Efficacy of low-dose insulin therapy for severely obtunded patients in diabetic ketoacidosis

To evaluate the efficacy of low-dose insulin therapy in cases of severe diabetic ketoacidosis (DKA), we examined admission clinical and biochemical parameters and responses to therapy in 48 diabetic patients who presented with DKA and were randomized to receive either high- or low-dose insulin. There were no differences in the initial clinical and biochemical parameters of the patients, regardless of assignment to low or high dose; however, a subgroup of 13 patients who were classified as severe DKA (based on their presentation in a comatose or stuporous state) had, as expected, more marked clinical and biochemical abnormalities than their alert cohorts. The responses to therapy (rate of glucose decrement and control of acidosis) were comparable in the high-dose and low-dose groups of comatose/stuporous patients and were not significantly different from the noncomatose cohorts. These data indicate that low-dose insulin therapy in severely ill comatose patients is as effective as high-dose.

Correlation of hyperandrogenism with hyperinsulinism in polycystic ovarian disease

We evaluated basal plasma total immunoreactive insulin (insulin), androstenedione, and testosterone in 14 obese women: 8 with polycystic ovarian disease (PCOD) and 6 obese controls. All 3 hormones were significantly elevated (P less than 0.02 to P less than 0.001) in PCOD patients. A significant correlation among basal levels of plasma insulin, androstenedione, and testosterone was demonstrated. The PCOD group had significantly higher levels of glucose at 1, 2, and 3 h, with similar significant increases in plasma insulin levels at 0, 2, and 3 h. A significant correlation was found between plasma insulin response areas and plasma testosterone (P less than 0.001) in the control and PCOD patients. These studies demonstrate that hyperandrogenism correlates with hyperinsulinism.

Accelerated insulin degradation: an alternate mechanism for insulin resistance

We have examined insulin and glucagon degrading activities of muscle and fat tissues in 11 subjects (4 lean controls, 3 insulin-resistant obese subjects, 2 non-insulin-dependent diabetic subjects, and 2 insulin-treated diabetic subjects) and correlated degrading activity with (1) basal insulin level and (2) state of insulin resistance. We found hyperinsulinemia and insulin resistance to be significantly correlated with accelerated insulin and glucagon degrading activity. Weight reduction in an insulin-resistant obese patients results in parallel reduction in both basal insulin level and insulin-glucagon degrading activity. These data are consistent with the hypothesis that an alternative mechanism for insulin resistance may be an accelerated insulin degradation at the level of target tissues.

Evaluation of a portable insulin infusion pump for outpatient management of brittle diabetes

Three "brittle" diabetic patients were given constant subcutaneous insulin infusion with a portable battery-driven pump, and their plasma glucose and hemoglobin A1 were measured at frequent intervals during inpatient or outpatient periods. Mean plasma glucose decreased significantly in all inhospital patients and remained significantly less than before pump therapy in two of three as outpatients during the 8--12 wk of follow-ups; however, complete normalization of glucose metabolism was not accomplished in any. All three demonstrated a progressive decline in hemoglobin A1 levels to normal or near-normal values. The need for long-term studies of open loop infusion systems in a research setting before their adaptation to routine care is emphasized.

Insulin binding and degradation by muscles from streptozotocin-diabetic rats

Insulin degradtion by muscle was examined in normal, streptozotocin-induced diabetic rats, and diabetic rats treated with insulin. Insulin degradation by the 100,000 X g supernatant fractions was identical in all three groups, but insulin metabolism by the intact epitrochlaris muscle was significantly increased in diabetic animals. Insulin treatment of the diabetic animals partially restored the activity toward normal. Specific binding of 125l-insulin to the intact muscles was also increased in the diabetic animals. Streptozotocin diabetes, therefore, increased the binding and degradation of insulin by intact muscle but did not alter the insulin degradation by the total soluble intracellular degradative activity.

