bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased Resting Metabolic Rates in Obese Subjects with Non-insulin-dependent Diabetes Mellitus and the Effect of Sulfonylurea Therapy
Authors: Bogardus Clifton , Taskinen Marja-Riitta , Zawadzki Joanna , Lillioja Stephen , Mott David , Howard Barbara V
Published: September 2013

Obese subjects with non-insulin-dependent diabetes mellitus (NIDDM) lose weight soon after diagnosis and tend to gain weight during hypoglycemic therapy. One explanation for these weight shifts is the change in caloric loss from glycosuria. We compared 24 obese Pima Indians with NIDDM to 24 Pima Indians with normal glucose tolerance to determine whether resting metabolic rate changes may be an additional factor influencing the weight shifts. The diabetic and nondiabetic subjects were equally obese, body fat 38 ± 1% versus 37 ± 1% (mean ± SEM), respectively, as determined by densitometry. In the morning after an overnight fast, resting metabolic rate (RMR) was measured by indirect calorimetry. The mean RMR of the diabetic subjects, 32.9 ± 0.5 kcal/day · kg fat-free mass (FFM), was 5% higher than that of the nondiabetic subjects, 31.4 ± 0.5 kcal/day kg FFM (P < 0.05). In nine of the diabetic subjects, 6 wk of tolazamide therapy was associated with reductions in mean FPG, 253 ± 16 to 144 ± 14 mg/dl (P < 0.01), mean daily urine glucose loss, 128 ± 26 to 11 ± 4 g (P < 0.01), and mean RMR, 31.9 ± 0.8 to 30.2 ± 0.6 kcal/day kg FFM (P < 0.04). Weight of the subjects was maintained constant from beginning to end of therapy (106.5 ± 9.6 versus 108.1 ± 9.9 kg) by decreasing daily calorie intake from 3070 ± 103 to 2784 ± 163 kcal (P < 0.01). We conclude that RMRs of obese, NIDDM subjects are increased compared with the RMRs of equally obese, nondiabetic subjects and that tolazamide therapy that decreases FPG reduces RMR in obese subjects with NIDDM.
Low Frequency of the Large Insertion in the Human Insulin Gene in Japanese
Authors: Haneda Masakazu , Kobayashi Masashi , Maegawa Hiroshi , Shigeta Yukio
Published: September 2013

We have studied the restriction fragment-length polymorphism in the 5'-flanking region of the human insulin gene in 47 nondiabetic Japanese subjects and in 52 subjects with non-insulin-dependent diabetes (NIDDM) to elucidate the ethnic variation of the genetic polymorphism and its relationship with NIDDM. Allelic frequencies in the nondiabetic subjects were 0.957 in class 1 (Bgl I fragments of 2800 ± 300 bp), 0 in class 2 (fragments of 3500 ± 300 bp), and 0.043 in class 3 (fragments of >3900 bp with a mean of 4500 bp). Corresponding frequencies in the NIDDM subjects were 0.962, 0, and 0.038, respectively. Four subjects with NIDDM who had the class 3 allele did not exhibit any particular clinical characteristics compared with the rest of the patients. Thus, the class 3 allele or the large insertion of the human insulin gene is much less frequent in Japanese than reported in other races, including Caucasians, and this class of allele is not associated with NIDDM in Japanese. Ethnic homogeneity is, thus, important in the analysis and interpretation of the genetic polymorphism.
Familial Insulin Resistance and Acanthosis Nigricans: Presence of a Postbinding Defect
Authors: Schwenk W Frederick , Rizza Robert A , Mandarino Lawrence J , Gerich John E , Hayles Alvin B , Haymond Morey W
Published: September 2013

Type A insulin resistance, associated with acanthosis nigricans and menstrual irregularity, has been ascribed to a decreased concentration of insulin receptors. We now report four affected females from one family, a mother and three daughters (including identical twins) who appear to have the type A syndrome. Two of the kindred had no apparent ovarian dysfunction, while the other two had hyperprolactinemia without other findings of polycystic ovary disease, suggesting a genetic disease with variable penetrance. All had normal erythrocyte and monocyte insulin binding. Insulin dose-response studies to assess glucose metabolism and insulinsensitivity were performed in the affected twins. The dose response to insulin was shifted to the right with a decrease in maximal response. These results are consistent with a postbinding defect in insulin action in these patients.
Pathogenesis and Prevention of the Dawn Phenomenon in Diabetic Patients Treated with CSII
Authors: Koivisto Veikko A , Yki-Järvinen Hannele , Helve Eero , Karonen Sirkka-Liisa , Pelkonen Risto
Published: September 2013

The mechanism of the dawn phenomenon was studied in 12 C-peptide-negative type I diabetic patients (age 30 ± 2 yr) treated with continuous subcutaneous insulin infusion. During constant basal infusion, nocturnal glycemia remained constant until 4 a.m., but began to rise thereafter in 10/12 patients, with the mean rise from 4.6 ± 0.4 mmol/L to 6.1 ± 0.7 mmol/L (P < 0.01) by 8 a.m. In these patients the rate of glucose production (Ra, 2.14 ± 0.04 mg/kg/min, 3-H3-glucose infusion) exceeded the rate of utilization (Rd, 1.89 ± 0.03 mg/kg/ min, P < 0.02). When the patients were restudied after the infusion rate was increased by 49 ± 7%, Ra fell to 1.75 ± 0.03 mg/kg/min (P < 0.01) and the dawn phenomenon was abolished. However, both Ra and Rd remained higher in the diabetic subjects (P / 0.05) than in eight healthy control subjects, in whom Ra (1.66 ± 0.02 mg/kg/min) was equal to Rd with glycemia remaining unchanged. Peripheral free insulin levels in the diabetic patients were similar during constant (12.3 ± 0.5 mU/L) and increased infusion rate (11.3 ± 0.4 mU/L), and higher than those of the control subjects (5.2 ± 0.2 mU/L, P < 0.05). A diurnal rise in serum cortisol levels occurred 1 h earlier in the diabetic than in the control subjects, and Ra was directly proportional to serum cortisol concentration (r = 0.61; P < 0.01). Serum growth hormone levels were also slightly higher in the diabetic than the control subjects.

