bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypoglycemic Thresholds for Cognitive Dysfunction in IDDM
Authors: Blackman John D , Towle Vernon L , Sturis Jeppe , Flewis Gary , Spire Jean-Paul , Polonsky Kenneth S
Published: September 2013

Fourteen poorly controlled insulin-dependent diabetes mellitus (IDDM) patients (HbA1c 11 ± 0.5%) with a mean ± SE duration of disease of 15 ± 2 yr were studied to evaluate the hypoglycemic threshold for cognitive dysfunction under insulin-induced hypoglycemia. The P300 event-related potential, a measure of cognitive function, and reaction time (RT) in response to visual stimuli under euglycemic conditions and at plasma glucose concentrations of 3.5 and 2.5 mM (63 and 45 mg/dl, respectively) during a constant insulin infusion were recorded. Baseline P300 latency was similar to that of a nondiabetic control group, but baseline RT was greater in the IDDM group. There was no increase in P300 latency or RT under euglycemic clamp conditions or at a plasma glucose level of 3.5 mM (63 mg/dl). However, when plasma glucose was lowered to 2.5 mM (45 mg/dl), there was an increase in P300 latency and a prolongation of RT. As plasma glucose returned to baseline, P300 latency and RT remained prolonged. After administration of intravenous glucose and a meal, P300 latency and RT returned to baseline. P140, an event-related potential reflecting sensory processes, was not altered. Because P300 latency changes paralleled RT changes, hypoglycemia appears to slow decision-making processes in IDDM. This study revealed that 1) baseline P300 latency is not elevated in poorly controlled IDDM patients, suggesting no cumulative cognitive dysfunction; 2) the hypoglycemic thresholds for cognitive dysfunction in poorly controlled IDDM are between 2.5 and 3.5 mM (45 and 63 mg/dl, respectively)and are similar to those found in control subjects, suggesting no maladaptive CNS response to hypoglycemia; 3) recovery of cerebral dysfunction, as judged by alterations in P300 latency and RT, lagsbehind the disappearance of hypoglycemia; and 4) there is individual variability to the adverse effects of hypoglycemia on cerebral function.
Growth Hormone Stimulates Skeletal Muscle Protein Synthesis and Antagonizes Insulin's Antiproteolytic Action in Humans
Authors: Fryburg David A , Louard Rita J , Gerow Karynn E , Gelfand Robert A , Barrett Eugene J
Published: September 2013

We examined the effects of a combined, local intra-arterial infusion of growth hormone (GH) and insulin on forearm glucose and protein metabolism in seven normal adults. GH was infused into the brachial artery for 6 h with a dose that, in a previous study, stimulated muscle protein synthesis (phenylalanine Rd) without affecting systemic GH, insulin, or insulinlike growth factor I concentrations. For the last 3 h of the GH infusion, insulin was coinfused with a dose that, in the absence of infused GH, suppressed forearm muscle proteolysis by 30–40% without affecting systemic insulin levels. Measurements of forearm glucose, amino acid balance, and [3H]phenylalanine and [14C]leucine kinetics were made at 3 and 6 h of the infusion. Glucose uptake by forearm tissues in response to GH and insulin did not change significantly between 3 and 6 h. By 6 h, the combined infusion of GH and insulin promoted a significantly more positive net balance of phenylalanine, leucine, isoleucine, and valine (all P < 0.05). The change in net phenylalanine balance was due to a significant increase in phenylalanine Rd (51%, P < 0.05) with no observable change in phenylalanine Ra. For leucine, a stimulation of leucine Rd (50%, P < 0.05) also accounted for the change in leucine net balance, with no suppression of leucine Ra. The stimulation of Rd, in the absence of an observed effect on Ra, suggests that GH blunts the action of insulin to suppress proteolysis in addition to blunting insulin's action on Rd.
Pioglitazone Increases Insulin Sensitivity by Activating Insulin Receptor Kinase
Authors: Kobayashi Masashi , Iwanishi Masanori , Egawa Katsuya , Shigeta Yukio
Published: September 2013

A new oral agent, 5-[4-(2-(5-ethyl 12-pyridyl)ethoxy]- benzoyl]-2,4-thiazolidinedione (pioglitazone), has been developed for treatment of non-insulin-dependent diabetes mellitus (NIDDM). This agent increases insulin sensitivity in vivo in genetically obese Wistar fatty rats. Administration of the agent (3 mg/kg/day) for 10 days to the rats ameliorated hyperglycemia and hyperinsulinemia, indicating that it decreased insulin resistance. To clarify the mechanism of the drug to increase insulin sensitivity, we examined insulin binding and kinase activity of insulin receptors from muscles of both untreated and treated rats. Pioglitazone treatment did not change insulin binding in Wistar fatty rats but increased insulin-stimulated autophosphorylation of insulin receptors to 78% over the level in the control but not the basal state. Kinase activity toward exogenous substrate, poly Glu4Tyr1, was also increased to 87% over the level of untreated control obese rats. In contrast, in lean rats, pioglitazone treatment did not increase autophosphorylation and kinase activity toward exogenous substrates. To further elucidate the mechanism, we incubated insulin receptors with the agent and measured kinase activity. Incubation of solubilized receptors with the agent did not increase kinase activity. However, the receptors from IM-9 cells, which were incubated with 10−8 M pioglitazone for 7 days, showed a 46% increase over the control in insulin-stimulated autophosphorylation and kinase activity. These results suggested that pioglitazone increased insulin sensitivity in part by activating kinase of the receptors through indirect effect on insulin receptors and that the drug may have useful benefits in insulin resistance of NIDDM.
Coordinate Regulation of Amylin and Insulin Expression in Response to Hypoglycemia and Fasting
Authors: Alam Tausif , Chen Ling , Ogawa Atsushi , Leffert Jonathan D , Unger Roger H , Luskey Kenneth L
Published: September 2013

