Comparison of SGLT2 inhibitors vs. DPP4 inhibitors for patients with metabolic dysfunction associated fatty liver disease and diabetes mellitus.

PURPOSE: This study aimed to examine the potential benefit of sodium-glucose cotransporter 2 (SGLT2) inhibitors for patients with metabolic dysfunction-associated fatty liver disease (MAFLD) and diabetes mellitus (DM) using a real-world database. METHODS: We analyzed individuals with MAFLD and DM newly initiated on SGLT2 or dipeptidyl peptidase 4 (DPP4) inhibitors from a large-scale administrative claims database. The primary outcome was the change in the fatty liver index (FLI) assessed using a linear mixed-effects model from the initiation of SGLT2 or DPP4 inhibitors. A propensity score-matching algorithm was used to compare the change in FLI among SGLT2 and DPP4 inhibitors. RESULTS: After propensity score matching, 6547 well-balanced pairs of SGLT2 and 6547 DPP4 inhibitor users were created. SGLT2 inhibitor use was associated with a greater decline in FLI than DPP4 inhibitor use (difference at 1-year measurement, - 3.8 [95% CI - 4.7 to - 3.0]). The advantage of SGLT2 inhibitor use over DPP4 inhibitor use for improvement in FLI was consistent across subgroups. The relationship between SGLT2 inhibitors and amelioration of FLI was comparable between individual SGLT2 inhibitors. CONCLUSIONS: Our analysis using large-scale real-world data demonstrated the potential advantage of SGLT2 inhibitors over DPP4 inhibitors in patients with MAFLD and DM.

Inhibition of intestinal cholesterol absorption might explain cholesterol-lowering effect of telmisartan.

WHAT IS KNOWN AND OBJECTIVE: Telmisartan, an angiotensin II type 1 receptor blocker (ARB), acts as a partial agonist for peroxisome proliferator-activated receptor-γ, and thus improves abnormalities of glucose metabolism and hypertriglyceridaemia in addition to its documented blood pressure-lowering effects. Recently, it has been demonstrated that telmisartan also lowers the levels of total cholesterol and low-density lipoprotein (LDL) cholesterol levels. This study was designed to investigate the mechanism of cholesterol reduction. METHODS: We measured serum levels of cholestanol, a cholesterol absorption marker, and lathosterol, a cholesterol synthesis marker, in 20 patients with both hypercholesterolaemia and hypertension. Ten patients were treated with telmisartan and the remaining 10 with fluvastatin. RESULTS: After 3 months of treatment, total and LDL cholesterol levels decreased in the telmisartan group (P<0.01 for both total and LDL cholesterol levels) and the fluvastatin group (P<0.001 for both total and LDL cholesterol levels). The change in cholestanol level after 3 months of treatment was positively correlated with the levels of total (R=0.72, P<0.05) and LDL cholesterol (R=0.81, P<0.01) in the telmisartan group. The change in lathosterol level was positively correlated with the levels of total (R=0.88, P=0.001) and LDL cholesterol (R=0.89, P=0.001) in the fluvastatin group. WHAT IS NEW AND CONCLUSIONS: Our results suggest that the cholesterol-lowering effect of telmisartan might be caused by inhibition of cholesterol absorption, whereas that of statins is by inhibition of cholesterol synthesis. If confirmed, co-treatment with the two agents may be useful for synergistically lowering cholesterol in hypertensive patients.

Anti-inflammatory properties of cytochrome P450 epoxygenase-derived eicosanoids.

The epoxyeicosatrienoic acids (EETs) are products of cytochrome P450 epoxygenases that have vasodilatory properties similar to that of endothelium-derived hyperpolarizing factor. The cytochrome P450 isoform CYP2J2 was cloned and identified as a potential source of EETs in human endothelial cells. Physiological concentrations of EETs or overexpression of CYP2J2 decreased cytokine-induced endothelial cell adhesion molecule expression, and EETs prevented leukocyte adhesion to the vascular wall by a mechanism involving inhibition of transcription factor NF-kappaB and IkappaB kinase. The inhibitory effects of EETs were independent of their membrane-hyperpolarizing effects, suggesting that these molecules play an important nonvasodilatory role in vascular inflammation.

Additional renoprotective effects of azelnidipine combined with angiotensin receptor blockers in patients with diabetic nephropathy.

