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Written byLeo
SourceLilac AcademicHave
you ever dieted to lose weight? When fasting, do you salivate when you smell the smell of food?
Food smell is an important sensory cue
to look for food during fasting.
Thus, olfactory sensitivity increases
under fasting conditions.
However, whether the olfactory system is involved in metabolic adaptation remains elusive
.
On November 14, 2022, a team led by Toshiyasu Sasaoka from the Department of Clinical Pharmacology at the University of Toyama in Japan discovered that food odor perception boosts lipid metabolism
in mice.
The study was published in the journal Nature Metabolism under the title Food odor perception promotes systemic lipid utilization
.
During fasting, food odor stimuli increase serum free fatty acids
through lipolysis, which is mediated by central melanocortin and sympathetic nervous system.
In addition, stimulation with food odors prior to feeding enhances lipid utilization
throughout the body.
Finally, this study also shows that intermittent fasting combined with food odor stimulation can improve glycemic control and prevent diet-induced insulin resistance
in obese mice.
Therefore, olfactory regulation is necessary to maintain metabolic homeostasis in energy-deficient or energy-surplus environments and can be considered as part of
dietary interventions for metabolic disorders.
During fasting, food odor triggers food exploration behavior
in miceIn order to reveal the effects of olfactory and visual food cues on exploration behavior during fasting in mice, The researchers placed mice that had been fasted for 24 hours in either spontaneous olfactory stimulation (SOS) or visual stimulation (SVS) devices
.
In the SOS cage, mice only explored tubes that released known food odors
.
Food visual stimulation administered at week 3 failed to elicit exploratory behavior
.
They then divided the mice into two groups: mice that underwent sham surgery and mice
that underwent olfactory bulbectomy.
After one week (week 4), visual stimulation of food still had no effect
on exploratory behavior in mice undergoing olfactory bulbectomy.
In contrast, olfactory bulboctomy mice suppressed odor-based exploration
at week 5.
Thus, fasting mice explore known favorite foods based on olfactory information rather than visual information.
Food odor exposure causes lipid mobilization
during fasting To elucidate metabolic changes in mice in the presence or absence of food odor stimuli, the researchers measured unesterified fatty acids (NEFA) serum levels, which are the main source of
energy during fasting.
Compared with the feeding level, the basal NEFA level of mice increased slightly (but not significantly) after 6 hours of fasting and significantly increased after 16~24 hours of
fasting.
Stimulation with food odor under 24-h fasting conditions further increases NEFA levels
in mice.
These characteristics appear to be advantageous because unsaturated fatty acids have beneficial
metabolic health compared to saturated fatty acids.
The mechanism connecting food odor detection and lipid mobilization In order to reveal the core mechanism
of lipid mobilization of food odor during fasting, The researchers explored whether hypothalamic melanocortin and the autonomic nervous system are involved in this process
.
They pretreated with the melanocortin 4 receptor (MC4R) antagonist SHU9119 and found that although SHU9119 had no direct effect on basal NEFA levels in the fasting state, it inhibited the increase
in olfactory-dependent NEFA.
The use of the MC4R agonist melanotan II is associated with elevated
NEFA.
In addition, pretreatment with the β-adrenergic blocker propranolol also reduced serum NEFA levels
during odor stimulation.
These results suggest that the hypothalamic MC4R and sympathetic nervous system are involved in lipid mobilization
induced by food odor perception.
By analyzing protein and gene expression profiles, the researchers further explored the lipid processing mechanisms
of peripheral tissues when food odors are smelled.
They found that phosphorylation levels of hormone-sensitive lipase (HSL) in the white adipose tissue (eWAT) of the epididymis were elevated after 30 minutes of exposure to odor during fasting, suggesting that in a fasted state, The perception of food odor enhances lipolysis of adipotic
tissue.
In the liver, phosphorylation of the molecule S6 ribosomal protein downstream of mTOR in the liver increases after 10 min of
exposure to odor during fasting.
To fully describe the systemic effects of food odor perception during fasting, the researchers performed RNA-seq analysis
on six tissues of mice after 60 minutes of exposure to odor during fasting.
Principal component analysis showed that olfactory stimulation mainly affected gene expression
in soleus muscle, eWANT, and pancreas.
In terms of lipid metabolism, differentially expressed genes are related to the digestion, absorption and metabolic pathways of fats and proteins.
Preexposure to food odor improves postprandial fat utilizationNext
, the researchers examined whether stimulating mice with food odor in a starvation state affected lipid dynamics after fat intake
。 The oral fat tolerance test (OFTT) has shown that pre-stimulation with normal food odors enhances lipid intake-induced elevated serum triglyceride levels
.
However, food odor stimulation during fasting did not affect subsequent food intake, blood glucose levels in the eating state, serum insulin or adiponectin levels
.
Metabolic cage analysis showed that odor stimulation during fasting reduced respiratory quotient (RQ)
after refeeding.
But in leptin receptor-deficient db/db mice, noThis change
in RQ has been detected.