Amylin is a 37–amino acid peptide synthesized in the pancreatic β-cell and cosecreted with insulin. In situ hybridization of nondiabetic rat pancreas shows that insulin and amylin RNA are both localized within the islet of Langerhans in a similar distribution. After 12 days of insulin-induced hypoglycemia (mean blood glucose 3.0 ± 0.4 mM [54 ± 8 mg/dl]), both insulin and amylin RNA fell > 95%. However, maintenance of euglycemia by simultaneous infusion of glucose with insulin did not suppress insulin or amylin RNA. Fasting suppressed amylin and insulin secretion from the isolated, perfused pancreas 70 and 58%, respectively, and with refeeding, secretion rates recovered to fed levels. Despite these changes in the rates of secretion, the relative ratio of amylin to insulin was not significantly different in fed, fasted, or refed rats. The molar ratio of insulin to amylin was estimated to be 100:2.3–2.6. Both insulin and amylin RNA was suppressed ∼ 50% in response to fasting. Thus, although the absolute amounts of insulin and amylin change substantially under the conditions tested, the relative amounts of these peptides do not change.
The Impact of Diabetes on the CNS
Authors: McCall Anthony L
Published: September 2013

The brain is not usually thought to be a target of chronic diabetes complications. Nonetheless, substantial evidence, summarized herein, suggests that diabetes causes brain damage. Clinical syndromes of diabetes-related brain abnormalities are discussed along with possible causes. Various physiological effects of diabetes are reviewed, and questions are raised about gaps in our knowledge. Appropriate directions for future research are suggested.
Sodium-Lithium Countertransport Activity and Insulin Resistance in Normotensive IDDM Patients
Authors: De Faria José B Lopes , Jones Sharon L , MacDonald Fiona , Chambers John , Mattock Martin B , Viberti Giancarlo
Published: September 2013

In insulin-dependent diabetes (IDDM), an overactivity of sodium-lithium countertransport (Na+/Li+ CT) has been associated with the risk of nephropathy and hypertension, two conditions of insulin resistance. We investigated the sensitivity to insulin with a hyperinsulinemic (≈ 719 pM [≈ 100 μU/ml]) euglycemic clamp in two groups of normotensive nonproteinuric IDDM patients; 12 (10 men, 2 women) had high Na+/Li+ CT activity (mean 0.47, range 0.42–0.68 mmol/L red blood cells [RBC]/h, group 1) and 12 (9 men, 3 women) had normal Na+/Li+ CT activity (mean 0.24, range 0.12–0.31 mmol/L RBC/h, group 2). The two groups were similar in age (mean ± SE 36 ± 2 vs. 33 ± 1 yr), duration of diabetes (19 ± 3 vs. 18 ± 2 yr), body mass index (26 ± 0.8 vs. 24 ± 0.6 kg/m2), arterial blood pressure (systolic/diastolic 121 ± 4/79 ± 2 vs. 122 ± 3/77 ± 2 mmHg), and glycemic control (HbA1 8.5 ± 0.4 vs. 8.0 ± 0.4%). Albumin excretion rate (AER) ranged between 4.7 and 148 (geometric mean 14) μg/min in group 1 and between 2.7 and 93 (geometric mean 11) μg/min in group 2. There were four microalbuminuric patients (AER > 30 μg/min) in each group. Whole-body glucose uptake was significantly reduced on average in group 1 compared with group 2 (41.6 ± 2.2 μmol.kg−1 · min−1 [7.48 ± 0.4 mg.kg−1 · min−1] vs. 49.6 ± 2.2 μmol.kg−1 · min−1 [8.93 ± 0.4 mg·kg−1 · min−1 P = 0.03), but some overlap existed between the two groups. dilution with [3-3H]glucose, was similarly suppressed in both study groups. The proportion of echocardiographically determined left ventricular hypertrophy was significantly higher in patients with high Na+/Li+ CT (33 vs. 0%, P = 0.046). Triglycerides (TG), the ratio of low-density lipoprotein (LDL) to high-density lipoprotein (HDL), and apolipoprotein B (apoB) were higher in group 1 (median [range] TG 0.90 [0.51–1.64] vs. 0.52 [0.37–1.26] mM, P = 0.002, LDL-HDL ratio 3.36 [1.43–5.72] vs. 2.28 [1.21–3.33], P = 0.019, apoB 1.06 [0.54–1.16] vs. 0.80 [0.61–1.33] g/L, P = 0.03). In clinically nonproteinuric normotensive IDDM patients, increased Na+/Li+ CT activity is associated with reduced insulin sensitivity, left ventricular hypertrophy, and lipid disturbances. These abnormalities either singly or in combination may contribute to vascular damage in a subset of patients with IDDM.
Prevention by Tetrandrine of Spontaneous Development of Diabetes Mellitus in BB Rats
Authors: Lieberman Irving , Lentz David P , Trucco Giuliana A , Seow W Kim , Thong Y H
Published: September 2013

Treatment of BB rats with the plant alkaloid tetrandrine (20 mg·kg−1· day−1), a novel anti-inflammatory compound, from 35 to 120 days of age reduced the cumulative incidence of spontaneous diabetes from 75.5 to 10.9% (P < 0.001). Dose-response studies with 0, 5, 10, and 20 mg·kg−1·day−1 of tetrandrine from 35 to 130 days resulted in spontaneous diabetes in 84.2, 63.1, 31.6, and 5.3% of the rats, respectively. When the start of treatment with 20 mg·kg−1·day−1 tetrandrine was delayed until 70 days of age, there was a significant reduction of the incidence of diabetes from 63.1 to 28.6% (P < 0.01). Histological examination of the pancreases from tetrandrine-treated rats showed a lesser degree of insulitis than controls (P < 0.01). Drug toxicity was not seen in the rats, as assessed by appearance, behavioral change, organ histology, and blood chemistry. These results provide some hope that tetrandrine may be of value in preventing diabetes and treating newly diagnosed diabetic subjects, either by itself or in combination with a more potent immunosuppressive agent.
Power Spectral Analysis of Heart-Rate Variations Improves Assessment of Diabetic Cardiac Autonomic Neuropathy
Authors: Bellavere Federico , Balzani Italo , De Masi Giovanni , Carraro Maurizio , Carenza Pasquale , Cobelli Claudio , Thomaseth Karl
Published: September 2013

