Circulating alanine disposal in diabetes mellitus.

Alanine was selected for study as a representative circulating glucose precursor in relation to the question of the source of the excess circulating glucose in diabetes mellitus. U-14C alanine and U-14C glucose infusions were given to healthy subjects and to subjects with untreated mild maturity, severe maturity, and juvenile diabetes. Comparative studies after a 24-hour fast were made in healthy and in mildly diabetic subjects. The alanine production rate was unaltered by fasting or diabetes. The glucose production rate was unaltered by fasting but increased in diabetes in relation to the severity of the disease. The fractions of alanine-to-glucose and of glucose-from-alanine were increased by fasting. The effect of diabetes was different. The fraction of alanine-to-glucose was much less in mild maturity diabetes than in health, and it was increased only in juvenile diabetes. In all the diabetic groups the glucose-from-alanine fraction was much less than in health. In every group the change in the alanine oxidation rate was reciprocal to that in the alanine-derived glucogenesis rate. The results are consistent with the possibility that the principal source of the excess circulating glucose in diabetes is glycogen.

Circulating alanine production and disposal in healthy subjects.

UNLABELLED: Circulating-alanine production and disposal rates were estimated in eight healthy postabsorptive subjects by means of U-14C alanine and U-14C glucose infusions. The mean circulating-alanine production rate was 368 +/- S.E.M. 28 mumol/min. -1.8(2). Approximately 50 percent of circulating-alanine carbon exchanged rapidly with that of circulating lactate. Approximately 30 per cent of circulating alanine exchanged with protein stores. Other disposal was 29 +/- 2 per cent to circulating glucose and 40 +/- 4 per cent to oxidation. CONCLUSIONS: (1) The carbon moieties of circulating alanine and lactate are freely exchangeable. (2) Assessment of the contribution of alanine to gluconeogenesis will depend on establishing the extent to which the precursor pyruvate carbon is derived from glycolysis or from proteolysis. (3) If the principal pyruvate precursor is glycolysis, then the principal specific function of the glucose-alanine cycle appears to be ammonia transport.

Glucose turnover and disposal in maturity-onset diabetes.

The glucose turnover rate in maturity-onset diabetes in man has been variously reported as increased, normal, and decreased. The present experiments suggest that these discrepancies may have been due to methodology, and to nonrecognition of a circadian cycle in the glucose turnover rate that is present in health, and marked in diabetes. During the early morning hours the glucose turnover rate in maturity-onset diabetes is increased in proportion to the fasting blood glucose level. It may reach three to four times the rate found in health. During the evening hours the increments are about one-half as great. The glucose outflow rate constant, k, lower in diabetes than in health, is also lower in both groups in the evening than in the morning. An analysis of the relative contributions of glucose overproduction and underutilization to the development of hyperglycemia in maturity-onset diabetes indicates that overproduction is the greater factor. The relative role of underutilization appears to increase as the fasting blood glucose level increases. The circulating glucose oxidation rate in maturity-onset diabetes is only slightly lower than in health, but the fraction oxidized is markedly lower, and only a small fraction is excreted. The principal conclusion is that in maturity-onset diabetes there is a hypertrophied flux of endogenous glucose, most of which is neither oxidized nor excreted. The precursors and the qualitative and quantitative metabolic fates of this excess glucose are unknown.

A comparison of the effects of tolazamide and tolbutamide upon blood glucose and serum insulin and lipid levels in diabetic subjects.

The effects of tolazamide (300 mg. daily), a new oral hypoglycemic sulfonylurea, and tolbutamide on the blood glucose, serum insulin, cholesterol and triglyceride levels were compared in 14 subjects with maturity-onset diabetes of varying severity. The mean effects of the two drugs in the pharmacologically equivalent doses were the same. In particular, the mean reduction of the blood glucose level was 19% and of the serum triglyceride level was 17% with both agents. However, an individual subject might respond to one agent and not to the other; neither the blood glucose nor the serum lipid response could be predicted from the pretreatment blood glucose level or the per cent of ideal body weight.

Pilot study for a diabetes detection program based upon rapid glucose microanalysis of postprandial capillary blood.

A pilot study was undertaken for a diabetes detection program based upon quantitative microanalysis for glucose of postprandial finger-tip blood from subjects attending a tuberculosis preventive survey. A glucose level of over 120 mg./100 ml. was regarded as a positive screen test. Fifty of the 967 subjects in the pilot study had positive tests. Ten of these were excluded from follow-up because of age and a borderline screen test, and eight refused follow-up or could not be traced. Glucose tolerance tests on the remaining subjects who "screened" positive indicated that 1% of the original number had had false-positive screen tests, while 1% were diabetic and 0.5% were possibly diabetic. These data indicate that this screening method is sufficiently sensitive to detect most of the individuals with undiagnosed diabetes in the population, without picking up an undue number of subjects who have slight abnormalities of glucose metabolism without known clinical significance.