Association of leptin receptor gene Q223R polymorphism on lipid profiles in comparison study between obese and non-obese subjects

Dual Effect of the GHRL Gene Variant in the Molecular Pathogenesis of Obesity

Obesity is as a global health problem due to its interaction with complex chronic disorders such as cardiovascular disorders, type 2 diabetes mellitus (T2DM) and cancer. Despite the fact that pathogenesis of obesity is not yet clearly understood, it is associated with a combination of psychological, environmental and various genetic factors. Here, employing a case-control design, we aimed to examine the effects of the GHRL c.152C>T (p.Arg51Gln) (rs34911341) and c.214G>T (p.Leu72Met) (rs696217) markers on susceptibility to obesity in a Turkish-Cypriot population, as well as to evaluate whether these markers affect biochemical parameters and show their putative functional consequences. This study involved 211 Turkish-Cypriot subjects (106 obese and 95 non obese). Genotyping for the GHRL gene polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Our results indicate that the GHRL Leu72Met polymorphism was found to be significantly higher in obese patients, with respect to genotypic (p = 0.0012) and allelic (p = 0.0005) frequencies. Strikingly, the rs696217 GT genotype (heterozygous) had significantly lower serum high-density lipoprotein cholesterol (HDL-C) (p = 0.015) than GG (wild type) genotypes. Overall, Leu72Met susceptibility variant may be considered as risk and crucial marker for both obesity and cholesterol metabolism in the community of Turkish-Cypriots. Thus, the dual effect of the GHRL gene Leu72Met variant may be used for clinical diagnosis.

Associations of MC4R, LEP, and LEPR Polymorphisms with Obesity-Related Parameters in Childhood and Adulthood

MC4R, LEP, and LEPR genes are involved in the hypothalamic leptin-melanocortin regulation pathway, which is important for energy homeostasis. Our study aimed to evaluate the associations between the MC4R rs17782313, LEP rs7799039, and LEPR rs1137101 polymorphisms with obesity-related parameters in childhood and adulthood. The data were obtained from the Kaunas Cardiovascular Risk Cohort study, which started in 1977 with 1082 participants aged 12-13 years. In 2012-2014, the follow-up survey was carried out. Genotype analysis of all respondents (n = 509) aged 48-49 years was performed for the gene polymorphisms using Real-Time Polymerase Chain Reaction. Anthropometric measurements were performed in childhood and adulthood. In childhood, only skinfold thicknesses were associated with gene variants being the lowest in children with MC4R TT genotype and LEP AG genotype. In adulthood, odds of obesity and metabolic syndrome was higher in MC4R CT/CC genotype than TT genotype carriers (OR 1.8; 95% CI 1.2-2.8 and OR 1.6; 95% CI 1.1-2.4, respectively). In men, physical activity attenuated the effect of the MC4R rs17782313 on obesity. The LEP GG genotype was associated with higher BMI, waist circumference, and visceral fat level only in men. No associations of the LEPR rs1137101 polymorphisms with anthropometric measurements and leptin level were found. In conclusion, the associations of the MC4R and LEP gene polymorphisms with obesity-related parameters strengthened with age.

The Relationship of Leptin (+19) AG, Leptin (2548) GA, and Leptin Receptor Gln223Arg Gene Polymorphisms with Obesity and Metabolic Syndrome in Obese Children and Adolescents

PURPOSE

Obesity is defined as the abnormal or excessive accumulation of fat over acceptable limits. Leptin is a metabolic hormone present in the circulation in amounts proportional to fat mass. Leptin reduces food intake and increases energy expenditure, thus regulating body weight and homeostasis. Various polymorphisms are present in the leptin gene and its receptor. These polymorphisms may be associated with obesity. This study aimed to show the association of leptin (+19) AG, leptin (2548) GA, and Gln223Arg leptin receptor polymorphisms with obesity and metabolic syndrome in Turkish children aged 6-17 years, and to conduct further investigations regarding the genetic etiology of obesity.

METHODS

A total of 174 patients diagnosed with obesity and 150 healthy children who were treated at Tokat Gaziosmanpaşa Medical School Hospital between September 2014 and March 2015 were included in this study. The ages of the children were between 6 and 17 years, and anthropometric and laboratory results were recorded. Genotyping of leptin (+19) AG, leptin (2548) GA, and leptin receptor Gln223Arg polymorphisms was performed by polymerase chain reaction.