In conclusion: (1) A dawn phenomenon is associated with an excessive rate of glucose production, rather than impaired utilization; (2) this may be explained, at least in part, by elevated counterregulatory hormone levels; and (3) a step-up in the overnight insulin delivery reduces hepatic glucose production and so prevents the dawn phenomenon.
Comparative Studies on Insulin-Like Growth Factor II and Insulin Processing by Vascular Endothelial Cells
Authors: Hachiya H L , Carpentier J -L , King G L
Published: September 2013

Processing of circulating polypeptide hormones by vascular endothelial cells may be critical to hormone transport from the vascular lumen to tissue sites of action. The comparative processing of insulin-like growth factor II (IGF II) and insulin by cultured bovine aortic endothelial cells was examined. These cells possess high-affinity receptors for IGF II and insulin, as shown by competitive-binding studies. At 37°C, internalization determined by both resistance to an acid wash and electron microscopy was rapid with 50–70% of bound IGF II and insulin internalized at 60 min. Subsequently, between 70 and 75% of the internalized hormones were released from the cells within 60 min.

Although most of both hormones were released intact, degradation of IGF II was greater than that of insulin by two- to threefold, as assessed by G-50 chromatography and trichloroacetic acid precipitability. Leupeptin, a specific lysosomal protease inhibitor, increased cell-associated 125I-labeled IGF II by 53.0 ± 6.0% and decreased degradation by 55%; however, it was without effect on 125I-labeled insulin. Chloroquine and monensin, which act at the lysosomes and at other sites, increased both cell-associated IGF II and insulin and decreased the degradation of both hormones. The increases in cell-associated 125I—IGF II produced by chloroquine (42.0 ± 7.4%) and monensin (78.3 ± 8.5%) were quantitatively similar to the decreases in IGF II degradation caused by the agents; however, the increase in cell-associated insulin was approximately threefold greater than could be accounted for simply by decreased insulin degradation.

These results demonstrate two functional pathways for the processing of internalized hormones in the endothelial cell: a lysosome-targeted degradative pathway and a nonlysosomal pathway that may mediate the release of primarily intact hormone from the cells. IGF II processing and insulin processing by endothelial cells are different, due in part to greater channeling of IGF II, compared with insulin, into the degradative pathway. The capacity of endothelial cells to differentially process polypeptide hormones represents a potential mechanism that may modulate hormone delivery to tissue Sites Of action.
Decreased Myo-Inositol Content and Na+-K+-ATPase Activity in Superior Cervical Ganglion of STZ-Diabetic Rat and Prevention by Aldose Reductase Inhibition
Authors: Greene D A , Mackway A M
Published: September 2013

Decreased sciatic nerve myo-inositol content and Na+-K+-ATPase activity have been associated with slowing of motor nerve conduction in the acutely diabetic rat and have been invoked as possible pathogenic factors in diabetic peripheral neuropathy. Aldose reductase inhibitors prevent these abnormalities in peripheral nerves of the streptozocin (STZ)-diabetic rat. Whether an analogous biochemical abnormality occurs in the autonomic nervous system and plays a role in the development of diabetic autonomic dysfunction is unknown. Therefore we examined the effect of 8 wk of untreated STZ diabetes and administration of 20 mg · kg−1 day−1 of the aldose reductase inhibitor sorbinil on myo-inositol level and Na+-K+-ATPase activity in rat superior cervical ganglia. Both myo-inositol concentration and Na+-K+-ATPase activity were reduced in ganglia from untreated STZ-diabetic rats, and sorbinil administration prevented these abnormalities. Thus, a sorbinil-responsive metabolic defect involving myotional abnormalities in the somatic and autonomic nervous systems in diabetes.
Interleukin 1 Inhibits Insulin Secretion From Isolated Perifused Rat Islets
Authors: Zawalich W S , Diaz V A
Published: September 2013

Preincubation of collagenase-isolated rat islets for 150 min with 100 U/ml purified human interleukin 1 (IL-1) altered their ability to secrete insulin. Whereas basal release rates with 4 mM glucose were comparable in control and IL-1-treated islets, both the first and second phases of release in response to 20 mM glucose were significantly reduced from IL-1-treated tissue. IL-1 pretreatment also impaired the secretory response to the combination of 100 nM cholecystokinin plus 7 mM glucose. However, the secretory response to 10 mM α-ketoisocaproate was comparable in control and IL-1-pretreated islets. Reducing the IL-1 exposure time to 60 min was accompanied by an augmented first phase of release to 20 mM glucose. Second phase secretion was diminished. The use of glucose measured after the perifusion was similar in control and IL-1-treated islets. Similar to other compounds that adversely impact on β-cell viability, the inhibitory effect of IL-1 on release may presage a cytotoxic action of monokine.
Sympathetic Outflow in Human Muscle Nerves Increases During Hypoglycemia
Authors: Fagius J , Niklasson F , Berne C
Published: September 2013

