Alpha2-Heremans-Schmid glycoprotein/fetuin-A is associated with insulin resistance and fat accumulation in the liver in humans

Discovery of the serum biomarker proteins in severe preeclampsia by proteomic analysis

Preeclapsia (PE) is a severe disorder that occurs during pregnancy, leading to maternal and fetal morbidity and mortality. PE affects about 3-8% of all pregnancies. In this study, we conducted liquid chromatography- mass spectrometry/mass spectrometry (LC-MS/MS) to analyze serum samples depleted of the six most abundant proteins from normal and PE-affected pregnancies to profile serum proteins. A total of 237 proteins were confidently identified with <1% false discovery rate from the two groups of duplicate analysis. The expression levels of those identified proteins were compared semiquantitatively by spectral counting. To further validate the candidate proteins with a quantitative mass spectrometric method, selective reaction monitoring (SRM) and enzyme linked immune assay (ELISA) of serum samples collected from pregnant women with severe PE (n = 8) or normal pregnant women (n = 5) was conducted. α2- HS-glycoprotein (AHSG), retinol binding protein 4 (RBP4) and α-1-microglobulin/bikunin (AMBP) and Insulin like growth factor binding protein, acid labile subunit (IGFBP-ALS) were confirmed to be differentially expressed in PE using SRM (P<0.05). Among these proteins, AHSG was verified by ELISA and showed a statistically significant increase in PE samples when compared to controls.

Fatty liver, abdominal visceral fat, and cardiometabolic risk factors: the Jackson Heart Study

OBJECTIVE

The goal of this study was to examine whether fatty liver and abdominal visceral adipose tissue (VAT) are jointly associated with cardiometabolic abnormalities.

METHODS AND RESULTS

Black participants were from the Jackson Heart Study (n=2882, 65% women) who underwent computed tomography. Fatty liver was measured by liver attenuation in Hounsfield units (LA), and VAT was quantified volumetrically. Cross-sectional associations between LA, VAT, and cardiometabolic risk factors were assessed using linear and logistic regression, and their joint associations were further examined in 4 subgroups: high-LA/low-VAT (n=1704), low-LA/low-VAT (n=422), high-LA/high-VAT (n=436), and low-LA/high-VAT (n=320). Both LA and VAT were associated with most cardiometabolic traits (all P<0.0001), which persisted after additional adjustment for each other (LA, P<0.01-0.0001; VAT, P<0.0001). In bootstrap analyses, the regression coefficient of VAT was significantly greater than LA for triglycerides, high-density lipoprotein cholesterol, impaired glucose, and metabolic syndrome (P=0.009-0.0001). The interaction between LA and VAT was significant for high-density lipoprotein cholesterol (P=0.002), impaired glucose (P=0.003), and metabolic syndrome (P=0.04). Among 4 subgroups, participants with higher VAT and lower LA had higher prevalence of cardiometabolic traits than those with each condition alone.

CONCLUSION

Both fatty liver and VAT are independent correlates of cardiometabolic risk, but the associations are stronger for VAT than for fatty liver.

Serum fetuin-A concentrations are elevated in subjects with impaired glucose tolerance and newly diagnosed type 2 diabetes

OBJECTIVE

Hepatic steatosis is associated with an increased risk of diabetes. Although the levels of serum fetuin-A, a liver-derived glycoprotein that impairs insulin signalling, are positively correlated with hepatic steatosis, the levels of fetuin-A in subjects with impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and newly diagnosed type 2 diabetes (NDD) have not been established. The aim of this study is to investigate the relationship among serum fetuin-A concentrations, IFG, IGT and NDD in Chinese subjects without nonalcoholic fatty liver disease (NAFLD).

DESIGN

A total of 360 age- and sex-matched subjects with normal glucose tolerance (NGT), IFG, IGT and NDD were recruited in this case-control study.

MEASUREMENTS

Each subject was assessed by abdominal ultrasound to exclude the presence of NAFLD. Serum fetuin-A concentrations were measured by enzyme-linked immunosorbent assay and compared between NGT, IFG, IGT and NDD groups. The association with clinical and metabolic parameters was also examined.

RESULTS

Serum fetuin-A concentrations were higher in NDD and IGT groups than NGT groups (341 ± 88, 335 ± 90, and 300 ± 75 μg/ml). In multiple linear regression analysis, IGT (P < 0·01) and NDD (P < 0·05) were the positively associated factors of serum fetuin-A concentrations, but age (P < 0·05) was a negatively associated factor after adjusting for age, anthropometric indices, lipid profile, estimated glomerular filtration rate (eGFR), adiponectin, C-reactive protein (CRP) and homeostasis model assessment (HOMA-IR).

CONCLUSIONS

IGT and NDD are positively associated with serum fetuin-A concentrations in subjects without NAFLD independent of cardiometabolic risk factors.

Effects of a three-month combined exercise programme on fibroblast growth factor 21 and fetuin-A levels and arterial stiffness in obese women

OBJECTIVE

We examined the relationship between brachial-ankle pulse wave velocity (baPWV) reflecting arterial stiffness and the levels of novel hepatokines fibroblast growth factor 21 (FGF21) and fetuin-A. In addition, we evaluated the effect of a 3-month combined aerobic and resistance exercise programme on FGF21 and fetuin-A levels as well as arterial stiffness in obese women.

METHODS

Forty nondiabetic, obese women (body mass index = 27·6 ± 2·4 kg/m(2) ) were included in the study and were compared before and after a 3-month exercise programme, which was composed of 45 min of aerobic exercise at an intensity of 60-75% of the age-predicted maximum heart rate (300 kcal/session) and 20 min of resistance training (100 kcal/session) five times a week. All exercise sessions were supervised by a professional exercise physiologist.

RESULTS

At baseline, baPWV levels were correlated with age, body mass index (BMI), systolic blood pressure (SBP), high density lipoprotein cholesterol, fasting glucose and serum FGF21 levels. In a multiple stepwise regression analysis using baPWV as a dependent variable, baPWV levels were associated with age, BMI, SBP, FGF21 and fetuin-A levels (R(2) = 0·744). After the exercise programme, BMI, waist circumference, SBP, diastolic blood pressure and triglyceride levels were significantly decreased. Moreover, baPWV values were significantly improved (P < 0·001) along with modest decrease in FGF21 levels (P = 0·043). However, fetuin-A levels were not changed significantly (P = 0·202).

CONCLUSIONS

A 3-month combined exercise programme decreases the FGF21 levels as well as arterial stiffness in obese Korean women.

Visceral obesity modulates the impact of apolipoprotein C3 gene variants on liver fat content

OBJECTIVE

It has not been solved whether subjects carrying the minor alleles of the -455T>C or -482C>T single nucleotide polymorphisms (SNPs) in the apolipoprotein-C3-gene (APOC3) have an increased risk for developing fatty liver and insulin resistance. We investigated the relationships of the SNPs with hepatic APOC3 expression and hypothesized that visceral obesity may modulate the effects of these SNPs on liver fat and insulin sensitivity (IS).

METHODS

APOC3 mRNA expression and triglyceride content were determined in liver biopsies from 50 subjects. In a separate group (N=330) liver fat was measured by (1)H-magnetic resonance spectroscopy. IS was estimated during an oral glucose tolerance test (OGTT) and the euglycemic, hyperinsulinemic clamp (N=222).

RESULTS

APOC3 mRNA correlated positively with triglyceride content in liver biopsies (r=0.29, P=0.036). Carriers of the minor alleles (-455C and -482T) tended to have higher hepatic APOC3 mRNA expression (1.80 (0.45-3.56) vs 0.77 (0.40-1.64), P=0.09), but not higher triglyceride content (P=0.76). In 330 subjects the genotype did not correlate with liver fat (P=0.97) or IS (OGTT: P=0.41; clamp: P=0.99). However, a significant interaction of the genotype with waist circumference in determining liver fat was detected (P=0.02) in which minor allele carriers had higher liver fat only in the lowest tertile of waist circumference (P=0.01). In agreement, during a 9-month lifestyle intervention the minor allele carriers of the SNP -482C>T in the lowest tertile also had less decrease in liver fat (P=0.04).

CONCLUSIONS

APOC3 mRNA expression is increased in fatty liver and is regulated by SNPs in APOC3. The impact of the APOC3 SNPs on fatty liver is small and depends on visceral obesity.

