Continuous infusion of glucose with model assessment: measurement of insulin resistance and beta-cell function in man

Omentectomy added to Roux-en-Y gastric bypass surgery: a randomized, controlled trial

BACKGROUND

Excess visceral adipose tissue predicts for incipient diabetes mellitus and cardiovascular disease. Human data are mixed regarding the benefits of selective visceral adipose tissue reduction. We investigated the effects of omentectomy added to laparoscopic Roux-en-Y gastric bypass on glucose homeostasis and lipids, inflammatory markers, and adipokines 90 days postoperatively in nondiabetic patients at the Legacy Good Samaritan Hospital and Oregon Health and Science University (Portland, OR).

METHODS

A single-blind, randomized study of laparoscopic Roux-en-Y gastric bypass plus omentectomy versus laparoscopic Roux-en-Y gastric bypass alone in 28 subjects (7 men and 21 women). The groups were matched at baseline for gender, age, and body mass index (BMI). The eligibility criteria included age ≥18 years, BMI ≥40 and <50 kg/m(2) without co-morbid conditions or BMI ≥35 and <50 kg/m(2) with co-morbid conditions. The primary outcome measures were changes in the fasting plasma glucose, insulin, and homostatic model assessment of insulin resistance. The secondary measures were BMI and the high-sensitivity C-reactive protein, tumor necrosis factor-α, interleukin, total and high-molecular-weight adiponectin, fibrinogen, and plasminogen activator inhibitor-1 levels.

RESULTS

After surgery, the BMI decreased significantly in both groups and was not different at the follow-up point. Although many outcome parameters improved with weight loss in both groups postoperatively, only the omentectomy group experienced statistically significant decreases in fasting glucose (P < .05), total (P = .004) and very-low-density lipoprotein (P = .001) cholesterol, and an increase in the high-molecular-weight/total adiponectin ratio (P = .013).

CONCLUSIONS

Omentectomy added to laparoscopic Roux-en-Y gastric bypass results in favorable changes in glucose homeostasis, lipid levels, and adipokine profile at 90 days postoperatively. These data support the hypothesis that selective ablation of visceral adipose tissue conveys metabolic benefits in nondiabetic humans.

Inflammatory-metabolic parameters in obese and nonobese normoandrogenemic polycystic ovary syndrome during metformin and oral contraceptive treatment

Our aim was to evaluate the optimal treatment strategy addressing cardiovascular risk in obese and nonobese patients with polycystic ovary syndrome (PCOS). We planned a prospectıve randomized clinical study. Normoandrogenemic and oligoamenorrheic women with PCOS and impaired glucose tolerance (n = 96) were enrolled in the study. Six months of treatment with metformin HCL or oral contraceptive pills (OCPs) were given to the patients. Group 1 were obese and receiving metformin. Group 2 were obese and receiving OCPs. Group 3 were nonobese and receiving metformin, and Group 4 were nonobese receiving OCPs. ADMA, homocysteine, high sensitive C-reactive protein (hs-CRP) and homeostasis model assessment estimate of insulin resistance (HOMA-IR) were investigated. ADMA, homocysteine, hs-CRP and HOMA-IR were similar in obese and nonobese groups before the treatment. After 6 months of treatment, a significant decrease was observed in ADMA, homocysteine and HOMA-IR levels in Groups 1 and 3. An increase in ADMA and hs-CRP levels was observed in Groups 2 and 4. In this study, metformin treatment leads to improvement in hormonal and metabolic parameters and decreases ADMA and homocysteine levels possibly independent of BMI. However, the use of oral contraceptives in obese and nonobese patients with PCOS with impaired glucose tolerance increases ADMA and hs-CRP levels and creates an increase in the metabolic risk.

Changes in insulin resistance indicators, IGFs, and adipokines in a year-long trial of aerobic exercise in postmenopausal women

Physical activity is a known modifiable lifestyle means for reducing postmenopausal breast cancer risk, but the biologic mechanisms are not well understood. Metabolic factors may be involved. In this study, we aimed to determine the effects of exercise on insulin resistance (IR) indicators, IGF1, and adipokines in postmenopausal women. The Alberta Physical Activity and Breast Cancer Prevention Trial was a two-armed randomized controlled trial in postmenopausal, inactive, cancer-free women. A year-long aerobic exercise intervention of 225  min/week (n=160) was compared with a control group asked to maintain usual activity levels (n=160). Baseline, 6- and 12-month serum levels of insulin, glucose, IGF1, IGF-binding protein 3 (IGFBP3), adiponectin, and leptin were assayed, and after data collection, homeostasis model assessment of IR (HOMA-IR) scores were calculated. Intention-to-treat analyses were performed using linear mixed models. The treatment effect ratio (TER) of exercisers to controls was calculated. Data were available on 308 (96.3%) women at 6 months and 310 (96.9%) women at 12 months. Across the study period, statistically significant reductions in insulin (TER=0.87, 95% confidence interval (95% CI)=0.81-0.93), HOMA-IR (TER=0.86, 95% CI=0.80-0.93), and leptin (TER=0.82, 95% CI=0.78-0.87), and an increase in the adiponectin/leptin ratio (TER=1.21, 95% CI=1.13-1.28) were observed in the exercise group compared with the control group. No significant differences were observed for glucose, IGF1, IGFBP3, adiponectin or the IGF1/IGFBP3 ratio. Previously inactive postmenopausal women who engaged in a moderate-to-vigorous intensity exercise program experienced changes in insulin, HOMA-IR, leptin, and adiponectin/leptin that might decrease the risk for postmenopausal breast cancer.

Bone remodeling, bone mass and weight gain in patients with stabilized schizophrenia in real-life conditions treated with long-acting injectable risperidone

BACKGROUND

Prolactin-raising antipsychotics, risperidone (antidopaminergic activity), may be associated with low bone mass. On the other hand, risperidone may cause an increase in body weight thought to be favorable for bone.

OBJECTIVES

(1) To determine bone remodeling parameters and bone mass in patients with schizophrenia on long-term treatment with long-acting injectable risperidone (LAIR) in naturalistic settings, and (2) to evaluate the change in body weight, metabolic profile and neuroendocrine status in these patients.

DESIGN

This was a prospective, cross-sectional study.

PATIENTS

Patients included 26 outpatients with controlled schizophrenia in real-life conditions (age 31.3 ± 1.3 years, BMI 28.1 ± 1.0) on long-term maintenance therapy with LAIR for a mean of 18.0 ± 1.6 months (range 6-36) with a mean dose of 38 ± 2 mg. 35 subjects matched for sex, age, BMI and education served as healthy controls.

METHODS

Serum osteocalcin, C-terminal telopeptide of type I collagen (CTx), vitamin D, leptin, prolactin, sex steroids, and parathyroid hormone were assessed. Indices of insulin sensitivity and resistance were determined following an oral glucose tolerance test (OGTT). Bone mineral density (BMD) was measured by dual X-ray absorptiometry at the lumbar spine (LS) and femoral neck (FN).