Power spectral analysis (PSA) of heart-rate variations has recently proved a useful tool in evaluating cardiovascular autonomic activity. It offers the possibility of examining both the functioning of parasympathetic and sympathetic pathways through breakdown into two frequency bands, and of their effects on heart-rate cyclic variability. We applied an autoregressive model for PSA to study overall autonomic tone in 20 male age-matched control subjects and 53 insulin-dependent (type I) diabetic subjects, subdivided into three groups of 20, 15, and 18, each group presenting different degrees of autonomic involvement. We found that 1) power spectrum density (PSD) values at high-frequency bands (parasympathetic dependent) were similar in diabetic subjects without cardiac autonomic neuropathy (CAN) and in control subjects, but differed significantly from diabetic subjects with mild CAN and severe CAN, both standing and lying; 2) PSD values at low frequency (mainly sympathetic dependent) were similar, or slightly different, in diabetic subjects without CAN and in control subjects, but differed significantly from diabetic subjects with mild and severe CAN, both standing and lying; 3) as an expression of parasympathetic versus sympathetic coherence, correlations, both standing and lying, existed between PSD values at low- and high-frequency bands in control and diabetic subjects without CAN, but not in diabetic subjects with CAN; and 4) different degrees of correlation characterized the PSD values of high and low frequencies versus traditional cardiovascular test values in the diabetic subjects. The best correlation was between PSD low-frequency values and the lying-to-standing maneuver. frequency values and the lying-to-standing maneuver. These data indicate that PSA 1) can discriminate between differing degrees of parasympathetic involvement, 2) can discriminate between different degrees of sympathetic involvement, and 3) offers a picture of overall autonomic activity that can be explored only partially by traditional cardiovascular autonomic tests and 4) can reveal parasympathetic versus sympathetic dyssynergia. These data suggest that cardiovascular autonomic tests may reflect different aspects of autonomic pathways. Hence, PSA appears to be a powerful tool in the determination of autonomic tone in diabetic CAN.
Dietary Substitution of Medium-Chain Triglycerides Improves Insulin-Mediated Glucose Metabolism in NIDDM Subjects
Authors: Eckel Robert H , Hanson Alan S , Chen Arnold Y , Berman Jeffrey N , Yost Trudy J , Brass Eric P
Published: September 2013

Dietary medium-chain triglycerides (MCT) may improve insulin-mediated glucose metabolism. To examine this possibility, 10 non-insulin-dependent diabetes mellitus (NIDDM) patients, 4 hypertriglyceridemic, and 6 normotriglyceridemic nondiabetic control subjects were examined with a 5-day cross-over design, in which the short-term metabolic effects of a 40% fat diet containing 77.5% of fat calories as MCT were compared with an isocaloric long-chain triglyceride-containing diet. In diabetic patients, MCT failed to alter fasting serum glucose concentrations but reduced preprandial glycemic excursions by 45% (F = 7.9, P < 0.01). On MCT, the amount of glucose needed to maintain euglycemia during an intravenous insulin infusion was increased in diabetic subjects by 30%, in hypertriglyceridemic subjects by 30%, and in normotriglyceridemic control subjects by 17%. MCT increased mean ± SE insulin-mediated glucose disposal (4.52 ± 0.56 vs. 2.89 ± 0.21 mg.kg−1 · min−1; n = 3, P < 0.05) but failed to alter basal glucose metabolism or insulin-mediated suppression of hepatic glucose output. Metabolic responses to MCT were observed independent of sulfonylurea therapy or severity of fasting hyperglycemia. No change in fasting serum insulin or triglyceride concentrations were seen with MCT administration. Although MCT increased mean fasting serum β-hydroxybutyrate levels from 0.10 ± 0.03 to 0.26 ± 0.06 mM (P < 0.05) in normotriglyceridemic nondiabetic subjects, no change was seen in diabetic patients. Thus, MCT-containing diets increased insulin-mediated glucose metabolism in both diabetic patients and nondiabetic subjects. In diabetic subjects, this effect appears to be mediated by increases in insulin-mediated glucose disposal. MCT may be a promising adjunct to conventional dietary and sulfonylurea treatment in NIDDM.
Why Intraperitoneal Delivery of Insulin With Implantable Pumps in NIDDM?
Authors: Duckworth William C , Saudek Christopher D , Henry Robert R
Published: September 2013

