Our study found a marked correlation between severity of ataxia and nutritional and metabolic changes in patients with AT. Statistical analysis showed significant 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 findings [33].
Chronic liver dysfunction can lead to the accumulation of toxic metabolites in the brain and cause neuroinflammation by increasing pro-inflammatory 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 significant correlation between Klockgether ataxia score (KAS) and GGT and age, which corroborates our findings [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 significant 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 significantly 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 significantly 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 et al. reported steady elevation of ALT and GGT levels from the age of 12 in AT, which is in line with our results [35]. Weiss et al. reported elevated liver enzymes in young AT patients (age 9.97 ± 5.09 years) associated with dyslipidemia, but not with age [36].
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 find a significant 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 significant indirect correlation of SARA scores and a trend towards significance 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 findings reinforce the importance to monitoring metabolic changes and evaluate nutritional status in these patients.
Table 1
Characteristics of patients with AT
Variables | | N (%) |
---|
Age (years) (n = 25) | 5–12 13–31 | 10 (40.0%) 15 (60.0%) |
Nutritional status | Underweight | 8 (32.0%) |
(n = 25) | Normal weight | 16 (64.0%) |
| Overweight | 1 (4.0%) |
Body fat mass | Low | 4 (16.6%) |
(n = 24) | Normal | 13 (54.1%) |
| High | 7 (29.1%) |
MUAC | Low | 13 (54.1%) |
(n = 24) | Normal | 8 (44.4%) |
Sexual maturation staging (n = 25) | Prepubertal Pubertal Late pubertal | 7 (28.0%) 11 (44.0%) 7 (28.0%) |
Symptom at disease onset | Ataxic gait | 15 (60.0%) |
(n = 25) | Hypotonus | 7 (28.0%) |
| Ocular telangiectasia | 3 (12.0%) |
Gait | Walking without aid | 7 (28.0%) |
(n = 25) | Walking with aid Inability to walk | 13 (52.0%) 5 (20.0%) |
ICARS scores | Mild ataxia | 3 (12,0%) |
(n = 25) | Moderate ataxia | 13 (52%) |
| Severe ataxia | 9 (36%) |
SARA scores | Mild ataxia | 7 (28.0%) |
(n = 25) | Moderate ataxia Severe ataxia | 9 (36.0%) 9 (36.0%) |
Abbreviations: MUAC: mid-upper arm circumference; ICARS; The International Cooperative Ataxia Rating Scale; SARA: Scale for the Assessment and Rating of Ataxia; N (%): absolute value and percent. |
Table 2
Comparison of biochemical markers in patients with AT by age groups
Variables | | Age group 1 (≤ 12 years) (n = 10) | Age group 2 (> 12 years) (n = 15) | p-valuea,b |
---|
AST | U/L | 29.9 (16.6–74.3)c | 37.7 (16.6–82.3) | 0.360a | |
ALT | U/L | 18.4 (11.4–45.0) | 31.4 (16.3–144.5) | 0.017a | |
GGT | U/L | 17.5 (7.0–97.0) | 37.0 (21.0–612.0) | < 0.001a | |
Fasting glucose | mg/dL | 87.1 (± 8.4)d | 87.4 (± 12.1) | 0.950b | |
Fasting insulin | µIU/mL | 5.9 (0.4–22.0) | 7.3 (3.3–80.1) | 0.102a | |
AFP | IU/mL | 165.1 (± 89.4) | 345.8 (± 171.4) | 0.006b | |
HOMA-IR index | | 1.15 (0.07–4.44) | 1.75 (0.51–20.94) | 0.102a | |
Abbreviations: AST: aspartate aminotransferase; ALT: alanine aminotransferase; AFP: alpha-fetoprotein; HOMA-IR: Homeostasis Model Assessment for Insulin Resistance. |
a Level of significance for Mann-Whitney U-test |
b Level of significance for independent Student’s t-test |
c Median (minimum-maximum) |
d Mean (standard deviation) |