Relationship Between Serum Amino Acid Concentration and Fluctuations in Appetite

Abstract

A number of observations suggest that amino acid metabolism may have something to do with the regulation of hunger. If amino acid solutions are infused too rapidly, anorexia or nausea may appear (I, 2), and gastric peristalsis has been found to cease during the intravenous administration of amino acids (3). In this laboratory measurements of the serum amino acid and blood sugar concentrations have been made under a variety of circumstances (4, 5). Simultaneously, crude estimations of appetite have been attempted. MethodJust before each blood sample was taken the subject was asked whether or not he was 'hungry.' An attempt was made to interpret his response according to the following scale: nauseated, minus I; no desire for food, 0; might eat if offered food, but not very hungry, I plus; ravenous, 4 plus; and 2 plus and 3 plus graded between I plus and 4 plus.In all of the experiments reported here the subjects were either normal volunteers or patients with no disease known to affect protein or carbohydrate metabolism. In experiment I nine subjects ate a standard breakfast containing approximately 20 gm of protein: two eggs, a glass of milk and a piece of toast. Venous blood was collected in the fasting state and at hourly intervals after the breakfast for 4 hours. The serum amino acid nitrogen concentration of each blood sample was determined in duplicate by the method of Albanese and Irby as previously described (4). The standard deviation in 230 such pairs was 0.16 mg%.In experiment II, with I1 subjects, 500 cc of 5% amino acids and 5% glucose2 were infused in 45 minutes. BloodCopyright 0 1997 NAASO. specimens were obtained in the fasting state and at hourly intervals for a period of 4 hours after the beginning of the infusion. In five instances blood samples were also obtained '/2 hour after the start of the infusion. Serum amino acid nitrogen was determined as described above, and the blood sugar concentration of each sample was determined by the Mattice modification of the Fohn-Wu method (6). For 286 such paired determinations the standard deviation was 2.7 mg%.In experiment III, with 13 subjects, 250 cc of a 10% aqueous solution of enzymatically digested casein' were infused in 45 minutes. Blood specimens were obtained immediately preceding the infusion and after the beginning of the infusion at the following intervals: 10 minutes, 30 minutes, 1 hour, 2 hours, 3 hours and 4 hours. Blood sugar concentration of each specimen was determined as described above, and serum amino acid concentration of each specimen, except those drawn at 10 and 30 minutes, was estimated as described above.In experiment IV each of 13 subjects drank 250 cc of the same 10% amino acid mixture used in experiment III. Both serum amino acid nitrogen and blood sugar were estimated in the fasting state and at %-hour intervals for 2 hours and for another 2 hours at 1-hour intervals. ResultsFor a long time we were unable to decide how these data could best be analyzed. In fact, it seemed unlikely that such crude estimations of the desire to ...

Passive and active roles of fat-free mass in the control of energy intake and body composition regulation

“…While these findings of a link between FFM, hunger and midbrain blood flow may suggest a centrally mediated mechanism whereby EE directly drives FFM-induced energy intake, there is also fragmentary evidence suggesting that energy intake is regulated by one or more molecular signals arising from the FFM or from specific organ masses, in particular the skeletal muscle. This notion, which has formed the basis of an 'aminostatic' theory of appetite control 13,14 and a 'protein-static' control of food intake in relation to the impetus for lean tissue growth or maintenance, 15 has particular relevance when considering the dynamic phase of body weight recovery during refeeding or obesity relapse, and hence when examining the relationship between deficits in FFM and increased energy intake ( Figure 2). …”

Blood Glucose Dynamics and Control of Meal Initiation: A Pattern Detection and Recognition Theory

“…The aminostatic hypothesis, originally postulated by Mellinkoff et al (81), proposed that amino acids were candidate signals generated from the breakdown of protein stores in muscle, circulated in the blood, and acted on the brain to match or balance energy intake and energy expenditure and body fat mass over the long term (days or weeks). Thus increased muscle catabolism and elevation of amino acids led to feeding, while postprandial uptake of amino acids from the plasma into muscle resulted in cessation of feeding and a period of satiety.…”

The glucostatic theory of appetite control and the risk of obesity and diabetes

“…These studies led to the classical lipostatic, 1 aminostatic, 2 and thermostatic 3 theories of food intake control as well as more recent hypotheses. [4][5][6] However, all of these theoretical ideas were preceded by the notion that glucose uptake and utilization played a central and metabolically privileged role in the control of hunger, satiety and the regulation of body energy balance.…”