1. Introduction
Diabetes mellitus is a major health problem. Epidemiologically,
individuals with diabetes are expected to double to more than 350
million by 2025 (Zimmet et al., 2003). There is an increasing rate of
obesity worldwide that is significantly correlated with diabetes, which
can be due to consuming high-calorie foods and low physical activity
(James et al., 2001). Hyperglycemia in prediabetes can lead to oxidative
stress and the upregulation of proinflammatory factors, which ultimately
lead to vascular dysfunction. To prevent the development of
comorbidities, it is fundamental to determine the mechanisms involved in
the progression from prediabetes to diabetes. Oxidative stress leads to
impaired glucose uptake in muscle and fat cells and decreases insulin
secretion from pancreatic β-cell (Maddux et al., 2001).
Vitamin A is one of the vital nutrients that should be included in the
diet in order to maintain health. It is essential for multiple life
mechanisms such as the reproductive system, immune system, vision and
differentiation at the cellular levels (Amestin et al., 2017). Moreover,
Vitamin A is a very powerful antioxidant that helps maintain the
functions of the heart, lungs, and kidneys, along with various other
organs in the human body (Coats et al., 2010).
Recently, multiple studies started to investigate the effect of Vitamin
A and its derivatives in multiple conditions. An evidence has shown that
there is a link between diabetes and vitamin A. This previous study
elucidated that Vitamin A can enhance insulin levels that are produced
by pancreatic β-cell. In Addition, researchers discovered receptor for
vitamin A on the cell surfaces of the beta cells (Amestin et al., 2017).
By reviewing the literature, it is evident that Vitamin A deficiency
predisposes individuals to type I and type II diabetes. Vitamin A
deficiency has been shown to decrease the release of insulin and its
synthesis and secretion in both humans and in diabetic animal models.
Furthermore, multiple epidemiological studies have demonstrated that
there is a link between vitamin A deficiency in both early onset and
delayed onset of type I diabetes (Isaia et al., 2001).
Lately, a wide attention has been developed to the protective
biochemical function of natural antioxidants contained vitamins, which
can prevent of the oxidative damage caused by free radical species
(Matos et al., 2018). Little information is available regarding the
antidiabetic an antioxidant effect of vitamin A in diabetes mellitus.
As diabetes has been shown to trigger oxidative damage, we hypothesized
that Vitamin A might have an improvement effects on glycemic control as
well as oxidative stress in diabetes mellitus.