Metabolic heterogeneity in impaired glucose tolerance

Association among serum ferritin, alanine aminotransferase levels, and metabolic syndrome in Korean postmenopausal women

We examined the relationships among serum ferritin, alanine aminotransferase (ALT) levels, and cardiovascular risk factors of metabolic syndrome in Korean postmenopausal women. We conducted a cross-sectional study of 959 postmenopausal women without an apparent cause of liver disease. Metabolic syndrome was defined as the presence of at least 3 of the following: elevated blood pressure, low high-density lipoprotein cholesterol, elevated serum triglycerides, elevated plasma glucose, and abdominal obesity. Serum ferritin and ALT levels were found to be correlated (r=0.374, P<.001) and to be associated with the components of metabolic syndrome. Subjects with metabolic syndrome showed significantly higher serum ferritin (74.7+/- 2.0 vs 59.6+/- 2.0 ng/mL, P<.001) and ALT levels (21.3+/-1.6 vs 18.7+/-1.5 IU/L, P<.001). Moreover, the greater the number of metabolic syndrome components present, the higher were the serum ferritin and ALT levels (P<.001). Multiple regression analysis showed that serum ALT levels are significantly associated with serum ferritin levels, waist circumference, fasting blood glucose, age, and white blood cell count (adjusted R(2)=0.147). Elevated iron stores were positively associated with serum ALT levels and metabolic syndrome in Korean postmenopausal women.

Increased acylation stimulating protein concentrations in nonalcoholic fatty liver disease are associated with insulin resistance

OBJECTIVES

As acylation stimulating protein (ASP) acts on adipocytes mainly as a paracrine factor to increase triglyceride synthesis and storage; hypothetically, it may play a similar role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD).

METHODS

Forty-six male patients with NAFLD (group A), age-matched 30 male patients with chronic viral hepatitis (group B) and 30 age-matched and body mass index (BMI)-matched healthy male subjects were enrolled in the study.

RESULTS

Among the NAFLD patients, 10 patients (24.4%) had simple steatosis and 36 patients (69.6%) had nonalcoholic steatohepatitis (NASH). The mean levels of ASP, complement 3, insulin, C-peptide, HOMA-IR, triglyceride, and very low-density lipoprotein (VLDL) were significantly higher in group A patients than both controls and group B. ASP levels correlated significantly in a positive manner with BMI, insulin, and HOMA-IR.

CONCLUSIONS

Dysregulation of the ASP pathway may have important metabolic consequences in NASH and is associated with insulin resistance.

Insulin resistance and ferritin as major determinants of nonalcoholic fatty liver disease in apparently healthy obese patients

OBJECTIVES

The aims of this study were to test the possible association between nonalcoholic fatty liver disease (NAFLD) and iron and insulin resistance, and to determine the prevalence of NAFLD in apparently healthy obese subjects.

DESIGN

Cross-sectional, clinical epidemiologic study.

SUBJECTS

A total of 210 apparently healthy obese patients, aged from 18 to 65 y, with a body mass index (BMI) of 28 kg/m2 or more, were enrolled in a body weight reduction program in our hospital.

MEASUREMENTS

All the subjects underwent screening and preprogram examinations, including anthropometric data measurements, biochemistry testing, and ultrasonography of the liver. NAFLD was defined as fatty liver diagnosed by ultrasonography plus persistent elevation of alanine aminotransferase (ALT) levels.

RESULTS

Of the 210 patients, 80% (168/210) had fatty liver. Persistent ALT elevation in two separate tests was further detected in 25.6% (43/168) of patients. Multiple logistic regression analysis showed waist circumference and insulin resistance to be independently associated with fatty liver. Serum ferritin level and insulin resistance were two major risk factors predicting NAFLD.

CONCLUSION

The prevalence of NAFLD was 20.5% (43/210) in obese patients. As both hyperinsulinemia induced by insulin resistance and iron overload represented by ferritin elevation might damage hepatocytes, we concluded that these two factors were significantly associated with NAFLD in obese patients.\

IUGR alters postnatal rat skeletal muscle peroxisome proliferator-activated receptor-gamma coactivator-1 gene expression in a fiber specific manner

Uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) increase the risk of insulin resistance in humans and rats. Aberrant skeletal muscle lipid metabolism contributes to the pathogenesis of insulin resistance. Peroxisome proliferator-activated receptor-gamma co-activator-1 (PGC-1) is a transcriptional co-activator that affects gene expression of key lipid metabolizing enzymes such as carnitine palmitoyl-transferase I (mCPTI). Because gene expression of lipid metabolizing enzymes is altered in IUGR postnatal skeletal muscle, and we hypothesized that PGC-1 expression would be similarly affected. To prove this hypothesis, bilateral uterine artery ligation and sham surgery were used to produce IUGR and control rats respectively. Western Blotting demonstrated that PGC-1 hind limb skeletal muscle protein levels were increased in perinatal and postnatal IUGR rats. Conventional RT-PCR demonstrated that PGC-1 mRNA levels were similarly increased in perinatal hind limb skeletal muscle and juvenile extensor digitorum longus (EDL), but were decreased in juvenile soleus. Because a gender specific trend was noted in PGC-1 mRNA levels, real time RT-PCR was used for further differentiation. Real time RT-PCR revealed that changes in postnatal skeletal muscle PGC-1 expression were more marked in male IUGR rats versus female IUGR rats. Down stream targets of PGC-1 followed a similar pattern of expression. We conclude that PGC-1 expression is altered in rat IUGR skeletal muscle and speculate that it contributes to the pathogenesis of insulin resistance in the IUGR rat.