RESULTS

An association between leptin receptor Gln223Arg gene polymorphism and obesity was detected.

CONCLUSION

Further studies are needed to determine the role of genetic etiologies and to indicate the role of leptin signal transmission impairment in the pathogenesis of obesity. We hope that gene therapy can soon provide a solution for obesity.

Comparison of Q223R leptin receptor polymorphism to the leptin gene expression in Greek young volunteers

<abstract><sec> <title>Objective</title> <p>The objective of the present study was to identify the leptin gene expression and the leptin receptor polymorphisms in blood samples and to correlate gene expression values with anthropometric characteristics.</p> </sec><sec> <title>Methods</title> <p>Blood from 140 Greek young volunteers was subjected to polymerase chain reaction–restricted fragment length polymorphism (PCR–RFLP), for the genomic region of Q223R polymorphism at codon 223 in the leptin receptor gene (<italic>LEPR</italic>) coding region. RNA extraction, cDNA synthesis and Quantitative Real-Time PCR was performed for assessing the expression of the leptin gene (<italic>LEP</italic>).</p> </sec><sec> <title>Results</title> <p>Leptin gene was identified in all tested specimens and the gene was expressed in 88.9% of all volunteers with BMI &lt; 25. In addition, it was observed that gene expression is affected by various external factors, such as Body Mass Index (BMI), eating behavior, gender and age. It was also shown that as for the Q223R polymorphism (A to G) allele G occurs with a frequency of 100% in men with BMI &gt; 30 and 75.9% in men and 88.9% in women with BMI 25–30. Volunteers with BMI 25–30 who were homozygous on the G allele were 50% and 77.8% in men and women respectively. All subjects with a BMI &gt; 30 were homozygous on the G allele at 100%.</p> </sec><sec> <title>Conclusions</title> <p>In this small-scale study, results have shown that the leptin gene expression correlates with BMI and that the allele G in Q223R polymorphism is linked to overweight individuals.</p> </sec></abstract>

Quantile-specific heritability of sibling leptin concentrations and its implications for gene-environment interactions

"Quantile-dependent expressivity" occurs when the effect size of a genetic variant depends upon whether the phenotype (e.g., leptin) is high or low relative to its distribution. Leptin concentrations are strongly related to adiposity, whose heritability is quantile dependent. Whether inheritance of leptin concentrations is quantile dependent, and whether this explains the greater heritability in women than men in accordance with their greater adiposity, and explains other gene-environment interactions, remains to be determined. Therefore, leptin and leptin receptor concentrations from 3068 siblings in 1133 sibships from the Framingham Heart Study Third Generation Cohort were analyzed. Free leptin index (FLI) was calculated as the ratio of leptin to soluble leptin receptor concentrations. Full-sib (β_FS) regression slopes were robustly estimated by quantile regression with nonparametric significance assigned from 1000 bootstrap samples. The analyses showed β_FS increased significantly with increasing percentiles of the offspring's age- and sex-adjusted leptin distribution (P_linear = 0.0001), which was accelerated at the higher concentrations (P_quadratic = 0.0003). β_FS at the 90th percentile (0.418 ± 0.066) was 4.7-fold greater than at the 10th percentile (0.089 ± 0.032, P_difference = 3.6 × 10^-6). Consistent with quantile-dependent expressivity, the β_FS was greater in female sibs, which was attributable to their higher leptin concentrations. Reported gene-environment interactions involving adiposity and LEP, LEPR, MnSOD, PPARγ, PPARγ2, and IRS-1 polymorphisms were consistent with quantile-dependent expressivity of leptin concentrations. β_FS for leptin receptor concentrations and free leptin index also increased significantly with increasing percentiles of their distributions (P_linear = 0.04 and P_linear = 8.5 × 10^-6, respectively). In conclusion, inherited genetic and shared environmental effects on leptin concentrations were quantile dependent, which likely explains male-female differences in heritability and some gene-environment interactions.

