Cross-sectional and prospective associations between proinsulin and cardiovascular disease risk factors in a population experiencing rapid cultural transition

Incident diabetes, hypertension and dyslipidemia in a Manitoba First Nation

Background

Diabetes and diabetes complications are substantially higher among Canadian First Nations populations compared with the general Canadian population. However, incidence data using detailed individual assessments from a population-based cohort have not been undertaken.

Objective

We sought to describe incident diabetes, hypertension and dyslipidemia in a population-based cohort from a Manitoba Ojibway First Nation community.

Design

Study data were from 2 diabetes screening studies in Sandy Bay First Nation in Manitoba, Canada, collected in 2002/2003 and 2011/2012. The cohort comprised of respondents to both screening studies (n=171). Health and demographic data were collected using a questionnaire. Fasting blood samples, blood pressure and anthropometric data were also collected objectively. Incident diabetes, hypertension and dyslipidemia were determined. Generalized linear models with Poisson distribution were used to estimate risk of incident diabetes and cardiometabolic conditions according to age and sex.

Results

There were 35 (95% CI: 26, 45) new cases of diabetes among 128 participants without diabetes at baseline (27 or 3.3% per year). While participants who were 50 years and older at baseline had a significantly higher risk of incident diabetes at follow-up compared with participants aged 18–29 at baseline (p=0.012), more than half of the incident cases of diabetes occurred among participants aged less than 40 at baseline. There were 28 (95% CI: 20, 37) new cases of dyslipidemia at follow-up among 112 without dyslipidemia at baseline (25%). There were 36 (95% CI: 31, 42) new cases of hypertension among 104 participants without hypertension at baseline (34.6%). Women had half the risk of developing hypertension compared with men (p=0.039).

Conclusions

Diabetes incidence is very high, and the number of new cases among those younger than 40 is a concern. Additional public health and primary care efforts are needed to address the diabetes burden in this First Nation community.

Detection of the single-chain precursor in the production and purification process of recombinant human insulin

High quality recombinant insulin requires being free of single-chain precursor (proinsulin), a task that depends on the selectivity and sensitivity of the monitoring process for detecting proinsulin. In this study we developed an enzyme-linked immunosorbent assay (ELISA) system that was specifically tailored to detect recombinant proinsulin. The proinsulin consists of six components: an initiating methionine, 48 amino acids from human growth hormones (HGH, used as the protection peptide), first connecting Arg-residue, B-chain of insulin, and second connecting Arg-peptide and A-chain of insulin. This form of proinsulin is more stable and can be efficiently expressed by E. coli than insulin. Herein, we evaluated the specificity, precision, recovery, sensitivity, and detection range of the proinsulin ELISA kit. The results showed that the ELISA kit is a very useful tool for monitoring the proinsulin yield in early stages of insulin production as well as the residual proinsulin in the final product, insulin.

Effect of insulin glulisine on microvascular blood flow and endothelial function in the postprandial state

OBJECTIVE

To investigate the effect of insulin glulisine on postprandial microvascular blood flow in type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 15 patients with type 2 diabetes received insulin glulisine or human insulin before a liquid meal test. Thereafter, skin microvascular blood flow was measured by laser Doppler fluxmetry and blood samples were taken for measurement of plasma levels of glucose, insulin, intact proinsulin, asymmetric dimethylarginine, nitrotyrosine, interleukin-18, matrix metalloproteinase-9, oxidized LDL, and free fatty acids.

RESULTS

Insulin glulisine injections resulted in higher postprandial insulin levels (means +/- SEM area under the curve [AUC](0-120) 51.0 +/- 6.8 vs. 38.2 +/- 5.4 mU/l; P = 0.004), while plasma glucose (AUC(0-240) 158 +/- 9 vs. 180 +/- 9 mg/dl; P < 0.05) and intact proinsulin (AUC(0-240) 26.2 +/- 3.5 vs. 31.2 +/- 4.3 pmol/l; P = 0.002) were lower. Microvascular blood flow increased after insulin glulisine injection (27.9 +/- 3.1 to 51.7 +/- 9.9 arbitrary units [AU]; P < 0.05), while only a minor increase was found during human insulin (27.9 +/- 3.1 to 34.4 +/- 7.8 AU; not significant). Asymmetric dimethylarginine and nitrotyrosine levels were reduced after insulin glulisine (P < 0.05).

