Ink4/Arf locus restores glucose tolerance and insulin sensitivity by reducing hepatic steatosis and inflammation in mice with impaired IRS2-dependent signalling

Cellular senescence molecules expression in type 2 diabetes mellitus: CDKN2A, CDKN2B, and lncRNA ANRIL

AIMS

Cellular senescence in type 2 diabetes mellitus (T2DM) has received widespread attention. However, the cellular senescence molecules involved in T2DM are unclear. Furthermore, there are no consistent biomarkers for cellular senescence in T2DM. Therefore, this study aimed to identify cellular senescence molecules in T2DM and investigate their expression in peripheral blood mononuclear cells of individuals with T2DM.

METHODS

Patients with T2DM (n = 40) and healthy controls (n = 40) were enrolled. We used different databases to identify cellular senescence molecules in T2DM and confirmed the obtained genes and lncRNA using real-time PCR.

RESULTS

Bioinformatics analysis indicated that CDKN2A and CDKN2B genes, and long noncoding RNA ANRIL are the most effective cellular senescence molecules in T2DM. Furthermore, CDKN2A and ANRIL expression decreased in individuals with T2DM.

CONCLUSIONS

Cellular senescence may have a protective effect against T2DM. In addition, the cellular senescence molecules CDKN2A and ANRIL may be potential biomarkers of cellular senescence in T2DM.

Genetic inactivation of the LIGHT (TNFSF14) cytokine in mice restores glucose homeostasis and diminishes hepatic steatosis

AIMS/HYPOTHESIS

Non-alcoholic fatty liver disease (NAFLD) is frequently associated with type 2 diabetes mellitus. Progression of NAFLD is mediated, among other things, by activation of inflammatory pathways. In the present study, the role of the proinflammatory cytokine LIGHT (TNFSF14) was explored in NAFLD and type 2 diabetes mellitus in mice deficient for the cytokine.

METHODS

Light-deficient (Light^-/-) mice and WT controls were fed a regular chow diet (RCD) or a high-fat high-cholesterol diet (HFHCD) for 16 weeks. The expression of LIGHT and its receptors, herpes virus entry mediator (HVEM) and lymphotoxin β receptor (LTβR), was investigated in both dietary regimens. Glucose tolerance, insulin sensitivity, non-alcoholic fatty liver (NAFL), systemic and tissue inflammation, and metabolic gene expression were explored in Light^-/- and WT mice fed an RCD and an HFHCD. The effect of Light deficiency was also evaluated in hepatic tissue and in inflammation in HFHCD-fed Irs2^+/- mice with impaired insulin signalling.

RESULTS

Light deficiency did not have an effect on metabolism, in NAFL or in tissue and systemic inflammation, in RCD-fed WT mice. HVEM and LTβR were markedly increased in livers of HFHCD-fed WT mice compared with RCD-fed WT controls. In WT mice under HFHCD, Light deficiency improved glucose tolerance and insulin sensitivity. Non-alcoholic fatty liver disease activity (NAS) score, hepatic CD3⁺ T lymphocytes and F4/80⁺ macrophages were decreased in HFHCD-fed Light^-/- mice compared with HFHCD-fed WT controls. Consistent with a potential role of adipose tissue in hepatic homeostasis, Light^-/- mice exhibited augmented anti-inflammatory F4/80⁺CD206⁺ adipose tissue macrophages and reduced proinflammatory F4/80⁺CD11c⁺ adipose tissue macrophages. Moreover, adipose tissue explants from Light^-/- mice showed diminished secretion of monocyte chemoattractant protein 1 (MCP1), TNF-α and IL-17 cytokines. Circulating Light^-/- leucocytes consistently displayed augmented levels of the patrolling Ly6C^low monocytes, decreased Th9 T cell subset and diminished plasma TNF-α and IL-6 levels. Similarly, Light deficiency in Irs2^+/- mice, which display impaired insulin signalling, also reduced NAFL as well as systemic and adipose tissue inflammation. Analysis of hepatic gene expression in Light^-/- mouse livers showed reduced levels of Zbtb16, the transcription factor essential for natural killer T (NKT) cell function, and two genes related to NAFLD and fibrosis, Klf6 and Tlr4.

CONCLUSIONS/INTERPRETATION

These results indicate that Light deficiency in HFHCD improves hepatic glucose tolerance, and reduces hepatic inflammation and NAFL. This is accompanied by decreased systemic inflammation and adipose tissue cytokine secretion and by changes in the expression of key genes such as Klf6 and Tlr4 involved in NAFLD. These results suggest that therapies to block LIGHT-dependent signalling might be useful to restore hepatic homeostasis and to restrain NAFLD.