RESULTS

Mild to moderate hyperprolactinemia (1,000-2,000 mU/l) was associated with asymptomatic hypogonadism. Prolactin values >2,000 mU/l occurred in a few female patients. Hypogonadism leads to a slight increase (upper limit of normal) in bone resorption marker (CTx) in patients with schizophrenia (p = 0.023). As for bone mass, although lower at the spine than in healthy subjects, it did not reach statistical significance (p = 0.094), while at the FN, BMD was not different from healthy subjects. Body weight increased on average 8.7 ± 1.6 kg in more than 50% of patients. Leptin levels adjusted for BMI in females were significantly higher in patients than in healthy female subjects (p = 0.018), while in males there was no difference between the groups (p = 0.833). A high prevalence of low vitamin D levels and more current smokers were found in patients with schizophrenia. As for the metabolic profile during treatment with risperidone, the low Matsuda index of insulin sensitivity (p = 0.039) confirmed insulin resistance in these patients.

CONCLUSION

A potential long-term consequence of asymptomatic hypogonadism due to risperidone-induced hyperprolactinemia might cause a slight rise in bone resorption marker (CTx). On the other hand, by increasing body weight, risperidone could have a protective effect on the bone and thus no change in bone mass was recorded when compared with healthy controls.

Sasa borealis leaves extract improves insulin resistance by modulating inflammatory cytokine secretion in high fat diet-induced obese C57/BL6J mice

Obesity is considered a mild inflammatory state, and the secretion of inflammation-related cytokines rises as adipose tissue expands. Inflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), interlukin 6 (IL-6) and monocyte-chemoattractant protein 1 (MCP-1), are modulated by adipose tissue and known to play an important role in insulin resistance which is the common characteristics of obesity related disorders. In this study we analyzed the effects of Sasa borealis leaves extract on inflammatory cytokines and insulin resistance in diet induced obese C57/BL6J mice. The obese state was induced by a high fat diet for 20 weeks and then the mice were divided into two groups; obese control group (OBC, n = 7) and experimental group (OB-SBE, n = 7). The OBC group was fed a high fat diet and the OB-SBE group was fed a high fat diet containing 5% Sasa borealis leaves extract (SBE) for 12 weeks. We also used mice fed a standard diet as a normal control (NC, n = 7). The body weight and adipose tissue weight in the OB group were significantly higher than those in the NC group. The effects of the high fat diet were reduced by SBE treatments, and the body weight and adipose tissue deposition in the OB-SBE group were significantly decreased compared to the OBC group. The OBC group showed higher serum glucose and insulin levels which resulted in a significant increase of incremental area under the curve (IAUC) and HOMA-IR than the NC group. Also, serum leptin, TNF-alpha, and IL-6 levels were significantly higher in the OBC group than in the NC group. In contrast, the OB-SBE group showed a reversal in the metabolic defects, including a decrease in glucose, insulin, IAUC, HOMA-IR, TNF-alpha, IL-6 and leptin levels. These results suggest that BSE can suppress increased weight gain and/or fat deposition induced by a high fat diet and theses effects are accompanied by modulation of the inflammatory cytokines, TNF-alpha and IL-6 secretion resulting in improved insulin resistance.

Effect of age and glucoregulation on cognitive performance

Type 2 diabetes has been associated with a number of physiological consequences including neuropathy, retinopathy, and incidence of vascular disease. Less is known about the effect on cognition of prediabetes, a period when glucose regulation is abnormal. It is not clear which aspect of impaired glucoregulation is most predictive of cognitive deterioration. In the present experiment, we measured cognitive function in 93 healthy male and female nondiabetic older participants who ranged in age from 55 to 88 years. Various biological measures were obtained including a glucose tolerance test during which glucose and insulin were measured. Participants were evaluated twice, once after drinking a saccharin solution and on another occasion after drinking a glucose solution (50 g). The analysis of the correlations between the biological measures and the results of the cognitive tasks revealed that evoked glucose measures such as peak glucose and glucose at 1 hour were most often correlated with cognitive performance. We observed that progressively worse glucose regulation predicted poorer performance on measures of working memory and executive function-that is, on the Arithmetic, Digit Span Backward, Letter-Number Sequencing, Spatial Span Forward, Spatial Span Backward (trend), and Modified Brown-Peterson tasks. Although, there was no significant facilitative effect of glucose on cognitive performance, it reduced the association between glucose regulation and cognition, apparently by slightly improving performance. These results suggest that cognitive functions may be impaired before glucoregulatory impairment reaches levels consistent with a type 2 diabetes diagnosis.

Measuring and estimating insulin resistance in clinical and research settings

AIM

This short review provides a theoretical outline for the measurement of insulin secretion and insulin resistance in humans.

DATA SYNTHESIS

To evaluate the ability to secrete insulin, disposition index must be considered, and it is necessary to assess insulin sensitivity when insulin secretion is induced for assessment. The clinical application of the measurement of insulin resistance is also introduced for further debate. The term "insulin effectiveness" is clinical jargon for insulin sensitivity. However, for clinical application, you need at least two types of insulin effectiveness to calculate a basal and bolus insulin administration dose, while peripheral (mainly muscle) and liver are two major target organs for insulin action. The term "insulin sensitivity" may be used to express insulin action of the muscle or of specific organs through their insulin receptors, while "insulin resistance" may be used to express the necessity of a dose of insulin administration to suppress hepatic glucose production that can be induced by substrates, glucagon, catecholamine, and so on.

CONCLUSIONS

This article covers several important issues on the measurement of insulin secretion and resistance that had not been well described in other review articles, and may be of help for future clinical investigation.

Threshold for effects of vitamin D deficiency on glucose metabolism in obese female African-American adolescents

CONTEXT

Vitamin D status can influence insulin resistance.

OBJECTIVE

The aim of the study was to determine the prevalence of vitamin D deficiency in obese African-American (AA) adolescent females in a southeastern latitude and to determine the relationship of 25-hydroxyvitamin D [25(OH)D] with insulin and glucose dynamics.

DESIGN

We conducted a cross-sectional study in a University Children's Hospital.

METHODS

Serum 25(OH)D, fasting glucose, PTH, serum calcium, serum lipids, serum transaminases, and C-reactive protein were assessed. Indices of insulin sensitivity and resistance were determined from an oral glucose tolerance test. Subjects were classified as vitamin D deficient or sufficient, based on the traditional vitamin D deficiency definition [serum 25(OH)D <20 ng/ml] and also by a lower 25(OH)D cut-point of 15 ng/ml or less.

RESULTS

A total of 51 AA adolescent females (body mass index, 43.3 +/- 9.9 kg/m(2); age, 14 +/- 2 yr) were studied. Serum 25(OH)D concentrations were 20 ng/ml or less in 78.4% and 15 ng/ml or less in 60.8% of subjects. There were no significant group differences in the metabolic outcomes when subjects were classified using the traditional vitamin D deficiency definition. The Matsuda index of insulin sensitivity was significantly lower (P = 0.02), and insulin area under the curve was significantly higher (P = 0.04) in subjects with 25(OH)D concentrations of 15 ng/ml or less vs. those with higher concentrations.

CONCLUSIONS

Vitamin D deficiency is highly prevalent in obese, AA female adolescents and may promote insulin resistance. Our data suggest that a 25(OH)D concentration of 15 ng/ml or less may be the threshold by which vitamin D deficiency confers negative effects on insulin sensitivity.

