Association of leptin gene -2548 G/A polymorphism with obesity: a meta-analysis

Genetic Association of LEP Gene Polymorphisms with Obesity in Moroccan Individuals: Case-Control Study and Updated Meta-analysis

Obesity is a global epidemic disease representing the fifth leading cause of death in the world. It was shown that it is caused by the interaction between environmental factors and genes including leptin gene (LEP). This paper aimed to analyze the association between the LEP gene polymorphisms rs7799039 and rs11761556 with obesity in Moroccan individuals as well as to perform an update meta-analysis of this genetic association. Both polymorphisms were genotyped in 146 obesity patients and 104 controls using real-time PCR technique. The genetic association analysis and the comparison of quantitative parameters were carried out using the R language. Moreover, a meta-analysis including 20 genetic association studies was performed using Review Manager 5.3 software. No significant association was found between the polymorphisms rs7799039 and rs11761556 and the risk of obesity. The comparison of biochemical and clinical parameters between the genotypes of the rs7799039 polymorphism, showed a significant increased triglycerides levels in carriers of AA or GA genotypes (P value = 0.040). The meta-analysis showed no significant association between the rs7799039 polymorphism and obesity under all genetic models. In conclusion, the case-control study and meta-analysis demonstrated that the LEP gene polymorphisms rs7799039 and rs11761556 cannot be considered as genetic risk factors for obesity.

The Role of Dietary Glycemic Index and Glycemic Load in Mediating Genetic Susceptibility via MC4R s17782313 Genotypes to Affect Cardiometabolic Risk Factors among Apparently Healthy Obese Individuals

Background

The association of genetic and dietary factors with occurrence and progression of chronic diseases such as metabolic syndrome (MetS) has long been addressed but there is a lack of evidence for complex interrelationships, including direct and indirect effects of these variables. Hence, this study is aimed at evaluating the mediating role of glycemic indices in the association of melanocortin-4 receptor (MC4R) rs17782313 polymorphism, sociodemographic, and psychological factors with the risk of MetS in obese adults using structural equation modeling.

Methods

We performed a cross-sectional analysis of data from 287 apparently healthy adults. Dietary glycemic index (GI) and glycemic load (GL) were calculated from a validated 147-item food frequency questionnaire (FFQ). MC4R s17782313 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Structural equation modeling was used to explore direct and indirect effects of genetic and nongenetic factors on MetS.

Results

MC4R gene variant was directly associated with the risk of MetS (B = 0.010; P = 0.023). On the other hand, this variant was found to be indirectly and positively associated with LDL-C (B = 6.589; P = 0.042) through mediatory effects of GI and GL. Moreover, GI and GL also mediated indirect positive effects of sex and age on LDL-C (B = 3.970; P ≤ 0.01; B = 0.878; P ≤ 0.01, respectively) and HDL (B = 2.203; P ≤ 0.01; B = 0.129; P ≤ 0.01, respectively). MC4R rs17782313 polymorphism had positive effects on GI (B = 1.577; P ≤ 0.01) and GL (B = 1.235; P ≤ 0.01).

Conclusion

Our data may state a hypothesis of the mediating effect of quantity and quality of carbohydrates consumed in relationship between genetic susceptibility to obesity and cardiometabolic risk factors. Further analyses should be carried out in high-quality cohort studies in order to confirm the findings.

Hunger Hormones in Disruptive Mood Dysregulation Disorder in Adolescents: An Exploratory Study

Background:

Hunger hormones, including ghrelin and leptin, are associated with appetitive behaviors in various psychiatric disorders. Biochemical and hormonal status in disruptive mood dysregulation disorder (DMDD) in adolescents is largely unexplored.

Objectives:

The study aimed to assess levels of leptin and ghrelin and find their association with lipid profiles in adolescents with DMDD.

Methods:

Twenty adolescents with a DSM 5 diagnosis of DMDD with age and gender-matched 19 healthy controls were recruited, followed by clinical assessment. They were assessed for leptin, ghrelin, and lipid profiles, respectively.

Results:

Adolescents with DMDD were comparable in age, education, family income, domicile status, psychiatric illness in the family, and body mass index (BMI) with matched controls. There was no difference in mean lipid profile and ghrelin in both groups. However, the DMDD group had statistically significant higher mean level of leptin as compared to the control group (t=1.84, p < 0.05). As measured by the Modified Overt Aggression Scale in DMDD, aggression showed a significant positive correlation with measures of lipid profile.

