Direct and indirect effects of insulin in suppressing glucose production in depancreatized dogs: role of glucagon

The subcellular locations of Ca(2+)-ATPases in the membranes of cauliflower (Brassica oleracea L.) inflorescences were investigated. After continuous sucrose gradient centrifugation a 111-kD calmodulin (CaM)-stimulated and caM-binding Ca(2+)-ATPase (BCA1; P. Askerlund [1996] Plant Physiol 110: 913-922; S. Malmstr?m, P. Askerlund, M.G. Plamgren [1997] FEBS Lett 400: 324-328) comigrated with vacuolar membrane markers, whereas a 116-kD caM-binding Ca(2+)-ATPase co-migrated with a marker for the plasma membrane. The 116 kD Ca(2+)-ATPase was enriched in plasma membranes obtained by aqueous two-phase partitioning, which is in agreement with a plasma membrane location of this Ca(2+)-ATPase. Countercurrent distribution of a low-density intracellular membrane fraction in an aqueous two-phase system resulted in the separation of the endoplasmic reticulum and vacuolar membranes. The 111-kD Ca(2+)-ATPase co-migrated with a vacuolar membrane marker after countercurrent distribution but not with markers for the endoplasmic reticulum. A vacuolar membrane location of the 111-kD Ca(2+)-AtPase was further supported by experiments with isolated vacuoles from cauliflower: (a) Immunoblotting with an antibody against the 111-kD Ca(2+)-ATPase showed that it was associated with the vacuoles, and (b) ATP-dependent Ca2+ uptake by the intact vacuoles was found to be CaM stimulated and partly protonophore insensitive.     

Importance of substrate changes in the decrease of hepatic glucose cycling during insulin infusion and declining glycemia in the depancreatized dog

We wished to determine whether the elevated glucose cycling (GC) between glucose and glucose-6-phosphate (G<-->G6P) in diabetes can be reversed with acute insulin treatment. In six insulin-deprived, anesthetized, depancreatized dogs, insulin was infused for 6-9 h at a starting dose of 45-150 pmol.kg-1.min-1 to normalize plasma glucose from 23.9 +/- 1.4 to 5.0 +/- 0.4 mmol/l and gradually decreased to and maintained at a basal rate (1.7 +/- 1.0 pmol.kg-1.min-1) during the last 3 h. GC, measured with [2-3H]- and [6-3H]glucose, fell markedly from 15.3 +/- 2.7 and normalized at 1.3 +/- 0.6 mumol.kg-1.min-1 (P < 0.001). This occurred because total hepatic glucose output fell much more (from 41.2 +/- 3.1 to 11.6 +/- 1.2) than did glucose production (from 25.9 +/- 1.9 to 10.3 +/- 1.0 mumol.kg-1.min-1) (both P < 0.01). Freeze-clamped liver biopsies were taken at timed intervals for measurements of hepatic enzymes and substrates. The elevated hepatic hexose-6-phosphate levels decreased with insulin infusion (151 +/- 24 vs. 71 +/- 13 nmol/g, P < 0.01). Maximal activities of glucose-6-phosphatase (G6Pase) (from 17.6 +/- 0.8 to 19.6 +/- 2.6 U/g) and glucokinase (from 1.1 +/- 0.2 to 1.0 +/- 0.2 U/g) did not change. Insulin infusion resulted in a threefold increase (P < 0.05) in the activity of glycogen synthase (active form), but had no effect on hepatic glycogen content.(ABSTRACT TRUNCATED AT 250 WORDS)     

Does insulin-induced increase in the amount of plasma membrane GLUTs quantitatively account for insulin-induced increase in glucose uptake?

