Effect of near physiologic insulin therapy on hypoglycemia counterregulation in type-1 diabetes

OBJECTIVES: The aim of this study was to examine hormonal counterregulation during insulin-induced hypoglycemia in type-1 diabetic patients during long-term near normoglycemic insulin therapy and intensive clinical care. METHODS: Type-1 diabetic patients (age 35.3 +/- 2 years, body mass index 22.8 +/- 1 kg x m(-2), mean diabetes duration 13.6 (11-17 years), mean HbA1c during the last year 6.6 +/- 0.1%) and nondiabetic subjects were studied during (0-120 min) and after (120-240 min) hypoglycemic (3.05 mmol/l) hyperinsulinemic (approximately 330 pmol/l) clamp tests. RESULTS: During hypoglycemia peak plasma concentrations of glucagon (199 +/- 16 vs. 155 +/- 11 ng/l, p < 0.05), epinephrine (4,514 +/- 644 vs. 1,676 +/- 513 pmol/l, p < 0.001), norepinephrine (2.21 +/- 0.14 vs. 1.35 +/- 0.19 nmol/l, p < 0.01) and cortisol (532 +/- 44 vs. 334 +/- 61 nmol/l) were reduced in the diabetic patients. Plasma lactate did not change from baseline values (0.51 +/- 0.06 mmol/l) in diabetic but doubled in healthy subjects (1.13 +/- 0.111 mmol/l, p < 0.001 vs. control). During the posthypoglycemic recovery period plasma concentrations of free fatty acids were higher in diabetic patients at 240 min (1.34 +/- 0.12 vs. 2.01 +/- 0.23 mmol/l, p < 0.05). CONCLUSION: Despite long-term near physiologic insulin substitution and the low incidence of hypoglycemia, hormonal hypoglycemia counterregulation was impaired in type-1 diabetic patients after a diabetes duration of more than 10 years.     

Both fasting glucose production and disappearance are abnormal in people with "mild" and "severe" type 2 diabetes

To determine whether regulation of fasting endogenous glucose production (EGP) and glucose disappearance (R(d)) are both abnormal in people with type 2 diabetes, EGP and R(d) were measured in 7 "severe" (SD), 9 "mild" (MD), and 12 nondiabetic (ND) subjects (12.7 +/- 0.6 vs. 8.1 +/- 0.4 vs. 5.1 +/- 0.4 mmol/l) after an overnight fast and during a hyperglycemic pancreatic clamp. Fasting insulin was higher in both the SD and MD than ND subjects, whereas fasting glucagon only was increased (P < 0.05) in SD. Fasting EGP, glycogenolysis, gluconeogenesis, and R(d) all were increased (P < 0.05) in SD but did not differ in MD or ND. On the other hand, when glucose ( approximately 11 mmol/l), insulin ( approximately 72 pmol/l), and glucagon ( approximately 140 pg/ml) concentrations were raised to values similar to those observed in the severe diabetic subjects, EGP was higher (P < 0.001) and R(d) lower (P < 0.01) in both SD and MD than in ND. The higher EGP in the SD and MD than ND during the clamp was the result of increased (P < 0.05) rates of glycogenolysis (4.2 +/- 1.7 vs. 3.5 +/- 1.0 vs. 0.0 +/- 0.8 micromol.kg(-1).min(-1)), since gluconeogenesis did not differ among groups. We conclude that neither glucose production nor disappearance is appropriate for the prevailing glucose and insulin concentrations in people with mild or severe diabetes. Both increased rates of gluconeogenesis (likely because of higher glucagon concentrations) and lack of suppression of glycogenolysis contribute to excessive glucose production in type 2 diabetics.     

Indomethacin does not affect endogenous glucose production in type 2 diabetes mellitus.

