A simple method for quantitation of insulin sensitivity and insulin release from an intravenous glucose tolerance test

Extreme Variations in Muscle Fiber Composition Enable Detection of Insulin Resistance and Excessive Insulin Secretion

CONTEXT

Muscle fiber composition is associated with peripheral insulin action.

OBJECTIVE

We investigated whether extreme differences in muscle fiber composition are associated with alterations in peripheral insulin action and secretion in young, healthy subjects who exhibit normal fasting glycemia and insulinemia.

METHODS

Relaxation time following a tetanic contraction was used to identify subjects with a high or low expression of type I muscle fibers: group 1 (n = 11), area occupied by type I muscle fibers = 61.0 ± 11.8%, and group 2 (n = 8), type I area = 36.0 ± 4.9% (P < 0.001). Biopsies were obtained from the vastus lateralis muscle and analyzed for mitochondrial respiration on permeabilized fibers, muscle fiber composition, and capillary density. An intravenous glucose tolerance test was performed and indices of glucose tolerance, insulin sensitivity, and secretion were determined.

RESULTS

Glucose tolerance was similar between groups, whereas whole-body insulin sensitivity was decreased by ~50% in group 2 vs group 1 (P = 0.019). First-phase insulin release (area under the insulin curve during 10 minutes after glucose infusion) was increased by almost 4-fold in group 2 vs group 1 (P = 0.01). Whole-body insulin sensitivity was correlated with percentage area occupied by type I fibers (r = 0.54; P = 0.018) and capillary density in muscle (r = 0.61; P = 0.005) but not with mitochondrial respiration. Insulin release was strongly related to percentage area occupied by type II fibers (r = 0.93; P < 0.001).

CONCLUSIONS

Assessment of muscle contractile function in young healthy subjects may prove useful in identifying individuals with insulin resistance and enhanced glucose-stimulated insulin secretion prior to onset of clinical manifestations.

Oversupplying metabolizable protein during late gestation to beef cattle does not influence ante- or postpartum glucose-insulin kinetics but does affect prepartum insulin resistance indices and colostrum insulin content

The objective of this study was to evaluate whether oversupplying metabolizable protein (MP) during late gestation influences glucose and insulin concentrations, and insulin resistance (IR) in late gestation and early lactation. Crossbred Hereford, first-lactation heifers were individually fed diets to supply 133% (HMP, n = 11) or 100% (CON, n = 10) of their predicted MP requirements for 55 ± 4 d (mean ± SD) prior to calving. All heifers received a common lactation ration formulated to meet postpartum requirements (103% MP and 126% ME). After feed was withheld for 12 h, cattle underwent an intravenous glucose tolerance test (IVGTT) on d -6.7 ± 0.9 and 14.3 ± 0.4 by infusing a 50% dextrose solution (1.36 g glucose/kg BW 0.75) through a jugular catheter with plasma collected at -10, 0 (immediately after infusion), 5, 10, 15, 20, 25, 30, 45, 60, 75, 90, and 120 min, respective to the infusion. Glucose and insulin concentrations were assessed. Insulin resistance indices (homeostasis model of insulin resistance [HOMA-IR], quantitative insulin sensitivity check index [QUICKI], revised quantitative insulin sensitivity check index [RQUICK], and RQUICKI incorporating serum beta-hydroxybutyrate concentrations [RQUICKIBHB]) were calculated from measurements of serum non-esterified fatty acids and beta-hydroxybutyrate and plasma glucose and insulin concentrations on d -34 ± 4, -15 ± 4, 7 ± 1, 28 ± 3, 70 ± 3, and 112 ± 3. Colostrum samples were collected within an hour of calving (prior to suckling) and analyzed for insulin concentration. Data were analyzed as a randomized block design using the PROC GLIMMIX of SAS, accounting for repeated measurements when necessary. Baseline (-10 min) plasma glucose and insulin concentrations were elevated (P ≤ 0.038) for HMP heifers during the antepartum IVGTT, but not (P ≥ 0.25) during the postpartum IVGTT. Plasma glucose and insulin concentrations throughout the antepartum or postpartum IVGTT did not differ (P ≥ 0.18) by prepartum treatment, nor did other glucose and insulin IVGTT parameters (i.e., max concentration and time to reach max concentration, nadir values, clearance rates and half-lives, area-under-the-curve, and insulin sensitivity index; P ≥ 0.20). Antepartum IVGTT IR indices indicated that HMP heifers were more (P ≤ 0.011) IR than their counterparts. Similarly, the prepartum HOMA-IR was greater (P = 0.033) for HMP heifers, suggesting increased IR. Postpartum IR indices did not (P ≥ 0.25) indicate that prepartum MP consumption impacted postpartum IR. Colostrum insulin concentration was increased (P = 0.004) by nearly 2-fold for HMP relative to CON heifers. These data demonstrate that prepartum MP overfeeding alters baseline glucose-insulin concentrations in late-pregnant beef heifers and increases colostrum insulin content without having carry-over effects on postpartum glucose-insulin concentrations and IR.

Beta cell function, incretin hormones, and incretin effect in obese children and adolescents with prediabetes

BACKGROUND

Defects of incretin hormones and incretin effect may be underlying mechanisms of abnormal glucose metabolism in youth.

OBJECTIVE

To assess incretin hormone dynamics during an oral glucose tolerance test (OGTT) and incretin effect in obese children with prediabetes in comparison with those with normal glucose tolerance (NGT).

METHODS

Overweight and obese children were enrolled and classified according to OGTT results as NGT and prediabetes. Insulin sensitivity, insulin secretion, incretin hormone concentrations during OGTT; and incretin effect derived from OGTT and intravenous glucose tolerance test were determined and compared between NGT and prediabetes groups.

RESULTS

Sixty-three patients (43 NGT and 20 prediabetes) were enrolled. Their median (interquartile range) age was 12.5 (11.1, 13.8) years. Peak glucagon-like peptide-1 (GLP-1) was demonstrated at 30 min during OGTT and was higher in the prediabetes group (49.2 [35.6, 63.6] versus 36.5 [27.6, 44.2] pmol/L, p = 0.009). However, incremental areas under the curves (iAUCs) of GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) were not different between the two groups. There was no difference in incretin effect between NGT and prediabetes (NGT: 66.5% [60.2%, 77.5%] vs. prediabetes: 70.0% [61.5%, 75.0%], p = 0.645). Incretin effect had positive correlations with iAUCs of both GLP-1 and GIP (GLP-1: r = 0.40, p = 0.004 and GIP: r = 0.37, p = 0.009).

CONCLUSIONS

Comparing between obese children with prediabetes and NGT, there were no differences in overall incretin hormone changes during OGTT and incretin effect. Incretin effect was positively correlated with iAUCs of GLP-1 and GIP.

Association of Insulin Resistance with Vascular Ageing in a General Caucasian Population: An EVA Study

The data on the relationship between insulin resistance and vascular ageing are limited. The aim of this study was to explore the association of different indices of insulin resistance with vascular ageing in an adult Caucasian population without cardiovascular disease. We selected 501 individuals without cardiovascular disease (mean age: 55.9 years, 50.3% women) through random sampling stratified by sex and age. Arterial stiffness was evaluated by measuring the carotid-to-femoral pulse wave velocity (cfPWV) and brachial-to-ankle pulse wave velocity (baPWV). The participants were classified into three groups according to the degree of vascular ageing: early vascular ageing (EVA), normal vascular ageing (NVA) and healthy vascular ageing (HVA). Insulin resistance was evaluated with the homeostatic model assessment of insulin resistance (HOMA-IR) and another five indices. The prevalence of HVA and EVA was 8.4% and 21.4%, respectively, when using cfPWV, and 7.4% and 19.2%, respectively, when using baPWV. The deterioration of vascular ageing, with both measurements, presented as an increase in all the analysed indices of insulin resistance. In the multiple regression analysis and logistic regression analysis, the indices of insulin resistance showed a positive association with cfPWV and baPWV and with EVA.

Severe insulin resistance syndromes

Severe insulin resistance syndromes are a heterogeneous group of rare disorders characterized by profound insulin resistance, substantial metabolic abnormalities, and a variety of clinical manifestations and complications. The etiology of these syndromes may be hereditary or acquired, due to defects in insulin potency and action, cellular responsiveness to insulin, and/or aberrations in adipose tissue function or development. Over the past decades, advances in medical technology, particularly in genomic technologies and genetic analyses, have provided insights into the underlying pathophysiological pathways and facilitated the more precise identification of several of these conditions. However, the exact cellular and molecular mechanisms of insulin resistance have not yet been fully elucidated for all syndromes. Moreover, in clinical practice, many of the syndromes are often misdiagnosed or underdiagnosed. The majority of these disorders associate with an increased risk of severe complications and mortality; thus, early identification and personalized clinical management are of the essence. This Review aims to categorize severe insulin resistance syndromes by disease process, including insulin receptor defects, signaling defects, and lipodystrophies. We also highlight several complex syndromes and emphasize the need to identify patients, investigate underlying disease mechanisms, and develop specific treatment regimens.

