The Metabolic Syndrome: A Concept Hard to Define

The metabolic syndrome integrates, in a single diagnosis, the manifestations of insulin resistance that may lead to increased cardiovascular morbidity and precedes type 2 diabetes. Here we discuss the strengths and limitations of the definitions of the metabolic syndrome and the epidemiology of the syndrome including information from non-Caucasian populations. The definitions proposed by the World Health Organization (WHO) and the National Cholesterol Education Program (NCEP) are the most frequently used. The relative risk of having long-term complications is greater for the WHO definition; this is explained by the inclusion of the insulin resistance criteria. The cut-off points used in these definitions should be, but are not, adjusted for ethnicity; as a result, in non-Caucasian subjects, there is lack of agreement among these criteria. In a Mexican population-based survey the prevalence was 13.61% using the WHO definition and 26.6% using the NCEP-III criteria. Cases identified by the WHO criteria had a more severe form of the disease. We propose that the metabolic syndrome should be viewed as a progressive long-term process that leads to major complications. Its definition should reflect the continuous nature of the disease; the categorical approach of the current criteria oversimplifies the complexity of the syndrome. The threshold for defining abnormality should be based on the associated risk of the identified phenotype. Refinement of the definition of both affected and nonaffected subjects is required. The available definitions include, in each of these categories, heterogeneous groups with a broad range of risk of future complications.

Management of the metabolic syndrome as a strategy for preventing the macrovascular complications of type 2 diabetes: controversial issues

The metabolic syndrome is known to increase cardiovascular morbidity and precede the development of type 2 diabetes. Even before the appearance of hyperglycemia, the components of the metabolic syndrome play a crucial role in the pathogenesis of the macrovascular complications. Thus, the recognition and treatment of the metabolic syndrome may be a strategy to prevent the most likely cause of death (i.e. cardiovascular events) in cases that eventually develop type 2 diabetes. In this review, controversial issues regarding the treatment of the two main components of the metabolic syndrome (i.e dyslipidemia and arterial hypertension) are discussed. Several disparities in the current NCEP-ATPIII recommendations, when applied to patients with the metabolic syndrome, are pointed out. In population-based studies, the number of individuals with the metabolic syndrome who would need LDL cholesterol lowering treatment following these guidelines is remarkably low compared to subjects belonging to the same risk strata (10 year risk 10-20%). Subjects with the metabolic syndrome do not fall into the same risk category, resulting in differing LDL-C targets. Also, the Framingham tables underestimate the cardiovascular risk associated with the metabolic syndrome; hence fewer cases qualify for drug therapy. In addition, LDL-C underestimates the number of atherogenic particles and is therefore not the ideal target for these patients. The selection of antihypertensive medication in the metabolic syndrome is also controversial. Thus, there is sufficient evidence for a review of the current management of the metabolic syndrome as part of a strategy to prevent the macrovascular complications in type 2 diabetes.

Coarsening dynamics of the one-dimensional Cahn-Hilliard model

The dynamics of one-dimensional Cahn-Hilliard model is studied. The stationary and particle-type solutions, the bubbles, are perused as a function of initial conditions, boundary conditions, and system size. We characterize the bubble solutions which are involved in the coarsening dynamics and establish the bifurcation scenarios of the system. A set of ordinary differential equation permits us to describe the coarsening dynamics in very good agreement with numerical simulations. We also compare these dynamics with the bubble dynamics deduced from the classical kink interaction computation where our model seems to be more appropriated. In the case of two bubbles, we deduce analytical expressions for the bubble's position and the bubble's width. Besides, a simple description of the ulterior dynamics is presented.

