Circulating monocytes are activated in newly diagnosed type 1 diabetes mellitus patients

Systemic Inflammatory Response Index (SIRI) as a Predictive Marker for Adverse Outcomes in Children with New-Onset Type 1 Diabetes Mellitus

(1) Background: Although most cases of new-onset type 1 diabetes mellitus (T1DM) are managed without serious events, life-threatening complications do arise in a subset of patients. Our objective was to assess the correlation between elevated SIRI values and adverse events related to the onset of T1DM. (2) Methods: This retrospective study, spanning ten years, included 187 patients with new-onset T1DM divided into three groups based on SIRI tertiles. The primary outcome was the occurrence of acute complications during hospital admission, while the secondary outcome was prolonged Intensive Care Unit (ICU) admission. (3) Results: Patients with high SIRI values were more likely to experience higher disease activity, leading to longer ICU admission times and more frequent complications. Multivariate logistic regression analysis revealed that the SIRI was independently associated with acute complications (p = 0.003) and prolonged ICU length of stay (p = 0.003). Furthermore, receiver operating characteristic analysis demonstrated the SIRI's superior predictive accuracy compared to venous pH (AUC = 0.837 and AUC = 0.811, respectively) and to the individual component cell lineages of the SIRI. (4) Conclusions: These findings emphasize the potential utility of the SIRI as a prognostic marker in identifying patients at increased risk during T1DM hospital admissions.

Transcriptional regulatory networks of circulating immune cells in type 1 diabetes: A community knowledgebase

Investigator-generated transcriptomic datasets interrogating circulating immune cell (CIC) gene expression in clinical type 1 diabetes (T1D) have underappreciated re-use value. Here, we repurposed these datasets to create an open science environment for the generation of hypotheses around CIC signaling pathways whose gain or loss of function contributes to T1D pathogenesis. We firstly computed sets of genes that were preferentially induced or repressed in T1D CICs and validated these against community benchmarks. We then inferred and validated signaling node networks regulating expression of these gene sets, as well as differentially expressed genes in the original underlying T1D case:control datasets. In a set of three use cases, we demonstrated how informed integration of these networks with complementary digital resources supports substantive, actionable hypotheses around signaling pathway dysfunction in T1D CICs. Finally, we developed a federated, cloud-based web resource that exposes the entire data matrix for unrestricted access and re-use by the research community.

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Re-use of transcriptomic type 1 diabetes (T1D) circulating immune cells (CICs) datasets

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We generated transcriptional regulatory networks for T1D CICs

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Use cases generate substantive hypotheses around signaling pathway dysfunction in T1D CICs

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Networks are freely accessible on the web for re-use by the research community

Assessment of Inflammation Biomarkers in Diabetic Macular Edema Treated with Intravitreal Dexamethasone Implant

Purpose: To evaluate inflammation biomarkers in diabetic macular edema (DME) treated with intravitreal dexamethasone implant (Ozurdex^®). Methods: This retrospective single-center study investigated 64 eyes of 64 patients with DME who were nonresponsive to prior antivascular endothelial growth factor and treated with intravitreal Ozurdex. The neutrophil/lymphocyte ratio (NLR), monocyte/lymphocyte ratio (MLR), and platelet/lymphocyte ratio were calculated. Visual acuity and optical coherence tomography markers, including hyper-reflective dots and subretinal fluid (SRF), were determined, and central retinal thickness was also evaluated monthly for 3 months. Results: The average age was 64.06 ± 7.81 (48-84) years. The baseline NLR and MLR were significantly higher in patients with better visual outcomes (P = 0.029 and P = 0.048, respectively). Better anatomical outcomes were observed in the presence of SRF (P = 0.027). No significant differences were observed in the rates of the presence of SRF and hyper-reflective points about the better functional outcome (P > 0.05). Conclusions: SRF as an imaging biomarker, and NLR and MLR as blood biomarkers, stand out as markers of inflammation and were found to be associated with better response to Ozurdex implantation in DME.