Azelnidipine has been reported to have antioxidant effects and attenuates tubulointerstitial ischemia. The aim of the present study was to determine whether azelnidipine exerts additional renoprotective effects to angiotensin II receptor blockers (ARBs) in hypertensive patients with diabetic nephropathy and microalbuminuria. 45 hypertensive patients with diabetes mellitus and microalbuminuria who were already being treated with ARBs were enrolled in this study. Azelnidipine was added to the drug treatment of 30 patients (8 mg/day, n = 15, or 16 mg/day, n = 15) whilst the remaining 15 control patients were not treated with azelnidipine. In all patients, urinary 8-hydroxydeoxyguanosine (8-OHdG) levels and urinary liver-type fatty acid-binding protein (L-FABP) levels were significantly correlated (r = 0.587, p = 0.0006). However, urinary albumin excretion (UAE) was not correlated with the levels of urinary 8-OHdG (r = 0.1975, p = 0.2956) or urinary L-FABP (r = 0.2057, p = 0.2759). Azelnidipine significantly reduced UAE, urinary 8-OHdG and urinary L-FABP after 6 (p < 0.05) and 12 months (p < 0.05). Although blood pressure was comparable between the azelnidipine doses of 8 and 16 mg/day, the UAE (p < 0.05 after 12 months), urinary 8-OHdG (p < 0.05 after 6 and 12 months) and urinary L-FABP (p < 0.05 after 6 and 12 months) levels were more significantly reduced in patients receiving the higher dose of 16 mg/day. These data may suggest that the addition of azelnidipine treatment to therapy with ARBs has dose-dependent antioxidant and renoprotective effects beyond blood pressure-lowering effects in hypertensive diabetic nephropathy patients.

Reversible primary hypothyroidism in Japanese patients undergoing maintenance hemodialysis.

BACKGROUND/METHODS: The presence or absence of hypothyroidism was assessed in 152 consecutive Japanese patients with end-stage renal disease on hemodialysis. Eight patients who had undergone treatment for thyroid disease before starting hemodialysis therapy, and 3 patients with amyloidosis due to rheumatoid arthritis were excluded. RESULTS: Of the remaining 141 hemodialysis patients, 14 (9.9%) (9 males and 5 females, aged 69.1 A+/- 8.8 years with a mean duration of hemodialysis of 69 A+/- 51 months) were in a hypothyroid state, defined as a thyroid-stimulating hormone (TSH) level > 5 mU/l. Antithyroid peroxidase antibodies were positive in only 1 of the 14 patients, while antithyroglobulin antibodies were negative in all of these patients. After iodide restriction, the serum TSH level decreased in all the patients from a mean of 16.49 A+/- 22.80 to 4.44 A+/- 3.35 mU/l after 1 month, 4.25 A+/- 2.24 mU/l after 2 months and 3.97 A+/- 2.22 mU/l after 3 months. The 3 months of iodide restriction were also associated with decreases in systolic blood pressure (142 A+/- 19 to 125 A+/- 16 mmHg, p < 0.05), diastolic blood pressure (79 A+/- 13 to 72 A+/- 9 mmHg, p < 0.05) and thyroid gland volume estimated by ultrasonography (13.7 A+/- 6.3 to 11.6 A+/- 5.2 ml, p < 0.05). CONCLUSION: A high prevalence of reversible primary hypothyroidism was found in end-stage renal disease patients on hemodialysis. Retention of excess iodide may be the mechanism responsible for reversible hypothyroidism rather than immunological perturbations. It is, therefore, recommended to attempt iodide restriction before starting l-thyroxine replacement therapy.

Statins as antioxidant therapy for preventing cardiac myocyte hypertrophy.

