Non-insulin-dependent Diabetes Mellitus Subjects Research Articles

Vitamin E/lipid peroxide ratio and susceptibility of LDL to oxidative modification in non-insulin-dependent diabetes mellitus.

The presence of conventional risk factors cannot sufficiently account for the excess risk of atherosclerosis in patients with non-insulin-dependent diabetes mellitus (NIDDM). Oxidative modification of LDL has been implicated in the pathogenesis of coronary atherosclerosis. Thirty-five patients with NIDDM, 20 nondiabetic, hypertriglyceridemic subjects (HTG-control), and 21 diabetic, normotriglyceridemic subjects (NTG-control) were enrolled in this study. Oxidative susceptibility of LDL was determined by monitoring formation of conjugated dienes. Mean lag time of LDL oxidation and vitamin E/lipid peroxide of LDL was lower in patients with NIDDM (43.2 +/- 3.9 minutes and 1.6 +/- 1.3) than in HTG-control (48.8 +/- 3.2 minutes and 2.3 +/- 1.2, respectively) and NTG-control subjects (54.2 +/- 6.1 minutes and 3.0 +/- 1.8, respectively). Mean LDL particle size in patients with NIDDM and HTG-control subjects (24.4 +/- 0.9 and 24.7 +/- 0.7 nm, respectively) was smaller than in NTG-control subjects (25.9 +/- 1.0 nm). Multiple stepwise regression analyses ascertained that the vitamin. E/lipid peroxide of LDL is a major determinant of LDL oxidation lag time. These results suggest that LDL in patients with NIDDM is more susceptible to oxidative modification primarily because of a reduced level of vitamin E/lipid peroxide of LDL. The enhanced susceptibility of LDL to oxidation may be a pivotal factor underlying the increased incidence of vascular disease in patients with NIDDM.

Pharmacokinetics of oral glyburide in subjects with non-insulin-dependent diabetes mellitus and renal failure

To test the hypothesis that renal failure has no effect on the pharmacokinetics of glyburide, five subjects with non-insulin-dependent diabetes mellitus (NIDDM) and end-stage renal disease requiring hemodialysis, and four NIDDM subjects with normal renal function were studied. On days 0, 1, and 15, subjects consumed 33 carbohydrate grams, and glucose, insulin, and C-peptide were measured for 4 hours. On day 1, subjects received 3 mg glyburide and measured plasma concentrations for 48 hours. On day 3, multiple dosing on 3 mg glyburide daily began. On day 15, plasma concentrations were measured for 48 hours. The pharmacokinetics and pharmacodynamics of glyburide, glucose, insulin, and C-peptide were determined as well as daily fasting blood glucose. Glucose area under the curve (AUC) and daily fasting glucose levels did not change in either controls or hemodialysis subjects. The mean serum glyburide blood levels and pharmacokinetics did not differ after initial or chronic glyburide administration in NIDDM subjects with end-stage renal disease treated with hemodialysis compared with controls. Glyburide half-life averaged 3.3 hours in control subjects and 5.0 hours in hemodialysis subjects. Hemodialysis subjects had increased C-peptide and insulin AUC with chronic dosing. Renal failure does not affect the pharmacokinetics of 3.0 mg oral glyburide.

Resistance training in the treatment of non-insulin-dependent diabetes mellitus.

Aerobic endurance exercise has traditionally been advocated in the treatment of non-insulin-dependent diabetes mellitus (NIDDM). However, the effect of aerobic endurance exercise programs on long-term glycaemic control is small to moderate. The aim of the present study was to determine the effect of circuit resistance training on long-term glycaemic control (HbA1c) and to examine the potential association between muscle size and glycaemic control in NIDDM subjects. Eight NIDDM subjects participated in a 3 month individualized progressive resistance training program (moderate intensity, high-volume) twice a week with measurements of HbA1c, lipids, blood pressure, VO2max and thigh muscle cross-sectional area. There was a significant improvement in HbA1c (8.8% - 8.2%; p < 0.05). Muscle endurance increased by 32 +/- 23% (p < 0.05), and the cross-sectional area of m. vastus lateralis increased by 21% (p < 0.001). There was a strong inverse correlation between HbA1c and muscle cross-sectional area (knee extensors) after the exercise period (r = -0.73; p < 0.05). Circuit resistance training seems to be feasible in moderately obese, sedentary elderly NIDDM subjects and the inclusion of circuit resistance training in exercise training programs for NIDDM subjects should be considered.

