Inflammatory markers and type 2 diabetes

Mitochondrial Impairment: A Link for Inflammatory Responses Activation in the Cardiorenal Syndrome Type 4

Cardiorenal syndrome type 4 (CRS type 4) occurs when chronic kidney disease (CKD) leads to cardiovascular damage, resulting in high morbidity and mortality rates. Mitochondria, vital organelles responsible for essential cellular functions, can become dysfunctional in CKD. This dysfunction can trigger inflammatory responses in distant organs by releasing Damage-associated molecular patterns (DAMPs). These DAMPs are recognized by immune receptors within cells, including Toll-like receptors (TLR) like TLR2, TLR4, and TLR9, the nucleotide-binding domain, leucine-rich-containing family pyrin domain-containing-3 (NLRP3) inflammasome, and the cyclic guanosine monophosphate (cGMP)-adenosine monophosphate (AMP) synthase (cGAS)-stimulator of interferon genes (cGAS-STING) pathway. Activation of these immune receptors leads to the increased expression of cytokines and chemokines. Excessive chemokine stimulation results in the recruitment of inflammatory cells into tissues, causing chronic damage. Experimental studies have demonstrated that chemokines are upregulated in the heart during CKD, contributing to CRS type 4. Conversely, chemokine inhibitors have been shown to reduce chronic inflammation and prevent cardiorenal impairment. However, the molecular connection between mitochondrial DAMPs and inflammatory pathways responsible for chemokine overactivation in CRS type 4 has not been explored. In this review, we delve into mechanistic insights and discuss how various mitochondrial DAMPs released by the kidney during CKD can activate TLRs, NLRP3, and cGAS-STING immune pathways in the heart. This activation leads to the upregulation of chemokines, ultimately culminating in the establishment of CRS type 4. Furthermore, we propose using chemokine inhibitors as potential strategies for preventing CRS type 4.

Atherosclerosis Burdens in Diabetes Mellitus: Assessment by PET Imaging

Arteriosclerosis and its sequelae are the most common cause of death in diabetic patients and one of the reasons why diabetes has entered the top 10 causes of death worldwide, fatalities having doubled since 2000. The literature in the field claims almost unanimously that arteriosclerosis is more frequent or develops more rapidly in diabetic than non-diabetic subjects, and that the disease is caused by arterial inflammation, the control of which should therefore be the goal of therapeutic efforts. These views are mostly based on indirect methodologies, including studies of artery wall thickness or stiffness, or on conventional CT-based imaging used to demonstrate tissue changes occurring late in the disease process. In contrast, imaging with positron emission tomography and computed tomography (PET/CT) applying the tracers 18F-fluorodeoxyglucose (FDG) or 18F-sodium fluoride (NaF) mirrors arterial wall inflammation and microcalcification, respectively, early in the course of the disease, potentially enabling in vivo insight into molecular processes. The present review provides an overview of the literature from the more than 20 and 10 years, respectively, that these two tracers have been used for the study of atherosclerosis, with emphasis on what new information they have provided in relation to diabetes and which questions remain insufficiently elucidated.

Dietary LPS traces influences disease expression of the diet-induced obese mouse

Lipopolysaccharides (LPS) from Gram negative bacteria are generally present in laboratory animal chow diets in unknown amounts, which has been correlated to significant immunological differences between animals receiving diets with either low or high "naturally" occurring LPS content. LPS in the blood stream has been linked to glucose intolerance through Toll-like receptor mediated release of pro-inflammatory cytokines, metabolic endotoxemia, adipose tissue inflammation. LPS uptake increases when co-administered with fat, therefore uncontrolled LPS levels in a high-fat diet may increase variation in development of disease when high-fat diets are used to induce obesity and type 2 diabetes. Three experiments were conducted, in which C57BL/6NTac mice received high-fat (60%) or low fat (10%) diets with or without LPS for 8 or 20 weeks investigating the short and long term effects. Three different doses of LPS were used to investigate dosage effect, and ampicillin to isolate the effect of dietary LPS. Dietary LPS increased LPS levels in the blood stream, and affected the level of glycated haemoglobin (HbA1c), a key parameter in this model, in a dose dependant manner (p < 0.05). There was a strong tendency toward slower glucose uptake in the LPS supplemented groups once obesity was established, but the differences disappeared after 20 weeks. A high-fat diet slightly increased serum LPS and altered ileal expression of il10 and tnfa (p < 0.05). In conclusion, LPS seems to affect the glucose metabolism in a time-dose dependant manner, and uncontrolled variation in LPS levels of a diet may therefore increase inter-study variation.

