Insulin is a prominent modulator of the cytokine-stimulated expression of acute-phase plasma protein genes

Associations Between GGT/HDL and MAFLD: A Cross-Sectional Study

PURPOSE

To explore the association between γ-glutamyl transpeptidase to high-density lipoprotein ratio (GGT/HDL), triglyceride glucose-body mass index (TYG-BMI), and metabolic associated fatty liver disease (MAFLD) in a Chinese population with type 2 diabetes (T2DM) by cross-sectional analysis. To investigate the role of GGT/HDL played in MAFLD by TYG-BMI.

PATIENTS AND METHODS

A total of 1434 adult patients hospitalized with T2DM at Hebei General Hospital (Shijiazhuang, China) were included in the study. Patients' demographic and clinical data were collected. Spearman correlation was used to test for an association between GGT/HDL or TYG-BMI and related risk factors of MAFLD among T2DM patients. Multiple logistic regression analyses were performed to investigate the association between GGT/HDL or TYG-BMI and MAFLD. Mediation analysis was used to explore whether TYG-BMI mediated the association between GGT/HDL and MAFLD.

RESULTS

A total of 1434 T2DM patients were enrolled, the MAFLD group showed a higher level of GGT/HDL compared to the non-MAFLD group. There was a progressive increase in the prevalence of MAFLD with increasing tertiles of GGT/HDL. After adjusting for confounding factors, multivariate logistic regression analysis revealed that high levels of GGT/HDL were independent risk factors for MAFLD in T2DM patients. BMI further grouped the patients: ≤ 23kg/m2,>23kg/m2. GGT/HDL was found to be an independent risk factor for MAFLD but only in T2DM patients with a BMI greater than 23 kg/m2. Mediation analysis indicated that GGT/HDL had a significant direct effect on MAFLD.

CONCLUSION

GGT/HDL was positively associated with MAFLD incidence in T2DM patients with a BMI greater than 23 Kg/m2, and TYG-BMI partly mediated the association.

The Impacts of Fish Oil and/or Probiotic Intervention on Low-Grade Inflammation, IGFBP-1 and MMP-8 in Pregnancy: A Randomized, Placebo-Controlled, Double-Blind Clinical Trial

Background: We investigated the impact of fish oil and/or probiotics on serum and vaginal inflammatory and metabolic proteins and their relation to the onset of gestational diabetes mellitus (GDM). Methods: Overweight/obese pregnant women received fish oil + placebo, probiotics + placebo, fish oil + probiotics or placebo + placebo from early pregnancy until six months postpartum (fish oil: 1.9 g docosahexaenoic acid and 0.22 g eicosapentaenoic acid; probiotics: Lactobacillus rhamnosus HN001 and Bifidobacterium animalis ssp. lactis 420, 10¹⁰ colony-forming units each). Serum high sensitivity C-reactive protein (hsCRP) and serum/vaginal (s/v) phosphorylated insulin-like growth factor binding-protein-1 (phIGFBP-1), IGFBP-1 and matrix metalloproteinase 8 (MMP-8) were analyzed. GDM was diagnosed according to 2 h 75 g OGTT. Results: The intervention had no impact on the change in proteins during pregnancy. Nevertheless, s-MMP-8 decreased and s-IGFBP-1 increased more in obese than in overweight women in the fish oil + probiotics group, while a decrease in s-MMP-8 was seen in obese women and an increase was seen in overweight women in the probiotics + placebo group. The late pregnancy s-phIGFBP-1 was higher in women who developed GDM in fish oil + probiotics-group compared to fish oil + placebo-group. The concentrations of s-phIGFBP-1 (635.9 ± 315.3 ng/mL vs. 753.2 ± 335.1 ng/mL, p = 0.005) and s-IGFBP-1 (3.78 ± 0.72 ng/mL vs. 3.96 ± 0.69 ng/mL, p = 0.042) were lower in early pregnancy in women who developed GDM than in women remaining healthy. Conclusions: The intervention per se had no impact on the proteins, but obesity and GDM may modify the effect. IGFBPs may affect the development of GDM.

Obesity, dyslipidemia, and high blood pressure are associated with cardiovascular risk, determined using high-sensitivity C-reactive protein concentration, in young adults

Objective

Few studies have investigated the relationships between high-sensitivity C-reactive protein (hs-CRP) concentration and conventional cardiometabolic markers in young adults. The aim of this study was to characterize the cardiometabolic profile of young adults who are at high cardiovascular risk, according to hs-CRP concentration.

Methods

A cross-sectional study was conducted in 300 young adults (18 to 30 years old) from southern Mexico (n = 150 normal-weight and n = 150 obese). Their circulating lipid and glucose concentrations were measured using colorimetric enzymatic assays, and their hs-CRP, ApoA, and ApoB concentrations were measured using turbidimetric assays.

Results

The most prevalent abnormalities in the participants with high cardiovascular risk, determined using an hs-CRP >28.57 nmol/L, were high waist circumference (85.7%), obesity (83.9%), high low-density lipoprotein-cholesterol (64.3%), low high-density lipoprotein-cholesterol (50%), Apo B in the highest tertile (39.3%), hypertriglyceridemia (35.7%), and high blood pressure (30.4%). In addition, there were strong associations between hs-CRP >28.57 nmol/L and obesity (odds ratio [OR] = 13.9), high waist circumference (OR = 8.0), hypertriglyceridemia (OR = 4.0), high blood pressure (OR = 3.4), hypercholesterolemia (OR = 2.8), and Apo B in the highest tertile (OR = 2.4).