The prediabetic problem: Development of non-insulin-dependent diabetes mellitus and related abnormalities

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with approximately two fold increase in coronary heart disease (CHD) in men and fourfold increase in CHD in women. In most studies, the duration of diabetes and severity of glycemia are only weakly related to CHD in NIDDM, suggesting that the prediabetic period may be important for the increased CHD in NIDDM subjects. Both hyperinsulinemia and/or insulin resistance predict the development of NIDDM. A number of studies have shown that increased cardiovascular risk factors (especially high triglyceride, blood pressure, and small dense low-density lipoprotein (LDL) and low high-density liproprotein (HDL) cholesterol) precede the onset of NIDDM. Recent data from the San Antonio Heart Study suggest that the atherogenic pattern of cardiovascular risk factors is more marked in prediabetic women than in prediabetic men, thus partially explaining the higher risk of CHD in prediabetic women than in prediabetic men. The atherogenic changes in cardiovascular risk factors appear to be mainly due to increased hyperinsulinemia and insulin resistance in nondiabetic subjects. Interventions to reduce cardiovascular disease in NIDDM subjects should emphasize the primary prevention of NIDDM and very aggressive treatment of traditional cardiovascular risk factors in prediabetic subjects. Treatment of hypertension and dyslipidemia in high-risk patients for NIDDM should avoid agents that further worsen insulin resistance (nicotinic acid, β blockers, and thiazides), as subjects with hypertension and dyslipidemia are already at increased risk of NIDDM.

The deidesheimer meeting: Significance of classical and new risk factors in non-insulin-dependent diabetes mellitus

The major risk factors appear to explain only a small proportion of the excess risk of coronary heart disease in patients with Non-Insulin-Dependent Diabetes Mellitus (NIDDM). Among novel risk markers that have been proposed to explain the susceptibility of NIDDM subjects to coronary heart disease are insulin resistance, elevated concentrations of proinsulin-line molecules, plasminogen activator inhibitor, and microalbuminuria. Several prospective studies have shown that hyperinsulinemia predicts coronary heart disease, perhaps independently of established risk factors. Some of this excess risk may be through the dyslipidemia, or the elevation in activity of plasminogen activator inhibitor, an inhibitor of fibrinolysis, which relate to hyperinsulinemia. However proinsulin-like molecules show similar relationships with both risk factors and with prevalent coronary heart disease as does insulin, despite low concentrations of these molecules in the circulation, suggesting a causative relationship is improbable. Furthermore, the link between insulin resistance and microalbuminuria, a powerful predictor of vascular disease in its own right, is poorly understood through known mechanisms. This clustering leads to the possibility of a link with coronary heart disease through other mechanisms. It is proposed that the pathogenesis of this link is endothelial dysfunction, which may predicate both impaired insulin action, through effects of blood flow and insulin transport, and the associated dyslipidemia, impaired fibrinolysis, microalbuminuria, and atherogenesis. In terms of etiology, the links of all these risk factors with evidence of growth retardation in early life may suggest a role of the thrifty phenotype hypothesis—impaired organogenesis resulting from poor maternal nutrition during pregnancy.