The normal response to insulin-induced hypoglycemia bears many characteristics of activation of the sympathetic nervous system. In this study, the impulse pattern of muscle nerve sympathetic activity (MSA) involved in cardiovascular homeostasis was identified by microneurography in the peroneal nerve of seven healthy and two adrenalectomized subjects. After recordings at rest and an intravenous injection of 0.15 IU insulin/kg body wt (0.10 IU insulin/kg body wt in adrenalectomized subjects), MSA was followed for 90 min. Nadir of hypoglycemia (2.0 ± 0.1 mM) was reached at 30 min. All subjects, including the two adrenalectomized subjects, exhibited an increase of MSA, which peaked at the glucose nadir. The time course of MSA increase was a mirror image of the blood glucose curve. This directly measured increase of MSA may be part of the hemodynamic adjustment to the fall in plasma volume known to occur in hypoglycemia. Another possible cause is direct stimulation of central sympathetic motoneurons.
Renal Effects of Nicardipine, a Calcium Entry Blocker, in Hypertensive Type II Diabetic Patients With Nephropathy
Authors: Baba T , Ishizaki T , Ido Y , Aoyagi K , Murabayashi S , Takebe K
Published: September 2013

We studied the renal effects of nicardipine, a calcium entry blocker, in eight patients with essential hypertension (group A, WHO I or II), six hypertensive type II diabetics with mild-to-moderate nephropathy (group B, urinary albumin 200–789 mg/day), and six hypertensive type II diabetics with severe or advanced nephropathy (group C, urinary albumin 1,596–4,300 mg/day). The patients received an intravenous dose of nicardipine hydrochloride (0.5 mg) or saline placebo in a random order. Glomerular filtration rate (GFR) and renal blood flow (RBF) were measured by means of thiosulfate sodium and p-aminohippurate, respectively, during the 30 min after the nicardipine or saline injection. Blood pressures were serially monitored during the study. Nicardipine reduced both systolic and diastolic blood pressures significantly (P < .05 to .01) at all measurement periods in all study groups compared with the respective placebo. Nicardipine increased RBF (P < .01), GFR (P < .05), and urinary Na+ excretion (P < .01) and decreased total renal vascular resistance (P < .01) in groups A and B, but these parameters remain unchanged in group C. The filtration fraction remained unaltered in all groups. The results indicate that nicardipine has several favorable renal effects with a concomitant hypotensive action in hypertensive type II diabetics with mild-to-moderate nephropathy, as observed in patients with uncomplicated essential hypertension, and the renal pharmacological responsiveness appears to be related to the severity of nephropathy. Nevertheless, nicardipine can be a useful agent in lowering blood pressure without deteriorating renal function in hypertensive type II diabetics with advanced nephropathy.
Cyclic AMP Phosphodiesterase in Diabetes: Effect of Glyburide
Authors: Solomon S S , Deaton J , Shankar T P , Palazzolo M
Published: September 2013

Low-Michaelis constant cAMP phosphodiesterase (PDE; EC3.1.4.C) activity is inhibited in tissues of rats with type I ketosis-prone diabetes and is restored to normal by insulin treatment. To determine whether the oral hypoglycemic agent glyburide affected tissue cAMP PDE activity in non-insulin-dependent oral agent-treatable diabetes, cAMP PDE activity was measured in the liver and fat of animals rendered diabetic by low-dose streptozocin (STZ-DM) and treated for 3 wk with oral glyburide (360 μg/kg). The results were compared with PDE activity in the liver and fat of untreated STZ-DM and normal control rats. At the time of death, low-KmcAMP PDE activity [as maximum velocity (Vmax)] in STZ-DM rats was decreased to 66% of control values in the liver and to 65% in fat (P < .001). PDE activity was restored toward normal by glyburide treatment: 91% in the liver (P < .01) and 80% in fat (P < .05). Calmodulin and calmodulin-like activity (PDE-activator activity) in the liver and fat was decreased in diabetes and restored toward normal after glyburide treatment (P < .05). These data demonstrate that oral agents as well as insulin can restore the activity of cAMP PDE in the lowdose STZ-DM model, which is in some ways similar to type II diabetes.
Brown Adipose Tissue in Lean and Obese Mice: Insulin-Receptor Binding and Tyrosine Kinase Activity
Authors: Tanti J -F , Grémeaux T , Brandenburg D , Obberghen E Van , Marchand-Brustel Y Le
Published: September 2013

Insulin-receptor binding and tyrosine kinase activity have been studied in brown adipose tissue from lean and obese mice. Brown adipose tissue carries functional insulin receptors comparable with those of conventional insulin target tissues. The α-subunit (Mr 130,000) was labeled with photoreactive insulin; the βsubunit (Mr, 95,000) was phosphorylated in a cell-free system, and its level of phosphorylation was increased in a dose-dependent manner by insulin. Two types of obese mice, mice rendered obese by gold thioglucose injection (GTG obese) and genetically obese ob/ob mice, were used. Insulin-receptor number was decreased by 60–70% in obese mice, when expressed per milligram of plasma membrane protein or per microgram of glycoprotein, whereas only a 30–40% diminution was observed in skeletal muscle, indicating that insulin receptors from brown adipose tissue are greatly affected by the downregulation process. Insulin-stimulated autophosphorylation of the insulin-receptor β-subunit was decreased by 60–70% in preparations of obese mice compared with lean mice in direct proportion to the diminished level of insulin-receptor number. Similarly, the ability of receptors to catalyze the phosphorylation of a synthetic substrate (copolymer glutamate-tyrosine) was reduced. These results suggest that the decrease in insulin-receptor number and in associated tyrosine kinase activity could explain the insulinresistant glucose uptake and the alteration in diet-induced thermogenesis described in obese animals.
Leucine Metabolism in Type II Diabetes Mellitus
Authors: Staten M A , Matthews D E , Bier D M
Published: September 2013

