Postmarketing surveillance of food additives.

Postmarketing surveillance of consumption and of anecdotal reports of adverse health effects has been recognized by a number of regulatory authorities as a potentially useful method to provide further assurance of the safety of new food additives. Surveillance of consumption is used to estimate more reliably actual consumption levels relative to the acceptable daily intake of a food additive. Surveillance of anecdotal reports of adverse health effects is used to determine the presence of infrequent idiosyncratic responses that may not be predictable from premarket evaluations. The high-intensity sweetner, aspartame, is a food additive that has been the subject of extensive evaluation during the postmarketing period and is thus used as an example to discuss postmarketing surveillance.

Intense sweeteners use and weight change among women: a critique of the Stellman and Garfinkel study.

OBJECTIVE: The purpose of this study was to evaluate the work of Stellman and Garfinkel who speculated, based on epidemiologic data, that users of intense sweeteners are more likely than nonusers to gain weight. METHODOLOGY: We analyzed the study's design and statistical analysis to determine whether the conclusions of Stellman and Garfinkel were supported by the data. RESULTS: Several methodological flaws and inappropriate statistical analyses were identified. These included: use of data from an unrelated study for which they were not intended; failure to correct for bias due to convenience sampling; use of data from a subpopulation without validation; and stratification of subjects by outcome data. CONCLUSION: Our analysis indicates that the data from the study in question do not allow one to draw conclusions about a relationship between use of intense sweeteners and weight change. Furthermore, data from well-designed clinical trials have shown that aspartame is not associated with weight gain, and when used as part of a balanced deficit diet, can facilitate weight loss.

Plasma concentrations and pharmacokinetics of phenylalanine in rats and mice administered aspartame.

Aspartame (L-aspartyl-L-phenylalanine methyl ester) is an esterified, dipeptide sweetener that is rapidly and completely metabolized in the gastrointestinal tract to phenylalanine, aspartic acid and methanol. The pharmacokinetics of phenylalanine (PHE) and tyrosine (TYR) were examined following the administration of oral doses of aspartame (APM) to fasted male Sprague-Dawley rats (0, 50, 100, 200, 500 and 1,000 mg/kg) and CD-1 mice (0, 100, 200, 500, 1,000 and 2,000 mg/kg). Peak plasma PHE/large neutral amino acid (LNAA) ratios were calculated. Maximal plasma PHE and TYR concentrations were observed within 1 h after dosing and returned to baseline within 4-8 h in both species regardless of the dose of APM. Mean PHE Cmaxs ranged from 73.6 to 1,161 nmol/ml in the rat, and from 78.6 to 1,967 nmol/ml in the mouse. TYR Cmaxs ranged from 91.6 to 502 nmol/ml and from 89.2 to 792 nmol/ml in the rat and mouse, respectively. AUCs and Cmaxs were linear with dose in both species. Peak plasma PHE/LNAA ratios ranged from 0.112 to 1.117 in rats and from 0.121 to 1.769 in mice. Comparison of these ratios with those observed previously in humans indicates that rodents require a 2-6 times higher dose of APM than humans to produce similar increases in plasma PHE/LNAA ratios.

Acceptable daily intake vs actual intake: the aspartame example.

This article discusses the acceptable daily intake (ADI) and the postmarketing surveillance of consumption levels for a food additive, using the widely used food additive aspartame (APM, L-aspartyl-L-phenylalanine methyl ester) as an example. The safety implications of the ADI and consumption levels are also discussed. Aspartame has been assigned an ADI of 40 mg/kg/day by the World Health Organization and regulatory authorities in Europe and Canada, and of 50 mg/kg/day by the US Food and Drug Administration. A number of different methods have been used to measure consumption levels of food additives. Consumption estimations for aspartame from one such method, the food intake survey, have been done in the United States, Canada, Germany, and Finland. APM consumption in all age groups and selected subpopulations, even at the 90th percentile, is approximately 2-10 mg/kg/day and is thus well below the ADI.

Aspartame and sucrose produce a similar increase in the plasma phenylalanine to large neutral amino acid ratio in healthy subjects.

