Treatment Effect of Niaspan, a Controlled-release Niacin, in Patients with Hypercholesterolemia: A Placebo-controlled Trial

Background

The present study was designed to determine the efficacy and safety of Niaspan (Kos Pharmaceuticals, Inc, Hollywood, FL), a new controlled-release formulation of niacin, in the treatment of primary hyperlipidemia, the occurrence and severity of flushing events, and potential adverse effects, particularly hepatotoxicity.

Methods and Results

The study was conducted as a multicenter, randomized, double-blind, placebo-controlled, parallel comparison of Niaspan in doses of 1000 mg/day and 2000 mg/day, administered once a day at bedtime. One hundred twenty-two patients with low-density lipoprotein cholesterol levels > 4.14 mM/L (160 mg/dL) with dietary intervention and high-density lipoprotein cholesterol ≤ 1.81 mM/L (70 mg/dL) were randomized to one of three treatment groups: placebo, and 1000 mg/day or 2000 mg/day of Niaspan. Safety and efficacy measures included 12-hour serum fasting lipid and lipoprotein concentrations, serum analyte levels for major organ function, flushing diaries, and adverse event records. The placebo group demonstrated no significant changes in serum lipoprotein concentrations over the treatment period of 12 weeks, except for a slight 4% increase in high-density lipoprotein cholesterol. Niaspan significantly lowered low-density lipoprotein cholesterol levels by 6% and 14% for the 1000 mg/day and 2000 mg/day doses, respectively. High-density lipoprotein cholesterol levels rose significantly, with a 17% increase occurring at the 1000 mg/day dose and a 23% increase occurring at the 2000 mg/day dose. Niaspan (2000 mg/day) produced significant decreases of 27% and 29%, respectively, for serum lipoprotein(a) and triglyceride concentration. Although the incidence of flushing was significant, these episodes were generally well tolerated.

Conclusion

Niaspan administered in doses of 1000 mg/day and 2000 mg/day at bedtime were well tolerated with few side effects and produced favorable effects on the major circulating lipoproteins of patients with primary dyslipidemias as specified by the enrollment criteria.

Retinoic acid receptors and tissue-transglutaminase mediate short-term effect of retinoic acid on migration and invasion of neuroblastoma SH-SY5Y cells

Long-term treatment with all trans-retinoic acid (RA) induces neuronal differentiation and apoptosis. However, the effect of short-term RA treatment on cell proliferation, migration and invasion of neuroblastoma cell lines (SH-SY5Y and IMR-32) remains unclear. RA induces expression of tissue-transglutaminase (TGase) and promotes migration and invasion after 24 h of treatment in SH-SY5Y cells, but not in IMR-32 cells. RA receptor (RAR) agonist (4-(E-2-[5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl]-1-propenyl) benzoic acid) and RAR/retinoid X receptor (RXR) agonist (9-cis-RA) promote expression of TGase, migration and invasion of SH-SY5Y cells, while RXR agonist has no significant effect. RAR antagonist blocks RA effect on migration and invasion, indicating that RAR receptors are required. Retinoid receptors are expressed and activated by RA in both cell lines. However, only transient activation of RAR is observed in IMR-32 cells. These findings suggest that different responses observed in SH-SY5Y and IMR-32 cells could be due to differential activation of retinoid receptors. Overexpression of TGase has no effect on migration or invasion, while overexpression of antisense TGase blocks RA-induced migration and invasion, indicating that other molecules along with TGase mediate RA effects. In addition to the long-term effects of RA that are coupled with cell differentiation, short-term effects involve migration and invasion of neuroblastoma SH-SY5Y cells.

Regulation of calcitonin gene-related peptide expression in dorsal root ganglia of rats by female sex steroid hormones