In healthy subjects, basal endogenous glucose production is partly regulated by paracrine intrahepatic factors. It is currently unknown whether paracrine intrahepatic factors also influence the increased basal endogenous glucose production in patients with type 2 diabetes mellitus. Administration of indomethacin to patients with type 2 diabetes mellitus stimulates endogenous glucose production and inhibits insulin secretion. Our aim was to evaluate whether this stimulatory effect on glucose production is solely attributable to inhibition of insulin secretion. In order to do this, we administered indomethacin to 5 patients with type 2 diabetes during continuous infusion of somatostatin to block endogenous insulin and glucagon secretion and infusion of basal concentrations of insulin and glucagon in a placebo-controlled study. Endogenous glucose production was measured 3 hours after the start of the somatostatin, insulin and glucagon infusion, for 4 hours after administration of placebo/indomethacin, by primed, continuous infusion of [6,6-(2)H(2)] glucose. At the time of administration of placebo or indomethacin, there were no significant differences in plasma glucose concentrations and endogenous glucose production rates between the two experiments (16.4 +/- 2.09 mmol/l vs. 16.6 +/- 1.34 mmol/l and 17.7 +/- 1.05 micromol/kg/min and 17.0 +/- 1.06 micromol/kg/min), control vs. indomethacin). Plasma glucose concentration did not change significantly in the four hours after indomethacin or placebo administration. Endogenous glucose production in both experiments was similar after both placebo and indomethacin. Mean plasma C-peptide concentrations were all below the detection limit of the assay, reflecting adequate suppression of endogenous insulin secretion by somatostatin. There were no differences in plasma concentrations of insulin (76 +/- 5 vs. 74 +/- 4 pmol/l) and glucagon (69 +/- 8 vs. 71 +/- 6 ng/l) between the studies with levels remaining unchanged in both experiments. Plasma concentrations of cortisol, epinephrine, and norepinephrine were similar in the two studies and did not change significantly. We conclude that indomethacin stimulates endogenous glucose production in patients with type 2 diabetes mellitus by inhibition of insulin secretion.     

A case of diabetic non-ketotic hyperosmolar coma with an increase with plasma 3-hydroxybutyrate.

We have seen a case of "diabetic non-ketotic hyperosmolar coma" with ketosis. An 84-year-old man was brought into the hospital in a deeply comatous and dehydrated state. The initial blood glucose level was 1252 mg/dl with plasma osmolarity of 435 mOsm/l, but no ketonuria was detected by the nitroprusside method (Ketostix). However, the plasma 3-hydroxybutyrate (3-OHBA) level was 5 mM in a newly developed bedside film test. The serum ketone bodies were later found to be 5.56 and 0.82 mmol/l for 3-OHBA and acetoacetate (AcAc), respectively. A marked increase in glucagon, cortisol and ADH with renal dysfunction (creatinine 5.0 mg/dl) were noted. An abnormal electrocardiogram, occular convergence and chorea like movement disappeared after correction of metabolic disturbances. The moderate level of IRI (14 microU/ml) on admission and a good response to glucagon 2 months after admission also indicate that the present case is a typical hyperosmolar non-ketotic coma. Because of a preferential increase in 3-OHBA, ketonuria seemed to be absent in the regular nitroprusside test. Marked dehydration is thought to cause renal dysfunction, and the increase in ADH may have helped to prevent further aggravation of ketoacidosis. We propose to change the term hyperosmolar non-ketotic coma (HNC) to diabetic hyperosmolar coma (DHC), because sometimes patients with hyperosmolar non-ketotic diabetic coma are ketotic, as seen in the present case. Determination of 3-OHBA or individual ketone bodies in blood is important and essential for the differential diagnosis of diabetic coma. The diagnosis of either ketoacidotic or hyperosmolar coma should be made depending on the major expression of ketoacidosis or hyperglycemic hyperosmolarity.     

Demonstration of a dawn phenomenon in normal adolescents

To ascertain whether the dawn phenomenon occurs in normal adolescents and, if so, to determine its mechanism, we measured nocturnal plasma glucose, insulin, glucagon, growth hormone, cortisol, and adrenocorticotropic hormone (ACTH) levels between 01.00 and 08.00 h in 10 healthy adolescents. The prehepatic insulin secretion rate was calculated based on C peptide levels. The metabolic clearance rate of insulin (MCRI) was calculated as the ratio of mean insulin secretion rate to mean insulin concentration. There was no change in plasma glucose, insulin, and glucagon between 01.00-04.00 and 05.00-08.00 h (paired t test). The MCRI was higher at 05.00-08.00 h compared to 01.00-04.00 h (9.30 +/- 1.50 vs. 4.87 +/- 1.11 ml.kg-1.min-1; p = 0.008). The prehepatic insulin secretion increased at 05.00-08.00 h relative to 01.00-04.00 h (1.1 +/- 0.2 vs. 0.6 +/- 0.1 pmol.kg-1.min-1; p = 0.013). Similarly, cortisol and ACTH levels were higher at 05.00-08.00 versus 01.00-04.00 h (323 +/- 33 vs. 102 +/- 22 nmol/l, p less than 0.001; 3.6 +/- 0.5 vs. 1.8 +/- 0.4 pmol/l, p = 0.006, respectively). Growth hormone was higher at 01.00-04.00 versus 05.00-08.00 h (7.6 +/- 1.2 and 3.0 +/- 0.9 microgram/l; p = 0.019). ACTH correlated with MCRI (r = 0.66; p = 0.002) and prehepatic insulin secretion (r = 0.75; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Interactions between oxytocin, glucagon and glucose in normal and streptozotocin-induced diabetic rats