In the normal state, pancreatic secretion of insulin results in a portal/peripheral gradient with the highest concentrations of insulin in the liver. In diabetic patients with absent or insufficient pancreatic insulin secretion who require exogenous insulin, this normal gradient is lost, resulting in numerous abnormalities. This consideration led to interest in the intraperitoneal delivery of insulin, hoping to produce a therapeutic state more closely resembling normal physiology. The development of implantable insulin pumps, which can deliver insulin intraperitoneally, led to numerous studies on insulin-dependent diabetes mellitus (IDDM) patients, demonstrating that insulin delivered intraperitoneally is rapidly and predictably absorbed with most of it going into the portal system, resulting in hepatic delivery of insulin. Studies in IDDM patients have demonstrated that good glucose control can be achieved with intraperitoneal delivery of insulin from implantable pumps with lesser glycemic fluctuations and, therefore, fewer episodes of hypoglycemia. Furthermore, intraperitoneal insulin results in carbohydrate and particularly lipid metabolism that more closely mimics the normal physiological state than produced by injections of insulin. Thus, implantable insulin pumps are being studied for use in IDDM. Many non-insulin-dependent diabetes mellitus (NIDDM) patients have insufficient pancreatic secretion and require exogenous insulin. Because of alterations in hepatic sensitivity to insulin, increments in insulin delivery to the liver may be even more important in NIDDM than IDDM. Furthermore, insulin resistance, which is an integral part of NIDDM, results in higher physiological levels of insulin, which are required for glucose control, and thus significant peripheral hyperinsulinemia occurs in patients receiving exogenous insulin. Because of hepatic extraction, intraperitoneal administration of insulin in NIDDM could provide sufficient insulin to the liver to control hepatic metabolism and reduce peripheral insulin levels, the risk for atherosclerosis, and other adverse effects of hyperinsulinemia. Because of these considerations, a Veterans Affairs Cooperative Study examining the use of implantable insulin pumps delivering intraperitoneal insulin in NIDDM patients was initiated to determine whether this is a feasible approach to NIDDM patients' therapy and whether this results in beneficial effects on carbohydrate and lipid metabolism and peripheral insulin levels
Stimulus-Secretion Coupling in β-Cells of Transplantable Human Islets of Langerhans: Evidence for a Critical Role for Ca2+ Entry
Authors: Misler Stanley , Barnett David W , Pressel David M , Gillis Kevin D , Scharp David W , Falke Lee C
Published: September 2013

With human islets isolated for transplantation, we examined the applicability to humans of a metabolic fuel hypothesis of glucose transduction and a Ca2+ hypothesis of depolarization-secretion coupling, both previously proposed for rodent islet β-cells. We report that several features of human β-cell physiology are well accounted for by these hypotheses. With whole-islet perifusion, we demonstrated that insulin secretion induced by glucose, tolbutamide, or elevated K+ is dependent on extracellular Ca2+. Insulin release induced by these secretagogues is enhanced by the dihydropyridine Ca2+ channel agonist BAYk8644 and depressed by the dihydropyridine Ca2+-channel antagonist nifedipine. All of the aforementioned secretagogues provoke increases in cytosolic free Ca2+, which are dependent on extracellular Ca2+ and are altered by the dihydropyridine drugs. Individual β-cells in the islet display diminished resting membrane conductance, graded depolarization, and complex electrical patterns, including bursts of action potentials in response to stimulatory concentrations of glucose or tolbutamide. Individual islet β-cells display voltage-dependent Ca2+ currents that are activated at membrane potentials traversed during the excursion of the action potential. In most cells, the Ca2+ currents are enhanced by BAYk8644 and depressed by nifedipine at concentrations that have parallel effects on secretagogue-induced increases in cytosolic Ca2+ and insulin secretion. These survey studies should provide the basis for more detailed investigations of the relationship of voltage-dependent ionic currents to electrical activity patterns and of electrical activity patterns to granule exocytosis in single human β-cells.
Attenuated Glucose Recovery from Hypoglycemia in the Elderly
Authors: Marker James C , Cryer Philip E , Clutter William E
Published: September 2013

Advanced age is a risk factor for hypoglycemia caused by sulfonylureas (and insulin) used to treat diabetes mellitus. Therefore, we hypothesized that there is an age-associated impairment of glucose counterregulation and further that this is the result of a sedentary life-style. To test these hypotheses, glycemic and neuroendocrine responses to hypoglycemia, produced by 0.05 U/kg body wt insulin i.v. were measured in nondiabetic elderly subjects (age 65.1 ± 0.9 yr n = 23)–and in a subset (n = 11) again after 1 yr of physical training (which increased VO2 max by 5.2 ± 0.9 ml · kg−1 · min−1 P < 0.05)–and compared with these responses in nondiabetic young subjects (23.8 ± 0.6 yr, n = 18). Recovery from hypoglycemia was attenuated (analysis of variance P < 0.001) in the elderly (plasma glucose recovery rate 29.4 ± 2.2 vs. 42.7 ± 5.0 μM/min, P < 0.02). This attenuation was the result of a smaller counterregulatory increment in glucose production (maximum increment 13.3 ± 1.1 vs. 17.2 ± 1.1 μmol · kg−1 · min−1; P < 0.05) rather than a greater increment in glucose utilization in the elderly. The attenuated glucose recovery was associated with higher plasma insulin concentrations (maximum increment 1385 ± 122 vs. 940 ± 72 pM, P < 0.01) and reduced glucagon responses to hypoglycemia (maximum increment 43 ± 6 vs. 66 ± 12 ng/L). The epinephrine, norepinephrine, cortisol, and growth hormone responses were similar, although the epinephrine response was slightly delayed and the growth hormone response appeared smaller in the elderly. Training had no effect on glucose recovery from or neuroendocrine responses to hypoglycemia in the elderly. Thus, we conclude that there is an age-associated impairment of glucose counterregulation best attributed to decreased insulin clearance, reduced glucagon secretion, or both. Delayed epinephrine secretion may also contribute. These are not the result of a sedentary life-style.
Relative Hypersecretion of Amylin to Insulin from Rat Pancreas After Neonatal STZ Treatment
Authors: Inoue Kaoru , Hisatomi Akitaka , Umeda Fumio , Nawata Hajime
Published: September 2013

