Chronic refined low-fat diet consumption reduces cholecystokinin satiation in rats

Purpose: Reduced ability of cholecystokinin (CCK) to induce satiation contributes to hyperphagia and weight gain in high-fat/high-sucrose (HF/HS) diet-induced obesity, and has been linked to altered gut microbiota. Rodent models of obesity use chow or low-fat (LF) diets as control diets; the latter has been shown to alter gut microbiota and metabolome. We aimed to determine whether LF-diet consumption impacts CCK satiation in rats and if so, whether this is prevented by addition of inulin to LF diet. Methods: Rats (n = 40) were fed, for 8 weeks, a chow diet (chow) or low-fat (10%) or high-fat/high-sucrose (45 and 17%, respectively) refined diets with either 10% cellulose (LF and HF/HS) or 10% inulin (LF-I and HF/HS-I). Caecal metabolome was assessed by ¹H-NMR-based metabolomics. CCK satiation was evaluated by measuring the suppression of food intake after intraperitoneal CCK injection (1 or 3 µg/kg). Results: LF-diet consumption altered the caecal metabolome, reduced caecal weight, and increased IAP activity, compared to chow. CCK-induced inhibition of food intake was abolished in LF diet-fed rats compared to chow-fed rats, while HF/HS diet-fed rats responded only to the highest CCK dose. Inulin substitution ameliorated caecal atrophy, reduced IAP activity, and modulated caecal metabolome, but did not improve CCK-induced satiety in either LF- or HF/HS-fed rats. Conclusions: CCK signaling is impaired by LF-diet consumption, highlighting that caution must be taken when using LF diet until a more suitable refined control diet is identified.