Preserved Insulin Sensitivity Research Articles

Comparison of β-Cell Function and Insulin Sensitivity Between Normal-Weight and Obese Chinese With Young-Onset Type 2 Diabetes.

Normal-weight individuals with usual-onset type 2 diabetes had reduced beta-cell function and greater insulin sensitivity compared to their obese counterparts. The relative contribution of beta-cell dysfunction and insulin resistance to young-onset type 2 diabetes (YOD) among normal-weight individuals is not well established. In 44 individuals with YOD (24 normal-weight and 20 obese) and 24 healthy controls with normoglycemia (12 normal-weight and 12 obese), we conducted 2-h 12mmol/L hyperglycemic clamps to measure acute (0-10 minute) and steady-state (100-120 minute) insulin and C-peptide responses, and insulin sensitivity index. Normal-weight individuals with YOD had lower acute insulin response, steady-state insulin and C-peptide responses, and higher insulin sensitivity index compared to their obese counterparts with YOD. When compared to BMI-matched healthy controls, normal-weight individuals with YOD had lower acute and steady-state insulin and C-peptide responses but similar insulin sensitivity index. The impairment of steady-state beta-cell response relative to healthy controls was more pronounced in normal-weight versus obese individuals with YOD. In conclusion, normal-weight Chinese with YOD exhibited worse beta-cell function but preserved insulin sensitivity relative to obese individuals with YOD and BMI-matched healthy individuals with normoglycemia. The selection of glucose-lowering therapy should account for pathophysiological differences underlying YOD between normal-weight and obese individuals.

Metabolomic and genetic architecture of gestational diabetes subtypes.

Physiological gestational diabetes mellitus (GDM) subtypes that may confer different risks for adverse pregnancy outcomes have been defined. The aim of this study was to characterise the metabolome and genetic architecture of GDM subtypes to address the hypothesis that they differ between GDM subtypes. This was a cross-sectional study of participants in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study who underwent an OGTT at approximately 28 weeks' gestation. GDM was defined retrospectively using International Association of Diabetes and Pregnancy Study Groups/WHO criteria, and classified as insulin-deficient GDM (insulin secretion <25th percentile with preserved insulin sensitivity) or insulin-resistant GDM (insulin sensitivity <25th percentile with preserved insulin secretion). Metabolomic analyses were performed on fasting and 1h serum samples in 3463 individuals (576 with GDM). Genome-wide genotype data were obtained for 8067 individuals (1323 with GDM). Regression analyses demonstrated striking differences between the metabolomes for insulin-deficient or insulin-resistant GDM compared to those with normal glucose tolerance. After adjustment for covariates, 33 fasting metabolites, including 22 medium- and long-chain acylcarnitines, were uniquely associated with insulin-deficient GDM; 23 metabolites, including the branched-chain amino acids and their metabolites, were uniquely associated with insulin-resistant GDM; two metabolites (glycerol and 2-hydroxybutyrate) were associated with the same direction of association with both subtypes. Subtype differences were also observed 1h after a glucose load. In genome-wide association studies, variants within MTNR1B (rs10830963, p=3.43×10-18, OR 1.55) and GCKR (rs1260326, p=5.17×10-13, OR 1.43) were associated with GDM. Variants in GCKR (rs1260326, p=1.36×10-13, OR 1.60) and MTNR1B (rs10830963, p=1.22×10-9, OR 1.49) demonstrated genome-wide significant association with insulin-resistant GDM; there were no significant associations with insulin-deficient GDM. The lead SNP in GCKR, rs1260326, was associated with the levels of eight of the 25 fasting metabolites that were associated with insulin-resistant GDM and ten of 41 1h metabolites that were associated with insulin-resistant GDM. This study demonstrates that physiological GDM subtypes differ in their metabolome and genetic architecture. These findings require replication in additional cohorts, but suggest that these differences may contribute to subtype-related adverse pregnancy outcomes.

Connexin43 in mesenchymal lineage cells regulates body adiposity and energy metabolism in mice.

