Sulfonylurea therapy fails to diminish insulin resistance in type I-diabetic subjects

To assess whether extrapancreatic effects of sulfonylureas in vivo are detectable in the absence of endogenous insulin secretion, insulin sensitivity was determined in six insulin-deficient type 1-diabetic subjects. Peripheral uptake and hepatic production of glucose and lipolysis were measured during hyperinsulinemia using the euglycemic clamp technique and 3-3H-glucose infusions twice, once during a period with glibornuride treatment (50 mg b.i.d.), and once without. Hepatic glucose production decreased in diabetic subjects during hyperinsulinemia (insulin infusion of 20 mU/m2 X min; plasma free insulin levels of 40 +/- 4 mU/l) from 2.9 +/- 0.6 mg/kg min to 0.2 +/- 0.1 mg/kg X min after 120 min, and plasma free fatty acid (FFA) concentrations decreased from 1.33 +/- 0.29 to 0.38 +/- 0.08 mmol/l. Hepatic production, peripheral uptake of glucose and plasma FFA concentrations before and during hyperinsulinemia were not influenced by pretreatment with glibornuride. Compared to 8 non-diabetic subjects, type 1-diabetics demonstrated a diminished effect of hyperinsulinemia on peripheral glucose clearance (2.4 +/- 0.04 vs 4.2 +/- 0.5 ml/kg X min, P less than 0.01), whereas hepatic glucose production and plasma FFA levels were similarly suppressed by insulin. The data indicate that sulfonylurea treatment did not improve the diminished insulin sensitivity of peripheral glucose clearance in type 1-diabetic subjects; insulin action on hepatic glucose production and lipolysis was unimpaired in diabetics and remained uninfluenced by glibornuride. Thus, extrapancreatic effects of sulfonylureas in vivo are dependent on the presence of functioning beta-cells.     

Human insulin

The two human insulins of clinical importance are (a) semisynthetic human insulin prepared from pork pancreas by enzymatically substituting threonine for alanine-the last amino acid in the beta chain-thereby transforming pork insulin in vitro to human insulin; and (b) biosynthetic human insulin synthesized biotechnologically in Escherichia coli-K12. Using this latter technique, it is possible to produce mass quantities of highly purified insulin for the treatment of insulin-dependent diabetics, avoiding the problems inherent in supplies of insulin produced from animal pancreas. It has been suggested that to avoid confusion the two human insulins should be called semisynthetic human insulin of pork origin and biosynthetic human insulin of E. coli origin, respectively. These insulins have four advantages over highly purified animal insulins: (a) they induce lower titers of circulating insulin antibodies; (b) their subcutaneous injection is associated with fewer skin reactions; (c) they are absorbed more rapidly from the injection site; and (d) less degradation occurs at the site of injection. These data indicate that newly diagnosed insulin-dependent diabetes, particularly in children, should be treated with either of the two human insulins. The warranty against inadequate supplies of insulin offered by biosynthetic human insulin makes the use of pork insulins unnecessary and beef insulins totally useless.     

Influence of insulin antibodies on pharmacokinetics and bioavailability of recombinant human and highly purified beef insulins in insulin dependent diabetics.

Sixteen insulin dependent diabetics of long standing, with undetectable fasting plasma C peptide concentrations, and eight non-diabetic controls were each infused intravenously with biosynthetic human and highly purified beef insulin (1 mU/kg/min) while euglycaemia was maintained by a Biostator. No difference was observed between the two insulins in respect of insulin pharmacokinetics or biological action. The diabetics showed appreciable insulin resistance, manifested by a 40% reduction in the rate of insulin mediated glucose disposal, which was unrelated to the presence of insulin antibodies. Insulin binding antibodies, however, increased insulin''s clearance rate and distribution space and prolonged its pharmacological and biological half lives. The rate at which insulin action was lost, after an intravenous infusion, was more rapid in diabetics without insulin antibody binding than in controls. In respect of their influence on insulin pharmacokinetics, moderate concentrations of insulin antibodies may be of positive advantage to all diabetics without endogenous insulin secretion and are not responsible for the insulin resistance of type 1 diabetes.     

