Comparative evaluation of simple insulin sensitivity methods based on the oral glucose tolerance test

Development of a Diabetes Dietary Quality Index: Reproducibility and Associations with Measures of Insulin Resistance, Beta Cell Function, and Hyperglycemia

AIMS

Various dietary risk factors for type 2 diabetes have been identified. A short assessment of dietary patterns related to the risk for type 2 diabetes mellitus may be relevant in clinical practice given the largely preventable nature of the disease. The aim of this study was to investigate the reproducibility of a short food frequency questionnaire based on available knowledge of diabetes-related healthy diets. In addition, we aimed to investigate whether a Diabetes Dietary Quality Index based on this questionnaire was related to metabolic risk factors, including measures of beta cell function and insulin sensitivity.

METHODS

A short food frequency questionnaire was composed by selecting fourteen questions (representing eight dietary factors) from existing food frequency questionnaires on the basis of their reported relationship with diabetes risk. Healthy participants (N = 176) from a Dutch family study completed the questionnaire and a subgroup (N = 123) completed the questionnaire twice. Reproducible items from the short questionnaire were combined into an index. The association between the Diabetes Dietary Quality index and metabolic risk factors was investigated using multiple linear regression analysis. Measures of beta cell function and insulin sensitivity were derived from a mixed meal test and an euglycemic-hyperinsulinemic and modified hyperglycemic clamp test.

RESULTS

Our results show that this new short food frequency questionnaire is reliable (Intraclass Correlations ranged between 0.5 and 0.9). A higher Diabetes Dietary Quality index score was associated with lower 2 h post-meal glucose (β -0.02, SE 0.006, p < 0.05), HbA1c (β -0.07, SE 0.02, p < 0.05), total cholesterol, (β -0.02, SE 0.07, p < 0.05), LDL cholesterol, (β -0.19, SE 0.07, p < 0.05), fasting (β -0.4, SE 0.16, p < 0.05) and post-load insulin, (β -3.9, SE 1.40, p < 0.05) concentrations and the incremental AUC of glucose during MMT (β -1.9, SE 0.97, p < 0.05). The scores obtained for the oral glucose insulin sensitivity-derived mixed meal test were higher in subjects who scored higher on the Diabetes Dietary Quality index (β 0.89, 0.39, p < 0.05). In contrast, we found no significant associations between the Diabetes Dietary Quality index and clamp measures of beta cell function.

CONCLUSIONS

We identified a questionnaire-derived Diabetes Dietary Quality index that was reproducible and inversely associated with a number of type 2 diabetes mellitus and metabolic risk factors, like 2 h post-meal glucose, Hba1c and LDL, and total cholesterol. Once relative validity has been established, the Diabetes Dietary Quality index could be used by health care professionals to identify individuals with diets adversely related to development of type 2 diabetes.

A machine learning-based classification of adult-onset diabetes identifies patients at risk of liver-related complications

Background & aims

Diabetes mellitus is a major risk factor for fatty liver disease development and progression. A novel machine learning method identified five clusters of patients with diabetes, with different characteristics and risk of diabetic complications using six clinical and biological variables. We evaluated whether this new classification could identify individuals with an increased risk of liver-related complications.

Methods

We used a prospective cohort of patients with a diagnosis of type 1 or type 2 diabetes without evidence of advanced fibrosis at baseline recruited between 2000 and 2020. We assessed the risk of each diabetic cluster of developing liver-related complications (i.e. ascites, encephalopathy, variceal haemorrhage, hepatocellular carcinoma), using competing risk analyses.

Results

We included 1,068 patients, of whom 162 (15.2%) were determined to be in the severe autoimmune diabetes subgroup, 266 (24.9%) had severe insulin-deficient diabetes, 95 (8.9%) had severe insulin-resistant diabetes (SIRD), 359 (33.6%) had mild obesity-related diabetes, and 186 (17.4%) were in the mild age-related diabetes subgroup. In multivariable analysis, patients in the SIRD cluster and those with excessive alcohol consumption at baseline had the highest risk for liver-related events. The SIRD cluster, excessive alcohol consumption, and hypertension were independently associated with clinically significant fibrosis, evaluated by liver biopsy or transient elastography. Using a simplified classification, patients assigned to the severe and mild insulin-resistant groups had a three- and twofold greater risk, respectively, of developing significant fibrosis compared with those in the insulin-deficient group.

Conclusions

A novel clustering classification adequately stratifies the risk of liver-related events in a population with diabetes. Our results also underline the impact of the severity of insulin resistance and alcohol consumption as key prognostic risk factors for liver-related complications.

Impact and implications

Diabetes represents a major risk factor for NAFLD development and progression. This study examined the ability of a novel machine-learning approach to identify at-risk diabetes subtypes for liver-related complications. Our results suggest that patients that had severe insulin resistance had the highest risk of liver-related outcomes and fibrosis progression. Moreover, excessive alcohol consumption at the diagnosis of diabetes was the strongest risk factor for developing liver-related events.

Morbid obesity is associated with hypertrophic outward remodeling and increased stiffness of small conduit arteries: An ultra-high frequency ultrasound study

BACKGROUND AND AIMS

Although many studies have been published on the effect of obesity on large and small arteries, there are no data in the literature regarding the effect of obesity on medium-sized arteries, and in particular of small conduit arteries. The aim of the present study was to investigate whether patients with severe obesity presented structural or functional alterations in different arterial segments.

METHODS AND RESULTS

34 patients with severe obesity (BMI≥35 kg/m²) and 34 age-and sex-matched normal weight patients were recruited as controls. Aortic stiffness (carotid-femoral pulse wave velocity) and wave reflection (augmentation index) were recorded. Ultrasound images of common carotid, radial and interdigital arteries were acquired for the assessment of wall-to-lumen ratio, wall cross-sectional area (WCSA), compliance, distensibility coefficient (DC) and Young's elastic modulus (Einc). Insulin sensitivity was calculated by oral glucose sensitivity index (OGIS). No differences between groups in carotid artery remodeling were found, while WCSA of the radial and interdigital arteries were higher in obese group than in controls. As regard the parameters of vascular elasticity, the DC of radial and interdigital arteries were lower (p = 0.025 and p = 0.001, respectively), as well as the Einc of radial arteries was higher (p = 0.021), in subject with obesity compared to controls. All these correlations were consistent after adjustment for the main covariates. Finally, in a multiple regression analysis OGIS was and independent determinant of interdigital artery DC (R² = 0.29, p = 0.001).

CONCLUSIONS

For the first time, we describe an outward remodeling and increased stiffness in small conduit arteries in severe obesity.

Metabolic changes after surgical fat removal: A dose-response meta-analysis

BACKGROUND

Bariatric surgery averts obesity-induced insulin resistance and the metabolic syndrome. By contrast, surgical fat removal is considered merely an esthetic endeavor. The aim of this article was to establish whether surgical fat removal, similar to bariatric surgery, exerts measurable, lasting metabolic benefits.

METHODS

PubMed, Embase, and Scopus were searched using the Polyglot Search Translator to find studies examining quantitative expression of metabolic markers. Quality assessment was done using the MethodologicAl STandard for Epidemiological Research scale. The robust-error meta-regression model was employed for this synthesis.

RESULTS

Twenty-two studies with 493 participants were included. Insulin sensitivity improved gradually with a maximum reduction in fasting insulin and homeostatic model assessment for insulin resistance of 17 pmol/L and 1 point, respectively, at postoperative day 180. Peak metabolic benefits manifest as a reduction of 2 units in body mass index, 3 kg of fat mass, 5 cm of waist circumference, 15 µg/L of serum leptin, 0.75 pg/ml of tumor necrosis factor-alpha, 0.25 mmol/L of total cholesterol, and 3.5 mmHg of systolic and diastolic blood pressure that were observed at day 50 but were followed by a return to preoperative levels by day 180. Serum high-density lipoproteins peaked at 50 days post-surgery before falling below the baseline. No significant changes were observed in lean body mass, serum adiponectin, resistin, interleukin-6, C-reactive protein, triglyceride, low-density lipoproteins, free fatty acids, and fasting blood glucose.

CONCLUSION

Surgical fat removal exerts several metabolic benefits in the short term, but only improvements in insulin sensitivity last beyond 6 months.

TyGIS: improved triglyceride-glucose index for the assessment of insulin sensitivity during pregnancy

Background

The triglyceride-glucose index (TyG) has been proposed as a surrogate marker of insulin resistance, which is a typical trait of pregnancy. However, very few studies analyzed TyG performance as marker of insulin resistance in pregnancy, and they were limited to insulin resistance assessment at fasting rather than in dynamic conditions, i.e., during an oral glucose tolerance test (OGTT), which allows more reliable assessment of the actual insulin sensitivity impairment. Thus, first aim of the study was exploring in pregnancy the relationships between TyG and OGTT-derived insulin sensitivity. In addition, we developed a new version of TyG, for improved performance as marker of insulin resistance in pregnancy.

Methods

At early pregnancy, a cohort of 109 women underwent assessment of maternal biometry and blood tests at fasting, for measurements of several variables (visit 1). Subsequently (26 weeks of gestation) all visit 1 analyses were repeated (visit 2), and a subgroup of women (84 selected) received a 2 h-75 g OGTT (30, 60, 90, and 120 min sampling) with measurement of blood glucose, insulin and C-peptide for reliable assessment of insulin sensitivity (PREDIM index) and insulin secretion/beta-cell function. The dataset was randomly split into 70% training set and 30% test set, and by machine learning approach we identified the optimal model, with TyG included, showing the best relationship with PREDIM. For inclusion in the model, we considered only fasting variables, in agreement with TyG definition.

Results

The relationship of TyG with PREDIM was weak. Conversely, the improved TyG, called TyGIS, (linear function of TyG, body weight, lean body mass percentage and fasting insulin) resulted much strongly related to PREDIM, in both training and test sets (R² > 0.64, p < 0.0001). Bland–Altman analysis and equivalence test confirmed the good performance of TyGIS in terms of association with PREDIM. Different further analyses confirmed TyGIS superiority over TyG.

Conclusions

We developed an improved version of TyG, as new surrogate marker of insulin sensitivity in pregnancy (TyGIS). Similarly to TyG, TyGIS relies only on fasting variables, but its performances are remarkably improved than those of TyG.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01649-8.

A low n-6 to n-3 polyunsaturated fatty acid ratio diet improves hyperinsulinaemia by restoring insulin clearance in obese youth

AIM

To examine the determinants and metabolic impact of the reduction in fasting and postload insulin levels after a low n-6 to n-3 polyunsaturated fatty acid (PUFA) ratio diet in obese youth.

MATERIALS AND METHODS

Insulin secretion and clearance were assessed by measuring and modelling plasma insulin and C-peptide in 17 obese youth who underwent a nine-point, 180-minute oral glucose tolerance test (OGTT) before and after a 12-week, eucaloric low n-6:n-3 polyunsaturated fatty acid (PUFA) ratio diet. Hepatic fat content was assessed by repeated abdominal magnetic resonance imaging.

