Correlation between neurological features, nutritional status and metabolic changes in patients with Ataxia-telangiectasia

Ataxia-telangiectasia (AT) is an autosomal recessive neurodegenerative disorder caused by variants of ATM (ataxia telangiectasia mutated) gene. There is no specic treatment, but clinical management has advanced resulting in longer patient survival. However, these patients develop metabolic changes over time. We aimed to assess the correlation between neurological features, nutritional status and metabolic changes in AT patients. Signicant correlations were found between the scores on the International Cooperative Ataxia Rating Scale (ICARS) and age (r = 0.748; p < 0.001), gamma glutamyl transferase (GGT) (r = 0.743; p < 0.001), insulin levels (r = 0.520; p = 0.016) and the Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) index (r = 0.585; p = 0.005) as well as the scores on the Assessment and Rating of Ataxia (SARA) and age (r = 0.704; p < 0.001), GGT (r = 0.701; p < 0.001), insulin levels (r = 0.706; p < 0.001) and HOMA-IR index (r = 0.764; p < 0.001).

Most typical symptoms of AT include early onset cerebellar ataxia and dilated capillaries at the angles of the eyes and on the skin (telangiectasia). In general, ataxia is the rst major clinical sign, and usually starts around 5-year-old [8,9]. High serum levels of alpha-fetoprotein (AFP) is a relevant biomarker to con rm the diagnosis of AT [10].
To date, there is no speci c treatment for AT. Advances in clinical management with multidisciplinary approaches have resulted in increased patient survival. However, these patients may develop metabolic changes and comorbidities that affect the disease course and their quality of life.
Studies conducted by our group have shown that age advanced is associated with insulin resistance and hepatic impairment in patients with AT [11,12]. With disease progression, AT patients usually present nutritional status impairment [13][14][15][16][17][18]. Thus, this study aimed to assess the correlation between neurological features, nutritional status and metabolic changes in patients with AT.

Methods
Patients This is a cross-sectional study with prospective data from patients with AT (n = 25) who met the diagnostic clinical criteria of the European Society for Immunode ciencies (ESID) [19]. The sample was comprised both male and female patients aged from 5 to 31 years who were followed up at the Division of Allergy, Clinical Immunology, Rheumatology and Neurology outpatient clinic of Universidade Federal de São Paulo (UNIFESP) Department of Pediatrics in São Paulo, Brazil.
The study was approved by UNIFESP Research Ethics Committee (nr. 0081/2018). All patients or their caregivers signed an informed consent to be enrolled in this study.

Anthropometric assessment
Anthropometric measurements included weight, height and skinfolds (tricipital, bicipital, subscapular and suprailiac) [20,21]. Those who were unable to stand were weighed on a digital wheelchair scale (Micheletti® electronic weighing platform for up to 500 kg). Recumbent height measurements were taken in supine position on a at, rm surface by using a non-extensible tape (in millimeters).
For nutritional status classi cation, body mass index (BMI)-for-age z-scores and height-for-age z-scores for children and adolescents were calculated. Adults were classi ed according to BMI [20,22]. The sum of skinfold measures was used to estimate body composition [23][24][25][26].
The stage of pubertal development was self-assessed using the Tanner rating scale (Marshall & Tanner) [27].

Neurological assessment
Two rating scales, The International Cooperative Ataxia Rating Scale (ICARS) and the Scale for the Assessment and Rating of Ataxia (SARA), were applied by two skilled physical therapists to evaluate ataxia severity in all patients. General neurological examination and a routine brain magnetic resonance imaging (MRI) were also evaluated.

Statistical analysis
The data were entered into an Excel spreadsheet (O ce Microsoft®) and analyzed using SPSS Statistics 19.0 (IBM®). Categorical variables were presented as absolute and percentage values. Continuous variables were analyzed for normality using the Shapiro-Wilk test. For comparisons between the two age groups evaluated, independent t-Student test was used to compare parametric variables (means and standard deviations) and the two-tailed Mann-Whitney U test was used to compare non-parametric variables (medians, minimum and maximum). Spearman's correlation coe cient was used to assess correlations. The level of statistical signi cance was set at 5% (p < 0.05).
As for neurological manifestations, mean age of symptom onset was 10 (± 4.3) months. Cerebellar ataxia was the most common sign seen in 15/25 (60%) patients. Mean age of loss of independent gait was 8 (± 2.0) years; 13/25 (52%) patients had the ability of walking with aid and 5/25 (20%) showed inability to walk.
ICARS scores indicated moderate ataxia in 13/25 (52%) patients and severe in 9/25 (36%). SARA scores indicated moderate ataxia in 9/25 (36%) patients and severe in 9/25 (36%). Table 1 shows the characteristics of patients with A-T. Table 1 Characteristics of patients with AT Our sample was classi ed into two age groups (≤ 12 years; >12 years) to compare biochemical markers. Signi cant differences were found between the age groups for ALT (p = 0.017), GGT (p < 0.001) and AFP (p = 0.006). Table 2 shows the comparison of biochemical markers between the two age groups. Figure 1 shows the comparison of GGT, ALT and AFP results between these groups. Table 2 Comparison of biochemical markers in patients with AT by age groups The median score on ICARS was 57 (7-87). Signi cant direct correlations were found between ICARS scores and age (r = 0.748; p < 0.001), GGT (r = 0.743; p < 0.001), insulin (r = 0.520; p = 0.016), and HOMA-IR index (r = 0.585; p = 0.005). There was a trend towards indirect signi cance of the correlation between these scores and height-for-age z-scores (r = − 0.427; p = 0.068).
A strong correlation was found between the two rating scales (r = 0.900; p < 0.001). Figure 2 shows the correlation between ICARS and SARA scores and age.

