Impaired fasting glucose vs. glucose intolerance in pre-menopausal women: distinct metabolic entities and cardiovascular disease risk?

Gestational diabetes mellitus and impaired glucose tolerance pregnant women

OBJECTIVE

To evaluate correlations between insulin secretion and resistance in patients with gestational diabetes mellitus (GDM) and gestational impaired glucose tolerance (GIGT).

METHODS

Three hundred thirty six pregnant women with an oral glucose tolerance test (OGTT) were tested and measured insulin function indices (IFI), insulin resistance indices (HOMA-IR) as well as blood serum triglycerides (TG), total cholesterol (TCH) and low density lipoprotein cholesterol (LDL-C) concentrations. GIGT patients were further divided into subgroups according to hyperglycemia appearance 1, 2 or 3 hours after glucose ingestion.

RESULTS

GDM and GIGT correlated with age (p<0.05), family history of diabetes (p<0.05) and pre-pregnancy body mass indices (BMIs) (p<0.05). Blood pressures were higher in GDM than in GIGT and normal glucose tolerance (NGT) patients (p<0.05). The IFIs were gradually reduced (p<0.05), whereas HOMA-IR was gradually enhanced (p<0.05) in the GIGT and GDM patients. Blood serum TG, TCH and LDL-C concentrations were higher in the GIGT and GDM groups (p<0.05) and the GIGT 1 hour hyperglycemia subgroup had highest pregnancy weight gain and HOMA-IR values (p<0.05). Conclusions : Advanced age, family history of diabetes, high BMIs and blood pressure were risk factors for GIGT and GDM, which were both caused by reduced insulin secretion and enhanced insulin resistance.

Strong association between insulin-mediated glucose uptake and the 2-hour, not the fasting plasma glucose concentration, in the normal glucose tolerance range

AIM

The aim of this study was to examine the relationship between whole-body insulin-mediated glucose disposal and the fasting plasma glucose concentration in nondiabetic individuals.

RESEARCH DESIGN AND METHODS

Two hundred fifty-three nondiabetic subjects with normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance, and combined glucose intolerance received a 75-g oral glucose tolerance test and euglycemic hyperinsulinemic clamp. Total glucose disposal (TGD) during the insulin clamp was compared in IFG and NGT individuals and was related to fasting and 2-hour plasma glucose concentrations in each group.

RESULTS

TGD varied considerably between NGT and IFG individuals and displayed a strong inverse relationship with the 2-hour plasma glucose (PG; r = 0.40, P < .0001) but not with the fasting PG. When IFG and NGT individuals were stratified based on their 2-hour PG concentration, the increase in 2-hour PG was associated with a progressive decrease in TGD in both groups, and the TGD was comparable among NGT and IFG individuals.

CONCLUSION

The present results indicate the following: 1) as in NGT, insulin-stimulated TGD varies considerably in IFG individuals; 2) the large variability in TGD in IFG and NGT individuals is related to the 2-hour PG concentration; and 3) after adjustment for the 2-hour proglucagon concentration, IFG subjects have comparable TGD with NGT individuals.

Impaired early- but not late-phase insulin secretion in subjects with impaired fasting glucose

