Clinical science
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Mean arterial pressure (MAP) is estimated at the brachial artery level by adding a fraction of pulse pressure (form factor; =0.33) to diastolic pressure. We tested the hypothesis that a fixed form factor can also be used at the aortic root level. We recorded systolic aortic pressure (SAP) and diastolic aortic pressure (DAP), and we calculated aortic pulse pressure (PP) and the time-averaged MAP in the aorta of resting adults (n=73; age 43+/-14 years). ⋯ In conclusion, the aortic form factor was strongly influenced by age, aortic pressure and wave reflection. An empirical formula (MAP=DAP+PP/3+5 mmHg) that is consistent with mechanical principles in the arterial system gave a more precise estimate of MAP in the aorta of resting humans. Only two distinct pressure-powered functions were carried out in the (SAP, DAP, MAP, PP) four-pressure set.
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Pyruvate dehydrogenase (PDH) has low activity in the circulating lymphocytes (CL) of obese adolescents and adults. In vitro, it is unresponsive to insulin at 5 micro-units/ml and is activated at 50 micro-units/ml, in contrast with activation and inhibition respectively at these concentrations in CL from controls. These changes are seen as being indicative of a molecular disorder underlying insulin resistance. ⋯ PDH responses in vitro to insulin in CL taken from the control subjects at t(-3) and t(240) and in CL taken from the obese subjects at t(-3) were as reported above, but were normal (i.e. the same as in control CL) in CL taken from the obese subjects at t(240). Baseline PDH activity was inversely correlated with body mass index and with fasting insulin, and directly correlated with S(I). These results show that a brief and sharp enhancement of blood insulin overcomes derangements in PDH that reflect systemic insulin resistance in obese adolescents.