Captopril potentiates the myocardial infarct size-limiting effect of ischemic preconditioning through bradykinin B2 receptor activation.

OBJECTIVES: To investigate the role of kinin in preconditioning against infarction, the present study assessed the effect of captopril, a kininase II inhibitor, on preconditioning and arterial plasma kinin levels. BACKGROUND: Recent studies suggest a possible contribution of kinin to preconditioning against infarction. However, its role and the site of kinin production remain uncharacterized. METHODS: Six groups of rabbits (n = 6 to 13) underwent 30-min coronary occlusion and 3-h reperfusion. The infarct size and area at risk were determined by tetrazolium staining and fluorescent particles, respectively. Arterial blood was sampled under baseline conditions, before the 30-min ischemia and after reperfusion for radioimmunoassay of the kinin level. RESULTS: Infarct size expressed as a percentage of area at risk (%IS/AR) was 42.9 +/- 2.9% (mean +/- SEM) in the control group, 34.5 +/- 3.3% in the group preconditioned with 2 min of ischemia/5 min of reperfusion and 41.7 +/- 5.1% in the group given captopril (1 mg/kg body weight) alone before the 30-min ischemia. These %IS/AR values were not significantly different between the three groups. However, a combination of captopril and subsequent preconditioning with 2 min of ischemia markedly limited %IS/AR to 21.2 +/- 2.4%. This potentiation of 2 min of preconditioning by captopril was not observed when 2 micrograms/kg body weight of Hoe 140, a specific bradykinin B2 receptor antagonist, was administered before preconditioning (%IS/AR = 41.2 +/- 5.7%), whereas Hoe 140 alone did not modify infarct size (%IS/AR = 38.5 +/- 5.1%). Arterial plasma kinin levels were comparable between the control rabbits, the group given captopril alone and the group that received captopril plus 2 min of preconditioning at baseline (3.8 +/- 1.0, 6.3 +/- 1.9 and 5.2 +/- 1.7 pg/ml, respectively), and there was no significant change in kinin levels after the captopril injection or the combination of captopril plus 2 min of preconditioning. CONCLUSIONS: The present results indicate that captopril is capable of potentiating preconditioning without increasing the arterial kinin level and that the beneficial effect of captopril can be inhibited by Hoe 140. These findings support the hypothesis that kinin produced locally in the heart during preconditioning may contribute to the cardioprotective mechanism through bradykinin receptor activation.

Gene structure of the P100 serine-protease component of the human Ra-reactive factor.

The Ra-reactive factor (RaRF) is a complement dependent anti-microbial factor that reacts with numerous microorganisms such as viruses, bacteria, fungi and protozoa. It is a complex of a mannan-binding lectin (MBL) and the serine protease, P100 (MASPI). P100 activates the C4 component of the complement system and its domain organization is similar to C1r and C1s. In this study, determination was made of the structure of the human P100 gene which was found longer than 67 kbp and to be comprised of 16 exons. Its non-protease region consisted of 10 exons, as in the case of C1r and C1s, and the introns were found present in the boundary separating two CUB domains, an EGF-like domain and two CCP domains and each CUB and CCP domain contained extra internal introns. The serine protease region was comprised of 6 exons in contrast to C1r and C1s, either of which consists of a single exon. The exon-intron structure was found to reflect the evolution of these molecules and P100 to have derived earlier in the stage of evolution than C1r or C1s.

Mechanisms of suppression of renal kallikrein activity in low renin essential hypertension and renoparenchymal hypertension.

The mechanism of suppression of renal kallikrein activity in low renin essential hypertensive and renoparenchymal hypertensive patients was investigated in this study. From Sephadex G-200 column chromatography studies, a single kallikrein peak was observed in both kallikrein radioimmunoassay and kininogenase activity in all samples from normal subjects, low renin essential hypertensive and renoparenchymal hypertensive patients, and in purified kallikrein solution. The enzyme-specific activity around the kallikrein peak in all urine samples from each group was significantly lower than that in purified kallikrein, and a significantly lower specific activity was found in both patient groups than was found in normal subjects. Moreover, it was also recognized that the specific activity of kallikrein decreased in all cases with the increase of the molecular weight of kallikrein, and this tendency was observed more obviously in the low renin essential hypertensive and renoparenchymal hypertensive patients than in the normal subjects. These results suggest the presence of a kallikrein-specific inhibitor with a low molecular weight in human urine, although the possibility of a variant form of kallikrein cannot be excluded.

The contribution of skeletal muscle tumor necrosis factor-alpha to insulin resistance and hypertension in fructose-fed rats.