Trained immunity modulates inflammation-induced fibrosis

Chronic inflammation and fibrosis can result from inappropriately activated immune responses that are mediated by macrophages. Macrophages can acquire memory-like characteristics in response to antigen exposure. Here, we show the effect of BCG or low-dose LPS stimulation on macrophage phenotype, cytokine production, chromatin and metabolic modifications. Low-dose LPS training alleviates fibrosis and inflammation in a mouse model of systemic sclerosis (SSc), whereas BCG-training exacerbates disease in this model. Adoptive transfer of low-dose LPS-trained or BCG-trained macrophages also has beneficial or harmful effects, respectively. Furthermore, coculture with low-dose LPS trained macrophages reduces the fibro-inflammatory profile of fibroblasts from mice and patients with SSc, indicating that trained immunity might be a phenomenon that can be targeted to treat SSc and other autoimmune and inflammatory fibrotic disorders.

Innate immune cells can be trained by some stimuli or pathogen exposures to be metabolically and epigenetically altered such that they have different responses to subsequent exposures. Here the authors show that low-dose LPS trained macrophages and BCG-trained macrophages have opposing effects on fibrosis and inflammation in the context of systemic sclerosis.

STAT3 activation in circulating myeloid-derived cells contributes to retinal microvascular dysfunction in diabetes

Background

Leukostasis is a key patho-physiological event responsible for capillary occlusion in diabetic retinopathy. Circulating monocytes are the main cell type entrapped in retinal vessels in diabetes. In this study, we investigated the role of the signal transducer and activator of transcription 3 (STAT3) pathway in diabetes-induced immune cell activation and its contribution to retinal microvascular degeneration.

Methods

Forty-one patients with type 1 diabetes (T1D) [mild non-proliferative diabetic retinopathy (mNPDR) (n = 13), active proliferative DR (aPDR) (n = 14), inactive PDR (iPDR) (n = 14)] and 13 age- and gender-matched healthy controls were recruited to the study. C57BL/6 J WT mice, SOCS3^fl/fl and LysM^Cre/+SOCS3^fl/fl mice were rendered diabetic by Streptozotocin injection. The expression of the phosphorylated human and mouse STAT3 (pSTAT3), mouse LFA-1, CD62L, CD11b and MHC-II in circulating immune cells was evaluated by flow cytometry. The expression of suppressor of cytokine signalling 3 (SOCS3) was examined by real-time RT-PCR. Mouse plasma levels of cytokines were measured by Cytometric Beads Array assay. Retinal leukostasis was examined following FITC-Concanavalin A perfusion and acellular capillary was examined following Isolectin B4 and Collagen IV staining.

Results

Compared to healthy controls, the expression of pSTAT3 in circulating leukocytes was statistically significantly higher in mNPDR but not aPDR and was negatively correlated with diabetes duration. The expression of pSTAT3 and its inhibitor SOCS3 was also significantly increased in leukocytes from diabetic mice. Diabetic mice had higher plasma levels of IL6 and CCL2 compared with control mice. LysM^Cre/+SOCS3^fl/fl mice and SOCS3^fl/fl mice developed comparative levels of diabetes, but leukocyte activation, retinal leukostasis and number of acellular capillaries were statistically significantly increased in LysM^Cre/+SOCS3^fl/fl diabetic mice.

Conclusion

STAT3 activation in circulating immune cells appears to contribute to retinal microvascular degeneration and may be involved in DR initiation in T1D.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1533-1) contains supplementary material, which is available to authorized users.

The Potential Role of Trained Immunity in Autoimmune and Autoinflammatory Disorders

During induction of trained immunity, monocytes and macrophages undergo a functional and transcriptional reprogramming toward increased activation. Important rewiring of cellular metabolism of the myeloid cells takes place during induction of trained immunity, including a shift toward glycolysis induced through the mTOR pathway, as well as glutaminolysis and cholesterol synthesis. Subsequently, this leads to modulation of the function of epigenetic enzymes, resulting in important changes in chromatin architecture that enables increased gene transcription. However, in addition to the beneficial effects of trained immunity as a host defense mechanism, we hypothesize that trained immunity also plays a deleterious role in the induction and/or maintenance of autoimmune and autoinflammatory diseases if inappropriately activated.

Diabetic retinopathy and dysregulated innate immunity

Diabetic retinopathy (DR) is the progressive degeneration of retinal blood vessels and neurons. Inflammation is known to play an important role in the pathogenesis of DR. During diabetes, metabolic disorder leads to the release of damage-associated molecular patterns (DAMPs) both in the retina and elsewhere in the body. The innate immune system provides the first line of defense against the DAMPs. In the early stages of DR when the blood retinal barrier (BRB) is intact, retinal microglia and the complement system are activated at low levels. This low-level of inflammation (para-inflammation) is believed to be essential to maintain homeostasis and restore functionality. However, prolonged stimulation by DAMPs in the diabetic eye leads to maladaptation of the innate immune system and dysregulated para-inflammation may contribute to DR development. In the advanced stages of DR where immune privilege is comprised, circulating immune cells and serum proteins may infiltrate the retina and participate in retinal chronic inflammation and retinal vascular and neuronal damage. This review discusses how the innate immune system is activated in diabetes and DR. The view also discusses why the protective immune response becomes detrimental in DR.

