Showing papers in "Diabetes in 1995"

U.K. prospective diabetes study 16. Overview of 6 years' therapy of type II diabetes: a progressive disease

Abstract: The objective of the U.K. Prospective Diabetes Study is to determine whether improved blood glucose control in type II diabetes will prevent the complications of diabetes and whether any specific therapy is advantageous or disadvantageous. The study will report in 1998, when the median duration from randomization will be 11 years. This report is on the efficacy of therapy over 6 years of follow-up and the overall incidence of diabetic complications. Subjects comprised 4,209 newly diagnosed type II diabetic patients who after 3 months' diet were asymptomatic and had fasting plasma glucose (FPG) 6.0–15.0 mmol/l. The study consists of a randomized controlled trial with two main comparisons: 1) 3,867 patients with 1,138 allocated to conventional therapy, primarily with diet, and 2,729 allocated to intensive therapy with additional sulfonylurea or insulin, which increase insulin supply, aiming for FPG <6 mmol/l; and 2) 753 obese patients with 411 allocated to conventional therapy and 342 allocated to intensive therapy with metformin, which enhances insulin sensitivity. In the first comparison, in 2,287 subjects studied for 6 years, intensive therapy with sulfonylurea and insulin similarly improved glucose control compared with conventional therapy, with median FPG at 1 year of 6.8 and 8.2 mmol/l, respectively (P < 0.0001). and median HbA1c of 6.1 and 6.8%, respectively (P < 0.0001). During the next 5 years, the FPG increased progressively on all therapies (P < 0.0001) with medians at 6 years in the conventional and intensive groups, FPG 9.5 and 7.8 mmol/l, and HbA1c 8.0 and 7.1%, respectively. The glycemic deterioration was associated with progressive loss of β-cell function. In the second comparison, in 548 obese subjects studied for 6 years, metformin improved glucose control similarly to intensive therapy with sulfonylurea or insulin. Metformin did not increase body weight or increase the incidence of hypoglycemia to the same extent as therapy with sulfonylurea or insulin. A high incidence of clinical complications occurred by 6-year follow-up. Of all subjects, 18.0% had suffered one or more diabetes-related clinical endpoints, with 12.1% having a macrovascular and 5.7% a microvascular endpoint. Sulfonylurea, metformin, and insulin therapies were similarly effective in improving glucose control compared with a policy of diet therapy. The study is examining whether the continued improved glucose control, obtained by intensive therapy compared with conventional therapy (median over 6 years HbA1c 6.6% compared with 7.4%), will be clinically advantageous in maintaining health.

Lipotoxicity in the pathogenesis of obesity-dependent NIDDM: Genetic and clinical implications

Abstract: We review evidence that increased tissue levels of fatty acyl CoA cause the beta-cell abnormalities of nondiabetic obesity and ultimately result in obesity-dependent diabetes. Nondiabetic obesity in Zucker rats is characterized by hypersecretion of insulin at normal fasting and subfasting glucose concentrations. This is a result of beta-cell hyperplasia and increased low Km glucose usage and oxidation. These abnormalities, the hyperinsulinemia, the hyperplasia of beta-cells, i.e., its in vitro equivalent, enhanced bromodeoxyuridine incorporation, and the increased low Km glucose usage can be induced by culturing normal islets with 2 mmol/l free fatty acids (FFAs). Once obese Zucker diabetic fatty rats become diabetic, glucose-stimulated insulin secretion (GSIS) is absent and beta-cell GLUT2 reduced. Islet triglyceride (TG) content is increased 10-fold, probably reflecting increased FFA delivery (plasma FFA levels > 1.5 mmol/l) beginning about 2 weeks before the onset of diabetes. These beta-cell abnormalities, GSIS loss, GLUT2 loss, and TG accumulation, are prevented by reducing plasma FFAs by caloric restriction and by nicotinamide injection. The loss of GSIS and the accumulation of TGs, but not the GLUT2 loss, can be induced in vitro in normal islets cultured in a 2 mmol/l FFA-containing medium, but prediabetic islets seem far more vulnerable to FFA-induced functional impairment and TG accumulation. It is proposed that in uncomplicated obesity, increased lipid availability (FFA levels < 1.5 mmol/l) induces both hyperinsulinemia and insulin resistance in parallel fashion, thereby maintaining normoglycemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Both Subcutaneously and Intravenously Administered Glucagon-Like Peptide I Are Rapidly Degraded From the NH2-Terminus in Type II Diabetic Patients and in Healthy Subjects

Abstract: To fate of exogenous glucagon-like peptide I (GLP-I)(7-36) amide was studied in nondiabetic and type II diabetic subjects using a combination of high-pressure liquid chromatography (HPLC), specific radioimmunoassays (RIAs), and a sensitive enzyme-linked immunosorbent assay (ELISA), whereby intact biologically active GLP-I and its metabolites could be determined. After GLP-I administration, the intact peptide could be measured using an NH2-terminally directed RIA or ELISA, while the difference in concentration between these assays and a COOH-terminal-specific RIA allowed determination of NH2-terminally truncated metabolites. Subcutaneous GLP-I was rapidly degraded in a time-dependent manner, forming a metabolite, which co-eluted on HPLC with GLP-I(9-36) amide and had the same immunoreactive profile. Thirty minutes after subcutaneous GLP-I administration to diabetic patients (n = 8), the metabolite accounted for 88.5 +/- 1.9% of the increase in plasma immunoreactivity determined by the COOH-terminal RIA, which was higher than the levels measured in healthy subjects (78.4 +/- 3.2%; n = 8; P < 0.05). Intravenously infused GLP-I was also extensively degraded, but no significant differences were seen between the two groups. Intact GLP-I accounted for only 19.9 +/- 3.4% of the increase in immunoreactivity measured with the COOH-terminal RIA in normal subjects (n = 8), and 25.0 +/- 4.8% of the increase in diabetic subjects (n = 8), the remainder being the NH2-terminally truncated metabolite.