CONCLUSIONS

Insulin glulisine is superior to human insulin in restoring postprandial metabolic and microvascular physiology.

Application of monoclonal antibody-based sandwich enzymeimmunoassay in detection of human serum proinsulin

AIM: To develop a highly sensitive and specific ELISA to detect the human serum proinsulin, and to explore the relationship between proinsulin and cardiovascular risk factors in a population-based epidemiological study.

METHODS: The assay was based on two monoclonal antibodies, an anti-C-peptide antibody bound to a microtest plate and a biotin-labeled anti-insulin antibody. The biotin-avidin ELISA was used to measure the serum proinsulin of 1196 subjects who aged 35-59 in Pizhou, Jiangsu Province.

RESULTS: With a detection limit of 0.83 pmol/L, the ELISA covered a standard linear range of 0.83-142 pmol/L, and the human insulin and human C-peptide did not cross-react at 1 200 and 3 960 pmol/L respectively. The inter- and inner-assay coefficient of variation of the ELISA were less than 11.4% and 11.2% respectively. The results of the population-based epidemiological study indicated that the concentration of proinsulin had significantly positive correlations with body mass index (BMI), waist, systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TCH), triglycerides (TG), low density lipoprotein cholesterol (LDL-C), and cardiovascular risk factors clustering and negative association with high density lipoprotein cholesterol (HDL-C).

CONCLUSION: The monoclonal-based BA-ELISA can be used to detect serum proinsulin in the clinical and epidemiological study. The mechanism underlying the relationship between proinsulin and cardiovascular risk factors may be related to the fibrinolysis and damages of β-cells.

Initiating oral glucose-lowering therapy with metformin in tyape 2 diabetic patients: an evidence-based strategy to reduce the burden of late-developing diabetes complications

A major aim of glucose-lowering therapy in people with diabetes is to delay or prevent the late-developing complications of diabetes that threaten the quality and duration of life. While intensive interventions to control hyperglycaemia may impair well-being to some extent, the balance of quality of life is usually highly positive. Diet and exercise therapy remains the cornerstone of management, and should usually be given a trial alone first. However, the magnitude and duration of benefit from this intervention is insufficient for most people. More frequent, early, use of metformin is an evidence-based strategy for reducing the risk of adverse outcomes of diabetes in people with type 2 diabetes with sub-optimal glucose control on lifestyle measures alone. This has been recognised in recent evidenced-based guidelines from the UK National Institute for Clinical Excellence and from Diabetes UK, which now support the use of metformin as initial pharmacological therapy for all people without contraindications to the drug. Other national and local guideline committees should consider updating their recommendations on diabetes management in line with these findings.

Relation of waist circumference and glycemic status to C-reactive protein in the Sandy Lake Oji-Cree

OBJECTIVE

To determine the prevalence of elevated C-reactive protein (CRP) in the Sandy Lake Oji-Cree, an aboriginal community residing in the Sioux Lookout zone of Northwestern Ontario, Canada, and to determine the associations of obesity and diabetes with CRP in a community with a very high prevalence of type II diabetes.

DESIGN

We surveyed 512 community members aged 18 y and older to determine the prevalence and the determinants of elevated CRP in Sandy Lake.

MEASUREMENTS

Clinical variables, indices of obesity and serum concentrations of CRP, insulin, serum amyloid A (SAA) and interleukin-6 (IL-6).

RESULTS

The prevalence of CRP >or=3.8 mg/l was significantly higher in women than in men (51% vs. 32%, P<0.0001). Regression analysis determined that body mass index and IL-6 were independent determinants of CRP concentration in women and waist circumference and IL-6 were independent determinants of CRP concentration in men. Diabetes was associated with elevated CRP in both sexes, but was only a moderate strong determinant in CRP concentration in multivariate regression analysis.