Cardiac hypertrophy is a major cause of morbidity and mortality worldwide. The hypertrophic process is mediated, in part, by small G proteins of the Rho family. We hypothesized that statins, inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, inhibit cardiac hypertrophy by blocking Rho isoprenylation. We treated neonatal rat cardiac myocytes with angiotensin II (AngII) with and without simvastatin (Sim) and found that Sim decreased AngII-induced protein content, [3H] leucine uptake, and atrial natriuretic factor (ANF) promoter activity. These effects were associated with decreases in cell size, membrane Rho activity, superoxide anion (O2*-) production, and intracellular oxidation, and were reversed with L-mevalonate or geranylgeranylpyrophosphate, but not with farnesylpyrophosphate or cholesterol. Treatments with the Rho inhibitor C3 exotoxin and with cell-permeable superoxide dismutase also decreased AngII-induced O2*- production and myocyte hypertrophy. Overexpression of the dominant-negative Rho mutant N17Rac1 completely inhibited AngII-induced intracellular oxidation and ANF promoter activity, while N19RhoA partially inhibited it, and N17Cdc42 had no effect. Indeed, Sim inhibited cardiac hypertrophy and decreased myocardial Rac1 activity and O2*- production in rats treated with AngII infusion or subjected to transaortic constriction. These findings suggest that statins prevent the development of cardiac hypertrophy through an antioxidant mechanism involving inhibition of Rac1.

Evidence for deactivation of both ectosolic and cytosolic 5'-nucleotidase by adenosine A1 receptor activation in the rat cardiomyocytes.

Adenosine, an important regulator of many cardiac functions, is produced by ectosolic and cytosolic 5'-nucleotidase. The activity of these enzymes is influenced by several ischemia-sensitive metabolic factors, e.g., ATP, ADP, H+, and inorganic phosphate. However, there is no clear evidence that adenosine itself affects 5'-nucleotidase activity. This study tested whether adenosine decreases the activity of ectosolic and cytosolic 5'-nucleotidase. Cardiomyocytes were isolated from adult male Wistar rats and suspended in the modified Hepes-Tyrode buffer solution. After stabilization, isolated cardiomyocytes were incubated with and without adenosine (10(-9) - 10(-4) M). Ectosolic and cytosolic 5'-nucleotidase activity was decreased by exogenous adenosine (ectosolic 5'-nucleotidase activity, 20.6 +/- 2.3 vs. 8.6 +/- 1.6 mumol/min per 10(6) cells [P < 0.05]; cytosolic 5'-nucleotidase activity, 2.47 +/- 0.58 vs. 1.61 +/- 0.54 mumol/min per 10(6) cells [P < 0.05] at 10(-6) M adenosine) after 30 min. The decrease in ectosolic and cytosolic 5'-nucleotidase activity was inhibited by 8-phenyltheophylline and pertussis toxin, and was mimicked by N6-cyclohexyladenosine, an adenosine A1 receptor agonist. Neither CGS21680C, and A2 receptor agonist, nor cycloheximide deactivated ectosolic and cytosolic 5'-nucleotidase. Thus, we conclude that activation of adenosine A1 receptors is coupled to Gi proteins and attenuates ectosolic and cytosolic 5'-nucleotidase activity in rat cardiomyocytes.

Role of phasic dynamism of p38 mitogen-activated protein kinase activation in ischemic preconditioning of the canine heart.

Although ischemic stress, including ischemic preconditioning (IP), activates p38 mitogen-activated protein kinase (MAPK), the relationship between p38 MAPK activation and the underlying cellular mechanisms of cardioprotection by IP is not verified in vivo. We examined the effects of the selective p38 MAPK inhibition on the cardioprotective effect of IP in the open-chest dogs. The coronary artery was occluded 4 times for 5 minutes, separated by 5 minutes of reperfusion (IP) followed by 90 minutes of occlusion and 6 hours of reperfusion. We infused SB203580 into the coronary artery during IP and 1 hour of reperfusion, during IP alone, and during sustained ischemia in the IP group. p38 MAPK activity markedly increased during IP but did not additionally increase at the onset of ischemia and was even attenuated at 15 minutes of sustained ischemia, and heat-shock protein (HSP) 27 was phosphorylated and translocated from cytosol to myofibril or nucleus without affecting total protein level at the onset of ischemia compared with the control group. SB203580 treatment (1 micromol/L) only during IP blunted the infarct size limitation by IP (37.3+/-6.3% versus 7.4+/-2.1% in the IP group, P:<0.01) and attenuated either phosphorylation or translocation of HSP27 during IP. Although the SB203580 treatment throughout the preischemic and postischemic periods had no significant effect on infarct size (33.3+/-9.4%) in this model, treatment with SB203580 only during ischemia partially mimicked the infarct size limitation by IP (26.8+/-3.5%). Thus, transient p38 MAPK activation during ischemic preconditioning mainly mediates the cardioprotection followed by HSP27 phosphorylation and translocation in vivo in the canine heart.

