Acute toxicology and pharmacokinetic assessment of a ribozyme (ANGIOZYME) targeting vascular endothelial growth factor receptor mRNA in the cynomolgus monkey.

The potential acute toxicity of a ribozyme (ANGIOZYME) targeting the flt-1 vascular endothelial growth factor (VEGF) receptor mRNA was evaluated in cynomolgus monkeys following i.v. infusion or s.c. injection. ANGIOZYME was administered as a 4-hour i.v. infusion at doses of 10, 30, or 100 mg/kg or a s.c. bolus at 100 mg/kg. End points included blood pressure, electrocardiogram (ECG), clinical chemistry, hematology, complement factors, coagulation parameters, and ribozyme plasma concentrations. ANGIOZYME was well tolerated, with no drug-associated morbidity or mortality. There was no clear evidence of ANGIOZYME-related adverse effects in this study. Slight increases in spleen weight and lymphoid hyperplasia were observed in several animals. However, these changes were not dose dependent. Steady-state concentrations of ANGIOZYME were achieved during the 4-hour infusion of 10, 30, or 100 mg/kg. Dose-dependent elimination of ANGIOZYME was observed, with faster clearance at the two highest doses. ANGIOZYME was slowly absorbed after s.c. administration, resulting in steady-state concentrations for the 9-hour sampling period. Monkeys in this toxicology study received significant plasma ANGIOZYME exposure by both the s.c. and i.v. routes.

Neonatal MSG reduces hypothalamic DA, beta-endorphin, and delays weight gain in genetically obese (A viable yellow/alpha) mice.

Neonatal treatment with monosodium glutamate (MSG) decreases proopiomelanocortin (POMC) peptides and results in obesity. The yellow mouse is a model of obesity induced by the viable yellow (Avy) gene at the agouti locus on Chromosome 2, which results in overproduction of a POMC receptor antagonist. Thus we hypothesized that MSG, when imposed on the genetically susceptible model, would alter the development of obesity. Both yellow obese (Avy) and black lean (alpha/alpha) males were injected on Postnatal Days 1, 3, 5, 7, and 9 with 2.0 mg/g body weight MSG or saline SC. Their food intake, growth parameters, and neurochemical status were examined. Paradoxically, MSG interacted with the yellow phenotype to delay the rapid rate of weight gain characteristic of this model (p < 0.05). Food intake was decreased (p < 0.05) in both phenotypes treated with MSG, as was hypothalamic content of dopamine (p < 0.05) and of the POMC peptide, beta-endorphin (p < 0.001). The yellow obese phenotype was more sensitive than the black lean phenotype to the neurochemical effect of early postnatal MSG administration. Recent reports suggest the agouti locus protein is an antagonist of the receptor for another POMC peptide, melanocyte-stimulating hormone (MSH). Therefore, the balance of functional activity between various POMC peptides appears to be an important factor in the development of both acquired and genetic obesity.

Postnatal MSG treatment attenuates angiotensin II (AII) induced drinking in rats.

Exogenous angiotensin II (AII) administration produces a robust drinking response, even in water-satiated rats. All receptors are located in the hypothalamus and circumventricular organs (CVOs). Early postnatal administration of monosodium glutamate (MSG) produces hypothalamic/CVO damage. Therefore MSG might damage hypothalamic/CVO neurons important for producing the drinking response to AII. Few noninvasive procedures or tests exist to indicate the presence of a MSG lesion. Thus, the present study sought to determine whether altered water consumption after AII administration would signify the presence of a MSG lesion, as well as to demonstrate hypothalamic/CVO involvement in AII-induced drinking. Adult rats (dosed as neonates with MSG or saline) were given various doses of AII and the beta-adrenergic agonist isoproterenol. MSG-treated rats drank significantly less water after 100 ug/kg, sc AII than control rats. MSG-treated rats also had an unexpectedly high mortality after 100 ug/kg, sc isoproterenol. Thus, measurement of the drinking response may be a sensitive, noninvasive method for detecting neurotoxic damage to hypothalamic/CVO sites critical for the central action of AII.