Metabolic modeling using statistical and spreadsheet software: Application to the glucose minimal model

Kinetic non-linear metabolic models are used extensively in medical research and increasingly for clinical diagnostic purposes. An example of such a model is the Glucose Minimal Model by Bergman and colleagues [1]. This model is similar to pharmacokinetic/pharmacodynamic models in that like pharmacokinetic/pharmacodynamic models, it is based on a small number of fairly simple ordinary differential equations and it aims to determine how the changing concentration of one blood constituent influences the concentration of another constituent. Although such models may appear prima facie, to be relatively simple, they have gained a reputation of being difficult to fit to data, especially in a consistent and repeatable fashion. Consequently, researchers and clinicians have generally relied on dedicated software packages to do this type of modeling. This article describes the use of statistical and spreadsheet software for fitting the Glucose Minimal Model to data from an insulin modified intravenous glucose tolerance test (IM-IVGTT). A novel aspect of the modeling is that the differential equations that are normally used to describe insulin action and the disposition of plasma glucose are first solved and expressed in their explicit forms so as to facilitate the estimation of Glucose Minimal Model parameters using the nonlinear (nl) optimization procedure within statistical and spreadsheet software. The most important clinical parameter obtained from the Glucose Minimal Model is insulin sensitivity (S_I). Using IM-IVGTT data from 42 horses in one experiment and 48 horses in a second experiment, we demonstrate that estimates of S_I derived from the Glucose Minimal Model fitted to data using STATA and Excel, are highly concordant with S_I estimates obtained using the industry standard software, MinMod Millennium. This work demonstrates that there is potential for statistical and spreadsheet software to be applied to a wide range of kinetic non-linear modeling problems.

Long-term caloric restriction ameliorates deleterious effects of aging on white and brown adipose tissue plasticity

Age-related increased adiposity is an important contributory factor in the development of insulin resistance (IR) and is associated with metabolic defects. Caloric restriction (CR) is known to induce weight loss and to decrease adiposity while preventing metabolic risk factors. Here, we show that moderate 20% CR delays early deleterious effects of aging on white and brown adipose tissue (WAT and BAT, respectively) function and improves peripheral IR. To elucidate the role of CR in delaying early signs of aging, young (3 months), middle-aged (12 months), and old (20 months) mice fed al libitum and middle-aged and old mice subjected to early-onset CR were used. We show that impaired plasticity of subcutaneous WAT (scWAT) contributes to IR, which is already evident in middle-aged mice. Moreover, alteration of thyroid axis status with age is an important factor contributing to BAT dysfunction in middle-aged animals. Both defects in WAT and BAT/beige cells are ameliorated by CR. Accordingly, CR attenuated the age-related decline in scWAT function and decreased the extent of fibro-inflammation. Furthermore, CR promoted scWAT browning. In brief, our study identifies the contribution of scWAT impairment to age-associated metabolic dysfunction and identifies browning in response to food restriction, as a potential therapeutic strategy to prevent the adverse metabolic effects in middle-aged animals.

Abnormalities in autonomic function in obese boys at-risk for insulin resistance and obstructive sleep apnea

STUDY OBJECTIVES

Current evidence in adults suggests that, independent of obesity, obstructive sleep apnea (OSA) can lead to autonomic dysfunction and impaired glucose metabolism, but these relationships are less clear in children. The purpose of this study was to investigate the associations among OSA, glucose metabolism, and daytime autonomic function in obese pediatric subjects.

METHODS

Twenty-three obese boys participated in: overnight polysomnography; a frequently sampled intravenous glucose tolerance test; and recordings of spontaneous cardiorespiratory data in both the supine (baseline) and standing (sympathetic stimulus) postures.

RESULTS

Baseline systolic blood pressure and reactivity of low-frequency heart rate variability to postural stress correlated with insulin resistance, increased fasting glucose, and reduced beta-cell function, but not OSA severity. Baroreflex sensitivity reactivity was reduced with sleep fragmentation, but only for subjects with low insulin sensitivity and/or low first-phase insulin response to glucose.

CONCLUSIONS

These findings suggest that vascular sympathetic activity impairment is more strongly affected by metabolic dysfunction than by OSA severity, while blunted vagal autonomic function associated with sleep fragmentation in OSA is enhanced when metabolic dysfunction is also present.

Corn Oil Lowers Plasma Cholesterol Compared with Coconut Oil in Adults with Above-Desirable Levels of Cholesterol in a Randomized Crossover Trial

Background

Few trials have examined the effects of coconut oil consumption in comparison with polyunsaturated fatty acid-rich oils such as corn oil.

Objective

This trial assessed the effects of consuming foods made with corn oil compared with coconut oil on lipids, glucose homeostasis, and inflammation.

Methods

This was a preliminary randomized crossover study of men (n = 12) and women (n = 13) with a mean age of 45.2 y, mean body mass index (in kg/m2) of 27.7, fasting LDL cholesterol ≥115 mg/dL and <190 mg/dL, and triglycerides (TGs) ≤375 mg/dL. Subjects consumed muffins and rolls providing 4 tablespoons (∼54 g) per day of corn oil or coconut oil as part of their habitual diets for 4 wk, with a 3-wk washout between conditions. Fasting plasma lipids and high-sensitivity C-reactive protein (hs-CRP) and glucose metabolism were assessed via an intravenous glucose tolerance test at baseline and 15 and 29 d of treatment. Responses were compared between treatments by ANCOVA.

Results

Median baseline concentrations of LDL cholesterol, non-HDL cholesterol, total cholesterol (total-C), HDL cholesterol, total-C:HDL cholesterol, and TGs were 123, 144, 188, 46.0, 4.21, and 92.5 mg/dL, respectively. Changes from baseline for corn oil and coconut oil conditions, respectively, were: LDL cholesterol (primary outcome; -2.7% compared with +4.6%), non-HDL cholesterol (-3.0% compared with +5.8%), total-C (-0.5% compared with +7.1%), HDL cholesterol (+5.4% compared with +6.5%), total-C:HDL cholesterol (-4.3% compared with -3.3%), and TGs (-2.1% compared with +6.0%). Non-HDL cholesterol responses were significantly different between corn and coconut oil conditions (P = 0.034); differences between conditions in total-C and LDL cholesterol approached significance (both P = 0.06). Responses for hs-CRP and carbohydrate homeostasis parameters did not differ significantly between diet conditions.

Conclusions

When incorporated into the habitual diet, consumption of foods providing ∼54 g of corn oil/d produced a more favorable plasma lipid profile than did coconut oil in adults with elevated cholesterol. This trial was registered at clinicaltrials.gov as NCT03202654.

The association between thyroid cancer and insulin resistance, metabolic syndrome and its components: A systematic review and meta-analysis

BACKGROUND

Thyroid cancer is rapidly increasing in incidence worldwide in the past several decades, same as the incidence of metabolic syndrome. We performed a system review and meta-analysis of the association between metabolic syndrome, its components and insulin resistance and thyroid cancer incidence.

METHODS

We searched several computer-assisted databases PUBMED, EMBASE and ISI Web of Science to identify studies published before 31st January 2018. Every study must report either risk estimates of thyroid cancer incidence with 95% confidence interval (CI) or related data can speculate. Two investigators independently identified eligible studies and extracted data. Evaluating the summaries of relative risk estimates use both fixed and random effects methods.

RESULTS

We found 42 articles met the inclusion criteria of this review. There is an increased risk for thyroid cancer for patients with insulin resistance (relative risk [RR] = 1.59, 95%confidence interval [CI] = 1.12-2.27, P = 0.01), dysglycemia (RR = 1.40, 95%CI = 1.15-1.70,P < 0.001), high BMI (RR = 1.35,95%CI = 1.23-1.48,P < 0.001) and hypertension(RR = 1.34,95%CI = 1.22-1.47, p < 0.001). However, patients with dyslipidemia, both total cholesterol (RR = 1.09, 95%CI = 0.98-1.21, P = 0.13) and triglyceride (RR = 1.01, 95%CI = 0.91-1.12, P = 0.82) was not associated with thyroid cancer.

CONCLUSIONS

Our meta-analysis showed Insulin Resistance, dysglycemia, high BMI and hypertension significantly increased the thyroid cancer risk. These results may help identify people with high risk of thyroid cancer and change to healthy life style.

The independent associations of protein consumption with body fat and glycaemic control in adult Chinese

PURPOSE

High-protein diets were popular in weight control. However, the role of protein intake in adiposity and related metabolic conditions among general populations is not clear. We aimed to evaluate the associations of protein intake with adiposity and glycaemic control among adult Chinese in a nationwide population-based survey.

METHODS

The data were from China Health and Nutrition Survey 2009. A total of 9360 men and women aged 18 years or older were included. Body fat percentage was calculated using validated Chinese-specific equations. Dietary intake levels of macronutrients were evaluated by food-weighing approach combined with a 3-day food intake recall.

RESULTS

Averagely, our participants have 12.5% energy intake from dietary protein. With multivariate adjustment including total energy intake, the odds ratios (95% CIs) of excessive adiposity (body fat percentage ≥ 20/30% for men/women), and central obesity (waist circumference ≥ 90/80 cm for men/women) were 1.51 (1.30, 1.75) and 1.40 (1.21, 1.62), respectively, comparing extreme quintiles of relative protein intake, while fat and carbohydrate were not associated with adiposity indices. Moreover, higher relative protein intake was associated with elevated concentration of fasting glucose (β ± SE: 1.233 ± 0.583), fasting insulin (23.211 ± 9.191), glycated hemoglobin (1.057 ± 0.369), and insulin resistance indicated by homeostasis model assessment of insulin resistance (7.558 ± 2.928) (all P < 0.05). Further adjusting for body mass index attenuated the associations.