Simvastatin decreases IL-6 and IL-8 production in epithelial cells.

Many cardiovascular studies have suggested that 3-hydroxy-3-methylglutaryl co-enzyme A reductase inhibitors (statins) have anti-inflammatory effects independent of cholesterol lowering. As a chronic inflammatory disease, periodontitis shares some mechanisms with atherosclerosis. Since oral epithelial cells participate importantly in periodontal inflammation, we measured simvastatin effects on interleukin-6 and interleukin-8 production by cultured human epithelial cell line (KB cells) in response to interleukin-1alpha. Simvastatin decreased production, an effect reversed by adding mevalonate or geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate. Simvastatin was found to reduce NF-kappaB and AP-1 promoter activity in KB cells. Dominant-negative Rac1 severely inhibited interleukin-1alpha-induced NF-kappaB and AP-1 promoter activity. Our results may indicate an anti-inflammatory effect of simvastatin on human oral epithelial cells, apparently involving Rac1 GTPase inhibition.

Cardioprotective effect afforded by transient exposure to phosphodiesterase III inhibitors: the role of protein kinase A and p38 mitogen-activated protein kinase.

BACKGROUND: Phosphodiesterase III inhibitors (PDEIII-Is) improve the hemodynamic status of heart failure via inotropic/vasodilatory effects attributable to the increase in intracellular cAMP level. Direct cardioprotection by PDEIII-Is and its underlying mechanisms, however, have not been identified. We tested the infarct size-limiting effect of PDEIII-Is and the roles of cAMP, protein kinase (PK) A, PKC, and mitogen-activated protein kinase (MAPK) families in open-chest dogs. Methods and Results-- Milrinone, olprinone (PDEIII-Is), or dibutyryl-cAMP (db-cAMP) was injected intravenously 30 minutes before 90-minute ischemia, followed by 6 hours of reperfusion. Olprinone was also examined with an intracoronary cotreatment with a PKA inhibitor (H89), a PKC inhibitor (GF109203X), an extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059), or a p38 MAPK inhibitor (SB203580) throughout the preischemic period. Either PDEIII-Is or db-cAMP caused substantial hemodynamic changes, which returned to control levels in 30 minutes. Collateral flow and percent risk area were identical for all groups. Both PDEIII-Is and db-cAMP increased myocardial p38 MAPK activity during the preischemic period, which was blocked by H89, but not by GF109203X. Both PDEIII-Is and db-cAMP reduced infarct size (19.1+/-4.1%, 17.5+/-3.3%, and 20.3+/-4.8%, respectively, versus 36.1+/-6.2% control, P<0.05 each). Furthermore, the effect of olprinone was blunted by either H89 (35.5+/-6.4%) or SB203580 (32.6+/-5.9%), but not by GF109203X or PD98059. H89, GF109203X, PD98059, or SB203580 alone did not influence infarct size. CONCLUSIONS: Pretreatment with PDEIII-Is has cardioprotective effects via cAMP-, PKA-, and p38 MAPK-dependent but PKC-independent mechanisms in canine hearts.

A Ca channel blocker, benidipine, increases coronary blood flow and attenuates the severity of myocardial ischemia via NO-dependent mechanisms in dogs.

OBJECTIVES: This study was undertaken to examine whether a dihydropyridine Ca channel blocker, benidipine, increases cardiac NO levels, and thus coronary blood flow (CBF) in ischemic hearts. BACKGROUND: Benidipine protects endothelial cells against ischemia and reperfusion injury in hearts. METHODS AND RESULTS: In open chest dogs, coronary perfusion pressure (CPP) of the left anterior descending coronary artery was reduced so that CBF decreased to one-third of the control CBF, and thereafter CPP was maintained constant (103+/-8 to 42+/-1 mmHg). Both fractional shortening (FS: 6.1+/-1.0%) and lactate extraction ratio (LER: -41+/-4%) decreased. Ten minutes after the onset of an intracoronary infusion of benidipine (100 ng/kg/min), CBF increased from 32+/-1 to 48+/-4 ml/100g/ min during 20 min without changing CPP (42+/-2 mmHg). Both FS (10.7+/-1.2%) and LER (-16+/-4%) also increased. Benidipine increased cardiac NO levels (11+/-2 to 17+/-3 nmol/ml). The increases in CBF, FS, LER and cardiac NO levels due to benidipine were blunted by L-NAME. Benidipine increased cyclic GMP contents of the coronary artery of ischemic myocardium (139+/-13 to 208+/-15 fmol/mg protein), which was blunted by L-NAME. CONCLUSION: Thus, we conclude that benidipine mediates coronary vasodilation and improves myocardial ischemia through NO-cyclic GMP-dependent mechanisms.