Prevalence of the Trp64Arg missense mutation of the β 3-adrenergic receptor gene in Japanese subjects

Prompted by the recent findings that a tryptophan to arginine (Trp64Arg) mutation in the β 3-adrenergic receptor gene was associated with an earlier onset of non-insulin-dependent diabetes mellitus (NIDDM) in Pima Indians, with abdominal obesity and insulin resistance in Finns, and with an increased capacity to gain weight in French whites, we studied the prevalence of this mutation in 231 diabetic and 95 nondiabetic Japanese subjects and assessed its contribution to the development of obesity and NIDDM. The allelic frequencies of the mutation were 0.18 in diabetic and 0.23 in nondiabetic subjects, showing no significant difference between the two groups ( P = .067). In nondiabetic subjects, body mass index (BMI) did not differ between those with and without the mutation (22.2 ± 3.5 v 21.4 ± 3.2 kg/m 2, P = .252). In NIDDM subjects, BMI at the time of study and maximal BMI before the start of treatment did not differ between those with and without the mutation (22.8 ± 2.6 v 23.2 ± 3.7 kg/m 2, P = .678, and 24.7 ± 2.6 v 24.9 ± 3.1 kg/m 2, P = .277). Homozygotes for the mutation did not have trends to have increased BMI in either diabetic or nondiabetic subjects. The age at diagnosis of NIDDM also did not differ between the two groups (48.8 ± 9.9 v 47.8 ± 12.5 years, P = .796). Fasting serum cholesterol and triglyceride levels and systolic and diastolic blood pressure before the start of treatment did not differ between NIDDM subjects with and without the mutation. In conclusion, although the Trp64Arg mutation is not uncommon in Japanese, it does not appear to be associated with obesity, NIDDM, age at diagnosis of NIDDM, or dyslipidemia. Our results suggest that the mutation has minor effects, if any, on the development of obesity and NIDDM in Japanese.

Transplantation of syngenic pancreatic islets into rats with streptozotocin induced non insulin dependent diabetes mellitus.

An important concept in understanding the pathogenesis of Non Insulin Dependent Diabetes Mellitus (NIDDM) has recently emerged: the concept that hyperglycemia is not only the principal metabolic derangement of diabetes but also a pathogenetic factor in its own right. Once it develops, either from insulin deficiency or from insulin resistance, hyperglycemia will exacerbate both defects, thereby closing a pathologic feedback loop1. Recognition of the important pathogenetic role of hyperglycemia per se in the evolution of NIDDM has important therapeutic implication. First normalization of the plasma glucose profile, should lead to an impairment in insulin secretion in NIDDM subjects. In fact significant improvements in insulin secretion and insulin action have been demonstrated after weight loss, sulfonylurea administration or insulin therapy, each of these therapeutic interventions leading to an improvement of glycemic control2.

Sialic acid, diabetes, and aging: A study on the erythrocyte membrane

Sialic acid (SA) content and Na + K + -ATPase activity of red blood cell (RBC) membranes were studied in 26 normoalbuminuric patients with insulin-dependent diabetes mellitus (IDDM), 25 normoalbuminuric patients with non—insulin-dependent diabetes mellitus (NIDDM), and 40 healthy nondiabetic subjects with a negative family history for diabetes. A decrease in RBC membrane SA content and Na + K + -ATPase activity was observed in older control subjects compared with younger controls. A significant correlation between age, Na + K + -ATPase activity, and SA content was also found. No difference was observed in RBC membrane SA content between IDDM and NIDDM subjects, but Na + K + -ATPase activity was significantly lower in IDDM patients. SA content was increased in NIDDM subjects compared with healthy subjects of similar age, whereas Na + K + ATPase activity was significantly lower in both IDDM and NIDDM subjects compared with controls. In NIDDM, Na + K + -ATPase activity was significantly correlated with age, whereas both Na + K + -ATPase activity and SA content were significantly correlated in IDDM and NIDDM patients. Hemoglobin A 1c (HbA 1c) levels did not show any significant correlation either with Na + K + -ATPase or with SA content in diabetic patients. The modified SA content and Na + K + -ATPase activity in elderly subjects described in the present study indicate a similar behavior of the erythrocyte membrane during both RBC senescence and aging of subjects.