RESULTS

Insulin clearance at fasting and during the OGTT was significantly increased after the diet, while body weight, glucose levels, absolute and glucose-dependent insulin secretion, and model-derived variables of β-cell function were not affected. Dietary-induced changes in insulin clearance positively correlated with changes in whole-body insulin sensitivity and β-cell glucose sensitivity, but not with changes in hepatic fat. Subjects with greater increases in insulin clearance showed a worse metabolic profile at enrolment, characterized by impaired insulin clearance, β-cell glucose sensitivity, and glucose tolerance, and benefitted the most from the diet, achieving greater improvements in glucose-stimulated hyperinsulinaemia, insulin resistance, and β-cell function.

CONCLUSIONS

We showed that a 12-week low n-6:n-3 PUFA ratio diet improves hyperinsulinaemia by increasing fasting and postload insulin clearance in obese youth, independently of weight loss, glucose concentrations, and insulin secretion.

Emerging Glycation-Based Therapeutics-Glyoxalase 1 Inducers and Glyoxalase 1 Inhibitors

The abnormal accumulation of methylglyoxal (MG) leading to increased glycation of protein and DNA has emerged as an important metabolic stress, dicarbonyl stress, linked to aging, and disease. Increased MG glycation produces inactivation and misfolding of proteins, cell dysfunction, activation of the unfolded protein response, and related low-grade inflammation. Glycation of DNA and the spliceosome contribute to an antiproliferative and apoptotic response of high, cytotoxic levels of MG. Glyoxalase 1 (Glo1) of the glyoxalase system has a major role in the metabolism of MG. Small molecule inducers of Glo1, Glo1 inducers, have been developed to alleviate dicarbonyl stress as a prospective treatment for the prevention and early-stage reversal of type 2 diabetes and prevention of vascular complications of diabetes. The first clinical trial with the Glo1 inducer, trans-resveratrol and hesperetin combination (tRES-HESP)-a randomized, double-blind, placebo-controlled crossover phase 2A study for correction of insulin resistance in overweight and obese subjects, was completed successfully. tRES-HESP corrected insulin resistance, improved dysglycemia, and low-grade inflammation. Cell permeable Glo1 inhibitor prodrugs have been developed to induce severe dicarbonyl stress as a prospective treatment for cancer-particularly for high Glo1 expressing-related multidrug-resistant tumors. The prototype Glo1 inhibitor is prodrug S-p-bromobenzylglutathione cyclopentyl diester (BBGD). It has antitumor activity in vitro and in tumor-bearing mice in vivo. In the National Cancer Institute human tumor cell line screen, BBGD was most active against the glioblastoma SNB-19 cell line. Recently, potent antitumor activity was found in glioblastoma multiforme tumor-bearing mice. High Glo1 expression is a negative survival factor in chemotherapy of breast cancer where adjunct therapy with a Glo1 inhibitor may improve treatment outcomes. BBGD has not yet been evaluated clinically. Glycation by MG now appears to be a pathogenic process that may be pharmacologically manipulated for therapeutic outcomes of potentially important clinical impact.

Reproducibility and discrimination of different indices of insulin sensitivity and insulin secretion

AIMS

Insulin sensitivity and insulin secretion can be estimated by multiple indices from fasting blood samples or blood samples obtained during oral glucose tolerance tests. The test-retest reliability of these indices in repeated measurements within the same individuals can strongly vary.

METHODS

We analyzed data of persons without diabetes who underwent two repeated OGTTs. For each measurement pair, we calculated multiple commonly used indices for the assessment of insulin secretion and insulin sensitivity. We then evaluated the coefficient of variation (standard deviation/mean) and discriminant ratio for each index.

RESULTS

89 persons underwent two OGTTs with a median interval of 86 days (IQR 64-249). Among indices of insulin sensitivity derived from fasting blood samples, the revised quantitative insulin sensitivity check index had the smallest coefficient of variation (2.8 ± 2.1%) whereas the C-peptide based homeostasis model assessment 2 had the highest discriminant ratio (1.97 (1.65-2.39)). As for insulin sensitivity indices that are based on OGTT, the oral glucose insulin sensitivity index had the smallest coefficient of variation (6.5 ± 5.1%). The highest discriminant ratio was found for the non-esterified fatty acids-based insulin sensitivity index (NEFA-ISI, 2.70 (2.30-3.22)). For the assessment of insulin secretion from fasting variables, the lowest mean coefficient of variation was found for C-peptide based homeostasis model assessment 2 beta with 10.8 ± 8% and the highest discriminant ratio for the C-peptide / Glucose-Ratio (2.18 (1.84-2.63)). Among indices assessing insulin secretion from an OGTT, the lowest coefficient of variation was found for the ratio of the areas under the C-peptide and glucose curves from 0 to 120 minutes with 11.3 ± 9.7%.

CONCLUSION

The data reveal large differences in the reproducibility and the discrimination capability of different indices that assess insulin sensitivity or insulin secretion. Our findings can aid the selection of an appropriate index in clinical studies.

Reversal of Insulin Resistance in Overweight and Obese Subjects by trans-Resveratrol and Hesperetin Combination-Link to Dysglycemia, Blood Pressure, Dyslipidemia, and Low-Grade Inflammation

The dietary supplement, trans-resveratrol and hesperetin combination (tRES-HESP), induces expression of glyoxalase 1, countering the accumulation of reactive dicarbonyl glycating agent, methylglyoxal (MG), in overweight and obese subjects. tRES-HESP produced reversal of insulin resistance, improving dysglycemia and low-grade inflammation in a randomized, double-blind, placebo-controlled crossover study. Herein, we report further analysis of study variables. MG metabolism-related variables correlated with BMI, dysglycemia, vascular inflammation, blood pressure, and dyslipidemia. With tRES-HESP treatment, plasma MG correlated negatively with endothelial independent arterial dilatation (r = -0.48, p < 0.05) and negatively with peripheral blood mononuclear cell (PBMC) quinone reductase activity (r = -0.68, p < 0.05)-a marker of the activation status of transcription factor Nrf2. For change from baseline of PBMC gene expression with tRES-HESP treatment, Glo1 expression correlated negatively with change in the oral glucose tolerance test area-under-the-curve plasma glucose (ΔAUGg) (r = -0.56, p < 0.05) and thioredoxin interacting protein (TXNIP) correlated positively with ΔAUGg (r = 0.59, p < 0.05). Tumor necrosis factor-α (TNFα) correlated positively with change in fasting plasma glucose (r = 0.70, p < 0.001) and negatively with change in insulin sensitivity (r = -0.68, p < 0.01). These correlations were not present with placebo. tRES-HESP decreased low-grade inflammation, characterized by decreased expression of CCL2, COX-2, IL-8, and RAGE. Changes in CCL2, IL-8, and RAGE were intercorrelated and all correlated positively with changes in MLXIP, MAFF, MAFG, NCF1, and FTH1, and negatively with changes in HMOX1 and TKT; changes in IL-8 also correlated positively with change in COX-2. Total urinary excretion of tRES and HESP metabolites were strongly correlated. These findings suggest tRES-HESP counters MG accumulation and protein glycation, decreasing activation of the unfolded protein response and expression of TXNIP and TNFα, producing reversal of insulin resistance. tRES-HESP is suitable for further evaluation for treatment of insulin resistance and related disorders.

Insulin Sensitivity After Living Donor Nephrectomy

BACKGROUND

The kidney is essential for glucose and insulin metabolism. Living kidney donors (LKDs) experience a reduction in glomerular filtration rate of 25 to 30 mL/min after donor nephrectomy. Little is known about the effect of glomerular filtration rate decline on insulin sensitivity in LKDs.

METHODS

We conducted a prospective pilot study on 9 LKDs (N = 9) who underwent dynamic metabolic testing (mixed meal tolerance test) to measure proxies of insulin sensitivity (homeostatic model assessment of insulin resistance, the area under curve [AUC] for insulin/glucose ratio, and Matsuda insulin sensitivity index) before and 3 months after donor nephrectomy. The primary outcome was the change in insulin sensitivity indices (delta [post-nephrectomy - pre-nephrectomy]).

RESULTS

Four of the donors had a body mass index (BMI) between 32.0 and 36.7 predonation. Post-donor nephrectomy, compared with prenephrectomy values, median insulin AUC increased from 60.7 to 101.7 hr*mU/mL (delta median 33.3, P = .04) without significant change in median glucose AUC levels from 228.9 to 209.3 hr*mg/dL (delta median 3.2, P = .77). There was an increase in the median homeostatic model assessment of insulin resistance from 2 to 2.9 (delta median 0.8, P = .03) and the AUC insulin/glucose ratio from 30.9 to 62.1 pmol/mmol (delta median 17.5, P = .001), whereas the median Matsuda insulin sensitivity index decreased from 5.9 to 2.9 (delta median -2, P = .05). The changes were more pronounced in obese (BMI >32) donors.

CONCLUSION

LKDs appear to have a trend toward a decline in insulin sensitivity post-donor nephrectomy in the short term, especially in obese donors (BMI >32). Further investigation with a larger sample size and longer follow-up is needed.

Effect of Vitamin D3 Supplementation on Insulin Sensitivity in Prediabetes With Hypovitaminosis D: A Randomized Placebo-Controlled Trial

Introduction The interplay of vitamin D and glucose metabolism is an area of ongoing research. The need for vitamin D supplementation trials in individuals with prediabetes and hypovitaminosis D has been stressed by earlier research studies. The objective of this study was to assess the effect of vitamin D3 supplementation on oral glucose insulin sensitivity (OGIS) index in patients with prediabetes and hypovitaminosis D. Methods  We enrolled 120 individuals with prediabetes (ADA definition) and hypovitaminosis D (vitamin D < 30 ng/mL) and randomized them into the vitamin D supplementation (60,000 IU weekly) group and the placebo group. Primary outcome measure (i.e., 2-hour OGIS index) and secondary outcome measures (i.e., fasting and postprandial blood glucose, glycosylated hemoglobin, body mass index, and insulin sensitivity indices, i.e., quantitative insulin sensitivity check index [QUICKI] and homeostatic model assessment for insulin resistance [HOMA-IR]) were analyzed for change with the 12 weeks of intervention. Results  A total of 52 subjects in the vitamin D group and 49 in the placebo group completed the study. Serum vitamin D levels (10.11 ± 2.73 to 52.2 ± 13.14 ng/mL; p < 0.0001) and OGIS index (376.4 ± 39.7 to 391.7 ± 40.7 mL/min/m2; p = 0.011) increased significantly on per-protocol analysis in the vitamin D group. There was no significant change observed in vitamin D levels and OGIS index in the placebo group. Between-group comparison showed a rise in OGIS index (15.3 ± 47.1 mL/min/m2) in the vitamin D group and decrease in OGIS index (-10.4 ± 44.7 mL/min/m2) in the placebo group, and the difference was statistically significant (p = 0.0029). The inter-group comparison showed relative fall in fasting glucose levels in the vitamin D group, with no significant change observed in the other secondary outcome measures. Conclusions The correction of hypovitaminosis D in subjects with prediabetes led to improved insulin sensitivity as assessed by OGIS index at 120 minutes, signifying the role of vitamin D in glucose homeostasis.

Consequences on islet and incretin hormone responses to dinner by omission of lunch in healthy men

BACKGROUND

Omission of breakfast results in higher glucose and lower insulin and incretin hormone levels after both lunch and dinner. Whether omission of lunch has a similar impact on the following meal is not known.

AIM

This study therefore explored whether omission of lunch ingestion affects glucose, islet and incretin hormones after dinner ingestion in healthy subjects.

