William E. Dulin

Studies on the ability of compounds to block the diabetogenic activity of streptozotocin.

Evidence is presented that the early hyperglycemia (two to four hours after injection) following streptozotocin administration is not a result of an interference with insulin action, since streptozotocin did not block insulin action on skeletal muscle in vitro. Compounds with known metabolic effects were tested for their ability to block streptozotocin-induced diabetes. Mannoheptulose, glucosamine, diazoxide, NAD, glucose, epinephrine, 3,5-dimethylpyrazole, 3-carboxy-5-methylpyrazole, glutamic acid, glycine, asparagine, cysteine, sodium tolbutamide, guanidoacetic acid, glutathione, p-aminobenzoic acid, and ethyl alcohol were ineffective as blocking agents. Pretreatment with pyrazinamid blocked streptozotocin diabetes,but was ineffective following streptozotocin treatment. 2-carboxypyrazine (the metabolite of pyrazinamide) did not block streptozotocin diabetogenic activity. Administration of 2-deoxyglucose blocked streptozotocin-induced diabetes; this is postulated to be the result of an interference with streptozotocin transport into the β cell. Pretreatment with nicotinamide, or treatment as long as two hours after streptozotocin, blocked the diabetogenic effect of streptozotocin. Nicotinic acid was ineffective. It is postulated that streptozotocin interferes with NAD formation in the β cell, and that nicotinamide treatment abolishes the streptozotocin effect by its ability to maintain ah adequate concentration of NAD in the β cell.

Effect of a New Hypoglycemic Agent, 3,5-Dimethylpyrazole, on Carbohydrate and Free Fatty Acid Metabolism

As a hypoglycemic agent, 3,5-dimethylpyrazole (U-6245) was found to be fifty-four times more potent orally than tolbutamide in glucose-injected, fasted intact rats. U-6245 increased glucose oxidation by intact rats. It lowered plasma free fatty acids but not blood sugar of eviscerate rats and was effective in decreasing the fasting bloodsugar levels of alloxan-diabetic rats which were unresponsive to tolbutamide. U-6245 markedly depressed plasma FFA fifteen minutes to three hours after its administration. The mechanism of hypoglycemic activity of 3,5-dimethylpyrazole is not the same as insulin, sulfonylureas or biguanides in that: (1) It is ineffective in lowering the blood sugar of eviscerates while insulin is. (2) U-6245 is active in alloxan diabetic rats which are unresponsive to tolbutamide. (3) The pyrazole increases glucose oxidation and biguanides do not. Although the mechanism of action of 3,5-dimethylpyrazole is not understood, data are presented which support the hypothesis that its action may depend on its effect on plasma FFA and also on the presence of the liver and/or intestinal tract. Since the pyrazole increases glucose oxidation in intact rats, it appears that at least part of its action may be due to the stimulation of glucose oxidation by the intestinal tract and/or liver.

Morphologic abnormalities observed in retina, pancreas and kidney of diabetic Chinese hamsters

SummaryIntracellular glycogen deposits were consistently found in the retina, kidney and pancreatic islets of diabetic-ketonuric Chinese hamsters. Accumulation of glycogen in the outer nuclear layer of the retina was mostly associated with severity of the disease, but was not related to age or sex. The type of retinal cell involved in the accumulation of glycogen was not clearly established. However, the position of the affected cell, side by side with retinal neurons, suggests that the glycogen deposits were within Müller cells. These giant glias normally synthesize and store glycogen. All ketonuric Chinese hamsters examined showed some accumulation of glycogen in distal tubules of the kidney. This abnormal glycogen was not found in glucosuric non-ketonuric or in nondiabetic Chinese hamsters. Variable amounts of glycogen were found inΒ cells of pancreatic islets of diabetic hamsters, as reported by others. However, accumulation of glycogen was also found inα and D islet cells from 2 middle aged Chinese hamsters with long term glucosuria and recent ketonuria. Abnormal glucose and glycogen metabolism seem to play an important role in the pathogenesis of diabetes in the Chinese hamster.

Effects of corticosterone, cortisone and hydrocortisone on fat metabolism in the chick.

