PubMed Health⌕ Search

Biomedical subjects

R G Tancredi

Publications and source records attributed to R G Tancredi.

21 records · Page 2Linked to original sources
PubMed1973

Insulin sensitivity of forearm tissues in prediabetic man.

In genetic prediabetic subjects (the glucose tolerant offspring of two diabetic parents or the identical twin of a known diabetic) serum insulin concentrations after glucose administration are subnormal. Maintenance of glucose tolerance in this setting is apparently paradoxical, suggesting increased tissue insulin sensitivity. Accordingly, forearm tissue insulin sensitivity in nine genetic prediabetic males was compared with that of seven males without familial diabetes. Diabetes was excluded in all subjects by preliminary oral glucose tolerance testing. On the preliminary 3 h oral glucose tolerance test (OGTT) the sum of increments in blood glucose above fasting was greater in prediabetic than in control subjects. Conversely, the sum of increments in serum insulin was subnormal for the first 2 h. The insulin index (the sum of increments in insulin divided by the sum of increments in glucose) was significantly lower in prediabetics throughout the test. High physiologic levels of insulin were produced in the forearm by intrabrachial arterial insulin infusion (100 muU/kg per min for 26 min). Balances of glucose and amino acids across forearm muscle became more positive, as did balances of glucose and free fatty acids across adipose tissue plus skin. There were no differences in response between prediabetic and normal subjects.Hence, the insulin sensitivity of peripheral tissues is normal in genetic prediabetes. Increased tissue insulin sensitivity is not essential to explain coexisting euglycemia and insulinopenia in prediabetes because blood glucose values on the OGTT are, in fact, elevated although still within the range considered normal.

Adipose Tissue↗
PubMed1972

Effects of intrabrachial arterial infusion of pyruvate on forearm tissue metabolism. Interrelationships between pyruvate, lactate, and alanine.

Postabsorptive release of alanine from forearm skeletal muscle is large relative to other amino acids, suggesting new synthesis by transamination of pyruvate. This hypothesis was tested and the pathway quantified in six subjects, each given two 30 min intrabrachial arterial pyruvate infusions. The first (12 mumoles/min) supplied approximately that amount of pyruvate produced endogenously by glycolysis in resting muscle. The second (36 mumoles/min) approximated endogenous pyruvate production by glycolysis during moderate exercise. Changes in balance across forearm tissues of pyruvate, glucose, lactate, and amino acids were measured. The time-course of pyruvate equilibration across fore-arm muscles was detailed in three additional subjects. The two infusions increased arterial pyruvate from 64 to 674 and 1776 mumoles/liter respectively. Muscle consumed 72% of the exogenous pyruvate during both infusions. Outputs of lactate and alanine increased, accounting respectively for 30.3 and 6.7% of the pyruvate at the low infusion rate, and 17.1 and 3.8% at the high rate. The remaining pyruvate probably was oxidized. Muscle release of valine, isoleucine, and leucine decreased during the high dose infusion. Additionally, adipose tissue plus skin released more alanine and lactate during the high dose infusion. Other metabolies were unchanged.Thus, both muscle and adipose tissue plus skin synthesize alanine from pyruvate. Lactate production considerably exceeds that of alanine. In muscle, increased availability of intracellular pyruvate serving as a nitrogen acceptor may facilitate branched chain amino acid oxidation. Muscle consumption of infused pyruvate is rapid, and detailed studies of its equilibration suggest that passage across the muscle cell membrane is rate limiting.

Adipose Tissue↗