The effect of age on insulin-degrading activity in rat tissue

Insulin-degrading activity was measured in the 100,000g supernatant fraction of muscle, liver, and kidney from rats of varying ages. Young animals (four weeks old) had the highest activity in all three tissues. By seven weeks of age the activity in both muscle and liver had decreased significantly as compared with four-week-old animals. A slight but nonsignificant decrease occurred in kidney. In animals over one year of age the insulin-degrading activity in all three tissues was significantly less than the activities at either four or seven weeks. In contrast the effect of age on degradation of albumin and parathormone was much less marked.

Initial site of insulin cleavage by insulin protease

Exposure of insulin to insulin protease (insulinase, EC 3.4.22.11), a degradative enzyme with considerable specificity toward insulin, results in alterations in the properties of the insulin molecule. Limited degradation by the enzyme results in a decrease in the ability of insulin to bind to membrane receptors with less change in the immunoprecipitability or trichloracetic acid precipitability of the hormone. Limited degradation by insulin protease also alters insulin so that the molecule becomes susceptible to attack by nonspecific endopeptidases which have no effect on unaltered insulin. These data demonstrate the production of an intermediate in the proteolytic degradation of insulin. By labeling with [14C]dansyl chloride, an insulin intermediate with three amino-terminal residues, glycine, phenylalanine, and leucine, was identified. Analysis of this intermediate demonstrated that it was composed of an intact A chain and a B chain cleaved between residues B16 and B17, with the three peptide chains held together by disulfide bonds. Based on these findings, we hypothesize that a stepwise degradation of insulin occurs in vivo and that an early step in the process is the cleavage between B16 and B17 that renders the molecule sucseptible to further degradation by nonspecific proteases.

Similar responsiveness of diabetic ketoacidosis to low-dose insulin by intramuscular injection and albumin-free infusion

We compared low-dose insulin regimens in a prospective randomized trial in 30 patients with diabetic ketoacidosis. One group received a loading dose of 0.44 U/kg body weight of regular insulin half intramuscularly and half intravenously followed by 7 U/h intramuscularly, whereas the other group received a loading dose of 0.44 U/kg intravenously followed immediately by a constant infusion of 7 U/h in albumin-free saline. The time for metabolic control of the ketoacidosis was not significantly different in the two groups. Five patients in each group developed mild hypokalemia (serum potassium, 3.0 to 3.4 meq/litre). No patient became hypoglycemic, and there were no deaths within the follow-up period (24 h). In the treatment of diabetic ketoacidosis, low doses of insulin administered by the priming dose-intermittent intramuscular route are as effective as the constant infusion method.

Factors influencing the handling of insulin by the isolated rat kidney

The renal handling of immunoreactive insulin was studied in the isolated perfused normothermic rat kidney to determine (a) the relative contributions of glomerular clearance and peritubular clearance to the renal clearance of insulin under different conditions, (b) what metabolic factors influence the ability of tubular cells to remove insulin from the glomerular filtrate and the peritubular circulation, and (c) whether the same factors influence the luminal and contraluminal uptake of insulin.In control kidneys the organ clearance of insulin (OCi) was 974+/-63 mul/min (SEM), of which a maximum of 46% could theoretically be accounted for by filtration. OCi was not altered by fasting, lack of exogenous fuel (glucose), or the addition of cyanide. The glomerular filtration rate did not correlate with the OCi, but there was a significant (P < 0.001) negative correlation (r = -0.828) between the peritubular clearance and glomerular filtration rate. Both N-ethylmaleimide and cold (10 degrees C) reduced the rate of insulin removal. Fractional excretion of filtered insulin (9.7+/-1.7% in controls) was not significantly altered by fasting or perfusing without glucose. In contrast, KCN increased fractional excretion of insulin to 41.9+/-3.7% whereas cold increased fractional excretion to 69.0+/-3.3%. This study indicates that renal tubular cells remove insulin from the tubular lumen and the peritubular compartment. Furthermore, the data suggest that insulin removal by tubular cells is a temperature-sensitive process consisting of two different systems. The system associated with the luminal aspect of the cell appears to be dependent on oxidative metabolism, whereas the system associated with the contraluminal aspects of the cell appears to be independent thereof. Under several circumstances when the glomerular clearance of insulin falls thereby reducing the amount of insulin absorbed by the luminal aspect of the cell, contraluminal uptake increases, and a constant rate of insulin removal is maintained by the kidney.