Aspartame (L-aspartyl-L-phenylalanine methyl ester) consumption has been postulated to increase brain phenylalanine levels by increasing the molar ratio of the plasma phenylalanine concentration to the sum of the plasma concentrations of the other large neutral amino acids (Phe/LNAA). Dietary manipulations with carbohydrate or protein can also produce changes in the Phe/LNAA value. To compare the effects of aspartame and carbohydrate on Phe/LNAA, beverages sweetened with aspartame, sucrose, and aspartame plus sucrose, and unsweetened beverage were ingested by 8 healthy, fasted subjects in a randomized, four-way crossover design. The beverages were sweetened with an amount of aspartame (500 mg) and/or sucrose (100 g) approximately equivalent to that used to sweeten 1 liter of soft drink. The baseline-corrected plasma Phe/LNAA values did not differ significantly following ingestion of aspartame or sucrose. Following aspartame alone, the high mean ratio increased 26% over baseline 1 h after ingestion. Following sucrose alone, the high mean ratio increased 19% at 2.5 h. Sucrose increased the Phe/LNAA value due to an insulin-mediated decrease in the plasma LNAA, while aspartame increased the ratio by increasing the plasma Phe concentration. These findings indicate that similar increases in plasma Phe/LNAA occur when healthy, fasting subjects ingest amounts of equivalent sweetness of sucrose or aspartame.

Absence of developmental effects in CF-1 mice exposed to aspartame in utero.

Aspartame (L-aspartyl-L-phenylalanine methyl ester) is a widely used high potency dipeptide sweetener. Developmental toxicology studies have been performed in several species documenting no effects of high doses of aspartame. Recently, a study by Mahalik and Gautieri [1984) Res. Commun. Psychol. Psychiatry Behav. 9, 385-403) reported a delay in the achievement age for the visual placing response in mice pups after maternal administration of high dosages of aspartame during late gestation. In the present study developmental parameters were determined in offspring of CF-1 mice after maternal administration of aspartame at 500, 1000, 2000, and 4000 mg/kg body wt by oral gavage. Aspartame was administered on Days 15 through 18 of gestation. Maternal body weight, food consumption, gestation length, reproductive indices, and litter size were not affected by aspartame treatment. In the pups, body weights, negative geotaxis, and surface and midair righting reflexes were not altered by treatment. There was no delay in the development of the visual placing response regardless of the method employed for assessment (grid or rope) or the manner by which the data were analyzed. There were also no changes in time of eye opening, reflex pupil closure, and ophthalmoscopic examination in the offspring. Thus, neither physical nor functional development was altered in mice after in utero exposure to extremely large dosages of aspartame. More specifically, in utero exposure to aspartame did not affect the development of the visual system in mice.

Identification of N-beta-L-aspartyl-L-phenylalanine as a normal constituent of human plasma and urine.

A new beta-aspartyl dipeptide, N-beta-L-aspartyl-L-phenylalanine (beta-AP), has been isolated and identified in urine and plasma from normal human volunteers. beta-AP was isolated from urine samples by high performance liquid chromatography (HPLC). Its identity and stereochemistry were demonstrated by HPLC and gas chromatography/mass spectrometry (GC-MS). The mean urinary beta-AP concentration in the subjects was 0.63 +/- 0.14 microgram/mg creatinine when averaged over two consecutive days of urine collection. Daily beta-AP excretion, determined from two 24-h urine samples collected from five individuals, was 801 +/- 117 micrograms/d (2.7 mumol/d). No diurnal rhythm was evident within the 24-h collection periods. beta-AP was also isolated from human plasma by HPLC and identified by GC-MS. Plasma from subjects contained approximately 5 ng beta-AP/ml. Furthermore, beta-AP was formed when asparagine and phenylalanine were incubated with an enzyme extract from human kidney. Thus, at least some of the beta-AP present in humans, and presumably other beta-aspartyl dipeptides as well, appears to be synthesized endogenously.

Protection by zinc against acetaminophen induced hepatotoxicity in mice.