To investigate changes in nuclear glycoproteins after transformation, nuclei and nuclear extracts were prepared from the normal and SV40-transformed WI-38 human lung fibroblasts grown in vitro. The nuclei of the normal and transformed cells were isolated by a vigorous pipetting method, and the isolated nuclei were verified by morphological and biochemical examinations. The nuclear glycocomponents, which were labelled with fluorescein isothiocyanate-lectins, were evenly found all through the isolated nuclei. Lectin blotting analysis showed that dozens of nuclear proteins contain both Man and GlcNAc moieties. The glycoproteins bearing the terminal N-acetylglucosamine sugar moieties were also demonstrated by in vitro galactosylation with [3H]-galactose. The result showed that nine glycoproteins specifically appeared or disappeared upon viral transformation or as SV40 replication products, indicating that there are significant differences in nuclear glycoproteins between the normal and SV40-transformed cells. These results suggest that the modification of Man and GlcNAc moieties are dynamic changes.     

Antazoline increases insulin secretion and improves glucose tolerance in rats and dogs

In vivo effects of an imidazoline devoid of alpha2-adrenoceptor antagonistic properties, antazoline, on insulin secretion and glycemia were investigated both in fasted rats and dogs. In both species, antazoline (1.5 mg/kg i.v.) transiently increased insulinemia without affecting basal plasma glucose levels. In contrast, during an i.v. glucose tolerance test, antazoline markedly potentiated insulin release and thus increased the glucose disappearance rate. In rats, during an oral glucose tolerance test, the intragastric administration of antazoline (1.5 mg/kg) clearly enhanced insulin secretion and reduced hyperglycemia. In dogs provided with a venous pancreatico-duodenal bypass, antazoline (0.5 mg/kg i.v.) induced an immediate and transient increase in insulin and somatostatin but not in glucagon pancreatico-duodenal outputs. In conclusion, intravenously and orally administered, the imidazoline antazoline is able to stimulate insulin secretion in vivo and improve glucose tolerance. The imidazoline compounds could therefore have a potential therapeutic relevance as new antihyperglycemic insulinotropic agents.     

Trifluoperazine inhibition of insulin-induced increase in skeletal muscle glucose uptake

Transplacental passage of fluorides was studied in 25 randomly selected neonates. Blood samples collected simultaneously from the mother and the umbilical cord showed that average fluoride concentration in the cord blood was 60% of that in mother's blood. When concentration in the mother's blood exceeded 0.4 ppm, the placenta acted as a selective barrier.     

Age-related changes in hepatic and splenic insulin receptors and serum insulin and glucose levels in inbred mice

A 62-year-old man and 26-year-old man with re-expansion pulmonary edema (RPE) after thoracic drainage as a treatment for pneumothorax are presented. Blood cell counting and biochemical serum analysis were performed throughout their treatment in both patients, and biochemical sputum analysis was in one patient. The results showed transient marked leukocytosis just after RPE. Total protein and albumin concentrations of sputum approximated to those of serum. The above results suggested that RPE is based on pulmonary microvascular injury, which may introduce leukocytosis.     

Portal and peripheral vein insulin responses to intravenous glucose in the rhesus monkey

Catheterization of the portal vein and bilateral femoral veins were performed under general anesthesia in 6 healthy male rhesus monkeys. Four days later, sequential, simultaneous peripheral and portal plasma samples were obtained for glucose and immunoreactive insulin determinations before and after administration of 0.5 Gm. of glucose per kilogram (over a 1-minute period) via the opposite peripheral catheter. Two phases of insulin secretion were noted in both portal and peripheral plasma samples. An immediate early-phase insulin response was noted with a peak response at 1 minute followed by a rapid decline to a nadir at 5 minutes. A second phase of insulin secretion was evident with a peak response at 10 minutes and a subsequent decline to basal levels by 60 minutes. Simultaneous portal vein and peripheral vein glucose concentrations were not significantly different from each other by paired analysis. Thus, in the rhesus monkey peripheral insulin concentrations following intravenous glucose exhibit a biphasic response closely paralleling pancreatic insulin secretion.     