Conclusion:

Adolescents with DMDD have elevated serum leptin levels. Further research is needed to confirm this finding.

Association of ADIPOQ-rs2241766 and FTO-rs9939609 genetic variants with body mass index trajectory in women of reproductive age over 6 years of follow-up: the PREDI study

BACKGROUND

Interindividual variations in body mass index (BMI) can be partially explained by genetic differences. We aimed to examine the association of the ADIPOQ-rs2241766, LEP-rs7799039 and FTO-rs9939609 genetic variants with BMI trajectory in women of reproductive age over 6 years of follow-up.

METHODS

This was a prospective study that used data from 435 women of the PREDI Study conducted in Brazil. Socioeconomic, biological and anthropometric data were collected at four time points: 2012 (baseline) in the maternity hospital, and 2013-14, 2016-17 and 2018 (1^st, 2^nd and 3^rd follow-ups) at the participant's home. Genotyping was performed by PCR-RFLP. Linear mixed-effect and Poisson regression models were used to address the association of ADIPOQ, LEP and FTO genotypes with BMI and overweight/obesity status.

RESULTS

Women carrying the risk allele (TA or AA) of the FTO-rs9939609 genetic variant had a 1.16 kg/m² higher BMI over the follow-up period than those carrying the wild-type genotype (TT), even when adjusted for potential confounders (95% CI: 0.23-2.10, p = 0.015). The risk of obesity associated with the FTO-TA or AA genotype decreased over the years, demonstrating an influence of time on its trajectory (IRR = 0.99, 95% CI: 0.98-0.99, p = 0.016). There was no variation in BMI trajectories for the ADIPOQ-rs2241766, LEP-rs7799039 or FTO-rs9939609 genetic variant.

CONCLUSIONS

The results of this study suggest that monitoring women of reproductive age with ADIPOQ-rs2241766 TG/GG or FTO-rs9939609 TA/AA genotypes may be an important strategy to reduce maternal excess body weight and, consequently, the long-term public health burden of obesity.

The Prognosis of Leptin rs2167270 G > A (G19A) Polymorphism in the Risk of Cancer: A Meta-Analysis

Background

Although the effect of the LEP G19A (rs2167270) polymorphism on cancers is assumed, the results of its influence have been contradictory. A meta-analysis was conducted to precisely verify the relationships between LEP G19A and the development of digestion-related cancers.

Methods

Investigators systematically searched the literature in PubMed, Embase, and Web of Science and used STATA software 14.0 for the meta-analysis. The odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the associations. Subgroup analyses stratified by ethnicity, cancer type, and cancer system were further conducted to assess the relationship between the LEP G19A polymorphism and digestion-related cancers.

Results

In the overall population, we found a significant relationship with overall cancer (allele comparison: OR = 0.921, p = 0.000; dominant comparison: OR = 0.923, p = 0.004; recessive comparison: OR = 0.842, p = 0.000; homozygote model: OR = 0.0843, p = 0.001). In a subgroup analysis conducted by ethnicity, we obtained significant results in Asians (Asian allele comparison: OR = 0.885, p = 0.000; dominant comparison: OR = 0.862, p = 0.000; homozygote model: OR = 0.824, p = 0.039; and heterozygote comparison: OR = 0.868, p = 0.000) but not in Caucasians. In a subgroup analysis conducted by cancer type and cancer system, we obtained significant results that the LEP G19A polymorphism may decrease the risk of colorectal cancer, esophageal cancer, digestive system cancer, and urinary system cancer.

Conclusions

This meta-analysis revealed that the LEP G19A polymorphism may decrease the risk of cancer.

Impaired Leptin Signalling in Obesity: Is Leptin a New Thermolipokine?

