Metabolic characteristics in individuals with impaired glucose homeostasis

Use of HOMA-IR in hepatitis C

Chronic infection with hepatitis C virus (HCV) can induce insulin resistance (IR) in a genotype-dependent manner and contributes to steatosis, progression of fibrosis and resistance to interferon plus ribavirin therapy. Our understanding of HCV-induced IR has improved considerably over the years, but certain aspects concerning its evaluation still remain elusive to clinical researchers. One of the most important issues is elucidating the ideal method for assessment of IR in the setting of hepatitis C. The hyperinsulinaemic euglycaemic clamp is the gold standard method for determining insulin sensitivity, but is impractical as it is labour intensive and time-consuming. To date, all human studies except for four where IR was evaluated in the HCV setting, an estimation of IR has been used rather than direct measurements of insulin-mediated glucose uptake. The most commonly used estimation in the HCV population is the homeostasis model assessment of insulin resistance (HOMA-IR) which is calculated from a single measurement of fasting insulin and glucose. In this article, we review the use and reporting of HOMA in the literature and provide guidance on its appropriate as well as inappropriate use in the hepatitis setting.

Surrogate markers of insulin resistance: A review

Insulin resistance is a hallmark of obesity, diabetes, and cardiovascular diseases, and leads to many of the abnormalities associated with metabolic syndrome. Our understanding of insulin resistance has improved tremendously over the years, but certain aspects of its estimation still remain elusive to researchers and clinicians. The quantitative assessment of insulin sensitivity is not routinely used during biochemical investigations for diagnostic purposes, but the emerging importance of insulin resistance has led to its wider application research studies. Evaluation of a number of clinical states where insulin sensitivity is compromised calls for assessment of insulin resistance. Insulin resistance is increasingly being assessed in various disease conditions where it aids in examining their pathogenesis, etiology and consequences. The hyperinsulinemic euglycemic glucose clamp is the gold standard method for the determination of insulin sensitivity, but is impractical as it is labor- and time-intensive. A number of surrogate indices have therefore been employed to simplify and improve the determination of insulin resistance. The object of this review is to highlight various aspects and methodologies for current and upcoming measures of insulin sensitivity/resistance. In-depth knowledge of these markers will help in better understanding and exploitation of the condition.

Insulin secretion and sensitivity in Bangladeshi prediabetic subjects

OBJECTIVE

There are still considerable controversies regarding the basic pathophysiological mechanisms of impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). The present study was undertaken to explore the beta-cell function and insulin sensitivity in a Bangladeshi prediabetic population.

METHODS

Twenty-four IFG and 112 IGT subjects, along with 40 healthy controls, were selected purposively following 2003 ADA cut-off values and 2006 WHO/IDF grouping. IGT subjects were subcategorized into 53 isolated IGT (I-IGT) and 59 combined IFG-IGT subjects. Plasma glucose and insulin (by chemiluminescent immunoassay) were measured at fasting and 2 h after 75 g of oral glucose load. Insulin sensitivity was assessed by homeostasis model assessment (HOMA-S%) and insulin sensitivity index for glycemia (ISI(gly)) and insulin secretion by HOMA-B%.

RESULTS

Compared to control, fasting and 2-h plasma insulin were higher in I-IGT and IFG-IGT subjects; similarly, HOMA-S% [median (range)] was lower in I-IGT and IFG-IGT subjects [116 (54-227) vs. 93 (23-187) and 79 (32-197)%, P<.05 and P<.001]; ISI(gly) was also lower in I-IGT and IFG-IGT subjects [0.95 (0.54-1.64) vs. 0.64 (0.26-1.24) and 0.65 (0.29-1.20), P<.001]. But HOMA-B% was compromised in IFG and IFG-IGT groups [88 (59-182) vs. 68 (37-107) and 74 (36-141)%, P<.001 and P<.05]. The IGT group (combination of I-IGT and IFG-IGT) showed higher fasting and 2-h insulin, and lower HOMA-S% as well as ISI(gly), but compromised HOMA-B% was not evident.

CONCLUSIONS

The pathophysiological mechanisms differ in IFG (having B-cell dysfunction) and I-IGT (an insulin-resistant condition). The pathophysiology of IFG-IGT (having both B-cell dysfunction and insulin resistance) indicates that it may be a different entity and not be included in IGT.

Glucose homeostasis abnormalities in cardiac intensive care unit patients

The aim of this study was to characterize the abnormalities in glucose homeostasis in intensive care unit patients following an acute coronary event. The study population included all non-diabetic patients ages 20-80 years that were admitted to a coronary intensive unit. Glucose, insulin and C-peptide levels during an oral glucose tolerance test (OGTT) were measured during the acute admission. From January to September 2003, 277 patients were admitted to the coronary unit. Of these, 127 patients underwent an OGTT. Of these, only 29 patients (23%) exhibited normal glucose metabolism. The remainder had type 2 diabetes (32%), impaired glucose tolerance (37%) or isolated impaired fasting glucose (8%, 100-125 mg/dl). Based on homeostasis model assessment (HOMA) calculations, diabetic patients had impaired beta-cell function and patients with elevated fasting glucose levels were insulin resistant. Beta-cell dysfunction during the acute stress seems to contribute to the glucose abnormalities. Most patients who experience an acute coronary event demonstrate abnormal glucose metabolism. Post glucose-load abnormalities are more common than abnormal fasting glucose level in this situation. It is postulated that the acute stress of a coronary event may contribute to the dysglycemia.

Ethnic difference in inter-East Asian subjects with normal glucose tolerance and impaired glucose regulation: a systematic review and meta-analysis focusing on fasting serum insulin

AIMS

To investigate ethnic difference by focusing on fasting serum insulin (FSI) in inter-East Asian subjects with normal glucose tolerance (NGT) and impaired glucose regulation (IGR).

METHODS

Data sources included MEDLINE and EMBASE between 2001 and 2007. We conducted a search for articles containing mean or geometric mean values of FSI in East Asian subjects with NGT, IGR, or type 2 diabetes (T2DM). The Monte Carlo method was used for simulation of the mean and standard deviation of individual measures in each ethnic group; calculation of the median ratio and 95% confidence interval of individual measures between ethnic groups.

RESULTS

Twenty-two articles fully met our pre-determined criteria and were included in the meta-analysis. Results of the meta-analysis revealed that FSI level is significantly lower in Japanese subjects with NGT, IGR, or T2DM than in Korean and Chinese subjects.

CONCLUSIONS

Ethnic difference in FSI level between East Asians was observed in not only T2DM patients but also subjects with NGT or IGR. The lower FSI level in Japanese subjects was accompanied by lower triglyceride level. These results suggest that ethnic difference in dietary habit was one of the most influential factors for the ethnic difference in FSI.

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.