Oxidative stress contributes to outcome severity in a Drosophila melanogaster model of classic galactosemia

Abstract

SUMMARYClassic galactosemia is a genetic disorder that results from profound loss of galactose-1P-uridylyltransferase (GALT). Affected infants experience a rapid escalation of potentially lethal acute symptoms following exposure to milk. Dietary restriction of galactose prevents or resolves the acute sequelae; however, many patients experience profound long-term complications. Despite decades of research, the mechanisms that underlie pathophysiology in classic galactosemia remain unclear. Recently, we developed a Drosophila melanogaster model of classic galactosemia and demonstrated that, like patients, GALT-null Drosophila succumb in development if exposed to galactose but live if maintained on a galactose-restricted diet. Prior models of experimental galactosemia have implicated a possible association between galactose exposure and oxidative stress. Here we describe application of our fly genetic model of galactosemia to the question of whether oxidative stress contributes to the acute galactose sensitivity of GALT-null animals. Our first approach tested the impact of pro- and antioxidant food supplements on the survival of GALT-null and control larvae. We observed a clear pattern: the oxidants paraquat and DMSO each had a negative impact on the survival of mutant but not control animals exposed to galactose, and the antioxidants vitamin C and α-mangostin each had the opposite effect. Biochemical markers also confirmed that galactose and paraquat synergistically increased oxidative stress on all cohorts tested but, interestingly, the mutant animals showed a decreased response relative to controls. Finally, we tested the expression levels of two transcripts responsive to oxidative stress, GSTD6 and GSTE7, in mutant and control larvae exposed to galactose and found that both genes were induced, one by more than 40-fold. Combined, these results implicate oxidative stress and response as contributing factors in the acute galactose sensitivity of GALT-null Drosophila and, by extension, suggest that reactive oxygen species might also contribute to the acute pathophysiology in classic galactosemia.

Subfertility and growth restriction in a new galactose-1 phosphate uridylyltransferase (GALT) - deficient mouse model

“…At the moment, the cause of death for the intoxicated pups remains unclear, despite the fact that oxidative stress had a pathogenic role in the galactose-induced lethality in the GALT-less Drosophila model of Classic Galactosemia. 34 Without further studies involving anti-oxidants supplementation, we cannot be certain whether the degree of oxidative stress experienced by these pups led to the lethal Figure 3). As we did not feed the newborn pups directly with galactose, we were concerned if galactose challenge of the lactating females, especially those homozygous for the GalT gene-trapped alleles, may render them sick and change their feeding behavior.…”

“…34 To assess oxidative stress in the galactose-intoxicated pups, we measured the GSH/GSSG ratio in the blood of the animals (Supplementary Figure 2). In the absence of galactose challenge of the mothers, there was no difference in the blood GSH/GSSG ratio between wild-type and homozygous GalT gene-trapped pups.…”

Systemic gene dysregulation in classical Galactosaemia: Is there a central mechanism?

“…Dysregulation of the oxidative phosphorylation pathway has been reported as having a role in the severity of outcome in the Drosophila melanogaster Galactosaemia model [45].…”

D-Galactose Causes Motor Coordination Impairment, and Histological and Biochemical Changes in the Cerebellum of Rats

“…However, often, treated patients develop disturbances of coordination throughout their life [5][6][7][8]. Moreover, the etiology of the disease is still poorly understood [9,10]. Patients with classical galactosemia present alteration in markers of oxidative stress and in activities of Na + , K + -ATPase, and Mg 2+ -ATPase in blood [11,12].…”