Domoic acid-treated cynomolgus monkeys (M. fascicularis): effects of dose on hippocampal neuronal and terminal degeneration.

Domoic acid is a tricarboxylic amino acid (structurally related to kainic acid and glutamic acid) that is found in the environment as a contaminant of some seafood. To determine the nature of any neurological damage caused by domoate, as well as the minimum neurotoxic dose, juvenile and adult monkeys were dosed intravenously with domoate at one of a range of doses from 0.25 to 4 mg/kg. When animals were perfused one week later, histochemical staining using a silver method to reveal degenerating axons and cell bodies showed two distinct types of hippocampal lesions. One lesion, termed 'Type A', was a small focal area of silver grains restricted to CA2 stratum lucidum, the site of greatest kainic acid receptor concentration in the brain. Type A lesions occurred over a dose range of 0.5 to 2.0 mg/kg in juvenile animals and 0.5 to 1.0 mg/kg in adult animals. No mortality occurred in any of the juvenile monkeys, but one juvenile animal that received 4.0 mg/kg sustained a second type of lesion, termed 'Type B', characterized by widespread damage to pyramidal neurons and axon terminals of CA4, CA3, CA2, CA1, and subiculum subfields of the hippocampus. Doses of more than 1.0 mg/kg in the adult monkeys either proved lethal or resulted in Type B lesions. Induction of c-fos protein had occurred in the hippocampal dentate gyrus and CA1 regions of moribund animals perfused within hours of their initial dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Human dietary responses to perceived manipulation of fat content in a midday meal.

The influence of knowledge about the macronutrient content of foods on dietary habits is poorly understood. The present study examined dietary responses to manipulations of information about the fat content of a midday meal provided to 17 free-living individuals. Following a one week baseline period, subjects were told that the meal provided each day for three 12-day blocks supplied a greater, lesser or equal amount of fat than their customary midday meal. They recorded daily intake. During the low-fat information period, subjects increased their total daily intake of energy relative to the high-fat period, their energy derived from protein relative to baseline and their energy derived from fat relative to all other periods. Information about the fat content of foods can influence food selection and should be considered when developing dietary interventions aimed at moderating fat intake.

Human dietary responses to covert manipulations of energy, fat, and carbohydrate in a midday meal.

Dietary responses to dilution or supplementation of the energy value and macronutrient content of foods are poorly characterized in humans. After a 1-wk baseline, 16 free-living, normal-weight adults were provided midday meals systematically varying in energy, fat, and carbohydrate contents for 5-d periods. Their compensatory free-feeding intake was monitored through diet records. In response to energy dilution by carbohydrate or fat, mean daily energy intake was 88% and 97% of baseline, respectively. Responses to the energy surfeit led to intakes 104% and 116% of baseline, respectively. However, the absolute magnitude of the carbohydrate supplement challenge was small. Adjustments of macronutrient-specific intake during the high-carbohydrate, low-carbohydrate, high-fat, and low-fat meal periods were 134%, 91%, 165%, and 95% of baseline, respectively. Although these group findings indicate that defense against covert dilution of the energy, fat, or carbohydrate contents of a meal is stronger than that to supplementation, individual responses were highly variable.

Angiotensin-related intakes of water and NaCl in Fischer 344 and Sprague-Dawley rats.