Conclusion

The principal cardiometabolic alterations associated with high cardiovascular risk, determined using hs-CRP, are obesity, dyslipidemia, and high blood pressure in young adults.

Identification of DNA response elements regulating expression of CCAAT/enhancer-binding protein (C/EBP) β and δ and MAP kinase-interacting kinases during early adipogenesis

Given the high and increasing prevalence of obesity and associated disorders, such as type-2 diabetes, it is important to understand the mechanisms that regulate lipid storage and the differentiation of fat cells, a process termed adipogenesis. Using the well-established mouse 3T3-L1 in vitro model of adipogenesis, we refine how the induction of two key adipogenic transcription factors, CCAAT/enhancer-binding proteins (C/EBPs) β and δ are regulated during early adipogenesis. We identify, in the gene promoters of Cebpb and Cebpd, the DNA response elements responsible for binding transcription factors that are activated by cAMP or glucocorticoids. We also show that mitogen-activated protein kinase (MAPK)-interacting kinase 2 (MNK2; Mknk2), which plays a distinct role in diet-induced obesity, is induced during early adipogenesis and identify the functional DNA response elements responsible for regulating its expression. Mknk2 expression is maintained in differentiated 3T3-L1 adipocytes and is expressed at high levels across a range of mouse adipose tissue depots. Together, these new insights help to clarify the transcriptional programme of early adipogenesis and identify Mknk2 as one of potentially many genes up-regulated during adipogenesis.

Cardiac Autonomic Neuropathy: A Progressive Consequence of Chronic Low-Grade Inflammation in Type 2 Diabetes and Related Metabolic Disorders

Cardiac autonomic neuropathy (CAN) is one of the earliest complications of type 2 diabetes (T2D), presenting a silent cause of cardiovascular morbidity and mortality. Recent research relates the pathogenesis of cardiovascular disease in T2D to an ensuing chronic, low-grade proinflammatory and pro-oxidative environment, being the hallmark of the metabolic syndrome. Metabolic inflammation emerges as adipose tissue inflammatory changes extending systemically, on the advent of hyperglycemia, to reach central regions of the brain. In light of changes in glucose and insulin homeostasis, dysbiosis or alteration of the gut microbiome (GM) emerges, further contributing to inflammatory processes through increased gut and blood-brain barrier permeability. Interestingly, studies reveal that the determinants of oxidative stress and inflammation progression exist at the crossroad of CAN manifestations, dictating their evolution along the natural course of T2D development. Indeed, sympathetic and parasympathetic deterioration was shown to correlate with markers of adipose, vascular, and systemic inflammation. Additionally, evidence points out that dysbiosis could promote a sympatho-excitatory state through differentially affecting the secretion of hormones and neuromodulators, such as norepinephrine, serotonin, and γ-aminobutyric acid, and acting along the renin-angiotensin-aldosterone axis. Emerging neuronal inflammation and concomitant autophagic defects in brainstem nuclei were described as possible underlying mechanisms of CAN in experimental models of metabolic syndrome and T2D. Drugs with anti-inflammatory characteristics provide potential avenues for targeting pathways involved in CAN initiation and progression. The aim of this review is to delineate the etiology of CAN in the context of a metabolic disorder characterized by elevated oxidative and inflammatory load.

Insulin attenuates TNFα-induced hemopexin mRNA: An anti-inflammatory action of insulin in rat H4IIE hepatoma cells

Proinflammatory cytokines, including TNF-α and IL-6, can contribute to insulin resistance. Conversely, insulin has some actions that can be considered anti-inflammatory. Hemopexin is a Class 2 acute phase reactant and control of its transcription is predominantly regulated by IL-6, with TNF-α and IL-1β also inducing hemopexin gene expression. Thus, we asked whether insulin could inhibit the ability of TNF-α to stimulate hemopexin mRNA expression. In cultured rat hepatoma (H4IIE) cells, TNF-α significantly increased hemopexin mRNA accumulation. The TNF-α-induced increase of hemopexin mRNA was dramatically attenuated by insulin, even though TNF-α reduced peak insulin activation of ERK. Thus, even though TNF-α can contribute to insulin resistance, the residual insulin response was still able to counteract TNF-α actions.

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The TNF-α-induced increase of hemopexin mRNA was dramatically attenuated by insulin.

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This occurred even though TNF-α significantly decreased insulin activation of ERK.

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This suggests an additional mechanism for the anti-inflammatory action of insulin.

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Cytokine-induced insulin resistance does not abolish insulin’s anti-inflammatory effect.

Incremental Predictive Value of Serum AST-to-ALT Ratio for Incident Metabolic Syndrome: The ARIRANG Study

Aims

The ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT) is of great interest as a possible novel marker of metabolic syndrome. However, longitudinal studies emphasizing the incremental predictive value of the AST-to-ALT ratio in diagnosing individuals at higher risk of developing metabolic syndrome are very scarce. Therefore, our study aimed to evaluate the AST-to-ALT ratio as an incremental predictor of new onset metabolic syndrome in a population-based cohort study.

Material and Methods

The population-based cohort study included 2276 adults (903 men and 1373 women) aged 40–70 years, who participated from 2005–2008 (baseline) without metabolic syndrome and were followed up from 2008–2011. Metabolic syndrome was defined according to the harmonized definition of metabolic syndrome. Serum concentrations of AST and ALT were determined by enzymatic methods.