New type 2 diabetes risk genes provide new insights in insulin secretion mechanisms

Type 2 diabetes results from the inability of beta cells to increase insulin secretion sufficiently to compensate for insulin resistance. Insulin resistance is thought to result mainly from environmental factors, such as obesity. However, there is compelling evidence that the decline of both insulin sensitivity and insulin secretion have also a genetic component. Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The vast majority of these genes affect beta cell function by molecular mechanisms that remain unknown in detail. Nevertheless, we and others could show that a group of genes affect glucose-stimulated insulin secretion, a group incretin-stimulated insulin secretion (incretin sensitivity or secretion) and a group proinsulin-to-insulin conversion. The most important so far type 2 diabetes risk gene, TCF7L2, interferes with all three mechanisms. In addition to advancing knowledge in the pathophysiology of type 2 diabetes, the discovery of novel genetic determinants of diabetes susceptibility may help understanding of gene-environment, gene-therapy and gene-gene interactions. It was also hoped that it could make determination of the individual risk for type 2 diabetes feasible. However, the allelic relative risks of most genetic variants discovered so far are relatively low. Thus, at present, clinical criteria assess the risk for type 2 diabetes with greater sensitivity and specificity than the combination of all known genetic variants.

Serum fetuin-A in metabolic and inflammatory pathways in patients with myocardial infarction

BACKGROUND

Although multifunctional glycoprotein α2HS-glycoprotein/human fetuin-A (AHSG) is involved in atherosclerosis, it is not clear whether high or low concentrations are more important. We studied the correlation of serum AHSG with adiponectin, leptin, resistin, C-reactive protein (CRP) and tumour necrosis factor-α (TNF-α) to see whether its metabolic effects or its involvement in subclinical inflammation are dominant in patients with established coronary disease.

MATERIALS AND METHODS

In this cross-sectional study, AHSG concentration was determined in sera of 171 patients (age: 62 ± 6 years, mean ± SD) with previous myocardial STEMI infarction and normal renal function and 81 age-matched healthy controls by radial immunodiffusion. Results  Patients had increased AHSG levels (673 ± 103 vs. 619 ± 96 mg L(-1), P < 0·001) compared to controls. Obese and diabetic patients had higher AHSG concentration than those with normal BMI or without diabetes but even the latter group had elevated AHSG levels (667 ± 101 mg L(-1), n = 88) compared to controls (P = 0·002). Serum AHSG correlated negatively with adiponectin (r = -0·236, P = 0·006) even after adjusting for BMI (r = -0·177, P = 0·043). AHSG determined adiponectin levels independently from BMI, age and other adipocytokines (P = 0·014). The correlation between leptin and AHSG (r = 0·321, P = 0·021) weakened following adjustment for BMI (r = 0·209, P = 0·072). Serum AHSG did not correlate significantly with CRP, resistin and TNF-α concentrations. BMI and resistin but not AHSG determined TNF-α levels independently.

CONCLUSIONS

AHSG is elevated in sera of patients with previous myocardial infarction. Association with adipokines favours the concept that AHSG is involved in atherosclerosis more likely through metabolic pathways (insulin resistance, obesity and adipocyte dysfunction) than by inflammation in patients with post-myocardial infarction.

The role of obesity in kidney disease: recent findings and potential mechanisms

Obesity epidemic is in rise in almost every industrialized country and continues to be a growing problem worldwide. In fact, obesity per se has been recognized as a chronic disease. Consequently, there has been a cascade of metabolic changes initiated by the markedly risen prevalence that contributes to the increased incidence of diabetes, hypertension, and cardiovascular disease. Moreover, obesity is also associated with an increased risk of chronic kidney disease (CKD). The majority of the studies indicate a direct relationship between body mass index (BMI) and CKD risk. Moreover, current evidence emphasized the fact that central obesity measurements, such as waist circumference, could be a better predictor of CKD progression and mortality than BMI. The detrimental effects of obesity on kidney outcome have been recognized in nondialysis-dependent (NDD)-CKD patients. However, survival in overweight or obese CKD patients undergoing maintenance hemodialysis is paradoxically opposed compared with the general population. This "reverse epidemiology," however, is valid mainly for the inflammated end-stage renal disease (ESRD) patients. In fact, renal transplant recipients with higher BMI have inferior patient and graft survival compared to patients with lower BMI. This review also provides perspectives concerning the mechanisms associated with obesity, such as the renin-angiotensin-aldosterone system (RAAS) activation, and the role of leptin, adiponectin, fetuin-A, and adipose tissue, as factors that contribute to the development of CKD. Prevention strategies for CKD patients are also discussed and should be considered by clinicians.

Serum fetuin-A associates with type 2 diabetes and insulin resistance in Chinese adults

Background

Previous studies have demonstrated that fetuin-A is related to insulin resistance among subjects with normal glucose tolerance but not patients with type 2 diabetes. There are limited data available concerning fetuin-A and insulin resistance in Chinese. We aimed to study the association of feuin-A with insulin resistance among participants with or without type 2 diabetes in a large sample size of adults aged 40 and older.

Methodology and Principal Findings

A community-based cross-sectional study was performed among 5,227 Chinese adults. The average age of our study was 61.5±9.9 years. Serum fetuin-A concentrations were not significantly different between male and female (296.9 vs. 292.9 mg/l, p = 0.11). Compared with the lowest quartile, the highest quartile of serum fetuin-A revealed a significant higher proportion of type 2 diabetic patients (34.8% vs. 27.3%, p<0.0001). In the multinomial logit models, the risk of type 2 diabetes was associated with each one quartile increase of serum fetuin-A concentrations when referenced not only to normal glucose tolerance (OR 1.24, 95% CI 1.07–1.43, p = 0.004) but also to impaired glucose regulation (OR 1.25, 95% CI 1.08–1.44, p = 0.003, respectively), after adjustment for age, sex, community, current smoking, and current drinking. The logistic regression analysis showed that fetuin-A were associated with elevated HOMA-IR and fasting serum insulin both among the participants with or without type 2 diabetes in the full adjusted analysis. There was no significant association between elevated serum fetuin-A concentrations and impaired glucose regulation (all p≥0.12).

Conclusions and Significance

Higher fetuin-A concentrations were associated with type 2 diabetes and insulin resistance in middle aged and elderly Chinese.

Genetic ablation of cGMP-dependent protein kinase type I causes liver inflammation and fasting hyperglycemia

OBJECTIVE

The nitric oxide/cGMP/cGMP-dependent protein kinase type I (cGKI) signaling pathway regulates cell functions that play a pivotal role in the pathogenesis of type 2 diabetes. However, the impact of a dysfunction of this pathway for glucose metabolism in vivo is unknown.

RESEARCH DESIGN AND METHODS

The expression of cGKI in tissues relevant to insulin action was analyzed by immunohistochemistry. The metabolic consequences of a genetic deletion of cGKI were studied in mice that express cGKI selectively in smooth muscle but not in other cell types (cGKI-SM mice).

RESULTS

In wild-type mice, cGKI protein was detected in hepatic stellate cells, but not in hepatocytes, skeletal muscle, fat cells, or pancreatic β-cells. Compared with control animals, cGKI-SM mice had higher energy expenditure in the light phase associated with lower body weight and fat mass and increased insulin sensitivity. Mutant mice also showed higher fasting glucose levels, whereas insulin levels and intraperitoneal glucose tolerance test results were similar to those in control animals. Interleukin (IL)-6 signaling was strongly activated in the liver of cGKI-SM mice as demonstrated by increased levels of IL-6, phospho-signal transducer and activator of transcription 3 (Tyr 705), suppressor of cytokine signaling-3, and serum amyloid A2. Insulin-stimulated tyrosine phosphorylation of the insulin receptor in the liver was impaired in cGKI-SM mice. The fraction of Mac-2–positive macrophages in the liver was significantly higher in cGKI-SM mice than in control mice. In contrast with cGKI-SM mice, conditional knockout mice lacking cGKI only in the nervous system were normal with respect to body weight, energy expenditure, fasting glucose, IL-6, and insulin action in the liver.

CONCLUSIONS

Genetic deletion of cGKI in non-neuronal cells results in a complex metabolic phenotype, including liver inflammation and fasting hyperglycemia. Loss of cGKI in hepatic stellate cells may affect liver metabolism via a paracrine mechanism that involves enhanced macrophage infiltration and IL-6 signaling.