Applicability of the National Cholesterol Education Program III (NCEP-III) guidelines for treatment of dyslipidemia in a non-Caucasian population: a Mexican nation-wide survey

We assessed the impact of the NCEP-III recommendations in a population-based, nation-wide Mexican survey. Information was obtained from 15,607 subjects aged 20 to 69 years. In this report, only samples obtained after a 9 to 12 hours fast are included (2,201 cases). A cardiovascular risk equivalent was found in 10.5% and > or = 2 risk factors were present in 41.7% of the population. In 10% of cases, the LDL-C concentration was high enough to be an indication for a lipid-lowering drug (> 160 mg/dL), independent of the presence of risk factors. A quarter of the population was eligible for some form of treatment (lifestyle modifications in 15.9%, drug therapy in an additional 11.7%). Among cases with > or = 2 risk factors, a small percentage (1.8%) were identified as having a 10 year-risk > 20% and 86.3% were considered as having a 10 year-risk < 10%. The majority of the metabolic syndrome cases (84%) were identified as low-risk subjects. As a result, only 17.6% of them qualified for drug-based LDL-C lowering. Our data helps to estimate of the magnitude of the burden imposed on the Mexican health system, of lowering LDL-C for cardiovascular prevention. If we apply our results to the 2,000 Mexican population census more than 5.8 million cases nationwide may require LDL lowering drug therapy following the NCEP-III criteria.

High prevalence of metabolic syndrome in Mexico

BACKGROUND

Our objective was to describe the prevalence of the metabolic syndrome using World Health Organization (WHO) and National Cholesterol Education Program (NCEP-III) definitions in a population-based survey.

METHODS

We performed an analysis of data from a Mexican nationwide, population-based study. The population was composed of 2,158 men and women aged 20-69 years sampled after a 9-12 h fasting period. Prevalence of the metabolic syndrome as defined by the NCEP-III definition and WHO criteria was estimated and case characteristics were assessed.

RESULTS

Age-adjusted prevalence was 13.61% for WHO criteria and 26.6% for the NCEP-III definition. Prevalence was 9.2 and 21.4%, respectively, in subjects without diabetes. Thirty five percent of affected cases were <40 years of age. In addition to criteria used for diagnosis, ca. 90% were either overweight or obese. In cases detected using WHO criteria, antihypertensive treatment or blood pressure reading >140/90 was found in 61.8%. The proportion of subjects who qualified for hypolipemiant treatment was lower: lifestyle modifications were needed in 42.1% and drug therapy was required in 18.9%. The same trends were found for cases detected using the NCEP definition.

CONCLUSIONS

Prevalence of the metabolic syndrome in Mexico is high. A large proportion of affected cases qualify for preventive actions for complications of the metabolic syndrome (i.e., weight loss, antihypertensive or hypolipemiant treatment). These results provide data for planning therapeutic programs for Mexican patients with the metabolic syndrome.

Tuberculosis and diabetes in southern Mexico

OBJECTIVE

To determine the impact of diabetes on the rates of tuberculosis in a region where both diseases are prevalent.

RESEARCH DESIGN AND METHODS

Data from a population-based cohort of patients with pulmonary tuberculosis undergoing clinical and mycobacteriologic evaluation (isolation, identification, drug-susceptibility testing, and IS6110-based genotyping and spoligotyping) were linked to the 2000 National Health Survey (ENSA2000), a national probabilistic, polystage, stratified, cluster household survey of the civilian, noninstitutionalized population of Mexico.

RESULTS

From March 1995 to March 2003, 581 patients with Mycobacterium tuberculosis culture and fingerprint were diagnosed, 29.6% of whom had been diagnosed previously with diabetes by a physician. According to the ENSA2000, the estimated prevalence of diabetes in the study area was 5.3% (95% CI 4.1-6.5). The estimated rates of tuberculosis for the study area were greater for patients with diabetes than for nondiabetic individuals (209.5 vs. 30.7 per 100000 person-years, P < 0.0001).

CONCLUSIONS

In this setting, the rate of tuberculosis was increased 6.8-fold (95% CI 5.7-8.2, P < 0.0001) in patients with diabetes due to increases in both reactivated and recently transmitted infection. Comorbidity with diabetes may increase tuberculosis rates as much as coinfection with human immunodeficiency virus (HIV), with important implications for the allocation of health care resources.