Assessment of insulin sensitivity/resistance and their relations with leptin concentrations and anthropometric measures in a pregnant population with and without gestational diabetes mellitus

Fifty-six pregnant women with gestational diabetes mellitus (GDM) and 42 normal glucose tolerant (NGT) pregnant women between 26 and 36 gestational weeks were included in the study prospectively. The body fat percentage (BFP) was calculated using the Siri formula from skinfold thickness (SFT) measurements. Both groups were comparable for gestational age, height, weight, and body mass index (P>.05). Insulin resistance assessed by homeostasis model assessment for insulin resistance (HOMA-IR) method was significantly higher in GDM patients compared to their NGT weight-matched control group. In contrast, the insulin sensitivity calculated from quantitative insulin sensitivity check index (QUICKI-IS) equation was significantly lower in GDM group. Calculated lean body mass was found to be similar in between both groups. Body fat percentage derived from SFT parameters was significantly higher in women with GDM. Women with GDM had significantly higher levels of serum insulin and leptin concentrations when compared with the NGT group. All SFT measurements were higher in GDM group when compared to those in NGT women. We did not find any correlation between leptin levels and insulin resistance; we found negative correlation between leptin levels and insulin sensitivity. Thus, we observed that leptin may contribute development of GDM by decreasing insulin sensitivity but not increasing insulin resistance. Also, we observed that the BFP estimated by the Siri formula from SFT measurements correlated significantly with HOMA-IR and QUICKI-IS and leptin concentrations in pregnant women. We suggest that by simply evaluating SFT, we may hold a view about BFP and leptin concentrations and insulin sensitivity in pregnant women.

The effect of serum and intrafollicular insulin resistance parameters and homocysteine levels of nonobese, nonhyperandrogenemic polycystic ovary syndrome patients on in vitro fertilization outcome

OBJECTIVE

To investigate the serum and follicular fluid concentrations of insulin resistance parameters and homocysteine and their effect on IVF outcome in nonobese, nonhyperandrogenemic polycystic ovary syndrome patients.

DESIGN

Prospective study.

SETTING

Department of Infertility of Dr. Zekai Tahir Burak Women's Health Research and Education Hospital.

PATIENT(S)

Ninty-seven women underwent IVF.

INTERVENTION(S)

Subjects were categorized according to IVF indications: group 1 with polycystic ovary syndrome (PCOS), group 2 with subfertile male partners, group 3 with unexplained infertiliy. Serum and follicular fluid parameters from the first follicle on the day of oocyte retrieval were analyzed.

MAIN OUTCOME MEASURE(S)

Serum and follicular fluid insulin resistance parameters, homocysteine, sex hormone levels, and laboratory and clinical IVF outcome were studied.

RESULT(S)

Serum insulin, homeostasis model assessment estimate of insulin resistance (HOMA-IR), and homocysteine levels were significantly higher in subjects having PCOS. However, these significant differences in serum insulin resistance and homocysteine levels were not seen in the follicular microenvironment. There were no differences in clinical pregnancy rates between study groups.

CONCLUSION(S)

Despite elevated serum insulin, HOMA-IR, and homocysteine levels, and their effects on oocyte numbers and maturation in PCOS patients, there were no differences in follicular parameters and clinical pregnancy rates between hyperinsulinemic and hyperhomocysteinemic PCOS patients and the other two groups.

Post-transplant diabetes mellitus in children following renal transplantation

PTDM plays a role in chronic allograft nephropathy and decreases graft and patient survival. Considering the serious outcome of chronic hyperglycemia, the importance of early recognition and the few data in children, in this retrospective analysis we studied the characteristics and risk factors of PTDM in 45 pediatric renal transplant recipients receiving Tac or CyA-based immunosuppression. Fasting blood sampling and OGTT were performed. PTDM has been developed in six patients (13%), while seven children (16%) had IGT, with the overall incidence of a glucose metabolic disorder of 29% in pediatric renal transplants. Patients in the PTDM + IGT group were younger and had higher systolic blood pressure and serum triglyceride level than children with normal glucose tolerance. Multivariate analysis identified Tac treatment, Tac trough level, steroid pulse therapy and family history of diabetes to be associated with the onset of PTDM. In pediatric renal transplants, OGTT and frequent assessment of blood glucose levels might be essential not only in the post-transplant management, but also prior to transplantation, particularly with family history of diabetes. Careful monitoring and modified protocols help to minimize the side effects of Tac and corticosteroids.

Diagnosis of gestational diabetes mellitus by use of the homeostasis model assessment-insulin resistance index in the first trimester

OBJECTIVE

Gestational diabetes mellitus (GDM) affects 2-10% of all pregnant women, causing increased morbidity and mortality, and is tested for in the second trimester of pregnancy. The purpose of the present study was to predict GDM in the first trimester.

DESIGN AND METHODS

The study included 271 patients who were between the 10th and 14th week of gestation. Fasting glucose and insulin were measured in the first trimester and the homeostasis model assessment-insulin resistance index (HOMA-IR) was calculated for each patient. These values were compared with the results of the second-trimester glucose tolerance test.

RESULTS

HOMA-IR values were higher in women with GDM. A cut-off value of 2.60 for HOMA-IR was calculated at the end of the study.

CONCLUSION

Accepting patients whose HOMA-IR value is higher than 2.60 in the first trimester seems to be a good method to predict GDM.

Blood glucose dynamics

Measurement of blood glucose concentration is central to the diagnosis and treatment of diabetes. Although there are large numbers of historic glucose measurements in individuals with diabetes, until recently there have been very few data sets that were recorded continuously or sampled frequently enough to reveal intrinsic blood glucose dynamics, or the change in blood glucose with time. There have even fewer such recordings from individuals not having diabetes to serve as a therapeutic target. As a result, blood glucose dynamics have generally not been used in the diagnosis or treatment of the disease. Although present blood glucose monitoring is based largely on discrete measurements, future monitoring will likely focus on analysis of blood glucose excursions. New measurements are now being obtained, and there is a need for new methods of analysis to extract the maximal information from the data. Several approaches are demonstrated here for characterization of blood glucose dynamics, and a patient profiling system is proposed. An example of new insights is the observation that there are four time scales of blood glucose variations in individuals without diabetes, and these time scales are modified or lost in diabetes.

Insulin and its role in chronic kidney disease

The body's resistance to the actions of insulin (type II diabetes defect) results in compensatory increased production and secretion by the pancreas and leads to hyperinsulinemia in order to maintain euglycemia. When insulin secretion cannot be increased adequately (type I diabetes defect) to overcome insulin resistance in maintaining glucose homeostasis, hyperglycemia and glucose intolerance ensues. Insulin resistance and glucose intolerance has been well recognized in patients with advanced chronic kidney diseases (CKD). The etiology may involve uremic toxins from protein catabolism, vitamin D deficiency, metabolic acidosis, anemia, poor physical fitness, inflammation, and cachexia. Glucose and insulin abnormalities in nondiabetic CKD patients are implicated in the pathogenesis of hyperlipidemia and may represent important risk factors for accelerated atherosclerosis in these patients. Insulin secretion inadequacy has been associated with growth retardation in adolescents with CKD. Normal adolescents demonstrate an increase in insulin secretion as they go into puberty. It seems that the puberty growth spurt in adolescents both with normal health and renal failure may require increased insulin secretion as one of its hormonal requirements. Finally, insulin resistance has been associated with CKD. Whether insulin resistance is an antecedent of CKD or a consequence of impaired kidney function has been a subject of debate. The goal of this review was to provide an update of the literature on insulin pathophysiology in CKD, current understanding of its mechanisms, and epidemiological association of insulin resistance and CKD.