Oxytocin has been suggested to have glucoregulatory functions in rats, man and other mammals. The hyperglycemic actions of oxytocin are believed to be mediated indirectly through changes in pancreatic function. The present study examined the interaction between glucose and oxytocin in normal and streptozotocin (STZ)-induced diabetic rats, under basal conditions and after injections of oxytocin. Plasma glucose and endogenous oxytocin levels were significantly correlated in cannulated lactating rats (r = 0.44, P less than 0.01). To test the hypothesis that oxytocin was acting to elevate plasma glucose, adult male rats were injected with 10 micrograms/kg oxytocin and killed 60 min later. Oxytocin increased plasma glucose from 6.1 +/- 0.1 to 6.8 +/- 0.2 mM (P less than 0.05), and glucagon from 179 +/- 12 to 259 +/- 32 pg/ml (P less than 0.01, n = 18). There was no significant effect of oxytocin on plasma insulin, although the levels were increased by 30%. A lower dose (1 microgram/kg) of oxytocin had no significant effect on plasma glucose or glucagon. To eliminate putative local inhibitory effects of insulin on glucagon secretion, male rats were made diabetic by i.p. injection of 100 mg/kg STZ, which increased glucose to greater than 18 mM and glucagon to 249 +/- 25 pg/ml (P less than 0.05). In these rats, 10 micrograms/kg oxytocin failed to further increase plasma glucose, but caused a much greater increase in glucagon (to 828 +/- 248 pg/ml) and also increased plasma ACTH. A specific oxytocin analog, Thr4,Gly7-oxytocin, mimicked the effect of oxytocin on glucagon secretion in diabetic rats. The lower dose of oxytocin also increased glucagon levels (to 1300 +/- 250 pg/ml), but the effect was not significant. A 3 h i.v. infusion of 1 nmol/kg per h oxytocin in conscious male rats significantly increased glucagon levels by 30 min in normal and STZ-rats; levels returned to baseline by 30 min after stopping the infusion. Plasma glucose increased in the normal, but not STZ-rats. The relative magnitude of the increase in glucagon was identical for normal and diabetic rats, but the absolute levels of glucagon during the infusion were twice as high in the diabetics. To test whether hypoglycemia could elevate plasma levels of oxytocin, male rats were injected i.p. with insulin and killed from 15-180 min later. Plasma glucose levels dropped to less than 2.5 mM by 15 min. Oxytocin levels increased by 150-200% at 30 min; however, the effect was not statistically significant.(ABSTRACT TRUNCATED AT 400 WORDS)     

Hormonal profile and glucose tolerance in late pregnancy and postpartum

Oral glucose tolerance, plasma insulin and basal levels of glucagon, hGH, hPRL, hPL, TSH, T4, T3, thyroxine-binding globulin (TBG), cortisol, corticosteroid-binding globulin (CBG) and estriol were measured in 23 normal pregnant women in late gestation (31 +/- 0.4 weeks of pregnancy). Twelve of these subjects could be re-examined 14 +/- 2 weeks postpartum. Blood glucose was lower basal and after glucose load (100 g) in the pregnant group. Fasting plasma insulin and glucose-induced insulin release were higher in pregnancy. The insulinogenic index and the beta cell response were significantly greater antepartum, while peripheral insulin activity was unchanged. The insulin:glucagon ratio as well as TSH and hGH showed no significant differences between ante- and postpartum values. However, T4, T3, TBG, cortisol, CBG, estriol, hPRL and hPL were significantly higher during gestation than after delivery. T4:TBG and T3:TBG ratios were much lower antepartum, while the cortisol:CBG ratio was comparable ante- and postpartum. To our knowledge this is the first report in which such an extensive hormonal and metabolic analysis was performed in the same women ante- and postpartum. It could be shown that glucose tolerance is not worsened during pregnancy in healthy subjects. The higher gestational insulin values are discussed with respect to the various significant hormonal changes.     