The progress in understanding and treatment of diabetic retinopathy

Diabetic retinopathy is the most frequently occurring complication of diabetes mellitus and remains a leading cause of vision loss globally. Its aetiology and pathology have been extensively studied for half a century, yet there are disappointingly few therapeutic options. Although some new treatments have been introduced for diabetic macular oedema (DMO) (e.g. intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') and new steroids), up to 50% of patients fail to respond. Furthermore, for people with proliferative diabetic retinopathy (PDR), laser photocoagulation remains a mainstay therapy, even though it is an inherently destructive procedure. This review summarises the clinical features of diabetic retinopathy and its risk factors. It describes details of retinal pathology and how advances in our understanding of pathogenesis have led to identification of new therapeutic targets. We emphasise that although there have been significant advances, there is still a pressing need for a better understanding basic mechanisms enable development of reliable and robust means to identify patients at highest risk, and to intervene effectively before vision loss occurs.

Biomarkers in Diabetic Retinopathy

There is a global diabetes epidemic correlating with an increase in obesity. This coincidence may lead to a rise in the prevalence of type 2 diabetes. There is also an as yet unexplained increase in the incidence of type 1 diabetes, which is not related to adiposity. Whilst improved diabetes care has substantially improved diabetes outcomes, the disease remains a common cause of working age adult-onset blindness. Diabetic retinopathy is the most frequently occurring complication of diabetes; it is greatly feared by many diabetes patients. There are multiple risk factors and markers for the onset and progression of diabetic retinopathy, yet residual risk remains. Screening for diabetic retinopathy is recommended to facilitate early detection and treatment. Common biomarkers of diabetic retinopathy and its risk in clinical practice today relate to the visualization of the retinal vasculature and measures of glycemia, lipids, blood pressure, body weight, smoking, and pregnancy status. Greater knowledge of novel biomarkers and mediators of diabetic retinopathy, such as those related to inflammation and angiogenesis, has contributed to the development of additional therapeutics, in particular for late-stage retinopathy, including intra-ocular corticosteroids and intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') agents. Unfortunately, in spite of a range of treatments (including laser photocoagulation, intraocular steroids, and anti-VEGF agents, and more recently oral fenofibrate, a PPAR-alpha agonist lipid-lowering drug), many patients with diabetic retinopathy do not respond well to current therapeutics. Therefore, more effective treatments for diabetic retinopathy are necessary. New analytical techniques, in particular those related to molecular markers, are accelerating progress in diabetic retinopathy research. Given the increasing incidence and prevalence of diabetes, and the limited capacity of healthcare systems to screen and treat diabetic retinopathy, there is need to reliably identify and triage people with diabetes. Biomarkers may facilitate a better understanding of diabetic retinopathy, and contribute to the development of novel treatments and new clinical strategies to prevent vision loss in people with diabetes. This article reviews key aspects related to biomarker research, and focuses on some specific biomarkers relevant to diabetic retinopathy.

Impaired inflammatory responses to multiple toll-like receptor ligands in alveolar macrophages of streptozotocin-induced diabetic mice

OBJECTIVE

To investigate the effect of hyperglycemic state on the activation of alveolar macrophages (AMs) mediated via Toll-like receptors (TLRs) typically associated with bacterial infection.

METHODS

AMs obtained from normoglycemic control mice and streptozotocin-induced diabetic mice were stimulated ex vivo with the following: a TLR2 ligand, peptidoglycan (PGN); a TLR4 ligand, lipopolysaccharide (LPS); or a TLR5 ligand, flagellin (FLG). Cytokine production and mRNA expression were measured by ELISA and real-time PCR, respectively. TLR expression was assessed by real-time PCR and flow cytometry.

