The present study showed that 20% of the A-T patients evaluated presented a suggestive diagnosis of significant liver fibrosis. It is important to emphasize that all the patients with suggestive of liver fibrosis had dyslipidemia and four had diabetes. The presence of suggestive diagnosis of fibrosis was associated with the severity of ataxia and with higher values of liver enzymes, ferritin, 120-minutes glycemia by OGTT and the HOMA-AD and lower values for the Matsuda index, compared to A-T patients without liver fibrosis.
Regarding the liver biomarkers evaluated, only liver enzymes (ALT, AST and GGT) were elevated in patients with a suggestive diagnosis of significant liver fibrosis. Values equal to or greater than twice the upper limit of normal for AST and ALT enzymes as predictors of significant liver fibrosis revealed a sensitivity of 80% and a specificity of 95%. In a previous study performed by our group, the values of the ALT and AST have shown alterations mainly during adolescence in A-T patients . In a retrospective study with A-T patients conducted by Donath et al. a steady upward evolution of ALT and GGT was observed, especially from the age of 12 . In another retrospective study, elevation of liver enzymes was observed in younger A-T patients with a mean age of 9.97±5.09 years and a significant association with the presence of dyslipidemia. Therefore, it is recommended periodic monitoring of the AST and ALT liver enzymes from the age of 10, which may contribute to the screening of liver fibrosis in A-T patients
In the present study, patients diagnosed with diabetes had fasting glucose within the normal range and were only identified by OGTT with 120-minutes glycemia above 200 mg/dL. The findings suggest the importance of performing the OGTT for early identification and treatment of diabetes, especially from adolescence. A cohort of A-T patients showed a progressive increase in glycated hemoglobin (HbA1c) and fasting glucose with advancing age. OGTT was considered to have good sensitivity for IR screening and the HbA1c a marker to assess the therapy response .
Regarding the indices used to assess IR, the values of the HOMA-AD and Matsuda differed significantly between patients with and without a suggestive diagnosis of significant liver fibrosis; fact not observed for HOMA-IR. A controlled study has also verified lower values of Matsuda index in A-T patients compared to healthy individuals (5.96 6 ± 0.77 vs.11.03 ± 1.69; p=0.019) and similar values of HOMA-IR between the groups . A recent study conducted with Brazilian children and adolescents for metabolic syndrome screening has found a better performance of HOMA-AD compared to HOMA-IR . Furthermore, Hung et al. observed that HOMA-AD appears to be sensitive in detecting small changes in insulin sensitivity in patients with or without diabetes . Therefore, to assess IR in A-T patients by HOMA-IR seems not to be the most appropriate method.
Regarding inflammatory biomarkers, only ferritin had higher values in patients with suggestive of liver fibrosis compared to those who did not. Experimental study with the aim of investigating the iron regulation, regulatory genes, and markers of oxidative stress in the liver tissue of ATM-deficiency mice, described higher values of serum and hepatic iron, ferritin, and hepcidin when compared to controls. This study suggested that the increase in tissue iron would be associated with hepatic oxidative stress resulting from iron-induced increase in hepcidin, which can suppress its export by ferroportin, which is considered a protective mechanism in response to oxidative stress . Therefore, it is suggested that the increase in ferritin may contribute to the chronic oxidative stress presented by A-T patients and, consequently, to the development of liver disease.
Another noteworthy fact was the significant and direct correlation between the median LSM obtained by TE and the ICARS score. In a retrospective study aiming to determine the evolution of liver disease and its relationship with age and neurological impairment in A-T patients, a significant and direct correlation was found of the Klockgether Ataxia Scale (KAS) score with age, AFP, GGT, and ALT . In a recent study conducted by our group, correlations were found between the severity of ataxia with age and metabolic changes including impairment of liver damage markers and IR in A-T patients .
Regarding the CAP values obtained by TE, no significant difference was observed between patients with and without suggestive diagnosis of significant fibrosis. By ultrasound, three of the five patients with suggestive of liver fibrosis presented steatosis. Therefore, only the presence of hepatic steatosis by both ultrasound and CAP was not related to hepatic fibrosis in A-T patients, which suggests that the presence of steatosis is not a predictive factor for fibrosis in these patients.
One of the mechanisms of ATM protein activation is attributed to the action of reactive oxygen species (ROS), resulting in increased concentrations of antioxidants and the repair of oxidative DNA damage. In the absence/deficiency of ATM, A-T patients have low antioxidant capacity and as a result macromolecules, lipids and DNA are exposed to constant oxidative stress and its damages [58–60]. NAFLD and A-T share a similar pathogenic mechanism of ROS generation and mitochondrial dysfunction that contributes to the development of lesions . Thus, it is postulated that oxidative stress has a relevant contribution in the genesis of liver disease associated with A-T.
The mechanisms involved in the evolution of NAFLD are not fully known. Changes in proteins such as ATM could play a role in these mechanisms since this protein is associated with DNA integrity and mitochondrial homeostasis. An experimental study showed that ATM-deficient mice presented a reduction and delay in DNA replication during liver regeneration. Furthermore, when partial hepatectomy was performed, an increase in apoptosis was observed, which indicates that the ATM protein is involved in the regeneration and survival of hepatocytes .
A recent study that analyzed the expression of messenger RNAs, total proteins, or phosphoproteins related to the ATM pathway of individuals with healthy liver, hepatic steatosis, and NASH, found a causal association between the ATM pathway and NAFLD. During the steatosis phase, there was low ATM activation, which caused mitochondrial dysregulation and greater DNA damage, in addition to reduced growth of the hepatocyte. In NASH, there was greater ATM depletion, with a greater degree of DNA damage and cell growth arrest due to the action of ATM in the cell cycle. In addition, to compensate for hepatocyte growth arrest, pre-oncogenic cells appeared, with a high rate of proliferation . Therefore, the ATM protein appears to play an important role both in the beginning and progression of NAFLD, including its evolution to HCC.
This study has as strengths the fact that it is unprecedented in the sense of describing a suggestive diagnosis of liver fibrosis in A-T patients through non-invasive methods and prospective data collection. As limitations, we can consider the absence of genotyping of the ATM gene variants and the small number of patients with suggestive of liver fibrosis, which limited the analysis.