Association of the leptin receptor Q223R (rs1137101) polymorphism with obesity measures in Sri Lankans

Objective

The role of genetic factors in the development of obesity is largely unreported in Sri Lankans. The Q223R (rs1137101) single nucleotide polymorphism (SNP) of the leptin receptor (LEPR) gene has been associated with obesity measures in various ethnicities. We investigated the association of the Q223R polymorphism with obesity related anthropometric measures and biochemical parameters fasting blood glucose and lipid profile in a sample of 530 Sri Lankan adult subjects (age 18–70 years) representing both urban and rural areas of residence.

Results

The LEPR Q223R variant G allele frequency was 0.54. The polymorphism was associated with body mass index (p = 0.04) and waist circumference (p = 0.02) measures in overweight and obese (BMI ≥ 25 kgm⁻²) subjects with the variant allele conferring a greater risk of adiposity. Residency in urban areas eliminated the protective effect of the non-risk genotype (AA) in the development of obesity.

Leptin gene polymorphism (rs7799039; G2548A) is associated with changes in serum lipid concentrations during pregnancy: a prospective cohort study

PURPOSE

Little is known about the effects of leptin and leptin receptor polymorphisms on lipid changes during pregnancy. The aims of this study were to evaluate the associations between the single nucleotide polymorphisms (SNPs) of leptin and leptin receptor genes and the lipid concentrations during pregnancy; and to test whether dietary intake is a mediator in these associations.

METHODS

A prospective cohort of 154 pregnant women was followed up in Rio de Janeiro, Brazil during the following gestational periods: 5-13th, 20-26th and 30-36th weeks. HDL-C, total cholesterol (TC) and triglyceride (TG) were measured by the enzymatic colorimetric method, and LDL-C was calculated. DNA was extracted by the phenol-chloroform method, and leptin (G2548A, rs7799039) and leptin receptor SNPs (Q223R; rs1137101 and K109R; rs1137100) were genotyped using real-time PCR. Statistical analyses included linear mixed-effect models.

RESULTS

Women with the AA genotype of G2548A polymorphism reported a higher fat and total energy intake and had a higher increase in TG concentration during pregnancy than women with AG or GG genotype. The association between G2548A SNP and TG concentrations was not attenuated by adjusting for total lipid (g) and energy (kcal) intake. We did not observe significant associations between the Q223R and K109R SNPs and the lipid concentrations.

CONCLUSIONS

Women homozygous for the A allele of the leptin SNP (G2548A) had a higher increase in TG concentrations per gestational week compared with women with the AG or GG genotype. This is an exploratory and hypothesis-generating study, and the results need confirmation in studies with larger sample sizes.'

Polymorphisms in Genes Involved in the Leptin-Melanocortin Pathway are Associated with Obesity-Related Cardiometabolic Alterations in a Southern Chilean Population

BACKGROUND

Polymorphisms in genes encoding proteins of the leptin-melanocortin pathway have been associated with obesity. The involvement of these polymorphisms with changes in body mass index (BMI) and anthropometric measures could also imply a contribution to the risk of metabolic syndrome (MetS) and metabolic alterations. We evaluated the relationship of leptin-melanocortin system polymorphisms with obesity, MetS, and other metabolic alterations in Southern Chilean individuals.

METHODS

Two-hundred individuals were grouped as normoweight (BMI 18.0-24.9 kg/m²), overweight (BMI 25.0-29.9 kg/m²), and obese (BMI ≥ 30 kg/m²) or according to MetS status. Anthropometric measures (BMI, abdominal circumference, waist-to-hip ratio [WHR]) and biochemical parameters (glycemia and lipid profile) were evaluated. Polymorphisms LEP rs7799039, LEPR rs1137101, MC3R rs3746619 and rs3827103, and MC4R rs17782313 were evaluated by real-time PCR using allelic discrimination assays.

RESULTS

LEPR rs1137101 GG genotype was related to reduced risk of obesity (odds ratio [OR] 0.26, 95% confidence interval [CI] 0.08-0.79; p = 0.018) and MetS (OR 0.36, 95% CI 0.15-0.88; p = 0.024), but it was not significant after Bonferroni correction for multiple tests as compared to the AA genotype (p > 0.01). Moreover, LEPR rs1137101 allele G (AG + GG) was related to lower BMI and WHR (p < 0.01). Further multiple linear regression analysis demonstrated that this genotype was also responsible for reduced BMI in 2.44 kg/m² and WHR in 0.033 units. MC4R rs17782313 allele C (TC + CC) was slightly associated with diminished risk of MetS (OR 0.48, 95% CI 0.23-0.98; p = 0.040) and reduced BMI values in 1.95 kg/m² (p < 0.05). Regarding lipid profile, LEPR rs1137101 allele G carriers had lower triglycerides and very-low-density lipoprotein (VLDL) cholesterol, whereas individuals carrying the MC4R rs17782313 allele C had higher high-density lipoprotein (HDL) cholesterol (p < 0.01). LEP rs7799039 allele A (GA + AA) was slightly associated with reduced total and low-density lipoprotein (LDL) cholesterol (p < 0.05).

