Biological variation of homeostasis model assessment-derived insulin resistance in type 2 diabetes

The biological variation of insulin resistance markers: data from the European Biological Variation Study (EuBIVAS)

OBJECTIVES

An insulin resistant state is characteristic of patients with type 2 diabetes, polycystic ovary syndrome, and metabolic syndrome. Identification of insulin resistance (IR) is most readily achievable using formulae combining plasma insulin and glucose results. In this study, we have used data from the European Biological Variation Study (EuBIVAS) to examine the biological variability (BV) of IR using the Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) and the Quantitative Insulin sensitivity Check Index (QUICKI).

METHODS

Ninety EuBIVAS non-diabetic subjects (52F, 38M) from five countries had fasting HOMA-IR and QUICKI calculated from plasma glucose and insulin samples collected concurrently on 10 weekly occasions. The within-subject (CVI) and between-subject (CVG) BV estimates with 95 % CIs were obtained by CV-ANOVA after analysis of trends, variance homogeneity and outlier removal.

RESULTS

The CVI of HOMA-IR was 26.7 % (95 % CI 25.5-28.3), driven largely by variability in plasma insulin and the CVI for QUICKI was 4.1 % (95 % CI 3.9-4.3), reflecting this formula's logarithmic transformation of glucose and insulin values. No differences in values or BV components were observed between subgroups of men or women below and above 50 years.

CONCLUSIONS

The EuBIVAS, by utilising a rigorous experimental protocol, has produced robust BV estimates for two of the most commonly used markers of insulin resistance in non-diabetic subjects. This has shown that HOMA-IR, in particular, is highly variable in the same individual which limits the value of single measurements.

The Effects of Flaxseed Consumption on Glycemic Control in Native American Postmenopausal Women with Hyperglycemia and Hyperlipidemia

Glucose control in postmenopausal women is influenced by many factors, such as hormones, lifestyle variables, and genetics. Limited data exist on the effect of whole flaxseed on glucose status in postmenopausal Native American women. The aim of this study was to investigate the glucose management effect of a flaxseed dietary intervention on postmenopausal Native American women. In this study, 55 Native American postmenopausal women (aged 47-63 years) with borderline hyperglycemia (>100 and <126 mg/dL) and mild to moderate hypercholestorolemia (≥200 to ≤380 mmol/L), who were not on hormone replacement therapy, were enrolled. Participants were randomly assigned to one of the three dietary regimens (control, flaxseed, and flaxseed + fiber) for three months, receiving interventions in the form of bread, muffins, and flaxseed powder. Despite daily consumption of flaxseed across diverse food formats, no significant changes in glucose (p = 0.3, p = 0.2), insulin levels (p = 0.59, p = 0.9), or HOMA-IR (p = 0.84, p = 0.66) were observed compared to their respective baseline values within the flaxseed and flaxseed + fiber groups, respectively. Conversely, the control group showed a significant rise in final glucose values from baseline (p = 0.01). However, the incorporation of ground flaxseed into low-glycemic foods holds potential for beneficial effects through maintaining glucose status among postmenopausal Native American women. This research provides critical insights into the effects of flaxseed, emphasizing the need for continued exploration to understand its role in supporting glucose management among postmenopausal Native American women. Further exploration is required to investigate the potential long-term impact and the use of flaxseed in managing glucose levels in this demographic.

Identifying pathways to early-onset metabolic dysfunction, insulin resistance and inflammation in young adult inpatients with emerging affective and major mood disorders

AIM

Young people with common mood disorders face the prospect of shortened life expectancy largely due to premature cardiovascular disease. Metabolic dysfunction is a risk factor for premature cardiovascular disease. There is an ongoing debate whether metabolic dysfunction can be simply explained by weight gain secondary to psychotropic medications or whether shared genetic vulnerability, intrinsic immune-metabolic disturbances or other system perturbations (e.g. dysregulated sympathetic nervous system, circadian dysfunction) are more relevant determinants of premature cardiovascular disease. Thus, we aimed to investigate underlying drivers of metabolic dysfunction and premature cardiovascular disease in young people in the early phases of common mood disorders.

METHODS

We evaluated the relationships between insulin resistance (assessed by HOMA2-IR) and body mass index (BMI), sex, diagnosis, medication, inflammatory markers and hormonal factors in 327 inpatients with emerging affective and major mood disorders admitted to the Young Adult Mental Health Unit, St Vincent's Private Hospital, Sydney.

RESULTS

While HOMA2-IR scores were positively associated with BMI (r_s  = 0.465, p < .001), they were also higher in those prescribed mood stabilizers (p = .044) but were not associated with specific diagnoses, other medication types or the number of prescribed medications. Further, high-sensitivity C-reactive protein levels (but not thyroid-stimulating hormone and ferritin levels) were positively associated with HOMA2-IR (r_s  = 0. 272, p < .001) and BMI (r_s  = . 409, p < .001).

CONCLUSIONS

In addition to BMI, other non-specific markers of inflammation are associated with early metabolic dysfunction in young people with emerging affective and major mood disorders.

The association of quantitative insulin sensitivity indices (HOMA-IR and QUICKI) with anthropometric and cardiometabolic indicators in adolescents

Introduction

Homoeostasis model assessment (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI) are used to evaluate insulin resistance. The aim of this study was to investigate the association between quantitative insulin sensitivity indices and anthropometric and cardiometabolic indicators in adolescents.