Hepatic and muscle insulin action during late pregnancy in the dog

We evaluated the effects of physiologic increases in insulin on hepatic and peripheral glucose metabolism in nonpregnant (NP) and pregnant (P; 3rd trimester) conscious dogs (n = 9 each) using tracer and arteriovenous difference techniques during a hyperinsulinemic euglycemic clamp. Insulin was initially (-150 to 0 min) infused intraportally at a basal rate. During 0-120 min (Low Insulin), the rate was increased by 0.2 mU x kg(-1) x min(-1), and from 120 to 240 min (High Insulin) insulin was infused at 1.5 mU x kg(-1) x min(-1). Insulin concentrations were significantly higher in NP than P during all periods. Matched subsets (n = 5 NP and 6 P) were identified. In the subsets, insulin was 7 +/- 1, 9 +/- 1, and 28 +/- 3 microU/ml (basal, Low Insulin, and High Insulin, respectively) in NP, and 5 +/- 1, 7 +/- 1, and 27 +/- 3 microU/ml in P. Net hepatic glucose output was suppressed similarly in both subsets (> or =50% with Low Insulin, 100% with High Insulin), as was endogenous glucose rate of appearance. During High Insulin, NP dogs required more glucose (10.8 +/- 1.5 vs. 6.2 +/- 1.0 mg x kg(-1) x min(-1), P < 0.05), and hindlimb (primarily skeletal muscle) glucose uptake tended to be greater in NP than P (18.6 +/- 2.5 mg/min vs. 13.6 +/- 2.0 mg/min, P = 0.06). The normal canine liver remains insulin sensitive during late pregnancy. Differing insulin concentrations in pregnant and nonpregnant women and excessive insulin infusion rates may explain previous findings of hepatic insulin resistance in healthy pregnant women.     

Exogenous somatostatin raises plasma insulin levels in patients with insulin-dependent diabetes mellitus

The effect of cyclic somatostatin on circulating insulin levels was studied in eight patients with insulin-dependent diabetes mellitus (IDDM). The study was performed after an overnight fast when their subcutaneous depots of insulin had been depleted during i.v. insulin substitution for 18 hours. A constant rate i.v. insulin infusion (0.4 mU/kg/min) was given for 240 min and somatostatin was co-infused between 60-120 min (100 micrograms/h) and 180-240 min (250 micrograms/h) respectively. Plasma insulin, blood glucose and hematocrit were measured at 15 min intervals. Hematocrit fell from 41.7 to 38.3% during the study period. Somatostatin increased the plasma insulin levels, corrected for the changes of hematocrit, by approximately 8% in the low dose (P less than 0.05) as well as in the high dose (P less than 0.05) period. It is concluded that somatostatin interferes with the clearance of insulin thereby increasing the circulating plasma insulin levels in IDDM patients without residual insulin secretion.     

Human insulin: study of safety and efficacy in man.

The safety and efficacy of a new highly purified neutral soluble human insulin produced by conversion of porcine insulin was compared with a highly purified neutral soluble porcine insulin in six normal men. The insulins were administered by subcutaneous injection at a dose of 0.075 U/kg body weight. Somatostatin was infused during the experiment to suppress endogenous insulin secretin. No difference was found in the plasma glucose, insulin, or metabolite responses. Thus the potency, onset, and duration of effect were identical with the two insulins. No short-term side effects to either insulin were observed. Highly purified, semi-synthetic human insulin offers a safe and effective means to explore the possible advantages of homologous human insulin in the management of diabetes mellitus.     

Free fatty acid-induced hepatic insulin resistance: a potential role for protein kinase C-delta

The mechanisms of the impairment in hepatic glucose metabolism induced by free fatty acids (FFAs) and the importance of FFA oxidation in these mechanisms remain unclear. FFA-induced peripheral insulin resistance has been linked to membrane translocation of novel protein kinase C (PKC) isoforms, but the role of PKC in hepatic insulin resistance has not been assessed. To investigate the biochemical pathways that are induced by FFA in the liver and their relation to glucose metabolism in vivo, we determined endogenous glucose production (EGP), the hepatic content of citrate (product of acetyl-CoA derived from FFA oxidation and oxaloacetate), and hepatic PKC isoform translocation after 2 and 7 h Intralipid + heparin (IH) or SAL in rats. Experiments were performed in the basal state and during hyperinsulinemic clamps (insulin infusion rate, 5 mU. kg(-1). min(-1)). IH increased EGP in the basal state (P < 0.001) and during hyperinsulinemia (P < 0.001) at 2 and 7 h. Also, 7-h infusion of IH induced resistance to the suppressive effect of insulin on EGP (P < 0.05). Glycerol infusion (resulting in plasma glycerol levels similar to IH infusion) did not have any effect on EGP. IH increased hepatic citrate content by twofold, independent of the insulin levels and the duration of IH infusion. IH induced hepatic PKC-delta translocation from the cytosolic to membrane fraction in all groups. PKC-delta translocation was greater at 7 compared with 2 h (P < 0.05). In conclusion, 1) increased FFA oxidation may contribute to the FFA-induced increase in EGP in the basal state and during hyperinsulinemia but is not associated with FFA-induced hepatic insulin resistance, and 2) the progressive insulin resistance induced by FFA in the liver is associated with a progressive increase in hepatic PKC-delta translocation.     