The purpose of this investigation was to assess protection by zinc against acetaminophen induced hepatotoxicity and to evaluate possible mechanisms of protection. Mice were treated with zinc (3 mg/kg, ip) or saline (ip) 48 and 24 hr before and sacrificed 12 hr after acetaminophen administration (375, 500, or 750 mg/kg, po). Liver toxicity was then assessed by histological examination. The incidence of hepatotoxicity was significantly less at 375 and 500 mg/kg of acetaminophen in zinc treated animals. The same dosage of zinc was not hepatoprotective when given 1 hr after acetaminophen. Mice were also treated with 1 to 10 mg/kg of zinc (ip) 48 and 24 hr prior to sacrifice, and metallothionein, cytochrome P-450, glutathione, and UDP-glucuronosyl transferase (GT) were determined in the liver. Metallothionein and UDP-GT were increased and P-450 and glutathione decreased at the higher dosages of zinc; however, only metallothionein was significantly changed at the dosage of zinc (3 mg/kg) used in the hepatoprotection experiments. Further, mice were similarly treated with 3 mg/kg of zinc before administration of 375 mg/kg of [3H]acetaminophen (po) and the amount of acetaminophen and acetaminophen bound to metallothionein were determined in the liver for 0.5 to 24 hr. In addition, after 6 hr the subcellular distribution and covalent binding to protein of acetaminophen were also determined. Zinc treatment had no significant effect in any of the above determinations. These results indicate that zinc protects against acetaminophen induced hepatotoxicity and that the observed protection is probably due to an induced biochemical change, but it is apparently not the result of any of the commonly invoked mechanisms.

Testicular toxicity of a novel 1,4-benzodiazepine (SC-32855) in rats and dogs.

SC-32855, a novel 1,4-benzodiazepine, was administered orally to adult male Beagle dogs (75 mg/kg/day for 10 days) and rats (550 mg/kg/day for 28 days). In both species, SC-32855 caused arrest of spermatogenesis and degeneration of the germinal epithelium, however, it had no effect on Sertoli or Leydig cells. There were no meaningful effects on the weights of the testis, epididymis or prostate in either species. Mean serum luteinizing hormone concentrations in dogs, which were 1.6 +/- 0.2 and 1.5 +/- 0.5 ng/ml prior to dosing, and 3.9 +/- 1.1 and 2.3 +/- 0.5 ng/ml after dosing for the control and treatment groups, respectively, were not significantly changed. Mean serum testosterone concentrations in dogs, which were 1.11 +/- 0.13 and 0.95 +/- 0.10 ng/ml prior to dosing, and 1.05 +/- 0.15 and 1.17 +/- 0.16 ng/ml after dosing for the control and treatment groups, respectively, were also not significantly changed. Further, SC-32855 in vitro did not inhibit the synthesis of testosterone in testicular microsomes isolated from normal rats or dogs. These data indicate that SC-32855 causes testicular damage, which is not secondary to decreased testosterone.

Preclinical toxicology profile of misoprostol.

The toxicity of misoprostol has been extensively examined in a variety of in vitro and in vivo studies. Preclinical studies evaluated acute and chronic toxicity, mutagenicity and carcinogenicity, and reproductive toxicity. Single oral dose studies in rodents and non-rodents indicate a safety margin of at least 500 to 1000 fold between lethal doses in animals and therapeutic doses in humans. Chronic toxicity studies (52 weeks) have been performed at daily oral doses of up to 300 and 9000 micrograms/kg body weight in dogs and rats, respectively. Rectal temperatures were increased at 100 and 300 micrograms/kg in dogs and serum iron was increased at 9000 micrograms/kg in rats. Stomach weights were increased in dogs and rats in a dose-correlated manner related, at least in part, to an increase in the number of normal epithelial cells (gastric hyperplasia). When drug treatment was stopped rectal temperatures, serum iron and stomach weights reverted to normal. Electron microscope studies on hyperplastic tissue showed that the ultrastructure was not affected. Hyperostosis has been observed, mainly in female mice, following prolonged drug treatment at high doses. Histological studies of bone tissues of rats and dogs and radiological studies of long bones of dogs following chronic administration of misoprostol showed that bone development was normal in all respects. Mutagenicity studies were negative and misoprostol was not fetotoxic or teratogenic in rats at oral doses up to 10000 micrograms/kg body weight, or in rabbits at doses up to 1000 micrograms/kg body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in thyroidal function and liver UDPglucuronosyltransferase activity in rats following administration of a novel imidazole (SC-37211).