Material and methods

This descriptive-analytic cross-sectional study was conducted on 80 adolescents aged 12 to 13 years in Isfahan, Iran. Anthropometric, cardiometabolic and QUICKI and HOMA-IR indicators were measured. In the results analysis, Pearson correlation coefficient and regression analysis were used.

Results

There was a significant positive correlation between most of the anthropometric indicators and the HOMA-IR index and a significant negative correlation with QUICKI (all p < 0.0001). Moreover, serum triglyceride level had a significant negative correlation with QUICKI index (R = –0.33, p = 0.002) and systolic blood pressure (R = 0.44, p < 0.0001), and triglyceride level (R = 0.66, p < 0.0001) had a significant positive correlation with HOMA index. The results of these two indices were highly correlated in most of the anthropometric and biochemical indices, except for the waist circumference to the neck circumference ratio and systolic blood pressure, which had a significant positive association with HOMA-IR, but did not show a significant association with QUICKI index.

Conclusions

A significant correlation between anthropometric and cardiometabolic indicators with insulin resistance indices (HOMA-IR and QUICKI) was found. Moreover, the results of these two indices were highly correlated in most of the anthropometric and biochemical indices, except for the waist circumference to the neck circumference ratio and systolic blood pressure.

A study on the glycemic, lipid and blood pressure control among the type 2 diabetes patients of north Kerala, India

AIM

The aim of the study was to detect the level of comprehensive diabetes control among the diabetic patients of Kerala, India.

METHODS

Patients (1200) were randomly selected from a diabetes care center. Their blood sugar, biochemical and anthropometric measurements were done and statistically analyzed.

RESULTS

Only 28.3% had their HbA1c at or below 7% and 45% above 9%. One-third of the female and one-fifth of the male patients had coronary artery disease. The prevalence of hypertension was almost equal in both sexes. However, there was a statistically significant higher systolic blood pressure (mean 162.12mmHg vs 147.49mmHg, p=0.01044) among females. The total cholesterol was above 200mg/dl in 42.1% of males and 45.61% of females. The triglyceride was >150mg/dl in 38.6% males and 50.88% females. Low high density lipoprotein (HDL) cholesterol levels were found in 20.07% of males and 41.12% of females (p=0.0445). The mean low density lipoprotein (LDL) was 121.75 (±32.29) CONCLUSION: The mean blood sugar values are found to be high, which will lead to a predictable increase in vascular disease, which in turn will affect the quality of health and productivity of the individual and the economic growth of the society as a whole. Studies suggest that therapeutic interventions to improve glycemic control may reduce the risk of cardiovascular disease and microvascular disease. This study shows that the level of diabetes control in Kerala is unsatisfactory. We need more medications, better strategies and more emphasis on glycemic management than we are currently able to apply.

Assessing the test–retest repeatability of insulin resistance measures: Homeostasis model assessment 2 and oral glucose insulin sensitivity

Background: Insulin resistance is commonly assessed using the homeostasis model assessment (HOMA) variants. HOMA is potentially insensitive to change because of its high coefficient of variation. The repeatability coefficient is an alternative means of assessing test repeatability. To be confident of clinical change, rather than biological variation, a subsequent test needs to differ from the former by more than the repeatability coefficient using the equation.Test 1 = Test 2 ± repeatability coefficient.The repeatability coefficients for measures of insulin resistance are unknown.Aim: To compare the repeatability coefficient of HOMA2 variants (Beta-cell function [%B], insulin sensitivity [%S], insulin resistance [IR]) to a dynamic measure of insulin resistance, and the oral glucose insulin sensitivity (OGIS) test.Setting: The raw data from a previously used data set were reanalysed.Methods: Glycaemic and insulinaemic tests were performed on 32 men and women both with (n = 10) and without type 2 diabetes (n = 22). From these data, eight fasting tests and three 50-g oral glucose tolerance tests were used to calculate HOMA2 and OGIS. The methods of Bland and Altman assessed repeatability.Results: Repeatability coefficients for all participants for the HOMA2 %B, %S and IR variants were 72.91, 189.75 and 0.9, which equates to 89%, 135% and 89% of their respective grand means. By contrast, OGIS had a repeatability coefficient of 87.13, which equates to 21% of the grand mean.Conclusion: Because of the high repeatability coefficient relative to the grand mean, use of HOMA2 measures for assessing insulin resistance in small population studies should be reconsidered.

A study on the glycemic, lipid and blood pressure control of type 2 diabetes patients of Kerala

AIM

Aim of the study was to detect the level of comprehensive diabetes control among the diabetic patients of Kerala, India.

METHOD

Patients (1200) were randomly selected from a diabetes care center. Their blood sugar and other biochemical and anthropometric measurements were done and statistically analyzed.

RESULT

Only 28.3% had their A1C at or below 7% and 45% above 9%. 1/3rd of the female and 1/5th of the male patients had CAD. The prevalence of hypertension was almost equal in both sexes. However, there was a statistically significant higher systolic BP (mean 162.12mm Hg vs 147.49mm Hg, p=0.01044) among females. The total Cholesterol was above 200mg/dl in 42.1% of males and 45.61% of females. The triglyceride was >150mg/dl in 38.6% males and 50.88% females. Low HDL cholesterol levels were found in 20.07% of males and 41.12% of females (p=0.0445). The mean LDL was 121.75 (±32.29247) DISCUSSION: The mean blood sugar values are found to be high which will lead to a predictable increase in vascular disease, which in turn will affect the quality of health and productivity of the individual and the economic growth of the society as a whole. Studies suggest that therapeutic interventions to improve glycemic control may reduce the risk of CVD and microvascular disease.