Leptin is a principal adipose-derived hormone mostly implicated in the regulation of energy balance through the activation of anorexigenic neuronal pathways. Comprehensive studies have established that the maintenance of certain concentrations of circulating leptin is essential to avoid an imbalance in nutrient intake. Indeed, genetic modifications of the leptin/leptin receptor axis and the obesogenic environment may induce changes in leptin levels or action in a manner that accelerates metabolic dysfunctions, resulting in a hyperphagic status and adipose tissue expansion. As a result, a vicious cycle begins wherein hyperleptinaemia and leptin resistance occur, in turn leading to increased food intake and fat enlargement, which is followed by leptin overproduction. In addition, in the context of obesity, a defective thermoregulatory response is associated with impaired leptin signalling overall within the ventromedial nucleus of the hypothalamus. These recent findings highlight the role of leptin in the regulation of adaptive thermogenesis, thus suggesting leptin to be potentially considered as a new thermolipokine. This review provides new insight into the link between obesity, hyperleptinaemia, leptin resistance and leptin deficiency, focusing on the ability to restore leptin sensitiveness by way of enhanced thermogenic responses and highlighting novel anti-obesity therapeutic strategies.

Leptin and Obesity: Role and Clinical Implication

The peptide hormone leptin regulates food intake, body mass, and reproductive function and plays a role in fetal growth, proinflammatory immune responses, angiogenesis and lipolysis. Leptin is a product of the obese (ob) gene and, following synthesis and secretion from fat cells in white adipose tissue, binds to and activates its cognate receptor, the leptin receptor (LEP-R). LEP-R distribution facilitates leptin's pleiotropic effects, playing a crucial role in regulating body mass via a negative feedback mechanism between adipose tissue and the hypothalamus. Leptin resistance is characterized by reduced satiety, over-consumption of nutrients, and increased total body mass. Often this leads to obesity, which reduces the effectiveness of using exogenous leptin as a therapeutic agent. Thus, combining leptin therapies with leptin sensitizers may help overcome such resistance and, consequently, obesity. This review examines recent data obtained from human and animal studies related to leptin, its role in obesity, and its usefulness in obesity treatment.

Dietary patterns interact with the variations of 18q21.23 rs17782313 locus on regulation of hypothalamic-pituitary axis hormones and cardio-metabolic risk factors in obesity

BACKGROUND

Evidence shows the role of polymorphisms in rs17782313 MC4R gene with increased risk of obesity in Asians adult. In the current report, we investigated the interaction between rs17782313 MC4R gene and major dietary patterns on α-melanocyte stimulating hormone (α-MSH), Agouti-related peptide (AgRP), serum lipids and blood pressure among obese individuals.

METHODS

This cross-sectional study was performed in 288 obese adults between 20 and 50 years of age. Anthropometric measurements and biochemical assays were conducted with standard methods. To evaluate appetite, the Visual Analogue Scale (VAS) was used. Dietary patterns were obtained by principal component analysis (PCA). Genotyping of rs17782313 was assessed by restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Three major dietary patterns were extracted: Prudent Dietary Pattern (PDP), Legume Dietary Pattern (LDP) and Mixed Dietary Pattern (MDP). Higher PDP score was associated with reduced SBP and insulin concentration while highest MDP score was associated with lower TG concentration (P < 0.05). Significant interactions were observed between higher adherence to PDP and rs17782313 CC genotype on increased SBP (P_Interaction = 0.04), serum insulin (P_Interaction = 0.05) and AgRP (P_Interaction = 0.03) and also between higher adherence to MDP and CC genotype of rs17782313 on reduced serum TG (P = 0.03).

CONCLUSIONS

The findings of the current study showed that being on CC genotype of rs17782313 polymorphism made obese individuals more prone to have higher SBP, insulin and AgRP even in highest adherence to PDP. However, adherence to MDP could attenuate the risky effects of being on CC genotype of rs17782313 by reducing serum TG concentrations.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Adiponectin and leptin gene variants and their effects on body weight trajectories in children from birth to 6 years of age: the PREDI Study