MATERIALS & METHODS

Twelve male volunteers (mean age 22 years, BMI 22.5 kg/m2) underwent two test days in random order with standard breakfast and dinner on both days with provision or omission of standard lunch in between.

RESULTS

The results showed that throughout the 300 minutes study period, glucose, insulin, glucagon and GIP levels after dinner ingestion did not differ between the two tests. In contrast, C-peptide, and GLP-1 levels were 26%-35% higher at later time points after dinner ingestion when lunch had been omitted (P < .05).

CONCLUSION

We conclude that omission of lunch increases GLP-1 and insulin secretion and possibly also insulin clearance resulting in unchanged glucose and insulin levels after dinner ingestion.

The role of physical activity in metabolic homeostasis before and after the onset of type 2 diabetes: an IMI DIRECT study

AIMS/HYPOTHESIS

It is well established that physical activity, abdominal ectopic fat and glycaemic regulation are related but the underlying structure of these relationships is unclear. The previously proposed twin-cycle hypothesis (TC) provides a mechanistic basis for impairment in glycaemic control through the interactions of substrate availability, substrate metabolism and abdominal ectopic fat accumulation. Here, we hypothesise that the effect of physical activity in glucose regulation is mediated by the twin-cycle. We aimed to examine this notion in the Innovative Medicines Initiative Diabetes Research on Patient Stratification (IMI DIRECT) Consortium cohorts comprised of participants with normal or impaired glucose regulation (cohort 1: N ≤ 920) or with recently diagnosed type 2 diabetes (cohort 2: N ≤ 435).

METHODS

We defined a structural equation model that describes the TC and fitted this within the IMI DIRECT dataset. A second model, twin-cycle plus physical activity (TC-PA), to assess the extent to which the effects of physical activity in glycaemic regulation are mediated by components in the twin-cycle, was also fitted. Beta cell function, insulin sensitivity and glycaemic control were modelled from frequently sampled 75 g OGTTs (fsOGTTs) and mixed-meal tolerance tests (MMTTs) in participants without and with diabetes, respectively. Abdominal fat distribution was assessed using MRI, and physical activity through wrist-worn triaxial accelerometry. Results are presented as standardised beta coefficients, SE and p values, respectively.

RESULTS

The TC and TC-PA models showed better fit than null models (TC: χ² = 242, p = 0.004 and χ² = 63, p = 0.001 in cohort 1 and 2, respectively; TC-PA: χ² = 180, p = 0.041 and χ² = 60, p = 0.008 in cohort 1 and 2, respectively). The association of physical activity with glycaemic control was primarily mediated by variables in the liver fat cycle.

CONCLUSIONS/INTERPRETATION

These analyses partially support the mechanisms proposed in the twin-cycle model and highlight mechanistic pathways through which insulin sensitivity and liver fat mediate the association between physical activity and glycaemic control.

Body Composition, Serum Concentrations of Androgens and Insulin Resistance in Different Polycystic Ovary Syndrome Phenotypes

Insulin resistance and hyperandrogenemia observed in polycystic ovary syndrome (PCOS) are associated with metabolic disturbances and could be connected with body composition pattern. To date, several studies defining the parameters of body composition using dual energy X-ray absorptiometry (DXA) method in the group of PCOS patients have been published, however, without the analysis in different phenotypes. The aim of the present study was to investigate the relationships between serum androgens concentration, insulin resistance and distribution of fat mass using DXA method in various PCOS phenotypes according to the Rotterdam criteria. We examined 146 women: 34 (38%) had PCOS phenotype A, 20 (23%) phenotype B, 20 (23%) phenotype C and 15 (16%) phenotype D (with mean age of each phenotype 25 years), and 57 control subjects (mean age of 25.5 years). Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Serum concentrations of testosterone, androstenedione and dehydroepiandrosterone sulfate (DHEA-S) were assessed and free androgen index (FAI) was calculated. In phenotypes A, B and C, we observed higher FAI in comparison to the control group (all p < 0.01). Serum concentrations of androstenedione and DHEA-S were higher in phenotypes A and C in comparison to the control group (all p < 0.01). However, only in phenotype A we found higher visceral adipose tissue (VAT) mass and android/gynoid ratio (A/G ratio) in comparison to the control group (all p < 0.01). In phenotype A, we observed connection of VAT with FAI (r = 0.58, p < 0.01). Accordingly, A/G ratio was related with FAI in all phenotypes (all p < 0.05). Additionally, in phenotype C, A/G ratio was related to serum concentrations of DHEA-S and androstenedione (r = 0.46, p = 0.03; r = 0.53, p = 0.01, respectively). We also found connections of HOMA-IR with VAT and A/G ratio in all phenotypes (all p < 0.05). Women with phenotype A had higher amount of VAT and A/G ratio in comparison to the control group. Serum concentration of androgens and insulin resistance are connected with VAT and A/G ratio in normoandrogenic and hyperandrogenic PCOS phenotypes.

Lipid Metabolism Links Nutrient-Exercise Timing to Insulin Sensitivity in Men Classified as Overweight or Obese

CONTEXT

Pre-exercise nutrient availability alters acute metabolic responses to exercise, which could modulate training responsiveness.

OBJECTIVE

To assess acute and chronic effects of exercise performed before versus after nutrient ingestion on whole-body and intramuscular lipid utilization and postprandial glucose metabolism.

DESIGN

(1) Acute, randomized, crossover design (Acute Study); (2) 6-week, randomized, controlled design (Training Study).

SETTING

General community.

PARTICIPANTS

Men with overweight/obesity (mean ± standard deviation, body mass index: 30.2 ± 3.5 kg⋅m-2 for Acute Study, 30.9 ± 4.5 kg⋅m-2 for Training Study).

INTERVENTIONS

Moderate-intensity cycling performed before versus after mixed-macronutrient breakfast (Acute Study) or carbohydrate (Training Study) ingestion.

RESULTS

Acute Study-exercise before versus after breakfast consumption increased net intramuscular lipid utilization in type I (net change: -3.44 ± 2.63% versus 1.44 ± 4.18% area lipid staining, P < 0.01) and type II fibers (-1.89 ± 2.48% versus 1.83 ± 1.92% area lipid staining, P < 0.05). Training Study-postprandial glycemia was not differentially affected by 6 weeks of exercise training performed before versus after carbohydrate intake (P > 0.05). However, postprandial insulinemia was reduced with exercise training performed before but not after carbohydrate ingestion (P = 0.03). This resulted in increased oral glucose insulin sensitivity (25 ± 38 vs -21 ± 32 mL⋅min-1⋅m-2; P = 0.01), associated with increased lipid utilization during exercise (r = 0.50, P = 0.02). Regular exercise before nutrient provision also augmented remodeling of skeletal muscle phospholipids and protein content of the glucose transport protein GLUT4 (P < 0.05).

CONCLUSIONS

Experiments investigating exercise training and metabolic health should consider nutrient-exercise timing, and exercise performed before versus after nutrient intake (ie, in the fasted state) may exert beneficial effects on lipid utilization and reduce postprandial insulinemia.

Incident Diabetes in Survivors of Critical Illness and Mechanisms Underlying Persistent Glucose Intolerance: A Prospective Cohort Study

OBJECTIVES

Stress hyperglycemia occurs in critically ill patients and may be a risk factor for subsequent diabetes. The aims of this study were to determine incident diabetes and prevalent prediabetes in survivors of critical illness experiencing stress hyperglycemia and to explore underlying mechanisms.

DESIGN

This was a prospective, single center, cohort study. At admission to ICU, hemoglobin A1c was measured in eligible patients. Participants returned at 3 and 12 months after ICU admission and underwent hemoglobin A1c testing and an oral glucose tolerance test. Blood was also collected for hormone concentrations, whereas gastric emptying was measured via an isotope breath test. β-cell function was modeled using standard techniques.

SETTING

Tertiary-referral, mixed medical-surgical ICU.

PATIENTS

Consecutively admitted patients who developed stress hyperglycemia and survived to hospital discharge were eligible.

MEASUREMENTS AND MAIN RESULTS

Consent was obtained from 40 patients (mean age, 58 yr [SD, 10], hemoglobin A1c 36.8 mmol/mol [4.9 mmol/mol]) with 35 attending the 3-month and 26 the 12-month visits. At 3 months, 13 (37%) had diabetes and 15 (43%) had prediabetes. At 12 months, seven (27%) participants had diabetes, whereas 11 (42%) had prediabetes. Mean hemoglobin A1c increased from baseline during the study: +0.7 mmol/mol (-1.2 to 2.5 mmol/mol) at 3 months and +3.3 mmol/mol (0.98-5.59 mmol/mol) at 12 months (p = 0.02). Gastric emptying was not significantly different across groups at either 3 or 12 months.

CONCLUSIONS

Diabetes and prediabetes occur frequently in survivors of ICU experiencing stress hyperglycemia. Based on the occurrence rate observed in this cohort, structured screening and intervention programs appear warranted.

Prediction of clamp-derived insulin sensitivity from the oral glucose insulin sensitivity index

AIMS/HYPOTHESIS

The euglycaemic-hyperinsulinaemic clamp is the gold-standard method for measuring insulin sensitivity, but is less suitable for large clinical trials. Thus, several indices have been developed for evaluating insulin sensitivity from the oral glucose tolerance test (OGTT). However, most of them yield values different from those obtained by the clamp method. The aim of this study was to develop a new index to predict clamp-derived insulin sensitivity (M value) from the OGTT-derived oral glucose insulin sensitivity index (OGIS).

METHODS

We analysed datasets of people that underwent both a clamp and an OGTT or meal test, thereby allowing calculation of both the M value and OGIS. The population was divided into a training and a validation cohort (n = 359 and n = 154, respectively). After a stepwise selection approach, the best model for M value prediction was applied to the validation cohort. This cohort was also divided into subgroups according to glucose tolerance, obesity category and age.

RESULTS

The new index, called PREDIcted M (PREDIM), was based on OGIS, BMI, 2 h glucose during OGTT and fasting insulin. Bland-Altman analysis revealed a good relationship between the M value and PREDIM in the validation dataset (only 9 of 154 observations outside limits of agreement). Also, no significant differences were found between the M value and PREDIM (equivalence test: p < 0.0063). Subgroup stratification showed that measured M value and PREDIM have a similar ability to detect intergroup differences (p < 0.02, both M value and PREDIM).

CONCLUSIONS/INTERPRETATION

The new index PREDIM provides excellent prediction of M values from OGTT or meal data, thereby allowing comparison of insulin sensitivity between studies using different tests.

