Abdominal fat, insulin sensitivity, inflammatory atheromatosis risk factors and polymorphisms of 174-G/C IL-6 promoter and Pro12Ala PPARγ in non-obese subjects
Grazyna Bednarek-Tupikowska, Eliza Kubicka, Urszula Tworowska-Bardzinska, Lukasz Laczmanski, Marek Bolanowski & Andrzej Milewicz
Some individuals with normal weight but probably visceral fat excess, called Metabolically Obese Normal-Weight (MONW), have disturbances typical for metabolic syndrome. We analyzed relationships between body fat distribution (estimated by DXA) and insulin resistance, serum inflammatory markers levels (CRP, IL-6, IL-18) and polymorphisms of IL-6 promoter and PPARγ in healthy, non-obese Polish subjects: 232 women (age 31.4±5.5; BMI 21.5±2.5) and 199 men (age 30.3±6.0; BMI 24.6±2.8).
Results: In non-obese subjects abdominal fat volume (AFV) was significantly correlated with serum level of fasting glucose, insulin and HOMA-IR, FIRI and QUICKI indices. AFV was also significantly associated with CRP in women, but not with IL-6 or IL-18. Similar correlation between AFV and CRP was noticed in men. In this group IL-18 was correlated with abdominal to gynoidal fat ratio as well. On the contrary, there were no significant correlations between AFV and serum levels of IL-6. There were no correlations between PPARγ polymorphism and AFV as well as body fat distribution. Fasting insulin levels, HOMA and FIRI were higher, while QUICKI was lower in men with Pro12Ala polymorphism. There were no differences between inflammation indices (CRP, IL-6, IL-18) in homozygotes GG, CC and heterozygotes GC of IL-6 gene polymorphism in non-obese subjects, but CC men had significantly lower fasting insulin compared with GC. Men CC had significantly higher BMI, total fat mass and gynoidal fat volume (GFV) then GG subjects and also higher GFV then GC. Women with genotype GC had significantly lower waist circumference then GG.
Conclusions: Excessive abdominal fat volume in non-obese subjects predisposes to higher levels of some atherogenic inflammatory markers and insulin resistance. The significance of genetic factors in the body fat distribution and the metabolic disorders occurrence in MONW subjects appears to be important but requires further study.