2,074 research outputs found
Adrenergic responsiveness of adipose tissue lipolysis in autonomic failure
No full textThe sympathetic nervous system mobilizes lipids from adipose tissue through stimulation of beta-adrenergic receptors. The increase in lipid supply augments lipid oxidation. Patients with autonomic failure provide a unique opportunity to further elucidate the role of the adrenergic system in adipose tissue metabolism. In 4 patients with severe pure autonomic failure (PAF), in 3 multiple system atrophy patients (MSA), and in 16 healthy young controls, we inserted a microdialysis catheter in abdominal adipose tissue. The catheter was perfused with incremental concentrations of the nonselective beta-adrenoreceptor agonist isoproterenol. Dialysate glucose, lactate, and glycerol were measured to assess glucose supply, glycolysis, and lipolysis, respectively. Basal dialysate glycerol concentrations were 84 +/- 28 microM in PAF and 130 +/- 64 microM in MSA patients. The increase in dialysate glycerol with isoproterenol was identical in PAF and in MSA patients. We found an almost complete overlap in dialysate glycerol concentrations during isoproterenol stimulation between PAF and MSA patients and healthy young control subjects. Our findings suggest that adipose tissue metabolism is remarkably well preserved in patients with chronic sympathetic denervation, both at rest and during local adrenergic stimulation. We propose that beta-adrenoreceptor upregulation is compensated by a desensitization of post receptor mechanisms or by an upregulation of antilipolytic pathways
Did you know? Fluid-and-electrolyte replacement and the uncertainty principle
No full textSurprises are not always welcome. We have studied total body water, quantified the volume and determined the extracellular space, interstitial, and plasma volumes. Nonetheless, estimating these parameters clinically (at the bedside) is frustratingly imprecise. The author ruminates over 50 years clinical experience in intensive care units and grapples with the literature
Bound leptin and sympathetic outflow in nonobese men
No full textLeptin exists in a free form and a receptor-bound form. Protein-bound rather than free leptin levels may be associated with regulation of muscle sympathetic nerve activity (MSNA). We determined MSNA and bound leptin concentrations in 25 men [age, 29 +/- 6 yr, body mass index (BMI), 24 +/- 3 kg/m(2)]. Baroreflex sensitivity was measured using phenylephrine and nitroprusside infusions. We measured bound leptin in patients with central (multiple system atrophy, n = 8; age, 59 +/- 8 yr; BMI, 23 +/- 2 kg/m(2)) and peripheral autonomic failure (pure autonomic failure, n = 4; age, 71 +/- 10 yr; BMI, 25 +/- 3 kg/m(2)). MSNA was correlated with protein-bound leptin concentrations (r(2) = 0.35; P < 0.01) but not with free leptin levels (r(2) = 0.09). MSNA at baseline was 15 +/- 2 bursts x minutes(-1) in subjects with lower and 24 +/- 3 bursts x minutes(-1) in subjects with higher bound leptin concentrations (P < 0.05). Blood pressure as well as baroreflex regulation of heart rate and MSNA was similar in both groups. Phenylephrine and nitroprusside responses were similar. Patients with multiple system atrophy and autonomic failure featured similar bound leptin levels. We conclude that protein-bound rather than free leptin levels are correlated with basal sympathetic outflow in normotensive, nonobese men. This relationship cannot be explained by a direct central nervous effect of protein-bound leptin. Instead, protein-bound leptin may increase sympathetic vasomotor tone indirectly via a baroreflex mechanism
Erythropoietin and arterial hypertension
No full textErythropoietin (EPO) has revolutionized the treatment of anemia in renal failure patients, both in the pre- and postdialysis phase. Not only does the treatment improve well being, but also it positively influences cardiac function and permits cardiac hypertrophy to regress. EPO can lead to an increase in blood pressure; the mechanisms of this effect are not entirely clear. By optimizing dialysis treatment, paying close attention to volume regulation, giving EPO subcutaneously and in a fashion to increase hematocrit gradually, the occurrence of blood pressure increases can be minimized. Hypertension has not proved to be a serious general problem in the EPO treated patient
- …
