ABSTRACT
OBJECT: Treatment with somatostatin analogues (SA) not only inhibits GH secretion but may also impair insulin secretion. In order to evaluate the influence of SA on glucose metabolism, we investigated insulin resistance (IR) and beta-cell function, using the recommended combination of homeostatic model assessment of IR (HOMA-IR) and beta-cell function (HOMA-beta). DESIGN AND METHODS: This is a prospective, cross-sectional study. We measured fasting insulin, blood glucose and IGF-I. Insulin and blood glucose measurements were taken 120 min after an oral glucose tolerance test with 75 g glucose. We studied 51 patients (27 female/24 male, age 54 years (20-75)). Eighteen patients were on Lanreotide Autogel (LA) treatment, 33 had no medical treatment. GH-levels of more than 2.5 ng/ml was reached by 59% of the patients, 74.5% had normal IGF-I levels. RESULTS: We found no significant influence of disease activity on HOMA-IR and HOMA-beta. In the 33 of 51 subjects without any drug treatment, median HOMA-beta was 170.4% (36.0-624.0%). In contrast, in the 18 patients on LA treatment, median HOMA-beta was found to be significantly lower (84.2% (36.5-346.2%); P = 0.001). Despite this, there was no difference in HOMA-IR in both groups (2.4 (0.7-8.4) vs 2.3 (0.7-6.1); P < 0.001) despite similar insulin values. CONCLUSION: In conclusion, we found that LA decreases beta-cell function significantly without affecting IR. Therefore, we think that insulin secretagogues are probably more effective in the treatment of diabetes mellitus in acromegalic patients on LA therapy than insulin sensitizers.
Subject(s)
Acromegaly/drug therapy , Acromegaly/metabolism , Glucose Tolerance Test , Insulin Resistance , Peptides, Cyclic/therapeutic use , Somatostatin/analogs & derivatives , Adult , Aged , Body Mass Index , Cross-Sectional Studies , Female , Gels , Humans , Insulin/blood , Insulin-Secreting Cells/drug effects , Male , Middle Aged , Peptides, Cyclic/administration & dosage , Prospective Studies , Somatostatin/administration & dosage , Somatostatin/therapeutic useABSTRACT
The composition and characteristics of b-type cytochromes from higher plant plasma membranes, purified using aqueous two-phase partitioning, were investigated. At least three different cytochromes were identified by their wavelength maxima and redox midpoint potentials (E(0)'). Cytochrome b-560.7 (E(0)' from + 110 to + 160 millivolts) was present in zucchini (Cucurbita pepo) hypocotyls and bean (Phaseolus vulgaris L.) hooks, although in different concentrations. The main component in cauliflower (Brassica oleracea L.) inflorescences (cytochrome b-558.8) is probably functionally similar to this cytochrome. The plasma membrane generally contains two to three cytochrome species. However, the occurrence and concentrations were species dependent. The high potential cytochrome can be reduced by ascorbate but not NADH, and may be involved in blue light perception.