Interstitial muscle insulin and glucose levels in normal and insulin-resistant Zucker rats

Tumour angiogenesis (antifactor VIII-related antigen antibody), p53 overexpression (DO-1) and proliferative activity (MIB-1) were immunohistochemically analysed for the prediction of long-term survival in 113 patients with squamous cervical carcinoma. The median follow-up time was 82 months (range 72-99). In early stages (IB-IIA), neovascularisation was significantly related to tumour size. Significantly more patients in stage IIA had high tumour vascularity compared to stage IB (P < 0.01) but no significant difference was found between early and advanced stages (IIB-IVB) of cervical carcinoma. p53 overexpression was correlated to the stage of disease (P < 0.01). No relationship was found between tumour angiogenesis, p53 overexpression or MIB-1 and pelvic lymph node metastases, histological subtype or differentiation. Tumours with more than 50% p53 overexpression was significantly correlated with survival in the univariate analysis, but no independent predictive value was found. It is concluded that immunohistochemically detectable p53 overexpression as measured by DO-1 and proliferative activity as measured by MIB-1 seems of no clinical value for the prediction of long-term survival in squamous cervical carcinoma. The predictive value of tumour angiogenesis for survival outcome has still to be determined in squamous cervical carcinoma.     

Importance of glucose control

The importance of glycemic control in reducing the microvascular complications of type 1 diabetes has been clearly demonstrated with a long-term prospective, randomized interventional trial. The data are not as strong with regards to type 2 diabetes. The results of several prospective studies and one interventional study, however, all report benefits of improved glycemic indices on reducing microvascular complications. The available literature evaluating the relationship between glycemic control and macrovascular disease in type 1 and type 2 diabetes demonstrates the importance of glucose control. One could make rational scientific arguments or criticize the design and interpretations of any one individual study. Yet collectively the evidence is powerful. Additionally, there have been no negative studies reported. Lowering the glycosylated hemoglobin to less than 2 percentage points above the upper limit of normal should be the first glycemic goal for most patients with diabetes. Obviously, some patients cannot obtain this degree of control for a variety of reasons. Moreover, the intensity of therapy needs to be individualized and tailored to each patient. In addition, intensive glycemic control does not necessarily mean multiple injections or insulin pumps or home glucose monitoring 10 times a day. Intensive glycemic control means that the glycohemoglobin (hemoglobin and A1C and blood glucose values are in a normal or near-normal range, no matter how simple or how complex the treatment regimen. The most controversial issue is with regards to the relationship between hyperinsulinemia and accelerated atherosclerosis. This association is not consistently found in many of the large prospective studies, and certainly there has never been a direct cause-and-effect relationship proven. Most experts in the field recommend that insulin be reserved for patients with type II diabetes when oral therapy cannot achieve near-normal glycemic control. Weight gain and hypoglycemia are adverse effects of sulfonylurea and insulin therapy. These adverse effects are dwarfed, however, by the acute and chronic complications of poorly controlled diabetes. Lastly, estimates on the economic benefits of reducing long-term microvascular and macrovascular complications in populations are staggering. Based on the available literature, all patients with diabetes should be educated and have access to an appropriate individualized treatment regimen with the goal to normalize or near-normalize glycemic control. This should be the standard of care until proven otherwise.     

Portal and peripheral blood immunoreactive insulin concentrations after glucose infusion during gastrectomy

We evaluated portal and peripheral blood immunoreactive insulin concentrations (IRI) after glucose infusion in patients undergoing gastrectomy. Seventy-four patients were divided into following two groups: 68 received 25g glucose infusion in an hour (glucose group), and the remainder received no glucose (control group). Portal blood IRI level in glucose group was about thirty-fold higher than that in control group. However, peripheral blood IRI did not correlate with portal blood IRI in glucose group. In addition, significant negative correlation between portal blood IRI and blood glucose was observed in glucose group. Our results reveal that adequate pancreatic insulin secretion occurs after glucose infusion during gastrectomy, but peripheral blood IRI does not reflect this pancreatic insulin secretion. The results also suggest that blood glucose may be regulated by the liver under these conditions.     