Dipivalyl epinephrine: a new pro-drug in the treatment of glaucoma

The dansyl chloride technique in conjunction with thin layer chromatography and autoradiography has shown that dipivalyl epinephrine is a pro-drug in the human eye. Dipivalyl epinephrine appears to be a more effective epinephrine compound, in that it penetrates the cornea approximately 17 times greater than epinephrine.

Diabetic ketoacidosis: low-dose insulin therapy by various routes

Since in normal persons the hypoglycemic effect of low-dose intramuscular exceeds that of subcutaneous insulin we studied the effect of routes of insulin therapy in diabetic ketoacidosis. Forty-five patients with diabetic ketoacidosis entered a randomized prospective protocol with insulin administered either intravenously, subcutaneously or intramuscularly. Initial priming dose of insulin had to be repeated in two of 15, three of 15 and six of 15 of the intravenous, subcutaneous and intramuscular groups respectively. The intravenous group had a more rapid fall in plasma glucose (P less than 0.01) and ketone bodies (P less than 0.05) during the first two hours. Thereafter, there were no significant differences in the rate of decline of plasma glucose or ketones nor in the time required for glucose to reach 250 mg per deciliter or for complete recovery from diabetic ketoacidosis. The data confirm the efficacy of low-dose insulin therapy for diabetic ketoacidosis and indicate that the optimal route of insulin administration is by initial intravenous combined with subcutaneous or intramuscular.

Proinsulin and C-peptide: a review

The recent work on proinsulin and C-peptide has been reviewed with major emphasis on the most significant findings since 1972. Proinsulin has now been established as the biosynthetic precursor of insulin in all species examined, including man, with a preproinsulin as a possible precursor of the prohormone. The conversion of proinsulin which appears to occur exclusively in the pancreas leads to equimolar production of insulin and C-peptide. Although proinsulin has a direct biologic effect which is one-tenth as much as that of insulin, C-peptide has no biologic activity on homologous or heterologous tissue and no ability to modify the action of insulin and/or proinsulin. Previous work on proinsulin immunoassay suggested that this prohormone, but not C-peptide, cross-reacts with insulin antiserum. On the other hand, in the C-peptide immunoassay, proinsulin but not insulin cross-reacts with the antiserum. Up to this time, therefore, it has not been possible to immunoassay human proinsulin or C-peptide specifically. The very recent work from the laboratory of Heding, however, has brought about major advances in this area in which human C-peptide and proinsulin can be separated in the plasma by the use of Sepharose particles. With this recent major advancement, it is now possible to measure human C-peptide specifically. This measurement has been shown to be a useful tool for the assessment of beta-cell function in diabetic patients treated with insulin and in insulinoma patients in whom endogenous C-peptide secretion is not suppressed with exogenous insulin-induced hypoglycemia. With the use of a specific enzyme which degrades insulin but not proinsulin, postprandial plasma proinsulin values have been measured in a large number of subjects under a variety of physiologic and pathologic conditions. These results, which are comparable to those obtained by the more laborious column chromatography, could be summarized as follows: (1) proinsulin values in lean, young normal subjects do not vary greatly in response to insulin secretagogues; (2) proinsulin secretion in response to glucose results in a greater percentage of proinsulin in the older age group than in the younger group; (3) in lean adult and juvenile diabetic patients, the percentage of proinsulin is not excessive, whereas obese diabetics and pregnant diabetics appear to secrete relatively greater proinsulin than their diabetic controls; and (4) whereas most hyperinsulinemic states (Cusing's syndrome, adult-onset diabetics, acromegaly, and glucocorticoid therapy) are not associated with an increase in percentage of proinsulin, hyperinsulinemia of insulinoma, selected cases of functional hypoglycemia, and genetic hyperproinsulinemia are associated with a greater percentage of proinsulin. Identification of a possible new proinsulin intermediate(s) in these conditions deserves further investigation...