CONCLUSION

In Chinese adults, higher habitual protein consumption may be associated with higher adiposity and worse glycaemic control, independent of total energy intake.

Deterioration of insulin release rate response to glucose during oral glucose tolerance test is associated with an increased risk of incident diabetes in normal glucose tolerance subjects

β-Cell dedifferentiation, characterized by loss of glucose sensitivity (β-cell glucose sensitivity [βCGS]), has been reported to play an important role in the development of type 2 diabetes (T2D). Traditionally, βCGS was derived from C-peptide-based method. However, C-peptide was not routinely examined in normal subjects and diabetes never treated with insulin. Thus, the aim of the study was to evaluate the use of insulin in oral glucose tolerance test (OGTT) in estimation of β-cell glucose response ability. A total of 1,599 subjects including normal glucose tolerance (NGT), impaired glucose tolerance (IGT) and T2D were included in the study. A subgroup of NGT subjects (n = 591) were followed up for an average duration of 56.88 ± 20.76 months. Insulin release rate (IRR_INS ) in the function of glucose (IRR_INS response to glucose [IRRG]) during OGTT was compared with βCGS. Both βCGS derived from C-peptide by deconvolution approach and IRRG by insulin release progressively declined from NGT to IGT and T2D. Both βCGS and IRRG were associated with deposit of first-phase insulin secretion (DI_1st ). After 56.88 ± 20.76 months, 32 (5.41%) NGT subjects had developed T2D. NGT subjects who progressed to diabetes after follow-up had lower IRRG and DI_1st levels than those who did not (P < 0.01). Furthermore, multiple logistic regression analyses showed that decreased IRRG was a significant independent risk predictor for future diabetes after adjustment of age, body mass index (BMI), homeostasis model assessment (HOMA)-insulin resistance, DI_1st and family history. NGT subjects with decreased IRRG during OGTT had defective early insulin secretion and were at higher risk of developing diabetes. IRRG could be a useful T2D predictor in NGT subjects. © 2017 IUBMB Life, 69(9):756-766, 2017.

IVGTT-based simple assessment of glucose tolerance in the Zucker fatty rat: Validation against minimal models

For the assessment of glucose tolerance from IVGTT data in Zucker rat, minimal model methodology is reliable but time- and money-consuming. This study aimed to validate for the first time in Zucker rat, simple surrogate indexes of insulin sensitivity and secretion against the glucose-minimal-model insulin sensitivity index (SI) and against first- (Φ1) and second-phase (Φ2) β-cell responsiveness indexes provided by C-peptide minimal model. Validation of the surrogate insulin sensitivity index (ISI) and of two sets of coupled insulin-based indexes for insulin secretion, differing from the cut-off point between phases (FPIR3-SPIR3, t = 3 min and FPIR5-SPIR5, t = 5 min), was carried out in a population of ten Zucker fatty rats (ZFR) and ten Zucker lean rats (ZLR). Considering the whole rat population (ZLR+ZFR), ISI showed a significant strong correlation with SI (Spearman's correlation coefficient, r = 0.88; P<0.001). Both FPIR3 and FPIR5 showed a significant (P<0.001) strong correlation with Φ1 (r = 0.76 and r = 0.75, respectively). Both SPIR3 and SPIR5 showed a significant (P<0.001) strong correlation with Φ2 (r = 0.85 and r = 0.83, respectively). ISI is able to detect (P<0.001) the well-recognized reduction in insulin sensitivity in ZFRs, compared to ZLRs. The insulin-based indexes of insulin secretion are able to detect in ZFRs (P<0.001) the compensatory increase of first- and second-phase secretion, associated to the insulin-resistant state. The ability of the surrogate indexes in describing glucose tolerance in the ZFRs was confirmed by the Disposition Index analysis. The model-based validation performed in the present study supports the utilization of low-cost, insulin-based indexes for the assessment of glucose tolerance in Zucker rat, reliable animal model of human metabolic syndrome.

Insulin secretion and sensitivity in healthy adults with low vitamin D are not affected by high-dose ergocalciferol administration: a randomized controlled trial

BACKGROUND

Epidemiologic data suggest that low serum 25-hydroxyvitamin D [25(OH)D] increases insulin resistance and the risk of type 2 diabetes. Few interventional trials have assessed the effect of vitamin D on insulin metabolism, and published results are discordant.

OBJECTIVE

The goal of this study was to perform a detailed assessment of the effect of ergocalciferol administration on glucose and insulin metabolism in healthy people with low total 25(OH)D(total).

DESIGN

This was a 12-wk, double-blinded, randomized controlled trial. We enrolled 90 healthy volunteers aged 18-45 y with serum 25(OH)D ≤20 ng/mL (by immunoassay) and administered 50,000 IU ergocalciferol/wk or placebo for 12 wk. Primary endpoints were change in first-phase insulin response and insulin sensitivity as measured by intravenous glucose tolerance test. Secondary endpoints included change in homeostasis model assessment of insulin resistance; fasting glucose, insulin, and lipids; body mass index (BMI); and blood pressure.

RESULTS

On-study 25(OH)D(total) was assessed by liquid chromatography-tandem mass spectrometry. In the treated group, 25(OH)D(total) rose from 18 ± 7 to 43 ± 12 ng/mL (P < 0.001) with no change in the placebo group. Despite this increase, at 12 wk, there were no between-group differences in either insulin response or insulin sensitivity; nor were there differences in any measured secondary endpoints. There was no evidence of effect modification by sex, race, glucose tolerance status, baseline 25(OH)D(total), or BMI.

CONCLUSION

In healthy persons with low 25(OH)D(total), ergocalciferol administration for 12 wk normalizes 25(OH)D(total) but does not improve insulin secretion, insulin sensitivity, or other markers of metabolic health.

Prevalence of Insulin Resistance in Subjects with Nonalcoholic Fatty Liver Disease and Its Predictors in a Chinese Population

OBJECTIVE

Insulin resistance (IR) is a key factor involved in the development and progression of nonalcoholic fatty liver disease (NAFLD). However, the prevalence of IR in NAFLD patients and its risk factors have been rarely reported, especially in China. This prospective study was undertaken to clarify these issues in the Chinese population.

METHODS

A total of 600 NAFLD patients and 300 age- and sex-matched healthy controls were recruited between January 1, 2011, and December 31, 2013. Demographic information and clinical characteristics were collected, and the presence of IR was evaluated using the homeostasis model. Uni- and multivariate analyses were conducted, and receiver operating characteristic (ROC) curves were generated to identify IR predictors.

RESULTS

NAFLD patients had a much higher prevalence of IR than healthy controls (37.8 vs. 2.3 %, P < 0.001). The rates of elevated alanine transferase (ALT) and aspartate transferase (AST) levels were much higher in NAFLD patients with IR than those without (53.7 vs. 41.6 % and 28.6 vs. 18.2 %, respectively, P < 0.001). Uni- and multivariate analyses revealed that female sex, general obesity, abdominal obesity, and hypertension were independent predictors for IR. The area under the ROC curve for fasting plasma insulin (FPI) detecting IR was 0.93 (P < 0.001), and the optimal cutoff was 11.3 μU/ml (sensitivity = 0.86, specificity = 0.92).

CONCLUSION

Chinese NAFLD patients are susceptible to IR. Female sex, general and abdominal obesity, and hypertension were independent predictors for IR in NAFLD patients. FPI is an optimal predictor for IR.

Insulin resistance in moderate to severe obstructive sleep apnea in nondiabetics and its response to continuous positive airway pressure treatment

Background:

The effects of nasal continuous positive airway pressure (CPAP) on insulin resistance (IR) in obstructive sleep apnea (OSA) are still under discussion especially in nondiabetics. Trials have found conflicting results in this regard.

Aims:

The study was to measure IR in nondiabetic patients with moderate to severe OSA and to evaluate the effect of nasal CPAP on IR in these patients.

Materials and Methods:

A total of 30 consecutively newly diagnosed patients with moderate to severe OSA was enrolled in the study. OSA was diagnosed by doing an overnight polysomnography. Plasma glucose and insulin levels were measured at baseline and after 1 month of CPAP treatment. IR was calculated by homeostasis model assessment (HOMA) method.

Results:

Of 30 OSA patients, 21 were males, and 9 were females. The mean age of the subjects was 49.9 years, and mean body mass index (BMI) was 29.33. All 30 patients had moderate to severe OSA with a mean apnea and hypopnea index (AHI) of 80.46/h. The Epworth sleepiness score (ESS) showed a significant change with 1 month of treatment with CPAP from baseline of 13 to 9.7 (P ≤ 0.0001). There was a significant reduction in fasting insulin levels from 21.75 to 19.39 (P = 0.009). There was a small fall in fasting glucose, but it was not significant. The HOMA IR also reduced from 5.78 to 4.82 which was significant (P = 0.024) without any significant change in BMI (P = 0.916). The HOMA IR did not showed any positive correlation with different variables of OSA severity, ESS (r = 0.156) (P = 0.410), AHI (r = 0.177) (P = 0.349), and percentage of test time <90% saturation (r = −0.296) (P = 0.112).