Connexin43 (Cx43) is the most abundant gap junction protein present in the mesenchymal lineage. In mature adipocytes, Cx43 mediates white adipose tissue (WAT) beiging in response to cold exposure and maintains the mitochondrial integrity of brown adipose tissue (BAT). We found that genetic deletion of Gja1 (Cx43 gene) in cells that give rise to chondro-osteogenic and adipogenic precursors driven by the Dermo1/Twist2 promoter led to lower body adiposity and partial protection against the weight gain and metabolic syndrome induced by a high-fat diet (HFD) in both sexes. These protective effects were related to increased locomotion, fuel utilization, energy expenditure, nonshivering thermogenesis, and better glucose tolerance in conditionally Gja1-ablated mice. Accordingly, Gja1-mutant mice exhibited reduced adipocyte hypertrophy, partially preserved insulin sensitivity, increased BAT lipolysis, and decreased whitening under HFD. This metabolic phenotype was not reproduced with more restricted Gja1 ablation in differentiated adipocytes, suggesting that Cx43 in adipocyte progenitors or other targeted cells restrains energy expenditures and promotes fat accumulation. These results reveal what we believe is a hitherto unknown action of Cx43 in adiposity, and offer a promising new pharmacologic target for improving metabolic balance in diabetes and obesity.

The ketogenic diet promotes triacylglycerol recycling in white adipose tissue and uncoupled fat oxidation in brown adipose tissue, but does not reduce adiposity in rats

The purpose of this study was to determine whether the weight-reducing and fat burning effects of the ketogenic diet (KD) could be attributed to alterations in the energy dissipating pathways of brown adipose tissue (BAT) uncoupled oxidation, and white adipose tissue (WAT) browning and triacylglycerol (TAG) recycling. To investigate this, male Wistar rats were fed one of the following three diets for either 8 or 16 weeks: a standard chow (SC), a high-fat, sucrose-enriched (HFS) obesogenic diet, or a KD. At the end of the intervention, subcutaneous inguinal (Sc Ing) and epididymal (Epid) fat, and interscapular and aortic BAT (iBAT and aBAT, respectively) were extracted. These tissues were used for the analysis of proteins involved in WAT browning and thermogenesis. Isolated adipocytes from WAT were assayed for basal and isoproterenol (Iso)-stimulated lipolysis and basal and insulin-stimulated lipogenesis, and BAT adipocytes were assayed for the determination of coupled and uncoupled glucose and palmitate oxidation. Adiposity similarly increased in HFS- and KD-fed rats at weeks 8 and 16. However, in HFS-fed animals insulin-stimulated lipogenesis and Iso-stimulated lipolysis were impaired in WAT adipocytes, whereas in KD-fed animals these pathways remained intact. The KD also significantly elevated WAT glycerol kinase levels, and favored TAG recycling under conditions of enhanced lipolysis. In BAT, the KD significantly increased uncoupling protein-1 levels and uncoupled fat oxidation. In summary, the KD preserved insulin sensitivity and lipolytic capacity in WAT and also upregulated energy-dissipating pathways in BAT, but it was not sufficient to prevent an increase in adiposity.

Enhanced insulin-regulated phagocytic activities support extreme health span and longevity in multiple populations.

The immune system plays a central role in many processes of age-related disorders and it remains unclear if the innate immune system may play roles in shaping extreme longevity. By an integrated analysis with multiple bulk and single cell transcriptomic, so as DNA methylomic datasets of white blood cells, a previously unappreciated yet commonly activated status of the innate monocyte phagocytic activities is identified. Detailed analyses revealed that the life cycle of these monocytes is enhanced and primed to a M2-like macrophage phenotype. Functional characterization unexpectedly revealed an insulin-driven immunometabolic network which supports multiple aspects of phagocytosis. Such reprogramming is associated to a skewed trend of DNA demethylation at the promoter regions of multiple phagocytic genes, so as a direct transcriptional effect induced by nuclear-localized insulin receptor. Together, these highlighted that preservation of insulin sensitivity is a key to healthy lifespan and extended longevity, via boosting the function of innate immune system in advanced ages.

Insulin and Ageing: Interventions for Healthier Lifestyle and Prolonged Lifespan

Insulin has effects on ageing and lifespan, and provides a mechanism for gene manipulations for people to have prolonged and healthier lives. In addition, preserved insulin sensitivity is associated with longevity. Certain models of deranged insulin signaling are associated with prolonged longevity or resistance to life-threatening factors, such as oxidative stress. Insulin and insulin signaling are associated with successful ageing and longevity. Calorie restriction enhances lifespan in numerous species. Adequate control of factors associated with risks for obesity, diabetes, cardiovascular disease, and other insulin and ageing sequelae can be retarded in the elderly with optimum sustenance of their lifestyles.