Influence of energy balance on the somatotrophic axis and matrix metalloproteinase expression in the endometrium of the postpartum dairy cow

Postpartum dairy cows enter a period of negative energy balance (NEB) associated with low circulating IGF1, during which the uterus must undergo extensive repair following calving. This study investigated the effects of NEB on expression of IGF family members and related genes in the involuting uterus. Cows were allocated to two treatments using differential feeding and milking regimes to produce mild NEB or severe NEB (SNEB). Uterine endometrial samples collected 2 weeks post partum were analysed by quantitative PCR. The expression of IGF-binding protein 4 (IGFBP4) mRNA increased in the endometrium of SNEB cows, with trends towards increased IGFBP1 and reduced IGFBP6 expression. There were no significant differences between treatments in mRNA expression of IGF1, IGF2 or of any hormone receptor studied, but significant correlations across all cows in the expression levels of groups of receptors suggested common regulatory mechanisms: type 1 IGF receptor (IGF1R), IGF2R and insulin receptor (INSR); GHR with ESR1; and ESR2 with NR3C1. The expression of IGF1R and INSR also positively correlated with the circulating urea concentration. Matrix metalloproteinases (MMPs) are important in tissue remodelling and can affect IGF signalling via interaction with IGFBPs. The expression levels of MMP1, MMP3, MMP9 and MMP13 mRNAs all showed major upregulation in the endometrium of cows in SNEB and all except MMP9 were highly correlated with expression of IGFBP4. Alpha(2)-HS-glycoprotein (AHSG) and PDK4, two genes implicated in insulin resistance, were also highly expressed in SNEB. These results suggest that cows in SNEB experience alterations to the IGF and insulin signalling pathways in the postpartum endometrium. This may affect the rate of tissue repair with a possible negative impact on subsequent fertility.

Plasma fetuin-A concentrations in young and older high- and low-active men

Fetuin-A is a liver-derived factor that may play a role in insulin resistance and age-related chronic diseases (eg, type 2 diabetes mellitus and cardiovascular [CV] disease). Regular exercise improves CV risk and insulin sensitivity; however, it is unknown whether chronic exercise training is related to circulating levels of fetuin-A. Therefore, this study examined whether plasma fetuin-A levels were related to age and chronic physical activity in men. We hypothesized that chronic physical activity would be related to lower plasma fetuin-A levels in younger and older men. In healthy high-active (HI) and low-active (LO) young (HI, n = 7; LO, n = 8) and older (HI, n = 12, LO, n = 11) men, we determined cardiorespiratory fitness (maximal oxygen uptake), plasma fetuin-A levels, plasma insulin, insulin resistance (homeostasis model assessment of insulin resistance), and the standard risk factors for CV disease. Groups were matched for body mass index. Fetuin-A was significantly higher (~20%) in both young and older LO men compared with their HI counterparts, and fetuin-A was inversely related to maximal oxygen uptake (r = -0.40, P = .014). Plasma fetuin-A levels showed trends to be significantly correlated with insulin (r = -0.34, P = .052) and homeostasis model assessment of insulin resistance (r = 0.33, P = .058) in the older individuals. In younger participants, fetuin-A was related to blood pressure and cholesterol measures. These results indicate that low levels of fetuin-A are related to cardiorespiratory fitness and a number of conventional CV and metabolic disease risk factors independent of age and body mass index. Therefore, the maintenance of low levels of circulating fetuin-A may be a novel mechanism contributing to enhanced insulin sensitivity with regular physical activity.

Serum fetuin-A is correlated with metabolic syndrome in middle-aged and elderly Chinese

OBJECTIVE

Fetuin-A is an important player in the enhancement of insulin resistance. We aimed to investigate the association of serum fetuin-A and metabolic syndrome (MetS) in a community based Chinese population.

METHODS

A total of 5469 subjects aged 40 years or above were recruited from two urban communities in Shanghai. Demographic, anthropometric and biochemical features were collected according to a standard protocol. Serum fetuin-A levels were measured using ELISA and the modified NCEP-ATP III criteria were adopted to diagnose MetS.

RESULTS

A higher level of serum fetuin-A was well associated with a variety of metabolic disorders and an increased prevalence of MetS. The relative risks for MetS were markedly elevated in a dose-dependent manner both before and after extended adjustment in total participants (adjusted odds ratios were 1.00, 1.11, 1.20 and 1.40 for fetuin-A quartiles 1, 2, 3 and 4, respectively; P value for trend = 0.0002). MetS risks were also significantly associated with serum fetuin-A in various subgroups of sex, age, body mass index and glycaemic status. Moreover, an elevated serum fetuin-A was also independently associated with MetS components including central obesity, high blood pressure, high blood glucose and high triglycerides. Stepwise regression analyses revealed fetuin-A as an independent determinant of insulin resistance measured by the index of homeostasis model (HOMA-IR) (β = 0.064; P = 0.009).

CONCLUSION

Serum fetuin-A levels were strongly and independently associated with MetS and its components in community-dwelling Chinese adults.

Association of the rs738409 polymorphism in PNPLA3 with liver damage and the development of nonalcoholic fatty liver disease

Background

In a genome-wide association scan, the single-nucleotide polymorphism (SNP) rs738409 in the patatin-like phospholipase 3 gene (PNPLA3) was strongly associated with increased liver fat content. We investigated whether this SNP is associated with the occurrence and progression of nonalcoholic fatty liver disease (NAFLD) in the Japanese population.

Methods

SNP rs738409 was genotyped by the Taqman assay in 253 patients with NAFLD (189 with nonalcoholic steatohepatitis [NASH] and 64 with simple steatosis) and 578 control subjects. All patients with NAFLD underwent liver biopsy. Control subjects had no metabolic disorders. For a case-control study, the χ²-test (additive model) was performed. Odds ratios (ORs) were adjusted for age, gender, and body mass index (BMI) by using multiple logistic regression analysis with genotypes (additive model), age, gender, and BMI as the independent variables. Multiple linear regression analysis was performed to test the independent effect of risk allele on clinical parameters while considering the effects of other variables (age, gender, and BMI), which were assumed to be independent of the effect of the SNP.

Results

The risk allele (G-allele) frequency of rs738409 was 0.44 in the control subjects and 0.60 in patients with NAFLD; this shows a strong association with NAFLD (additive model, P = 9.4 × 10^-10). The OR (95% confidence interval) adjusted for age, gender, and BMI was 1.73 (1.25-2.38). Multiple linear regression analysis indicated that the G-allele of rs738409 was significantly associated with increases in aspartate transaminase (AST) (P = 0.00013), alanine transaminase (ALT) (P = 9.1 × 10^-6), and ferritin levels (P = 0.014), and the fibrosis stage (P = 0.011) in the patients with NAFLD, even after adjustment for age, gender, and BMI. The steatosis grade was not associated with rs738409.

Conclusions

We found that in the Japanese population, individuals harboring the G-allele of rs738409 were susceptible to NAFLD, and that rs738409 was associated with plasma levels of ALT, AST, and ferritin, and the histological fibrosis stage. Our study suggests that PNPLA3 may be involved in the progression of fibrosis in NAFLD.

Relationships of circulating sex hormone-binding globulin with metabolic traits in humans

OBJECTIVE

Recent data suggested that sex hormone-binding globulin (SHBG) levels decrease when fat accumulates in the liver and that circulating SHBG may be causally involved in the pathogenesis of type 2 diabetes in humans. In the present study, we investigated mechanisms by which high SHBG may prevent development to diabetes.

RESEARCH DESIGN AND METHODS

Before and during a 9-month lifestyle intervention, total body and visceral fat were precisely measured by magnetic resonance (MR) tomography and liver fat was measured by (1)H-MR spectroscopy in 225 subjects. Insulin sensitivity was estimated from a 75-g oral glucose tolerance test (IS(OGTT)) and measured by a euglycemic hyperinsulinemic clamp (IS(clamp), n = 172). Insulin secretion was measured during the OGTT and an ivGTT (n = 172).

