The Combined Hypoglycemic Effect of Quercetagetin and Lutein from Marigold and Related Molecular Mechanisms in Mice

Marigold (<i>Tagetes erecta</i> L.) is rich in bioactive compounds, with lutein and quercetagetin as the primary components. However, the effects of these two substances on type 2 diabetes mellitus (T2DM) and their underlying molecular mechanisms remain incompletely understood. This study was designed to explore the hypoglycemic potential of quercetagetin and lutein, both individually and in combination, and to decipher the underlying molecular pathways. A T2DM mouse model was established using a high-fat diet (HFD) in combination with streptozotocin (STZ) administration. The results showed that quercetagetin and lutein effectively reduced fasting blood glucose and insulin levels, restored glucose metabolic homeostasis, and improved insulin sensitivity in T2DM mice. Additionally, these compounds improved blood lipid profiles, reduced the production of inflammatory factors, alleviated histological damage, and restored intestinal barrier function. Further mechanistic analysis revealed that quercetagetin and lutein could ameliorate intestinal dysbiosis, decrease intestinal lipopolysaccharide (LPS) content, mitigate local intestinal inflammation, and upregulate the expression of tight junction proteins. These alterations suggest that quercetagetin and lutein collectively contribute to the improvement of intestinal barrier dysfunction and systemic inflammation in type 2 diabetic (T2DM) mice.