While daily vegetable consumption can lower the risk of cancer and lifestyle-related diseases, how the antioxidant properties of carotenoids in vivo work against oxidative stress is still unclear.
As such, researchers from Okayama University and Nagoya University set out to investigate the antioxidant properties of dietary compounds, focusing on the effects of Ax-C-8 in rats whose kidneys suffered from iron-induced oxidative injury.
Maintenance and suppression
They divided 21 four-week-old male rats into one control group and two other groups: in one, each rat was injected with an iron solution while on a regular chow diet and in the other, each rat was also injected with the solution but put on a powdered Ax-C-8 diet for 30 days.
They subsequently found that Ax-C-8 maintained kidney function and antioxidant enzyme activities even after iron-induced oxidative injury.
Additionally, “Ax-C-8 pre-treatment suppressed the elevation of creatinine and blood urea nitrogen” in the rats, and managed to suppress tubular necrosis in their kidneys.
However, the researchers said the rats that had each been given 25mg of Ax-C-8 or more a day died from the intake amount.
The study said this dosage was equivalent to a daily 300mg/kg in humans, and almost 1,000 times higher than the dosage used in CARET (Carotene and Retinol Efficacy Trial) in Western countries, as well as a clinical trial on astaxanthin in Japan.
Daily intake of 5mg of Ax-C-8, on the other hand, was not lethally toxic to the rats.
The study stated that Ax-C-8 supplementation’s ability to significantly inhibit iron-induced kidney tissue injury suggested it to be “an effective compound that prevents oxidative stress in vivo”.
Astaxanthin also has considerable potential as a chemo-preventive compound against numerous types of carcinogens, evidenced by its ability to suppress their cellular proliferation. This indicates that an appropriate dosage of Ax-C-8 may be able to prevent iron-induced carcinogenesis of the kidney.
However, the study also said “antioxidants in human studies have not been effective”, presumably because of the nature of ROS (reactive oxygen species), which can react instantly with biomolecules.
Hence, the use of antioxidants for chemoprevention requires more trials of suitable duration to properly determine their efficacy for this purpose.
The study concluded: “We observed for the first time that Ax-C-8 protects against iron-mediated renal tubular injury in a rat model. Further study is warranted to determine the pathological conditions for the chemoprevention of oxidative stress.”
Source: Journal of Clinical Biochemistry and Nutrition
“Astaxanthin ameliorates ferric nitrilotriacetate induced renal oxidative injury in rats”
Authors: Yasumasa Okazaki, Shigeru Okada, Shinya Toyokuni