Aims/hypothesis. Whether excess glucose (glucotoxicity) and excess non-esterified fatty acids (lipotoxicity) act synergistically or separately to alter beta-cell function on Type 2 diabetes remains controversial. We examined the influence of non-esterified fatty acids, with or without concomitant increased glucose concentrations, on human islet function and on the expression of genes involved in lipid metabolism. Methods. Human islets isolated from non-diabetic and non-obese donors were cultured with 5.5, 16 or 30 mmol/l glucose, and when appropriate with 1 or 2 mmol/l non-esterified fatty acids. After 48 h, glucose-stimulated insulin secretion, insulin content, triglyceride content and expression of different genes were evaluated. Results. Non-esterified fatty acids decreased glucosestimulated insulin secretion, insulin content and increased triglyceride content of human isolated islets, independently from the deleterious effect of glucose. Increased glucose concentrations also decreased glucosestimulated insulin secretion and insulin content, but had no influence on triglyceride content. Glucose-stimulated insulin secretion of islets appeared to be significantly correlated with their triglyceride content. Glucose and non-esterified fatty acids modified the gene expression of carnitine palmitoyltransferase-I, acetyl-CoA carboxylase, acyl-CoA oxidase and uncoupling protein 2. Conclusion/interpretation. In our model of isolated human islets, increased glucose and non-esterified fatty acids separately reproduced the two major beta-cell alterations observed in vivo, i.e. loss of glucose-stimulated insulin secretion and reduction in islet insulin content. Our results also suggest that this deleterious effect was, at least in part, mediated by modifications in lipid metabolism gene expression. [Diabetologia (2004) 47:463-469]

No abstract

The amino acid sequences of two cuttlefish protamine variants Spl and Sp2 have been established from automated sequence analysis and mass spectrometry data. Spl (57 residues) and Sp2 (56 residues) have molecular masses of 8410 and 8253 Da, respectively. They are almost identical proteins which differ only by one residue of arginine and the position of two of the serine residues (14 and 37 in Spl; 13 and 35 in Sp2). With an arginine content of about 77%, cuttlefish protamine is one of the most basic proteins which have ever been characterized and the first typical protamine sequenced in invertebrates. It is closely similar to sperm basic proteins identified in squids but strongly differs from the protamine-like components isolated from the sperm of bivalve molluscs.In invertebrates, the nuclear basic proteins associated with DNA in mature sperm cells show a great variability, according to the degree of evolution of the concerned species. In echinoderms, for example, histones persist in spermatozoa [l -31. In other species, such as annelids [4] and molluscs [5 -81, histones together with protamine-like proteins are present in spermatozoa. A third situation can be found in more evoluted species as cephalopods : histones are completely replaced by arginine-rich proteins similar to protamines observed in teleost fishes [9].In a previous work [lo], we reported the characterization of a typical protamine from mature cuttlefish spermatozoa. This protamine, called protein Sp, already appears in elongated spermatids in a phosphorylated form [I 11, whereas it is found dephosphorylated in mature sperm cells.Here, we present the amino acid sequence of protein Sp, which is constituted of two different structural variants Spl and Sp2. MATERIALS AND METHODS MaterialsMature male cuttlefishes Sepia officinalis were collected in May at the Station Marine de Wimereux (France). Spermatophores were excised and spermatozoa were immediatly frozen in liquid nitrogen and stored at -80 "C until use.Correspondence to P. Sautiere, URA 409 CNRS, Universitk de Lille 11, Institut de Recherches sur le Cancer, Place de Verdun, F-59045 LILLE CCdex, FranceAbbreviations. Sp, cuttlefish sperm protamine; FAB-MS, fastatom-bombardment mass spectrometry; '"Cf PD-MS, 252Cf plasma-desorption mass spectrometry; ES-MS, electrospray mass spectrometry.Enzymes. Chymotrypsin (EC 3.4.21 .l); pancreatic elastase (EC 3.4.21.36); Astacusfluviatilis protease (EC 3.4.99.6).Note. The novel amino acid sequence data published here have been deposited with the EMBL sequence data bank. Purijication and fractionation of protein SpNuclear basic proteins were extracted from sperm nuclei and the protamine (protein Sp) subsequently purified as described previously [lo].The separation of protamine variants was performed in some experiments by reverse-phase HPLC on a CI8 pBondapak column (Waters Associates) eluted with a gradient of 0 -50% acetonitrile in 0.05% heptafluorobutyric acid. In other experiments, the fractionation was assayed by ion-exchange HPLC on a Spherogel TSK...

No abstract