RESULTS

SHBG levels correlated positively with insulin sensitivity (IS(OGTT), P = 0.037; IS(clamp), P = 0.057), independently of age, sex, and total body fat. In a multivariate model, these relationships were also significant after additional adjustment for levels of the adipokine adiponectin and the hepatokine fetuin-A (IS(OGTT), P = 0.0096; IS(clamp), P = 0.029). Adjustment of circulating SHBG for liver fat abolished the relationships of SHBG with insulin sensitivity. In contrast, circulating SHBG correlated negatively with fasting glycemia, before (r = -0.17, P = 0.009) and after (r = -0.14, P = 0.04) adjustment for liver fat. No correlation of circulating SHBG with adjusted insulin secretion was observed (OGTT, P = 0.16; ivGTT, P = 0.35). The SNP rs1799941 in SHBG was associated with circulating SHBG (P ≤ 0.025) but not with metabolic characteristics (all P > 0.18).

CONCLUSIONS

Possible mechanisms by which high circulating SHBG prevents the development of type 2 diabetes involve regulation of fasting glycemia but not alteration of insulin secretory function.

The "thrifty" gene encoding Ahsg/Fetuin-A meets the insulin receptor: Insights into the mechanism of insulin resistance

Ahsg (fetuin-A) is a 55-59kDa phosphorylated glycoprotein synthesized in the adult predominantly by hepatocytes, from which it enters the circulation. When dysregulated, this glycoprotein operates to influence the clinical sequelae of insulin resistance-type 2 diabetes and cardiovascular disease. The pathological sequelae likely arise from two separable molecular "faces" of Ahsg-one acting at the level of the insulin receptor and a second face influencing ectopic biomineralization in the intima. A detailed understanding of these two functional faces of Ahsg is not yet clear for lack of structural studies. Ahsg has a physiological role in the biomineralization of bone, which when dysregulated can lead to ectopic calcification of soft tissues in the vasculature. Ahsg has a second physiological function in regulating how insulin signals through its receptor, a transmembrane tyrosine kinase. Dysregulation of this "face" of Ahsg results in morbid sequelae such as impaired glucose disposal and fatty liver. Ahsg binds to tandem fibronectin type 3 (Fn3) domains present in the 194 amino acid residue extracellular portion of the β-subunit of the insulin receptor, distant from the high-affinity pocket formed by two complementing α-subunits where insulin binds. Only two proteins are known to bind directly to the insulin receptor ectodomain - insulin and Ahsg - the former turns on the receptor's intrinsic tyrosine kinase (TK) activity, and the latter shuts it down. Recent X-ray crystallographic studies of the ectodomain of the insulin receptor now sharpen our understanding of the receptor's extracellular α-subunit and linked β-subunit. Ahsg genotype and its circulating level have been correlated with body morphometrics (obese versus lean and visceral adiposity) in epidemiological studies enrolling thousands of patients. Epidemiological studies from the clinic reveal high levels of circulating Ahsg in insulin resistance and diabetes. This review endeavors to explain how one protein can mediate diverse pathologies, but specifically addresses its metabolic "face" blunting insulin receptor activity, an action leading to insulin resistance.

Adipokine pattern in subjects with impaired fasting glucose and impaired glucose tolerance in comparison to normal glucose tolerance and diabetes

AIM

Altered adipokine serum concentrations early reflect impaired adipose tissue function in obese patients with type 2 diabetes (T2D). It is not entirely clear whether these adipokine alterations are already present in prediabetic states and so far there is no comprehensive adipokine panel available. Therefore, the aim of this study was to assess distinct adipokine profiles in patients with normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT) or T2D.

METHODS

Based on 75 g oral glucose tolerance tests, 124 individuals were divided into groups of IFG (n = 35), IGT (n = 45), or NGT (n = 43). Furthermore, 56 subjects with T2D were included. Serum concentrations of adiponectin, chemerin, fetuin-A, leptin, interleukin (IL)-6, retinol-binding protein 4 (RBP4), monocyte chemoattractant protein (MCP)-1, vaspin, progranulin, and soluble leptin receptor (sOBR) were measured by ELISAs.

RESULTS

Chemerin, progranulin, fetuin-A, and RBP4, IL-6, adiponectin and leptin serum concentrations were differentially regulated among the four investigated groups but only circulating chemerin was significantly different in patients with IGT compared to those with IFG. Compared to T2D the IFG subjects had higher serum chemerin, progranulin, fetuin-A and RBP4 levels which was not detectable in the comparison of the T2D and IGT group.

CONCLUSION

Alterations in adipokine serum concentrations are already detectable in prediabetic states, mainly for chemerin, and may reflect adipose tissue dysfunction as an early pathogenetic event in T2D development. In addition, distinct adipokine serum patterns in individuals with IFG and IGT suggest a specific role of adipose tissue in the pathogenesis of these prediabetic states.

Global proteomic profiling reveals altered proteomic signature in schizophrenia serum

Schizophrenia is one of the most severe psychiatric disorders affecting 1% of the world population. There is yet no empirical method to validate the diagnosis of the disease. The identification of an underlying molecular alteration could lead to an improved disease understanding and may yield an objective panel of biomarkers to aid in the diagnosis of this devastating disease. Presented is the largest reported liquid chromatography-mass spectrometry-based proteomic profiling study investigating serum samples taken from first-onset drug-naive patients compared with samples collected from healthy volunteers. The results of this large-scale study are presented along with enzyme-linked immunosorbent assay-based validation data.

Association between higher serum fetuin-A concentrations and abnormal albuminuria in middle-aged and elderly chinese with normal glucose tolerance

OBJECTIVE

To study the association of serum fetuin-A as a potential risk factor with abnormal albuminuria in Chinese individuals with normal glucose tolerance (NGT).

RESEARCH DESIGN AND METHODS

The cross-sectional analysis included 607 men and 1,042 women aged 40 or older with NGT.

RESULTS

Women with combined microalbuminuria and macroalbuminuria (n=68) had significantly higher serum fetuin-A concentrations than those with normal albumin excretion (n=974) (314.3 vs. 280.4 mg/l, P=0.007). Compared with the lowest quartile, the highest quartile of serum fetuin-A had 40% increased risk of abnormal albuminuria after the multiple adjustments in women (Pfor trend=0.02). However, the associations were not detected in men.

CONCLUSIONS

Higher serum fetuin-A was associated with abnormal albuminuria independent of BMI, waist circumference, homeostasis model assessment of insulin resistance, blood pressure, and other determinants of albuminuria in middle-aged and elderly Chinese women with NGT.

Serum fetuin A/α2HS-glycoprotein levels in patients with non-alcoholic fatty liver disease: relation with liver fibrosis

BACKGROUND

Serum concentrations of fetuin A/α2HS-glycoprotein (AHSG) have been linked to human metabolic alterations and can serve as an indicator of liver cell function. We assayed serum levels of AHSG in patients with non-alcoholic fatty liver disease (NAFLD), a hepatic manifestation of the metabolic syndrome, and examined their association with clinical, biochemical and histological phenotypes.

METHODS

Serum AHSG levels were determined by enzyme linked immunosorbent assay in 99 patients with biopsy-proven NAFLD and 75 age- and gender-matched controls.

RESULTS

Serum AHSG levels were significantly higher in patients with NAFLD (940 ± 120 μg/mL) compared with healthy controls (800 ± 130 μg/mL, Student's t test, P < 0.001). Bivariate analyses (Spearman's rank correlation) in patients with NAFLD showed a statistically significant association between AHSG levels and insulin resistance as assessed by the HOMA (homeostasis model assessment) index (r = 0.31, P < 0.01) and the liver fibrosis score index (r = 0.36, P < 0.001). The association between AHSG and fibrosis remained statistically significant even after adjustment for potential confounders, including the HOMA index ([beta] = 1.65, t = 2.38, P < 0.05).

CONCLUSION

Serum AHSG levels are significantly increased in adult patients with biopsy-proven NAFLD and are associated with insulin resistance. Importantly, our pilot data indicate that serum AHSG levels may identify NAFLD patients with higher fibrosis scores.

