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R Bonadonna

Publications and source records attributed to R Bonadonna.

25 records · Page 2Linked to original sources
PubMed1987

Acute elevation of free fatty acid levels leads to hepatic insulin resistance in obese subjects.

Raised levels of free fatty acids (FFA) compete with glucose for utilization by insulin-sensitive tissues, and, therefore, they may induce insulin resistance in the normal subject. The influence of experimental elevations in FFA levels on glucose metabolism in native insulin-resistant states is not known. We studied seven women with moderate obesity (63% above their ideal body weight) but normal glucose tolerance with the use of the insulin clamp technique with or without an infusion of Intralipid + heparin. Upon raising plasma insulin levels to approximately 60 microU/mL while maintaining euglycemia, whole body glucose utilization (3H-3-glucose) rose similarly without (from 66 +/- 7 to 113 +/- 11 mg/min m2, P less than .02) or with (from 70 +/- 7 to 137 +/- 19 mg/min m2, P less than .02) concomitant lipid infusion. In contrast, endogenous glucose production was considerably (73%) suppressed (from 66 +/- 7 to 15 +/- 8 mg/min m2, P less than .001) during the clamp without lipid, but declined only marginally (from 70 +/- 7 to 48 +/- 7 mg/min m2, NS) with lipid administration. The difference between the control and the lipid study was highly significant (P less than .02), and amounted to an average of 3.8 g of relative glucose overproduction during the second hour of the clamp. Blood levels of lactate rose by 34 +/- 15% (.1 greater than P greater than .05) in the control study but only by 17 +/- 10% (NS) during lipid infusion. Blood pyruvate concentrations fell in both sets of experiments (by approximately 45% at the end of the study) with similar time courses.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1985

Influence of cell age and ketoaminic linkage on rapid glycosylation of hemoglobin in human red cells in vitro.

In vitro the rate of synthesis of the aldiminic linkage between Hb and glucose depends on glucose concentration, length of incubation and some other physiological factors. To understand better the regulation of this synthesis and to verify the role of cell age and of basal HbA1 levels on the rate of synthesis of pre-A1, we studied red cells from 7 normal controls and 7 diabetics, with high HbA1 levels. We found that the content of HbA1 (stable glycosylated hemoglobin) is able to negatively affect the rate of synthesis of new pre-A1, according to a curvilinear model. These results suggest that in vitro the glycosylation process is saturable, and that elevated values of HbA1 are able to slow the synthesis of pre-A1 in vitro.

Adult↗
PubMedDate not supplied

Estimation of organ transport function for recirculating indicator dilution curves.

The transport function of an indicator through an organ allows the calculation of important physiological parameters, but its estimation, especially in the presence of recirculation, can be difficult. In this paper, we estimate the transport function of 3H-mannitol (an extracellular tracer of glucose) in the human leg skeletal muscle. To do so, an indicator bolus is administered into the femoral artery and its recirculating dilution curves are nonuniformly sampled in both the femoral artery and the femoral vein. A new deconvolution-based method is used to simultaneously estimate the indicator transport function and the organ plasma flow. Subsequently, the indicator mean transit time and distribution volume are calculated. The reliability of the method is assessed by Monte Carlo simulation. The ability to estimate parameters, like mean transit time and extracellular distribution volume, is critical to the study of pathophysiologic states such as diabetes, insulin resistance, and hypertension.

Bias↗