Effect of Ocimum sanctum Leaf Powder on Blood Lipoproteins, Glycated Proteins and Total Amino Acids in Patients with Non-insulin-dependent Diabetes Mellitus

The effect of tulasi ( Ocimum sanctum ) powder supplementation on glycaemic control, lipidaemic control, total amino acids and uronic acid was studied in 27 non-insulindependent diabetes mellitus subjects. All the patients were on hypoglycaemic drugs. The above parameters were monitored at the start and on the thirtieth day. After 1 month of supplementation, a significant lowering of the blood glucose (20.8%), glycated proteins (11.2%), total amino acids (13.5%) and uronic acid (13.7%) was observed. A significant reduction was also noticed in the levels of total cholesterol (11.3%), low-density lipoprotein-cholesterol (14.0%), very low-density lipoprotein-cholesterol (16.3%) and triglycerides (16.4%). No appreciable change was noticed in high-density lipoproteincholesterol.

Increased expression of insulin/insulin-like growth factor-I hybrid receptors in skeletal muscle of noninsulin-dependent diabetes mellitus subjects.

Insulin receptors (IR) and IGF-I receptors (IGF-IR) have been shown to form hybrid receptors in tissues coexpressing both molecules. To date there is no information about the distribution of hybrids in tissues of normal or diabetic subjects. We developed a microwell-based immunoassay to quantitate hybrids in small human tissues samples. Microwells were coated with MA-20 anti-IR antibody or alpha-IGF-IR-PA antibody directed against the IGF-IR alpha-subunit, and incubated with skeletal muscle extracts of patients with noninsulin-dependent diabetes mellitus (NIDDM) and normal controls. Immobilized receptors were incubated with 125I-insulin or 125I-IGF-I in the presence or absence of the two unlabeled ligands. Hybrids were quantified as the fraction of 125I-IGF-I binding immunoadsorbed with MA-20 and expressed as percentage of total IGF-IR (type I+hybrids) immobilized with alpha-IGF-IR-PA. The immunoassay was validated using Western blotting analysis. Relative abundance of hybrids detected in NIDDM patients was higher than in controls. The percentage of hybrids was negatively correlated with IR number and in vivo insulin sensitivity measured by an insulin tolerance test, whereas the percentage was positively correlated with insulinemia. Insulin binding affinity was lower in NIDDM patients than in controls, and was correlated with the percentage of hybrids. Maximal IGF-I binding was significantly higher in muscle from NIDDM patients compared to controls and was positively correlated with the percentage of hybrid receptors whereas IGF-I binding affinity did not differ between the two groups. These results raise the possibility that alterations in expression of hybrid receptors may contribute to decreased insulin sensitivity, and to increased sensitivity to IGF-I. Because IGF-I has been proposed as a hypoglycemic agent in NIDDM, these results are relevant to the development of new approaches to the treatment of insulin resistance of NIDDM.

Glucose and insulin independently reduce the fibrinolytic potential of human vascular smooth muscle cells in culture.

Hyperglycaemia and hyperinsulinaemia have both been related to accelerated atherosclerosis in non-insulin-dependent diabetes mellitus (NIDDM). Plasma fibrinolytic potential is reduced in NIDDM and it is known that glucose and insulin can modulate plasminogen activator inhibitor (PAI-1) and tissue-plasminogen activator (t-PA) secretion and can therefore regulate local fibrinolysis. Vascular smooth muscle cells (vSMC) play an important role in the development of atherosclerotic lesions; however, the role of insulin and glucose in regulating PAI-1 and t-PA production in vSMC is presently not known. Therefore, we cultured arterial vSMC explanted from human umbilical cords and exposed them to increasing concentrations of glucose (5, 12, 20, 27, 35 mmol/l) or insulin (0.1, 0.5, 1, 10 nmol/l) in a serum free medium. After 24 h, PAI-1 and t-PA antigens and activity were evaluated in the culture medium; in cells exposed to 20 mmol/l glucose and to 0.5 nmol/l insulin PAI-1 gene expression was also evaluated. An increase in PAI-1 antigen was observed at each glucose concentration (by 138, 169, 251 and 357% as compared to 5 mmol/l glucose) which was paralleled by an increase in PAI-1 activity. t-PA concentration was also increased by glucose but its activity was sharply reduced. An increase in PAI-1 antigen was detected at each insulin level (by 121, 128, 156 and 300% as compared to no insulin). PAI-1 activity was slightly increased at the lowest insulin concentrations but markedly increased by 10 nmol/l insulin. t-PA antigen was also increased by insulin; however, its activity was markedly reduced at each concentration. As compared to control cells, PAI-1 mRNA was increased by 2.5 and 2.0 fold by 20 mmol/l glucose and 0.5 nmol/l insulin, respectively. We conclude that in human vSMC both glucose and insulin can affect the fibrinolytic balance so as to reduce fibrinolytic potential. This might contribute to decreased local fibrinolysis and thereby might accelerate the atherothrombotic process in NIDDM subjects.