Alterations in insulin clearance and hepatic blood flow during the night do not contribute to the 'dawn phenomenon' in type 1 diabetes

To assess mechanisms leading to the 'dawn phenomenon' in type 1 diabetes mellitus, overnight insulin clearance, hepatic blood flow and insulin sensitivity of glucose metabolism were determined in 9 type 1 diabetic subjects treated with continuous subcutaneous insulin infusions. Glucose clamp studies were performed twice, once after midnight (from 24.00 to 02.00 h), and once in the early morning (from 06.00 to 08.00 h) during insulin infusion at 15 mU/m2/min. Insulin clearance was 482 +/- 57 ml/m2/min during the first, and 528 +/- 56 ml/m2/min during the second clamp (nonsignificant). Hepatic plasma flow assessed by measuring indocyanine green clearance was 984 +/- 115 and 1,040 +/- 163 ml/min, after the first and after the second clamp, respectively (nonsignificant). Glucose uptake during the two clamps was not significantly different. Since hepatic blood flow is known to influence insulin clearance and hepatic glucose metabolism, the data demonstrate that overnight changes in hepatic blood flow and insulin clearance do not contribute to the previously described early morning increase in insulin requirements in type 1 diabetic subjects (dawn phenomenon).     

Comparison of local and systemic effects of insulin on myocardial glucose extraction in ischemic heart disease

Physiological increases in circulating insulin level significantly increase myocardial glucose uptake in vivo. To what extent this represents a direct insulin action on the heart or results indirectly from reduction in circulating concentrations of free fatty acids (FFA) is uncertain. To examine this, we measured myocardial glucose, lactate, and FFA extraction in 10 fasting men (ages 49-76 yr) with stable coronary artery disease during sequential intracoronary (10 mU/min, coronary plasma insulin = 140 +/- 20 microU/ml) and intravenous (100 mU/min, systemic plasma insulin = 168 +/- 26 microU/ml) insulin infusion. Basally, hearts extracted 2 +/- 2% of arterial glucose and extracted 27 +/- 6% of FFA. Coronary insulin infusion increased glucose extraction to 5 +/- 3% (P < 0.01 vs. basal) without changing plasma FFA or heart FFA extraction. Conversion to intravenous infusion lowered plasma FFA by approximately 50% and heart FFA extraction by approximately 75%, increasing heart glucose extraction still further to 8 +/- 3% (P < 0. 01 vs. intracoronary). This suggests the increase in myocardial glucose extraction observed in response to an increment in systemic insulin concentration is mediated equally by a reduction in circulating FFA and by direct insulin action on the heart itself. Coronary insulin infusion increased myocardial lactate extraction as well (from 20 +/- 10% to 29 +/- 9%, P < 0.05), suggesting the local action may include stimulation of a metabolic step distal to glucose transport and glycolysis.     

Soluble, prolonged-acting insulin derivatives. I. Degree of protraction and crystallizability of insulins substituted in the termini of the B-chain

Hydrophilic insulins, more positively charged than human insulin at neutral pH, have been prepared by substitution with basic amino acids at the termini of the B-chain and by blocking the C-terminal carboxyl group of the B-chain. The isoelectric pH of the insulin is thereby moved from 5.4 towards physiological levels. Slightly acid solutions of derivatives, in which charge has been added in the C-terminus of the B-chain, have a prolonged action in vivo, in particular if the carboxyl group is blocked. It is found that the prolonged-acting hydrophilic insulins crystallize instantly when the pH is adjusted to 7. The prolonged action is ascribed to this readiness to crystallization combined with a low solubility, which may be further decreased by increased concentration of zinc ions. Hydrophobic insulins have a prolonged action independent of the site of substitution even if the derivative is soluble at physiological pH. Some derivatives were prepared from porcine insulin by tryptic transpeptidation. N-terminal B-chain substituted insulins were prepared by alkylation of a biosynthetic single-chain insulin precursor, followed by tryptic transpeptidation rendering the double chain insulin derivative. The observed blood glucose lowering in the rabbits implies that neither N- nor C-terminal B-chain substitution results in substantial deterioration of biological potency. An index for the degree of protraction based on the blood glucose data is used to compare the insulins.     

