Undaria pinnatifida Sporophyll and Gracilaria verrucosa Attenuate obesity-induced fat accumulation, adipose tissue macrophage infiltration, and systemic insulin resistance

• UPS and GV reduced lipid accumulation and boosted lipolysis in adipocytes. • UPS and GV alleviated HFD-induced obesity and inflammation in DIO mice. • UPS and GV decreased macrophage infiltration into the adipose tissue of DIO mice. • Systemic IR improved due to reduced fat accumulation and inflammation by UPS and GV. The potential health-promoting effects of two edible seaweeds, Undaria pinnatifida sporophyll (UPS) and Gracilaria verrucosa (GV), were investigated by using in vitro and in vivo models. Water extracts of UPS and GV inhibited lipid accumulation in 3T3-L1 adipocytes by downregulating adipogenesis-related genes and stimulated lipolysis in mature adipocytes. In C57BL/6 mice, supplementation with UPS and GV powders ameliorated diet-induced obesity, insulin resistance, and systemic inflammation, resulting in lighter subcutaneous adipose tissue and decreased macrophage markers ( F4/80 , Cd11c , Cd206 ) and proinflammatory genes ( Tnf-α, Il-1β, Il-6, Ccl2 ) in gonadal adipose tissue. Liver weight and hepatic triglyceride levels were also significantly lowered. Taken together, UPS and GV supplementation effectively prevented diet-induced obesity and chronic inflammation making them promising dietary ingredients for managing obesity and its associated disorders.