With isolated perfused pancreases from normal and diabetic model rats, we studied alterations of the secretion of islet amyloid polypeptide, or amylin, which has been recently identified as a major component of amyloid deposits in the pancreatic islets of patients with non-insulin-dependent diabetes mellitus. Neonatal (n) Wistar-King albino rats given streptozocin (STZ) on the 2nd (n2STZ) or 5th (n5STZ) neonatal day exhibited moderate and marked elevations, respectively, of plasma glucose and HbA1 as adults compared with control rats given the vehicle. The release of amylin from the perfused pancreases in response to glucose and arginine paralleled that of insulin in all three groups. However, the molar ratio of secreted amylin to insulin in response to 16.7 mM glucose by n5STZ pancreases (6.55 ± 0.71%) was significantly greater that for either n2STZ (1.71 ± 0.24%, P < 0.05) or the control (0.60 ± 0.03%, P < 0.05) pancreases. The secreted amylin-insulin ratio of n2STZ pancreases also was significantly > that of the controls (P < 0.05). The increased amylin-insulin molar ratios of both n2STZ and n5STZ pancreases also occurred during infusions of 33.3 mM glucose and 10 mM arginine. These findings suggest that amylin secretion may be preserved in diabetic rats with reduced β-cell mass and that hyperglycemia may increase amylin production independently of that of insulin, which may be significant in the pathogenesis of non-insulin-dependent diabetes mellitus.
Prospective Study of Microalbuminuria as Predictor of Mortality in NIDDM
Authors: Mattock Martin B , Morrish Nicholas J , Viberti Giancarlo , Keen Harry , Fitzgerald Anthony P , Jackson Gordon
Published: September 2013

Retrospective studies of patients with non-insulin-dependent diabetes mellitus (NIDDM) have suggested that microalbuminuria predicts early all-cause (mainly cardiovascular) mortality independently of arterial blood pressure. These findings have not been confirmed in prospective studies, and it is not known whether the predictive power of microalbuminuria is independent of other major cardiovascular risk factors. During 1985–1987, we examined a representative group of 141 nonproteinuric patients with NIDDM for the prevalence of coronary heart disease and several of its established and putative risk factors, including raised urinary albumin excretion (UAE) rate. Thirty-six patients had microalbuminuria (UAE 20–200 μg/min), and 105 had normal UAE (< 20 μg/min). At follow-up, an average of 3.4 yr later, 14 patients had died. There was a highly significant excess mortality (chiefly from cardiovascular disease) among those with microalbuminuria (28%) compared to those without microalbuminuria (4%, P < 0.001). In univariate survival analysis, significant predictors of all-cause mortality included microalbuminuria (P < 0.001), hypercholesterolemia (P < 0.01), hypertriglyceridemia (P < 0.05), and preexisting coronary heart disease (P < 0.05). The predictive power of microalbuminuria persisted after adjustment for the effects of other major risk factors (P < 0.05). We conclude that microalbuminuria is a significant risk marker for mortality in NIDDM, independent of the other risk factors examined. Its presence can be regarded as an index of increased cardiovascular vulnerability and a signal for vigorous efforts at correction of known risk factors.
Colocalization of GLUT2 Glucose Transporter, Sodium/glucose Cotransporter, and γ-Glutamyl Transpeptidase in Rat Kidney With Double-Peroxidase Immunocytochemistry
Authors: Cramer Steven C , Pardridge William M , Hirayama Bruce A , Wright Ernest M
Published: September 2013

Glucose is reabsorbed from the glomerular filtrate in the proximal segment of the renal tubule in two stages. The first stage is uphill transport across the brush border membrane by Na+-glucose cotransport and the second stage is downhill transport across the basolateral membrane by facilitated diffusion. Genes for both a renal Na+-glucose cotransporter (SGLT1) and a renal facilitated glucose transporter (GLUT2) have been cloned and sequenced. To examine whether SGLT1 and GLUT2 colocalize to the same tubular epithelial cells in rat kidney, double-immunoperoxidase studies with dual chromogens and paraformaldehyde perfusion-fixed frozen sections of rat kidney were performed. Antipeptide antisera were prepared against rat GLUT2 (amino acids 510–522) and rabbit SGLT1 (amino acids 402–420). Proximal tubules were identified immunocytochemically with an antiserum raised against a synthetic peptide corresponding to the 21 amino acids at the COOH-terminal of the heavy chain of rat γ-glutamyl transpeptidase, which is a proximal tubule-specific enzyme. The anti-GLUT2 antiserum strongly stained the basolateral membrane of 46% of cortical tubules, whereas the SGLT1 antiserum stained the brush border of 56% of the cortical tubules. The γ-glutamyl transpeptidase antiserum also stained the brush border of 51% of the cortical tubules. GLUT2 and SGLT1 colocalized to 40% of cortical epithelium, but 16% of cortical epithelial cells were immunopositive for brush border SGLT1 and immunonegative for basolateral GLUT2. These γ-glutamyl transpeptidase staining results suggest that at least 50% of the tubules in the cortex are proximal tubules and that SGLT1 and GLUT2 colocalize to most proximal tubules. The fact that SGLT1 antiserum immunoreacted with tubules unreactive to the GLUT2 antiserum suggests that either the SGLT1 epitope is conserved on a related brush border protein or that there is another GLUT transporter responsible for the exit of sugar from these proximal tubule cells.
Antibodies to GAD and Tryptic Fragments of Islet 64K Antigen as Distinct Markers for Development of IDDM: Studies With Identical Twins
Authors: Christie Michael R , Tun Richard Y M , Lo Simon S S , Cassidy David , Brown Thomas J , Hollands Jacqueline , Shattock Marion , Bottazzo Gian Franco , Leslie R David G
Published: September 2013

Insulin-dependent diabetes mellitus (IDDM) is associated with antibodies to a 64,000-Mr islet cell protein, at least part of which is identified as glutamic acid decarboxylase (GAD). These antibodies are detected as two distinct antibody specificities to 50,000-Mr and 37,000/40,000-Mr tryptic fragments of the autoantigen (50K and 37K antibodies, respectively). We determined the frequencies of antibodies to intact GAD, tryptic fragments of islet 64,000-Mr antigen, islet cell antibodies (ICAs), and insulin autoantibodies (IAAs) in sera from 58 nondiabetic identical twins of patients with IDDM, of whom 12 subsequently developed diabetes. ICA, antibodies to intact GAD, and those to tryptic fragments were detected at similar frequencies in prediabetic twins (67–75%), but only 25% had IAA. Of 46 twins who remain nondiabetic, GAD antibodies, 50K antibodies, and ICA were detected in 6 (13%), 7 (15%), and 5 (11%), respectively, whereas only 1 (2%) possessed 37K antibodies and 2 (4%) had IAA. Eight of 9 twins with 37K antibodies and all 6 twins with ICA > 20 Juvenile Diabetes Foundation U have developed diabetes. Antibodies to GAD are sensitive markers for diabetes development but may also be present in genetically susceptible individuals who are unlikely to develop disease. Antibodies to 37,000/40,000-Mr fragments of the 64,000-Mr antigen or high-titer ICA were the best markers for diabetes development in these twins.
No Independent Association Between HSP70 Gene Polymorphism and IDDM
Authors: Pugliese Alberto , Awdeh Zuheir L , Galluzzo Aldo , Yunis Edmond J , Alper Chester A , Eisenbarth George S
Published: September 2013