Adipocyte fatty acid-binding protein is associated with markers of obesity, but is an unlikely link between obesity, insulin resistance, and hyperandrogenism in polycystic ovary syndrome women

OBJECTIVE

Many polycystic ovary syndrome (PCOS) women suffer from adiposity and insulin resistance (IR), which play an important role in the development and maintenance of PCOS. Adipocyte fatty acid-binding protein (A-FABP) is mainly expressed in adipocytes, and circulating A-FABP has been associated with markers of obesity and IR. Thus, as observed with other adipose tissue derived factors, secreted A-FABP might be involved in the pathogenesis of obesity-associated disorders such as PCOS.

DESIGN

Plasma A-FABP concentrations were measured in 102 non-diabetic PCOS women, and associations with markers of obesity, IR, inflammation, and hyperandrogenism were investigated by correlation and multiple linear regression analyses. The effect of lifestyle intervention on A-FABP was studied in a second cohort of 17 obese PCOS women.

RESULTS

A-FABP correlated with body mass index (BMI; R = 0.694, P < 0.001), dual-energy X-ray-absorptiometry (DEXA) fat mass (R = 0.729, P < 0.001), DEXA lean body mass (R = 0.399, P = 0.001), HOMA %S (R = -0.435, P < 0.001), hsCRP (R = 0.355, P = 0.001), and free testosterone (fT; R = 0.230, P = 0.02). Adjusted for age, smoking, and glucose metabolism the association of A-FABP with HOMA %S was still significant (P < 0.001), whereas the associations with fT (P = 0.09) and hsCRP (P = 0.25) were not. Inclusion of BMI into the model abolished the impact of A-FABP on HOMA %S. In BMI-matched PCOS women (n = 20 pairs), neither HOMA %S (P = 0.3) nor fT (P = 0.6) were different despite different A-FABP levels (P < 0.001), and in 17 obese PCOS women undergoing a lifestyle intervention, changes in IR were not paralleled by changes in A-FABP.

CONCLUSIONS

Circulating A-FABP was correlated with markers of obesity, but had no major impact on IR, inflammation, or hyperandrogenemia in PCOS women.

Indian Asian men have less peripheral arterial disease than European men for equivalent levels of coronary disease

OBJECTIVES

Indian Asians have high rates of heart disease and stroke, but risks of peripheral arterial disease appear to be low. This paradox, and reasons for it, have not been explored. We compared ethnic differences in peripheral arterial disease for a given level of coronary disease.

METHODS

We studied 83 European and 84 Indian Asian men with a range of coronary disease. Extent of coronary atheroma was quantified by coronary artery calcification score on multislice CT. Femoral intima-media thickness (IMT) was measured by ultrasound.

RESULTS

Femoral IMT was 1.58, 2.06, 2.12, and 2.69 mm in Europeans, and 0.61, 1.41, 1.81 and 2.29 in Indian Asians by increasing categories of coronary atheroma (p=0.003 for ethnic difference, adjusted for age and lumen diameter). Adjustment for smoking and systolic blood pressure, the only risk factors adversely distributed in Europeans, only partly accounted for this ethnic difference (p=0.05). Other risk factors, including lipids, obesity, insulin and glycaemic status, more adversely distributed in Indian Asians, could not account for ethnic differences. Prevalence of abnormal ankle brachial index and lower limb atherosclerotic plaque was also greater in Europeans.

CONCLUSIONS

For a given level of coronary disease, Indian Asians have less lower limb atherosclerosis than Europeans, unexplained by established risk factors. Further study of these populations would help tease out relative contributions of risk factors to atherosclerosis in different vessel beds.

Association of Resistin Gene 3'-Untranslated Region EX4-44G-->A Polymorphism with Obesity- and Insulin-Related Phenotypes in Turkish Type 2 Diabetes Patients

Resistin, an adipocyte-secreted hormone, has been associated with obesity, insulin resistance and type 2 diabetes mellitus (T2DM) in some, but not all, rodent models. In humans, the exact function of resistin is unkown. Because 3'-untranslated region (3'-UTR) single nucleotide substitutions (SNPs) have been shown to affect gene expression, we examined the EX4-44G-->A SNP in the 3'-UTR of exon 3 within the resistin gene. The objective of this study was to investigate, for the first time in a Turkish study group, whether the 3'-UTR EX4-44G-->A variation in the resistin gene influences the development of T2DM, obesity and insulin-related phenotypes. We analyzed the genotype frequencies of the EX4-44G-->A polymorphism of the resistin gene in 116 type 2 diabetic and 102 normal subjects. Serum lipids, obesity-related and insulin-related phenotypes were analyzed. No significant difference for genotypic frequencies were observed for the BseRI restriction site in type 2 diabetic patients as compared to controls. Waist-to-hip ratio, BMI, body fat and apoAI levels were found to be affected by resistin genotype. In the control group, BMI (p < 0.01), HIS (p < 0.05) and BF (p < 0.05) levels were found to be elevated, whereas HOMA beta-cell index (p < 0.01) and apo AI (p < 0.05) levels were found to be decreased in GG genotype carriers. In the diabetic group, the GG genotype carriers were found to have higher BMI levels (p < 0.001), waist-to-hip ratio (p < 0.05), body fat (p < 0.01), HOMA (p < 0.001) and fasting insulin (p < 0.05), but lower HbA1c levels in comparison to GC + AA carriers. These data suggest that, in the Turkish study group, the EX4-44G-->A polymorphism of the resistin gene is associated with insulin and obesity-related phenotypes.

Metformin Plus Low-Dose Glimeperide Significantly Improves Homeostasis Model Assessment for Insulin Resistance (HOMAIR) and β-Cell Function (HOMAβ-cell) Without Hyperinsulinemia in Patients With Type 2 Diabetes Mellitus

OBJECTIVE

Type 2 diabetes mellitus is characterized by insulin resistance and defects in insulin secretion from pancreatic beta-cells, which have been studied by using euglycemic/hyperinsulinemic clamps. However, it is difficult to study insulin resistance and beta-cell failure by these techniques in humans. Therefore, the aim of this study was to evaluate the effect of three different antidiabetic therapeutic regimens on insulin resistance and beta-cell activity by using a mathematical model, Homeostasis Model Assessment for insulin resistance (HOMA(IR)) and beta-cell function (HOMA(beta-cell)).

RESEARCH DESIGN AND METHODS

Seventy type 2 diabetic patients were randomly assigned to one of three therapeutic regimens: (A) metformin + American Diabetic Association (ADA)-recommended diet + physical activity; (B) metformin + low-dose glimepiride + ADA diet + physical activity; or (C) ADA diet + physical activity (no drugs). Blood samples were obtained before and after the treatment to determine serum levels of fasting and post-prandial blood glucose, fasting insulin, and glycosylated hemoglobin (HbA1c), and HOMA(IR) and HOMA(beta-cell) were calculated.

