Effect of chronic administration with human thioredoxin-1 transplastomic lettuce on diabetic mice

Human thioredoxin-1 (hTrx-1) is a defensive protein induced by various stresses and exerts antioxidative and anti-inflammatory effects. Previously, we described a transplastomic lettuce overexpressing hTrx-1 that exerts a protective effect against oxidative damage in a pancreatic β-cell line. In this study, we treated diabetic mice (Akita mice) with exogenous hTrx-1 and evaluated the effects.

Treatment with drinking water and single applications of exogenous hTrx-1 did not influence the feeding, drinking behavior, body weight, blood glucose, or glycosylated hemoglobin (HbA_1c) levels in Akita mice. However, chronic administration of a 10% hTrx-1 lettuce-containing diet was associated with a significant reduction from the baseline of HbA_1c levels compared with mice fed a wild-type lettuce-containing diet. It also resulted in an increased number of goblet cells in the small intestine, indicating that mucus was synthesized and secreted.

Our results revealed that the administration of an hTrx-1 lettuce-containing diet improves the baseline level of HbA_1c in Akita mice. This effect is mediated through goblet cell proliferation and possibly related to protection against postprandial hyperglycemia by mucus, which results in the improvement of blood glucose control. These findings suggest that the hTrx-1 lettuce may be a useful tool for the continuous antioxidative and antidiabetic efficacies of the hTrx-1 protein.