Next-generation, personalised, model-based critical care medicine: a state-of-the art review of in silico virtual patient models, methods, and cohorts, and how to validation them

Critical care, like many healthcare areas, is under a dual assault from significantly increasing demographic and economic pressures. Intensive care unit (ICU) patients are highly variable in response to treatment, and increasingly aging populations mean ICUs are under increasing demand and their cohorts are increasingly ill. Equally, patient expectations are growing, while the economic ability to deliver care to all is declining. Better, more productive care is thus the big challenge. One means to that end is personalised care designed to manage the significant inter- and intra-patient variability that makes the ICU patient difficult. Thus, moving from current "one size fits all" protocolised care to adaptive, model-based "one method fits all" personalised care could deliver the required step change in the quality, and simultaneously the productivity and cost, of care. Computer models of human physiology are a unique tool to personalise care, as they can couple clinical data with mathematical methods to create subject-specific models and virtual patients to design new, personalised and more optimal protocols, as well as to guide care in real-time. They rely on identifying time varying patient-specific parameters in the model that capture inter- and intra-patient variability, the difference between patients and the evolution of patient condition. Properly validated, virtual patients represent the real patients, and can be used in silico to test different protocols or interventions, or in real-time to guide care. Hence, the underlying models and methods create the foundation for next generation care, as well as a tool for safely and rapidly developing personalised treatment protocols over large virtual cohorts using virtual trials. This review examines the models and methods used to create virtual patients. Specifically, it presents the models types and structures used and the data required. It then covers how to validate the resulting virtual patients and trials, and how these virtual trials can help design and optimise clinical trial. Links between these models and higher order, more complex physiome models are also discussed. In each section, it explores the progress reported up to date, especially on core ICU therapies in glycemic, circulatory and mechanical ventilation management, where high cost and frequency of occurrence provide a significant opportunity for model-based methods to have measurable clinical and economic impact. The outcomes are readily generalised to other areas of medical care.

Add on DPP-4 inhibitor alogliptin alone or in combination with pioglitazone improved β-cell function and insulin sensitivity in metformin treated PCOS

PURPOSE

Impaired β-cell function remains unaddressed in PCOS. The aim of the study was to evaluate whether dipeptidyl peptidase-4 (DPP-4) inhibitor alogliptin (ALO) alone or in combination with pioglitazone (PIO) improves β-cell function along with insulin resistance (IR) in metformin (MET) treated obese women with PCOS with persistent IR.

MATERIALS AND METHODS

In 12-week randomized study, ALO 25 mg QD (n=15) or ALO 25 mg QD and PIO 30 mg QD (n=15) was added to MET 1000 mg BID in PCOS women (aged 34.4 ± 6.5 years, BMI 39.0 ± 4.9 kg/m², HOMA-IR 4.82 ± 2.52, mean ± SD). Model derived parameters of glucose homeostasis from the meal tolerance test (MTT) were determined. The ability of the β-cell function was assessed by the adaptation index (AI).

RESULTS

MET-ALO and MET-ALO-PIO resulted in a significant decrease of HOMA-IR (by 1.6±2.3 (p=0.039) and 2.9±3.3 (p=0.001), respectively) and an increase in insulin sensitivity (IS) after meal ingestion (oral glucose IS) by 31.4±97.5 ml·min^-1·m^-2 (p=0.007) vs 39.0±58.1 ml·min^-1·m^-2 (p=0.039), respectively. AI across the entire group was significantly improved from 329.6±200.6 to 442.5±303.9 (p=0.048).

CONCLUSIONS

ALO alone and in combination with PIO improved IR along with dynamic IS and meal related β-cell function when added to MET treated PCOS.

Glucose tolerance & insulin secretion & sensitivity characteristics in Indian children with cystic fibrosis: A pilot study

Background & objectives

Cystic fibrosis (CF) is a life-limiting genetic condition resulting in chronic respiratory infections, pancreatic enzyme insufficiency and associated complications. This pilot study was undertaken to assess the glucose tolerance and insulin secretion and sensitivity among Indian children with CF.

Methods

Children with CF under regular follow up at the Paediatric Pulmonology Clinic of a tertiary care hospital in New Delhi, India, were enrolled. Children who had a history of acute exacerbation or intake of systemic steroids within the last two weeks were excluded. Anthropometry, pulmonary function and disease severity (Shwachman) score were assessed. Fasting venous sample was drawn to assess glucose, insulin, haemoglobin and calcium. Oral glucose tolerance test was performed, and blood glucose and insulin were assessed at 30, 60, 90 and 120 min. Insulin secretion and sensitivity indices were calculated.

Results

Twenty nine patients with a mean age of 11.2±4.1 yr were enrolled. Stunting, thinness, anaemia and hypocalcaemia were present in 31.0, 13.8, 37.0 and 48.3 per cent of the patients, respectively. Abnormal glucose tolerance (AGT) was present in 21.4 per cent. Insulin secretion was similar in individuals with AGT and normal glucose tolerance (NGT), but insulin sensitivity index was lower (0.12±0.02 vs 0.15±0.01, P<0.001) and homeostatic model assessment of insulin resistance higher [1.63 (0.53-1.76) vs 0.83 (0.28-4.43), P<0.05] in individuals with AGT compared to NGT.

Interpretation & conclusions

AGT was observed in 21.4 per cent of children with CF. The CF patients with AGT had significantly lower insulin sensitivity compared to patients with NGT. Future multicentric studies with a large sample should be conducted to assess insulin secretion and sensitivity indices in CF patients compared to healthy controls.

Insulin resistance and normal thyroid hormone levels: prospective study and metabolomic analysis

While hyperthyroidism and hypothyroidism cause dysglycemia, the relationship between thyroid hormone levels within the normal range and insulin resistance (IR) is unclear. In 940 participants with strictly normal serum concentrations of free triiodothyronine (fT₃), free thyroxine (fT₄), and thyroid-stimulating hormone (TSH) followed up for 3 yr, we measured insulin sensitivity (by the insulin clamp technique) and 35 circulating metabolites. At baseline, across quartiles of increasing fT₃ levels (or fT₃/fT₄ ratio) most features of IR emerged [i.e., male sex, greater body mass index (BMI), waist circumference, heart rate, blood pressure, fatty liver index, free fatty acids, and triglycerides; reduced insulin-mediated glucose disposal; and β-cell glucose sensitivity). In multiadjusted analyses, fT₃ was reciprocally related to insulin sensitivity and, in a subset of 303 subjects, directly related to endogenous glucose production. In multiple regression models adjusting for sex, age, BMI, and baseline value of insulin sensitivity, higher baseline fT₃ levels were significant predictors of decreases in insulin sensitivity. Moreover, baseline fT₃ predicted follow-up increases in glycemia independently of sex, age, BMI, insulin sensitivity, β-cell glucose sensitivity, and baseline glycemia. Serum tyrosine levels were higher with IR and were directly associated with fT₃; higher α-hydroxybutyrate levels signaled enhanced oxidative stress, thereby impairing tyrosine degradation. In 25 patients with morbid obesity, surgery-induced weight loss improved IR and consensually lowered fT₃ levels. High-normal fT₃ levels are associated with IR both cross-sectionally and longitudinally, and predict deterioration of glucose tolerance. This association is supported by a metabolite pattern that points at increased oxidative stress as part of the IR syndrome.

Discriminatory ability of simple OGTT-based beta cell function indices for prediction of prediabetes and type 2 diabetes: the CODAM study

AIMS/HYPOTHESIS

The hyperglycaemic clamp technique and the frequently sampled IVGTT are unsuitable techniques to assess beta cell function (BCF) in large cohorts. Therefore, the aim of this study was to evaluate the discriminatory ability of simple OGTT-based BCF indices for prediction of prediabetes (meaning impaired fasting glucose and/or impaired glucose tolerance) and type 2 diabetes.

METHODS

Glucose metabolism status was assessed by 2 h 75 g OGTT at baseline (n = 476, mean age 59.2 years, 38.7% women) and after 7 years of follow-up (n = 416) in the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) study (1999-2009). Baseline plasma glucose, insulin and C-peptide values during OGTTs were used to calculate 21 simple indices of BCF. Disposition indices (BCF index × Matsuda index), to compensate for the prevailing level of insulin resistance, were calculated for the BCF indices with the best discriminatory abilities. The discriminatory ability of the BCF indices was estimated by the area under the receiver operating characteristics curve (ROC AUC) with an outcome of incident prediabetes (n = 73) or type 2 diabetes (n = 60 and n = 18 cases, respectively, in individuals who were non-diabetic or had normal glucose metabolism at baseline).

RESULTS

For incident prediabetes (n = 73), all ROC AUCs were less than 70%, whereas for incident type 2 diabetes, I₃₀/I₀, CP₃₀/CP₀, ΔI₃₀/ΔG₃₀, ΔCP₃₀/ΔG₃₀ (where I, CP and G are the plasma concentrations of insulin, C-peptide and glucose, respectively, at the times indicated), and corrected insulin response at 30 min had ROC AUCs over 70%. In at-baseline non-diabetic individuals, disposition indices ΔI₃₀/ΔG₃₀, ΔCP₃₀/ΔG₃₀ and corrected insulin response at 30 min had ROC AUCs of over 80% for incident type 2 diabetes. Moreover, these BCF disposition indices had significantly better discriminatory abilities for incident type 2 diabetes than the Matsuda index alone.

CONCLUSIONS/INTERPRETATION

BCF indices reflecting early-phase insulin secretion have the best ability to discriminate individuals who will develop prediabetes and type 2 diabetes. Of these, ΔCP₃₀/ΔG₃₀, often referred to as the C-peptidogenic index, performed consistently well.

Variable reliability of surrogate measures of insulin sensitivity after Roux-en-Y gastric bypass

Roux-en-Y gastric bypass (RYGB) induces weight loss and improves insulin sensitivity when evaluated by the hyperinsulinemic-euglycemic clamp (HEC). Surrogate indices of insulin sensitivity calculated from insulin and glucose concentrations at fasting or after an oral glucose tolerance test (OGTT) are frequently used, but have not been validated after RYGB. Our aim was to evaluate whether surrogate indices reliably estimate changes in insulin sensitivity after RYGB. Four fasting surrogates (inverse-HOMA-IR, HOMA2-%S, QUICKI, revised-QUICKI) and three OGTT-derived surrogates (Matsuda, Gutt, OGIS) were compared with HEC-estimated peripheral insulin sensitivity (R_d or R_d/I, depending on how the index was originally validated) and the tracer-determined hepatic insulin sensitivity index (HISI) in patients with preoperative type 2 diabetes (n = 10) and normal glucose tolerance (n = 10) 1 wk, 3 mo, and 1 yr postoperatively. Post-RYGB changes in inverse-HOMA-IR and HOMA2-%S did not correlate with changes in R_d at any visit, but were comparable to changes in HISI at 1 wk. Changes in QUICKI and revised-QUICKI correlated with R_d/I after surgery. Changes in the Matsuda and Gutt indices did not correlate with changes in R_d/I and R_d, respectively, whereas OGIS changes correlated with R_d changes at 1 yr post-RYGB. In conclusion, surrogate measures of insulin sensitivity may not reflect results obtained with gold standard methodology after RYGB, underscoring the importance of critical reflection when surrogate endpoints are used. Fasting surrogate indices may be particularly affected by post-RYGB changes in insulin clearance, whereas the validity of OGTT-derived surrogates may be compromised by surgical rearrangements of the gut.