Conclusion:

Moderate to severe OSA is associated with an increase in IR and effective treatment with CPAP rapidly improves the insulin sensitivity in nondiabetic patients with OSA without any change in BMI.

Impact of glucose dosing regimens on modeling of glucose tolerance and β-cell function by intravenous glucose tolerance test in diet-induced obese mice

Insulin sensitivity declines in overweight and obese individuals and, under normal conditions, insulin secretion adaptively increases which in healthy non‐diabetic subjects maintains normal glycemia. This adaptation is best described by the disposition index derived from modeling of insulin and glucose data from an intravenous glucose tolerance testing (IVGTT). One caveat of the IVGTT is that basing the glucose dose on the individual total body weight can result in large differences in the amount of glucose given to lean and obese individuals. The effect this has on determination of insulin sensitivity and β‐cell function is unknown. In this study, we therefore evaluated alternative glucose dosing regimens for determination of the impact of glucose dosing on measures of β‐cell function in normal and diet‐induced obese (DIO) mice. The glucose dosing regimens used for the IVGTT were 0.35 mg per kg total body weight (BW) or per kg lean BW or a fixed glucose dose based on the average BW for all experimental mice. Each regimen detected a similar decrease in insulin sensitivity in DIO mice. The different glucose dosing regimens gave, however, diverging results in regard to glucose elimination and the acute insulin response. Thus, the fixed‐dose regimen was the only that revealed impairment of glucose elimination, whereas dosing according to total BW was the only regimen which showed significant increases in acute insulin response in DIO mice. The fixed‐dose glucose dosing regimen was the only that revealed a significant decline in the disposition index value in DIO mice, which is characteristic of type 2 diabetes in humans. Our results therefore show that using different glucose dosing regimens during IVGTT in DIO mice one can model different aspects of physiology which are similar to prediabetes and type 2 diabetes in humans, with the fixed‐dose regimen producing a phenotype that most closely resembles human type 2 diabetes.

It is unclear what effect the amount of glucose given during an intravenous glucose tolerance test has on measures of glucose tolerance in diet‐induced obese mice. We tested glucose dosing based on total body weight, lean body mass, or a body weight‐independent fixed dose. The fixed‐dose glucose dosing regimen was the only that revealed impaired insulin sensitivity, insufficient insulin secretion, and a diminished disposition index, all hallmarks of type 2 diabetes, and is thus the optimal glucose dosing regimen for intravenous glucose tolerance testing in diet‐induced obese mice.

A novel approach to monitor glucose metabolism using stable isotopically labelled glucose in longitudinal studies in mice

The aetiology of insulin resistance is still an enigma. Mouse models are frequently employed to study the underlying pathology. The most commonly used methods to monitor insulin resistance are the HOMA-IR, glucose or insulin tolerance tests and the hyperinsulinemic euglycaemic clamp (HIEC). Unfortunately, these tests disturb steady state glucose metabolism. Here we describe a method in which blood glucose kinetics can be determined in fasted mice without noticeably perturbing glucose homeostasis. The method involves an intraperitoneal injection of a trace amount of [6,6-2H2]glucose and can be performed repeatedly in individual mice. The validity and performance of this novel method was tested in mice fed on chow or high-fat diet for a period of five weeks. After administering the mice with [6,6-2H2]glucose, decay of the glucose label was followed in small volumes of blood collected by tail tip bleeding during a 90-minute period. The total amount of blood collected was less than 120 μL. This novel approach confirmed in detail the well-known increase in insulin resistance induced by a high-fat diet. The mice showed reduced glucose clearance rate, and reduced hepatic and peripheral insulin sensitivity. To compensate for this insulin resistance, β-cell function was slightly increased. We conclude that this refinement of existing methods enables detailed information of glucose homeostasis in mice. Insulin resistance can be accurately determined while mechanistic insight is obtained in underlying pathology. In addition, this novel approach reduces the number of mice needed for longitudinal studies of insulin sensitivity and glucose metabolism.

Different types of dietary advice for women with gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) affects a significant number of women each year and is associated with a wide range of adverse outcomes for women and their babies. Dietary counselling is the main strategy in managing GDM, but it remains unclear which dietary therapy is best.

OBJECTIVES

To assess the effects of different types of dietary advice for women with GDM on pregnancy outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (17 May 2012) and the WOMBAT Perinatal Trials Registry (17 April 2012).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster-RCTs assessing the effects of different types of dietary advice for women with GDM on pregnancy outcomes.We intended to compare two or more forms of the same type of dietary advice against each other, i.e. standard dietary advice compared with individualised dietary advice, individual dietary education sessions compared with group dietary education sessions. We intended to compare different intensities of dietary intervention with each other, i.e. single dietary counselling session compared with multiple dietary counselling sessions.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed risk of bias of included studies. Data were checked for accuracy.

MAIN RESULTS

We included nine trials; 429 women (436 babies) provided outcome data. All nine included trials had small sample sizes with variation in levels of risk of bias. A total of 11 different types of dietary advice were assessed under six different comparisons, including:low-moderate glycaemic index (GI) food versus high-moderate GI food, low-GI diet versus high-fibre moderate-GI diet, energy-restricted diet versus no energy restriction diet, low-carbohydrate diet (≤ 45% daily total energy intake from carbohydrate) versus high-carbohydrate diet (≥ 50% daily total energy intake from carbohydrate), high-monounsaturated fat diet (at least 20% total energy from monounsaturated fat) versus high-carbohydrate diet (at least 50% total energy from carbohydrate), standard-fibre diet (American Diabetes Association (ADA) diet) (20 grams fibre/day) versus fibre-enriched diet (80 grams fibre/day).In the low-moderate GI food versus moderate-high GI food comparison, no significant differences were seen for macrosomia or large-for-gestational age (LGA), (two trials, 89 babies) (risk ratio (RR) 0.45, 95% confidence interval (CI) 0.10 to 2.08), (RR 0.95, 95% CI 0.27 to 3.36), respectively; or caesarean section (RR 0.66, 95% CI 0.29 to 1.47, one trial, 63 women).In the low-GI diet versus high-fibre moderate-GI diet comparison, no significant differences were seen for macrosomia or LGA (one trial, 92 babies) (RR 0.32, 95% CI 0.03 to 2.96), (RR 2.87, 95% CI 0.61 to 13.50), respectively; or caesarean section (RR 1.80, 95% CI 0.66 to 4.94, one trial, 88 women).In the energy-restricted versus unrestricted diet comparison, no significant differences were seen for macrosomia (RR 1.56, 95% CI 0.61 to 3.94, one trial, 122 babies); LGA (RR 1.17, 95% CI 0.65 to 2.12, one trial, 123 babies); or caesarean section (RR 1.18, 95% CI 0.74 to 1.89, one trial, 121 women).In the low- versus high-carbohydrate diet comparison, none of the 30 babies in a single trial were macrosomic; and no significant differences in caesarean section rates were seen (RR 1.40, 95% CI 0.57 to 3.43, one trial, 30 women).In the high-monounsaturated fat versus high-carbohydrate diet comparison, neither macrosomia or LGA (one trial 27 babies) (RR 0.65, 95% CI 0.91 to 2.18), (RR 0.54 95% CI 0.21 to 1.37), respectively showed significant differences. Women having a high-monounsaturated fat diet had a significantly higher body mass index (BMI) at birth (mean difference (MD) 3.90 kg/m², 95% CI 2.41 to 5.39, one trial, 27 women) and at six to nine months postpartum (MD 4.10 kg/m², 95% CI 2.34 to 5.86, one trial, 27 women) when compared with those having a high-carbohydrate diet. However, these findings were based on a single, small RCT with baseline imbalance in maternal BMI.Perinatal mortality was reported in only trial which recorded no fetal deaths in either the energy- restricted or unrestricted diet group.A single trial comparing ADA diet (20 grams gram fibre/day) with fibre-enriched fibre enriched diet (80 grams gram fibre/day) did not report any of our prespecified primary outcomes.Very limited data were reported on the prespecified outcomes for each of the six comparisons. Only one trial reported on early postnatal outcomes. No trial reported long-term health outcomes for women and their babies. No data were reported on health service cost or women's quality of life.

AUTHORS' CONCLUSIONS

Data for most comparisons were only available from single studies and they are too small for reliable conclusions about which types of dietary advice are the most suitable for women with GDM. Based on the current available evidence, we did not find any significant benefits of the diets investigated.Further larger trials with sufficient power to assess the effects of different diets for women with GDM on maternal and infant health outcomes are needed. Outcomes such as longer-term health outcomes for women and their babies, women's quality of life and health service cost should be included.

