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Obesity is associated with chronic low-grade inflammation of visceral adipose tissue (AT) characterized by an increasing number of AT macrophages (ATMs) and linked to type 2 diabetes. AT inflammation is histologically indicated by the formation of so-called crown-like structures, as ATMs accumulate around dying adipocytes, and the occurrence of multinucleated giant cells (MGCs). However, to date, the function of MGCs in obesity is unknown. Therefore, the aim of this study was to characterize MGCs in AT and unravel the function of these cells. We demonstrated that MGCs occurred in obese patients and after 24 weeks of a high-fat diet in mice, accompanying signs of AT inflammation and then representing ∼3% of ATMs in mice. Mechanistically, we found evidence that adipocyte death triggered MGC formation. Most importantly, MGCs in obese AT had a higher capacity to phagocytize oversized particles, such as adipocytes, as shown by live imaging of AT, 45-µm bead uptake ex vivo, and higher lipid content in vivo. Finally, we showed that interleukin-4 treatment was sufficient to increase the number of MGCs in AT, whereas other factors may be more important for endogenous MGC formation in vivo. Most importantly, our data suggest that MGCs are specialized for clearance of dead adipocytes in obesity. [ABSTRACT FROM AUTHOR]

We intended to establish a computational model by using NIH Image J and Adobe Photoshop software to evaluate the effect of TRH on streptozocin (STZ) treated diabetic rats on the insulin immunohistochemistry sections of pancreatic islet cell mass. Diabetes Mellitus (DM), a disorder of epidemic proportions, is a heterogeneous group of disorders characterized by hyperglycemia and glucose intolerance. Multiple treatment options are currently available for DM. In the recent era of research efforts on Islet cell transplant, β cell apoptosis has become a major impediment for both Diabetes Type 1 and type 2. In vivo bone marrow transplantation, ex vivo β cell generation and in vivo stimulation of regeneration have been conducted in an attempt to increase β cell mass and function. Various functional and immunohistochemical assays have been traditionally used to evaluate β-cell regeneration. In our study, we investigated the effects of Thyrotropin Releasing Hormone (TRH) on diabetic rats' pancreatic islet function, which may have a role in β-cell recovery, by establishing a computational modeling combined with two image analysis software. We performed IHC analyses to identify pancreatic islets after rats were sacrificed and the pancreas was fixed. Based on these microscope images, we were able to develop a method with image analysis software to quantify the difference in pancreatic islet mass between diabetic and treatment groups (Control, Diabetic and TRH treated rat groups). The previous investigation utilized the microscope images for a qualitative survey. In this paper, however, we focused on specifically the quantitative analysis of changes in the β-cell mass due to TRH. The positive islet image density was identified by Adobe Photoshop software using the total area (measured using NIH Image J) as a parameter. We discovered that rat exposure to TRH increases islet cell expression and hence the total area independent to the exposure to STZ, supporting the idea that TRH affects β cell mass recovery either by neogenesis or proliferation. Previous stereological methods include β cell mass, β cell average size, cell density and counting the number of β-cells associated with the duct. Measurement of total area using NIH Image J provides a substantial method of assaying effects on β cell mass. Measurement of total area was consistent and correlated well with physiological measures of β cell function in each of the Control, Diabetic and TRH treated pancreatic sections. [ABSTRACT FROM AUTHOR]

Objective: Cardiovascular disease (CVD) risk prediction represents an increasing clinical challenge in the treatment of diabetes. We used a panel of vascular imaging, functional assessments, and biomarkers reflecting different disease mechanisms to identify clinically useful markers of risk for cardiovascular (CV) events in subjects with type 2 diabetes (T2D) with or without manifest CVD.Research Design and Methods: The study cohort consisted of 936 subjects with T2D recruited at four European centers. Carotid intima-media thickness and plaque area, ankle-brachial pressure index, arterial stiffness, endothelial function, and circulating biomarkers were analyzed at baseline, and CV events were monitored during a 3-year follow-up period.Results: The CV event rate in subjects with T2D was higher in those with (n = 440) than in those without (n = 496) manifest CVD at baseline (5.53 vs. 2.15/100 life-years, P < 0.0001). New CV events in subjects with T2D with manifest CVD were associated with higher baseline levels of inflammatory biomarkers (interleukin 6, chemokine ligand 3, pentraxin 3, and hs-CRP) and endothelial mitogens (hepatocyte growth factor and vascular endothelial growth factor A), whereas CV events in subjects with T2D without manifest CVD were associated with more severe baseline atherosclerosis (median carotid plaque area 30.4 mm2 [16.1-92.2] vs. 19.5 mm2 [9.5-40.5], P = 0.01). Conventional risk factors, as well as measurements of arterial stiffness and endothelial reactivity, were not associated with CV events.Conclusions: Our observations demonstrate that markers of inflammation and endothelial stress reflect CV risk in subjects with T2D with manifest CVD, whereas the risk for CV events in subjects with T2D without manifest CVD is primarily related to the severity of atherosclerosis. [ABSTRACT FROM AUTHOR]

