Fig 2: Voglibose alters the composition and transport of SCFAs in KKAy mice. Fecal SCFA concentra-tions including (A) acetic acid, (B) butyric acid, (C) propionic acid, (D) pentanoic acid-4-methyl, (E) hexanoic acid and (F) total SCFAs were quantified. Data are expressed as the mean ± SEM, n = 5–6. (G) MCT1, SMCT1, (H) ZO-1 and occludin protein abundance in the ileum tissue. (I) Quantification of proteins in (G,H). (J) Quantitative PCR analysis of occludin and ZO-1. Data are expressed as the mean ± SEM and individual data was shown in square (DM) and circle (Vogli), n = 3–6. * p < 0.05, ** p < 0.01, *** p < 0.001. DM, diabetic model group; Vogli, voglibose-treated group.

Fig 3: Expression of MCT1 and APC, and PARP1 and AIF in the corpus callosum of CPZ-fed mice. The immunofluorescent staining and intensity quantification of MCT1 (A) and APC (B) in the corpus callosum of mice in different groups. (C) WB assays (PARP1, AIF and ß-actin as a loading control). Scale bars = 50 µm. Data are presented as mean ± SEM. N = 3 per experimental group; experiment repeated two times. *p < 0.05, **p < 0.01, and ***p < 0.001 versus the control group; #p < 0.05, ##p < 0.01, and ###p < 0.001 versus the CPZ group.

Fig 4: Bsg deficiency leads to depletion of TCA cycle intermediates in the liver.(A) Schematic illustrating the facilitation by the MCT/BSG complex of the import of substrates used by the TCA cycle. (B and C) Static metabolome analysis for lactate and pyruvate in livers and kidneys (B) and TCA cycle intermediates in livers (C) from fasted Bsg+/+ or Bsg–/– mice. White columns and circles, Bsg+/+ mice; gray columns and black circles, Bsg–/– mice. Data are presented as means ± SEM (n = 7–8). Scatter plots display the data for individual mice. P values represent results for a comparison of Bsg+/+ and Bsg–/– mice for the indicated metabolite (2-tailed unpaired Student’s t test). (D) Levels of 13C3-labeled lactate and pyruvate in the media from isolated Bsg+/+ or Bsg–/– hepatocytes, respectively. White columns, Bsg+/+ hepatocytes; gray columns, Bsg–/– hepatocytes. n = 5 for independent experiments. (E) 13C3-labeled lactate/pyruvate flux into TCA cycle intermediates, such as citrate, fumarate, and malate, in isolated hepatocytes.

Fig 5: BSG regulates lactate and pyruvate import through interaction with MCTs.(A) Immunofluorescence staining for BSG and MCT1 in the liver and renal cortex of tissues from wild-type (Bsg+/+) and Bsg-deficient (Bsg–/–) mice. Scale bar: 100 µm. (B) Representative photographs of isolated Bsg+/+ or Bsg–/– hepatocytes by immunocytochemical staining. Scale bar: 20 µm. (C and D) Western blotting analysis of BSG and MCT1 expression in the liver (C) and the kidneys (D) of Bsg+/+ and Bsg–/– mice. The intensities of the BSG and MCT1 bands were normalized to those of ß-actin, a housekeeping protein that was used as a loading control. White columns and circles, Bsg+/+ mice; gray columns and black circles, Bsg–/– mice. Data are presented as means ± SEM (n = 5–6). Scatter plots display the data for individual mice. (E) Immunoelectron microscopic assessment of BSG expression in mitochondria of the liver and kidneys. Scale bar: 200 nm. (F) MCT1 expressions in plasma membranes and mitochondria of Bsg+/+ and Bsg–/– hepatocytes as determined by Western blotting. White columns and circles, Bsg+/+ hepatocytes; gray columns and black circles, Bsg–/– hepatocytes. Data are presented as means ± SEM (n = 3). Scatter plots display the data for individual mice. (G) Blood lactate concentrations in Bsg+/+ and Bsg–/– mice during lactate tolerance tests. (H and I) Serum pyruvate (H) and blood lactate (I) concentrations during pyruvate tolerance tests. For G–I, data are presented as means ± SEM; n = 7 (G) or 5–9 (H and I). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, not significant (P =0.05), for a comparison of Bsg+/+ and Bsg–/– mice at the indicated time point (2-tailed unpaired Student’s t test). (J) A schematic illustrating lactate and pyruvate dynamics via MCT-Bsg complexes in hepatocytes derived from Bsg+/+ mice compared with Bsg–/– hepatocytes.