[The metabolic syndrome: a concept in evolution]

The concept metabolic syndrome intends to incorporate in a single disorder all biologic consequences of insulin resistance and associated conditions. The objective of this paper was to discuss strengths and limitations of current definitions of the metabolic syndrome, its epidemiology, and its association with non-alcoholic steatohepatitis (NASH). Definitions proposed by the World Health Organization (WHO) and the National Cholesterol Education Program (NCEP) are specific but possess low sensitivity for detecting insulin resistance. Cut-off points used in these definitions should be "but are not" adjusted for ethnicity; as a result, in non-Caucasian subjects there is lack of agreement among these. For example, in a Mexican population-based survey prevalence was 13.61% using the WHO definition and 26.6% employing NCEP-III criteria. Cases identified with WHO criteria have a more severe form of the disease. NASH is the most common cause of abnormal levels of serum aminotransferases. It shares some aspects of its pathophysiology with the metabolic syndrome and its prevalence is higher among cases with metabolic syndrome compared to with general population. NASH appears to be the hepatic manifestation of the metabolic syndrome.

Prevalence of oral mucosal lesions in elderly people in Santiago, Chile

BACKGROUND

Oral prevalence studies are important to know the state of health and the needs of treatment. Our aim was to determine the prevalence of oral mucosal lesions and associated factors among aging Chileans.

METHODS

A random sample by age, gender, and socioeconomic status was obtained, comprising 889 individuals older than 65 years. Individuals were interviewed and examined in Santiago, the capital of Chile, according to the World Health Organization guidelines.

RESULTS

The prevalence of one or more oral mucosal lesions in the sample was 53%. Logistic regression model revealed that denture use increased the probability of one or more oral mucosal lesions by threefold, while age, gender, smoking, medication use, xerostomia, and social or cultural factors had no effect. The most common lesion was denture stomatitis (22.3%), followed by irritative hyperplasia (9.4%), oral mucosal varicosities (9%), solitary pigmented lesions (4%), traumatic ulcer (3.5%), angular cheilitis (2.9%), multiple pigmented lesions (2.8%), hemangioma (2.3%), lichen planus (2.1%), leukoplakia (1.7%), recurrent aphthous stomatitis (1.4%), nicotine stomatitis (1.3%), median rhomboid glossitis (0.9%), actinic cheilitis (0.9%), pyogenic granuloma (0.7%), oral squamous papiloma (0.6%), and mucocele (0.2%). One case of oral cancer was observed. Different factors increased the probability of specific oral mucosal pathologies.

CONCLUSIONS

We can conclude that oral mucosal lesions are common in elderly people in Santiago, suggesting the necessity for improved standards of prevention, and diagnostic and opportune treatment of these lesions.

BALB/C mice injected with LSTRA leukemic cell line are cured by in vivo treatment with IL-2 + GM-CSF

We studied the effects of the in vivo administration of interleukin-2 (IL-2) (at low doses) + GM-CSF in BALB/C mice injected intraperitoneally with LSTRA murine leukemic cell line in order to test the possible role of this immunotherapeutic approach in the eradication of leukemia. Mice were injected intraperitoneally on day -1 with different concentrations of LSTRA cells. On day 0, mice received a lethal dose of TBI of 700 cGy from a Cs(137) source, followed by a single high dose of recombinant human-granulocyte-colony stimulating factor (rh-G-CSF) (1 microg/g) intraperitoneally 2h after TBI. This procedure rescued 80% of mice but only mice injected with the lower concentration of LSTRA cells (10(3)) could be cured. The lethal dose (LD 100/60) of LSTRA in normal mice was 10(4). The subcutaneous administration of rh-IL-2 (4.000 IU/mouse per day, from day +1 to +28) + rm-GM-CSF (1 microg/kg per day) from day +7 to +28 cured mice injected with 10(4) LSTRA cells and 40% of mice injected with 10(5) cells. Mice injected with 10(6) cells died from leukemia. We observed an increase in LAK activity on days +21 and +28 without an increase in NK activity. We show that BALB/C mice injected with LSTRA cell line can be cured by in vivo activation with IL-2 + GM-CSF depending on the cell dose injected. The curability of leukemia was confirmed at the molecular level with a PCR method.

