Improved isolation of a 50 kDa anorexigenic protein from rat urine

Contribution to characterization of anorectic protein similar to satietin from urine

An anorectic substance similar to satietin was purified from ethanolic-acid precipitate of rat urine by gel filtration and ion exchange chromatography. The obtained glycoprotein (molecular mass 67 kDa) reduced food intake after intraperitoneal and intracisternal administration in mice in a dose-dependent manner (in the range of 5-80 mg/kg). The anorectic effect was specific. In the presence of sodium dodecylsulphate the substance dissociated into small proteins with a molecular mass of 9-11 kDa. Its anorectic effect was long lasting and differed from that of the anorectic peptide cholecystokinin octapeptide. Our finding supports the idea that anorectic protein isolated from plasma, membranes, and urine may be related substances.

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.

Experimental anorexigenic effect of a membrane proteoglycan isolated from plants

The cessation of eating under normal physiological conditions is a voluntary act induced by a conscious sensation known as satiety. In pathological situations there is loss of appetite or anorexia. We have been able to isolate and characterize a proteoglycan from membranes of mono- and dicotyledonous plant sprouts which reduced the food intake significantly when injected into murine model systems without any rebound. Due to its membrane origin, it has been termed 'satiomem'. The plant proteoglycan (50 kDa) consisted of 70-85% carbohydrates and 15-30% proteins.

A novel plant membrane proteoglycan which causes anorexia in animals

Hunger and satiety are complex interplay of several factors in human and animal species. Reduced food intake has also been observed under various pathological conditions. Earlier, we have been able to isolate an endogenous glycoprotein from erythrocyte membranes, which causes anorexia in rats. In the present study, a similar anorexigenic proteoglycan from Mung bean sprout membranes has been isolated and purified. The proteoglycan (50 kDa) consisted of 70-85% carbohydrate with galactose, glucose galactosamine and mannose as the main sugars. Protein part on analysis showed higher glutamic acid and serine content. This proteoglycan reduces food intake when injected in rats deprived of food for 96 hr as well as normally fed rats, mice and rabbits without any rebound. The TCA-soluble proteoglycan from different plant sources have also been compared for their anorexigenic activity. The similarities observed among plant and animal cell membrane proteoglycans with satietins isolated from human blood plasma could be due to membrane origin of satietins.

The influence of food on food intake: methodological problems and mechanisms of action

Emphasis has been placed on the understanding of the regulation of food intake in the hope of aiding the battle against obesity and of helping to ameliorate the anorexia of cancer and eating disorders. Available data suggest that the regulatory system is multifaceted and complex. This review focuses on current research on the regulation of appetite and satiety by carbohydrates, fats, and proteins as well as by artificial sweeteners. Some methodological problems and potential mechanisms of action at the biochemical level are discussed. Evidence suggests that organisms are more successful in defending against calorie dilution than in adjusting to increases in calories. The implications of that defense relative to the use of ersatz nutrients are explored.

Isolation of an anorexigenic protein from membranes

Satiety means an internal state that leads to termination of eating. We have isolated an anorexigenic glycoprotein (M.W. 50,000 dalton) from human and rat erythrocyte membrane and from rat liver plasma membrane. The substance isolated from all these membrane sources has almost same onset and offset anorectic effect in rats deprived of food for 96 h as well as in normally fed rats without any rebound. Similar properties of membrane anorectic substance and plasma satietin indicated that it has membrane origin. The results also suggest that the loss of appetite in chronic diseases involving damage or turn-over of cell membranes could be due to release of a glycopeptide from cellular membranes into the circulation.