Acute exercise reverses starvation-mediated insulin resistance in humans

Within 2-3 days of starvation, pronounced insulin resistance develops, possibly mediated by increased lipid load. Here, we show that one exercise bout increases mitochondrial fatty acid (FA) oxidation and reverses starvation-induced insulin resistance. Nine healthy subjects underwent 75-h starvation on two occasions: with no exercise (NE) or with one exercise session at the end of the starvation period (EX). Muscle biopsies were analyzed for mitochondrial function, contents of glycogen, and phosphorylation of regulatory proteins. Glucose tolerance and insulin sensitivity, measured with an intravenous glucose tolerance test (IVGTT), were impaired after starvation, but in EX the response was attenuated or abolished. Glycogen stores were reduced, and plasma FA was increased in both conditions, with a more pronounced effect in EX. After starvation, mitochondrial respiration decreased with complex I substrate (NE and EX), but in EX there was an increased respiration with complex I + II substrate. EX altered regulatory proteins associated with increases in glucose disposal (decreased phosphorylation of glycogen synthase), glucose transport (increased phosphorylation of Akt substrate of 160 kDa), and FA oxidation (increased phosphorylation of acetyl-CoA carboxylase). In conclusion, exercise reversed starvation-induced insulin resistance and was accompanied by reduced glycogen stores, increased lipid oxidation capacity, and activation of signaling proteins involved in glucose transport and FA metabolism.

GLUCOSE TOLERANCE TESTS MODELING & PATIENT-SIMULATION FOR DIAGNOSIS

Diabetes mellitus is a heterogeneous clinical syndrome characterized by hyperglycemia and long-term specific complications: retinopathy, neuropathy, nephropathy, and cardiomyopathy. Automatic neuropathy leads to visceral denervation producing a variety of clinical abnormalities: cardiac and respiratory dysrythaemias, gastrointestinal motility disorders, urinary bladder dysfunction and impotence. Diabetes mellitus is a leading cause of blindness; renal failure and limb amputation all over the world. The need to detect diabetic risk factors and treat organ disorders and complications associated with diabetes provides the impetus for us to develop the technology for assessment of diabetes, its etiology and severity, as well as for assessing the efficacy of pharmacological therapy.

This paper concerns:

(i) modelling of blood-glucose regulation and tolerance-testing,

(ii) demonstrating patient-simulation of the blood-glucose regulatory models, by means of which the model parameters can be evaluated and related to physiological parameters, and

(iii) elucidating how the glucose-regulatory system model's pole-zero representation and the blood glucose-insulin transfer-function can explain the blood glucose response data in intravenous and oral glucose tolerance tests.

An easy-to-implement simple clinical-application method is developed to simulate the response of the blood-glucose regulatory model in diabetic patients during intravenous glucose tolerance test and to estimate the model parameters, which can then enable differential diagnosis of diabetes and its severity as well as in early detection of risk-to-diabetes.

In the oral glucose-tolerance test, the role of the gut is to facilitate transport of glucose across the intestinal wall. The Michaelis-Menten equation, describing this enzyme-catalyzed reaction rate, can be employed to conclude that the intestinal glucose absorption rate into the blood-compartment from the gut during the oral glucose-tolerance test is constant, almost resembling a rectangular pulse Nevertheless, we have formulated a new rate-control model to simulate the oral glucose-tolerance test data, by means of the response-function of a second-order system of a single-compartment (consisting of the gut and the blood-glucose pool), with the oral glucose-bolus as the impulse-input.

We have also demonstrated application of this rate-control model to patients undergoing oral glucose-tolerance test, to evaluate the model parameters. By categorizing the ranges of these parameters for normals and diabetics (varying from mild to severe), we can reliably apply this model and procedure clinically.

Impact of birth weight and early infant weight gain on insulin resistance and associated cardiovascular risk factors in adolescence

Background

Low birth weight followed by accelerated weight gain during early childhood has been associated with adverse metabolic and cardiovascular outcomes later in life. The aim of this study was to examine the impact of early infant weight gain on glucose metabolism and cardiovascular risk factors in adolescence and to study if the effect differed between adolescents born small for gestational age (SGA) vs. appropriate for gestational age (AGA).

Methodology/Principal Findings

Data from 30 SGA and 57 AGA healthy young Danish adolescents were analysed. They had a mean age of 17.6 years and all were born at term. Data on early infant weight gain from birth to three months as well as from birth to one year were available in the majority of subjects. In adolescence, glucose metabolism was assessed by a simplified intravenous glucose tolerance test and body composition was assessed by dual-energy X-ray absorptiometry. Blood pressures as well as plasma concentrations of triglycerides and cholesterol were measured. Early infant weight gain from birth to three months was positively associated with the fasting insulin concentration, HOMA-IR, basal lipid levels and systolic blood pressure at 17 years. There was a differential effect of postnatal weight gain on HOMA-IR in AGA and SGA participants (P for interaction = 0.03). No significant associations were seen between postnatal weight gain and body composition or parameters of glucose metabolism assessed by the simplified intravenous glucose tolerance test. In subgroup analysis, all associations with early infant weight gain were absent in the AGA group, but the associations with basal insulin and HOMA-IR were still present in the SGA group.

Conclusion

This study suggests that accelerated growth during the first three months of life may confer an increased risk of later metabolic disturbances – particularly of glucose metabolism – in individuals born SGA.

Design and clinical pilot testing of the model-based dynamic insulin sensitivity and secretion test (DISST)

BACKGROUND

Insulin resistance is a significant risk factor in the pathogenesis of type 2 diabetes. This article presents pilot study results of the dynamic insulin sensitivity and secretion test (DISST), a high-resolution, low-intensity test to diagnose insulin sensitivity (IS) and characterize pancreatic insulin secretion in response to a (small) glucose challenge. This pilot study examines the effect of glucose and insulin dose on the DISST, and tests its repeatability.

METHODS

DISST tests were performed on 16 subjects randomly allocated to low (5 g glucose, 0.5 U insulin), medium (10 g glucose, 1 U insulin) and high dose (20 g glucose, 2 U insulin) protocols. Two or three tests were performed on each subject a few days apart.

RESULTS

Average variability in IS between low and medium dose was 10.3% (p=.50) and between medium and high dose 6.0% (p=.87). Geometric mean variability between tests was 6.0% (multiplicative standard deviation (MSD) 4.9%). Geometric mean variability in first phase endogenous insulin response was 6.8% (MSD 2.2%). Results were most consistent in subjects with low IS.

CONCLUSIONS

These findings suggest that DISST may be an easily performed dynamic test to quantify IS with high resolution, especially among those with reduced IS.

Low-carbohydrate diet does not affect intramyocellular lipid concentration or insulin sensitivity in lean, physically fit men when protein intake is elevated

It has been speculated that dietary carbohydrate restriction is solely responsibly for mobilization of endogenous lipid stores, elevation of plasma free fatty acid (FFA) concentration, and an associated reduction in insulin sensitivity seen in starvation and low-carbohydrate diets. In 6 healthy men, dietary carbohydrate was eliminated but gluconeogenic substrate supply was maintained by 3 days of very low-carbohydrate/high-protein (HPLC) diet. Results were compared with 3-day starvation and 3-day mixed-carbohydrate diet. Intramyocellular lipid (IMCL) concentration was measured by ¹H magnetic resonance spectroscopy, and insulin sensitivity was determined by intravenous glucose tolerance test. Fasting plasma glucose was significantly reduced ([starvation] 3.5 ± 0.3 vs [HPLC] 4.2 ± 0.4 and [mixed] 4.5 ± 0.3 mmol L⁻¹, P < .01), and IMCL to water ratio (25.6 ± 5.9 vs 13.6 ± 6.1 and 13.6 ± 3.3 × 10⁻³, P < .01) and fasting FFA (1179 ± 294 vs 387 ± 232 and 378 ± 120 μmol L⁻¹, P < .05) were significantly elevated after starvation but were unchanged after HPLC. Minimal model insulin sensitivity was reduced after starvation (5.7 ± 1.5 vs 14.5 ± 4.8 and 16.5 ± 6.8 L min⁻¹ mU⁻¹, P < .05). Plasma glucose, plasma FFAs, IMCLs, and insulin sensitivity are maintained when an HPLC diet is consumed, despite other forms of carbohydrate deprivation producing marked changes in these measures. We conclude that dietary carbohydrate restriction does not cause circulating FFA to become elevated. However, it remains possible that circulating carbohydrate status has an important influence on plasma FFA and therefore insulin sensitivity in healthy people.

An empirical index of insulin sensitivity from short IVGTT: validation against the minimal model and glucose clamp indices in patients with different clinical characteristics

AIMS/HYPOTHESIS

Minimal model analysis for insulin sensitivity has been validated against the glucose clamp and is an accepted method for estimating insulin sensitivity from IVGTT. However minimal model analysis requires a 3 h test and relevant expertise to run the mathematical model. The aim of this study was to suggest a simple predictor of minimal model analysis index using only 1 h IVGTT.

METHODS

We studied participants with different clinical characteristics who underwent 3 h regular (n = 336) or insulin-modified (n = 160) IVGTT, or 1 h IVGTT and euglycaemic-hyperinsulinaemic clamp (n = 247). Measures of insulin sensitivity were insulin sensitivity index estimated by minimal model analysis (S(I)) and the mean glucose infusion rate (clamp) (M). A calculated S(I) (CS(I)) predictor, CS(I) = Alpha X K(G)/(DeltaAUC(INS)/T), was suggested, based on the calculation of the rate of glucose disappearance K(G) and the suprabasal AUC of insulin concentration DeltaAUC(INS) over T = 40 min. For all the participants, alpha was assumed equal to the regression line slope between K(G)/(DeltaAUC(INS)/T) and S(I) in control participants.