The impact of preconceptional obesity on trajectories of maternal lipids during gestation

Growing challenges of maternal obesity necessitate to focus metabolic management on alternative factors than glycaemia. The objective is to assess longitudinal changes in lipids and inflammatory parameters during pregnancies stratified by pregestational BMI. Therefore, 222 pregnant women (normal-weight BMI < 25: n = 91 (41%), overweight BMI 25–29.9: n = 69 (31%), obese BMI ≥ 30: n = 62 (28%)) underwent a detailed metabolic characterization including fasting lipids and glucometabolic parameters at <21^st gestational week (GW) with follow-up assessments at further three visits (24–28^th GW, 32–34^th GW, >36^th GW). Overweight and obesity was related to dyslipidemia already at baseline, i.e. elevated triglycerides (TG, p < 0.001), decreased high-density-lipoprotein-C (p = 0.009) and increased ultrasensitive-c-reactive-protein (usCRP, p < 0.001) independent of gestational diabetes prevalence. Trajectories of lipids during pregnancy progress revealed an unexpected less pronounced increase in TG, low-density-lipoprotein-C and total-cholesterol in overweight/obese women. usCRP remained associated with higher BMI throughout pregnancy showing no time-dependent longitudinal changes. Newborns of obese/overweight women were affected by higher birth-weight percentiles. Regarding lipids only maternal TG showed tendency for relation to prevalence of large-for-gestational-age offspring, particularly at the end of pregnancy (p = 0.048). Overweight and obese women show significant differences in trajectories of lipids during pregnancy that distinguish them from normal-weight women. Further studies should evaluate if targeting lipid metabolism could improve clinical management of maternal obesity.

Insulin sensitivity and secretion in youth onset type 2 diabetes with and without visceral adiposity

AIM

To investigate insulin sensitivity and insulin secretion patterns among Asian Indian youth without and with type 2 diabetes (T2DM-y defined as onset of diabetes at or below 25 years) with normal and high visceral fat (VF) levels.

METHODS

We recruited 74 T2DM-y individuals, within 18 months of diagnosis and compared them to 77 age-matched controls with normal glucose tolerance (NGT). Using L4/L5 abdominal CT images, VF levels were categorized as normal or high according to their median values. Oral glucose tolerance tests (glucose and insulin measures) were used to derive Matsuda index, insulin resistance (HOMA-IR) and oral disposition index (DIo). Relationships between measures of insulin sensitivity and secretion and T2DM-y by VF level were assessed using standardized multinomial regression models.

RESULTS

Participants were categorized into four groups: NGT-normal VF; NGT-high VF; T2DM-normal VF, and T2DM-high VF. Among NGTs, those with high VF had significantly lower insulin sensitivity (0.013 vs.0.019 pM(-1)) and Matsuda index (10.2 vs.13.8), than normal VF. When compared, T2DM-high VF had lowest insulin sensitivity (0.009 vs.0.019, 0.013, 0.012 pM-1; p<0.001), Matsuda index (6.4 vs. 13.8, 10.2, 8.6; p<0.001), OGIS120 (305 vs. 396, 382, 316; p<0.001) and DIo (0.48 vs. 3.75, 3.20, 0.55 mmol/L; p<0.001). At every category of 2 h PG values, NGT-high VF had lower DIo than NGT-normal VF participants. In standardized multinomial models, that included DIo and Matsuda index adjusted for age, gender, BMI, and leptin, DIo (Odds ratio: 0.001; 95%Confidence interval: 0.000-0.020), matsuda index (0.26; 0.07-0.93), age (2.92; 1.18-7.19) and leptin (3.17; 1.12-8.99) were associated with high VF among T2DM.

CONCLUSION

Lower DIo and Matsuda index, younger age and higher leptin were independently associated with high visceral fat among T2DM participants. Also, lower DIo was seen with increasing 2 h PG values even among normal glucose tolerant individuals.

Pathophysiological characteristics and effects of obesity in women with early and late manifestation of gestational diabetes diagnosed by the International Association of Diabetes and Pregnancy Study Groups criteria

CONTEXT

Appropriate risk stratification is essential in gestational diabetes (GDM) diagnosis to optimize therapeutic strategies during pregnancy. However, there are sparse data related to the newly recommended International Association of Diabetes and Pregnancy Study Groups criteria and their use in early pregnancy.

OBJECTIVE

This study sought to evaluate clinical and pathophysiological characteristics less up to gestational week (GW) 21 in women with early and late GDM onset.

DESIGN AND SETTING

This was a prospective study conducted at the Medical University of Vienna.

PATIENTS AND INTERVENTIONS

Pregnant women (n = 211) underwent an oral glucose tolerance test at 16 GW (interquartile range, 14-18 wk) with multiple measurements of glucose, insulin, and C-peptide for evaluation of insulin sensitivity and ß-cell function in addition to detailed obstetrical risk assessment. Clinical followups were performed until end of pregnancy.

MAIN OUTCOME MEASURE

We performed a metabolic characterization of early-onset GDM.

RESULTS

Of 81 women, 49 (23%) showed early (GDMEarly ≤ 21 GW) and 32 (15%) later manifestation (GDMLate ≥ 24 GW) whereas 130 (62%) remained normal-glucose-tolerant (NGT). In contrast with GDMLate, GDMEarly were affected by decreased insulin sensitivity (GDMEarly vs NGT, P < .001; GDMEarlyvs GDMLate, P < .001; GDMLate vs NGT, P = .410). However, both early and late manifested subjects showed impairments in ß-cell function. GDMEarly showed highest levels of preconceptional and actual body mass index (BMI), which was related to fasting glucose (r = 0.42, P < .001) and particularly insulin sensitivity (r = -0.51, P < .001). Differences in glucose disposal between the subgroups remained constant in multivariable analysis including the strongest risk factors for GDM, ie, age, history of GDM, and BMI in our population.

CONCLUSIONS

Early manifestation of GDM is affected by insulin resistance that is partly explained by higher degree in obesity. However, ß-cell dysfunction was also detectable in GDMLate, indicating defective compensatory mechanisms emerging already in early pregnancy.

Modeling and design of challenge tests: Inflammatory and metabolic biomarker study examples

Given the complexity of pharmacological challenge experiments, it is perhaps not surprising that design and analysis, and in turn interpretation and communication of results from a quantitative point of view, is often suboptimal. Here we report an inventory of common designs sampled from anti-inflammatory, respiratory and metabolic disease drug discovery studies, all of which are based on animal models of disease involving pharmacological and/or patho/physiological interaction challenges. The corresponding data are modeled and analyzed quantitatively, the merits of the respective approach discussed and inferences made with respect to future design improvements. Although our analysis is limited to these disease model examples, the challenge approach is generally applicable to the vast majority of pharmacological intervention studies. In the present five Case Studies results from pharmacodynamic effect models from different therapeutic areas were explored and analyzed according to five typical designs. Plasma exposures of test compounds were assayed by either liquid chromatography/mass spectrometry or ligand binding assays. To describe how drug intervention can regulate diverse processes, turnover models of test compound-challenger interaction, transduction processes, and biophase time courses were applied for biomarker response in eosinophil count, IL6 response, paw-swelling, TNFα response and glucose turnover in vivo. Case Study 1 shows results from intratracheal administration of Sephadex, which is a glucocorticoid-sensitive model of airway inflammation in rats. Eosinophils in bronchoalveolar fluid were obtained at different time points via destructive sampling and then regressed by the mixed-effects modeling. A biophase function of the Sephadex time course was inferred from the modeled eosinophil time courses. In Case Study 2, a mouse model showed that the time course of cytokine-induced IL1β challenge was altered with or without drug intervention. Anakinra reversed the IL1β induced cytokine IL6 response in a dose-dependent manner. This Case Study contained time courses of test compound (drug), challenger (IL1β) and cytokine response (IL6), which resulted in high parameter precision. Case Study 3 illustrates collagen-induced arthritis progression in the rat. Swelling scores (based on severity of hind paw swelling) were used to describe arthritis progression after the challenge and the inhibitory effect of two doses of an orally administered test compound. In Case Study 4, a cynomolgus monkey model for lipopolysaccharide LPS-induced TNFα synthesis and/or release was investigated. This model provides integrated information on pharmacokinetics and in vivo potency of the test compounds. Case Study 5 contains data from an oral glucose tolerance test in rats, where the challenger is the same as the pharmacodynamic response biomarker (glucose). It is therefore convenient to model the extra input of glucose simultaneously with baseline data and during intervention of a glucose-lowering compound at different dose levels. Typically time-series analyses of challenger- and biomarker-time data are necessary if an accurate and precise estimate of the pharmacodynamic properties of a test compound is sought. Erosion of data, resulting in the single-point assessment of drug action after a challenge test, should generally be avoided. This is particularly relevant for situations where one expects time-curve shifts, tolerance/rebound, impact of disease, or hormetic concentration-response relationships to occur.

β-cell function, incretin effect, and incretin hormones in obese youth along the span of glucose tolerance from normal to prediabetes to type 2 diabetes

Using the hyperglycemic and euglycemic clamp, we demonstrated impaired β-cell function in obese youth with increasing dysglycemia. Herein we describe oral glucose tolerance test (OGTT)-modeled β-cell function and incretin effect in obese adolescents spanning the range of glucose tolerance. β-Cell function parameters were derived from established mathematical models yielding β-cell glucose sensitivity (βCGS), rate sensitivity, and insulin sensitivity in 255 obese adolescents (173 with normal glucose tolerance [NGT], 48 with impaired glucose tolerance [IGT], and 34 with type 2 diabetes [T2D]). The incretin effect was calculated as the ratio of the OGTT-βCGS to the 2-h hyperglycemic clamp-βCGS. Incretin and glucagon concentrations were measured during the OGTT. Compared with NGT, βCGS was 30 and 65% lower in youth with IGT and T2D, respectively; rate sensitivity was 40% lower in T2D. Youth with IGT or T2D had 32 and 38% reduced incretin effect compared with NGT in the face of similar changes in GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) in response to oral glucose. We conclude that glucose sensitivity deteriorates progressively in obese youth across the spectrum of glucose tolerance in association with impairment in incretin effect without reduction in GLP-1 or GIP, similar to that seen in adult dysglycemia.

Hypertension in obese type 2 diabetes patients is associated with increases in insulin resistance and IL-6 cytokine levels: potential targets for an efficient preventive intervention

Increased body weight as well as type 2 diabetes (T2D) are found to be associated with increased incidence of hypertension, although the mechanisms facilitating hypertension in T2D or nondiabetic individuals are not clear. Therefore, in this study we compared the levels of insulin resistance (IR:OGIS), plasma insulin (PI:RIA) levels, and pro-inflammatory cytokines (IL-6 and TNF-α: ELISA), being risk factors previously found to be associated with hypertension, in T2D patients showing increased body weight (obese and overweight, BMI ≥ 25 kg/m²) with hypertension (group A, N = 30), or without hypertension (group B, N = 30), and in nonobese (BMI < 25 kg/m²), normotensive controls (group C, N = 15). We found that OGIS index was the lowest (A: 267 ± 35.42 vs. B: 342.89 ± 32.0, p < 0.01) and PI levels were the highest (A: 31.05 ± 8.24 vs. B: 17.23 ± 3.23, p < 0.01) in group A. In addition, IL-6 levels were higher in group A (A: 15.46 ± 5.15 vs. B: 11.77 ± 6.09; p < 0.05) while there was no difference in TNF-α levels. Our results have shown that appearance of hypertension in T2D patients with increased body weight was dependent on further increase in IR which was associated with the rise in pro-inflammatory IL-6 cytokine. The results imply that lifestyle intervention aimed to decrease IR might be beneficial in reducing the risk for hypertension in those T2D individuals.