OBJECTIVE: The aim of this study was to determine the role of tumor necrosis factor-alpha (TNF-alpha) in skeletal muscle tissue in insulin resistance and hypertension and the effect of anti-hypertensive medicine on skeletal muscle TNF-alpha in fructose-induced insulin-resistant and hypertensive rats (fructose-fed rats: FFR). DESIGN AND METHODS: Six-week-old male Sprague-Dawley rats were fed either normal rat chow or fructose-rich chow. For the last 2 weeks of a 6-week period of either diet, the rats were treated with a vehicle (control or FFR); temocapril, an angiotensin converting enzyme inhibitor (ACEI); or CS-866, an angiotensin II type 1 receptor blocker (ARB). The euglycemic hyperinsulinemic glucose clamp technique was performed to evaluate insulin sensitivity (M value). TNF-alpha levels in soleus and extensor digitorum longus (EDL) muscles and epididymal fat pads were measured. We also measured the TNF-alpha concentration in an incubated medium secreted from soleus muscle strips with or without angiotensin II. RESULTS: TNF-alpha levels were significantly higher in the soleus and EDL muscles, but not in the epididymal fat, in the FFRs compared with the control rats. Temocapril and CS-866 lowered systolic blood pressure, improved insulin resistance, and reduced TNF-alpha in both skeletal muscles. There were significant negative correlations between M values and TNF-alpha levels in both soleus and EDL muscles. Also, the soleus muscle strip incubation with 10(-7) mol/l angiotensin II increased TNF-alpha secreted into the incubation medium compared to the incubation without angiotensin II. These results suggest that skeletal muscle TNF-alpha is linked to insulin resistance and hypertension and that angiotensin II may be one of the factors that regulate skeletal muscle TNF-alpha.

Plasma calcitonin gene-related peptide levels in patients with various hypertensive diseases.

OBJECTIVE: To clarify the pathophysiological role of calcitonin gene-related peptide (CGRP) in hypertensive diseases. METHOD: Using a sensitive radioimmunoassay established in our laboratory, plasma CGRP levels were evaluated in control subjects and in patients with essential hypertension, phaeochromocytoma or primary aldosteronism. RESULTS: The CGRP levels in the three hypertensive groups were significantly higher than in normal controls, but no statistically significant difference was observed among CGRP levels in the three hypertensive groups. In the three cases of secondary hypertensives (one patient with phaeochromocytoma and two with primary aldosteronism), a significant decrease in plasma CGRP levels and a marked reduction in blood pressure were observed after adrenalectomy. CONCLUSION: These results suggest that increased plasma CGRP levels in hypertensive patients could be a compensatory reaction to elevated blood pressure.

Fenofibrate improves insulin sensitivity in connection with intramuscular lipid content, muscle fatty acid-binding protein, and beta-oxidation in skeletal muscle.

We investigated the effect of fenofibrate, a peroxisome proliferator-activated receptor-alpha agonist, on insulin sensitivity including lipid metabolism in skeletal muscle. Six-week-old male Sprague-Dawley rats were divided into two groups: those fed a standard chow (control) or a fructose-rich chow (fructose-fed rats (FFRs)) for 6 weeks. FFRs were treated either with a vehicle or with 30 mg/kg per day of fenofibrate for the last 2 weeks. Insulin sensitivity (M-value) was estimated by the euglycemic hyperinsulinemic glucose clamp method. Fatty acid-binding protein (FABP) in skeletal muscle was measured by ELISA, and the expression of FABP mRNA was analyzed by semi-quantitative RT-PCR. The serum and muscle triglyceride (sTG and mTG) levels and the activity of 3-hydroxyacyl-CoA dehydrogenase (HADH), a beta-oxidation enzyme, in muscle were also determined. FFRs showed a lower M-value and higher blood pressure, sTG and mTG than did the control group. The mTG was correlated positively with sTG and negatively with the M-value. Fenofibrate treatment for 2 weeks did not change blood pressure but significantly improved the M-value, sTG and mTG. FABP content and mRNA in the soleus muscle were significantly elevated in FFRs compared with those in the control group. Fenofibrate treatment further increased FABP. The HADH activity was comparable between the control group and FFRs, but significantly increased by fenofibrate treatment. These results suggest that fenofibrate improves insulin sensitivity not only by lowering serum lipids and subsequent influx of fatty acids into muscles but also by reducing intramuscular lipid content via further induction of FABP and stimulation of beta-oxidation in muscles.