CONCLUSIONS

These results suggest that polymorphisms at LEP, LEPR, and MC4R may be useful biomarkers of obesity-related cardiometabolic alterations in our population.

Leptin and Leptin Receptor Genes Are Associated With Obesity-Related Traits Changes in Response to Aerobic Training Program

Leońska-Duniec, A, Jastrzębski, Z, Jażdżewska, A, Krzysztof, F, and Cięszczyk, P. Leptin and leptin receptor genes are associated with obesity-related traits changes in response to aerobic training program. J Strength Cond Res 32(4): 1036-1044, 2018-Leptin (LEP) and leptin receptor (LEPR) genes have been studied for their potential association with development of human obesity and its related complications. Therefore, we have decided to check whether selected body mass, body composition, and metabolic variables observed in physically active participants will be modulated by the polymorphisms. The genotype distribution was examined in a group of 201 women measured for chosen traits before and after the completion of a 12-week aerobic training program. Our results revealed a significant interaction between training and LEP genotype for glucose level. A training-related decrease in plasma glucose concentration in the LEP AG heterozygotes differed significantly from the change in the homozygotes. The polymorphism was also associated with fat-free mass (FFM), total body water (TBW), total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-C) levels. Another finding was a significant interaction between training and LEPR for LDL-C level. As opposed to AG and GG, AA homozygotes demonstrated a training-related decrease in LDL-C level. Our findings also showed that the LEPR G allele is connected with obesity-related traits. The participants with the GG genotype had higher body mass, body mass index (BMI), FFM, and TBW during the entire study period. This study provides evidence that polymorphisms in the LEP and LEPR genes are associated with the magnitude of the effects of regular physical activity on glucose and LDL-C levels, respectively. In addition, we found the association of the G allele of the LEPR polymorphism with body mass and BMI.

Effect modification by region in the associations of LEP G2548A and LEPR Q223R polymorphisms with statin-induced CK elevation

We investigated the associations of LEP G2548A and LEPR Q223R polymorphisms with statin-induced creatine kinase (CK) elevation among Chinese patients with hyperlipidemia. A total of587 enrolled individuals were treated with 20 mg/d oral simvastatin for 8 consecutive weeks. Genotyping of LEP G2548A and LEPR Q223R were conducted using PCR-RFLP. Multiple regression analyses showed that, in the Dongzhi region only, patients carrying the LEP AA genotype had a significantly greater increase in CK levels compared to those carrying the AG+GG genotypes after four weeks (P = 0.004) and eight weeks (P < 0.001) consecutive simvastatin treatment. Patients were further divided into three groups based on the tertiles of the CK distribution. Compared to subjects in the lowest tertile of CK elevation, the adjusted relative odds of having the AG+GG genotypes among subjects in the highest tertile was 0.5 (95% CI, 0.3 to 0.7) and 0.4 (95% CI, 0.2 to 0.6) after the fourth and eighth weeks, respectively. The interaction terms between the Beijing or Dongzhi region and the LEP GA+AA genotypes were marginally significant for CK elevation at the fourth week (P = 0.057) and significant for CK elevation at the eighth week (P = 0.002). The adverse effect of the LEP G2548A polymorphism on increasing CK levels may be dependent on the environmental milieu. It suggests that lifestyle interventions might offset the side effects of simvastatin therapy among those with genetic susceptibility. Further research is needed to identify specific individual-level factors for clinical practice that modify the effect of genotype.

Leptin Receptor Gene Polymorphism and the Risk of Cardiovascular Disease: A Systemic Review and Meta-Analysis

OBJECTIVE

Few studies have assessed the association between leptin receptor (LEPR) gene polymorphism and the risk of cardiovascular disease (CVD). Of the few epidemiological studies on this topic, the results are still controversial.