CONCLUSION

This study shows that the level of diabetes control in Kerala is unsatisfactory. We need more medications, better strategies, and more emphasis on glycemic management than we are currently able to apply.

Variability of HOMA and QUICKI insulin sensitivity indices

Assessment of insulin sensitivity based on a single measurement of insulin and glucose, is both easy to understand and simple to perform. The tests most often used are HOMA and QUICKI. The aim of this study was to assess the biological variability of estimates of insulin sensitivity using HOMA and QUICKI indices. After a 12-h fast, blood was sampled for insulin and glucose determination. Sampling lasted for 90 min with an intersample interval of 2 min. A total of 56 subjects were included in the study, and in nine subjects sampling was done before and after weight reduction, so total number of analyzed series was 65. To compute the reference value of the insulin sensitivity index, averages of all 46 insulin and glucose samples were used. We also computed point estimates (single value estimates) of the insulin sensitivity index based on the different number of insulin/glucose samples (1-45 consecutive samples). To compute the variability of point estimates a bootstrapping procedure was used using 1000 resamples for each series and for each number of samples used to average insulin and glucose. Using a single insulin/glucose sample HOMA variability was 26.18 ± 4.31%, and QUICKI variability was 3.30 ± 0.54%. For 10 samples variability was 11.99 ± 2.22% and 1.62 ± 0.31% respectively. Biological variability of insulin sensitivity indices is significant, and it can be reduced by increasing the number of samples. Oscillations of insulin concentration in plasma are the major cause of variability of insulin sensitivity indices.

Evaluation of Leptin as a Marker of Insulin Resistance in Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a leading cause of mortality and morbidity worldwide, whose incidence is rapidly increasing in India. T2DM is caused by varying degrees of insulin resistance (IR) and relative insulin deficiency. Leptin, an adipokine with the primary function of regulating energy balance, is found to mediate insulin secretion and sensitivity in peripheral tissues. Hence, we aimed to determine the role of leptin in the development of IR in newly diagnosed T2DM patients.

AIM

This study aims to compare the leptin levels and homeostatic model assessment-IR (HOMA-IR) levels in the study population.

MATERIAL AND METHODS

The study included a total of sixty patients newly diagnosed with T2DM. Their fasting blood samples were collected to estimate the glucose, insulin, and leptin levels. IR was calculated using HOMA-IR formula. Statistical analysis was done by Pearson's correlation, Spearman's correlation, and One-sample Wilcoxon Signed Rank test.

RESULTS

Leptin and HOMA-IR levels were significantly high in T2DM patients (P < 0.001) when compared with reference values. Body mass index showed a significant positive correlations with insulin (r = 0.40, P < 0.01), HOMA-IR (r = 0.37, P < 0.01), and leptin levels (r = 0.90, P < 0.01). Leptin levels showed significant positive correlations with plasma insulin (r = 0.35, P < 0.01) and HOMA-IR levels (r = 0.31, P < 0.05). The correlation between leptin and HOMA-IR levels was more pronounced and significant among the obese T2DM subjects (r = 0.82, P = 0.01).

CONCLUSION

Hyperleptinemia reflecting leptin resistance plays an important role in the development of IR in obeseT2DM patients, making leptin a possible biomarker for the same.

Design of the Magnetic Resonance Imaging Evaluation of Mineralocorticoid Receptor Antagonism in Diabetic Atherosclerosis (MAGMA) Trial

Mineralocorticoid receptor (MR) activation plays an essential role in promoting inflammation, fibrosis, and target organ damage. Currently, no studies are investigating MR antagonism in patients with type 2 diabetes mellitus (T2DM) with chronic kidney disease, at high risk for cardiovascular complications, who are otherwise not candidates for MR antagonism by virtue of heart failure. Further, there is limited information on candidate therapies that may demonstrate differential benefit from this therapy. We hypothesized that MR antagonism may provide additional protection from atherosclerosis progression in higher-risk patients who otherwise may not be candidates for such a therapeutic approach. In this double-blind, randomized, placebo-controlled trial, subjects with T2DM with chronic kidney disease (≥ stage 3) will be randomized in a 1:1 manner to placebo or spironolactone (12.5 mg with eventual escalation to 25 mg daily over a 4-week period). The co-primary efficacy endpoint will be percentage change in total atheroma volume in thoracic aorta and left ventricular mass at 52 weeks in patients treated with spironolactone vs placebo. Secondary outcomes include 24-hour mean systolic blood pressure, central aortic blood pressure, and insulin resistance (HOMA-IR) at 6 weeks. A novel measure in the study will be changes in candidate miRNAs that regulate expression of NR3C2 (MR gene) as well as measuring monocyte/macrophage polarization in response to therapy with spironolactone. We envision that our strategy of simultaneously probing the effects of a drug combined with analysis of mechanisms of action and predictive response will likely provide key information with which to design event-based trials.