RESULTS

AMs from diabetic mice produced significantly less TNF-α after PGN or FLG stimulation, and less IL-6 after FLG stimulation, compared with AMs from control mice. The decrease in the production of these cytokines was associated with reduced mRNA expression of the corresponding cytokines. In contrast, production of TNF-α and IL-6 after LPS stimulation did not differ between groups. Furthermore, there was no substantial difference in the expression of TLR2, TLR4, and TLR5 in AMs between the groups. The increased JNK phosphorylation induced by PGN or FLG stimulation was downregulated in AMs from diabetic mice.

CONCLUSIONS

Hyperglycemic state impairs the reactivity of AMs to multiple TLR ligands. This effect might result from hyperglycemia-induced alteration of intracellular signaling and is unlikely due to the modulation of TLR expression.

Type-specific human papillomavirus detection in cervical smears in Romania

To study type 1 diabetes (T1D), excellent animal models exist, both spontaneously diabetic and virus-induced. Based on knowledge from these, this review focuses on the environmental factors leading to T1D, concentrated into four areas which are: (1) The thymus-dependent immune system: T1D is a T cell driven disease and the beta cells are destroyed in an inflammatory insulitis process. Autoimmunity is breakdown of self-tolerance and the balance between regulator T cells and aggressive effector T cells is disturbed. Inhibition of the T cells (by e.g. anti-CD3 antibody or cyclosporine) will stop the T1D process, even if initiated by virus. Theoretically, the risk from immunotherapy elicits a higher frequency of malignancy. (2) The activity of the beta cells: Resting beta cells display less antigenicity and are less sensitive to immune destruction. Beta-cell rest can be induced by giving insulin externally in metabolic doses or by administering potassium-channel openers. Both procedures prevent T1D in animal models, whereas no good human data exist due to the risk of hypoglycemia. (3) NKT cells: According to the hygiene hypothesis, stimulation of NKT cells by non-pathogen microbes gives rise to less T cell reaction and less autoimmunity. Glycolipids presented by CD1 molecules are central in this stimulation. (4) Importance of the intestine and gliadin intake: Gluten-free diet dramatically inhibits T1D in animal models, and epidemiological data are supportive of such an effect in humans. The mechanisms include less subclinical intestinal inflammation and permeability, and changed composition of bacterial flora, which can also be obtained by intake of probiotics. Gluten-free diet is difficult to implement, and short-term intake has no effect. Regarding the onset of the T1D disease process, slow-acting enterovirus and gliadin deposits are speculated to be etiological in genetically susceptible individuals, followed by the mentioned four pathogenetic factors acting in concert. Neutralization of any one of these factors is capable of stopping T1D development, as lessons are learned from the animal models.

Thiol oxidative stress induced by metabolic disorders amplifies macrophage chemotactic responses and accelerates atherogenesis and kidney injury in LDL receptor-deficient mice

BACKGROUND

Strengthening the macrophage glutathione redox buffer reduces macrophage content and decreases the severity of atherosclerotic lesions in LDL receptor-deficient (LDLR(-/-)) mice, but the underlying mechanisms were not clear. This study examined the effect of metabolic stress on the thiol redox state, chemotactic activity in vivo, and the recruitment of macrophages into atherosclerotic lesions and kidneys of LDL-R(-/-) mice in response to mild, moderate, and severe metabolic stress.

METHODS AND RESULTS

Reduced glutathione (GSH) and glutathione disulfide (GSSG) levels in peritoneal macrophages isolated from mildly, moderately, and severe metabolically-stressed LDL-R(-/-) mice were measured by HPLC, and the glutathione reduction potential (E(h)) was calculated. Macrophage E(h) correlated with the macrophage content in both atherosclerotic (r(2)=0.346, P=0.004) and renal lesions (r(2)=0.480, P=0.001) in these mice as well as the extent of both atherosclerosis (r(2)=0.414, P=0.001) and kidney injury (r(2)=0.480, P=0.001). Compared to LDL-R(-/-) mice exposed to mild metabolic stress, macrophage recruitment into MCP-1-loaded Matrigel plugs injected into LDL-R(-/-) mice increased 2.6-fold in moderately metabolically-stressed mice and 9.8-fold in severely metabolically-stressed mice. The macrophage E(h) was a strong predictor of macrophage chemotaxis (r(2)=0.554, P<0.001).

CONCLUSIONS

Thiol oxidative stress enhances macrophage recruitment into vascular and renal lesions by increasing the responsiveness of macrophages to chemoattractants. This novel mechanism contributes at least in part to accelerated atherosclerosis and kidney injury associated with dyslipidemia and diabetes in mice.