Limitations in the use of indices using glucose and insulin levels to predict insulin sensitivity: impact of race and gender and superiority of the indices derived from oral glucose tolerance test in African Americans

OBJECTIVE To examine the utility of commonly used insulin sensitivity indices in nondiabetic European Americans (EAs) and African Americans (AAs). RESEARCH DESIGN AND METHODS Two-hundred forty nondiabetic participants were studied. Euglycemic-hyperinsulinemic clamp was the gold standard approach to assess glucose disposal rates (GDR) normalized by lean body mass. The homeostatic model assessment for insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI) were calculated from fasting plasma glucose and insulin (FIL). Oral glucose tolerance test (OGTT) was performed to determine Matsuda index, the simple index assessing insulin sensitivity (SI(is)OGTT), Avignon index, and Stomvoll index. Relationships among these indices with GDR were analyzed by multiple regression. RESULTS GDR values were similar in EA and AA subgroups; even so, AA exhibited higher FIL and were insulin-resistant compared with EA, as assessed by HOMA-IR, QUICKI, Matsuda index, SI(is)OGTT, Avignon index, and Stumvoll index. In the overall study population, GDR was significantly correlated with all studied insulin sensitivity indices (/r/ = 0.381-0.513); however, these indices were not superior to FIL in predicting GDR. Race and gender affected the strength of this relationship. In AA males, FIL and HOMA-IR were not correlated with GDR. In contrast, Matsuda index and SI(is)OGTT were significantly correlated with GDR in AA males, and Matsuda index was superior to HOMA-IR and QUICKI in AAs overall. CONCLUSIONS Insulin sensitivity indices based on glucose and insulin levels should be used cautiously as measures of peripheral insulin sensitivity when comparing mixed gender and mixed race populations. Matsuda index and SI(is)OGTT are reliable in studies that include AA males.

Assessment of insulin sensitivity (S I) and glucose effectiveness (S G) from a standardized hyperglucidic breakfast test in type 2 diabetics exhibiting various levels of insulin resistance

We investigated the measurement of insulin sensitivity (S I) with a standardized hyperglucidic breakfast (SHB) compared to minimal model analysis of an intravenous glucose tolerance test (S I-IVGTT) in 17 patients clinically referred as type 2 diabetics, not yet treated by insulin, and representing a wide range of body mass index and S I. To classify the patients, ten meal-tolerance test-based calculations of S I (MTT-S I) were compared to S I-IVGTT, and their reference values and distribution were measured on a separate sample of 200 control SHBs and 209 control IVGTTs. Eight MTT-SI indices exhibit significant correlations with S I-IVGTT: Mari's OGIS index, BIGTT-SI|0-30-120, BIGTT-SI|0-60-120, 1/G b I m, Caumo's oral minimal model (OMM), Sluiter's index "A" = 10(4)/(I p·G p), Matsuda's composite index given by the formula ISIcomp = 10(4)/(I b G b I m G m)(0.5), S I = 1/I b G b I m G m with r (2) ranging between 0,53 and 0,28. S I-IVGTT and S I-MTT exhibited in the lower range a very different (non-normal) pattern of distribution and thus the cutoff value for defining insulin resistance varied among indices. With such cutoffs, S I-MTT < 6.3 min(-1)/(μU/ml) 10(-4) with Caumo's OMM was the best predictor of insulin resistance defined as S I-IVGTT < 2 min(-1)/(μU/ml) 10(-4). Other indices, including OGIS and BIGTT, resulted in more misclassifications of patients. HOMA-IR and QUICKI were poor predictors. The formula [Formula: see text] satisfactorily predicts IVGTT-derived glucose effectiveness in type 2 diabetics. Thus, SHB appears suitable for the measurement of S I and S G in type 2 diabetics, and the OMM seems to provide the most accurate SHB-derived index in this population.

A single nucleotide polymorphism associates with the response of muscle ATP synthesis to long-term exercise training in relatives of type 2 diabetic humans

OBJECTIVE

Myocellular ATP synthesis (fATP) associates with insulin sensitivity in first-degree relatives of subjects with type 2 diabetes. Short-term endurance training can modify their fATP and insulin sensitivity. This study examines the effects of moderate long-term exercise using endurance or resistance training in this cohort.

RESEARCH DESIGN AND METHODS

A randomized, parallel-group trial tested 16 glucose-tolerant nonobese relatives (8 subjects in the endurance training group and 8 subjects in the resistance training group) before and after 26 weeks of endurance or resistance training. Exercise performance was assessed from power output and oxygen uptake (VO(2)) during incremental tests and from maximal torque of knee flexors (MaxT(flex)) and extensors (MaxT(ext)) using isokinetic dynamometry. fATP and ectopic lipids were measured with (1)H/(31)P magnetic resonance spectroscopy.

RESULTS

Endurance training increased power output and VO(2) by 44 and 30%, respectively (both P < 0.001), whereas resistance training increased MaxT(ext) and MaxT(flex) by 23 and 40%, respectively (both P < 0.001). Across all groups, insulin sensitivity (382 ± 90 vs. 389 ± 40 mL · min(-1) · m(-2)) and ectopic lipid contents were comparable after exercise training. However, 8 of 16 relatives had 26% greater fATP, increasing from 9.5 ± 2.3 to 11.9 ± 2.4 μmol · mL(-1) · m(-1) (P < 0.05). Six of eight responders were carriers of the G/G single nucleotide polymorphism rs540467 of the NDUFB6 gene (P = 0.019), which encodes a subunit of mitochondrial complex I.

CONCLUSIONS

Moderate exercise training for 6 months does not necessarily improve insulin sensitivity but may increase ATP synthase flux. Genetic predisposition can modify the individual response of the ATP synthase flux independently of insulin sensitivity.

Effects of different protein content and glycaemic index of ad libitum diets on diabetes risk factors in overweight adults: the DIOGenes multicentre, randomized, dietary intervention trial

BACKGROUND

Dietary regimens providing different levels of protein and glycemic index (GI) foods when prescribed for weight management may also influence insulin sensitivity.

PROCEDURES AND OUTCOMES

Overweight/obese adults in 8 European countries who lost ≥ 8% of initial body-weight (BW) after following a low calorie diet (LCD) were later randomly assigned with a 2x2 factorial design into 4 ad libitum dietary groups with two different protein content levels and dissimilar glycemic index, which were compared to a healthy reference diet. Specific markers assessing insulin resistance were measured. The LCD was initially applied to 932 adults and 773 were randomised to the 5 ad libitum diets. The 6-months programme was completed by 548 participants. The assignment to the Low Protein /High Glycemic Index diet induced a statistically higher HOMA-IR increase during the 6 months period as compared to the control. Contrariwise, the insulin response was lower in the High Protein/Low Glycemic Index diet after 60 and 90 min of an Oral Glucose Tolerance test subsequently carried out after the 6-months intervention. The Low Glycemic Index diets (either with high or low protein content) also lead to a decrease in fructosamine levels during the trial.

CONCLUSION/INTERPRETATION

After a weight loss period, an increase in the dietary protein proportions and a decrease in the consumption of foods with a high Glycemic Index within an ad libitum dietary intervention aiming to weight maintenance produced favorable effects on glycaemic control and insulin sensitivity in overweight/obese subjects.

The Finnish Diabetes Risk Score is associated with insulin resistance but not reduced β-cell function, by classical and model-based estimates

AIMS

The Finnish Diabetes Risk Score (FINDRISC) is widely used for risk stratification in Type 2 diabetes prevention programmes. Estimates of β-cell function vary widely in people without diabetes and reduced insulin secretion has been described in people at risk for diabetes. The aim of this analysis was to evaluate FINDRISC as a tool to characterize reduced β-cell function in individuals without known diabetes.

METHODS

In this population-based cohort from the Hoorn municipal registry, subjects received an oral glucose tolerance test and a meal tolerance test on separate days, in random order, within 2 weeks. One hundred and eighty-six subjects, age 41-66 years, with no known Type 2 diabetes were included. Of those, 163 (87.6%) had normal glucose metabolism and 23 (12.4%) had abnormal glucose metabolism (19 with impaired glucose metabolism; four with newly diagnosed Type 2 diabetes based on study results). Insulin sensitivity and β-cell function (classical: insulinogenic index; ratio of areas under insulin/glucose curves; model-based: glucose sensitivity; rate sensitivity; potentiation) estimates were calculated from oral glucose tolerance test and meal tolerance test data.

RESULTS

FINDRISC was associated with insulin sensitivity (r = -0.41, P < 0.0001), insulin/glucose areas under the curve (meal tolerance test: r = 0.29, P < 0.0001; oral glucose tolerance test: r = 0.21, P = 0.01) and potentiation factor (meal tolerance test: r = 0.21, P = 0.01). After adjusting for insulin sensitivity, these associations with β-cell function were no longer significant.

CONCLUSIONS

After adjustment for insulin sensitivity, FINDRISC was not associated with reduced β-cell function in subjects without known Type 2 diabetes. While insulin secretion and insulin sensitivity are both components in Type 2 diabetes development, insulin sensitivity appears to be the dominant component behind the association between FINDRISC and diabetes risk.

Improvement in insulin sensitivity and β-cell function following ileal interposition with sleeve gastrectomy in type 2 diabetic patients: potential mechanisms

INTRODUCTION

Bariatric surgery in morbidly obese type 2 diabetic (T2DM) patients is associated with high rates of diabetes remission. We investigated the mechanisms of the anti-diabetic effect of the laparoscopic ileal interposition with sleeve gastrectomy (LII-SG) in normal weight (NW), overweight (OW) and obese (OB) T2DM patients.

METHODS

Ninety-four patients (aged 54 ± 8 years) with long-standing (median 10 years), treated diabetes (median HbA(1c) = 8.6%), who were NW (15), OW (64) or OB (15) based on BMI, underwent LII-SG. Insulin sensitivity and parameters of ß-cell function were measured from an Oral Glycaemic Tolerance Test pre- and post-operatively.

RESULTS

At a median of 13.4 months post-operatively, weight loss averaged 9.4 ± 1.3, 16.8 ± 0.8 and 23.2 ± 1.7 kg in NW, OW and OB subjects, respectively (p < 0.0001). Insulin sensitivity was fully restored (395 [108] vs 208 [99] ml min⁻¹ m⁻²), fasting insulin secretion rate decreased (68 [52] vs 146 [120] pmol min⁻¹ m⁻²) and total insulin output increased (52 [26] vs 39 [28] nmol m⁻², all p ≤ 0.001). ß-cell glucose sensitivity doubled (37 [33] vs 18 [24] mol min⁻¹ m⁻² mM⁻¹, p < 0.0001). The only parameter predicting remission of diabetes was a lower baseline insulin sensitivity (p = 0.005).

CONCLUSIONS

LII-SG induced changes on T2DM by mechanisms in part distinct from weight loss, principally involving restoration of insulin sensitivity and improvement of ß-cell function.

