Joseph C. Shipp

Insulin Across Respiratory Mucosae by Aerosol Delivery

Insulin, a protein of about 5,700 molecular weight, was delivered by aerosol inhalation to three normal volunteers and to four patients with diabetes mellitus. Direct evidence of absorption of insulin across mucosae of the respiratory tract was an increase in plasma IRI. Biologic activity of insulin absorbed by inhalation was shown by hypoglycemia temporally correlated with the increase in plasma IRI. No untoward reactions were observed.

Interrelation between carbohydrate and fatty acid metabolism of isolated perfused rat heart

Abstract The metabolic interrelationships of carbohydrate and fatty acid metabolism in the perfused rat heart were studied. Palmitale consistently reduced the oxidation of glucose-U-C 14 ; this effect was associated with less glycogen breakdown, more incorporation of glucose label into glycogen and, in some instances, more lactate formation. Acetate and pyruvate had similar effects but also reduced the glucose uptake. The oxidation of palmitate-1-C 14 was not decreased by the presence of glucose or pyruvate; acetate did not alter the uptake but reduced the oxidation of palmitate and increased the fraction recovered in tissue triglyceride. The results showed that free fatty acids were oxidized in preference to glucose, and suggested a controlling effect of fatty acids on glucose metabolism. The observed effects of palmitate, acetate and pyruvate on glucose-U-C 14 metabolism supported the hypothesis that their inhibition of glucose oxidation occurred, in part, at the pyruvate-acetyl Co-A level.

Accumulation of myocardial triglycerides ketotic diabetes; evidence for increased biosynthesis.

The accumulation of triglycerides in the myocardium of nonketotic and overtly ketotic diabetic rats was studied. There was no increase in heart triglycerides of nonketotic rats taken off insulin treatment, although the rats exhibited several indices of diabetes. In nonketotic diabetic rats untreated with insulin, myocardial triglycerides repeatedly increased and declined to control levels. In severely ketotic rats, heart triglycerides increased about threefold and did not decline with time. In order to understand the mechanism of increase in myocardial triglycerides in ketotic diabetes, the biosynthesis of triglycerides was studied with heart homogenates. The total esterification of sn-glycero-3-phosphate was unaltered, but the synthesis of diglycerides and triglycerides was increased in the myocardium of the ketotic rat. On treatment of the diabetic rats with insulin, the synthesis of di- and triglycerides in heart homogenates reverted to control values. Thus the results of the present study demonstrate that (1) a persistent increase in myocardial triglyceride content was observed only in the ketotic diabetic rat and (2) increased synthesis of triglycerides is a factor in its accumulation in the myocardium of the ketotic rat.

Effect of pH, pCO2 and bicarbonate on metabolism of glucose by perfused rat heart

Abstract 1. 1. Effects of pH, pCO 2 and bicarbonate on metabolism of [ 14 C 6 ]glucose in the isolated perfused rat heart were studied. 2. 2. With an alkaline extracellular pH, glucose uptake, lactate production and glycogen breakdown increased, and oxidation of exogenous glucose remained constant. These findings are compatible with enhancement of phosphofructokinase (EC 2.7.1.11) activity. 3. 3. At an acid extracellular pH, glucose uptake and lactate production decreased, glycogen levels were unchanged, and 14 CO 2 production was unchanged until pH fell below 7.0, at which time 14 CO 2 decreased. 4. 4. Glucose uptake, lactate production, 14 CO 2 production and glycogen levels were similar in hearts perfused at pH 7.50 with either a bicarbonate buffer or 30 mM Tris.

OXIDATION OF CARBON-14-LABELED ENDOGENOUS LIPIDS BY ISOLATED PERFUSED RAT HEART.

Lipids of the rat heart were labeled with carbon-14 in vivo. The production of C14O2 during the subsequent perfusion of these glycogen-depleted hearts with buffer, but without added substrate, provided direct evidence of the oxidation of endogenous heart lipids. The net decrease in phospholipid content alone could account for 75 percent of the total metabolic CO2 formed.

Metabolism of lipoprotein lipid in the isolated perfused rat heart

Abstract 1. 1. The disappearance from the perfusate, localization within heart lipids, and oxidation of 14C-labeled lipid from three ultracentrifugally separated lipoprotein fractions were studied in the isolated perfused rat heart. 2. 2. With d 3. 3. With d 1.006−1.070 lipoprotein, 14CO2 and 14C-label in the heart lipids accounted for all of the triglyceride fatty acid uptake. The final concentration of triglycerides in the perfusate was very low and no net increase in free fatty acid in the buffer was observed. The amount of triglyceride fatty acid recovered in CO2 was less than, and that in heart lipids equal to, that observed with d 4. 4. With d 1.070−1.210 lipoprotein, the lack of change in concentration or specific activity of phospholipid with perfusion suggested that phospholipids were not extracted, or metabolized by the perfused heart. The 14C-labeled lipid extracted was primarily free fatty acid; the major non-oxidative fate of this free fatty acid was incorporation into tissue phospholipids.