Pancreatic B-cell function in non-insulin-dependent diabetes mellitus during successive periods of sulfonylurea and insulin treatment: serum C-peptide response to glucagon and urine C-peptide excretion

Serum C-peptide responses to glucagon and daily urine C-peptide excretion in successive periods of different treatment in two groups of patients with non-insulin-dependent diabetes mellitus (NIDDM) (mean interval between two tests less than 1 month) were compared. In group A patients (n = 8), the glycemic control was improved after transferring the treatment from sulfonylurea (SU) to insulin (fasting plasma glucose: SU: 192 +/- 47, insulin: 127 +/- 21 mg/dl, mean +/- S.D., p less than 0.01). Fasting serum C-peptide immunoreactivity (CPR) was significantly lower at the period of insulin treatment (SU: 1.93 +/- 1.01, insulin: 1.47 +/- 0.79 ng/ml, p less than 0.05), but there was no difference in the increase in serum CPR (maximal--fasting) (delta serum CPR) during glucagon stimulation in the two periods of treatment (SU: 1.70 +/- 0.72, insulin: 1.47 +/- 0.98 ng/ml). In group B patients (n = 7), there was no significant difference in glycemic control after transferring the treatment from insulin to SU (fasting plasma glucose: insulin: 127 +/- 24, SU: 103 +/- 13 mg/dl). Fasting serum CPR was significantly lower during the period of insulin treatment (insulin: 1.39 +/- 0.64, SU: 2.21 +/- 0.86 ng/ml, p less than 0.025), but delta serum CPR during glucagon stimulation still showed no significant difference between the two periods (insulin: 1.97 +/- 1.16, SU: 2.33 +/- 1.57 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Hormonal and metabolic counterregulation during and after high-dose insulin-induced hypoglycemia in diabetes mellitus type 2.

Non-obese type 2 diabetic subjects in good metabolic control (n=6, HbA1c 7.0 +/- 0.3%, mean diabetes duration: 5.7 +/- 1 years) and matched non-diabetic subjects (control; n = 6) were studied during hyperinsulinemic (approximately 3 nmol/l)-hypoglycemic (approximately 3.1 mmol/l) clamp tests (0-120 min) and the subsequent recovery period (120-240 min). Plasma glucagon rose gradually but not significantly, whereas norepinephrine and epinephrine similarly increased approximately 2 and approximately 25-fold in both groups. Islet amyloid polypeptide (IAPP) decreased to approximately 41% and approximately 24% of basal values during hypoglycemia and rapidly rose approximately 4.7-fold during the recovery period, while plasma C-peptide remained suppressed in both groups. Within 140 min, plasma free fatty acids similarly decreased to approximately 70 micromol/l (p < 0.05), but then rose to values being approximately 50% higher in diabetic than in control subjects (240 min: 907 +/- 93 vs. 602 +/- 90 micromol/l; p < 0.05). Glucose infusion rates were comparable during hypoglycemia, but approximately 40% lower during recovery in diabetic patients (1.88 +/- 0.27 vs. 3.44 +/- 0.27 mg x kg(-1) x min(-1), p < 0.001). These results demonstrate that (i) hypoglycemia induced by high-dose insulin largely abolishes the counterregulatory response of glucagon, but not of catecholamines in nondiabetic and well-controlled type 2 diabetic subjects, (ii) the rapid posthypoglycemic increase of plasma IAPP occurs independently of plasma insulin, and (iii) the superior rise in plasma free fatty acids may account at least in part for the posthypoglycemic insulin resistance of type 2 diabetic patients.     

Glucose, insulin and glucagon in the diabetic goose.

The relationships between plasma glucose, insulin and glucagon were studied in geese made diabetic by subtotal pancreatectomy. As early as the first hours after the operation, the plasma glucose increases and a permanent diabetes develops. This diabetic state is characterized by two features: a very low plasma insulin level, which does not vary during the survival of the diabetic animals and a concentration of plasma glucagon (of pancreatic origin) which transiently diminishes then rises far above the normal level, and is correlated with the basal concentration of plasma glucose. The impaired glucose tolerance observed in diabetic animals is related to the suppression of the glucose-insulin and glucose-glucagon feedback mechanisms.     

