C. albicans N-linked mannans potentiate the induction of trained immunity via Dectin-2.

The interaction between the Candida albicans cell wall and pattern recognition receptors is crucial for the initiation of host immune responses which, ultimately, contribute to the clearance of this pathogenic fungus. In the present study, we investigate the ability of C. albicans mannans to modulate immune response and induce innate immune memory (also termed trained immunity). Using mutants of C. albicans that are defective in, or lack mannosyl residues, we show that alterations in the mannosylation of the C. albicans cell wall affect the innate cytokine response and strongly reduce the secretion of T cell-derived cytokines. Subsequently, we demonstrate that the branching of N-linked mannan, but not O-linked mannan, is essential to potentiate the induction of trained immunity, a process mediated by Dectin-2. In conclusion, N-linked mannan is needed, in addition to ß-glucans, for an effective induction of trained immunity by C. albicans.

The impact of prior exposure to hypoglycaemia on the inflammatory response to a subsequent hypoglycaemic episode.

BACKGROUND: Hypoglycaemia has been shown to induce a systemic pro-inflammatory response, which may be driven, in part, by the adrenaline response. Prior exposure to hypoglycaemia attenuates counterregulatory hormone responses to subsequent hypoglycaemia, but whether this effect can be extrapolated to the pro-inflammatory response is unclear. Therefore, we investigated the effect of antecedent hypoglycaemia on inflammatory responses to subsequent hypoglycaemia in humans. METHODS: Healthy participants (n = 32) were recruited and randomised to two 2-h episodes of either hypoglycaemia or normoglycaemia on day 1, followed by a hyperinsulinaemic hypoglycaemic (2.8 ± 0.1 mmol/L) glucose clamp on day 2. During normoglycaemia and hypoglycaemia, and after 24 h, 72 h and 1 week, blood was drawn to determine circulating immune cell composition, phenotype and function, and 93 circulating inflammatory proteins including hs-CRP. RESULTS: In the group undergoing antecedent hypoglycaemia, the adrenaline response to next-day hypoglycaemia was lower compared to the control group (1.45 ± 1.24 vs 2.68 ± 1.41 nmol/l). In both groups, day 2 hypoglycaemia increased absolute numbers of circulating immune cells, of which lymphocytes and monocytes remained elevated for the whole week. Also, the proportion of pro-inflammatory CD16+-monocytes increased during hypoglycaemia. After ex vivo stimulation, monocytes released more TNF-α and IL-1ß, and less IL-10 in response to hypoglycaemia, whereas levels of 19 circulating inflammatory proteins, including hs-CRP, increased for up to 1 week after the hypoglycaemic event. Most of the inflammatory responses were similar in the two groups, except the persistent pro-inflammatory protein changes were partly blunted in the group exposed to antecedent hypoglycaemia. We did not find a correlation between the adrenaline response and the inflammatory responses during hypoglycaemia. CONCLUSION: Hypoglycaemia induces an acute and persistent pro-inflammatory response at multiple levels that occurs largely, but not completely, independent of prior exposure to hypoglycaemia. Clinical Trial information Clinicaltrials.gov no. NCT03976271 (registered 5 June 2019).

Acid ceramidase regulates innate immune memory.

Innate immune memory, also called "trained immunity," is a functional state of myeloid cells enabling enhanced immune responses. This phenomenon is important for host defense, but also plays a role in various immune-mediated conditions. We show that exogenously administered sphingolipids and inhibition of sphingolipid metabolizing enzymes modulate trained immunity. In particular, we reveal that acid ceramidase, an enzyme that converts ceramide to sphingosine, is a potent regulator of trained immunity. We show that acid ceramidase regulates the transcription of histone-modifying enzymes, resulting in profound changes in histone 3 lysine 27 acetylation and histone 3 lysine 4 trimethylation. We confirm our findings by identifying single-nucleotide polymorphisms in the region of ASAH1, the gene encoding acid ceramidase, that are associated with the trained immunity cytokine response. Our findings reveal an immunomodulatory effect of sphingolipids and identify acid ceramidase as a relevant therapeutic target to modulate trained immunity responses in innate immune-driven disorders.

Hypoglycaemia induces a sustained pro-inflammatory response in people with type 1 diabetes and healthy controls.