UKPDS 19: heterogeneity in NIDDM: separate contributions of IRS-1 and beta 3-adrenergic-receptor mutations to insulin resistance and obesity respectively with no evidence for glycogen synthase gene mutations. UK Prospective Diabetes Study.

Insulin receptor substrate-1 (IRS-1), beta 3-adrenergic-receptor (beta 3-AR) and glycogen synthase (GS) genes are candidate genes for non-insulin-dependent diabetes mellitus (NIDDM), insulin resistance, dyslipidaemia and obesity. We studied white Caucasian subjects with NIDDM, 227 being randomly selected, 49 NIDDM within the top two percentiles of insulin resistance; 54 with dyslipidaemia in the top quintile of triglyceride/insulin and the bottom quintile of HDL, and 166 non-diabetic control subjects. We examined the association of the simple tandem repeat DNA polymorphisms (STRPs) near the IRS-1 and GS genes, and the prevalence of mutations at codons of IRS-1 513 and 972, beta 3-AR 64 and GS 464 using restriction fragment length polymorphism (RFLP). The STRP alleles in IRS-1 were significantly different between NIDDM and control subjects (p = 0.015). The IRS-1 972 mutation was significantly different between the four groups with increased prevalence in the insulin resistant and dyslipidaemia subjects (18 and 26% compared with 11% in control subjects; p < 0.0005). Those with or without IRS-1 mutations had similar clinical characteristics and impaired insulin sensitivity. beta 3-AR 64 mutation was not significantly different between the four groups but those with the mutation were more obese, with a test for linear association between number of alleles and degree of obesity in an analysis of variance showing a significant association (p = 0.029). The GS 464 mutation was not detected in any of the diabetic or control subjects and the population association study using GS STRP showed no difference in allelic frequencies between NIDDM patients and control subjects. A mutation in lipoprotein lipase at codon 291, associated in the general population with low HDL cholesterol, was not at increased prevalence in the NIDDM patients with dyslipidaemia. In conclusion, IRS-1 972 had an increased prevalence in subjects with insulin resistance, with or without dyslipidaemia. beta 3-AR 64 was associated with increased obesity but not with insulin resistance or dyslipidaemia. These separate contributions to different features of NIDDM are an example of the polygenic inheritance of this heterogeneous disorder.

Proteinuria predicts stroke and other atherosclerotic vascular disease events in nondiabetic and non-insulin-dependent diabetic subjects.

Increased urinary albumin and protein excretion is associated with cardiovascular disease mortality independent of other cardiovascular risk factors in subjects with non-insulin-dependent diabetes mellitus (NIDDM). We assessed the relationship between the different degrees of proteinuria at baseline and the incidence of stroke, as well as other atherosclerotic vascular disease events, in a prospective study of nondiabetic and NIDDM subjects. Our study was based on the 7-year follow-up of cohorts of nondiabetic (n = 1375) and NIDDM (n = 1056) subjects in Finland. The urinary protein concentration at baseline was stratified into three categories: no proteinuria (< 150 mg/L), borderline (150 to 300 mg/L), and clinical proteinuria (> 300 mg/L). The association between the different degrees of proteinuria and the atherosclerotic vascular events was similar in nondiabetic and NIDDM subjects. Cardiovascular disease mortality was higher both in nondiabetic and NIDDM subjects with clinical proteinuria than in those without proteinuria. The incidence of stroke was 1.6% in nondiabetic subjects without proteinuria, 3.2% in subjects with borderline proteinuria, and 8.5% in subjects with clinical proteinuria (P < .001 for trend). In NIDDM patients, the corresponding rates were 7.2%, 11.1%, and 23.0%, respectively (P < .001 for trend). The association between clinical proteinuria and the incidence of stroke remained significant both in nondiabetic and in NIDDM subjects after adjustment for other cardiovascular risk factors. Clinical proteinuria was also associated with the incidence of coronary heart disease events and that of lower-extremity amputation. NIDDM independently increased the risk of atherosclerotic vascular disease events regardless of the proteinuria status. Clinical proteinuria significantly predicted stroke and other atherosclerotic vascular disease events independent of other cardiovascular risk factors. This finding is compatible with the view that increased urinary protein excretion rate may be associated with widespread vascular damage.

