Cathelicidin regulates myeloid cell accumulation in adipose tissue and promotes insulin resistance during obesity

A Synthetic Peptide Designed to Neutralize Lipopolysaccharides Attenuates Metaflammation and Diet-Induced Metabolic Derangements in Mice

Metabolic endotoxemia has been suggested to play a role in the pathophysiology of metaflammation, insulin-resistance and ultimately type-2 diabetes mellitus (T2DM). The role of endogenous antimicrobial peptides (AMPs), such as the cathelicidin LL-37, in T2DM is unknown. We report here for the first time that patients with T2DM compared to healthy volunteers have elevated plasma levels of LL-37. In a reverse-translational approach, we have investigated the effects of the AMP, peptide 19-2.5, in a murine model of high-fat diet (HFD)-induced insulin-resistance, steatohepatitis and T2DM. HFD-fed mice for 12 weeks caused obesity, an impairment in glycemic regulations, hypercholesterolemia, microalbuminuria and steatohepatitis, all of which were attenuated by Peptide 19-2.5. The liver steatosis caused by feeding mice a HFD resulted in the activation of nuclear factor kappa light chain enhancer of activated B cells (NF-ĸB) (phosphorylation of inhibitor of kappa beta kinase (IKK)α/β, IκBα, translocation of p65 to the nucleus), expression of NF-ĸB-dependent protein inducible nitric oxide synthase (iNOS) and activation of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome, all of which were reduced by Peptide 19-2.5. Feeding mice, a HFD also resulted in an enhanced expression of the lipid scavenger receptor cluster of differentiation 36 (CD36) secondary to activation of extracellular signal-regulated kinases (ERK)1/2, both of which were abolished by Peptide 19-2.5. Taken together, these results demonstrate that the AMP, Peptide 19-2.5 reduces insulin-resistance, steatohepatitis and proteinuria. These effects are, at least in part, due to prevention of the expression of CD36 and may provide further evidence for a role of metabolic endotoxemia in the pathogenesis of metaflammation and ultimately T2DM. The observed increase in the levels of the endogenous AMP LL-37 in patients with T2DM may serve to limit the severity of the disease.

Metabolic Inflammation and Insulin Resistance in Obesity

Obesity is becoming an epidemic in the United States and worldwide and increases risk for many diseases, particularly insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. The mechanisms linking obesity with these diseases remain incompletely understood. Over the past 2 to 3 decades, it has been recognized that in obesity, inflammation, with increased accumulation and inflammatory polarization of immune cells, takes place in various tissues, including adipose tissue, skeletal muscle, liver, gut, pancreatic islet, and brain and may contribute to obesity-linked metabolic dysfunctions, leading to insulin resistance and type 2 diabetes mellitus. Therapies targeting inflammation have shed light on certain obesity-linked diseases, including type 2 diabetes mellitus and atherosclerotic cardiovascular disease, but remain to be tested further and confirmed in clinical trials. This review focuses on inflammation in adipose tissue and its potential role in insulin resistance associated with obesity.

Markers of neutrophil extracellular traps are associated with adverse clinical outcome in stable coronary artery disease

Background Neutrophil extracellular traps, comprising chromatin and granule proteins, have been implicated in atherothrombosis. Design and methods We investigated whether the circulating neutrophil extracellular traps markers, double-stranded DNA and myeloperoxidase-DNA were associated with clinical outcome and hypercoagulability in patients with stable coronary artery disease. Patients with angiographically verified stable coronary artery disease ( n = 1001) were included. Follow-up was 2 years, recording 106 clinical endpoints (unstable angina, non-haemorrhagic stroke, myocardial infarction or death). Serum collected at baseline was used to determine double-stranded DNA and myeloperoxidase-DNA levels. Results The neutrophil extracellular traps markers were weakly intercorrelated ( r = 0.103, P = 0.001). Patients with the highest quartile of double-stranded DNA had weakly but significantly elevated hypercoagulability markers (prothrombin fragment 1+2, D-dimer, free and total tissue factor pathway inhibitor ( P < 0.001 for all)). Men, smokers, patients with metabolic syndrome and patients with a previous myocardial infarction had significantly elevated double-stranded DNA levels ( P ≤ 0.002 for all). Significantly higher double-stranded DNA levels were observed in the group experiencing a clinical endpoint compared to the group without ( P = 0.019). When categorising double-stranded DNA into quartiles, a distinct cut-off between the lowest and upper three quartiles was observed. Adjusting for relevant covariates, patients in the upper three quartiles had an odds ratio of 2.01 (95% confidence interval 1.12, 3.58, P = 0.019) for experiencing a clinical endpoint. Myeloperoxidase-DNA was not significantly associated with clinical outcome or hypercoagulability. Conclusions Double-stranded DNA levels were significantly related to adverse clinical outcome after 2 years, but only weakly associated with hypercoagulability. These observations suggest that the detrimental effects of neutrophil extracellular traps in coronary artery disease might extend beyond those related to hypercoagulability.

Elevated levels of the antimicrobial peptide LL-37 in hidradenitis suppurativa are associated with a Th1/Th17 immune response

Hidradenitis suppurativa (HS) is an inflammatory skin disease with poorly understood immunopathogenic mechanisms. LL-37 is an antimicrobial peptide, which is transcribed from the CAMP (cathelicidin antimicrobial peptide) gene. Previous reports showed upregulated levels of CAMP and LL-37 in HS lesions, and therefore, the aim of this study was to compare levels of LL-37 in HS to other inflammatory skin diseases and to establish immunomodulatory functions of LL-37 in HS. We confirm an upregulation of the LL-37 peptide in lesional HS skin with comparable levels as in psoriasis patients and are able to positively correlate the presence of LL-37 in HS with the presence of T cells, macrophages, neutrophils, IFN-γ, IL-17, IL-23, TNF-α, IL-32 and IL-1β. Mechanistically, LL-37 boosts the proliferation of unspecifically activated CD4⁺ T cells via an increased calcium signalling independent of antigen-presenting cells. Targeting LL-37 may therefore represent a new therapeutic option for the treatment of this recalcitrant disease, but it has to be kept in mind that LL-37 also has an antimicrobial function.

Neutrophils as protagonists and targets in chronic inflammation

Traditionally, neutrophils have been acknowledged to be the first immune cells that are recruited to an inflamed tissue and have mainly been considered in the context of acute inflammation. By contrast, their importance during chronic inflammation has been studied in less depth. This Review aims to summarize our current understanding of the roles of neutrophils in chronic inflammation, with a focus on how they communicate with other immune and non-immune cells within tissues. We also scrutinize the roles of neutrophils in wound healing and the resolution of inflammation, and finally, we outline emerging therapeutic strategies that target neutrophils.

Local effects of adipose tissue in psoriasis and psoriatic arthritis

The structure and physiological state of the local white adipose tissue (WAT) located underneath the lesional psoriatic skin and inside of the joints affected by psoriatic arthritis play an important role in the pathophysiology of these diseases. WAT pads associated with inflammatory sites in psoriasis and psoriatic arthritis are, correspondingly, dermal WAT and articular adipose tissue; these pads demonstrate inflammatory phenotypes in both diseases. Such local WAT inflammation could be the primary effect in the pathophysiology of psoriasis leading to the modification of the local expression of adipokines, a change in the structure of the basement membrane and the release of keratinocytes with consequent epidermal hyperproliferation during psoriasis. Similar articular adipose tissue inflammation can lead to the induction of structural modifications and synovial inflammation in the joints of patients with psoriatic arthritis.