Urinary kallikrein in Dahl-Iwai salt-sensitive and -resistant rats.

This study was designed to evaluate the differences between the renal kallikrein in newly established Dahl-Iwai rats under salt loading and that of Sprague-Dawley rats (SD). Urinary kallikrein quantity and activity was markedly lower in Dahl-Iwai rats than in SD even during the control period. Moreover, kallikrein quantity and activity in Dahl-Iwai salt-sensitive rats (SS) were clearly diminished in comparison with salt-resistant rats (SR). The kallikrein activity/ quantity ratio was also lower in SS and SR than in SD during the control period. After salt loading, systolic blood pressure increased only in SS. Kallikrein activity in SS and SR, and kallikrein quantity in SS were increased, whereas those in SD did not change. Although the kallikrein activity/quantity ratio in SR reached the same level in SD after salt loading, that in SS was lower throughout the experiment. These results suggest that Dahl-Iwai rats are less able hereditarily to produce renal kallikrein and that there may exist structurally abnormal kallikrein that may have a lower activity. Different kinetics of renal kallikrein between SS and SR by salt loading might be explained by kallikrein inhibitors or abnormal kallikrein or nonkallikrein kininogenase. These different kinetics of renal kallikrein may play some role on blood pressure elevation in SS.

Alteration of muscle fiber composition linking to insulin resistance and hypertension in fructose-fed rats.

The aim of this study was to examine the role of muscle fiber composition in insulin resistance and the effect of a calcium channel antagonist on insulin sensitivity in fructose-induced insulin resistant and hypertensive rats. Six-week-old male Sprague-Dawley rats were fed either normal rat chow (control) or fructose-rich diet (FFR). For the last 2 weeks of a 6-week period of either diet, the rats were treated, by gavage, with gum arabic solution (control or FFR) or a dihydropyridine calcium channel antagonist, benidipine hydrochloride (3 mg/kg/day: FFR + Ca), then the euglycemic hyperinsulinemic glucose clamp technique was performed to evaluate insulin sensitivity. Blood pressure was measured weekly for 6 weeks. At the end of the glucose clamp, the soleus muscle was dissected out for determination of muscle fiber composition by ATPase methods. Blood pressure was elevated at 2 weeks after the start of fructose-rich chow feeding and persisted thereafter throughout the study. Blood pressure at the glucose clamp in the FFR was significantly higher than that in the control group (142 +/- 2 v 155 +/- 2 mm Hg, P < .01) and the calcium antagonist significantly lowered blood pressure of FFR (136 +/- 6 mm Hg for FFR +/- Ca, P < .05). The average rate of glucose infusion during glucose clamp, as a measure of insulin sensitivity (M value), was significantly lower in the FFR than in the control (15.4 +/- 0.4 v 10.9 +/- 0.6 mg/kg/min, P < .01). The calcium channel antagonist partially improved the M value compared to that of FFR (13.4 +/- 0.7 mg/kg/min in FFR +/- Ca, P < .01 compared to FFR, P < .05 compared to control). The composite ratio of type I fiber in soleus muscle was significantly decreased in FFR compared to control (81.7 +/- 1.5% v 75.0 +/- 1.7%, P < .01), and the composite ratio of type I fiber in rats treated with the calcium channel antagonist (FFR +/- Ca) recovered to the control level (79.9 +/- 1.1%, P < .05 compared to FFR). The M value was significantly correlated with the compositions of type I and type II fibers (for type I fibers, r = 0.80, P < .01; for type II fibers, r = -0.81, P < .01). These results suggest that fiber composition of skeletal muscle links insulin resistance and that a calcium channel antagonist may modulate muscle fiber composition in hypertensive animal model, fructose-fed rats.

Effects of digoxin-specific antibody Fab fragment (Digibind) on blood pressure and renal water-sodium metabolism in 5/6 reduced renal mass hypertensive rats.

