Effects of rosiglitazone on aortic function in rats with insulin resistant-hypertension

Acta Physiologica Sinica, April 25, 2005, 57 (2):125-131 http://www.actaps.com.cn 125 1 2 1 1 1 1,* 1 ; 2 421001 : (rosiglitazone, ROSI) (insulin resistant-hypertensive rats, IRHR) Sprague-Dawley 8 IRHR (L-phenylephrine, PE) (KCl) (acetylcholine, ACh) (sodium nitroprusside, SNP) (nitric oxide synthase, NOS) N- -L- (N ω -nitro-l-arginine methyl ester, L-NAME) 30 min ACh (nitric oxide, NO) (1) IRHR (2) PE KCl ACh ROSI (3) L-NAME ACh ROSI (4) SNP (5) ROSI (6) NO ROSI NO ROSI IRHR NOS NO : ; ; ; ; : Q463 Effects of rosiglitazone on aortic function in rats with insulin resistant-hypertension LING Hong-Yan 1, FENG Shui-Dong 2, ZHOU Shou-Hong 1, WANG Bing-Xiang 1, LIU Xian-Qing 1, HU Bi 1,* 1 Department of Physiology; 2 Department of Epidemiology, Nanhua University, Hengyang 421001, China Abstract: Rosiglitazone (ROSI), thiazolidione peroxisome proliferator-activated receptor-γ (PPAR-γ) activator, reduces insulin resistance in patients with type 2 diabetes (T2DM). It also improves vascular reactivity in T2DM patients and some animal models by unclear mechanisms. In order to investigate the effect of ROSI on aortic systolic and diastolic function of insulin resistant-hypertensive rats (IRHR) and the underlying mechanism, male Sprague-Dawley (SD) rats were fed with high fructose (HF) for 8 weeks to induce IRHR model. To verify IRHR model, systolic blood pressure (SBP), fasting blood sugar (FBS), fasting serum insulin (FSI) were measured respectively in each group, and insulin sensitive index (ISI) was also calculated. Subsequently, the vascular function test was performed. The thoracic aortic ring of SD rats was mounted on a bath system. The effect of rosiglitazone on the contraction elicited by L-phenylephrine (PE) and potassium chloride (KCl) and the relaxation induced by acetylcholine (ACh) and sodium nitroprusside (SNP) were measured. To explore the mechanism, nitric oxide synthase (NOS) inhibitor N -nitro-l-arginine methyl ester (L-NAME) was used and serum nitric oxide (NO) was measured. The results obtained were as follows: (1) Rosiglitazone reduced the level of SBP, serum insulin and improved insulin resistance in IRHRs. (2) The contractive responses of thoracic aortic rings to PE and KCl were enhanced and the relaxation response to ACh was depressed significantly in the HF group, and the effect was reversed by ROSI. (3) After pretreatment with L-NAME, the relaxation response to ACh was further impaired in the HF group, this effect was partly reversed by ROSI. (4) Sodium nitroprusside (SNP)-induced vasodilator responses did not differ significantly among the groups. (5) Aortic systolic and diastolic function of the control group was not affected markedly by ROSI. (6) Compared with the control group, Received 2004-07-29 Accepted 2004-12-20 This work was supported by the Natural Science Foundation of Hunan Province (No. 01JJY2147). * Corresponding author. Tel: +86-734-8282753; E-mail: linghongyan0203@126.com