Tuberculosis in poorly controlled type 2 diabetes: altered cytokine expression in peripheral white blood cells

BACKGROUND

Although the biological basis for the increased susceptibility of diabetic patients to tuberculosis remains unclear, the world is undergoing a type 2 diabetes pandemic. We hypothesize that chronic hyperglycemia leads to immunocompromise that facilitates progression to active tuberculosis. To assess this possibility, we determined whether patients with tuberculosis and diabetes (particularly those with chronic hyperglycemia), compared with patients with tuberculosis who did not have diabetes, presented altered cytokine responses to a mycobacterial antigen.

METHODS

Samples of whole blood from patients with tuberculosis and diabetes and from patients with tuberculosis who did not have diabetes was stimulated in vitro with purified protein derivative from Mycobacterium tuberculosis. We then determined whether there was an association between the levels of innate and adaptive cytokines secreted in response to the antigen and diabetes status, or diabetes with chronic hyperglycemia (measured by glycosylated hemoglobin level), after controlling for possible confounders.

RESULTS

Innate and type 1 cytokine responses were significantly higher in patients with tuberculosis who had diabetes than in nondiabetic control subjects. The effect was consistently and significantly more marked in diabetic patients with chronic hyperglycemia.

CONCLUSIONS

These data provide preliminary evidence that type 2 diabetes, especially type 2 diabetes involving chronic hyperglycemia, is associated with an altered immune response to M. tuberculosis. More-detailed knowledge of the underlying mechanisms should focus on the effect of chronic hyperglycemia on the immune response to help in understanding the enhanced susceptibility of diabetic patients to tuberculosis.

An increased MRP8/14 expression and adhesion, but a decreased migration towards proinflammatory chemokines of type 1 diabetes monocytes

In the early development of type 1 diabetes macrophages and dendritic cells accumulate around the islets of Langerhans at sites of fibronectin expression. It is thought that these macrophages and dendritic cells are derived from blood monocytes. Previously, we showed an increased serum level of MRP8/14 in type 1 diabetes patients that induced healthy monocytes to adhere more strongly to fibronectin (FN). Here we show that MRP8/14 is expressed and produced at a higher level by type 1 diabetes monocytes, particularly after adhesion to FN, creating a positive feedback mechanism for a high fibronectin-adhesive capacity. Also adhesion to endothelial cells was increased in type 1 diabetes monocytes. Despite this increased adhesion the transendothelial migration of monocytes of type 1 diabetes patients was decreased towards the proinflammatory chemokines CCL2 and CCL3. Because non-obese diabetic (NOD) mouse monocytes show a similar defective proinflammatory migration, we argue that an impaired monocyte migration towards proinflammatory chemokines might be a hallmark of autoimmune diabetes. This hampered monocyte response to proinflammatory chemokines questions whether the early macrophage and dendritic cell accumulation in the diabetic pancreas originates from an inflammatory-driven influx of monocytes. We also show that the migration of type 1 diabetes monocytes towards the lymphoid tissue-related CCL19 was increased and correlated with an increased CCR7 surface expression on the monocytes. Because NOD mice show a high expression of these lymphoid tissue-related chemokines in the early pancreas it is more likely that the early macrophage and dendritic cell accumulation in the diabetic pancreas is related to an aberrant high expression of lymphoid tissue-related chemokines in the pancreas.

Effects on immune response of antidiabetic ingredients from white-skinned sweet potato (Ipomoea batatas L.)

OBJECTIVES

The present report describes the effects of antidiabetic ingredients from white-skinned sweet potato (AWSSP) on the immune response of human cells.

METHODS

We studied the effects of inactive Staphylococcus aureus cells coated with AWSSP on phagocytic activity, phagosome-lysosome fusion, and superoxide anion release by human leukocytes in vitro.

RESULTS

AWSSP increased phagocytic activity and phagosome-lysosome fusion in neutrophils and monocytes in a dose-dependent manner. In contrast, AWSSP had no significant effect on superoxide anion release (O2-) from human neutrophils.

CONCLUSIONS

These results show that AWSSP is useful in the prevention and improvement of diabetic symptoms by stimulating human immunity and that Ipomoea batatas L. is a beneficial food because it increases immune activity in addition to its antidiabetic effects.