Severe muscle wasting is a well-recognized characteristic of untreated insulin-deficient diabetes mellitus, a condition in which leucine turnover and oxidation are accelerated. To ascertain whether a similar circumstance exists in type II diabetes when insulin is present but with reduced efficacy, we investigated leucine turnover and oxidation in five obese type II diabetic women by tracer infusion of L-[1-13C,15N]leucine in the postabsorptive state both before and after intensive insulin therapy. With conventional treatment, the type II diabetic women received 61 ± 33 (SD) U/day of insulin, and their fasting plasma glucose averaged 194 ± 41 (SD) mg/dl. Leucine carbon flux (Qc), nitrogen flux (QN), and oxidation (C) averaged 6.4 ± 1.2,15.6 ± 4.6, and 1.4 ± 0.3 mmol/h, respectively. These values were not different from the respective values of 6.6 ± 1.3, 17.0 ± 8.3, and 1.0 ± 0.2 mmol/h in matched obese nondiabetic controls, suggesting that leucine metabolism is not altered in insulin-treated type II diabetics. After a week of intensive insulin therapy in which the same diabetic subjects received 94 ± 36 U/day of insulin, postabsorptive plasma glucose declined to 117 ± 26 mg/dl. Leucine Qc(6.2 ± 1.0), QN (14.8 ± 3.7), and C (1.5 ± 0.5 mmol/h) were unaltered by the increased insulin therapy. Thus, obese type II diabetics had normal leucine kinetics but were hyperglycemic while receiving conventional insulin therapy. Additional intensive insulin therapy in these diabetic subjects improved plasma glucose but did not alter leucine kinetics. Thus, these data demonstrate a differential sensitivity of insulin's action on carbohydrate versus amino acid metabolism in type II diabetics.
Rubella Virus–Induced Diabetes in the Hamster
Authors: Rayfield E J , Kelly K J , Yoon J -W
Published: September 2013

The congenital rubella syndrome provides the best documentation in humans that a viral infection is associated with the subsequent development of insulin-dependent diabetes mellitus. We have developed an animal model in neonatal golden Syrian hamsters infected with rubella virus passaged in β-cells that closely parallels the diabetes observed with congenital rubella. The hamsters develop hyperglycemia and hypoinsulinemia, which are sustained throughout the 15-wk study period. A mononuclear infiltration of the islets, isolation of rubella virus from whole pancreas, the presence of viral antigen in β-cells by immunofluorescent localization, and cytoplasmic islet cell antibodies (40%) are demonstrated. These data suggest that an autoimmune process and diabetes develop after rubella virus infection in neonatal hamsters. This model may uncover the precise mechanism by which rubella virus induces similar disease in humans.
Streptozocin Diabetes Alters Immunoreactive β-Endorphin Levels and Pain Perception After 8 wk in Female Rats
Authors: Forman L J , Estilow S , Lewis M , Vasilenko P
Published: September 2013

Plasma, pituitary, and hypothalamic levels of the endogenous opioid peptide β-endorphin were measured by radioimmunoassay and column chromatography in female rats 8 wk after the induction of diabetes with streptozocin (STZ) and in control female rats. In addition, pain perception was determined by measuring the latency to paw lick or jump after being placed on a hot plate. Plasma levels of immunoreactive β-endorphin (IR-BE) were significantly reduced in STZ-induced diabetic female rats, as were the content and concentration of IR-BE in the neurointermediate lobe of the pituitary (NIL) and the content of IR-BE in the hypothalamus. The concentration but not the content of IR-BE in the anterior pituitary (AP) of the STZ-induced diabetic rats was increased significantly. Streptozocininduced diabetes also resulted in a significant reduction in the total protein content of the AP, NIL, and hypothalamus. Column chromatography indicated that the decrease in IR-BE in the plasma, NIL, and hypothalamus represented a decrease in β-endorphin, whereas the increase in IR-BE in the AP represented an increase in both β-endorphin and β-lipotropin. Diabetic animals consistently showed decreased latencies to paw lick or jump when subjected to hot-plate testing after 7 wk. These findings suggest that in female rats, central and peripheral endogenous opiate levels and tolerance to nociceptive thermal stimulation were diminished by 8 wk of chemically induced diabetes.
Diabetes Mellitus in Ataxia-Telangiectasia, Fanconi Anemia, Xeroderma Pigmentosum, Common Variable Immune Deficiency, and Severe Combined Immune Deficiency Families
Authors: Morrell Daphne , Chase Charles L , Kupper Lawrence L , Swift Michael
Published: September 2013

The hypothesis that heterozygous carriers of genes for certain autosomal recessive syndromes may be predisposed to diabetes was tested by comparing diabetes incidence from age 20 to 69 yr in blood relatives to that in spouse controls among 7999 adult family members of patients with one of five autosomal recessive syndromes: ataxia-telangiectasia (A-T), Fanconi anemia (FA), xeroderma pigmentosum (XP), common variable immune deficiency (CVID), and severe combined immune deficiency (SCID). FA and A-T families were studied because earlier findings in family members and the frequency of diabetes in homozygotes suggested that heterozygotes might also be predisposed to diabetes. The XP, CVID, and SCID families were included to see what analysis of family data would reveal when there was no prior evidence for a gene-diabetes association. The diabetes rate ratios of 2.6 and 4.2 among FA and SCID females, respectively, were significantly elevated. For female FA heterozygotes specifically, the estimated relative risk of 5.1 for developing diabetes was also significantly elevated. Among males, the most pronounced, although not statistically significant, findings were an elevated rate ratio of 2.2 for A-T males and a low-rate ratio of 0.5 for CVID males. The results suggest that heterozygotes for some of the diabetes-associated autosomal recessive syndromes may themselves be predisposed to diabetes.
Insulin Sensitivity and Exogenous Insulin Clearance in Graves' Disease: Measurement by the Glucose Clamp Technique and Continuous Indirect Calorimetry
Authors: Randin Jean-Pierre , Tappy Luc , Scazziga Bianca , Jequier Eric , Felber Jean-Pierre
Published: September 2013