RESULTS

CS(I) and S(I) showed high correlation (R(2) = 0.68-0.96) and regression line slopes of approximately one in the majority of groups. CS(I) tended to overestimate S(I) in type 2 diabetic participants, but results were more reliable when CS(I) was computed with insulin-modified rather than regular IVGTT. CS(I) showed behaviours similar to S(I) as regards relationships with BMI, acute insulin response and sex. CS(I) showed good correlation with M (R(2) = 0.82).

CONCLUSIONS/INTERPRETATION

A short test can achieve a good approximation of minimal model analysis and clamp insulin sensitivity. The importance of a method such as CS(I) is that it allows analysis of IVGTT datasets with samples limited to 1 h.

DISTq: An Iterative Analysis of Glucose Data for Low-Cost, Real-Time and Accurate Estimation of Insulin Sensitivity

Insulin sensitivity (SI) estimation has numerous uses in medical and clinical situations. However, highresolution tests that are useful for clinical diagnosis and monitoring are often too intensive, long and costly for regular use. Simpler tests that mitigate these issues are not accurate enough for many clinical diagnostic or monitoring scenarios. The gap between these tests presents an opportunity for new approaches.

The quick dynamic insulin sensitivity test (DISTq) utilises the model-based DIST test protocol and a series of population estimates to eliminate the need for insulin or C-peptide assays to enable a high resolution, low-intensity, real-time evaluation of SI. The method predicts patient specific insulin responses to the DIST test protocol with enough accuracy to yield a useful clinical insulin sensitivity metric for monitoring of diabetes therapy.

The DISTq method replicated the findings of the fully sampled DIST test without the use of insulin or C-peptide assays. Correlations of the resulting SI values was R=0.91. The method was also compared to the euglycaemic hyperinsulinaemic clamp (EIC) in an in-silico Monte-Carlo analysis and showed a good ability to re-evaluate SI_EIC (R=0.89), compared to the fully sampled DIST (R=0.98)

Population-derived parameter estimates using a-posteriori population-based functions derived from DIST test data enables the simulation of insulin profiles that are sufficiently accurate to estimate SI to a relatively high precision. Thus, costly insulin and C-peptide assays are not necessary to obtain an accurate, but inexpensive, real-time estimate of insulin sensitivity. This estimate has enough resolution for SI prediction and monitoring of response to therapy. In borderline cases, re-evaluation of stored (frozen) blood samples for insulin and C-peptide would enable greater accuracy where necessary, enabling a hierarchy of tests in an economical fashion.

Increased prevalence of insulin resistance in patients with differentiated thyroid carcinoma

BACKGROUND

Patients with insulin resistance (IR) have a higher prevalence of thyroid nodules. In the present study, we present original data showing that patients with differentiated thyroid carcinoma (DTC) also have a higher frequency of IR.

METHODS

Twenty women with DTC (group 1, G1) and 20 euthyroid individuals (control group, CG) were investigated for IR. G1 and CG subjects were matched in pairs by age, gender, and body mass index (BMI). The diagnosis of IR was made when the homeostasis model assesment of insulin resistance (HOMA-IR) index was higher than 2.5. According to the BMI, 20 women (10 with DTC and 10 of the CG) had a BMI < 25, whereas the other 20 had higher BMI values (overweight and obese patients).

RESULTS

IR was present in the 50% of G1, but only in the 10% of the CG (P < 0.001). In the groups with lower BMI (<25), we found IR in 30% of G1 and no cases in the CG, whereas in those with BMI > 25 the IR was present in 70% of G1 and 20% of CG. There were no differences between the two subgroups regarding the time in which the IR tests were performed. IR was present in 56.3% of patient with papillary anol 25% of follicular thyroid carcinomas, respectively.

CONCLUSIONS

We conclude that such a high prevalence of IR would be an important risk factor for developing DTC, as it is well known with some other nonthyroid carcinomas.

Evaluation of different methods for assessment of insulin sensitivity in Gottingen minipigs: introduction of a new, simpler method

The use of animal models in diabetes research requires reliable tests for evaluation of insulin sensitivity and beta-cell function. Minipigs are being increasingly used in metabolic research, and the aim of this study was to compare different tests and indexes for evaluation of insulin sensitivity and beta-cell function in Göttingen minipigs. Hyperinsulinemic, isoglycemic clamp, intravenous (IVGTT) and oral glucose tolerance tests (OGTT), and a modified insulin tolerance test were performed in minipigs fed either low- or high-energy diet. Furthermore, the reproducibility of IVGTT-derived parameters was assessed. Previously described insulin sensitivity indexes [steady-state glucose infusion rate/glucose concentration/insulin concentration from clamp (M/G/I); oral glucose insulin sensitivity (OGIS) and ISI(comp) from OGTT; S(I) from minimal model analysis of IVGTT; and quantitative insulin sensitivity check index from fasting values] were calculated together with an insulin sensitivity index from the modified insulin tolerance test (ISI(ITT)) and a new simple index (S2) derived from the first 30 min of the IVGTT. beta-Cell function was assessed from the IVGTT and the OGTT. Reproducibility of the IVGTT-derived parameters was calculated as median intraindividual coefficient of variation (CV%).M/G/I correlated significantly only with S2 (P < 0.05, r = 0.54). S2 furthermore correlated with S(I) (P < 0.001, r = 0.81), ISI(ITT) (P < 0.001, r = 0.57), and the two indexes from OGTT, ISI(comp) (P < 0.001, r = 0.78) and OGIS (p < 0.05, r = 0.48). No correlation was found between beta-cell function indexes from OGTT and IVGTT. The median CV% of the new S2 index was 13. In conclusion, the new simple index of insulin sensitivity, S2, was revealed to be useful for evaluation of insulin sensitivity in pigs.

Computer controlled sequential simulation method: reconsidering evaluation of measurements from frequently sampled intravenous glucose tolerance test

This work describes quantification of regulatory mechanisms glucose-insulin, using data from a frequently sampled intravenous glucose tolerance test (FSIVGTT) and a mechanistically motivated model with time delays. FSIVGTT was performed on 14 young healthy volunteers. The constructed model computationally takes into account the form of the short-time glucose infusion used. Estimated model parameters are used to derive relationships quantifying the following mechanisms of regulatory systems glucose-insulin of the volunteers enrolled: (1) glucose uptake by body cells; (2) cessation (suppression) of glucose output from liver; (3) glucose clearance. The model presented correctly approximates initial peaks and subsequent waves in plasma glucose concentration-time profiles after the glucose infusion. These results indicate that the model presented is an appropriate tool for assessing glucose behavior during a FSIVGTT.

Telmisartan and metabolic syndrome after heart transplantation

INTRODUCTION

Metabolic syndrome (MS) is a cardiovascular risk predictor. Prevalence of MS after heart transplantation (HTx) is high. Recent data suggest a positive metabolic effect of telmisartan.

AIM

To describe the influence of telmisartan on lipid and glycide metabolism in MS after HTx.

METHODS

Fifteen patients aged 55+/-12 yr, 88+/-25 months after HTx with MS receiving statins were followed. The reason for telmisartan administration was arterial hypertension with either drug intolerance or poor control. Body mass index (BMI), waist circumference, total cholesterol, low density lipoprotein LDL-cholesterol, high density lipoprotein-cholesterol, triglycerides, C-reactive protein (CRP), fasting glucose, immunoreactive insulin (IRI), C-peptide and the homeostasis model assessment (HOMA) index were determined. Ambulatory blood pressure monitoring was performed. After initial evaluation, telmisartan 80 mg was started. After 20 +/- 5 wk follow-up, identical parameters were measured. Statistical significance was evaluated using Student's t-test.

RESULTS

BMI, waist circumference, systolic and diastolic blood pressures, serum lipids and CRP remained unchanged after telmisartan. Significant reduction in fasting glucose (6.7 vs. 5.6 mmol/L, p < 0.02), IRI (8.8 vs. 8.5 U/mL p = 0.05), HOMA (7.3 vs. 5.8 mmol/L x muU/mL, p < 0.05) and C-peptide (4.0 vs. 3.3 ng/mL, p < 0.02) was found.

CONCLUSIONS

Telmisartan had a positive impact on insulin sensitivity parameters (fasting glucose, IRI, C-peptide and HOMA) in this population. No effect on obesity, serum lipids and systemic inflammation was observed.

