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Detection and Characterization of CD8+ Autoreactive Memory Stem T Cells in Patients With Type 1 Diabetes

Diabetes - Fri, 04/20/2018 - 13:00

Stem memory T cells (Tscm) constitute the earliest developmental stage of memory T cells, displaying stem cell–like properties, such as self-renewal capacity. Their superior immune reconstitution potential has sparked interest in cancer immune therapy, vaccine development, and immune reconstitution, whereas their role in autoimmunity is largely unexplored. Here we show that autoreactive CD8+ Tscm specific for β-cell antigens GAD65, insulin, and IGRP are present in patients with type 1 diabetes (T1D). In vitro, the generation of autoreactive Tscm from naive precursors required the presence of the homeostatic cytokine interleukin-7 (IL-7). IL-7 promotes glucose uptake via overexpression of GLUT1 and upregulation of the glycolytic enzyme hexokinase 2. Even though metabolism depends on glucose uptake, the subsequent oxidation of pyruvate in the mitochondria was necessary for Tscm generation from naive precursors. In patients with T1D, high expression of GLUT1 was a hallmark of circulating Tscm, and targeting glucose uptake via GLUT1 using the selective inhibitor WZB117 resulted in inhibition of Tscm generation and expansion. Our results suggest that autoreactive Tscm are present in patients with T1D and can be selectively targeted by inhibition of glucose metabolism.

Categories: Diabetes

A Novel Strategy to Prevent Advanced Atherosclerosis and Lower Blood Glucose in a Mouse Model of Metabolic Syndrome

Diabetes - Fri, 04/20/2018 - 13:00

Cardiovascular disease caused by atherosclerosis is the leading cause of mortality associated with type 2 diabetes and metabolic syndrome. Insulin therapy is often needed to improve glycemic control, but it does not clearly prevent atherosclerosis. Upon binding to the insulin receptor (IR), insulin activates distinct arms of downstream signaling. The IR-Akt arm is associated with blood glucose lowering and beneficial effects, whereas the IR-Erk arm might exert less desirable effects. We investigated whether selective activation of the IR-Akt arm, leaving the IR-Erk arm largely inactive, would result in protection from atherosclerosis in a mouse model of metabolic syndrome. The insulin mimetic peptide S597 lowered blood glucose and activated Akt in insulin target tissues, mimicking insulin’s effects, but only weakly activated Erk and even prevented insulin-induced Erk activation. Strikingly, S597 retarded atherosclerotic lesion progression through a process associated with protection from leukocytosis, thereby reducing lesional accumulation of inflammatory Ly6Chi monocytes. S597-mediated protection from leukocytosis was accompanied by reduced numbers of the earliest bone marrow hematopoietic stem cells and reduced IR-Erk activity in hematopoietic stem cells. This study provides a conceptually novel treatment strategy for advanced atherosclerosis associated with metabolic syndrome and type 2 diabetes.

Categories: Diabetes

RAGE Deletion Confers Renoprotection by Reducing Responsiveness to Transforming Growth Factor-{beta} and Increasing Resistance to Apoptosis

Diabetes - Fri, 04/20/2018 - 13:00

Signaling via the receptor of advanced glycation end products (RAGE)—though complex and not fully elucidated in the setting of diabetes—is considered a key injurious pathway in the development of diabetic nephropathy (DN). We report here that RAGE deletion resulted in increased expression of fibrotic markers (collagen I and IV, fibronectin) and the inflammatory marker MCP-1 in primary mouse mesangial cells (MCs) and in kidney cortex. RNA sequencing analysis in MCs from RAGE–/– and wild-type mice confirmed these observations. Nevertheless, despite these gene expression changes, decreased responsiveness to transforming growth factor-β was identified in RAGE–/– mice. Furthermore, RAGE deletion conferred a more proliferative phenotype in MCs and reduced susceptibility to staurosporine-induced apoptosis. RAGE restoration experiments in RAGE–/– MCs largely reversed these gene expression changes, resulting in reduced expression of fibrotic and inflammatory markers. This study highlights that protection against DN in RAGE knockout mice is likely to be due in part to the decreased responsiveness to growth factor stimulation and an antiapoptotic phenotype in MCs. Furthermore, it extends our understanding of the role of RAGE in the progression of DN, as RAGE seems to play a key role in modulating the sensitivity of the kidney to injurious stimuli such as prosclerotic cytokines.