Results

During an average follow-up period of 2.6-years, 395 individuals (17.4%) developed metabolic syndrome. In a multivariable adjusted model, the odds ratio (95% confidence interval) for new onset of metabolic syndrome, comparing the fourth quartile to the first quartile of the AST-to-ALT ratio, was 0.598 (0.422–0.853). The AST-to-ALT ratio also improved the area under the receiver operating characteristic curve (AUC) for predicting new cases of metabolic syndrome (0.715 vs. 0.732, P = 0.004). The net reclassification improvement of prediction models including the AST-to-ALT ratio was 0.23 (95% CI: 0.124–0.337, P<0.001), and the integrated discrimination improvement was 0.0094 (95% CI: 0.0046–0.0143, P<0.001).

Conclusions

The AST-to-ALT ratio independently predicted the future development of metabolic syndrome and had incremental predictive value for incident metabolic syndrome.

Risks of borderline liver enzyme abnormalities to the incidence of impaired fasting glucose and diabetes mellitus: a 7 year follow up study of workers

Background

The aim of this study was to identify the relationships between borderline serum liver enzyme abnormalities and the incidence of impaired fasting glucose (IFG) and diabetes mellitus (DM) during a 7-year follow-up of workers, and to evaluate the quantitative level of risks.

Methods

A total of 749 workers in an electronics manufacturing company were divided into the normal fasting blood glucose (n = 633), IFG (n = 98), and DM (n = 18) groups, according to the results of their health checkup in 2006. Among 633 workers in the normal group, excluding 55 workers who were impossible to follow, incidence rate and relative risks of 578 workers to the IFG or DM in 2013 according to the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase (γ-GTP) were investigated. The liver enzyme levels were categorized as A (normal), B (borderline elevation), and R (definite elevation) following the standard of the National Health Insurance Service of Korea.

Results

The incidence rate of IFG or DM based on ALT level was 9.7 % for the A, 30.0 % for B, and 15.4 % for R. According to γ-GTP, the incidence rate was 9.8 % for A, 34.5 % for B, and 25.0 % for R. The relative risk(RR) to the incidence of IFG or DM depending on the level of ALT were 3.09 in B and 1.59 in R compared to A. According to γ-GTP, RR was 3.52 in B and 2.55 in R compared to A. AST level was not related to the incidence of IFG or DM. A multiple logistic regression analysis with the incidence of IFG or DM as a dependent variable resulted in an odds ratio of 2.664(1.214–5.849) for B level ALT, 3.685(1.405–9.667) for B level of γ-GTP even after adjustment for other variables such as age, sex, body mass index, AUDIT score, systolic blood pressure, and triglyceride.

Conclusions

Even borderline elevations of ALT and γ-GTP, but not AST, increased the incidence and risk of IFG or DM after 7 years. Borderline elevation of ALT and γ-GTP was identified as an independent risk factor of IFG or DM.

Does the sympathetic nervous system contribute to the pathophysiology of metabolic syndrome?

The metabolic syndrome (MS), formally known as syndrome X, is a clustering of several risk factors such as obesity, hypertension, insulin resistance, and dislypidemia which could lead to the development of diabetes and cardiovascular diseases (CVD). The frequent changes in the definition and diagnostic criteria of MS are indications of the controversy and the challenges surrounding the understanding of this syndrome among researchers. Obesity and insulin resistance are leading risk factors of MS. Moreover, obesity and hypertension are closely associated to the increase and aggravation of oxidative stress. The recommended treatment of MS frequently involves change of lifestyles to prevent weight gain. MS is not only an important screening tool for the identification of individuals at high risk of CVD and diabetes but also an indicator of suitable treatment. As sympathetic disturbances and oxidative stress are often associated with obesity and hypertension, the present review summarizes the role of sympathetic nervous system and oxidative stress in the MS.

Evaluation of lasting high levels of CRP among the patients with metabolic syndrome

"Low-grade" systemic inflammation is common findings in patients with metabolic syndrome (MetS). When we assessed 256 MetS patients, we found eight patients who presented high levels of C-reactive protein (CRP) which are between 40 and 15 mg/L for more than 3 years. They have not satisfied any criteria of inflammatory diseases such as rheumatoid arthritis and the area of visceral fat estimated by computed tomography was more than 200 cm(2). All the other MetS patients of visceral fat over 200 cm(2) presented low levels of CRP which are less than 10 mg/L. Insulin resistance and ultrasound study of carotid plaques showed no differences between high and low levels of CRP patients. There are a series of MetS patients who show high levels of CRP without clinical symptoms of inflammatory diseases. High levels of CRP merely cannot be explained by visceral fat area, insulin resistance, or carotid plaques.

Interaction Between Persistent Organic Pollutants and C-reactive Protein in Estimating Insulin Resistance Among Non-diabetic Adults

Objectives

Chronic inflammation is now thought to play a key pathogenetic role in the associations of obesity with insulin resistance and diabetes. Based on our recent findings on persistent organic pollutants (POPs) including the lack of an association between obesity and either insulin resistance or diabetes prevalence among subjects with very low concentrations of POPs, we hypothesized that POP concentrations may be associated with inflammation and modify the associations between inflammation and insulin resistance in non-diabetic subjects.