Diabetes and Cardiovascular Disease: The “Common Soil” Hypothesis

Abstract: Unlike classical microvascular complications, large-vessel atherosclerosis can precede the development of diabetes, suggesting that rather than atherosclerosis being a complication of diabetes, both conditions have common genetic and environmental antecedents, i.e., they spring from a "common soil." It is now known that adverse environmental conditions, perhaps related to less-than-optimal nutrition, in fetal and early life are associated with an enhanced risk of both diabetes and cardiovascular disease many decades later. These same adverse environmental conditions are also associated with the development in adult life of abdominal obesity and the insulin-resistance syndrome (IRS). The IRS consists of glucose intolerance, hyperinsulinemia, dyslipidemia (high triglyceride and low high-density lipoprotein [HDL] cholesterol levels), and hypertension. Although the mechanism underlying this cluster is controversial, the statistical association is well established. All of the elements of the IRS have been documented as risk factors for type II diabetes. Some, but not all, of these elements are also cardiovascular disease risk factors, in particular, hypertension and low HDL cholesterol. Other factors associated with the IRS that may enhance cardiovascular disease risk are plasminogen activator inhibitor 1 and small, dense low-density lipoprotein particles. Whether insulin itself is a risk factor remains controversial, but recent epidemiological evidence has been mostly negative. This question has marked clinical relevance because if the IRS enhances cardiovascular disease risk by virtue of its concomitant factors and not the hyperinsulinemia per se, this would tend to alleviate concerns that intensive insulin management of type II diabetic subjects could enhance the risk of large-vessel atherosclerosis. Clinical trials are urgently needed to settle this point.

Dynamics of beta-cell mass in the growing rat pancreas. Estimation with a simple mathematical model.

Abstract: The growth and development of the endocrine pancreas has been studied for many years, but questions remain concerning the regulation of the mass of insulin-producing beta-cells both in the normal growing pancreas and during the pathogenesis of diabetes. The homeostatic control of beta-cell mass in both normal and pathophysiological conditions is based on the balance of cell proliferation, cell growth, and cell death. To gain insight into the relative contribution of each of these dynamic processes, we first mathematically analyzed the data available on the components involved in the maintenance of beta-cell mass, including rates of replication, beta-cell volume, and the beta-cell mass itself, at various ages in normal Sprague-Dawley rats. Then these data were combined in a simple mass balance equation to construct a mathematical model of the dynamics of the beta-cell mass in the normal growing rat pancreas. Such a model has allowed us to infer the contributions of fluxes that cannot be measured, i.e., neogenesis and cell death, to the known mass of beta-cells. Another important contribution of this model is to raise unanswered questions concerning the control of the balance of cell death and cell renewal in the endocrine pancreas.

Hyperglycemia and diabetic kidney disease. The case for transforming growth factor-beta as a key mediator.

Abstract: Renal cells are a rich source of transforming growth factor (TGF)-beta, and they serve as targets for its actions. Our hypothesis that activation of the TGF-beta system in the kidney is implicated in the development of diabetic renal disease stems from the close similarity of actions of TGF-beta and high ambient glucose on renal cell growth and extracellular matrix metabolism. Proximal tubule cells and glomerular mesangial cells cultured in high glucose concentration express increased TGF-beta 1 mRNA and protein levels, and treatment with anti-TGF-beta antibodies results in prevention of the effects of high glucose to induce cellular hypertrophy and stimulate collagen biosynthesis. Several in vivo studies by different groups of investigators have reported overexpression of TGF-beta in the glomeruli in human and experimental diabetes. We have also observed that the development of renal hypertrophy in the insulin-dependent diabetic BB rat and NOD mouse is associated with increased expression of TGF-beta 1 in the kidney and that short-term administration of antibodies capable of neutralizing the activity of TGF-beta in the streptozotocin mouse model of diabetes results in attenuation of whole kidney and glomerular hypertrophy and overexpression of mRNAs encoding matrix components. Together, these findings are consistent with the hypothesis that the diabetic state stimulates TGF-beta expression in the kidney and that in turn this growth factor may mediate, in an autocrine/paracrine manner, some of the principal early manifestations of diabetic renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Loss and Bone Turnover in Diabetes

Abstract: There have been conflicting reports about the effect of diabetes on bone density. In 1978, we studied 109 patients, 46 with type I and 63 with type II diabetes; ∼12 years later we restudied 35 of the 66 surviving patients. In the original study, radial bone density did not differ significantly between patients with either type of diabetes but was significantly lower than in nondiabetic control subjects. In eight osteopenic patients, bone formation rate and other histological indexes of osteoblast recruitment and function were markedly depressed compared with those in nondiabetic control subjects. In patients remeasured ∼2.5 years (41 patients) and ∼12.5 years (35 patients) after baseline, bone loss had continued at the expected rate in patients with type I diabetes, with maintenance of the same deficit, but was slower than expected in patients with type II diabetes, such that the initial deficit had been completely corrected. In six of the eight patients who had undergone bone biopsy, one with type I and five with type II diabetes, the mean bone mineral density z-score of the spine and femoral neck ∼12 years later was >0 and in one subject was significantly higher than normal at both sites. Based on these data and on previous studies, we propose that in patients with diabetes, low bone formation retards bone accumulation during growth, metabolic effects of poor glycemic control lead to increased bone resorption and bone loss in young adults, and low bone turnover retards agerelated bone loss. These effects account for low bone density in young patients with type I diabetes and normal or increased bone density in older patients with type II diabetes.

