Effect of the Long-Term Oral Consumption of Brazil Nut Oil on Adiposity and Glucose Homeostasis in MSG-Induced Obese Male and Female Rats

Background/Objectives: Brazil nut (Bertholletia excelsa (Be)) consumption, in the form of oil or seed, has been associated with health benefits in both the lean and obese conditions; however, the influence of sex on these effects is unknown. We analyzed the effects of oral Be-oil supplementation on adiposity and glucose homeostasis in hypothalamic obese and lean male and female rodents. Methods: Male and female Wistar rats were submitted to hypothalamic lesions by monosodium glutamate (MSG; 4 g/kg). An equimolar saline solution was administered to lean, or control (CON), rats. The MSG (obese) and CON (lean) males and females were subdivided into Be-oil-supplemented (1 mL/kg; 3 times/week/8 weeks) and non-supplemented (Ns; saline) groups. Food consumption, feed efficiency ratio, body weight, and white and brown adipose tissue (WAT/BAT) content were recorded. Fasting values of glucose, triglycerides, total cholesterol, and insulin resistance (IR) were assessed. Results: MSG-obese rats presented increased adiposity, IR, and metabolic dysfunction in both sexes without altering food intake. Independently of sex, long-term oral supplementation with Be-oil did not prevent obesity development and led to reduced feed efficiency. Sex-dependent effects of Be-oil supplementation were noted, with MSGBe males showing slight improvements in glucose control and insulin responsiveness, despite worsened triglycerides and a reduction in islet number in the pancreas. In contrast, although MSGBe females presented reduced visceral WAT hypertrophy, IR worsened without alterations in insulin secretion, islet histology, or oral glucose tolerance. Conclusions: In both sexes, oral Be-oil supplementation did not prevent obesity development in MSG-hypothalamic obese rats; however, it exerted sex-dependent metabolic effects, with more positive effects on glucose homeostasis in MSG-obese males.