Insulin-like Growth Factor-1, Psoriasis, and inflammation: a mènage a trois

Psoriatic patients have an increased prevalence of metabolic syndrome (MS) and cardiovascular disease (CVD), likely mediated by systemic inflammation, and exhibited low circulating levels of insulin-like growth factor (IGF)-IIGF-I, a marker of MS and CVD in the general population. The aim of the study was to determine the association of IGF-I and inflammation, and to assess the cardio-metabolic risk calculating the visceral adiposity index (VAI), in a group of psoriatic patients without MS. IGF-I, fibrinogen, C-reactive protein (CRP), and interleukin (IL)-6 levels were determined in 20 patients with moderate to severe psoriasis (age range 23-77 yrs) without MS, according to criteria of the National Cholesterol Education Program’s Adult Panel III (ATP III), and 20 age and BMI-matched controls. The standard deviation score (SDS) of IGF-I levels according to age (zSDS), the homeostasis model assessment of insulin resistance (HOMA-IR), the whole-body insulin sensitivity index (ISI), and VAI were also calculated. Psoriasis Area and Severity Index (PASI) mean value was 17.8±11. HDL cholesterol and IGF-I zSDS values were lower (p<0.001) and waist circumference (p<0.001), VAI, fibrinogen, and IL-6 (p<0.005) were higher compared with controls, while HOMA-IR and ISI were not statistically different. Lower IGF-I zSDS values were associated to higher values of BMI (p=0.04), waist circumference, VAI (p<0.001), PASI (p=0.011), or IL-6 (p<0.001). At the multivariate analysis PASI was the major determinant of IGF-I zSDS (p=0.016), accounting for 37% of its variability. In a subset of psoriatic patients without MS, the chronic inflammation might be an important modulator of low IGF-I status, as a further possible mechanistic link between psoriasis and associated metabolic co-morbidities. The negative correlation between age-related IGF-I values and VAI suggested the involvement of the adipocytes dysfunction in low IGF-I status more than MS per se. Further studies are needed to address whether these results are valid beyond this subset of psoriatic patients as well.