Excess body weight confers a high risk to human health. Body weight variation between subjects can be partially explained by genetic differences. The aim of the present study was to investigate the association of genetic variants in the ADIPOQ (rs2241766) and LEP (rs7799039) genes with body weight trajectories in children from birth to 6 years of age. This was a prospective cohort (PREDI Study). Socio-economic, biological and anthropometric data were collected at four time points: at birth in the maternity unit; 1-2, 4-5 and 6 years old at the participants' homes. Genotyping was performed by PCR-restriction fragment length polymorphism. Poisson regression and linear mixed-effect regression models were used to address the association of ADIPOQ and LEP genotypes with BMI. Excessive body weight at pre-pregnancy (β = 0·339, P = 0·01) and excessive gestational weight gain (β = 0·51, P < 0·001) were associated with children's BMI trajectory from birth to 6 years. The ADIPOQ-rs2241766 TG or GG genotype was associated with a higher risk of excess body weight in the first 6 years of life (both sexes relative risk 1·25, 95 % CI 1·01, 1·56; female relative risk 1·67, 95 % CI 1·20, 2·31). BMI increased over the years according to the presence of the TG or GG genotype (β = 0·01, 95 % CI 0·01, 0·02), particularly in females (β = 0·02, 95 % CI 0·01, 0·04). The ADIPOQ-rs2241766 TG and GG genotypes increased the risk of excess body weight in children from birth to 6 years of age and had a positive effect on body weight trajectories in girls. The LEP-rs7799039 genetic variant was not associated with body weight trajectory in children.

The interaction between dietary Non-Enzymatic Antioxidant Capacity (NEAC) with variants of Melanocortin-4 receptor (MC4R) 18q21.23-rs17782313 locus on hypothalamic hormones and cardio-metabolic risk factors in obese individuals from Iran

Background: In the current study, we aimed to evaluate the interaction between dietary Non-Enzymatic Antioxidant Capacity (NEAC) and rs17782313 polymorphism on hypothalamic hormones and cardio-metabolic risk factors. Methods: A total of 287 subjects (aged 20-50 years, 147 males and 140 females) enrolled in the cross-sectional study. Dietary NEAC was assessed using databases of NEAC measurements compiled from outcomes for three different analyses: oxygen radical absorbance capacity (ORAC), ferric reducing-antioxidant power (FRAP), and total radical-trapping antioxidant parameter (TRAP) and genotyping for the near MC4R rs17782313 was carried out by Polymerase chain reaction-restriction fragments length polymorphism (PCR-RFLP) method. Results: The significant interactions were found between adherence to the dietary NEAC and MC4R rs17782313 in relation to high-density lipoprotein-cholesterol (HDL-C), glucose, α-melanocyte stimulating hormone (α-MSH), insulin and quantitative insulin sensitivity check index (QUICKI) (P _Interaction = 0.03, 0.01, 0.04, 0.04 and 0.04, respectively). In homozygous subjects for the minor allele, the serum insulin level and QUICKI in participants with the highest adherence to TRAP were significantly higher than those with the lowest adherence (p < 0.001). There was a significant inverse association between high ORAC score and risk of metabolic syndrome even after adjusting for potential confounders (OR: 0.33; 95%CI:0.13-0.81) and also a significant inverse association between high NEAC (ORAC, FRAP and TRAP assays) score and high triglyceride (TG) level was found in obese adults. Conclusion: In conclusion, our study found for the first time that the NEAC significantly interacts with the rs17782313 genotypes to influence several metabolic risk factors in obesity.

Genetics of Severe Obesity

PURPOSE OF REVIEW

This review aims to present current information on genes underlying severe obesity, with the main emphasis on the three genes LEP, LEPR and MC4R.

RECENT FINDINGS

There is a substantial amount of evidence that variants in at least ten different genes are the cause of severe monogenic obesity. The majority of these are involved in the leptin-melanocortin signalling pathway. Due to the frequency of some of the identified variants, it is clear that monogenic variants also make a significant contribution to common obesity. The artificial distinction between rare monogenic obesity and common polygenic obesity is now obsolete with the identification of MC4R variants of strong effect in the general population.

Presence and distribution of leptin and its receptor in the gut of adult zebrafish in response to feeding and fasting

Leptin is an anorectic hormone secreted mainly by peripheral adipocytes but also by other central and peripheral tissues. It acts by means of a receptor called OB-R, influencing not only appetite and body mass but being also involved in many fields like endocrinology, metabolism and reproduction. Immunohistochemistry and qRT-PCR techniques were, respectively, used to demonstrate the presence of leptin and its receptor in the gut of adult zebrafish and to evaluate the leptin gene expression response to feeding and fasting. Immunoreactivity for the antibodies utilized was demonstrated in feeding but not in fasting fish, and the gene expression analysis corroborates the data obtained by immunohistochemistry. Therefore, all the obtained results support the hypothesis of the role of this hormone in food regulation in zebrafish.