These results suggest that preprandial stimulation with food odor promotes postprandial lipid utilization in a leptin receptor-related manner, independent of orexinergic and dopaminergic reward pathways
in the brain.
Consistent with reduced respiratory quotient, premeal stimulation of odor increases serum triglycerides and cholesterol
in chylomicrons and VLDR components.
So, which tissues are involved in olfactory-induced lipid metabolism? Under refeeding conditions, metabolomic analysis targeting the tricarboxylic acid cycle showed that most metabolites were increased in the liver but decreased
in soleus muscle in mice pre-stimulated by odor during fasting.
Thus, stimulation of food odor during fasting promotes tissue-specific regulation of metabolic activity during re-eating, significantly enhancing metabolic flow
in the liver.
In addition, the researchers observed that pre-stimulation with odor during fasting reduced HSL phosphorylation in eWAT and Ucp1 and Pgc1a mRNA
in brown adipose tissue after refeeding.
These are thermogenic markers and these alterations represent an inhibition
of sympathetic regulation of adipose tissue during re-eating.
Finally, they studied the effect of
food odor stimulation in mice fed a high-fat diet under diet-induced obesity conditions
。 Under intermittent fasting conditions, odor stimulation of fatty foods had no additional effect
on body weight and food intake in mice.
But importantly, odor stimuli from intermittent fatty foods during fasting reduce blood sugar levels, insulin resistance index, and insulin secretion index
.
In the oral glucose tolerance test, peak glucose levels were reduced
in the odor-stimulated group.
Thus, chronic food odor stimulation increases the benefits of intermittent fasting on glucose metabolism without additional weight alteration
for diet-induced obesity.
This study shows that food odor perception during fasting triggers biphasic regulation of lipid metabolism, i.
e.
, food odor perception during fasting promotes lipid mobilization during fasting, Lipid utilization during subsequent refeeding can prevent insulin resistance in obese mice on a diet.
The link between smell and lipid metabolism helps maintain metabolic health
in energy-deficient and energy-overloaded environments in mice.
The results of this study may be beneficial for the development of an olfactory-based strategy to prevent metabolic disorders and chronic energy imbalance
.
That said, the temptations of smelling delicious food during your fasting to lose weight are not necessarily bad, these temptations can help mobilize your fat! Of course, resisting these temptations is key
.
Link to the paper:
style="font-family: , "Microsoft YaHei";letter-spacing: normal;color: rgb(136, 136, 136);font-size: 12px;" _mstmutation="1" _istranslated="1">
Open reprint, welcome to forward to Moments and WeChat groups
SourceLilac AcademicHave
you ever dieted to lose weight? When fasting, do you salivate when you smell the smell of food?
Food smell is an important sensory cue
to look for food during fasting.
Thus, olfactory sensitivity increases
under fasting conditions.
However, whether the olfactory system is involved in metabolic adaptation remains elusive
.
On November 14, 2022, a team led by Toshiyasu Sasaoka from the Department of Clinical Pharmacology at the University of Toyama in Japan discovered that food odor perception boosts lipid metabolism
in mice.
The study was published in the journal Nature Metabolism under the title Food odor perception promotes systemic lipid utilization
.
During fasting, food odor stimuli increase serum free fatty acids
through lipolysis, which is mediated by central melanocortin and sympathetic nervous system.
In addition, stimulation with food odors prior to feeding enhances lipid utilization
throughout the body.
Finally, this study also shows that intermittent fasting combined with food odor stimulation can improve glycemic control and prevent diet-induced insulin resistance
in obese mice.
Therefore, olfactory regulation is necessary to maintain metabolic homeostasis in energy-deficient or energy-surplus environments and can be considered as part of
dietary interventions for metabolic disorders.
During fasting, food odor triggers food exploration behavior
in miceIn order to reveal the effects of olfactory and visual food cues on exploration behavior during fasting in mice, The researchers placed mice that had been fasted for 24 hours in either spontaneous olfactory stimulation (SOS) or visual stimulation (SVS) devices
.
In the SOS cage, mice only explored tubes that released known food odors
.
Food visual stimulation administered at week 3 failed to elicit exploratory behavior
.
They then divided the mice into two groups: mice that underwent sham surgery and mice
that underwent olfactory bulbectomy.
After one week (week 4), visual stimulation of food still had no effect
on exploratory behavior in mice undergoing olfactory bulbectomy.
In contrast, olfactory bulboctomy mice suppressed odor-based exploration
at week 5.
Thus, fasting mice explore known favorite foods based on olfactory information rather than visual information.
Food odor exposure causes lipid mobilization
during fasting To elucidate metabolic changes in mice in the presence or absence of food odor stimuli, the researchers measured unesterified fatty acids (NEFA) serum levels, which are the main source of
energy during fasting.
Compared with the feeding level, the basal NEFA level of mice increased slightly (but not significantly) after 6 hours of fasting and significantly increased after 16~24 hours of
fasting.
Stimulation with food odor under 24-h fasting conditions further increases NEFA levels
in mice.
