Pyruvate tolerance test in chronic uremic patients

Insulin resistance in uremia: an in vivo and in vitro study

Insulin-mediated glucose metabolism was examined in vivo and in vitro in a chronically uremic (4-week) rat model established by a 90% nephrectomy. Using the euglycemic insulin clamp technique, uremic rats demonstrated a 28% reduction (P less than .01) in total body glucose disposal compared with pair-fed controls. Suppression of hepatic glucose production by insulin was not impaired. The ability of insulin to promote glycogen synthesis by the soleus muscle in vitro was normal in uremic rats. In contrast, the ability of insulin to enhance both glycolysis and glucose oxidation by the soleus muscle was significantly reduced (P less than .01) in uremic rats. These results provide evidence that at least two intracellular metabolic defects, ie, in the glycolytic and glucose oxidative pathways, contribute to the insulin resistance of chronic uremia.

Glucose turnover in chronic uremia: increased recycling with diminished oxidation of glucose

The effects of chronic renal failure and hemodialysis on the glucose turnover rate, glucose carbon recycling, and glucose oxidation were evaluated in eight chronically uremic subjects. Six normal subjects served as controls. The studies were repeated in seven uremic subjects after they had been established on hemodialysis for 3 to 18 months. Glucose 13C(microliters) was administered by a prime-constant-rate infusion, and the isotopic enrichment of the whole glucose molecule (m + 6), ie, all six carbon atoms of glucose labeled with 13C and that of the C1 atom of glucose in the plasma were measured by mass spectrometry. It was assumed that the C1 atom of the glucose molecule represented the 13C enrichment of the individual glucose carbons. The "true" rate of glucose production was estimated from the dilution of the glucose 13C (microliters) mass (m + 6) in the plasma. In contrast to the whole glucose molecule (m + 6), recycling of tracer carbon resulted in an increased 13C enrichment of the C1 atom of the glucose molecule and an underestimation of glucose turnover ("apparent"). Glucose carbon recycling was estimated from the difference between the "true" and "apparent" rates of glucose turnover. The contribution of glucose to respiratory CO2 was quantified by comparing the 13C enrichment of expired CO2 with that of the plasma glucose carbon. The plasma glucose concentration after an overnight fast was similar in the uremic and control subjects (72.3 +/- 9.5 and 79.0 +/- 9.5 mg/dL, respectively; mean +/- SD).2+ while the "true" rates of glucose production were similar in both groups (normal: 2.02 +/- 0.19 mg/kg X min; uremic: 2.19 +/- 0.53 mg/kg X min).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolites of glucose in the blood of patients with renal failure

The blood concentrations of pyruvate and of some of its metabolites and the red cell 2,3-diphosphoglycerate concentration were compared with the severity of uraemia in 103 patients with renal failure. In chronic renal failure 2,3-butylene glycol was distinctly elevated, and a positive linear correlation (2p Less Than 0.001) with the urea was found. The values were even higher in corresponding patients with uraemic pericarditis, but,--taking into account their relation to the urea--,they were not elevated in acute renal failure. Acetaldehyde, acetoin and acetate behaved in part likewise. Severe uraemia, which clinically was demonstrated by uraemic pericarditis, was characterized biochemically, without regard to the urea, by very elevated values of 2,3-butylene glycol and acetaldehyde and of the pyruvate: lactate ratio. In addition, the chronic patients who were not undergoing regular haemodialysis, did not show the expected rise of 2,3-diphospho-glycerate along with progressive anaemia. The data suggest that the uraemic state is characterized by the impairment of the oxidative glucose metabolism between pyruvate and the tricarbonic acid cycle more precisely than by the blood urea.