Normal glucose-induced suppression of glucose production but impaired stimulation of glucose disposal in type 2 diabetes: evidence for a concentration-dependent defect in uptake

The present studies were undertaken to determine whether people with type 2 diabetes are resistant to the effects of glucose as well as insulin. Diabetic and nondiabetic subjects were studied on three occasions. Hormone secretion was inhibited with somatostatin. Insulin concentrations were kept at "basal" levels (referred to as low insulin infusion) from 0 to 180 min then increased to approximately 200 pmol/l from 181 to 360 min (referred to as high insulin infusion). Glucose concentrations were clamped at either approximately 95, approximately 130, or approximately 165 mg/dl on each occasion. In the presence of basal insulin concentrations, a progressive increase in glucose from 95 to 130 to 165 mg/dl was accompanied by a comparable and progressive decrease (P = 0.001 to 0.003 by analysis of variance [ANOVA]) in endogenous glucose production (measured with [6-(3)H]glucose) and total glucose output (measured with [2-(3)H]glucose) and incorporation of 14CO2 into glucose (an index of gluconeogenesis) in both diabetic and nondiabetic subjects, indicating normal hepatic (and perhaps renal) response to glucose. In the nondiabetic subjects, an increase in glucose concentration from 95 to 130 to 165 mg/dl resulted in a progressive increase in glucose disappearance during both the low (19.9 +/- 1.8 to 23.6 +/- 1.8 to 25.4 +/- 1.6 micromol x kg(-1) x min(-1); P = 0.003 by ANOVA) and high (36.4 +/- 3.1 to 47.6 +/- 4.5 to 61.1 +/- 7.0 micromol x kg(-1) x min(-1); P = 0.001 by ANOVA) insulin infusions. In contrast, in the diabetic subjects, whereas an increase in glucose from 95 to 130 mg/dl resulted in an increase in glucose disappearance during both the low (P = 0.001) and high (P = 0.01) dose insulin infusions, a further increase in glucose concentration to 165 mg/dl had no further effect (P = 0.41 and 0.38) on disappearance at either insulin dose (low: 14.2 +/- 0.8 to 18.2 +/- 1.1 to 18.7 +/- 2.4 micromol x kg(-1) x min(-1); high: 21.0 +/- 3.2 to 33.9 +/- 6.4 to 32.5 +/- 8.0 micromol x kg(-1) x min(-1) for 95, 130, and 165 mg/dl, respectively). We conclude that whereas glucose-induced stimulation of its own uptake is abnormal in type 2 diabetes, glucose-induced suppression of endogenous glucose production and output is not. The abnormality in uptake occurs in the presence of both basal and high insulin concentrations and is evident at glucose concentrations above but not below 130 mg/dl, implying a defect in a glucose-responsive step.     

Monosodium glutamate (MSG)-obese rats develop glucose intolerance and insulin resistance to peripheral glucose uptake

Different levels of insulin sensitivity have been described in several animal models of obesity as well as in humans. Monosodium glutamate (MSG)-obese mice were considered not to be insulin resistant from data obtained in oral glucose tolerance tests. To reevaluate insulin resistance by the intravenous glucose tolerance test (IVGTT) and by the clamp technique, newborn male Wistar rats (N = 20) were injected 5 times, every other day, with 4 g/kg MSG (N = 10) or saline (control; N = 10) during the first 10 days of age. At 3 months, the IVGTT was performed by injecting glucose (0.75 g/kg) through the jugular vein into freely moving rats. During euglycemic clamping plasma insulin levels were increased by infusing 3 mU.kg-1.min-1 of regular insulin until a steady-state plateau was achieved. The basal blood glucose concentration did not differ between the two experimental groups. After the glucose load, increased values of glycemia (P < 0.001) in MSG-obese rats occurred at minute 4 and from minute 16 to minute 32. These results indicate impaired glucose tolerance. Basal plasma insulin levels were 39.9 +/- 4 microU/ml in control and 66.4 +/- 5.3 microU/ml in MSG-obese rats. The mean post-glucose area increase of insulin was 111% higher in MSG-obese than in control rats. When insulinemia was clamped at 102 or 133 microU/ml in control and MSG rats, respectively, the corresponding glucose infusion rate necessary to maintain euglycemia was 17.3 +/- 0.8 mg.kg-1.min-1 for control rats while 2.1 +/- 0.3 mg.kg-1.min-1 was sufficient for MSG-obese rats. The 2-h integrated area for total glucose metabolized, in mg.min.dl-1, was 13.7 +/- 2.3 vs 3.3 +/- 0.5 for control and MSG rats, respectively. These data demonstrate that MSG-obese rats develop insulin resistance to peripheral glucose uptake.     