Effect of insulin treatment in vivo on heart glycerides and glycogen of alloxan-diabetic rats

Abstract The effect of insulin treatment in vivo on cardiac glycerides and glycogen was studied in alloxan-diabetic rats. In untreated alloxan-diabetic rats, heart glycerides and glycogen were increased two- to threefold. The increase in heart glycerides and glycogen and in concentrations of serum FFA were maximal 36 hr after alloxan; serum glucose continued to rise through 48 hr. Insulin, started 24-hr postalloxan, restored heart glycerides to control values within 12 hr and reduced heart glycogen content and serum glucose and FFA concentrations. Heart glycogen and serum FFA were normal 24 hr after insulin treatment.

Regulation of Triacylglycerol Lipolysis in the Perfused Hearts of Normal and Diabetic Rats

Effects of insulin, palmitate, and acetate on lipolysis of endogenous triacylglycerols were studied in the isolated perfused hearts of control and ketotic diabetic rats. In the absence of fatty acid, the rate and net amount of lipolysis were increased in diabetic hearts. After 120 min of perfusion, the residual triacylglycerol content was similar in both hearts, suggesting that the accumulation of triacylglycerols in the heart of ketotic diabetic rats was due to the expansion of the mobiliza-ble fraction. Insulin, in physiologic concentrations, inhibited triacylglycerol lipolysis in control hearts, provided glucose was present in the perfusate. In diabetic hearts perfused with glucose, insulin up to 500 μU/ml did not inhibit triacylglycerol lipolysis. A physiologic concentration of palmitate (0.5 mM) completely inhibited triacylglycerol lipolysis in both control and diabetic hearts. Palmitate inhibition of lipolysis in both control and diabetic hearts could be observed in absence of perfusate glucose. Heart intra-cellular lipoprotein lipase activity was determined to check whether the inhibitory actions of insulin and palmitate could be explained by reduction in this lipase activity. Perfusion of control hearts with insulin and glucose had no effect on the lipase activity. Lipase activity of the control heart was unaffected and that of the diabetic heart was inhibited after perfusion with palmitate. The results of this study show (1) insulin in physiologic concentrations inhibits heart triacylglycerol lipolysis probably through increased glucose transport and glycolysis; (2) inclusion of palmitate in the perfusate results in inhibition of triacylglycerol lipolysis in both control and diabetic hearts and in the case of the diabetic heart, the palmitate effect is due to the inhibition of the intracellular lipoprotein lipase activity; and (3) an increased synthesis of triacylglycerol coupled with an inhibition of its lipolysis by free fatty acids and ketone bodies may explain the accumulation of triacylglycerols in the hearts of diabetic rats.

Glucose metabolism in leucocytes from patients with diabetes mellitus, with and without hypercholesteremia.

The metabolism of glucose by the Embden-Meyerhof, pentose cycle and citric acid cycle pathways was determined in human polymorphonuclear leucocytes from control subjects and from patients with diabetes mellitus, with and without hypercholesteremia. In controls over 85 per cent of glucose uptake was metabolized to lactic acid by the Embden-Meyerhof pathway; about 5 per cent of glucose uptake was recovered as Co2, mostly from oxidation in the pentose cycle. Minimal citric acid cycle activity, a finding which correlated well with the paucity of mitochondria in the leucocyte, was shown by the slight and similar degree of oxidation of pyruvate and acetate. Glucose metabolism in leucocytes from diabetics differed in two respects. The per cent of glucose uptake oxidized in the pentose cycle was increased in leucocytes from all diabetics. In the insulin-treated diabetics glucose uptake and lactic acid formation were similar to controls. In contrast, glucose uptake and lactic acid formation were reduced in leucocytes from adult, latent, hypercholesteremic diabetics. Pyruvate and acetate oxidation was similar in diabetics and controls. Thus, in terms of leucocyte metabolism, hypercholesteremia in the human diabetic was correlated with reduced glycolysis and not with reduced pentose cycle activity.

Acetate-1-C14 metabolism and the effect of acetate on glucose and palmitate metabolism in the perfused rat heart

Abstract The metabolism of acetate and the effect of acetate on the metabolism of glucose and palmitate were studied in the isolated perfused rat heart. Results with 1, 5 and 10 mM acetate-1-C 14 showed that oxidation, the major cellular fate, was maximal with 5 mM. In hearts perfused for 15, 30 and 60 minutes with 5 mM acetate, oxidation increased progressively. Acetate in concentrations of 2 and 5 mM, but not 0.2 mM, consistently reduced oxidation of glucose-U-C 14 , and increased net lactate production. This glucose sparing effect of acetate, similar to that with long chain fatty acids, was compatible with an action of acetate on glucose metabolism at, or below, pyruvate decarboxylation. The uptake and oxidation of palmitate-1-C 14 and its incorporation into tissue lipids were unaltered by 0.5 and 5 mM acetate, a finding consistent with more rapid activation of palmitate, as compared to acetate.