Feeding suppression induced by a fecal anorexigenic substance (FS-T)

A step towards developing the expertise to control hunger and satiety: regulatory role of satiomem--a membrane proteoglycan

Regulation of hunger and satiety is a complex process thought to be controlled by a complex interplay of neurotransmitters in the hypothalamic region of the brain. Reduced food intake or anorexia has also been observed under various disease or disorder conditions including AIDS and cancer. On the other hand, increased appetite because of some impairment of central mechanisms regulating the food intake could also cause/obesity. A large number of substances including neuropeptides, hormones, drugs, and synthetic peptides have been implicated in the regulation of appetite and food intake behavior in normal as well as disease or disorder conditions. Most of these substances are not directly involved in the regulation of normal hunger and satiety but exert their effect indirectly via other media. Some of them are involved under certain pathologic conditions and during the course they become involved directly or indirectly in the triggering of hunger and satiety regulatory mechanism. Recently, we have been able to isolate and purify an endogenous proteoglycan from membranes of animal and plant sources. This membrane anchored proteoglycan termed as 'Satiomem' reduces food intake without any rebound effects and has no apparent toxicity. It also fulfils all the criteria of a true satiety or anorexigenic substance. The release of satiomem from the cell surface could be mediated by a specific phospholipase-C. Satiomem seems to be involved in transducing activating signals and may also act as a source of second messenger for the regulatory mechanism of appetite. This article summarizes the regulatory aspects of hunger and satiety mechanisms controlled by endogenous substances with the emphasis on our present knowledge about satiomem.

Impaired hypophagia induced by fecal anorexigenic substance in Zucker obese rats

Influence of fecal anorexigenic substance (FS-T) on feeding by Zucker obese rats was compared to that by their lean littermates and Wistar King A rats. FS-T, which has been found to suppress food intake mainly by activation of glucoreceptor neurons in the ventromedial hypothalamus, was injected intraperitoneally in a dose of 7 U/kg at 1930 hr, immediately before the dark period. Potency of FS-T in feeding suppression was much less in the obese rats than in their lean littermates or the Wistar King A rats. Meal size of the obese rats was decreased after the injection, but meal duration was unaffected. The suppressive effect on the lean rats and the Wistar King A rats included decrease of both size and duration of the meal. These results suggest that chemosensitivity in the ventromedial hypothalamus of Zucker obese rats may be impaired, which may be one explanation of the obesity in Zucker obese rats.

Food intake suppression in rats by a substance isolated from human feces

A substance which suppresses food intake was isolated from human feces. This substance was extracted and partially purified using Sephacryl S-200 column chromatography and a DEAE-Sephadex A-25 column chromatography. To assess the biological activity, rats were subjected to various applications. The intraperitoneal administration and the intracerebroventricular microinfusion of this substance suppresses short- and long-term food intake. The central infusion suppresses feeding with a potency over 1000 times that the peripheral administration. The central infusion of the heat-treated substance was without effect. These results suggest that a substance present in human feces (probably of a proteic nature) suppresses food intake in rats, at the level of the central nervous system.

Endogenous sugar acid control of hypothalamic neuron activity and gastric acid secretion in rats

The feeding related endogenous sugar acids, 2-deoxytetronic acid, 2-DTA and 3-deoxypentonic acid, 3-DPA, were investigated for their peripheral and central (hypothalamic) control of gastric acid secretion, and effects on activity of lateral hypothalamic (LHA) neurons in rats. Peripheral gastric acid secretion was not affected by either 2-DTA or 3-DPA. Slight gastric acid secretion was elicited by 3-DPA only when it was applied directly into the gastric related site of the LHA. Gastric acid secretion induced by 2-deoxy-D-glucose (2DG) was suppressed by application of 2-DTA in the LHA. 3-DPA had no effect on 2DG induced secretion. Electrophoretic application of 2-DTA significantly inhibited the activity of both gastric and non-gastric type glucose-sensitive neurons in the LHA, and 3-DPA significantly excited both types of glucose-sensitive neurons. The results agree with previous reports that 2-DTA and 3-DPA are endogenous satiety and hunger factors, respectively, and act by modulating hypothalamic control of gastric acid secretion which is mediated through gastric type and non-gastric type glucose-sensitive neurons.

Immunological study of the rat hypothalamic ventromedial nucleus

Specific anti-sera were prepared by injecting the homogenates of rat ventromedial nucleus (VMH) and caudate nucleus (Cd) into the rabbit. Anti-VMH serum, after absorption of common components in rat normal serum and anti-Cd serum, reacted specifically to the rat VMH with only one precipitation line. Anti-VMH serum was successfully applied to 80 VMH neurons by electrophoresis through 5 barreled micropipettes. Fresh anti-VMH serum caused an irreversible response (increase and subsequent sudden cessation of firing) in 8 of the 25 VMH neurons tested. Anti-VMH serum reversibly inhibited 32 of 80 VMH neurons and 13 of these were also tested with glucose. Discharge rates of 12 of the 13 neurons increased by glucose. Most of these neurons were not affected by anti-Cd serum or normal rabbit serum. Results of these immunological and electrophysiological studies suggest the existence of specific membrane receptor binding sites on the glucoreceptor neurons in the VMH. These sites afford one route for producing the excitatory effect that glucose has on VMH neurons.