Insulin resistance and cognitive performance in type 2 diabetes - The Maastricht study

AIMS

Type 2 diabetes, hyperinsulinemia, and insulin resistance are associated with cognitive impairment. Experimental studies indicate that insulin signaling in the brain is related to cognitive performance. Here we evaluated whether insulin-related variables contribute to the variance in cognitive performance among individuals with type 2 diabetes.

METHODS

A total of 806 individuals with type 2 diabetes (mean age 62±8years, HbA1c 6.9±1.1%) completed a neuropsychological test battery. Insulin-related variables evaluated were: fasting plasma insulin, C-peptide, and the Homeostasis Model Assessment (HOMA2-IR; in individuals without insulin treatment; n=641). The unadjusted coefficient of determination (R²), obtained from multiple linear regression analyses, was used to estimate the proportion of variance in cognition explained by insulin-related variables.

RESULTS

Sex, age, and educational level together explained 18.0% (R²) of the variance in memory function, 26.5% in information processing speed, and 22.8% in executive function and attention. Fasting insulin, C-peptide, or HOMA2-IR did not increase the explained variance (maximum ΔR² 0.3%, P≥0.14). Similar results were obtained when insulin-related variables were added to models that additionally included glycemic control, cardiovascular risk factors, and depression.

CONCLUSIONS

Our results show that measures of peripheral insulin resistance are unrelated to cognitive performance among individuals with adequately controlled type 2 diabetes.

Traffic-related air pollution is associated with cardio-metabolic biomarkers in general residents

PURPOSE

The study was conducted to explore the mechanisms linking traffic-related air pollution and cardio-metabolic risk.

METHODS

The participants included 371 men and women aged from 45 to 75 in an urban residential area in Shanghai, China. The participants were divided into four categories (≤50, 51-100, 101-200 and >200 m) according to the residential distance to major road. Additionally, the personal fine particulate matter (PM2.5) was measured from 8:00 am to 6:00 pm to assess the PM2.5 exposure in general residents. Then, the continuous subclinical measurements and biological effects related to cardio-metabolic disorders were detected. The generalized linear regression analysis was applied for estimating the adjusted hazards ratio for cardio-metabolic disorders relative to traffic-related air pollution.

RESULTS

The average personal PM2.5 is 111.1 μg/m(3) in the participants living within 50 m to major road, which is significantly higher than the personal PM2.5 (68.2 μg/m(3)) in the participants living more than 200 m away from the major road. The participants living within 50 m to major road compared with those living more than 200 m away have 1.15 times higher of heart rate (HR), 1.95 times higher of fasting insulin, 1.30 times higher of homeostasis model assessment of insulin resistance (HOMA-IR), 1.56 times higher of low-density lipoprotein cholesterol (LDL-C), 8.39 times higher of interleukin 6 (IL-6), 4.30 times higher of augmentation index (AI), 1.60 times higher of systolic blood pressure (SBP) and 1.91 times higher of diastolic blood pressure (DBP). Contrary to the increase in above biological effects, there were 1.06 times lower of low frequency (LF), 1.05 times lower of high frequency (HF), 2.54 times lower of IL-10, 4.61 times lower of nitric oxide (NO), 1.19 times lower of superoxide dismutase (SOD) and 1.85 times lower of total antioxidant capacity (T-AOC). There was no clear exposure-response relationship can be observed in the fasting glucose, LF/HF, cholesterol and high-density lipoprotein (HDL).

CONCLUSION

Long-term exposure to traffic-related air pollution may contribute to the development or exacerbation of cardio-metabolic disorders. The mechanisms linking air pollution and cardio-metabolic disorders may be associated with the increased systemic inflammation and oxidative stress, reduced insulin sensitivity and elevated arterial stiffness and blood pressure.

Greater body mass index is a better predictor of subclinical cardiac damage at long-term follow-up in men than is insulin sensitivity: a prospective, population-based cohort study

BACKGROUND

To examine whether lower insulin sensitivity as determined by homeostatic model assessment (HOMA-%S) was associated with increased left ventricular mass (LVM) and presence of LV diastolic dysfunction at long-term follow-up, independently of body mass index (BMI), in middle-aged, otherwise healthy males.

METHODS

Prospective population-based cohort study with a median (IQR) follow-up time of 28 (27-28) years, in which traditional cardiovascular risk factors, including HOMA-%S and BMI, were assessed at baseline, and echocardiographic determination of LVM and LV diastolic function was performed at follow-up. Associations between risk factors and echocardiographic variables were tested using multivariable linear and binary logistic regression.

RESULTS

The study population comprised 247 men with a median (IQR) age of 47 (47-48) years. Mean (SD) BMI was 25.1 +/- 3.0 kg/m(2), and median (IQR) HOMA-%S was 113.0 (68.3-284.6). Subjects with low insulin sensitivity (lowest HOMA-%S quartile (Q1)) had significantly greater BMI, fasting plasma insulin, and higher fasting blood glucose (FBG) (p <0.02 for all). BMI and HOMA-%S were significantly correlated (r = -0.383, p <0.0001). At follow-up, mean (SD) LVM and LVMI were 202 +/- 61 g and 103 +/- 31 g/m(2), respectively, whereas median (IQR) E/é was 10 (8-12). Moreover, 36 % had grade 2 or 3 diastolic dysfunction. In multivariable analyses, greater BMI, but not low insulin sensitivity was independently associated with later detection of increased LVM and diastolic dysfunction.

