Acute effects of aspartame on systolic blood pressure in spontaneously hypertensive rats

Comparison of aspartame- and sugar-sweetened soft drinks on postprandial metabolism

Aim: We compared the impact of artificially- and sugar-sweetened beverages co-ingested with a mixed meal on postprandial fat and carbohydrate oxidation, blood glucose, and plasma insulin and triglyceride concentrations. Methods: Eight college-aged, healthy males completed three randomly assigned trials, which consisted of a mixed macronutrient meal test with 20oz of Diet-Coke (AS), Coca-Cola (NS), or water (CON). One week separated each trial and each participant served as his own control. Resting energy expenditure (REE) via indirect calorimetry, blood pressure, and blood samples were obtained immediately before, 5, 10, 30, 60, 120, and 180 min after meal and beverage ingestion. A two-way (treatment × time) repeated-measures ANOVA was conducted to assess REE, fat and carbohydrate oxidation rates, blood glucose, and plasma insulin and triglyceride concentrations. Results: There was a significant main effect of treatment on total fat oxidation (P = 0.006), fat oxidation was significantly higher after AS (P = 0.006) and CON (P = 0.001) compared to following NS. There was a significant main effect of treatment on total carbohydrate oxidation (P = 0.005), carbohydrate oxidation was significantly lower after AS (P = 0.014) and CON (P = 0.001) compared to following NS. Plasma insulin concentration AUC was significantly lower after AS (P = 0.019) and trended lower in CON (P = 0.054) compared to following NS. Conclusion: Ingestion of a mixed meal with an artificially-sweetened beverage does not impact postprandial metabolism, whereas a sugar-sweetened beverage suppresses fat oxidation and increases carbohydrate oxidation compared to artificially-sweetened beverage and water.

Childhood beverage intake and risk of hypertension and hyperlipidaemia in young adults

An epidemiological analysis assessing beverage consumption and risk factors for cardiovascular disease was conducted. Participants were 9-16 years old at enrolment, completed food frequency questionnaires in 1996-2001 and self-reported outcomes in 2010-2014. Exclusion criteria included missing data on relevant variables and covariates, prevalent disease before 2005, and implausible/extreme weight or energy intake. Intakes of orange juice, apple/other fruit juice, sugar-sweetened beverages and diet soda were related to the risk of incident hypertension or hyperlipidaemia using Cox proportional hazards regression, adjusting for diet, energy intake, age, smoking, physical activity and body mass index. There were 9,043 participants with 618 cases of hypertension and 850 of hyperlipidaemia in 17 years of mean follow-up. Sugar-sweetened beverage intake but not fruit juice nor diet soda was associated with hypertension (hazard ratio (95% confidence interval): 1.16 (1.03, 1.31)) in males. This study can guide beverage consumption as it relates to early predictors of cardiovascular disease.

Soft drink and non-caloric soft drink intake and their association with blood pressure: the Health Workers Cohort Study

Background

A few prospective studies have investigated the potential association of soft drink and non-caloric soft drink intake with high blood pressure using methods that adequately consider changes in intake over time and hypertensive status at baseline.

Objective

To prospectively examine the association of soft drink and non-caloric soft drink intake with systolic and diastolic blood pressure in a sample of Mexican adults, overall and by hypertension status.

Methods

We used data from the Health Workers Cohort Study spanning from 2004 to 2018 (n = 1,324 adults). Soft drink and non-caloric soft drink intake were assessed with a semiquantitative food frequency questionnaire. We fit multivariable-adjusted fixed-effects models to test the association of soft drink and non-caloric soft drink intake with systolic and diastolic blood pressure. The models were adjusted for potential confounders and considering the potential modifying effect of hypertension status at baseline.

Results

A one-serving increase in soft drink intake was associated with a 2.08 mm Hg (95% CI: 0.21, 3.94) increase in systolic blood pressure and 2.09 mm Hg (95% CI: 0.81, 3.36) increase in diastolic blood pressure over ten years. A stronger association between soft drink intake and diastolic pressure was observed among participants with versus without hypertension at baseline. We found no association between non-caloric soft drink intake and blood pressure.

Conclusions

Our findings support the hypothesis that soft drink intake increases blood pressure. While further studies should be conducted to confirm our findings, food policies and recommendations to limit soft drink intake are likely to help reduce blood pressure at the population level. We probably did not find an association between non-caloric soft drink intake and blood pressure because of the low consumption of this type of beverage in the cohort. More studies will be needed to understand the potential effect of non-caloric beverages on blood pressure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-022-00792-y.

Long-term consumption of artificial sweeteners does not affect cardiovascular health and survival in rats

Background

Recent epidemiological cohort studies have suggested that consumption of artificial sweeteners (AS) is associated with adverse cardiovascular events and mortality. However, these population association studies cannot establish a causal relationship. In this study we investigated the effect of long-term (1-year) consumption of AS (Equal and Splenda, two commonly used AS) on cardiovascular health and survival in rats.

Methods

Adult Sprague-Dawley rats (both sexes, 4-5 months old) were randomized into the following 3 groups: control (n = 21), AS Equal (n = 21) and Splenda (n = 18). In the AS groups, Equal or Splenda was added to the drinking water (2-packets/250 ml), while drinking water alone was used in the control rats. The treatment was administered for 12 months. Cardiovascular function and survival were monitored in all animals.

