Food intake modulation by hop phytoestrogen (PE) in overweight neutered cats

Abstract

Estrogen inhibition of food intake diminishes with neutering, often resulting in unhealthy weight gain. A potent hop PE, 8‐prenylnaringinen (8PN), may be a suitable source of estrogen‐replacement to stem excessive post‐neutering food intake. Ad libitum‐fed, adult (3.9–4.3 y), neutered males (n=6) of 105–148% of pre‐neuter weight (4.7–7.0 kg) received daily for 5 d subcutaneous (SQ) injections (20 μL/kg) of 8PN at 10, 50, 100, & 200 μg/kg, 17β‐estradiol (E2) at 0.1 μg/kg, and vehicle of sesame oil:ethanol (9:1). Using a Latin‐square design with 2‐week blocks and 9 washout days between injection treatments, food intake was found decreased (P<0.05) with injections of E2 (−41±7%) and 8PN at 100 (−17±3%) and 200 (−29±5%) μg/kg. Effectiveness of oral daily dosage for 5 d was subsequently evaluated. Vehicle (ethanol) and 8PN at 10‐fold the minimally effective SQ dose (1 mg/kg) were air‐dried on voluntarily ingested kibbles. Food intakes during 8PN and vehicle ingestions were not significantly different, indicating low oral 8PN bioavailability relative to E2. Potency for food intake modulation by 8PN appears much greater than that reported for genistein, a soybean PE, but much less than that found for E2.