Insulin sensitivity was measured in a group of seven thyrotoxic patients and in a group of seven normal subjects by means of the glucose clamp technique. Infusion of insulin at a rate of 0.80 ± 0.05 mU/kg · min in the hyperthyroid patients and of 0.55 ± 0.04 mU/kg · min in the control group was performed to obtain a steady-state plasma insulin concentration of approximately 50 μU/ml. Substrate oxidation rates were measured in the postabsorptive state and during the 2 h of the clamp by means of continuous indirect calorimetry.

In the postabsorptive state, hyperthyroid patients presented a preferential oxidation of lipids. During the period 60–120 min of the clamp, mean plasma glucose (92 ± 2 versus 93 ± 2 mg/dl), insulin (50 ± 5 versus 58 ± 3 μU/ml), and total glucose metabolism (5.8 ± 0.7 versus 6.1 ± 0.3 mg/kg - min) were similar in the hyperthyroid patients and the control subjects. The rate of glucose oxidation was higher in hyperthyroid patients than in control subjects (4.3 ± 0.5 versus 2.2 ± 0.2 mg/kg min, P < 0.001), while that of lipid oxidation was similar in both groups (0.6 ± 0.2 versus control 0.7 ± 0.1 mg/kg - min). The calculated metabolic clearance rate of insulin was markedly higher in the hyperthyroid patients (1144 ± 132 ml/min) than in the normal subjects (812 ± 56 mi/min, P < 0.025).

It is concluded that insulin sensitivity is not altered in the thyrotoxic state. The major route of insulin-stimulated glucose disposal in the hyperthyroid patients appears to be glucose oxidation.
The Role of Autoregulation of the Hepatic Glucose Production in Man: Response to a Physiologic Decrement in Plasma Glucose
Authors: Hansen I , Firth R , Haymond M , Cryer P , Rizza R
Published: September 2013

In man, a decrease in plasma glucose concentration results in a compensatory increase in hepatic glucose release. Studies in vitro have suggested that a low glucose concentration per se may directly stimulate hepatic glucose release, an effect often referred to as autoregulation. Whether autoregulation occurs in man in response to a physiologic decrement in blood glucose is not known. Therefore, seven healthy, nonobese subjects were studied on two occasions to determine the role of autoregulation in mediating the increase in glucose production that accompanies a physiologic decrement in plasma glucose concentration. On both occasions, plasma glucose concentrations were clamped successively at 95, 65, and 95 mg/dl for 2 h each. Insulin (∼14 μU/ml) and glucagon (∼70 pg/ml) were maintained constant on both occasions by an infusion of somatostatin and insulin. Phentolamine and propranolol also were infused on one occasion to produce combined alpha- and beta-adrenergic blockade. In the absence of adrenergic blockade, glucose production increased by approximately 1.3 mg/kg min when the plasma glucose concentration was decreased from 95 to 65 mg/dl and decreased by approximately 1.5 mg/kg min when glucose was increased from 65 to 95 mg/dl. In the presence of adrenergic blockade, the increase and decrease in glucose production averaged 0 and 0.5 mg/kg·min, respectively, representing 70–100% inhibition. We conclude that, in the presence of low physiologic insulin concentrations, autoregulation is not a major contributor to the hepatic response to a physiologic decrement in plasma glucose concentration in man.
Control of Blood Glucose Levels in Alloxan-diabetic Rabbits by Iontophoresis of Insulin
Authors: Kari Bruce
Published: September 2013

Cathodal iontophoresis was used to deliver insulin in 23 alloxan-diabetic, male, New Zealand white rabbits. Currents of 0.2–0.8 mA were used to deliver insulin from reservoirs containing insulin concentrations of 10–500 U/ml in aqueous solution. Regardless of the level of current used, within 1 h of turning the current on, blood glucose levels decreased and serum insulin concentrations increased. Moreover, in most cases, blood glucose levels continued to decrease and serum insulin concentrations continued to increase after the current was turned off, suggesting that iontophoresis could be used to accumulate insulin in the skin and subcutaneous tissues. The amount of insulin that was delivered by iontophoresis could be controlled by the level of current used up to 0.4 mA; increasing the current to 0.8 mA did not deliver more insulin. This may have been due to greater production of hydroxide ions at 0.8 mA, which competed with insulin to carry the current, thus slowing the movement of insulin. The amount of insulin delivered could also be controlled by the amount of insulin available for iontophoresis, i.e., as the insulin reservoir concentration increased, more insulin was delivered at the same current level. Finally, skin preparation was also important in controlling insulin delivery. To deliver enough insulin to reduce blood glucose levels, the stratum corneum had to be disrupted or removed by gentle scraping.
Effects of D-glucose, L-leucine, and 2-ketoisocaproate on Insulin mRNA Levels in Mouse Pancreatic Islets
Authors: Welsh Michael , Brunstedt Janne , Hellerström Claes
Published: September 2013