Early disturbances in insulin secretion in the development of type 2 diabetes mellitus

After a short description of normal glucose homeostasis, recent findings in relation to insulin release in three groups with a high risk of future development of type 2 diabetes are described. Hyperglycemic clamps in subjects with impaired glucose tolerance (IGT) clearly indicate that pancreatic beta cell function is decreased, in addition to the decreased insulin sensitivity. In women with former gestational diabetes mellitus (GDM), insulin release is also lower than in controls. In Caucasian first-degree relatives (FDRs) with normal glucose tolerance, various studies have shown that beta cell function is lower than in controls, while on the average insulin sensitivity is normal. This implies that beta cell function is disturbed earlier in subjects at risk of developing diabetes than is often appreciated. In the near future, the genetic studies currently underway will presumably unravel the pathogenesis of disturbances both in insulin secretion and in insulin action, in type 2 diabetes mellitus.

Deterioration of the metabolic risk profile in women. Respective contributions of impaired glucose tolerance and visceral fat accumulation

OBJECTIVE

To determine whether the impaired glucose tolerance (IGT) state contributes to the deterioration of the metabolic profile in women after taking into account the contribution of visceral adipose tissue (AT) accumulation, as measured by computed tomography.

RESEARCH DESIGN AND METHODS

We studied 203 women with normal glucose tolerance (NGT) and 46 women with IGT, defined as a glycemia between 7.8 and 11.1 mmol/l measured 2 h after a 75-g oral glucose load.

RESULTS

Women with IGT were characterized by a higher visceral AT accumulation and by higher concentrations of fasting plasma glucose, insulin, and C-peptide as well as by higher plasma concentrations of cholesterol, triglycerides, and apolipoprotein B (apoB) and by greater cholesterol-to-HDL-cholesterol ratio, reduced LDL peak particle size, lower HDL-cholesterol and HDL2-cholesterol concentrations, and higher blood pressure (P < 0.01) than women with NGT. When we matched 27 pairs of women for visceral AT and fat mass as well as for menopausal status, differences previously found in LDL-cholesterol, LDL peak particle size, HDL-cholesterol, and HDL2-cholesterol concentrations as well as in the cholesterol-to-HDL-cholesterol ratio and blood pressure were eliminated, whereas triglyceride concentrations remained significantly higher in women with IGT.

CONCLUSIONS

A high visceral AT accumulation is a major factor involved in the deterioration of many metabolic variables in women with IGT, with the notable exception of triglyceride concentrations, which remained significantly different between women with NGT and women with IGT after adjustment for visceral fat.

Insulin sensitivity, glucose effectiveness, and insulin secretion in nondiabetic offspring of patients with non-insulin-dependent diabetes mellitus: a cross-sectional study

To evaluate the factors that determine the worsening of intravenous glucose tolerance in subjects at high risk for developing non-insulin-dependent diabetes mellitus (NIDDM), 15 glucose-tolerant offspring of NIDDM patients and 21 control subjects were studied. Each subject underwent a frequently sampled intravenous glucose tolerance (FSIGT) test. The intravenous glucose tolerance index (K(G) index) was calculated between minutes 10 and 40 of a FSIGT test. Insulin sensitivity (S(I)), glucose effectiveness at zero insulin (GEZI), and first- and second-phase insulin responsiveness (phi1 and phi2) were estimated using glucose and insulin kinetic minimal models. The acute insulin response to glucose (AIRg) was calculated as the area under the insulin curve above the basal level between 0 and 10 minutes, and the suprabasal insulin effect was determined by the product of S(I) times AIRg. Offspring had a lower S(I) than control subjects (14.1 +/- 7.5 v 9.25 +/- 4.20 x 10(-5) x min(-1)(pmol x L(-1))(-1), P < .01), and their AIRg was similar (3,284 +/- 2,280 v 3,105 +/- 1,499 pmol x L(-1), NS). Sample division according to the median K(G) value showed that control subjects with low tolerance had a lower AIRg (4,417 +/- 2,531 v 2,043 +/- 1,068 pmol x L(-1), P < .05) and a lower suprabasal insulin effect (0.057 +/- 0.03 v 0.023 +/- 0.009 min(-1), P < .05) than control subjects with high tolerance. Offspring with low tolerance had a lower AIRg (2,574 +/- 1,197 v 3,707 +/- 1,656 pmol x L(-1), P < .05) and a lower GEZI (0.101 +/- 0.05 v 0.212 +/- 0.08 x 10(-1) x min(-1), P < .05) than offspring with high tolerance. Offspring with high and low tolerance showed lower phi1 (375 +/- 155 v 272 +/- 181 v 698 +/- 336 (pmol x L(-1))min(mmol x L(-1)), NS) than control subjects with high tolerance. In conclusion, our data suggest that decreases in GEZI and AIRg are the main factors responsible for the worsening of intravenous glucose tolerance in the offspring of NIDDM patients.