High concentration of MSG alters antioxidant defence system in lobster cockroach Nauphoeta cinerea (Blattodea: Blaberidae)

Abstract

Objective: Monosodium glutamate (MSG) is a food additive that has been shown to be toxic to rodents at high concentrations. The available studies in Drosophila melanogaster suggest that MSG toxicity depends on concentration and gender, thus the safety of MSG as a food enhancer still requires further investigation. We have documented impaired locomotor activity and altered oxidative stress markers in cockroaches co-exposed to methylmercury and monosodium glutamate (MSG). We herein examined the susceptibility of Nauphoeta cinerea to high and low concentrations (4% and 1%) of MSG, while monitoring the activities of acetylcholinesterase (AChE), as well as markers of oxidative stress and antioxidant activity over 30 days.

Results: There was no significant alteration in the parameters assessed at 1% MSG while 4% MSG caused an increase in the activity of reactive oxygen and nitrogen species, with a corresponding reduction in the activities of acetylcholinesterase, glutathione-S-transferase and catalase, suggesting the capacity of MSG to alter redox homeostasis in Nauphoeta cinerea.

Keywords: Acetylcholinesterase; Catalase; Food additive; Glutathione-S-Transferase; Monosodium glutamate; Nauphoeta cinerea; Oxidative stress; Total thiol.

Fig. 1

Acetylcholinesterase (AChE) activities of nymphs exposed to 4% MSG (a) and 1% MSG (b). The data are expressed as mean ± standard error mean (SEM). (a) differs significantly from the basal (p < 0.05)

Fig. 2

Oxidative stress markers in head homogenate of nymphs exposed to 4% MSG and 1% MSG. a, b RONs levels. c, d TBARs levels. The data are expressed as mean ± standard error mean (SEM). (a) differs significantly from the basal (p < 0.05)

Fig. 3

Antioxidant levels in head homogenate of nymphs exposed to 4% MSG and 1% MSG. a, b Catalase activities. c, d Glutathione-S-transferase (GST) activities. The data are expressed as mean ± standard error mean (SEM). (a) differs significantly from the basal (p < 0.05)