To elucidate a possible mechanism for regulation of insulin mRNA levels in the pancreatic B-cell, isolated mouse pancreatic islets were cultured in the presence of either glucose, leucine, or 2-ketoisocaproate, and insulin mRNA levels were compared with insulin biosynthesis, insulin release, and islet O2 uptake. It was observed that leucine or 2-ketoisocaproate was as effective as 20 mM glucose in supporting high insulin mRNA levels, high basal rates of insulin release or insulin synthesis, and rapid O2 uptake. Furthermore, islets cultured with either leucine or 2-ketoisocaproate could be stimulated to increase their insulin biosynthesis by a high glucose concentration. In addition the insulin release and respiration of such islets could be increased by exposure to 2-ketoisocaproate + glutamine. It is concluded that the maintenance of high concentrations of insulin mRNA levels and high rates of insulin biosynthesis and release are all processes correlated with metabolic fluxes in islets rather than the presence of the glucose molecule per se.
Protein Kinase C Agonists Acutely Normalize Decreased Ouabain-inhibitable Respiration in Diabetic Rabbit Nerve: Implications for (Na,K)-ATPase Regulation and Diabetic Complications
Authors: Greene Douglas A , Lattimer Sarah A
Published: September 2013

Diminished (Na,K)-ATPase activity in diabetic peripheral nerve is attributed to an underlying depletion of free myo-inositol, but no biochemical mechanism linking myo-inositol metabolism and (Na,K)-ATPase has emerged. Since inositol phospholipid turnover releases inositol-(1,4,5)-tris-phosphate and diacylglycerol, two putative “second messengers” that modulate protein kinase C, the effect of protein kinase C agonists on (Na,K)-ATPase activity was examined in diabetic nerve. Phorbol myristate acetate or the diacylglycerol sn-1,2-dioctanoylglycerol acutely normalized depressed ouabain-inhibitable respiration [a measure of (Na,K)-ATP-ase activity], suggesting that myo-inositol metabolism modulates (Na,K)-ATPase activity via protein kinase C, and that reduced myo-inositol impairs (Na,K)-ATPase activity in diabetic nerve by this mechanism.
Insulin Induces Progressive Insulin Resistance in Cultured Rat Adipocytes: Sequential Effects at Receptor and Multiple Postreceptor Sites
Authors: Garvey W Timothy , Olefsky Jerrold M , Marshall Stephen
Published: September 2013

We have examined the ability of insulin to regulate insulin action in primary cultured adipocytes, and found that insulin induces progressive insulin resistance in this target tissue. To assess effects at both receptor and postreceptor sites, we cultured cells in the absence (control) and presence of 100 ng/ml insulin, and, after various times, measured the dose response of insulin's ability to bind cell-surface receptors and stimulate 2-deoxyglucose transport. In control cells, insulin binding (0.2 ng/ml) was increased 10–13% due to an apparent increase in receptor affinity (6–24 h). A comparable increase in affinity was also observed in treated cells; however, concomitantly, insulin decreased the number of cell-surface receptors causing a slowly progressive net decrease in binding after a 6– 10-h lag (maximal 30% at 24 h). When insulin action was assessed in control cells, the functional consequence of increased receptor binding was hypersensitization (i.e., increased insulin sensitivity) manifested by a leftward shift in the 2-deoxyglucose dose-response curve. On the other hand, in the treated cells, insulin produced insulin resistance initially by decreasing insulin sensitivity. The ED50 for insulin stimulation of glucose transport increased 84% from 0.31 to 0.57 ng/ml at 6 h without a net change in insulin binding; this was the result of a decrease in coupling efficiency between occupied receptors and the insulin effect. Receptor uncoupling progressively increased in severity, but before the full effect was reached insulin also caused a rapid decline in maximally stimulated glucose transport rates (between 6 and 10 h). This decrease in insulin responsiveness (maximal 52%) exacerbated overall insulin resistance, and was indicative of a postreceptor defect in the glucose transport system. Finally, insulin-induced receptor downregulation contributed, along with uncoupling, to a further decrease in insulin sensitivity, and constituted a more long-term regulatory mechanism. We also observed that insulin could regulate the basal glucose transport system by preventing a progressive rise in basal transport observed in control cells.

In conclusion, primary cultured adipocytes can be used to study long-term regulation of insulin action. We found that insulin induces progressive insulin resistance with sequential effects at multiple sites in the insulin action pathway, including decreased coupling efficiency between occupied receptors and stimulated glucose transport, a postreceptor defect in insulin responsiveness of the glucose transport system, and receptor downregulation. These mechanisms may be relevant to the cellular defects in insulin action present in clinical states of insulin resistance and hyperinsulinemia.
Aldehyde Dehydrogenase Activity and Large Vessel Disease in Diabetes Mellitus: A Preliminary Study
Authors: Jerntorp Peter , Öhlin Hans , Almér Lars-Olof
Published: September 2013

Type II diabetic subjects, 26 with symptoms and/or signs of large vessel disease (LVD group) and 26 free from clinical vascular disease (FVD group), matched for sex, age, body weight, and duration of diabetes after diagnosis, together with 28 healthy controls participated in a preliminary study on new potential risk factors of large vessel disease.

The activity of erythrocyte aldehyde dehydrogenase (ALDH) was significantly higher (P < 0.005) in the LVD than in the FVD group and in the controls, as indicated by a shorter half-life of acetaldehyde in homogenates of erythrocytes and plasma (100 ± 11, 203 ± 28, and 180 ± 21 min, respectively). The results were unaffected by antidiabetes therapy, blood glucose control, alcohol consumption, or by recognized risk factors of angiopathy, such as blood pressure, hyperlipidemia, or smoking. Whether ALDH activity is a primary factor in large vessel disease or is merely a secondary phenomenon is unknown. However, ALDH activity is a critical factor determining chlorpropamide alcohol flush (CPAF), which has been suggested to be an inherited trait in some type II diabetic subjects.

