Angiotensin receptor blocker telmisartan suppresses renal gluconeogenesis during starvation

Figures & data

Table 1 Physiological data

	Control (n=7)	DM (n=7)	DM + ARB (n=7)
Body weight (g)	251±4	203±8‡	211±9†
Systolic blood pressure (mmHg)	97±7	113±5	85±6§
Urinary protein (mg/day)	4.4±1.1	14.3±2.6†	6.5±0.5§
Creatinine clearance (mL/min/100 g body weight)	0.83±0.06	2.59±0.55*	1.74±0.23
HbA1c (%)	3.4±0.1	9.0±0.3‡	8.7±0.3‡
Insulin (ng/mL)	1.63±0.90	0.13±0.03	0.16±0.03

Notes:

* P<0.05

† P<0.01

‡ P<0.001 versus control

§ P<0.05 versus DM.

Abbreviations: ARB, angiotensin receptor blocker; HbA_1c, glycated hemoglobin; DM, diabetes mellitus.

Figure 1 Plasma glucose concentration (A and B) and urinary glucose excretion (C and D) following 24 hours of starvation (A and C) or under post-prandial conditions (B and D).

Notes: Treatment with telmisartan reduced the plasma glucose levels after 24 hours of starvation, but not under the postprandial conditions, whereas the rate of urinary glucose excretion was decreased under both conditions. *P<0.05, ^†P<0.01 versus control, ^‡P<0.05, ^§P<0.01 versus DM. N=7 in each group.
Abbreviations: ARB, angiotensin receptor blocker; DM, diabetes mellitus.

Figure 2 Pre-embedding immuno-electron microscopy for SGLT2.

Notes: The renal expression of SGLT2 in the brush border membrane of the proximal tubules (arrows) was increased in the DM rats compared with that observed in the control rats, while ARB treatment suppressed the SGLT2 expression. The figures for the SGLT2 expression reflect data obtained under the starvation conditions, while the results include some findings obtained under fed conditions (data not shown). The bar indicates 50 μm. *P<0.01 versus control, ^†P<0.01 versus DM. N=5–7 in each group.
Abbreviations: ARB, angiotensin receptor blocker; SGLT, sodium-glucose co-transporters; DM, diabetes mellitus.

Figure 3 Light microscopic immunostaining (A) and a Western blot analysis (B and C) for SGLT2.

Notes: SGLT2 staining was positive in the brush border membrane (marked with *) of the S1 (A) and S2 segments (B) of the proximal convoluted tubules, but not the S3 segment (C) of the proximal straight tubules, in the diabetic rats (upper panel). The SGLT2 expression in the S1 segment of the proximal convoluted tubules in the control rats (D) was enhanced strongly in the DM rats (E), while ARB therapy (F) reversed this increase to the control level (lower panel). The figures for the SGLT2 expression reflect data obtained under starvation conditions, while the results include some findings obtained under fed conditions (data not shown). The arrows indicate apical vesicles. The bar indicates 1 μm. N=3 in each group.
Abbreviations: ARB, angiotensin receptor blocker; SGLT, sodium-glucose co-transporters; DM, diabetes mellitus.

Figure 4 Expression of renal gluconeogenesis restriction enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase).

Notes: Light microscopic immunostaining (A) and Western blotting analysis for PEPCK (B) and G6Pase (C). The renal expression of PEPCK in the proximal tubules (stained in brown color, arrows) and distal tubules (asterisk) was increased in the DM rats compared with that observed in the control rats. ARB, telmisartan, treatment consequently suppressed the PEPCK expression. The renal expression of G6Pase was increased in the DM rats, whereas it was only faintly expressed in the control rats and diabetic rats treated with ARB. The figures for the PEPCK expression reflect data obtained under starvation conditions, while the results include some findings obtained under fed conditions (data not shown). The bar indicates 50 μm. *P<0.05, ^†P<0.01 versus control, ^‡P<0.05 versus DM. N=5–7 in each group.
Abbreviations: ARB, angiotensin receptor blocker; DM, diabetes mellitus.

Figure 5 Cytoplasmic glucose-6-phosphate (A and C) and glucose (B and D) levels in the kidney (A and B) and liver (C and D).

Notes: The renal cytoplasmic glucose-6-phosphate and glucose levels were significantly increased in the DM rats compared with those observed in the control rats. ARB treatment subsequently suppressed the renal cytoplasmic glucose levels. The hepatic glucose-6-phosphate and glucose concentrations after 24-hour starvation did not show significant change among the three groups. *P<0.05, ^†P<0.01 versus control, ^‡P<0.05 versus DM. N=5–7 in each group.
Abbreviations: ARB, angiotensin receptor blocker; DM, diabetes mellitus.

Figure 6 Hepatic gluconeogenesis and glycogen storage.

Notes: The hepatic PEPCK expression evaluated by immunostaining (A) and Western blotting (B) was significantly increased in the diabetic rat compared with that in the control rat. The glycogen concentrations in the liver (C) were significantly increased in the diabetic rats compared with that in the control rats. ARB treatment significantly restored the hepatic glycogen levels. The bar indicates 50 μm. *P<0.01 versus control, ^†P<0.05 versus DM. N=5–7 in each group.
Abbreviations: ARB, angiotensin receptor blocker; PEPCK, phosphoenolpyruvate carboxykinase; DM, diabetes mellitus.

Figure 7 Intravenous insulin tolerance test (ITT) (A) and the K index of ITT (B).

Notes: The plasma glucose levels were continuously elevated at 30 minutes after insulin-glucose injection in the diabetic rats (black square in A), whereas they returned to normal control level (triangle) in the diabetic rats treated with telmisartan (open circle). The K values of insulin tolerance tests were significantly lower in the DM rats (black bar) than in the control (white bar); this trend was reversed back to the control level by telmisartan treatment (hatched bar). *P<0.01 versus control, ^†P<0.01 versus DM. N=4 in each group.
Abbreviations: ARB, angiotensin receptor blocker; DM, diabetes mellitus.