AIM: To determine the duration and the extension of the pro-inflammatory response to hypoglycaemia both in people with type 1 diabetes and healthy controls. MATERIALS AND METHODS: Adults with type 1 diabetes (n = 47) and matched controls (n = 16) underwent a hyperinsulinaemic-euglycaemic hypoglycaemic (2.8 ± 0.1 mmoL/L [49.9 ± 2.3 mg/dL]) glucose clamp. During euglycaemia, hypoglycaemia, and 1, 3 and 7 days later, blood was drawn to determine immune cell phenotype, monocyte function and circulating inflammatory markers. RESULTS: Hypoglycaemia increased lymphocyte and monocyte counts, which remained elevated for 1 week. The proportion of CD16+ monocytes increased and the proportion of CD14+ monocytes decreased. During hypoglycaemia, monocytes released more tumour necrosis factor-α and interleukin-1ß, and less interleukin-10, after ex vivo stimulation. Hypoglycaemia increased the levels of 19 circulating inflammatory proteins, including high sensitive C-reactive protein, most of which remained elevated for 1 week. The epinephrine peak in response to hypoglycaemia was positively correlated with immune cell number and phenotype, but not with the proteomic response. CONCLUSIONS: Overall, despite differences in prior exposure to hypoglycaemia, the pattern of the inflammatory responses to hypoglycaemia did not differ between people with type 1 diabetes and healthy controls. In conclusion, hypoglycaemia induces a range of pro-inflammatory responses that are sustained for at least 1 week in people with type 1 diabetes and healthy controls.

Arterial wall inflammation assessed by 18F-FDG-PET/CT is higher in individuals with Type 1 diabetes and associated with circulating inflammatory proteins.

AIMS: The article investigates whether chronic hyperglycaemia in Type 1 diabetes (T1D) is associated with a proinflammatory immune signature and with arterial wall inflammation, driving the development of atherosclerosis. METHODS AND RESULTS: Patients with T1D (n = 41), and healthy age-, sex-, and body mass index-matched controls (n = 20) were recruited. Arterial wall inflammation and haematopoietic activity were measured with 2'-deoxy-2'-(18F)-fluoro-D-glucose (18F-FDG) positron emission tomography/computed tomography. In addition, flow cytometry of circulating leucocytes was performed as well as targeted proteomics to measure circulating inflammatory markers. 18F-FDG uptake in the wall of the abdominal aorta, carotid arteries, and iliac arteries was higher in T1D compared with that in the healthy controls. Also, 18F-FDG uptake in the bone marrow and spleen was higher in patients with T1D. CCR2 and CD36 expressions on circulating monocytes were higher in patients with T1D, as well as several circulating inflammatory proteins. In addition, several circulating inflammatory markers (osteoprotegerin, transforming growth factor-alpha, CX3CL1, and colony-stimulating factor-1) displayed a positive correlation with FDG uptake. Within T1D, no differences were found between people with a high and low HbA1c. CONCLUSION: These findings strengthen the concept that chronic hyperglycaemia in T1D induces inflammatory changes that fuel arterial wall inflammation leading to atherosclerosis. The degree of hyperglycaemia appears to play a minor role in driving this inflammatory response in patients with T1D.

Disease Duration and Chronic Complications Associate With Immune Activation in Individuals With Longstanding Type 1 Diabetes.

CONTEXT: Type 1 diabetes (T1D) is associated with alterations of the immune response which persist even after the autoimmunity aspect is resolved. Clinical factors that cause dysregulation, however, are not fully understood. OBJECTIVE: To identify clinical factors that affect immune dysregulation in people with longstanding T1D. DESIGN: In this cross-sectional study, 243 participants with longstanding T1D were recruited between February 2016 and June 2017 at the Radboudumc, the Netherlands. Blood was drawn to determine immune cell phenotype and functionality, as well as circulating inflammatory proteome. Multivariate linear regression was used to determine the association between glycated hemoglobin (HbA1c) levels, duration of diabetes, insulin need, and diabetes complications with inflammation. RESULTS: HbA1c level is positively associated with circulating inflammatory markers (P < .05), but not with immune cell number and phenotype. Diabetes duration is associated with increased number of circulating immune cells (P < .05), inflammatory proteome (P < .05), and negatively associated with adaptive immune response against Mycobacterium tuberculosis and Rhizopus oryzae (P < .05). Diabetes nephropathy is associated with increased circulating immune cells (P < .05) and inflammatory markers (P < .05). CONCLUSION: Disease duration and chronic complications associate with persistent alterations in the immune response of individuals with long standing T1D.