Calcitonin gene-related peptide (CGRP), a potent vasodilator primarily synthesized in dorsal root ganglia (DRG) neurons, has been shown to decrease vascular resistance and thus regulate blood flow to a variety of organs in rats. Serum CGRP levels in the human have been reported to increase with pregnancy and decrease postpartum. It has been suggested that female sex steroid hormones play a role in cardiovascular function, but the mechanisms are unknown. In this study, we examined the effects of estradiol-17beta (E(2)) and progesterone (P(4)) on the expression of CGRP in DRG in adult rats both in vivo and in vitro. Ovariectomized (ovx) animals were injected s.c. with 5 microg E(2), 4 mg P(4), or 5.0 microg E(2) + 4 mg P(4) in 0.5 ml sesame oil or with oil only, and groups of 4 rats were killed at 0, 24, or 48 h. DRGs were then removed and analyzed for CGRP mRNA and immunoreactive (i-)CGRP content by Northern blotting and RIA, respectively. Primary cultures of DRG neurons from adult female rats were used to assess the effects of varying doses of E(2) (1, 10, 100 nM), P(4) (10, 100, 1000 nM), or E(2) (10 nM) + P(4) (100 nM) in the absence or presence of nerve growth factor (NGF; 20 ng/ml); and CGRP mRNA content in the cells and i-CGRP in the medium were quantitated at 24 or 48 h after incubation. Results of in vivo studies showed that E(2) caused a significant increase in CGRP mRNA at 24 h (1.8-fold) and in i-CGRP levels both at 24 h (2. 8-fold) and at 48 h (3.4-fold) in DRG of ovx rats. P(4) also stimulated expression of both CGRP mRNA and i-CGRP. In the in vitro studies, either E(2) or P(4) alone or the two in combination were without effect on CGRP expression in cultured DRG neurons at all the doses tested. However, in the presence of NGF, both CGRP mRNA and peptide levels were significantly enhanced by E(2), P(4), and E(2)+P(4) in a time-dependent (2.0- to 2.8-fold at 24 h, 3.0- to 5. 0-fold at 48 h) and dose-dependent manner, with maximal effects achieved at 1.0 nM (E(2)) and 100 nM (P(4)) at 24 h of incubation. In summary, both E(2) and P(4), either alone or in combination, stimulate CGRP peptide synthesis in DRG neurons through increasing CGRP mRNA. The effects of these steroid hormones are mediated through amplifying the NGF-induced synthesis of CGRP in these neurons. Thus, we propose that the cardiovascular functions of female sex steroid hormones may be mediated, at least in part, by the up-regulation of neuronal CGRP synthesis, via NGF-mediated mechanisms.

Pregnancy and steroid hormones enhance the vasodilation responses to CGRP in rats

We recently reported that calcitonin gene-related peptide (CGRP) reversed the hypertension induced by nitric oxide inhibition in pregnant rats and that this effect appeared to be progesterone dependent. In the present study, we examined whether the vasodilator responses to CGRP are increased during pregnancy and whether these responses are steroid hormone dependent. Three groups of ovariectomized (Ovx) rats (n = 4-8 rats/group) were studied 3 days after daily treatment (subcutaneous injection) with progesterone (P; 2 mg/injection, twice daily for 3 days, in 0.2 ml of sesame oil), 17beta-estradiol (E; 2.5 microgram/injection, twice daily for 3 days, in 0.2 ml of sesame oil), or vehicle (sesame oil). A fourth group (n = 6 rats) of pregnant rats was studied on day 19 of gestation. A fifth group of adult, nonpregnant rats (n = 6 rats), regardless of stage of estrous cycle, was also used in this study. Mean arterial blood pressure (MAP) was continuously monitored in fully awake and free-moving instrumented rats. MAP was measured before and after administration of either saline or varying bolus doses of CGRP (9-360 pmol/kg body wt). CGRP produced a dose-dependent decrease in MAP in all rats with a significant (P < 0.05) reduction in MAP beginning with a CGRP dose of 90 pmol/kg and with maximal effects observed at 360 pmol/kg. Decreases in MAP in response to CGRP were significantly (P < 0.05) greater in pregnant compared with nonpregnant rats. Similarly to pregnant rats, Ovx rats given both E and P treatments produced greater decreases in MAP in response to CGRP at 90, 180, and 360 pmol/kg doses compared with both ovary-intact and Ovx nonpregnant rats, which were not different from each other. In summary, these data show that 1) the hypotensive effects of CGRP are dose dependent and 2) the hypotensive effects of CGRP are enhanced during pregnancy and in Ovx rats treated with either E or P. Therefore, we suggest that the decrease in vascular tone that is seen during pregnancy may be mediated, at least in part, by a sex steroid hormone-induced increase in the vascular sensitivity to the vasodilator effects of CGRP.