Elevated insulin sensitivity and β-cell function during pregnancy in mothers of growth-restricted newborns

The "Barker hypothesis" suggests that low birth weight might predict future risk of developing obesity, cardiovascular disease, and type 2 diabetes. Identification of the causes of fetal growth restriction (FGR) is critical for preventive and management strategies. Some studies indicate that maternal carbohydrate metabolism might be involved in FGR development. We aimed to evaluate, in a large number of normotensive pregnant women with normal glucose tolerance, the effect of insulin sensitivity and β-cell function on unexplained fetal growth. A total of 1,814 Caucasian pregnant women with normal prepregnancy body mass index were tested with a 75-g, 2-h glucose load (24-28 gestation wk). Insulin sensitivity was evaluated with fasting (QUICKI) and dynamic index (OGIS) and β-cell function with a modified insulinogenic index as ΔAUC(insulin)/ΔAUC(glucose) and disposition index. FGR was a birth weight below the 5th percentile for gestational age. FGR developed in 99 (5.5%) pregnant women that showed significantly higher QUICKI, OGIS, insulinogenic, and disposition index with respect to women with normal-weight babies (P < 0.0001). By using multiple regression analysis in the FRG group, QUICKI and OGIS appeared as significant independent variables (P < 0.0001 and P < 0.0366, respectively). We conclude that elevated insulin sensitivity seems to be one of the factors involved in determining unexplained fetal growth retardation; its assessment, even only in the fasting state, could be useful to guide any possible monitoring and therapeutic strategies to reduce fetal complications.

The heritability of beta cell function parameters in a mixed meal test design

AIMS/HYPOTHESIS

We estimated the heritability of individual differences in beta cell function after a mixed meal test designed to assess a wide range of classical and model-derived beta cell function parameters.

METHODS

A total of 183 healthy participants (77 men), recruited from the Netherlands Twin Register, took part in a 4 h protocol, which included a mixed meal test. Participants were Dutch twin pairs and their siblings, aged 20 to 49 years. All members within a family were of the same sex. Insulin sensitivity, insulinogenic index, insulin response and postprandial glycaemia were assessed, as well as model-derived parameters of beta cell function, in particular beta cell glucose sensitivity and insulin secretion rates. Genetic modelling provided the heritability of all traits. Multivariate genetic analyses were performed to test for overlap in the genetic factors influencing beta cell function, waist circumference and insulin sensitivity.

RESULTS

Significant heritabilities were found for insulinogenic index (63%), beta cell glucose sensitivity (50%), insulin secretion during the first 2 h postprandial (42-47%) and postprandial glycaemia (43-52%). Genetic factors influencing beta cell glucose sensitivity and insulin secretion during the first 30 postprandial min showed only negligible overlap with the genetic factors that influence waist circumference and insulin sensitivity.

CONCLUSIONS/INTERPRETATION

The highest heritability for postprandial beta cell function was found for the insulinogenic index, but the most specific indices of heritability of beta cell function appeared to be beta cell glucose sensitivity and the insulin secretion rate during the first 30 min after a mixed meal.

Body and liver fat mass rather than muscle mitochondrial function determine glucose metabolism in women with a history of gestational diabetes mellitus

OBJECTIVE

Ectopic lipid storage in muscle (intramyocellular lipids [IMCL]) and liver (hepatocellular lipids [HCL]) coexists with impaired myocellular flux through ATP synthase (fATPase) in certain cohorts with increased risk of type 2 diabetes. Because women with a history of gestational diabetes mellitus (pGDM) have elevated ectopic lipids and diabetes risk, we tested whether deteriorated energy metabolism contributes to these abnormalities.

RESEARCH DESIGN AND METHODS

A total of 23 glucose-tolerant nonobese pGDM and eight women with normal glucose metabolism during pregnancy with similar age, body mass, and physical activity underwent oral glucose tolerance tests (OGTT) and intravenous glucose tolerance tests at 4-5 years after delivery. OGTT values <463 mL ⋅ min(-1) ⋅ m(-2) were considered to indicate insulin resistance. pGDM were further stratified into insulin-resistant (pGDM-IR) and insulin-sensitive (pGDM-IS) groups. IMCL, HCL, and fATPase were measured with (1)H/(31)P magnetic resonance spectroscopy.

RESULTS

pGDM had 36% higher fat mass and 12% lower insulin sensitivity. Log-transformed fATPase was lower in pGDM (10.6 ± 3.8 µmol ⋅ mL muscle(-1) ⋅ min(-1) vs. 12.1 ± 1.4 µmol ⋅ mL muscle(-1) ⋅ min(-1), P < 0.03) and related to plasma adiponectin after adjustment for body fat (r = 0.44, P < 0.04). IMCL were 61% and 69% higher in pGDM-IR (P < 0.05 vs. pGDM-IS) and insulin resistant women (P < 0.003 vs. insulin sensitive), respectively. HCL were doubled (P < 0.05) in pGDM and insulin resistant women, and correlated positively with body fat mass (r = 0.50, P < 0.01) and inversely with insulin sensitivity (r = -0.46, P < 0.05).

CONCLUSIONS

Glucose-tolerant pGDM show increased liver fat but only slightly lower muscular insulin sensitivity and ATP synthesis. This suggests that alteration of hepatic lipid storage represents an early and predominant abnormality in this cohort.

Insulin resistance, adipose depots and gut: interactions and pathological implications

This review article focuses on the many metabolic actions of insulin at the level of muscle, liver and adipose tissue. In terms of pathogenetic mechanisms, the condition of insulin resistance is complex, as multiple genetic and environmental factors, among which an increasingly sedentary lifestyle associated with high-fat diet, mutually interact according to variable patterns in time in any given individual. It is well recognized that obesity (in particular abdominal obesity) favours the development of insulin resistance. Here we evaluate the impact of obesity and ectopic fat accumulation (visceral and hepatic) on insulin resistance at the level of different target organs, i.e., muscle, liver and adipose tissue. The roles of the gut and the liver, in particular of bile acids and gut microflora, are also discussed as possible determinants of energy balance and glucose metabolism.

Dissociated incretin response to oral glucose at 1 year after restrictive vs. malabsorptive bariatric surgery

AIM

Compare the response to oral glucose of the two incretin hormones, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) at 1 year after restrictive vs. malabsorptive bariatric surgery.

METHODS

Vertical banded gastroplasty (VBG, n = 7) or jejunoileal bypass (JIB, n = 5) was performed in 12 women, aged 26-39 years, with severe obesity [body mass index (BMI) 46.6 +/- 2.3 kg/m(2)]. After 1 year, 75 g glucose was administered and plasma levels of glucose, insulin, GIP and GLP-1 were determined regularly during the following 2 h.

RESULTS

At 1 year after operation, reduction in body weight, actual body weight, fasting glucose or insulin, or the glucose and insulin responses to oral glucose did not differ significantly between the groups. Similarly, fasting GIP and GLP-1 levels did not differ significantly between the groups. In contrast, the GIP and GLP-1 responses to oral glucose were different between the groups in a dissociated pattern. Thus, AUC(GIP) was significantly higher after VBG than after JIB (53 +/- 8 vs. 26 +/- 6 pmol/l/min, p = 0.003). In contrast, AUC(GLP-1) was significantly higher after JIB than after VBG (49 +/- 5 vs. 20 +/- 3 pmol/l/min, p = 0.007).

CONCLUSIONS

We conclude that at 1 year after bariatric surgery, the two incretins show dissociated responses in that the GIP secretion is higher after VBG whereas GLP-1 secretion is higher after JIB. This dissociated incretin response is independent from reduction in body weight, glucose tolerance or insulin secretion.

Soluble CD40 ligand levels in essential hypertensive men: evidence of a possible role of insulin resistance

BACKGROUND

Elevated levels of the proinflammatory cytokine soluble CD40 ligand (sCD40L) were reported in subjects with diabetes, impaired glucose tolerance, metabolic syndrome (MS), obesity, and insulin resistance. Metabolic abnormalities might also account for increased sCD40L in subjects with essential hypertension.

METHODS

Several metabolic and vascular correlates of sCD40L levels have been investigated in 90 nondiabetic never-treated essential hypertensive men.

RESULTS

Median sCD40L level was 8.7 ng/ml (interquartile range: 4.9-11.7). On the basis of sCD40L, subjects were divided by tertiles (thresholds at 6.6 and 11.0 ng/ml). The three groups did not differ for age, body mass index (BMI), smokers, blood pressure (BP), prevalence of nondippers, lipids and lipoproteins, renal function, and albuminuria. Carotid intima-media thickness (IMT: 0.79 +/- 0.22, 0.83 +/- 0.29, and 0.85 +/- 0.30 mm) and percentage of subjects with wall thickening (IMT >0.9 to <1.3 mm: 23, 27, and 27%, respectively) were superimposable in the three groups. No differences were observed in high-sensitivity C-reactive protein (hs-CRP) and no correlation emerged between sCD40L and hs-CRP. An increase through sCD40L tertiles emerged for basal insulin (11.2 +/- 5.6, 14.7 +/- 7.7, and 16.8 +/- 13.5 microU/ml, P = 0.10) and fasting glucose (95 +/- 11, 103 +/- 16, and 105 +/- 14 mg/dl, P = 0.028). Consistently, along with the increase in sCD40L, a worsening in insulin sensitivity was observed, which was expressed as homeostasis model assessment for insulin sensitivity (HOMA%S: 99 +/- 52, 77 +/- 43, and 72 +/- 35, P < 0.05), composite insulin sensitivity index (ISIcomp; Matsuda index: 5.11 +/- 2.65, 3.61 +/- 1.98, and 3.28 +/- 1.87, P = 0.025), or oral glucose insulin sensitivity (OGIS) index (OGIS: 421 +/- 67, 386 +/- 90, and 362 +/- 72, P = 0.004).

CONCLUSIONS

In newly diagnosed hypertensive men, sCD40L levels are inversely related to insulin sensitivity, with no correlation with BP, other cardiovascular risk factors, or the degree of subclinical atherosclerosis.

Differential islet and incretin hormone responses in morning versus afternoon after standardized meal in healthy men

CONTEXT

The insulin response to meal ingestion is more rapid in the morning than in the afternoon. Whether this is explained by a corresponding variation in the incretin hormones is not known.

OBJECTIVE

Our objective was to assess islet and incretin hormones after meal ingestion in the morning vs. afternoon.

DESIGN, SETTINGS, AND PARTICIPANTS

Ingestion at 0800 and 1700 h of a standardized meal (524 kcal) in healthy lean males (n = 12) at a University Clinical Research Unit.

MAIN OUTCOME MEASURES

We assessed early (30-min) area under the curve (AUC30) of plasma levels of insulin and intact (i) and total (t) glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) after meal ingestion and made an estimation of beta-cell function by model analysis of glucose and C-peptide.

RESULTS

Peak glucose was lower in the morning than in the afternoon (6.1 +/- 0.2 vs. 7.4 +/- 0.3 mmol/liter, P = 0.001). AUC30(insulin) (4.9 +/- 0.6 vs. 2.8 +/- 0.4 nmol/liter . 30 min; P = 0.012), AUC30(tGLP-1) (300 +/- 40 vs. 160 +/- 30 pmol/liter . 30 min, P = 0.002), AUC30(iGIP) (0.7 +/- 0.1 vs. 0.3 +/- 0.1 nmol/liter . 30 min, P = 0.002), and AUC30(tGIP) (1.1 +/- 0.1 vs. 0.6 +/- 0.1 nmol/liter . min, P = 0.007) were all higher in the morning. AUC30(iGLP-1) (r = 0.68; P = 0.021) and AUC30(iGIP) (r = 0.78; P = 0.001) both correlated to AUC30(insulin). Model analysis of beta-cell function showed a higher first-hour potentiation factor in the morning (P = 0.009). This correlated negatively with the 60-min glucose level (r = -0.63; P < 0.001).

