Pomegranate peel is an agro-industrial residue obtained after fruit processing with high total polyphenol (TP) content, making it an attractive by-product for its reuse. Pomegranate peel extract (PPE) and its bioactive compounds have shown positive effects on obesity models. Effects on favouring mitochondrial biogenesis and function have also been described. However, once phenolic compounds are extracted, their stability can be affected by diverse factors. Microencapsulation could improve PPE stability, allowing its incorporation into functional foods. Nevertheless, studies on the potential biological effects of PPE microparticles (MPPE) in obesity models are lacking. This study aims to evaluate the effect of MPPE on brown adipose tissue (BAT) mitochondrial structure and function and metabolic alterations related to obesity in mice fed a high-fat diet (HFD). PPE was microencapsulated by spray drying using inulin (IN) as a wall material and physically–chemically characterised. Eight-week-old male C57BL/6J mice (n 40) were randomly distributed into five groups: control diet (CD), HFD, HFD + IN, HFD + PPE (50 mg/kg per d TP) and HFD + MPPE (50 mg/kg per d TP), for 14 weeks. A glucose tolerance test and indirect calorimetry were conducted. Blood and adipose tissue samples were obtained. MPPE supplementation prevented HFD-induced body weight gain (P < 0·001), fasting glycaemia (P = 0·007) and total cholesterol rise (P = 0·001). MPPE resulted in higher BAT mitochondrial complex IV activity (P = 0·03) and prevented HFD-induced mitochondrial cristae alteration (P = 0·02). In conclusion, MPPE prevented HFD-induced excessive body weight gain and associated metabolic disturbances, potentially by activating complex IV activity and preserving mitochondrial cristae structure in BAT in mice fed with a HFD.

The present study assessed the effect of dietary supplementation of pomegranate peel (methanolic) extract (PPE) on the nutrient digestibility, faecal fermentative metabolites and antioxidant status of dogs. Six medium-sized dogs of mixed breeds were allocated to two groups in a replicated cross-over design and fed a basal diet with and without supplementation of PPE at 50 mg/kg body weight. Each of the experimental periods consisted of 30 d, with a 21 d washout period in between. Results indicated that PPE supplementation led to no significant changes in nutrient digestibility except a trend of improvement (P = 0·070) in crude fibre digestibility. PPE supplementation significantly (P < 0·001) influenced faecal pH, ammonia and lactate production, indicative of positive effects of PPE polyphenols. PPE supplementation further increased faecal SCFA concentration accompanied by a reduction (P < 0·01) in branched-chain fatty acids. PPE supplementation also improved (P < 0·05) indices of erythrocytic antioxidants, namely reduced glutathione, catalase, glutathione peroxidase and glutathione S-transferase together with an improvement in lipid peroxidation. Overall, it can be concluded that dietary supplementation with PPE at 50 mg/kg body weight had a positive impact on hindgut fermentation and antioxidant status in dogs, thereby demonstrating its potential as a gut health-promoting nutraceutical.