Enforced expression of protein kinase C in skeletal muscle causes physical inactivity, fatty liver and insulin resistance in the brain

Among the multitude of dysregulated signalling mechanisms that comprise insulin resistance in divergent organs, the primary events in the development of type 2 diabetes are not well established. As protein kinase C (PKC) activation is consistently present in skeletal muscle of obese and insulin resistant subjects, we generated a transgenic mouse model that overexpresses constitutively active PKC-β₂ in skeletal muscle to test whether activation of PKC is sufficient to cause an aversive whole-body phenotype. Upon this genetic modification, increased serine phosphorylation in Irs1 was observed and followed by impaired ³H-deoxy-glucose uptake and muscle glycogen content, and transgenic mice exhibited insulin and glucose intolerance as they age. Muscle histochemistry revealed an increase in lipid deposition (intramyocellular lipids), and transgenic mice displayed impaired expression of transcriptional regulators of genes involved in fatty acid oxidation (peroxisome proliferator-activated receptor-γ, PGC-1β, acyl-CoA oxidase) and lipolysis (hormone-sensitive lipase). In this regard, muscle of transgenic mice exhibited a reduced capacity to oxidize palmitate and contained less mitochondria as determined by citrate synthase activity. Moreover, the phenotype included a profound decrease in the daily running distance, intra-abdominal and hepatic fat accumulation and impaired insulin action in the brain. Together, our data suggest that activation of a classical PKC in skeletal muscle as present in the pre-diabetic state is sufficient to cause disturbances in whole-body glucose and lipid metabolism followed by profound alterations in oxidative capacity, ectopic fat deposition and physical activity.

Insulin-sensitive obesity

The association between obesity and impaired insulin sensitivity has long been recognized, although a subgroup of obese individuals seems to be protected from insulin resistance. In this study, we systematically studied differences in adipose tissue biology between insulin-sensitive (IS) and insulin-resistant (IR) individuals with morbid obesity. On the basis of glucose infusion rate during euglycemic hyperinsulinemic clamps, 60 individuals with a BMI of 45 +/- 1.3 kg/m(2) were divided into an IS and IR group matched for age, sex, and body fat prior to elective surgery. We measured fat distribution, circulating adipokines, and parameters of inflammation, glucose, and lipid metabolism and characterized adipose tissue morphology, function, and mRNA expression in abdominal subcutaneous (sc) and omental fat. IS compared with IR obese individuals have significantly lower visceral fat area (138 +/- 27 vs. 316 +/- 91 cm(2)), number of macrophages in omental adipose tissue (4.9 +/- 0.8 vs. 13.2 +/- 1.4%), mean omental adipocyte size (528 +/- 76 vs. 715 +/- 81 pl), circulating C-reactive protein, progranulin, chemerin, and retinol-binding protein-4 (all P values <0.05), and higher serum adiponectin (6.9 +/- 3.4 vs. 3.4 +/- 1.7 ng/ml) and omental adipocyte insulin sensitivity (all P values <0.01). The strongest predictors of insulin sensitivity by far were macrophage infiltration together with circulating adiponectin (r(2) = 0.98, P < 0.0001). In conclusion, independently of total body fat mass, increased visceral fat accumulation and adipose tissue dysfunction are associated with IR obesity. This suggests that mechanisms beyond a positive caloric balance such as inflammation and adipokine release determine the pathological metabolic consequences in patients with obesity.

NF-kappaB mediates lipid-induced fetuin-A expression in hepatocytes that impairs adipocyte function effecting insulin resistance

Fetuin-A, a hepatic secretory protein, has recently been implicated in insulin resistance and Type 2 diabetes. It is an endogenous inhibitor of insulin receptor tyrosine kinase. However, regulation of fetuin-A synthesis in relation to insulin resistance is unclear. In the present paper, we report that both non-esterified ('free') fatty acids and fetuin-A coexist at high levels in the serum of db/db mice, indicating an association between them. For an in-depth study, we incubated palmitate with HepG2 cells and rat primary hepatocytes, and found enhanced fetuin-A secretion to more than 4-fold over the control. Interestingly, cell lysates from these incubations showed overexpression and activity of NF-kappaB (nuclear factor kappaB). In NF-kappaB-knockout HepG2 cells, palmitate failed to increase fetuin-A secretion, whereas forced expression of NF-kappaB released fetuin-A massively in the absence of palmitate. Moreover, palmitate stimulated NF-kappaB binding to the fetuin-A promoter resulting in increased reporter activity. These results suggest NF-kappaB to be the mediator of the palmitate effect. Palmitate-induced robust expression of fetuin-A indicates the occurrence of additional targets, and we found that fetuin-A severely impaired adipocyte function leading to insulin resistance. Our results reveal a new dimension of lipid-induced insulin resistance and open another contemporary target for therapeutic intervention in Type 2 diabetes.

Serum fetuin-A, cardiovascular risk factors, and six-year follow-up outcome in patients with coronary heart disease

High circulating fetuin-A has recently been linked to risk of primary cardiovascular disease (CVD). The clinical importance of fetuin-A in patients at markedly increased cardiovascular risk, however, has not been fully elucidated. We studied the association between serum fetuin-A and future cardiovascular outcome in patients with prevalent coronary heart disease (CHD). Fetuin-A levels were measured in 1,049 patients with CHD. Associations with traditional cardiovascular risk factors and with secondary CVD events during 6 years of follow-up (median 73.4 months, interquartile range 57.4 to 74.3) were analyzed. Serum fetuin-A levels were significantly increased in patients with prevalent hypertriglyceridemia (0.71 vs 0.69 g/L, p = 0.013). No association with baseline metabolic syndrome was found (odds ratio 0.95 for highest vs lowest fetuin-A quintile, 95% confidence interval 0.59 to 1.53, p = 0.82). In Cox proportional hazards analyses, serum fetuin-A levels were not significantly associated with secondary CVD events (hazard ratio 0.67 for highest vs lowest fetuin-A quintile, 95% confidence interval 0.37 to 1.21, p = 0.18). In conclusion, fetuin-A is significantly associated hypertriglyceridemia but not with other traditional cardiovascular risk factors or metabolic syndrome in patients with manifest CHD. Measurement of serum fetuin-A levels may not emerge as a valuable tool for evaluating future CVD risk in patients aggressively treated for advanced atherosclerosis.

Serum fetuin-A is an independent marker of insulin resistance in Japanese men

AIM

Fetuin-A, also known as alpha2-Heremans Schmid glycoprotein, is an abundant plasma protein synthesized predominantly in the liver. Fetuin-A inhibits insulin receptor autophosphorylation, which is mediated by its intrinsic tyrosine kinase activity. In this study, we examined the association between the serum fetuin-A level and insulin resistance in Japanese men.

METHODS

We recruited 300 unrelated Japanese men without known chronic diseases, such as diabetes mellitus, or a history of regular drug use, and who underwent health examinations. From a 75-g oral glucose tolerance test, the study population included 194 individuals with normal glucose tolerance, 91 with impaired glucose tolerance and/or impaired fasting glucose, and 15 with diabetes mellitus. Serum fetuin-A concentrations were measured using an ELISA kit.

RESULTS

Serum fetuin-A concentrations were positively correlated with fasting insulin levels (r = 0.269, p<0.001), HOMA-IR (r = 0.274, p<0.001) and LDL-cholesterol (r = 0.172, p<0.01), and negatively correlated with HDL-cholesterol concentrations (r = -0.191, p<0.001). Fetuin-A concentrations were also positively correlated with serum leptin (r = 0.150, p<0.01) and negatively with adiponectin concentrations (r = -0.208, p<0.001). Stepwise regression analyses confirmed that the fetuin-A concentration was independently associated with the fasting insulin level and HOMA-IR, as were body mass index, triglyceride, LDL-cholesterol, leptin and adiponectin concentrations.

CONCLUSION

Our data suggest that increased serum fetuin-A levels constitute an independent marker of insulin resistance and an atherogenic lipid profile in Japanese men.

Examination of association with candidate genes for diabetic nephropathy in a Mexican American population

BACKGROUND AND OBJECTIVES

Diabetic nephropathy (DN) is a multifactorial complication characterized by persistent proteinuria in susceptible individuals with type 1 and type 2 diabetes. Disease burden in people of Mexican-American descent is particularly high, but there are only a few studies that characterize genes for DN in this ethnic group. Two genes, carnosine dipeptidase 1 (CNDP1) and engulfment and cell motility 1 (ELMO1) previously showed association with DN in other ethnic groups. CNDP1 and ELMO1 were examined along with eight other genes that are less well characterized for DN in a new study of Mexican-Americans.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The target sample was patients of Mexican-American ancestry collected from three centers: 455 patients with DN and 437 controls with long-term diabetes but no incident nephropathy. Forty-two, 227, and 401 single nucleotide polymorphisms (SNPs) in CNDP1, ELMO1, and the other eight genes, respectively, were examined.