Increased release of nitric oxide in ischemic hearts after exercise in patients with effort angina.

OBJECTIVES: The aim of this study was to determine whether the release of nitric oxide (NO) from the ischemic heart increases during exercise in patients with effort angina. BACKGROUND: Myocardial ischemia increases NO production in the canine heart, but no such increase has been demonstrated in the ischemic human heart. METHODS: Fifteen patients with effort angina underwent supine ergometer exercise tests. All patients had severe proximal stenosis (>90%) in the left anterior descending coronary artery. The control group consisted of 17 subjects without coronary artery disease or systemic hemodynamic abnormalities. RESULTS: Neither the lactate extraction ratio (LER) nor the difference in NO concentration between coronary venous and arterial blood (deltaVA[NO]) was affected by exercise in the control subjects. In patients with effort angina, neither variable differed from that in the control group at rest; however, exercise markedly decreased LER and significantly increased deltaVA(NO) (from 4.7 +/- 0.3 to 16.5 +/- 1.6 micromol/liter, p < 0.001) in the patient group. The extent of decrease in LER was significantly correlated with the extent of increase in deltaVA(NO) in the patients with effort angina (r2 = -0.837, p < 0.001). CONCLUSIONS: Provocation of myocardial ischemia by exercise stress increases NO production in the hearts of patients with effort angina.

Role of nitric oxide in regulation of coronary blood flow during myocardial ischemia in dogs.

OBJECTIVES: This study was undertaken to examine whether nitric oxide released in ischemic myocardium decreases the coronary vascular resistance and attenuates the severity of contractile and metabolic dysfunction. BACKGROUND: Endothelium-derived relaxing factor, recently identified as nitric oxide, is a potent relaxant of coronary smooth muscle. METHODS: The left anterior descending coronary artery was perfused through an extracorporeal bypass tube placed in the carotid artery in 56 open chest dogs. After hemodynamic stabilization, we occluded this bypass tube to decrease coronary blood flow to one third of the control flow. Thereafter, we maintained a constant coronary perfusion pressure (40.9 +/- 3.1 mm Hg). RESULTS: Under ischemic conditions, the coronary arteriovenous differences in nitrate and nitrite (end products of nitric oxide) increased (from 3.5 +/- 0.4 [mean +/- SEM] to 12.9 +/- 2.1 mumol/liter, p < 0.01). NG-Monomethyl L-arginine (3 micrograms/kg body weight per min, intracoronary) decreased the coronary arteriovenous differences in nitrate and nitrite (5.0 +/- 0.9 mumol/liter, p < 0.05) and coronary blood flow (from 29.8 +/- 0.5 to 18.1 +/- 1.1 ml/100 g per min, p < 0.001). Fractional shortening (from 3.7 +/- 1.0 to -1.3 +/- 0.7%, p < 0.001) and lactate extraction ratio (from -44.0 +/- 4.1 to -59.2 +/- 4.9%, p < 0.005) of the perfused area also decreased. These values were restored by the concomitant administration of L-arginine. Blood flow to the endomyocardium was decreased relative to the epimyocardium. A reduction in coronary blood flow and worsening of myocardial contractile and metabolic functions due to the administration of NG-monomethyl L-arginine during ischemia were observed in denervated hearts. A reduction in coronary blood flow in ischemic myocardium was observed with the administration of NW-nitro-L-arginine methyl ester as well, although neither NW-nitro-L-arginine methyl ester nor NG-monomethyl L-arginine changed coronary blood flow and myocardial contractile and metabolic functions in the nonischemic myocardium. The cyclic guanosine monophosphate content of epicardial coronary artery increased due to myocardial ischemia; this increase was attenuated with NG-monomethyl L-arginine treatment. CONCLUSIONS: We conclude that endogenous nitric oxide predominantly decreases the coronary vascular resistance of ischemic endomyocardium, thereby improving myocardial contractility and metabolic function.