Insulin action on glucose transport and plasma membrane GLUT4 content in skeletal muscle from patients with NIDDM.

We investigated the response of the glucose transport system to insulin, in the presence of ambient glucose concentrations, in isolated skeletal muscle from seven patients with non-insulin-dependent diabetes mellitus (NIDDM) (age, 55 +/- 3 years, BMI 27.4 +/- 1.8 kg/m2) and seven healthy control subjects (age, 54 +/- 3 years, BMI 26.5 +/- 1.1 kg/m2). Insulin-mediated whole body glucose utilization was similar between the groups when studied in the presence of ambient glucose concentrations (approximately 10 mmol/l for the NIDDM patients and 5 mmol/l for the control subjects). Samples were obtained from the vastus lateralis muscle, by means of an open muscle biopsy procedure, before and after a 40-min insulin infusion. An increase in serum insulin levels from 54 +/- 12 to 588 +/- 42 pmol/l, induced a 1.6 +/- 0.2-fold increase in glucose transporter protein (GLUT4) in skeletal muscle plasma membranes obtained from the control subjects (p < 0.05), whereas no significant increase was noted in plasma membrane fractions prepared from NIDDM muscles, despite a similar increase in serum insulin levels. At concentrations of 5 mmol/l 3-O-methylglucose in vitro, insulin (600 pmol/l) induced a 2.2-fold (p < 0.05) increase in glucose transport in NIDDM muscles and a 3.4-fold (p < 0.001) increase in the control muscles. Insulin-stimulated 3-O-methylglucose transport was positively correlated with whole body insulin-mediated glucose uptake in all participants (r = 0.78, p < 0.001) and negatively correlated with fasting plasma glucose levels in the NIDDM subjects (r = 0.93, p < 0.001). Muscle fibre type distribution and capillarization were similar between the groups. Our results suggest that insulin-stimulated glucose transport in skeletal muscle from patients with NIDDM is down-regulated in the presence of hyperglycaemia. The increased flux of glucose as a consequence of hyperglycaemia may result in resistance to any further insulin-induced gain of GLUT4 at the level of the plasma membrane.

Effects of posture on the plasma hormonal and renal water-electrolyte excretory responses to acute water loading in diabetic subjects with hypoadrenergic orthostatic hypotension

The effects of posture on the plasma hormonal and renal water-electrolyte excretory responses to acute water loading (20 mL/kg BW, orally) were studied in six non-insulin-dependent diabetes mellitus (NIDDM) subjects with hypoadrenergic orthostatic hypotension (HOH), eight NIDDM subjects without HOH, and seven nondiabetic subjects. The three groups were similar with respect to basal levels of mean blood pressure (MBP), serum sodium and osmolality, plasma renin activity (PRA), the plasma volume regulatory hormones α-atrial natriuretic peptide (ANP), arginine vasopressin (AVP) and aldosterone, and urinary water and sodium excretion. In the supine state, while allowing the subjects to stand only to void, water loading resulted in no changes in MBP and similar responses of these plasma and urinary parameters in the three groups. In the standing state, water loading produced responses of MBP, and plasma and urinary parameters comparable to those in the supine state in the diabetic group without HOH and the nondiabetic group. In the diabetic group with HOH, however, MBP and hourly urinary water and sodium excretion rates were low compared to those in the other two groups. During water loading, plasma ANP decreased, and, despite the fall of MBP, plasma AVP remained unchanged, and PRA and plasma aldosterone increased normally in the diabetic group with HOH. These results demonstrate that, in NIDDM subjects with HOH, changing from lying to standing induces deranged renal water and sodium handling after water loading, accompanied by a decrease in plasma ANP, and inadequate responses of plasma AVP, PRA, and plasma aldosterone to hypotension.

