Cross-sectional and longitudinal changes of glucose effectiveness in relation to glucose tolerance: the insulin resistance atherosclerosis study

Glucose Effectiveness Decreases in Relationship to a Subtle Worsening of Metabolic Parameters in Young Japanese with Normal Glucose Tolerance

Background: The aim of the study was to investigate the relationship between glucose effectiveness (Sg) and some metabolic parameters in male and female young Japanese. Methods: We measured plasma glucose and immunoreactive insulin levels in 1309 young Japanese persons (age <40 years) with normal glucose tolerance (NGT) before and at 30, 60, and 120 min during a 75 gram oral glucose tolerance test. We also measured serum adiponectin and high-sensitivity C-reactive protein (hsCRP) levels and oral glucose effectiveness (SgI_O), and investigated factors related to SgI_O. Results: The results of Spearman correlation analysis revealed that high-density lipoprotein cholesterol (HDL) and adiponectin were positively correlated with SgI_O, whereas the proportion of males, body mass index, waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure, triglycerides (TG), and hsCRP were inversely correlated with SgI_O. The results of multiple regression analysis indicated negative correlations between SgI_O and the proportion of males, WC, and SBP and a positive correlation with HDL. The results of multiple regression analysis excluding WC indicated negative correlations between SgI_O and the proportion of males, SBP, and TG and positive correlations with HDL and adiponectin. Conclusions: Sg decreased with a subtle worsening of metabolic parameters, even in young persons with NGT. Decreased Sg may be involved in the development of glucose intolerance in individuals with worse metabolic parameters.

Glucose effectiveness: Lessons from studies on insulin-independent glucose clearance in mice

Besides insulin-mediated transport of glucose into the cells, an important role is also played by the non-insulin-mediated transport. This latter process is called glucose effectiveness (acronym SG ), which is estimated by modeling of glucose and insulin data after an intravenous glucose administration, and accounts for ≈70% of glucose disposal. This review summarizes studies on SG , mainly in humans and rodents with focus on results achieved in model experiments in mice. In humans, SG is reduced in type 2 diabetes, in obesity, in liver cirrhosis and in some elderly populations. In model experiments in mice, SG is independent from glucose levels, but increases when insulin secretion is stimulated, such as after administration of the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide. SG is reduced in insulin resistance induced by high-fat feeding and by exogenous administration of glucagon. Glucose-dependent (insulin-independent) glucose disposal is therefore important for glucose elimination, and it is also well regulated. It might be of pathophysiological relevance for the development of type 2 diabetes, in particular during insulin resistance, and might also be a target for glucose-reducing therapy. Measuring SG is essentially important when carrying out metabolic studies to understand glucose homeostasis.

Decrease of FGF19 contributes to the increase of fasting glucose in human in an insulin-independent manner

PURPOSE

The ileum-derived fibroblast growth factor 19 (FGF19) plays key roles in hepatic glucose homeostasis in animals in an insulin-independent manner. Here, we analyzed the association of FGF19 with glucose effectiveness (GE, the insulin-independent glucose regulation), as well as hepatic glucose production (HGP) in Chinese subjects.

METHODS

GE was measured by frequently sampled intravenous glucose tolerance test (FSIVGTT) in normal glucose tolerance (NGT), isolated-impaired glucose tolerance (I-IGT), and isolated-impaired fasting glucose (I-IFG) subjects. The oral glucose tolerance test-derived surrogate of GE (oGE) was determined in NGT, I-IFG, combined glucose intolerance (CGI), and type 2 diabetes (T2DM) subjects. HGP was assessed by labeled ([3-³H]-glucose) hyperinsulinemic-euglycemic clamp in NGT subjects. Insulin secretion and sensitivity were calculated by the hyperglycemic and hyperinsulinemic-euglycemic clamps in a subgroup of NGT, I-IGT, and I-IFG subjects. Serum FGF19 levels were determined by ELISA.

RESULTS

FGF19 positively correlated with GE (r = 0.29, P = 0.004) as determined by FSIVGTT. The result was further confirmed by oGE (r = 0.261, P < 0.001). FGF19 was negatively associated with FPG (r = - 0.228, P = 0.025), but the association no longer existed after adjusting for GE (r = - 0.177, P = 0.086). FGF19 was negatively associated with basal HGP (r = - 0.697, P = 0.006). However, the correlation between FGF19 and insulin secretion and sensitivity were not found.

