Effect of Consumption of a Lyophilized Nasturtium (Tropaeolum Majus L), on the Insulin Response, Lipid Profile, Antioxidant Capacity and Gene Expression in Pre-diabetic Subjects: Bogotá-Colombia

Epidemiological and animal studies have shown that consumption of fruits and vegetables decreases the risk of chronic diseases. Especially in T2D, the primary prevention is considered as a public health priority. Some studies show an inverse association between vegetables intake and T2D prevention, although the underlying mechanisms and the effect of individual antioxidant compounds are still unclear.

Brassicaceae plant family (e.g., broccoli, cabbage, brussels sprouts, watercress, Nasturtium, garden cress, kale, cauliflower), have a high content of bioactive compounds such as e.g. glucosinolates (GSLs), isothiocyanates (ICTs) and polyphenols, associated, recently, with diabetes prevention (18). Human studies in diabetic patients have shown that the consumption of broccoli sprouts powder (BSP) containing high concentration of the GLS sulphoraphane for 4 weeks decreases serum insulin concentration, homoeostasis model assessment of insulin resistance (HOMA-IR), LDL, inflammation and antioxidant markers. Besides sulphoraphane other GLSs have showed a protective effect in diabetes. Recently, mice fed with very high fat diet (VHFD) supplemented with 5% of moringa concentrate rich in benzyl isothiocyanate showed that moringa isothiocyanates (MICs) improved glucose tolerance and insulin signaling; reduced plasma leptin, resistin, cholesterol, IL-1β, TNFα, and lower hepatic glucose-6-phosphatase (G6Pase) gene expression. This evidence suggest that MICs could play a role in T2D prevention probably by inhibiting rate-limiting steps in liver gluconeogenesis resulting in direct or indirect increase in insulin signaling and sensitivity.

Recently in vitro studies in human and osteosarcoma hepatoma cells (HepG2 cells) stimulated with benzyl isothiocyanate (BITC) from Tropaeolum majus, show that this compound is able of 1) regulate the insulin signaling pathway, 2) down-regulate the gene and protein expression of gluconeogenic enzymes G6Pase and phosphoenol piruvatokinase (PEPCK) and 3) up-regulate the gene expression of antioxidant and phase II detoxification genes manganese superoxide dismutase (MnSOD), nuclear factor (erythroid derived)-like2 (NRF2), NAD(P)H dehydrogenase (quinone 1) (NQO1) and sulfiredoxin-1 (SFRXN1) (21). According with this evidence BITC could mimics the fasting state, in which insulin stimuli is absent and transcription factors remain in the nucleus modulating gene expression of their target genes, with the advantage of down-regulating gluconeogenesis instead of increase it suggesting that BITC could have a therapeutic role in the prevention or treatment of T2D.

Despite of strong evidence of 1) chronic inflammation as an underlying cause of T2D, and 2) high levels of oxidative stress under T2D conditions the use of ITC-rich foods as therapeutics in T2D remains virtually unknown. For that reason this research proposal has the intention of evaluating if the ingestion of freeze-dried nasturtium has a positive effect on the insulin response, lipid profile, oxidative stress biomarkers and gene expression of RESISTIN, GLUT 4, acetyl-CoA carboxylase-a (ACC), fatty acid synthase (FASN), NRF-2, NQO1, SFRXN1, glutathione peroxidase 2 (GPx-2), FOXO1, FOXO3 and FOXO6 in subjects with glucose intolerance.