METHODS

PubMed and Embase were screened for studies from their inception to 9 October 2016. The pooled odds ratio (OR) with the corresponding confidence intervals (CI) were used to measure the effect size for studies that reported the association under allelic, homozygous, and dominant models. Pre-specified characteristics were conducted in the subgroup analysis. Heterogeneity between subgroups was evaluated by meta-regression analysis.

RESULTS

Seven eligible studies involving 44,133 participants were included in our meta-analysis. Borderline significant association was observed between the LEPR gene polymorphism (rs1137101, rs1137100, rs6700896, and rs8179183) and the increased risk of CVD with considerable heterogeneity under the allelic model, and the overall pooled OR (95% CI) was 1.10 (0.99, 1.22). The LEPR gene variant rs6700896, 109G allele, and 109GG genotype were significantly associated with the increased risk of CVD. Furthermore, stratified group analysis revealed that the association was more pronounced for stroke. Race-differences might also cause the considerable heterogeneity and non-significant association.

CONCLUSIONS

This is the first systematic review and meta-analysis to investigate the association between LEPR gene variants and CVD risk. Some LEPR gene variants were significantly associated with the increased risk of CVD. However, the present study is limited in its small number of included studies, considerable heterogeneity, and observational study design. Further research is still warranted to confirm the magnitude of the association.

Effects of LEP G2548A and LEPR Q223R Polymorphisms on Serum Lipids and Response to Simvastatin Treatment in Chinese Patients With Primary Hyperlipidemia

Objectives:

To investigate whether LEP G2548A and LEPR Q223R polymorphisms influence serum lipid levels and whether the 2 polymorphisms affect the efficacy of simvastatin treatment in Chinese patients with primary hyperlipidemia.

Methods:

We used an extreme sampling approach by selecting 212 individuals from the top and bottom 15% of adjusted lipid-lowering response residuals to simvastatin (n = 106 in each group of good or bad response) from a total of 734 samples with primary hyperlipidemia. They were treated with simvastatin orally 20 mg/d. Fasting serum lipids were measured at baseline and after 4 and 8 weeks of treatment. Genotyping was carried out using polymerase chain reaction-restriction fragment length polymorphism.

Results:

More patients in the good response group (27%) had LEPR Q223R than in the bad response group (16%, P = .046). Secondary stratified analyses showed that patients carrying the RR genotype of the LEPR Q223R gene had significantly higher high-density lipoprotein cholesterol levels than those with the QR genotype at baseline ( P = .034) among good responders. After 29 consecutive days of treatment with simvastatin, patients carrying the RR genotype had a significantly larger decrease in triglycerides (change: −0.74 ± 0.92, P = .036) and total cholesterol levels (change: −1.77 ± 0.68, P = .023) compared with those carrying QR genotype among bad responders. After Bonferroni correction, the results were not statistically significant.

Conclusion:

LEPR Q223R polymorphism, but not LEP G2548A, could modulate the efficacy of simvastatin in Chinese patients with primary hyperlipidemia.

Association of Leptin Receptor Gene Polymorphisms with Genetic Susceptibility to Ischemic Stroke

BACKGROUND

Ischemic stroke is a multifactorial disease that is influenced by both genetic and environmental factors. Identification of the genetic factors that are underlining this disease is important. Leptin receptor (LEPR) mediates the leptin-regulated human energy homeostasis, and mutations of LEPR can increase cardiovascular risks and may predispose an individual to ischemic stroke.

METHODS

We analyzed distribution of 3 single nucleotide polymorphisms (SNPs) of LEPR gene (Lys109Arg, Gln223Arg, and Lys656Asn) in 101 patients with ischemic stroke and 105 controls by polymerase chain reaction-restriction fragment length polymorphism strategy.

RESULTS

Our results showed that there were significant differences in the genotype and allele distribution of Lys109Arg and Gln223Arg polymorphisms of the LEPR gene between case and control. The 109GG and 223GG genotype were associated with a significantly increased risk of ischemic stroke (odds ratio [OR], 3.23; P = .001 and OR, 2.87; P = .008, respectively). The 109G and 223G alleles carriers were correlated with an increased incidence of ischemic stroke (OR, 2.72; P = .001; OR, 2.94; P = .004). By haplotype analyses, we found that 109A/223G/656G haplotype was associated with an increased risk of ischemic stroke although this was not observed in the control group (OR, 3.86; P = .029).