A role for heat shock proteins (HSPs) in autoimmunity has recently been suggested by several authors. Autoantibodies against HSPs have been associated with such autoimmune diseases as systemic lupus erythematosus, polymyositis, and the NOD mouse model of diabetes. Moreover, genes for the major 70,000-Mr HSP (HSP70) are located within the MHC. To investigate a potential association of an HSP70–2 gene polymorphism with insulin-dependent diabetes mellitus (IDDM), we analyzed restriction-fragment–length polymorphism (RFLP) of this gene in 29 families with one or more member affected by IDDM. With the enzyme PstI, as reported previously, two HSP70–2 alleles of 8.5- and 9.0-kb were found. The 8.5-kb allele was found more frequently on diabetic haplotypes compared with control haplotypes (41 of 66 [62%] vs. 20 of 46 [43%], P = 0.03). This association was due to the conservation of alleles on extended haplotypes we previously reported to be associated with diabetes on initial analysis of families. Twenty-three of 26 diabetic DR3 haplotypes and 3 of 3 normal DR3 haplotypes and all instances of [HLA-B8, SC01, DR3] and [HLA-B18, F1C30, DR3] had the 8.5-kb allele, whereas 0 of 9 normal DR2 haplotypes and 0 of 2 diabetic DR2 haplotypes had the 8.5-kb allele (P = 8 × 10−7 DR3 vs. DR2 haplotypes). The alleles were equally distributed among DR4 haplotypes. Our studies indicate that the 8.5-kb allele is part of [HLA-B8, SC01, DR3] and [HLA-B18, F1C30, DR3] haplotypes, and the 9.0-kb allele is associated with DR2 but no independent association (greater than DR association) is found between HSP70–2 alleles and diabetes.
Association of 24-h Cardiac Parasympathetic Activity and Degree of Nephropathy in IDDM Patients
Authors: Mølgaard Henning , Christensen Per D , Sørensen Keld E , Christensen Cramer K , Mogensen Carl E
Published: September 2013

In insulin-dependent diabetic patients, nephropathy is a predictor of mortality and coronary heart disease. Impaired cardiac vagal function is an important factor in the pathophysiology of sudden cardiac death in coronary heart disease. Autonomic neuropathy in diabetes in particular involves vagal function. Bedside tests and 24-h measurements of cardiac parasympathetic activity were compared in 37 insulin-dependent diabetic patients, and the relationship between 24-h vagal activity and degree of nephropathy was investigated. Nephropathy was classified according to urinary albumin excretion as normoalbuminuria, incipient, and overt nephropathy. Mean age (∼ 30 yr) was not different among groups. The 24-h measurements of parasympathetic activity appeared more sensitive than bedside tests, as 33% of patients without cardiac autonomic neuropathy in bedside tests had 24-h vagal activity values below the 95% confidence limits of 14 healthy control subjects. Patients with incipient or overt nephropathy had significantly lower mean values for vagal activity during both wake and sleep time than healthy control subjects. Increasing degree of nephropathy was associated significantly with increasing attenuation of 24-h vagal activity (P < 0.001). The covariation of degree of neuropathy and nephropathy may suggest common pathogenetic mechanisms. The reduced 24-h vagal activity, even in the early stages of nephropathy, could be an important risk factor for cardiac death in insulin-dependent diabetic patients.
Differential Expression of Retinal Insulin Receptors in STZ-Induced Diabetic Rats
Authors: Zetterström Charlotta , Benjamin Ann , Rosenzweig Steven A
Published: September 2013

A major complication of diabetes mellitus is retinopathy, which is characterized by increased neovascularization and neuronal degeneration in the retina. The biochemical processes underlying these changes are largely unknown. To better understand the role(s) of insulin or its lack and the resultant hyperglycemia in the etiology of these events, peripheral and neuronal (having 125 kDa and 115 kDa alpha subunits, respectively) insulin receptor subtype levels in the retinas of Streptozocin-induced diabetic rats were quantified. Immunoblot analysis of wheat germ agglutinin-agarose purified retinal membrane proteins revealed that retinas from diabetic rats expressed higher insulin receptor levels than retinas from control rats. This increase reflected a doubling of neuronal and a ∼20% decrease in peripheral insulin receptor subtypes, respectively. Insulin-treated diabetic rats had neuronal receptor levels equal to control values, at the same time having a further reduced number of peripheral insulin receptors relative to controls. Affinity labeling analysis of WGA-purified retinal membrane proteins indicated a 1.5-fold increase in neuronal and a 9% decrease in peripheral receptor subtypes, corroborating the immunoblot analysis. Neuronal insulin receptors in WGA-purified cortical synaptosomal membranes also were increased in diabetic rats, with insulin treatment reducing this effect. The up-regulated receptors retained their ability to undergo insulin-dependent autophosphorylation and, as such, did not appear functionally impaired. These data suggest that the expression of neuronal insulin receptors in retina and brain and peripheral insulin receptors in the retina of diabetic rats is sensitive to levels of insulin/glucose in peripheral circulation.
Nutrition and Somatomedin XXIX: Molecular Regulation of IGFBP-1 in Hepatocyte Primary Culture
Authors: Villafuerte B C , Goldstein S , Robertson D G , Pao C -I , Murphy L J , Phillips L S
Published: September 2013