Distinct subcellular localisation of intramyocellular lipids and reduced PKCε/PKCθ activity preserve muscle insulin sensitivity in exercise-trained mice.

Athletes exhibit increased muscle insulin sensitivity, despite increased intramuscular triacylglycerol content. This phenomenon has been coined the 'athlete's paradox' and is poorly understood. Recent findings suggest that the subcellular distribution of sn-1,2-diacylglycerols (DAGs) in the plasma membrane leading to activation of novel protein kinase Cs (PKCs) is a crucial pathway to inducing insulin resistance. Here, we hypothesised that regular aerobic exercise would preserve muscle insulin sensitivity by preventing increases in plasma membrane sn-1,2-DAGs and activation of PKCε and PKCθ despite promoting increases in muscle triacylglycerol content. C57BL/6J mice were allocated to three groups (regular chow feeding [RC]; high-fat diet feeding [HFD]; RC feeding and running wheel exercise [RC-EXE]). We used a novel LC-MS/MS/cellular fractionation method to assess DAG stereoisomers in five subcellular compartments (plasma membrane [PM], endoplasmic reticulum, mitochondria, lipid droplets and cytosol) in the skeletal muscle. We found that the HFD group had a greater content of sn-DAGs and ceramides in multiple subcellular compartments compared with the RC mice, which was associated with an increase in PKCε and PKCθ translocation. However, the RC-EXE mice showed, of particular note, a reduction in PM sn-1,2-DAG and ceramide content when compared with HFD mice. Consistent with the PM sn-1,2-DAG-novel PKC hypothesis, we observed an increase in phosphorylation of threonine1150 on the insulin receptor kinase (IRKT1150), and reductions in insulin-stimulated IRKY1162 phosphorylation and IRS-1-associated phosphoinositide 3-kinase activity in HFD compared with RC and RC-EXE mice, which are sites of PKCε and PKCθ action, respectively. These results demonstrate that lower PKCθ/PKCε activity and sn-1,2-DAG content, especially in the PM compartment, can explain the preserved muscle insulin sensitivity in RC-EXE mice.

Irisin Preserves Cardiac Performance and Insulin Sensitivity in Response to Hemorrhage.

Irisin, a cleaved product of the fibronectin type III domain containing protein-5, is produced in the muscle tissue, which plays an important role in modulating insulin resistance. However, it remains unknown if irisin provides a protective effect against the detrimental outcomes of hemorrhage. Hemorrhages were simulated in male CD-1 mice to achieve a mean arterial blood pressure of 35–45 mmHg, followed by resuscitation. Irisin (50 ng/kg) and the vehicle (saline) were administrated at the start of resuscitation. Cardiac function was assessed by echocardiography, and hemodynamics were measured through femoral artery catheterization. A glucose tolerance test was used to evaluate insulin sensitivity. An enzyme-linked immunosorbent assay was performed to detect inflammatory factors in the muscles and blood serum. Western blot was carried out to assess the irisin production in skeletal muscles. Histological analyses were used to determine tissue damage and active-caspase 3 apoptotic signals. The hemorrhage suppressed cardiac performance, as indicated by a reduced ejection fraction and fractional shortening, which was accompanied by enhanced insulin resistance and hyperinsulinemia. Furthermore, the hemorrhage resulted in a marked decrease in irisin and an increase in the production of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). Additionally, the hemorrhage caused marked edema, inflammatory cell infiltration and active-caspase 3 positive signals in skeletal muscles and cardiac muscles. Irisin treatment led to a significant improvement in the cardiac function of animals exposed to a hemorrhage. In addition, irisin treatment improved insulin sensitivity, which is consistent with the suppressed inflammatory cytokine secretion elicited by hemorrhages. Furthermore, hemorrhage-induced tissue edema, inflammatory cell infiltration, and active-caspase 3 positive signaling were attenuated by irisin treatment. The results suggest that irisin protects against damage from a hemorrhage through the modulation of insulin sensitivity.