Reappraisal of the intravenous glucose tolerance index for a simple assessment of insulin sensitivity in mice

Mice are increasingly used in studies where measuring insulin sensitivity (IS) is a common procedure. The glucose clamp is labor intensive, cannot be used in large numbers of animals, cannot be repeated in the same mouse, and has been questioned as a valid tool for IS in mice; thus, the minimal model with 50-min intravenous glucose tolerance test (IVGTT) data was adapted for studies in mice. However, specific software and particular ability was needed. The aim of this study was to establish a simple procedure for evaluating IS during IVGTT in mice (CS(I)). IVGTTs (n = 520) were performed in NMRI and C57BL/6J mice (20-25g). After glucose injection (1 g/kg), seven samples were collected for 50 min for glucose and insulin measurements, analyzed with a minimal model that provided the validated reference IS (S(I)). By using the regression CS(I) = alpha(1) + alpha(2) x K(G)/AUC(D), where K(G) is intravenous glucose tolerance index and AUC(d) is the dynamic area under the curve, IS was calculated in 134 control animals randomly selected (regression CS(I) vs. S(I): r = 0.66, P < 0.0001) and yielded alpha(1) = 1.93 and alpha(2) = 0.24. K(G) is the slope of log (glucose(5-20)) and AUC(D) is the mean dynamic area under insulin curve in the IVGTT. By keeping fixed alpha(1) and alpha(2), CS(I) was validated in 143 control mice (4.7 +/- 0.2 min*microU(-1)*ml(-1), virtually identical to S(I): 4.7 +/- 0.3, r = 0.89, P < 0.0001); and in 123 mice in different conditions: transgenic, addition of neuropeptides, incretins, and insulin (CS(I): 6.0 +/- 0.4 vs. S(I): 6.1 +/- 0.4, r = 0.94, P < 0.0001). In the other 120 animals, CS(I) revealed its ability to segregate different categories, as does S(I). This easily usable formula for calculating CS(I) overcomes many experimental obstacles and may be a simple alternative to more complex procedures when large numbers of mice or repeated experiments in the same animals are required.

The effect of birthweight upon insulin resistance and associated cardiovascular risk factors in adolescence is not explained by fetal growth velocity in the third trimester as measured by repeated ultrasound fetometry

AIMS/HYPOTHESIS

Smallness for gestational age (SGA) is associated with increased risk of developing components of the metabolic syndrome. Although SGA can imply intrauterine growth restriction (IUGR), more information is required to link specific fetal growth patterns to adult outcomes.

METHODS

We examined the impact of fetal growth velocity during the third trimester (FGV) vs birthweight for gestational age on early markers of the metabolic syndrome in 123 healthy men and women (mean age 17.5 years) born at term. FGV was determined by ultrasound measurements.

RESULTS

After correction for confounders including current BMI, SGA was significantly associated with raised basal plasma insulin (+19% above appropriate for gestational age), homeostasis model assessment of insulin resistance (+21%), cholesterol:HDL-cholesterol ratio (+13%) and systolic BP (+4.8%) (all p < 0.05). Furthermore SGA was associated with increased fat mass (+9.6%) and trunk-fat per cent (+6.8%) and with reduced lean body mass as determined by dual-energy X-ray absorptiometry scans (-4.1% below appropriate for gestational age) (all p < 0.05). In contrast, IUGR in the third trimester was associated only with an elevated cholesterol:HDL-cholesterol ratio (+11% above not-IUGR).

CONCLUSIONS/INTERPRETATION

In the present study, FGV did not explain the impact of birthweight upon the metabolic phenotype in adolescence. This suggests that fetal growth prior to the third trimester or postnatal catch-up growth plays a more important role.

Diet restriction and ageing in the dog: major observations over two decades

This report reviews decade two of the lifetime diet restriction study of the dog. Labrador retrievers (n 48) were paired at age 6 weeks by sex and weight within each of seven litters, and assigned randomly within the pair to control-feeding (CF) or 25 % diet restriction (DR). Feeding began at age 8 weeks. The same diet was fed to all dogs; only the quantity differed. Major lifetime observations included 1.8 years longer median lifespan among diet-restricted dogs, with delayed onset of late life diseases, especially osteoarthritis. Long-term DR did not negatively affect skeletal maturation, structure or metabolism. Among all dogs, high static fat mass and declining lean body mass predicted death, most strongly at 1 year prior. Fat mass above 25 % was associated with increasing insulin resistance, which independently predicted lifespan and chronic diseases. Metabolizable energy requirement/lean body mass most accurately explained energy metabolism due to diet restriction; diet-restricted dogs required 17 % less energy to maintain each lean kilogram. Metabonomics-based urine metabolite trajectories reflected DR-related differences, suggesting that signals from gut microbiota may be involved in the DR longevity and health responses. Independent of feeding group, increased hazard of earlier death was associated with lower lymphoproliferative responses to phytohaemagglutinin, concanavalin A, and pokeweed mitogen; lower total lymphocytes, T-cells, CD4 and CD8 cells; lower CD8 percentages and higher B-cell percentages. When diet group was taken into account, PWM responses and cell counts and percentages remained predictive of earlier death.

First phase release coefficient of insulin in subjects with normal glucose tolerance on glucose infusion analyzed by computer simulation

We report here a mathematical model using computer simulation to solve the phase fractionation coefficient (f) of instantaneous insulin release on glucose infusion. By extensive model testing with the cited parameters obtained from the literature, the values of the factor f were shown to lie in range of 0.93+/-0.02 (mean+/-2S.D., n=15), indicating that the high pulsatile bolus of glucose by i.v. infusion may trigger acute insulin release (AIR) corresponding to a fraction of more than 90% of the stored insulin release in the first phase from the secretory granules of pancreatic beta cells. In addition, the value of the factor f was shown to be independent of both the glucose infusion method and the non-insulin-dependent uptake of glucose.

Variants of transcription factor 7-like 2 (TCF7L2) gene predict conversion to type 2 diabetes in the Finnish Diabetes Prevention Study and are associated with impaired glucose regulation and impaired insulin secretion

AIMS/HYPOTHESIS

We investigated the association of variants of the transcription factor 7-like 2 (TCF7L2) gene with: (1) incident diabetes in the Finnish Diabetes Prevention Study (DPS, Study I); (2) type 2 diabetes and impaired glucose regulation (i.e. IGT or IFG) in a cross-sectional study (Study II); and (3) insulin secretion, insulin sensitivity and adipose tissue expression of TCF7L2 in offspring of type 2 diabetic probands (III).

SUBJECTS AND METHODS

Study I (the DPS) included 507 individuals with IGT who were randomly allocated to control and intervention groups and followed for an average of 3.9 years to monitor for progression to diabetes. Study II was a population-based cross-sectional study of 1,766 men, aged 50-70 years, randomly selected from the population of Kuopio, eastern Finland. Study III included 238 non-diabetic offspring of patients with type 2 diabetes. Genotyping of rs12255372 and rs7903146 of TCF7L2 was carried out.

RESULTS

In the DPS, the TT genotype of rs12255372 was significantly associated with an adjusted 2.85-fold risk (95% CI 1.17-6.95, p = 0.021) of incident diabetes in the control group, but not in the intervention group. In Study II, the adjusted odds ratio in subjects with the TT genotype was 3.40 (1.45-7.97, p = 0.005) for the comparison of diabetic subjects with normoglycaemic subjects. The T allele of rs12255372 was significantly associated with decreased insulin secretion (Studies II, III). Expression of TCF7L2 in adipose tissue tended to be lower in subjects with the TT risk genotypes of rs12255372 and rs7903146.

CONCLUSIONS/INTERPRETATION

The variant of rs12255372 of TCF7L2 was associated with incident type 2 diabetes in the DPS and in a separate population-based cross-sectional study. Impaired insulin secretion is likely to be the main cause for our findings.

Short-term suppression of plasma free fatty acids fails to improve insulin sensitivity when intramyocellular lipid is elevated

AIMS

Metabolic responses to manipulation of the plasma free fatty acid (FFA) concentration were assessed in six healthy men via cross-over design to determine whether FFAs independently influence insulin sensitivity.

METHODS

Intramyocellular lipid (IMCL) was measured by proton magnetic resonance spectroscopy and insulin sensitivity via frequently sampled intravenous glucose tolerance test (IVGTT) after 67 h of two identical low carbohydrate/high fat (LC) diets which were used to elevate IMCL and plasma FFAs. To uncouple the influence of FFAs and IMCL on insulin sensitivity, FFAs were suppressed 30 min prior to and during IVGTT in one treatment [LC + nicotinic acid (NA)] by NA ingestion.

RESULTS

Vastus lateralis IMCL was significantly elevated in LC (13.3 +/- 1.1 x 10(-3)) and LC + NA (13.5 +/- 1.1 x 10(-3)) (P < 0.01 for both), but was not different between conditions (P > 0.05). Plasma FFAs were raised in LC (0.79 +/- 0.08 mmol/l) and LC + NA (0.80 +/- 0.11 mmol/l) (P < 0.01 for both) and were significantly reduced by NA ingestion prior to (0.36 +/- 0.05 mmol/l, P < 0.01) and during IVGTT (P < 0.05) in LC + NA. Despite marked differences in plasma FFA availability, insulin sensitivity and glucose tolerance were not different between LC and LC + NA (P > 0.05 for both).

CONCLUSIONS

Plasma FFAs appear to exert no immediate effect on insulin sensitivity/glucose tolerance independent of their action on intracellular lipid moieties. Further research is required to elucidate the duration of FFA suppression required to restore insulin sensitivity following lipid-induced insulin resistance.

Gallbladder disease is associated with insulin resistance in a high risk Hispanic population

BACKGROUND/AIMS

We tested whether cholesterol gallstone disease (GS) is associated to insulin resistance and serum C-reactive protein (CRP) in a high risk population.

METHODS

This was a nested case-control study on 881 Chilean subjects that included clinical examination, abdominal ultrasound and blood chemistries. Insulin resistance was determined by the homeostasis model assessment index (IR-HOMA).