CONCLUSIONS

FGF19 levels are associated positively with GE and negatively with HGP. The increase of FPG in human is at least partially due to the decrease of FGF19 in an insulin-independent manner.

Glucose effectiveness and its components in relation to body mass index

BACKGROUND

Obesity is known to induce a deterioration of insulin sensitivity (S_I ), one of the insulin-dependent components of glucose tolerance. However, few studies investigated whether obesity affects also the insulin-independent component, that is glucose effectiveness (S_G ). This cross-sectional study aimed to analyse S_G and its components in different body mass index (BMI) categories.

MATERIALS AND METHODS

Three groups of subjects spanning different BMI (kg m^-2 ) categories underwent a 3-h frequently sampled intravenous glucose tolerance test: Lean (LE; 18.5 ≤ BMI < 25, n = 73), Overweight (OW; 25 ≤ BMI < 30, n = 90), and Obese (OB; BMI ≥ 30, n = 41). OB has been further divided into two subgroups, namely Obese I (OB-I; 30 ≤ BMI < 35, n = 27) and Morbidly Obese (OB-M; BMI ≥ 35, n = 14). Minimal model analysis provided S_G and its components at zero (GEZI) and at basal (BIE) insulin.

RESULTS

Values for S_G were 1.98 ± 1.30 × 10^-2 ·min^-1 in all subjects grouped and 2.38 ± 1.23, 1.84 ± 0.82, 1.59 ± 0.61 10^-2 ·min^-1 in LE, OW and OB, respectively. In all subjects grouped, a significant inverse linear correlation was found between the log-transformed values of S_G and BMI (r = -0.3, P < 0.0001). S_G was significantly reduced in OW and OB with respect to LE (P < 0.001) but no significant difference was detected between OB and OW (P = 0.35) and between OB-I and OB-M (P = 0.25). Similar results were found for GEZI. BIE was not significantly different among NW, OW and OB (P = 0.11) and between OB-I and OB-M (P ≥ 0.07).

CONCLUSIONS

S_G and its major component GEZI deteriorate in overweight individuals compared to those in the normal BMI range, without further deterioration when BMI increases above 30 kg m^-2 .

Assessing the predictive accuracy of oral glucose effectiveness index using a calibration model

PURPOSE

Current reference methods for measuring glucose effectiveness (GE) are the somatostatin pancreatic glucose clamp and minimal model analysis of frequently sampled intravenous glucose tolerance test (FSIVGTT), both of which are laborious and not feasible in large epidemiological studies. Consequently, surrogate indices derived from an oral glucose tolerance test (OGTT) to measure GE (oGE) have been proposed and used in many studies. However, the predictive accuracy of these surrogates has not been formally validated. In this study, we used a calibration model analysis to evaluate the accuracy of surrogate indices to predict GE from the reference FSIVGTT (Sg_MM).

METHODS

Subjects (n = 123, mean age 48 ± 11 years; BMI 35.9 ± 7.3 kg/m²) with varying glucose tolerance (NGT, n = 37; IFG/IGT, n = 78; and T2DM, n = 8) underwent FSIVGTT and OGTT on two separate days. Predictive accuracy was assessed by both root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE).

RESULTS

As expected, insulin sensitivity, Sg_MM, and oGE were reduced in subjects with T2DM and IFG/IGT when compared with NGT. Simple linear regression analyses revealed a modest but significant relationship between oGE and Sg_MM (r = 0.25, p < 0.001). However, using calibration model, measured Sg_MM and predicted Sg_MM derived from oGE were modestly correlated (r = 0.21, p < 0.05) with the best fit line suggesting poor predictive accuracy. There were no significant differences in CVPE and RMSE among the surrogates, suggesting similar predictive ability.

CONCLUSIONS

Although OGTT-derived surrogate indices of GE are convenient and feasible, they have limited ability to robustly predict GE.

Assessment of glucose effectiveness from short IVGTT in individuals with different degrees of glucose tolerance

AIMS

Minimal model analysis of intravenous glucose tolerance test (IVGTT) data represents the reference method to assess insulin sensitivity (S_I) and glucose effectiveness (S_G) that quantify the insulin-dependent and insulin-independent processes of glucose disappearance, respectively. However, test duration (3 h) and need for modeling expertise limit the applicability of this method. Aim of this study was providing a simple predictor of S_G applicable to short test (1 h), as previously done with S_I.

