Standard diet

Standard diet (SD), high-carbohydrate diet (HCD), high-fat diet (HFD) or high-fructose diet (HFrD) were purchased from Envigo (Milan, Italy). The product containing Acacia senegal (L.) Willd, tyndallized L. acidophilus, tyndallized L. reuteri, Pea protein, Grape seed extract and β-galactosidase was kindly provided by DEVINTEC SAGL (Lugano, Switzerland). The human doses shown in Table 1 were converted to mouse doses based on the body surface formulation [26 (link)]. The total dose of NTN administered to each mouse was: 37 mg/kg. Unless otherwise stated, all compounds employed in this study were obtained from Sigma-Aldrich (Poole, UK). For oral administration, NTN was dissolved in saline and given to the mice three times a day by oral gavage.

Adult C57BL/6JSAH female mice (8–10 weeks old) were sourced from SAHMRI Bioresources and housed in home cages in groups of two to five under a 12‐h light cycle (07.00–19.00 h) and constant temperature of 23°C with ad libitum access to water and a standard laboratory chow (Teklad standard diet, Envigo, Huntingdon, UK). For dose–response and inhibitor (method optimisation) studies, mice remained group‐housed under breeding colony conditions until use. For oestrous cycle studies, mice were pair‐housed in individually ventilated cages with crinkle‐nest and cotton nestlet bedding material and cardboard tubes as enrichment. After at least a week's acclimatisation, vaginal smears were collected and assessed daily for at least a further week to determine oestrous cycle stage.