Human Obese Gene Expression: Adipocyte-Specific Expression and Regional Differences in the Adipose Tissue

Abstract: The obese (ob) gene, the mutation of which results in severe hereditary obesity and diabetes in mice, has recently been isolated through positional cloning. In this study, we isolated a full-length human ob complementary DNA (cDNA) clone and examined the tissue distribution of ob gene expression in humans. The nucleotide sequences of the human ob cDNA coding region were 83% identical to those of the mouse and rat ob cDNA coding regions. Analysis of the deduced amino acid sequences revealed that the human ob protein is a 166-amino acid polypeptide with a putative signal sequence and is 84 and 83% homologous to the mouse and rat ob proteins, respectively. Northern blot analysis using the cloned human ob cDNA fragment as a probe identified a single messenger RNA (mRNA) species 4.5 kb in size found abundantly in the adipose tissues obtained from the subcutaneous, omental, retroperitoneal, perilymphatic, and mesenteric fat pads. However, no significant amount of ob mRNA was present in the brain, heart, lung, liver, stomach, pancreas, spleen, small intestine, kidney, prostate, testis, colon, or skeletal muscle. The ob mRNA level in the adipose tissue varied from region to region even in the same individual. Furthermore, in the human adipose tissue, ob gene expression occurred in mature adipocytes rather than in stromal-vascular cells. This study is the first report of the elucidation of ob gene expression in human tissues, thereby leading to better understanding of the physiological and clinical implications of the ob gene.

A prospective study of the role of coxsackie B and other enterovirus infections in the pathogenesis of IDDM. Childhood Diabetes in Finland (DiMe) Study Group.

Abstract: Coxsackievirus B infections have been associated with clinical manifestation of insulin-dependent diabetes mellitus (IDDM) in several studies, but their initiating role in the slowly progressing beta-cell damage is not known. This is the first prospective study designed to assess the role of coxsackie B and other enterovirus infections in the induction and acceleration of this process. Three separate series were studied: 1) an intrauterine exposure series comprising 96 pregnant mothers whose children subsequently manifested IDDM and 96 control mothers whose children remained nondiabetic; 2) a cohort of 22 initially unaffected siblings of diabetic children who were followed until they developed clinical IDDM (mean observation time, 29 months) and 110 control siblings who remained nondiabetic; 3) a case-control series comprising 90 children with newly diagnosed IDDM and 90 control subjects. Enterovirus infections were identified on the basis of significant increases in serum IgG, IgM, or IgA class antibodies against a panel of enterovirus antigens (capture radioimmunoassay). Enterovirus antibodies were significantly elevated in pregnant mothers whose children subsequently manifested IDDM, particularly in cases in which IDDM appeared at a very young age, before the age of 3 years (P < 0.005). Serologically verified enterovirus infections were almost two times more frequent in siblings who developed clinical IDDM than in siblings who remained nondiabetic (mean, 1.0 vs. 0.6 infections/follow-up year; P < 0.001). This difference was seen both close to the diagnosis of IDDM and several years before diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Local Ventromedial Hypothalamus Glucopenia Triggers Counterregulatory Hormone Release

Abstract: To test the hypothesis that nuclei of the ventromedial hypothalamus (VMH) play a key role in the detection of counterregulatory responses to hypoglycemia, we delivered the glucopenic agent 2-deoxyglucose via bilaterally placed microdialysis probes into the VMH of conscious, chronically catheterized rats. The goal was to produce cellular glucopenia localized to the VMH. The volume of brain tissue exposed to 2-deoxyglucose was determined by adding [3H]2-deoxyglucose to the dialysate; its distribution in cerebral tissue was almost exclusively limited to the VMH. Rats with microdialysis probes placed into the frontal lobes served as a control group. Local perfusion of 2-deoxyglucose (but not glucose) into the VMH caused a prompt twofold increase in plasma glucose in association with a striking elevation of plasma glucagon (3.5-fold), epinephrine (30-fold), and norepinephrine (3.5-fold). No effect was seen when 2-deoxyglucose was delivered into the frontal lobes. We conclude that glucopenia localized to the VMH triggers the release of counterregulatory hormones that defend against hypoglycemia. Thus, the neurons that sense glucopenia may be situated in the VMH.

Effect of Intracerebroventricular Insulin Infusion on Diabetic Hyperphagia and Hypothalamic Neuropeptide Gene Expression

Abstract: To test the hypothesis that diabetic hyperphagia results from insulin deficiency in the brain, diabetic rats (streptozotocin-induced) were given an intracerebroventricular (ICV) infusion of saline or insulin (at a dose that did not affect plasma glucose levels) for 6 days. Food and water intake were significantly increased in diabetic rats, but only food intake was affected by ICV insulin. Diabetic hyperphagia was reduced 58% by ICV insulin compared with ICV saline (P < 0.05) and was accompanied by a 69% increase in diabetes-induced weight loss (P < 0.05). To evaluate whether central nervous system (CNS) insulin deficiency affects expression of neuropeptides involved in food intake, in situ hybridization was done for neuropeptide Y (NPY), which stimulates feeding, in the hypothalamic arcuate nucleus and for cholecystokinin (CCK) and corticotropin-releasing hormone (CRH), which inhibit feeding, in the hypothalamic paraventricular nucleus. In diabetic rats, NPY mRNA hybridization increased 280% (P < 0.05), an effect reduced 40% by ICV insulin (P < 0.05). CCK mRNA hybridization increased 50% in diabetic rats (P < 0.05), a response reduced slightly by ICV insulin (P < 0.05), whereas CRH mRNA hybridization decreased 33% in diabetic rats (P < 0.05) and was unchanged by ICV insulin. The results demonstrate that CNS infusion of insulin to diabetic rats reduces both hyperphagia and overexpression of hypothalamic NPY mRNA. This observation supports the hypothesis that a deficiency of insulin in the brain is an important cause of diabetic hyperphagia and that increased hypothalamic NPY gene expression contributes to this phenomenon.

