Walton W. Shreeve

Excretion of amino acids in nephrosis.

Summary (1) By microbiological assay, concentrations of 18 amino acids have been examined in the blood and urine of patients with nephrosis and in normal individuals under various circumstances. There were observed in an adult male patient, with nephrotic syndrome associated with glomerulonephritis, large increases over the normal rates of urinary excretion of many amino acids, both essential and nonessential, but more notably of the essential. A female adult patient, with clinical findings only of nephrosis, showed considerably less deviation from normal with a trend toward increased excretion of amino acids in the fasting state. There was a general tendency to moderately low concentrations of several amino acids in the blood of both nephrotic subjects. 2) After elevation of the blood concentrations by intravenous loading of a mixture of amino acids, the percentage of filtered amino acids (determined by simultaneous measurement of inulin clearance) which were excreted generally increased in the case of normal individuals as well as in the nephrotic subjects. No. consistent differences could beobserved between normal and nephrotic subjects as a result of “loading” of the blood with amino acids. 3) Intravenous administration of ACTH for 9 to 10 days to 2 normal subjects and 1 nephrotic subject produced no distinct changes in rates of excretion of amino acids in the normal individuals. but appeared to be associated with a moderate decrease in excretion of virtually all amino acids in the patient with nephrosis. Further study is required to confirm this observation.

Release and Production of Insulin by Isolated, Perifused Rat Pancreatic Islets: Control by Glucose

Rat pancreatic islets, isolated from the whole gland by digestion with collagenase, were incubated in a continuous flow system in which various concentrations of glucose were contained in the buffer solution. The pattern of release of immunoreactive insulin (IRI) consisted generally of successive main phases with multiple minor fluctuations within the broader cyclic release. Threshold and responsiveness of various phases of IRI release with different glucose concentrations and flow rates have been investigated.

Hormonal Effects on C-14 Acetate Metabolism in the Human.

Summary These data suggest the following tentative conclusions: 1. Adrenal 17-hydroxycorticoids appear to exert an effect on utilization of acetate and to decrease oxidation of this 2 carbon fragment to CO2. 2. Tn the human as in tissues of lower animals and in plant seeds, carboxyl carbon of acetate is more readily oxidized than is methyl carbon. The finding of a decrease in lipid synthesis form methyl labeled acetate in association with a decrease in oxidation of this compound as compared to carboxyl labeled acetate suggests that the carboxyl carbon may also be used preferentially for lipid synthesis in the human. 3. The syndrome of lipoatrophic diabetes appears to be associated with a decreased ability to store and perhaps to synthesize lipids in the adipose tissue rather than an increase in utilization of lipids of adipose tissue. 4. The stable adult diabetic may have a defect in conversion of 2 carbon fragments to fatty acids, even when the fasting blood sugar is normal.

Human plasma triglyceride labeling after high-sucrose feeding. I. Incorporation of sucrose-U-14C

Abstract A 14 C-labeled sucrose load was given to 23 patients (including 18 obese females) after 1 wk on a low-sucrose, high-starch diet, then again after 1 wk of isocaloric high-sucrose, low-starch diet. Peak radio-activities of total plasma triglycerides (TG- 14 C) and of triglyceride-fatty acids (TGFA- 14 C) occurred between 3 and 6 hr after the acute oral loading during either dietary period. After high-sucrose diet (HSD) the peak activity of TGFA- 14 C appeared to occur earlier than after lowsucrose diet (LSD). On HSD the appearance of sucrose- 14 C in plasma TG- 14 C was significantly greater up to 12 hr after the acute loading, with maximal increments of 50% or more occurring at 3 hr, compared to a mean increase of merely 13%–14% in the fasting concentration of plasma TG after HSD. The increment results mainly from a greater and earlier appearance of 14 C in TGFA, rather than in the glyceride-glycerol. This implies that enhanced hepatic lipogenesis is responsible, not an increased availability of α-glycerolphosphate, nor any gross defect in removal of plasma TG. On HSD the rate of excretion of breath 14 CO 2 was also slightly but significantly greater during the first 2 hr following the acute loading, though not afterwards. There is a positive correlation of individual changes in excretion of 14 CO 2 with changes in plasma TG- 14 C and plasma TGFA- 14 C. The individual and temporal relationships between changes in the oxidative and the lipogenic processes, as well as the selectivity of the pathways affected, suggest that important factors are an increased rate of intestinal absorption of sucrose and increased pancreatic insulin secretion. Correlation studies further indicate a lesser response to the high-sucrose feeding in hyperglyceridemic patients, but such patients tend to convert more sucrose to plasma TG even on a low-sucrose diet. Thus, measurement of plasma TG- 14 C in the sucrose- 14 C loading test on LSD may disclose abnormal lipogenic potential.