Subjects with impaired fasting glucose (IFG) are at increased risk for type 2 diabetes. We recently demonstrated that IFG subjects have increased hepatic insulin resistance with normal insulin sensitivity in skeletal muscle. In this study, we quantitated the insulin secretion rate from deconvolution analysis of the plasma C-peptide concentration during an oral glucose tolerance test (OGTT) and compared the results in IFG subjects with those in subjects with impaired glucose tolerance (IGT) and normal glucose tolerance (NGT). One hundred and one NGT subjects, 64 subjects with isolated IGT, 24 subjects with isolated IFG, and 48 subjects with combined (IFG + IGT) glucose intolerance (CGI) received an OGTT. Plasma glucose, insulin, and C-peptide concentrations were measured before and every 15 min after glucose ingestion. Insulin secretion rate (ISR) was determined by deconvolution of plasma C-peptide concentration. Inverse of the Matsuda index of whole body insulin sensitivity was used as a measure of insulin resistance; 56 subjects also received a euglycemic hyperinsulinemic clamp. The insulin secretion/insulin resistance (disposition) index was calculated as the ratio between incremental area under the ISR curve (∆ISR[AUC]) to incremental area under the glucose curve (∆G[AUC]) factored by the severity of insulin resistance (measured by Matsuda index during OGTT or glucose disposal during insulin clamp). Compared to NGT, the insulin secretion/insulin resistance index during first 30 min of OGTT was reduced by 47, 49, and 74% in IFG, IGT, and CGI, respectively (all < 0.0001). The insulin secretion/insulin resistance index during the second hour (60-120 min) of the OGTT in subjects with IFG was similar to that in NGT (0.79 ± 0.6 vs. 0.72 ± 0.5, respectively, P = NS), but was profoundly reduced in subjects with IGT and CGI (0.31 ± 0.2 and 0.19 ± 0.11, respectively; P < 0.0001 vs. both NGT and IFG). Early-phase insulin secretion is impaired in both IFG and IGT, while the late-phase insulin secretion is impaired only in subjects with IGT.

Serum lipid and hsCRP levels in prediabetes--impaired fasting glucose (IFG) and impaired glucose tolerance (IGT)

AIM

To evaluate cardiovascular risk in prediabetes (IFG and IGT) assessed by serum lipid and hsCRP levels.

SUBJECTS AND METHODS

445 subjects with prediabetes (248 with IFG, 197 with IGT), 318 patients with newly-diagnosed diabetes (NDD) and a group of 477 age- and BMI-matched subjects with normal glucose tolerance (NGT) were enrolled. Glucose tolerance was studied during oral glucose tolerance test (OGTT) and 2006 WHO criteria were applied. Serum hsCRP and lipids (total cholesterol, triglycerides, HDL-cholesterol (HDL-c) and free fatty acids (FFAs) were measured.

RESULTS

Both IFG and IGT showed significantly atherogenic changes in serum lipid and hsCRP levels when compared to NGT. Subjects with IGT presented with significantly higher triglycerides (p=0.01) and FFAs (p<0.0001) and significantly lower HDL-c (p=0.04) as compared to IFG. IFG showed significantly higher levels of HDL-c (p<0.0001) and lower levels of triglycerides (p<0.0001), FFAs (p<0.001) and hsCRP (p=0.04) as compared to NDD, while IGT differed from NDD only in the lower hsCRP (p=0.04).

CONCLUSIONS

Both IFG and IGT are associated with increased cardiovascular risk as assessed by serum lipid and hsCRP levels. The risk is different in the two categories of prediabetes, IGT being characterized by a more atherogenic risk profile, similar to that in NDD.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

Isolated impaired fasting glucose and peripheral insulin sensitivity: not a simple relationship

OBJECTIVE

In a recent consensus statement, the American Diabetes Association (ADA) concluded that individuals with impaired fasting glucose (IFG) have "normal muscle insulin sensitivity." To subject this conclusion to further validation, we evaluated the relationship between glucose tolerance categories and peripheral insulin sensitivity in a large nondiabetic population.

RESEARCH DESIGN AND METHODS

Insulin sensitivity was directly quantified by determining the steady-state plasma glucose (SSPG) concentration during an insulin suppression test in 446 nondiabetic individuals divided into four groups: normal glucose tolerance (NGT, n = 318), isolated IFG (n = 63), isolated impaired glucose tolerance (IGT, n = 33), and combined IFG and IGT (IFG/IGT, n = 32).

RESULTS

Insulin sensitivity was significantly different in all three groups with pre-diabetes (IFG, IGT, IFG/IGT) as compared with NGT (P < 0.05). Using tertiles of SSPG concentration in the NGT group as operational definitions of insulin resistance (highest tertile) and insulin sensitivity (lowest tertile), there was considerable heterogeneity within the pre-diabetic groups. Thus, 57% of IFG individuals were insulin resistant, and 13% were insulin sensitive. The IFG/IGT group was most homogeneous, with 94% classified as insulin resistant and only 3% as insulin sensitive.