Albuminuria and Poor Glycemic Control Predict Mortality in NIDDM

Abstract: The impact of microalbuminuria and macroalbuminuria on mortality was evaluated prospectively in 328 Caucasian patients with non-insulin-dependent diabetes mellitus (NIDDM) followed for 5 years. One hundred ninety-one (109 men and 82 women) patients with normoalbuminuria (albumin excretion rate [AER] P P 1c level (%), 1.2 (1.0–1.4); and age (years), 1.08 (1.03–1.13). Significant predictors of cardiovascular mortality included preexisting coronary heart disease, 6.1 (2.8–13.5); macroalbuminuria, 2.5 (1.1–5.8); HbA 1c level (%), 1.3 (1.1–1.6); and systolic blood pressure (10 mmHg), 1.2 (1.0–1.4). Univariate Cox survival analysis in the normoalbuminuric group revealed that AER above the median of 8 mg/24 h was associated with an increased all-cause mortality risk of 2.7 (0.93–7.69) ( P = 0.07). We conclude that abnormally elevated urinary albumin excretion and poor glycemic control indicate a substantially increased allcause, mainly cardiovascular, mortality risk in NIDDM patients.

Predicting Future Diabetes in Latino Women With Gestational Diabetes: Utility of Early Postpartum Glucose Tolerance Testing

Abstract: We tested 32 routine clinical parameters for their ability to discriminate between a high risk and a low risk of non-insulin-dependent diabetes mellitus (NIDDM) within 5-7 years after pregnancies complicated by gestational diabetes mellitus (GDM). Latino women (n = 671) with GDM who did not have diabetes 4-16 weeks after delivery returned for at least one 75-g oral glucose tolerance test (OGTT) within 7.5 years. Multivariate analysis was used to identify parameters ascertained during or immediately after the index pregnancy that were independently associated with the development of diabetes during follow-up. Life table analysis revealed a 47% cumulative incidence rate of NIDDM 5 years after delivery for this cohort of patients who did not have diabetes at the initial postpartum examination. Four variables were identified as independent predictors of NIDDM: the area under the OGTT glucose curve at 4-16 weeks postpartum, the gestational age at the time of diagnosis of GDM, the area under the OGTT glucose curve during pregnancy, and the highest fasting serum glucose concentration during pregnancy. Examination of relative risks (RRs) of NIDDM between the highest and lowest quartiles of the cohort for each variable, adjusted for the other three variables, revealed that the postpartum OGTT provided the best discrimination between high-risk and low-risk individuals (adjusted RR = 11.5 [95% confidence interval 4.5-29.1] compared with adjusted RRs of only 0.5-2.5 for the other three variables).(ABSTRACT TRUNCATED AT 250 WORDS)

Apoptotic cell death triggered by nitric oxide in pancreatic beta-cells.

Abstract: Nitric oxide (NO) is believed to be an effector molecule that mediates interleukin (IL)-1 beta-induced destruction and dysfunction of pancreatic beta-cells. We have demonstrated that both exogenous NO and NO generated endogenously by IL-1 beta brought about apoptosis of isolated rat pancreatic islet cells as well as pancreatic beta-cell tumor-derived cell line HIT. This apoptosis was characterized by cleavage of DNA into nucleosomal fragments of 180-200 bp and morphologically by nuclear shrinkage, chromatic condensation, and apoptotic body formation. The IL-1 beta-induced internucleosomal DNA cleavage occurred in a time- and dose-dependent manner. Actinomycin D, cycloheximide, and nitric oxide synthase inhibitors inhibited the DNA cleavage, which was correlated with the amount of NO produced, indicating that NO produced by HIT cells themselves could mediate the apoptosis. Furthermore, in the presence of tumor necrosis factor (TNF)-alpha, large amounts of NO were produced by IL-1 beta and DNA cleavage occurred more noticeably, although TNF-alpha alone did not generate NO. Streptozotocin (STZ), a diabetogenic reagent containing a nitroso moiety, also released NO and induced internucleosomal DNA cleavage in HIT cells. These results suggest that NO-induced internucleosomal DNA cleavage is an important initial step in the destruction and dysfunction of pancreatic beta-cells induced by inflammatory stimulation or treatment with STZ.

