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How Does Circadian Rhythm Impact Salt Sensitivity of Blood Pressure in Mice? A Study in Two Close C57Bl/6 Substrains.

Combe R, Mudgett J, El Fertak L, Champy MF, Ayme-Dietrich E, Petit-Demoulière B, Sorg T, Herault Y, Madwed JB, Monassier L - PLoS ONE (2016)

Bottom Line: High-salt/normal potassium vs.High salt/low potassium, standard vs. modified light cycle, Non-invasive tail cuff blood pressure vs. telemetry).Finally, from a methodological perspective, light cycle inversion has no effect on this circadian BP phenotype and tail-cuff method is less sensitive than telemetry to detect BP phenotypes due to salt challenges.

View Article: PubMed Central - PubMed

Affiliation: Institut Clinique de la Souris, Institut de Génétique et de Biologie Moléculaire, Université de Strasbourg, Illkirch, France.

ABSTRACT

Background: Mouse transgenesis has provided the unique opportunity to investigate mechanisms underlying sodium kidney reabsorption as well as end organ damage. However, understanding mouse background and the experimental conditions effects on phenotypic readouts of engineered mouse lines such as blood pressure presents a challenge. Despite the ability to generate high sodium and chloride plasma levels during high-salt diet, observed changes in blood pressure are not consistent between wild-type background strains and studies.

Methods: The present work was designed in an attempt to determine guidelines in the field of salt-induced hypertension by recording continuously blood pressure by telemetry in mice submitted to different sodium and potassium loaded diets and changing experimental conditions in both C57BL/6N and C57BL/6J mice strain (Normal salt vs. Low salt vs. High-salt/normal potassium vs. High salt/low potassium, standard vs. modified light cycle, Non-invasive tail cuff blood pressure vs. telemetry).

Results: In this study, we have shown that, despite a strong blood pressure (BP) basal difference between C57BL/6N and C57BL/6J mice, High salt/normal potassium diet increases BP and heart rate during the active phase only (dark period) in the same extent in both strains. On the other hand, while potassium level has no effect on salt-induced hypertension in C57BL/6N mice, high-salt/low potassium diet amplifies the effect of the high-salt challenge only in C57BL/6J mice. Indeed, in this condition, salt-induced hypertension can also be detected during light period even though this BP increase is lower compared to the one occurring during the dark period. Finally, from a methodological perspective, light cycle inversion has no effect on this circadian BP phenotype and tail-cuff method is less sensitive than telemetry to detect BP phenotypes due to salt challenges.

Conclusions: Therefore, to carry investigations on salt-induced hypertension in mice, chronic telemetry and studies in the active phase are essential prerequisites.

No MeSH data available.


Related in: MedlinePlus

Effect of high salt diets on the circadian blood pressure variations in C57BL/6N and C57BL/6J mice under a reverse light/dark cycle.2.5 days continuous telemetric recordings of systolic blood pressure after 2 weeks of NS, HS or HS/LK diet challenge. A) n = 8 per group B) n = 6 per group C) n = 8 per group D) n = 9 per group. Two-way ANOVA followed by Sidak’s post-hoc test *: p<0.05 for interaction.
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pone.0153472.g004: Effect of high salt diets on the circadian blood pressure variations in C57BL/6N and C57BL/6J mice under a reverse light/dark cycle.2.5 days continuous telemetric recordings of systolic blood pressure after 2 weeks of NS, HS or HS/LK diet challenge. A) n = 8 per group B) n = 6 per group C) n = 8 per group D) n = 9 per group. Two-way ANOVA followed by Sidak’s post-hoc test *: p<0.05 for interaction.

Mentions: The effects of the different high salt diets on BP were not due to a disturbance of the circadian rhythm neither in mice under a normal light/dark cycle nor under a modified light/dark cycle (Fig 4). Both C57BL6/N and C57BL6/J mice exhibited a decrease in BP during resting period i.e. when the light was turned on at 11:00 pm and an increase in BP during the active period i.e. when the light was turned off at 11:00 am. The shifts in BP were consistent from day to day and occurred at the same time as the light cycle showing a good adaptation of mice to experimental changes of the light/dark cycle. The circadian BP variation was similar in mice fed a NS diet compared to mice fed with HS or HS/LK diets in both strains. Therefore, a shift in the circadian BP rhythm cannot explain the dark-period restricted hypertension phenotype induced by the different high-salt diets.