CONCLUSION

Greater baseline BMI, but not lower insulin sensitivity was independently associated with greater LVM and diastolic dysfunction at long-term follow-up.

Biological variation of cardiovascular risk factors in patients with diabetes

Biological variation refers to the natural fluctuations found when repeated measurements are made in a biological system. Generally, biological variation remains within narrow boundaries in health, but may differ in pathological states, with implications for the diagnosis and monitoring of disease processes. In disease, biological variation may alter such that any subsequent measurement may need to have a greater difference compared with a healthy control to be biologically relevant. Treatments such as insulin or anti-hypertensive therapy have been shown to reduce biological variability closer to normal levels and theoretically this may help prevent complication development or progression in conditions such as diabetes. This article reviews how biological variation can influence our identification and assessment of vascular risk factors in a person with diabetes. The role of biological variation in the diagnosis of diabetes (glucose and HbA1c) is then examined. Finally, the influence that common treatments in diabetes have in modifying biological variation is described.

Air-Pollution and Cardiometabolic Diseases (AIRCMD): a prospective study investigating the impact of air pollution exposure and propensity for type II diabetes

There is a paucity of prospective cohort studies investigating the impact of environmental factors on the development of cardiometabolic (CM) disorders like type II diabetes (T2DM). The objective of the Air-Pollution and Cardiometabolic Diseases (AIRCMD) study is to investigate the impact of personal level air pollution measures [personal black carbon (BC)/sulfate measures] and ambient fine particulate matter [(PM2.5)/NO2] levels on propensity to type II diabetes in Beijing, China. Subjects with metabolic syndrome will undergo four repeated study visits within each season over a one year period following an initial screening visit. At each study visit, subjects will be monitored for sub-acute exposure to personal and ambient measures of air-pollution exposure and will undergo a series of functional CM outcomes. The primary endpoints include independent associations between integrated 5-day mean exposure to PM2.5 and BC and homeostasis model assessment of insulin resistance (HOMA-IR) measures, 24-hour mean diastolic and mean arterial pressure and endothelial-dependent vasodilatation. The secondary endpoints will explore the mechanistic explanation for a causal relationship between exposures and propensity for type II diabetes and will include additional functional outcomes such as arterial compliance, heart rate variability and plasma adipokines. The novel aspects of the study include the launch of infrastructure for future translational investigations in highly polluted urbanized environments and the creation of novel methodologies for linking personalized exposure measurements with functional CM outcomes. We believe that AIRCMD will allow for unprecedented new investigations into the association between environmental risk factors and CM disorders.

Neural correlates of stress- and food cue-induced food craving in obesity: association with insulin levels

OBJECTIVE

Obesity is associated with alterations in corticolimbic-striatal brain regions involved in food motivation and reward. Stress and the presence of food cues may each motivate eating and engage corticolimibic-striatal neurocircuitry. It is unknown how these factors interact to influence brain responses and whether these interactions are influenced by obesity, insulin levels, and insulin sensitivity. We hypothesized that obese individuals would show greater responses in corticolimbic-striatal neurocircuitry after exposure to stress and food cues and that brain activations would correlate with subjective food craving, insulin levels, and HOMA-IR.

RESEARCH DESIGN AND METHODS

Fasting insulin levels were assessed in obese and lean subjects who were exposed to individualized stress and favorite-food cues during functional MRI.

RESULTS

Obese, but not lean, individuals exhibited increased activation in striatal, insular, and hypothalamic regions during exposure to favorite-food and stress cues. In obese but not lean individuals, food craving, insulin, and HOMA-IR levels correlated positively with neural activity in corticolimbic-striatal brain regions during favorite-food and stress cues. The relationship between insulin resistance and food craving in obese individuals was mediated by activity in motivation-reward regions including the striatum, insula, and thalamus.

CONCLUSIONS

These findings demonstrate that obese, but not lean, individuals exhibit increased corticolimbic-striatal activation in response to favorite-food and stress cues and that these brain responses mediate the relationship between HOMA-IR and food craving. Improving insulin sensitivity and in turn reducing corticolimbic-striatal reactivity to food cues and stress may diminish food craving and affect eating behavior in obesity.

The biological variation of N-terminal pro-brain natriuretic peptide in postmenopausal women with type 2 diabetes: a case control study

BACKGROUND

The incidence of heart failure in type 2 diabetes is high and it has poorer prognosis when compared with patients without diabetes. Access to echocardiography is limited and alternative methods to identify early heart failure such as the measurement of natriuretic peptides levels have been proposed. However, their wide biological variation could limit their clinical utility. Our aim was to determine if the intrinsic biological variation of one of these peptides, N-terminal proBNP, is as wide in type 2 diabetes as it is in health and to calculate the critical difference values that could be utilised in clinical practice to ensure changes observed between two samples are due to intervention rather than to its biological variability.

METHODOLOGY/PRINCIPAL FINDINGS

12 postmenopausal women with diet controlled type 2 diabetes and without heart failure were compared with 11 control postmenopausal women without diabetes. N-terminal proBNP levels were measured on 10 occasions. The biological variation was calculated according to Fraser's methods. The mean NT-proBNP level was similar in both groups (mean ± standard deviation; type 2 diabetes, 10.7 pmol/L± 8.5 versus 8.49±6.0 pmol/L, p = 0.42). The biological variation was also similarly wide. The critical difference in patients with type 2 diabetes was between -70% and ±236%.