In conclusion, high ALDH activity was shown to be associated with an increased risk of large vessel disease in diabetes.
The Third Phase of In Vitro Insulin Secretion: Evidence For Glucose Insensitivity
Authors: Bolaffi Janice L , Heldt Anneliese , Lewis Laura D , Grodsky Gerold M
Published: September 2013

In this study, in vitro B-cell models are described, which may be applicable for studying the reported B-cell desensitization produced by hyperglycemia in IDDM and NIDDM. Using a programmable perifusion/ perfusion system, insulin secretion from perifused islets was measured at 10–30-min intervals for 24–50 h. After 3–4 h continuous glucose (11 mM), a new phase of insulin release occurs in which secretion declines to, and remains at, ∼25% maximal release. Results were similar when using: (1) perifused islets embedded in Cytodex 3, or Bio-Gel P-2,100–200 mesh; (2) batchincubated islets with hourly changes of medium; and (3) the isolated pancreas perfused for 8 h. Three different media, Hana HB104 (fortified, fully defined medium), RPMI-1640 + 10% FBS, and perfusion bufferalbumin, were used. Despite reduced secretion to continuous glucose, each system responded vigorously to an acute stimulation with glucose-forskolin. Decreased secretion was primarily caused by decreased secretagogue efficiency (reduced fractional secretion). Prolonged stimulation with glucose or glucose-IBMX produced a similar waning of secretion regardless of the amount of insulin released. It is concluded that the third phase of insulin secretion may represent a secretagogue-induced, signal desensitization of the B-cell, rather than exhaustion of a B-cell compartment of Stored insulin.
Insulin-Like Growth Factors in Vitreous: Studies in Control and Diabetic Subjects with Neovascularization
Authors: Grant M , Russell B , Fitzgerald C , Merimee T J
Published: September 2013

Vitreous and serum were obtained at the time of vitrectomy from 23 diabetic subjects with proliferative retinopathy and from 8 nondiabetic subjects. The mean concentration of IGF-I in vitreous from diabetic patients with neovascularization was 6.3 ± 0.93 versus 2.7 ± 0.96 ng/mi. Chi-square and rank analysis indicated that higher concentrations of IGF-I occurred in diabetic vitreous (P < 0.01 by both analyses). IGF-II concentrations in vitreous of control and diabetic subjects were not significantly different. A positive correlation existed between the concentrations of IGF-I and IGF-II in vitreous and their concentrations in serum in diabetic subjects, but not in control subjects. When vitreous concentrations of IGF-I were calculated for diabetic subjects studied previously with rapid acceleration of retinal disease, these concentrations varied from 20 to 30 ng/ml. The concentrations of IGF-I in the vitreous of most diabetic subjects with severe neovascularization are thus in the range known to stimulate cellular differentiation and growth in several systems. Whether they do so in the eye, and thus contribute to the development of retinopathy, remains to be determined.
Relationship of Muscle Capillary Basement Membrane to Renal Structure and Function in Diabetes Mellitus
Authors: Ellis Eileen N , Mauer S Michael , Goetz Frederick C , Sutherland David E R , Steffes Michael W
Published: September 2013

Muscle capillary basement membrane (MCBM) thickening has been considered to reflect microvascular changes in other tissues in diabetes mellitus. To explore the relationships between MCBM width and nephropathy,27 patients aged 22–55 yr with type I diabetes for 14–33 yr were studied with creatinine clearances, urinary albumin excretion rates, multiple blood pressure measurements, glycosylated hemoglobin measurements, and renal and quadriceps muscle biopsies that were evaluated using standard stereologic techniques. MCBM width did not correlate with age, duration of diabetes, creatinine clearance, urinary albumin excretion, or fractional volume of the glomerular mesangium. MCBM width did correlate, although weakly, with glomerular basement membrane width (r = 0.47) and glycosylated hemoglobin (r = 0.44). There was no difference in MCBM width between patients with and without clinical nephropathy. Patients with normal fractional volume of mesangium exhibited a full range of MCBM width. Thus, while MCBM width may reflect glycemic control and glomerular basement membrane thickening, it does not relate to the functional or structural renal changes associated with progressive diabetic nephropathy.
Magnesium Deficiency in IDDM Related to Level of Glycosylated Hemoglobin
Authors: Sjögren Anders , Florén Claes-Henrik , Nilsson Âke
Published: September 2013

Magnesium and potassium were analyzed in plasma, erythrocytes, and urine collected during 24 h and in muscle biopsies from 25 subjects with insulin-dependent, type I diabetes mellitus (IDDM). Magnesium was also measured in mononuclear cells. The results were compared with those of 28 healthy controls, and were also correlated with the degree of diabetic control as estimated by analysis of the level of glycosylated hemoglobin (HbA1c). Subjects with IDDM had significantly lower muscle (P < 0.01) and plasma (P < 0.001) concentrations of magnesium compared with those of healthy controls. The HbA1c levels correlated significantly with the concentrations of magnesium in muscle (r = −0.62, P < 0.001), plasma (r = −0.62, P < 0.001), and mononuclear cells (r = −0.47, P < 0.05). The results indicate that some patients with IDDM have lowered contents of magnesium in striated muscular and/ or plasma, and that those parameters are dependent on the degree of diabetic control.
Defect of the First-Phase Insulin Secretion to Glucose Stimulation in the Perfused Pancreas of the Nonobese Diabetic (NOD) Mouse
Authors: Kano Yasuyuki , Kanatsuna Takahiro , Nakamura Naoto , Kitagawa Yoshihiro , Mori Hiroshi , Kajiyama Shizuo , Nakano Koji , Kondo Motoharu
Published: September 2013