SC-37211, an imidazole with antianaerobic activity, was administered po to male rats for 2 weeks at dosages of 20, 60, and 200 mg/kg/day. Histological changes in the thyroid included irregularly shaped follicles and slightly enlarged follicular cells. Serum triiodothyronine (T3) and/or thyroxine (T4) were significantly decreased in treated animals at all dosages; these decreases were not observed following a 2-week recovery period. The half-life of serum [125I]thyroxine was also significantly decreased in rats treated with SC-37211. Morphological changes in the thyroid are likely the result of thyroid-stimulating hormone (TSH) stimulation, a response to decreased serum T3 and T4 concentrations. The decreases in T3 and T4 were not due to decreases in iodide uptake or organification. There were dose-dependent increases in liver weights, liver-to-body weight ratios, and UDPglucuronosyltransferase activity toward p-nitrophenol and T4. Therefore, the decreases in serum T3 and T4 were probably due to an increase in hepatic metabolism rather than to a direct effect of SC-37211 on the thyroid.

The effects of disopyramide phosphate on serum glucose and glucose counterregulation in the dog.

The effect of oral administration of the antiarrhythmic disopyramide phosphate (DPP) on serum glucose and glucose counterregulation was determined in beagle dogs. In addition, the hypoglycemic effect of DPP, a racemate, and its optical isomers was determined. DPP produced dose-dependent significant decreases in serum glucose concentrations. Maximum decreases in serum glucose concentrations were approximately 10% at 10 mg/kg, 15% at 30 mg/kg, and 30% at 100 mg/kg when DPP was given as single doses, and 30% at 100 mg/kg when DPP was given as three divided doses. In each case, serum glucose concentrations returned to control values within 24 to 30 hr. To evaluate the effect of DPP on glucose counterregulation the recovery from acute insulin-induced hypoglycemia was determined. No differences of any practical significance were observed between the insulin tolerance curves of control and 50-, and 100-mg/kg DPP groups. Thus, the overall glucose counterregulatory response following insulin challenge was unaffected by DPP. The hypoglycemic effects of DPP, (S)-(+)-DPP, and (R)-(-)-DPP were compared by examining the ratio of the areas under the curve of serum glucose concentration to serum drug concentration. The absolute ratio for the (S)-(+) isomer was significantly greater than that of the (R)-(-) isomer, indicating that the hypoglycemic effect of DPP is largely due to its (S)-(+) isomer.

Feed refusal factors in pure cultures of Fusarium roseum 'graminearum'.

Isolations from 1972 Wisconsin feed refusal corn yielded predominantly cultures of Fusarium roseum 'graminearum.' With one possible exception, none of the selected isolates of this fungus induced emesis in pigeons, whereas six of nine isolates produced feed refusal responses in all test animals. A single isolate of F. roseum 'equiseti' also induced a severe refusal response and possibly slight emesis. None of the other fungi isolated from this corn (F. moniliforme, Acremoniella atra) or controls caused either emesis or feed refusal. Zearalenone was detected in all isolates and was shown to be partially responsible for refusal activity. The remaining activity was ascribed to one or more nonvolatile, neutral, relatively polar molecules. T-2 toxin, although not detected in these isolates, was shown to have dramatic refusal activity in rats.

Isolation of acetyl T-2 toxin from Fusarium poae.

Acetyl T-2 toxin (3,4,15-triacetoxy-8-isovaleroxy-12,13-epoxy-delta9-trichothecene) was isolated and characterized as a naturally occurring emetic trichothecene from liquid cultures of Fusarium poae (NRRL 3287). Acetyl T-2 toxin was shown to be much less toxic than T-2 toxin in pigeon assays.