High-Glucose–Triggered Apoptosis in Cultured Endothelial Cells

Abstract: High ambient glucose concentration, linked to vascular complications in diabetes in vivo, modulates mRNA expression of fibronectin, collagen, tissue-type plasminogen activator, and plasminogen activator inhibitor and induces delayed replication and excess cell death in cultured vascular endothelial cells. To determine the role of high ambient glucose (30 mmol/l) in apoptosis, paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were exposed to both high (30 mmol/l) and low (5 mmol/l) concentrations of glucose for short-term (24, 48, and 72 h) and long-term (13 +/- 1 days) experiments. Incubation of HUVECs with high glucose for > 48 h increased DNA fragmentation (13.7 +/- 6.5% of total DNA, mean +/- SD) versus cultures kept in 5 mmol/l glucose (10.9 +/- 5.6%, P < 0.005), as measured by [3H]thymidine assays. Data were confirmed by apoptosis-specific fluorescence-activated cell sorter analysis of confluent HUVEC cultures, which displayed after long-term exposure to 30 mmol/l glucose a 1.5-fold higher prevalence of apoptosis than control cultures exposed to 5 mmol/l glucose (P < 0.005). In contrast, no increase in DNA fragmentation in response to 30 mmol/l glucose was seen for standardized cell lines (K 562, P 815, YT) and fibroblasts. Expression of clusterin mRNA, originally reported to be a molecular marker of apoptosis, was only slightly affected by short-term (24-h) high-glucose exposure but was significantly reduced after long-term incubation in 30 mmol/l glucose (82.2 +/- 13.8% of control) versus 5 mmol/l glucose, which questions the role of clusterin gene expression as a marker of apoptosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of Blood Flow and Impaired Autoregulation in the Pathogenesis of Diabetic Retinopathy

Abstract: Several mechanisms are implicated in the pathogenesis of diabetic retinopathy. They include biochemical, hemodynamic, and hormonal factors, all of which have an important role in the development of diabetic retinopathy. These factors are not independent of each other, but rather they interact and together are responsible for the well-known lesions of vascular occlusion, microaneurysms, hemorrhages' hard exudates, and eventually new vessel formation.

The ob Gene and Insulin: A Relationship Leading to Clues to the Understanding of Obesity

Abstract: Obesity and non-insulin-dependent diabetes are estimated to affect millions of people in the world. This pathology is multifactorial, comprising complex interactions of genetic and environmental factors and lacking a specific therapy. Great interest arose from the recent discovery of the ob gene expressed only in adipose tissue and coding for a protein that appears to regulate adiposity, potentially by acting as a satiety factor. We report here that in normal rats, ob mRNA is respectively up- or downregulated by a rise in insulinemia (induced by 2-day insulin infusion while maintaining euglycemia) or a decrease in insulinemia (induced by a 3-day fast). Our results also show that in genetically obese fa/fa rats studied longitudinally, white adipose tissue ob mRNA levels increase in parallel with early occurring and steadily increasing hyperinsulinemia. This results in adult obese animals having markedly higher ob mRNA levels than age-matched normoinsulinemic lean rats. Furthermore, in adult obese rats, ob mRNA escapes down-regulation as normalization of hyperinsulinemia due to fasting fails to reduce the high ob mRNA levels.

Decreased insulin secretion and increased insulin resistance are independently related to the 7-year risk of NIDDM in Mexican-Americans.

Abstract: The relative importance of insulin resistance and abnormal insulin secretion as risk factors for the development of non-insulin-dependent diabetes mellitus (NIDDM) is still controversial. Few data are available on insulin secretion as a risk factor for the development of NIDDM, especially in subjects with normal glucose tolerance. We examined the relation of fasting insulin (as a markerof insulin resistance) and the ratio of change in insulin to change in glucose during the first 30min after glucose ingestion (ΔI 30 /ΔG 30 ) (as a marker ofinsulin secretion) as predictors of the 7-year development of NIDDM in 714 initially nondiabetic Mexican-Americans. NIDDM developed in 99 subjects. The relative risk of NIDDM increased with higherquartiles of fasting insulin (quartile 1 [low], 1.0; quartile 2, 1.5; quartile 3, 2.0; and quartile 4 [high], 3.7; P 30 /ΔG 30 (quartile 1 [low], 6.9; quartile 2, 1.9; quartile 3, 1.1; quartile 4 [high], 1.0; P 30 /ΔG 30 had independent increases in NIDDM incidence ( P 30 /ΔG 30 significantly predicted NIDDM in subjects with both impaired and normal glucose tolerance at baseline. We conclude that both decreasedinsulin secretion (as assessed by low ΔI 30 /ΔG 30 ) and increased insulin resistance (as assessed by fasting insulin) predict the development of NIDDM in Mexican-Americans, a group previously characterized as having hyperinsulinemia and insulin resistance. This study provides the first evidence that decreased insulin secretion predicts the development of NIDDM in subjects with normal glucose tolerance, suggesting that deficient insulin secretion and insulin resistance occur early as a precursor of NIDDM.

Microvascular Function in Human Diabetes: A Physiological Perspective

Abstract: The late complications of diabetes represent in large part microvascular dysfunction. The development of techniques to measure microvascular function has resulted in a clearer picture of the stages of development of microangiopathy and the key pathophysiological processes involved. Considerable evidence supports the hemodynamic hypothesis of pathogenesis, which argues that early insulin-dependent diabetes is characterized by increased microvascular pressure and flow. Resultant injury to the microvascular endothelium causes adaptive microvascular sclerosis contributing to a loss of vasodilatory reserve and autoregulatory capacity with increasing disease duration. High susceptibility to microangiopathy appears to be characterized by both high capillary pressure and increased permeability, although the interrelationship between these variables needs to be better defined. In normotensive non-insulin-dependent diabetes subjects, a different pattern of microvascular functional abnormalities is apparent; it is hypothesized that these differences represent the impact of a prediabetic insulin-resistant phase on microvascular behavior and may in part explain the differential expression of vascular pathology in the two major types of diabetes. The physiological framework that has been defined reveals those pivotal processes upon which scientific attention should be centered and facilitates the generation of plausible molecular and cellular mechanisms that fit the physiological facts.