METHODS

Three groups of subjects reflecting different glucose tolerance degrees underwent a 3 h IVGTT: subjects with normal glucose tolerance (NGT, n = 164), with defective glucose regulation (DGR, n = 191), and with type 2 diabetes (T2D, n = 39). Minimal model analysis provided reference S_G and its components at zero (GEZI) and basal (BIE) insulin. The simple predictor CS_G (calculated S_G) was described by the formula CS_G = α₀ + α₁ × K_G/G_peak, being K_G the glucose disappearance rate (between 10 and 50 min) and G_peak the maximum of the glucose curve during the test; α₀ and α₁ coefficients were provided by linear regression analysis.

RESULTS

CS_G and S_G showed a markedly significant relationship in the whole dataset (r = 0.72, p < 0.0001) and in the single groups (r = 0.70 in NGT, r = 0.71 in DGR and r = 0.70 in T2D, p < 0.0001 for all); α₁ × K_G/G_peak was significantly related to GEZI (r ≥ 0.60).

CONCLUSIONS

The interest for insulin-independent glucose disappearance is increasing, due to the recent availability of SGLT2 pharmacological agents, lowering glycemic levels without requiring insulin action. This study proposes a reliable predictor of S_G based on IVGTT lasting 1 h only, and not requiring mathematical modeling skills.

Relationships of Insulin Action to Age, Gender, Body Mass Index, and Waist Circumference Present Diversely in Different Glycemic Statuses among Chinese Population

INTRODUCTION

To study the influence of different glycemic statuses on the relationship of insulin action to age, gender, body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR) among Chinese population.

METHODS

A total of 35,327 participants (17,456 males and 17,871 females) were included in this nationally representative cross-sectional study. Glycemic status was defined according to the 2010 American Diabetes Association criteria. Fasting insulin was measured by the chemiluminescence method.

RESULTS

Insulin and HOMA-IR levels were the highest in newly diagnosed diabetes and were lowest in normal fasting glucose (NFG) (P < 0.001). Insulin and HOMA-IR levels were higher in females (P < 0.001) than in males with previously diagnosed diabetes and impaired fasting glucose (IFG) and NFG, meanwhile decreased with age (P < 0.001) among IFG and NFG participants. As compared with participants with a BMI from 18.5 to 19.9, those in the lowest BMI category (<18.5) had a significantly elevated risk of IR (OR, 1.96; 95% CI, 1.01-3.80), as did those in the higher BMI categories among NFG participants. The risk of IR increased with WC and WHtR, and the response was linear (P < 0.001 for linear trend) for the participants with NFG but not in those with IFG.

CONCLUSIONS

Different glycemic statuses significantly affect the relationships of insulin action to age, gender, BMI, WC, and WHtR among Chinese population.

Glucose effectiveness, but not insulin sensitivity, is improved after short-term interval training in individuals with type 2 diabetes mellitus: a controlled, randomised, crossover trial

AIMS/HYPOTHESIS

The role of glucose effectiveness (S _G) in training-induced improvements in glucose metabolism in individuals with type 2 diabetes is unknown. The objectives and primary outcomes of this study were: (1) to assess the efficacy of interval walking training (IWT) and continuous walking training (CWT) on S _G and insulin sensitivity (S _I) in individuals with type 2 diabetes; and (2) to assess the association of changes in S _G and S _I with changes in glycaemic control.

METHODS

Fourteen participants with type 2 diabetes underwent three trials (IWT, CWT and no training) in a crossover study. Exclusion criteria were exogenous insulin treatment, smoking, pregnancy, contraindications to structured physical activity and participation in recurrent training (>90 min/week). The trials were performed in a randomised order (computerised-generated randomisation). IWT and CWT consisted of ten supervised treadmill walking sessions, each lasting 60 min, over 2 weeks. IWT was performed as repeated cycles of 3 min slow walking and 3 min fast walking (aiming for 54% and 89% of [Formula: see text], respectively, which was measured during the last minute of each interval), and CWT was performed aiming for a moderate walking speed (73% of [Formula: see text]). A two-step (pancreatic and hyperinsulinaemic) hyperglycaemic clamp was implemented before and after each trial. All data were collected in a hospitalised setting. Neither participants nor assessors were blinded to the trial interventions.