CONCLUSIONS

LEPR 109GG and 223GG genotypes and the 109G and 223G alleles are associated with the risk of ischemic stroke. Our data suggest that LEPR Lys109Arg and Gln223Arg polymorphisms could be used as genetic predictive factor for ischemic stroke.

Effects of body weight reduction on plasma leptin and adiponectin/leptin ratio in obese patients with type 1 diabetes mellitus

The aim of this study was to explore the changes in the adipokines leptin and adiponectin in obese patients with type 1 diabetes mellitus (T1DM) who underwent seven days of fasting and 21 days of low-calorie diet (LCD). The plasma leptin and adiponectin concentrations were measured in 14 obese patients with T1DM at baseline, immediately after 7 days of fasting, and after 21 days of LCD. 13 non-obese patients with T1DM were studied only after an overnight fasting. Bioimpedance technique was used for determination of body composition. Obese T1DM patients lost 6.0 kg (6.0; 6.8) (median, 25 %; 75 %) and decreased their fat tissue after fasting and LCD. Plasma leptin in obese T1DM was significantly higher than in non-obese T1DM patients: 9.10 (5.06; 25.89) vs. 1.71 (1.12; 7.08) microg . l(-1) and transiently decreased immediately after fasting: 3.45 microg . l(-1) (1.47; 7.00), (P<0.05). Adiponectin/leptin ratio in obese T1DM was significantly lower than in non-obese T1DM patients: 0.67 (0.57; 1.49) vs. 3.50 (2.46; 6.30) . 10(3) and transiently increased immediately after fasting: 2.22 (1.26; 3.24) . 10(3), (P<0.05). We conclude that obese patients with T1DM are characterized by hyperleptinemia that is reduced by prolonged fasting, but only slightly affected by low calorie diet.

Emerging role of leptin in rheumatoid arthritis

Numerous studies have suggested the importance of leptin against autoimmune diseases such as systemic lupus erythematosus (SLE), multiple sclerosis (MS) and psoriasis. To summarize our current understanding of the role of leptin in inflammatory responses and rheumatoid arthritis (RA), a systematic review was conducted to assess the discrepancy of leptin in RA and its effect on immunity according to different studies. Recently, emerging data have indicated that leptin is involved in the pathological function of RA, which is common in autoimmune disorders. This review discusses the possible consequences of leptin levels in RA. Blocking the key signal pathways of leptin and inhibiting the leptin activity-like leptin antagonist may be a promising way for potential therapeutic treatment of RA at risk of detrimental effects. However, leptin was increased in patients with RA and may also regulate joint damage. Thus, more understanding of the mechanism of leptin in RA would be advantageous in the future.

Kinetics of leptin binding to the Q223R leptin receptor

Studies in human populations and mouse models of disease have linked the common leptin receptor Q223R mutation to obesity, multiple forms of cancer, adverse drug reactions, and susceptibility to enteric and respiratory infections. Contradictory results cast doubt on the phenotypic consequences of this variant. We set out to determine whether the Q223R substitution affects leptin binding kinetics using surface plasmon resonance (SPR), a technique that allows sensitive real-time monitoring of protein-protein interactions. We measured the binding and dissociation rate constants for leptin to the extracellular domain of WT and Q223R murine leptin receptors expressed as Fc-fusion proteins and found that the mutant receptor does not significantly differ in kinetics of leptin binding from the WT leptin receptor. (WT: k_a 1.76×10⁶±0.193×10⁶ M⁻¹ s⁻¹, k_d 1.21×10⁻⁴±0.707×10⁻⁴ s⁻¹, K_D 6.47×10⁻¹¹±3.30×10⁻¹¹ M; Q223R: k_a 1.75×10⁶±0.0245×10⁶ M⁻¹ s⁻¹, k_d 1.47×10⁻⁴±0.0505×10⁻⁴ s⁻¹, K_D 8.43×10⁻¹¹±0.407×10⁻¹¹ M). Our results support earlier findings that differences in affinity and kinetics of leptin binding are unlikely to explain mechanistically the phenotypes that have been linked to this common genetic variant. Future studies will seek to elucidate the mechanism by which this mutation influences susceptibility to metabolic, infectious, and malignant pathologies.