NOD mice have a severely impaired ability to recruit leukocytes into sites of inflammation

The accumulation of macrophages (M Phi) and dendritic cells (DC) in the pancreas plays a crucial role in the pathogenesis of autoimmune diabetes. We studied the recruitment of monocytes, M Phi and DC to sites of inflammation, i.e. the peritoneal cavity and a subcutaneously elicited air pouch in the NOD mouse model of autoimmune diabetes. The leukocyte recruitment was studied from 1 to 7 days after injection of thioglycollate (peritoneum), C5a (peritoneum, air pouch), CCL2 and CCL3 (air pouch). C57BL/6 and BALB/c mice served as controls. Morphological and flow cytometric analysis of the recruited cells was performed, IL-1 beta, TNF-alpha, IL-6, IL-12 and IL-10 in exudates measured, and in vitro CCL2-chemotaxis of exudate M Phi (Boyden chamber) determined. NOD mice were strongly impaired in the recruitment of M Phi, DC, monocytes, and granulocytes. Chemokine-injected air pouches of NOD mice showed an increased IL-10 and a decreased IL-1 beta level, while the other cytokines were normally or very lowly expressed. In addition, NOD exudate M Phi displayed an impaired in vitro CCL2-induced migration. Our data show that NOD mice have an impaired ability to recruit leukocytes into sites of inflammation elicited in the peritoneum and the air pouch. A raised IL-10/IL-1 beta ratio at these sites and a deficient migratory capacity of NOD monocytes are important determinants in this impairment.

Characterization of monocyte-derived dendritic cells in recent-onset diabetes mellitus type 1

Dendritic cells (DC) may play an important role in the immunopathogenesis of type 1 diabetes mellitus (DM-1). In this study, we have analyzed phenotypical changes during cytokine-driven maturation from CD14+ monocytes to mature DC and DC-dependent T-cell stimulation in recent-onset pediatric DM-1 patients and healthy controls. DC maturation was monitored by flow cytometric analyses for the expression of surface markers (HLA-DR, CD1a, CD40, CD80, CD86, CD83, CD14, CD32, mannose-receptor, and CD11c). Flow cytometric analysis of isolated peripheral blood monocytes did not reveal apparent differences between patients and controls. During DC maturation no obvious differences in the expression patterns of surface markers over time or evidence for maturation impairments in DM-1 patients could be appreciated. Solely, a marginal, but significant, transient down-regulation of CD1a on Day 3 (mean MDFI 3.82 vs 7.25; P = 0.021), which was accompanied by an increase of IL-6, could be observed. The comparison of mature DCs (Day 10) between patients and controls indicated no significant differences, except for CD83 (mean MDFI 1.7 vs 1.5; P = 0.042) and CD80 (mean MDFI 15.92 vs 12.73; P = 0.042). Moreover, no difference in T-cell stimulatory capacity was seen. In conclusion, our analysis of a cohort of recent-onset DM-1 patients and controls does not support a role for disease-related alterations in cytokine-driven maturation of monocyte-derived DC.

Diabetic state induces lipid loading and altered expression and secretion of lipoprotein lipase in human monocyte-derived macrophages

Non-insulin-dependent diabetes mellitus (NIDDM) is frequently associated with macroangiopathies and coronary heart diseases. Lipoprotein lipase (LPL), an enzyme known to undergo significant functional alterations in diabetic state, is also a potential atherogenic protein. Since, to the best of our knowledge, there are no data concerning LPL secreted by macrophages of NIDDM patients we conducted a study to assess the expression and activity of LPL secreted by monocyte-derived macrophages from NIDDM patients with cardiovascular complications versus cardiovascular patients without diabetes (controls). Isolated cells from NIDDM patients, after 7 days in culture in the presence of 20% autologous serum, readily exhibit a foam cell phenotype, in contrast to the cells from controls. Macrophages were mainly loaded with triglycerides, whose cellular amount was well correlated to triglyceridemia of NIDDM subjects. Concomitantly, macrophages from NIDDM patients displayed a approximately six-fold decrease of mRNA expression and a approximately two-fold reduction of the activity of secreted LPL, as compared to control cells. These data suggest that in complicated diabetic state, macrophage loading leading to foam cell formation is accelerated, at least in part, due to a diminished expression and activity of LPL. These observations add and extend the data that may explain the occurrence of accelerated atherogenesis and of the atherosclerotic complications associated with diabetes.

