Limits...
Altered motivation masks appetitive learning potential of obese mice.

Harb MR, Almeida OF - Front Behav Neurosci (2014)

Bottom Line: Eating depends strongly on learning processes which, in turn, depend on motivation.We found that (i) the rate of pavlovian conditioning to an appetitive reward develops as an inverse function of body weight; (ii) higher body weight associates with increased latency to collect food reward; and (iii) mice with lower body weights are more motivated to work for a food reward, as compared to animals with higher body weights.Notably, however, all groups adjusted their consumption of the different food types, such that their body weight-corrected daily intake of calories remained constant.

View Article: PubMed Central - PubMed

Affiliation: NeuroAdaptations Group, Max Planck Institute of Psychiatry Munich, Germany ; Neuroscience Domain, Institute of Life and Health Sciences (ICVS), University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal.

ABSTRACT
Eating depends strongly on learning processes which, in turn, depend on motivation. Conditioned learning, where individuals associate environmental cues with receipt of a reward, forms an important part of hedonic mechanisms; the latter contribute to the development of human overweight and obesity by driving excessive eating in what may become a vicious cycle. Although mice are commonly used to explore the regulation of human appetite, it is not known whether their conditioned learning of food rewards varies as a function of body mass. To address this, groups of adult male mice of differing body weights were tested two appetitive conditioning paradigms (pavlovian and operant) as well as in food retrieval and hedonic preference tests in an attempt to dissect the respective roles of learning/motivation and energy state in the regulation of feeding behavior. We found that (i) the rate of pavlovian conditioning to an appetitive reward develops as an inverse function of body weight; (ii) higher body weight associates with increased latency to collect food reward; and (iii) mice with lower body weights are more motivated to work for a food reward, as compared to animals with higher body weights. Interestingly, as compared to controls, overweight and obese mice consumed smaller amounts of palatable foods (isocaloric milk or sucrose, in either the presence or absence of their respective maintenance diets: standard, low fat-high carbohydrate or high fat-high carbohydrate). Notably, however, all groups adjusted their consumption of the different food types, such that their body weight-corrected daily intake of calories remained constant. Thus, overeating in mice does not reflect a reward deficiency syndrome and, in contrast to humans, mice regulate their caloric intake according to metabolic status rather than to the hedonic properties of a particular food. Together, these observations demonstrate that excess weight masks the capacity for appetitive learning in the mouse.

No MeSH data available.


Related in: MedlinePlus

Mice adjust their intake of different foods to maintain a similar daily caloric intake relative to body mass. Comparisons between control (CON), overweight (O/weight) and obese mice are based on data depicted in Figures 4, 5. (A) Shows caloric intake during 24 h test phase from sucrose and milk, relative to body mass either in the presence of ad lib maintenance diet (NC, LF-HC, HF-HC) or in the absence of maintenance diet (food-deprived). (B) Shows caloric intake from sucrose and milk in ad lib presence or absence of maintenance diet, as a percentage of the average daily number calories consumed under standard feeding (solid chow only) conditions. Data shown are means ± s.e.m.; significant pair-wise differences are denoted by **p < 0.01 and ***p < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4214228&req=5

Figure 6: Mice adjust their intake of different foods to maintain a similar daily caloric intake relative to body mass. Comparisons between control (CON), overweight (O/weight) and obese mice are based on data depicted in Figures 4, 5. (A) Shows caloric intake during 24 h test phase from sucrose and milk, relative to body mass either in the presence of ad lib maintenance diet (NC, LF-HC, HF-HC) or in the absence of maintenance diet (food-deprived). (B) Shows caloric intake from sucrose and milk in ad lib presence or absence of maintenance diet, as a percentage of the average daily number calories consumed under standard feeding (solid chow only) conditions. Data shown are means ± s.e.m.; significant pair-wise differences are denoted by **p < 0.01 and ***p < 0.001.

Mentions: Lastly, we calculated the relative amount of energy intake derived from each of the respective liquid and solid diets (controls: sucrose, milk and NC; overweight: sucrose, milk and LF-HC; obese: sucrose, milk and HF-HC) with respect to each group's average daily calorie intake (data in Figure 4B). As shown in Figure 6, control, overweight and obese mice can adjust the relative amounts of each liquid and solid diet in order to maintain a relatively similar daily level of calorie ingestion, irrespective of weight status. Together, these results show that animals with higher body mass do not have a reward deficit syndrome but neglect the otherwise highly-rewarding milk and sucrose in favor of their energy-denser solid foods.


