TNF-α gene expression in relation to TNF-α level and bone mineral density in Polish patients with celiac disease

Kinga Skoracka^1,2*Szymon Hryhorowicz³Michal Michalak⁴Marta Kaczmarek-Ryś^3,5,6Iga Dziechciowska³Agnieszka Dobrowolska¹Iwona Krela-Kaźmierczak^1,7

• ¹Department of Gastroenterology, Dietetics and Internal Diseases, Poznan University of Medical Sciences, Poznan, Poland
• ²Doctoral School, Poznan University of Medical Sciences, Poznań, Poland
• ³Instytut Genetyki Czlowieka Polskiej Akademii Nauk, Poznań, Poland
• ⁴Department of Computer Science and Statistics, Poznan University of Medical Sciences, Poznań, Poland
• ⁵University Clinical Hospital, Poznań, Poland, Poznań, Poland
• ⁶University Center of Cancer Diagnostics, Poznan University of Medical Sciences, Poznań, Poland
• ⁷Laboratory of Nutrigenetics, Department of Gastroenterology, Dietetics and Internal Diseases, Poznan University of Medical Sciences, Poznań, Poland

Abstract Background: Osteopenia and osteoporosis are common complications of celiac disease (CD). Objectives: Given the inflammatory background of bone disorders, this study aimed to assess the impact of TNF-α gene expression and its serum level on bone mineral density (BMD) in individuals with CD. 2 Patients and Methods: The study at the start included 70 adults: 51 women and 9 men with CD, and 10 healthy controls: 8 women, 2 men. In the first phase of the study, densitometric measurements of the lumbar spine (L1–L4) and femoral neck (FN) were performed using dual-energy x-ray absorptiometry (DXA) to identify patients with celiac disease and decreased BMD. These patients constituted Group A (CD with osteopenia/osteoporosis, n = 12). Group B (CD with normal BMD, n = 6), and Group C (healthy controls with normal BMD, n = 6) were matched for sex, age and body mass to patients in group A. In the second phase of the study, TNF-α gene expression was quantified using the real-time quantitative PCR (qRT-PCR) method, and serum TNF-α levels were measured with an enzyme-linked immunosorbent assay (ELISA). In third phase, statistical analyses were conducted to investigate the correlations between TNF-α expression and serum TNF-α levels with bone and anthropometric parameters. Results: No statistically significant differences in TNF-α gene expression or TNF-α serum levels were found between the groups. In Group A, TNF-α expression did not correlate with bone or anthropometric measures. However, in Group B, lower TNF-α expression correlated with higher BMI, FN BMD, L1–L4 BMD, and Z-scores. In contrast, healthy controls showed a positive correlation between TNF-α expression and BMD, T-score, and Z-score of the FN. There was also no statistically significant correlation between TNF-α cytokine concentration, and the parameters studied in groups A and B. Conclusions: In this study, TNF-α, both in terms of gene expression and serum level, does not appear to correlate with BMD status in individuals with CD and osteopenia/osteoporosis. Larger longitudinal studies integrating additional cytokines and signaling pathways are needed to clarify the role of TNF-α in bone loss in celiac disease.