CONCLUSIONS

Type 2 diabetes does not appear to significantly influence the marked biological variation of N-terminal proBNP in postmenopausal women. The critical difference values reported in this study could be used to titrate therapy or monitor response to interventions although the change required in between samples is wide and this might limit its utility.

Selection of the appropriate method for the assessment of insulin resistance

Insulin resistance is one of the major aggravating factors for metabolic syndrome. There are many methods available for estimation of insulin resistance which range from complex techniques down to simple indices. For all methods of assessing insulin resistance it is essential that their validity and reliability is established before using them as investigations. The reference techniques of hyperinsulinaemic euglycaemic clamp and its alternative the frequently sampled intravenous glucose tolerance test are the most reliable methods available for estimating insulin resistance. However, many simple methods, from which indices can be derived, have been assessed and validated e.g. homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI). Given the increasing number of simple indices of IR it may be difficult for clinicians and researchers to select the most appropriate index for their studies. This review therefore provides guidelines and advices which must be considered before proceeding with a study.

Green tea improves metabolic biomarkers, not weight or body composition: a pilot study in overweight breast cancer survivors

BACKGROUND

Overweight status after breast cancer treatment may increase a woman's risk for recurrent disease and/or early onset cardiovascular disease. Green tea has been proposed to promote weight loss and favourably modify glucose, insulin and blood lipids. This pilot study tested the effect of daily decaffeinated green tea consumption for 6 months on weight and body composition, select metabolic parameters and lipid profiles in overweight breast cancer survivors.

METHODS

The effect of daily decaffeinated green tea intake on weight, body composition and changes in resting metabolic rate, energy intake, glucose, insulin, homeostasis model assessment--insulin resistance (HOMA-IR) and lipids was evaluated in overweight breast cancer survivors. Participants had a mean weight of 80.2 kg; body mass index (BMI) 30.1 kg m⁻²; and body fat 46.4%. Participants (n = 54) were randomised to 960 mL of decaffeinated green or placebo tea daily for 6 months.

RESULTS

Mean (SD) tea intake among study completers (n = 39) was 5952 (1176) mL week⁻¹ and was associated with a significant reduction in energy intake (P = 0.02). Change in body weight of -1.2 kg (green tea) versus +0.2 kg (placebo) suggests a weight change effect, although this was not statistically significant. Decaffeinated green tea intake was associated with elevated high-density lipoprotein (HDL) levels (P = 0.003) and nonsignificant improvements in the HDL/LDL ratio and HOMA-IR (-1.1 ± 5.9: green tea; +3.2 ± 7.2: herbal).

CONCLUSIONS

Intake of decaffeinated green tea for 6 months was associated with a slight reduction in body weight and improved HDL and glucose homeostasis in overweight breast cancer survivors.

Asthma and insulin resistance in children

BACKGROUND AND OBJECTIVE

Increased BMI is a risk factor for asthma in children and may be related to adipokines. Adipokines affect insulin-stimulated glucose uptake in vitro but, to date there is little evidence for such a role in vivo. We explored relationships between obesity and allergic asthma in children.

METHODS

Twenty-one allergic asthmatics (AA) and 10 non-allergic healthy controls, aged 6-17.9 years were studied. AA group included children with a positive mannitol challenge test, >25 ppb of exhaled nitric oxide and a positive skin prick test. BMI z-scores were calculated. Blood levels of insulin, glucose, leptin, resistin, tumour necrosis factor-alpha, IL-4, IL-5 and IL-6 were measured. Insulin resistance (IR) was estimated using the homeostasis model assessment (HOMA).

RESULTS

There was no significant difference in BMI z-scores between AA and healthy controls (mean: 0.01 vs -0.10). However, significant differences were found in the blood levels of IL-6 (P = 0.05), IL-4 (P = 0.04), IL-5 (P = 0.01) and leptin (P = 0.02). IR was only found in the AA group (42.85%). Homeostasis model assessment insulin resistance (HOMA-IR) was significantly related to IL-6 (r = 0.44, P = 0.05) and tumour necrosis factor-alpha (r = -0.45, P = 0.05).

CONCLUSIONS

IR was observed in AA. Our findings are suggestive of a complex interaction between the inflammatory state and adiposity, allergy and asthma.

Soy isoflavones, Mediterranean diet, and physical exercise in postmenopausal women with insulin resistance

OBJECTIVE

The aim of this study was to evaluate whether a standard dose of 40 mg of soy isoflavones prescribed in routine clinical practice for treatment of menopausal symptoms has some influence on glucose homeostasis in postmenopausal women with insulin resistance (IR).

METHODS

A total of 116 postmenopausal women with IR were randomly assigned to a group of Mediterranean diet and physical exercise (control group) or a group of Mediterranean diet, physical exercise, and daily oral ingestion of 40 mg of soy isoflavones (soy isoflavones group). Anthropometric measures, Kupperman Index values, Cervantes Scale score, and blood samples for glucose, insulin, lipid profile, creatinine, uric acid, homocysteine, folic acid, vitamin B12, selenium, and estradiol were determined at baseline and at intervals of 6, 12, 18, and 24 months.