The importance of increased endogenous digitalis-like factor (EDLF) in volume-expanded hypertension has been generally agreed. To further clarify the role of EDLF on the development of hypertension and renal water-sodium handling in 5/6 reduced renal mass hypertensive rats (RRM), we studied the effects of acute administration of digoxin-specific antibody Fab fragment (Digibind) in the early phase and the chronic phase of hypertension in RRM. RRM and sham-operated rats were given 1% saline for 1 or 4 weeks. RRM were injected Digibind (60 mg/kg) or vehicle (0.9% saline) intravenously in the first or fourth week under thiobutabarbital anesthesia. All sham-operated rats were administered Digibind under the same condition. Digibind altered neither blood pressure, heart rate, urine volume, nor urinary sodium excretion in sham-operated rats. However, Digibind produced a gradual but significant decline in mean arterial pressure to the level slightly above that in sham-operated rats from 153 +/- 5 to 131 +/- 5 mm Hg in the first week and from 181 +/- 6 to 129 +/- 4 mm Hg in the fourth week without any significant change in heart rate. The decrease in mean arterial pressure at 160 min after Digibind administration in the fourth week (-48 +/- 5 mm Hg) was greater than that in the first week (-22 +/- 4 mm Hg). No differences were observed in urine volume, urinary sodium excretion, or plasma norepinephrine concentration between Digibind and vehicle-treated RRM in either week. These data suggest that EDLF would contribute to both the early and chronic phase in the development of hypertension in RRM.

Effects of the angiotensin converting enzyme inhibitor temocapril on insulin sensitivity and its effects on renal sodium handling and the pressor system in essential hypertensive patients.

The effects of the angiotensin converting enzyme (ACE) inhibitor temocapril on insulin sensitivity and its effects on renal sodium handling and the pressor system were investigated in essential hypertensive patients (EHT). Seven EHT were hospitalized and underwent a 2-h euglycemic hyperinsulinemic glucose clamp before and after 2 weeks' administration of temocapril (4 mg/day). Insulin sensitivity was calculated using the M value from the infusion rate of glucose with hyperinsulinemia using the glucose clamp method. Renal clearances of sodium, lithium, creatinine, and paraaminohippuric acid were used to calculate fractional proximal and distal tubular reabsorption of sodium (FPR(Na), FDR(Na)) and renal plasma flow (RPF) before and during insulin infusion by the glucose clamp method. Temocapril decreased blood pressure and increased M value significantly. Before temocapril treatment, hyperinsulinemia by the glucose clamp induced significant decreases of urinary excretion of sodium (U(Na) V) and fractional excretion of sodium (FENa). After treatment, these decreases were attenuated, and the change of U(Na) V (deltaU(Na) V) with hyperinsulinemia was significantly higher and deltaFENa showed a higher tendency, compared with before the treatment. FPR(Na) showed no change with hyperinsulinemia before treatment, but significantly decreased after treatment. DeltaFPR(Na) was significantly lower after treatment than that before treatment. FDR(Na) showed an increase with hyperinsulinemia, and deltaFDR(Na) was similar between before and after treatment. RPF showed no change with hyperinsulinemia, and no difference was found in deltaRPF between before and after treatment. Plasma norepinephrine level (PNE) and plasma renin activity (PRA) showed increases, whereas plasma aldosterone concentration (PAC) did not change with hyperinsulinemia. There were no significant differences in deltaPNE, deltaPRA, and deltaPAC between before and after treatment. From these results, it is suggested that in EHT 1) temocapril improves insulin resistance, and 2) although temocapril shows no significant influence on the augmentation of pressor systems by hyperinsulinemia, this agent attenuates the sodium-retaining action of hyperinsulinemia, which may be attributable to suppression of insulin-induced sodium reabsorption at the proximal tubules. These effects may lead to additional beneficial effects in the treatment of essential hypertensives with insulin resistance.

The transient increase of urinary digitalis-like substance excreted during excess sodium intake in reduced renal mass rats.

Urinary immunoreactive endogenous digitalis-like substance (EDLS) excretion was studied in gradually reduced renal mass rats (RRM). Urinary EDLS increased immediately after the start of 1% NaCl ingestion, then it returned to the basal level 2 weeks later. Both urinary sodium excretion and urinary EDLS were significantly higher in 3/6 and 4/6 RRM than in control until 2 weeks after starting 1% NaCl. However, there was no difference in blood pressure between the groups. Transient EDLS increase may play an important role in maintaining sodium and water homeostasis, but its transient increase apparently does not contribute to blood pressure elevation.

The effects of an angiotensin-converting enzyme inhibitor and an angiotensin II receptor antagonist on insulin resistance in fructose-fed rats.

