Avaliação da função das células beta pancreáticas e da ação da insulina in vivo em ratos mantidos com dieta à base de óleo de coco

Abstract

Coconut oil has been widely advertised as a healthy edible oil with a slimming and cardioprotective function. However, this oil consists predominantly of saturated fatty acids, which promote insulin resistance and may compromise pancreatic beta cell function. Thus, the present study aimed to evaluate pancreatic beta cell function and insulin action in vivo in rats maintained on a coconut oil-based diet. Newly weaned male Wistar rats (30 days old) randomly assigned into three groups were used: C, consisting of rats fed a control diet (AIN-93G); M, consisting of rats fed a diet containing a mixture of soybean oil and coconut oil; and OC, consisting of rats fed a diet containing coconut oil. Food intake was measured and weight was measured periodically. After 60 days of treatment with the respective diets, the animals underwent an oral glucose tolerance test and an intraperitoneal insulin tolerance test to evaluate pancreatic beta cell functional capacity and hepatic and peripheral insulin action. The rats in the three groups evaluated had equal initial body weights. After 60 days of treatment with the respective diets, the OC group exhibited lower body weight compared to group M (p<0.042) and C (p<0.008). Group M exhibited increased absolute and relative liver weight compared to group C (p<0.042 and p<0.012, respectively), while OC exhibited relative liver weight similar to group M, but higher compared to group C (p<0.020). The absolute and relative weights of muscle and adipose tissue did not differ between the groups. Total food consumption was similar in the three groups evaluated. The intake of monounsaturated and polyunsaturated fatty acids, and specifically omega 3, 6 and 9 were significantly lower in the OC group compared to the M group (p<0.000), and the latter group was lower than the C group (p<0.000). In contrast, saturated fatty acid intake was higher in the OC group compared to the M and C groups (p<0.000). Group M also exhibited higher saturated fatty acid intake compared to group C (p<0.000). Fasting blood glucose did not differ between groups, but fasting insulinemia and HOMA-B index were higher in the OC group relative to the M (p<0.006) and C (p<0.004) groups. The OC group had a higher fasting glucose/fasting insulinemia ratio compared to the M (p<0.036) and C (p<0.028) groups, but the M group had lower Kitt compared to the C group (p<0.048); the OC group did not differ from either the M group (p=0.974) or the C group (p=0.074). Therefore, it is concluded that coconut oil-based diet increases hepatic and peripheral insulin resistance, but does not alter glucose homeostasis by promoting increased functional capacity of pancreatic beta cells.