Elevated Levels of Authentic Plasma Hydroperoxides in NIDDM

Abstract: Using a precise technique for measuring authentic plasma lipid hydroperoxides (ROOHs), we show that individuals with non-insulin-dependent diabetes mellitus (NIDDM) have higher levels of ROOH than do control subjects. ROOHs were measured by the ferrous oxidation with xylenol orange assay coupled with the selective ROOH reductant triphenylphosphine. Formation of the ferric xylenol orange complex was determined at 560 nm and calibrated against H2O2. For 22 individuals with NIDDM, a concentration of 9.04 +/- 4.3 mumol/l (mean +/- SD) ROOH was recorded. This concentration was higher (P 0.1). A trend to lower vitamin E levels in the NIDDM group (9.03 +/- 3.31 vs. 10.31 +/- 5.02 micrograms/ml in control subjects) failed to achieve significance at the 95% confidence level. Plasma ROOHs in the diabetic group did not correlate with total plasma cholesterol, triglyceride, fasting glucose, HbA1, vitamin E, or TBARM levels. These data indicate that measurement of authentic ROOHs shows NIDDM to be associated with oxidative stress, which may be unrelated to abnormalities in lipid metabolism and glycemic control.

Evolution of beta-cell dysfunction in the male Zucker diabetic fatty rat.

Abstract: The molecular basis for the beta-cell dysfunction that characterizes non-insulin-dependent diabetes mellitus (NIDDM) is unknown. The Zucker diabetic fatty (ZDF) male rat is a rodent model of NIDDM with a predictable progression from the prediabetic to the diabetic state. We are using this model to study beta-cell function during the development of diabetes with the goal of identifying genes that play a key role in regulating insulin secretion and, thus, may be potential targets for therapeutic intervention aimed at preserving or improving beta-cell function. As a first step, we have characterized morphology, insulin secretion, and pattern of gene expression in islets from prediabetic and diabetic ZDF rats. The development of diabetes was associated with changes in islet morphology, and the islets of diabetic animals were markedly hypertrophic with multiple irregular projections into the surrounding exocrine pancreas. In addition, there were multiple defects in the normal pattern of insulin secretion. The islets of prediabetic ZDF rats secreted significantly more insulin at each glucose concentration tested and showed a leftward shift in the dose-response curve relating glucose concentration and insulin secretion. Islets of prediabetic animals also demonstrated defects in the normal oscillatory pattern of insulin secretion, indicating the presence of impairment of the normal feedback control between glucose and insulin secretion. The islets from diabetic animals showed further impairment in the ability to respond to a glucose stimulus. Changes in gene expression were also evident in islets from prediabetic and diabetic ZDF rats compared with age-matched control animals. In prediabetic animals, there was no change in insulin mRNA levels. However, there was a significant 30-70% reduction in the levels of a large number of other islet mRNAs including glucokinase, mitochondrial glycerol-3-phosphate dehydrogenase, voltage-dependent Ca2+ and K+ channels, Ca(2+)-ATPase, and transcription factor Islet-1 mRNAs. In addition, there was a 40-50% increase in the levels of glucose-6-phosphatase and 12-lipoxygenase mRNAs. There were further changes in gene expression in the islets from diabetic ZDF rats, including a decrease in insulin mRNA levels that was associated with reduced islet insulin levels. Our results indicate that multiple defects in beta-cell function can be detected in islets of prediabetic animals well before the development of hyperglycemia and suggest that changes in the normal pattern of gene expression contribute to the development of beta-cell dysfunction.

Free Fatty Acid as a Link in the Regulation of Hepatic Glucose Output by Peripheral Insulin

Abstract: Overproduction of glucose by the liver in the face of insulin resistance is a primary cause of hyperglycemia in non-insulin-dependent diabetes mellitus (NIDDM). However, mechanisms involved in control of hepatic glucose output (HGO) remain less than clear, even in normal individuals. Recent results have supported an indirect extrahepatic effect of insulin as the primary locus of insulin action to restrain HGO. One suggested extrahepatic site is the pancreatic alpha-cell. To examine whether insulin's extrahepatic site is independent of the alpha-cells, HGO suppression was examined independent of changes in glucagon secretion or insulin antagonism of glucagon action. Euglycemic glucose clamps (n = 40) with somatostatin infusion were performed in conscious dogs (n = 5). Paired experiments were conducted in which insulin was infused either portally (1.2, 3.0, 6.0 pmol.min-1.kg-1) or peripherally at half the portal infusion rate (0.6, 1.5, 3.0 pmol.min-1.kg-1). Additional zero and saturating portal-dose experiments (100 pmol.min-1.kg-1) were also performed. For the paired experiments, portal insulin infusion resulted in portal insulin concentrations approximately two to three times higher than in the corresponding peripheral insulin infusion experiments, while at the same time peripheral insulin concentrations were approximately matched. Equal peripheral insulin concentration resulted in equivalent HGO suppression irrespective of the portal concentrations. Thus, insulin affects a signal at a peripheral site, other than alpha-cell, that in turn suppresses hepatic glucose production. To investigate the nature of this signal, we measured alanine, lactate, and free fatty acids (FFAs).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-Stimulated Muscle Glucose Clearance in Patients With NIDDM: Effects of One-Legged Physical Training