The aim of this study was to compare the effects of an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II receptor (AT) antagonist on insulin resistance, especially on muscle fiber composition in fructose-induced insulin-resistant and hypertensive rats. Six-week-old male Sprague-Dawley rats were fed either normal rat chow (control) or a fructose-rich diet (FFR). For the last two weeks of a six-week period of either diet, the rats were treated with gum arabic solution as a vehicle (control or FFR), angiotensin-converting enzyme inhibitor (FFR+ACE), temocapril (1 mg/kg/ day) or an angiotensin II receptor antagonist (FFR+AT), CS-866 (0.3 mg/kg/day), by gavage, and then the euglycemic hyperinsulinemic glucose clamp technique was performed to evaluate insulin sensitivity. At the end of the glucose clamp, the soleus muscle was dissected for determination of the muscle fiber composition by ATPase methods. Blood pressure at the glucose clamp in the FFR group was significantly higher than that of the control group, and both temocapril and CS-866 significantly lowered the blood pressure of the FFR group. The average rate of glucose infusion during the glucose clamp, as a measure of insulin sensitivity (M value), was significantly lower in the FFR rats compared to the controls (15.4 +/- 0.4, 10.9 +/- 0.6 mg/kg/min, for control and FFR, respectively, P < .01). Both temocapril and CS-866 partially improved the M values compared to FFR (13.2 +/- 0.7, 12.8 +/- 0.5 mg/kg/min, for FFR+ACE, FFR+AT, respectively, P < .01 compared with FFR, P < .05 compared with control). The composite ratio of type I fibers of the soleus muscle was decreased significantly in the FFR rats compared with the controls (82% +/- 2%, 75% +/- 2%, for control and FFR, respectively, P < .01), and both temocapril and CS-866 restored a composite ratio of type I fibers to the same level as that of the controls (81% +/- 1%, 80% +/- 1% for FFR+ACE and FFR+AT, respectively). The M value was significantly correlated with the composition of type I and type II fibers. These results suggest that the fiber composition of skeletal muscle is correlated to insulin resistance, and that both ACE inhibitors and AT antagonists may modulate the muscle fiber composition in a hypertensive and insulin-resistant animal model, fructose-fed rats, to the same extent.

Effects of angiotensin receptor antagonist and angiotensin converting enzyme inhibitor on insulin sensitivity in fructose-fed hypertensive rats and essential hypertensives.

This study was designed to investigate the effects of angiotensin II (AII) receptor antagonist and angiotensin converting enzyme (ACE) inhibitor on insulin resistance, and the mechanism by which ACE inhibitor improves insulin-dependent glucose uptake (insulin sensitivity) in an insulin-resistant hypertensive rat model (fructose-fed rats, FFR) and in essential hypertensives (EHT). Male Sprague-Dawley rats were fed on fructose-rich or standard chow for 4 weeks and treated either with 10 mg/kg/day of delapril (n = 8), 1 mg/kg/day of TCV-116 (AII receptor antagonist; n = 13), or vehicle (n = 9) for the latter 2 weeks. Steady-state plasma glucose (SSPG) was measured with the subjects in the conscious state; simultaneously, we infused insulin (2.5 mU/kg/min) and glucose (8 mg/kg/min) to determine insulin sensitivity in each group. Thirteen EHT were hospitalized and the 2-h euglycemic hyperinsulinemic glucose clamp (GC) method was performed in a fasting condition before and after 2 weeks' administration of TCV-116 (8 mg/day) in 7 EHT and of delapril (120 mg/day) in 6 EHT. Insulin sensitivity was evaluated as M-value calculated from the infusion rate of glucose. Mean blood pressure (MBP) was higher in FFR (137.7 +/- 73.8 mm Hg, P < .05) compared to controls (120.8 +/- 2.7 mm Hg), and was lower in both the delapril (108.1 +/- 6.3 mm Hg, P < .05) and TCV-116 (112.8 +/- 4.3 mm Hg, P < .05) groups than in FFR.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of aging on the insulin actions for the glucose metabolism and renal function in normotensives and essential hypertensives.