The insulinlike growth factors (IGFs) circulate in association with insulinlike growth factor binding proteins (IGFBPs) that modulate IGF action, but mechanisms of IGFBP regulation are poorly understood. We investigated the regulation of IGFBPs in primary cultures of rat hepatocytes, measuring the appearance of export proteins by ligand blotting after separation via SDS/PAGE, and evaluating mRNA with cDNA probes. Northern blotting studies revealed that IGFBP-1 was expressed at high levels in cultured hepatocytes, in which sustained release of both insulinlike growth factor I and albumin marks preservation of differentiated status. In contrast, transcripts of IGFBP-3 and IGFBP-2 were not detected. Release of IGFBP-1 was unaffected by exposure to glucose (20–500 mg/dl) or to provision of amino acids (0.25'6.25 times normal rat arterial plasma levels). Hormonal studies revealed little effect of glucagon, inhibition by insulin, stimulation by dexamethasone, and blunting of dexamethasone effects by added insulin. Adding dexamethasone provided progressive stimulation: 5-, 11-, and 26-fold at 10−9, 10−8, and 10−7 M, all P < 0.01; increases in IGFBP-1 protein (ligand blot) and IGFBP-1 mRNA (Northern blot) were highly correlated (r = 0.62, P < 0.001). In contrast, adding insulin resulted in progressive suppression of both IGFBP-1 protein and IGFBP-1 mRNA, 43% at 10−10 M, 74% at 10−9 M, and 83% (maximal) at 10−8 M; ED50 of ∼ 10−10 M is within the physiological range of insulin concentrations. Directly adding growth hormone and insulinlike growth factor I had little effect, whereas adding insulinlike growth factor I attenuated the effect of insulin to decrease IGFBP-1 release. Exposure to insulin at 10−6 M did not change IGFBP-1 gene expression at 30 min, but suppressed IGFBP-1 mRNA 37% at 90 min and 97% at 180 min (t1/2 ∼110 min). IGFBP-1 release by normal rat hepatocytes is stimulated by dexamethasone and inhibited by insulin, apparently modulated at pretranslational levels. This system should be useful for further studies of biological regulation and underlying molecular mechanisms.
Genetic Marker Associations With Proliferative Retinopathy in Persons Diagnosed With Diabetes Before 30 yr of age
Authors: Cruickshanks Karen J , Vadheim Constance M , Moss Scot E , Roth M -P , Riley William J , MacLaren Noel K , Langfield Deston , Sparkes Robert S , Klein Ronald , Rotter Jerome I
Published: September 2013

It has been suggested that HLA-DR4 is a marker of genetic predisposition to proliferative retinopathy. To investigate this relationship and potential associations between other polymorphic genes and proliferative retinopathy, a sample (n = 428) of participants in the population-based Wisconsin Epidemiologic Study of Diabetic Retinopathy was selected for typing for HLA-A, -B, -C, and -DR and a panel of other polymorphic genes. The presence of proliferative retinopathy was determined from grading of stereoscopic color fundus photographs taken at 2 examinations, 4 yr apart. In logistic regression models with repeated measures, persons with HLA-DR4 who were negative for DR3 were five times more likely to have proliferative retinopathy than those negative for both antigens after adjusting for other potential risk factors (Odds ratio = 5.43, 95% Confidence Interval (Cl) = 1.04, 28.30). HLA-C2, AK-2, and MNSs-S also were associated positively with proliferative retinopathy, and HLA-DR8 was associated inversely with this complication of diabetes in each case before adjusting for the number of comparisons. These data suggest that the genetically determined immunopathic mechanisms leading to diabetes, and in linkage disequilibrium with DR4, may independently contribute to the development of proliferative retinopathy.
Improvement of Nerve Conduction in Diabetic Neuropathy: A Follow-up Study 4 Yr After Combined Pancreatic and Renal Transplantation
Authors: Solders Göran , Tydén Gunnar , Persson Anders , Groth Carl-Gustav
Published: September 2013

Eighteen patients with long-standing insulin-dependent (type 1) diabetes mellitus and polyneuropathy were studied after combined pancreatic and renal transplantation. Repeated tests were performed on peripheral nerve function (electroneurography) and on autonomic function (R-R test) 6 mo and 1, 2, and 4 yr after the transplantation. Eighteen diabetic patients with only a kidney graft served as controls. After initial improvement of nerve conduction in both groups, probably caused by the elimination of uremia, further improvement was seen only in the euglycemic pancreas-graft recipients. Improvement of autonomic (parasympathetic) function was slight after 48 mo and was similar in both groups.
Evidence for Unique Distribution of Kimmelstiel-Wilson Nodules in Glomeruli
Authors: Sandison Ann , Newbold K Mark , Howie Alexander J
Published: September 2013

Different distributions of segmental lesions within glomeruli correspond to different pathogenetic mechanisms. A graphic method of analysis of the position of segmental lesions was applied to 106 Kimmelstiel-Wilson nodules in 10 renal biopsies from patients with diabetic glomerulonephropathy, 4 with IDDM and 6 with NIDDM. The nodules were randomly distributed in a horseshoe-shaped area corresponding to the peripheral or intralobular mesangium. This distribution was different from that of segmental lesions studied previously in the glomerular tip lesion, in vasculitic-type glomerulonephritis, and in hyperfiltration associated with reduced renal mass. Our finding is consistent with ideas that Kimmelstiel-Wilson nodules have a distinct pathogenesis not related to hyperfiltration or any other process previously investigated as a cause of characteristic distribution of segmental lesions.
Ketone Body Metabolism in NIDDM: Effect of Sulfonylurea Treatment
Authors: Avogaro Angelo , Valerio Anna , Gnudi Luigi , Maran Alberto , Zolli Mario , Duner Elena , Riccio Antonio , Prato Stefano Del , Tiengo Antonio , Nosadini Romano
Published: September 2013