CONCLUSIONS

Peripheral insulin sensitivity varies considerably in nondiabetic individuals, with IFG individuals showing the most heterogeneity within the pre-diabetes group. We believe that this heterogeneity in insulin sensitivity, and the relatively few patients in whom insulin sensitivity has been measured directly in the past, explain the discrepancy between our findings and those of the recent ADA consensus statement.

Prediabetes: a position statement from the Australian Diabetes Society and Australian Diabetes Educators Association

Prediabetes, the presence of impaired fasting glucose/glycaemia and/or impaired glucose tolerance, affects about 16.4% of Australian adults. People with prediabetes are at increased risk of developing diabetes, and cardiovascular and other macrovascular disease. Management includes reducing cardiovascular disease risk factors, specifically lipid and blood pressure abnormalities, and smoking-cessation counselling. To help prevent progression to diabetes, people with prediabetes who are overweight or obese require intensive lifestyle intervention. Medication to help prevent diabetes may also be used, but only after a minimum of 6 months of lifestyle intervention. In people with prediabetes, there is no role for routinely testing: capillary blood glucose; glycated haemoglobin (HbA(1c)) levels; serum insulin or pancreatic C-peptide levels; or testing for ischaemic heart disease or the microvascular complications of diabetes. Follow-up assessment of glycaemia in prediabetes requires a formal 75 g oral glucose tolerance test, initially performed annually, with subsequent individualised testing frequency.

The use of oral glucose tolerance tests to risk stratify for new-onset diabetes after transplantation: An underdiagnosed phenomenon

BACKGROUND

Fasting glucose measurements are insensitive at detecting new-onset diabetes after transplantation (NODAT) and ignore the diagnosis of impaired glucose tolerance (IGT). Both NODAT and IGT confer a higher risk of developing cardiovascular disease. IGT is also a risk factor for NODAT. The aim of this study was to use an oral glucose tolerance test (OGTT) to risk stratify for NODAT and IGT in renal transplant recipients and to relate cardiovascular and phenotypic risk with glycemic dysregulation.

METHODS

In all, 858 renal transplant recipients are under follow up at the University Hospital of Wales, Cardiff, UK. Excluded patients had pretransplant diabetes (78), NODAT (89), or were transplanted less than six months (47), leaving 646 recipients. All remaining recipients with two fasting blood glucoses between 5.6 and 6.9 mmol/L were invited to have an OGTT. A diagnosis of NODAT, IGT, and impaired fasting glucose (IFG) was based on World Health Organization guidelines.

RESULTS

We identified 134 patients who fulfilled the inclusion criteria, of whom 122 had an OGTT (91% of cohort). In all, 51% of patients were found to have abnormal glucose metabolism: 10% NODAT, 14% combined IGT/IFG, 9% IGT alone, and 18% IFG alone. Clinical phenotype was not predictive of diabetic risk on multivariate analysis.

CONCLUSIONS

Our results confirm fasting glucose underestimates the prevalence of NODAT and ignores the prevalence of IGT. These findings suggest routine use of an OGTT in renal transplant recipients is a valuable clinical tool to risk stratify each patient for the development of NODAT and cardiovascular disease.

Contributions of beta-cell dysfunction and insulin resistance to the pathogenesis of impaired glucose tolerance and impaired fasting glucose

Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are intermediate states in glucose metabolism that exist between normal glucose tolerance and overt diabetes. Epidemiological studies demonstrate that the two categories describe distinct populations with only partial overlap, suggesting that different metabolic abnormalities characterize IGT and IFG. Insulin resistance and impaired beta-cell function, the primary defects observed in type 2 diabetes, both can be detected in subjects with IGT and IFG. However, clinical studies suggest that the site of insulin resistance varies between the two disorders. While subjects with IGT have marked muscle insulin resistance with only mild hepatic insulin resistance, subjects with IFG have severe hepatic insulin resistance with normal or near-normal muscle insulin sensitivity. Both IFG and IGT are characterized by a reduction in early-phase insulin secretion, while subjects with IGT also have impaired late-phase insulin secretion. The distinct metabolic features present in subjects with IFG and IGT may require different therapeutic interventions to prevent their progression to type 2 diabetes.