Glycogen synthase activity is reduced in cultured skeletal muscle cells of non-insulin-dependent diabetes mellitus subjects. Biochemical and molecular mechanisms.

To determine whether glycogen synthase (GS) activity remains impaired in skeletal muscle of non-insulin-dependent diabetes mellitus (NIDDM) patients or can be normalized after prolonged culture, needle biopsies of vastus lateralis were obtained from 8 healthy nondiabetic control (ND) and 11 NIDDM subjects. After 4-6 wk growth and 4 d fusion in media containing normal physiologic concentrations of insulin (22 pM) and glucose (5.5 mM), both basal (5.21 +/- 0.79 vs 9.01 +/- 1.25%, P < 0.05) and acute insulin-stimulated (9.35 +/- 1.81 vs 16.31 +/- 2.39, P < 0.05) GS fractional velocity were reduced in NIDDM compared to ND cells. Determination of GS kinetic constants from muscle cells of NIDDM revealed an increased basal and insulin-stimulated Km(0.1) for UDP-glucose, a decreased insulin-stimulated Vmax(0.1) and an increased insulin-stimulated activation constant (A(0.5)) for glucose-6-phosphate. GS protein expression, determined by Western blotting, was decreased in NIDDM compared to ND cells (1.57 +/- 0.29 vs 3.30 +/- 0.41 arbitrary U/mg protein, P < 0.05). GS mRNA abundance also tended to be lower, but not significantly so (0.168 +/- 0.017 vs 0.243 +/- 0.035 arbitrary U, P = 0.08), in myotubes of NIDDM subjects. These results indicate that skeletal muscle cells of NIDDM subjects grown and fused in normal culture conditions retain defects of basal and insulin-stimulated GS activity that involve altered kinetic behavior and possibly reduced GS protein expression. We conclude that impaired regulation of skeletal muscle GS in NIDDM patients is not completely reversible in normal culture conditions and involves mechanisms that may be genetic in origin.

Cellular sodium membrane transport and cardiovascular risk factors in non—Insulin-dependent diabetes mellitus

Associations have been described between cardiovascular risk factors and abnormalities of both sodium-lithium countertransport (SLC) and sodium-hydrogen ion exchange in subjects with insulin-dependent diabetes mellitus. The data in subjects with non-insulin-dependent diabetes mellitus (NIDDM) are few and more conflicting. This investigation examines erythrocyte SLC rates and platelet sodium-hydrogen ion-exchange kinetics and their relationship to cardiovascular risk factors in 45 nondiabetic and 35 NIDDM white men. The two groups did not differ significantly in erythrocyte SLC or platelet buffering capacity, sodium-hydrogen ion-exchange maximal rate (Vmax), or K m for extracellular sodium. Within the whole group, controlling for the presence of diabetes, SLC correlated weakly with triglyceride concentration ( r = .23, P = .05), but not with urinary albumin excretion rate (AER), systolic or diastolic blood pressure, body mass index (BMI), or concentrations of glucose, insulin, or total or high-density lipoprotein (HDL) cholesterol. Platelet sodium-hydrogen exchange was not significantly related to any cardiovascular risk factor studied. In conclusion, (1) SLC activity was not increased in NIDDM subjects; (2) SLC rates correlated weakly with serum triglyceride concentrations; (3) platelet sodium-hydrogen exchange Vmax and K m for extracellular sodium and platelet buffering capacity did not differ between diabetic and nondiabetic groups; and (4) there was no significant relationship between platelet Na + H +-exchange kinetics and any of the cardiovascular risk factors studied.