These characteristics appear to be advantageous because unsaturated fatty acids have beneficial
metabolic health compared to saturated fatty acids.
The mechanism connecting food odor detection and lipid mobilization In order to reveal the core mechanism
of lipid mobilization of food odor during fasting, The researchers explored whether hypothalamic melanocortin and the autonomic nervous system are involved in this process
.
They pretreated with the melanocortin 4 receptor (MC4R) antagonist SHU9119 and found that although SHU9119 had no direct effect on basal NEFA levels in the fasting state, it inhibited the increase
in olfactory-dependent NEFA.
The use of the MC4R agonist melanotan II is associated with elevated
NEFA.
In addition, pretreatment with the β-adrenergic blocker propranolol also reduced serum NEFA levels
during odor stimulation.
These results suggest that the hypothalamic MC4R and sympathetic nervous system are involved in lipid mobilization
induced by food odor perception.
By analyzing protein and gene expression profiles, the researchers further explored the lipid processing mechanisms
of peripheral tissues when food odors are smelled.
They found that phosphorylation levels of hormone-sensitive lipase (HSL) in the white adipose tissue (eWAT) of the epididymis were elevated after 30 minutes of exposure to odor during fasting, suggesting that in a fasted state, The perception of food odor enhances lipolysis of adipotic
tissue.
In the liver, phosphorylation of the molecule S6 ribosomal protein downstream of mTOR in the liver increases after 10 min of
exposure to odor during fasting.
To fully describe the systemic effects of food odor perception during fasting, the researchers performed RNA-seq analysis
on six tissues of mice after 60 minutes of exposure to odor during fasting.
Principal component analysis showed that olfactory stimulation mainly affected gene expression
in soleus muscle, eWANT, and pancreas.
In terms of lipid metabolism, differentially expressed genes are related to the digestion, absorption and metabolic pathways of fats and proteins.
Preexposure to food odor improves postprandial fat utilizationNext
, the researchers examined whether stimulating mice with food odor in a starvation state affected lipid dynamics after fat intake
。 The oral fat tolerance test (OFTT) has shown that pre-stimulation with normal food odors enhances lipid intake-induced elevated serum triglyceride levels
.
However, food odor stimulation during fasting did not affect subsequent food intake, blood glucose levels in the eating state, serum insulin or adiponectin levels
.
Metabolic cage analysis showed that odor stimulation during fasting reduced respiratory quotient (RQ)
after refeeding.
But in leptin receptor-deficient db/db mice, noThis change
in RQ has been detected.
These results suggest that preprandial stimulation with food odor promotes postprandial lipid utilization in a leptin receptor-related manner, independent of orexinergic and dopaminergic reward pathways
in the brain.
Consistent with reduced respiratory quotient, premeal stimulation of odor increases serum triglycerides and cholesterol
in chylomicrons and VLDR components.
So, which tissues are involved in olfactory-induced lipid metabolism? Under refeeding conditions, metabolomic analysis targeting the tricarboxylic acid cycle showed that most metabolites were increased in the liver but decreased
in soleus muscle in mice pre-stimulated by odor during fasting.
Thus, stimulation of food odor during fasting promotes tissue-specific regulation of metabolic activity during re-eating, significantly enhancing metabolic flow
in the liver.
In addition, the researchers observed that pre-stimulation with odor during fasting reduced HSL phosphorylation in eWAT and Ucp1 and Pgc1a mRNA
in brown adipose tissue after refeeding.
These are thermogenic markers and these alterations represent an inhibition
of sympathetic regulation of adipose tissue during re-eating.
Finally, they studied the effect of
food odor stimulation in mice fed a high-fat diet under diet-induced obesity conditions
。 Under intermittent fasting conditions, odor stimulation of fatty foods had no additional effect
on body weight and food intake in mice.
But importantly, odor stimuli from intermittent fatty foods during fasting reduce blood sugar levels, insulin resistance index, and insulin secretion index
.
In the oral glucose tolerance test, peak glucose levels were reduced
in the odor-stimulated group.
Thus, chronic food odor stimulation increases the benefits of intermittent fasting on glucose metabolism without additional weight alteration
for diet-induced obesity.
This study shows that food odor perception during fasting triggers biphasic regulation of lipid metabolism, i.
e.
, food odor perception during fasting promotes lipid mobilization during fasting, Lipid utilization during subsequent refeeding can prevent insulin resistance in obese mice on a diet.
The link between smell and lipid metabolism helps maintain metabolic health
in energy-deficient and energy-overloaded environments in mice.
The results of this study may be beneficial for the development of an olfactory-based strategy to prevent metabolic disorders and chronic energy imbalance
.
That said, the temptations of smelling delicious food during your fasting to lose weight are not necessarily bad, these temptations can help mobilize your fat! Of course, resisting these temptations is key
.
Link to the paper:
style="font-family: , "Microsoft YaHei";letter-spacing: normal;color: rgb(136, 136, 136);font-size: 12px;" _mstmutation="1" _istranslated="1">
Open reprint, welcome to forward to Moments and WeChat groups