RESULTS

No region in CNDP1 or ELMO1 showed significant P values. Of the other eight candidate genes, an association of DN with a SNP pair, rs2146098 and rs6659783, was found in hemicentin 1 (HMCN1) (unadjusted P = 6.1 x 10(-5)). Association with a rare haplotype in this region was subsequently identified.

CONCLUSIONS

The associations in CNDP1 or ELMO1 were not replicable; however, an association of DN with HMCN1 was found. Additional work at this and other loci will enable refinement of the genetic hypotheses regarding DN in the Mexican-American population to find therapies for this debilitating disease.

The impact of liver fat vs visceral fat in determining categories of prediabetes

AIMS/HYPOTHESIS

Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are risk factors for type 2 diabetes and cardiovascular disease; however, their impact on these endpoints differs. Because liver fat and visceral fat are important determinants of glucose and lipid metabolism, we investigated whether these fat compartments and their humoral products, the adipokine adiponectin and the hepatokine fetuin-A, differ in their impact on the glucose categories.

METHODS

In 330 individuals at risk of type 2 diabetes, glucose tolerance status was determined by a 2 h 75 g OGTT. Total-body and visceral fat were precisely quantified by magnetic resonance (MR) tomography and liver fat by (1)H-MR spectroscopy.

RESULTS

A total of 210 individuals had normal glucose tolerance (NGT), 41 isolated IFG, 43 isolated IGT and 36 IFG+IGT. Total-body fat was not different (p = 0.51), although a small but continuous increase in visceral fat was found among the categories after adjustment for age and sex (NGT: 3.07 +/- 0.10 kg; IFG: 3.11 +/- 0.21 kg; IGT: 3.61 +/- 0.21 kg; IFG+IGT: 3.84 +/- 0.23 kg [SEs], p = 0.03). A larger difference was found for liver fat (NGT: 4.73 +/- 0.42%; IFG: 5.86 +/- 0.92%; IGT: 8.65 +/- 0.92%; IFG + IGT: 11.11 +/- 1.01%, p < 0.0001). The differences among the categories were small for adiponectin (p = 0.14), but larger for fetuin-A (p = 0.015). Among fat compartments, liver fat (p < 0.0001) and among circulating variables fetuin-A (p = 0.016) were the strongest determinants of the categories.

CONCLUSIONS/INTERPRETATION

Liver fat, more than visceral fat, strongly increases when glycaemia and glucose tolerance move from NGT to isolated IFG, isolated IGT and IFG+IGT. Because liver-derived circulating fetuin-A determines, although weakly, prediabetes categories, it is worth searching for hepatokines more strongly predicting prediabetes.

Mechanisms of dexamethasone-induced disturbed sleep and fatigue in paediatric patients receiving treatment for ALL

BACKGROUND

Dexamethasone contributes to high cure rates in paediatric acute lymphoblastic leukaemia (ALL) but significantly and adversely alters sleep and fatigue. Herein we explored three mechanisms (pharmacokinetics, serum albumin and pharmacogenetics) through which dexamethasone may cause debilitating fatigue and disrupted sleep.

METHODS

We enrolled 100 patients on a 10-d study: 5-d of no dexamethasone (OFF DEX) followed by 5-d of dexamethasone (ON DEX) during continuation chemotherapy. Sleep variables were collected with continuous actigraphy on days 1 through 5, both OFF DEX and ON DEX. On days 2 and 5 of each 5-d period, parents and patients 7 years of age and older completed a sleep diary and Fatigue Scale questionnaire. Blood was collected at 0 (pre-dexamethasone), 1, 2, 4 and 8 h after the first oral dexamethasone dose for pharmacokinetic analysis. Serum albumin concentration was retrospectively analysed in stored samples. Patient DNA was genotyped for 99 polymorphic loci in candidate genes associated with glucocorticoid metabolism.

RESULTS

Dexamethasone clearance was significantly greater in younger patients than in older ones and in lower risk patients. In multiple regression models, risk group was significantly related to pharmacokinetic parameters. We found that polymorphisms in three genes (AHSG, IL6, POLDIP3) were significantly associated with sleep measures but not with fatigue.

CONCLUSION

Risk group had the most significant relationship with disrupted sleep in patients while on dexamethasone. Serum albumin levels had neither a direct relationship with sleep or fatigue variables nor an indirect relationship through systemic exposure to dexamethasone. We identified candidate genes that may help explain the adverse events of disrupted sleep in paediatric patients receiving dexamethasone.

Mechanisms linking obesity, chronic kidney disease, and fatty liver disease: the roles of fetuin-A, adiponectin, and AMPK

Obesity is a risk factor for chronic kidney disease (CKD) and nonalcoholic fatty liver disease (NAFLD). Recent studies identify mechanisms common to both diseases linked through an interorgan communication orchestrated by fetuin-A and adiponectin. In liver and kidney, the energy sensor 5'-AMP activated protein kinase (AMPK) is pivotal to directing podocytes and hepatocytes to compensatory and potentially deleterious pathways, leading to inflammatory and profibrotic cascades culminating in end-organ damage. Regulation of these early upstream pathways may provide new therapeutic targets for these increasingly common sequelae of obesity.

Circulating palmitoleate strongly and independently predicts insulin sensitivity in humans

OBJECTIVE

We investigated whether palmitoleate, which prevents insulin resistance in mice, predicts insulin sensitivity in humans.

RESEARCH DESIGN AND METHODS

The fasting fatty acid pattern in the plasma free fatty acid (FFA) fraction was determined in 100 subjects at increased risk for type 2 diabetes. Insulin sensitivity was estimated during an oral glucose tolerance test (OGTT) at baseline and after 9 months of lifestyle intervention and measured during the euglycemic-hyperinsulinemic clamp (n = 79).

RESULTS

Circulating palmitoleate (OGTT:F ratio = 8.2, P = 0.005; clamp:F ratio = 7.8, P = 0.007) but not total FFAs (OGTT:F ratio = 0.6, P = 0.42; clamp:F ratio = 0.7, P = 0.40) correlated positively with insulin sensitivity, independently of age, sex, and adiposity. High baseline palmitoleate predicted a larger increase in insulin sensitivity. For 1-SD increase in palmitoleate, the odds ratio for being in the highest versus the lowest tertile of adjusted change in insulin sensitivity was 2.35 (95% CI 1.16-5.35).

CONCLUSIONS

Circulating palmitoleate strongly and independently predicts insulin sensitivity, suggesting that it plays an important role in the pathophysiology of insulin resistance in humans.

Endocrine factors associated with non-alcoholic fatty liver disease in women with polycystic ovary syndrome: do androgens play a role?

OBJECTIVE

To characterise the metabolic profile of women with polycystic ovary syndrome (PCOS) and non-alcoholic fatty liver disease (NAFLD) and to determine whether circulating androgens differ in PCOS women with NAFLD compared to PCOS subjects without NAFLD.

METHODS

Retrospective study of 21 women with PCOS, elevated liver enzymes and ultrasound evidence of hepatic steatosis matched with 32 PCOS women with normal liver enzymes. Extensive demographic, endocrine and metabolic data were compared. Pearson's correlation coefficients were calculated to assess for potential relationships between the free androgen index (FAI) and other dependent variables.

RESULTS

PCOS subjects with NAFLD demonstrate greater insulin resistance but have similar circulating androgen levels.

CONCLUSION

In this pilot study, insulin resistance was the most prominent feature characterising NAFLD complicating PCOS. Total testosterone, FAI, DHEAS and 17-hydroxyprogesterone levels were similar between patients with PCOS and without NAFLD.

Dissociation between fatty liver and insulin resistance in humans carrying a variant of the patatin-like phospholipase 3 gene

OBJECTIVE

In a genome-wide association scan, the rs738409 C>G single nucleotide polymorphism (SNP) in the patatin-like phospholipase 3 gene (PNPLA3) was strongly associated with increased liver fat but not with insulin resistance estimated from fasting values. We investigated whether the SNP determines liver fat independently of visceral adiposity and whether it may even play a role in protecting from insulin resistance.

RESEARCH DESIGN AND METHODS

Liver fat was measured by (1)H magnetic resonance spectroscopy and total and visceral fat by magnetic resonance tomography in 330 subjects. Insulin sensitivity was estimated during an oral glucose tolerance test and the euglycemic-hyperinsulinemic clamp (n = 222). PNPLA3 and tumor necrosis factor-alpha mRNA and triglyceride content were measured in liver biopsies from 16 subjects.