RESULTS

Fasting and post-prandial levels of glucose, HbA1c, and fasting insulin and calculated HOMA(IR) and HOMA(beta-cell) values before treatment were significantly higher than the respective values after treatment for all groups of patients (P < 0.01). Significant differences were also found when comparing the treatment-induced reduction in fasting blood glucose (51.8%; P < 0.01), post-prandial blood glucose (55.0%; P < 0.05), and HOMA(IR) (65.3%; P < 0.01) in patients of Group B with that in patients receiving other therapeutic options (Groups A and C).

CONCLUSIONS

Metformin plus low-dose glimepiride (plus ADA diet and physical activity) is a more effective treatment for type 2 diabetes than either metformin plus ADA diet and physical activity or ADA diet and physical activity alone. Determination of HOMA(IR) and HOMA(beta-cell) values is an inexpensive, reliable, less invasive, and less labor-intensive method than other tests to estimate insulin resistance and beta-cell function in patients with type 2 diabetes mellitus.

Measurement of pulse wave velocity: site matters

BACKGROUND

Aortic pulse wave velocity (PWV) predicts mortality from cardiovascular disease, ischaemic heart disease and stroke. However, a comparison of associations between PWV measured at different sites and atherosclerosis in coronary, carotid and femoral arteries has not been made.

METHODS

In 159 men (ages 45-82 years) with and without known coronary artery disease, PWV measurements were made between carotid-femoral, carotid-radial and femoral-posterior tibial sites, using an ultrasound technique. Coronary artery calcification (CAC) scores were measured by multislice computed tomography. Carotid and femoral intima-media thickness (IMT) and presence of plaque were determined by ultrasound. Known coronary artery disease was confirmed by angiography. Participants were grouped into four categories of CAC score: 0-10, 11-100, 101-400, > 400 Hounsfield Units (HU). Measurements of blood pressure, heart rate and fasting bloods were made in all individuals.

RESULTS

Carotid-femoral PWV correlated positively with CAC score and increased with incremental coronary calcification category (median carotid-femoral PWV 16.8 m/s in those with CAC score > 400 HU and 13.8 m/s in those with CAC score < 10 HU; P = 0.003). Carotid-femoral PWV also correlated with carotid and femoral IMT (P < 0.001, P = 0.004, respectively) and with carotid and femoral plaque (P = 0.001, P = 0.038, respectively). Increased carotid-femoral PWV also correlated with increasing age (P < 0.001), systolic blood pressure (P < 0.001), mean arterial pressure and pulse pressure (P < 0.001). Carotid-radial and femoral-posterior tibial PWV were not significantly associated with CAC score, carotid or femoral IMT or carotid plaque.

CONCLUSIONS

Carotid-femoral PWV is a better indicator of atherosclerosis than either carotid-radial or femoral-posterior tibial PWV, and should be used preferentially in studies of atherosclerosis and in stratifying risk in clinical settings.

Impaired Glucose Tolerance and Impaired Fasting Glucose Share Similar Underlying Pathophysiologies

Both impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are pre-diabetic states. IGT was defined as having normal fasting plasma glucose (< 6.1 mmol/l) and abnormal 2-hr post-challenge plasma glucose. IFG was defined as having abnormal fasting plasma and normal 2-hr post-challenge plasma glucose (< 7.8 mmol/l). To explore whether these two abnormalities share similar underlying pathophysiologies, we evaluated risk factors of IGT and IFT using the models of factor analysis. The present study included 107 subjects with IGT and 52 with IFG. An oral glucose tolerance test and insulin suppression test, which could quantify insulin resistance, were performed on separate days. The risk factors include waist-to-hip ratio (WHR), triglycerides, high-density lipoprotein (HDL)-cholesterol, blood pressure, and fasting plasma glucose, which are associated with metabolic syndrome and insulin resistance. Factor analysis is a commonly used statistical method that could reduce a large number of risk factors into smaller numbers of groups, also called dimension. Accordingly, the complicated data could be interpreted more easily, since the related risk factors are grouped in one dimension. The results showed that the risk factors of IGT and IFG have similar grouping patterns. Triglyceride, insulin resistance, and HDL-cholesterol were grouped in one dimension (the lipid dimension), while WHR, mean blood pressure and fasting plasma glucose were grouped in another dimension (the metabolic dimension). In conclusion, except for WHR, the grouping patterns of the components in both IGT and IFG were nearly identical. These results suggest that IGT and IFG may share similar pathophysiologies.

Adiponectin and insulin resistance in young and healthy smokers

Smoking is closely associated with insulin resistance, though the mechanism is not clear. Adiponectin, a novel anti-atherosclerotic and anti-inflammatory adipose tissue product, which is closely associated with insulin resistance, was reported to be low in smokers with cofactors for atherosclerosis. However, the effects of smoking on circulating adiponectin levels in otherwise healthy people are unknown. In this study, a case control design was implemented to search for the effect of smoking on plasma adiponectin and insulin sensitivities in healthy people. Sixty-four healthy male smokers, with no family history of hypertension and diabetes mellitus were compared with appropriate 36 age and body mass index matched controls. Both the patients and controls were the soldiers of a troop with regular daily physical activity. Plasma adiponectin, high sensitive C-reactive protein (hsCRP), insulin and lipid levels, and insulin sensitivity as assessed by homeostasis model assessment index (HOMA) of the smokers were measured and compared with those of the controls. The plasma adiponectin, hsCRP, insulin levels and HOMA indexes of the two groups were similar. These parameters were not affected by the amount of cigarettes per day. HDL-cholesterol levels were lower (p = 0.01) and systolic blood pressures were higher (p = 0.02) in the smokers. These results indicate that smoking may not affect plasma adiponectin and insulin levels in young and healthy men with high exercise capacity.

Differences in insulin sensitivity in pregnant women with overweight and gestational diabetes mellitus

AIM

The purpose of the present study was to investigate changes in insulin sensitivity using homeostasis model assessment (HOMA) and the quantitative insulin sensitivity check index (QUICKI) in normal-weight and overweight women with normal glucose tolerance (NGT) and gestational diabetes mellitus (GDM) during pregnancy.

METHODS

Ninety-two pregnant women in the first trimester, 202 in the second trimester and 154 in the third trimester were enrolled in this study. Fasting plasma glucose and insulin concentrations were measured in all women in the first, second and third trimesters. HOMA indices (insulin resistance, HOMA-IR and beta-cell function, HOMA-beta) and QUICKI were calculated from fasting glucose and insulin concentrations.

RESULTS

HOMA-IR values in overweight women with NGT and in women with GDM were significantly (p < 0.01) higher than those in normal-weight women with NGT. HOMA-IR in women with GDM increased significantly (p < 0.05) during pregnancy, but HOMA-IR values in normal-weight and overweight women with NGT did not change significantly with advance of gestation. QUICKI values in overweight women with NGT and in women with GDM were also significantly (p < 0.01) lower than those in normal-weight women with NGT, and QUICKI in women with GDM decreased significantly (p < 0.05) during pregnancy. HOMA-beta in normal-weight women with NGT increased significantly (p < 0.01) during pregnancy.

CONCLUSION

We showed that insulin sensitivities determined by using HOMA-IR and QUICKI in overweight women with NGT and women with GDM were lower than those in normal-weight women with NGT, and that insulin sensitivity in women with GDM declined with advance of gestation.