Methods

Cross-sectional associations among serum POPs, C-reactive protein (CRP), and homeostasis model assessment of insulin resistance (HOMA-IR) were investigated in 748 non-diabetic participants aged ≥20 years. Nineteen types of POPs in 5 subclasses were selected because the POPs were detectable in ≥60% of the participants.

Results

Among the five subclasses of POPs, only organochlorine (OC) pesticides showed positive associations with CRP concentrations, while polychlorinated biphenyls (PCBs) showed inverse associations with CRP concentrations. There were statistically significant interactions between CRP and OC pesticides and between CRP and PCBs, in estimating HOMA-IR (P for interaction <0.01 and <0.01, respectively). CRP was not associated with HOMA-IR among subjects with low concentrations of OC pesticides or PCBs, while CRP was strongly associated with HOMA-IR among subjects with high concentrations of these POPs.

Conclusions

In the current study, OC pesticides were associated with increased levels of CRP, a marker of inflammation, and both OC pesticides and PCBs may also modify the associations between CRP and insulin resistance.

Does fat fuel the fire: independent and interactive effects of genetic, physiological, and environmental factors on variations in fat deposition and distribution across populations

Markers of inflammation (MOI) have been reported to influence bone health in adults, with reports of inverse associations. Adipose has also been linked to bone. In children, the interrelationships are unclear. The objective of this study was to evaluate the relationship between MOI (i.e. CRP, TNFR2, IL-6) and bone mineral content (BMC) and determine the contribution of fat deposition/distribution in children. Forty-nine children (59% male) 7-12 y participated. Body composition was evaluated by DXA, and MOI and insulin sensitivity (S(I)) were obtained during an IVGTT. Multiple linear regression was used for analyses. TNFR2 was inversely associated with BMC. In boys, TNFR2 was inversely associated with BMC, and in girls IL-6 was inversely associated with BMC, and total and percent fat influenced the relationships. Our results suggest a potential inhibitory role of inflammation on bone as well as a negative impact of adiposity. Future investigations are warranted to further investigate these relationships.

Anti-Inflammatory Action of Insulin via Induction of Gadd45-β Transcription by the mTOR Signaling Pathway

Insulin regulates a large number of genes in a tissue-specific manner. We have previously identified genes modulated by insulin in the liver and in liver-derived cells that have not yet been characterized as insulin regulated, and results of these previous studies indicated that numerous genes are induced by insulin via the MEK-ERK pathway. We now describe new studies indicating that Gadd45-β can be induced by acute insulin treatment. Although other regulators of Gadd45-β expression may utilize the MEK-ERK pathway, the data indicate that insulin utilizes signaling pathways separate from either MEK-ERK, PI3-K, or p38 signaling pathways in the regulation of Gadd45-β transcription. Our findings show that activation of a downstream effector of multiple signaling pathways, mTOR, was required for insulin-induction of Gadd45-β gene transcription. Increased expression of Gadd45-β can inhibit c-Jun N-terminal kinase (JNK) activity. Since TNFα is increased during inflammation, and acts, at least in part, via the JNK signaling pathway, insulin induction of Gadd45-β suggests a mechanism for the anti-inflammatory actions of insulin.

High-sensitivity C-reactive protein predicts cardiovascular risk in diabetic and nondiabetic patients: effects of insulin-sensitizing treatment with pioglitazone

Systemic inflammatory activity has turned out to play a key pathogenic role in vascular atherosclerosis, insulin resistance, and type 2 diabetes mellitus. Inflammatory biomarkers may therefore be a valuable tool for risk evaluation. Among them, the best evidence to date supports the use of high-sensitivity C-reactive protein (hs-CRP) to monitor insulin resistance and cardiovascular risk in diabetic and nondiabetic individuals. Data suggest that hs-CRP may also participate directly in the process of atherogenesis. A growing number of clinical trials tested the hypothesis that antidiabetic drugs specifically targeting insulin resistance could benefit individuals by reducing inflammation, atherogenesis, and thus cardiovascular risk. One such class are the thiazolidinediones (pioglitazone and rosiglitazone). These agents act as selective ligands of the nuclear transcription factor peroxisome proliferator-activated receptor-gamma (PPARgamma). This article reviewed published data on hs-CRP changes with the thiazolidinedione agent pioglitazone. Here we found pronounced insulin-sensitizing and anti-inflammatory properties in different clinical settings, including diabetic and nondiabetic individuals. Coadministration of pioglitazone to antilipidemic statin therapy resulted in additional effects on low-grade inflammation, and hs-CRP reduction has been demonstrated to occur independently of glucose lowering. The anti-inflammatory effect appeared to be a rapid physiologic reaction on PPARgamma activation and could be observed within a short-term interval after starting pioglitazone therapy. In summary, clinical study results underline the benefit of an early insulin resistance treatment to oppose systemic vascular inflammation and cardiometabolic syndrome in patients with elevated levels of high-sensitivity C-reactive protein.