To investigate the development of impaired insulin secretion in type I diabetes mellitus, the pancreata of ICR and NOD mice (10–50 wk of age) were perfused. According to insulin responses to 30 mM glucose and to 19 mM arginine, we classified the NOD mice into four groups: those having normal insulin secretion to glucose and to arginine similar to that of control ICR mice (group 1); those with a defect in the first-phase insulin secretion to glucose stimulation but with almost normal insulin secretion to arginine, total insulin release to glucose being significantly smaller than that of group 1 (group 2); those having only a small insulin response to either stimulus, but a fasting plasma glucose level still within the normal range (group 3); and those being overtly diabetic, showing no insulin response to either stimulus (group 4). The severity of insulitis and insulin concentration of the pancreas in each group of NOD mice was well correlated with the insulin release from the perfused pancreas. These results indicate that the initial sign of B-cell damage in NOD mice is a defect of the first phase of glucose-induced insulin secretion, which is followed by a total loss of ability to respond to glucose or arginine stimulation.
Thermal Sensitivity Tester: Device for Quantitative Assessment of Thermal Sense in Diabetic Neuropathy
Authors: Arezzo Joseph C , Schaumburg Herbert H , Laudadio Charles
Published: September 2013

The Thermal Sensitivity Tester (TST) is a portable device designed to quantify the ability to discriminate small differences in temperature at the distal extremities of the hands and feet. The testing surfaces are two identical nickel-coated copper plates, which can be set and maintained over a wide range of temperature levels. The threshold for detecting the colder surface is determined using a two-alternative, forced-choice algorithm. The mean threshold in the normal population is 0.67°C and 1.01°C for the index finger and great toe, respectively. The TST is especially useful in diabetic neuropathy and for rapid screening of large populations under field conditions.
Occurrence of Dawn Phenomenon Without Change in Insulin Clearance in Patients With Insulin-Dependent Diabetes Mellitus
Authors: Campbell Peter J , Gerich John E
Published: September 2013

To assess the possible role of increased insulin clearance in the pathogenesis of the dawn phenomenon, we compared plasma free-insulin concentrations, free-insulin clearance rates, and plasma glucose concentrations in eight subjects with insulin-dependent diabetes mellitus (IDDM) during infusion of insulin from midnight to 0800 h (0.15 mU · kg−1 · min−1) with a Biostator and a Harvard pump. During infusion of insulin with the Biostator, plasma free insulin decreased 40% (from 14 ± 1 to 9 ± 1 μU/ml, P < .01), insulin clearance increased 54% (from 11 ± 1 to 17 ± 2 ml/min, P < .05), and plasma glucose increased from 101 ± 4 to 217 ± 27 mg/dl, P < .01. During infusion of insulin with the Harvard pump, neither plasma free insulin (14 ± vs. 13 ± 1 μU/ml) nor free-insulin clearance (12 ± 2 vs. 13 ± 2 ml/min) changed significantly, but plasma glucose increased from 100 ± 3 to 167 ± 21 mg/dl, P < .01. The increases in plasma glucose during infusion of insulin with the Biostator and the Harvard pump were not significantly different (t = 1.44, P = .19). When insulin was delivered directly into test tubes with the Biostator and the Harvard pump, insulin concentrations in the test tubes decreased 46% over 8 h (P < .05) with the Biostator, whereas no decrease was observed with the Harvard pump. We conclude that the dawn phenomenon can occur without an increase in insulin clearance and that the apparent overnight increase in insulin clearance observed in studies with the Biostator iS artifactual.
Ether-Linked Lysophospholipids Initiate Insulin Secretion: Lysophospholipids May Mediate Effects of Phospholipase A2 Activation on Hormone Release
Authors: Metz Stewart A
Published: September 2013

Phospholipase A2 activation may be a pivotal step in glucose-induced insulin secretion; however, recent studies have focused on only one by-product (arachi-donic acid). To examine the possible role of the other by-product (lysophospholipids), the lysoderivatives of alkylacyl-(ether linked) or diacylphospholipids were applied to rat islets in static incubations. 1-O-alkyl-2-lyso-sn-glyceryl-3-phosphorylcholine [lyso-PAF, the precursor of platelet-activating factor (PAF)] or lyso-phosphatidylcholine initiated insulin release at 1.7 mM glucose. Two preparations of PAF itself (0.005–5000 ng/ml) were without effect at 1.7 or 16.7 mM glucose, but PAF was nearly equipotent to lyso-PAF at >20 μg/ ml. A precursor-product relationship was suggested because the precursors (alkylacyl-or diacylglyceryl-phosphorylcholine) of all three active metabolites were inactive. The stimulatory effect of lyso-PAF is largely independent of any toxic or lytic effect, being biphasic, reversible, unassociated with impairment of the subsequent physiologic functioning of treated islets, and inhibitable (by Ni2+, La3+, or nordihydroguaiaretic acid but not by other lipoxygenase inhibitors). It also occurred at threshold concentrations at which islet morphology and 51Cr retention were preserved. Furthermore, lyso-PAF-induced insulin secretion was markedly impaired by reduced ambient temperature (16°C) or by the impermeant anion isethionate, further implying initiation of true exocytotic granule release and fission. Lyso-PAF (but not arachidonic acid) also circumvented the inhibition of glucose-induced insulin release caused by phospholipase inhibitors. Generation of endogenous lysophospholipids through exogenous application of phospholipase A2 also initiated insulin release, an effect responding to a panel of potential inhibitors identically to that induced by exogenously provided lysophospholipids. We propose that glucose activates phospholipase A2 in the pancreatic islet, leading to the generation of lysophospholipids; the latter may couple energy production to insulin release, at least in part via the promotion of Ca2+ translocation.