RESULTS

Liver fat correlated strongly with insulin sensitivity (P < 0.0001) independently of age, sex, total fat, and visceral fat. G allele carriers of the SNP rs738409 had higher liver fat (P < 0.0001) and an odds ratio of 2.38 (95% CI 1.37-4.20) for having fatty liver compared to C allele homozygotes. Interestingly, insulin sensitivity (oral glucose tolerance test: P = 0.99; clamp: P = 0.32), serum C-reactive protein levels, lipids, or liver enzymes (all P > 0.14) were not different among the genotypes. Additional adjustment for liver fat actually revealed increased insulin sensitivity in more obese carriers of the G allele (P = 0.01). In liver biopsies triglyceride content correlated positively with expression of the proinflammatory gene tumor necrosis factor-alpha in C allele homozygotes (n = 6, P = 0.027) but not in G allele carriers (n = 10, P = 0.149).

CONCLUSIONS

PNPLA3 may be an important key to understand the mechanisms discriminating fatty liver with and without metabolic consequences.

Fetuin-A and change in body composition in older persons

CONTEXT

Fetuin-A inhibits the insulin receptor in vitro. Higher serum fetuin-A concentrations are associated with type 2 diabetes longitudinally and greater adiposity in cross-sectional analyses. Whether higher fetuin-A concentrations are associated with accumulation of adiposity over time is unknown.

OBJECTIVE

To determine the association of fetuin-A levels with changes in body composition over 5 yr.

STUDY DESIGN

Observational cohort study nested in the Health Aging and Body Composition Study.

PREDICTOR

Serum fetuin-A levels.

OUTCOMES

Visceral adipose tissue (VAT), abdominal sc adipose tissue, and thigh muscle area by computed tomography, and waist circumference and body mass index were measured at baseline and again after 5 yr. Percent change and extreme change (>1.5 sds) in each measure were calculated.

RESULTS

Over 5 yr, subjects lost body mass in each measure, including 6% decline in VAT. Yet each sd (0.42 g/liter) higher fetuin-A concentration was associated with a 5.5% increase in VAT over 5 yr (95% confidence interval 1.9-9.2%; P = 0.003) in models adjusted for age, sex, race, clinical site, diabetes, physical activity, triglycerides, kidney function, and the baseline VAT score. Similarly, higher fetuin-A concentrations were associated with extreme VAT gain (relative risk 1.70, 95% confidence interval 1.12-2.60, P = 0.01). Fetuin-A concentrations were not statistically significant associated with change in any other measures of body composition (P > 0.20).

CONCLUSIONS

Higher fetuin-A concentrations are associated with the accumulation of VAT in well-functioning, community-living older persons. The mechanisms linking fetuin-A, VAT, and insulin resistance remain to be determined.

Pathomechanisms of type 2 diabetes genes

Type 2 diabetes mellitus is a complex metabolic disease that is caused by insulin resistance and beta-cell dysfunction. Furthermore, type 2 diabetes has an evident genetic component and represents a polygenic disease. During the last decade, considerable progress was made in the identification of type 2 diabetes risk genes. This was crucially influenced by the development of affordable high-density single nucleotide polymorphism (SNP) arrays that prompted several successful genome-wide association scans in large case-control cohorts. Subsequent to the identification of type 2 diabetes risk SNPs, cohorts thoroughly phenotyped for prediabetic traits with elaborate in vivo methods allowed an initial characterization of the pathomechanisms of these SNPs. Although the underlying molecular mechanisms are still incompletely understood, a surprising result of these pathomechanistic investigations was that most of the risk SNPs affect beta-cell function. This favors a beta-cell-centric view on the genetics of type 2 diabetes. The aim of this review is to summarize the current knowledge about the type 2 diabetes risk genes and their variants' pathomechanisms.

Abundantly expressed hepatic genes and their differential expression in liver of prelaying and laying geese

Geese have a short egg-laying period and a low egg production rate. To induce and maintain egg laying, genes related to generating hepatic lipid for yolk deposition should be adequately expressed. Liver mRNA from 6 laying geese was extracted and used for construction of a full-length enriched cDNA library. About 2,400 clones containing gene sequences were determined and National Center for Biotechnology Information Gallus gallus Gene Index databases were used to compare and analyze these sequences. Ten highly expressed genes were selected to determine the differential expression between laying and prelay goose liver. Tissue distribution data showed that very low density apolipoprotein II, liver type fatty acid binding protein, vitellogenin I, and vitellogenin II transcripts were specifically expressed in the liver of laying geese. Ovoinhibitor, preproalbumin, alpha-2-hs-glycoprotein, and vitamin D binding protein mRNA were highly expressed in the liver and to a lesser extent in other tissues. Ovotransferrin mRNA was expressed in liver, ovary, oviduct, shell gland, brain, and adipose tissues. The concentration of transthyretin mRNA was high in the liver and brain. The mRNA concentrations of liver type fatty acid binding protein, alpha-2-hs-glycoprotein, and transthyretin in the livers of laying and prelay geese were not different. The concentrations of hepatic ovotransferrin, ovoinhibitor, preproalbumin, very low density apolipoprotein II, vitellogenin I, vitellogenin II, and vitamin D binding protein mRNA were higher in the liver of laying geese than in prelay geese, suggesting that these genes may be involved in laying function or lipid metabolism related to egg formation.

Association of AHSG gene polymorphisms with fetuin-A plasma levels and cardiovascular diseases in the EPIC-Potsdam study

BACKGROUND

Elevated circulating levels of fetuin-A in blood have been associated with increased risk of cardiovascular disease. The goal of our study was to prospectively investigate the potential causal nature of the association between fetuin-A levels and myocardial infarction (MI) and ischemic stroke by applying a Mendelian randomization approach.

METHODS AND RESULTS

Five tagging single-nucleotide polymorphisms (rs2248690, rs2070633, rs2070635, rs4917, and rs6787344) capturing the common genetic variation of the fetuin-A coding gene alpha(2)-Heremans-Schmid glycoprotein (AHSG) were genotyped in a case-cohort comprising 214 MI cases, 154 ischemic stroke cases, and 2152 persons who remained free of cardiovascular disease events in the European Prospective Investigation into Cancer and Nutrition-Potsdam study. One single-nucleotide polymorphism (rs6787344) was discarded because of Hardy-Weinberg disequilibrium. All AHSG tagging single-nucleotide polymorphisms were associated with fetuin-A plasma levels (P<0.0001). AHSG rs4917 C>T showed the strongest association, explaining 21.2% of the phenotypic variance independent of potential confounding factors (+35.5 microg/mL increase per C-allele, P= 2 x 10(-121)). Furthermore, the rs4917 C-allele showed a significant association with MI (adjusted hazard rate ratio [RR] 1.34, 95% CI 1.05 to 1.70, P=0.02). Based on this association, the expected RR for MI corresponding to 1 SD in fetuin-A was 1.54 and, thus, strikingly matches the previously observed association between fetuin-A plasma levels and MI risk (RR 1.59).

CONCLUSIONS

These data provide evidence for the causal nature of the recently reported association between fetuin-A plasma levels and MI risk, thereby suggesting an involvement of fetuin-A in the pathogenesis of cardiovascular disease.

Non-invasive assessment and quantification of liver steatosis by ultrasound, computed tomography and magnetic resonance

Hepatic steatosis is the most prevalent liver disorder in the developed world. It is closely associated with features of metabolic syndrome, especially insulin resistance and obesity. The two most common conditions associated with fatty liver are alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Liver biopsy is considered the gold standard for the assessment of liver fat, but there is a need for less invasive diagnostic techniques. New imaging modalities are emerging, which could provide more detailed information about hepatic tissue or even replace biopsy. In the present review, available imaging modalities (ultrasound, computed tomography, magnetic resonance imaging and proton magnetic resonance spectroscopy) are presented which are employed to detect or even quantify the fat content of the liver. The advantages and disadvantages of the above-mentioned imaging modalities are discussed. Although none of these techniques is able to differentiate between microvesicular and macrovesicular steatosis and to reveal all features visible using histology, the proposed diagnostic modalities offer a wide range of additional information such as anatomical and morphological information non-invasively. In particular, magnetic resonance imaging and proton magnetic resonance spectroscopy are able to quantify the hepatic fat content hence avoiding exposure to radiation. Except for proton magnetic resonance spectroscopy, all modalities offer additional information about regional fat distribution within the liver. MR elastography, which can estimate the amount of fibrosis, also appears promising in the differentiation between simple steatosis and steatohepatitis.