Summary (1) Hydrocortisone and corticosterone caused an increase in liver, visceral and carcass fat in the chick while cortisone was without effect. (2) The relative effectiveness of these 3 steroids on body growth inhibition in the growing chick is in the following order: hydrocortisone, corticosterone and cortisone. (3) None of these 3 hormones caused an inhibition of relative adrenal weights.

Reversal of streptozotocin diabetes with nicotinamide.

Summary Animals given nicotinamide either as a pretreatment or as long as 2 hr (but not 4 hr) after streptozotocin were protected from diabetes. Nicotinic acid and NAD pretreatment were ineffective in preventing streptozotocin diabetes. It was postualted that streptozotocin may interfere with NAD formation in the beta cell and that treatment with nicotinamide reverses the streptozotocin effect by reversing its effect on levels of NAD within beta cells.

Effect of diet limitation on the development of diabetes in prediabetic Chinese hamsters

SummaryPrediabetic Chinese hamsters born of two ketonuric diabetic parents were hyperphagic from birth. Carcass lipids and total solids were increased but plasma and pancreatic insulin were not, suggesting that hyperphagia was not due to hyperinsulinism. Hyperphagia was controlled by diet limitation of prediabetic pups. Diet limitation for the weaning period only did not alter development of diabetes, but diet limitation for the first 150 days significantly reduced onset and severity. These 150 day diet-limited prediabetics were switched to nonrestricted feeding and subsequently developed mild diabetes. Prediabetic siblings, fedad libitum, developed glucosuria and ketonuria, and died prematurely compared with diet-limited siblings. Prediabetics limited to a normal food intake for 30 months have remained essentially clinically normal. The data strongly suggest that appetite control mechanisms are abnormal prior to clinical signs of diabetes in the prediabetic Chinese hamster and that control of hyperphagia will retard anameliorate the course of diabetes.

Anti-Inflammatory Activity of Δ1-9α-Fluorohydrocortisone Acetate

Summary A comparison of anti-inflammatory effects of hydrocortisone with several of its analogues has been made. It was found that Δ1-9 α-hydrocortisone acetate was 3.1 times as active as hydrocortisone; 9 α-fluorohydrocortisone acetate was 7.3 times as active, while Δ1-9 α-fluorohydrocortisone acetate was 14 times as effective as hydrocortisone, as determined by the cotton pellet implantation method.

Adrenal Corticoid Activities of 2-Methylhydrocortisone Acetate and 2-Methyl-9a-Fluorohydrocortisone Acetate

Summary (1) Two new analogues of hydrocortisone, 2-methylhydrocortisone acetate and 2-methyl-9 α-fluorohydrocortisone acetate, have been tested for corticoid activity on the following assays: anti-inflammatory, glycogen deposition, muscle work, and sodium retention. A summary of the data is presented in Table VI. (2) The sodium-retaining activity of 2-methyl-9 α-fluorohydrocortisone acetate is 90 x desoxycorticosterone acetate and is, therefore, one of the most potent mineralocorticoids.

Hypoglycemic Activity of 3,5 Dimethylisoxazole

Summary 3, 5 dimethylisoxazole (U-21221) was found to be 188 times more potent orally than tolbutamide in glucose-primed fasted intact rats. U-21221 also increased glucose oxidation by intact rats. It did not lower blood sugar of eviscerate rats but was active in alloxan diabetic animals which were unresponsive to tolbutamide. It was suggested that the mechanism of action of 3,5 dimethylisoxazole was by stimulation of glucose oxidation by the gut and/or liver.

Effects of 2-methylation on glucocorticoid activity of various C-21 steroids.

Summary The anti-inflammatory and glycogen deposition activities of some C-21 steroids and their 2-methyl analogues have been described. The 2-methyl analogues were more potent than the parent compound in the cases of hydrocortisone, 9α-fluorohydrocortisone, 6-dehydrohydrocortisone, 11β, 17α-dihydroxyprogesterone and 9α-fluoro-11β, 17α-dihydroxyprogesterone. In the cases of 11β-hydroxyprogesterone, corticosterone, 9α-fluorocorticosterone, 9α-fluoro-llβ-hydroxyprogesterone and 11-ketoprogesterone the 2-methyl did not potentiate the activity. The 2-methyl analogues of cortisone, 9α-fluorocortisone and 11-dehydrocorticosterone were less effective than the parent steroid.