The effect of age on plasma proinsulin-like material after oral glucose

The total plasma insulin and proinsulin-like material after oral glucose was studied in 68 lean subjects of varying ages with normal glucose tolerance tests. Although each subject had a normal test, the mean glucose levels increased with increasing age. When younger subjects (ages 15 to 44) were compared with older (45 to 74), no significant differences in total insulin responses were seen, but plasma proinsulin-like material was significantly higher in the older age subjects. All values after stimulation were significantly greater in subjects 45 to 74 years of age than in those 15 to 44 years of age (p less than 0.01). A significant correlation between the amount of proinsulin and the age of the subject was seen. These findings may reflect a decreased conversion of proinsulin to insulin in the aging pancreas or could reflect decreased clearance of proinsulin in older subjects.

Insulin and proinsulin in normal and chemical diabetic children

Plasma levels of total immunoreactive insulin and immunoreactive proinsulin were studied in 10 normal children and 15 children with chemical diabetes ranging in age from 5 to 13 years. Eleven of the children with chemical diabetes demonstrated significantly elevated TIRI during fasting and following glucose administration. There was a delay in the increment of plasma TIRI in four children with chemical diabetes, but otherwise their TIRI levels were normal. In these four children IRP was not significantly different from normal; however, in the remaining children with chemical diabetes, those with elevated TIRI, the IRP was elevated following glucose administration. Although the IRP was significantly elevated in the hyperinsulinemic group, the TIRI was also increased to such an extent that the glucose intolerance demonstrated in these patients could not be attributed to the elevated IRP.

The efficacy of low-dose versus conventional therapy of insulin for treatment of diabetic ketoacidosis

The effect of low-dose intramuscular insulin therapy was compared with that of high-dose insulin therapy by intravenous and subcutaneous routes in 48 patients with diabetic ketoacidosis. A simplified protocol was devised to compare efficacy of the two methods of therapy in a randomized manner. Plasma glucose dropped to less than 250 mg/dl in the low-dose group in 6.7 +/- 0.8 h and in the high-dose group in 4.5 +/- 0.8 h (P = not significant). The amount of insulin necessary to lower plasma glucose to 250 mg/dl was 263 +/- 45 U in the high-dose group and 46 +/- 5 U in the low-dose group. Twenty five percent in the high-dose group and none in the low-dose group developed hypoglycemia. Other biochemical and clinical variables in the two groups were comparable. No treatment complications were noted in the low-dose group. Our studies suggest that low-dose intramuscular insulin therapy is simple and as effective as high-dose therapy in the treatment of diabetic ketoacidosis without the risk of hypoglycemia and with a diminished incidence of hypokalemia. Furthermore, the favorable response of these patients to low-dose insulin therapy suggests the absence of insulin resistance in diabetic ketoacidosis.

Comparison of the effectiveness of various routes of insulin injection: insulin levels and glucose response in normal subjects

The difference in absorption of insulin and its glucose lowering-effect after the administration of crystalline insulin by the intravenous, intramuscular, and subcutaneous routes was compared in 14 lean normal subjects. Insulin in a dose of 0.1 U/kg body weight was given by the three different routes. Blood was drawn from the opposite arm at regular intervals for the determination of insulin, glucose, glucagon, cortisol, and potassium. Intravenous insulin produced the highest pharmacological level of insulin in 2 minutes (2099 +/- 414 muU/ml) with marked hypoglycemia at 30 minutes (a 68% drop). Intravenous insulin injection produced an increase in plasma glucagon and cortisol reaching a 2-fold increase above the fasting level 30 minutes after the glucose nadir. An equivalent amount of intramuscular insulin produced a maximal increase in plasma insulin at 50 minutes (45 +/- 4 muU/ml) and caused a 35% drop in plasma glucose at 60 minutes, which effects were greater than those caused by subcutaneous injection (highest IRI = 36 +/- 3.5 muU/ml and 23% glucose drop at 180 minutes). No significant increase in glucagon or cortisol was noted with equivalent amounts of subcutaneous or intramuscular insulin injection. Our studies suggest that, in normal lean subjects, insulin injection by the intramuscular route provides a faster absorption of insulin with a concomitant greater drop in plasma glucose than does injection by the subcutaneous route.