Diabetes, Insulin, Tolbutamide, and Glucose Load in the Degradation of C-14-labeled Lactate and Pyruvate

In two insulin-dependent diabetic patients, mild ketoacidosis was accompanied by a decrease in the formation of C-14-O2 from DL-lactate-2-C-14 to about two thirds of the values obtained when the patients were in good control. One patient received the labeled compound by single intravenous injection in trace amount and the other by intravenous infusion with a load of DL-sodium lactate. Prior intravenous administration of insulin in these two patients caused no increase in output of C-14-O2 above that in the control state, and a minor, insignificant increase in two milder diabetic patients (one given DL-lactate-2-C-14 with an infusion of glucose, the other DL-lactate-2-C-14 without glucose). The activity of C-14 in expired carbon dioxide of diabetic patients (in good control) was 10 to 25 per cent less than that of one nondiabetic subject after administration of DL-lactate-2-C-14. In the latter patient, and in another nondiabetic given pyruvate-2-C-14, the rapid intravenous injection of 25 gm. of glucose twenty minutes before the labeled compound was accompanied by more rapid and extensive formation of C-14-O2 than in the fasting state. Tolbutamide in two studies (one with DL-lactate-2-C-14 and a prior glucose load in a nondiabetic, and the other with DL-lactate-3-C-14 in a mild diabetic) had no apparent effect on the formation of C-14-O2. Comparison of lactate-2-C-14 with lactate-3-C-14 in one diabetic patient showed 50 per cent higher specific activity of C-14-O2 from the former labeled compound. Studies of the concentration of lactic acid in the blood and rate of disappearance of DL-lactate-2-C-14 further indicated mild lactic acidemia which was associated with decreased elimination of lactic acid-C-14 from the blood of these diabetic patients.

Human plasma triglyceride labeling after high sucrose feeding. II. Study on triglyceride kinetics and postheparin lipolytic activity

Kinetic studies of the very-low-density lipoprotein triglycerides (VLDL-TG) turnover by endogenous labeling with glycerol-2-3-H were performed in 13 patients in the postabsorptive state, first after 10-14 days on a low-sucrose high-starch diet, then again after 10-14 days of isocaloric high-sucrose low-starch diet (HSD). After HSD, a significant decrease in the fractional turnover rates of VLDL-TG was observed, as well as a modest but significant increase in its pool size, but the net turnover rates remained unchanged. Using Michaelis-Menten formulation, we have further calculated the Vmax and Kms of the removal system for VLDL-TG and found that the Vmax and Kms do not differ significantly between the two dietary periods. These results suggest that the removal mechanism for VLDL-TG has not changed after 10-14 days on the HSD, at least when the patients are studied in the postabsorptive state. Measurements of postheparin lipolytic acitivty under fed condition in 17 patients (including the 13 patients above) have shown a decrease after HSD. However, a defect in the removal of plasma-TG related to decreased activity of tissue-lipoprotein lipase in the fed state has not been conclusively uncovered by the kinetic studies performed in the postabsorptive state, and cannot contribute significantly to the expansion of VLDL-TG pool.

Formation of 14CO2 and 3HOH from glucose-1-14C, -1-3H during oral cortisone glucose tolerance tests in obese patients

Abstract Glucose-1-14C was given to 10 nonobese and 19 obese adult female subjects in the oral load of a cortisone glucose tolerance test (CGTT); the extent of reduction of expiration of 14CO2 in the obese was compared with the abnormality of the blood glucose concentration curve of CGTT and the k value of an intravenous glucose tolerance test (IGTT) in the same patients. In some patients glucose-1-3H was also included in the oral load and the rate of formation of tritiated body water (3HOH) taken as a general measure of glucose utilization. Obese patients excreted only about half as much 14CO2 as nonobese subjects during the first 90 min after ingestion and about two thirds as much after 3 hr. Calculation of total formed breath and body 14CO2 indicated similar differences. At a time (2 hr) of maximum difference in blood glucose concentration in the CGTT that of the obese group was 25 per cent higher than that of the nonobese, with much less significance of difference than for the 14CO2. The mean k value of the IGTT for the obese group was 60 per cent of that for the nonobese group. Within the obese group the reduction in total formed 14CO2 was highly correlated with the nonisotopic parameters of glucose tolerance and was correlated to a lesser extent with parameters of obesity. Since formation of 3HOH from glucose-1-3H was not significantly reduced in the obese group, the abnormality of metabolism of glucose-1-14C in the obese patients appears to be a diversion of 14C to some organic products with concomitant decrease in formation of 14CO2. The tritium data suggest no decrease in the absorption or overall initial utilization of glucose.

Chronic effects of mannoheptulose in hyperglycemic-obese mice☆

Abstract Mice of the Bar Harbor strain, C57BL65 obob, received mannoheptulose in the drinking water and by subcutaneous injection once daily. Control mice were injected with saline. Obese mice appeared to gain slightly more weight during the first two to three weeks after start of the experiment, while lean mice were not significantly affected. After 5 to 8 weeks conversions of glucose-6- 14 C,-6- 3 H (trace amount intraperitoneally) to saponifiable fatty acids of liver and carcass, to body water ( 3 H), and to expired carbon dioxide ( 14 C) were not significantly different in mice given mannoheptulose. Fasting blood glucose was also unaffected, but plasma immuno-reactive insulin was 100 per cent higher in obese and 50 per cent higher in lean mice of the treated groups. As in other studies incorporation of 14 C and 3 H into hepatic fatty acids was greater in obese than lean mice without significant differences in carcass fatty acids. Formation of 14 CO 2 was reduced in both obese groups, but more significantly so in the control than the treated group. The findings do not correspond to those in other species which show inhibitory effects of mannoheptulose on insulin release, but intermittent suppression of insulin release with discharge of accumulated insulin at other times could explain the results.

Carbon-14 as a Tracer for Metabolic Studies in Man

Extensive use of organic compounds labeled with isotopic carbon, has helped biochemists and physiologists in their endeavors to elucidate vital mechanisms.