Effects of ghrelin on insulin and glucagon secretion: a study of isolated pancreatic islets and intact mice

We combined in vitro and in vivo methods to investigate the effects of ghrelin, a novel gastric hormone, on insulin and glucagon release. Studies of isolated mouse islets showed that ghrelin concentrations in the physiological range (0.5-3 nmol l(-1)) had no effect on glucose-stimulated insulin release, while low ghrelin concentrations (1-100 pmol l(-1)) inhibited and high (0.1 and 1 micromol l(-1)) stimulated. The insulin response to glucose was enhanced in the presence of a high ghrelin concentration (100 nmol l(-1)). Glucagon release was stimulated by ghrelin (0.1 pmol l(-1) to 1 micromol l(-1)); this effect was maintained in the presence of glucose (0-20 mmol l(-1)). In intact mice, basal plasma insulin was suppressed by 1 and 10 nmol kg(-1) of ghrelin, 2 and 6 min after i.v. injection. Ghrelin (0.2-10 nmol kg(-1) i.v.) suppressed also the glucose-stimulated insulin response and impaired the glucose tolerance (at a ghrelin dose of 3.3 nmol kg(-1)). Ghrelin (1 or 10 nmol kg(-1) i.v.) inhibited the insulin response to the phospholipase C stimulating agent carbachol and enhanced the insulin response to the phosphodiesterase inhibitor isobutyl-methylxanthine (IBMX) but did not affect the response to the membrane-depolarizing amino acid l-arginine. These observations suggest that the inhibitory effect of ghrelin on glucose-induced insulin release is in part exerted on phospholipase C pathways (and not on Ca(2+)entry), while the stimulatory effect of high doses of ghrelin depends on cyclic AMP. In contrast to the spectacular glucagon-releasing effect of ghrelin in vitro, ghrelin did not raise plasma glucagon. Carbachol, IBMX and l-arginine stimulated glucagon release. These responses were impaired by ghrelin, suggesting that it suppresses the various intracellular pathways (phospholipase C, cyclic AMP and Ca(2+)), that are activated by the glucagon secretagogues. Together these observations highlight (but do not explain) the different effects of ghrelin on glucagon release in vitro and in vivo. The results show that ghrelin has powerful effects on islet cells, suggesting that endogenous ghrelin may contribute to the physiological control of insulin and glucagon release. However, the narrow "window" of circulating ghrelin concentrations makes this doubtful.     

Helodermin stimulates glucagon secretion in the mouse

Helodermin is structurally similar to VIP (vasoactive intestinal peptide) and PHI (peptide histidine isoleucine). Since VIP and PHI both stimulate insulin and glucagon secretion, we investigated the effects of helodermin on insulin and glucagon secretion in the mouse, both in the basal state and during administration of glucose and the cholinergic agonist carbachol. After intravenous injection at dose levels between 0.5 and 8.0 nmol/kg, helodermin markedly enhanced basal plasma glucagon levels, for example at 8 nmol/kg from 139 +/- 14 to 421 +/- 86 pg/ml (p less than 0.001) after 6 minutes, without affecting basal plasma insulin levels. Together with glucose (2.8 mmol/kg), helodermin (2 and 8 nmol/kg) augmented plasma glucagon levels but had no effect on plasma insulin levels. When injected together with the cholinergic agonist carbachol (0.16 mumol/kg), helodermin markedly potentiated the increase in plasma glucagon levels (more than three-fold; p less than 0.001), again without affecting the plasma insulin levels. Combined alpha- and beta-adrenoceptor blockade (yohimbine + L-propranolol) reduced the augmenting effect of helodermin on glucagon secretion by approximately 60%. It is concluded helodermin stimulates glucagon secretion in the mouse by an effect that is partially antagonized by combined alpha- and beta-adrenoceptor antagonism.     

Effect of a two-month detraining on glucose tolerance and insulin sensitivity in athletes--link to adrenal steroid hormones

Reduction in physical activity has been demonstrated to associate with the increased risk in insulin resistance and type 2 diabetes. To determine whether alteration in insulinemia, due to abstention from regular exercise training, is associated with changes in serum dehydroepiandrosterone sulfate (DHEA-S) and cortisol, 18 highly trained badminton players (21.2 +/- 0.3 years) were enrolled into a 2-month detraining study. Fasting serum insulin, glucose, DHEA-S, and cortisol were determined at trained state and at day 60 of detraining. Glucose tolerance and insulin sensitivity were assessed by an oral glucose tolerance test (OGTT). The 2-month detraining increased fasting glucose and insulin concentrations and body weight slightly, but did not significantly affect glucose tolerance and insulin response curve, in which 10 subjects had increased and 8 subjects had slightly decreased in the area under curve for insulin (IAUC). In the subjects with increased IAUC, serum cortisol was also elevated (from 0.44 +/- 0.07 to 0.83 +/- 0.26 U/l, P < 0.05) in parallel, and serum creatine kinase (CK) was unaltered during detraining. Whereas in the subjects with decreased IAUC, serum cortisol (from 0.51 +/- 0.19 to 0.54 +/- 0.14 U/l, no significance) was not changed and serum creatine kinase (from 461 +/- 179 to 151 +/- 21 U/l) was decreased during detraining. Two groups of detrained subjects exhibited a similar reduction in serum DHEA-S levels and slight elevation in body weight. The novel finding of the study is that the changes in serum cortisol, but not DHEA-S, were associated with the change in insulin sensitivity during early phase of lifestyle change from physically active to sedentary, and this response appears to be varied individually among athletes.     