Development of sugar-induced blood pressure elevation after uninephrectomy in a resistant rat strain

Certain rat strains acutely increase blood pressure (BP) when given diets high in NaCl. Prior results showed that "salt-sensitive" rat strains, at least the ones studied, also increase BP in response to sugar loading. To examine this relationship further and learn more about the pathogenesis of sucrose-induced BP elevations, we examined the effects of unilateral nephrectomy (uninephrectomy) on sucrose-induced BP changes. The rationale is based upon the findings that renal mass removal sensitizes BP response to salt loading. Over 15 weeks, augmented sugar (sucrose) consumption by Long-Evans (LE) rats did not increase BP markedly compared to rats consuming a diet relatively low in sugar unless uninephrectomy was performed. The differences in BP caused by the high sugar diet in a uninephrectomized rat could not be explained adequately by alterations in catecholamine excretion, plasma renin activity, excesses in blood volume, or the other parameters examined. However, salt-induced hypertension has been attributed to the presence of circulating substances affecting ion transport. Among the dietary groups, there was a significant correlation between the ability of plasma to depress PAH and TEA renal slice uptake and the difference in BP. This is consistent with the presence of a circulating factor affecting cell transport that has its greatest activity in the high sugar-uninephrectomy group of LE rats. We conclude that reducing renal mass potentiates sugar-induced BP elevation similar to salt-induced BP elevation in a normally resistant rat strain, and the rise of BP may be caused by a circulating factor.

Excess sucrose and glucose ingestion acutely elevate blood pressure in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) were fed 6 different diets. The baseline diet (I) derived equal calories from sucrose, proteins, and fats. Three other diets (II, III, VI) derived the majority of calories from refined CHO, sucrose or glucose, with decreases in calories from proteins or fats. The last two diets (IV, V) were relatively low in sucrose with a higher percentage of the total calories from proteins and fats, respectively. From 3 to 15 weeks on the diets, the highest average BP was in rats consuming high concentrations of sucrose or glucose (II, III, VI). Urinary excretory rates of norepinephrine (NE) at 5, 10 and 15 weeks and epinephrine at 5 and 10 weeks were significantly elevated in rats ingesting diets high in refined CHO, and NE positively correlated with blood pressure (BP) at 5 and 10 weeks of the study. At the end of the study, serum insulin levels were not different, but plasma renin and serum glucagon levels were lower in SHR consuming the diets with high CHO concentrations. We conclude that equally elevated BP are seen with relatively high intakes of either sucrose or glucose, whether the balance of calories is derived from lessening fat or protein. This is secondary, at least in part, to alterations in NE metabolism.

Influence of oat bran on sucrose-induced blood pressure elevations in SHR

To determine whether oat fiber influences BP, we gave spontaneously hypertensive rats (SHR) a diet high in sucrose and low in protein (calories: sucrose 52%, protein 15%, fat 33%) or a diet low in sucrose and high in protein (calories: sucrose 13%, protein 52%, fat 35%). The amount of fat in these particular diets has not been shown to influence BP, so we modified the 2 diets by replacing fat with oat bran (10% w/w). Accordingly, we examined 4 groups of 5 rats consuming different diets: high sucrose, high sucrose + oat bran, low sucrose, and low sucrose + oat bran. Not unexpectedly, SHR consuming the diet high in sucrose had a significantly higher BP after 2 weeks than those consuming the diet low in sucrose. The significant difference in BP continued over the next 3 weeks. At the end of 6 week duration of study, we found the following BP: SHR ingesting the high sucrose diet, 217 mm Hg +/- 5 (SEM) vs SHR consuming the low sucrose diet, 187 mm Hg +/- 4 (SEM) p less than .0001]. SHR eating the low sucrose diet and consuming supplemental bran showed no significant change in BP after 6 weeks compared to SHR eating the basic diet alone, 188 mm Hg +/- 6 (SEM); however, 5 SHR consuming the high sucrose diet with added oat bran showed a significantly lower BP 200 mm Hg +/- 2 (SEM) than SHR ingesting the basic high sucrose diet devoid of oat bran [p less than .01]. We conclude that addition of oat bran to the diet can ameliorate sucrose-induced BP elevations in SHR.