High glucose induces transactivation of the alpha2-HS glycoprotein gene through the ERK1/2 signaling pathway

AIM

Alpha2-Heremans Schmid glycoprotein (AHSG), also known as fetuin-A, is secreted from the liver and inhibits tyrosine kinase activity of the insulin receptor. Hyperglycemia in type 2 diabetes is not only a secondary manifestation of insulin resistance, but could also be responsible for directly inducing insulin resistance in target tissues. In this study, we examined the effect of high glucose (HG) on AHSG gene transcription in the human hepatoma cell line HepG2.

METHODS

AHSG transcriptional activity and protein expression were evaluated using reporter gene assays and Western blot analysis, respectively.

RESULTS

D-glucose, but not L-glucose or mannitol, dose-dependently enhanced AHSG promoter activity. HG (25 mM) also increased AHSG protein expression. No protein kinase C inhibitors (bisindolylmaleimide, Ro-31-8220), an inhibitor of hexosamine biosynthesis pathway (6-diazo-5-oxo-L-norleucine), or a superoxide radical scavenger (tempol) affected HG-induced transactivation. MAPK/ERK kinase inhibitors (PD98059, U0126), but not the JNK inhibitor (SP600125) or p38 inhibitor (SB203580), significantly inhibited promoter activation by HG.

CONCLUSION

Our data suggest that HG enhances AHSG transcription through activation of the ERK1/2 signaling pathway. Increased AHSG expression in the liver may be a cause of glucose toxicity in the diabetic state.

[Individualized prevention of type 2 diabetes]

The global estimated prevalence of diabetes today is 246 million people. By 2025, the figure is expected to rise to 380 million. In Germany about 7 to 8% of the population is diagnosed with diabetes. However, there are a large proportion of people with unknown diabetes and the total number of subjects with diabetes is estimated at 7 to 8 million, indicating that every tenth individual is affected by the disease. Several recent studies unanimously revealed that it is possible to prevent type 2 diabetes. Particularly lifestyle intervention showed promising results. However, there is large variability in the effect of the intervention, and people with a good response (responders) and with a low response (non-responders) can be identified. Meanwhile, several genetic and phenotypic markers have been identified, which can help predict the success of the lifestyle intervention, allowing for a more effective individualized prevention of type 2 diabetes.

Extended-release niacin decreases serum fetuin-A concentrations in individuals with metabolic syndrome

BACKGROUND

Fetuin-A, a liver-secreted phosphoprotein and physiological inhibitor of insulin receptor tyrosine kinase, is associated with insulin resistance, metabolic syndrome (MetS), and an increased risk for type 2 diabetes. However, studies on the modulation of circulating levels of fetuin-A are limited. The goal of this study was to determine the effect of niacin administration on serum total- and phosphorylated fetuin-A (phosphofetuin-A) concentrations in individuals with MetS and correlate with changes in serum lipids, insulin sensitivity, and markers of inflammation.

METHODS

Fifteen sedentary, obese, male participants, who met the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria for MetS, were treated with extended-release niacin (Niaspan) for 6 weeks. Blood samples were obtained before and after treatment with niacin.

RESULTS

Serum fetuin-A and phosphofetuin-A concentrations were decreased following niacin administration (p < 0.005). Changes in fetuin-A concentrations were correlated with changes in triglyceride (r = 0.62, p = 0.01) and C-reactive protein (CRP) concentrations (r = 0.58, p < 0.05) after niacin treatment. Changes in high-density lipoproteins (HDL)-cholesterol following niacin intervention were negatively correlated with changes in serum fetuin-A (p < 0.05) and phosphofetuin-A concentrations (p < 0.05). Serum cortisol levels were significantly elevated after niacin administration.

CONCLUSIONS

Niacin treatment lowers serum total- and phosphofetuin-A concentrations in individuals with MetS, and these changes correlate with the beneficial changes in serum lipids. Because niacin is known to induce insulin resistance, these findings suggest that fetuin-A may not be a mediator of niacin-induced insulin resistance but it may blunt the insulin resistance induced by niacin by decreasing its circulating concentrations.

Negative energy balance alters global gene expression and immune responses in the uterus of postpartum dairy cows

Most dairy cows suffer uterine microbial contamination postpartum. Persistent endometritis often develops, associated with reduced fertility. We used a model of differential feeding and milking regimes to produce cows in differing negative energy balance status in early lactation (mild or severe, MNEB or SNEB). Blood hematology was assessed preslaughter at 2 wk postpartum. RNA expression in endometrial samples was compared using bovine Affymetrix arrays. Data were mapped using Ingenuity Pathway Analysis. Circulating concentrations of IGF-I remained lower in the SNEB group, whereas blood nonesterified fatty acid and β-hydroxybutyrate concentrations were raised. White blood cell count and lymphocyte number were reduced in SNEB cows. Array analysis of endometrial samples identified 274 differentially expressed probes representing 197 recognized genes between the energy balance groups. The main canonical pathways affected related to immunological and inflammatory disease and connective tissue disorders. Inflammatory response genes with major upregulation in SNEB cows included matrix metalloproteinases, chemokines, cytokines, and calgranulins. Expression of several interferon-inducible genes including ISG20, IFIH1, MX1, and MX2 were also significantly increased in the SNEB cows. These results provide evidence that cows in SNEB were still undergoing an active uterine inflammatory response 2 wk postpartum, whereas MNEB cows had more fully recovered from their energy deficit, with their endometrium reaching a more advanced stage of repair. SNEB may therefore prevent cows from mounting an effective immune response to the microbial challenge experienced after calving, prolonging the time required for uterine recovery and compromising subsequent fertility.

The DGAT2 gene is a candidate for the dissociation between fatty liver and insulin resistance in humans

The enzyme DGAT (acyl-CoA:diacylglycerol acyltransferase) catalyses the final step of triacylglycerol (triglyceride) synthesis. Mice overexpressing hepatic DGAT2 fed a high-fat diet develop fatty liver, but not insulin resistance, suggesting that DGAT2 induces a dissociation between fatty liver and insulin resistance. In the present study, we investigated whether such a phenotype also exists in humans. For this purpose, we determined the relationships between genetic variability in the DGAT2 gene with changes in liver fat and insulin sensitivity in 187 extensively phenotyped subjects during a lifestyle intervention programme with diet modification and an increase in physical activity. Changes in body fat composition [MR (magnetic resonance) tomography], liver fat and intramyocellular fat ((1)H-MR spectroscopy) and insulin sensitivity [OGTT (oral glucose tolerance test) and euglycaemic-hyperinsulinaemic clamp] were determined after 9 months of intervention. A change in insulin sensitivity correlated inversely with changes in total body fat, visceral fat, intramyocellular fat and liver fat (OGTT, all P<0.05; clamp, all P< or =0.03). Changes in total body fat, visceral fat and intramyocellular fat were not different between the genotypes of the SNPs (single nucleotide polymorphisms) rs10899116 C>T and rs1944438 C>T (all P> or =0.39) of the DGAT2 gene. However, individuals carrying two or one copies of the minor T allele of SNP rs1944438 had a smaller decrease in liver fat (-17+/-10 and -24+/-5%; values are means+/-S.E.M.) compared with subjects homozygous for the C allele (-39+/-7%; P=0.008). In contrast, changes in insulin sensitivity were not different among the genotypes (OGTT, P=0.76; clamp, P=0.53). In conclusion, our findings suggest that DGAT2 mediates the dissociation between fatty liver and insulin resistance in humans. This finding may be important in the prevention and treatment of insulin resistance and Type 2 diabetes in subjects with fatty liver.

Role of immunogenic fetuin A on L5178Y-R lymphoma tumorigenesis

In the present study, we report the detection of immunogenic fetuin-A on L5178Y-R (LY-R) lymphoma cells. Fetuin-A was recognized by antibodies present in the serum of LY-R tumor-bearing and immunized mice, but not by sera of mice immunized with the non-tumorigenic variant LY-S or by healthy mouse sera. However, according with Western blot analysis with commercial anti-fetuin antibodies, fetuin-A is present in both cell types which suggests that the fetuin recognized by anti-LY-R antibodies is an immunogenic form associated only with the tumorigenic LY-R cells and might be involved in tumor progression in this lymphoma.

Causes and metabolic consequences of Fatty liver

Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.