Insulin sensitivity in African-American and white women: association with inflammation

Whether the contribution of inflammation to risk for chronic metabolic disease differs with ethnicity is not known. The objective of this study was to determine: (i) whether ethnic differences exist in markers of inflammation and (ii) whether lower insulin sensitivity among African Americans vs. whites is due to greater inflammatory status. Subjects were African-American (n = 108) and white (n = 105) women, BMI 27-30 kg/m(2). Insulin sensitivity was assessed with intravenous glucose tolerance test and minimal modeling; fat distribution with computed tomography; body composition with dual-energy X-ray absorptiometry; markers of inflammation (tumor necrosis factor (TNF)-alpha, soluble tumor necrosis factor receptor (sTNFR)-1, sTNFR-2, C-reactive protein (CRP), and interleukin (IL)-6) with enzyme-linked immunosorbent assay (ELISA). Whites had greater intra-abdominal adipose tissue (IAAT), insulin sensitivity, and concentrations of TNF-alpha, sTNFR-1, and sTNFR-2 than African Americans. Greater TNF-alpha in whites vs. African Americans was attributed to greater IAAT in whites. Among whites, but not African Americans, CRP was independently and inversely associated with insulin sensitivity, after adjusting for IAAT (r = -0.29 P < 0.05, and r = -0.13 P = 0.53, respectively). Insulin sensitivity remained lower in African Americans after adjusting for CRP (P < 0.001). In conclusion, greater IAAT among whites may be associated with greater inflammation. Insulin sensitivity was lower among African Americans, independent of obesity, fat distribution, and inflammation.

Elevated C-reactive protein levels and metabolic syndrome in the elderly: The role of central obesity data from the InChianti study

Metabolic syndrome (MS) and "low grade" systemic inflammation (LGSI) are very common findings in the older population. Although MS and LGSI have been associated in adults, it is not known what is the real contribution of MS, and its single components, to LGSI in older persons, due to the potential confounding effect of comorbidity and aging. We investigated the relationship between increased C-reactive protein (CRP) plasma levels, a marker of LGSI, and MS in 1044 older (> or =65 years) community dwelling Italian individuals enrolled the InChianti study. Metabolic syndrome was defined by the NCEP-ATP III-AHA/NHLBI criteria. High sensitivity CRP (hs.CRP) levels were measured by enzyme-linked immunosorbent assay, and defined as high when >3mg/L. The overall prevalence of MS was 31%. The prevalence of high hs.CRP was 54.5% in subjects with, and 41.3% in those without MS (p<0.001). MS was associated with high hs.CRP levels after adjustment for age, gender, and comorbidity (OR: 1.93, 95% CI: 1.46-2.55). Compared to subjects with MS and no LGSI, individuals with MS and LGSI were characterized by higher waist circumference, BMI, and HOMA score. Multivariate logistic regression analysis confirmed the association between waist circumference and high hs.CRP levels in subjects with MS (waist circumference III vs. I tertile OR: 2.60, 95% CI: 1.79-3.77) independent of age, gender, and important confounding variables including comorbidity. Additional analyses, conducted with and without dichotomization of hs.CRP levels, confirmed the central role of waist circumference in the LGSI phenomenon, independent of gender and diagnosis of MS. We conclude that in older individuals, MS is associated with LGSI, but the association is mainly supported by a strong independent correlation between waist circumference and high hs.CRP levels. In the absence of this specific MS component, it seems that the contribution of MS to LGSI would be modest at best.

Levels of serum sialic acid and thiobarbituric acid reactive substances in subjects with impaired glucose tolerance and type 2 diabetes mellitus

Cardiovascular disease is a common cause of death for diabetic patients. High sialic acid levels (SA) and increased oxidative stress are important factors for cardiovascular diseases. We aimed to research whether SA and thiobarbituric acid reactive substances (TBARS) levels are associated with the degree of the diabetic regulation and investigate if SA and TBARS levels can be controlled with the regulation of the blood glucose levels. A total of 179 subjects were included in the study. Three groups, which were comprised of subjects with type 2 diabetes mellitus (DM) (DM group [DMG], n=149), impaired glucose tolerance (IGT) (IGT group [IGTG], n=15), and normal oral glucose tolerance (NGT) (NGTgroup [NGTG], n=15) were constituted. Glucose, cholesterol, high-density lipoprotein (HDL) and glycated hemoglobin (HbA1C), SA, and TBARS were measured in the sera of the patients. SA and TBARS levels were significantly increased in subjects with type 2 DM (P<0.001 for both). SA concentrations showed significant correlation with triglycerides (r=0.229; P<0.05), fasting glucose (r=0.508; P<0.01), 2-hr postprandial glucose (r=0.455; P<0.01), and HbA1C (r=0.467; P<0.01), and there was a positive correlation between TBARS and HbA1C (r=0.251; P<0.01). Diabetic patients were found to have higher risk for inflammation and oxidative stress. The regulation of blood glucose levels may contribute to the decline of both SA and TBARS levels.

The integration of lipid-sensing and anti-inflammatory effects: how the PPARs play a role in metabolic balance

The peroxisomal proliferating-activated receptors (PPARs) are lipid-sensing transcription factors that have a role in embryonic development, but are primarily known for modulating energy metabolism, lipid storage, and transport, as well as inflammation and wound healing. Currently, there is no consensus as to the overall combined function of PPARs and why they evolved. We hypothesize that the PPARs had to evolve to integrate lipid storage and burning with the ability to reduce oxidative stress, as energy storage is essential for survival and resistance to injury/infection, but the latter increases oxidative stress and may reduce median survival (functional longevity). In a sense, PPARs may be an evolutionary solution to something we call the 'hypoxia-lipid' conundrum, where the ability to store and burn fat is essential for survival, but is a 'double-edged sword', as fats are potentially highly toxic. Ways in which PPARs may reduce oxidative stress involve modulation of mitochondrial uncoupling protein (UCP) expression (thus reducing reactive oxygen species, ROS), optimising forkhead box class O factor (FOXO) activity (by improving whole body insulin sensitivity) and suppressing NFkB (at the transcriptional level). In light of this, we therefore postulate that inflammation-induced PPAR downregulation engenders many of the signs and symptoms of the metabolic syndrome, which shares many features with the acute phase response (APR) and is the opposite of the phenotype associated with calorie restriction and high FOXO activity. In genetically susceptible individuals (displaying the naturally mildly insulin resistant 'thrifty genotype'), suboptimal PPAR activity may follow an exaggerated but natural adipose tissue-related inflammatory signal induced by excessive calories and reduced physical activity, which normally couples energy storage with the ability to mount an immune response. This is further worsened when pancreatic decompensation occurs, resulting in gluco-oxidative stress and lipotoxicity, increased inflammatory insulin resistance and oxidative stress. Reactivating PPARs may restore a metabolic balance and help to adapt the phenotype to a modern lifestyle.