Spirometric variability in a longitudinal study of school-age children

OBJECTIVES

To describe spirometric reproducibility in a longitudinal study of students from Mexico City, and also the frequency of subjects fulfilling quality criteria proposed for children.

SUBJECTS AND METHODS

Three thousand three hundred forty-seven participants from the third through sixth grades of elementary school were recruited to perform biannual spirometry, yielding a maximum of seven evaluations and a total of 15,563 tests. Standard recommendations of the American Thoracic Society (ATS) were followed, using dry rolling-seal volume spirometers.

RESULTS

During their first spirometric test, > 95% of the subjects fulfilled each of the quality criteria proposed by ATS for adults, though not all of them did so simultaneously. For example, only 72.4% obtained three acceptable maneuvers, reproducibility for FEV(1) and FVC to < 200 mL, and a small back-extrapolated volume that increased to 92.3% by the second test. Between phase 1 and phase 7 of the study, spirometry quality increased significantly, as a result of subject and technician training. Intratest and intertest (with a 6-month difference) spirometric variability was less in boys than in girls. Intratest variability was also lower in younger and taller subjects. Technicians contributed significantly to intratest and intertest variability, the latter decreasing if the same technician performed both evaluations.

CONCLUSION

Children > 7 years old can fulfill ATS criteria of quality after the first spirometric evaluation. To maintain quality of spirometric tests in longitudinal studies of children, a strict control is required, especially of technician performance.

Spirometric function in children of Mexico City compared to Mexican-American children

We set out to describe the pattern of lung function growth in Mexican students from 8-20 years of age, using internationally accepted equipment and methodology, and to compare it to values reported for Mexican-American children. Out of a total of 6,803 students from primary school to high school studied cross-sectionally in the Mexico City metropolitan area, we selected 4,009 asymptomatic, nonobese, nonsmoker subjects to generate spirometric prediction equations. We describe regression equations for the main spirometric variables (log transformed) based on age, height, and weight, and separated for males and females. Spirometric function in the population studied was above that predicted for European (Quanjer et al. [1987] Pediatr Pulmonol 19:135-142) or Mexican-American children, for the same age, height, and gender. On average, forced expiratory volume in 1 sec (FEV(1)) in Mexican children was 9.5% above that of Europeans (Quanjer et al. [1987] Pediatr Pulmonol 19:135-142), 14% and 5% above Hispanics reported by (Coultas et al. [1988] Am Rev Respir Dis 138:1386-1392) and (Hsu et al. [1979] J Pediatr 95:14-23), respectively, and 5% above Mexican-Americans from the third National Health and Nutrition Examination Survey study. Similarly, FVC was 8%, 14%, 8%, and 5.6% above the figures predicted by the same authors. The largest errors of prediction of foreign equations occurred in extremely tall or short subjects, and therefore a single proportional adjustment is unfeasible.

Randomised controlled trial of montelukast plus inhaled budesonide versus double dose inhaled budesonide in adult patients with asthma

BACKGROUND

Inhaled corticosteroids (ICS) affect many inflammatory pathways in asthma but have little impact on cysteinyl leukotrienes. This may partly explain persistent airway inflammation during chronic ICS treatment and failure to achieve adequate asthma control in some patients. This double blind, randomised, parallel group, non-inferiority, multicentre 16 week study compared the clinical benefits of adding montelukast to budesonide with doubling the budesonide dose in adults with asthma.

METHODS

After a 1 month single blind run in period, patients inadequately controlled on inhaled budesonide (800 microg/day) were randomised to receive montelukast 10 mg + inhaled budesonide 800 microg/day (n=448) or budesonide 1600 microg/day (n=441) for 12 weeks.