Glucose turnover and hormonal changes during insulin-induced hypoglycemia in trained humans

Eight athletes (T), studied the third morning after the last exercise session, and seven sedentary males (C) (maximal O2 consumption 65 +/- 4 vs. 49 +/- 4 (SE) ml X kg-1 X min-1, for T and C men, respectively) had insulin infused until plasma glucose, at an insulin level of 1,600 pmol X l-1, was 1.9 mmol X l-1. Glucose turnover was determined by primed constant rate infusion of 3-[3H]glucose. Basal C-peptide (0.46 +/- 0.04 vs. 0.73 +/- 0.06 pmol X ml-1) and glucagon (4 +/- 0.4 vs. 10 +/- 2 pmol X l-1) were lower (P less than 0.05) and epinephrine higher (0.30 +/- 0.06 vs. 0.09 +/- 0.03 nmol X l-1) in T than in C subjects. During and after insulin infusion production, disappearance and clearance of glucose changed identically in T and C subjects. However, in spite of identical plasma glucose concentrations, epinephrine (7.88 +/- 0.99 vs. 3.97 +/- 0.40 nmol X l-1), growth hormone (97 +/- 17 vs. 64 +/- 6 mU X l-1), and pancreatic polypeptide (361 +/- 84 vs. 180 +/- 29 pmol X l-1) reached higher levels (P less than 0.05) and glucagon (28 +/- 3 vs. 47 +/- 10 pmol X l-1) lower levels in T than in C subjects. Blood pressures changed earlier in athletes during insulin infusion, and early recovery of heart rate, free fatty acid, and glycerol was faster. Responses of norepinephrine, cortisol, C-peptide, and lactate were similar in the two groups. Training radically changes hormonal responses but not glucose kinetics in insulin hypoglycemia.     

Receptor binding and biological potency of despentapeptide insulin

The receptor binding and biological potency of despentapeptide insulin (DPI) was assessed in human adipocytes, rat adipocytes and rat hepatocytes. DPI displayed a lower affinity for binding to both human adipocytes (half-maximum displacement at 0.89 +/- 0.04 and 0.20 +/- 0.02 nmol/l for DPI and insulin respectively; P less than 0.001) and rat adipocytes (half-maximum displacement at 7.12 +/- 1.06 and 1.14 +/- 0.18 nmol/l respectively, P less than 0.05). However, although DPI was less potent than unmodified insulin in stimulating glucose uptake in rat adipocytes (half-maximal stimulation at 2.0 +/- 0.67 and 0.47 +/- 0.18 nmol/l respectively; P less than 0.05), DPI was equipotent with insulin in human adipocytes (half-maximal stimulation at 0.034 +/- 0.001 and 0.027 +/- 0.001 nmol/l respectively; P greater than 0.2). In rat hepatocytes, DPI was twofold less potent in binding displacement activity (half-maximum displacement at 3.8 +/- 0.9 and 1.7 +/- 0.3 nmol/l respectively; P less than 0.01) but appeared to be equivalent in stimulating amino butyric acid uptake (half-maximum stimulation at 0.98 +/- 0.12 and 0.95 +/- 0.26 nmol/l respectively). The difference in affinity of DPI binding to rat liver membranes was less marked (1.3 fold decreased compared with insulin: 5.3 +/- 0.7 and 4.2 +/- 0.6 nmol/l respectively; P less than 0.001). Thus, the decreased receptor affinity of DPI was reflected in decreased biological potency in rat adipocytes, but not in human adipocytes nor rat hepatocytes. These data suggest differences in the binding-action linking in the cells of different tissues and different species.     

Intraoperative protein sparing with glucose.