Categories: Diabetes

Fibroblast Growth Factor 21 Protects Photoreceptor Function in Type 1 Diabetic Mice

Diabetes - Fri, 04/20/2018 - 13:00

Retinal neuronal abnormalities occur before vascular changes in diabetic retinopathy. Accumulating experimental evidence suggests that neurons control vascular pathology in diabetic and other neovascular retinal diseases. Therefore, normalizing neuronal activity in diabetes may prevent vascular pathology. We investigated whether fibroblast growth factor 21 (FGF21) prevented retinal neuronal dysfunction in insulin-deficient diabetic mice. We found that in diabetic neural retina, photoreceptor rather than inner retinal function was most affected and administration of the long-acting FGF21 analog PF-05231023 restored the retinal neuronal functional deficits detected by electroretinography. PF-05231023 administration protected against diabetes-induced disorganization of photoreceptor segments seen in retinal cross section with immunohistochemistry and attenuated the reduction in the thickness of photoreceptor segments measured by optical coherence tomography. PF-05231023, independent of its downstream metabolic modulator adiponectin, reduced inflammatory marker interleukin-1β (IL-1β) mRNA levels. PF-05231023 activated the AKT-nuclear factor erythroid 2–related factor 2 pathway and reduced IL-1β expression in stressed photoreceptors. PF-05231023 administration did not change retinal expression of vascular endothelial growth factor A, suggesting a novel therapeutic approach for the prevention of early diabetic retinopathy by protecting photoreceptor function in diabetes.

Categories: Diabetes

Urinary IgG4 and Smad1 Are Specific Biomarkers for Renal Structural and Functional Changes in Early Stages of Diabetic Nephropathy

Diabetes - Fri, 04/20/2018 - 13:00

Diabetic nephropathy (DN) is the major cause of end-stage kidney disease, but early biomarkers of DN risk are limited. Herein we examine urinary IgG4 and Smad1 as additional early DN biomarkers. We recruited 815 patients with type 2 diabetes; 554 patients fulfilled the criteria of an estimated glomerular filtration rate (eGFR) >60 mL/min and no macroalbuminuria at baseline, with follow-up for 5 years. Patients without macroalbuminuria were also recruited for renal biopsies. Urinary IgG4 and Smad1 were determined by enzyme-linked immunoassays using specific antibodies. The specificity, sensitivity, and reproducibility were confirmed for each assay. Increased urinary IgG4 was significantly associated with lower eGFR. The level of urinary IgG4 also significantly correlated with surface density of peripheral glomerular basement membrane (Sv PGBM/Glom), whereas Smad1 was associated with the degree of mesangial expansion—both classic pathological findings in DN. Baseline eGFR did not differ between any groups; however, increases in both urinary IgG4 and Smad1 levels at baseline significantly predicted later development of eGFR decline in patients without macroalbuminuria. These data suggest that urinary IgG4 and Smad1 at relatively early stages of DN reflect underlying DN lesions and are relevant to later clinical outcomes.

Categories: Diabetes

Altered Odor-Induced Brain Activity as an Early Manifestation of Cognitive Decline in Patients With Type 2 Diabetes

Diabetes - Fri, 04/20/2018 - 13:00

Type 2 diabetes is reported to be associated with olfactory dysfunction and cognitive decline. However, whether and how olfactory neural circuit abnormalities involve cognitive impairment in diabetes remains uncovered. This study thus aimed to investigate olfactory network alterations and the associations of odor-induced brain activity with cognitive and metabolic parameters in type 2 diabetes. Participants with normal cognition, including 51 patients with type 2 diabetes and 41 control subjects without diabetes, underwent detailed cognitive assessment, olfactory behavior tests, and odor-induced functional MRI measurements. Olfactory brain regions showing significantly different activation between the two groups were selected for functional connectivity analysis. Compared with the control subjects, patients with diabetes demonstrated significantly lower olfactory threshold score, decreased brain activation, and disrupted functional connectivity in the olfactory network. Positive associations of the disrupted functional connectivity with decreased neuropsychology test scores and reduced pancreatic function were observed in patients with diabetes. Notably, the association between pancreatic function and executive function was mediated by olfactory behavior and olfactory functional connectivity. Our results suggested the alteration of olfactory network is present before clinically measurable cognitive decrements in type 2 diabetes, bridging the gap between the central olfactory system and cognitive decline in diabetes.