Inhibition of insulin degradation by nonsuppressible insulin-like activity

Nonsuppressible insulin-like activity, provided by three sources, was evaluated for its effect on the proteolytic degradation of insulin utilizing insulin protease obtained from rat liver homogenate as well as liver cell membranes. All three preparations of nonsuppressible insulin-like activity were found to be competitive inhibitors of insulin degradation. In addition human plasma was fractionated yielding an acetone precipitate which was found to have nonsuppressible insulin-like activity and to be a competitive inhibitor of insulin protease.

Allergic response to glucagon injection as a result of insulin contamination

A 25-year-old obese woman with adult onset diabetes, with known insulin allergy, was evaluated for her insulin response to glucagon. Intravenous injection of glucagon produced severe generlaized allergic reaction. Skin tests with various insulin and glucagon preparations showed allergic reaction to be most pronounced with beef regular single peak and single component insulin, pork regular single peak, beef lente single peak, and neutral regular (beef-pork) single peak insulin. Allergic reactions to numerous glucagon preparations were found to be directly proportional to the amount of insulin contamination in those preparations. Purification of one glucagon lot by column chromatography verified the presence of proinsulin and insulin contaminants in the preparation.

Effect of steroidogenesis on ascorbic acid content and uptake in isolated adrenal cells

Isolated adrenal cell preparation was used to investigate the relationship between ascorbic acid and steroidogenesis by two methods: (1) in vivo incorporation of exogenous [1-14C]ascorbic acid into endogenous ascorbic acid of adrenal by intraperitoneal injection of labeled ascorbic acid into rats and studying the depletion of labeled ascorbic acid under a variety of experimental conditions; and (2) study of the uptake of [14C]ascorbic acid by IAC in response to steroidogenic stimuli and various steroids. These studies demonstrate that: 1. IAC preparation by the trypsin digestion method results in almost total depletion of ascorbic acid from adrenal cells, i.e., ascorbic acid content of the cell preparation was less than 1% of the original ascorbic acid in quartered adrenal gland. 2. In spite of such a severe depletion of ascorbic acid, steroidogenesis in response to ACTH and dibutyryl cyclic AMP (dcAMP) is quite pronounced. 3. ACTH and dcAMP affect depletion of endogenously labeled ascorbic acid in IAC by a process that is both concentration- and time-dependent, but is independent of steroidogenic processes. 4. ACTH and dcAMP both inhibit the uptake of exogenous [1-14C]ascorbic acid, which is time-dependent but independent of the steroidogenic phenomenon. 5. The uptake of [14C]ascorbic acid by IAC is independent of extra-to-intracellular gradient of glucocorticoids or mineralocorticoids.

Effect of ascorbic acid on ACTH-induced cyclic AMP formation and steroidogenesis in isolated adrenal cells of vitamin E-deficient rats

Isolated adrenal cells from Vitamin E-deficient and control rats were prepared by a trypsin digestion method. Cyclic adenosine 3',5'-monophosphate (cyclic AMP) formation was studied in response to adrenocorticotropin (ACTH) in the presence and absence of ascorbate by measuring the conversion of prelabeled adenosine 5'-triphosphate [14C]ATP to cyclic [14C]AMP. Ascorbate (0.5 mM) inhibited ACTH-induced cyclic [14C]AMP formation in adrenal cells isolated from Vitamin E-deficient rats but had no effect in the control cells. The inhibitory effect of ascorbate on ACTH-induced cyclic AMP formation in Vitamin E-deficient rats decreased as the concentration of ACTH increased. In Vitamin E-deficient rats ascorbate inhibited ACTH-induced cyclic [14C]AMP formation after 30 min of incubation. There was no further significant accumulation of cyclic [14C]AMP at 60 min or 120 min although in the absence of ascorbate cyclic [14C]AMP continued to be formed. The in vitro addition of alpha-tocopherol reduced the inhibition of ACTH-induced cyclic [14C]AMP formation by ascorbate in Vitamin E-deficient rats. These studies suggest that alpha-tocopherol and ascorbate may affect ACTH-induced cyclic AMP formation through interaction with the membrane-bound enzyme adenylate cyclase.