Longitudinal assessment of insulin sensitivity in pregnancy. Validation of the homeostasis model assessment

OBJECTIVE

To validate the use of the homeostasis model assessment (HOMA) for measurement of insulin sensitivity in obese women during gestation and the postpartum period.

DESIGN

Three consecutive measurements of insulin resistance (IR) were performed during and after pregnancy to compare the homeostasis model assessment insulin sensitivity index (HOMA-IR) to glucose utilization rates obtained during hyperinsulinaemic euglycaemic clamps (G(Rd)).

PATIENTS

Six obese women (mean second trimester BMI = 30.4 kg/m(2)) with normal glucose tolerance were studied during the second and third trimesters of pregnancy and once in the postpartum period. Thus, there were a total of 18 measurements for analysis.

RESULTS

Correlations between the rate of glucose disappearance (G(Rd)) (the gold standard) and the HOMA-derived metabolic parameters of insulin sensitivity were significant, with a multiple R(2) of 43.5% (P = 0.003). However, when controlling for variations between patients using dummy variables, we observed that one patient differed from the other five in the relationship between G(Rd) and HOMA-IR. Applying this regression we obtained a R(2) of 72.6% (P < 0.001). When the regression constant was omitted, we observed that the individual trends during pregnancy and postpartum in two patients differed statistically from the other patients between the two assessments, and we obtained a multiple R(2) of 97.3% (< 0.001).

CONCLUSIONS

HOMA estimation of insulin resistance is appropriate for use during both the second and third trimesters of pregnancy and postpartum in obese women with normal glucose tolerance. It lacks sensitivity for the evaluation of individuals, where more precise measures of insulin sensitivity should be utilized.

The metabolic syndrome: a glance at its history

Although the modern era of what we now call the 'metabolic syndrome' or the 'insulin resistance syndrome' seems to have started less than two decades ago with the description of syndrome X by G.M. Reaven in the late 1980s, the history of this syndrome is much longer. In particular, a considerable number of scientists, starting as early as almost 90 years ago, have described the very common coexistence of the various components of the syndrome, including hypertension, and some of them gave several names to this clustering. On the other hand, during the past few years several international organizations have tried to form a reference context of what is included under the terms 'metabolic syndrome' and 'insulin resistance syndrome', proposing various 'definitions' for them. This review summarizes the history of the syndrome, from the early descriptions and other valuable contributions to the recent attempts to define it, as a small piece in honour of the pioneer workers in this field during the twentieth century.

Parenterally administered dipeptide alanyl-glutamine prevents worsening of insulin sensitivity in multiple-trauma patients

BACKGROUND

Dipeptide alanyl-glutamine is a commonly used substrate in major trauma patients. Its importance and effects are widely discussed; as yet, it has not been elucidated whether its administration influences glucose homeostasis.

OBJECTIVE

We studied the effect of alanyl-glutamine administration on insulin resistance.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Intensive care unit of a tertiary level hospital.

PATIENTS

Multiple-trauma patients.

INTERVENTIONS

Patients were randomized into two groups and assigned to receive parenterally an equal dose of amino acids either with alanyl-glutamine in the dose of 0.4 g x kg body weight(-1) x 24 hrs(-1) (group AG) or without alanyl-glutamine (control group C). This regimen started 24 hrs after injury and continued for 7 days. To assess insulin sensitivity, we performed an euglycemic clamp on day 4 and day 8 after injury.

MEASUREMENTS AND MAIN RESULTS

We randomized 40 patients, 20 into each group. At day 4, insulin-mediated glucose disposal was higher in group AG (2.4 +/- 0.7 mg x kg(-1) x min(-1) glucose), with significant difference from group C (1.9 +/- 0.6 mg x kg(-1) x min(-1), p = .044). At day 8, glucose disposal was higher in group AG (2.2 +/- 0.7 mg x kg(-1) x min(-1) glucose), with significant difference in comparison with group C (1.2 +/- 0.6, p < .001). Diminution of the main glucose homeostasis variables in group C between days 4 and 8 of the study was statistically significant (p < .001); however, differences in these variables in group AG were without statistical significance.

CONCLUSIONS

Parenteral supplementation of alanyl-glutamine dipeptide was associated with better insulin sensitivity in multiple-trauma patients.

Improved insulin action following short-term exercise training: role of energy and carbohydrate balance

Short-term exercise training improves insulin action, but the impact of replacing the energy expended during exercise to prevent energy deficit is unclear. The purpose of this study was to establish the role of an energy deficit in mediating improved insulin action after short-term exercise training. Two groups of previously sedentary, overweight/obese subjects performed 6 consecutive days of moderate-intensity walking to expend approximately 500 kcal/day. In one group, energy and carbohydrate expended during exercise was replaced [balance group (BAL), n = 8] and in the other group, energy was not replaced [deficit group (DEF), n = 8]. Insulin action (blood glucose uptake during glucose infusion) and selected lipids and adipokines were measured pre- and posttraining. Training increased estimated daily energy expenditure by approximately 500 kcal/day (DEF = 469 +/- 45, BAL = 521 +/- 48), generating an energy deficit in DEF (-481 +/- 24 kcal/day) but not BAL (+8 +/- 20 kcal/day). Insulin action increased 40% in DEF (P = 0.032) but not BAL (-8.4%, P = 0.107). Hepatic glucose production was suppressed during glucose infusion in DEF (30.2 +/- 9.5%, P = 0.037) but not BAL (-10.0 +/- 7.4%, P = 0.417). Fasting leptin concentrations declined in DEF but not BAL. Six days of exercise training without energy replacement significantly increased insulin action. Restoring energy balance by refeeding the energy and carbohydrate expended during exercise resulted in no change in insulin action. These findings suggest that changes in short-term energy and/or carbohydrate balance play a key role in mediating the beneficial effects of exercise on whole body and hepatic insulin action.

Endocrine and metabolic effects of rosiglitazone in non-obese women with polycystic ovary disease

We hypothesized that the administration of rosiglitazone, an insulin-sensitizing agent of the thiazolidinedione class, would improve the ovulatory dysfunction, hirsutism, hyperandrogenemia, and hyperinsulinemia of polycystic ovary syndrome (PCOS) patients. Forty women with PCOS and impaired glucose tolerance test (IGT) were randomly assigned to the 8-month treatment with rosiglitazone at either 2 mg/day or 4 mg/day. We compared changes in ovulatory function, hirsutism, hormonal levels (total and free testosterone, estradiol, estrone, androstenedione, LH and FSH), and measures of glycemic parameters (fasting and post-challenge levels of glucose and insulin, HOMA-IR, hemoglobin A1c), between the study groups. The patients' baseline characteristics were similar across all treatment arms. Fifteen of 20 women in the 2 mg group and 19 of 20 women in the 4 mg group achieved normal glucose tolerance; 14 of 20 women in the 2 mg group and 17 of 20 women in the 4 mg group achieved ovulatory menses at the end of the study period. The decreases of free testosterone levels were better in the 4 mg group than the 2 mg rosiglitazone group (-1.89+/-0.35 pg/ml vs. -2.21+/-0.39 pg/ml; P<0.01). There were neither any serious adverse events nor any liver enzyme elevations in our study patients during the treatment period. This study demonstrated that rosiglitazone improves the ovulatory dysfunction, hirsutism, hyperandrogenemia, and insulin resistance of PCOS in a dose-related fashion, with minimal adverse effects. This drug may be a good choice for lifetime treatment of patients with PCOS, especially for the ones who failed to show satisfactory results in metformin therapy.