Superoxide production and LDL oxidation by diabetic neutrophils

The mechanism(s) resulting in the premature atherosclerosis of diabetes is unknown. Increased phagocyte release of reactive oxygen species such as Superoxide anion (O 2 −), resulting in low-density lipoprotein (LDL) oxidation, could be one possible cause. The purpose of the present study was to compare the abilities of polymorphonuclear leukocytes (PMN) from 12 non-insulin-dependent diabetes mellitus (NIDDM) subjects free of vascular disease to produce O 2 − anion and oxidize LDL with PMN from age- and gender-matched normoglycemic controls. PMN were activated with phorbol 12-myristate 13-acetate (PMA) to measure O 2 − production. In addition, the PMN were activated with PMA and opsonized zymosan (OZ) to assess LDL oxidation over 5 hours. LDL oxidation was measured by conjugated diene formation and apolipoprotein B (apo B) fluorescence. PMN superoxide production stimulated by PMA was similar between groups. LDL oxidation by PMN was also not different between the NIDDM and control groups. The results of this study indicate that PMN O 2 − production and LDL oxidation are not enhanced in NIDDM subjects without vascular disease. Other factors, such as reduced antioxidant concentrations and non-enzymatic glycation of LDL, may play a greater role in the premature atherosclerosis of diabetes.

The effect of non-insulin-dependent diabetes mellitus and obesity on glucose transport and phosphorylation in skeletal muscle.

Defects of glucose transport and phosphorylation may underlie insulin resistance in obesity and non-insulin-dependent diabetes mellitus (NIDDM). To test this hypothesis, dynamic imaging of 18F-2-deoxy-glucose uptake into midthigh muscle was performed using positron emission tomography during basal and insulin-stimulated conditions (40 mU/m2 per min), in eight lean nondiabetic, eight obese nondiabetic, and eight obese subjects with NIDDM. In additional studies, vastus lateralis muscle was obtained by percutaneous biopsy during basal and insulin-stimulated conditions for assay of hexokinase and citrate synthase, and for immunohistochemical labeling of Glut 4. Quantitative confocal laser scanning microscopy was used to ascertain Glut 4 at the sarcolemma as an index of insulin-regulated translocation. In lean individuals, insulin stimulated a 10-fold increase of 2-deoxy-2[18F]fluoro-D-glucose (FDG) clearance into muscle and significant increases in the rate constants for inward transport and phosphorylation of FDG. In obese individuals, the rate constant for inward transport of glucose was not increased by insulin infusion and did not differ from values in NIDDM. Insulin stimulation of the rate constant for glucose phosphorylation was similar in obese and lean subjects but reduced in NIDDM. Insulin increased by nearly twofold the number and area of sites labeling for Glut 4 at the sarcolemma in lean volunteers, but in obese and NIDDM subjects translocation of Glut 4 was attenuated. Activities of skeletal muscle HK I and II were similar in lean, obese and NIDDM subjects. These in vivo and ex vivo assessments indicate that impaired glucose transport plays a key role in insulin resistance of NIDDM and obesity and that an additional impairment of glucose phosphorylation is evident in the insulin resistance of NIDDM.

Searching for NIDDM susceptibility genes: studies of genes with triplet repeats expressed in skeletal muscle.

The expansion of trinucleotide repeats has been associated with late-onset neurodegenerative disorders. Although the genes harbouring the triplet expansions may be widely expressed, the pathological expression of these diseases is restricted to specific tissues. Non-insulin-dependent diabetes mellitus (NIDDM) shares several features with diseases resulting from such dynamic mutations including late-onset and specific but limited sites of tissue pathology-muscle, fat, liver and insulin-secreting pancreatic beta cells. In order to examine the contribution of genes containing polymorphic CAG/CTG repeats to the development of NIDDM, we screened an adult human skeletal muscle cDNA library for expressed sequences containing tandem repeats of CAG and/ or CTG. Ten different loci with polymorphic CAG/ CTG repeats were identified, of which seven had a heterozygosity greater than 0.20. There was no evidence for linkage between these seven loci and NIDDM in a group of affected Mexican-American sib pairs. Nor was there a significant difference in the distribution of alleles between Caucasian patients with NIDDM and normal healthy control subjects or evidence for repeat expansion in diabetic subjects. Thus, muscle genes with polymorphic CAG/CTG repeats do not appear to play a significant role in the development of NIDDM.