Sustained Proinflammatory Effects of Hypoglycemia in People With Type 2 Diabetes and in People Without Diabetes.

Iatrogenic hypoglycemia activates the immune system and is associated with an increased risk for atherosclerotic disease. We determined acute and long-term effects of insulin-induced hypoglycemia on inflammatory markers in humans with or without type 2 diabetes. A total of 15 adults with type 2 diabetes and 16 matched control subjects (17 men and 14 women, age 59.6 ± 7.1 years, BMI 28.5 ± 4.3 kg/m2) underwent a hyperinsulinemic-euglycemic (5.31 ± 0.32 mmol/L) hypoglycemic (2.80 ± 0.12 mmol/L) glucose clamp. Blood was drawn during euglycemia and hypoglycemia and 1, 3, and 7 days later to determine circulating immune cell composition, function, and inflammatory proteins. In response to hypoglycemia, absolute numbers of circulating lymphocytes and monocytes significantly increased and remained elevated for 1 week. The proportion of CD16+ monocytes increased, and the proportion of CD14+ monocytes decreased, which was sustained for 1 week in people without diabetes. During hypoglycemia, ex vivo stimulated monocytes released more tumor necrosis factor-α and interleukin 1ß, and less interleukin 10, particularly in people with diabetes. hs-CRP and 25 circulating inflammatory proteins increased, remaining significantly elevated 1 week after hypoglycemia. While levels at euglycemia differed, responses to hypoglycemia were broadly similar in people with or without type 2 diabetes. We conclude that hypoglycemia induces a proinflammatory response at the cellular and protein level that is sustained for 1 week in people with type 2 diabetes and control subjects.

The Gut Microbiome Composition Is Altered in Long-standing Type 1 Diabetes and Associates With Glycemic Control and Disease-Related Complications.

OBJECTIVE: People with type 1 diabetes are at risk for developing micro- and macrovascular complications. Little is known about the gut microbiome in long-standing type 1 diabetes. We explored differences in the gut microbiome of participants with type 1 diabetes compared with healthy control subjects and associated the gut microbiome with diabetes-related complications. RESEARCH DESIGN AND METHODS: Microbiome data of 238 participants with type 1 diabetes with an average disease duration of 28 ± 15 years were compared with 2,937 age-, sex-, and BMI-matched individuals. Clinical characteristics and fecal samples were collected, and metagenomic shotgun sequencing was performed. Microbial taxonomy was associated with type 1 diabetes-related characteristics and vascular complications. RESULTS: No significant difference in the α-diversity of the gut microbiome was found between participants with type 1 diabetes and healthy control subjects. However, 43 bacterial taxa were significantly depleted in type 1 diabetes, while 37 bacterial taxa were significantly enriched. HbA1c and disease duration explained a significant part of the variation in the gut microbiome (R2 > 0.008, false discovery rate [FDR] <0.05), and HbA1c was significantly associated with the abundance of several microbial species. Additionally, both micro- and macrovascular complications explained a significant part of the variation in the gut microbiome (R2 > 0.0075, FDR < 0.05). Nephropathy was strongly associated with several microbial species. Macrovascular complications displayed similar associations with nephropathy. CONCLUSIONS: Our data show that the gut microbiome is altered in people with (long-standing) type 1 diabetes and is associated with glycemic control and diabetes-related complications. As a result of the cross-sectional design, the causality of these relationships remains to be determined.

The association between hypomagnesemia and poor glycaemic control in type 1 diabetes is limited to insulin resistant individuals.

