Metformin effects on peripheral sensitivity to insulin in non diabetic obese subjects

Using the euglycaemic insulin-clamp technique we examined the effects of one-month metformin treatment on peripheral glucose utilization in non diabetic obese subjects. Two groups of obese subjects were studied in comparison with untreated lean women. Group 1 (n = 6) experienced weight loss (BMI: 32.6 +/- 1.7 vs 34.8 +/- 1.6 kg/m2, p < 0.05) but not group 2 (n = 7; BMI before and after treatment: 34.6 +/- 3.2 and 34.8 +/- 3.1 kg/m2). After a continuous insulin infusion of 40, 100, and 350 mU/m2/min we estimated the tissue sensitivity to insulin by the determination of Km, the glucose disposal (M), and the amount of glucose metabolized per U insulin (M/I ratio). After the metformin treatment the mean Km decreased by 31% in group 1 (p < 0.05) but not significantly in group 2; M and M/I were not modified in the two study groups. In conclusion, in non diabetic obese subjects, metformin seems not to affect peripheral insulin-mediated glucose metabolism unless there is weight loss.

Decreased nocturnal plasma melatonin levels in patients with recurrent acute intermittent porphyria attacks

Acute intermittent porphyria (AIP) is a hereditary disease characterized biochemically by a defect in the heme pathway enzyme porphobilinogen deaminase. There is wide variability in the neurologic clinical expression of AIP, and the disorder remains latent in most gene carriers. The natural history of the disease and results in a porphyric rat model suggest a significant relationship between tryptophan metabolites and clinical expression of the disease. In the present study, we examined urine and blood tryptophan metabolite levels in AIP women before, during and after acute attacks and treatment by heme arginate. Heme arginate treatment promptly decreased total tryptophan levels (from 69 +/- 9, to 44 +/- 5, mean +/- SEM, mumole/l, p < 0.001), serotonin blood levels (from 629 +/- 103, to 356 +/- 80, nmole/l, p < 0.01) and the urinary excretion of 5-HIAA (from 3.9 +/- 0.6, to 2.2 +/- 0.4, mumole/mmole creatinine, p < 0.01). The plasma level of melatonin was found much lower than the normal control level at night (86.2 +/- 70.3, vs the normal range, 409 +/- 78.9, pmole/l +/- SEM) and day time (38.8 +/- 22.0, vs 75 +/- 13.7). Heme arginate treatment did not influence melatonin levels. Our results support the involvement of abnormal tryptophan metabolism in the pathophysiology of AIP acute attacks. Low melatonin plasma levels in porphyric women suggest that the defect of the pineal hormone may be responsible for the recurrent aspect of porphyric attacks. A desynchronization of biological rhythms in AIP patients may increase the inducibility of hepatic ALA synthase to environmental risk factors and, specially, to sex steroid hormones.

Thyroid hormone extraction by plasma exchange: a study of extraction rate

How to obtain an optimal efficiency of plasma exchanges in the treatment of severe hyperthyroidism has not been defined. In order to evaluate how long the exchanges must be continued to be fully effective in extracting thyroid hormones, we evaluated the extraction rate by repeated plasma sampling in two hyperthyroid patients and three euthyroid subjects who underwent a total of seven exchanges. Plasma concentrations of thyroid hormones were also determined just before, just after, and 24 hours following the exchange. The hormonal removal rate did not fall dramatically during the exchange, so that its efficiency--in terms of hormone extraction--depends closely on its duration. The determination of plasma thyroid hormone concentrations after the exchange does not appear to be useful in evaluating the thyroid hormone loss since these concentrations may not change in spite of the hormonal extraction.

Immunological specificity of monoclonal antibodies to Chlamydia psittaci ovine abortion strain

Fifty-one monoclonal antibodies were prepared by two different techniques against Chlamydia psittaci strain A22 isolated from an ovine abortion. These antibodies were tested for reactivity by the indirect immunofluorescent antibody technique with eleven reference Chlamydia strains (nine C. psittaci, one Chlamydia trachomatis and one Chlamydia pneumoniae). Four classes of specificity were recognized for monoclonal antibodies: genus, species, subspecies and type specificity. The type-specific monoclonal antibodies were non-reactive with ovine arthritis isolates. Twenty monoclonal antibodies were specific for two mammalian strains: ovine abortion A22 and K mouse. Some monoclonal antibodies were reactive with C. pneumoniae strains and non-reactive with C. trachomatis strains. All these monoclonal antibodies were very useful for improving the diagnosis of chlamydial infection, the antigenic analysis and the serotyping of C. psittaci.