RESULTS

Mean homeostasis model assessment of IR (HOMA-IR) values remained unchanged from the baseline in the control group but steadily decreased in the soy isoflavones group at 6 months (P = 0.042). There were no statistically significant differences between both groups in mean HOMA-IR scores at baseline, but statistically significantly lower values were found in the soy isoflavones group at 6 months (P = 0.009), 12 months (P = 0.011), 18 months (P = 0.018), and 24 months (P = 0.012). Changes in HOMA-IR values were also clearly related to body mass index (P < 0.001), abdominal circumference (P < 0.001), and treatment (P = 0.044) when a linear regression analysis was carried out.

CONCLUSIONS

Daily intake of 40 mg of soy isoflavones together with a Mediterranean diet and exercise reduced IR in postmenopausal women who had IR in the first place. It was significantly better than lifestyle changes alone. If corroborated, this may be a useful intervention for these women.

Biological variation in fasting serum insulin-like growth factor binding protein-1 (IGFBP-1) among individuals with a varying glucose tolerance

OBJECTIVE

To evaluate the biological variation of serum insulin-like growth factor binding protein-1 (IGFBP-1) in individuals with different degrees of glucose tolerance.

RESEARCH DESIGN AND METHODS

IGFBP-1 was measured in 42 fasted subjects with: normal glucose tolerance (NGT=15), impaired fasting glucose (IFG=9), impaired glucose tolerance (IGT=9) and type 2 diabetics (DM=9). Short- and long-term reproducibility was determined for IGFBP-1.

RESULTS

The longer-term reproducibility (CV) of serum IGFBP-1 was 20.9%, 29.5%, 33.1% and 48.0% for subjects with NGT, IFG, IGT and DM respectively. The results for the short-term serum IGFBP-1 yielded CVs for these same respective categories of 8.2%, 16.1%, 29.2% and 13.8%.

CONCLUSIONS

IGFBP-1 measurement was least variable in NGT individuals over both long-term and short-term intervals and variability increased with deteriorating glucose tolerance. Due to its biological variation, IGFBP-1 serum level is more reliable in normal subjects than in individuals with type 2 diabetes.

The mean and the biological variation of insulin resistance does not differ between polycystic ovary syndrome and type 2 diabetes

Background

There is an assumption that the mean and biological variation of insulin resistance (IR) is less in polycystic ovary syndrome (PCOS), and intuitively higher in type 2 diabetes (T2DM). To test this hypothesis we compared the mean and biological variation in IR in PCOS to that of T2DM and to age- and weight-matched controls.

Methods

Twelve PCOS, 11 matched healthy women; 12 postmenopausal diet-controlled T2DM and 11 matched healthy postmenopausal women were recruited. Blood samples were collected at 4-d intervals on 10 consecutive occasions. The biological variability of IR was derived on duplicate samples.

Results

Mean and biological variability of HOMA-IR for PCOS did not differ from T2DM. Both measures were higher than the matched controls. There was no difference in insulin or IR measures between the body mass index matched pre- and postmenopausal women. Percentage β cell function were 208.8%, 62.3%, 106.5% and 111.9%, respectively, in PCOS, postmenopausal women with T2DM, healthy premenopausal and healthy postmenopausal women.

Conclusions

The progression from PCOS to the development of T2DM is unlikely to be due to a further increase in IR (or variability), but rather the progressive failure of pancreatic beta cells with a decrease in insulin production. The clinical trial registration number for this study is ISRCTN65353256.

Variability of lipids in patients with Type 2 diabetes taking statin treatment: implications for target setting

AIMS

To determine the biological variability of lipids in patients with Type 2 diabetes (T2DM) who are on statin treatment and then to assess any implications for current lipid targets.

METHODS

A cross-over study of biological variation of lipids in 26 patients with T2DM taking either simvastatin 40 mg or atorvastatin 10 mg. After 3 months on one statin, fasting lipids were measured on 10 occasions over a 5-week period. Following 3 months on the other statin, 10 further samples were taken over 5 weeks. The main outcome measures were biological variability of total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol and triglycerides.

RESULTS

The coefficient of variation (CV) of TC, LDL, HDL and triglycerides on simvastatin was 8.17, 13.11, 7.95 and 12.06%, respectively, whereas the CV on atorvastatin was 6.92, 10.30, 5.13 and 19.71%, respectively, with no statistically significant differences between statins. Treating to sustain a target TC < 5.0 mmol/l or LDL < 3.0 mmol/l means needing to maintain a mean TC of 4.3-4.4 mmol/l or LDL of 2.4-2.5 mmol/l. Treating to consistently achieve an LDL < 2.0 mmol/l means aiming for a mean of only 1.5-1.6 mmol/l.

CONCLUSION

In patients with T2DM taking either simvastatin or atorvastatin, the mean TC and LDL concentrations needed to consistently remain below a target are much lower than the target value itself. This means that guideline target limits extrapolated from the mean values of patients participating in clinical studies may overestimate the lipid reductions required.

