Limits...
Diurnal variation of human sweet taste recognition thresholds is correlated with plasma leptin levels.

Nakamura Y, Sanematsu K, Ohta R, Shirosaki S, Koyano K, Nonaka K, Shigemura N, Ninomiya Y - Diabetes (2008)

Bottom Line: The diurnal variation for sweet thresholds in the normal feeding condition (three meals) was independent of meal timing and thereby blood glucose levels.Furthermore, when leptin levels were phase-shifted following imposition of one or two meals per day, the diurnal variation of thresholds for sweet taste shifted in parallel.This synchronization of diurnal variation in leptin levels and sweet taste recognition thresholds suggests a mechanistic connection between these two variables in humans.

View Article: PubMed Central - PubMed

Affiliation: Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.

ABSTRACT

Objective: It has recently been proposed that the peripheral taste organ is one of the targets for leptin. In lean mice, leptin selectively suppresses gustatory neural and behavioral responses to sweet compounds without affecting responses to other taste stimuli, whereas obese diabetic db/db mice with defects in leptin receptor lack this leptin suppression on sweet taste. Here, we further examined potential links between leptin and sweet taste in humans.

Research design and methods: A total of 91 nonobese subjects were used to determine recognition thresholds using a standard stair-case methodology for various taste stimuli. Plasma leptin levels were determined by an enzyme-linked immunosorbent assay at several timepoints during the day under normal and restricted-meal conditions.

Results: The recognition thresholds for sweet compounds exhibited a diurnal variation from 0800 to 2200 h that parallels variation for leptin levels, with the lowest thresholds in the morning and the highest thresholds at night. This diurnal variation is sweet-taste selective-it was not observed in thresholds for other taste stimuli (NaCl, citric acid, quinine, and mono-sodium glutamate). The diurnal variation for sweet thresholds in the normal feeding condition (three meals) was independent of meal timing and thereby blood glucose levels. Furthermore, when leptin levels were phase-shifted following imposition of one or two meals per day, the diurnal variation of thresholds for sweet taste shifted in parallel.

Conclusions: This synchronization of diurnal variation in leptin levels and sweet taste recognition thresholds suggests a mechanistic connection between these two variables in humans.

Show MeSH

Related in: MedlinePlus

A: Percent changes in plasma leptin levels and taste recognition thresholds at 2200 h compared with basal values collected at 0800 h (control = 100%). Statistical analysis (t test) for differences in 2200 h values among meal conditions was done by using raw values. n = 47 subjects tested (44 for saccharin) for three meals (▪), n = 16 for two meals (▒), and n = 24 for one meal (□). **P < 0.01 (t test), *P < 0.05. B: Correlation coefficients between postingestive increases in blood glucose (□) or insulin (▪) levels after dinner (at 1900 h) versus leptin levels and recognition thresholds for sucrose, glucose, saccharin, NaCl, HCl, quinine, or MSG before dinner (at 1700 h) among individuals (n = 32–82). Correlation coefficients were obtained by using data for all subjects having a common dinner, thereby consuming the same calorie (1,000 kcal) and nutritional contents regardless of whether they had breakfast and/or lunch before dinner. ***P < 0.001 (t test), **P < 0.01, *P < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2551675&req=5

f2: A: Percent changes in plasma leptin levels and taste recognition thresholds at 2200 h compared with basal values collected at 0800 h (control = 100%). Statistical analysis (t test) for differences in 2200 h values among meal conditions was done by using raw values. n = 47 subjects tested (44 for saccharin) for three meals (▪), n = 16 for two meals (▒), and n = 24 for one meal (□). **P < 0.01 (t test), *P < 0.05. B: Correlation coefficients between postingestive increases in blood glucose (□) or insulin (▪) levels after dinner (at 1900 h) versus leptin levels and recognition thresholds for sucrose, glucose, saccharin, NaCl, HCl, quinine, or MSG before dinner (at 1700 h) among individuals (n = 32–82). Correlation coefficients were obtained by using data for all subjects having a common dinner, thereby consuming the same calorie (1,000 kcal) and nutritional contents regardless of whether they had breakfast and/or lunch before dinner. ***P < 0.001 (t test), **P < 0.01, *P < 0.05.

Mentions: As shown in Table 2, there were significant increases in threshold values for sucrose, glucose, and saccharin as well as in leptin levels at 2200 h compared with the values at 0800 h (t tests, P < 0.05). This was not the case for the other taste stimuli (P > 0.05). Percent changes in thresholds (in log-transformed values) between the two time points (2200 vs. 0,800 h) in the normal feeding condition were ∼20% for sugars, which were significantly larger than those for other taste stimuli (t tests, P < 0.05) but smaller than that for leptin (∼50%, P < 0.01) (Fig. 2A). Skipping meals led to significant decreases in percent changes in leptin levels and recognition thresholds for sweeteners (P < 0.01–0.05). Increases in blood glucose and insulin levels of individuals after meals were negatively correlated with leptin levels and recognition thresholds for sweeteners but not for other tastes before meals (Fig. 2B). This suggests that leptin levels and sweet sensitivities before meals may influence postingestive increases in glucose and insulin levels.