We examined the hypothesis that glucose infusion inhibits amino acid oxidation during colorectal surgery. We randomly allocated 14 patients to receive intravenous glucose at 2 mg x kg(-1) x min(-1) (glucose group) starting with the surgical incision or an equivalent amount of normal saline 0.9% (control group). The primary endpoint was whole body leucine oxidation; secondary endpoints were leucine rate of appearance and nonoxidative leucine disposal as determined by a stable isotope tracer technique (L-[1-(13)C]leucine). Circulating concentrations of glucose, lactate, insulin, glucagon, and cortisol were measured before and after 2 h of surgery. Leucine rate of appearance, an estimate of protein breakdown, and nonoxidative leucine disposal, an estimate of protein synthesis, decreased in both groups during surgery (P < 0.05). Leucine oxidation intraoperatively decreased from 13 +/- 3 to 4 +/- 3 micromol x kg(-1) x h(-1) in the glucose group (P < 0.05 vs. control group) whereas it remained unchanged in the control group. Hyperglycemia during surgery was more pronounced in patients receiving glucose (9.7 +/- 0.5 mmol/l, P < 0.05 vs. control group) than in patients receiving normal saline (7.1 +/- 1.0 mmol/l). The administration of glucose caused an increase in the circulating concentration of insulin (P < 0.05) resulting in a lower glucagon/insulin quotient than in the control group (P < 0.05). Intraoperative plasma cortisol concentrations increased in both groups (P < 0.05), whereas plasma concentrations of lactate and glucagon did not change. The provision of small amounts of glucose was associated with a decrease in amino acid oxidation during colorectal surgery.     

铃蟾肽对四氧嘧啶引起的大鼠糖尿病的预防作用

本工作从三个不同的层次对铃蟾肽防止胰岛 B 细胞损伤的作用进行了研究:(1)在整体水平,预先注射铃蟾肽(50μg/kg,iv)可明显抑制单独给予四氧嘧啶(200mg/kg,s.c.)引起的大鼠血糖升高和血浆胰岛素水平下降的趋势。(2)在离体胰腺灌流实验发现,在四氧嘧啶之前预灌流铃蟾肽(10~(-2)mmol/L)可使胰腺对高糖刺激产生反应性分泌;而仅以四氧嘧啶灌流时,胰腺对高糖刺激无反应。(3)在离体胰岛水平,初步研究了在四氧嘧啶引起胰岛 B 细胞功能改变时,铃蟾肽对胰岛内胰岛素、胰高血糖素和生长抑素分泌的影响。结果表明,铃蟾肽可防止四氧嘧啶引起的胰岛素和生长抑素分泌的抑制及胰高血糖素分泌的增加趋势。     

Stevioside induces antihyperglycaemic, insulinotropic and glucagonostatic effects in vivo: studies in the diabetic Goto-Kakizaki (GK) rats.

Extracts of leaves from the plant Stevia rebaudiana Bertoni have been used in the traditional treatment of diabetes in Paraguay and Brazil. Recently, we demonstrated a direct insulinotropic effect in isolated mouse islets and the clonal beta cell line INS-1 of the glycoside stevioside that is present in large quantity in these leaves. Type 2 diabetes is a chronic metabolic disorder that results from defects in both insulin and glucagon secretion as well as insulin action. In the present study we wanted to unravel if stevioside in vivo exerts an antihyperglycaemic effect in a nonobese animal model of type 2 diabetes. An i.v. glucose tolerance test (IVGT) was carried out with and without stevioside in the type 2 diabetic Goto-Kakizaki (GK) rat, as well as in the normal Wistar rat. Stevioside (0.2 g/kg BW) and D-glucose (2.0 g/kg BW) were administered as i.v. bolus injections in anaesthetized rats. Stevioside significantly suppressed the glucose response to the IVGT in GK rats (incremental area under the curve (IAUC): 648 +/- 50 (stevioside) vs 958 +/- 85 mM x 120 min (control); P < 0.05) and concomitantly increased the insulin response (IAUC: 51116 +/- 10967 (stevioside) vs 21548 +/- 3101 microU x 120 min (control); P < 0.05). Interestingly, the glucagon level was suppressed by stevioside during the IVGT, (total area under the curve (TAUC): 5720 +/- 922 (stevioside) vs 8713 +/- 901 pg/ml x 120 min (control); P < 0.05). In the normal Wistar rat stevioside enhanced insulin levels above basal during the IVGT (IAUC: 79913 +/- 3107 (stevioside) vs 17347 +/- 2882 microU x 120 min (control); P < 0.001), however, without altering the blood glucose response (IAUC: 416 +/- 43 (stevioside) vs 417 +/- 47 mM x 120 min (control)) or the glucagon levels (TAUC: 5493 +/- 527 (stevioside) vs 5033 +/- 264 pg/ml x 120 min (control)). In conclusion, stevioside exerts antihyperglycaemic, insulinotropic, and glucagonostatic actions in the type 2 diabetic GK rat, and may have the potential of becoming a new antidiabetic drug for use in type 2 diabetes.     

