Interleukin-1 Alpha Polymorphisms Are Associated With Body Mass Index in Male But Not in Female Adolescents

The interactions between interleukin-1 family genes: IL1A, IL1B, IL1RN, and obesity parameters

Background

Obesity has been recognized as a worldwide growing problem, producing many pathologies including the promotion of “proinflammatory state.” The etiology of human obesity is still only partially understood; however, the genetic background has been proved. Its nature is complex, and currently, it appears that the combined effects of the interactions among multiple genes should receive more attention. Due to the fact that obesity promotes proinflammatory conditions, in this study, we investigated the genetic polymorphism of IL-1 family genes in healthy people with normal and elevated body mass index (BMI) and fat %.

Results

The single-nucleotide polymorphisms (SNPs) within the IL1A -889C > T (rs1800587), IL1B + 3954 T > C (rs1143634), and IL1RN -87G > A (rs2234677) genes alone were associated neither with BMI nor fat % values in tested group. The associations between SNP–SNP interaction and BMI for the IL1B × IL1RN interactions were significant for dominant model (p = 0.02) and codominant model (p = 0.03). The same SNP-SNP interaction (IL1B × IL1RN) was associated also with fat % for codominant (p = 0.01) and recessive (p = 0.002) models.

Conclusions

This study further confirmed that IL-1 family genes are involved in genetic background of obesity. It has been shown that interaction IL1B × IL1RN was associated with both BMI and fat % with rare T allele protecting form higher values. Thus, even if certain polymorphisms in single genes of IL-1 family cannot be defined as related to obesity in examined population, the genetic interrelationships should be analyzed.

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.