CCL2 Serum Levels and Adiposity Are Associated with the Polymorphic Phenotypes -2518A on CCL2 and 64ILE on CCR2 in a Mexican Population with Insulin Resistance

Expression of obesity- and type-2 diabetes-associated genes in omental adipose tissue of individuals with obesity

AIMS

Obesity and type 2 diabetes mellitus are two pathologies that share metabolic abnormalities in most of the cases; however, there are differences as well. Some studies have reported that approximately 30% of obese patients have normal glucose and lipid levels in blood despite an accumulation of abdominal adipose tissue. Here, we compare the gene expression in adipose tissue of several genes associated with obesity and/or diabetes between obese patients without T2D and obese patients with T2D.

METHODS

Omental adipose tissue was collected during the patients elective bariatric surgery. Gene expression was determined by real-time PCR. Phenotypic variables were correlated with gene expression and 2^^-ΔΔCt relative expression analysis between groups was performed.

RESULTS

The stronger correlations in the obese without T2D or reference group was between ICAM1 and HbA1c; HP and TC and LDL while in the obese with diabetes or case group the correlation occurred between CSF1 and BMI. A correlation between HP and TC was found in the case group as well. The expression of VEGFA, CCND2, IL1R1 and PTEN was downregulated in the obese with T2D group.

CONCLUSIONS

This study identified genes whose expression is different between obese subjects with and without diabetes. Those genes are related to inflammation, cholesterol transport, adipocyte differentiation/expansion and browning.

Innate-Immunity Genes in Obesity

The main functions of adipose tissue are thought to be storage and mobilization of the body’s energy reserves, active and passive thermoregulation, participation in the spatial organization of internal organs, protection of the body from lipotoxicity, and ectopic lipid deposition. After the discovery of adipokines, the endocrine function was added to the above list, and after the identification of crosstalk between adipocytes and immune cells, an immune function was suggested. Nonetheless, it turned out that the mechanisms underlying mutual regulatory relations of adipocytes, preadipocytes, immune cells, and their microenvironment are complex and redundant at many levels. One possible way to elucidate the picture of adipose-tissue regulation is to determine genetic variants correlating with obesity. In this review, we examine various aspects of adipose-tissue involvement in innate immune responses as well as variants of immune-response genes associated with obesity.

The Effects of Sex and Body Weight on Renal Graft Function-The Role of CCL2

There are reports on the effects of excessive recipient body weight on renal graft function. Increased CCL2 (chemokine CC-mortif ligand 2) production is observed in patients with excessive body weight. CCL2 also exacerbates the inflammatory process in the renal graft. A total of 49 renal graft recipients of both sexes having undergone renal biopsy within the last 18 months were retrospectively reviewed. At their most recent appointment the patients’ plasma concentrations of CCL2 were evaluated. Renal function was assessed retrospectively. CCL2 concentrations were higher in men than women (p < 0.047), while higher CCL2 levels were associated with a decrease in eGFR (estimated glomerular filtration rate) during the first year post Tx (kidney transplantation). CCL2 negatively correlated with eGFR at 5 years (R = −0.45, p < 0.040997) and positively correlated with the degree of tubular atrophy in renal biopsy specimens (R = 0.43, p < 0.027293) and with systolic pressure. Men showed significantly higher BMI (body mass index) values at the time of Tx and at their last appointment than women did (p < 0.000403; p < 0.000613, respectively). Men showed poorer long-term renal graft function, with significantly lower eGFR values at 4 and 5 years into the post-transplantation period. The male sex and excessive body weight have adverse effects on short- and long-term renal graft function, which is associated with increased levels of CCL2.

Does C-C Motif Chemokine Ligand 2 (CCL2) Link Obesity to a Pro-Inflammatory State?

The mechanisms of how obesity contributes to the development of cardio-metabolic diseases are not entirely understood. Obesity is frequently associated with adipose tissue dysfunction, characterized by, e.g., adipocyte hypertrophy, ectopic fat accumulation, immune cell infiltration, and the altered secretion of adipokines. Factors secreted from adipose tissue may induce and/or maintain a local and systemic low-grade activation of the innate immune system. Attraction of macrophages into adipose tissue and altered crosstalk between macrophages, adipocytes, and other cells of adipose tissue are symptoms of metabolic inflammation. Among several secreted factors attracting immune cells to adipose tissue, chemotactic C-C motif chemokine ligand 2 (CCL2) (also described as monocyte chemoattractant protein-1 (MCP-1)) has been shown to play a crucial role in adipose tissue macrophage infiltration. In this review, we aimed to summarize and discuss the current knowledge on CCL2 with a focus on its role in linking obesity to cardio-metabolic diseases.