Reduced plasma concentrations of nitrogen oxide in individuals with essential hypertension.

Patients with essential hypertension exhibit blunted endothelium-dependent vasodilator responses, which may be largely attributable to reduced bioactivity of nitric oxide (NO). Therefore, we measured the end product of NO, nitrate plus nitrite (nitrogen oxide), and examined the relationship between the degree of hypertension and plasma nitrate plus nitrite levels in patients with essential hypertension. The combined plasma concentration of nitrate plus nitrite, end products of NO metabolism, was reduced in individuals with essential hypertension relative to that in control subjects (15.7+/-1.1 versus 22.8+/-1.4 mmol x L(-1), P<.001); individuals with borderline hypertension showed values that were intermediate between those of the other two groups (18.2+/-1.2 mmol x L(-1), P<.001). The plasma nitrogen oxide concentration showed significant inverse correlations with both systolic and diastolic blood pressures. The basal concentration of nitrogen oxide in the plasma was reduced, at least in the peripheral circulation, in individuals with essential hypertension.

Role of Ca2+-activated K+ channels in the protective effect of ACE inhibition against ischemic myocardial injury.

Angiotensin-converting enzyme (ACE) inhibitors increase the production of nitric oxide (NO) and prostacyclin and open Ca2+-activated K+ channels. The effects of these actions of ACE inhibitors on infarct size were investigated in open-chest dogs subjected to myocardial ischemia and reperfusion. Infarct size was assessed 6 hours after the onset of reperfusion, subsequent to 90 minutes of occlusion of the left anterior descending coronary artery. The ACE inhibitor cilazaprilat was administered into the coronary artery 10 minutes before coronary occlusion, and infusion was continued until 1 hour after reperfusion. The bradykinin and NO concentrations in coronary venous blood 10 minutes after the onset of reperfusion were significantly higher in dogs treated with cilazaprilat (3 microg x kg(-1) x min(-1)) than in control animals. Although there were no significant differences in collateral flow during ischemia, infarct size in the cilazaprilat group was smaller than that in the control group (15.1+/-3.0% versus 46.7+/-4.2% of the area at risk, P<0.0001). The infarct size-limiting effect of cilazaprilat was partially reduced by either N(G)-nitro-L-arginine methyl ester (an inhibitor of NO synthase) or iberiotoxin (a blocker of Ca2+-activated K+ channels) and was abolished by N(G)-nitro-L-arginine methyl ester plus iberiotoxin. Indomethacin (an inhibitor of cyclooxygenase) had no effect on the beneficial action of cilazaprilat. Inhibition of ACE thus reduced myocardial infarct size, an effect that was mediated by NO and the opening of Ca2+-activated K+ channels in canine hearts.

Reversible reduction in plasma concentration of nitric oxide induced by cigarette smoking in young adults.

The concentration of nitrate plus nitrite, metabolic end products of nitric oxide, in serum prepared from systemic venous blood was significantly (p <0.001) decreased in both heavy (14.5 +/- 1.3 micromol/L) and moderate (17.6 +/- 2.3 micromol/L) smokers relative to that in nonsmokers (22.6 +/- 0.4 micromol/L).

Effect of acute dynamic exercise on circulating plasma nitric oxide level and correlation to norepinephrine release in normal subjects.

Physical exercise increased the levels of the end product of nitric oxide in normal subjects. The increased nitric oxide may contribute to vasodilation during exercise.

Activation of ecto-5'-nucleotidase by protein kinase C and its role in ischaemic tolerance in the canine heart.