Abstract: Physical training increases insulin action in skeletal muscle in healthy men. In non-insulin-dependent diabetes mellitus (NIDDM), only minor improvements in whole-body insulin action are seen. We studied the effect of training on insulin-mediated glucose clearance rates (GCRs) in the whole body and in leg muscle in seven patients with NIDDM and in eight healthy control subjects. One-legged training was performed for 10 weeks. GCR in whole body and in both legs were measured before, the day after, and 6 days after training by hyperinsulinemic (28, 88, and 480 mU x min(-1) x m(-2)), isoglycemic clamps combined with the leg balance technique. On the 5th day of detraining, one bout of exercise was performed with the nontraining leg. Muscle biopsies were obtained before and after training. Whole-body GCRs were always lower (P < 0.05) in NIDDM patients compared with control subjects and increased (P < 0.05) in response to training. In untrained muscle, GCR was lower (P < 0.05) in NIDDM patients (13 +/- 4, 91 +/- 9, and 148 +/- 12 ml/min) compared with control subjects (56 +/- 12, 126 +/- 14, and 180 +/- 14 ml/min). It Increased (P < 0.05) in both groups in response to training (43 +/- 10, 144 +/- 17, and 205 +/- 24 [NIDDM patients] and 84 +/- 10, 212 +/- 20, and 249 +/- 16 ml/min [control subjects]). Acute exercise did not increase leg GCR. In NIDDM patients, the effect of training was lost after 6 days, while the effect lasted longer in control subjects. Training increased (P < 0.05) muscle lactate production and glucose storage as well as glycogen synthase (GS) mRNA in both groups. We conclude that training increases insulin action in skeletal muscle in control subjects and NIDDM patients, and in NIDDM patients normal values may be obtained. The increase in trained muscle cannot fully account for the increase in whole-body GCR. Improvements in GCR involve enhancement of insulin-mediated increase in muscle blood flow and the ability to extract glucose. They are accompanied by enhanced nonoxidative glucose disposal and increases in GS mRNA. The improvements in insulin action are short-lived.

Effects of a 48-h Fat Infusion on Insulin Secretion and Glucose Utilization

Abstract: To determine the effects of prolonged elevation of plasma free fatty acids (FFAs) on insulin secretion, we infused Liposyn II (4.3 μmol · kg −1 · min −1 ) plus heparin (0.4 U · kg −1 · min −1 ) intravenously into six healthy volunteers for 48 h. Another six volunteers received saline infusions and served as control subjects. In all 12 subjects (11 men and 1 woman), plasma glucose was clamped at ∼8.6 mmol/l. Liposyn/heparin infusion resulted in a 9.4-fold increase in plasma FFA concentration (from 132 to 1,237 μmol/l), a 46% increase in insulin secretion rates (from 241 to 352 pmol/min, P −1 · min −1 , P 1 ) potentiated glucose-stimulated insulin secretion for 48 h and 2 ) initially caused peripheral insulin resistance that disappeared during the 2nd day, probably as a result of elevated circulating insulin levels. We conclude that in healthy volunteers under hyperglycemic conditions, fat infusion produced insulin resistance that was compensated for after ∼24 h by persistent hypersecretion of insulin.

Interferon expression in the pancreases of patients with type I diabetes.

Abstract: We have used a reverse transcriptase-polymerase chain reaction (RT-PCR) protocol to examine the expression of cytokines in the pancreases and islets of patients with type I diabetes. We detect a significant increase in the level of expression of interferon (IFN)-alpha in the pancreases of the diabetic patients as compared with the control pancreases. In contrast, IFN-beta was detected at comparable levels in both groups, while IFN-gamma was detected in three of four control pancreases and one of four pancreases from the diabetic individuals. The IFN-alpha cDNAs generated by the RT-PCR were cloned and sequenced to determine which alpha-subtypes were being expressed. We found that the repertoire of subtypes was quite limited in any one individual (diabetic or not), although each individual was different with respect to the pattern of subtypes expressed. We also examined these pancreases for the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, IL-2, IL-4, and IL-6. We found no detectable expression of TNF-alpha or IL-2 in any pancreases, and the expression of the other cytokines was variable, with no pattern emerging from the comparison of the diabetic and nondiabetic individuals. We conclude that, of the cytokines examined, only IFN-alpha was significantly increased in the diabetic patients, a result that is consistent with the possibility that this cytokine is directly involved in the development of type I diabetes.

Formation of immunochemical advanced glycosylation end products precedes and correlates with early manifestations of renal and retinal disease in diabetes.

Abstract: Elevated levels of advanced glycosylation end products (AGEs) have been found in multiple tissues in association with diabetic vascular complications and during the microalbuminuric phase of diabetic nephropathy. In this study, we have used an AGE-specific enzyme-linked immunosorbent assay (ELISA) to measure skin AGEs to determine whether elevated levels can be detected before the onset of overt microangiopathy. Subjects with type I diabetes ( n = 48) were graded for the degree of nephropathy (normal [23], microalbuminuria [12], or macroalbuminuria [12]) and retinopathy (none [13], background [20], or proliferative [15]). Subgroups with a premicroalbuminuric phase of albumin excretion (≤28 mg/24 h, n = 27) or with the earliest stages of retinopathy ( n = 27) were identified. A significant increase in tissue AGEs was found as urinary albumin increased during the premicroalbuminuric phase of nephropathy even when the data were adjusted for age and duration of diabetes ( P = 0.005). Immunoreactive AGEs also increased as normal renal status advanced to microalbuminuria and macroalbuminuria ( P = 0.0001 across groups). Significant elevation of AGEs was also found in association with the earliest stages of clinically evident retinopathy (early background versus minimal grades). In addition, higher AGE levels were found in subjects with proliferative retinopathy when compared with those with less severe retinopathy ( P

Insulin Action and Glucose Metabolism in Nondiabetic Control and NIDDM Subjects: Comparison Using Human Skeletal Muscle Cell Cultures