How Does Circadian Rhythm Impact Salt Sensitivity of Blood Pressure in Mice? A Study in Two Close C57Bl/6 Substrains.

Combe R, Mudgett J, El Fertak L, Champy MF, Ayme-Dietrich E, Petit-Demoulière B, Sorg T, Herault Y, Madwed JB, Monassier L - PLoS ONE (2016)

Effect of high salt diets on the circadian blood pressure variations in C57BL/6N and C57BL/6J mice under a reverse light/dark cycle.2.5 days continuous telemetric recordings of systolic blood pressure after 2 weeks of NS, HS or HS/LK diet challenge. A) n = 8 per group B) n = 6 per group C) n = 8 per group D) n = 9 per group. Two-way ANOVA followed by Sidak’s post-hoc test *: p<0.05 for interaction.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4835052&req=5

pone.0153472.g004: Effect of high salt diets on the circadian blood pressure variations in C57BL/6N and C57BL/6J mice under a reverse light/dark cycle.2.5 days continuous telemetric recordings of systolic blood pressure after 2 weeks of NS, HS or HS/LK diet challenge. A) n = 8 per group B) n = 6 per group C) n = 8 per group D) n = 9 per group. Two-way ANOVA followed by Sidak’s post-hoc test *: p<0.05 for interaction.
Mentions: The effects of the different high salt diets on BP were not due to a disturbance of the circadian rhythm neither in mice under a normal light/dark cycle nor under a modified light/dark cycle (Fig 4). Both C57BL6/N and C57BL6/J mice exhibited a decrease in BP during resting period i.e. when the light was turned on at 11:00 pm and an increase in BP during the active period i.e. when the light was turned off at 11:00 am. The shifts in BP were consistent from day to day and occurred at the same time as the light cycle showing a good adaptation of mice to experimental changes of the light/dark cycle. The circadian BP variation was similar in mice fed a NS diet compared to mice fed with HS or HS/LK diets in both strains. Therefore, a shift in the circadian BP rhythm cannot explain the dark-period restricted hypertension phenotype induced by the different high-salt diets.

Bottom Line: High-salt/normal potassium vs.High salt/low potassium, standard vs. modified light cycle, Non-invasive tail cuff blood pressure vs. telemetry).Finally, from a methodological perspective, light cycle inversion has no effect on this circadian BP phenotype and tail-cuff method is less sensitive than telemetry to detect BP phenotypes due to salt challenges.

View Article: PubMed Central - PubMed

Affiliation: Institut Clinique de la Souris, Institut de Génétique et de Biologie Moléculaire, Université de Strasbourg, Illkirch, France.

ABSTRACT

Background: Mouse transgenesis has provided the unique opportunity to investigate mechanisms underlying sodium kidney reabsorption as well as end organ damage. However, understanding mouse background and the experimental conditions effects on phenotypic readouts of engineered mouse lines such as blood pressure presents a challenge. Despite the ability to generate high sodium and chloride plasma levels during high-salt diet, observed changes in blood pressure are not consistent between wild-type background strains and studies.

Methods: The present work was designed in an attempt to determine guidelines in the field of salt-induced hypertension by recording continuously blood pressure by telemetry in mice submitted to different sodium and potassium loaded diets and changing experimental conditions in both C57BL/6N and C57BL/6J mice strain (Normal salt vs. Low salt vs. High-salt/normal potassium vs. High salt/low potassium, standard vs. modified light cycle, Non-invasive tail cuff blood pressure vs. telemetry).

Results: In this study, we have shown that, despite a strong blood pressure (BP) basal difference between C57BL/6N and C57BL/6J mice, High salt/normal potassium diet increases BP and heart rate during the active phase only (dark period) in the same extent in both strains. On the other hand, while potassium level has no effect on salt-induced hypertension in C57BL/6N mice, high-salt/low potassium diet amplifies the effect of the high-salt challenge only in C57BL/6J mice. Indeed, in this condition, salt-induced hypertension can also be detected during light period even though this BP increase is lower compared to the one occurring during the dark period. Finally, from a methodological perspective, light cycle inversion has no effect on this circadian BP phenotype and tail-cuff method is less sensitive than telemetry to detect BP phenotypes due to salt challenges.

Conclusions: Therefore, to carry investigations on salt-induced hypertension in mice, chronic telemetry and studies in the active phase are essential prerequisites.

No MeSH data available.


Related in: MedlinePlus