CCR2/CCL2 and CMKLR1/RvE1 chemokines system levels are associated with insulin resistance in rheumatoid arthritis

Rheumatoid arthritis (RA) has been associated with insulin resistance (IR). Due to an excess in storage of white adipose tissue, IR has an inflammatory process that overlaps with RA. This is performed by the activation/migration of monocytes carried out by the CCR2/CCL2 and CMKLR1/RvE1 chemokines systems. Furthermore, these can potentiate chronic inflammation which is the central axis in the immunopathogenesis of RA. We evaluated the association between the relative expression of CCR2 and CMKLR1 and the serum levels of their ligands CCL2 and RvE1, in the context of adiposity status with IR as a comorbidity in RA. We studied 138 controls and 138 RA-patients classified with and without IR. We evaluated adiposity, RA activity, IR status and immunometabolic profiles by routine methods. Insulin, CCL2 and RvE1 serum levels were determined by ELISA. Relative expression of CCR2, CMKLR1 and RPS28 as constitutive gene by SYBR green RT-qPCR and 2-ΔΔCT method. Increased measurements were observed of body adiposity and metabolic status as follows: RA with IR>control group with IR>RA without IR> control group without IR. CCR2 and CMKLR1 relative expression was increased in RA without IR versus control without IR. CCR2: 2.3- and 1.3-fold increase and CMKLR1: 3.5- and 2.7-fold increase, respectively. Whereas, CCR2 expression correlates with CMKLR1 expression (rho = 0.331) and IR status (rho = 0.497 to 0.548). CMKLR1 expression correlates with inflammation markers (rho = 0.224 to 0.418). CCL2 levels were increased in the RA groups but levels of RvE1 were increased in RA without IR. We conclude that in RA with IR, the chemokine receptors expression pattern showed a parallel increase with their respective ligands. RA and IR in conjunction with the pathological distribution of body fat mass might exacerbate chronic inflammation. These results suggest that high CCL2 levels and compensatory RvE1 levels might not be enough to resolve the inflammation by themselves.

Ageing influences the relationship of circulating miR-33a and miR- 33b levels with insulin resistance and adiposity

OBJECTIVE

The identification of circulating microRNAs related to abnormal metabolic function may be useful in the context of ageing, adiposity and insulin resistance. The miR-33 a/b has been shown to control the expression of genes involved in fatty acid biosynthesis, impaired metabolism and insulin resistance. In this study, we aimed to identify differences in circulating miR-33 a/b levels according to age-related metabolic impairment and increased adiposity.

METHODS

This study included 80 individuals (30.2% with obesity, 70% females) classified according to insulin resistance (Stern's criteria) and age [young (20-39 years) and senior (40-59 years)]. Body fat was evaluated using bioelectrical impedance, biochemical markers by colorimetric, enzymatic and immuno-turbidimetry methods. TaqMan measures of circulating miR-33 a and miR-33 b with quantitative reverse transcription polymerase chain reaction in serum were assessed in association with clinical outputs.

RESULTS

Circulating miR-33 a and miR-33 b levels showed significant association with fatness, the lipid profile and biomarkers of impaired glucose metabolism. Both miR-33 a and miR-33 b were associated with visceral adiposity index in non-insulin resistance and insulin resistance individuals. More important, for miR-33 a circulating levels in senior group, receiver operating characteristic curve analyses showed area under the curve 0.804 ( p = 0.010; 95% confidence interval = 0.655-0.952).

CONCLUSION

Ageing influenced the relationship of circulating miR-33 a and miR-33 b with insulin resistance and increased adiposity.

Chemokine gene polymorphisms association with increased risk of type 2 diabetes mellitus in Tatar ethnic group, Russia