Association of Single Nucleotide Polymorphism -2548 G/A (rs12112075) of leptin gene with endometrial cancer and uterine leiomyomas

AIM

The aim of this study was to analyse the frequencies of genotypes and alleles of Single Nucleotide Polymorphism (SNP) -2548 G/A (rs12112075) of leptin gene (LEP) and an attempt to evaluate the effect this DNA marker has on endometrial cancer (EC) and uterine leiomyomas (UL).

MATERIAL AND METHODS

The study comprised 120 patients treated for endometrial cancer and 90 patients treated for uterine leiomyomas. 90 disease-free individuals were used as controls. In total, 300 patients were investigated in this research.

RESULTS

In this paper we have demonstrated that genotype AG of SNP -2548 G/A of LEP may reduce the risk of developing endometrial cancer, whereas allele A itself may be a risk factor of this malignancy. No association was found between the studied polymorphism and uterine leiomyomas.

CONCLUSIONS

-2548 G/A SNP of LEP may play a significant role in the development of EC, however, uterine leiomyomas are not associated with this DNA marker.

Adipokine genes and radiographic hand osteoarthritis in Finnish women: a cross-sectional study

OBJECTIVES

Available evidence suggests that genetic factors and overweight play major roles in the aetiology of osteoarthritis (OA). We analysed the association of 18 single-nucleotide polymorphisms (SNPs) from nine adipokine and adipokine receptor genes (LEP, LEPR, ADIPOQ, RETN, NAMPT, SERPINA12, ITLN1, RARRES2, and APLN) with radiographic hand OA.

METHOD

The study design was cross-sectional. Bilateral hand radiographs of 542 occupationally active Finnish female dentists and teachers aged 45-63 years were examined and classified for the presence of hand OA using reference images. Hand OA was defined as at least three finger joints with radiographic OA of grade 2-4. The genotypes were determined using polymerase chain reaction-based methods. Body mass index (BMI) was calculated based on self-reported height and measured weight. Associations of the individual SNPs and their haplotypes with hand OA were tested using logistic regression analysis.

RESULTS

The minor allele of RETN rs10401670 was associated with a decreased [odds ratio (OR) = 0.73, 95% confidence interval (CI) 0.55-0.97, p = 0.03] and RARRES2 rs4721 with an increased (OR 1.41, 95% CI 1.07-1.87, p = 0.01) prevalence of hand OA. Also, LEPR AC (OR 1.54, 95% CI 1.01-2.35, p = 0.05) and RETN GGTT (OR 0.58, 95% CI 0.37-0.93, p = 0.02) haplotypes were associated with hand OA. These associations were modified by BMI when comparing normal and overweight women. However, the associations lost their statistical significance after adjusting for multiple testing.

CONCLUSION

Our results suggest weak associations between the studied variations in LEPR, RARRES2, and RETN genes and hand OA in Finnish women, and that the associations are modified by BMI. However, these associations could not be verified in the current study.

Lack of Association between NYD-SP18 Variant and Obesity. The Health Alcohol and Psychosocial Factors in Eastern Europe Study

Aim

To replicate the finding that the polymorphism rs6971091 within the NYD-SP18 gene is associated with body mass index (BMI).

Method

We analysed data of 29,284 adults (46.2% of males, mean age 58.9 (SD 7.3), mean BMI 28.6 (5.0 kg/m²)) examined within the Health Alcohol and Psychosocial Factors in Eastern Europe study in the Czech Republic, Poland, Lithuania and Russia.

Results

BMI did not differ by rs6971091 genotype. In men, the mean BMI (SEs) in GG, GA and AA carriers were 27.8 (0.05), 27.9 (0.06) and 27.9 (0.14) kg/m², respectively, (p = 0.26); in women, the corresponding values were 29.2 (0.06), 29.1 (0.07) and 29.1 (0.16), p = 0.57. In Czech subjects (n = 6,752), for whom the FTO rs17817449 genotype was available, there was no interaction between the NYD-SP18 and FTO polymorphisms in determination of BMI. Adjustment for age, energy and fat intake and physical activity did not materially change the results. There was no association of the NYD-SP18 genotype with waist-hip ratio.