Rats of the Fischer 344 (F344) strain drank less water after either peripheral or central acute administration of angiotensin III (ANG III) than rats of the Sprague-Dawley (SD) strain. In contrast, water intakes following acute administration of ANG II were comparable in the two strains. Chronic peripheral administration of ANG II produced a salt appetite in SD but not in F344 rats; ANG III was ineffective in both strains. These data suggest that some aspects of responsiveness to ANG peptides are reduced in F344 rats. In two of three studies, water intake after acute peripheral administration of either ANG I or the beta-adrenergic agonist isoproterenol did not differ between strains; in one study, the response to both dipsogens was lower in F344 rats. Plasma renin activity was elevated to the same level by isoproterenol in both strains of rats. These results suggest that the ability of isoproterenol to release renin, the subsequent generation of ANG I, and the conversion to ANG II are similar in the two strains. However, this similarity did not extend to cardiovascular responses. Rats of the F344 strain showed a smaller decrease in blood pressure following administration of isoproterenol than did those of the SD strain. Whether this is related to differences in either the regulation of beta-adrenoreceptors or postreceptor effects in vascular smooth muscle between strains will require additional investigation.

Water intake induced in rats by serotonin and 5-hydroxytryptophan: different mechanisms?

The present studies were designed to investigate further the mechanism by which water intake is induced in rats by peripheral administration of either serotonin (5HT) or its precursor 5-hydroxytryptophan (5HTP). Consistent with previous studies that have implicated mediation by the renal renin-angiotensin system (RAS), we now report that bilateral nephrectomy completely abolishes the drinking response to various doses of 5HT. In contrast, nephrectomy had little effect on the drinking induced by 5HTP. Thus, 5HTP may induce drinking by mechanisms other than its peripheral conversion to 5HT and subsequent activation of the RAS. The drinking responses to both 5HT and 5HTP were blocked by peripheral administration of the 5HT receptor antagonist, metergoline, but the drug was at least ten-fold more potent against 5HTP than 5HT. Intracerebroventricular (ICV) administration of metergoline also prevented the drinking response to peripherally-administered 5HTP. The drinking responses to both 5HT and 5HTP were enhanced by peripheral administration of low doses of an angiotensin I converting enzyme inhibitor, captopril. Collectively, these findings support previous conclusions that 5HT-induced intake of water is mediated exclusively by the renal RAS. However, 5HTP-induced drinking may additionally involve a renin-independent, serotonin-mediated mechanism, possibly in the brain.

Medial hypothalamic lesions in Syrian hamsters: characterization of hyperphagia and weight gain.

Syrian golden hamsters (Mesocricetus auratus) received bilateral lesions aimed at the ventromedial hypothalamus (VMH) or a sham lesion. In the first study, some of the animals in each surgical group were housed in standard sedentary conditions while others had free access to running wheels. The lesions produced a 30% increase in the daily intake of chow, and this was accomplished exclusively by increased meal sizes. As a result, lesioned hamsters gained body weight relative to controls both on the chow diet and in a subsequent high fat diet phase. The effects were comparable in both sedentary and exercising groups. The lesions produced increases in body length and fat content. In the second study, lesions were made in the VMH or in adjacent nuclei and, after an initial period on chow, the hamsters were then given a choice between chow and high fat diet. The lesioned hamsters showed no unusual preference for the high fat diet but, as before, those with damage to the VMH or paraventricular nucleus (PVN) showed exaggerated body weight gain. Hamsters with these lesions were hyperinsulinemic in both fed and fasted conditions at the end of the study.

Voluntary exercise, food intake, and plasma metabolites in streptozotocin-diabetic Syrian hamsters.

Diabetes mellitus was induced in Syrian hamsters by treatment with streptozotocin. The efficacy of and survival from this treatment are compared across several drug regimens, and in exercising versus sedentary hamsters. Stable diabetes, with plasma glucose levels typically below 400 mg/dl, is accompanied by a decrease of approximately 50% in voluntary wheel running in a 14L:10D cycle. Wheel running in diabetics is, however, almost completely abolished in continuous light. The diabetic hamsters are hyperphagic on chow, eating about 60% more than controls, exclusively by increasing the size of individual meals. Their intake is normalized on a high fat diet. The high fat diet greatly exacerbates the extant ketonemia in diabetics, and produces hypertriglyceridemia. Exercise has no apparent effect on plasma metabolic fuels of diabetic hamsters.