Cardiovascular disease in diabetes mellitus type 2: a potential role for novel cardiovascular risk factors

A major consequence of diabetes mellitus type 2 is the accelerated development of atherosclerosis. Assessment of conventional risk factors such as plasma lipids, lipoproteins and hypertension only partly account for the excessive risk of developing cardiovascular disease in this population. Increasing evidence has emerged suggesting that conditions associated with diabetes mellitus type 2, such as insulin resistance, hyperinsulinemia and hyperglycemia, may also play a significant role in regulating 'novel' cardiovascular risk factors. These factors and their potential roles in the development of atherosclerosis and cardiovascular events are discussed in this review.

Immunological effects of a hyperinsulinaemic euglycaemic insulin clamp in healthy males

The purpose of this study was to determine the in-vivo and in-vitro effects of insulin, at physiological and supraphysiological concentrations, on the human immune system. Ten healthy young men went through a sequential two-step hyperinsulinaemic euglycaemic clamp. Plasma insulin concentrations were increased from baseline (9.0 microU/ml) to 49.1 microU/ml after 1 h of insulin infusion (step I) and to 1281 microU/ml (step II) after 2 h of infusion. As control experiments infusions of isotonic saline were performed. The unstimulated natural killer (NK) cell activity among blood mononuclear cells (BMNC) increased in response to supraphysiological plasma insulin levels (baseline versus step II: 20.6 +/- 11.3 versus 27.8 +/- 14.4%). The percentages of the D16+ NK cells did not change, indicating an enhanced cytotoxic capability per individual NK cell. Insulin also slightly increased the activity of NK cells in vitro. A decline at step II in the concentrations of monocytes (0.29 +/- 0.09 versus 0.12 +/- 0.03 x 10(9)/L), lymphocytes (1.57 +/- 0.46 versus 1.22 +/- 0.25 x 10(9)/L), and CD16+(24.2 +/- 17.5 versus 16.7 +/- 11.2 x 10(7)/L), CD14+ (20.9 +/- 10.8 versus 8.6 +/- 3.9 x 10(7)/L), HLA-DR+ (37.2 +/- 22.1 versus 19.2 +/- 10.7 x 10(7)/L) and CD45RO+ (91.6 +/- 33.4 versus 61.7 +/- 6.4 x 10(7)/L) cells as well as in the percentages of CD14+ cells (11.2 +/- 4.7 versus 6.4 +/- 2.3%) and CD14+/HLA-DR+ monocytes (9.7 +/- 3.9 versus 4.8 +/- 2.8%) were observed. No changes were found at step I. Hyperinsulinaemia did not change the percentages of the CD3+, CD4+, CD8+, CD19+, CD56+, CD11a+, CD45RO+ and CD45RA+ cells, the numbers of circulating immunoglobulin (Ig)G-, IgA- and IgM- secreting cells, or the proliferative responses of BMNC to phytohaemagglutinin, purified derivative of tuberculin or interleukin (IL)-2. Hyperinsulinaemia did not change the in-vitro sensibility to insulin. In conclusion, supraphysiological insulin levels increased the activity of the individual NK cells, but decreased the numbers of NK cells, lymphocytes and activated monocytes. The findings are presumably of minor clinical relevance but may indicate an insulin-induced immune activation.

Tissue culture supernatants from human islets of Langerhans activate the oxidative burst response of human monocytes in vitro

Macrophages play a major role in the pathogenesis of insulin-dependent diabetes mellitus in animals. These cells are the first to invade the pancreas and macrophage-eradicating treatments reduce the incidence of the disease. In humans, however, their role is less clear. In this study we investigated the hypothesis that the pancreatic environment per se could activate macrophages. Tissue culture supernatants from human islets of Langerhans were tested for chemotactic activity and oxidative burst response in monocytes isolated from healthy adults. Preincubation with the supernatants enhanced the oxidative burst response evoked by fMLP (up to 379%) and opsonized zymosan (up to 173%). The activity decreased by dilution and was no longer detectable at 1:16. No increased activity was seen in supernatants from a number of other human endocrine and non-endocrine primary cells, suggesting a factor specific for islet tissue. The increased oxidative burst response could partially be eliminated by heat- and proteinase K treatment, suggesting that the activity could be of polypeptide nature. The factor could not be absorbed by polyvalent rabbit antibodies directed towards a variety of cytokines not by a mixture of high-titer anti-cytokine antibodies. It is possible that islet factors could also promote such monocyte activation in vivo in monocytes attracted to the islets of Langerhans by other means. This could contribute to the development of insulin-dependent diabetes in humans.