Left ventricular filling in hypertensive blacks and whites following adrenergic blockade

Left ventricular diastolic filling was investigated in 12 black and 15 white subjects before and after double-blinded randomized treatment of mild to moderate hypertension with combined alpha- and beta-adrenergic receptor blockade (labetalol) and beta-blockade alone (atenolol). At baseline (off medication), both groups were similar for age (46 +/- 8 years v 48 +/- 12 years), mean blood pressure (121 +/- 8 mm Hg v 115 +/- 8 mm Hg), left ventricular dimensions, left ventricular mass index (118 +/- 24 g/m2 v 113 +/- 13 g/m2), and left ventricular filling as reflected by transmitral flow velocity ratio A/E (0.97 +/- 0.33 v 0.92 +/- 0.19, normal age-matched control A/E ratio is 0.64 +/- 14). There were 6 blacks and 6 whites in the labetalol group; 6 blacks and 9 whites in the atenolol group. At six weeks of treatment, whites in the labetalol group showed a significantly greater drop in mean blood pressure (114 +/- 7/102 +/- 11, P less than .007 v 123 +/- 9/114 +/- 11, P = NS) and correspondingly greater improvement in A/E ratio (1.04 +/- 0.14/0.74 +/- 0.23, P less than .024 v 1.02 +/- 0.23/0.89 +/- 0.16, P = NS). However, this difference was no longer significant when controlling for age and blood pressure level. In the atenolol group, whites showed a significant increase in the rapid filling phase velocity E, while late filling phase velocity A significantly dropped only in blacks, without significant improvement in A/E ratio in either subgroup. In conclusion, greater improvement in left ventricular filling is seen with combined alpha-beta-blockade than beta-blockade alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of age on left ventricular filling in children of hypertensive parents

Doppler transmitral flow velocity A/E ratio is a useful noninvasive estimate of left ventricular (LV) filling. However, the A/E ratio increases with age. To evaluate the effect of age on LV filling in children, Doppler transmitral flow velocity A/E ratios and echocardiographic measurements were obtained in 51 normal children (mean age 12 +/- 4 years) of hypertensive parents (study children), sex- and age-matched against 28 normal children (mean age 12 +/- 4 years) from normotensive parents (control children). There was a significant correlation between age and LV systolic and diastolic internal dimensions (r = 0.74 and 0.83, respectively, P less than .0001, in study children, and r = 0.70 and 0.79, respectively, P less than .0001, in control children), total wall thickness (r = 0.72, P less than .0001, in study children, and 0.61, P less than .001, in control children), and with LV mass index (r = 0.56, P less than .0001 and r = 0.45, P less than .02, respectively). In contrast, there was no correlation between age and transmitral flow velocity A/E ratio in either group (r = 0.12 and 0.07, respectively). In conclusion, age does not have an effect on LV filling in normal children from either normotensive or hypertensive parents. Therefore, age correction of A/E ration, which is necessary in adults, is not required in children. Because of a strong correlation between age and LV mass as well as LV mass index, age should be taken into account when defining criteria for LV hypertrophy in children.

Effect of intravenous enalaprilat in moderate and severe systemic hypertension

The antihypertensive effect and tolerability of enalaprilat, an intravenously administered angiotensin converting enzyme inhibitor, was studied in 65 patients with moderate or severe hypertension. In this randomized, double-blind study, enalaprilat was compared with placebo in 42 (22 enalaprilat, 20 placebo) moderate hypertensive (diastolic blood pressure [BP] 100 to 114 mm Hg) patients. It was compared with furosemide in 23 (12 enalaprilat, 11 furosemide) severe hypertensive (diastolic BP 115 to 130 mm Hg) patients. Enalaprilat (1.25 or 5.0 mg), placebo (5% dextrose) or furosemide (40 or 80 mg) was given every 6 hours intravenously up to 48 hours. In the moderate hypertension stratum, the mean supine diastolic BP was significantly (p less than or equal to 0.01) reduced from baseline at all timepoints in the enalaprilat group. These diastolic BP reductions were significantly (p less than or equal to 0.01) greater in the enalaprilat group than the placebo at 1 to 24 hours (-12 vs -4 mm Hg), with 59% of the patients responding to enalaprilat compared with 30% of the patients responding to placebo. An even greater reduction (p less than or equal to 0.01) was seen at 25 to 48 hours (-14 vs -7 mm Hg, with 73% enalaprilat vs 58% placebo responders). Significant (p less than or equal to 0.01) reductions in mean, supine systolic BP were also seen at 1 to 24 hours (-22 vs -2 mm Hg) and 25 to 48 hours (-24 vs -8 mm Hg) during the 48 hours of the double-blind treatment phase in the enalaprilat group compared with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular function in mild hypertension after adrenergic blockade