Abstract: Myoblasts from human skeletal muscle were isolated from needle biopsy samples of vastus lateralis and fused to differentiated multinucleated myotubes. Specific high-affinity insulin and insulin-like growth factor I (IGF-I) binding, glucose transporter proteins GLUT1 and GLUT4, glycogen synthase and pyruvate dehydrogenase proteins, and their specific mRNAs were identified in fused myotubes. Insulin and IGF-I stimulated 2-deoxyglucose uptake twofold with half-maximal stimulation by insulin at 0.98 +/- 0.12 nmol/l and maximal stimulation at 17.5 nmol/l. Acute insulin treatment (33 nmol/l) doubled glycogen synthase activity and glucose incorporation into glycogen while increasing pyruvate dehydrogenase approximately 30%. In cells cultured from NIDDM subjects, both basal (6.9 +/- 1.0 vs. 13.0 +/- 1.7 pmol.mg protein-1.min-1) and acute insulin-stimulated transport (13.5 +/- 2.0 vs. 22.4 +/- 1.3 pmol.mg protein-1.min-1) were significantly reduced compared with nondiabetic control subjects (both P < or = 0.005). GLUT1 protein content of total membranes from NIDDM subjects was decreased compared with control subjects, while GLUT4 levels were similar between groups. A significant correlation (r = 0.65, P < or = 0.05) was present when maximal rates of insulin-stimulated glucose transport in cell culture from subjects were compared with their corresponding in vivo glucose disposal determined by hyperinsulinemic glucose clamp. In summary, differentiated human skeletal muscle cultures exhibit biochemical and molecular features of insulin-stimulated glucose transport and intracellular enzyme activity comparable with the in vivo situation. Defective insulin-stimulated glucose transport persists in muscle cultures from NIDDM subjects and resembles the reduced insulin-mediated glucose uptake present in vivo. We conclude that this technique provides a relevant cellular model to study insulin action and glucose metabolism in normal subjects and determine the mechanisms of insulin resistance in NIDDM.

Diabetic Ketoacidosis in Obese African-Americans

Abstract: Our preliminary data indicate that 15% of African-American patients presenting with diabetic ketoacidosis (DKA) are obese. To determine underlying mechanisms, we analyzed the clinical characteristics and indexes of insulin secretion and insulin sensitivity in 35 obese patients with DKA, 22 obese patients with hyperglycemia, 10 lean patients with DKA, and 10 obese nondiabetic subjects. Studies were performed 1 day after resolution of DKA and after 12 weeks of follow-up. At presentation, both obese DKA and obese hyperglycemic patients had no detectable insulin response to intravenous glucose, but they did respond to glucagon administration. The acute insulin response (AIR) to glucagon in obese DKA patients (0.9 ± 0.1 ng/ml) was lower than in obese hyperglycemic subjects (1.5 ± 0.1 ng/ml, P

Maternal enteroviral infection during pregnancy as a risk factor for childhood IDDM. A population-based case-control study

Abstract: Using the nationwide childhood-onset diabetes register in Sweden, we were able to trace children who contracted diabetes before the age of 15 years and who were born at a specific hospital in Sweden where maternal sera from delivery had been stored during the years 1969-1989. Sera obtained at delivery from 57 mothers of diabetic children were compared with sera from 203 mothers of control subjects who were delivered at the same hospital during the same time period. The sera were analyzed blindly using a group-specific enzyme-linked immunosorbent assay for enteroviral IgG and IgM antibodies before and after urea wash as an avidity test. On the same plates, IgG antibodies to herpes, mumps, and toxoplasmosis were analyzed. The mean absorbance values of enteroviral IgG antibodies against enteroviral antigens (echo30, coxsackie B5, and echo9) were significantly higher among mothers whose children later developed diabetes (P = 0.002, P = 0.02, and P = 0.04, respectively). When reduction in activity after urea wash, indicating recently formed antibodies, was compared, the differences were even more pronounced (P < 0.001 for all three antigens). No significant differences were found for antibodies against herpes (all types), herpes type 2, mumps, or toxoplasmosis. When IgM activity and/or a significant decrease in avidity index, an indication of recent enterovirus infection, was used as a risk exposure, the odds ratio standardized for year of birth (95% confidence interval) was 3.19 (1.39-7.30). We conclude that the results of this study indicate that enteroviral infection during pregnancy is a risk factor for childhood-onset diabetes in the offspring.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelial Dysfunction Precedes Development of Microalbuminuria in IDDM

Abstract: In patients with insulin-dependent diabetes mellitus (IDDM), microalbuminuria is a predictor of widespread severe microangiopathy and macroangiopathy. Patients with microalbuminuria show generalized dysfunction of the vascular endothelium, but it is unknown whether endothelial dysfunction precedes the development of microalbuminuria. We examined a cohort of 17 IDDM patients at baseline and on three occasions during a follow-up of (median) 64 months (range 51-89). All had normal (< 15 micrograms/min) urinary albumin excretion (UAE) at the first three examinations. At the fourth examination, 11 patients had normal UAE and 6 had microalbuminuria (median 25.7 micrograms/min [range 15.3-42.8]). Compared with patients with normal UAE, microalbuminuric patients had significantly higher plasma levels of von Willebrand factor (vWF), a marker of endothelial dysfunction, at the second (200% [168-274] vs. 131% [69-186]), third (208% [188-270] vs. 125% [82-190]), and fourth examinations (231% [202-269] vs. 132% [88-208], P < 0.0001), but not at baseline (128% [98-161] vs. 122% [87-210]). An increase in vWF preceded the occurrence of microalbuminuria by approximately 3 years. The groups did not differ with regard to age, diabetes duration, blood pressure, mean glycated hemoglobin and cholesterol, smoking habits, or extent of retinopathy. Endothelial dysfunction, as estimated by plasma vWF concentration, precedes and may predict the development of microalbuminuria in IDDM.