126 Acta Physiologica Sinica, April 25, 2005, 57(2):125-131 serum nitric oxide was significantly reduced in the HF group, but after rosiglitazone treatment it was remarkably increased. These findings suggest that ROSI can improve aortic diastolic function of insulin resistant-hypertensive rats the mechanism of this effect might be associated with an increase in nitric oxide mediated partly by NOS pathway, a decrease in the level of blood pressure, serum insulin and the improvement of insulin resistance. Key words: rosiglitazone maleate; insulin resistance; hypertension; aorta, thoracic; nitric oxide synthase (rosiglitazone, ROSI) (insulin resistance, IR) ROSI IR C- [1,2] ; ROSI ( NO C ) [3,4] DOCA-salt [5,6] ROSI ROSI Sprague- Dawley (SD) SD [7] ROSI SD ROSI SD 1 1.1 D- KCl PE ACh SNP L-NAME Sigma NO BL310 Hitach 717 γ HX-1 ECG-6511 Kohden 1.2 (IRHR) SD 76 (200 20) g ( 4~5 ) (22 2) 12 h/24 h 1 SD (C n=38): 4 (HF n=38): ( 60% 11% 29% Reaven GM [8] ) 4 4 (C n =19): 4 (C+R n =19): ( 5 mg/kg d 1 ) 4 (HF n=19): 4 + (HF+R n=19): 4 1.3 NO 1.3.1 8 12 38 10 min - ( ) (systolic blood pressure SBP) 1.3.2 Hitach 717 (fasting blood sugar FBS) (fasting serum insulin FSI) [9] (insulin sensitive index, ISI) ISI 4.88 1.3.3 NO NO 550 nm 0.5 cm NO 1.4 (7 / ) 1% (30 mg/kg) 95% O 2 5% CO 2 K-H (mmol/l : NaCl 118.3 KCl 4.7 CaCl 2 2.5 MgSO. 4 7H2 O 1.2 KH 2 PO 4 1.2 NaHCO 3 25 glucose 11.1)

: 3~4 mm 1.5 15 ml 95% O 2 5% CO 2 K-H (37 ) BL310 1.0 g 90 min 15 min K- H KCl (100 mmol/l) (1) PE(1 10 6 mol/l) ACh (3 10 9 ~1 10 6 mol/l) SNP (1 10 11 ~1 10 6 mol/l) (2) PE (1 10 9 ~1 10 5 mol/l) KCl (20~120 mmol/l) (3) L-NAME (1 10 5 mol/l) 30 min ACh 127 K-H 3~5 PE (1 10 6 mol/ L) KCl (100 mmol/l) (IC 50 ) log (PD 2 ) 1.6 mean SD (ANOVA-oneway) q P<0.05 2 2.1 SBP FBS FSI NO 1 SBP FSI ISI (P<0.01) NO (P< 1. SBP FBS FSI NO Table 1. Effect of rosiglitazone on SBP, FBS, FSI, NO in SD rats Index C C+R HF HF+R SBP (mm Hg) 120.24±4.38 120.59±2.96 156.30±5.02 ** 125.20±4.81 ++ FBS (mmol/l) 5.36±0.55 5.39±0.64 5.62±0.43 5.41±0.42 FSI (mu/l) 17.62±3.50 17.01±3.93 34.82±4.92 ** 19.51±4.46 ++ ISI[ ln(fbs FSI)] 4.55±0.38 4.52±0.31 5.28±0.36 ** 4.66±0.29 ++ NO (µmol/l) 40.67±3.69 41.09±3.17 36.25±2.41 ** 39.01±3.02 + n=12 n=12 n=12 n=12 mean SD. ** P <0.01 vs control group; + P <0.05, ++ P <0.01 vs HF group. HF, high fructose. 1. SD 1 10 6 mol/l PE (A) 100 mmol/l KCl (B) Fig. 1. Rosiglitazone reversed contractive responses to PE (1 10 6 mol/l, A) and KCl (100 mmol/l, B) in thoracic artery rings from high fructose-induced SD rats. mean SD, n =7. ** P <0.01 vs control group, ++ P <0.01 vs HF group.