CONCLUSIONS

The prevalence of elevated CRP in this aboriginal community is remarkably high. These data further demonstrate that the association between CRP and specific indices of obesity and metabolism vary according to gender and glycemic status.

The association between leptin and proinsulin is lost with central obesity

OBJECTIVE

Hyperproinsulinaemia and hyperleptinaemia are interrelated features of the insulin resistance syndrome that are linked to the prospective risk of cardiovascular diseases. Whether the association between leptin and proinsulin is different between groups displaying different degrees of risk for cardiovascular diseases is not known. We therefore examined this association in men versus women and in pre- versus postmenopausal women from a population-based sample.

DESIGN AND SUBJECTS

Healthy subjects (n = 158; 85 men and 73 pre- and postmenopausal women) from the Northern Sweden Monitoring of Trends and Determinants in Cardiovascular Disease population were studied with a cross-sectional design.

METHODS

Anthropometric measurements (body mass index and waist circumference) and oral glucose tolerance tests were performed. Enzyme-linked immunosorbent assays were used for the analyses of specific insulin and proinsulin, and radioimmunoassay for leptin. Insulin resistance and beta-cell function were calculated according to the homeostasis assessment model. Partial correlation coefficients adjusted for age and measures of adiposity were calculated and multiple linear regression analyses were performed with leptin as dependent variable.

RESULTS

In nonobese men and premenopausal women and in obese postmenopausal women, leptin was significantly associated with proinsulin after stratification for waist circumference. Furthermore, a multivariate analyses taking age and measures of adiposity into account, showed that high fasting proinsulin was a significant predictor of high leptin in these groups. In contrast, this association was lost with increasing central obesity in men and premenopausal women.

CONCLUSIONS

This study shows that both the degree of adiposity and the hormonal milieu influence the association between circulating leptin and proinsulin in a normal population. Therefore, the insulin resistance syndrome seems to be characterized by lost association between leptin and proinsulin, which may be explained by dysfunction in the adipoinsular axis.

Association of parity with risk of type 2 diabetes and related metabolic disorders

OBJECTIVE

The relationship between parity and risk of diabetes is controversial, and little information is available regarding associations between parity and measures of insulin resistance and beta-cell function. The objective of this study was to investigate the association between parity and risk of glucose intolerance and related metabolic disorders using data from a population-based study in a Native Canadian community.

RESEARCH DESIGN AND METHODS

Female participants (n = 383, aged 12-79 years) provided fasting blood samples for the determination of glucose, insulin, C-peptide, and proinsulin concentrations. A 75-g oral glucose tolerance test was administered, and diabetes and impaired glucose tolerance were diagnosed according to World Health Organization criteria. Waist circumference and percent body fat were determined. Information regarding occurrence of live births and previously diagnosed diabetes was obtained from interviewer-administered questionnaires.

RESULTS

Parity was associated with a significantly reduced risk of diabetes (nulliparous vs. >or=1 birth, odds ratio 0.43, 95% CI 0.19- 0.94, P < 0.05) after adjustment for age and waist circumference. In addition, nondiabetic nulliparous women had significantly elevated concentrations of fasting insulin and proinsulin relative to nondiabetic parous women (all P < 0.05) in analyses adjusted for age and waist circumference.

CONCLUSIONS

Our results are consistent with those from other populations experiencing high rates of diabetes and suggest the presence of a diabetes-prone phenotype within the nulliparous subcohort of this population, which may contribute to infertility.

Current literature in diabetes

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of diabetes/metabolism. Each bibliography is divided into 17 sections: 1 Books, Reviews & Symposia; 2 General; 3 Genetics; 4 Epidemiology; 5 Immunology; 6 Prediction; 7 Prevention; 8 INTERVENTION: a&rpar General; b&rpar Pharmacology; 9 Pathology: a&rpar General; b&rpar Cardiovascular; c&rpar Neurological; d&rpar Renal; 10 Endocrinology & Metabolism; 11 Nutrition; 12 Animal Studies; 13 Techniques. Within each section, articles are listed in alphabetical order with respect to author (9 Weeks journals - Search completed at 1st Aug 2001)