Satiety regulation

Obviously, regulation of food intake depends on many neurotransmitters and hormones but this final section will outline the role played by central 5-HT transmission in this process. It had been the belief for some time that increased 5-HT transmission in the brain reduces food intake (Blundell 1977) and this certainly explains the satiety in rats that follows infusion of 5-HT into the paraventricular nucleus (PVN) of the hypothalamus. However, recent studies using microdialysis have found that 5-HT efflux in the lateral hypothalamus is itself increased by food intake, suggesting the existence of a feedback control system. In fact, because the increase in 5-HT efflux is greater in genetically obese rats than in their lean counterparts, it has been proposed that there is a deficiency in the 5-HT inhibition of food intake in obesity. 

In addition to fiber and carbohydrate content, protein intake from legumes may have weight-loss benefits for obese individuals just because proteins enhance post-meal satiety (Rolls, 1995). However, a possible specific role for phytoestrogens in obesity has been postulated through the modulation of the satiety response, a neuroendocrine mechanism controlled by leptin (a hormone secreted by adipose tissue and already known to be regulated by... 

Serotonin (5-hydroxytryptamine [5-HT]) pathways play an important role in postprandial satiety. Treatments that increase intrasynaptic serotonin or directly activate serotonin receptors tend to reduce food consumption, whereas interventions that dampen serotonergic neurotransmission or block receptor activation reportedly increase food consumption and promote weight gain (Blundell, 1984 Teibowitz, 1986). Moreover, CNS serotonin pathways have been implicated in the modulation of mood, impulse regulation and be-... 

Fu, J., Kim, J., Oveisi, F., Astarita, G., and Piomelli, D. (2008). Targeted enhancement of oleoylethanolamide production in proximal small intestine induces across-meal satiety in rats. Am.J. Physiol Regul Integr. Comp. Physiol 295, R45—R50. 

Lee MD, Somerville EM, Kennett GA, Dourish CT, Clifton PG. Tonic regulation of satiety by 5-HT receptors in the mouse converging evidence from behavioural and c-fos immunoreactivity studies Eur J Neurosci 2004 19(ll) 3017-3025. 

Fig. 21.2 Major effects of AMPK activation on numerous tissues. AMPK plays a key role in regulating whole body energy storage and expenditure. In hypothalamus, AMPK is involved in regulation of satiety and food intake. Activation of AMPK in the hypothalamus increases food intake, whereas inhibition decreases intake. In peripheral tissues such as skeletal muscle and liver, activation of AMPK increases energy expenditure by stimulating mitochondrial genesis and energy substrate utilization. AMPK also regulates lipolysis in adipose tissue and insulin secretion in pancreas.

Of special interest in the control of obesity are factors that regulate appetite and satiety. 

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