Human insulin and porcine insulin in the treatment of diabetic children: comparison of metabolic control and insulin antibody production.

Semisynthetic human insulin and highly purified porcine insulin were compared in a double blind crossover study in 21 diabetic children. Glycosylated haemoglobin values at the end of four month treatment periods were higher after treatment with human insulin than after treatment with porcine insulin (mean 15.7% (SD 2.3%) v 14.2% (2.3%); p less than 0.01). Higher fasting blood glucose concentrations occurred during treatment with human insulin than with porcine insulin (mean 12.0 (SD 2.1) v 11.0 (2.4) mmol/1; mean 216 (SD 38) v 198 (43) mg/100 ml; p less than 0.05), but there were no significant differences at other time points during the day. The incidence of hypoglycaemia was similar for both treatment groups. Concentrations of antibody reactive with porcine and human insulins were similar for the two treatment groups, although greater fluctuation was observed in the amount of antibody reactive with human insulin. Semisynthetic human insulin is safe and effective in diabetic children, although further work is needed to devise regimens which achieve optimal blood glucose control.     

Effect of exogenous insulin on plasma free carnitine levels during exercise in normal man

Preliminary data from our laboratory have shown that the decrease in plasma free carnitine levels normally found during prolonged exercise is blunted in type 1 diabetic man. This study was designed to test the hypothesis that this might be due to the sustained peripheral hyperinsulinemia seen during exercise in diabetics treated by subcutaneous insulin. Ten male subjects underwent 90 min of cycle ergometry at 60% of their maximal oxygen uptake capacity on two occasions, one with and the other without a constant 0.13 mU.kg-1.min-1 i.v. insulin infusion. Blood samples were taken at rest, during exercise, and after exercise for measurement of plasma glucose, insulin, C-peptide, free fatty acids, and carnitine. Plasma glucose dropped significantly (p less than 0.01) from basal during both infusions, but values at 30, 45, and 60 min of exercise were lower (p less than 0.05) during insulin infusion compared with the saline infusion. Exercise produced a significant (p less than 0.01) fall in plasma insulin in both infusions. However, from 30 to 90 min of exercise, the plateau insulin level was higher during the insulin infusion compared with the saline infusion (91.4 +/- 3.0 vs. 32.9 +/- 3.0 pmol/L; p less than 0.001). Plasma C-peptide decreased significantly (p less than 0.01) during exercise and recovery in both infusions, but values between infusions were not significantly different. Plasma free fatty acids increased significantly (p less than 0.01) at 90 min of exercise during the saline infusion, while during the insulin infusion this was noted during recovery only.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanism of action of insulin in diabetic patients: a dose-related effect on glucose production and utilisation

Six insulin-requiring diabetics were studied after insulin had been withheld for 24 hours. On three separate occasions each received a two-hour infusion of insulin at a low dose (2·6 U/h) and a high dose (10·6 U/h) and an infusion of saline as control. The rates of production and utilisation of glucose were measured isotopically. The rate of fall of plasma glucose concentration was faster on the high-dose infusion of insulin than on the low, whereas the fall in plasma free fatty acids, glycerol, and keton bodies was the same on both insulin infusions. The mechanism whereby the two rates of insulin administration lowered plasma glucose concentration differed: during the low-dose infusion the decrease in the glucose concentration was produced entirely by a fall of hepatic glucose output, whereas during the high-dose insulin infusion the glucose concentration fell because both the rate of glucose production fell and the rate of glucose utilisation rose. In all experiments there was a direct relation between a fall in serum potassium concentration and the fall in plasma glucose concentration irrespective of the mechanism that reduced the glucose concentration.These results indicate that in uncontrolled diabetics low-dose insulin infusions lower the blood glucose concentration entirely by reducing glucose production from the liver and that the effect of insulin on potassium transport is independent of its effect on glucose uptake.     

