C.E. Holmlund

Insulin-like activity of a microbial protease on isolated fat cells

Abstract A protease produced by Streptomyces griseus has been found to display insulin-like effects on the metabolism of isolated fat cells from rat epididymal tissue. These effects include enhanced conversion of glucose to carbon dioxide and lipid, and repression of the lipolysis stimulated by corticotropin and norepinephrine. Greater than 95% of the proteolytic activity could be abolished without significantly altering the insulin-like activity of the protease. The significance of these observations is discussed.

Inhibition by phlorizin of insulin- and protease-stimulated glucose utilization in isolated adipose cells

1. 1. Utilization of extracellular glucose, determined by its conversion to CO2 and total lipid, has been employed to study the effect of phlorizin on isolated adipose cells incubated with and without insulin, α-chymotrypsin, trypsin and pronase (Streptomyces griseus protease, Type VI). 2. 2. In dilute glucose medium, the effect of insulin on glucose utilization is to lower the apparent Km, and also to increase the vmax. Phlorizin competitively inhibited glucose utilization without affecting intracellular metabolism, including the reactions involved in lipolysis and oxidation of 14C-labeled cellular materials. 3. 3. Phlorizin at 0.92 mM inhibited glucose utilization by isolated adipose cells to the same extent in the presence and absence of insulin, α-chymotrypsin or trypsin. Moreover, the degree of inhibition was essentially identical for both parameters measured (CO2 production and lipid synthesis), and remained constant over a wide range of concentrations of these agents. It appears that phlorizin blocks only the process of glucose entry, and does not affect the mechanisms whereby glucose utilization is increased by insulin or proteolytic enzymes.

Growth inhibition of Tetrahymena pyriformis by 3-dialkylaminoethoxysteroids

Abstract The relative degree of growth inhibition of T. pyriformis caused by a series of dialkylaminoethoxysteroids was found to correspond to the extent that these compounds lower serum sterol in experimental animals.

Effects of avenaciolide on lipolysis and on glucose, amino acid and palmitic acid metabolism in isolated adipose cells

Abstract Avenaciolide, an antifungal lactone, inhibited the lipolysis in adipose cells mediated by lipolytic hormones (adrenocorticotropin and norepinephrine) and phosphodiesterase inhibitors (caffeine and theophylline). Although without effect on the basal oxidation of glucose, avenaciolide abolished the stimulation of glucose oxidation caused by insulin or proteolytic enzymes. It also eliminated the stimulatory effects of these substances on lipogenesis, but inhibited this process to some extent per se as well. Oxidation and esterification of palmitic acid were inhibited, but little effect on amino acid metabolism was noted.

MICROBIAL FORMATION AND HYDROLYSIS OF TESTOLOLACTONE.

Abstract Testolic acid has been isolated and identified as the major final product from the fermentation of androstenedione with Cephalosporium acremonium . The occurrence of testolic acid in fermentations with other microorganisms reported to produce testololactone is noted. Testolic acid is produced by enzymatic hydrolysis of testololactone and is probably not a precursor in the microbiological formation of testololactone.

Effects of arsenite of lipolysis and metabolism of glucose, palmitic acid and amino acids by isolated adipose cells

Abstract 1. 1. Arsenite at an optimum concentration of 0.05 mM was found to stimulate about 2-fold the basal glucose utilization (oxidation and lipogenesis) by isolated fat cells. Stimulation of lipogenesis by arsenite at or below the optimum concentration resulted from enhanced synthesis of both fatty acid and glyceride-glycerol, the former being greater than the latter. Reduction in lipogenesis by arsenite at a concentration slightly greater than optimum resulted primarily from inhibition of fatty acid synthesis; glycerol synthesis was not affected. 2. 2. Arsenite at an optimum concentration of 0.1 mM stimulated esterification of palmitic acid, while no significant enhancement in protein synthesis or amino acid oxidation was noted. Metabolism of glucose, palmitic acid and amino acid is greatly inhibited by arsenite at concentrations exceeding 0.1 mM. 3. 3. Lipolysis mediated by lipolytic hormones (adrenocorticotropin and norepinephrine) and phosphodiesterase inhibitors (caffeine and theophylline), employed either singly or in combination, was inhibited by arsenite.

Microbiological formation of 1α,2α-dihydroxysteroids

Abstract Selected steroids give rise to 1α,2α-dihydroxylated products when fermented with nocardia corallina (ATCC 999). Preparation of the 1α,2α-dihydroxy derivatives of 17α-ethynyl-17β-hydroxyandrost-4-en-3-one (I), 9α-fluoro-11β,17β-dihydroxy-17α-methylandrost-4-en-3-one (VI), and 11β,21-dihydroxy-16α,17α-isopropylidenedioxypregn-4-ene-3,20-dione (XII) is described. Induction of the required enzymes by prior exposure of N. corallina to androstenedione was necessary to obtain the 1α,2α-dihydroxy products from I and XII.

Paper electrophoresis of steroids in borate buffers

Abstract Certain polyhydroxylated steroids form negatively charged complexes in borate buffer which migrate toward the anode during paper electrophoresis. The relative migration rates are tabulated.

Effects of deoxyfrenolicin on isolated adipose cells. I. Glucose and fructose utilization.

Abstract Deoxyfrenolicin, at an optimal concentration of about 15 to 20 μg ml , stimulated to a greater extent than did insulin the oxidation of glucose and fructose, presumably via the pentose cycle, by isolated adipose cells. Stimulation of glucose uptake and lipogenesis from glucose and fructose were lower than by insulin, however. At a higher concentration (60 μg ml ) of deoxyfrenolicin, the stimulatory effects were reduced or abolished. Deoxyfrenolicin, at a suboptimal concentration (10.5 μg ml ), stimulated still further the maximally stimulated lipogenesis from glucose and fructose in response to insulin or several “insulin-like” proteases. It is suggested that deoxyfrenolicin stimulated sugar utilization in isolated adipose cells, at least in part, through a mechanism different from the actions of insulin or proteases.

Effects of piericidin A on the metabolism of isolated adipose cells

Abstract The effects of piericidin A, a structural analog of coenzyme Q, on the metabolism of isolated adipose cells were studied. Piericidin A inhibited both the basal and the insulin-stimulated glucose and fructose utilization (oxidation and lipogenesis). Piericidin A completely abolished the stimulatory effects of proteases ( Bacillus subtilis protease, Streptomyces griseus protease and α-chymotrypsin) on glucose utilization. The utilization of palmitic acid was inhibited by piericidin A to a greater extent than amino acids. Piericidin A accelerated glycogenolysis, but exerted no significant effects on the level of lipid content or the oxidation of the cellular components. The lipolysis induced by lipolytic hormones (corticotropin and norepinephrine) or phosphodiesterase inhibitors (caffeine and theophylline) or by both was also blocked by piericidin A. The effects of peiricidin A on the isolated adipose cells were interpreted as probably being due to plasma membrane effects and possible effects on the adenyl cyclase system.