Pathogenesis, Murine Models, and Clinical Implications of Metabolically Healthy Obesity

Although obesity is commonly associated with numerous cardiometabolic pathologies, some people with obesity are resistant to detrimental effects of excess body fat, which constitutes a condition called “metabolically healthy obesity” (MHO). Metabolic features of MHO that distinguish it from metabolically unhealthy obesity (MUO) include differences in the fat distribution, adipokine types, and levels of chronic inflammation. Murine models are available that mimic the phenotype of human MHO, with increased adiposity but preserved insulin sensitivity. Clinically, there is no established definition of MHO yet. Despite the lack of a uniform definition, most studies describe MHO as a particular case of obesity with no or only one metabolic syndrome components and lower levels of insulin resistance or inflammatory markers. Another clinical viewpoint is the dynamic and changing nature of MHO, which substantially impacts the clinical outcome. In this review, we explore the pathophysiology and some murine models of MHO. The definition, variability, and clinical implications of the MHO phenotype are also discussed. Understanding the characteristics that differentiate people with MHO from those with MUO can lead to new insights into the mechanisms behind obesity-related metabolic derangements and diseases.

Abstract 115: Lean PCOS and IR: A sine QUA non?

Background: There is conflicting evidence with regards to insulin resistance (IR) among lean and obese PCOS. There is a lack of consensus on optimal screening strategy for IR in lean PCOS.Aims and Objectives: The objective was to compare indices of IR, insulin sensitivity and beta cell function (ßF) on a detailed 5 point OGTT (0,30,60,90,120 minute) between Obese (n= 52) and lean (n=28) (BMI ≥23/<23 kg/m2) PCOS and their age- and BMI-matched controls.Results: The OGTT showed cases had higher insulin values and Area Under Curve (AUC) with similar glucose levels as compared to their respective controls (p<0.05). Lean PCOS were more hyperinsulinemic as compared to obese controls (p<0.05). Matsuda index was significantly higher while first and 2nd phase Glucose Stimulated Insulin Secretion (GSIS) with ßF though higher wasn’t significant in lean cases as compared to obese cases (p<0.009). Though both the groups were hyperinsulinemic, lean cases had preserved insulin sensitivity compared to the obese cases. On applying ROC to OGTT values, 90 minute insulin value (52.3 μIU/ml) had the best predictive power for IR. 40% subjects classified as non IR on the basis of fasting value were found to cross this threshold, with more lean cases demonstrating this phenomenon as compared to obese.Conclusion: Increased IR was found in lean PCOS compared to lean and obese controls with 90 minute insulin value diagnosing additional IR missed on routine OGTT.

Predijabetes - od dijagnoze do prognoze

Pre-diabetes is a condition of intermittent hyperglycemia, insufficient to define diabetes, which is characterized by combination of insulin resistance, alpha and beta cell dysfunction. It carries a risk for type 2 diabetes, often with pre-existing vascular complications, atherosclerotic cardiovascular disease, fatty liver and kidney disease. A reliable diagnosis is made on the basis of the oral glucose tolerance test (oGTT) and the levels of glycosylated hemoglobin, HbA1c. Based on that, the presence of 3 basic disorders within pre-diabetes is determined: elevated fasting glycemia, glucose intolerance or both. However, this is not enough to predict the outcome. Extensive epidemiological studies have defined the minimum tests that should be performed in people with pre-diabetes. These are: calculation of body mass index (BMI), analysis of body composition, oGTT with analysis of glycemia, insulin and c-peptide in 0, 60 and 120 min, or just analysis of insulin and c-peptide with calculation of HOMA IR and HOMA B index, triglycerides, HDL cholesterol, transaminases, gamma GT, albuminuria and glomerular filtration according to CKD-EPI creatinine formula. Based on these parameters, 6 subtypes of pre-diabetes have been proposed that can predict outcomes: 1. Moderately obese with initial disturbance in insulin sensitivity, but normal insulin secretion; 2. Normal body weight with normal insulin sensitivity of tissues, but somewhat reduced insulin secretion; 3. Moderate obesity or grade I obesity with moderately reduced insulin sensitivity and insulin secretion; 4. Grade I obesity, more subcutaneous than visceral fat, with preserved insulin sensitivity and secretion; 5. Grade I, II degree or morbidly obese with fatty liver and low insulin sensitivity and secretion and 6. Obesity I, II degree or morbidly obese with increased visceral adipose tissue and risk of kidney disease. Monitoring of outcomes found that the metabolically healthier subtypes of pre-diabetes are 1, 2 and 4. Type 2 diabetes is most common in subtypes 3 and 5. Phenotype 5 has the highest cardiovascular risk and phenotype 6 has the highest mortality. Chronic kidney disease is most common in subtype 6. The presence of fatty liver increases mortality. Identification of pre-diabetes has preventive therapeutic potential. It is important to make a diagnosis, clarify the prognosis and prevent comorbidity by proper diet and physical activity and drugs to treat type 2 diabetes and obesity.