1. Ischaemic preconditioning (IP) protects the myocardium against irreversible ischaemic injury by activating protein kinase C (PKC). The mechanism by which PKC protects the myocardium is unknown. We have shown that PKC increases the activity of ecto-5'-nucleotidase (ecto-5'-N) and thereby the production of adenosine in cardiomyocytes which may protect the myocardium against ischaemia-reperfusion injury in vivo. 2. The objective of this study was to elucidate the possible role of PKC-induced activation of ecto-5'-N in the cardioprotection associated with IP in the canine heart. 3. IP increased the activities of both ecto-5'-N and PKC, and minimized ischaemic damage (infarct size: 7.5 +/- 1.8 vs. 42.3 +/- 2.8%, P < 0.01 vs. the control group). Treatment with the PKC activator (4 beta-phorbol 12-myristate-13-acetate) also reduced infarct size (13.5 +/- 2.9%, P < 0.01 vs. the control group). 8-Sulfophenyltheophylline (an antagonist of adenosine receptors) or alpha,beta-methyleneadenosine 5'-diphosphate (an inhibitor of ecto-5'-N) eliminated the cardioprotective effect of the PKC activator (infarct size: 36.6 +/- 3.9 and 34.7 +/- 4.2%, respectively), suggesting that PMA limits infarct size by increasing the activity of ecto-5'-N and the adenosine level. 4. The PMA-induced cardioprotection was blunted by GF109203X (an inhibitor of PKC, infarct size: 36.2 +/- 3.1%), but not by pretreatment with dexamethasone (infarct size, 14.2 +/- 2.6%). 5. We conclude that the PMA- and IP-induced cardioprotection is attributable to phosphorylation and activation of ecto-5'-N.

Cellular mechanisms of cardioprotection afforded by inhibitors of angiotensin converting enzyme in ischemic hearts: role of bradykinin and nitric oxide.

Angiotensin converting enzyme (ACE) inhibitors inhibit the degradation of bradykinin and contribute to accumulation of bradykinin and NO, both of which may be beneficial for diseased hearts. To test this idea, we administered imidaprilat and cilazaprilat, respectively to the canine ischemic myocardium. In the open chest dogs with low constant coronary perfusion pressure (CPP, from 104 +/- 3 to 42 +/- 3 mmHg), coronary blood flow (CBF, 91 +/- 1 to 32 +/- 2 ml/100 g/min), fractional shortening (FS), and lactate extraction ratio (LER) decreased. Either imidaprilat or cilazaprilat increased CBF, FS, and LER with increases in cardiac bradykinin and NO levels. The beneficial effects of ACE inhibitors were blunted by either L-NAME (an inhibitor of NO synthase) and HOE140 (an inhibitor of bradykinin receptors), respectively. ACE inhibitors, on the other hand, are reported to attenuate the severity of myocardial stunning, which effect is partially attributable to bradykinin- and NO-dependent mechanisms. Further, ACE inhibitors limited infarct size following coronary occlusion and reperfusion. This infarct size-limitation was blunted by either L-NAME and IBTX (the antagonist of K(Ca) channels). Bradykinin is also reported to close K(Ca) channels. Thus, we concluded that ACE inhibitors attenuate both reversible and irreversible myocardial cellular injury via bradykinin/NO-dependent mechanisms. In experimental and clinical settings, the cardioprotective effects of ACE inhibitors on the diseased heart may be attributable to these mechanisms.

Effects of bezafibrate and simvastatin on plasma lipoproteins in hypercholesterolemia resistant to hormone replacement therapy.

OBJECTIVES: Estrogen replacement therapy has favorable effects on serum lipoprotein levels in postmenopausal women with hypercholesterolemia. However, there are some patients who fail to respond to hormone replacement therapy (HRT) to lower the serum cholesterol level. In these cases, a conventional lipid-lowering therapy will be applied in addition to HRT, while the effects of these drugs are not well understood. In this study, we studied the effects of simvastatin and bezafibrate administered in addition to HRT. METHODS: Patients who were hypercholesterolemic even after HRT were randomly assigned to three treatment groups: HRT only (control group, n=10), HRT+simvastatin (10 mg/day, n=10), or HRT+bezafibrate (400 mg/day, n=10). Serum lipids and lipoprotein levels were measured throughout 12 weeks. RESULTS: The serum triglyceride levels were decreased by 24+/-28 and 38+/-13% in the HRT+simvastatin and HRT+bezafibrate groups, respectively. HRT+simvastatin decreased the total cholesterol (21+/-10%) and low-density lipoprotein cholesterol (28+/-12%) levels without affecting the high-density lipoprotein cholesterol (HDL-C) level, while HRT+bezafibrate increased the HDL-C level (12+/-11%). CONCLUSIONS: Treatment with simvastatin or bezafibrate in addition to HRT should be considered in cases of postmenopausal hypercholesterolemia in which HRT alone fails to lower the serum lipoprotein levels.