both the NODAP group (R2 = 49%) and in the T2DM group (R2 = 25%). The variance in the Matsuda index was explained the most by intra-pancreatic fat (R2 = 48%) in the NODAP group and by visceral fat (R2 = 38%) in the T2DM group. The differing association between intra-pancreatic fat and insulin resistance can be used to differentiate NODAP from T2DM. Insulin resistance in NODAP appears to be predominantly driven by increased intra-pancreatic fat deposition.

Abstract 1201: A mendelian randomization study for the potential causal effect of genetically driven insulin resistance on invasive breast cancer

Abstract Objectives Insulin resistance (IR), traditionally measured by fasting blood levels of glucose (FG) and fasting insulin (FI), has been considered a potential risk factor for breast cancer development. However, findings from previous epidemiologic studies of the relationships between IR and breast cancer were inconsistent, partially due to selection bias, confounding, short time exposure to biomarkers, measurement errors, and reverse causation. We tried to address those challenges by using a Mendelian Randomization (MR) method where FG and FI were analyzed via genetic instrumental variables. Our study aimed to examine the potential causal effect of genetically driven IR on breast cancer development and hoped to understand the underlying mechanisms between IR and breast cancer. Methods We conducted a two-sample MR analysis using the most updated publicly available data from a genome-wide association study (GWAS) of Meta-Analysis of Glucose and Insulin related traits Consortium (MAGIC), Breast Cancer Association Consortium (BCAC), and Atlas of GWAS Summary Statistics (ATLAS), focusing on European women. We utilized different datasets for breast cancer outcomes to complement MR analyses with the inverse-variance weighted method. To determine the extent of pleiotropic signal, we applied Cochran's Q test and the MR-Egger regression analysis. Given obesity and diabetes's established role for breast cancer, we excluded those related single-nucleotide polymorphisms (SNPs) from the MR analysis. Results Of 44 SNPs associated with IR, 38 FG SNPs showed slightly positive effects on breast cancer risk across datasets (OncoArray/iCOGS, odds ratio (OR) = 1.002, 95% confidence interval (CI): 0.831- 1.209; ATLAS-General: OR = 1.146, 95% CI: 0.507 - 2.592; ATLAS-GEEA: OR = 1.034, 95% CI: 0.748 - 1.429; ATLAS-GEEAB: OR = 1.029, 95% CI: 0.747 - 1.416). After excluding SNPs associated with diabetes and obesity, the directions of the association between FG and breast cancer in the OncoArray/iCOGS datasets changed but not in the ATLAS-General dataset. Similarly, 6 FI SNPs had a positive association with breast cancer across the datasets. No significant directional pleiotropy was observed. Conclusions Our findings indicate a marginal association between genetically driven IR and breast cancer risk suggesting complex evidence for causal association. Our study may support the potential value of interventions to lower IR, thus reducing breast cancer risk. Citation Format: Sihao Han, Nicholas Mancuso, Zuofeng Zhang, Jeanette Papp, Eric Sobel, Jiemin Yao, Su Yon Jung. A mendelian randomization study for the potential causal effect of genetically driven insulin resistance on invasive breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1201.

Evaluation of cyclooxygenase oxylipins as potential biomarker for obesity-associated adipose tissue inflammation and type 2 diabetes using targeted multiple reaction monitoring mass spectrometry

Introduction: Obesity is associated with adipose tissue inflammation which in turn drives insulin resistance and the development of type 2 diabetes. Oxylipins are a collection of lipid metabolites, subdivided in different classes, which are involved in inflammatory cascades. They play important roles in regulating adipose tissue homeostasis and inflammation and are therefore putative biomarkers for obesity-associated adipose tissue inflammation and the subsequent risk of type 2 diabetes onset. The objective for this study is to design an assay for a specific oxylipin class and evaluate these as potential prognostic biomarker for obesity-associated adipose tissue inflammation and type 2 diabetes. Methods: An optimized workflow was developed to extract oxylipins from plasma using solid-phase extraction followed by analysis using ultra-high performance liquid chromatography coupled to a triple quadrupole mass spectrometer in multiple reaction monitoring mode. This workflow was applied to clinical plasma samples obtained from obese-type 2 diabetes patients and from lean and obese control subjects. Results: The assay was analytically validated and enabled reproducible analyses of oxylipins extracted from plasma with acceptable sensitivities. Analysis of clinical samples revealed discriminative values for four oxylipins between the type 2 diabetes patients and the lean and obese control subjects, viz. PGF2α, PGE2, 15-keto-PGE2 and 13,14-dihydro-15-keto-PGE2. The combination of PGF2α and 15-keto-PGE2 had the most predictive value to discriminate type 2 diabetic patients from lean and obese controls. Conclusions: This proof-of-principle study demonstrates the potential value of oxylipins as biomarkers to discriminate obese individuals from obese-type 2 diabetes patients.