Conclusion

This study in a large Slavonic population sample suggests that the rs6971091 variant within the NYD-SP18 gene is not an important determinant of obesity in middle-aged persons.

Interactions with the MC4R rs17782313 variant, mental stress and energy intake and the risk of obesity in Genome Epidemiology Study

Background

The melanocortin-4 receptor (MC4R) regulates metabolism by modulating eating behavior and MC4R variants (rs17782313 and rs571312) are associated with obesity in Asians and Caucasians. However, the impact of their interactions with nutritional and lifestyle factors on obesity are poorly described. Therefore, we investigated the interaction of MC4R variants and dietary patterns on the risk of obesity in Korean middle-aged adults.

Methods

Data collected included, genetic variations, anthropometric and biochemical measurements, dietary and lifestyle habits, and food intake. Data were obtained from the 8830 adults aged 40–69 years in the Ansung and Ansan cohort of the Korean Genome Epidemiology Study.

Results

The MC4R rs18882313 minor allele had a higher frequency in the obese group (P < 0.01). MC4R genotypes were not associated with differences in daily energy and macronutrient intakes. However, the intakes of processed foods and fat (as percentages of energy) were significantly higher and intake of fruits were significantly lower in subjects with MC4R minor alleles (P < 0.05). Interestingly, there was a positive interaction between MC4R variants and mental stress levels that were associated with the risk of obesity after adjusting for age, gender, residence area, daily energy intake, smoking status and physical activity (interaction P = 0.0384). Only in subjects with high stress were MC4R minor alleles associated with higher BMIs after adjusting for confounders. The association was present without modulating energy and nutrient intake. In the group with energy intakes higher than estimated energy requirement (EER), subjects with MC4R minor alleles had higher BMIs than those with the major alleles (P < 0.001).

Conclusions

The interactions of mental stress and energy intakes with the MC4R minor allele genotype might be associated with increased risk of obesity in Korean adults. This research might identify subjects with a specific MC4R minor alleles as a human subset of people with a low metabolic tolerance for excessive energy intake, especially when under stress.

Lack of association between leptin G-2548A polymorphisms and obesity risk: Evidence based on a meta-analysis

BACKGROUND

The prevalence of obesity is increasing in most industrialized and developing countries. We aimed to investigate the association between leptin (LEP) G-2548A polymorphisms and the risk of obesity.

METHODS

We searched the PubMed, Web of Science, and China National Knowledge Infrastructure databases for studies that evaluated the association between LEP G-2548A polymorphisms and obesity risk prior to March 2014. The odds ratio (OR) and its 95% confidence interval (95% CI) were calculated to estimate the risk of obesity. Meta-analysis of subgroup populations and different control sources was conducted using homozygote (AA vs. GG), allelic (A vs. G), dominant (AA+GA vs. GG), recessive (AA vs. GG+GA), and heterozygote (AG vs. GG) models. The heterogeneity of the studies was assessed using χ(2)-tests based on Q-statistics. The pooled ORs were calculated using a random-effects model if there was no heterogeneity; otherwise, a random-effects model was used. Two authors extracted the data independently. The funnel plots, Begg's and Egger's test were used to assess publication bias. All statistical analyses were performed using STATA 12.0 software.

RESULTS

Nine case-controlled publications that evaluated the association between LEP G-2548A polymorphisms and obesity risk, which included 2594 subjects (1235 obesity cases and 1359 controls), were included in our meta-analysis. No significant association between this polymorphism and obesity risk was observed (P>0.05). Significant heterogeneity was detected among the studies. The results of subgroup analysis according to ethnicity and different control groups suggested that LEP G-2548A polymorphisms might increase the obesity risk in African populations in the homozygote (AA vs. GG: OR=2.38, 95% CI=1.15-4.93, P=0.020) and recessive (AA vs. GG+GA: OR=2.03, 95% CI=1.34-3.06, P=0.001) models.

CONCLUSIONS

Overall, this meta-analysis indicated that LEP G-2548A polymorphisms are not associated with obesity risk, although significant associations were observed in the homozygote model (AA vs. GG) and the recessive model (AA vs. GG+GA) in Africa populations. Further studies are still needed to validate and confirm this association.