Type 1 diabetic mellitus patients with increased atherosclerosis risk display decreased CDKN2A/2B/2BAS gene expression in leukocytes

Background

Type 1 diabetes mellitus (T1DM) patients display increased risk of cardiovascular disease (CVD) and are characterized by a diminished regulatory T (Treg) cell content or function. Previous studies have shown an association between decreased CDKN2A/2B/2BAS gene expression and enhanced CVD. In the present study the potential relationship between CDKN2A/2B/2BAS gene expression, immune cell dysfunction and increased cardiovascular risk in T1DM patients was explored.

Methods

A cross-sectional study was performed in 90 subjects divided into controls and T1DM patients. Circulating leukocyte subpopulations analysis by flow cytometry, expression studies on peripheral blood mononuclear cell by qPCR and western blot and correlation studies were performed in both groups of subjects.

Results

Analysis indicated that, consistent with the described T cell dysfunction, T1DM subjects showed decreased circulating CD4+CD25+CD127− Treg cells. In addition, T1DM subjects had lower mRNA levels of the transcription factors FOXP3 and RORC and lower levels of IL2 and IL6 which are involved in Treg and Th17 cell differentiation, respectively. T1DM patients also exhibited decreased mRNA levels of CDKN2A (variant 1 p16^Ink4a), CDKN2A (p14^Arf,variant 4), CDKN2B (p15^Ink4b) and CDKN2BAS compared with controls. Notably, T1DM patients had augmented pro-atherogenic CD14++CD16+-monocytes, which predict cardiovascular acute events and enhanced common carotid intima-media thickness (CC-IMT).

Conclusions

Decreased expression of CDKN2A/2B/2BAS in leukocytes associates with increased CC-IMT atherosclerosis surrogate marker and proatherogenic CD14++CD16+ monocytes in T1DM patients. These results suggest a potential role of CDKN2A/2B/2BAS genes in CVD risk in T1DM.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1977-1) contains supplementary material, which is available to authorized users.

Changes in CDKN2A/2B expression associate with T-cell phenotype modulation in atherosclerosis and type 2 diabetes mellitus

Previous studies indicate a role of CDKN2A/2B/2BAS genes in atherosclerosis and type 2 diabetes mellitus (T2DM). Progression of these diseases is accompanied by T-cell imbalance and chronic inflammation. Our main objective was to investigate a potential association between CDKN2A/2B/2BAS gene expression and T cell phenotype in T2DM and coronary artery disease (CAD) in humans, and to explore the therapeutic potential of these genes to restore immune cell homeostasis and disease progression. Reduced mRNA levels of CDKN2A (p16^Ink4a), CDKN2B (p15^Ink4b), and CDKN2BAS were observed in human T2DM and T2DM-CAD subjects compared with controls. Protein levels of p16^Ink4a and p15^Ink4b were also diminished in T2DM-CAD patients while CDK4 levels, the main target of p16^Ink4a and p15^Ink4b, were augmented in T2DM and T2DM-CAD subjects. Both patient groups displayed higher activated CD3+CD69+ T cells and proatherogenic CD14++CD16+ monocytes, while CD4+CD25+CD127 regulatory T (Treg cells) cells were decreased. Treatment of primary human lymphocytes with PD0332991, a p16^Ink4a/p15^Ink4b mimetic drug and a proven CDK4 inhibitor, increased Treg cells and the levels of activated transcription factor phosphoSTAT5. In vivo PD0332991 treatment of atherosclerotic apoE-/- mice and insulin resistant apoE-/-Irs2+/- mice augmented Foxp3-expressing Treg cells and decreased lesion size. Thus, atherosclerosis complications in T2DM associate with altered immune cell homeostasis, diminished CDKN2A/2B/2BAS expression, and increased CDK4 levels. The present study also suggests that the treatment with drugs that mimic CDKN2A/2B genes could potential be considered as a promising therapy to delay atherosclerosis.

The GLP-1 analogue lixisenatide decreases atherosclerosis in insulin-resistant mice by modulating macrophage phenotype

AIMS/HYPOTHESIS

Recent clinical studies indicate that glucagon-like peptide-1 (GLP-1) analogues prevent acute cardiovascular events in type 2 diabetes mellitus but their mechanisms remain unknown. In the present study, the impact of GLP-1 analogues and their potential underlying molecular mechanisms in insulin resistance and atherosclerosis are investigated.

METHODS

Atherosclerosis development was evaluated in Apoe ^-/- Irs2 ^+/- mice, a mouse model of insulin resistance, the metabolic syndrome and atherosclerosis, treated with the GLP-1 analogues lixisenatide or liraglutide. In addition, studies in Apoe ^-/- Irs2 ^+/- mice and mouse-derived macrophages treated with lixisenatide were performed to investigate the potential inflammatory intracellular pathways.