Association of chemokine receptor CX3CR1 V249I and T280M polymorphisms with chronic kidney disease

The chemokine fractalkine (CX3CL1) and its receptor CX3CR1 are involved in the activation of leukocytes. Two common single-nucleotide polymorphisms of the CX3CR1 gene, V249I and T280M, have been associated with reduced fractalkine signaling, leading to decreased adhesive function and leukocyte chemotaxis. We hypothesized that variation in the CX3CR1 gene could be associated with chronic kidney disease (CKD), a disease of inflammatory activation. We studied the association between CX3CR1 V249I and T280M polymorphisms, and fractalkine and highly sensitive C-reactive protein (hs-CRP) levels in 123 patients with CKD and 100 healthy controls (HCs). Genotype analysis was done by polymerase chain reaction-restriction fragment length polymorphism, and fractalkine and hs-CRP levels were analyzed by enzyme-linked immunosorbent assay. MM genotype of T280M was absent in CKD patients, while in controls it was seen in 1% of the individuals. The allele frequencies in both the groups were similar (P = 0.059). Compared to HC, M280M + T280M genotype was more frequent in CKD (P = 0.041). The frequency of II genotype of V249I was 0.8% in CKD, whereas in HC, it was 2%. I249I + V249I genotype was more frequent in CKD as compared to HC (P = 0.034). No difference in allelic frequency of V249I was noted between the two groups (P = 0.061, odds ratios = 1.74, 95% confidence intervals = 0.96–3.12). Plasma fractalkine and serum hs-CRP levels were higher in CKD subjects (P = 0.004 and P < 0.0001). No association of either genotype was found with fractalkine and hs-CRP levels. Polymorphisms at I249 and M280 genotype in CX3CR1 gene are associated with CKD; however, there was no association of fractalkine or inflammatory marker with these genotypes.

Effects of Roux-en-Y gastric bypass on fasting and postprandial levels of the inflammatory markers YKL-40 and MCP-1 in patients with type 2 diabetes and glucose tolerant subjects

BACKGROUND

The inflammatory markers YKL-40 and monocyte chemoattractant protein-1 (MCP-1) are elevated in morbidly obese patients and decline after weight loss. The objective of our study was to investigate the possible changes of YKL-40 and MCP-1, in both the fasting and the postprandial states, following Roux-en-Y gastric bypass (RYGB) in subjects with type 2 diabetes (T2D) and normal glucose tolerance (NGT).

METHODS

Ten obese patients with T2D and 10 subjects with NGT were examined in the fasting state and after a standard meal prior to and after (1 week, 3 months, and 1 year) RYGB.

RESULTS

Fasting state MCP-1 levels decreased after RYGB in both groups (P values < 0.0001) whereas fasting YKL-40 levels were unchanged (P values ≥ 0.120). Postprandial MCP-1 levels showed a tendency towards a decrease on most study days; however, the changes were only significant at 1 week (P = 0.001) and 1 yr (P < 0.0001) in the T2D group and at 3 mo after RYGB in the NGT group (P = 0.009). YKL-40 levels showed a slight, postprandial suppression on all study days in the T2D group (all P values ≤ 0.021).

CONCLUSIONS

Fasting MCP-1 levels, but not YKL-40 levels, decrease after RYGB in subjects with T2D and NGT. Postprandial changes of inflammatory markers are discrete and inconsistent.

Impact of noninsulin-dependent type 2 diabetes on carotid wall 18F-fluorodeoxyglucose positron emission tomography uptake

OBJECTIVES

In this study, the impact of noninsulin-dependent type 2 diabetes mellitus on carotid wall (18)F-fluorodeoxyglucose (FDG) uptake in patients with documented or suspected cardiovascular disease was evaluated.

