Food intake and body weight change across the rodent oestrous cycle, each showing a nadir at oestrus (Olofsson 2009). We aimed to assess whether the rate of intestinal glucose absorption also changes throughout the oestrous cycle.
Female C57BL/6 mice (8-9 weeks) were humanely killed at defined oestrus, metoestrus, dioestrus and proestrus cycle stages (N=9-10 mice per stage). Jejunal segments (1 cm length) were mounted in Ussing chambers and the change in short-circuit current (∆Isc) upon mucosal addition of 50 mM glucose measured as transepithelial glucose transport in the presence of 0, 0.1, 0.3 or 1 mM phlorizin (PZ, an inhibitor of sodium-glucose co-transporter-1, SGLT-1).
Transepithelial glucose transport was lower at oestrus compared to proestrus (P=0.013). PZ reduced glucose transport predominantly in the distal jejunum (dose-region interaction: P<0.005), by > 80% at 0.3 mM and ~90% at 1.0 mM. In the absence of PZ, glucose transport was higher in the distal compared to proximal jejunum (P<0.001). In contrast, glucose transport did not differ between regions in the presence of PZ.
Jejunal glucose transport is primarily SGLT-1-mediated in mice, with greater transport capacity in distal compared to proximal jejunum. Importantly, jejunal glucose uptake was lowest at oestrus, demonstrating similar timing as previously reported nadirs in body weight and food intake. This suggests that these processes are coordinated throughout the oestrous cycle. The relative contributions of food intake and hormonal changes to altered glucose absorption remain to be elucidated.