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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 of differing body masses are sensitive to the rewarding properties of both, low-calorie foods (isocaloric 15% sucrose solution and milk containing 5% fat) and energy-dense solid chow. Ingestion of the different foods was monitored in control (CON, n = 15), overweight (O/weight, n = 18) and obese (n = 14) mice during hours 0–3, 3–6, and 6–24 of presentation of the liquid foods and their maintenance solid diet (NC, LF-HC, HF-HC). (A) Body masses of the 3 groups of mice at the start of the experiment. (B) Average daily ingestion of calories from maintenance diets, corrected for body weight; data from 3 consecutive 24 h periods. (C,D) Body mass-corrected calories derived from sucrose or milk consumption over a 24 h period. (E) Preferences of CON, O/weight and obese mice for sucrose, milk and maintenance diet. The inset shows the total amount of energy ingested (maintenance diet + sucrose + milk) over 24 h. Depicted data are means ± s.e.m. *, **, ***Represent significant differences between indicated groups at p < 0.05, 0.01, and 0.001, respectively.
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Figure 4: Mice of differing body masses are sensitive to the rewarding properties of both, low-calorie foods (isocaloric 15% sucrose solution and milk containing 5% fat) and energy-dense solid chow. Ingestion of the different foods was monitored in control (CON, n = 15), overweight (O/weight, n = 18) and obese (n = 14) mice during hours 0–3, 3–6, and 6–24 of presentation of the liquid foods and their maintenance solid diet (NC, LF-HC, HF-HC). (A) Body masses of the 3 groups of mice at the start of the experiment. (B) Average daily ingestion of calories from maintenance diets, corrected for body weight; data from 3 consecutive 24 h periods. (C,D) Body mass-corrected calories derived from sucrose or milk consumption over a 24 h period. (E) Preferences of CON, O/weight and obese mice for sucrose, milk and maintenance diet. The inset shows the total amount of energy ingested (maintenance diet + sucrose + milk) over 24 h. Depicted data are means ± s.e.m. *, **, ***Represent significant differences between indicated groups at p < 0.05, 0.01, and 0.001, respectively.

Mentions: In a first step, we monitored the 24 h consumption of two isocaloric liquid foods (15% sucrose and milk with a 5% content of fat) by 12-month old control, overweight and obese mice that had ad lib access to the experimental (NC, HF-HC, or LF-HC) diets on which they had been maintained for 36 weeks. The three experimental groups differed in body weight (control: 42.8 ± 1.2 g; overweight: 49.9 ± 0.6 g; obese: 59.4 ± 0.8 g Figure 4A). The groups also differed in their average daily intake of calories (relative to body weight, monitored over 3 consecutive days), with the controls ingesting significantly more calories than the overweight and obese groups (P < 0.01; Figure 4B).


Altered motivation masks appetitive learning potential of obese mice.

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

Mice of differing body masses are sensitive to the rewarding properties of both, low-calorie foods (isocaloric 15% sucrose solution and milk containing 5% fat) and energy-dense solid chow. Ingestion of the different foods was monitored in control (CON, n = 15), overweight (O/weight, n = 18) and obese (n = 14) mice during hours 0–3, 3–6, and 6–24 of presentation of the liquid foods and their maintenance solid diet (NC, LF-HC, HF-HC). (A) Body masses of the 3 groups of mice at the start of the experiment. (B) Average daily ingestion of calories from maintenance diets, corrected for body weight; data from 3 consecutive 24 h periods. (C,D) Body mass-corrected calories derived from sucrose or milk consumption over a 24 h period. (E) Preferences of CON, O/weight and obese mice for sucrose, milk and maintenance diet. The inset shows the total amount of energy ingested (maintenance diet + sucrose + milk) over 24 h. Depicted data are means ± s.e.m. *, **, ***Represent significant differences between indicated groups at p < 0.05, 0.01, and 0.001, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Mice of differing body masses are sensitive to the rewarding properties of both, low-calorie foods (isocaloric 15% sucrose solution and milk containing 5% fat) and energy-dense solid chow. Ingestion of the different foods was monitored in control (CON, n = 15), overweight (O/weight, n = 18) and obese (n = 14) mice during hours 0–3, 3–6, and 6–24 of presentation of the liquid foods and their maintenance solid diet (NC, LF-HC, HF-HC). (A) Body masses of the 3 groups of mice at the start of the experiment. (B) Average daily ingestion of calories from maintenance diets, corrected for body weight; data from 3 consecutive 24 h periods. (C,D) Body mass-corrected calories derived from sucrose or milk consumption over a 24 h period. (E) Preferences of CON, O/weight and obese mice for sucrose, milk and maintenance diet. The inset shows the total amount of energy ingested (maintenance diet + sucrose + milk) over 24 h. Depicted data are means ± s.e.m. *, **, ***Represent significant differences between indicated groups at p < 0.05, 0.01, and 0.001, respectively.
Mentions: In a first step, we monitored the 24 h consumption of two isocaloric liquid foods (15% sucrose and milk with a 5% content of fat) by 12-month old control, overweight and obese mice that had ad lib access to the experimental (NC, HF-HC, or LF-HC) diets on which they had been maintained for 36 weeks. The three experimental groups differed in body weight (control: 42.8 ± 1.2 g; overweight: 49.9 ± 0.6 g; obese: 59.4 ± 0.8 g Figure 4A). The groups also differed in their average daily intake of calories (relative to body weight, monitored over 3 consecutive days), with the controls ingesting significantly more calories than the overweight and obese groups (P < 0.01; Figure 4B).

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