BACKGROUND

Inflammation is a pivotal process in the progression of atherosclerosis, which can be noninvasively imaged by FDG positron emission tomography (FDG-PET).

METHODS

Carotid artery wall FDG uptake was quantified in 134 patients (age 60.2 ± 9.7 years; diabetic subjects, n = 43). The pre-scan glucose (gluc) level corrected mean of the maximum standardized uptake value (SUV) values ((mean)SUV(gluc)), mean of the maximum target-to-background ratio ((mean)TBR(gluc)), and single hottest segment (SHS(gluc)) of FDG uptake in the artery wall were calculated. Associations between FDG uptake, the presence of risk factors for atherosclerosis, and diabetes were then assessed by multiple regression analysis with backward elimination.

RESULTS

The study demonstrated a significant association between diabetes and FDG uptake in the arterial wall (diabetes (mean)SUV(gluc) β = 0.324, (mean)TBR(gluc) β = 0.317, and SHS(gluc) β = 0.298; for all, p < 0.0001). In addition, in diabetic patients, both body mass index ≥ 30 kg/m(2) ((mean)SUV(gluc) β = 0.4, (mean)TBR(gluc) β = 0.357, and SHS(gluc) β = 0.388; for all, p < 0.015) and smoking ((mean)TBR(gluc), β = 0.312; SHS(gluc), β = 0.324; for all, p < 0.04) were significantly associated with FDG uptake.

CONCLUSIONS

Type 2 diabetes was significantly associated with carotid wall FDG uptake in patients with known or suspected cardiovascular disease. In diabetic patients, obesity and smoking add to the risk of increased FDG uptake values.

Vascular inflammation in patients with impaired glucose tolerance and type 2 diabetes: analysis with 18F-fluorodeoxyglucose positron emission tomography

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of atherosclerotic cardiovascular disease. Vascular inflammation is a key factor in both the pathogenesis and outcome of atherosclerosis. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising tool for indentifying and quantifying vascular inflammation within atherosclerotic plaques. This study was designed to examine the vascular inflammation measured using FDG-PET in patients with impaired glucose tolerance and T2DM, in comparison with age- and sex-matched control subjects with normal glucose tolerance.

METHODS AND RESULTS

We investigated vascular inflammation using FDG-PET in 90 age- and sex-matched subjects with different glucose tolerance (30 normal glucose tolerance subjects, 30 impaired glucose tolerance subjects, and 30 T2DM subjects). Vascular 18F-FDG uptake was measured as both the mean and maximum blood-normalized standardized uptake value, known as the target-to-background ratio (TBR). Both mean and maximum TBR measurements were significantly different, based on glucose tolerance, although the carotid intima-media thickness measurements were not significantly different. The maximum TBR values in patients with impaired glucose tolerance and T2DM were significantly increased compared with the normal subjects. In addition, subjects with metabolic syndrome had increased maximum TBR values compared with those without metabolic syndrome. Age-, sex-, and body mass index-adjusted maximum TBR levels were positively correlated with triglyceride, hemoglobin A1c, insulin resistance, high-sensitivity C-reactive protein, and Framingham risk score and were negatively correlated with high-density lipoprotein cholesterol and adiponectin levels.

CONCLUSIONS

The results of the present study suggest that impaired glucose tolerance and T2DM are associated with vascular inflammation in carotid atherosclerosis detected by FDG-PET.

Intestinal, adipose, and liver inflammation in diet-induced obese mice

Chronic inflammation and increased visceral adipose tissue (VAT) are key elements of the metabolic syndrome. Both are considered to play a pathogenic role in the development of liver steatosis and insulin resistance. The aim of the present study was to investigate the hypothesis that an inflamed intestine, induced both by diet and chemical irritation, could induce persistent inflammation in VAT. Female C57BL/6JOlaHsd mice were used. In study I, groups of mice (n = 6 per group) were given an obesity-inducing cafeteria diet (diet-induced obesity) or regular chow only (control) for 14 weeks. In study II, colitis in mice (n = 8) was induced by 3% dextran sulfate sodium in tap water for 5 days followed by 21 days of tap water alone. Healthy control mice (n = 8) had tap water only. At the end of the studies, all mice were killed; and blood and tissues were sampled and processed for analysis. Body weight of diet-induced obese mice was greatly increased, with evidence of systemic inflammation, insulin resistance, and liver steatosis. Tissue inflammation indexed by proinflammatory cytokine expression was recorded in liver, mesenteric fat, and proximal colon/distal ileum, but not in subcutaneous or perigonadal fat. In dextran sulfate sodium-induced colitis mice, mesenteric fat was even more inflamed than the colon, whereas a much milder inflammation was seen in liver and subcutaneous fat. The studies showed both diet- and colitis-initiated inflammation in mesenteric fat. Fat depots contiguous with intestine and their capacity for exaggerated inflammatory responses to conditions of impaired gut barrier function may account for the particularly pathogenic role of VAT in obesity-induced metabolic disorders.

