[PDF] Effects of L-leucine on the insulin production, oxidative metabolism and mitochondrial ultrastructure of isolated mouse pancreatic islets in tissue culture | Semantic Scholar (2024)

It rather seems as if long-term exposure of islet B-cells to sulphonylureasin vitro were accompanied by functional deficiency, which might involve an adaptation to substrates other than glucose.

The present data suggest that the most favourable conditions for long-term storage of isolated islets in culture may be obtained when the islets are maintained as free-floating explants in a culture medium consisting of RPMI 1640 supplemented with serum.

The functional and ultrastructural findings suggest that vit A inhibitioh of second phase insulin release is not specific for glucose and may be mediated in part through impairment of mitochondrial function and intracellular glucose oxidation.

These results define culture media, with or without serum, wherein at least 75% of single rat islet beta cells can survive for a minimum of 9 days, which will allow for studies on beta-cell toxic conditions and potentially protective agents.

Mice treated for 4 days with tolbutamide displayed decreased serum glucose values with a concomitant decrease of their islet insulin content, and the somatostatin content of high- and medium-glucose cultured islets was higher than that of freshly isolated islets.

In accepting the remit “the fetal endocrine pancreas” for a second time, a specific theme has been chosen which is developed in an essay that is partly a review of recent work and partly unashamedly speculative.

In conclusion, short-term daily supplementation with a low dose of fish protein may have beneficial effects on blood levels of glucose and LDL-cholesterol as well as glucose tolerance and body composition in overweight adults.

The continuous addition of newly synthesized and labelled insulin to the small intracellular insulin pool of the high-glucose cultured B-cells produced a very high specific radioactivity of the insulin.

It is suggested that the effects of glucose on the oxidation of alanine and leucine were mediated by metabolism of the sugar, and that amino acids do not act as insulin secretagogues by serving as fuels for the beta-cells.

Observations of an increased mitochondrial volume in islet cells cultured at low glucose probably do not reflect a degenerative process, but rather adaptive changes towards oxidation of energy yielding substrates other than glucose.

With the present technic for organ culture of isolated mouse islets, the β cells retain several of their characteristic metabolic responses during prolonged in vitro culture, which should be useful for providing new information on the long-term effects on the structure and metabolism of the pancreatic β cell.

The results suggest that the insulin biosynthesis remains sensitive to glucose even when islets have been previously exposed to a low-glucose concentration for a prolonged period of time and support the view that the impaired insulin release in response to glucose observed during fasting reflects a lack of glycaemic stimulus to the B-cell.

The observed correlated impairment in insulin secretion and islet glucose metabolism during starvation is discussed, and possible mechanisms behind the correlated impairment are discussed.

The B-cells of obob mice appear to be well adapted to a high rate of hormone biosynthesis, since at 16.7 mM glucose 44% of [3H]leucine incorporated into TCA-precipitable proteins was bound to the insulin antibodies coupled to Sepharose 4B.

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