Insulin resistance and risk of vascular events, interventions and mortality in type 1 diabetes.

To identify determinants associated with insulin resistance and to assess the association between insulin resistance and cardiovascular events, vascular interventions and mortality in people with type 1 diabetes at high risk of cardiovascular disease. Prospective cohort study. One hundred and ninety-five people with type 1 diabetes from the Secondary Manifestations of ARTerial disease (SMART) cohort were included. Insulin resistance was quantified by the estimated glucose disposal rate (eGDR) with higher eGDR levels indicating higher insulin sensitivity (i.e. lower eGDR levels indicating higher insulin resistance). Linear regression models were used to evaluate determinants associated with eGDR. The effect of eGDR on cardiovascular events, cardiovascular events or vascular interventions (combined endpoint) and on all-cause mortality was analysed using Cox proportional hazards models adjusted for confounders. In 195 individuals (median follow-up 12.9 years, IQR 6.7-17.0), a total of 25 cardiovascular events, 26 vascular interventions and 27 deaths were observed. High eGDR as a marker for preserved insulin sensitivity was independently associated with a lower risk of cardiovascular events (HR: 0.75; 95% CI: 0.61-0.91), a lower risk of cardiovascular events and vascular interventions (HR: 0.74; 95% CI: 0.63-0.87) and a lower risk of all-cause mortality (HR: 0.81; 95% CI: 0.67-0.98). Insulin resistance as measured by eGDR is an additional risk factor for cardiovascular disease in individuals with type 1 diabetes. Modification of insulin resistance by lifestyle interventions or pharmacological treatment could be a viable therapeutic target to lower the risk of cardiovascular disease.

Back Cover: Dietary Naringenin Preserves Insulin Sensitivity and Grip Strength and Attenuates Inflammation but Accelerates Weight Loss in a Mouse Model of Cancer Cachexia

Mol. Nutr. Food Res. 2021, 65, 202100268 DOI: 10.1002/mnfr.202100268 In article number 2100268, Martha A. Belury and co-workers found that dietary supplementation of naringenin improves multiple aspects of metabolic disturbance during cancer cachexia progression in the C-26 mouse model. The cover image by graphic designer Pamela Galante is a pattern depicting food sources of naringenin, the metabolic interplay between tumor, adipose, and muscle tissues, inflammation, and the insulin receptor.

Dietary Naringenin Preserves Insulin Sensitivity and Grip Strength and Attenuates Inflammation but Accelerates Weight Loss in a Mouse Model of Cancer Cachexia.

Cancer cachexia is characterized by the loss of skeletal muscle resulting in functional impairment, reduced quality of life and mortality. Naringenin, a flavonoid found in citrus fruits, improves insulin sensitivity and reduces inflammation and tumor growth in preclinical models. Therefore, the study hypothesizes that dietary supplementation of naringenin will improve insulin sensitivity, decrease inflammation, slow body weight loss, and delay tumor growth in a mouse model of cancer cachexia. Mice are fed 2 wt% dietary naringenin before and during initiation of cancer cachexia using inoculated adenocarcinoma-26 cells (C-26). Food intake, body weight, body composition, muscle function, insulin tolerance, and inflammatory status are assessed. Although naringenin-fed tumor-bearing mice exhibit reductions in body weight and food intake earlier than control diet-fed tumor-bearing mice, dietary naringenin is protective against loss of muscle strength, and attenuates the onset of insulin resistance and markers of inflammation. Dietary supplementation of naringenin improves multiple aspects of metabolic disturbance and inflammation during cancer cachexia progression in [C-26 tumor-bearing] mice. However, the acceleration of anorexia and weight loss is also observed. These findings emphasize the link between inflammation and insulin resistance as a basis for understanding their roles in the pathogenesis of cancer cachexia.