It has been suggested that hyperinsulinemia compensating insulin resistance in glucose metabolism may be a pathogenic factor in essential hypertension. On the other hand, age-associated increases in the prevalence of glucose intolerance and hypertension are also well established. The aim of this study is to clarify the influence of aging on insulin sensitivity in glucose metabolism and on renal sodium handling under hyperinsulinemia, which may relate to high blood pressure in insulin-resistant subjects. Fifty-two normotensive subjects and 61 patients with essential hypertension were evaluated in this study. The subjects of these groups were divided into young (<40 years old) and middle-elderly (> or = 40 years old): young normotensives (Y-NT, n = 22); middle-elderly normotensives (ME- NT, n = 30); young hypertensives (Y-HT, n = 9); and middle-elderly hypertensives (ME-HT, n = 52). Using the euglycemic hyperinsulinemic glucose clamp, insulin sensitivity was assessed as M value. Just before the start and the termination of the glucose clamp, creatinine clearance (Ccr) and urinary excretion of sodium (UNaV) were measured. In addition, renal plasma flow assessed as para-aminohippuric acid clearance was also measured at the same time in several subjects; 8 Y-NT, 8 ME-NT, 3 Y-HT, and 10 ME-HT. The M value was significantly lower in ME-NT, Y-HT, and ME-HT, compared to Y-NT, although blood sugar and immunoreactive insulin levels were similar in all four groups. In normotensive subjects, there was a significant, negative correlation between age and M value. However, this correlation was not observed in hypertensive patients. UNaV decreased in ME-NT, Y-HT, and ME-HT, but not in Y-NT under hyperinsulinemia by the glucose clamp, whereas Ccr showed no significant change in any group. In all subjects, the change of UNaV (deltaUNaV) correlated significantly and positively with the M value. Renal plasma flow significantly increased under hyperinsulinemia by the glucose clamp in only Y-HT, but not in the other groups. There was a significant, positive correlation between deltaUNaV and the change of renal plasma flow under hyperinsulinemia by the glucose clamp. These results suggested that both the impairments of the insulin sensitivity and insulin-induced vasodilation at the renal artery with aging may partially contribute to age-related elevation of blood pressure through renal sodium retention by compensating hyperinsulinemia. On the other hand, it seems reasonable to assume that these abnormalities, which can contribute to high blood pressure in essential hypertension, already may exist at lower ages in essential hypertensive patients.

The role of renal natriuretic depressor systems on hypertensive mechanisms in reduced renal mass hypertensive rats.

The pathophysiological role of renal natriuretic depressor systems and endogenous digitalis like factor (EDLF) on blood pressure (BP) elevation was studied in reduced renal mass rats (RRM) with saline loading for a model of volume dependent hypertension. Fifty-four male Sprague-Dawley rats were operated on to remove varying proportions of their kidney mass (5/6 RRM, n = 13; 4/6 RRM, n = 16; 3/6 RRM, n = 12) or sham operated (control, n = 13). They were given 1% saline to drink for 4 weeks. BP was elevated significantly at the 1st week in 5/6 RRM and continued to increase until the 4th week, but this was not seen in the other 3 groups. Urine volume (UV) and urinary sodium excretion (UNaV) increased after saline loading in all groups. Urinary kallikrein excretion was significantly lower in order of the 5/6, 4/6 and 3/6 RRM at the basal state and after saline loading. A significant negative correlation was observed between urinary kallikrein and BP. Urinary PGE2 was increased in each RRM in order of the 5/6, 4/6 and 3/6 RRM groups. A significant positive correlation was observed between urinary PGE2 and BP, UV or UNaV. The basal urinary DA excretion was significantly lower in 3 RRMs than in the control. After saline drinking, urinary DA increased in 3 RRMs, while differences disappeared in the control and RRMs. Urinary EDLF increased immediately after the initiation of saline loading in all groups, except the control group, and returned to the basal level 2 weeks later in 3/6 and 4/6 RRM. Only in 5/6 RRM, the urinary EDLF remained higher than the basal level.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the Chinese medicine, TSJN on insulin resistance and hypertension in fructose-fed rats.

The aim of this study was to determine the effect of Tang-Shen-Jiao-Nang (TSJN), a Chinese medicine used to treat diabetes mellitus, on insulin resistance and hypertension in fructose-fed rats (FFR). Six-week-old male Sprague-Dawley rats were fed either normal rat chow (control) or a fructose-rich chow (FFR) for 6 wk. For the last 2 or 4 wk of a 6-wk period of either diet, the rats were treated by gavage with gum arabic solution as a vehicle (control or FFR) or TSJN (800 mg/kg/d; FFR+TS), and then we performed the euglycemic hyperinsulinemic glucose clamp technique to estimate insulin sensitivity. Systolic blood pressure was measured weekly for 6 wk. At the end of the glucose clamp, the soleus muscle was dissected out for determination of muscle fiber composition by ATPase methods. Systolic blood pressure was elevated at 2 wk after the start of the fructose-rich chow feeding and persisted thereafter throughout the study. Systolic blood pressure during the glucose clamp in the FFR group was significantly higher than that in the control group. Although there was no effect on systolic blood pressure in rats treated with TSJN for the last 2 wk of their 6-wk diet, those treated with TSJN for the last 4 wk of their 6-wk diet had lower systolic blood pressure than did the rats in the FFR group. The average rate of glucose infusion during the glucose clamp, as a measure of insulin sensitivity (M value), was significantly lower in the FFR than in the controls (10.9 +/- 0.6 and 15.4 +/- 0.4, mg/kg/min, for FFR and controls, respectively; p< 0.01). Treatment with TSJN for 2 wk significantly improved the M value compared to that of the control level (15.1 +/- 0.5 mg/kg/min). The composite ratio of type I fibers in the soleus muscle was significantly decreased in the FFR compared to controls (75.0 +/- 1.7 and 81.7 +/- 1.5%, for FFR and controls, respectively; p< 0.01), and treatment with TSJN for 2 wk led to a recovery composite ratio of type I fiber to the same level as that of the control group (78.7 +/- 1.7% in FFR + TS). The M value was significantly correlated with the compositions of type I and type II fibers (for type I fibers, r= 0.45, p < 0.01, for type II fibers, r= -0.44, p< 0.05). These results suggest that the Chinese medicine TSJN may improve insulin resistance, lower the systolic blood pressure, and modulate muscle fiber composition in hypertensive and insulin-resistant fructose-fed rats.