Altered motivation masks appetitive learning potential of obese mice.

Harb MR, Almeida OF - Front Behav Neurosci (2014)

Mice adjust their intake of different foods to maintain a similar daily caloric intake relative to body mass. Comparisons between control (CON), overweight (O/weight) and obese mice are based on data depicted in Figures 4, 5. (A) Shows caloric intake during 24 h test phase from sucrose and milk, relative to body mass either in the presence of ad lib maintenance diet (NC, LF-HC, HF-HC) or in the absence of maintenance diet (food-deprived). (B) Shows caloric intake from sucrose and milk in ad lib presence or absence of maintenance diet, as a percentage of the average daily number calories consumed under standard feeding (solid chow only) conditions. Data shown are means ± s.e.m.; significant pair-wise differences are denoted by **p < 0.01 and ***p < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214228&req=5

Figure 6: Mice adjust their intake of different foods to maintain a similar daily caloric intake relative to body mass. Comparisons between control (CON), overweight (O/weight) and obese mice are based on data depicted in Figures 4, 5. (A) Shows caloric intake during 24 h test phase from sucrose and milk, relative to body mass either in the presence of ad lib maintenance diet (NC, LF-HC, HF-HC) or in the absence of maintenance diet (food-deprived). (B) Shows caloric intake from sucrose and milk in ad lib presence or absence of maintenance diet, as a percentage of the average daily number calories consumed under standard feeding (solid chow only) conditions. Data shown are means ± s.e.m.; significant pair-wise differences are denoted by **p < 0.01 and ***p < 0.001.
Mentions: Lastly, we calculated the relative amount of energy intake derived from each of the respective liquid and solid diets (controls: sucrose, milk and NC; overweight: sucrose, milk and LF-HC; obese: sucrose, milk and HF-HC) with respect to each group's average daily calorie intake (data in Figure 4B). As shown in Figure 6, control, overweight and obese mice can adjust the relative amounts of each liquid and solid diet in order to maintain a relatively similar daily level of calorie ingestion, irrespective of weight status. Together, these results show that animals with higher body mass do not have a reward deficit syndrome but neglect the otherwise highly-rewarding milk and sucrose in favor of their energy-denser solid foods.

Bottom Line: Eating depends strongly on learning processes which, in turn, depend on motivation.We found that (i) the rate of pavlovian conditioning to an appetitive reward develops as an inverse function of body weight; (ii) higher body weight associates with increased latency to collect food reward; and (iii) mice with lower body weights are more motivated to work for a food reward, as compared to animals with higher body weights.Notably, however, all groups adjusted their consumption of the different food types, such that their body weight-corrected daily intake of calories remained constant.

View Article: PubMed Central - PubMed

Affiliation: NeuroAdaptations Group, Max Planck Institute of Psychiatry Munich, Germany ; Neuroscience Domain, Institute of Life and Health Sciences (ICVS), University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal.

ABSTRACT
Eating depends strongly on learning processes which, in turn, depend on motivation. Conditioned learning, where individuals associate environmental cues with receipt of a reward, forms an important part of hedonic mechanisms; the latter contribute to the development of human overweight and obesity by driving excessive eating in what may become a vicious cycle. Although mice are commonly used to explore the regulation of human appetite, it is not known whether their conditioned learning of food rewards varies as a function of body mass. To address this, groups of adult male mice of differing body weights were tested two appetitive conditioning paradigms (pavlovian and operant) as well as in food retrieval and hedonic preference tests in an attempt to dissect the respective roles of learning/motivation and energy state in the regulation of feeding behavior. We found that (i) the rate of pavlovian conditioning to an appetitive reward develops as an inverse function of body weight; (ii) higher body weight associates with increased latency to collect food reward; and (iii) mice with lower body weights are more motivated to work for a food reward, as compared to animals with higher body weights. Interestingly, as compared to controls, overweight and obese mice consumed smaller amounts of palatable foods (isocaloric milk or sucrose, in either the presence or absence of their respective maintenance diets: standard, low fat-high carbohydrate or high fat-high carbohydrate). Notably, however, all groups adjusted their consumption of the different food types, such that their body weight-corrected daily intake of calories remained constant. Thus, overeating in mice does not reflect a reward deficiency syndrome and, in contrast to humans, mice regulate their caloric intake according to metabolic status rather than to the hedonic properties of a particular food. Together, these observations demonstrate that excess weight masks the capacity for appetitive learning in the mouse.

No MeSH data available.


Related in: MedlinePlus