Discussion
Our study found a marked correlation between severity of ataxia and nutritional and metabolic changes in patients with AT. Statistical analysis showed signi cant difference when ICARS and SARA rating scales were compared with, GGT, fasting insulin and HOMA-IR index. It is noteworthy that both ICARS and SARA were able to detect those patients with severe ataxia, which evidences their rating agreement especially for the most severe form of the disease. This study shows correlations between worsening of ataxia manifestations with age and metabolic changes including impairment of liver function and insulin resistance in patients with AT.
Patients with AT may develop diabetes as a complication in late adolescence and they usually present with high blood glucose levels without glycosuria or ketosis and high levels of insulin in response to glucose administration [31]. Two studies with patients with AT undergoing the 2-hour oral glucose tolerance test reported increased postprandial blood glucose levels and insulin resistance [11,32].

Some previous data have shown that insulin acts on all types of cells in the central nervous system (CNS)
including neurons, astrocytes, oligodendrocytes, ependymal cells, brain endothelial cells and microglia. In fact, all cell types in the CNS express insulin receptors, which suggests their ability to respond to insulin.
On a functional basis, insulin resistance can affect brain function and result in cognitive and neurodegenerative changes which could explain our ndings [33].
Chronic liver dysfunction can lead to the accumulation of toxic metabolites in the brain and cause neuroin ammation by increasing pro-in ammatory cytokines and oxidative and nitrosative stress (nitric oxide) [34]. A recent retrospective cohort study of 67 patients with AT aged 1 to 38 years found a signi cant correlation between Klockgether ataxia score (KAS) and GGT and age, which corroborates our ndings [35]. Our results suggest that liver dysfunction in patients with AT may indicate greater disease severity and more severe neurological symptoms. Therefore, it is recommended to evaluate liver function (especially GGT) as part of routine evaluations in patients with AT as GGT seems to have a more signi cant relationship with neurological decline.
A comparison of biochemical markers between the age groups (≤ 12 years and > 12 years) in our study revealed that liver enzyme, ALT, GGT and AFP, were signi cantly higher among older patients. Elevated AFP levels are characteristic of AT and they apparently increase with age [10].
Regarding liver enzymes, a study carried out by our group found that levels of ALT and AST were more signi cantly altered from adolescence in patients with AT. Those patients who developed liver dysfunction tended to be older and had higher sum of insulin levels than those with hepatic steatosis only or no liver dysfunction [11]. Donath  Most patients with AT, particularly those with the classic form of the disease, have malnutrition and stunted growth even with adequate energy intake. It is thus believed to be a multifactorial condition associated with the severity of neurological impairment [8]. Although we did not nd a signi cant correlation between ataxia scores and BMI, all eight patients with malnutrition, regardless of their age, showed moderate or severe ataxia. Moreover, stunted growth may also be associated with neurological decline in these patients as there was a signi cant indirect correlation of SARA scores and a trend towards signi cance of ICARS scores with height-for-age z-scores.
This study has some limitations. First, ATM gene variants were not genotyped in the patients with AT evaluated. Second, hepatic biopsies and additional nutritional assessments were not performed. Third, serial brain imaging studies were not conducted.
In conclusion, our study demonstrates a relevant correlation between severity of ataxia and disease progression with metabolic changes such as liver function impairment and insulin resistance in patients with AT. Therefore, with disease progression patients with AT may present with liver dysfunction and insulin resistance, and these ndings reinforce the importance to monitoring metabolic changes and evaluate nutritional status in these patients.

Consent for publication
Patients and parents gave consent to be included in the study through consent form.

Availability of data and material
All data generated or analysed during this study are included in this published article.

Competing interests
The authors declare that they have no competing interests.

Funding
Nothing to disclose.
Authors' contributions TLNB: Acquisition of data; drafting of the manuscript; statistical analysis and interpretation of data of the manuscript.
IRR: Acquisition of data and critical revision for important intellectual content.
KKT: Acquisition of neurological data.
FAM: Acquisition of neurological data.
JLP: Study supervision and critical revision for important intellectual content.
OGPB: Study supervision and critical revision for important intellectual content.
FLAF: Carried out the biochemical analysis.