Relation of C-reactive protein to insulin resistance and cardiovascular risk factors in youth

OBJECTIVE

Insulin resistance and C-reactive protein (CRP) levels are strongly correlated in adults. This study explored the relationship in youth.

RESEARCH DESIGN AND METHODS

Associations between CRP levels, cardiovascular risk, and insulin resistance measured by the euglycemic clamp were investigated in 342 healthy Minneapolis youth.

RESULTS

There was no difference in mean CRP levels among boys (n = 189, CRP 1.10 +/- 0.46 mg/l) and girls (n = 153, CRP 1.16 +/- 0.63 mg/l; P = 0.32). There was also no difference between CRP and Tanner stage. CRP, adjusted for BMI, was significantly greater in black subjects compared with white subjects (P = 0.03). CRP was strongly related to adiposity in both girls and boys. CRP levels were related to fasting insulin levels (r = 0.16, P = 0.003) but this association was not significant after adjustment for BMI (r = 0.07, P = 0.21). Similarly, M, the euglycemic clamp measurement of insulin sensitivity, was significantly related to CRP levels (r = -0.13, P = 0.02) but not when M was normalized to lean body mass (M(lbm)) (r = -0.10, P = 0.09). There was a significant inverse correlation between M(lbm) and CRP quartiles, which disappeared after adjustment for BMI. There was no significant association between CRP levels and lipids, blood pressure, physical activity, or left ventricular mass.

CONCLUSIONS

In contrast to adult subjects, after adjustment for adiposity, CRP levels in children age 10-16 years were not significantly associated with insulin resistance or with other factors comprising the metabolic syndrome. This is consistent with the concept that insulin resistance may precede the development of CRP elevation in the evolution of the metabolic syndrome.

Inflammation, insulin resistance, and obesity

Obesity, in particular visceral obesity, has strong associations with cardiovascular disease and is related to many factors that are constituents of the metabolic syndrome. Increasing evidence suggests that features of the metabolic syndrome, including visceral obesity, are associated with a low-grade inflammatory state. Indeed, visceral fat is a source of several molecules, such as leptin, adiponectin, tumor necrosis factor-alpha, and interleukin 6, that are collectively called adipokines. All of them may induce a proinflammatory state and oxidative damage, leading to initiation and progression of atherosclerosis. Reduced-energy diets might represent an effective and healthful approach for long-term weight loss in patients with metabolic syndrome by reducing the underlying inflammatory condition.

Principles of interleukin (IL)-6-type cytokine signalling and its regulation

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important family of mediators involved in the regulation of the acute-phase response to injury and infection. Besides their functions in inflammation and the immune response, these cytokines play also a crucial role in haematopoiesis, liver and neuronal regeneration, embryonal development and fertility. Dysregulation of IL-6-type cytokine signalling contributes to the onset and maintenance of several diseases, such as rheumatoid arthritis, inflammatory bowel disease, osteoporosis, multiple sclerosis and various types of cancer (e.g. multiple myeloma and prostate cancer). IL-6-type cytokines exert their action via the signal transducers gp (glycoprotein) 130, LIF receptor and OSM receptor leading to the activation of the JAK/STAT (Janus kinase/signal transducer and activator of transcription) and MAPK (mitogen-activated protein kinase) cascades. This review focuses on recent progress in the understanding of the molecular mechanisms of IL-6-type cytokine signal transduction. Emphasis is put on the termination and modulation of the JAK/STAT signalling pathway mediated by tyrosine phosphatases, the SOCS (suppressor of cytokine signalling) feedback inhibitors and PIAS (protein inhibitor of activated STAT) proteins. Also the cross-talk between the JAK/STAT pathway with other signalling cascades is discussed.

Principles of interleukin (IL)-6-type cytokine signalling and its regulation

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important family of mediators involved in the regulation of the acute-phase response to injury and infection. Besides their functions in inflammation and the immune response, these cytokines play also a crucial role in haematopoiesis, liver and neuronal regeneration, embryonal development and fertility. Dysregulation of IL-6-type cytokine signalling contributes to the onset and maintenance of several diseases, such as rheumatoid arthritis, inflammatory bowel disease, osteoporosis, multiple sclerosis and various types of cancer (e.g. multiple myeloma and prostate cancer). IL-6-type cytokines exert their action via the signal transducers gp (glycoprotein) 130, LIF receptor and OSM receptor leading to the activation of the JAK/STAT (Janus kinase/signal transducer and activator of transcription) and MAPK (mitogen-activated protein kinase) cascades. This review focuses on recent progress in the understanding of the molecular mechanisms of IL-6-type cytokine signal transduction. Emphasis is put on the termination and modulation of the JAK/STAT signalling pathway mediated by tyrosine phosphatases, the SOCS (suppressor of cytokine signalling) feedback inhibitors and PIAS (protein inhibitor of activated STAT) proteins. Also the cross-talk between the JAK/STAT pathway with other signalling cascades is discussed.