Of the four syntaxins specialized for exocytosis, syntaxin (Syn)-2 is the least understood. In this study, we used Syn-2/epimorphin knockout mice to examine the role of Syn-2 in insulin secretory granule (SG) exocytosis. Unexpectedly, Syn-2 knockout mice exhibited paradoxical superior glucose homeostasis resulting from an enhanced insulin secretion. This was confirmed in vitro by pancreatic islet perifusion showing an amplified biphasic glucose-stimulated insulin secretion arising from an increase in size of the readily releasable pool of insulin SGs and enhanced SG pool refilling. The increase in insulin exocytosis was attributed mainly to an enhanced recruitment of the larger pool of newcomer SGs that undergoes no residence time on plasma membrane before fusion and, to a lesser extent, also the predocked SGs. Consistently, Syn-2 depletion resulted in a stimulation-induced increase in abundance of exocytotic complexes we previously demonstrated as mediating the fusion of newcomer SGs (Syn-3/VAMP8/SNAP25/Munc18b) and predocked SGs (Syn-1A/VAMP2/SNAP25/Muncn18a). This work is the first to show in mammals that Syn-2 could function as an inhibitory SNARE protein that, when relieved, could promote exocytosis in pancreatic islet β-cells. Thus, Syn-2 may serve as a potential target to treat diabetes. [ABSTRACT FROM AUTHOR]

Human pancreatic islets consist of multiple endocrine cell types. To facilitate the detection of rare cellular states and uncover population heterogeneity, we performed single-cell RNA sequencing (RNA-seq) on islets from multiple deceased organ donors, including children, healthy adults, and individuals with type 1 or type 2 diabetes. We developed a robust computational biology framework for cell type annotation. Using this framework, we show that α- and β-cells from children exhibit less well-defined gene signatures than those in adults. Remarkably, α- and β-cells from donors with type 2 diabetes have expression profiles with features seen in children, indicating a partial dedifferentiation process. We also examined a naturally proliferating α-cell from a healthy adult, for which pathway analysis indicated activation of the cell cycle and repression of checkpoint control pathways. Importantly, this replicating α-cell exhibited activated Sonic hedgehog signaling, a pathway not previously known to contribute to human α-cell proliferation. Our study highlights the power of single-cell RNA-seq and provides a stepping stone for future explorations of cellular heterogeneity in pancreatic endocrine cells. [ABSTRACT FROM AUTHOR]

Objective: To investigate the long-term association of exposure to perfluoroalkylated substances, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), during childhood (9 years) and adolescence (15 years) on indicators of adiposity and glucose metabolism in adolescence (15 years) and young adulthood (21 years). Secondarily, we aim to clarify the degree of tracking of exposure from childhood into young adulthood.Research Design and Methods: Data derived from a large multicenter prospective cohort study, in which the same participants have been observed from childhood (N = 590), during adolescence (N = 444), and into young adulthood (N = 369). Stored plasma samples were analyzed for PFOS and PFOA. Indicators of adiposity comprising body height, body weight, sum of four skinfolds, and waist circumference, as well as indicators of glucose metabolism, comprising fasting blood glucose, triglyceride, and insulin levels, β-cell function, and insulin resistance, have been collected at all study waves. Multiple linear regression was applied in order to model earlier exposure on later outcome while controlling for baseline outcome levels, sex, age, and socioeconomic factors.Results: Childhood exposure to PFOS was associated with indicators of adiposity at 15 years of age that are displayed in elevated BMI, skinfold thickness, and waist circumference, as well as increased skinfold thickness and waist circumference at 21 years of age. PFOA exposure in childhood was associated with decreased β-cell function at 15 years of age. We did not observe associations between exposure during adolescence and indicators of adiposity and glucose metabolism in young adulthood.Conclusions: This study found evidence for childhood exposure to PFOS and PFOA predicting adiposity at 15 and 21 years of age and impaired β-cell function at 15 years of age, respectively. [ABSTRACT FROM AUTHOR]

Identification of new adipokines that potentially link obesity to insulin resistance represents a major challenge. We recently showed that NOV/CCN3, a multifunctional matricellular protein, is synthesized and secreted by adipose tissue, with plasma levels highly correlated with BMI. NOV involvement in tissue repair, fibrotic and inflammatory diseases, and cancer has been previously reported. However, its role in energy homeostasis remains unknown. We investigated the metabolic phenotype of NOV(-/-) mice fed a standard or high-fat diet (HFD). Strikingly, the weight of NOV(-/-) mice was markedly lower than that of wild-type mice but only on an HFD. This was related to a significant decrease in fat mass associated with an increased proportion of smaller adipocytes and to a higher expression of genes involved in energy expenditure. NOV(-/-) mice fed an HFD displayed improved glucose tolerance and insulin sensitivity. Interestingly, the absence of NOV was associated with a change in macrophages profile (M1-like to M2-like), in a marked decrease in adipose tissue expression of several proinflammatory cytokines and chemokines, and in enhanced insulin signaling. Conversely, NOV treatment of adipocytes increased chemokine expression. Altogether, these results show that NOV is a new adipocytokine that could be involved in obesity-associated insulin-resistance. [ABSTRACT FROM AUTHOR]