We assessed the metabolism of the two KBs, AcAc and 3-BOH; the relationships between ketogenesis and FFA inflow rate; and the effect of chronic sulfonylurea treatment in mild NIDDM patients (plasma glucose < 10 mM). We studied 10 nonobese NIDDM patients in a crossover, randomized, double-blind, placebo-controlled fashion. Each patient was studied 4 times: after a run-in period with placebo, after 3 mo of placebo treatment, after 3 mo of glibenclamide treatments, respectively, and after 3 mo of sulfonylurea treatment during an acute exogenous Intralipid infusion. Ten normal, nondiabetic subjects served as the control group. Glibenclamide treatment decreased plasma FFAs. When these substrates were exogenously increased, plasma FFAs were comparable with placebo and baseline concentrations. In NIDDM patients, baseline and placebo blood total KB concentration was significantly higher than in control subjects (216 ± 22 and 244 ± 25, respectively vs. 127 ± 18 μM; P < 0.01). Glibenclamide treatment significantly decreased total KBs to 177 ± 19 μM (P < 0.05). When FFAs were exogenously increased, total KBs were similar to the placebo and baseline period. In the baseline study, the AcAc/3-BOH ratio was 0.72 ± 0.06 in control subjects, whereas in NIDDM patients, the ratio was 1.61 ± 0.13 at baseline (P < 0.001 vs. control subjects), 1.66 ± 0.15 during placebo, 1.57 ± 0.09 during glibenclamide (NS vs. baseline), and 1.51 ± 0.23 during glibenclamide plus placebo FFAs. Both the AcAc interconversion rate to 3-BOH and the 3-BOH interconversion rate to AcAc were significantly lower in NIDDM patients than in control subjects. In conclusion, in NIDDM patients the major portion of overall ketogenesis must be ascribed to AcAc production. 3-BOH production is decreased because of an impaired interconversion between the two ketones. A direct effect of glibenclamide on ketogenesis in vivo is disputable because blood KB concentrations increase to a similar extent for a given plasma FFA concentration in the presence or absence of this drug.
Variation in Sorbitol Accumulation and Polyol-Pathway Activity in Cultured Human Proximal Tubule Cells
Authors: Flath Mary C , Bylander John E , Sens Donald A
Published: September 2013

The polyol pathway is present in tissues of several organs where its activation may participate in the development of diabetic complications. We measured the accumulation of polyol-pathway intermediates in HPT cells isolated from 21 different human kidneys from nondiabetic individuals. When exposed to 27.5 mM glucose in the growth media, cells isolated from ∼75% of individuals (accumulators) accumulated sorbitol within 1–4 days, whereas 25% (nonaccumulators) accumulated only negligible amounts, even when the period of exposure was extended to 2 wk. Surprisingly, measurement of the activities of the polyol-pathway enzymes showed no difference in the levels of either AR or SDH between accumulators and nonaccumulators, even when the conversion of galactose to galactitol was used to measure AR activity in intact cells independently of SDH. Measurement of sorbitol in the growth media indicated that nonaccumulators were not releasing sorbitol into the growth media. Fructose levels in the conditioned growth media were 4 times higher in the sorbitol-accumulating cells. Together, these results indicate that the tendency of cells from an individual to accumulate significant amounts of sorbitol may reflect the cells' ability to metabolize sorbitol in steps subsequent to the polyol pathway.
Impaired Insulin-Mediated Skeletal Muscle Blood Flow in Patients With NIDDM
Authors: Laakso Markku , Edelman Steven V , Brechtel Ginger , Baron Alain D
Published: September 2013

Patients with non-insulin-dependent diabetes metlitus (NIDDM) exhibit decreased rates of skeletal muscle insulin-mediated glucose uptake (IMGU). Because IMGU is equal to the product of the arteriovenous glucose difference (AVGΔ) across and blood flow (F) into muscle (IMGU = AVGΔ × F), reduced tissue permeability (AVGΔ) and/or glucose and insulin delivery (F) can potentially lead to decreased IMGU. The components of skeletal muscle IMGU were studied in six obese NIDDM subjects (103 ± 9 kg) and compared with those previously determined in six lean (weight 68 ± 3 kg), and six obese (94 ± 3 kg) with normal glucose tolerance. The insulin dose-response curves for whole body and leg muscle IMGU were constructed using the combined euglycemic clamp and leg balance techniques during sequential insulin infusions (range of serum insulin 130–80,000 pmol/L). In lean, obese, and NIDDM subjects, whole body IMGU, femoral AVGΔ, and leg IMGU increased in a dose-dependent fashion over the range of insulin with an ED50 of 400–500 pmol/L in lean, 1000–1200 pmol/L in obese, and 4000–7000 pmol/L in NIDDM subjects (P < 0.01 lean vs. obese and NIDDM). In lean and obese subjects, maximally effective insulin concentrations increased leg blood flow ∼2-fold from basal with an ED50 of 266 pmol/L and 957 pmol/L, respectively (P < 0.01 lean vs. obese). In contrast, leg F did not increase from the basal value in NIDDM subjects (2.7 ± 0.1 vs. 3.5 ± 0.5 dl/min, NS). In the physiological range of insulin concentrations NIDDM subjects had lower body IMGU, leg F, femoral AVGΔ, and leg IMGU than obese and lean subjects, but at maximally effective insulin concentrations, femoral AVGA did not differ between obese and NIDDM subjects. Thus, 1) both reduced skeletal muscle tissue permeability and blood flow are found in NIDDM subjects and 2) impaired insulin-mediated augmentation of skeletal muscle blood flow in obese NIDDM patients is due to the diabetic state per se and not to the obesity status. Whether reduced skeletal muscle blood flow is the result or the cause of insulin resistance in patients with NIDDM remains to be elucidated.