Pleiotrophin Deficiency Induces Browning of Periovarian Adipose Tissue and Protects against High-Fat Diet-Induced Hepatic Steatosis.

(1) Background: Pleiotrophin preserves insulin sensitivity, regulates adipose tissue lipid turnover and plasticity, energy metabolism and thermogenesis. The aim of this study was to determine the role of pleiotrophin in hepatic lipid metabolism and in the metabolic crosstalk between the liver and brown and white adipose tissue (AT) in a high-fat diet-induced (HFD) obesity mice model. (2) Methods: We analyzed circulating variables, lipid metabolism (hepatic lipid content and mRNA expression), brown AT thermogenesis (UCP-1 expression) and periovarian AT browning (brown adipocyte markers mRNA and immunodetection) in Ptn−/− mice either fed with standard-chow diet or with HFD and in their corresponding Ptn+/+ counterparts. (3) Results: HFD-Ptn−/− mice are protected against the development of HFD-induced insulin resistance, had lower liver lipid content and lower expression of the key enzymes involved in triacylglycerides and fatty acid synthesis in liver. HFD-Ptn−/− mice showed higher UCP-1 expression in brown AT. Moreover, Ptn deletion increased the expression of specific markers of brown/beige adipocytes and was associated with the immunodetection of UCP-1 enriched multilocular adipocytes in periovarian AT. (4) Conclusions: Ptn deletion protects against the development of HFD-induced insulin resistance and liver steatosis, by increasing UCP-1 expression in brown AT and promoting periovarian AT browning.

501-P: Lower Plasma Membrane Sn-1,2-Diacylglycerol Content and PKCepsilon/theta Activity Explain the Athlete’s Paradox

Increases in intramyocellular lipids (IMCL) are strongly associated with muscle insulin resistance. An important exception to this observation occurs in athletes, who manifest increased IMCL content despite increased muscle insulin sensitivity. This phenomenon has been coined the “Athlete’s Paradox” and is not well understood. Here, we examined the hypothesis that the Athlete’s Paradox can be explained by lower plasma membrane (PM) associated sn-1,2-diacylglycerol (DAG) content leading to lower PKCε and PKCθ translocation in skeletal muscle despite increased muscle triglyceride (TAG) content. To address this hypothesis we studied 3 groups of male C57BL/6J mice following 6 weeks of: 1) Regular chow feeding (RC), 2) High-fat diet feeding (HFD); 3) RC-feeding and running wheel exercise (EX). DAG stereoisomers were assessed in five subcellular compartments [PM, endoplasmic reticulum (ER), mitochondria (Mito), and lipid droplet (LD)] using a novel liquid chromatography-tandem mass spectrometry/cellular fractionation method. Consistent with the Athlete’s Paradox we found that EX mice manifested improved glucose tolerance and muscle insulin sensitivity compared to HFD mice, as assessed by glucose tolerance and hyperinsulinemic-euglycemic clamp studies, despite similar increases in muscle TAG content (RC=5.7 ± 3.2 µg/mg; HFD=17.8 ± 6.0 µg/mg; EX=13.7 ± 5.2 µg/mg) compared to RC mice (RC vs. HFD P&amp;lt;0.01, RC vs. EX P&amp;lt;0.01 and HFD vs. EX P=NS). However, in contrast to the EX and RC mice the HFD group had a 2-fold increase in PM sn-1,2-DAG content compared to the RC and EX mice (both P&amp;lt;0.01), which was associated with a 2-3 fold increase in PKCε and PKCθ translocation (both P&amp;lt;0.05 compared to HFD) and reduced insulin-stimulated InsrY1162/AKT473 phosphorylation and glucose transport (all P&amp;lt;0.01 vs. HFD). Conclusion: Lower PM sn-1,2-DAG content and PKCε/PKCθ activity provides an explanation for the preserved insulin sensitivity in EX mice and thus the Athlete’s Paradox. Disclosure R. C. Gaspar: None. M. Kahn: None. G. Cline: None. J. R. Pauli: None. R. J. Perry: None. K. Petersen: Advisory Panel; Spouse/Partner; AstraZeneca, iMetabolic Biopharma Corporation, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc., Consultant; Spouse/Partner; Aegerion Pharmaceuticals Inc., Novo Nordisk, Research Support; Self; Gilead Sciences, Inc., Merck &amp; Co., Inc. G. I. Shulman: Consultant; Self; 89bio, Inc., BridgeBio, Ionis Pharmaceuticals, Maze Therapeutics, Novo Nordisk, Other Relationship; Self; AstraZeneca, Esperion Therapeutics, Inc, Generian Pharmaceuticals, Inc., Gilead Sciences, Inc., iMetabolic Biopharma Corporation, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc., The Liver Company. K. Lyu: None. B. T. Hubbard: None. B. Leitner: None. P. Luukkonen: Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Research Support; Self; Novo Nordisk Foundation. S. Hirabara: None. I. Sakuma: None. A. Nasiri: Employee; Spouse/Partner; Medtronic. D. Zhang: None. Funding São Paulo Research Foundation (2019/11338-9, 2017/20542-3); National Institutes of Health (R01DK116774, P30DK045735)