Effects of cilnidipine on muscle fiber composition, capillary density and muscle blood flow in fructose-fed rats.

The aim of this study was to examine the roles of muscle fiber composition, capillary density and muscle blood flow in insulin resistance (IR) and the effect of cilnidipine, a calcium channel blocker in fructose-fed rats (FFR). Six-week-old male Sprague-Dawley rats were fed either normal rat chow or fructose-rich chow for 6 weeks. For the last 2 weeks, the rats were treated by gavage with a vehicle (Control and FFR groups) or with cilnidipine (FFR+Cil group). Blood pressure (BP) and insulin sensitivity were assessed in the sixth week. Muscle fiber composition, capillary density and blood flow in the soleus muscle were evaluated. BP of FFR was significantly higher than that of the controls. Cilnidipine significantly lowered BP in FFR. Insulin sensitivity was significantly lower in FFR than in the controls. Cilnidipine significantly improved IR in FFR. The composite ratio of type I fibers in the soleus muscle was significantly lower in FFR than in the controls, but that of type II fibers was significantly higher in FFR. Treatment with cilnidipine resulted in recovery of this ratio to that of the controls. Insulin sensitivity was found to be significantly correlated with the composite ratio of either type I fibers or type II fibers. There were no intergroup differences in capillary density. Muscle blood flow in the FFR+Cil group was higher than that in the Control or FFR groups. These results suggest that muscle fiber composition is linked to IR and that cilnidipine may improve IR in FFR either by modulating muscle fiber composition or by increasing muscle blood flow.

Effects of the Chinese medicine Jiang-Tang-Ke-Li on insulin resistance in fructose-fed rats.

The aim of this study was to determine the effect of Jiang-Tang-Ke-Li (JTKL), a Chinese medicine used to treat diabetes mellitus, on insulin resistance and hypertension in fructose-fed rats (FFR). Six-week-old male Sprague-Dawley rats were fed either normal rat chow (control) or a fructose-rich chow (FFR) for 6 weeks. For the last 2 weeks of the 6-week period of either diet, the rats were treated by gavage with gum arabic solution as a vehicle (control or FFR) or JTKL (3.24 g/kg/day; FFR+JT), and then an euglycemic hyperinsulinemic glucose clamp technique was performed to estimate insulin sensitivity. Systolic blood pressure was measured each week of the 6-week period. At the end of the glucose clamp, the soleus and extensor digitorum longus (EDL) muscles were dissected out for determination of the role of tumor necrosis factor (TNF)-alpha by an ELISA assay. Systolic blood pressures in the FFR groups were significantly higher than that in the control group, although there was no effect on systolic blood pressure for the last 2 weeks of treatment with JTKL. The average rate of glucose infusion during the glucose clamp, as an index of insulin sensitivity (M value), was significantly lower in the FFR than in the control rats, and treatment with JTKL for 2 weeks significantly increased the M value to that of control. TNF-alpha levels were significantly higher in the soleus and EDL muscles of the FFR (480+/-46 and 570+/-45 pg/g wet tissue in the soleus and EDL muscles, respectively) than in those of the control rats (177+/-34 and 206+/-33 pg/g wet tissue in the soleus and EDL muscles, respectively; p<0.01). Treatment with JTKL for 2 weeks significantly lowered TNF-alpha levels to the control levels (189+/-22 and 239+/-92 pg/g wet tissue in the soleus and EDL muscles, respectively). The results suggest that the Chinese medicine JTKL improves insulin resistance and modulates TNF-alpha in the soleus and EDL muscles in hypertensive and insulin-resistant fructose-fed rats.