Results

It was found that rats in the AS groups consistently consumed more sweetened water than those in the control group. AS did not affect body weight, non-fasting blood cholesterol, triglycerides, blood pressure or pulse wave velocity. There were no significant differences in left ventricular wall thicknesses, chamber dimension, cardiac function or survival. AS did not affect heart rate or atrial effective refractory period. However, rats in both Equal and Splenda groups had prolonged PR intervals (63 ± 5ms in Equal, 68 ± 6 ms in Splenda, vs 56 ± 8 ms in control, p < 0.05) and a tendency of increased atrial fibrillation inducibility.

Conclusion

Long-term consumption of AS does not affect cardiovascular structure, function or survival but may cause some electrophysiological abnormalities with prolonged PR intervals and a tendency of increased atrial fibrillation inducibility in rats.

Sucrose-sweetened beverages increase fat storage in the liver, muscle, and visceral fat depot: a 6-mo randomized intervention study

BACKGROUND

The consumption of sucrose-sweetened soft drinks (SSSDs) has been associated with obesity, the metabolic syndrome, and cardiovascular disorders in observational and short-term intervention studies. Too few long-term intervention studies in humans have examined the effects of soft drinks.

OBJECTIVE

We compared the effects of SSSDs with those of isocaloric milk and a noncaloric soft drink on changes in total fat mass and ectopic fat deposition (in liver and muscle tissue).

DESIGN

Overweight subjects (n = 47) were randomly assigned to 4 different test drinks (1 L/d for 6 mo): SSSD (regular cola), isocaloric semiskim milk, aspartame-sweetened diet cola, and water. The amount of intrahepatic fat and intramyocellular fat was measured with (1)H-magnetic resonance spectroscopy. Other endpoints were fat mass, fat distribution (dual-energy X-ray absorptiometry and magnetic resonance imaging), and metabolic risk factors.

RESULTS

The relative changes between baseline and the end of 6-mo intervention were significantly higher in the regular cola group than in the 3 other groups for liver fat (132-143%, sex-adjusted mean; P < 0.01), skeletal muscle fat (117-221%; P < 0.05), visceral fat (24-31%; P < 0.05), blood triglycerides (32%; P < 0.01), and total cholesterol (11%; P < 0.01). Total fat mass was not significantly different between the 4 beverage groups. Milk and diet cola reduced systolic blood pressure by 10-15% compared with regular cola (P < 0.05). Otherwise, diet cola had effects similar to those of water.

CONCLUSION

Daily intake of SSSDs for 6 mo increases ectopic fat accumulation and lipids compared with milk, diet cola, and water. Thus, daily intake of SSSDs is likely to enhance the risk of cardiovascular and metabolic diseases. This trial is registered at clinicaltrials.gov as NCT00777647.

Cardiovascular and ventilatory effects of various acidic, basic and neutral L-amino acids in normotensive rats

Cardiovascular effects have been attributed to the amino acids which are precursors of catecholamines or other neurotransmitters. To study if even other amino acids may exert cardiovascular or ventilatory effects, a number of various acidic, basic and neutral L-amino acids were injected intravenously to anaesthetised normotensive rats at the doses of 0.2-1.6 mmol/kg. All amino acids were able to produce either blood pressure, heart rate or ventilation rate changes. Hence, in this study the production of cardiovascular or ventilatory effects was not limited to the known precursors of neurotransmitters. Therefore, in addition to increased formation and release of neurotransmitters, other mechanisms are apparently involved in the cardiovascular and ventilatory effects of various L-amino acids.

Mechanisms of phenylalanine-induced pressor effects in conscious rats

Phenylalanine and tyrosine reportedly decrease blood pressure in conscious restrained rats. However, tyrosine has recently been found to increase blood pressure in anesthetized animals, questioning the generality of findings obtained in restrained animals. The present study therefore evaluated the effects of phenylalanine on mean arterial pressure (MAP) and heart rate (HR) in unrestrained, conscious rats. Phenylalanine (0.32-1.33 mmol/kg i.p.) increased MAP and decreased HR, effects that were antagonized by carbidopa and prazosin but not by desipramine. In addition, both DOPA and tyrosine (1.33 mmol/kg) increased MAP. In contrast, phenylalanine-induced increases in plasma concentrations of its indirectly acting sympathomimetic amine metabolite, phenethylamine, were small and temporally unrelated to the phenylalanine-induced MAP elevation, and desipramine inhibited MAP increases produced by exogenous phenethylamine. These observations indicate that phenylalanine increases MAP in conscious, unrestrained animals by augmenting peripheral catecholamine synthesis and release rather than by affecting phenethylamine bioavailability.

Effects of oral aspartame on plasma phenylalanine in humans and experimental rodents. Short note

All aspartame does given to humans cause greater elevations in plasma (and, presumably, brain) phenylalanine than in plasma tyrosine. In contrast, doses of aspartame usually used in experiments on rodents preferentially elevate tyrosine. Since phenylalanine can inhibit brain catecholamine synthesis while tyrosine is the antidote for this effect, we determined the aspartame dose that would be needed to elevate phenylalanine more than tyrosine in rodents, using published data. In general rodents need 60 times as much aspartame, on a mg/kg basis, as humans to obtain comparable elevations in phenylalanine with respect to tyrosine.