Triphenyltin chloride induces glucose intolerance by the suppression of insulin release from hamster pancreatic beta-cells

An increased activity of phospholipase A2 has been observed in the plasma of patients with uremia. This enzyme converts phosphatidylcholine to lysophosphatidylcholine (LPC), an inhibitor of platelet aggregation. We measured the levels of plasma phospholipids including LPC, and platelet aggregation in 7 patients with uremia. Platelet response to agonists was defective, mainly with collagen (p < 0.001). The patients' levels of LPC in plasma were similar to those of controls (109.7 +/- 41.6 vs. 80.4 +/- 16.8 nmol/ml) and did not correlate with the platelet response to adenosine diphosphate (r = -0.51). The amount of phosphatidylcholine was increased with respect to normal plasma (1,041.0 +/- 201.8 vs. 760.8 +/- 142.7 nmol/ml, p < 0.01), while the levels of other phospholipids were normal. These results do not suggest a participation of plasma LPC in the genesis of the platelet defect observed in patients with uremia.     

Benefits of lispro insulin: control of postprandial glucose levels is within reach

How well would the following fit into your schedule? You must know when you will eat throughout the day, and about an hour beforehand you must inject an appropriate amount of insulin to offset the amount of carbohydrate you intend to consume. For many diabetic patients who use regular insulin, these are the requirements. Dr Bohannon describes a newly approved insulin that goes into action and gets out of the body faster, more closely mimicking the body's natural insulin response to food.     

Plasmatic levels of glucose and insulin in siblings of diabetic children (author's transl)

Observation of glucose and plasmatic insulin curve after oral administration of glucose in 16 brothers of juvenile diabetics. The findings were: slight curve alterations that would be compatible with chemical diabetes.     

Induction of insulin resistance by glucosamine reduces blood flow but not interstitial levels of either glucose or insulin

Streptozocin-induced diabetes is associated with alterations in insulin signaling in rat skeletal muscle, including increased insulin receptor substrate-1 phosphorylation and phosphotidylinositol 3-kinase activity. In the current study, we determined the effects of streptozocin-induced diabetes and treatment of diabetes by islet cell transplantation on several proximal insulin-activated signaling proteins. Three groups of male Lewis rats (untreated streptozocin-diabetic animals, islet cell-transplanted diabetic rats, and nondiabetic control rats) were studied in the basal state or 30 min after i.p. insulin injection (20 U/rat). Mixed hindlimb skeletal muscle lysates were used to determine the expression and enzymatic activities of the extracellular regulated kinase 2 (ERK2), p90 ribosomal S6 kinase (RSK2), Akt, and p70 S6 kinase (p70S6k). In all three groups of rats, insulin significantly increased ERK2, RSK2, Akt, and p70S6k activities. There was no effect of diabetes on insulin-stimulated ERK2 activity or ERK2 protein levels. RSK2 expression and insulin-stimulated RSK2 activity were significantly elevated in diabetic rats compared with those in the control animals. Insulin-stimulated Akt activity was also significantly greater in the diabetic animals, but there was no change in protein expression. In contrast, there was a decrease in insulin-stimulated p70S6k activity with no change in protein expression in the diabetic rats. Islet transplantation partially (RSK2) or fully (Akt, p70S6k) normalized these diabetes-induced changes in insulin signaling proteins. We conclude that streptozocin diabetes results in the dysregulation of several critical insulin-activated proteins in rat skeletal muscle, but islet cell transplantation is an effective therapy to partially correct these alterations in insulin signaling.     