Association of insulin resistance and hyperinsulinemia with disturbed lipid metabolism in patients with essential hypertension.

To clarify the association of insulin resistance and hyperinsulinemia with lipid metabolism in patients with essential hypertension (EHT), we used the euglycemic hyperinsulinemic glucose clamp technique (GC) and the 75-g oral glucose tolerance test (OGTT) to compare the characteristics of glucose and lipid metabolism in insulin-resistant patients with essential hypertension (EHT-R) with those in insulin-non-resistant patients with essential hypertension (EHT-N) and normotensive subjects (NT). Twenty-eight NT and 42 EHT whose body mass index (BMI) was less than 28 kg/m2 were studied to eliminate the effects of obesity on insulin sensitivity and lipid metabolism. Insulin sensitivity was evaluated by GC and expressed as metabolic clearance rate of glucose (M value, mg/m2/min). Mean -ISD of the M value in NT (145.0 mg/m2/min) was chosen as the cutoff point for insulin resistance. On the basis of this value, 33.3% of the EHT were EHT-R. There was no significant difference in age or BMI among the three groups. Blood samples were collected before GC to measure levels of total cholesterol (TC), triglyceride (TG), free fatty acid (FFA), and HDL cholesterol (HDL-C). EHT-R had significantly higher levels of fasting blood sugar, fasting immunoreactive insulin, insulin at 120 min (IRI-120), and summation of insulin or blood sugar (BS) during the OGTT, as compared with NT and EHT-N. EHT-R also had significantly higher FFA and TG than the other two groups, while there was no difference in FFA or TG between EHT-N and NT. TC and HDL-C were similar in the three groups. There was either a significant negative correlation, or a trend toward negative correlation, between M value and FFA (r= -0.50, p < 0.05) or TG (r= -0.24, p < 0.1). There were significant positive correlations between IRI-120 and FFA (r=0.35, p< 0.05) or TG (r=0.29, p< 0.05). There was a positive correlation (r= -0.36, p< 0.01) between sigma BS and FFA, while no other significant relation was found between sigma BS and serum lipids. In summary, (i) 33.3% of EHT were found to be insulin resistant, when insulin resistance was defined as M value < 145.0 mg/m2/min, i.e., mean -ISD of the M value of NT; (ii) these EHT-R had higher levels of BS, insulin, FFA, and TG than did NT and EHT-N; (iii) EHT-N showed no difference in the levels of BS, insulin, or lipid, as compared with NT; and (iv) the levels of FFA and of TG correlated negatively with insulin sensitivity and positively with the insulin level during the OGTT. These results suggest that disturbances of glucose and lipid metabolism in EHT may be related to both insulin resistance and compensatory hyperinsulinemia, and that EHT-R may have more risk factors for arteriosclerotic complications than EHT-N.

Endogenous immunoreactive ouabain-like and digoxin-like factors in reduced renal mass hypertensive rats.

We evaluated the urinary excretion of immunoreactive endogenous ouabain-like factor (OLF) and digoxin-like factor (DLF) to investigate their pathophysiological roles in sodium metabolism and blood pressure in 5/6-reduced renal mass rats, a model of volume-expanded hypertension. About five-sixths of the kidney mass (5/6 RRM, n = 9) was removed from male Sprague-Dawley rats, or the rats were sham operated (control, n = 10). Both groups were fed regular diets with tap water for 1 wk as a control period, followed by 1% saline solution for 4 wk. Systolic blood pressure (SBP), urine volume (UV), urinary sodium excretion (UNaV), DLF, and OLF were measured on the last 2 d of every week throughout the experimental period. SBP and UNaV were significantly higher in 5/6 RRM rats than in control rats. Urinary DLF significantly increased, reaching peak value in the first week, while OLF increased continuously, reaching peak value in the fourth week. In the first week, there were a significant positive correlations between the change in DLF and the changes in UNaV and SBP. However, the change in OLF was not correlated with changes in either UNaV or SBP. Both SBP and UNaV showed a significant positive correlation with OLF (p<0.001, r=0.547, p<0.001, r=0.658, respectively), whereas DLF significantly correlated with UNaV (p< 0.001, r= 0.584) but not with SBP in 5/6 RRM. These findings suggest that endogenous OLF and DLF coexist in rat urine and that an increased level of OLF, but not DLF, may contribute to the development and maintenance of hypertension. DLF may contribute to renal sodium excretion in this volume-expanded hypertensive rat model.