Categories: Diabetes

Metabolic Syndrome Is Associated With Impaired Diastolic Function Independently of MRI-Derived Myocardial Extracellular Volume: The MESA Study

Diabetes - Fri, 04/20/2018 - 13:00

The relationship of metabolic syndrome (MetS) and insulin resistance (one of its key pathophysiological mediators) with diastolic dysfunction and myocardial fibrosis is not well understood. This study aimed to evaluate the association of MetS with diastolic function and myocardial extracellular matrix (ECM) using cardiac MRI (CMRI) in a large community-based population. This cross-sectional analysis included 1,582 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) with left ventricular ejection fraction ≥50% and no history of cardiac events. Diastolic function was assessed using tagged CMRI parameters including end-diastolic strain rate (EDSR) and strain relaxation index (SRI). ECM was evaluated using extracellular volume (ECV) quantification. Participants’ mean age was 67.4 ± 8.6 years, and 48.1% were males. MetS was present in 533 individuals (33.7%), and type 2 diabetes in 250 (15.8%). In the multivariable analyses, MetS (irrespective of the presence of type 2 diabetes) and higher insulin resistance were associated with impaired diastolic function (higher SRI and lower EDSR), independent of ECV. In conclusion, MetS, irrespective of the presence of type 2 diabetes, was independently associated with impaired diastole. These functional myocardial changes seem to result from intrinsic cardiomyocyte alterations, irrespective of the myocardial interstitium (including fibrosis).

Categories: Diabetes

Circulating miRNA Profiles Associated With Hyperglycemia in Patients With Type 1 Diabetes

Diabetes - Fri, 04/20/2018 - 13:00

We investigated plasma microRNA (miRNA) profiles associated with variation of hyperglycemia, measured as hemoglobin A1c (HbA1c), in two panels of patients with type 1 diabetes (T1D). Using the HTG Molecular Diagnostics EdgeSeq platform, 2,083 miRNAs were measured in plasma from 71 patients included in a screening panel. Quantitative real-time PCR was used to measure the candidate miRNAs in plasma from 95 patients included in an independent replication panel. We found 10 miRNAs replicated in both panels and 4 with high statistical significance. The strongest positive correlations with HbA1c were found with miR-125b-5p (rs = 0.40, P = 6.0 x 10–5) and miR-365a-3p (rs = 0.35, P = 5.9 x 10–4). The strongest negative correlations were found with miR-5190 (rs = –0.30, P = 0.003) and miR-770-5p (rs = –0.27, P = 0.008). Pathway analysis revealed that 50 Kyoto Encyclopedia of Genes and Genomes pathways were significantly enriched by genes targeted by these four miRNAs. The axon guidance signaling pathway was enriched (P < 1 x 10–7) by genes targeted by all four miRNAs. In addition, three other pathways (Rap1 signaling, focal adhesion, and neurotrophin signaling) were also significantly enriched but with genes targeted by only by three of the identified miRNAs. In conclusion, our study identified four circulating miRNAs that were influenced by variation in hyperglycemia. Dysregulation of these miRNAs, which are associated with hyperglycemia in patients with T1D, may contribute to the development of diabetes complications. However, there are multitudes of possible mechanisms/pathways through which dysregulation of these miRNAs may impact risk of diabetes complications.

Categories: Diabetes

Fetal Genotype and Maternal Glucose Have Independent and Additive Effects on Birth Weight

Diabetes - Fri, 04/20/2018 - 13:00

Maternal glycemia is a key determinant of birth weight, but recent large-scale genome-wide association studies demonstrated an important contribution of fetal genetics. It is not known whether fetal genotype modifies the impact of maternal glycemia or whether it acts through insulin-mediated growth. We tested the effects of maternal fasting plasma glucose (FPG) and a fetal genetic score for birth weight on birth weight and fetal insulin in 2,051 European mother-child pairs from the Exeter Family Study of Childhood Health (EFSOCH) and the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study. The fetal genetic score influenced birth weight independently of maternal FPG and impacted growth at all levels of maternal glycemia. For mothers with FPG in the top tertile, the frequency of large for gestational age (birth weight ≥90th centile) was 31.1% for offspring with the highest tertile genetic score and only 14.0% for those with the lowest tertile genetic score. Unlike maternal glucose, the fetal genetic score was not associated with cord insulin or C-peptide. Similar results were seen for HAPO participants of non-European ancestry (n = 2,842 pairs). This work demonstrates that for any level of maternal FPG, fetal genetics has a major impact on fetal growth and acts predominantly through independent mechanisms.