We previously used the Doppler transmitral flow velocity ratio A/E (A = late ventricular filling peak velocity; E = early ventricular filling peak velocity) and the age-adjusted ratio A/E/Age to detect left ventricular filling abnormalities in untreated mild hypertension. This study is a double-blind assessment of the effect of combined alpha- and beta-blockade (labetalol) and beta-blockade alone (atenolol) on left ventricular filling in mild hypertension. Twenty-seven patients blindly randomized to labetalol (12 patients) and atenolol (15 patients) treatment completed the echocardiographic and Doppler studies. Clinical and echo-Doppler data obtained at baseline and 6 weeks after initiation of therapy showed no difference between the two groups for age (49 +/- 10 vs 46 +/- 10 years), mean blood pressure (before therapy, 118 +/- 9 vs 117 +/- 8 mm Hg; after therapy, 108 +/- 12 mm Hg), left ventricular dimensions, wall thickness, systolic function, and mean late filling velocity A. There was no significant change in left ventricular mass and mass index with labetalol (left ventricular mass, 211 +/- 36 vs 216 +/- 38; mass index, 110 +/- 17 vs 112 +/- 16) or atenolol (245 +/- 41 vs 271 +/- 65; 120 +/- 18 vs 130 +/- 35). The mean velocity E, A/E, and A/E/Age ratios significantly improved with labetalol (p less than 0.05) but did not change significantly with atenolol. The improvement in A/E and A/E/Age ratios was primarily due to an increase in early filling velocity E.(ABSTRACT TRUNCATED AT 250 WORDS)

Refined carbohydrates affect blood pressure and retinal vasculature in spontaneously hypertensive and Wistar-Kyoto rats

Spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats received diets differing in amount and source of carbohydrates (CHO). When the CHO was in excess and the source was refined sugar or starch rather than natural ingredients, blood pressure (BP) rose, more so in SHR. This BP increase was observed whether sucrose, glucose, fructose or starch was the principal CHO. Increased urinary excretion of norepinephrine, dopamine and epinephrine also occurred. After only 2-3 months retinal capillary basement membrane damage was demonstrated in SHR and WKY rats ingesting large amounts of sucrose. No similar changes occurred on a high-starch diet. The damage consisted of thickening of capillary basement membranes, loss of homogeneity, and debris inclusions. These results suggest: that high dietary ingestion of CHO in the form of refined CHO augments BP in SHR and WKY rats via increased catecholamine production and/or release, and that the temporally foreshortened experimental period offered by the SHR/WKY model may be valuable in the study of diet-induced retinopathies.

Refined carbohydrate increases blood pressure and catecholamine excretion in SHR and WKY

In spontaneously hypertensive (SHR) and normotensive (WKY) rats fed different diets, blood pressure (BP) increased significantly in both strains when the carbohydrate (CHO) source was from refined rather than from natural ingredients. This BP increase was observed whether sucrose, glucose, or starch was the principal CHO. Urinary excretion of norepinephrine, dopamine, and, to some extent, epinephrine also increased, while myocardial concentrations were unaffected. Despite a comparable elevation of catecholamine excretion in both SHR and WKY rats fed high amounts of refined CHO, the BP increases were greater in the former. The strain differences were explained by the known dissimilar response of their blood vessels to catecholamines. The results suggest that BP elevation after high CHO ingestion is mediated via increased catecholamine production and/or release, thus implying a neurogenic mechanism.

Vasopressin response to hyperosmotic stimulus: blood pressure effect in normal subjects and patients with impaired sympathetic system

We have investigated the interaction of plasma vasopressin and plasma catecholamines in quadriplegic patients (with severed sympathetic tracts) and compared them to others with intact sympathetic system following I.V. administration of a hyperosmolar radiocontrast agent during a routine diagnostic pyelography. Baseline systolic and diastolic pressure as well as plasma norepinephrine were significantly lower in the quadriplegic subjects. At 5 minutes after administration of the hyperosmolar solution, systolic and diastolic pressure as well as plasma vasopressin rose in the quadriplegic subjects but not in normal subjects despite a significant and equal rise in serum osmolality occurring in both groups. These results demonstrate that an interaction between the two systems exists in humans: an intact sympathetic nervous system attenuates the vasopressin response to hyperosmolar stimuli and in its absence vasopressin may function as a pressor agent.