128 Acta Physiologica Sinica, April 25, 2005, 57(2):125-131 2. SD 1 10 9 ~1 10 5 mol/l PE(A) 20~120 mmol/l KCl (B) Fig. 2. Rosiglitazone reversed high fructose-induced increase in contractive responses to cumulative doses of PE (A) and KCl (B) in thoracic aortic rings from SD rats. mean SD, n=7. * P <0.05, ** P <0.01 vs control group; ++ P <0.01 vs HF group. 3. SD ACh Fig. 3. Rosiglitazone reversed high fructose-induced decrease in endothelium-dependent relaxation responses to ACh (1 10 6 mol/l, A) and cumulative doses of ACh (3 10 9 ~1 10 6 mol/l, B) in thoracic aortic rings from SD rats. mean SD, n =7. ** P <0.01 vs control group; ++ P<0.01 vs HF group. 0.01) FBS ( 5.62 0.43 5.36 0.55 P > 0.05); + SBP FSI ISI (P < 0.01) NO (P < 0.05); 2.2 IRHR 2.2.1 IRHR PE KCl PE KCl 100 mmol/l KCl (61.33 3.12)% (110.64 4.15)% [ (51.61 2.82)% (100 2.94)% P<0.01] PD 2 ( 6.49 0.25.67 0.02 6.92 0.30 1.63 0.02 P< 0.05); PE KCl 100 mmol/l KCl (54.68 2.71)% (103.23 4.56)% (P < 0.01)

: PD 2 ( 6.58 0.23 1.66 0.01) (P <0.05); PD 2 ( 6.44 0.29 1.67 0.03) ( 1 2) 2.2.2 IRHR ACh SNP ACh PE (1 10 6 mol/l) (57.63 5.45)% [(80.19 4.82)% P<0.01] PD 2 ( 7.21 0.31 129 6.60 0.25 P<0.01); + ACh [(76.48 5.12)%] (P<0.01) PD 2 (6.99 0.27) (P<0.01); PD 2 (7.20 0.36) ( 3) SNP PD 2 + 8.66 0.41 8.76 0.33 8.78 0.44 8.75 0.42( P < 0.05)( 4) 4. SD SNP Fig. 4. Effects of rosiglitazone on relaxation responses to SNP (1 10 6 mol/l, A) and cumulative doses of SNP (1 10 11 ~1 10 6 mol/l, B) in thoracic artery rings from SD rats. mean SD, n =7. 5. L-NAME (1 10 5 mmol/l) SD ACh Fig. 5. After pretreatment with L-NAME, rosiglitazone improved high fructose-induce decrease in endothelium-dependent relaxation responses to ACh (1 10 6 mol/l, A) and cumulative doses of ACh (3 10 9 ~1 10 6 mol/l, B) in thoracic aortic rings from SD rats. mean SD, n =7. * P<0.05, ** P <0.01. P <0.01 vs control group; + P<0.05, ++ P <0.01 vs HF group.

130 2.2.3 L-NAME(1 10 5 mmol/l) IRHR ACh L-NAME (1 10 5 mmol/l) ACh ACh [(26.75 3.16)%] [(55.43 4.07)% P<0.01] PD 2 ( 6.30 0.29 4.01 0.35 P<0.01]; + ACh [(76.48 5.12)%] (P < 0.01) PD 2 (5.12 0.40) (P<0.01); PD 2 (6.18 0.37) ( 5) 3 IR IR IR IR IR [10,11] PPARγ PPARγ X [12,13] [5,14] PPARγ [15,16] NO NO VSMC [17] NO [18] ACh NO ACh - Acta Physiologica Sinica, April 25, 2005, 57(2):125-131 NO NO NOS L- NO [19] NOS L-NAME ACh IRHR ACh NOS IRHR NO Eto [20] Ca 2+ K + Ca 2+ IR NO SNP ACh PE KCl PE KCl Ca 2+ [21] PE α1 Ca 2+ KCl Ca 2+ Ca 2+ Ca 2+ Ca 2+ Ca 2+ NO IRHR IRHR ROSI IRHR NOS NO ( K + Ca 2+ )

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