Insulin control of glucose metabolism in man: a new kinetic analysis

Analyses of the control of glucose metabolism by insulin have been hampered by changes in bloog glucose concentration induced by insulin administration with resultant activation of hypoglycemic counterregulatory mechanisms. To eliminate such mechanisms, we have employed the glucose clamp technique which allows maintenance of fasting blood glucose concentration during and after the administration of insulin. Analyses of six studies performed in young healthy men in the postabsorptive state utilizing the concurrent administration of [14C]glucose and 1 mU/kg per min (40 mU/m2 per min) porcine insulin led to the development of kinetic models for insulin and for glucose. These models account quantitatively for the control of insulin on glucose utilization and on endogenous glucose production during nonsteady states. The glucose model, a parallel three-compartment model, has a central compartment (mass = 68 +/- 7 mg/kg; space of distribution = blood water volume) in rapid equilibrium with a smaller compartment (50 +/- 17 mg/kg) and in slow equilibrium with a larger compartment (96 +/-21 mg/kg). The total plasma equivalent space for the glucose system averaged 15.8 liters or 20.3% body weight. Two modes of glucose loss are introduced in the model. One is a zero-order loss (insulin and glucose independent) from blood to the central nervous system; its magnitude was estimated from published data. The other is an insulin-dependent loss, occurring from the rapidly equilibrating compartment and, in the basal period, is smaller than the insulin-independent loss. Endogenous glucose production averaged 1.74 mg/kg per min in the basal state and enters the central compartment directly. During the glucose clamp experiments plasma insulin levels reached a plateau of 95 +/-8 microU/ml. Over the entire range of insulin levels studied, glucose losses were best correlated with levels of insulin in a slowly equilibrating insulin compartment of a three-compartment insulin model. A proportional control by this compartment on glucose utilization was adequate to satisfy the observed data. Insulin also rapidly decreased the endogenous glucose production to 33% of its basal level (0.58 mg/kg per min), this suppression being maintained for at least 40 min after exogenous insulin infusion was terminated and after plasma insulin concentrations had returned to basal levels. The change in glucose utilization per unit change in insulin in the slowly equilibrating insulin compartment is proposed as a new measure for insulin sensitivity. This defines insulin effects more precisely than previously used measures, such as plasma glucose/plasma insulin concentration ratios. Glucose clamp studies and the modeling of the coupled kinetics of glucose and insulin offers a new and potentially valuable tool to the study of altered states of carbohydrate metabolism.

Recombinant factor VIIa use in cardiac surgery--expanding the arsenal therapy for intractable bleeding?

A 72-year-old patient was admitted for mitral valve replacement because of infective endocarditis. Severe intractable bleeding in the early postoperative period was successfully treated with recombinant activated factor VII (rFVIIa). Thereafter, recovery was uneventful, and the patient was discharged on postoperative day 16. The current clinical aspects and experience of rFVIIa use in cardiac surgery are discussed.

Effects of tryptophan loading on verbal, spatial and affective working memory functions in healthy adults

Serotonin (5-HT) appears to modulate affective behaviours by providing a homeostatic threshold around which other transmitters respond. This general principle of activity should hold for other types of behaviour, including cognition, but has not been extensively examined. We hypothesized, based on past findings, that increased 5-HT would constrain prefrontally guided working memory functions that are mediated by catecholamine neurotransmitters. Healthy adults ingested amino acid compounds designed to deplete and load systemic tryptophan levels in a repeated-measures crossover design. Outcome variables included total plasma tryptophan, serum prolactin levels and self-report measures of mood, as well as measures of motor skill, attention, memory span and working memory for verbal, spatial and affective stimuli. Our findings indicate decrements in working memory for verbal and affective stimuli following tryptophan loading versus depletion, as well as subtle changes in vigilant attention and motor coordination. Implications for the aetiology and treatment of affective disorders and psychosis are discussed.

Cytokine profiles of pediatric patients treated with antibiotics for pyelonephritis: potential therapeutic impact

Urinary tract infections are common in infants and children. Pyelonephritis may result in serious complications, such as renal scarring, hypertension, and renal failure. Identification of the timing of release of inflammatory cytokines in relation to pyelonephritis and its treatment is essential for designing interventions that would minimize tissue damage. To this end, we measured urinary cytokine concentrations of interleukin-1 beta (IL-1 beta), IL-6, and IL-8 in infants and children with pyelonephritis and in healthy children. Children that presented to our institution with presumed urinary tract infection were given the diagnosis of pyelonephritis if they had a positive urine culture, pyuria, and one or more of the following indicators of systemic involvement: fever, elevated peripheral white blood cell count, or elevated C-reactive protein. Urine samples were obtained at the time of presentation prior to the administration of antibiotics, immediately after completion of the first dose of antibiotics, and at follow up 12 to 24 h after presentation. IL-1 beta, IL-6, and IL-8 concentrations were measured by enzyme-linked immunosorbent assay. Creatinine concentrations were also determined, and cytokine/creatinine ratios were calculated to standardize samples. Differences between pre-antibiotic and follow-up cytokine/creatinine ratios were significant for IL-1 beta, IL-6, and IL-8 (P < 0.01). Differences between pre-antibiotic and control cytokine/creatinine ratios were also significant for IL-1 beta, IL-6, and IL-8 (P < 0.01). Our study revealed that the urinary tract cytokine response to infection is intense but dissipates shortly after the initiation of antibiotic treatment. This suggests that renal damage due to inflammation begins early in infection, underscoring the need for rapid diagnosis and intervention.