RESULTS

Both groups showed progressive improvement in several measures of asthma control compared with baseline. Mean morning peak expiratory flow (AM PEF) improved similarly in the last 10 weeks of treatment compared with baseline in both the montelukast + budesonide group and in the double dose budesonide group (33.5 v 30.1 l/min). During days 1-3 after start of treatment, the change in AM PEF from baseline was significantly greater in the montelukast + budesonide group than in the double dose budesonide group (20.1 v 9.6 l/min, p<0.001), indicating faster onset of action in the montelukast group. Both groups showed similar improvements with respect to "as needed" beta agonist use, mean daytime symptom score, nocturnal awakenings, exacerbations, asthma free days, peripheral eosinophil counts, and asthma specific quality of life. Both montelukast + budesonide and double dose budesonide were generally well tolerated.

CONCLUSION

The addition of montelukast to inhaled budesonide is an effective and well tolerated alternative to doubling the dose of inhaled budesonide in adult asthma patients experiencing symptoms and inadequate control on budesonide alone.

[Characteristics of mixed hyperlipidemia cases in a population-based study: results from the Mexican National Survey of Chronic Diseases]

OBJECTIVE

To describe the characteristics of mixed hyperlipidemia cases, using data derived from the Encuesta Nacional de Enfermedades Crónicas (Mexican National Survey of Chronic Diseases, ENEC).

MATERIAL AND METHODS

The ENEC was conducted in 1993, in 417 Mexican cities. Blood measurements of lipids, glucose, and insulin were obtained from 2206 cases. Differences between dyslipidemia patients and non cases were obtained using analysis of variance or the chi-squared test.

RESULTS

Mixed hyperlipidemia was diagnosed in 282 subjects (12.8%). Cases were 42.7+/-12.6 years old. Fifty six percent were males and 46.4% had HDL cholesterol levels < 0.9 mmol/l. Other cardiovascular risk factors were also present. The prevalence of mixed hyperlipidemia was high even among young adults. A logistic regression model showed that obesity, age, male gender, residence in some regions of Mexico, diabetes, arterial hypertension, and fasting insulin levels >21 mU/ml, were factors associated with mixed hyperlipidemia.

CONCLUSIONS

Mixed hyperlipidemia is a very common condition in Mexican adults. It is more common in males older than 30 years, with additional cardiovascular risk factors. Study findings suggest that the metabolic syndrome plays a role in the pathogenesis of this disorder.

Prevalence and characteristics of early-onset type 2 diabetes in Mexico

OBJECTIVE

To investigate the prevalence and characteristics of patients with type 2 diabetes diagnosed before the age of 40 years (early-onset disease) in a nationwide, population-based study.

METHODS

Using a multistage sampling procedure, we enrolled a representative sample of Mexican urban adults aged 20 to 69 years. Weight, height, blood pressure, and plasma levels of glucose, insulin, and other metabolic parameters were measured in all subjects.

RESULTS

We identified 993 subjects with type 2 diabetes, including 143 subjects aged 20 to 39 years (14% of those with diabetes). Subjects with early-onset diabetes had a greater prevalence of obesity and higher plasma insulin and lipid levels than did age-matched controls, and a greater prevalence of high-density lipoprotein cholesterol levels <35 mg/dL and severe hypertriglyceridemia than did older subjects with diabetes. Those (n = 32) with a normal body mass index (20 to 25 kg/m(2)) tended to have insulin deficiency as the main abnormality, whereas the "metabolic syndrome" characterized the remaining 111 subjects with early-onset diabetes.

CONCLUSION

Most patients with early-onset type 2 diabetes in Mexico are obese or overweight, suggesting that obesity treatment and prevention programs may be effective in reducing the prevalence of this disease.