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

Abstract Adipose-resident Tregs protect against systemic inflammation and metabolic disease by limiting expansion of pro-inflammatory cells, preserving insulin sensitivity and maintaining glucose tolerance. Although their basic markers and roles have been studied, less is known about the transcriptional machinery regulating their differentiation and function. B lymphocyte-induced maturation protein-1 (Blimp-1) is a transcriptional regulator known to be involved in development, polarization, and maintenance of various immune cells including CD4+ T cells. Using Blimp-1 reporter mice, we discovered that Blimp-1 is constitutively expressed in a subset of visceral adipose tissue (VAT) Tregs, and that Blimp-1+ VAT Tregs are phenotypically distinct from their Blimp-1-counterparts. We also found that Treg-specific Blimp-1 deletion led to altered differentiation and function of VAT and inguinal adipose tissue Tregs. Surprisingly, during diet-induced obesity, Blimp-1 Treg deficient mice gained less weight, had reduced body fat percentage, and exhibited improved insulin sensitivity compared to wild type mice. Furthermore, this was accompanied by upregulation of thermogenic genes such as Ucp1, Prdm16 and Dio2 in inguinal adipose tissue, and increased overall fatty acid oxidation. It has previously been shown that IL-10 can induce thermogenesis. Therefore, we repeated these experiments utilizing mice with Treg-specific deletion of IL-10 and found that they phenocopied the Blimp-1 Treg deficient mice. Based on these results, we hypothesize that cross-talk between Tregs and adipocytes via a Blimp-1-IL-10 axis suppresses thermogenesis, and that absence of Blimp-1+ Tregs is metabolically protective during diet-induced obesity.

ICOS signaling limits regulatory T cell accumulation and function in visceral adipose tissue.

A unique population of Foxp3+ regulatory T cells (TRs) resides in visceral adipose tissue (VAT) that regulates adipose inflammation and helps preserve insulin sensitivity. Inducible T cellco-stimulator (ICOS) is highly expressed on effector (e)TRs that migrate to nonlymphoid tissues, and contributes to their maintenance and function in models of autoimmunity. In this study, we report an unexpected cell-intrinsic role for ICOS expression and downstream phosphoinositide 3-kinase (PI3K) signaling in limiting the abundance, VAT-associated phenotype, and function of TRs specifically in VAT. Icos-/- mice and mice expressing a knock-in form of ICOS that cannot activate PI3K had increased VAT-TR abundance and elevated expression of canonical VAT-TR markers. Loss of ICOS signaling facilitated enhanced accumulation of TRs to VAT associated with elevated CCR3 expression, and resulted in reduced adipose inflammation and heightened insulin sensitivity in the context of a high-fat diet. Thus, we have uncovered a new and surprising molecular pathway that regulates VAT-TR accumulation and function.

76938 Does Decreased Adipose Tissue Eosinophil Content Impair Adipocyte Biology in Human Subjects with Obesity and Insulin Resistance?