In a cohort of adults with type 1 diabetes, we examined the prevalence of hypomagnesemia and the correlation of serum magnesium levels with metabolic determinants, such as glycaemic control (as HbA1c), inflammatory markers and circulating cytokines. Furthermore, we assessed if a surrogate for insulin resistance is essential for the possible association of serum magnesium with metabolic determinants. Individuals with type 1 diabetes, aged above 18 years, were included and clinical characteristics were obtained from questionnaires and clinical records. In venous blood samples we measured cytokines and adipose-tissue specific secretion proteins. Serum magnesium concentrations were measured and correlated with clinical data and laboratory measurements using univariate and multivariate regression models. Hierarchical multiple regression of serum magnesium with insulin resistance was adjusted for diabetes and potential magnesium confounders. The prevalence of hypomagnesemia (serum magnesium levels < 0.7 mmol/L) was 2.9% in a cohort consisting of 241 individuals with type 1 diabetes. The magnesium concentration in the cohort was not associated with HbA1c (r = - 0.12, P-value = 0.068) nor with any inflammatory marker or adipokine. However, insulin dose (IU/kg), a surrogate measure of resistance in type 1 diabetes, moderated the association of serum magnesium (mmol/L) with HbA1c (mmol/mol) with a B coefficient of - 71.91 (95% CI: - 119.11; -24.71), P-value = 0.003) and Log10 high-sensitivity C-reactive protein (Log10 mg/L) - 2.09 (95% CI: - 3.70; - 0.48), P-value = 0.011). The association of low serum magnesium levels with glycaemic control (HbA1c) and high-sensitivity C-reactive protein in individuals with type 1 diabetes is limited to subjects using a high insulin dose and suggests that insulin resistance, a type 2 diabetes feature, is a prerequisite for hypomagnesemia.

The Effect of Phenotype and Genotype on the Plasma Proteome in Patients with Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Protein profiling in patients with inflammatory bowel diseases [IBD] for diagnostic and therapeutic purposes is underexplored. This study analysed the association between phenotype, genotype, and the plasma proteome in IBD. METHODS: A total of 92 inflammation-related proteins were quantified in plasma of 1028 patients with IBD (567 Crohn's disease [CD]; 461 ulcerative colitis [UC]) and 148 healthy individuals to assess protein-phenotype associations. Corresponding whole-exome sequencing and global screening array data of 919 patients with IBD were included to analyse the effect of genetics on protein levels (protein quantitative trait loci [pQTL] analysis). Intestinal mucosal RNA sequencing and faecal metagenomic data were used for complementary analyses. RESULTS: Thirty-two proteins were differentially abundant between IBD and healthy individuals, of which 22 proteins were independent of active inflammation; 69 proteins were associated with 15 demographic and clinical factors. Fibroblast growth factor-19 levels were decreased in CD patients with ileal disease or a history of ileocecal resection. Thirteen novel cis-pQTLs were identified and 10 replicated from previous studies. One trans-pQTL of the fucosyltransferase 2 [FUT2] gene [rs602662] and two independent cis-pQTLs of C-C motif chemokine 25 [CCL25] affected plasma CCL25 levels. Intestinal gene expression data revealed an overlapping cis-expression [e]QTL-variant [rs3745387] of the CCL25 gene. The FUT2 rs602662 trans-pQTL was associated with reduced abundances of faecal butyrate-producing bacteria. CONCLUSIONS: This study shows that genotype and multiple disease phenotypes strongly associate with the plasma inflammatory proteome in IBD, and identifies disease-associated pathways that may help to improve disease management in the future.

Insulin acutely activates metabolism of primary human monocytes and promotes a proinflammatory phenotype.

Increased glycolysis is a metabolic trait of activated innate immune cells and supports functional changes including cytokine production. Insulin drives glycolysis in nonimmune cells, yet its metabolic effects on human innate immune cells remain unexplored. Potential effects of insulin on immune cell metabolism may occur acutely after a postprandial increase in plasma insulin levels or as a consequence of chronically elevated insulin levels as observed in obese insulin-resistant individuals and patients with diabetes. Here, we investigated the effects of acute and chronic exposure to insulin on metabolism and function of primary human monocytes. Insulin acutely activated the PI3K/Akt/mTOR pathway in monocytes and increased both oxygen consumption and glycolytic rates. Functionally, acute exposure to insulin increased LPS-induced IL-6 secretion and reactive oxygen species production. To model chronically elevated insulin levels in patients with diabetes, we exposed monocytes from healthy individuals for 24 h to insulin. Although we did not find any changes in expression of metabolic genes that are regulated by insulin in non-immune cells, chronic exposure to insulin increased LPS-induced TNFα production and enhanced MCP-1-directed migration. Supporting this observation, we identified a positive correlation between plasma insulin levels and macrophage numbers in adipose tissue of overweight individuals. Altogether, insulin acutely activates metabolism of human monocytes and induces a shift toward a more proinflammatory phenotype, which may contribute to chronic inflammation in patients with diabetes.