RESULTS

Treatment of Apoe ^-/- Irs2 ^+/- mice with either lixisenatide or liraglutide improved glucose metabolism and blood pressure but this was independent of body weight loss. Both drugs significantly decreased atheroma plaque size. Compared with vehicle-treated control mice, lixisenatide treatment generated more stable atheromas, with fewer inflammatory infiltrates, reduced necrotic cores and thicker fibrous caps. Lixisenatide-treated mice also displayed diminished IL-6 levels, proinflammatory Ly6C^high monocytes and activated T cells. In vitro analysis showed that, in macrophages from Apoe ^-/- Irs2 ^+/- mice, lixisenatide reduced the secretion of the proinflammatory cytokine IL-6 accompanied by enhanced activation of signal transducer and activator of transcription (STAT) 3, which is a determinant for M2 macrophage differentiation. STAT1 activation, which is essential for M1 phenotype, was also diminished. Furthermore, atheromas from lixisenatide-treated mice showed higher arginase I content and decreased expression of inducible nitric oxide synthase, indicating the prevalence of the M2 phenotype within plaques.

CONCLUSIONS/INTERPRETATION

Lixisenatide decreases atheroma plaque size and instability in Apoe ^-/- Irs2 ^+/- mice by reprogramming macrophages towards an M2 phenotype, which leads to reduced inflammation. This study identifies a critical role for this drug in macrophage polarisation inside plaques and provides experimental evidence supporting a novel mechanism of action for GLP-1 analogues in the reduction of cardiovascular risk associated with insulin resistance.

Effects of an Encapsulated Fruit and Vegetable Juice Concentrate on Obesity-Induced Systemic Inflammation: A Randomised Controlled Trial

Phytochemicals from fruit and vegetables reduce systemic inflammation. This study examined the effects of an encapsulated fruit and vegetable (F&V) juice concentrate on systemic inflammation and other risk factors for chronic disease in overweight and obese adults. A double-blinded, parallel, randomized placebo-controlled trial was conducted in 56 adults aged ≥40 years with a body mass index (BMI) ≥28 kg/m². Before and after eight weeks daily treatment with six capsules of F&V juice concentrate or placebo, peripheral blood gene expression (microarray, quantitative polymerase chain reaction (qPCR)), plasma tumour necrosis factor (TNF)α (enzyme-linked immunosorbent assay (ELISA)), body composition (Dual-energy X-ray absorptiometry (DEXA)) and lipid profiles were assessed. Following consumption of juice concentrate, total cholesterol, low-density lipoprotein (LDL) cholesterol and plasma TNFα decreased and total lean mass increased, while there was no change in the placebo group. In subjects with high systemic inflammation at baseline (serum C-reactive protein (CRP) ≥3.0 mg/mL) who were supplemented with the F&V juice concentrate (n = 16), these effects were greater, with decreased total cholesterol, LDL cholesterol and plasma TNFα and increased total lean mass; plasma CRP was unchanged by the F&V juice concentrate following both analyses. The expression of several genes involved in lipogenesis, the nuclear factor-κB (NF-κB) and 5' adenosine monophosphate-activated protein kinase (AMPK) signalling pathways was altered, including phosphomevalonate kinase (PMVK), zinc finger AN1-type containing 5 (ZFAND5) and calcium binding protein 39 (CAB39), respectively. Therefore, F&V juice concentrate improves the metabolic profile, by reducing systemic inflammation and blood lipid profiles and, thus, may be useful in reducing the risk of obesity-induced chronic disease.

Hepatic lipase deficiency produces glucose intolerance, inflammation and hepatic steatosis

Metabolic syndrome and type 2 diabetes mellitus constitute a major problem to global health, and their incidence is increasing at an alarming rate. Non-alcoholic fatty liver disease, which affects up to 90% of obese people and nearly 70% of the overweight, is commonly associated with MetS characteristics such as obesity, insulin resistance, hypertension and dyslipidemia. In the present study, we demonstrate that hepatic lipase (HL)-inactivation in mice fed with a high-fat, high-cholesterol diet produced dyslipidemia including hypercholesterolemia, hypertriglyceridemia and increased non-esterified fatty acid levels. These changes were accompanied by glucose intolerance, pancreatic and hepatic inflammation and steatosis. In addition, compared with WT mice, HL(-/-) mice exhibited enhanced circulating MCP1 levels, monocytosis and higher percentage of CD4+Th17+ cells. Consistent with increased inflammation, livers from HL(-/-) mice had augmented activation of the stress SAPK/JNK- and p38-pathways compared with the activation levels of the kinases in livers from WT mice. Analysis of HL(-/-) and WT mice fed regular chow diet showed dyslipidemia and glucose intolerance in HL(-/-) mice without any other changes in inflammation or hepatic steatosis. Altogether, these results indicate that dyslipidemia induced by HL-deficiency in combination with a high-fat, high-cholesterol diet promotes hepatic steatosis and inflammation in mice which are, at least in part, mediated by the activation of the stress SAPK/JNK- and p38-pathways. Future studies are warranted to asses the viability of therapeutic strategies based on the modulation of these kinases to reduce hepatic steatosis associated to lipase dysfunction.