CONCLUSIONS

The early release of GLP-1 and GIP are more pronounced in the morning than in the afternoon. This may contribute to the more rapid early insulin response, more pronounced potentiation of beta-cell function, and lower glucose after the morning meal.

Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes: an analysis from the Whitehall II study

BACKGROUND

Little is known about the timing of changes in glucose metabolism before occurrence of type 2 diabetes. We aimed to characterise trajectories of fasting and postload glucose, insulin sensitivity, and insulin secretion in individuals who develop type 2 diabetes.

METHODS

We analysed data from our prospective occupational cohort study (Whitehall II study) of 6538 (71% male and 91% white) British civil servants without diabetes mellitus at baseline. During a median follow-up period of 9.7 years, 505 diabetes cases were diagnosed (49.1% on the basis of oral glucose tolerance test). We assessed retrospective trajectories of fasting and 2-h postload glucose, homoeostasis model assessment (HOMA) insulin sensitivity, and HOMA beta-cell function from up to 13 years before diabetes diagnosis (diabetic group) or at the end of follow-up (non-diabetics).

FINDINGS

Multilevel models adjusted for age, sex, and ethnic origin confirmed that all metabolic measures followed linear trends in the group of non-diabetics (10,989 measurements), except for insulin secretion that did not change during follow-up. In the diabetic group (801 measurements), a linear increase in fasting glucose was followed by a steep quadratic increase (from 5.79 mmol/L to 7.40 mmol/L) starting 3 years before diagnosis of diabetes. 2-h postload glucose showed a rapid increase starting 3 years before diagnosis (from 7.60 mmol/L to 11.90 mmol/L), and HOMA insulin sensitivity decreased steeply during the 5 years before diagnosis (to 86.7%). HOMA beta-cell function increased between years 4 and 3 before diagnosis (from 85.0% to 92.6%) and then decreased until diagnosis (to 62.4%).

INTERPRETATION

In this study, we show changes in glucose concentrations, insulin sensitivity, and insulin secretion as much as 3-6 years before diagnosis of diabetes. The description of biomarker trajectories leading to diabetes diagnosis could contribute to more-accurate risk prediction models that use repeated measures available for patients through regular check-ups.

FUNDING

Medical Research Council (UK); Economic and Social Research Council (UK); British Heart Foundation (UK); Health and Safety Executive (UK); Department of Health (UK); National Institute of Health (USA); Agency for Health Care Policy Research (USA); the John D and Catherine T MacArthur Foundation (USA); and Academy of Finland (Finland).

A double-blind, randomized, placebo-controlled trial of the short-term effect of vitamin D3 supplementation on insulin sensitivity in apparently healthy, middle-aged, centrally obese men

AIM

To determine the short-term effect of vitamin D(3) supplementation on insulin sensitivity in apparently healthy, middle-aged, centrally obese men.

SUBJECTS AND METHODS

A double-blind randomized controlled trial was conducted at a tertiary care facility in which 100 male volunteers aged > or = 35 years received three doses of vitamin D(3) (120,000 IU each; supplemented group) fortnightly or placebo (control group). Hepatic fasting insulin sensitivity [homeostasis model assessment (HOMA), quantitative insulin-sensitivity check index, HOMA-2], postprandial insulin sensitivity [oral glucose insulin sensitivity (OGIS)], insulin secretion (HOMA%B, HOMA2-%B), lipid profile and blood pressure were measured at baseline and at 6 weeks' follow-up.

RESULTS

Seventy-one of the recruited subjects completed the study (35 in supplemented group, 36 in control group). There was an increase in OGIS with supplementation by per protocol analysis (P = 0.038; intention-to-treat analysis P = 0.055). The age- and baseline 25-hydroxyvitamin D level-adjusted difference in change in OGIS was highly significant (mean difference 41.1 +/- 15.5; P = 0.01). No changes in secondary outcome measures (insulin secretion, basal indices of insulin sensitivity, blood pressure or lipid profile) were found with supplementation.

CONCLUSION

The trial indicates that vitamin D(3) supplementation improves postprandial insulin sensitivity (OGIS) in apparently healthy men likely to have insulin resistance (centrally obese but non-diabetic).

Effects of conjugated linoleic acid plus n-3 polyunsaturated fatty acids on insulin secretion and estimated insulin sensitivity in men

BACKGROUND/OBJECTIVES

Dietary addition of either conjugated linoleic acid (CLA) or n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) has been shown to alter adiposity and circulating lipids, risk markers of cardiovascular diseases. However, CLA may decrease insulin sensitivity, an effect that may be reversed by n-3 LC-PUFA. Thus, the potential of CLA plus n-3 LC-PUFA to affect insulin secretion and sensitivity in non-diabetic young and old, lean and obese subjects was tested.

SUBJECTS/METHODS

CLA (3 g daily) plus n-3 LC-PUFA (3 g daily) or control oil (6 g daily) was given to lean (n=12; BMI 20-26 kg/m(2)) or obese (n=10; BMI 29-35 kg/m(2)) young (20-37 years old) or lean (n=16) or obese (n=11) older men (50-65 years) for 12 weeks. The study had a double-blind, placebo-controlled randomized crossover design, and primary end points were insulin secretion and sensitivity during a standardized meal test, evaluated by modeling glucose, insulin and C-peptide data.

RESULTS

The combination was well tolerated. There was no significant difference in fasting levels of glucose, insulin or C-peptide after CLA/n-3 LC-PUFA treatment compared with control oil. Neither insulin secretion nor estimated sensitivity was affected by CLA/n-3 LC-PUFA in lean or obese young subjects or in older lean subjects. However, in older obese subjects, estimated insulin sensitivity was reduced with CLA/n-3 LC-PUFA compared with control (P=0.024).

CONCLUSIONS

The results do not support beneficial effects of CLA/n-3 LC-PUFA for beta-cell dysfunction or insulin resistance in humans but suggest that insulin sensitivity in older obese subjects is reduced.

Hepatic dysfunction and insulin insensitivity in type 2 diabetes mellitus: a critical target for insulin-sensitizing agents

The liver plays an essential role in maintaining glucose homeostasis, which includes insulin-mediated processes such as hepatic glucose output (HGO) and uptake, as well as in clearance of insulin itself. In type 2 diabetes, the onset of hyperglycaemia [itself a potent inhibitor of hepatic glucose output (HGO)], alongside hyperinsulinaemia, indicates the presence of hepatic insulin insensitivity. Increased HGO is central to the onset of hyperglycaemia and highlights the need to target hepatic insulin insensitivity as a central component of glucose-lowering therapy. The mechanisms underlying the development of hepatic insulin insensitivity are not well understood, but may be influenced by factors such as fatty acid oversupply and altered adipocytokine release from dysfunctional adipose tissue and increased liver fat content. Furthermore, although the impact of insulin insensitivity as a marker of cardiovascular disease is well known, the specific role of hepatic insulin insensitivity is less clear. The pharmacological tools available to improve insulin sensitivity include the biguanides (metformin) and thiazolidinediones (rosiglitazone and pioglitazone). Data from a number of sources indicate that thiazolidinediones, in particular, can improve multiple aspects of hepatic dysfunction, including reducing HGO, insulin insensitivity and liver fat content, as well as improving other markers of liver function and the levels of mediators with potential involvement in hepatic function, including fatty acids and adipocytokines. The current review addresses this topic from the perspective of the role of the liver in maintaining glucose homeostasis, its key involvement in the pathogenesis of type 2 diabetes and the tools currently available to reduce hepatic insulin insensitivity.

Assay-dependent variability of serum insulin levels during oral glucose tolerance test: influence on reference intervals for insulin and on cut-off values for insulin sensitivity indices

BACKGROUND

The oral glucose tolerance test (oGTT) is the most common method to estimate indices of insulin sensitivity in clinical as well as in epidemiological studies. The aim of this study was to investigate the variability of insulin levels for reference intervals and of insulin sensitivity indices during oGTT by three different insulin immunoassays.

METHODS

Serum insulin levels were determined during oGTT of randomly selected adult subjects (total n=101, with n=68 with normal glucose tolerance) by the LIAISON (LIA), the Elecsys (EL) and the AutoDELFIA (AD) method.

RESULTS

Sensitivity and precision of all three insulin assays were comparable. Insulin levels demonstrated a close (p<0.001) interassay correlation (LIA vs. EL: r=0.987, LIA vs. AD: r=0.966, EL vs. AD: r=0.965). Insulin levels and insulin sensitivity indices (n=68) of the AD method were significantly different compared to the LIA or EL assay (p<0.001). Basal insulin levels demonstrated an assay-dependent significant body mass index (BMI) dependency (LIA: r=0.24, p=0.05; AD: r=0.44, p<0.001; EL: r=0.36, p<0.01) in the regression analysis. At 120 min post glucose, gender was the relevant influencing factor on insulin levels of the LIA (r=0.40, p<0.001), AD (r=0.37, p<0.01) and EL (r=0.40 p<0.001) method.

CONCLUSIONS

We conclude that assay-dependent reference intervals should be used for the clinical interpretation of insulin levels from oGTT and of insulin sensitivity indices. Moreover, BMI and gender have to be considered as influencing factors.

Ghrelin levels are suppressed and show a blunted response to oral glucose in women with polycystic ovary syndrome

OBJECTIVE

Abnormal ghrelin regulation may influence the development of obesity-associated conditions including polycystic ovary syndrome (PCOS). Our aim was to compare ghrelin regulation between PCOS cases and controls.

DESIGN

We compared serum ghrelin (total) levels, fasting and 30-min post-oral (75 g) glucose load, between 50 PCOS cases and 28 female controls, including 22 body mass index (BMI)/fat mass-matched pairs. All subjects were of UK British/Irish origin.

METHODS

Measurements included serum ghrelin (RIA technique (LINCO Research, St Charles MO, USA)), fat mass, serum testosterone, fasting serum insulin and plasma glucose levels. Insulin sensitivity was calculated as the homeostasis model assessment of insulin resistance (HOMA2 IR).

RESULTS

Fasting serum ghrelin levels were significantly lower in PCOS cases versus BMI/fat mass-matched controls (geometric mean (s.d. range), 1104 pg/ml (764-1595) vs 1756 pg/ml (1314-2347) respectively; P=2.3 x 10(-4)). Ghrelin suppression following oral glucose load was significantly blunted in PCOS cases versus BMI/fat mass-matched controls (geometric mean ghrelin suppression (s.d. range), 160 pg/ml (88-289) vs 424 pg/ml (220-818) respectively; P=2.0 x 10(-4)). Whole-group comparisons (50 PCOS cases versus 28 controls) adjusted for fat mass and age revealed similar results. In PCOS cases, there was a significant negative correlation between fasting serum ghrelin and HOMA2 IR (r(2)=-0.40, P=5.7 x 10(-3)). Following adjustment for HOMA2 IR, fat mass and age, comparisons between the whole groups of PCOS cases and controls revealed attenuated but significant differences in fasting serum ghrelin (P=1.3 x 10(-3)) and ghrelin suppression (P=1.8 x 10(-3)).

CONCLUSIONS

In women with PCOS, serum ghrelin levels are suppressed, showing a negative relationship with HOMA2 IR and a blunted response to oral glucose.