Study Protocol: insulin and its role in cancer

BACKGROUND

Studies have shown that metabolic syndrome and its consequent biochemical derangements in the various phases of diabetes may contribute to carcinogenesis. A part of this carcinogenic effect could be attributed to hyperinsulinism. High levels of insulin decrease the production of IGF-1 binding proteins and hence increase levels of free IGF-1. It is well established that bioactivity of free insulin growth factor 1 (IGF-1) increases tumor turnover rate. The objective is to investigate the role of insulin resistance/sensitivity in carcinogenesis by studying the relation between insulin resistance/sensitivity and IGF-1 levels in cancer patients. We postulate that hyperinsulinaemia which prevails during initial phases of insulin resistance (condition prior to overt diabetes) increases bioactivity of free IGF-1, which may contribute to process of carcinogenesis.

METHODS/DESIGN

Based on our pilot study results and power analysis of the same, we have designed a two group case-control study. 800 proven untreated cancer patients (solid epithelial cell tumors) under age of 50 shall be recruited with 200 healthy subjects serving as controls. Insulin resistance/sensitivity and free IGF-1 levels shall be determined in all subjects. Association between the two parameters shall be tested using suitable statistical methods.

DISCUSSION

Well controlled studies in humans are essential to study the link between insulin resistance, hyperinsulinaemia, IGF-1 and carcinogenesis. This study could provide insights to the role of insulin, insulin resistance, IGF-1 in carcinogenesis although a precise role and the extent of influence cannot be determined. In future, cancer prevention and treatment strategies could revolve around insulin and insulin resistance.

Validity and reproducibility of HOMA-IR, 1/HOMA-IR, QUICKI and McAuley's indices in patients with hypertension and type II diabetes

The aim of this study was to evaluate the validity and reliability of homeostasis model assessment-insulin resistance (HOMA-IR) index, its reciprocal (1/HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and McAuley's index in hypertensive diabetic patients. In 78 patients with hypertension and type II diabetes glucose, insulin and triglyceride levels were determined after a 12-h fast to calculate these indices, and insulin sensitivity (IS) was measured with the hyperinsulinemic euglycemic clamp technique. Two weeks later, subjects had again their glucose, insulin and triglycerides measured. Simple and multiple linear regression analysis were applied to assess the validity of these indices compared to clamp IS and coefficients of variation between the two visits were estimated to assess their reproducibility. HOMA-IR index was strongly and inversely correlated with the basic IS clamp index, the M-value (r=-0.572, P<0.001), M-value normalized with subjects' body weight or fat-free mass and every other clamp-derived index. 1/HOMA-IR and QUICKI indices were positively correlated with the M-value (r=0.342, P<0.05 and r=0.456, P<0.01, respectively) and the rest clamp indices. McAuley's index generally presented less strong correlations (r=0.317, P<0.05 with M-value). In multivariate analysis, HOMA-IR was the best fit of clamp-derived IS. Coefficients of variation between the two visits were 23.5% for HOMA-IR, 19.2% for 1/HOMA-IR, 7.8% for QUICKI and 15.1% for McAuley's index. In conclusion, HOMA-IR, 1/HOMA-IR and QUICKI are valid estimates of clamp-derived IS in patients with hypertension and type II diabetes, whereas the validity of McAuley's index needs further evaluation. QUICKI displayed better reproducibility than the other indices.

Effects of glimepiride on insulin secretion and sensitivity in patients with recently diagnosed type 2 diabetes mellitus

BACKGROUND

The exact mechanism of the efficacy of glimepiride in the achievement of glycemic control has not yet been clearly defined.

OBJECTIVE

This study was conducted to examine the influence of glimepiride on insulin secretion and sensitivity in patients with type 2 diabetes mellitus (DM) of recent onset.

METHODS

This 24-week, open-label, controlled trial was conducted at the Division of Endocrinology and Metabolism, Veterans Affairs Medical Center (Phoenix, Arizona). Study participants were aged 32 to 75 years and had recent-onset (established by a short duration of symptoms 6 weeks to 6 months prior to the study) type 2 DM, or were age-matched healthy volunteers (control group). In the diabetic patients, glimepiride tablets were administered orally, initially at 2 mg once daily in the morning, with the dosage increased by 1 mg every 2 weeks until fasting plasma glucose (FPG) decreased to 6.7 mmol/L; the dosage was then maintained for the remainder of the 24-week study period. Oral glucose tolerance tests (OGTTs) were conducted in the control group and before treatment and at 24 weeks after the achievement and maintenance of glycemic control (glycosylated hemoglobin <7.0%) in the diabetic group. For OGTT, plasma insulin and glucose levels were determined after the subjects fasted overnight and then at every 15 minutes for 2 hours after glucose challenge.

RESULTS

Fourteen diabetic men (mean [SEM] age, 50 [6] years; range, 32-75 years) and 10 male healthy controls (mean [SD] age, 48 [5] years; range, 30-68 years) were enrolled. In the DM group, FPG decreased significantly after treatment ( P<0.001); fasting plasma insulin was markedly elevated before treatment (P<0.001 vs controls) and decreased after treatment ( P<0.01) but did not normalize; first-phase insulin secretion was markedly inhibited before treatment ( P<0.001 vs controls) and normalized after treatment ( P<0.001) total insulin secretion significantly improved after treatment ( P<0.01) but did not normalize. Finally, the pretreatment insulin sensitivity index decreased significantly (P<0.01) after treatment and normalized in 6 of 14 patients (42.9%) with type 2 DM.

CONCLUSIONS

In this study, glimepiride achieved desirable glycemic control in patients with recent-onset type 2 DM through improvement in insulin secretion and sensitivity.