Differential regulation of insulin action and tumor necrosis factor alpha system activity by metformin

BACKGROUND

Tumor necrosis factor alpha has a key role in insulin resistance. We study the effects of metformin on glucose tolerance, insulin resistance, beta cell function, and soluble tumor necrosis factor receptor (sTNFR) levels.

METHODS

We performed a double-blind, randomized metformin-placebo study. Twenty-three subjects with impaired glucose tolerance or impaired fasting glucose were studied. Oral glucose tolerance, homeostasis model assessment, and continuous infusion of glucose with model assessment tests were used to evaluate glucose tolerance, insulin sensitivity, and beta cell function, respectively. Soluble tumor necrosis factor receptor levels were measured before and after therapy. Repeated measures analysis of variance was used for statistical analysis.

RESULTS

After 12-week treatment, fasting glucose (110.1 +/- 9.9 to 98.9 +/- 15.7 mg/dl, P < .001), fasting insulin (11.6 +/- 5.4 to 8.8 +/- 3.5 mU/L, P = .05), fasting C-peptide (2.5 +/- 0.7 to 1.8 +/- 0.5 ng/mL, P < .05), and achieved C-peptide (5.2 +/- 1.2 to 4.2 +/- 1 ng/mL, P < .05) levels decreased in the metformin group. In addition, there was an improvement in insulin sensitivity (37.4% +/- 15.2% to 50.4% +/- 23.2%, P < .05) with unchanged sTNFR1 (2.0 +/- 0.8 to 2.3 +/- 1.2 microg/L, P = NS) and sTNFR2 (4.8 +/- 1.7 to 4.4 +/- 1.2 microg/L, P = NS) levels.

CONCLUSIONS

Metformin is able to reverse insulin resistance and hyperglycemia in high-risk subjects for type 2 diabetes mellitus independently of the effects on tumor necrosis factor alpha system activity.

Limited accuracy of surrogates of insulin resistance during puberty in obese and lean children at risk for altered glucoregulation

This study evaluated the accuracy of surrogate indexes of insulin sensitivity (SI) in children. Surrogates (homeostasis model assessment index of insulin resistance, quick insulin sensitivity index, and 40/insulin ratio index) were cross-sectionally investigated in 66 obese and lean children (17 Tanner stage I, 19 Tanner stage II-III, and 30 Tanner stage IV-V) as indexes of insulin resistance in comparison with the minimal model. The pubertal decrease in SI was found with the minimal model (-47%; P = 0.01), but not with surrogates, which were not correlated to SI. Baseline insulin (Ib) did not mirror the decrease in SI, did not significantly change when plotted against pubertal stage or age, and was not correlated to SI. Ib and surrogates were positively correlated with the body mass index. The disposition index, which quantifies the feedback between SI and insulin release, was widely scattered and decreased during puberty (P = 0.05). The specificity and sensitivity of surrogates as predictors of insulin resistance were poor (e.g. 81.1% and 30.7%, respectively, for the homeostasis model assessment index of insulin resistance). Thus, during puberty, surrogates are not accurate predictors of insulin resistance. Because reference methods are rather expensive and invasive, additional studies of alternative techniques for evaluating SI are needed to allow accurate measurement of insulin resistance in children.

Plasma homocysteine levels in polycystic ovary syndrome and congenital adrenal hyperplasia

The purpose of this study was to determine whether polycystic ovary syndrome (PCOS) and nonclassic 21-hydroxylase deficiency (CAH) are related to hyperhomocysteinemia, and to investigate if there is a correlation between homocysteine levels and insulin sensitivity in women with PCOS and CAH. Fifty patients with PCOS, 50 patients with CAH and 25 control women were included in the study. Blood samplings were performed in the early follicular phase for measuring hormone profile, Vitamin B(12), folate, homocysteine levels and fasting blood glucose. Ovulatory status was assessed with timed serum progesterone measurements. Homeostasis model assessment-insulin resistance (HOMA-IR) was calculated as a measure of insulin resistance. Mean homocysteine levels were found as (8.9 + 1.9 micromol/l and 17.7 + 3.6 micromol/l) in the normal group and PCOS respectively (p<0.001), but there was no statistical significance between nonclassic 21-hydroxylase deficiency (9.0 + 2.2 micromol/l) and control group. Most of the patients in PCOS group (35 of 50) were significantly insulin resistant. However, there was no insulin resistant patient in CAH or control group. When we compare the two subgroups of PCOS women, the patients with insulin resistance had significantly higher homocysteine levels than the ones who were not insulin resistant. There were positive correlations among serum homocysteine, insulin and androgen levels in PCOS patients. There were no correlations among these parameters in CAH and control groups. Increased homocysteine levels may contribute to increased cardiovascular disease risk in patients with PCOS. The reason for hyperhomocysteinemia seems to be related to insulin resistance but not high androgen levels.

M�llerian-inhibiting substance in women with polycystic ovary syndrome: Relationship with hormonal and metabolic characteristics

The aim of the present study was to examine the relationship between Mullerian-inhibiting substance (MIS) levels and metabolic characteristics in women with polycystic ovary syndrome. Increased ovarian MIS production may exert a paracrine negative control on follicle growth sufficiently to prevent selection of a dominant follicle.

The impact of insulin resistance on the outcome of laparoscopic ovarian electrocautery in infertile women with the polycystic ovary syndrome

In this study we assessed how insulin resistance affects pregnancy rates in infertile women with the polycystic ovary syndrome (PCOS) treated with laparoscopic ovarian electrocautery. Sixty-four PCOS women were included in the study in a consecutive fashion. Following the CIGMA (continuous infusion of glucose with model assessment) test, 28 women were classified as insulin resistant and 36 women as non-insulin resistant. After the ovarian electrocautery patients were observed for 12-18 months. If pregnancy did not ensue, they were referred for one or more cycles of in vitro fertilization (IVF). Following ovarian electrocautery the non-insulin-resistant women more frequently achieved a regular menstrual cycle and ovulation than the insulin-resistant PCOS women. Consequently 18 (50%) of the non-insulin-resistant PCOS women achieved a pregnancy versus only five (18%) of women in the insulin-resistant PCOS group. Following treatment with both ovarian electrocautery and IVF, 27 (75%) of the non-insulin resistant PCOS women achieved a successful pregnancy, while 13 (46%) of the insulin-resistant PCOS group achieved this. In conclusion, insulin resistance may be an important marker of a poor outcome of treatment in PCOS infertility. Further studies are needed to evaluate the possible effect of treatment alternatives to alleviate the unfavorable influences of insulin resistance and hyperinsulinemia on ovulation induction in PCOS women.