Diurnal variation of human sweet taste recognition thresholds is correlated with plasma leptin levels.

Nakamura Y, Sanematsu K, Ohta R, Shirosaki S, Koyano K, Nonaka K, Shigemura N, Ninomiya Y - Diabetes (2008)

A: Percent changes in plasma leptin levels and taste recognition thresholds at 2200 h compared with basal values collected at 0800 h (control = 100%). Statistical analysis (t test) for differences in 2200 h values among meal conditions was done by using raw values. n = 47 subjects tested (44 for saccharin) for three meals (▪), n = 16 for two meals (▒), and n = 24 for one meal (□). **P < 0.01 (t test), *P < 0.05. B: Correlation coefficients between postingestive increases in blood glucose (□) or insulin (▪) levels after dinner (at 1900 h) versus leptin levels and recognition thresholds for sucrose, glucose, saccharin, NaCl, HCl, quinine, or MSG before dinner (at 1700 h) among individuals (n = 32–82). Correlation coefficients were obtained by using data for all subjects having a common dinner, thereby consuming the same calorie (1,000 kcal) and nutritional contents regardless of whether they had breakfast and/or lunch before dinner. ***P < 0.001 (t test), **P < 0.01, *P < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2551675&req=5

f2: A: Percent changes in plasma leptin levels and taste recognition thresholds at 2200 h compared with basal values collected at 0800 h (control = 100%). Statistical analysis (t test) for differences in 2200 h values among meal conditions was done by using raw values. n = 47 subjects tested (44 for saccharin) for three meals (▪), n = 16 for two meals (▒), and n = 24 for one meal (□). **P < 0.01 (t test), *P < 0.05. B: Correlation coefficients between postingestive increases in blood glucose (□) or insulin (▪) levels after dinner (at 1900 h) versus leptin levels and recognition thresholds for sucrose, glucose, saccharin, NaCl, HCl, quinine, or MSG before dinner (at 1700 h) among individuals (n = 32–82). Correlation coefficients were obtained by using data for all subjects having a common dinner, thereby consuming the same calorie (1,000 kcal) and nutritional contents regardless of whether they had breakfast and/or lunch before dinner. ***P < 0.001 (t test), **P < 0.01, *P < 0.05.
Mentions: As shown in Table 2, there were significant increases in threshold values for sucrose, glucose, and saccharin as well as in leptin levels at 2200 h compared with the values at 0800 h (t tests, P < 0.05). This was not the case for the other taste stimuli (P > 0.05). Percent changes in thresholds (in log-transformed values) between the two time points (2200 vs. 0,800 h) in the normal feeding condition were ∼20% for sugars, which were significantly larger than those for other taste stimuli (t tests, P < 0.05) but smaller than that for leptin (∼50%, P < 0.01) (Fig. 2A). Skipping meals led to significant decreases in percent changes in leptin levels and recognition thresholds for sweeteners (P < 0.01–0.05). Increases in blood glucose and insulin levels of individuals after meals were negatively correlated with leptin levels and recognition thresholds for sweeteners but not for other tastes before meals (Fig. 2B). This suggests that leptin levels and sweet sensitivities before meals may influence postingestive increases in glucose and insulin levels.

Bottom Line: The diurnal variation for sweet thresholds in the normal feeding condition (three meals) was independent of meal timing and thereby blood glucose levels.Furthermore, when leptin levels were phase-shifted following imposition of one or two meals per day, the diurnal variation of thresholds for sweet taste shifted in parallel.This synchronization of diurnal variation in leptin levels and sweet taste recognition thresholds suggests a mechanistic connection between these two variables in humans.

View Article: PubMed Central - PubMed

Affiliation: Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.

ABSTRACT

Objective: It has recently been proposed that the peripheral taste organ is one of the targets for leptin. In lean mice, leptin selectively suppresses gustatory neural and behavioral responses to sweet compounds without affecting responses to other taste stimuli, whereas obese diabetic db/db mice with defects in leptin receptor lack this leptin suppression on sweet taste. Here, we further examined potential links between leptin and sweet taste in humans.

Research design and methods: A total of 91 nonobese subjects were used to determine recognition thresholds using a standard stair-case methodology for various taste stimuli. Plasma leptin levels were determined by an enzyme-linked immunosorbent assay at several timepoints during the day under normal and restricted-meal conditions.

Results: The recognition thresholds for sweet compounds exhibited a diurnal variation from 0800 to 2200 h that parallels variation for leptin levels, with the lowest thresholds in the morning and the highest thresholds at night. This diurnal variation is sweet-taste selective-it was not observed in thresholds for other taste stimuli (NaCl, citric acid, quinine, and mono-sodium glutamate). The diurnal variation for sweet thresholds in the normal feeding condition (three meals) was independent of meal timing and thereby blood glucose levels. Furthermore, when leptin levels were phase-shifted following imposition of one or two meals per day, the diurnal variation of thresholds for sweet taste shifted in parallel.

Conclusions: This synchronization of diurnal variation in leptin levels and sweet taste recognition thresholds suggests a mechanistic connection between these two variables in humans.

Show MeSH
Related in: MedlinePlus