Insulin action during late pregnancy in the conscious dog

Our aim was to assess the magnitude of peripheral insulin resistance and whether changes in hepatic insulin action were evident in a canine model of late (3rd trimester) pregnancy. A 3-h hyperinsulinemic (5 mU.kg(-1).min(-1)) euglycemic clamp was conducted using conscious, 18-h-fasted pregnant (P; n = 6) and nonpregnant (NP; n = 6) female dogs in which catheters for intraportal insulin infusion and assessment of hepatic substrate balances were implanted approximately 17 days before experimentation. Arterial plasma insulin rose from 11 +/- 2 to 192 +/- 24 and 4 +/- 2 to 178 +/- 5 microU/ml in the 3rd h in NP and P, respectively. Glucagon fell equivalently in both groups. Basal net hepatic glucose output was lower in NP (1.9 +/- 0.1 vs. 2.4 +/- 0.2 mg.kg(-1).min(-1), P < 0.05). Hyperinsulinemia completely suppressed hepatic glucose release in both groups (-0.4 +/- 0.2 and -0.1 +/- 0.2 mg.kg(-1).min(-1) in NP and P, respectively). More exogenous glucose was required to maintain euglycemia in NP (15.2 +/- 1.3 vs. 11.5 +/- 1.1 mg.kg(-1).min(-1), P < 0.05). Nonesterified fatty acids fell similarly in both groups. Net hepatic gluconeogenic amino acid uptake with high insulin did not differ in NP and P. Peripheral insulin action is markedly impaired in this canine model of pregnancy, whereas hepatic glucose production is completely suppressed by high circulating insulin levels.     

Metabolic effects of low-dose incremental insulin infusion in diabetic man

An incremental insulin infusion technique to assess insulin action at physiological circulating levels in diabetic man is described. Insulin was infused during sequential one hour periods at rates of 0.01, 0.05 and 0.10 u/kg/h. Serum free insulin concentrations had reached a plateau by the second 30 minutes of each infusion period. Blood glucose concentrations fell at a similar rate during the two lower rates of insulin infusion, but the fall was significantly greater with the highest insulin infusion. Glucose production and utilisation were measured isotopically using a 3-3H glucose infusion technique. Glucose production was inhibited with the lowest insulin infusion rate and a marked increase in glucose metabolic clearance rate occurred with the highest insulin infusion. Key intermediary metabolites were measured and blood glycerol, total ketone bodies, and plasma non-esterified fatty acids fell with the lowest insulin infusion rate. It is concluded that this technique allows identification of the effect of insulin upon different metabolic processes.     

Long-term mild jogging increases insulin action despite no influence on body mass index or VO2 max

Physical training has been shown to improve glucose tolerance and insulin sensitivity. In the present study, insulin action was determined using the euglycemic clamp technique in six untrained nonobese subjects before, during, and after long-term mild regular jogging. After 1 yr of jogging, steady-state plasma insulin levels (I) decreased significantly, and the metabolic clearance rate of insulin was increased by 87%, although insulin infusion rate during the clamp was constant for each individual. The amount of glucose infused (glucose metabolism, M) tended to increase from 6.16 +/- 0.94 to 8.15 +/- 1.94 mg.kg-1.min-1 after regular jogging for 1 yr, although that was not statistically significant. However, M/I increases significantly from 0.060 +/- 0.012 to 0.184 +/- 0.056 (P less than 0.05) after 1 yr. The concentrations of plasma free fatty acids during the hyperinsulinemic clamp decreased more significantly after 1 yr of jogging (P less than 0.05). The concentrations of plasma glycerol decreased gradually before and after long-term regular jogging, showing only a 50-60% reduction in 120 min. Therefore, long-term mild regular jogging, which did not influence either body mass index or maximal O2 uptake, appears to improve insulin action in both carbohydrate and lipid metabolism and to increase the metabolic clearance rate of insulin.     

