Fig 2: Immunodetection of GPR109a in jejunum of 10-week-old m+/db mice (A) and 10-week-old db/db mice (D). (B,E) are the nuclear DAPI staining of (A,D) respectively; (C,F) are their corresponding merged images. Higher magnification of niacin receptor staining of m+/db (G) and db/db (H); (I) shows jejunal sections prepared in the absence of primary antibodies (negative control). Immunodetection of niacin receptor in Caco-2 cells grown in 5.6 mM (J) and 25.2 mM glucose (M); (K,N) show nuclear 4',6-diamidino-2-phenylindole (DAPI) staining of (J) and (M) respectively; (L,O) are the corresponding merged images.

Fig 3: (A) Effects of high glucose concentration (25.2 mM) on the mRNA expression of GPR109a in Caco-2 cells vs. low glucose concentration (5.6 mM). Results are expressed as means ± standard error of the mean (SEM), n = 3, control = 5.6 mM glucose, control vs. 25.2 mM glucose, * p < 0.05; (B) Effects of high glucose (25.2 mM) on GPR109a protein expression in Caco-2 cells vs. control 5.6 mM glucose concentrations. Results are expressed as means ± SEM, n = 6, control = 5.6 mM vs. 25.2 mM, * p < 0.05.

Fig 4: (A) Effects of age and Type 2 Diabetes Mellitus (T2DM) on the mRNA expression of GPR109a in jejunal mucosa. Mouse mRNA abundance was determined by real-time PCR using jejunal mucosa and data were calculated as the percentage of their corresponding m+ non-diabetic controls. All results are expressed relative to enterocytes of non-diabetic rats, and are given as mean ± standard error of the mean (SEM), n = 3–4; 10 db vs. 10 m+, ** p < 0.01; (B) Effects of age and T2DM on the protein expression of GPR109a in jejunal enterocytes. Western blot analysis showing the relative expression of GPR109a in homogenates of enterocytes prepared from jejuna of m+/db and db/db mice of 4, 10 or 12 weeks of age. Data were calculated as the percentage change compared to their corresponding m+ non-diabetic control. Results are expressed as means ± SEM, n = 3–5, 10m+ vs. 10 db, * p < 0.05. 4m+, 8m+, 10m+ and 12m+ represent 4-, 8-, 10- and 12-week-old m+/db mice respectively; whereas 4 db, 8 db, 10 db and 12 db represent 4-, 8-, 10- and 12-week-old db/db mice, respectively.