Recent studies have shown that chemokines play an important role in the development of chronic inflammation in adipose tissue, obesity pathogenesis, glucose intolerance and type 2 diabetes. It has also been revealed that some SNPs in chemokine genes are associated with obesity, insulin resistance, type 2 diabetes and diabetes complications in different ethnic groups. The aim of this study was to determine the associations between SNPs in chemokine genes and type 2 diabetes in participants of Tatar ethnic group, living in Bashkortostan. Case-control and cross-sectional study were included in our study design. Five SNPs were genotyped in 440 type 2 diabetes (160 men and 280 women), 58.8 ± 9.2 years old (mean ± SD), BMI 29.3 ± 3.9 kg/m² (mean ± SD) patients of Tatar ethnicity, and a control group of 500 Tatars (180 men and 320 women), 55.2 ± 11.6 years old (mean ± SD), BMI 25.9 ± 4.3 kg/m² (mean ± SD). The SNPs rs6749704 in CCL20 [odds ratio (OR) = 2.77 (95% CI 1.81-4.25), р = 0.0001], rs2107538 in CCL5 [odds ratio (OR) = 1.80 (95% CI 1.46-2.22), p = 0.0001] were significantly associated with type 2 diabetes. Regression analysis revealed that rs1696941 in CCL11 was associated with the onset age and duration of type 2 diabetes as well as with HbA_1c level (p = 0.034, p = 0.036 and p = 0.0054, respectively). The SNPs rs223828 in CCL17 and rs6749704 in CCL20 were correlated with obesity as estimated by BMI (p = 0.0004, p = 0.029, respectively). Rs223828 in CCL17 revealed the association with postprandial glucose level (p = 0.024) and HbA_1c (p = 0.008). These data demonstrate that variants of chemokine genes are associated with type 2 diabetes and obesity of Tatar ethnic group inhabiting Bashkortostan Republic. Novel associations of the polymorphic loci in CCL20 (rs6749704) and CCL5 (rs2107538) genes with type 2 diabetes had been identified as a result of the conducted research.

A possible association between the -2518 A>G MCP-1 polymorphism and insulin resistance in school children

Objective Monocyte chemoattractant protein 1 (MCP-1) has been suggested to be involved in the pathophysiology of insulin resistance (IR); therefore, variants in the MCP-1 gene may contribute to the development of this disease. The aim of this study was to analyze the relationship of the -2518 A>G MCP-1 (rs1024611) gene polymorphism with insulin resistance in Mexican children. Subjects and methods A cross-sectional study was performed in 174 children, including 117 children without insulin resistance and 57 children with IR, with an age range of 6-11 years. Levels for serum insulin and high-sensitivity C-reactive protein were determined. The -2518 A>G MCP-1 polymorphism was identified by the polymerase chain reaction-restriction fragment length polymorphism method. Insulin resistance was defined as a HOMA-IR in the upper 75th percentile, which was ≥ 2.4 for all children. Results Genotype frequencies of the rs1024611 polymorphism for the insulin-sensitive group were 17% AA, 48% AG and 35% GG, and the frequency of G allele was 59%, whereas frequencies for the insulin-resistant group were 12% AA, 37% AG and 51% GG, and the frequency of G allele was 69%. The genotype and allele frequencies between groups did not show significant differences. However, the GG genotype was the most frequent in children with IR. The GG genotype was associated with insulin resistance (OR = 2.2, P = 0.03) in a genetic model. Conclusion The -2518 A>G MCP-1 gene polymorphism may be related to the development of insulin resistance in Mexican children.

TREM-1 associated macrophage polarization plays a significant role in inducing insulin resistance in obese population

BACKGROUND

TREM-1 acts as an amplifier of inflammation expressed on macrophages. The objective of this study was to evaluate the relationship between TREM-1 and macrophage polarization, and association of TREM-1 and M1 macrophage polarization with insulin resistance (IR) in obese population compared to non-obese population.

METHODS

We enrolled 38 patients after obtaining IRB approval for this study. We evaluated the mRNA and protein expression levels of general macrophage marker (CD68), M1 marker (CD86, CCR7, iNOS, IFNγ, TNF-α and IL-6,), M2 marker (CD206, CD163, IL-10, IL-4) and chemokine axis (MCP-1, CCR2 and CCR5) along with TREM-1 and TREM-2 in omentum fat, subcutaneous fat, and liver biopsy tissues of non-obese (N = 5), obese non-diabetics, (N = 16) and obese diabetics (N = 17).

RESULTS

The results of our study showed over-expression of TREM-1, M1 markers and down-regulation of TREM-2 and M2 markers in the omentum, subcutaneous and liver biopsies of obese patients (diabetics and non-diabetics) compared to non-obese patients. Overall, the obese diabetic group showed a significant (p < 0.05) higher number of patients with over expression of M1 markers (TREM-1, CD68, CD86, CCR-7, iNOS, IFN-γ, TNF-α, IL-6, MCP-1, CCR-2 and CCR-5) and down-regulation of M2 markers (CD206, CD163 and IL-4) in liver biopsy compared to obese non-diabetics.

CONCLUSIONS

TREM-1 expression is significantly increased along with the M1 markers in liver biopsy of obese diabetic (17/17) and obese non-diabetic patients (9/16). Our data suggests that TREM-1 overexpression and M1 macrophage polarization are associated with obesity-induced IR.