The lung as an alternative route of delivery for insulin in controlling postprandial glucose levels in patients with diabetes

STUDY OBJECTIVES: To determine the efficacy of the lung as an alternative route of delivery for insulin in controlling glucose below diabetic levels (11.2 mmol/L) 2 h after the ingestion of a meal in patients with type 2 diabetes mellitus. DESIGN: Single-blinded, nonrandomized, placebo-controlled pilot study consisting of two visits. SETTING: A primary care facility. PATIENTS: Seven patients with type 2 diabetes mellitus. INTERVENTIONS: On the first study visit, fasting glucose levels were normalized. Then, patients inhaled 1.5 U/kg insulin by aerosol into the lungs 5 min before ingesting a test meal. On the second visit, patients inhaled placebo aerosol 5 min before ingesting the same meal. On both visits, plasma samples were collected and analyzed for glucose levels for 3 h during the postprandial state. MEASUREMENTS AND RESULTS: No one coughed after inhalation of insulin aerosol or demonstrated hypoglycemia. During the postprandial period, glucose levels were significantly lower at 20 min (5.12+/-1.08 mmol/L), 1 h (7.87+/-0.73 mmol/L), 2 h (8.05+/-1.24 mmol/L) and 3 h (7.50+/-1.43 mmol/L) following inhalation of insulin than when the placebo was used. Data for the placebo were 10.36+/-1.23 mmol/L at 20 min, 14.0+/-1.68 mmol/L at 1 h, 16.18+/-1.45 mmol/L at 2 h, and 14.37+/-2.11 mmol/L at 3h (for all comparisons, p < 0.05). On the insulin visit, glucose levels were < 11.2 mmol/L 2 h after the meal in six of seven patients. None attained this level at the placebo visit. In addition, glucose levels were within the normal postprandial range of < 7.84 mmol/L in four of seven patients 2 h after eating on the insulin visit. CONCLUSIONS: These results suggest that, once plasma glucose levels are normalized, postprandial glucose levels can be maintained below diabetic levels by delivering 1.5 U/kg insulin into the lungs 5 min before the ingestion of a meal.     

Glucagon-like peptide-1 reduces hepatic glucose production indirectly through insulin and glucagon in humans

The effect of glucagon-like peptide-1 (GLP-1) on hepatic glucose production and peripheral glucose utilization was investigated with or without infusion of somatostatin to inhibit insulin and glucagon secretion in 13 healthy, non-diabetic women aged 59 years. After 120 min 3-(3)H-glucose infusion, GLP-1 was added (4.5 pmol kg(-1) bolus + 1.5 pmol kg(-1) min(-1)). Without somatostatin (n = 6), GLP-1 decreased plasma glucose (from 4.8 +/- 0.2 to 4.2 +/- 0.3 mmol L(-1), P = 0.007). Insulin levels were increased (48 +/- 3 vs. 243 +/- 67 pmol L(-1), P = 0.032), as was the insulin to glucagon ratio (P = 0.044). The rate of glucose appearance (Ra) was decreased (P = 0.003) and the metabolic clearance rate of glucose (MCR) was increased during the GLP-1 infusion (P = 0.024 vs. saline). Also, the rate of glucose disappearance (Rd) was reduced during the GLP-1 infusion (P = 0.004). Since Ra was reduced more than Rd, the net glucose flow was negative, which reduced plasma glucose. Somatostatin infusion (500 microg h(-1), n = 7) abolished the effects of GLP-1 on plasma glucose, serum insulin, insulin to glucagon ratio, Ra, Rd, MCR and net glucose flow. The results suggest that GLP-1 reduces plasma glucose levels mainly by reducing hepatic glucose production and increasing the metabolic clearance rate of glucose through indirectly increasing the insulin to glucagon ratio in healthy subjects.