SECTION 5.6
Obesity
83
Afferent signals decreasing appetite
or increasing energy expenditure
Gastrointestinal tract
Glucagon, cholecystokinin,
glucagon-like peptides,
bombesin peptides, glucose
Afferent signals increasing appetite
or decreasing energy expenditure
Gastrointestinal tract
Opioids, neurotensin,
growth hormone-releasing
hormone, somatostatin
Endocrine system
Epinephrine (ß-adrenergic effect),
estrogens
Adipose tissue
Leptin
Peripheral
nervous system
Norepinephrine
(ß-adrenergic effect)
Central nervous system
Dopamine, 7-aminobutyric acid,
serotonin, cholecystokinin
Endocrine system
Epinephrine (a-adrenergic effect),
androgens, glucocorticoids,
insulin, peptide YY, progesterone
Peripheral
nervous system
Norepinephrine
(a-adrenergic effect))
Hypothalamic tracts
Norepinephrine, serotonin,
neuropeptide Y,
melanocyte-concentrating hormone,
glucagon-like peptide I,
corticotropin-releasing hormone
Central nervous system
Galanin, opioids,
growth hormone-releasing
hormone, somatostatin
Efferents
Sympathetic nervous system
parasympathetic nervous system,
thyroid hormones
Energy intake and expenditure
F IG U R E 5 -6
Afferent and efferent pathways of regulation of energy intake and expenditure. [Reproduced with permission from
M. Rosenbaum, R. L. Leibel, and J. Hirsch. Obesity.
N. E ngl. J. o f M ed .
337:396 (1997).]
Starvation
W eigh t lo s s and d e c r e a s e d a d ip o se tissu e
'l'
,
Leptin 1
I
T ransport a c r o s s b lo o d -b ra in barrier
\
Leptin recep tor-h yp oth alam u s
1
N eu rop ep tid e Y an d Y 5 receptor
O vereatin g (h yp erp h agia) o b esity
W eigh t gain an d in crea sed a d ip o se tissu e
Leptin
I
Transport a c r o s s b lood -b rain barrier
I
Leptin recep tor-h yp oth alam u s
I
M elan ocyte-stim u latin g h orm on e-
M eianocortin receptor
B iological r e s p o n s e s :
F ood intake f
E nergy exp en d itu re
\
Fertility^
T em perature^
P arasym p ath etic activity t
B iological r e s p o n s e s :
F ood intake !
E n ergy exp en d itu re t
S y m p a th etic activity t
F IG U R E 5 -7
An overview of the action of leptin on food intake, energy expenditure, and biological responses
(t increased and J, decreased).