Categories: Diabetes

Novel lncRNA Erbb4-IR Promotes Diabetic Kidney Injury in db/db Mice by Targeting miR-29b

Diabetes - Tue, 03/20/2018 - 13:00

Transforming growth factor-β/Smad signaling plays an important role in diabetic nephropathy. The current study identified a novel Smad3-dependent long noncoding RNA (lncRNA) Erbb4-IR in the development of type 2 diabetic nephropathy (T2DN) in db/db mice. We found that Erbb4-IR was highly expressed in T2DN of db/db mice and specifically induced by advanced glycosylation end products (AGEs) via a Smad3-dependent mechanism. The functional role of Erbb4-IR in T2DN was revealed by kidney-specific silencing of Erbb4-IR to protect against the development of T2DN, such as elevated microalbuminuria, serum creatinine, and progressive renal fibrosis in db/db mice, and to block AGE-induced collagen I and IV expression in mouse mesangial cells (mMCs) and mouse tubular epithelial cells (mTECs). Mechanistically, we identified that the Erbb4-IR–microRNA (miR)-29b axis was a key mechanism of T2DN because Erbb4-IR was able to bind the 3' untranslated region of miR-29b genomic sequence to suppress miR-29b expression at transcriptional level. In contrast, silencing of renal Erbb4-IR increased miR-29b and therefore protected the kidney from progressive renal injury in db/db mice and prevented mTECs and mMCs from AGE-induced loss of miR-29b and fibrotic response in vitro. Collectively, we identify that Erbb4-IR is a Smad3-dependent lncRNA that promotes renal fibrosis in T2DN by suppressing miR-29b. Targeting Erbb4-IR may represent a novel therapy for T2DN.

Categories: Diabetes

Sirt1: A Guardian of the Development of Diabetic Retinopathy

Diabetes - Tue, 03/20/2018 - 13:00

Diabetic retinopathy is a multifactorial disease, and the exact mechanism of its pathogenesis remains obscure. Sirtuin 1 (Sirt1), a multifunctional deacetylase, is implicated in the regulation of many cellular functions and in gene transcription, and retinal Sirt1 is inhibited in diabetes. Our aim was to determine the role of Sirt1 in the development of diabetic retinopathy and to elucidate the molecular mechanism of its downregulation. Using Sirt1-overexpressing mice that were diabetic for 8 months, structural, functional, and metabolic abnormalities were investigated in vascular and neuronal retina. The role of epigenetics in Sirt1 transcriptional suppression was investigated in retinal microvessels. Compared with diabetic wild-type mice, retinal vasculature from diabetic Sirt1 mice did not present any increase in the number of apoptotic cells or degenerative capillaries or decrease in vascular density. Diabetic Sirt1 mice were also protected from mitochondrial damage and had normal electroretinography responses and ganglion cell layer thickness. Diabetic wild-type mice had hypermethylated Sirt1 promoter DNA, which was alleviated in diabetic Sirt1 mice, suggesting a role for epigenetics in its transcriptional suppression. Thus strategies targeted to ameliorate Sirt1 inhibition have the potential to maintain retinal vascular and neuronal homeostasis, providing opportunities to retard the development of diabetic retinopathy in its early stages.

Categories: Diabetes

Diabetes Reduces Severity of Aortic Aneurysms Depending on the Presence of Cell Division Autoantigen 1 (CDA1)

Diabetes - Tue, 03/20/2018 - 13:00

Diabetes is a negative risk factor for aortic aneurysm, but the underlying explanation for this phenomenon is unknown. We have previously demonstrated that cell division autoantigen 1 (CDA1), which enhances transforming growth factor-β signaling, is upregulated in diabetes. We hypothesized that CDA1 plays a key role in conferring the protective effect of diabetes against aortic aneurysms. Male wild-type, CDA1 knockout (KO), apolipoprotein E (ApoE) KO, and CDA1/ApoE double-KO (dKO) mice were rendered diabetic. Whereas aneurysms were not observed in diabetic ApoE KO and wild-type mice, 40% of diabetic dKO mice developed aortic aneurysms. These aneurysms were associated with attenuated aortic transforming growth factor-β signaling, reduced expression of various collagens, and increased aortic macrophage infiltration and matrix metalloproteinase 12 expression. In the well-characterized model of angiotensin II–induced aneurysm formation, concomitant diabetes reduced fatal aortic rupture and attenuated suprarenal aortic expansion, changes not seen in dKO mice. Furthermore, aortic CDA1 expression was downregulated ~70% within biopsies from human abdominal aortic aneurysms. The identification that diabetes is associated with upregulation of vascular CDA1 and that CDA1 deletion in diabetic mice promotes aneurysm formation provides evidence that CDA1 plays a role in diabetes to reduce susceptibility to aneurysm formation.