1640-P: Common and Ethnic-Specific Molecular Networks and Drivers of Insulin Resistance in African and European Ancestry Individuals

Our understanding of how genetic variants influence molecular regulatory networks in glucose responsive tissues, and in turn affect cellular processes related to insulin resistance (IR) in different ethnic groups, remains incomplete. We employ a network modelling approach to integrate measures of insulin sensitivity, transcriptomic data in the adipose and muscle tissues, and genetic data from African Americans (AAs) in the AAGMEx cohort (N=256). Data from European ancestry (EA) individuals from AREA (N=99) and METSIM (N=770) cohorts are used as contrast. Multiscale Embedded GEne coexpression Network Analysis (MEGENA) in AAs identifies 167 and 63 transcript subnetworks (modules) enriched for Matsuda index and SI-correlated genes in adipose and muscle, respectively. Among these IR-associated modules, 11 in adipose and 6 in muscle, are enriched for the cis-eSNP genes. Bayesian probabilistic causal networks (BN) are constructed and subsequently used to identify key network drivers. Integration of MEGENA and BN in AAs identifies 99 and 39 key regulators for IR-associated adipose and muscle modules, respectively. Among the IR-associated modules in AAs, 23 in adipose and 5 in muscle are strongly preserved in the respective networks in the EA cohorts. Top 3 IR-associated preserved adipose modules are enriched for immune system, mitochondria and hormonal response and these modules are potentially regulated by KYNU, LDHD and ENO1, respectively. We identify 50 and 24 IR-associated but AA-specific modules (not preserved in EAs) in adipose and muscle, respectively. Conversely, we find 28 IR-associated but EA-specific modules in adipose. Ethnic group specific and shared modules reveal novel molecular mechanisms for IR. Enrichment of cis-eSNP genes in the network neighborhoods of key drivers suggest that regulatory SNPs may configure the networks by modulating transcript expression in adipose and muscle tissues, and are likely causal determinants for IR. Disclosure P. Xu: None. M. Wang: None. N.K. Sharma: None. M. Comeau: None. M. Civelek: None. C.D. Langefeld: None. B. Zhang: None. S.K. Das: None. Funding National Institutes of Health (R01DK118243, R01DK090111)

The Peripheral Peril: Injected Insulin Induces Insulin Insensitivity in Type 1 Diabetes.

Insulin resistance is an underappreciated facet of type 1 diabetes that occurs with remarkable consistency and considerable magnitude. Although therapeutic innovations are continuing to normalize dysglycemia, a sizable body of data suggests a second metabolic abnormality-iatrogenic hyperinsulinemia-principally drives insulin resistance and its consequences in this population and has not been addressed. We review this evidence to show that injecting insulin into the peripheral circulation bypasses first-pass hepatic insulin clearance, which leads to the unintended metabolic consequence of whole-body insulin resistance. We propose restructuring insulin therapy to restore the physiological insulin balance between the hepatic portal and peripheral circulations and thereby avoid the complications of life-long insulin resistance. As technology rapidly advances and our ability to ensure euglycemia improves, iatrogenic insulin resistance will become the final barrier to overcome to restore normal physiology, health, and life in type 1 diabetes.

Deoxyhypusine Synthase Promotes a Pro-Inflammatory Macrophage Phenotype

Obesity is characterized by adipose tissue expansion, macrophage infiltration, and the development of chronic low-grade meta-inflammation that drives insulin resistance and metabolic dysfunction. Eukaryotic translation initiation factor 5A (eIF5A) is the only protein known to be uniquely post-translationally modified and activated by deoxyhypusine synthase (DHPS) to generate a hypusine (Hyp) residue. Activated eIF5A controls the translation of a subset of mRNAs that play a role in inflammation, but a role for the DHPS/eIF5AHyp axis in obesity-associated adipose tissue inflammation has not been tested. We found DHPS/eIF5AHyp levels to be increased in the stromal vascular fraction of adipose tissue from mice fed a high fat diet and in murine macrophages activated to a proinflammatory M1 phenotype. DHPS deficiency in M1 macrophages decreased global mRNA translation and protein synthesis of key inflammatory mediators, IL-1β and MIP-1α. Transcriptomes of LPS+IFN-γ-stimulated DHPS-deficient macrophages revealed reduced characteristics of an M1 signature and a phenotypic switch consistent with characteristics of an anti-inflammatory M2 signature. In support of these observations, macrophage migration in a zebrafish tailfin injury model was reduced with chemical inhibition of DHPS, and DHPS deficiency in myeloid cells of HFD-fed mice inhibited M1 macrophage accumulation in adipose tissue and improved glucose tolerance. Together, these findings indicate that DHPS is required for the translation of a subset of mRNAs required for inflammation and chemotaxis in macrophages and may contribute to a proinflammatory M1-like phenotype.