Apolipoprotein B and A-I distribution in Mexican urban adults: results of a nationwide survey

The apolipoprotein (apo) B and A-I distribution found in a survey performed in 417 Mexican cities is described. Information was obtained from 15,607 subjects aged 20 to 69 years. In this report, only samples obtained after a 9- to 12-hour fast were included (1,674 cases, 652 men and 1,022 women). The population is representative of the Mexican urban adults. Mean lipid concentrations were: cholesterol,182.7 mg/dL; triglycerides, 213 mg/dL; high-density lipoprotein (HDL) cholesterol, 38.3 mg/dL; and low-density lipoprotein (LDL) cholesterol, 116 mg/dL. The mean concentration of apo B was 77.8 +/- 25.9 mg/dL and 71 +/- 22.8 in men and women, respectively. A continuous increase of apo B was observed as subjects got older. A tendency to decrease after age 60 was observed in men, but not in women. The body mass index (BMI) is a major determinant for the apo B concentrations. The 90th percentile of the apo B concentration identifies a similar proportion of abnormal subjects than the LDL cholesterol concentration of 160 mg/dL. The 120 mg/dL concentration, upper normal limit level used in other populations, identified as abnormal only 3.8% of the cases. Regardless of the lipid abnormality, an apo B above the 90th percentile was associated with higher levels of glucose, cholesterol, triglycerides, and non-HDL cholesterol, despite a similar age and BMI. The overall mean concentration of apo A-I was 122.3 +/- 31 mg/dL and 129 +/- 34 in men and women, respectively. In conclusion, our data show that the apo B and apo A-I concentrations in Mexican urban adults are lower compared with the levels reported in other ethnic groups. Previously used reference ranges are not useful in the population report herein. These observations strengthen the need for obtaining data in population-based studies worldwide.

Optical absorption for parallel cylinder arrays

We study the long-wavelength electromagnetic resonances of interacting cylinder arrays. By using a normal-modes expansion where the effects of geometry and material are separated, it is shown that two parallel cylinders with different radii have electromagnetic modes distributed symmetrically about depolarization factor 1 / 2. Both sets couple to longitudinal and transverse components of the external field, but amplitudes of symmetric depolarization factors become exchanged when considering longitudinal or transverse polarization. We also find that amplitudes satisfy sum rules that depend on the ratio of the cylinders radii. The main effect of the difference in radii is a spectral shift towards the isolated cylinder resonance as this difference increases.

Antiganglioside antibodies in acute self-limiting ataxic neuropathy: incidence and significance

Antidisialosyl antibodies have been previously associated to chronic and acute ataxic neuropathies. We studied the presence of these antibodies in nine patients with acute self-limiting ataxic neuropathy (ASLAN) using ELISA and TLC immunodetection. One patient showed serum IgG immunoreactivity against gangliosides GD3 and GQ1b. The patient's IgG was able to bind to the nodes of Ranvier on frozen human dorsal root. Our studies confirmed that antidisialosyl reactivity is associated to ataxic neuropathy and its specific binding to the dorsal root could explain the predominant sensory involvement. Nevertheless, the low incidence of this reactivity indicates that a different pathogenic mechanism should be involved in most ASLAN patients.

Cdc42-dependent modulation of tight junctions and membrane protein traffic in polarized Madin-Darby canine kidney cells

Polarized epithelial cells maintain the asymmetric composition of their apical and basolateral membrane domains by at least two different processes. These include the regulated trafficking of macromolecules from the biosynthetic and endocytic pathway to the appropriate membrane domain and the ability of the tight junction to prevent free mixing of membrane domain-specific proteins and lipids. Cdc42, a Rho family GTPase, is known to govern cellular polarity and membrane traffic in several cell types. We examined whether this protein regulated tight junction function in Madin-Darby canine kidney cells and pathways that direct proteins to the apical and basolateral surface of these cells. We used Madin-Darby canine kidney cells that expressed dominant-active or dominant-negative mutants of Cdc42 under the control of a tetracycline-repressible system. Here we report that expression of dominant-active Cdc42V12 or dominant-negative Cdc42N17 altered tight junction function. Expression of Cdc42V12 slowed endocytic and biosynthetic traffic, and expression of Cdc42N17 slowed apical endocytosis and basolateral to apical transcytosis but stimulated biosynthetic traffic. These results indicate that Cdc42 may modulate multiple cellular pathways required for the maintenance of epithelial cell polarity.