RESULTS

Thirteen individuals completed all procedures and were included in the analyses. IWT improved S _G (mean ± SEM: 0.6 ± 0.1 mg kg^-1 min^-1, p < 0.05) but not S _I (p > 0.05), whereas CWT matched for energy expenditure and time duration improved neither S _G nor S _I (both p > 0.05). Changes in S _G, but not in S _I, were associated with changes in mean (β = -0.62 ± 0.23, r ² = 0.17, p < 0.01) and maximum (β = -1.18 ± 0.52, r ² = 0.12, p < 0.05) glucose levels during 24 h continuous glucose monitoring.

CONCLUSIONS/INTERPRETATION

Two weeks of IWT, but not CWT, improves S _G but not S _I in individuals with type 2 diabetes. Moreover, changes in S _G are associated with changes in glycaemic control. Therefore, increased S _G is likely an important mechanism by which training improves glycaemic control in individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02320526 FUNDING: CFAS is supported by a grant from TrygFonden. During the study period, the Centre of Inflammation and Metabolism (CIM) was supported by a grant from the Danish National Research Foundation (DNRF55). The study was further supported by grants from Diabetesforeningen, Augustinusfonden and Krista og Viggo Petersens Fond. CIM/CFAS is a member of DD2-the Danish Center for Strategic Research in Type 2 Diabetes (the Danish Council for Strategic Research, grant no. 09-067009 and 09-075724).

Factors determining insulin requirements in women with type 1 diabetes mellitus during pregnancy: a review

Most women with type 1 diabetes mellitus (T1DM) have increased insulin requirements during pregnancy. However, a minority of women have a fall in insulin requirements. When this occurs in late gestation, it often provokes concern regarding possible compromise of the feto-placental unit. In some centres, this is considered as an indication for delivery, including premature delivery. There are, however, many other factors that affect insulin requirements in pregnancy in women with type 1 diabetes mellitus and the decline in insulin requirements may represent a variant of normal pregnancy. If there is no underlying pathological process, expedited delivery in these women is not warranted and confers increased risks to the newborn. We will explore the factors affecting insulin requirements in gestation in this review. We will also discuss some novel concepts regarding beta-cell function in pregnancy.

Index of glucose effectiveness derived from oral glucose tolerance test

Aim of this study was to formulate an index for glucose effectiveness (Sg), SgIo, based on 3-point (0, 30 and 120 min) 75 g oral glucose tolerance test (OGTT). The equation for SgI(O) was developed in the Chikuma cohort (n = 502). Firstly, post-loading plasma glucose without insulin action and Sg (PPG-without insulin and Sg) was calculated as follows: fasting plasma glucose (mg/dl) + [0.75 × 75,000]/[0.19 × BW(kg) × 10]. Secondly, 'PPG-without insulin/with Sg' was obtained from inverse correlation between log(10)DI(O) and 2-h post-glucose plasma glucose at OGTT (2hPG) in each glucose tolerance category: DI(O) denotes oral disposition index, a product of the Matsuda Index and δIRI(0-30)/δPG(0-30). Thirdly, expected 2hPG (2hPG(E)) of a given subject was obtained from the regression, and the ratio of 2hPG to 2hPG(E) (2hPG/2hPG(E)) was determined as an adjustment factor. Lastly, SgI(O) ([mg/dl]/min) was calculated as [PPG-without insulin and Sg]-[PPG-without insulin / with Sg] x [(2hPG) / 2hPG(E)]. SgI(O) was validated against Sg obtained by frequently sampled intravenous glucose tolerance test in the Jichi cohort (n = 205). Also, the accuracy of prediction of Sg by SgIo was tested by the Bland-Altman plot. SgI(O) was 3.61 ± 0.73, 3.17 ± 0.74 and 2.15 ± 0.60 in subjects with normal glucose tolerance (NGT), non-diabetic hyperglycemia and diabetes, respectively, in the Chikuma cohort. In the Jichi cohort, SgI(O) was significantly correlated with Sg in the entire group (r = 0.322, P < 0.001) and in subjects with NGT (r = 0.286, P < 0.001), and SgIo accurately predicted Sg. In conclusion, SgI(O) could be a simple, quantitative index for Sg.