ABSTRACT IMPACT: Extrapolating from mouse data we explored eosinophil content in human adipose tissue and its effect on adipocyte biology potentially leading to the discovery of novel therapeutic targets for treatment of obesity and insulin resistance. OBJECTIVES/GOALS: The interaction between immune cells and adipose tissue (AT) in obesity has not been fully elicited. Mouse models of diet-induced-obesity show AT resident eosinophils (EOS) help preserve insulin sensitivity (IS). As data in human obesity are lacking, here we explored AT-EOS content and their role in AT metabolism in subjects with and without obesity. METHODS/STUDY POPULATION: We recruited lean (L) subjects and patients with obesity (Ob) to undergo abdominal subcutaneous AT biopsy and evaluation of insulin resistance (IR) by determination of HOMA-IR. Circulating EOS were isolated from all participants under fasting conditions and exposed to high glucose (HG) or high lipids (HL) for 4 hrs. AT EOS number was assessed via FACS analysis. Circulating EOS and AT mRNA was assessed by qPCR for multiple genes involved in inflammation and cell migration. To evaluate the effect of EOS on primary human adipocytes, in vitro cultures were exposed for 4 days to either interleukin-4 (IL-4), interleukin-13 (IL-13) or to human EOS. Adipocytes mRNA levels were evaluated for genes involved in adipogenesis and lipid metabolism. RESULTS/ANTICIPATED RESULTS: 16 lean, IS subjects (BMI 22.5+ 0.4kg/m2) and 22 age-matched IR patients with obesity (BMI: 38.9 + 1.0kg/m2) participated. We observed a ratio of 2:1 in AT EOS content of L vs Ob subjects (P&lt;0.03). To assess the reduced AT-EOS content in obesity, we evaluated expression of Chemokine-C receptor 3 (CCR3) in circulating EOS. We show decreased CCR3 mRNA levels in Ob vs L subjects (P=0.006). We expect HL in vitro experiments on peripheral EOS of L subjects to affect CCR3 mRNA levels. In AT of Ob subjects, we found a significant decreased expression of Eotaxin 2, the main EOS chemokine binding CCR3 expressed on EOS. Preliminary data from in vitro primary adipocytes culture suggest for IL-4 and IL-13 to increase mRNA level of Peroxisome Proliferator Activated Receptor Gamma (PPARG), the master regulator of adipogenesis. DISCUSSION/SIGNIFICANCE OF FINDINGS: Comparable to animal studies, we found a decrease of AT-EOS content in patients with obesity. Alterations in CCR3/Eotaxin 2 signaling may be involved. IL-4 &amp;IL-13 are secreted predominantly by EOS and appear to directly regulate gene expression in human adipocytes. These data represent the first evidence for a novel role of EOS in human AT biology.

Diagnostic accuracy of the tri-ponderal mass index in identifying the unhealthy metabolic obese phenotype in obese patients

IntroductionThe metabolically healthy obese phenotype (FOMS) defines obese patients who have preserved insulin sensitivity and absence of metabolic complications. This phenotype is associated with a lower risk of cardiovascular disease and type 2 diabetes in adulthood. ObjectivesTo determine the prevalence of FOMS and the obese phenotype with metabolic risk (FORM) in a cohort of obese children and adolescents and to establish the predictive capacity of the tri-ponderal mass index (TMI) and other anthropometric parameters in order to identify these patients. Patients and methodsA cross-sectional study was conducted on 239 obese patients (125 males) from 8 to 18 years of age. Grade 3 obesity was present in 45.9% of the patients. ROC curves were used to find the best cut-off point for: TMI, body mass index (BMI), BMI z-score (BMIzs), and waist/height index (WHI). FOMS components: plasma blood glucose, plasma triglycerides, HDL-cholesterol, and blood pressure. ResultsThe prevalence of FOMS in the study cohort was 37.6%. No differences between genders were observed, and it was increasing with the age and the level of obesity. The TMI has a sensitivity of 75.8 and a specificity of 42.2 to identify the FORM patients. The best cut-off point for TMI is 18.7 kg/m3, for BMI it was 30.4 kg/m2, for BMIzs +3.5 SD, and 0.62 for WHI. ConclusionsThe diagnostic accuracy of TMI in identifying obese adolescents with metabolic risk was similar to BMI and WHI. However, the TMI makes it easier and simplifies the classification of the obesity level in both genders.