Categories: Diabetes

ELOVL4-Mediated Production of Very Long-Chain Ceramides Stabilizes Tight Junctions and Prevents Diabetes-Induced Retinal Vascular Permeability

Diabetes - Tue, 03/20/2018 - 13:00

Tight junctions (TJs) involve close apposition of transmembrane proteins between cells. Although TJ proteins have been studied in detail, the role of lipids is largely unknown. We addressed the role of very long-chain (VLC ≥26) ceramides in TJs using diabetes-induced loss of the blood-retinal barrier as a model. VLC fatty acids that incorporate into VLC ceramides are produced by elongase elongation of very long-chain fatty acids protein 4 (ELOVL4). ELOVL4 is significantly reduced in the diabetic retina. Overexpression of ELOVL4 significantly decreased basal permeability, inhibited vascular endothelial growth factor (VEGF)– and interleukin-1β–induced permeability, and prevented VEGF-induced decrease in occludin expression and border staining of TJ proteins ZO-1 and claudin-5. Intravitreal delivery of AAV2-hELOVL4 reduced diabetes-induced increase in vascular permeability. Ultrastructure and lipidomic analysis revealed that -linked acyl-VLC ceramides colocalize with TJ complexes. Overall, normalization of retinal ELOVL4 expression could prevent blood-retinal barrier dysregulation in diabetic retinopathy through an increase in VLC ceramides and stabilization of TJs.

Categories: Diabetes

Issues and Events

Diabetes - Tue, 03/20/2018 - 13:00
Categories: Diabetes

In This Issue of Diabetes

Diabetes - Tue, 03/20/2018 - 13:00
Categories: Diabetes

New Understanding of {beta}-Cell Heterogeneity and In Situ Islet Function

Diabetes - Tue, 03/20/2018 - 13:00

Insulin-secreting β-cells are heterogeneous in their regulation of hormone release. While long known, recent technological advances and new markers have allowed the identification of novel subpopulations, improving our understanding of the molecular basis for heterogeneity. This includes specific subpopulations with distinct functional characteristics, developmental programs, abilities to proliferate in response to metabolic or developmental cues, and resistance to immune-mediated damage. Importantly, these subpopulations change in disease or aging, including in human disease. Although discovering new β-cell subpopulations has substantially advanced our understanding of islet biology, a point of caution is that these characteristics have often necessarily been identified in single β-cells dissociated from the islet. β-Cells in the islet show extensive communication with each other via gap junctions and with other cell types via diffusible chemical messengers. As such, how these different subpopulations contribute to in situ islet function, including during plasticity, is not well understood. We will discuss recent findings revealing functional β-cell subpopulations in the intact islet, the underlying basis for these identified subpopulations, and how these subpopulations may influence in situ islet function. Furthermore, we will discuss the outlook for emerging technologies to gain further insight into the role of subpopulations in in situ islet function.

Categories: Diabetes

The Diabetes Gene and Wnt Pathway Effector TCF7L2 Regulates Adipocyte Development and Function

Diabetes - Tue, 03/20/2018 - 13:00

The gene encoding for transcription factor 7-like 2 (TCF7L2) is the strongest type 2 diabetes mellitus (T2DM) candidate gene discovered to date. The TCF7L2 protein is a key transcriptional effector of the Wnt/β-catenin signaling pathway, which is an important developmental pathway that negatively regulates adipogenesis. However, the precise role that TCF7L2 plays in the development and function of adipocytes remains largely unknown. Using a combination of in vitro approaches, we first show that TCF7L2 protein is increased during adipogenesis in 3T3-L1 cells and primary adipocyte stem cells and that TCF7L2 expression is required for the regulation of Wnt signaling during adipogenesis. Inactivation of TCF7L2 protein by removing the high-mobility group (HMG)-box DNA binding domain in mature adipocytes in vivo leads to whole-body glucose intolerance and hepatic insulin resistance. This phenotype is associated with increased subcutaneous adipose tissue mass, adipocyte hypertrophy, and inflammation. Finally, we demonstrate that TCF7L2 mRNA expression is downregulated in humans with impaired glucose tolerance and adipocyte insulin resistance, highlighting the translational potential of these findings. In summary, our data indicate that TCF7L2 has key roles in adipose tissue development and function that may reveal, at least in part, how TCF7L2 contributes to the pathophysiology of T2DM.

Categories: Diabetes

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