Lateral hypothalamic control of metabolic factors related to feeding

Abstract

Summary.States of hunger and satiety are under ischymetric (i. e., rate of cellular energy production) control which depends on both substrate availability and hormonal composition. The latter varies in response to external (olfactory, gustatory and gastrointestinal) stimuli sensed by specific receptors and projected on lateral hypothalamic (LH) units from which departs the descendant control pathway of metabolic glands. This neurohormonal loop is responsible for the anticipatory glycemic and other changes observed during a meal and the preabsorptive "satiation" ending the meal long before the postabsorptive cellular repletion will induce the state of more permanent "satiety". New data on LH "sweet" taste projection and hypothalamo-pancreatic control are shown and strengthen the above view.Key words: Oro-glycemic reflex, hypothalamic taste units, preabsorptive satiation, insulin, glucagon, metabolism. Ischymetric Dependence of Hunger and SatietyAlthough homeorheusis 1 of glycemia is achieved through continuous utilization of endogenous reserves, the ultimate source of replenishment is located in the environment and has to be behaviorally acquired. In fact, numerous observations of feeding in animals [25], and reports of hunger [28] in humans in relation to severe hypoglycemia led to the concept of a glucostatic mechanism of feeding and to its immensely seminal description as the glucostatic theory by Jean Mayer [23, 24]. The subsequent failure to explain persistent feeding in spite of large 1 Homeorheusis: the dynamic version of homeostasis, where rheusis (in Greek: flow) replaces stasis (in Greek: stagnation). It designates the maintenance of a value at a level which may vary, but only according to a biologically determined program, such as circadian or annual rhythms intravenous (iv) loads of glucose [1,2, 20, 51], together with the same reasoning for lipids and amino acids, led to other sorts of "molecular static" theories (for rev. see [59]). All of them were justified by some reasonably good experimental evidence. Today, this partial validation of all of the previous hypotheses is explained by the ischymetric (ischys: power or rate of energy production) hypothesis [34, 38] which proposes that the ultimate stimulus of the specific arousal of hunger is the drop below a critical level of power production in specific diencephalic cells sharing the general metabolism of the body.The hypothalamus can be considered from the metabolic point of view as a microcosm of the somatic macrocosm. Hypothalamic units are constantly informed of the repletion/depletion state of the inner milieu (for rev. see [44]) and, at the same time, of recent ingestants [31, 32]. Taking into account the actual situation of energogenic reserves (adipose and other) and potential repletion (ingestants), hypothalamic units produce their own metabolic hormones [14, 58] and modulate the release of metabolic hormones from peripheral glands. The hypothalamus receives much more information than the plasma-concentration-oriented pancreatic endoc...

Taste Responses of Neurons of the Hamster Solitary Nucleus Are Enhanced by Lateral Hypothalamic Stimulation

“…These data suggest that taste activity may vary between states of hunger and satiety. Because the LH is involved in both feeding behavior and metabolic homeostasis (Grossman and Grossman 1982;Nicolaidis 1981) and reciprocally connected to both pontine and medullary taste nuclei (van der Kooy et al 1984;Whitehead et al 2000), it is in a position to influence gustatory afferent activity. LH stimulation induces feeding FIG. 6.…”

Lipoprotein lipase is produced, regulated, and functional in rat brain.

“…Although LP lipase activity decreased in all brain regions, the largest decrease occurred in hypothalamic LP lipase. LP lipase-dependent fatty acid uptake into brain cells in the hypothalamus is particularly noteworthy because food intake and body weight are to a large extent regulated in this brain region (13,14). Lesions in the ventromedial nucleus of the hypothalamus in rats result in increased food intake and weight gain (15); similar lesions in the lateral hypothalamus variably cause decreases in food intake and weight loss (15,16).…”

Substrate oxidation influences liking, wanting, macronutrient selection, and consumption of food in humans

“…Indeed, the leastcarbohydrate-rich bread (number of slices and proportion) was consumed after the sweetest carbohydrate breakfast (HC), which induced the highest EE;,the amount of carbohydrate-rich bread consumed during the snack correlated negatively with EE; and multiple linear regressions showed that the amount of carbohydrate-rich bread consumed was related only to EE. The influence of EE on food intake has been observed in rats, leading to the ischymetric hypothesis, which suggests that feeding is controlled by the intensity of metabolic rate (35,36). According to this hypothesis, a rise in the total oxidation rate results in a decrease in food intake and vice versa (8,37).…”