Vasodilator effects of L-arginine are stereospecific and augmented by insulin in humans

The amino acid l-arginine, the precursor of nitric oxide (NO) synthesis, induces vasodilation in vivo, but the mechanism behind this effect is unclear. There is, however, some evidence to assume that the l-arginine membrane transport capacity is dependent on insulin plasma levels. We hypothesized that vasodilator effects of l-arginine may be dependent on insulin plasma levels. Accordingly, we performed two randomized, double-blind crossover studies in healthy male subjects. In protocol 1 (n = 15), subjects received an infusion of insulin (6 mU x kg(-1) x min(-1) for 120 min) or placebo and, during the last 30 min, l-arginine or d-arginine (1 g/min for 30 min) x In protocol 2 (n = 8), subjects received l-arginine in stepwise increasing doses in the presence (1.5 mU x kg(-1) x min(-1)) or absence of insulin. Renal plasma flow and glomerular filtration rate were assessed by the para-aminohippurate and inulin plasma clearance methods, respectively. Pulsatile choroidal blood flow was assessed with laser interferometric measurement of fundus pulsation, and mean flow velocity in the ophthalmic artery was measured with Doppler sonography. l-arginine, but not d-arginine, significantly increased renal and ocular hemodynamic parameters. Coinfusion of l-arginine with insulin caused a dose-dependent leftward shift of the vasodilator effect of l-arginine. This stereospecific renal and ocular vasodilator potency of l-arginine is enhanced by insulin, which may result from facilitated l-arginine membrane transport, enhanced intracellular NO formation, or increased NO bioavailability.     

Transfer from porcine insulin to human insulin in insulin-dependent diabetes mellitus: effects on insulin binding to IgG and glycemic control

Thirty type I diabetic patients who were treated for at least 2 years with a combination of regular and lente monocomponent porcine insulins were allocated in a double-blind study to either continued porcine insulin treatment or a transfer to the corresponding semi-synthetic human insulins. Insulin binding to IgG measured by an immunoelectrophoretic method, was followed at 3-month intervals for 1 year, and did not change after the transfer. The glycemic control, as assessed by hemoglobin A1 levels, tended to deteriorate in the human insulin group during the first 3 months of the trial and then return to the baseline level. It is concluded that a transfer from highly purified porcine insulin to human insulin apparently does not change the insulin binding to IgG in already sensitized patients.     

Effects of portal free fatty acid elevation on insulin clearance and hepatic glucose flux

We tested the hypothesis that, due to greater hepatic free fatty acid (FFA) load, portal delivery of FFAs, as in visceral obesity, induces hyperinsulinemia and increases endogenous glucose production to a greater extent than peripheral FFA delivery. For 5 h, 10 microeq.kg(-1).min(-1) portal oleate (n = 6), equidose peripheral oleate (n = 5), or saline (n = 6) were given intravenously to conscious dogs infused with a combination of portal and peripheral insulin to enable calculation of hepatic insulin clearance during a pancreatic euglycemic clamp. Peripheral FFAs were similar with both oleate treatments and were threefold greater than in controls. Portal FFAs were 1.5- to 2-fold greater with portal than with peripheral oleate. Peripheral insulin concentrations were greatest with portal oleate, intermediate with peripheral oleate (P < 0.001 vs. portal oleate or controls), and lowest in controls, consistent with corresponding reductions in plasma insulin clearance and hepatic insulin clearance. Although endogenous glucose production did not differ between the two routes of oleate delivery, total glucose output (endogenous glucose production plus glucose cycling) was greater with portal than with peripheral oleate (P < 0.001) despite the higher insulin levels. In conclusion, during euglycemic clamps in dogs, the main effect of short-term elevation in portal FFA is to generate peripheral hyperinsulinemia. This may, in the long term, contribute to the metabolic and cardiovascular risk of visceral obesity.     

Metabolic and hormonal parameters after insulin-induced hypoglycemia in man, comparison between biosynthetic human insulin and purified pork insulin

Although clinically undistinguishable, some authors have found important differences in the counterregulatory response between Biosynthetic Human Insulin (BHI) and Purified Pork Insulin (PPI). To reassess the problem 10 healthy volunteers of both sexes underwent paired iv insulin tolerance test with both BHI and PPI (0.10 U/kg b.w.). To check the humoral response the variations of glucose, free fatty acids (FFA), prolactin, growth hormone, ACTH and plasma renin activity were evaluated. Blood glucose depression and further recovery by BHI and PPI administration paralleled each other, so were, prolactin, FFA, and plasma renin activity. A slight section of ACTH, and GH was observed under BHI challenge. There were not statistically significant differences between both insulins on any of the six parameters studied. The data do not confirm earlier published reports indicating hormonal and metabolic differences between human and porcine insulin.