Euglena Attenuates High-Fat-Diet-Induced Obesity and Especially Glucose Intolerance

<b>Background:</b> Obesity, a global disease, can lead to different chronic diseases and a series of social health problems. Lifestyle changes, especially dietary changes, are the most effective way to treat obesity. <i>Euglena</i>, a novel food, has attracted much attention. Previous studies have shown that <i>Euglena</i> is an important modulator of the host immune response. In this study, the effects of <i>Euglena</i> as a nutritional intervention in high-fat-diet-induced obese C57BL/6J mice were investigated regarding adipose tissue accumulation and lipid and glucose metabolism by gavage at the dose of 100 mg/kg bodyweight for 9 weeks. This study is one of the few to investigate, in detail, the preventive effects of dietary <i>Euglena</i> on obesity. <b>Methods:</b> Five-week-old male C57BL/6J mice were fed with a high-fat diet (HFD) to induce obesity. An obesity model was created by feeding the high-fat diet for a period of 10 weeks. Obese mice were randomized into 2 groups with the same mean body weight, and no significant differences were observed between the groups: (1) the mice in the HEG group were maintained on a high-fat diet and daily gavaged with <i>Euglena</i> (100 mg/kg body weight) dissolved in saline (<i>n</i> = 7); and (2) the mice in the HFD group were maintained on a high-fat diet and daily gavaged with saline with the same volume (<i>n</i> = 7). The experiment finished after a nine-week period. <b>Results:</b> The results showed that <i>Euglena</i> could reduce the accumulation of white body fat, including subcutaneous fat and visceral fat, and mainly targeted subcutaneous fat. <i>Euglena</i> also reduced adipocyte particle size expansion, promoted lipolysis in adipose (adipose triglyceride lipase and hormone-sensitive triglyceride lipase) and liver tissue (reduced non-esterified fatty acid content), and improved obesity-induced ectopic fat deposition and glucose tolerance. <b>Conclusions:</b> Our findings suggest that <i>Euglena</i>, as a nutritional intervention in HFDs, efficiently reduces body weight and white adipose tissue deposition. The mechanism of <i>Euglena</i> is mainly though enhancing lipolysis. It is worth noting that <i>Euglena</i> β-glucan recovers the hyperglycemia and accumulation of ectopic fat within the liver induced by HFD. Our study is one of the few studies to report in detail the preventive effects of dietary <i>Euglena</i> on obesity in vivo. This study revealed that <i>Euglena</i> also has an important ameliorative effect on obesity and metabolic disorders, which laid a theoretical foundation for its future application in functional foods.