[Pathogenesis of the metabolic syndrome]

After an initial attempt by the WHO to define metabolic syndrome (MS) on a pathophysiologically oriented approach requiring the assessment of insulin resistance markers, the NCEP-ATPIII and more recently the IDF proposed more clinically oriented criteria to help, toward a preventive medicine goal, to identify patients who are likely to have features of the MS and be at increased risk of type 2 diabetes and cardio vascular disease. The notion of MS is built around abnormalities of the metabolism of lipids and carbon hydrates, a rise of blood pressure, and visceral obesity of abdominal localization. These parameters report only partially on mechanisms leading to the development of the MS. The physiopathology of MS is partially understood even today and likely results from the combination of environmental, genetic and epigenetic factors. Abdominal visceral obesity, a state of low-grade chronic inflammation and insulin resistance are the main processes susceptible to explain the various constituents of this syndrome.

Beta cell death in hyperglycaemic Psammomys obesus is not cytokine-mediated

AIMS/HYPOTHESIS

It has recently been proposed that IL-1beta may be responsible for beta cell death in type 2 diabetes mellitus. Major support for this assumption was derived from experiments in the gerbil Psammomys obesus (sand rat), a model for nutritionally induced non-insulin-dependent type 2 diabetes. Using gerbil-specific primers for the analysis of gene expression, we investigated the validity of this hypothesis.

METHODS

Gene expression was analysed by real-time RT-PCR of isolated and laser-microdissected islets and by in situ RT-PCR, both in beta cells and in immune cells, as well as in lymph nodes and spleen.

RESULTS

We were unable to detect Il-1beta and the IL-1beta-inducible enzyme inducible nitric oxide synthase (iNos) by in situ RT-PCR, either in the pancreatic beta cells, or in the small number of non-activated immune cells of healthy and diabetic Psammomys obesus after 1 and 3 weeks on a high-energy diet. Very low levels of Il-1beta and iNos mRNA were detectable in collagenase-isolated and laser-microdissected islets of normoglycaemic gerbils by real-time RT-PCR without any increase of these mRNAs in islets from diabetic animals. These results were confirmed by electron microscopy with immunogold staining for IL-1beta and insulin.

CONCLUSIONS/INTERPRETATION

The diabetic syndrome induced in Psammomys obesus by high-energy diet is a classical type 2 diabetes model, which does not show any evidence of an involvement of the proinflammatory cytokine IL-1beta or of activated immune cells in its pathogenesis. This is clearly at variance with the situation in type 1 diabetes.

The metabolic syndrome

The metabolic syndrome (MS) is a cluster of metabolic abnormalities leading to increased risk for cardiovascular diseases and diabetes type 2. Its prevalence is increasing with aging. There exists actually an epidemic of MS. Visceral obesity and the resulting insulin resistance (IR) are the major determinant in the development of the MS. Abdominal obesity results in a low grade inflammation via the adipose tissue and macrophages secreted adipokines. This inflammation, via the generated pro-inflammatory molecules, interferes with the normal insulin signalling and thus contributes to the etiopathogenesis of the MS. Large clinical studies showed that CRP is increased in obese subjects and concomitantly to the number of existing component of the MS. Treatment of the MS is aimed to improve the IR by lifestyle changes including exercise and diet alone or in combination with medication targeting the individual components but having also anti-inflammatory actions. More research is needed to bring new therapies to be able to decrease the incidence and prevalence of the MS among the population and thus increasing their quality of life.