Elevated levels of acute-phase proteins and plasminogen activator inhibitor-1 predict the development of type 2 diabetes: the insulin resistance atherosclerosis study

Elevated serum levels of acute-phase proteins, indicating chronic subclinical inflammation, have been associated with cardiovascular disease as well as the insulin resistance syndrome. Chronic inflammation may also be a risk factor for developing type 2 diabetes. We studied the concentrations of C-reactive protein (CRP), fibrinogen, and plasminogen activator inhibitor-1 (PAI-1) in 1,047 nondiabetic subjects in relation to incident diabetes within 5 years in the Insulin Resistance Atherosclerosis Study. Subjects with diabetes at follow-up (n = 144) had higher baseline levels of fibrinogen (mean +/- SD; 287.8 +/- 58.8 vs. 275.1 +/- 56.0 mg/dl; P = 0.013) as well as of CRP (median [interquartile range]; 2.40 [1.29, 5.87] vs. 1.67 mg/l [0.75, 3.41]; P = 0.0001) and PAI-1 (24 [15, 37.5] vs. 16 ng/ml [9, 27]; P = 0.0001) than nonconverters. The odds ratio (OR) of converting to diabetes was significantly increased with increasing baseline concentrations of the inflammatory markers. In contrast to PAI-1, the association of CRP and fibrinogen with incident diabetes was significantly attenuated after adjustment for body fat (BMI or waist circumference) or insulin sensitivity (S(I)), as assessed by a frequently sampled intravenous glucose tolerance test. In a logistic regression model that included age, sex, ethnicity, clinical center, smoking, BMI, S(I), physical activity, and family history of diabetes, PAI-1 still remained significantly related to incident type 2 diabetes (OR [95% CI] for 1 SD increase: 1.61 [1.20-2.16]; P = 0.002). Chronic inflammation emerges as a new risk factor for the development of type 2 diabetes; PAI-1 predicts type 2 diabetes independent of insulin resistance and other known risk factors for diabetes.

NIDDM as a disease of the innate immune system: association of acute-phase reactants and interleukin-6 with metabolic syndrome X

Non-insulin-dependent diabetes mellitus (NIDDM) is commonly associated with hypertriglyceridaemia, low serum HDL-cholesterol concentrations, hypertension, obesity and accelerated atherosclerosis (metabolic syndrome X). Since a similar dyslipidaemia occurs with the acute-phase response, we investigated whether elevated acute-phase/stress reactants (the innate immune system's response to environmental stress) and their major cytokine mediator (interleukin-6, IL-6) are associated with NIDDM and syndrome X, and may thus provide a unifying pathophysiological mechanism for these conditions. Two groups of Caucasian subjects with NIDDM were studied. Those with any 4 or 5 features of syndrome X (n = 19) were compared with a group with 0 or 1 feature of syndrome X (n = 25) but similar age, sex distribution, diabetes duration, glycaemic control and diabetes treatment. Healthy non-diabetic subjects of comparable age and sex acted as controls. Overnight urinary albumin excretion rate, a risk factor for cardiovascular disease, was also assayed in subjects to assess its relationship to the acute-phase response. Serum sialic acid was confirmed as a marker of the acute-phase response since serum concentrations were significantly related to established acute-phase proteins such as alpha-1 acid glycoprotein (r = 0.82, p < 0.0001). There was a significant graded increase of serum sialic acid, alpha-1 acid glycoprotein, IL-6 and urinary albumin excretion rate amongst the three groups, with the lowest levels in non-diabetic subjects, intermediate levels in NIDDM patients without syndrome X and highest levels in NIDDM patients with syndrome X. C-reactive protein and cortisol levels were also higher in syndrome X-positive compared to X-negative patients and serum amyloid A was higher in both diabetic groups than in the control group. We conclude that NIDDM is associated with an elevated acute-phase response, particularly in those with features of syndrome X. Abnormalities of the innate immune system may be a contributor to the hypertriglyceridaemia, low HDL cholesterol, hypertension, glucose intolerance, insulin resistance and accelerated atherosclerosis of NIDDM. Microalbuminuria may be a component of the acute-phase response.

Transcriptional regulation of genes for ornithine cycle enzymes

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The acute phase protein response in patients receiving subcutaneous IL-6

IL-6, tumour necrosis factor-alpha (TNF-alpha) and IL-1 are thought to be the key mediators of the acute phase response although much of the evidence is based on in vitro studies. It is not clear to what extent each of the acute phase proteins are regulated in vivo by each of these cytokines. The aim of this study was to examine the effects of IL-6 treatment in eight patients with cancer on the concentrations of an extensive range of positive and negative acute phase proteins. It was part of a larger investigation to assess the value of IL-6 in the management of chemotherapy-induced thrombocytopenia. IL-6 was administered by a daily subcutaneous injection for 7 days at a dose level of 1, 3, or 10 micrograms/kg/day. Increases in the positive acute phase proteins, serum amyloid A, C-reactive protein, alpha 1-acid glycoprotein, alpha 1-antichymotrypsin, haptoglobin, alpha 1-antitrypsin, fibrinogen, complement component C3, and caeruloplasmin, were observed, with the greatest incremental changes and fastest responses being seen for C-reactive protein and serum amyloid A protein. The negative acute phase proteins transferrin, transthyretin and retinol binding protein all fell to a nadir within 48-96 h after the first IL-6 injection. Increases in complement component C4 were only found in two patients, which may be related to the increase in circulating TNF-alpha concentrations found only in these patients. This study has therefore shown that IL-6 is capable of causing changes in the majority of acute phase proteins in vivo. Although secondary induction of TNF-alpha was not observed in the majority of patients examined, it is still possible however that other cytokines involved in regulation of the acute phase response, such as IL-1, may have been induced and contributed to the overall response.

