Effect of Lychee Peel and Seed Flour Consumption on the Anti/Pro-Oxidant System and Cardiomyocyte Contractile Function.

Background/aims: Type 2 diabetes mellitus (T2DM) represents a high risk for developing cardiovascular diseases, with alterations in contractile function and calcium (Ca2+) handling. In addition, there is an increase of reactive oxygen species in T2DM, with the pathways of altered glucose metabolism, oxidative damage to pancreatic β-cells, and endothelial dysfunction being involved in this process. Studies have shown that both the extract and lychee peel and seed flour are rich in antioxidant phenolic compounds, which could be beneficial in preventing and/or reversing oxidative stress (OS) in obesity associated with type 2 diabetes mellitus (T2DMOb). However, the relationship between oxidative stress in T2DMOb and the involvement of lychee peel and seed flour is still not well understood. This study aimed to evaluate the effect of lychee peel and seed flour consumption on the anti/pro-oxidant system and cardiomyocyte contractile function in obese rats induced to T2DM.

Methods: Obesity in Wistar rats (n = 38) was induced by a high-fat diet and, later, they were induced to T2DM. The experimental protocol consisted of a total period of 17 weeks and was divided into four moments (Figure 1): 1) obesity induction (4 weeks); 2) maintenance of obesity (8 weeks); 3) induction of T2DM (12th week) in obese (Ob) rats and redistribution of groups; and 4) obesity and T2DM maintenance and treatments with lychee peel and seed flours (5 weeks). After 12 weeks, the Ob rats were randomized into T2DMOb (n = 8), T2DMOb treated with lychee peel flour (T2DMObPF, n = 10), and T2DMOb treated with lychee seed flour (T2DMObSF, n = 10). Analyzes of the nutritional and metabolic profiles, cardiac remodeling, and OS biomarkers were evaluated. Contractile function by isolated cardiomyocyte analysis and Ca2+ handling was determined.

Results: Treatments with lychee peel and seed flour were not able to change body weight, adiposity, biochemical and cardiac morphological parameters, or OS biomarkers in relation to T2DMOb animals. Lychee treatments did not accentuate the elevation of fractional shortening visualized in T2DMOb. Regarding relaxation, the maximum rate of relaxation was higher in the T2DMOb group compared to the Ob group, but the lychee treatments did not promote positive alterations in this parameter. In addition, the time to 50% relaxation was also longer in the presence of T2DM (T2DMOb > Ob); the treatments with lychee peel flour favored a reduction in the time to 50% relaxation. T2DMOb rats presented an increase in diastolic Ca2+ in relation to the Ob group; the treatment with lychee seed flour reduced this parameter, despite not improving the time to 50% decay Ca2+ and, consequently, relaxation. Furthermore, the treatments with lychee peel and seed flour did not change the sensitivity of myofilaments to Ca2+ in T2DMOb animals.

Conclusion: The treatments with lychee peel and seed flour showed no significant effects on anti/pro-oxidant parameters. However, lychee peel flour demonstrated notable effectiveness in reducing myocardial relaxation time in a T2DMOb model. These results suggest that while the antioxidant properties of lychee seed and peel flours were not significantly altered, lychee peel flour may have specific therapeutic potential to improve cardiac function in T2DMOb.