Galanin and pancreastatin inhibit stimulated insulin secretion in the mouse: comparison of effects

The effects of the two intrapancreatic peptides galanin and pancreastatin on basal and stimulated insulin and glucagon secretion in the mouse were compared. It was found that at 2 min after intravenous injection of galanin or pancreastatin (4.0 nmol/kg), basal plasma glucagon and glucose levels were slightly elevated. Galanin was more potent than pancreastatin to elevate basal plasma glucagon levels: they increased from 60 +/- 15 to 145 +/- 19 pg/ml (p less than 0.01) after galanin compared to from 35 +/- 5 to 55 +/- 8 pg/ml (p less than 0.05) after pancreastatin. Plasma insulin levels were lowered by galanin (p less than 0.05), but not by pancreastatin. CCK-8 (6.3 nmol/kg) or terbutaline (3.6 mumol/kg) markedly increased the plasma insulin levels. Galanin (4.0 nmol/kg) completely abolished the insulin response to CCK-8 (p less than 0.001), but pancreastatin (4.0 nmol/kg) was without effect. Galanin inhibited the insulin response to terbutaline by approximately 60% (p less than 0.01), but pancreastatin inhibited the insulin response to terbutaline by approximately 35% only (p less than 0.05). CCK-8 and terbutaline did both elevate plasma glucagon levels by moderate potencies: neither pancreastatin nor galanin could affect these responses. Thus, in the mouse, galanin and pancreastatin both inhibit basal and stimulated insulin secretion, and stimulate basal glucagon secretion. Galanin is thereby more potent than pancreastatin. The study also showed that galanin potently inhibits insulin secretion stimulated by the octapeptide of cholecystokin and by the beta 2-adrenoceptor agonist terbutaline, and that pancreastatin inhibits terbutaline-induced insulin secretion.     

Estimations of muscle interstitial insulin, glucose, and lactate in type 2 diabetic subjects

Previous measurement of insulin in human muscle has shown that interstitial muscle insulin and glucose concentrations are approximately 30-50% lower than in plasma during hyperinsulinemia in normal subjects. The aims of this study were to measure interstitial muscle insulin and glucose in patients with type 2 diabetes to evaluate whether transcapillary transport is part of the peripheral insulin resistance. Ten patients with type 2 diabetes and ten healthy controls matched for sex, age, and body mass index were investigated. Plasma and interstitial insulin, glucose, and lactate (measured by intramuscular in situ-calibrated microdialysis) in the medial quadriceps femoris muscle were analyzed during a hyperinsulinemic euglycemic clamp. Blood flow in the contralateral calf was measured by vein plethysmography. At steady-state clamping, at 60-120 min, the interstitial insulin concentration was significantly lower than arterial insulin in both groups (409 +/- 86 vs. 1,071 +/- 99 pmol/l, P < 0.05, in controls and 584 +/- 165 vs. 1, 253 +/- 82 pmol/l, P < 0.05, in diabetic subjects, respectively). Interstitial insulin concentrations did not differ significantly between diabetic subjects and controls. Leg blood flow was significantly higher in controls (8.1 +/- 1.2 vs. 4.4 +/- 0.7 ml. 100 g(-1).min(-1) in diabetics, P < 0.05). Calculated glucose uptake was less in diabetic patients compared with controls (7.0 +/- 1.2 vs. 10.8 +/- 1.2 micromol. 100 g(-1).min(-1), P < 0.05, respectively). Arterial and interstitial lactate concentrations were both higher in the control group (1.7 +/- 0.1 vs. 1.2 +/- 0.1, P < 0. 01, and 1.8 +/- 0.1 vs. 1.2 +/- 0.2 mmol/l, P < 0.05, in controls and diabetics, respectively). We conclude that, during hyperinsulinemia, muscle interstitial insulin and glucose concentrations did not differ between patients with type 2 diabetes and healthy controls despite a significantly lower leg blood flow in diabetic subjects. It is suggested that decreased glucose uptake in type 2 diabetes is caused by insulin resistance at the cellular level rather than by a deficient access of insulin and glucose surrounding the muscle cell.