High prevalence of low HDL cholesterol concentrations and mixed hyperlipidemia in a Mexican nationwide survey

The prevalence of lipid abnormalities revealed in a survey done in 417 Mexican cities is described. Information was obtained on 15,607 subjects, aged 20 to 69 years. In this report, only samples obtained after a 9- to 12-h fast were included (2,256 cases: 953 men and 1,303 women). The population is representative of Mexican urban adults. Mean lipid concentrations were: cholesterol, 4.80 mmol/l; triglycerides, 2.39 mmol/l; HDL cholesterol, 1.00 mmol/l; and LDL cholesterol, 3.06 mmol/l. The most prevalent abnormality was HDL cholesterol below 0.9 mmol/l (46.2% for men and 28.7% for women). Hypertriglyceridemia (>2.26 mmol/l) was the second most prevalent abnormality (24.3%). Severe hypertriglyceridemia (>11.2 mmol/l) was observed in 0.42% of the population. Increased LDL cholesterol (> or =4.21 mmol/l) was observed in 11.2% of the sample. Half of the hypertriglyceridemic subjects had a mixed dyslipidemia or low HDL cholesterol. More than 50% of the low HDL cholesterol cases were not related to hypertriglyceridemia. Insulin resistance was found in 59% of them. In conclusion, the prevalence of hypoalphalipoproteinemia and other forms of dyslipidemia in Mexican adults is very high and it is among the highest previously reported worldwide.

Modulation of adenosine transport by insulin in human umbilical artery smooth muscle cells from normal or gestational diabetic pregnancies

1. Adenosine transport was measured in human cultured umbilical artery smooth muscle cells, isolated from non-diabetic or gestational diabetic pregnancies, under basal conditions and after pretreatment in vitro with insulin. 2. Adenosine transport in non-diabetic smooth muscle cells was significantly increased by insulin (half-maximal stimulation at 0.33 +/- 0.02 nM, 8 h) and characterized by a higher maximal rate (V(max)) for nitrobenzylthioinosine (NBMPR)-sensitive (es) saturable nucleoside transport (17 +/- 5 vs. 52 +/- 12 pmol (microg protein)(-1) min(-1), control vs. insulin, respectively) and maximal binding sites (B(max)) for [(3)H]NBMPR (0.66 +/- 0.07 vs. 1.1 +/- 0.1 fmol (microg protein)(-1), control vs. insulin, respectively), with no significant changes in Michaelis-Menten (K(m)) and dissociation (K(d)) constants. 3. In contrast, in smooth muscle cells from diabetic pregnancies, where the values of V(max) for adenosine transport (59 +/- 4 pmol (microg protein)(-1) min(-1)) and B(max) for [(3)H]NBMPR binding (1.62 +/- 0.16 fmol (microg protein)(-1)) were significantly elevated by comparison with non-diabetic cells, insulin treatment (1 nM, 8 h) reduced the V(max) for adenosine transport and B(max) for [(3)H]NBMPR binding to levels detected in non-diabetic cells. 4. In non-diabetic cells, the stimulatory effect of insulin on adenosine transport was mimicked by dibutyryl cGMP (100 nM) and reduced by inhibitors of phosphatidylinositol 3-kinase (10 nM wortmannin), nitric oxide synthase (100 microM N (G)-nitro-L-arginine methyl ester, L-NAME) or protein synthesis (1 microM cycloheximide), whereas inhibition of adenylyl cyclase (100 microM SQ-22536) had no effect. 5. Wortmannin or SQ-22536, but not L-NAME or cycloheximide, attenuated the inhibitory action of insulin on the diabetes-induced stimulation of adenosine transport. 6. Protein levels of inducible NO synthase (iNOS) were similar in non-diabetic and diabetic cells, but were increased by insulin (1 nM, 8 h) only in non-diabetic smooth muscle cells. 7. Our results suggest that adenosine transport via the es nucleoside transporter is modulated differentially by insulin in either cell type. Insulin increased adenosine transport in non-diabetic cells via NO and cGMP, but inhibited the diabetes-elevated adenosine transport via activation of adenylyl cyclase, suggesting that the biological actions of adenosine may be altered under conditions of sustained hyperglycaemia in uncontrolled diabetes.