RESULTS

Compared to controls (n = 582), age and sex adjusted median IR-(HOMA) was significantly elevated in subjects with GS (n = 299) (P < 0.001). Risks of GS in subjects with insulin resistance and different body mass index (BMI) were: BMI < 25, 2.2 (1.1-4.7); BMI 25-30, 1.5 (0.9-2.5) and BMI > 30, 1.7 (1.0-2.9). Risk of GS in subjects with metabolic syndrome was 1.7 (CI, 1.2-2.5) and with fatty liver, 1.5 (1.1-2.2). Risk of GS in subjects with CRP > 1 mg/dL was 1.0 (0.7-1.7).

CONCLUSIONS

GS is associated to insulin resistance, fatty liver and to metabolic syndrome, but not to serum CRP in a high risk Hispanic population. Insulin resistance could have a major role in the pathogenesis of GS favoring the production of cholesterol supersaturated bile and altering gallbladder function.

Common polymorphisms of calpain-10 are associated with abdominal obesity in subjects at high risk of type 2 diabetes

AIMS/HYPOTHESIS

The mechanisms by which the calpain-10 gene (CAPN10) affects the risk of type 2 diabetes are unclear. Therefore, we investigated the effects of four polymorphisms in CAPN10 (single nucleotide polymorphism [SNP]-43, SNP-44, Insertion/Deletion [Indel]-19 and SNP-63) on insulin secretion, insulin action and abdominal fat distribution in offspring of patients with type 2 diabetes.

SUBJECTS AND METHODS

Insulin secretion was determined by an IVGTT, insulin action by the hyperinsulinaemic-euglycaemic clamp and abdominal fat distribution by computed tomography in 158 non-diabetic offspring (age 34.9+/-6.3 years [mean+/-SD], BMI 26.2+/-4.9 kg/m(2)) of type 2 diabetic patients.

RESULTS

SNP-43 (p=0.009 over the three genotypes, adjusted for age, sex, BMI and family relationship) and haplotypes carrying the A allele of SNP-43 were associated with intra-abdominal fat area. The A allele of SNP-43 was associated with intra-abdominal fat area in men (p=0.014) but not in women. SNP-44, InDel-19 and SNP-63 were not associated with intra-abdominal fat area or insulin action. Furthermore, we demonstrated in a separate sample of middle-aged men (n=234) who had a history of type 2 diabetes in first-degree relatives that the A allele of SNP-43 was associated with a large waist circumference, and high insulin levels in an OGTT.

CONCLUSIONS/INTERPRETATION

SNP-43 of CAPN10 may contribute to the risk of diabetes by regulating abdominal obesity in subjects with high risk of type 2 diabetes.

Recombinant methionyl human leptin therapy in replacement doses improves insulin resistance and metabolic profile in patients with lipoatrophy and metabolic syndrome induced by the highly active antiretroviral therapy

CONTEXT

Highly active antiretroviral therapy (HAART) for HIV-1 infection has been associated with a metabolic syndrome characterized by insulin resistance, hyperlipidemia, and redistribution of body fat (lipodystrophy). A subset of patients with predominant lipoatrophy has low levels of the adipocyte-secreted hormone leptin.

OBJECTIVE

The objective of the study was to assess whether administration of recombinant methionyl human leptin (r-metHuLeptin) improves insulin resistance and other metabolic abnormalities in HIV+ leptin-deficient subjects with HAART-induced lipoatrophy.

DESIGN, SETTING, PATIENTS, AND INTERVENTION

We conducted a randomized, placebo-controlled, double-blinded, crossover study from 2002 to 2004 in seven HIV+ men with HAART-induced lipoatrophy, serum leptin level less than 3 ng/ml, and fasting triglyceride level greater than 300 mg/dl, who were administered placebo for 2 months before or after administration of r-metHuLeptin at physiological doses for an additional 2 months.

MAIN OUTCOME MEASURES

Insulin resistance, lipid levels, inflammatory markers, body composition, and HIV control were measured.

RESULTS

Compared with placebo, r-metHuLeptin therapy improved fasting insulin levels, insulin resistance (as expressed by the homeostasis model assessment index and an insulin suppression test), and high-density lipoprotein. Body weight and fat mass decreased on r-metHuLeptin, mainly due to a decrease in truncal fat but not peripheral fat or lean body mass. r-metHuLeptin was well tolerated, and HIV control was not adversely affected.

CONCLUSIONS

r-metHuLeptin replacement at physiological doses in HIV+ leptin-deficient patients with HAART-induced lipoatrophy improves insulin resistance, high-density lipoprotein, and truncal fat mass. Future larger and more long-term studies in HAART-induced lipoatrophy, including patients with more severe metabolic abnormalities, are warranted to evaluate the physiological and potentially therapeutic role of r-metHuLeptin for this condition and to fully clarify the underlying mechanisms of action.

Visceral obesity is associated with high levels of serum squalene

OBJECTIVE

To investigate the impact of visceral obesity on cholesterol metabolism in normoglycemic offspring of patients with type 2 diabetes.

RESEARCH METHODS AND PROCEDURES

The proportion of intra-abdominal fat (IAF) was measured by abdominal computer tomography, and serum cholesterol synthesis and absorption markers were determined by gas-liquid chromatography in 109 normoglycemic offspring of patients with type 2 diabetes. Insulin action was measured with the hyperinsulinemic euglycemic clamp. The gene encoding squalene synthase (farnesyl-diphosphate farnesyltransferase 1) was screened with the single-strand conformation polymorphism analysis and direct sequencing.

RESULTS

Cholesterol synthesis markers correlated positively with IAF (r = 0.213 to 0.309, p < or = 0.027) and negatively with the rates of insulin-stimulated whole-body glucose uptake (r = -0.372 to -0.248, p < or = 0.010). However, serum squalene, the first measured precursor of cholesterol synthesis, showed a positive correlation with IAF (r = 0.309, p = 0.001) without any association with subcutaneous fat or insulin sensitivity. Variation in the farnesyl-diphosphate farnesyltransferase 1 gene did not explain elevated serum squalene levels in viscerally obese subjects. From the cholesterol absorption markers, cholestanol was associated negatively with IAF and positively with whole-body glucose uptake (p < 0.05).

DISCUSSION

High serum squalene levels are associated with visceral obesity but not with subcutaneous obesity. Whether this finding is causally connected to visceral obesity remains to be established.

Effect of short-term starvationversushigh-fat diet on intramyocellular triglyceride accumulation and insulin resistance in physically fit men

It is currently believed that intramyocellular triglyceride (IMTG) accumulation and insulin resistance are a consequence of dietary fat ingestion and/or the elevated circulating lipid levels associated with chronic fat surplus. The purpose of this study was to compare the effect of short-term starvation versus low-carbohydrate (CHO)/high-fat diet on IMTG accumulation and the development of insulin resistance in physically fit men. Intramyocellular triglyceride content, measured as intramyocellular lipid (IMCL) by proton magnetic resonance spectroscopy (1H-MRS), and glucose tolerance/insulin sensitivity, assessed by frequently sampled intravenous glucose tolerance test (IVGTT), were determined after 67 h of: (a) water-only starvation (S); and (b) very low-CHO/high-fat diet (LC). These diets had in common significant restriction of CHO availability but large differences in fat content. All results were compared with those measured after a mixed CHO diet (C). Dietary interventions were administered by cross-over design. The level of dietary-induced IMTG accumulation (P = 0.46), insulin resistance (P = 0.27) and glucose intolerance (P = 0.29) was not different between S and LC treatments. Intramyocellular triglyceride content and insulin sensitivity were negatively correlated (r = -0.63, P < 0.01). Therefore, whilst insulin resistance may be due to fat accumulation at a cellular level, in the integrated human organism this outcome is not exclusively a function of dietary fat intake. The comparable level of IMTG accumulation and insulin resistance following S and LC may suggest that these metabolic perturbations are largely a consequence of the increased lipolytic response associated with CHO restriction.

High amount of visceral fat mass is associated with multiple metabolic changes in offspring of type 2 diabetic patients

OBJECTIVE

To investigate the relative contribution of total body fat mass (TFM) and intra-abdominal fat mass (IAFM) to metabolic consequences of obesity in offspring of type 2 diabetic parents.

DESIGN

Cross-sectional study of 129 nondiabetic offspring of diabetic parents (59 men, 70 women, age 35.7 +/- 6.3 y, body mass index 26.2 +/- 4.6 kg/m2). Study subjects were grouped according to TFM (assessed with bioelectrical impedance) and IAFM (assessed with CT). Insulin sensitivity was assessed with the euglycemic hyperinsulinemic clamp, insulin secretion with the intravenous glucose tolerance test and energy expenditure with indirect calorimetry. Furthermore, C-reactive protein (CRP) and adiponectin levels were measured.

RESULTS

Insulin resistance, low rates of oxidative and nonoxidative glucose disposal, high rates of lipid oxidation and reduced energy expenditure during hyperinsulinemia were associated with high IAFM, independently of TFM. Adiponectin level was reduced and CRP level increased in subjects with high IAFM.

CONCLUSIONS

The metabolic changes relating to obesity are largely attributable to high IAFM, and are present even in normal weight subjects with high IAFM.