The Degree of Liver Steatosis Is Associated with Abnormally High Serum Levels of Markers of Blood–Brain Barrier Dysfunction and Systemic Inflammation in Patients with Morbid Obesity

Background and Objectives: The pathogenesis of liver steatosis is associated with obesity and systemic inflammation, particularly in subjects with body mass index (BMI) above 40 kg/m2 and altered serum levels of tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10). Recent evidence suggests that disruption of the blood–brain barrier (BBB) may be associated with the development of steatosis, although limited data are available in humans. Thus, we assessed serum levels of neuron-specific enolase (NSE), transglutaminase 2 (TGM2), and glial fibrillary acidic protein (GFAP) as indirect markers of BBB dysfunction and examined their associations with steatosis severity, TNF-α and IL-10 in patients with morbid obesity. Materials and Methods: We biopsied the liver during bariatric surgery to assess steatosis by histology and serum markers by ELISA. Results: Most study subjects were women aged 38.7 ± 9.9 years with an average BMI of 42.3 ± 7.9 kg/m2 and a steatosis prevalence of 78.9%. After grading steatosis as none (n = 8), mild (n = 17), moderate (n = 8), or severe (n = 5), we found no differences in sex, age, BMI, comorbidities, or laboratory variables, including liver enzymes. One-way ANOVA showed that serum IL-10 was 4-fold less in severe steatosis than in mild steatosis (p = 0.038), whereas TNF-α levels increased twice in severe steatosis compared to no steatosis (p = 0.029). NSE and GFAP serum levels, but not TGM2, increased proportionally to steatosis stage, showing differences between severe steatosis and no steatosis (p = 0.012 and p = 0.0002, respectively). Pearson correlation coefficients showed that NSE and GFAP were significantly associated with TNF-α (r = 0.600 and r = 0.402, respectively), but not with IL-10. Conclusions: Steatosis severity is significantly associated with markers of BBB disruption and systemic inflammation in patients with morbid obesity, suggesting a link between the BBB and liver steatosis.