Use and abuse of HOMA modeling

Homeostatic model assessment (HOMA) is a method for assessing beta-cell function and insulin resistance (IR) from basal (fasting) glucose and insulin or C-peptide concentrations. It has been reported in >500 publications, 20 times more frequently for the estimation of IR than beta-cell function. This article summarizes the physiological basis of HOMA, a structural model of steady-state insulin and glucose domains, constructed from physiological dose responses of glucose uptake and insulin production. Hepatic and peripheral glucose efflux and uptake were modeled to be dependent on plasma glucose and insulin concentrations. Decreases in beta-cell function were modeled by changing the beta-cell response to plasma glucose concentrations. The original HOMA model was described in 1985 with a formula for approximate estimation. The computer model is available but has not been as widely used as the approximation formulae. HOMA has been validated against a variety of physiological methods. We review the use and reporting of HOMA in the literature and give guidance on its appropriate use (e.g., cohort and epidemiological studies) and inappropriate use (e.g., measuring beta-cell function in isolation). The HOMA model compares favorably with other models and has the advantage of requiring only a single plasma sample assayed for insulin and glucose. In conclusion, the HOMA model has become a widely used clinical and epidemiological tool and, when used appropriately, it can yield valuable data. However, as with all models, the primary input data need to be robust, and the data need to be interpreted carefully.

Modeling approaches to type 2 diabetes

The incidence of type 2 diabetes is increasing rapidly, but clinical maintenance of normoglycemia remains challenging. The systemic, multifactorial character of diabetes is a key reason its treatment is so difficult. In the past 25 years, a number of mathematical and computational models have been developed to study this disease. These models offer promise in identifying the underlying disease pathophysiology in individual patients and in understanding the general pathophysiology characterizing the disease in large populations. To exploit these models most effectively, it is necessary to understand both the strengths and limitations of each model. This review outlines a selection of the models available for the study of diabetes, with a particular focus on the types of problems for which each model is well suited and the limitations that restrict how each model can be used.

Effect of age and glucoregulation on cognitive performance

Non-insulin dependent diabetes mellitus (NIDDM) has been associated with a number of physiological consequences including neuropathy, retinopathy and incidence of vascular disease. Recently, several authors reviewed studies that suggested that NIDDM is associated with cognitive impairments leading to a higher incidence of dementia. In the present experiment, we measured cognitive function in 57 healthy male and female non-diabetic older participants who ranged in age from 55 to 84. Various biological measures were obtained including a glucose tolerance test during which glucose and insulin were measured. Participants were separated into better and poorer glucoregulatory groups on the basis of their blood glucose levels during the tolerance test. Participants were evaluated twice, once after drinking a saccharin solution and on another occasion after drinking a glucose solution (50 g). Older participants (72 years and over) with poorer glucoregulation had the worse performance in tests evaluating working memory, verbal declarative memory and executive functions. Glucose administration appeared to only attenuate the decrements observed in the saccharin condition in the older participants for some of the tests. These results suggest that cognitive functions may be impaired before glucoregulatory impairment reaches levels consistent with a type II diabetes diagnosis.

Insulin-lowering agents in the management of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a medical condition that has brought multiple specialists together. Gynecologists, endocrinologists, cardiologists, pediatricians, and dermatologists are all concerned with PCOS patients and share research data and design clinical trials to learn more about the syndrome. Insulin resistance is a common feature of PCOS and is more marked in obese women, suggesting that PCOS and obesity have a synergistic effect on the magnitude of the insulin disorder. Hyperinsulinemia associated with insulin resistance has been causally linked to all features of the syndrome, such as hyperandrogenism, reproductive disorders, acne, hirsutism, and metabolic disturbances. Women with PCOS should be evaluated for cardiovascular risk factors, such as lipid profile and blood pressure. Modification of diet and lifestyle should be suggested to those who are obese. Several insulin-lowering agents have been tested in the management of PCOS. In particular, metformin is the only drug currently in widespread clinical use for treatment of PCOS. In a high percentage of patients, treatment with metformin is followed by regularization of menstrual cycle, reduction in hyperandrogenism and in cardiovascular risk factors, and improvement in response to therapies for induction of ovulation.

Evaluation of HOMA and QUICKI as measures of insulin sensitivity in prepubertal children

BACKGROUND

Simple fasting sample methods to measure insulin sensitivity (SI) such as homeostasis model assessment (HOMA) and quantitative insulin-sensitivity check index (QUICKI) have been widely promoted in adult studies but have not been formally evaluated in children. The aim of this study was to compare HOMA and QUICKI to the minimal model as measures of SI in prepubertal children.

METHOD

The study population consisted of twins (n = 44), premature (n = 17), small for gestational age (SGA) (15), and normal (n = 3) prepubertal children. The insulin-sensitivity index derived by the minimal model (SIMM) was calculated by the minimal model with plasma glucose and insulin data from a 90-min frequently sampled intravenous glucose test with tolbutamide. The HOMA resistance index (RHOMA) and QUICKI were calculated from fasting plasma glucose and insulin values.

RESULTS

The correlation between RHOMA and SIMM (r = -0.4, p < 0.001) was no better than that between fasting insulin and SIMM (r = -0.4, p < 0.001). QUICKI was poorly correlated with SIMM (r = 0.2, p = 0.02). The correlation between SIMM and RHOMA is largely confined to low SI values (< 10 x 10(-4)/min microU/mL.) In seven SGA subjects, the introduction of growth hormone treatment led to an expected fall in SIMM by 8.2 +/- 2.8 x 10(-4)/min microU/mL (p = 0.02) that was not detected by either RHOMA (p = 0.1) or QUICKI (p = 0.2). Similarly, SIMM values were lower in obese (n = 9) compared to non-obese subjects (p = 0.04); however, no difference was found between these two groups with either RHOMA (p = 0.21) or QUICKI (p = 0.8).

CONCLUSION

As measures of SI in prepubertal children, RHOMA is no better than fasting insulin and QUICKI, a poor measure. Neither RHOMA nor QUICKI was able to detect changes in SI induced by either obesity or growth hormone therapy.

Importance of obtaining independent measures of insulin secretion and insulin sensitivity during the same test: results with the Botnia clamp

OBJECTIVE

To validate and apply a method for independent assessment of insulin secretion and insulin sensitivity (S(I)) during the same test; that is, an intravenous glucose tolerance test followed by a euglycemic-hyperinsulinemic clamp, also called the Botnia clamp. This test was then applied to nondiabetic subjects with (FH+) and without (FH-) a first-degree family history of diabetes.

RESEARCH DESIGN AND METHODS

The Botnia clamp measures the first-phase insulin response (FPIR) to 0.3g/kg glucose i.v. and insulin sensitivity (M-value) from a 2-h euglycemic clamp begun 60 min after the glucose bolus. The M-value obtained during the Botnia clamp was compared with M-values obtained during a regular euglycemic clamp without prior glucose bolus. Repeated tests were performed in random order in subjects with normal and abnormal glucose tolerance. Finally, the test was applied to subjects with and without a family history of type 2 diabetes.

RESULTS

S(I) and insulin secretion from this test showed a high degree of reproducibility, and the M-value obtained with the Botnia clamp correlated strongly with the M-value from a euglycemic clamp without prior glucose bolus (r = 0.953, P < 0.005). FH+ subjects showed decreased S(I) (P = 0.02), but similar FPIR, compared with FH- subjects. However, insulin secretion adjusted for the degree of insulin resistance was significantly impaired (P = 0.04).

CONCLUSIONS

In conclusion, the Botnia clamp provides reliable and independent measures of S(I) and beta-cell function during the same test. As illustrated above, knowledge of the degree of S(I) is mandatory when presenting data on insulin secretion.