Discovery of common pathways that mediate both pancreatic β-cell function and end-organ function offers the opportunity to develop therapies that modulate glucose homeostasis and separately slow the development of diabetes complications. Here, we investigated the in vitro and in vivo effects of pharmacological agonism of the prostaglandin I2 (IP) receptor in pancreatic β-cells and in glomerular podocytes. The IP receptor agonist MRE-269 increased intracellular 3',5'-cyclic adenosine monophosphate (cAMP), augmented glucose-stimulated insulin secretion (GSIS), and increased viability in MIN6 β-cells. Its prodrug form, selexipag, augmented GSIS and preserved islet β-cell mass in diabetic mice. Determining that this preservation of β-cell function is mediated through cAMP/protein kinase A (PKA)/nephrin-dependent pathways, we found that PKA inhibition, nephrin knockdown, or targeted mutation of phosphorylated nephrin tyrosine residues 1176 and 1193 abrogated the actions of MRE-269 in MIN6 cells. Because nephrin is important to glomerular permselectivity, we next set out to determine whether IP receptor agonism similarly affects nephrin phosphorylation in podocytes. Expression of the IP receptor in podocytes was confirmed in cultured cells by immunoblotting and quantitative real-time PCR and in mouse kidneys by immunogold electron microscopy, and its agonism 1) increased cAMP, 2) activated PKA, 3) phosphorylated nephrin, and 4) attenuated albumin transcytosis. Finally, treatment of diabetic endothelial nitric oxide synthase knockout mice with selexipag augmented renal nephrin phosphorylation and attenuated albuminuria development independently of glucose change. Collectively, these observations describe a pharmacological strategy that posttranslationally modifies nephrin and the effects of this strategy in the pancreas and in the kidney. [ABSTRACT FROM AUTHOR]

Although the plasma insulin assay is now 40 years old, it is not widely used in clinical practice. However, simple methods (such as the various indexes relating fasting insulin to fasting glucose), the increase in plasma insulin at the 30th minute of an oral glucose tolerance test, and the increase in insulin or C-peptide after stimulation by glucagon are relatively reliable compared with more sophisticated approaches to assess beta-cell sensitivity to glucose, kinetics of insulin secretion, residual insulin secretion, or insulin sensitivity. But these measures are of no decisive help in distinguishing between the various forms of impaired fasting glucose or non-insulin-dependent diabetes, such as type 2 diabetes, slow type 1 diabetes, the various forms of maturity-onset diabetes of the young, or the mitochondrial genome defects. No data are available to show that the measurement of plasma insulin may be of help to adapt the treatment of a diabetic patient, except for the need of insulin therapy. There are some suggestions that fasting plasma insulin and, more precisely, the homeostasis model assessment indexes may help to predict the progression toward diabetes or the progressive deterioration of beta-cell function in diabetic patients. [ABSTRACT FROM AUTHOR]

Examines the presence of hyperglycemia-induced alterations in mesangial cell functions and extracellular matrix protein accumulation in diabetic glomerulopathy. Synthesis of fibronectin protein in mesangial cells; Effects of glucose on cellular metabolism; Role of hexosamine biosynthesis pathway in cellular metabolism.

Examines the role of human fructosamine-3-kinase (FN3K) in cell protection. Importance of nonenzymatic glycation on the pathogenesis of diabetic complications; Decomposition of fructolysines by FN3K phosphorylation; Use of electrospray tandem mass spectrometry in purifying FN3K.

The past several years have seen an explosive increase in our understanding of the transcriptional basis of adipose cell differentiation. In particular, a key role has been illustrated for PPAR-gamma, a member of the nuclear hormone receptor superfamily. PPAR-gamma has also been recently identified as the major functional receptor for the thiazolidinedione class of insulin-sensitizing drugs. This review examines the evidence that has implicated this transcription factor in the processes of adipogenesis and systemic insulin action. In addition, several models are discussed that may explain how a single protein can be involved in these related but distinct physiological actions. I also point out several important areas where our knowledge is incomplete and more research is needed. Finally, I discuss how advances in our understanding of nuclear receptor function, particularly the docking of cofactors in a ligand-dependent fashion, should lead to improved drugs that utilize the PPAR-gamma system for the treatment of insulin resistance. [ABSTRACT FROM AUTHOR]