The effect of interleukin-1 on C-reactive protein expression in Hep3B cells is exerted at the transcriptional level

The combination of interleukin 6 (IL-6) and interleukin 1 (IL-1) synergistically induces the human acute-phase reactant, C-reactive protein (CRP) in Hep3B cells. While previous studies have indicated that IL-6 induces transcription of CRP, the mode of action of IL-1 has not been clearly defined. It has been suggested that the effect of IL-1 might be post-transcriptional, exerted through the 5'-untranslated region (5'-UTR). To evaluate the role of IL-1 in CRP gene expression, we studied the effects of interleukin-6 (IL-6) and interleukin-1 beta (IL-1 beta) on both the endogenous CRP gene and on transfected CRP-CAT constructs in Hep3B cells. In kinetic studies of the endogenous CRP gene, IL-1 beta alone had no effect on CRP mRNA levels, but when added to IL-6, synergistically enhanced both CRP mRNA levels and transcription, as determined by Northern-blot analyses and nuclear run-on studies. IL-6 alone and the combination of [IL-1 beta + IL-6] each induced increases in mRNA levels roughly comparable with observed increases in transcription. These findings indicate that the effect of IL-1 beta on CRP expression is exerted largely at the transcriptional level in this system. This conclusion was confirmed by studies in Hep3B cells transiently transfected with CRP-CAT constructs, each containing 157 bp of the CRP 5'-flanking region but differing in the length of the 5'-UTR from 104 bp to 3 bp. All constructs responded in the same way; IL-6, but not IL-1 beta, induced significant chloramphenicol acetyltransferase (CAT) expression which was synergistically enhanced 2- to 3-fold by IL-1 beta. These results indicate that IL-1 beta stimulates transcriptional events in the presence of IL-6 and that the upstream 157 bases of the CRP promoter contain elements capable of both IL-6 induction and the synergistic effect of IL-1 beta on transcription.

Phosphorylation of the human leukemia inhibitory factor (LIF) receptor by mitogen-activated protein kinase and the regulation of LIF receptor function by heterologous receptor activation

We used a bacterially expressed fusion protein containing the entire cytoplasmic domain of the human leukemia inhibitory factor (LIF) receptor to study its phosphorylation in response to LIF stimulation. The dose- and time-dependent relationships for phosphorylation of this construct in extracts of LIF-stimulated 3T3-L1 cells were superimposable with those for the stimulation of mitogen-activated protein kinase (MAPK). Indeed, phosphorylation of the cytoplasmic domain of the low-affinity LIF receptor alpha-subunit (LIFR) in Mono Q-fractionated, LIF-stimulated 3T3-L1 extracts occurred only in those fractions containing activated MAPK; Ser-1044 served as the major phosphorylation site in the human LIFR for MAPK both in agonist-stimulated 3T3-L1 lysates and by recombinant extracellular signal-regulated kinase 2 in vitro. Expression in rat H-35 hepatoma cells of LIFR or chimeric granulocyte-colony-stimulating factor receptor (G-CSFR)-LIFR mutants lacking Ser-1044 failed to affect cytokine-stimulated expression of a reporter gene under the control of the beta-fibrinogen gene promoter but eliminated the insulin-induced attenuation of cytokine-stimulated gene expression. Thus, our results identify the human LIFR as a substrate for MAPK and suggest a mechanism of heterologous receptor regulation of LIFR signaling occurring at Ser-1044.

Kinetic modeling and mathematical analysis indicate that acute phase gene expression in Hep 3B cells is regulated by both transcriptional and posttranscriptional mechanisms

To evaluate the possible role of posttranscriptional mechanisms in the acute phase response, we determined the kinetics of transcription (by nuclear run-on assay) and mRNA accumulation of five human acute phase genes in Hep 3B cells incubated with conditioned medium from LPS-stimulated monocytes. Increase in mRNA accumulation was comparable to increase in transcription rate for fibrinogen-alpha and alpha-1 protease inhibitor, suggesting largely transcriptional regulation. In contrast, mRNA accumulation was about 10-20-fold greater than transcriptional increase for serum amyloid A, C3, and factor B, suggesting participation of posttranscriptional mechanisms. Since finding a disparity between the magnitudes of increase in mRNA and transcription does not definitively establish involvement of posttranscriptional mechanisms, we subjected our data to modeling studies and dynamic mathematical analysis to evaluate this possibility more rigorously. In modeling studies, accumulation curves resembling those observed for these three mRNAs could be generated from the nuclear run-on results only if posttranscriptional regulation was assumed. Dynamic mathematical analysis of relative transcription rates and relative mRNA abundance also strongly supported participation of posttranscriptional mechanisms. These observations suggest that posttranscriptional regulation plays a substantial role in induction of some, but not all acute phase proteins.